JP2006100081A - Conductive paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit material which uses conductive paste that is excellent in low-temperature rapid curing performance with heat resistance, moisture resistance, thermal shock resistance, and bending resistance, and shows excellent bonding characteristics to an organic film, a metal substrate, a glass substrate or the like. <P>SOLUTION: The conductive paste contains conductive powder (A), and polyester resin (B) in which a monomer is copolymerized having double bond for 0.5-50 mol% of an acid component and/or a glycol component, when the total of the acid component and the glycol component of polyester resin assumed is set as 100 mol%. It also contains an isocyanate compound (C). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive paste. More specifically, the conductive paste is applied, printed, or cured on a film such as polyethylene terephthalate (PET), vinyl chloride, or nylon, a metal substrate, or a glass substrate. It is related to conductive paste used for forming circuits, bonding terminals and lead wires of electronic components, and protecting electronic devices from electromagnetic interference (EMI). The present invention relates to a conductive paste that is suitable for a PET film, an ITO (indium tin oxide) transparent conductive film, etc., which is a low substrate, and has excellent low-temperature curability and excellent bending resistance and adhesion. Furthermore, the present invention relates to a conductive paste that is excellent in connector insertion / removal resistance and connector blocking resistance and suitable for circuit formation and adhesives for parts such as home appliances, automobiles, and OA equipment.

  A membrane circuit obtained by printing a conductive paste on a PET film or the like is lightweight and widely used for keyboards, switches, and the like. However, the required properties have become stricter year by year, and in addition to flex resistance and adhesion, which have been more demanding than before, further low temperature and short time curability is required in terms of production cost and substrate dimensional stability. ing. Furthermore, development of the conductive paste excellent in connector insertion / extraction resistance and connector blocking resistance with the refinement | miniaturization of a pattern is desired.

  There exists patent document 1 as a well-known electroconductive paste. This is a silver paste for membrane circuits using a polybutadiene resin and a blocked isocyanate compound whose isocyanate group is blocked with an oxime compound or caprolactam as a binder, but it has relatively good bending resistance. However, the durability in heat resistance, moisture resistance, and thermal shock resistance is poor.

  Further, in Patent Document 2, a silver paste having excellent bending resistance using a flaky (flaky) silver powder, a copolymerized polyester resin, and a blocked isocyanate compound as a binder is known. It requires about 30 minutes at 150 ° C., and the ITO conductive film having low heat resistance has a problem that the curing temperature is too high. In addition, with the recent fine patterning, connector insertion / removal resistance and connector blocking resistance are also inferior.

  There is Patent Document 3 as a known fast-curing conductive paste. Although it is a conductive paste using blocked isocyanate blocked with imidazole as a curing agent, it has drawbacks in pot life, and further, it has poor durability in heat resistance, moisture resistance and thermal shock resistance.

  Examples of the resin exhibiting good adhesion to films such as polyethylene terephthalate, vinyl chloride, and nylon, and metals include epoxy resins and phenol resins. Patent Documents 4 and 5 are conductive pastes made of an epoxy resin and a phenol resin and excellent in moisture resistance. Patent Documents 6 and 5 are conductive pastes made of an epoxy resin and a sulfonium salt and excellent in heat resistance and moisture resistance. . These conductive pastes are not satisfactory in a strict bending property such as 360 ° where R of the bent portion is 0 mm. In addition, good adhesion to metal foils and films cannot be obtained.

  Patent Document 7 is a conductive paste made of an acrylic resin and excellent in heat resistance, but has a drawback of being inferior in reliability under high temperature and high humidity.

  Patent Document 8 is a conductive paste excellent in heat resistance and moisture resistance made of a polyamide-imide silicon polymer, and Patent Document 9 is a conductive paste excellent in heat resistance and humidity resistance made of a polyamide-imide silicon polymer and an epoxy resin. It is a sex paste. These conductive pastes are also unsatisfactory with a strict bendability such as 360 ° where the bent portion R is 0 mm.

  Patent Document 10 is a conductive paste excellent in moisture resistance and temperature cycle resistance composed of at least one resin selected from a resol type phenol resin and an epoxy resin, a polyester resin, and a polyvinyl butyral resin. Severe bendability such as 360 ° where the bent portion R is 0 mm is not good.

JP 59-206459 A JP-A-1-159906 Japanese Patent Laid-Open No. 60-223871 Japanese Patent Application Laid-Open No. 8-245762 JP 7-278274 A Japanese Patent Laid-Open No. 9-259636 JP-A-55-149356 JP-A-6-116517 JP-A-6-136300 JP 7-41706 A

  In order to obtain good adhesiveness and flexibility in the binder resin composition used for the conductive paste, a main component mainly composed of polyester having a glass transition temperature of 10 ° C. or lower and a block isocyanate compound as a curing agent are usually blended. Although it is used, in the case of a batch type oven, heating at 130 to 170 ° C. for about 30 minutes is required. Even in the case of an IR (far infrared) conveyor oven, it takes 3 minutes or more at a substrate surface temperature of 150 ° C. Thus, when it hardens | cures at high temperature, there exists a problem which damages a base material and the base material which can be used is limited. In addition, since a flexible polyester resin is used as the main component even after sufficient curing, there is a problem that the connector insertion / removal resistance and connector blocking resistance are inferior.

When these conductive pastes are used at a low temperature for a short time, sufficient curing cannot be obtained, a decrease in adhesion and hardness is observed, and furthermore, connector insertion / removal resistance and connector blocking resistance are extremely poor.
In recent years, when an ITO-deposited transparent conductive film is used as a substrate, there are problems of curling and dimensional stability. Even when a PET film is used as a substrate, low-temperature and short-time curing is strongly demanded in order to suppress oligomer generation from the film and improve productivity.

  On the other hand, a dry type conductive paste that does not contain a curing agent is also used, but low temperature fast curability is good, but poor adhesion to the ITO-deposited transparent conductive film, and when used for PET film In addition, there is a problem that the use is limited due to poor bending resistance, connector insertion / removal resistance, connector blocking resistance, and the like.

  In order to solve these problems, the present inventors have excellent adhesiveness and flexibility, and have low-temperature fast curing properties and durability such as heat resistance, moisture resistance, and thermal shock resistance, As a result of intensive studies on a resin composition suitable for a conductive paste excellent in connector insertion / removal resistance and connector blocking resistance, when the total of the acid component and glycol component of the polyester resin is 100 mol%, the acid component and / or Or a polyester resin containing a monomer having a double bond in 0.5 to 50 mol% of the glycol component has excellent adhesion and flexibility, and is excellent in reactivity with an isocyanate compound and can be cured at low temperature. Furthermore, the present inventors have found that the connector insertion / removal resistance and connector blocking resistance are excellent, and have reached the present invention.

  That is, in the present invention, when the total of the conductive powder (A), the acid component of the polyester resin, and the glycol component is 100 mol%, a double bond is added to 0.5 to 50 mol% of the acid component and / or glycol component. It is related with the electrically conductive paste characterized by including the polyester resin (B) and the isocyanate compound (C) which are copolymerizing the monomer which has this.

  The conductive paste of the present invention has excellent adhesion and flexibility to films such as polyethylene terephthalate, ITO-deposited PET film, vinyl chloride, nylon, metal substrates, glass substrates, and the like, and it cannot be obtained by the prior art. Excellent low-temperature fast-curing properties, combined with durability such as heat resistance, moisture resistance, and thermal shock resistance. Furthermore, it is excellent in connector insertion / extraction resistance and connector blocking resistance. As a result, it is possible to meet highly required quality in extremely harsh fields such as electric products, electronic parts, and inter-automobile applications.

  The conductive powder (A) used in the present invention is preferably silver powder alone or mainly composed of silver powder. Examples of the shape of the silver powder include a known flake shape (flaky shape), a spherical shape, a dendritic shape (dendritic shape), and a shape in which spherical primary particles are aggregated three-dimensionally. A silver powder having a shape in which the primary particles are three-dimensionally aggregated is particularly preferable.

  The flaky silver powder preferably has an average particle diameter (50% D) measured by a light scattering method of 1 to 15 μm, more preferably 2 to 8 μm, still more preferably 2 to 5 μm.

  In addition to silver powder, conductive powder includes carbon-based 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, silver It can be used by mixing silver filler with inorganic fillers such as base metal powder, silica, talc, mica, barium sulfate, etc. plated and alloyed with precious metals such as, but from the environmental characteristics such as conductivity and moisture resistance, cost It is preferable to blend carbon black and / or graphite powder in the total conductive powder mainly composed of silver powder at 20 wt% or less, more preferably 10 wt% or less. Of course, carbon black and / or graphite-based materials also have a considerably higher resistance than silver, but can be used depending on the application because they are inexpensive and chemically stable.

The blending ratio of the conductive powder (A) and the binder used in the present invention varies depending on the type of the conductive powder, but when (A) is mainly silver powder, the (A) / binder ratio is 60/40 to 95/5. (Weight ratio) is preferable, and more preferably 80/20 to 90/10. When (A) is less than 60 in the (A) / binder ratio, good electrical conductivity, flex resistance, heat resistance, moisture resistance, thermal shock resistance and other durability may not be obtained. Flexibility and adhesion may be reduced.
When the conductive powder (A) is mainly carbon black and / or graphite, the (A) / binder ratio is preferably 40/60 to 70/30 (weight ratio), more preferably 45/55 to 65/35. is there. When (A) is less than 60 in the (A) / binder ratio, good electrical conductivity, flex resistance, heat resistance, moisture resistance, thermal shock resistance and other durability may not be obtained. Flexibility and adhesion may be reduced.

  The binder used in the present invention is a monomer having a double bond in 0.5 to 50 mol% of the acid component and / or glycol component when the total of the acid component and glycol component of the polyester resin is 100 mol%. A polyester resin (B) copolymerized with an isocyanate compound (C).

  By using this polyester resin as a binder, in addition to good adhesion and bending resistance, it has surprisingly been achieved with excellent low-temperature curability that has not been obtained so far, and excellent connector insertion and removal resistance In addition, connector blocking resistance can be obtained.

  The polyester resin (B) used in the present invention is a monomer having a double bond in 0.5 to 50 mol% of the acid component and / or glycol component when the total of the acid component and glycol component is 100 mol%. Must be copolymerized. Although the mechanism is unknown, it is preferable to combine a polyester resin (B) containing this unsaturated group and an isocyanate compound (C) as a curing agent in combination with a catalyst such as a tin-based compound (E). Thus, the curing speed is remarkably increased as compared with the conventional polyester resin, and the curing temperature can be reduced.

  The polyester resin (B) used in the present invention is obtained by copolymerizing a monomer having a double bond in part of the acid component and / or glycol component, and the total of the acid component and glycol component of the polyester resin is 100 mol%. The copolymerization amount is 0.5 to 50 mol% of the acid component and / or glycol component. Preferably it is 2-30 mol%, More preferably, it is 5-20 mol%. When the monomer containing a double bond is less than 0.5 mol%, the effect on the curability of the polyester resin (B) and the polyisocyanate compound (C) may be diminished. The possibility of gelation by heavy bond cleavage increases, making it difficult to produce high molecular weight polyesters.

Moreover, it is preferable that the double bond density | concentration of the polyester resin (B) used for this invention is 10-2500 equivalent / 10 < ⁶ > g in a polyester resin (A), More preferably, it is 50-1500 equivalent / 10 < ⁶ > g. More preferably, it is 150-1000 equivalent / 10 < ⁶ > g. The double bond concentration is adjusted by adjusting the copolymerization amount of the monomer having the double bond. If it is less than 10 equivalent / 10 ⁶ g, the effect on the curability may be diminished, and if it exceeds 2500 equivalent / 10 ⁶ g, it may be difficult to produce a high molecular weight polyester. The double bond concentration is a value determined on the basis of the ratio of protons bonded to the double bond by ¹ H-NMR measurement of the polyester resin. The unit is expressed in equivalents / 10 ⁶ g, and is contained in 1 ton of resin. It shows the number of equivalents of heavy bonds.

  In order to copolymerize a monomer having a double bond with the polyester resin (B) used in the present invention, for example, a dicarboxylic acid containing an unsaturated double bond is used. Dicarboxylic acids containing unsaturated double bonds include α, β-unsaturated dicarboxylic acids such as fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, and alicyclic dicarboxylic acids containing unsaturated double bonds. Examples of the acid include 2,5-norbornane dicarboxylic acid anhydride, tetrahydrophthalic anhydride, and dimer acid. Of these, fumaric acid, maleic acid and 2,5-norbornene dicarboxylic acid (endo-bicyclo- (2,2,1) -5-heptene-2,3-dicarboxylic acid) are preferable in that they can be cured in a short time. And particularly preferred is fumaric acid.

  The other acid component copolymerized with the polyester resin (B) is preferably 60 mol% or more, more preferably 70 mol% or more of aromatic dicarboxylic acid among all acid components. If the aromatic dicarboxylic acid content is less than 60 mol%, the strength of the coating film decreases, and durability such as low-temperature flex resistance, heat resistance, moisture resistance, and thermal shock resistance may decrease. When a high degree of moisture resistance is required, the aromatic dicarboxylic acid is preferably 80 mol% or more. From the viewpoint of bending resistance, it is combined with an aliphatic glycol having a main chain having 5 or more carbon atoms to be described later. It is particularly preferred to polymerize.

  Among the other dicarboxylic acids copolymerized with the polyester resin (B), examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. Of these, terephthalic acid and isophthalic acid are preferably used in combination in view of physical properties and solvent solubility. Furthermore, as other dicarboxylic acids, aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, azelaic acid, dibasic acids having 12 to 28 carbon atoms, 1,4-cyclohexanedicarboxylic acid 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, hydrogenated dimer acid, hydrogenated naphthalene dicarboxylic acid, alicyclic dicarboxylic acid such as tricyclodecane dicarboxylic acid, and hydroxycarboxylic acid such as hydroxybenzoic acid and lactic acid.

  The glycol component copolymerized with the polyester resin (B) used in the present invention is ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,3-butanediol, , 5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3 -Propanediol, diethylene glycol, 1,4-cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, or polyether glycol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. Door can be. Furthermore, lactones such as ε-caprolactone and δ-valerolactone, and oxycarboxylic acids such as p-hydroxyethoxybenzoic acid are also examples of raw materials for the polyester resin.

  Among these, in order to impart solvent solubility, it is preferable to copolymerize at least 30 mol% of a glycol having an alkyl group as a side chain. More preferably, it is preferable to copolymerize 40 mol% or more. Examples of the glycol having an alkyl group in the side chain include 1,2-propylene glycol, 1,3-butanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-methyl-1,3-propanediol. 2-ethyl-2-butyl-1,3-propanediol, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, and the like. Among these, 3-methyl-1,5-pentanediol, neopentyl glycol, and 2-methyl-1,3-propanediol are particularly preferable from the viewpoints of solvent solubility and curability.

  Furthermore, from the viewpoint of durability such as bending resistance and moisture resistance, it is preferable to copolymerize an aliphatic glycol having 5 or more carbon atoms in the main chain. Specific examples include 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 1,9-nonanediol, 1, 10-decanediol etc. are mentioned, It uses individually or in combination of 2 or more types. By using these long-chain glycols, good adhesion, flexibility and heat resistance are obtained, and surprisingly, the moisture resistance is remarkably improved. In particular, 1,5-pentanediol, 1,6-hexanediol, and 3-methyl-1,5-pentanediol are preferable, and these are preferably used at 70 mol% or more.

  Furthermore, you may copolymerize alicyclic glycol. Alicyclic glycols have the effect of improving flex resistance and impact resistance without lowering the glass transition temperature. Moreover, durability, such as moisture resistance, is also favorable. Examples of the alicyclic glycol include 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, tricyclodecane glycol, and dimer diol. Of these, 1,4-cyclohexanedimethanol is preferred from the viewpoints of solubility and moisture resistance.

  The preferable glass transition temperature of the polyester resin (B) is 25 ° C. or lower, more preferably −20 to 15 ° C.

  In addition, an alkylene oxide adduct of bisphenol A, an alkylene oxide adduct of bisphenol F, and a polyhydric polyol such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, polyglycerin, etc. Also good.

  For the purpose of improving the reactivity with the isocyanate compound, it is particularly preferable to copolymerize a polyvalent carboxylic acid such as trimellitic anhydride or pyromellitic anhydride at 5 mol% or less of the total acid components. Furthermore, it is preferable to add ε-caprolactone to the terminal after polymerization of the polyester resin. By modifying the terminal with a lactone, the reactivity with the isocyanate compound is further improved. Further, a sulfonic acid metal base-containing dicarboxylic acid such as sodium 5-sulfoisophthalate may be used in combination. Further, after polymerization of the polyester resin, an acid anhydride such as trimellitic anhydride or phthalic anhydride may be post-added to give an acid value.

  It is preferable to add a radical polymerization inhibitor (D) to the conductive paste of the present invention. Although it is mainly used to prevent gelation due to double bond cleavage when polymerizing the polyester resin (B), it may be added after polymerization in order to increase the storage stability of the polyester resin. Examples of the radical polymerization inhibitor (D) include known ones such as phenol antioxidants, phosphorus antioxidants, amine antioxidants, sulfur antioxidants, and inorganic compound antioxidants.

  Examples of phenolic antioxidants include 2,5-di-t-butylhydroquinone, 4,4′-butyldenbis (3-methyl-6-t-butylphenol), 1,1,3-tris (2-methyl-4 -Hydroxy-5-tert-butylphenyl) butane, 1,3,5-tris-methyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris (3 , 5-di-t-butyl-4-hydroxyphenyl) isocyanurate, or a derivative thereof.

  Phosphorous antioxidants include tri (nonylphenyl) phosphite, triphenyl phosphite, diphenylisodecyl phosphite, trioctadecyl phosphite, tridecyl phosphite, diphenyldecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-t-butylphenyl ditridecyl phosphite), distearyl-pentaerythritol diphosphite, trilauryl trithiophosphite, etc., or derivatives thereof.

  Examples of amine-based antioxidants include phenyl-β-naphthylamine, phenothiazine, N, N′-diphenyl-p-phenylenediamine, N, N′-di-β-naphthyl-p-phenylenediamine, and N-cyclohexyl-N ′. -Phenyl-p-phenylenediamine, aldol-α-naphthylamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, or derivatives thereof.

  Examples of the sulfur-based antioxidant include thiobis (N-phenyl-β-naphthylamine, 2-mercaptobenchazole, 2-mercaptobenzimidazole, tetramethylthiuram disulfide, nickel isopropyl xanthate, and derivatives thereof.

  Nitro compound antioxidants include 1,3,5-trinitrobenzene, p-nitrosodiphenylamine, p-nitrosodimethylaniline, 1-chloro-3-nitrobenzene, o-dinitrobenzene, m-dinitrobenzene, p-di Examples thereof include nitrobenzene, p-nitrobenzoic acid, nitrobenzene, 2-nitro-5-cyanothiophene, and derivatives thereof.

Examples of the inorganic compound antioxidant include FeCl ₃ , Fe (CN) ₃ , CuCl ₂ , CoCl ₃ , Co (ClO ₄ ) ₃ , Co (NO ₃ ) ₃ , and Co ₂ (SO ₄ ) ₃ .

  As the radical polymerization inhibitor (D) used in the present invention, among the above-mentioned antioxidants, phenol-based antioxidants and amine-based antioxidants are preferable in terms of thermal stability, and have a melting point of 120 ° C. or higher and a molecular weight. Is more preferably 200 or more, more preferably a melting point of 170 ° C. or more. Specific examples include phenothiazine and 4,4'-butyldenbis (3-methyl-6-t-butylphenol).

  The addition amount of the radical polymerization inhibitor (D) is preferably in the range of 0.001 to 0.5 parts by weight, more preferably 0.01 to 0.1 parts by weight with respect to 100 parts by weight of the polyester resin (B). It is. If it is less than 0.001 part by weight, the thermal stability at the time of polyester polymerization is low and there is a risk of gelation due to double bond cleavage, which may make it difficult to produce a high molecular weight polyester. And may adversely affect the physical properties of the cured coating film.

  The number average molecular weight of the polyester resin (B) used in the present invention is 3,000 or more, preferably 8,000 or more, and more preferably 15,000 or more. When the number average molecular weight is less than 3,000, the bending resistance is lowered. In addition, the paste viscosity may decrease. The reduced viscosity of the polyester resin (B) is preferably 0.2 dl / g or more, more preferably 0.4 dl / g or more, and further preferably 0.5 dl / g or more.

  The polyester resin (B) of the present invention preferably has no melting point (non-crystalline) from the viewpoint of adhesiveness, flexibility, solvent solubility and the like.

  The polyester resin (B) of the present invention is 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, vinyl chloride / vinyl acetate, as long as the content of the invention is not impaired. Modification of polymers, epoxy resins, phenol resins, acrylic resins, polyacrylonitrile resins, polybutadiene resins, hydrogenated polybutadiene resins, nitrocellulose, cellulose acetate butyrate (CAB), cellulose acetate acetate propionate (CAP), etc. You may mix | blend cellulose and a polyamide-imide resin in the range which does not deteriorate a characteristic.

  The polyester resin (B) is polymerized by a known method such as a transesterification method or a direct polymerization method.

  The electrically conductive paste of this invention needs to mix | blend an isocyanate compound (C) as a hardening | curing agent which can react with a polyester resin (B). The preferable compounding quantity of an isocyanate compound (C) is 1-40 weight part with respect to 100 weight part of polyester resins (B), More preferably, it is 5-40 weight part. Furthermore, it is preferable to use it in a block form from the viewpoint of storage stability. When the isocyanate compound (C) is less than 1 part by weight, it is not sufficiently cured. Moreover, when it exceeds 40 weight part, it may become weak or may not fully react.

  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 block isocyanate agent include phenols such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, chlorophenol, oximes such as acetoxime, methylethyl ketoxime, cyclohexanone oxime, methanol, Alcohols such as 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, and ε-caprolactam , Δ-valerolactam, γ-butyrolactam, β-propylolactam, and other lactams, and other aromatic amines, imides, acetylacetone 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.

  Furthermore, it is preferable to mix a curing catalyst. Examples of isocyanate curing catalysts include tin-based dibutyltin dilaurate and dioctyltin dilaurate, zinc-based zinc decanoate, bismuth-based neodecanoate, bismuth-based bismuth 2-ethylhexanoate, and K-KAT. Zirconium type such as XC-4205 and XC-6121 (manufactured by Enomoto Kasei Co., Ltd.), aluminum type such as K-KAT XC-5218 (manufactured by Enomoto Kasei Co., Ltd.), potassium type such as potassium octylate and potassium acetate, Tetraethylenediamine, bis (dimethylaminoethyl) ether, N, N ′, N′-trimethylaminoethylpiperazine and other amine-based catalysts described in the catalog of Tosoh Corporation, 1,8-diasabicyclo (5,4,0)- Undecene-7,1,5-diazabicyclo (4,3,0) -nonene-5, UC T SA series, U-CAT series, POLYCAT8 (manufactured by San-Apro Ltd.), an amine system such as Kao riser series (manufactured by Kao Corporation) can be mentioned. Of these, particularly tin compounds (E) are particularly preferred.

  As for the compounding quantity of a curing catalyst, 0.01-0.5 weight part is preferable with respect to 100 weight part of polyester resins (B), More preferably, it is 0.05-0.3 weight part.

  In the conductive paste of the present invention, a curing agent other than the isocyanate compound may be used in combination. 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.

  These other curing agents may be used in combination with a known catalyst or accelerator selected according to the type.

  In the present invention, a solvent may be used in combination. There is no restriction | limiting in the kind, Ester type | system | group, ketone type | system | group, ether ester type | system | group, chlorine type | system | group, alcohol type | system | group, ether type, hydrocarbon type etc. are mentioned. Among these, in the case of screen printing, high boiling point solvents such as ethyl carbitol acetate, butyl cellosolve acetate, isophorone, cyclohexanone, and γ-butyrolactone are preferable.

  You may add additives, such as a well-known antifoamer, a leveling agent, a dispersing agent, to the electrically conductive paste of this invention.

  Hereinafter, the present invention will be described by way of examples. 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. using an Ubbelohde viscosity tube.

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

3. 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.

4). Acid value (mgKOH / g)
A 0.2 g 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.

5. Preparation of test piece Conductive paste is annealed to 75 μm thick PET film, dried to a thickness of 8 to 10 μm. A pattern having a length of 50 mm (for resistivity measurement, heat resistance measurement, moisture resistance measurement, thermal shock resistance, connector insertion / removal resistance, connector blocking resistance) was screen-printed. A test piece was prepared by drying the substrate film at 120 ° C. for 3 minutes using a conveyor type far-infrared oven. Regarding the adhesion and hardness, the ITO-deposited PET film was evaluated in the same manner as the PET film. As the ITO-deposited PET film, RNA 188 (manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm was used as it was.

6). Specific resistance The sheet resistance film thickness was measured using the film thickness and the 4 deep needle resistance measuring device using the test piece created in step 1, and the specific resistance was calculated from these.

7). 4. Adhesion The test piece prepared in (1) was evaluated by a cellophane tape peeling test.

8). 4. Pencil hardness The test piece prepared in (1) was placed on a SUS304 plate having a thickness of 2 mm, and measured according to JIS K-5400 using a high-grade pencil specified in JIS S-6006.

9. 4. Flexibility The test piece prepared in (5) was evaluated by the resistance change rate of the conductor by repeating 360-degree bending at the same location five times under the conditions of 25 ° C., load 50 g / cm ² and R = 0.
Resistance change rate (%) = {(R−R ○) / R ○} × 100
However, R = initial circuit resistance R = resistance value after bending test O: resistance change rate is 200% or less Δ: resistance change rate is more than 200%, 1000% or less ×: resistance change rate is more than 1000% XX: Disconnection within 5 bends

10. 4. Moisture resistance The test pieces prepared in the above were heat-treated in a constant temperature and humidity chamber at 85 ° C. and a relative humidity of 85% RH for 500 hours, and then the adhesion of the conductor, pencil hardness, and bending resistance were evaluated. The substrate was a 75 μm PET film.

11. 4. Connector insertion / extraction resistance The test piece prepared in (1) was adhered with a 125 μm reinforcing film on the back surface, and repeated insertion and removal 10 times using a fine pitch connector, and the degree of peeling of the conductive paste coating film was evaluated.
○: No peeling Δ: Slight peeling ×: Peeling

12 4. Connector blocking resistance A fine-pitch connector is attached to the back of the test piece made in step 125 with a 125 μm reinforcing film adhered, and left at 60 ° C. and 95% RH for 500 hours. Evaluated by degree.
○: No perforation △: Slight perforation ×: Perforation

Synthesis example. 1 (Polyester resin a)
In a four-necked flask equipped with a Gubileu fractionator, 97 parts of dimethyl terephthalic acid, 19 parts of dimethyl isophthalic acid, 93 parts of ethylene glycol, 73 parts of neopentyl glycol, 0.102 part of tetrabutyl titanate as a reaction catalyst, as a radical polymerization inhibitor Of phenothiazine was transesterified at 180 ° C. for 3 hours. Subsequently, 61 parts of sebacic acid and 12 parts of fumaric acid were charged to carry out esterification. 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 resulting polyester resin was terephthalic acid / isophthalic acid / sebacic acid / fumaric acid // ethylene glycol / neopentyl glycol = 50/10/30/10 // 55/45 (molar ratio) with a reduced viscosity of 0.00. The molecular weight was 70 dl / g, the number average molecular weight was 22,000, the acid value was 1.1 mgKOH / g, and the glass transition temperature was 6 ° C. The results are shown in Table 1.

Synthesis example. 2 (Polyester resin b)
In a four-necked flask equipped with a Gubileu rectification tower, 97 parts of dimethyl terephthalic acid, 85 parts of dimethyl isophthalic acid, 1.9 parts of trimellitic anhydride, 236 parts of 3-methyl-1,5-pentanediol, and 0.4 parts of tetrabutyl titanate. 102 parts were charged, 0.048 part of phenothiazine as a radical polymerization inhibitor was added, and the S-exchange was performed at 180 ° C. for 3 hours. Subsequently, 6 parts of fumaric acid was charged to carry out esterification. 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 polyester resin obtained was terephthalic acid / isophthalic acid / fumaric acid / trimellitic acid // 3-methyl-1,5-pentanediol = 50/44/5/1 // 100 (molar ratio), reduced. The viscosity was 0.45 dl / g, the number average molecular weight was 12,000, the acid value was 0.7 mg KOH / g, and the glass transition temperature was 0 ° C. The results are shown in Table 1.

Synthesis example. 3 (Polyester resin c)
Synthesis example. In the same manner as in Example 1, a polyester resin c was synthesized. Phenothiazine is a synthetic example. Similarly to 1, it was added so as to be 200 ppm with respect to the obtained polyester resin. The composition of the obtained polyester resin was terephthalic acid / isophthalic acid / fumaric acid // 2-methyl-1,3-propanediol / 1,6-hexanediol = 30/55/15 // 50/50 (molar ratio). ), Reduced viscosity 0.55 dl / g, acid value 0.5 mgKOH / g, glass transition temperature 25 ° C. The results are shown in Table 1.

Synthesis example. 4 (Polyester resin d)
Synthesis example. In the same manner as in 1, a polyester resin d was synthesized. The composition of the obtained polyester resin was terephthalic acid / isophthalic acid / fumaric acid / trimellitic acid // 3-methyl-1,5-pentanedioldiol / 1,4-cyclohexanedimethanol = 50/39/10/1. // 80/20 (molar ratio), reduced viscosity 0.65 dl / g, number average molecular weight 21,000, acid value 0.9 mgKOH / g, glass transition temperature 3 ° C. The results are shown in Table 1.

Comparative synthesis example. 5 (Comparative polyester resin e)
Synthesis example. Comparative polyester resin d was synthesized in the same manner as in 1. However, since a monomer containing a double bond was not used, phenothiazine was not blended. The composition of the obtained polyester resin was terephthalic acid / isophthalic acid / sebacic acid // ethylene glycol / neopentyl glycol = 50/20/30 // 55/45 (molar ratio). The reduced viscosity was 0.75 dl / g, the number average molecular weight was 23,000, the acid value was 1.5 mgKOH / g, and the glass transition temperature was 7 ° C. The results are shown in Table 2.

Comparative synthesis example. 6-8
Synthesis example. Comparative polyester resins f to h were synthesized in the same manner as in Example 1. Although the comparative polyester resin f did not use the monomer containing a double bond, in order to match conditions with a synthesis example, it is an example which added 200 ppm with respect to the polyester resin from which the phenothiazine was obtained. The results are shown in Table 2.

Adjustment of silver powder A-1 Commercially available flaky silver powder was used as it was. The average particle size (50% D) determined by the light scattering method was 4.5 μm and the specific surface area was 0.7 m ² / g.

Example 1
Silver powder A-1 89 parts, Polyester resin a butyl cellosolve acetate dissolved 9.6 solid part, Coronate 2507 as solid block compound, 1.4 solid part, Polyflow S as leveling agent 0.5 part After sufficiently premixing 0.02 part of dibutyltin dilaurate as a catalyst, it was dispersed three times with a chilled three-roll kneader. 4. Obtained silver paste It was printed, dried and evaluated by the method described in 1. The specific resistance was good at 5.5 × 10 ⁻⁵ Ω · cm. The resistance to bending was very good at 25 ° C., R = 0, the resistance change rate after 5 times of 360 ° bending was + 35%, no disconnection was observed. In addition, the moisture resistance was slightly reduced in physical properties, but was within the practical range. Further, despite being cured at a low temperature for a short time, the connector insertion / removal resistance and connector blocking resistance were also very good. Moreover, despite the low-temperature and short-time curing, good adhesion and hardness to the ITO-deposited PET film were obtained. The results are shown in Table 3.

  Similarly to Example 1, conductive pastes of Examples 2 to 4 were prepared and evaluated. The results are shown in Table 2. All the examples show good reactivity under low-temperature and short-time curing conditions, and various physical properties including connector insertion / removal resistance and connector blocking resistance are good.

  Example 2 is an example using the polyester resin b. However, when a glycol having 5 or more carbon atoms in the main chain is used as described above, the physical property change is also caused by severe moisture resistance such as 85 ° C. and 85% RH. It was very good. Examples 3 and 4 are examples using polyester resins c and d, but good moisture resistance can be obtained by using side chain-containing glycol or alicyclic glycol even if the main chain has less than 5 carbon atoms. Is obtained.

  In the same manner as in Example 1, the conductive pastes of Comparative Examples 1 to 4 were prepared and evaluated. The results are shown in Table 4.

  Comparative Examples 1 to 3 are examples of polyester resins that do not have double bonds, but under low temperature and short time curing conditions, they are inferior in curability, inferior in basic physical properties such as adhesion, hardness, and bending resistance. The connector insertion / removal resistance and connector blocking resistance were completely poor.

  Comparative Example 4 is a case where the polyester resin a of the present invention is used, but there is no isocyanate compound as a curing agent. Since the polyester resin a is a low Tg polyester resin, the performance is remarkably inferior without a curing agent.

  Comparative Example 5 is an example in which a high Tg comparative polyester resin h is used and an evaporative drying type is used without blending a curing agent, but the hardness and adhesion are good, but the flex resistance is poor, and the connector resistance is low. Insertion / removability and connector blocking resistance were completely poor.

  The conductive paste of the present invention has excellent adhesion and flexibility to films such as polyethylene terephthalate, ITO-deposited PET film, vinyl chloride, nylon, metal substrates, glass substrates, and the like, and it cannot be obtained by the prior art. Excellent low-temperature fast-curing properties, combined with durability such as heat resistance, moisture resistance, and thermal shock resistance. Furthermore, it is excellent in connector insertion / extraction resistance and connector blocking resistance. As a result, it is possible to meet highly required quality in extremely harsh fields such as electric products, electronic parts, and inter-automobile applications.

Claims (6)

  When the total of each of the conductive powder (A), the acid component of the polyester resin, and the glycol component is 100 mol%, the monomer having a double bond is added to 0.5 to 50 mol% of the acid component and / or glycol component. A conductive paste comprising a polymerized polyester resin (B) and an isocyanate compound (C).   The monomer having a double bond is at least one selected from the group consisting of fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, 2,5-norbornane dicarboxylic acid anhydride and tetrahydrophthalic anhydride. The conductive paste according to claim 1, wherein   The conductive paste according to claim 1 or 2, further comprising a radical polymerization inhibitor (D).   The blending ratio of the polyester resin (B), the isocyanate compound (C), and the radical polymerization inhibitor (D) is (B) / (C) / (D) = 100/1 to 40 / 0.001 to 0.5. The conductive paste according to claim 3, wherein the weight ratio is (weight ratio).   The conductive paste according to claim 1, comprising a tin compound (E) as a curing catalyst.   The conductive paste according to any one of claims 1 to 5, wherein the isocyanate compound (C) is blocked.