JP2015069751A - Conductive paste, metallic thin film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductive paste producing a conductive metallic thin film by a firing method in which a part of a resin binder is removed by super heat steam treatment, whose firing temperature can be reduced, and capable of widely be applied even to a base material having no heat resistance.SOLUTION: Provided is conductive paste for super heat steam treatment and comprising conductive metal powder, a resin binder, a heat base generator and a solvent, in which the resin binder includes a polymer having an ester linkage at the main chain. Also provided is a method for producing a metallic thin film in which a coating film is formed using the conductive paste, and next, the coating film is subjected to firing treatment with super heat steam to obtain a metallic thin film.

Description

  The present invention relates to a conductive thin film containing a specific resin as a binder, a conductive paste containing a thermal base generator, and a metal thin film excellent in conductivity produced by baking with superheated steam from a coating film formed using the conductive paste. .

  In recent years, a technique of forming a desired pattern by a printing method such as a screen printing method using a conductive paste containing a metal fine particle dispersion and forming a wiring or the like on a circuit board has attracted attention.

  In the conductive paste, silver, copper, or nickel is generally used as the metal as the metal fine particles. Silver is not only expensive, but also has poor migration resistance, and can be a serious defect when there is a high demand for circuit miniaturization. Nickel has poor conductivity. Since copper is inexpensive and has good migration resistance, it is expected to exhibit excellent characteristics as metal fine particles for conductive paste. However, copper is easily oxidized, and the resulting oxide has poor conductivity. The conductivity deteriorates due to the oxide layer formed on the copper surface at the time of heat treatment when forming a copper thin film from the conductive copper paste and at the time of storage of the copper thin film during production and storage of the conductive copper paste.

  A method for treating a conductive copper paste coating film containing copper fine particles in a reducing atmosphere is disclosed. In addition to the well-known heat treatment in nitrogen gas containing 3% of hydrogen gas (Non-patent Document 1), several methods are disclosed. For example, in the microwave surface wave plasma treatment (Patent Document 1), the thickness of the coating film that can be treated is limited to 2 μm or less. Further, the treatment with gaseous formic acid and / or formaldehyde (Patent Document 2) can be carried out at a low temperature of 200 ° C. or less, but there are concerns about the toxicity of formic acid gas and formaldehyde gas and the difficulty of treatment with a thick coating film.

  There has been disclosed a photosintering method in which only a coating film containing copper oxide is heated to form a copper coating without irradiating high-energy pulse light and raising the temperature of the substrate. (For example, Patent Document 3) Although this method has an advantage that it can be processed at room temperature in a short time, there is a problem that an irradiation apparatus is expensive and conditions for not damaging the substrate are narrow.

  Furthermore, a method of applying pressure during heating and baking is disclosed. For example, Patent Document 4 and Patent Document 5 disclose a method of forming a conductive film by heat-treating a dispersion of conductive fine particles and then applying pressure while heating. These methods are advantageous in terms of cost and are easy to sinter with silver particles, but in the case of copper particles, the oxidation reaction proceeds easily during heating and pressurization, and the oxide film on the particle surface sinters. Therefore, a film having high conductivity cannot be obtained.

  Patent Document 6 discloses a method of obtaining a copper film by placing a shielding object directly on a coating film containing copper particles and subjecting it to heat and pressure treatment. In this method, the reaction with oxygen in the outside air can be suppressed to some extent, but there is a limit, and if the shield cannot be recycled, a problem of waste arises.

  In Patent Document 7, by applying a conductive paste using copper as a conductive powder to a base material and then performing a superheated steam treatment, it is in a lower oxygen state than in a firing treatment in the atmosphere, and more than air. By using water vapor having a large specific heat capacity, heat-firing can be performed safely and in a short time, and thus a technique has been disclosed in which the specific resistance of a coated metal thin film can be reduced.

  It is known that by reducing the particle size of the metal particles, the firing temperature between the metal particles can be significantly reduced compared to the melting point of the metal bulk. When the average particle size of metal fine particles is about several nanometers to several tens of nanometers, the melting point of the metal particles is significantly lower than that of bulk metal, and the particles are fused at a low temperature. Thus, a conductive thin film is obtained.

  In a copper paste containing copper particles, when trying to cause a melting point decrease due to a reduction in the particle size of the copper fine particles, the copper fine particles are easily oxidized, and the tendency becomes more remarkable in the case of copper nanoparticles having a nano-size particle size. , Face problems with. Since the conductivity of the oxidized copper fine particles is remarkably lowered, it is a big problem to suppress oxidation while maintaining dispersibility in order to use as a conductive copper paste.

  When an appropriate resin binder is blended in the conductive paste, the resin binder uniformly disperses the conductive metal powder in the dispersion process by utilizing the affinity for the metal particles, and improves the conductivity of the formed metal thin film. And the effect of improving the adhesiveness of a metal thin film and an insulating base material is exhibited. However, the resin binder is insulative and may inhibit the fusion of the conductive metals during firing, thereby inhibiting the conductivity of the metal thin film.

  When forming a conductive pattern using a dispersion containing copper fine particles, in order to ensure good conductivity, the resin binder adsorbed on the copper fine particles is decomposed or detached, and the copper fine particles are sufficiently separated from each other. It is necessary to contact and promote fusion. However, until now, there has not been much consideration regarding the decomposability and detachability of the resin binder, and there is a possibility that the polymer will not sufficiently decompose in the firing process, and the formed wiring may not be able to ensure good conductivity There is.

JP 2010-192841 A International Publication No. 2011/0334016 Pamphlet International Publication No. 2006/071419 Pamphlet JP 2005-177710 A JP 2008-124446 A JP 2010-146734 A Japanese Patent No. 4835590

Nakagomi et al., “Electronic circuit formation with new copper nanoparticle paste”, MES 2006 16th Microelectronics Symposium Proceedings, October 2006, p. 51

  The present invention has been made against the background of such prior art problems. That is, the object of the present invention is to produce a conductive metal thin film by a baking method in which a part of the resin binder is removed by superheated steam treatment, to lower the baking temperature, and to a substrate having no heat resistance. An object of the present invention is to provide a conductive paste that can be widely applied.

As a result of intensive studies in order to achieve this object, the present inventor has completed the present invention.
That is, the present invention
(1) A conductive paste containing a conductive metal powder, a resin binder, a thermal base generator, and a solvent, wherein the resin binder contains a polymer having an ester bond in the main chain, and the conductivity for superheated steam treatment paste.
(2) The polymer having an ester bond in the main chain contains at least one selected from a polyester resin, a polyester urethane resin, a polycarbonate resin, a polyester ether resin, and a polyesteramide resin (1 ) Conductive paste.
(3) The conductive paste according to (1) or (2), wherein the thermal base generator contains at least one selected from carbamate derivatives and guanidine derivatives.
(4) The conductive paste according to any one of (1) to (3), wherein the conductive metal powder contains a metal powder composed of one or more of copper, copper oxide, and copper complex. .
(5) Production of a metal thin film, wherein a coating film is formed using the conductive paste according to any one of (1) to (4), and then the coating film is subjected to baking treatment with superheated steam to obtain a metal thin film. Method.
(6) A metal thin film produced by the method of (5).

  Since the conductive paste of the present invention can lower the temperature at which conductivity is exhibited in baking by superheated steam treatment, it can be widely applied to substrates that do not have heat resistance.

  The conductive paste of the present invention contains conductive metal powder, a resin binder, a thermal base generator, and a solvent as essential components. The ratio of each component is preferably 400 parts by mass, more preferably 350 parts by mass, and even more preferably 300 parts by mass with respect to 100 parts by mass of the conductive metal powder. Preferably the minimum of a solvent is 20 mass parts, More preferably, it is 30 mass parts, More preferably, it is 50 mass parts. The upper limit of the resin binder is 15 parts by mass, more preferably 12 parts by mass, and still more preferably 10 parts by mass. Preferably the minimum of a resin binder is 1 mass part, More preferably, it is 2 mass parts, More preferably, it is 3 mass parts. If the ratio of the solvent and the resin binder is less than this range, there are problems such as inability to disperse well and poor adhesion to the base material after firing. If this is exceeded, the resin binder will not be thermally decomposed, and there will be problems such as no electrical conductivity or increased electrical resistance.

  As the conductive metal powder used in the present invention, either a metal powder fused by heat treatment or a non-fused metal powder can be used. Examples of the metal used for the conductive metal powder used in the present invention include copper, nickel, cobalt, silver, platinum, gold, molybdenum, titanium, and the like, and copper is particularly preferable. In addition, the metal nanoparticles in the present invention contain metal powder composed of any one or more of metal, metal oxide, metal complex, and metal alloy, and any of copper powder, copper oxide powder, and copper complex powder A metal powder containing at least one of these is particularly preferred. In addition, metal powder with a part or all of the surface coated with metal, metal oxide, metal complex and metal alloy, a structure in which different kinds of metals are laminated, or an organic or inorganic material plated with metal may be used. . These conductive metal powders may be commercially available products or can be prepared using known methods.

  The average particle size of the conductive metal powder used in the present invention is preferably 5 μm or less, more preferably 3 μm or less, still more preferably 1 μm or less, and particularly preferably 800 nm or less. When the average particle diameter of the conductive metal powder is larger than 5 μm, the metal particles are precipitated in the dispersion, and the printability of the fine circuit is inferior.

  Although the minimum of the average particle diameter of the electroconductive metal powder used for the electroconductive paste of this invention is not specifically limited, It is preferable that it is 10 nm or more. If the thickness is less than 10 nm, it is difficult to obtain a highly conductive metal thin film because a large amount of dispersion medium is required in order to obtain economical restrictions on the conductive metal powder and to obtain a stable dispersion. The conductive metal powder used in the present invention may be used by mixing products having different particle diameters.

  The resin binder used in the conductive paste of the present invention is not particularly limited as long as it is a polymer having an ester bond in the main chain. If superheated steam treatment is performed in the presence of a hot base generator, a base is generated by the action of heat, and the ester bond is hydrolyzed by the action of water in the superheated steam due to the catalytic action of the base. In the main chain decomposes to lower the molecular weight. As a result, it is expected that the resin binder that has covered the surface of the metal fine particles is detached from the surface, the surface of the metal fine particles is exposed, and is easily brought into contact with each other and fused. Preferable examples of the resin binder used in the conductive paste of the present invention include polymers having an ester bond in the main chain such as polyester resin, polyester urethane resin, polycarbonate resin, polyester ether resin, and polyesteramide resin. . Of these, polyester resins and polyester urethane resins are preferred. It is preferable from the stability of the conductive metal fine particle dispersion that the resin used for the resin binder has an ester bond.

  As a kind of monomer in polymerizing polyester or polyester polyurethane, as an acid component, aromatic dicarboxylic acid or its ester such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid (CHDA), cis Examples include -1,2-cyclohexanedicarboxylic anhydride (HPPA), adamantane dicarboxylic acid, tricyclodecanedicarboxylic acid and the like.

  Examples of the copolymerizable glycol component include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, cyclohexanedimethanol (CHDM), tricyclodecane dimethanol, adamantane dimethanol, and the like.

  The diisocyanate component that can be used for polymerization of polyester polyurethane includes known aliphatic, alicyclic or aromatic organic polyisocyanates containing two isocyanate groups in the molecule. Specifically, for example, 4,4′-diphenylmethane diisocyanate, p-phenylene diisocyanate, toluylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hexamethidine diisocyanate, isophorone diisocyanate (IPDI), 4,4 ′. -Dicyclohexyl methane diisocyanate etc. are mentioned. In particular, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate or 2,4-tolylene diisocyanate or a mixture containing them as a main component is preferable.

  As the resin binder, in addition to the polymer having an ester bond in the main chain, a polymer having no ester bond in the main chain can be blended. The ratio of the polymer having an ester bond in the main chain to the total resin binder depends on the kind and amount of the thermal base generator, the firing temperature and time with superheated steam, and is not particularly limited. However, when the resin binder is mostly decomposed during firing, depending on the type of conductive metal powder used, the adhesion to the substrate is not good after firing, or the conductive layer obtained after firing is cracked. There is a case. For this reason, the blending ratio of the polymer having an ester bond in the main chain to the total resin binder is more preferably 97% by weight or less, further preferably 95% by weight or less, and particularly preferably 90% by weight or less. If the ratio of the total resin binder of the polymer having an ester bond in the main chain is too small, thermal decomposition and volume shrinkage of the resin binder during firing are reduced, and the contact state between the conductive metal powders is not good, so that conductivity is developed. It becomes difficult to do. A preferable blending ratio of the polymer having an ester bond in the main chain is 5% by weight or more, more preferably 10% by weight or more, and particularly preferably 20% by weight or more.

  The thermal base generator used in the present invention is not particularly limited as long as it generates a basic compound at the firing temperature. A compound that does not generate a base when the conductive paste is stored and when a coating film is formed but generates a base only at a high temperature during firing is desirable. Specifically, 1-methyl-1- (4-biphenylyl) ethyl carbamate, 1,1-dimethyl-2-cyanoethyl carbamate, N- (isopropoxycarbonyl) -2,6-dimethylpiperazine, N- (benzyl) Roxycarbonyl) -2,6-dimethylpiperazine, carbamate derivatives such as N- (2-nitrobenzyloxycarbonyl) cyclohexylamine; urea derivatives such as urea and N, N-dimethyl-N′-methylurea; guanidine trichloroacetate, Methylguanidine trichloroacetate, guanidine phenylsulfonylacetate, guanidine p-methanesulfonylacetate, guanidine phenylpropiolate, guanidine p-phenylene-bis-phenylpropiolate, 1,2-ethane-bis (N, N'-diethylguanidinium 4-Feni Guanidine derivatives such as (sulfonylphenylsulfonyl) acetic acid and (1,4-butane-bisguanidinium) 4-phenyl (sulfonylphenylsulfonyl) acetic acid; dihydropyridine derivatives such as 1,4-dihydronicotinamide; quaternary organic silanes and organic boranes Ammonium salts, dicyanamide, phenylsulfonylacetic acid tetraammonium, phenylpropiolic acid tetraammonium and the like can be mentioned. Among these, carbamate derivatives and guanidine derivatives are particularly preferable from the viewpoint of easy base generation and storage stability.

  The amount of the heat base generator added is preferably 1% by weight to 10% by weight, and more preferably 2% by weight to 7% by weight with respect to the resin binder. When there are too many thermal base generators, there exists a possibility that an undecomposed thing and a thermal decomposition residue may have a bad influence on the electroconductivity of a metal thin film, and adhesiveness with a base material.

  The solvent used in the conductive paste of the present invention is selected from those that dissolve the binder resin, and may be an organic compound or water. The solvent has a role of adjusting the viscosity of the dispersion in addition to the role of dispersing the metal fine particles in the dispersion. Examples of the organic solvent suitably used as the solvent include alcohol, ether, ketone, ester, aromatic hydrocarbon, amide and the like.

  You may mix | blend a hardening | curing agent with the electrically conductive paste of this invention as needed. Examples of the curing agent that can be used in the present invention include phenol resins, amino resins, isocyanate compounds, and epoxy resins. The amount of the curing agent used is preferably in the range of 1 to 100% by weight of the binder resin.

  When using the metal paste which is easily oxidized in the air such as copper powder as the conductive metal powder in the conductive paste of the present invention, a reducing agent may be included. In the present invention, the reducing agent means an agent capable of reducing a metal compound such as a metal oxide, hydroxide, or salt to a metal. Examples of the reducing agent include sodium borohydride, lithium borohydride, hydrazine, aldehydes such as formalin and acetaldehyde; sulfites; carboxylic acids such as formic acid, succinic acid, succinic acid, and ascorbic acid; or lactone, ethanol, butanol, Monoalcohols such as aliphatic monoalcohols such as octanol and alicyclic monoalcohols such as terpineol; aliphatic diols such as ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol; polyhydric alcohols such as glycerin and trimethylolpropane; Polyethers such as polyethylene glycol and polypropylene glycol; Alkanol amines such as diethanolamine and monoethanolamine; Hydroquinone, resorcinol, aminophenol Glucose or sodium citrate, and the like. Residue of the reducing agent or the reducing agent decomposition product on the metal thin film may cause deterioration of properties of the obtained copper thin film. Therefore, it is desirable that the reducing agent is evaporated by superheated steam treatment. For this reason, when a reducing agent is blended in the conductive paste of the present invention, it is particularly desirable to use alcohols or polyhydric alcohols. Specific preferred examples of the reducing agent include terpineol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, ascorbic acid, and resorcinol.

  As a method for dispersing the conductive metal powder in the paste, a general method for dispersing the powder in a liquid can be used. For example, after mixing a conductive metal powder and a binder resin solution and, if necessary, a mixture of an additional solvent, dispersion may be performed by an ultrasonic method, a mixer method, a three-roll method, a ball mill method, or the like. Of these dispersing means, a plurality of dispersing means can be combined for dispersion. These dispersion treatments may be performed at room temperature, or may be performed by heating in order to lower the viscosity of the dispersion or increase the solubility of the resin. If necessary, the reducing agent used may be added at any stage before, during, or after dispersion of the conductive metal powder.

  In order to form a coating film from the conductive paste of the present invention, a general method used when the dispersion is applied or printed on an insulating substrate can be used. For example, a conductive paste is applied or printed by a method such as a screen printing method, a dip coating method, a spray coating method, a spin coating method, a roll coating method, a die coating method, an ink jet method, a relief printing method, an intaglio printing method, and then air-dried. A coating film can be formed by evaporating at least a part of the solvent by heating or reduced pressure. The coating film may be provided on the entire surface of the insulating base material or may be provided partially, or may be a pattern formed product such as a conductive circuit.

  The thickness of the metal thin film of the present invention can be appropriately set according to necessary characteristics such as electric resistance and adhesiveness, and is not particularly limited. The range of the thickness of the conductive thin film that can be formed varies depending on the dispersion composition and the method of coating or printing, but is preferably 0.05 to 40 μm, more preferably 0.1 to 20 μm, and still more preferably 0.2 to 10 μm. It is. In order to obtain a thick metal thin film, it is necessary to increase the thickness of the coating film, which is likely to cause economic deterioration such as an adverse effect due to residual solvent and a need to reduce the coating film forming speed. On the other hand, if the coating film is too thin, the occurrence of pinholes tends to be significant.

  When forming the metal thin film of the present invention, it is possible to perform overprinting or multilayer printing. Here, overprinting refers to printing the same pattern a number of times, thereby increasing the thickness of the conductive thin film, or conducting with a high aspect ratio (ratio of film thickness to line width). Can be obtained. Multi-layer printing refers to printing different patterns in a superimposed manner, whereby different functions can be exhibited for each layer. Partial overprinting and / or multilayer printing may be performed, and overprinting and multilayer printing may be performed in combination. It is also possible to perform multilayer printing with a thin film different from the conductive thin film of the present invention, for example, an insulating layer.

  A metal thin film can be produced by forming a coating film using the conductive paste of the present invention and then subjecting the coating film to heat treatment with superheated steam. Superheated steam is high-temperature steam heated to several hundred degrees by adding secondary energy to saturated steam. Superheated steam has a heat capacity approximately four times that of air at the same temperature, and it is known that when heated with superheated steam, the substance is heated in a short time. The coating film formed using the conductive paste of the present invention is preferably subjected to baking with superheated steam after drying. A preferable drying temperature is 60 to 120 ° C., and a drying time is 3 to 20 minutes. The drying treatment and baking with superheated steam may be performed continuously or may be performed through other steps. After coating, baking with superheated steam without a drying step is likely to cause bumping, which is not preferable. The drying process and the superheated steam process may be performed continuously or may be performed with another process interposed therebetween. Examples of the process sandwiched between the drying process and the superheated steam process include a process of applying a reducing agent to the coating film. In this case, the coating film may or may not contain a reducing agent in advance, and if it is contained, any of the same type, different type, and a mixture of the same type and different type It is also possible to do. By the treatment of applying a reducing agent to the coating film, effects such as a decrease in volume resistivity of the coating film, a decrease in overheat treatment temperature, and a decrease in overheat treatment time may be exhibited.

  When methanol, ethanol, ethylene glycol, or propylene glycol is contained in superheated steam, conductivity may be improved. Examples of the method for producing superheated steam containing an alcohol compound include a method of heating a saturated vapor of a solution in which an alcohol compound is dissolved in water, and a method of mixing and heating an alcohol compound and water, and each saturated vapor. The optimum range of the alcohol compound content in the superheated steam varies depending on the type of the compound, but is used in the range of 0.01 to 20% by weight. When the content of the alcohol compound is less than 0.01% by weight, the effect of improving the conductivity is not observed, and when it exceeds 20% by weight, the binder resin may be significantly dissolved or decomposed. A preferred range is from 0.1 to 5% by weight.

  The temperature of the superheated steam used in the method for producing a metal thin film of the present invention is preferably 150 ° C. or higher, particularly preferably 200 ° C. or higher. The upper limit of the temperature is determined by the heat resistance characteristics of the insulating base material or binder resin used, but is 400 ° C. or lower. Is preferred. The heating time is also selected from the amount and characteristics of the object to be processed, but is preferably 10 seconds to 30 minutes. If the temperature of the superheated steam is too low, a conductive layer having a low specific resistance cannot be obtained. If the temperature of the superheated steam is too high, most or all of the binder resin is removed, the adhesion between the conductive thin film and the insulating substrate may be impaired, and the insulating substrate may be deteriorated. In particular, care must be taken when using an insulating substrate made of an organic material.

  When copper powder is used as the conductive metal powder in the conductive paste of the present invention, the surface of the copper powder is easily oxidized in the air, so that the thin film layer can be subjected to rust prevention treatment. As a preferable rust prevention treatment method, a method of providing an adsorption layer of an organic compound or an inorganic compound capable of adsorbing copper on the surface of the metal thin film layer can be mentioned. Here, when the conductive metal powder contained in the metal thin film layer contains conductive metal powder that is not fused to each other, the adsorption layer may be formed on the surface of the individual conductive metal powder. preferable. Another preferred rust prevention treatment method is a method of providing a waterproof insulating resin layer on the metal thin film layer. The method of providing an organic compound or inorganic compound adsorption layer on the surface of the metal thin film layer, and further covering with an insulating resin layer is an example of a preferred embodiment of the present invention.

  Examples of organic compounds or inorganic compounds (hereinafter sometimes referred to as surface treatment agents) that can form an adsorption layer on the surface of the metal thin film layer in the present invention include nitrogen-containing heterocyclic compounds such as benzotriazole, tolyltriazole, and tetrazole, mercapto Examples thereof include sulfur-containing compounds such as propionic acid, mercaptoacetic acid, thiophenol and triazinedithiol, amino compounds such as octylamine and isobutylamine, silane coupling agents, titanium coupling agents and chromate treatment agents. The adsorption layer is formed by immersing the metal thin film in the treatment agent in which the surface treatment agent is dissolved or by applying the treatment agent to the metal thin film. When the thickness of the surface treatment agent layer is increased, the conductivity may be lowered or the adhesive processability may be deteriorated. Therefore, the thickness of the surface treatment layer is preferably a thin layer of 0.05 μm or less. Examples of the method for thinning the surface treatment agent layer include reducing the concentration of the treatment liquid and removing excess surface treatment agent with a solvent that dissolves the surface treatment agent.

  Examples of the waterproof insulating resin provided on the metal thin film layer in the present invention include polyester resin, acrylic resin, polyurethane resin, butyral resin, and the like. By coating the metal thin film layer with one or more of these resins, the rust prevention effect can be exhibited. The method of coating the conductive thin film layer with a waterproof insulating resin is not particularly limited. However, the method is a method in which a resin solution is applied or printed on a metal thin film layer and then the solvent is stripped off. A method of bonding to the thin film layer can be exemplified as a preferable method. Bonding a polyimide film or a polyester film with an adhesive is an example of a particularly preferred embodiment. The thickness of the insulating resin layer is desirably 1 to 30 μm.

  In order to describe the present invention in more detail, examples are given below, but the present invention is not limited to the examples. In addition, the measured value described in the Example is measured by the following method.

1. Measurement of molecular weight The number average molecular weight in terms of polystyrene was measured by GPC (gel permeation chromatography).

2. Measurement of electric resistivity (specific resistance) The electric resistivity was measured by a four-terminal method using a low resistivity meter (trade name: Loresta CP, manufactured by Mitsubishi Chemical) and a four-point probe (NSCP probe).

3. Evaluation of adhesion Use 1cm width of cello tape (registered trademark) “CT405AP-15” manufactured by Nichiban Co., Ltd., and attach the adhesive tape to the metal thin film surface for 5cm long and damage the metal thin film surface when peeled off. Whether or not it was received was judged by visual observation. When some damage such as peeling, floating and cracking was observed on the metal thin film, it was judged as x, and when no damage was found, it was judged as ○.

Example 1
The composition of the following ratio was disperse | distributed with the 3 roll mill, and the dispersion paste 1 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on a polyimide film with the screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 1A.
Binder resin solution 2.5 parts 35 wt% n-butyl carbitol acetate solution of copolymer polyester 1)
The copolyester 1 is a copolyester having terephthalic acid / isophthalic acid / sebacic acid // ethylene glycol / neopentyl glycol = 50/20/30 // 70/30 (molar ratio) and a number average molecular weight of 15,000. .
Copper fine particles 20 parts RCA-16, manufactured by DOWA Electronics Co., Ltd., average particle size 0.8 μm)
Thermal base generator 0.03 parts N- (isopropoxycarbonyl) -2,6-dimethylpiperazine Solvent 4 parts Ethyl carbitol acetate

Example 2
A dispersion paste was prepared by replacing the thermal base generator described in Example 1 with N- (benzyloxycarbonyl) -2,6-dimethylpiperazine to obtain dispersion paste 2. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on a polyimide film with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 2A.

Example 3
A dispersion paste was prepared using N- (2-nitrobenzyloxycarbonyl) cyclohexylamine as the thermal base generator described in Example 1, and dispersion paste 3 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on a polyimide film with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 3A.

Example 4
A dispersion paste was prepared by using 1,2-ethane-bis (N, N′-diethylguanidinium) 4-phenyl (sulfonylphenylsulfonyl) acetic acid as the thermal base generator described in Example 1 to obtain dispersion paste 4. It was. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on a polyimide film with the screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 4A.

Example 5
A dispersion paste was prepared by using (1,4-butane-bisguanidinium) 4-phenyl (sulfonylphenylsulfonyl) acetic acid as the thermal base generator described in Example 1, and dispersion paste 5 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on a polyimide film with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 5A.

Comparative Example 1
In Example 1, a dispersion paste was prepared without adding a hot base generator, and a dispersion paste 6 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on a polyimide film with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 6A.

  Subsequently, nine sheets of the metal thin film laminate 1A were subjected to baking treatment with superheated steam for 10 minutes at 150, 180, 200, 230, 250, 270, 300, 320, and 350 ° C., and 9 kinds of baking temperatures were different. A metal thin film laminate 1B was obtained. A steam superheater (“DHF Super-Hi 10” manufactured by Daiichi High-Frequency Industry Co., Ltd.) was used as a superheated steam generator, and the heat treatment was performed in a heat treatment furnace supplying 10 kg / hour of superheated steam. As the firing temperature increases, the specific resistance of the metal thin film laminate decreases. About the metal thin-film laminated body 1B, the specific resistance in each process temperature was plotted, and the temperature (conducting expression baking temperature) which begins to express specific resistance 50micrometer (ohm * cm), and adhesive force were evaluated. For the metal thin film laminates 2A to 6A, the conductivity expression temperature and adhesive strength of the metal thin film laminates 2B to 6B were evaluated in the same manner as the metal thin film laminate 1A. The evaluation results are shown in Table 1. It can be seen that the conductive paste of the present invention exhibits conductivity at a lower firing temperature in firing by superheated steam treatment.

According to the present invention, in a method for producing a conductive copper thin film by superheated steam treatment, the copper thin film can be formed at a lower temperature than the conventional one and a predetermined specific resistance value can be formed. Moreover, since it has adhesive force with an insulating base material, even if it uses it for a flexible insulating base material, it is hard to generate | occur | produce problems, such as peeling from an insulating base material and a float, with a time-dependent change. The metal thin film of the present invention is useful as a metal thin film forming material such as a metal / resin laminate, an electromagnetic shielding metal thin film, a plating conductive layer, a metal wiring material, a conductive material, and the like. It can be applied to electrodes and the like.

Claims (6)

  A conductive paste for superheated steam treatment, comprising a conductive metal powder, a resin binder, a thermal base generator, and a solvent, wherein the resin binder contains a polymer having an ester bond as a main chain.   The polymer having the ester bond in the main chain contains at least one selected from a polyester resin, a polyester urethane resin, a polycarbonate resin, a polyester ether resin, and a polyesteramide resin. Conductive paste.   The conductive paste according to claim 1, wherein the thermal base generator contains at least one selected from carbamate derivatives and guanidine derivatives.   The conductive paste according to any one of claims 1 to 3, wherein the conductive metal powder contains metal powder made of at least one of copper, copper oxide, and copper complex.   The manufacturing method of a metal thin film which forms a coating film using the electrically conductive paste in any one of Claims 1-4, and then performs a baking process by superheated steam to this coating film, and obtains a metal thin film.   A metal thin film produced by the method of claim 5.