JP2015076232A - Conductive paste, conductive thin film and electric circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste which can impart conductivity by a baking method based on a superheated steam treatment and by low-temperature baking, and is widely applicable to substrates not having heat resistance.SOLUTION: A conductive paste comprises a conductive metal powder, a resin binder, a solvent and an additive, and the additive is a hydroxycarboxylic acid. Conductivity is imparted by printing with the conductive paste or applying the conductive paste and subjecting the resultant body to superheated steam treatment.

Description

The present invention relates to a conductive paste capable of obtaining a conductive thin film exhibiting good conductivity. More specifically, the present invention relates to a conductive paste and an electronic material, wiring, and circuit formation using the same.

  Formation of a conductive layer or a conductive pattern by printing is performed by applying a conductive paste using conductive particles to screen printing or letterpress printing. In screen printing, flaky metal particles having a particle size of several μm or more are used as the conductive particles to be used, and the conductivity is ensured by setting the circuit thickness to 10 μm or more. In recent years, the density of conductive circuits has been rapidly increasing. In order to enable the formation of higher density circuits, finer metal fine particles have been developed.

  As the metal as the conductive particles, silver, copper, or nickel is generally used. Silver is not only expensive, but also has poor migration resistance, and it can become a serious defect depending on the application, while the demand for miniaturization of the circuit is increased. Nickel has poor conductivity. Copper is easily oxidized and the resulting oxide has poor conductivity. The conductivity deteriorates due to the heat treatment at the time of copper paste production or storage or at the time of copper thin film formation from the copper paste, or the oxide layer formed on the copper surface at the time of copper thin film storage. Furthermore, the harmful effects of copper oxidation also occur when a cover film is bonded to a copper paste circuit to prevent oxidation or insulation. The formation and progress of the oxide layer on the copper surface may cause distortion between the cover film adhesive and the copper thin layer, resulting in a decrease in adhesion. Strain is also generated between the copper paste layer and the base material. This decrease in adhesion often occurs when stored for a long time at a temperature of 150 ° C. or higher.

  In order to prevent harmful effects caused by oxidation of copper particles, various studies have been made on copper paste. Patent Document 1 discloses a conductive paint containing metal copper powder, a resol type phenol resin, an amino compound, an amino group-containing coupling agent, and a 1,2-N-acyl-N-methyleneethylenediamine compound having a specific blending ratio. It is said that the amino compound functions as a conductivity improver and also as a reducing agent, preventing oxidation of the metal copper powder and contributing to maintaining the conductivity. Moreover, in patent document 1, when the particle size of metal copper powder is less than 1 micrometer, it is easy to be oxidized, and since the electroconductivity of the coating film obtained falls, it is considered unpreferable. On the other hand, it has been attempted to coat the surface of the copper powder with silver and use it as a conductive filler for a conductive paste. For example, in Patent Document 2, copper powder is dispersed in a chelating agent solution, a silver ion solution, A conductive paste is disclosed in which a reducing agent is sequentially added to deposit a silver coating on the surface of copper powder and this is used as a conductive filler.

  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. For example, Patent Document 3 discloses a method in which a metal paste in which copper fine particles having a particle size of 1000 mm or less are dispersed in an organic solvent containing a specific component is prepared, and a metal paste coating film is baked at 500 ° C. to form a metal thin film. Is disclosed, and electrical wiring can be formed by this method. However, the metal paste disclosed in Patent Document 3 is formed of only volatile components except for copper powder, and the adhesion to the base material after firing is weak. Also, since the firing temperature is high, the choice of base material is greatly limited. Patent Document 4 discloses a method of making an ultrafine copper powder having a particle size of 0.1 μm or less from copper hydroxide and a reducing agent using ultrasonic waves. In Example of Patent Document 4, an electron microscope is used. Only the average particle diameter and shape of the copper ultrafine powder were confirmed, and it was not disclosed whether it was actually useful as a conductive filler for conductive paste. Since there is no description about suppressing the formation of an oxide film of copper ultrafine powder, it is presumed that a copper oxide film was formed on the surface of the copper ultrafine powder and was not useful as a conductive filler.

  Fine particles typified by nanoparticles are very easy to aggregate and difficult to disperse because of their very large surface area. The dispersibility of the metal fine particles can be improved by adsorbing the binder resin or dispersant to the metal fine particles, and the effect of preventing the aggregation of the fine particles to increase the storage stability and ensuring the fluidity of the dispersion. I can expect. However, as the metal fine particles become finer, a larger amount of binder resin or dispersant is required, and the binder resin or dispersant tends to prevent the metal fine particles from contacting each other and hinder the improvement in conductivity. In such a case, it may be necessary to remove the binder resin or the dispersant by sublimation or decomposition evaporation. In addition, the adhesiveness with a substrate such as a film or glass tends to deteriorate due to firing. In addition to the problems peculiar to these metal particles, problems caused by oxidation are added to copper particles. The deterioration of conductivity due to oxidation of copper particles becomes more prominent as the particle diameter becomes smaller.

  Patent Document 5 discloses a method for producing a copper thin film, which includes at least two steps: a step of performing a heat treatment with superheated steam on a coating film containing a copper particle dispersion, and a step of applying a rust prevention treatment. . In the example of Patent Document 5, the superheated steam treatment temperature is 300 ° C., and there is a problem that it is actually limited to a base material having heat resistance.

JP-A-11-293185 JP-A-1-119602 Japanese Patent No. 2561537 JP 2005-23417 A JP 2011-58068 A

  The present invention has been made against the background of such prior art problems. That is, the object of the present invention is to develop conductivity by a baking method by superheated steam treatment, and to exhibit conductivity by baking at a low temperature, and is widely applied to substrates having no heat resistance. It is to provide a conductive paste that can be 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) In a conductive paste containing conductive metal powder, a resin binder, a solvent, and an additive, the additive is hydroxycarboxylic acid, and the conductive paste is made conductive by superheated steam treatment after printing or coating with the conductive paste. A conductive paste characterized by manifestation.
(2) The conductive paste according to (1), wherein the additive is a hydroxycarboxylic acid represented by the following chemical formula.
In Chemical Formula 1, R1 represents —H or —COOH, R2 represents —H or —CH2COOH, and R3 represents —H or —OH.
(3) The conductive paste according to (2), wherein the additive is malic acid or citric acid.
(4) The conductive paste according to any one of (1) to (3), wherein the conductive metal powder is copper.
(5) The conductive paste according to any one of (1) to (4), wherein the hydroxycarboxylic acid is contained in an amount of 1.0 to 5.0 (% by weight) based on the weight of the conductive metal powder. .
(6) The conductive paste according to any one of (1) to (5), which is used for superheated steam treatment.
(7) The conductive paste according to any one of (1) to (6), which is used for a superheated steam treatment at 180 ° C. or higher.
(8) A conductive thin film obtained by subjecting the conductive paste according to any one of (1) to (7) to a superheated steam treatment after printing or coating.
(9) An electric circuit obtained by subjecting the conductive paste according to any one of (1) to (7) to a superheated steam treatment after printing or coating.

  Since the conductive paste of the present invention can exhibit conductivity at low temperatures in baking by superheated steam treatment, it can be widely applied to substrates having no heat resistance.

  The conductive paste of the present invention contains conductive metal powder, a solvent, a resin binder, and additives 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 with respect to 100 parts by mass of the conductive metal powder, 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 content of the solvent or the resin binder is less than this range, there may be problems such as inability to disperse well and poor adhesion to the substrate after firing. If the content of the solvent or the resin binder is more than this range, the resin binder may be difficult to be thermally decomposed, and there may be a problem such that the conductivity is not exhibited or the electric resistance is increased.

  As the conductive metal powder, it is possible to use either a material in which the fine particles are fused by heat treatment or a material that is not fused. Examples of the metal include copper, nickel, cobalt, silver, platinum, gold, molybdenum, and titanium, and silver and copper are particularly preferable. These metal fine particles may be a commercially available product or can be prepared using a known method. In addition, a structure in which different kinds of metals are stacked, or an organic or inorganic material plated with metal may be used.

The average particle size of the conductive metal powder used in the present invention is preferably 0.1 to 5 μm. If the thickness is less than 0.1 μm, there is a problem that the paste is easily oxidized during the preparation and storage of the paste, or cannot be dispersed well and precipitation occurs with time.
Here, the average particle diameter was measured using a Fischer sub-sieve sizer (FSSS) by an air permeation method.

The shape of the conductive metal powder includes a spherical shape, a flake shape, an aggregate, a dendritic shape, a needle shape and an irregular shape. The shape of the conductive metal powder used in the present invention is not particularly limited, and metal powders having different shapes may be mixed and used.

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 an average particle diameter 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.

  Examples of the resin binder used in the conductive paste of the present invention include polyester, polyurethane, polycarbonate, polyether, polyamide, polyamideimide, polyimide, and acrylic. Those having an ester bond, a urethane bond, an amide bond, an ether bond, an imide bond, etc. in the resin are preferred from the viewpoint of the stability of the copper fine particle dispersion. Polyester or polyester polyurethane is more preferable.

  As the types of monomers for polymerizing polyester or polyester polyurethane, the acid component includes aromatic dicarboxylic acids or esters such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid (CHDA), cis Examples include -1,2-cyclohexanedicarboxylic acid anhydride (HHPA), 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, Examples include 4'-dicyclohexylmethane diisocyanate. In particular, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate or 2,4-tolylene diisocyanate or a mixture containing them as a main component is preferable.

  Examples of the hydroxycarboxylic acid represented by Chemical Formula 1 include tartaric acid, glyceric acid, malic acid, citric acid, isocitric acid, hydroxycitric acid, and quinic acid. By adding and dispersing these hydroxycarboxylic acids, there is an effect of dissolving the copper oxide present on the surface of the copper powder electrode and an effect of reducing the copper oxide with the reducing power of the hydroxycarboxylic acid. The lower limit of the amount of hydroxycarboxylic acid added is preferably 0.2% by weight or more, more preferably 0.5% by weight or more, and particularly preferably 1.0% by weight or more with respect to the amount of conductive metal powder added. The upper limit of the weight of the hydroxycarboxylic acid to be added is 5.0% by weight. Hydroxycarboxylic acid may be mixed and dispersed after dissolving in advance with approximately the same amount of water.

In Chemical Formula 1, R1 represents —H or —COOH, R2 represents —H or —CH2COOH, and R3 represents —H or —OH.

  The solvent used in the conductive paste of the present invention is selected from those that dissolve the resin when a binder resin that functions to stabilize dispersion is used, and may be an organic compound or water. . The dispersion medium has a role of adjusting the viscosity of the dispersion in addition to the role of dispersing the copper 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 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 a reducing agent may be included. A reducing agent refers to 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, hydrazines, aldehydes such as formalin and acetaldehyde, sulfites, carboxylic acids such as formic acid, succinic acid, succinic acid and ascorbic acid, or lactones, ethanol, Aliphatic monoalcohols such as butanol and octanol, monoalcohols such as alicyclic monoalcohols such as terpineol, aliphatic diols such as ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol, glycerin and trimethylolpropane Polyhydric alcohols such as polyethylene glycol and polypropylene glycol, alkanolamines such as diethanolamine and monoethanolamine, hydroquinone, resorcino Le, aminophenol, glucose, or sodium citrate, and the like. Residue of the reducing agent or reducing agent decomposition product on the copper thin film may cause deterioration of the properties of the obtained copper thin film. Therefore, it is desirable that the reducing agent is evaporated by superheated steam treatment. As the reducing agent, alcohols and polyhydric alcohols are particularly desirable. 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 reduce the viscosity of the dispersion. 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 a conductive paste, a general method used when applying or printing a dispersion 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 dispersion medium by heating or decompression. 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 conductive 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.

  In forming the conductive 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.

  When the insulating substrate is made of a polyimide resin, a conductive paste film is formed on the primary dried product of the polyimide precursor solution or the primary dried product of the polyimide solution or the polyamideimide solution, and then superheated steam It is preferable to adopt a method of performing the heat treatment by the method. With the 10% to 30% by weight solvent remaining in the polyimide precursor solution or the primary dry product of the polyimide solution, a conductive paste is subsequently applied and dried to form a coating film. Subsequently, by performing a heat treatment with superheated steam, the adhesion between the polyimide resin layer and the coating film tends to be strong.

  After forming the coating film of the conductive paste, pressure treatment (calendar treatment) can be performed within a range where the coating film is not destroyed. There exists a tendency for electroconductivity to improve by a calendar process. The calendar treatment is generally a pressure treatment between a metal roll and an elastic roll depending on the material, for example, a pressure treatment of 1 to 250 kg / cm, more preferably 50 to 200 kg / cm. The calendar treatment is particularly preferably performed by heating to a temperature equal to or higher than the glass transition temperature of the binder resin of the conductive paste. You may perform a calendar process in the state which laminated | stacked the other layer on the coating film of the electrically conductive paste.

  Superheated steam is high-temperature steam that has obtained energy of, for example, several hundred degrees Celsius beyond its boiling point by adding secondary energy to a saturated steam gas at 100 degrees Celsius. Superheated steam has a heat capacity about four times that of high-temperature air, and can be dried and sintered in a short time. Since it can be dried and baked without being oxidized in an oxygen-free state, it is often used for food and pharmaceutical applications such as food heating, roasting, and sterilization.

  After the coating film of the conductive paste is subjected to a drying process and then, if necessary, a calendar process, a heating process with superheated steam can be performed. The drying treatment and the superheated steam treatment may be performed continuously or may be performed through other steps. If the superheated steam treatment is performed without applying a drying step after coating, bumping is likely to occur, which is not preferable.

  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 superheated steam treatment is preferably performed as a baking treatment for the coating film of the conductive paste. The baking treatment by the superheated steam treatment tends to exhibit a particularly high effect when the average particle diameter of the metal fine particles is in the range of 0.1 μm to 5 μm. Although it varies depending on the surface state of the conductive metal powder such as crystallinity and degree of oxidation, so-called nanoparticles have a large surface activity and start to be fused at a temperature much lower than the generally known melting point of the bulk. In the present invention, the firing treatment refers to a heat treatment in which at least a part of the metal fine particles are fused, and it is not necessarily required to decompose or scatter the binder resin and the dispersant.

  The temperature of the superheated steam used in the present invention is 150 ° C. or higher, particularly preferably 200 ° C. or higher, and more preferably 300 ° C. or higher. The upper limit of the temperature is determined by the insulating base material used and the heat resistance characteristics of the binder resin, but is preferably 400 ° C. or lower. 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. When the temperature of the superheated steam is too low, a conductive layer having a low volume resistivity 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 conductive thin film layer can be exemplified. Here, when the conductive metal powder contained in the conductive thin film layer contains conductive metal powders that are not fused to each other, the adsorption layer is formed on the surface of each conductive metal powder. Is preferred. Another preferred rust prevention treatment method includes a method of providing a waterproof insulating resin layer on the conductive thin film layer. A method of providing an organic compound or inorganic compound adsorption layer on the surface of the conductive thin film layer and further covering with an insulating resin layer is an example of a preferred embodiment of the present invention.

  Examples of the organic compound or inorganic compound (hereinafter sometimes referred to as a surface treatment agent) that can form an adsorption layer on the surface of the conductive thin film layer in the present invention include nitrogen-containing heterocyclic compounds such as benzotriazole, tolyltriazole, and tetrazole, Examples thereof include sulfur-containing compounds such as mercaptopropionic 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 conductive thin film in the treatment agent in which the surface treatment agent is dissolved, or by applying the treatment agent to the conductive 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 conductive thin film layer in the present invention include a polyester resin, an acrylic resin, a polyurethane resin, and a butyral resin. By coating the copper thin film layer with one or more of these resins, the rust prevention effect can be exhibited. The method for coating the conductive thin film layer with a waterproof insulating resin is not particularly limited, but the method is a method in which a resin solution is applied or printed on a copper 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. Molecular weight The number average molecular weight in terms of polystyrene was measured by GPC (gel permeation chromatography).

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

(1) Electrical resistance measurement method The electrical resistivity was measured by a four-terminal method using a resistivity meter (trade name: Loresta-GP MCP-T610, manufactured by Mitsubishi Chemical) and a four-probe probe (ASP probe). .

(2) Adhesive strength evaluation method Nichiban Co., Ltd. cello tape (registered trademark) “CT405AP-15” having a width of 1 cm is used. Whether or not the surface was damaged 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
A composition having the following blending ratio was put into a four-necked flask equipped with a stirrer and stirred and heated to obtain a copolymerized polyester 1 according to a conventional method.
Dimethyl terephthalate 50 parts Dimethyl isophthalate 20 parts Dimethyl sebacate 30 parts Neopentyl glycol 45 parts Ethylene glycol 55 parts The composition of the copolymerized polyester is terephthalic acid / isophthalic acid // ethylene glycol / neopentyl glycol = 50 / The number average molecular weight was 15000 and the glass transition temperature was 65 ° C. at 50 // 55/45 (molar ratio).

Then, 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 1.8 parts (35% by weight solution in which copolymer polyester 1 is dissolved in n-butyl carbitol acetate)
20 parts of copper fine particles (RCA-16 [spherical copper powder, average particle size 0.8 μm, manufactured by DOWA Electronics Co., Ltd.)

Hydroxycarboxylic acid (citric acid) 1 part Water 1 part Ethyl carbitol acetate 3 parts

In order to impart adhesiveness to the substrate, a coating solution containing a polyamideimide resin was prepared. A composition having the following blending ratio was put into a four-necked flask equipped with a stirrer and stirred and heated to obtain a polyamideimide resin 1 according to a conventional method.

Byron 220 [Toyobo Co., Ltd.] 100 parts Benzophenone tetracarboxylic dianhydride ([BTDA], Daicel Corporation) 20 parts
MDI [Isocyanate, manufactured by Nippon Polyurethane Co., Ltd.] 5 parts

The coating composition liquid was used by mixing and stirring the following (1) to (6).
(1) Polyamideimide resin 1 1.0 part
(2) Epoxy 604 (epoxy resin, manufactured by Mitsubishi Chemical) 0.2 parts
(3) Triphenylphosphine 0.05 part
(4) Benzophenone tetracarboxylic dianhydride (BTDA) 0.05 parts
(5) Toluene 1.0 part
(6) 1.0 part of methyl ethyl ketone

  Using the obtained coating liquid composition liquid, a polyimide film (trade name Apical NPI, manufactured by Kaneka Corporation, thickness 25 μm) is coated with a wire bar (# 4), dried at 80 ° C. for 5 minutes, and then 220 ° C. for 90 seconds. It heat-processed with the hot air dryer, and produced the polyimide film 1 with an adhesive layer.

Example 2
Dispersion paste was prepared by using hydroxycarboxylic acid described in Example 1 as malic acid to obtain dispersion paste 2. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer 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
Dispersion paste was prepared by using hydroxycarboxylic acid described in Example 1 as glyceric acid to obtain dispersion paste 3. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer 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
Dispersion paste was prepared using hydroxycarboxylic acid described in Example 1 as hydroxycitric acid to obtain dispersion paste 4. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer by 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
Dispersion paste was prepared by using hydroxycarboxylic acid described in Example 1 as tartaric acid to obtain Dispersion Paste 5. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer 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
A dispersion paste was prepared without adding the hydroxycarboxylic acid described in Example 1, and a dispersion paste 6 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer 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.

Comparative Example 2
A dispersion paste was prepared by using hydroxycarboxylic acid described in Example 1 as formic acid to obtain dispersion paste 7. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer with the screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 7A.

Subsequently, the metal thin film laminates 1A to 7A were baked with superheated steam at 150, 180, 200, 230, and 250 ° C. for 10 minutes to obtain metal thin film laminates 1B to 7B. A steam superheater (“DHF Super-Hi 10” manufactured by Daiichi High Frequency Industrial Co., Ltd.) was used as a superheated steam generator, and was performed in a heat treatment furnace that supplied superheated steam at 10 kg / hour. About the metal thin film laminated bodies 1B-7B, the specific resistance in each process temperature was plotted, and the temperature (conductivity expression temperature) and adhesive force which express specific resistance 50micrometer (ohm * cm) were evaluated. The evaluation results are shown in Table 1.

Example 6
A dispersion paste was prepared in which the amount of hydroxycarboxylic acid (citric acid) added in Example 1 was 0.8 part, and dispersion paste 8 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 8A.

Example 7
A dispersion paste was prepared in which the amount of hydroxycarboxylic acid (citric acid) added in Example 1 was 0.5 part, and a dispersion paste 9 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 9A.

Example 8
A dispersion paste was prepared in which the amount of hydroxycarboxylic acid (citric acid) added in Example 1 was 0.2 part, and dispersion paste 10 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained metal thin film laminated body 10A.

Subsequently, the metal thin film laminates 8A to 10A were subjected to baking treatment with superheated steam at 150, 180, 200, 230, and 250 ° C. for 10 minutes to obtain metal thin film laminates 8B to 10B. A steam superheater (“DHF Super-Hi 10” manufactured by Daiichi High Frequency Industrial Co., Ltd.) was used as a superheated steam generator, and was performed in a heat treatment furnace that supplied superheated steam at 10 kg / hour. For the metal thin film laminates 8B to 10B, the specific resistance at each treatment temperature was plotted, and the temperature (conductivity development temperature) and the adhesive strength at which the specific resistance was 50 μ (Ω × cm) were evaluated. The evaluation results are shown in Table 2.

Example 9
A composition having the following blending ratio was placed in a four-necked flask equipped with a stirrer and stirred and heated to obtain a copolymer polyester polyurethane 1 according to a conventional method.
40 parts of cis-1,2-cyclohexanedicarboxylic anhydride (HHPA)
1,4-cyclohexanedicarboxylic acid (CHDA) 60 parts Neopentyl glycol 40 parts Ethylene glycol 50 parts
3-methylpropanediol 10 parts Isophorone diisocyanate 100 parts The resulting copolymer polyester polyurethane had a number average molecular weight of 31555 and a glass transition temperature of 13 ° C.

Then, the composition of the following ratio was disperse | distributed with the 3 roll mill, and the dispersion paste 2 was obtained. Furthermore, it printed so that the thickness after drying might be set to 10 micrometers on the polyimide film 1 with an adhesive layer with a screen printing method, and it dried with hot air at 80 degreeC for 5 minutes, and obtained 11 A of metal thin film laminated bodies.

Binder resin solution 1.8 parts (35% by mass solution of copolyester polyurethane 1 dissolved in n-butyl carbitol acetate)
20 parts of copper fine particles (RCA-16 [spherical copper powder, average particle size 0.8 μm, manufactured by DOWA Electronics Co., Ltd.)
Hydroxycarboxylic acid (citric acid) 1 part Water 1 part Ethyl carbitol acetate 3 parts

Subsequently, the metal thin film laminate 11A was baked with superheated steam at 150, 180, 200, 230, and 250 ° C. for 10 minutes to obtain a metal thin film laminate 11B. A steam superheater (“DHF Super-Hi 10” manufactured by Daiichi High Frequency Industrial Co., Ltd.) was used as a superheated steam generator, and was performed in a heat treatment furnace that supplied superheated steam at 10 kg / hour. About the metal thin film laminated body 11B, the specific resistance in each process temperature was plotted, and the temperature (conductivity expression temperature) and adhesive force which express specific resistance 50micro (ohm * cm) were evaluated. The evaluation results are shown in Table 3.

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 fired at a lower temperature than conventional and a copper thin film having a predetermined volume 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 (9)

  In a conductive paste containing conductive metal powder, a resin binder, a solvent, and an additive, the additive is hydroxycarboxylic acid, and develops conductivity by superheated steam treatment after printing or coating with the conductive paste. A conductive paste characterized by The conductive paste according to claim 1, wherein the additive is a hydroxycarboxylic acid represented by the following chemical formula.

In Chemical Formula 1, R1 represents —H or —COOH, R2 represents —H or —CH2COOH, and R3 represents —H or —OH.   The conductive paste according to claim 2, wherein the additive is malic acid or citric acid.   The conductive paste according to claim 1, wherein the conductive metal powder is copper.   The conductive paste according to any one of claims 1 to 4, wherein the hydroxycarboxylic acid is contained in an amount of 1.0 to 5.0 (wt%) based on the weight of the conductive metal powder. The conductive paste according to claim 1, wherein the conductive paste is used for superheated steam treatment.   The conductive paste according to claim 1, which is used for a superheated steam treatment at 180 ° C. or higher.   The electroconductive thin film by which the electrically conductive paste in any one of Claims 1-7 was superheated and steam-processed after printing or application | coating.   An electric circuit obtained by subjecting the conductive paste according to any one of claims 1 to 7 to a superheated steam treatment after printing or coating.