JP2010118449A - Method of manufacturing conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of baking a composition containing copper particulates without introducing an external gas to manufacture a low-resistance conductive film. <P>SOLUTION: The method of manufacturing a copper film includes a step of covering a base material printed and coated with copper particulates made of copper and/or copper oxide having an average particle size of 1 nm or more to 200 nm or less, with a covering member and a reducer and heating the coated copper particulates to sinter the copper particulates. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a conductive film.

  In recent years, manufacturing of electronic devices has been demanding processes with higher material utilization efficiency at lower energy costs due to the protection of the global environment, the scarcity of various materials such as rare metals, and soaring petroleum energy. Manufacturing of printed wiring boards is one of them. In many cases, copper plating is used to form a wiring pattern on a printed circuit board. However, copper plating is basically performed once on the entire surface of the substrate, and then patterned by photolithography and etching. As a result, the amount of copper remaining to the final product is negligible with respect to the amount of plating, which significantly reduces the material utilization efficiency. Photolithography is a technology with excellent resolution, but its use requires enormous energy, and enormous materials are discarded in the process. Therefore, although an additive plating method in which copper is plated only on the patterning portion has been developed as a more efficient plating method, an expensive base material containing a catalyst in the base material is required. Since it is electroless plating, it has not yet become mainstream because it takes time and is easily peeled off from the substrate. Furthermore, as a fundamental problem, plating requires treatment of a large amount of waste liquid to prevent environmental pollution. Therefore, there is a need for a method for producing a conductive film that replaces plating and has low material cost and high material utilization efficiency.

  As a method for producing a conductive film such as a wiring pattern by an additive method rather than a subtractive method such as plating, a method of patterning and baking a conductive paste is widely used. The conductive paste is subjected to a process of drawing a pattern directly on a base material using screen printing or the like and baking it to form a wiring pattern. This method is advantageous in that since the paste is directly patterned, there is little material loss and the energy is low.

In general, commercially available conductive pastes include a high-temperature fired paste that requires a high temperature of 800 ° C. or higher for firing, and a polymer paste that requires a low temperature of approximately 200 ° C. for firing. When the high-temperature fired paste is made of silver, it can realize a resistivity almost the same as bulk silver. However, the base material to which the conductive paste can be applied is greatly limited in terms of heat resistance temperature, and there is a problem that a flexible printed circuit board that is particularly important for a printed wiring board cannot be used. On the other hand, when the polymer paste is fired, the resistivity is about 10 ⁻⁵ Ω · cm when silver is used as the material, and about 10 ⁻⁴ Ω · cm when copper is used as the material. It cannot be realized until. However, since the firing temperature is low, it can be applied to a flexible printed circuit board.

  The particle size of silver or copper particles contained in any paste is about several μm. In the high-temperature fired paste, the particles are fused to each other by firing, but in the polymer paste, the particles are not integrated with each other even when fired, and only contact. Further, the fact that the particle diameter of the particles is several μm has a problem that the line width of about 30 μm is too large for patterning. In general, patterning with a particle size of several μm is up to about 50 μm in line width.

  As described above, when the conductive paste is used, there is a problem that is not found in the plating in which it is difficult to increase the resolution and the trade-off relationship between the baking temperature and the resistivity. Accordingly, there has been a demand for a conductive paste that can be fired at a low temperature, has a resistivity as low as the bulk, and can achieve high resolution.

  In recent years, in order to solve such problems, metal nanoparticle pastes in which metal particles are made into nanoparticles having a particle diameter of 100 nm or less have been developed. This is because by reducing the particle size of the metal particles to the nanometer order, the activity of the surface is increased and the particles can be fused even at a relatively low temperature. Furthermore, since the particle size is reduced, there is an advantage that it can be adapted to a higher definition pattern.

  Metal nanoparticle pastes are attracting attention because they break the trade-off relationship between firing temperature and resistivity, which was a problem with conventional pastes. Furthermore, it is possible to deal with a 30/30 μm line and space pattern for higher definition of the pattern, and a thin line having a line width of about 10 μm has been reported.

  Metal nanoparticle pastes that achieve high bulk resistivity by low-temperature firing, while maintaining the advantages of high material utilization efficiency and low energy cost processes, are being researched and developed mainly for silver and copper.

  In metal nanoparticle pastes, silver nanoparticles are the most actively developed metal nanoparticles. This is greatly influenced by the fact that the resistivity of silver in the bulk is extremely low and the fact that the silver does not oxidize even when heated, so that baking is easy. Furthermore, silver nanoparticles can be sintered at a low temperature of about 150 ° C., and patterning into a polyester film has been attempted (see Patent Document 1). Some pastes and inks using such silver nanoparticles are already available on the market and can be obtained relatively easily. For example, L-Ag1T sold by ULVAC Material Co., Ltd. can be fired at 150 ° C. for 1 hour to obtain a conductor film of several μΩ · cm. As a lower temperature, “Flow Metal” (registered trademark) sold by Bando Chemical Co., Ltd. can obtain a conductor of 8 μΩ · cm by baking at 120 ° C. for 20 minutes.

  As described above, the silver nanoparticle paste achieves a bulk resistivity by low-temperature firing, which was the initial target. However, the cost of silver itself is high, and there is a problem with resistance to migration.

  Similarly, copper nanoparticles have been actively developed as metal nanoparticle pastes. This is because copper has a low resistivity in the bulk like silver, and copper has a low cost and migration resistance is superior to silver. However, since copper is easily oxidized, it must be fired in a reducing atmosphere. Controlling the atmosphere to create this reducing atmosphere has complicated the firing process, which has been a major obstacle to the widespread use of copper nanoparticle pastes. In addition, firing of the copper nanoparticle paste requires a high temperature of about 250 ° C. to 350 ° C., which greatly limits the types of base materials that can be fired. Therefore, it is extremely difficult to print and fire the copper nanoparticle paste on the polyester film like the silver nanoparticle paste.

  According to the method disclosed in Patent Document 2 for firing the copper nanoparticle paste, a reducing atmosphere is created by flowing hydrogen gas into the furnace before firing and heating is performed for 2 hours. Although a low resistance conductive film can be obtained by this firing method, a hydrogen reduction atmosphere is required, and the heating time is as long as 2 hours.

  According to the method disclosed in Patent Document 3 for firing the copper nanoparticle paste, a low resistivity conductive film can be obtained from the copper nanoparticle paste by firing using atomic hydrogen. This method requires a hydrogen gas as a supply source of atomic hydrogen, and also requires a tungsten catalyst heated to about 1700 ° C. for atomizing the supplied hydrogen gas, and the firing environment is complicated.

  According to the method disclosed in Patent Document 4 for firing a copper nanoparticle paste, a low-resistance conductive film can be obtained from copper nanoparticles by supplying glycerin as a vapor. However, in this method, in order to remove organic substances on the surface of the copper nanoparticles by combustion, not only heating in a reducing atmosphere but also heating in a state exposed to oxygen is necessary. Therefore, the atmosphere of oxidation and reduction is changed about 5 times and heated, which is a complicated firing process.

Therefore, even if any of these disclosed methods is used, atmosphere control cannot be lacked in firing the copper nanoparticle paste, and for this reason, complicated processes such as introduction of gas from the outside are forced. This is a major obstacle to being widely used as a metal nanoparticle paste, even if copper is a low cost, low resistivity and excellent migration resistance material.
JP 2003-308731 A International Publication No. 2003/051562 Pamphlet Japanese Patent No. 3870273 Japanese Patent No. 3939735

  In order to fire the copper nanoparticle paste, it is indispensable to control the atmosphere to suppress oxidation, and for this purpose, it is necessary to introduce a gas from the outside. In many cases, it is necessary to evacuate the furnace once before introducing the gas for efficient gas replacement.

  However, such a process is complicated as compared with the case of firing the silver nanoparticle paste, and requires a large-scale apparatus.

  An object of the present invention is to provide a method for producing a low-resistance conductive film by firing a composition containing copper fine particles without introducing a gas from the outside.

  In order to solve the above problems, the present invention has the following configuration.

That is, this invention is a manufacturing method of an electrically conductive film,
A first step of attaching a composition comprising fine particles comprising copper and / or copper oxide having an average particle size of 1 nm or more and 200 nm or less on a substrate;
A second step of covering the composition inside a cavity that is covered with a coating member on the substrate obtained in the first step and is shielded from the outside air;
A third step of heating the composition inside the cavity at 120 ° C. or more and 350 ° C. or less in the presence of a reducing agent without supplying gas from the outside of the covering member to the inside of the cavity,
The covering member includes an internal pressure rise preventing means inside the cavity,
The clearance in the cavity of the covering member is 0.01 mm or more and 20 mm or less,
It is a manufacturing method of an electrically conductive film.

  According to the present invention, a composition containing copper fine particles can be baked using a simple apparatus without supplying gas from the outside, and a conductive film having low resistivity can be obtained.

  The present inventor has eagerly studied a method for obtaining a conductive film having a low resistivity without supplying a gas from outside using a simple apparatus, and using a covering member having specific conditions. Thus, the above-mentioned problems have been solved by firing in the presence of a reducing agent, and the present invention has been achieved. Note that the low-resistivity conductive film here is preferably a conductive film having a resistivity of 100 μΩ · cm or less in view of practicality as an electronic material.

  The first step of the method for producing a conductive film in the present invention is a composition containing fine particles comprising copper and / or copper oxide having an average particle diameter of 1 nm or more and 200 nm or less on a substrate (hereinafter referred to as “copper particle composition”). This is a step of attaching a certain).

  The fine particles composed of copper and / or copper oxide contained in the copper particle composition (hereinafter sometimes simply referred to as “copper fine particles” in this specification) are copper fine particles, copper oxide fine particles, copper fine particles and oxidized particles. A mixture of copper fine particles or copper fine particles whose surface is oxidized. Here, copper oxide is cuprous oxide, cupric oxide or a mixture thereof. In the present invention, since the amount of the reducing agent to be described later can be reduced, the amount of copper oxide in the composition containing copper fine particles is preferably small. The sum of the mass of copper and twice the mass of cupric oxide is preferably less than the mass of copper.

  The average particle diameter of the copper fine particles in the copper particle composition is 1 nm or more and 200 nm or less so that the particles sinter even when the melting point of copper is below. Here, the average particle diameter is the average particle diameter of primary particles, and the primary particles are the minimum three-dimensional unit structure composed of two or more atoms that can be recognized by an electron microscope. The average particle size of primary particles is determined by selecting 100 arbitrary particles out of the range that can be observed with an electron microscope based on the number average and averaging the particle size by the number of particles. Any 100 particles to be extracted at this time need not be within one field of view in the electron microscope, and may be extracted from any plurality of fields. The magnification of the microscope is 10,000 times or more so that the particle diameter can be clearly measured. There are no particular restrictions on the shape of the primary particles, and various forms such as spheres, polyhedrons, flat plates, and needles are possible, and their particle sizes depend on the diameter of the same volume sphere, that is, the equivalent volume sphere equivalent diameter. Define. If the average particle size is larger than 200 nm, the temperature necessary for sintering the particles increases, which may unfavorably limit the substrate on which the present invention can be carried out.

  The composition containing the copper fine particles of the present invention has a particle size of more than 200 nm to the extent that copper particles having a particle size of more than 200 nm can be joined by sintering of copper fine particles having a particle size of 1 nm to 200 nm. Large coarse copper particles may be included. The particle size of the coarse copper and / or copper oxide particles (hereinafter sometimes referred to as “coarse copper particles”) to be added is preferably greater than 200 nm and 10 μm or less. In order not to inhibit the binding, the range is selected so that the average particle size of the copper fine particles and the coarse copper particles in the composition after the addition is 1 nm or more and 200 nm or less. A suitable addition amount is a primary particle of all the copper particles contained in the composition in the range in which the average particle size of the copper fine particle and the coarse copper particle in the copper particle composition after the addition is 1 nm or more and 200 nm or less. The ratio of the number of primary particles of coarse copper particles to 1% is 1% or more and 5% or less. Addition of larger coarse copper particles is not preferable because it hinders sintering.

  The fine particles comprising copper and / or copper oxide of the present invention may contain a metal element other than copper, such as silver, to the extent that the object of the present invention is not impaired.

  The fine particles made of copper and / or copper oxide may have organic materials attached to or coated on the surface thereof. Examples of the organic matter to be attached or coated include those added for particle size control during the synthesis of fine particles, and those attached for imparting dispersibility and oxidation resistance. As such an organic substance, a low molecular compound such as octylamine and a high molecular compound such as polyvinylpyrrolidone are known.

  Many methods for synthesizing fine particles comprising copper and / or copper oxide are known, and commercially available products are also available. As an example of a known synthesis method, a method of obtaining copper fine particles by a gas evaporation method as described in Japanese Patent No. 2561537 and Japanese Patent Application Laid-Open No. 2002-121606. JP-A-2004-256857, JP-A-2005-281781, JP-A-2008-069374, a method for obtaining copper fine particles by causing a reducing agent to act on a copper compound, JP-A-2007-056321 , A method for obtaining copper fine particles by thermal decomposition of a copper compound as described in JP-A-2008-013466, and a copper oxide fine particle obtained by allowing a reducing agent to act on a copper compound as described in WO 2004/050559 The method of obtaining can be mentioned.

  The copper particle composition in the present invention is a composition in which fine particles comprising copper and / or copper oxide having an average particle diameter of 1 nm or more and 200 nm or less are dispersed in a dispersion medium, and other components shown below are added as necessary. May be included.

  Although the suitable ratio of the weight of the copper fine particle contained in a copper particle composition is suitably selected according to the method of attaching a composition to a base material, it is 10 to 95 mass% suitably.

  As a dispersion medium contained in the copper particle composition, water, a known organic solvent, or a liquid obtained by mixing them is used. The liquid used as the dispersion medium is preferably one that vaporizes at least at the heating temperature in the third step. Specific examples of preferred organic solvents include 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-octanol, terpineol, benzyl alcohol, ethylene glycol, propylene glycol, 1,3-propanediol, 1, 4-butanediol, diethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, 1,2-dimethoxyethane, methyl ethyl ketone , Methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, ethyl acetate, Acid butyl, isoamyl acetate, ethyl lactate, propylene carbonate, 1,4-dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, toluene, xylene, decalin, Examples include tetralin, chlorobenzene, 1,2-dichloroethane, 1,1,1-trichloroethane, and the like.

  The copper particle composition in the present invention may contain a reducing agent (described later in the second step), a polymer component, and a polymer precursor.

  The polymer component is added for the purpose of improving the adhesion of the conductive film and the base material in order to improve the dispersion of fine particles composed of copper and / or copper oxide and to control the viscosity characteristics of the copper particle composition. The polymer component may be dissolved in a dispersion medium, or may be dispersed in a dispersion medium in the form of fine particles. Preferred polymers as the polymer component include acrylic polymers (that is, polymers or copolymers of acrylic monomers such as (meth) acrylic acid ester, (meth) acrylic acid, (meth) acrylamide, (meth) acrylonitrile), polyvinyl Examples include pyrrolidone, polyvinyl acetal, polyester, polyamide, polyimide, polyurethane, and the like.

  The polymer precursor is a precursor that generates a polymer by heating in the third step, and is an uncured epoxy resin (a mixture of an epoxy compound and a curing agent), an uncured phenol resin (a mixture of a resole and a curing agent), or an uncured epoxy resin. Examples thereof include a cured cyanate resin (a mixture of a cyanate compound and a curing agent).

  In addition, the copper particle composition in the present invention can contain any additive used for paints and printing inks such as thixotropic agents, leveling agents, and antifoaming agents.

  The base material in the present invention is a flat member. There may be irregularities and through holes as long as there is no hindrance to the implementation of the present invention. The substrate is preferably one that does not melt or deform during firing in the third step. Examples of suitable members include resin films, resin plates, glass plates, paper, and green sheets.

  Examples of resin for the resin film include polyester resin (polyethylene terephthalate, polyethylene naphthalate, liquid crystal polyester, etc.), polyimide resin, polyetherimide resin, polyaramid resin, polyethersulfone resin, polyphenylene sulfide resin, polyphenylene ether resin, and the like. Can do. Examples of the resin used for the resin plate include thermosetting resins (cured products) such as epoxy resins, phenol resins, cyanate resins, maleimide resins, and benzoxazine resins, in addition to the same thermoplastic resins exemplified in the resin film. be able to. The resin plate may be a fiber reinforced resin obtained by impregnating a reinforced fiber base material with a thermosetting resin and curing. At this time, paper, cotton cloth, polyester woven cloth, glass fiber woven cloth or the like is preferable as the reinforcing fiber base.

  The green sheet is a precursor that becomes a ceramic substrate by firing, and is usually formed by molding components such as an alumina aggregate, a glass material, and an organic binder into a sheet shape.

  The adhesion of the copper particle composition onto the base material may be performed by attaching or applying the copper particle composition to the entire surface or almost the entire surface of the base material, or may be applied or applied only to a specific portion of the base material. Moreover, embedding (printing) in the recessed part (a groove | channel, a through-hole, etc.) of a base material is also included in adhesion on the base material of a copper particle composition. Preferred methods for attaching or applying the copper particle composition include bar coaters, gravure roll coaters, slit die coaters, knife coaters, lip coaters, comma coater methods, reverse roll coaters, spray coaters, dip coaters, spin coaters and the like. Can be mentioned. Preferable methods for printing the copper particle composition include stencil printing method (screen printing method, etc.), relief printing method (flexo printing method, etc.), intaglio printing method (gravure printing method, etc.), lithographic printing method, inkjet method, dispenser. Law.

  In the manufacturing method of the electrically conductive film of this invention, you may provide the process of volatilizing a part of dispersion medium in the copper particle composition adhered to the base material using means, such as a heating, after a 1st process.

  The second step of the method for producing a conductive film of the present invention is a step of covering the composition inside a cavity that is covered with a covering member on the substrate and is shielded from the outside air. Here, the covering member includes a means for preventing an increase in internal pressure inside the cavity. Further, the clearance in the cavity of the covering member is 0.01 mm or more and 20 mm or less.

  A covering member is a member which attaches the copper particle composition on a base material, covers it in a part, forms a cavity, and surrounds the inside of a cavity so that a copper particle composition may be shielded from external air.

  The shape of the covering member may be a lid-like member (cover type) that covers a part of the base material and covers the part to which the copper particle composition is adhered (FIG. 1). It may be a box-shaped member (case type) that covers and encloses the copper particle composition (FIG. 2). The covering member may be composed of a single part or may be a combination of a plurality of parts. In particular, in the case of a case-type covering member, it is usually realized by a combination of a plurality of members. The The covering member is made of a heat-resistant material such as metal (iron, steel, stainless steel, aluminum, etc.), glass, heat-resistant resin (epoxy resin, phenol resin, polyimide, etc.) so that it is not melted or deformed by heating in the third step. Resin, polyether ether ketone resin, fluororesin, etc.) or a combination thereof.

  A cavity is a space formed by a covering member and a base material, in which a copper particle composition is surrounded.

  The covering member includes an internal pressure rise prevention mechanism inside the cavity. The internal pressure rise prevention mechanism inside the cavity (hereinafter sometimes referred to as “cavity internal pressure rise prevention mechanism”) prevents the pressure inside the cavity from rising due to heating in the third step by letting the gas inside the cavity escape to the outside. It is a mechanism that prevents or restricts the backflow of outflowing gas and the inflow of outside air. When the dispersion medium is vaporized by heating in the third step, most of the oxygen originally in the cavity is discharged by the dispersion medium vapor through the cavity internal pressure rise prevention mechanism to the outside of the cavity, so that the cavity is in a low oxygen state. it can.

  A typical mode of the cavity internal pressure rise prevention mechanism is a through hole provided with a check valve. A check valve is a valve that allows fluid to flow in one direction but prevents flow in the reverse direction. The check valve includes a swing disk inside, a ball and spring, a flap, a diaphragm, two valve chambers as disclosed in JP 2005-337415, and 1 There are several types with different structures and operating mechanisms, such as a valve with two silicone rubber valves, but there is no particular limitation.

  Another aspect of the cavity internal pressure rise prevention mechanism is a through hole provided with an electromagnetic valve. In this case, a sensor that detects the differential pressure between the pressure in the cavity and the atmospheric pressure is provided separately, and the output of the sensor is linked to the opening and closing of the solenoid valve. To do.

  Yet another aspect of the cavity internal pressure rise prevention mechanism is a through hole provided with a gas storage mechanism. The gas storage mechanism is a mechanism for storing the gas that has come out of the through hole while maintaining the pressure at atmospheric pressure. Specifically, a bag of plastic or rubber can be used.

  As an aspect of the cavity internal pressure rise prevention mechanism, only a through hole can be used. If the cross-sectional area and length of the through-hole are appropriate, the outflow of gas into the cavity ends and the inflow of the outside atmosphere into the cavity can be made sufficiently small when there is almost no pressure difference between the inside and outside. is there.

  When the covering member is a cover type, the cavity internal pressure rise prevention mechanism is provided with a groove on the surface of the covering member that contacts the substrate, and functions as a through hole when the covering member covers the substrate. It may be something like this. Further, when the covering member is composed of a plurality of parts, the through hole is provided with a groove on one or both of the joining surfaces of the two contacting parts, and the through hole may be a through hole when the parts are joined. Good.

  When the cavity internal pressure rise prevention mechanism is only the through hole, there is an advantage that the structure of the covering member is simple and easy to produce, which is preferable.

  The installation position of the cavity internal pressure rise prevention mechanism is preferably installed at the edge of the cavity so that the gas inside the cavity can be efficiently discharged during heating in the third step.

  The intracavity clearance refers to the shortest distance between the upper surface of the base material and the surface of the covering member facing the base material inside the cavity. Here, the upper surface of the base material is a surface on which the copper particle composition is attached on the base material. However, it is the upper surface of the groove when the copper particle composition is injected into the groove provided on the substrate, and the upper surface and the bottom surface of the through hole when injected into the through hole. The cavity-internal substrate facing surface is a surface inside the cavity of the covering member and is a surface facing the upper surface of the substrate. A plurality of cavities defined by the substrate upper surface and the substrate facing surface inside the cavity of the coating member when the surface of the substrate upper surface and / or the surface inside the cavity of the coating member has a shape such as unevenness, curvature, or inclination Select the inner clearance that minimizes the distance.

  For example, in the case of FIG. 3A where the covering member is a case type, the distance shown in FIG. 3A 6 is used, and in the case of FIG. 3B where the covering member is a cover type, the distance shown in FIG. The distances shown are the intracavity clearances. In the case of FIG. 3C in which the copper particle composition is injected into a groove provided in the base material, the distance indicated by FIG. 3C 6 is the intracavity clearance. In the case of FIG. 3D in which the copper particle composition is injected into the through-hole provided in the base material, the distance indicated by FIG.

  When the clearance in the cavity of the covering member is large, it becomes impossible to efficiently expel a gas such as oxygen in the cavity out of the cavity due to the vaporization of the dispersion medium in the copper particle composition. If the distance is too small, there is a risk that the dispersion medium and the reducing agent once vaporized are cooled by the coating member and come into contact with the copper particle composition when liquefied on the cavity inner substrate facing surface of the coating member. Therefore, the clearance in the cavity of the covering member is 0.01 mm or more and 20 mm or less, preferably 0.1 mm or more and 5 mm or less.

  The 3rd process of the manufacturing method of the electrically conductive film of this invention is a process of heating a copper particle composition in 120 degreeC or more and 350 degrees C or less in the presence of a reducing agent, without supplying gas from the outside.

  In the present invention, an inert gas such as nitrogen or argon or a reducing gas such as hydrogen, glycerin or ethylene glycol is not introduced from the outside when the copper particle composition is heated. Examples of firing by introducing an inert gas include, for example, Example 1-5 in Japanese Patent No. 3939375. Moreover, as an example in which reducing gas is introduced and baked, for example, Example 1 in International Publication No. 2003-05156 can be cited.

  Since the heating of the copper particle composition in the third step is performed in the presence of a reducing agent, the reducing agent needs to be present in the cavity. As a method for causing the reducing agent to exist in the cavity, there are a method in which the reducing agent is preliminarily mixed in the copper particle composition, and a method in which the reducing agent is disposed in a place different from the copper particle composition in the cavity. Any of them may be used. Or you may use combining these two methods.

  When the reducing agent is blended in the copper particle composition in advance, a reducing agent soluble in the dispersion medium may be blended in the copper particle composition or a liquid reducing agent may be used as the dispersion medium.

  When the reducing agent is disposed at a location different from the copper particle composition in the cavity, for example, the reducing agent may be disposed on the surface of the substrate where the copper particle composition is not attached, or the substrate may be placed on the covering member. It is also possible to arrange in a portion that is not. When the reducing agent is placed at a location different from the copper particle composition in the cavity, it is vaporized at the heating temperature in the third step so that the reducing agent can diffuse to the site where the copper particle composition is adhered during heating. A liquid or sublimable solid reducing agent is selected.

  The reducing agent is selected to have a reducing power sufficient to reduce copper oxide to metallic copper at the heating temperature in the third step. The action of the reducing agent prevents oxygen remaining in the cavity from interfering with sintering, and when copper oxide is contained in the copper particle composition, it is reduced to metal copper.

  Specific examples of preferable reducing agents for the method for producing a conductive film of the present invention include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,8-octanediol. Polyols such as 2-ethyl-1,3-hexanediol, α-ketoalcohols such as acetoin, propioin, butyroin, and adipoin, aminoalcohols such as monoethanolamine and diethanolamine, hydroquinone, catechol, and tert-butylhydroquinone Polyphenols such as 4-tert-butylcatechol, p-aminophenol and salts thereof, p- (methylamino) phenol and salts thereof, N- (p-hydroxyphenyl) glycine, N, N, N ′, N ′ -Tetra Aromatic amines (including salts) such as til-p-phenylenediamine, 1-phenyl-3-pyrazolidone, 1-phenyl-4-methyl-3-pyrazolidone, 1-phenyl-4, 4-dimethyl-3- Examples include pyrazolidones such as pyrazolidone, ascorbic acid, isoascorbic acid, ascorbic acid esters, and the like.

  In the method for producing a conductive film of the present invention, when a composition containing fine particles made of copper oxide is used as the composition containing fine particles, the dispersion medium is vaporized by heating the composition in the third step. In a low oxygen environment generated by exhausting the gas in the cavity of the covering member, the copper fine particles can be sintered while the copper oxide is reduced to metal copper by the reducing agent. As a result, a conductive film having a structure in which copper is continuous and having high conductivity can be manufactured.

  Moreover, when using the copper particle composition containing a polymer component and a polymer precursor, the electrically conductive film which consists of a continuous layer of metallic copper and a polymer can be manufactured with the manufacturing method of this invention. In this case, the polymer contained in the conductive film can contribute to improving the fastness of the coating film and improving the adhesion to the substrate.

  The heating temperature of the copper particle composition in the third step is 120 ° C. or higher and 350 ° C. depending on the properties of the fine particles comprising copper and / or copper oxide, the heat resistance temperature of the base material, the reactivity of the reducing agent, the desired treatment time, etc. Selected from: When the heating temperature is high, the material of the base material and the shielding material that can be used is limited, and the energy to be input becomes large. Moreover, when heating temperature is low, heating time will become long. Therefore, the heating temperature is preferably 120 ° C. or higher and 260 ° C. or lower, and more preferably 150 ° C. or higher and 260 ° C. or lower.

  The method for producing a conductive film of the present invention comprises conventionally proposed copper and / or copper oxide by appropriately selecting the fine particles comprising copper and / or copper oxide, the reducing agent, and the heating temperature in the third step. Compared with the manufacturing method of the electrically conductive film using microparticles | fine-particles, it is possible to bake in a short time. It is particularly preferable that baking can be performed in a short time within 10 minutes because productivity is increased.

  Any known method can be used for the method of heating the copper particle composition in the third step. As a preferred heating method, heating with a hot plate can be mentioned. When the covering member is a cover type, it is preferable to bring the hot plate into contact with the back surface of the substrate, that is, the surface opposite to the surface covered with the covering member. When the covering member is a case type, it is preferable to place the covering member on the hot plate. As the heating mechanism of the hot plate, a known method such as an electric heater, a heating medium, or steam can be used.

  Examples of other heating methods include a method in which the base material and the covering member are installed in a hot air oven, and a method by radiant heat from a lamp heater (halogen lamp heater or carbon lamp heater).

  If the cavity internal pressure information prevention mechanism is a through-hole, heat the copper particle composition from the opposite side of the base material using a hot plate so that the reducing agent does not immediately flow out of the through-hole during heating in the third step. And it is preferable to make a reducing agent retain in a cavity by keeping the base material opposing surface of a coating | coated member below the boiling point of a reducing agent, and condensing a reducing agent on a base material opposing surface. Further, at this time, it is more preferable to use a material having low thermal conductivity for the substrate facing surface of the covering member as a method for easily keeping the substrate facing surface of the covering member at a low temperature. Examples of such a material having low thermal conductivity include glass and heat-resistant resin (epoxy resin, phenol resin, polyimide resin, polyether ether ketone resin, fluorine resin, etc.).

  The conductive film obtained by the method for producing a conductive film of the present invention includes wiring for circuit boards, wiring for membrane wiring boards, wiring for film connectors, interlayer wiring for multilayer boards, conductor mesh for electromagnetic wave shielding materials, wiring for flat panel displays ( (Gate bus line and source bus line), current collecting electrode for plasma display, current collecting electrode for solar cell, antenna for IC tag, printed coil and the like.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

  In the following examples, the resistivity of the conductive film was measured by a four-terminal four-probe method using a Lorester GP manufactured by Dia Instruments Co., Ltd. The part where the resistivity was measured is the part where the composition was applied. When a plurality of solid patterns were printed by screen printing, the resistivity was measured for all the solid patterns, and the average value was taken as the resistivity. A scanning microscope (Hitachi S-4800) was used to observe the synthesized copper fine particles and the conductive film. Moreover, Shintaro Awatori Rentaro AR-100 manufactured by Shinky Corporation was used for the mixer.

  SH111 manufactured by Toray Dow Corning Co., Ltd. was used for the silicon grease, and Kapton (500 V, thickness 125 μm) was used for the polyimide film.

(Reference Example 1)
The covering member was produced as follows.

  The covering members 1 (a) and 1 (b) shown in FIG. 4 were produced by cutting aluminum. The covering member 1 (b) was fitted with polydimethylsiloxane (PDMS) so that the covering member 1 (a) and 1 (b) functioned as a check valve.

  Further, by cutting aluminum, seven covering members (covering members 2 (a) to 2 (g)) having different cavity sizes w and cavity depths d shown in FIG. 5 were produced. The size w of the cavity of the covering members 2 (a) to 2 (e) is 30 mm, and the depth d of the cavity is 1.2 mm for the covering member 2 (a), 5.0mm for 2 (b), 2 ( c) is 10.0 mm, 2 (d) is 20.0 mm, and 2 (e) is 30.0 mm. The cavity depth of the covering members 2 (f) and 2 (g) is 1.2 mm, and the width w of the cavity is 60 mm for 2 (f) and 90 mm for 2 (g). As indicated by 4 in FIG. 5, grooves are formed in the covering members 2 (a) to 2 (g) so that through holes are formed when the covering member is covered with a flat plate.

  Moreover, the coating member (covering member 3) shown in FIG. 6 was produced by apply | coating silicon grease to a slide glass and arrange | positioning on a glass plate.

  As shown in FIG. 7, in order to cover the coating member 2 (a) to 2 (g) or the cavity of the coating member 3 with a base material on which the composition is adhered, 8 corresponds to 8 in FIG. 7. A glass plate (covering member 4) having a thickness of 1.5 mm was used as the covering member.

(Reference Example 2)
Copper fine particles A were synthesized as follows.

  Copper hydroxide (II) (Wako Pure Chemical Industries, 98 mg, 1 mmol) was suspended in methanol (10 ml) in an eggplant-shaped flask equipped with a Teflon-coated stir bar, and 2-undecylimidazole (Wako Pure Chemical Industries, Ltd.) was suspended here. Manufactured, 74 mg, 0.33 mmol) and hydrazine hydrate (80% aqueous solution, manufactured by Kanto Chemical Co., 1 g, 20 mmol) diluted with methanol (10 ml) were added. The mixture was stirred overnight at room temperature, and the precipitated solid was collected by filtration with a membrane filter and thoroughly washed with methanol. Thereafter, the obtained solid was dried under reduced pressure to obtain 59 mg of copper fine particles (copper fine particles A). As a result of measuring the particle diameter with a scanning electron microscope, the average particle diameter was about 50 nm. As a result of the powder X-ray diffraction measurement, it was found that the main component of the obtained particles was copper and contained almost no copper oxide.

Example 1
An average molecular weight of 10000 polyvinylpyrrolidone (Tokyo Kasei Co., Ltd. P0471) 0.28 g of 0.72 g of the reducing agent shown in Table 1, ethylene glycol (Wako Pure Chemical Industries, Ltd. 058-00986), glycerin (Kanto Chemical Co., Inc. 17029- 00), diethylene glycol (Wako Pure Chemical Industries, Ltd. 045-25915) and 2,3-butanediol (Wako Pure Chemical Industries, Ltd. 022-03242), and copper nanoparticles having an average particle diameter of 50 nm (Sigma Aldrich 684007- 25G) It knead | mixed using 4.0g, 3 rolls, and a mixer (compositions 1-4).

(Example 2)
An average molecular weight of 10,000 polyvinylpyrrolidone (Tokyo Kasei Co., Ltd. P0471) 0.28 g was dissolved in 0.72 g of N-methylpyrrolidone (Kanto Chemical Co., Ltd. 25336-00), and copper nanoparticles with an average particle size of 50 nm (Sigma Aldrich 684007). -25G) Kneaded using 4 g, 3 rolls and a mixer (Composition 5).

(Example 3)
0.1 g of L (+)-ascorbic acid (Wako Pure Chemical Industries, Ltd. 016-04805) and 0.28 g of polyvinylpyrrolidone having an average molecular weight of 40000 (Wako Pure Chemical Industries, Ltd. 161-17032) were dissolved in 0.62 g of purified water. Then, 4 g of copper nanoparticles having an average particle diameter of 50 nm (Sigma Aldrich 684007-25G) were kneaded using three rolls and a mixer (Composition 6).

Example 4
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on a polyimide film having a size of 29 mm square using Compositions 1 to 4 by screen printing. Next, as shown in FIG. 7A, the printed polyimide film was put into the cavity of the covering member 1 (a), covered with the covering member 1 (b), and the four corners were fixed with screws. Next, four hot plates were set at 100 ° C., 150 ° C., 200 ° C., and 250 ° C., respectively. The composition coated with the covering member is then heated with the covering member for 1 minute on a 100 ° C. hot plate, then with a 150 ° C. hot plate for 1 minute, then with a 200 ° C. hot plate for 1 minute, and then Heated on a hot plate at 250 ° C. for 5 minutes. When the polyimide film was taken out from the covering member after heating, it was found that the composition became a conductive film by firing, and the resistivity was low as shown in Table 1. Moreover, about what baked the composition 1, when the polyimide film was torn and the cross section was observed with the scanning microscope, it was confirmed that particle | grains are sintered (FIG. 10).

(Example 5)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on the polyimide film having a size of 29 mm square using the composition 5 by screen printing. Moreover, the reducing agent shown in Table 1, ethylene glycol (Wako Pure Chemical Industries, Ltd. 058-00986), glycerin (Kanto Chemical Co., Ltd. 17029-00), diethylene glycol (Wako Pure Chemical Industries, Ltd. 045-25915), 2, 0.01 g of 3-butanediol (Wako Pure Chemical Industries, Ltd. 022-03242) was dropped on the polyimide film so as not to cover the printing pattern. Next, as shown in FIG. 7B, the printed polyimide film was put into the cavity of the covering member 1 (a), covered with the covering member 1 (b), and fixed at the four corners with screws. Next, four hot plates were set at 100 ° C., 150 ° C., 200 ° C., and 250 ° C., respectively. The composition was then heated as in Example 4. When the composition was taken out from the covering member after heating, it was confirmed that the composition became a conductive film by firing, and the resistivity was low as shown in Table 1.

(Example 6)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on the composition 6 on a polyimide film having a size of 29 mm square using screen printing. Next, as shown in FIG. 7A, the printed polyimide film was placed in the cavity of the covering member 1 (a), covered with the covering member 1 (b), and fixed at the four corners with screws. The composition was then heated as in Example 4. After heating, when the polyimide film was taken out from the covering member, the composition became a conductive film having a thickness of 8 μm by firing, and it was confirmed that the resistivity was as low as 89.2 μΩ · cm (Table 1).

(Example 7)
After mixing 4.0 g of copper fine particles A synthesized in Reference Example 2 and 1 g of ethylene glycol (Wako Pure Chemical Industries, Ltd. 058-00986) and kneading using three rolls, 2,2-bis (4-glycidyloxyphenyl) ) 0.2 g of propane (Tokyo Chemical Industry B1796) was added and stirred with a mixer (Composition 7). The copper fine particles A are particles in which 2-undecylimidazole is attached around the copper particles, and 2-undecylimidazole is detached from the copper particles during firing, and 2,2-bis (4-glycidyloxyphenyl) propane Functions as a curing agent.

  A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on the polyimide film having a size of 29 mm square by screen printing on the composition 7. Next, as shown in FIG. 7A, the printed polyimide film was placed in the cavity of the covering member 1 (a), covered with the covering member 1 (b), and fixed at the four corners with screws. Next, four hot plates were set at 150 ° C., 200 ° C., 250 ° C., and 300 ° C., respectively. Next, the composition coated with the covering member is heated on the hot plate at 150 ° C. for 1 minute together with the covering member, then heated on the 200 ° C. hot plate for 1 minute, then heated on the 250 ° C. hot plate for 1 minute, and then Heated on a hot plate at 300 ° C. for 5 minutes. When the composition was taken out from the covering member after heating, it was confirmed that the composition was cured as a conductive film having a thickness of 9 μm by firing, and its resistivity was as low as 18.3 μΩ · cm ( Table 1).

(Example 8)
Copper nanoparticles were synthesized by the method disclosed in Example 1 of JP 2007-39765 A (copper fine particles B). 0.28 g of polyvinylpyrrolidone (Wako Pure Chemical Industries, Ltd. 161-17032) having an average molecular weight of 10,000 is dissolved in 0.72 g of ethylene glycol (Wako Pure Chemical Industries, Ltd. 058-00986) and mixed with 4.0 g of synthesized copper fine particles B. Then, the mixture was kneaded using three rolls and a mixer (Composition 8).

  A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on the polyimide film having a size of 29 mm square by using the composition 8 on a polyimide film having a size of 29 mm square. Next, as shown in FIG. 7A, the printed polyimide film was put into the cavity of the covering member 1 (a), covered with the covering member 1 (b), and fixed at the four corners with screws. Next, five hot plates were set at 150 ° C., 200 ° C., 250 ° C., 300 ° C., and 350 ° C., respectively. Next, the composition coated with the covering member is heated on the hot plate at 150 ° C. for 1 minute together with the covering member, then heated on the 200 ° C. hot plate for 1 minute, then heated on the 250 ° C. hot plate for 1 minute, and then Heated on a 300 ° C. hot plate for 1 minute, then heated on a 350 ° C. hot plate for 5 minutes. When the composition was taken out from the covering member after heating, the composition was baked to form a conductive film having a thickness of 6 μm, and the resistivity was confirmed to be as low as 13.1 μΩ · cm (Table 1).

Example 9
Using a # 5 bar coater, a copper oxide nanoparticle dispersion (Nanometal Ink CuIT, ULVAC Material Co., Ltd.) marketed on a green sheet (NEC Vacuum Glass Co., Ltd. GCS71E) with a thickness of about 1 mm and a size of 25 mm square. I applied a solid coating. Next, as shown in FIG. 7C, the solid green sheet is put into the cavity of the covering member 1 (a), and glycerin (Kanto Chemical Co., Ltd. 17029-00) 0. 01 g was dropped into the cavity, the lid was covered with the covering member 1 (b), and the four corners were fixed with screws. Next, five hot plates were set at 150 ° C., 200 ° C., 250 ° C., 300 ° C., and 350 ° C., respectively. The composition coated with the covering member is then heated with the covering member for 1 minute on a 150 ° C. hot plate, then for 1 minute on a 200 ° C. hot plate, then for 1 minute on a 250 ° C. hot plate, Heated on a 300 ° C. hot plate for 1 minute, then heated on a 350 ° C. hot plate for 5 minutes. After heating, when the polyimide film was taken out from the covering member, the composition became a conductive film having a thickness of 4 μm by firing, and the resistivity was confirmed to be as low as 7.2 μΩ · cm (Table 1).

(Example 10)
A copper nanoparticle paste (NCU-04) commercially available from Daiken Chemical Industry Co., Ltd. was applied to a 25 mm square polyimide film using a # 5 bar coater. Next, as shown in FIG.7 (c), the solid-coated polyimide film is put into the cavity of the coating | coated member 1 (a), and ethylene glycol (Wako Pure Chemical Industries, Ltd. 058-00986) 0 is put around a polyimide film. .01 g was dropped into the cavity, covered with the covering member 1 (b), and fixed at the four corners with screws. Next, four hot plates were set at 150 ° C., 200 ° C., 250 ° C., and 300 ° C., respectively. Next, the composition coated with the covering member is heated on the hot plate at 150 ° C. for 1 minute together with the covering member, then heated on the 200 ° C. hot plate for 1 minute, then heated on the 250 ° C. hot plate for 1 minute, and then Heated on a hot plate at 300 ° C. for 5 minutes. After heating, when the polyimide film was taken out from the covering member, the copper nanoparticle paste was baked to form a conductive film having a thickness of 5 μm, and its resistivity was confirmed to be as low as 22.1 μΩ · cm. (Table 1).

(Example 11)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on a 100 mm square polyimide film using Compositions 1 to 4 by screen printing. Next, as shown in FIG.7 (d), the composition was coat | covered by setting the cavity of the coating | coated member 2 (a) facing down on a polyimide film. Next, a stainless steel plate of about 500 g was placed as a weight on the covering member 2 (a) to ensure airtightness. Next, the composition including the covering member and the weight was placed on a hot plate at 25 ° C., and the hot plate was heated up to 250 ° C. over 10 minutes and then held for 1 minute, and the composition was taken out. The composition was made into a conductive film by firing, and the resistivity was confirmed to be low as shown in Table 1.

Example 12
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on a 30 mm square polyimide film using Compositions 1 to 4 by screen printing. The printed film was then cut in half so that one solid pattern and one line and space pattern remained. Next, as shown in FIG. 7E, one piece of the cut polyimide film was put in the cavity of the covering member 3 and covered with the covering member 4. At this time, silicon grease was applied to the contact portion between the covering member 3 and the covering member 4 to ensure airtightness. The composition was then heated as in Example 4. When the composition was taken out from the covering member after heating, it was confirmed that the composition became a conductive film by firing, and the resistivity was low as shown in Table 1.

(Example 13)
Etching as shown in FIG. 9 was applied to a 29 mm square polyimide film. Composition 1 was embedded in the groove of this film using a squeegee. Next, the polyimide film printed as shown in FIG. 7 (g) was put in the cavity of the covering member 2 (a), and the covering member 4 was covered. At this time, silicon grease was applied to the contact portion between the covering member 2 (a) and the covering member 4 to ensure airtightness. The composition was then heated as in Example 4. When the composition was taken out from the covering member after heating, it was confirmed that the composition became a conductive film by firing, and the resistivity was as low as 11 μΩ · cm (Table 1).

(Example 14)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on the polyimide film having a size of 29 mm square using the composition 1 by screen printing. Next, as shown in FIG. 7A, the printed polyimide film was put into the cavity of the covering member 2 (a), and the covering member 4 was covered. At this time, silicon grease was applied to the contact portion between the covering member 2 (a) and the covering member 4 to ensure airtightness. Next, the three hot plates were set at 100 ° C., 150 ° C. and 200 ° C., respectively, and heated for 7 to 90 minutes as shown in Table 2. As a result, it was confirmed that the resistivity of the conductive film hardly increased in spite of heating for a long time, and the inflow of oxygen into the cavity was suppressed.

(Example 15)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on the five 1-mm 29 mm square polyimide films of the composition 1 using screen printing. Next, the polyimide films printed as shown in FIG. 7A were put in the cavities of the separate covering members 2 (a) and covered with the covering members 4. At this time, silicon grease was applied to the contact portion between the covering member 2 (a) and the covering member 4 to ensure airtightness. Next, seven hot plates were set at 100 ° C., 150 ° C., 175 ° C., 200 ° C., 250 ° C., 300 ° C., and 350 ° C., respectively. Next, the composition coated with the covering member was heated from the low temperature side using each hot plate at the heating temperature and heating time shown in Table 5 together with the covering member. When samples 6 to 10 were taken out from the covering member after heating, it was confirmed that the composition became a conductive film by firing, and the resistivity was low as shown in Table 2.

(Example 16)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were printed on the polyimide film having a size of 29 mm square using the composition 1 by screen printing. The printed polyimide film was placed in the cavity of the covering member 1 (a), covered with the covering member 1 (b), and fixed at the four corners with screws. Next, the composition was put together with the covering member in a hot air oven at 25 ° C., heated to 250 ° C. over 30 minutes, and held for 1 minute. When the covering member was taken out from the oven after heating and the composition therein was taken out, it was confirmed that the fired composition had a thickness of 5 μm and a resistivity as low as 17 μΩ · cm (Table 2). ).

(Example 17)
Composition 1 was applied to a polyimide film using a # 5 bar coater. Next, five samples of 90, 180, 270, 450, and 810 mm ² were cut out from the solid-coated film so as not to include a portion where the film surface was exposed.

  Samples 1 to 5 were put in the cavities of the respective coating members 2 (a) and covered with the coating member 4 as shown in FIG. 7 (f). At this time, silicon grease was applied to the contact portion between the covering member 2 (a) and the covering member 4 to ensure airtightness. At this time, the ratio of the application area of the composition to the area of the bottom surface of the cavity is 10, 20, 30, 50, 90%.

  The composition was then heated as in Example 4. After the heating, when the polyimide film was taken out from the covering member, the composition became a conductive film by firing, and the resistivity was confirmed to be low as shown in Table 3.

(Example 18)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were respectively printed on the four polyimide films having a size of 29 mm square by using screen printing. Next, as shown in FIG. 7A, four printed polyimide films were put into the cavities of the covering members 2 (a) to (d) one by one, and each was covered with the covering member 4. At this time, silicon grease was applied to the contact portion between the covering members 2 (a) to (d) and the covering member 4 to ensure airtightness. Next, four hot plates were set at 100 ° C., 150 ° C., 200 ° C., and 250 ° C., respectively. Next, the composition coated with the covering member is heated together with the covering member for 1 minute each on a hot plate at 100 ° C., then heated on a hot plate at 150 ° C. for 2 minutes, and then heated on a hot plate at 200 ° C. for 5 minutes, Subsequently, it heated for 15 minutes with a 250 degreeC hotplate. When the polyimide film was taken out from each covering member after heating, it was confirmed that the composition became a conductive film by firing, and the resistivity was low as shown in Table 4.

(Example 19)
A 100 μm line and space pattern and a 10 mm square solid pattern as shown in FIG. 8 were respectively printed on 13 polyimide films having a size of 29 mm square by screen printing. Next, as shown in FIG. 7A, four printed polyimide films were placed in the cavity of the covering member 2 (f) and nine sheets were placed so as not to overlap the covering member 2 (g). Next, each was covered with a covering member 4. At this time, silicon grease was applied to the contact portion between the covering members 2 (f) and 2 (g) and the covering member 4 to ensure airtightness. The composition was then heated as in Example 4. When the composition was taken out from each covering member after heating, it was confirmed that the composition became a conductive film by firing, and the resistivity was low as shown in Table 4. Further, in the covering members 2 (f) and 2 (g), the maximum difference in resistivity between the films was about 2 μΩ · cm.

(Example 20)
The composition 1 was solid-coated using a # 5 bar coater on the upper surface of a glass cube having a side of about 20 mm. Next, as shown in FIG. 7 (f), the solid glass cube was put into the cavity of the covering member 2 (e) and covered with the covering member 4. At this time, silicon grease was applied to the contact portion between the covering member 2 (e) and the covering member 4 to ensure airtightness. Next, four hot plates were set at 100 ° C., 150 ° C., 200 ° C., and 250 ° C., respectively. Next, the composition coated with the covering member is heated on the hot plate at 100 ° C. for 3 minutes together with the covering member, then heated on the hot plate at 150 ° C. for 3 minutes, then heated on the hot plate at 200 ° C. for 3 minutes, and then Heated on a hot plate at 250 ° C. for 15 minutes. When the composition was taken out from the covering member after heating, it was confirmed that the fired composition had a thickness of 7 μm and a resistivity of 9.9 μΩ · cm and a low resistivity (Table 4).

(Comparative Example 1)
The same operation as in Example 4 was carried out except that the cover member 1 (b) was not covered. By not covering, the coating is incomplete and the vapor released from the composition immediately diffuses into the atmosphere. As a result, the resistivity of the film obtained by firing the compositions 1 to 4 exceeded the measurement limit of the measuring device and was overloaded, and it was confirmed that the resistivity was extremely high (Table 1).

(Comparative Example 2)
It implemented like Example 5 except not having dripped a reducing agent. By heating in the absence of a reducing agent, the copper particles react with oxygen in the cavities to produce copper oxide. As a result, the obtained film was oxidized, and its resistivity exceeded the measurement limit of the measuring instrument and was overloaded, and it was confirmed that the resistivity was extremely high (Table 1).

(Comparative Example 3)
The same procedure as in Example 20 was performed, except that a 20 mm square polyimide film was used instead of a glass cube. The clearance in the cavity at this time is 29.8 mm, which exceeds 20 mm, which is the upper limit of the preferred range. When the polyimide film was taken out from the covering member after heating, the composition was a conductive film having a thickness of 9 μm by firing, but it was confirmed that the resistivity was as high as 450 μΩ · cm (Table 4).

FIG. 1 is a diagram illustrating coating of a composition by a cover-type coating member in the present invention. FIG. 2 is a diagram illustrating the coating of the composition by the case-type coating member in the present invention. FIG. 3 is a diagram illustrating the adhesion and coating of the composition according to the present invention, and illustrates the intracavity clearance according to the present invention. FIG. 4 is a schematic view showing the sizes of the covering members 1 (a) and (b) used in Examples 4 to 10, Example 16, and Comparative Examples 1 and 2. FIG. 5 is a schematic diagram showing the sizes of the covering members 2 (a) to (g) used in Example 11, Examples 13 to 15, Examples 17 to 20, and Comparative Example 3. FIG. 6 is a schematic view showing the size of the covering member 3 used in Example 12. FIG. 7 is a schematic view showing a state of coating of the composition with a covering member performed in Examples 4 to 20 and Comparative Examples 1 to 3. FIG. 8 shows that the compositions used in Examples 4 to 8, Examples 11 to 12, Examples 14 to 16, Examples 18 to 19, and Comparative Examples 1 to 2 were adhered to a polyimide film or glass by screen printing. FIG. FIG. 9 is a schematic diagram of the pattern used in Example 13 when the polyimide film was etched to embed the composition into the polyimide film. FIG. 10 is a photomicrograph when the cross section of the fired film is observed with a scanning electron microscope when ethylene glycol is used as the reducing agent in the composition fired in Example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 Cover member 3 Composition 4 Cavity internal pressure rise prevention mechanism 5 Cavity 6 Cavity clearance 7 Polydimethylsiloxane 8 Cover member (glass plate)
9 Reducing agent

Claims (4)

A first step of attaching a composition comprising fine particles comprising copper and / or copper oxide having an average particle size of 1 nm or more and 200 nm or less on a substrate;
A second step of covering the composition inside a cavity that is covered with a coating member on the substrate obtained in the first step and is shielded from the outside air;
A third step of heating the composition inside the cavity at 120 ° C. or more and 350 ° C. or less in the presence of a reducing agent without supplying gas from the outside of the covering member to the inside of the cavity,
The covering member includes an internal pressure rise preventing means inside the cavity,
The manufacturing method of the electrically conductive film whose clearance in a cavity of this coating | coated member is 0.01 mm or more and 20 mm or less.   The method for producing a conductive film according to claim 1, wherein the cavity internal pressure rise preventing means is a through hole.   The method for producing a conductive film according to claim 1 or 2, wherein the step of heating the composition in the third step is a step of heating the composition using a hot plate. The method for producing a conductive film according to any one of claims 1 to 3, wherein the time for heating the composition in the third step is within 10 minutes.