WO2021192523A1 - Copper ink and method for forming electroconductive film - Google Patents

Copper ink and method for forming electroconductive film Download PDF

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Publication number
WO2021192523A1
WO2021192523A1 PCT/JP2021/000997 JP2021000997W WO2021192523A1 WO 2021192523 A1 WO2021192523 A1 WO 2021192523A1 JP 2021000997 W JP2021000997 W JP 2021000997W WO 2021192523 A1 WO2021192523 A1 WO 2021192523A1
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Prior art keywords
copper
copper ink
conductive film
dispersant
firing
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PCT/JP2021/000997
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French (fr)
Japanese (ja)
Inventor
三田　倫広
祐一 川戸
英俊 有村
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石原ケミカル株式会社
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Priority to CN202180021070.3A priority Critical patent/CN115298269A/en
Publication of WO2021192523A1 publication Critical patent/WO2021192523A1/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/66—Copper alloys, e.g. bronze
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/023—Emulsion inks
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
    • C09D11/033—Printing inks characterised by features other than the chemical nature of the binder characterised by the solvent
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/08—Printing inks based on natural resins
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/52—Electrically conductive inks
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D17/00—Pigment pastes, e.g. for mixing in paints
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables

Definitions

  • the present invention relates to a copper ink suitable for screen printing and a conductive film forming method using the same.
  • a method has been known in which a conductive paste is printed on a substrate by screen printing, and the printed conductive paste is irradiated with light and fired to form a conductive film on the substrate (for example, a patent).
  • the conductive paste contains copper fine particles, copper coarse particles, and a binder resin in a solvent.
  • the copper fine particles are coated with an azole compound.
  • the binder resin is added to improve the adhesion to the substrate (see paragraph 0017 of Patent Document 1 and paragraph 0019 of Patent Document 2).
  • the binder resin is polyvinylpyrrolidone resin
  • the amount is 3 to 9% by mass with respect to the total amount of copper fine particles and coarse copper particles
  • the binder resin is polyvinyl butyral resin
  • the amount is copper fine particles and coarse copper. It is 3 to 6% by mass with respect to the total amount of particles (see paragraph 0007 of Patent Document 1 and paragraph 0020 of Patent Document 2).
  • the binder resin added to the conductive paste has a problem of increasing the electrical resistance of the formed conductive film.
  • the present invention solves the above-mentioned problems, and in copper ink for forming a conductive film by firing, it is possible to print on a base material by screen printing, and the electrical resistance of the formed conductive film is lowered.
  • the purpose is.
  • the copper ink of the present invention is an ink for firing in a formic acid atmosphere, and contains copper fine particles, a dispersion medium containing the copper fine particles, and a dispersant for dispersing the copper fine particles in the dispersion medium.
  • the copper fine particles include those having a median diameter of 10 nm or more and 100 nm or less, the dispersion medium contains an organic solvent having a hydroxy group, and the dispersant is a polymer compound.
  • the dispersant is preferably polyester.
  • the dispersant may be a polymer compound having a basic group.
  • the dispersant is preferably an alkylammonium salt or a block copolymer having a basic group.
  • a binder resin is added, and the binder resin is a resin that is soluble in the organic solvent, and may be 0.1% by weight or more and less than 1% by weight with respect to the entire copper ink.
  • the binder resin is preferably a thermoplastic cellulose ether of ethyl cellulose.
  • the conductive film forming method of the present invention is a conductive film forming method for forming a conductive film pattern on a base material, and forms a copper ink film pattern on a base material by screen printing using the above copper ink. It is characterized by having a step and a step of firing the copper ink film on the base material in a formic acid atmosphere to form a conductive film on the base material.
  • the hydrogen bond between the copper fine particles and the organic solvent provides the rheological characteristics required for screen printing, so that the base material can be printed by screen printing.
  • formic acid promotes the decomposition of the dispersant, so that the electrical resistance of the formed conductive film is lowered.
  • the dispersant is a polymer compound having a basic group
  • the basic group of the dispersant reacts with formic acid, so that the decomposition of the dispersant is further promoted and the electrical resistance of the formed conductive film is lowered.
  • FIG. 1A and 1B are cross-sectional configuration views showing the formation of a conductive film using copper ink according to an embodiment of the present invention in chronological order.
  • the copper ink is for firing in a formic acid atmosphere, and contains copper fine particles, a dispersion medium containing the copper fine particles, and a dispersant.
  • the dispersant disperses the copper fine particles in the dispersion medium.
  • the copper fine particles are copper particles and include those having a median diameter (d50) of 10 nm or more and 100 nm or less.
  • the dispersion medium contains an organic solvent having a hydroxy group.
  • the dispersant is a polymeric compound.
  • This copper ink is an ink suitable for screen printing, contains copper fine particles as conductive particles, and exhibits conductivity by firing.
  • the copper fine particles fine particles having a single median diameter may be used, or fine particles having two or more types of median diameters may be mixed and used.
  • the concentration of the copper fine particles is set to a value at which a sufficient amount of copper fine particles for forming the conductive film can be obtained.
  • the particle size range (median diameter range) of the small particles is 10 nm or more and 100 nm or less, and the large particles.
  • the particle size range is preferably 0.5 ⁇ m or more and 5 ⁇ m or less.
  • the particle shape of the large particles may be spherical or flaky.
  • the small particles are sintered at a relatively low temperature, and the firing proceeds by connecting the large particles, so that the large particles do not greatly contribute to the electrical resistance of the conductive film formed.
  • the film thickness of the conductive film is as thin as 10 ⁇ m or less, large particles are unnecessary. Large particles are necessary for raising the thickness of the conductive film and allowing formic acid to penetrate into the film when the film thickness is thick. If the particle size of the large particles is less than 0.5 ⁇ m, voids for formic acid to penetrate into the film cannot be obtained. When the particle size of the large particles exceeds 5 ⁇ m, the dispersibility of the copper ink is lowered and the screen printability is also lowered.
  • the dispersion medium contains an organic solvent having a hydroxy group.
  • the hydroxy group is familiar because it forms a hydrogen bond with the surface of the copper fine particles, and therefore the organic solvent having a hydroxy group is excellent in the dispersibility of the copper fine particles.
  • the organic solvent of the dispersion medium may have a derivative of a hydroxy group. Derivatives of hydroxy groups are, for example, acetyl groups.
  • a polymer is a molecule with a large molecular weight, and has a structure composed of a large number of repetitions of units that can be obtained substantially or conceptually from a molecule with a small molecular weight (International Union of Pure and Applied Chemistry (IUPAC)).
  • the polymer compound of the dispersant is preferably an organic compound having a weight average molecular weight of 1000 or more.
  • the polymer compound of the dispersant is, for example, polyester.
  • the dispersant may be a polymer compound having a basic group.
  • a dispersant is, for example, an alkylammonium salt, or a block copolymer having a basic group.
  • Binder resin is added to the conventional conductive paste and conductive ink for screen printing. Binder resins are required to adjust the rheological properties (viscoelasticity) of conductive pastes and the like to be suitable for screen printing.
  • the copper ink of the present invention does not require the addition of a binder resin. In the present embodiment, the binder resin is not added to the copper ink.
  • the copper fine particles are dispersed in the dispersion medium because the surface is covered with the dispersant molecules.
  • the dispersion medium contains an organic solvent having a hydroxy group. Therefore, in the copper ink, a hydrogen bond is generated between the oxygen atom of the copper oxide of the surface oxide film and the hydrogen atom of the hydroxy group of the organic solvent.
  • the particle size of the copper fine particles is small, the influence of hydrogen bonds on each copper fine particle becomes large. Appropriate hydrogen bonds occur when the median diameter of the copper fine particles is 10 nm or more and 100 nm or less.
  • the copper ink of the present invention does not require the addition of a binder resin.
  • the binder resin is not added to the copper ink.
  • a small amount of binder resin may be added to the copper ink.
  • the binder resin is a resin that is soluble in the organic solvent of the dispersion medium, and is 0.1% by weight or more and less than 1% by weight with respect to the entire copper ink.
  • the binder resin is, for example, a thermoplastic cellulose ether of ethyl cellulose.
  • the amount of the binder resin is less than 0.1% by weight based on the entire copper ink, the effect at the time of printing is not so much as compared with the case where the binder resin is not added. It is not necessary to increase the amount of the binder resin to 1% by weight or more, and the electric resistance of the conductive film to be formed increases.
  • This conductive film forming method is a method of forming a conductive film pattern on a base material using copper ink.
  • the pattern of the copper ink film 1 is formed on the base material 2 by screen printing using the copper ink.
  • the copper ink film 1 on the base material 2 is fired in a formic acid atmosphere. In the firing, the dispersion medium in the copper ink film 1 is dried, the copper fine particles 11 in the copper ink film 1 are sintered, and the conductive film 3 is formed as shown in FIG. 1 (b).
  • this conductive film forming method includes a step of forming a pattern of a copper ink film 1 on a base material 2 by screen printing using copper ink, and firing the copper ink film 1 on the base material 2 in a formic acid atmosphere. It has a step of forming a conductive film 3 on the base material 2.
  • the base material 2 is a molded insulating material, has a screen-printable surface, and is, for example, a flexible substrate or a rigid substrate.
  • the firing of the copper ink film 1 in a formic acid atmosphere is thermal firing, and is performed using a formic acid reflow device.
  • a formic acid reflow device is generally a device that performs solder reflow using formic acid reduction.
  • a device for performing solder reflow is used for firing the copper ink film 1 in a formic acid atmosphere.
  • the copper ink contains copper fine particles 11 having a small particle size, the temperature required for firing is low and the time is short.
  • the copper ink contains copper fine particles 11 having a small particle size
  • the rheological characteristics required for screen printing can be obtained by hydrogen bonding between the copper fine particles 11 and the organic solvent, and a binder resin is added. You don't have to. Since the copper ink does not contain the binder resin, or even if it contains the binder resin, the amount is very small, so that the electric resistance of the conductive film 3 to be formed becomes low.
  • the copper fine particles 11 having a small particle size reduce the gaps between the copper fine particles 11 and further reduce the electric resistance of the conductive film 3 formed.
  • the volume resistivity of the formed conductive film 3 can be reduced to about 4 to 5 ⁇ ⁇ cm, which is about 1/10 of the resistivity of the conventional conductive film formed by using screen printing, and the resistivity of bulk copper. It is 1.7 ⁇ ⁇ cm, and the resistivity of plated copper is quite close to about 2 ⁇ ⁇ cm.
  • the electrical resistance of the conductive film 3 formed by firing the copper ink does not decrease to this extent simply by using the copper fine particles 11 having a small particle size and reducing the amount of the binder resin added.
  • the inventor of the present application has conducted many experiments to develop a copper ink and a conductive film forming method for forming such a conductive film 3 having a low electric resistance.
  • the dispersant In the conventional conductive paste and conductive ink, the dispersant remains without being decomposed at the time of firing, so that the electric resistance of the formed conductive film becomes high.
  • the copper ink of the present invention is for firing in a formic acid atmosphere, and since the dispersant is a polymer compound, the conductive film formed by promoting the decomposition of the dispersant by formic acid during firing in a formic acid atmosphere. The electrical resistance of 3 becomes low.
  • the dispersant is a polymer compound having a basic group, the basic group of the dispersant reacts with formic acid, so that the decomposition of the dispersant is further promoted and the electrical resistance of the formed conductive film 3 is lowered.
  • the conductive circuit produced by this conductive film forming method will be described with reference to FIG. 1 (b).
  • the conductive circuit 4 has a base material 2 and a pattern of the conductive film 3.
  • the pattern of the conductive film 3 is formed on the base material 2 by the above-described conductive film forming method.
  • a thick conductive film 3 having a thickness of about 10 ⁇ m to 40 ⁇ m can be formed on the base material 2, and the electric resistance of the conductive film 3 can be lowered.
  • a copper ink as an example of the present invention and a copper ink for comparison were prepared, and an attempt was made to form a conductive film using the copper ink.
  • Copper ink was made by the following method. Copper fine particles were gradually added to the dispersion medium and the dispersant measured to a predetermined concentration, and the mixture was stirred by a rotation / revolution mixer and then mixed and stabilized by a disperser such as a disper or a mill.
  • a base material a plate obtained by cutting out 0.5 mm thick non-alkali glass (manufactured by Corning Inc., trade name "Eagle XG") was used. Then, the produced copper ink was screen-printed on the base material, and the printed copper ink film was fired. The feasibility of forming a conductive film, the film thickness of the conductive film, and the volume resistivity were evaluated by changing conditions such as copper ink, firing temperature, and firing time.
  • the copper fine particles small particles having a median diameter of 40 to 50 nm and spherical particles having a median diameter of 0.5 ⁇ m were mixed and used at a weight ratio of 7: 3 (the same applies to Examples 2 to 13 and Comparative Examples).
  • the concentration of the copper fine particles was set to 85% by weight with respect to the entire copper ink (hereinafter, the same in terms of weight%).
  • An organic solvent having a hydroxy group (manufactured by Japan Terpene Chemical Co., Ltd., trade name "Tersolv MTPH”) and an organic solvent having a hydroxy group and an acetyl group (manufactured by Japan Terpene Chemical Co., Ltd., trade name “Tersolv THA-90”) are used as dispersion media. They were mixed and used (weight ratio 1: 1). Polyester (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -2152”) was used as the dispersant, and the concentration thereof was set to 3% by weight. No binder resin was added to the copper ink. Next, a copper ink film was formed on the substrate by screen printing using this copper ink.
  • the copper ink film was fired by a formic acid reflow device.
  • the firing temperature was 300 ° C. and the firing time was 10 minutes.
  • a conductive film was formed.
  • the film thickness of the conductive film was 16 ⁇ m, and the volume resistivity was 5 ⁇ ⁇ cm.
  • the copper ink, firing temperature, and firing time were the same as in Example 1, and a thicker conductive film than in Example 1 was formed.
  • the film thickness of the conductive film was 21 ⁇ m, and the volume resistivity was 5 ⁇ ⁇ cm.
  • the copper ink, firing temperature, and firing time were the same as in Example 2, and a thicker conductive film than in Example 2 was formed.
  • the film thickness of the conductive film was 38 ⁇ m, and the volume resistivity was 5 ⁇ ⁇ cm.
  • An alkylammonium salt (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -9076") was used as a dispersant, and the concentration was set to 3% by weight.
  • the components other than the dispersant, the firing temperature, and the firing time in the copper ink were the same as in Example 3. After firing, a conductive film was formed. The film thickness of the conductive film was 39 ⁇ m, and the volume resistivity was 10 ⁇ ⁇ cm.
  • a block copolymer having a basic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -2013”) was used as a dispersant, and the concentration thereof was set to 3% by weight.
  • the components other than the dispersant, the firing temperature, and the firing time in the copper ink were the same as in Example 4. After firing, a conductive film was formed. The film thickness of the conductive film was 7 ⁇ m, and the volume resistivity was 6 ⁇ ⁇ cm.
  • a block copolymer having a basic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -2155") was used as a dispersant, and the concentration was set to 3% by weight.
  • the components of the copper ink other than the dispersant were the same as in Example 1.
  • the firing temperature was 250 ° C., which was lower than that of Example 5, and the firing time was 30 minutes, which was longer than that of Example 5.
  • a conductive film was formed.
  • the film thickness of the conductive film was 32 ⁇ m, and the volume resistivity was 10 ⁇ ⁇ cm.
  • the copper ink film to be printed is thickened, it becomes difficult to fire the film, so that the volume resistivity of the formed conductive film may increase. However, as the film thickness of the conductive film increases, the electrical resistance of the conductive film decreases.
  • the copper ink and firing temperature were the same as in Example 6, and the firing time was 60 minutes, which was longer than in Example 6.
  • the film thickness of the conductive film was 28 ⁇ m, and the volume resistivity was 10 ⁇ ⁇ cm.
  • the copper ink was the same as in Example 6, and the firing temperature and firing time were the same as in Example 5.
  • the film thickness of the conductive film was 41 ⁇ m, and the volume resistivity was 8 ⁇ ⁇ cm.
  • the copper ink, firing temperature, and firing time were the same as in Example 8, and a conductive film slightly thinner than in Example 8 was formed.
  • the film thickness of the conductive film was 30 ⁇ m, and the volume resistivity was 7 ⁇ ⁇ cm.
  • Example 9 The copper ink and firing time were the same as in Example 9, the firing temperature was 350 ° C., which was higher than in Example 9, and a thinner conductive film than in Example 9 was formed.
  • the film thickness of the conductive film was 3 ⁇ m, and the volume resistivity was 3 ⁇ ⁇ cm, which was lower than that of Example 9.
  • Example 10 The copper ink, firing temperature, and firing time were the same as in Example 10, and a thicker conductive film than in Example 10 was formed.
  • the film thickness of the conductive film was 27 ⁇ m, and the volume resistivity was 5 ⁇ ⁇ cm, which was higher than that of Example 10.
  • the copper ink and firing time were the same as in Example 11, and the firing temperature was set to 300 ° C., which was lower than that in Example 11.
  • the film thickness of the conductive film was 28 ⁇ m, and the volume resistivity was 7 ⁇ ⁇ cm, which was higher than that of Example 11.
  • the copper ink and firing time were the same as in Example 12, and the firing temperature was 350 ° C., which was higher than in Example 12.
  • the film thickness of the conductive film was 32 ⁇ m, and the volume resistivity was 5 ⁇ ⁇ cm, which was lower than that of Example 12.
  • the copper fine particles of the copper ink small particles having a median diameter of 40 to 50 nm and flaky particles having a median diameter of 2 to 3 ⁇ m were mixed and used at a weight ratio of 7: 3 (the same applies to Examples 14 to 31).
  • the other components of the copper ink were the same as in Example 13.
  • the firing temperature was set to 300 ° C., which was lower than that of Example 13, and the firing time was set to 10 minutes, which was the same as that of Example 13.
  • a conductive film was formed.
  • the film thickness of the conductive film was 32 ⁇ m, which was the same as in Example 13, and the volume resistivity was 8 ⁇ ⁇ cm, which was higher than that in Example 13.
  • the copper ink and firing time were the same as in Example 14, the firing temperature was 350 ° C., which was higher than in Example 14, and a thinner conductive film than in Example 14 was formed.
  • the film thickness of the conductive film was 10 ⁇ m, and the volume resistivity was 5 ⁇ ⁇ cm.
  • Example 15 The copper ink, firing temperature, and firing time were the same as in Example 15 to form a thicker conductive film than in Example 15.
  • the film thickness of the conductive film was 36 ⁇ m, and the volume resistivity was 6 ⁇ ⁇ cm.
  • the copper ink, firing temperature, and firing time were the same as in Example 16.
  • the film thickness of the conductive film was 35 ⁇ m, and the volume resistivity was 7 ⁇ ⁇ cm.
  • the volume resistivity is estimated to be in the range of variation as compared with Example 16.
  • Binder resin was added to the copper ink.
  • the other components of the copper ink were the same as in Examples 14 to 17. Specifically, 0.09% by weight of ethyl cellulose thermoplastic cellulose ether (manufactured by Dow Chemical Co., Ltd., trade name "Etocell STD4") was added to the copper ink as a binder resin.
  • the firing temperature was 300 ° C. and the firing time was 10 minutes. After firing, a conductive film was formed. The film thickness of the conductive film was 32 ⁇ m, and the volume resistivity was 8 ⁇ ⁇ cm.
  • Copper ink (binder resin added) and firing time were the same as in Example 18.
  • the firing temperature was 350 ° C.
  • the film thickness of the conductive film was 10 ⁇ m, and the volume resistivity was 5 ⁇ ⁇ cm.
  • Copper ink (added binder resin), firing temperature and firing time were made the same as in Example 19 to form a thicker conductive film than in Example 19.
  • the film thickness of the conductive film was 36 ⁇ m, and the volume resistivity was 6 ⁇ ⁇ cm.
  • Copper ink (added binder resin), firing temperature and firing time were the same as in Example 20.
  • the film thickness of the conductive film was 35 ⁇ m, and the volume resistivity was 7 ⁇ ⁇ cm.
  • the volume resistivity is estimated to be in the range of variation as compared with Example 20.
  • More binder resin than in Example 21 was added to the copper ink.
  • the other components of the copper ink were the same as in Example 21. Specifically, 0.21% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink.
  • the firing temperature and firing time were the same as in Example 21.
  • the film thickness of the conductive film was 37 ⁇ m, and the volume resistivity was 7 ⁇ ⁇ cm.
  • Copper ink (added binder resin), firing temperature and firing time were the same as in Example 22.
  • the film thickness of the conductive film was 36 ⁇ m, and the volume resistivity was 7 ⁇ ⁇ cm.
  • More binder resin than in Example 23 was added to the copper ink.
  • the other components of the copper ink were the same as in Example 23. Specifically, 0.30% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink.
  • the firing temperature was 250 ° C. and the firing time was 10 minutes.
  • the film thickness of the conductive film was 6 ⁇ m, and the volume resistivity was 6 ⁇ ⁇ cm.
  • Copper ink (added binder resin), firing temperature and firing time were the same as in Example 24, and a thicker conductive film than in Example 24 was formed.
  • the film thickness of the conductive film was 41 ⁇ m, and the volume resistivity was 9 ⁇ ⁇ cm, which was higher than that of Example 24.
  • the copper ink (added binder resin) was the same as in Example 24, the firing temperature was 350 ° C., and the firing time was 10 minutes.
  • the film thickness of the conductive film was 4 ⁇ m, and the volume resistivity was 4 ⁇ ⁇ cm.
  • Copper ink (added binder resin), firing temperature and firing time were the same as in Example 26, and a thicker conductive film than in Example 26 was formed.
  • the film thickness of the conductive film was 35 ⁇ m, and the volume resistivity was 6 ⁇ ⁇ cm, which was higher than that of Example 26.
  • Example 27 More binder resin than in Example 27 was added to the copper ink.
  • the other components of the copper ink were the same as in Example 27. Specifically, 0.43% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink.
  • the firing temperature and firing time were the same as in Example 27.
  • the film thickness of the conductive film was 38 ⁇ m, and the volume resistivity was 8 ⁇ ⁇ cm, which was higher than that of Example 27.
  • Copper fine particles were set to 80% by weight with respect to the entire copper ink. More binder resin than in Example 28 was added to the copper ink. The other components of the copper ink were the same as in Example 28. Specifically, 0.80% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink. The firing temperature was 300 ° C. and the firing time was 10 minutes. The film thickness of the conductive film was 32 ⁇ m, and the volume resistivity was 8 ⁇ ⁇ cm.
  • the copper ink (added binder resin) was the same as in Example 29, the firing temperature was 350 ° C., and the firing time was 10 minutes.
  • the film thickness of the conductive film was 6 ⁇ m, and the volume resistivity was 6 ⁇ ⁇ cm.
  • Copper ink (added binder resin), firing temperature and firing time were the same as in Example 30, and a thicker conductive film than in Example 30 was formed.
  • the film thickness of the conductive film was 31 ⁇ m, and the volume resistivity was 7 ⁇ ⁇ cm.
  • Example 1 The copper fine particles and the dispersion medium were the same as in Example 1.
  • a copolymer having an acidic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -102") was used as a dispersant, and the concentration thereof was set to 3% by weight. No binder resin was added to the copper ink.
  • a copper ink film was formed on the substrate by screen printing using this copper ink. Then, the copper ink film was fired by a formic acid reflow device. The firing temperature was 300 ° C. and the firing time was 10 minutes. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
  • Comparative Example 2 A polymer salt having an acidic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -106") was used as a dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
  • DISPERBYK registered trademark
  • Comparative Example 3 A polymer having an acidic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -111") was used as a dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
  • Comparative Example 4 An unsaturated polycarboxylic acid polymer (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -P105”) was used as a dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
  • DISPERBYK registered trademark
  • Comparative Example 5 Phosphonate (dodecylphosphonic acid (reagent)) was used as the dispersant, and the concentration thereof was set to 3% by weight.
  • the components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
  • Comparative Example 6 Oleic acid (reagent) was used as the dispersant, and the concentration thereof was set to 3% by weight.
  • the components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
  • the dispersant inhibited the formation of the conductive film.
  • a firing device other than the formic acid reflow device may be used in the step of firing the copper ink film in a formic acid atmosphere to form a conductive film on the substrate.

Abstract

A copper ink for forming electroconductive films through burning, the copper ink being printable by screen printing on substrates and forming electroconductive films having reduced electrical resistance.　The copper ink is for burning in a formic acid atmosphere, and comprises: fine copper particles; a dispersion medium which contains the fine copper particles; and a dispersant with which the fine copper particles are dispersed in the dispersion medium. The fine copper particles include ones having a median diameter of 10-100 nm. The dispersion medium includes an organic solvent having a hydroxy group. The dispersant is a polymer.

Description

銅インク及び導電膜形成方法Copper ink and conductive film forming method
　本発明は、スクリーン印刷に適した銅インク、及びそれを用いた導電膜形成方法に関する。 The present invention relates to a copper ink suitable for screen printing and a conductive film forming method using the same.
　従来から、導電性ペーストをスクリーン印刷によって基板に印刷し、印刷された導電性ペーストに光を照射して焼成することにより、基板上に導電膜を形成する方法が知られている（例えば、特許文献１、２参照）。その導電性ペーストは、溶剤中に銅微粒子、銅粗粒子、バインダー樹脂を含む。銅微粒子は、アゾール化合物で被覆される。バインダー樹脂は、基板に対する密着性を向上させるために添加される（特許文献１の段落００１７、特許文献２の段落００１９参照）。バインダー樹脂がポリビニルピロリドン樹脂である場合、その量は、銅微粒子と銅粗粒子の総量に対して３～９質量％、バインダー樹脂がポリビニルブチラール樹脂である場合、その量は、銅微粒子と銅粗粒子の総量に対して３～６質量％である（特許文献１の段落０００７、特許文献２の段落００２０参照）。 Conventionally, a method has been known in which a conductive paste is printed on a substrate by screen printing, and the printed conductive paste is irradiated with light and fired to form a conductive film on the substrate (for example, a patent). Refer to Documents 1 and 2). The conductive paste contains copper fine particles, copper coarse particles, and a binder resin in a solvent. The copper fine particles are coated with an azole compound. The binder resin is added to improve the adhesion to the substrate (see paragraph 0017 of Patent Document 1 and paragraph 0019 of Patent Document 2). When the binder resin is polyvinylpyrrolidone resin, the amount is 3 to 9% by mass with respect to the total amount of copper fine particles and coarse copper particles, and when the binder resin is polyvinyl butyral resin, the amount is copper fine particles and coarse copper. It is 3 to 6% by mass with respect to the total amount of particles (see paragraph 0007 of Patent Document 1 and paragraph 0020 of Patent Document 2).
　しかしながら、導電性ペーストに添加されるバインダー樹脂は、形成される導電膜の電気抵抗を高くするという問題がある。 However, the binder resin added to the conductive paste has a problem of increasing the electrical resistance of the formed conductive film.
特開２０１５－１３３３１７号公報Japanese Unexamined Patent Publication No. 2015-133317 特開２０１６－１３１０７８号公報Japanese Unexamined Patent Publication No. 2016-13107
　本発明は、上記問題を解決するものであり、焼成して導電膜を形成するための銅インクにおいて、スクリーン印刷によって基材に印刷可能とするとともに、形成される導電膜の電気抵抗を低くすることを目的とする。 The present invention solves the above-mentioned problems, and in copper ink for forming a conductive film by firing, it is possible to print on a base material by screen printing, and the electrical resistance of the formed conductive film is lowered. The purpose is.
　本発明の銅インクは、ギ酸雰囲気下での焼成用のインクであって、銅微粒子と、前記銅微粒子を含有する分散媒と、前記銅微粒子を前記分散媒中で分散させる分散剤とを含有し、前記銅微粒子は、メジアン径が１０ｎｍ以上１００ｎｍ以下のものを含み、前記分散媒は、ヒドロキシ基を有する有機溶剤を含み、前記分散剤は、高分子化合物であることを特徴とする。 The copper ink of the present invention is an ink for firing in a formic acid atmosphere, and contains copper fine particles, a dispersion medium containing the copper fine particles, and a dispersant for dispersing the copper fine particles in the dispersion medium. The copper fine particles include those having a median diameter of 10 nm or more and 100 nm or less, the dispersion medium contains an organic solvent having a hydroxy group, and the dispersant is a polymer compound.
　この銅インクにおいて、前記分散剤は、ポリエステルであることが好ましい。 In this copper ink, the dispersant is preferably polyester.
　この銅インクにおいて、前記分散剤は、塩基性基を有する高分子化合物であってもよい。 In this copper ink, the dispersant may be a polymer compound having a basic group.
　この銅インクにおいて、前記分散剤は、アルキルアンモニウム塩、又は塩基性基を有するブロック共重合物であることが好ましい。 In this copper ink, the dispersant is preferably an alkylammonium salt or a block copolymer having a basic group.
　この銅インクにおいて、バインダー樹脂が添加されないことが好ましい。 It is preferable that no binder resin is added to this copper ink.
　この銅インクにおいて、バインダー樹脂が添加され、前記バインダー樹脂は、前記有機溶剤に溶ける樹脂であり、銅インク全体に対して０．１重量％以上１重量％未満であってもよい。 In this copper ink, a binder resin is added, and the binder resin is a resin that is soluble in the organic solvent, and may be 0.1% by weight or more and less than 1% by weight with respect to the entire copper ink.
　この銅インクにおいて、前記バインダー樹脂は、エチルセルロースの熱可塑性セルロースエーテルであることが好ましい。 In this copper ink, the binder resin is preferably a thermoplastic cellulose ether of ethyl cellulose.
　本発明の導電膜形成方法は、基材上に導電膜のパターンを形成する導電膜形成方法であって、上記の銅インクを用いてスクリーン印刷によって銅インク膜のパターンを基材上に形成する工程と、前記基材上の前記銅インク膜をギ酸雰囲気下で焼成してその基材上に導電膜を形成する工程とを有することを特徴とする。 The conductive film forming method of the present invention is a conductive film forming method for forming a conductive film pattern on a base material, and forms a copper ink film pattern on a base material by screen printing using the above copper ink. It is characterized by having a step and a step of firing the copper ink film on the base material in a formic acid atmosphere to form a conductive film on the base material.
　本発明の銅インクによれば、銅微粒子と有機溶剤との間の水素結合によって、スクリーン印刷に必要なレオロジー特性が得られるので、スクリーン印刷によって基材に印刷可能となる。また、ギ酸雰囲気下での焼成時、ギ酸によって分散剤の分解が促進されるので、形成される導電膜の電気抵抗が低くなる。分散剤が塩基性基を有する高分子化合物である場合、分散剤の塩基性基がギ酸と反応するため、分散剤の分解がいっそう促進され、形成される導電膜の電気抵抗が低くなる。 According to the copper ink of the present invention, the hydrogen bond between the copper fine particles and the organic solvent provides the rheological characteristics required for screen printing, so that the base material can be printed by screen printing. Further, when firing in a formic acid atmosphere, formic acid promotes the decomposition of the dispersant, so that the electrical resistance of the formed conductive film is lowered. When the dispersant is a polymer compound having a basic group, the basic group of the dispersant reacts with formic acid, so that the decomposition of the dispersant is further promoted and the electrical resistance of the formed conductive film is lowered.
図１（ａ）（ｂ）は本発明の一実施形態に係る銅インクを用いた導電膜の形成を時系列順に示す断面構成図である。1A and 1B are cross-sectional configuration views showing the formation of a conductive film using copper ink according to an embodiment of the present invention in chronological order.
　本発明の一実施形態に係る銅インクを説明する。銅インクは、ギ酸雰囲気下での焼成用であって、銅微粒子と、その銅微粒子を含有する分散媒と、分散剤とを含有する。分散剤は、銅微粒子を分散媒中で分散させる。銅微粒子は、銅の粒子であり、メジアン径（ｄ５０）が１０ｎｍ以上１００ｎｍ以下のものを含む。分散媒は、ヒドロキシ基を有する有機溶剤を含む。分散剤は、高分子化合物である。 The copper ink according to the embodiment of the present invention will be described. The copper ink is for firing in a formic acid atmosphere, and contains copper fine particles, a dispersion medium containing the copper fine particles, and a dispersant. The dispersant disperses the copper fine particles in the dispersion medium. The copper fine particles are copper particles and include those having a median diameter (d50) of 10 nm or more and 100 nm or less. The dispersion medium contains an organic solvent having a hydroxy group. The dispersant is a polymeric compound.
　この銅インクは、スクリーン印刷に適したインクであり、導電性粒子として銅微粒子を含有し、焼成によって導電性を発現する導電性インクである。 This copper ink is an ink suitable for screen printing, contains copper fine particles as conductive particles, and exhibits conductivity by firing.
　銅微粒子として、単一のメジアン径を持つ微粒子を用いても、２種類以上のメジアン径を持つ微粒子を混合して用いてもよい。銅微粒子の濃度は、導電膜を形成するのに十分な銅微粒子量が得られる値とされる。粒径が小さい銅微粒子（小粒子）と粒径が大きい銅微粒子（大粒子）を混合して用いる場合、小粒子の粒径範囲（メジアン径の範囲）は、１０ｎｍ以上１００ｎｍ以下、大粒子の粒径範囲は０．５μｍ以上５μｍ以下であることが望ましい。大粒子の粒子形状は、球形でもフレーク状でもよい。銅インクの焼成において、小粒子が比較的低温で焼結し、大粒子間をつなぐことにより焼成が進むので、大粒子は、形成される導電膜の電気抵抗に大きくは寄与しない。導電膜の膜厚が１０μｍ以下の薄い場合、大粒子は不要である。大粒子は、導電膜の膜厚が厚い場合に、嵩上げ及び、ギ酸を被膜内部まで浸透させるために必要である。大粒子の粒径が０．５μｍ未満であると、ギ酸が被膜の内部まで浸透するための空隙が得られない。大粒子の粒径が５μｍを超えると、銅インクの分散性が低下し、スクリーン印刷性も低下する。 As the copper fine particles, fine particles having a single median diameter may be used, or fine particles having two or more types of median diameters may be mixed and used. The concentration of the copper fine particles is set to a value at which a sufficient amount of copper fine particles for forming the conductive film can be obtained. When copper fine particles (small particles) with a small particle size and copper fine particles (large particles) with a large particle size are mixed and used, the particle size range (median diameter range) of the small particles is 10 nm or more and 100 nm or less, and the large particles. The particle size range is preferably 0.5 μm or more and 5 μm or less. The particle shape of the large particles may be spherical or flaky. In the firing of copper ink, the small particles are sintered at a relatively low temperature, and the firing proceeds by connecting the large particles, so that the large particles do not greatly contribute to the electrical resistance of the conductive film formed. When the film thickness of the conductive film is as thin as 10 μm or less, large particles are unnecessary. Large particles are necessary for raising the thickness of the conductive film and allowing formic acid to penetrate into the film when the film thickness is thick. If the particle size of the large particles is less than 0.5 μm, voids for formic acid to penetrate into the film cannot be obtained. When the particle size of the large particles exceeds 5 μm, the dispersibility of the copper ink is lowered and the screen printability is also lowered.
　本実施形態では、分散媒は、ヒドロキシ基を有する有機溶剤を含む。ヒドロキシ基は銅微粒子表面と水素結合を形成するためなじみがよく、そのためヒドロキシ基を有する有機溶剤は、銅微粒子の分散性に優れる。同様の理由で、分散媒の有機溶剤は、ヒドロキシ基の誘導体を有してもよい。ヒドロキシ基の誘導体は、例えばアセチル基である。 In this embodiment, the dispersion medium contains an organic solvent having a hydroxy group. The hydroxy group is familiar because it forms a hydrogen bond with the surface of the copper fine particles, and therefore the organic solvent having a hydroxy group is excellent in the dispersibility of the copper fine particles. For the same reason, the organic solvent of the dispersion medium may have a derivative of a hydroxy group. Derivatives of hydroxy groups are, for example, acetyl groups.
　高分子とは、分子量が大きい分子で、分子量が小さい分子から実質的または概念的に得られる単位の多数回の繰り返しで構成した構造を有する（国際純正・応用化学連合（ＩＵＰＡＣ））。分散剤の高分子化合物は、重量平均分子量が１０００以上の有機化合物であることが望ましい。 A polymer is a molecule with a large molecular weight, and has a structure composed of a large number of repetitions of units that can be obtained substantially or conceptually from a molecule with a small molecular weight (International Union of Pure and Applied Chemistry (IUPAC)). The polymer compound of the dispersant is preferably an organic compound having a weight average molecular weight of 1000 or more.
　分散剤の高分子化合物は、例えば、ポリエステルである。 The polymer compound of the dispersant is, for example, polyester.
　分散剤は、塩基性基を有する高分子化合物であってもよい。そのような分散剤は、例えば、アルキルアンモニウム塩、又は塩基性基を有するブロック共重合物である。 The dispersant may be a polymer compound having a basic group. Such a dispersant is, for example, an alkylammonium salt, or a block copolymer having a basic group.
　従来のスクリーン印刷用の導電性ペーストや導電性インクは、バインダー樹脂が添加される。バインダー樹脂は、導電性ペースト等のレオロジー特性（粘弾性）をスクリーン印刷に適するように調整するために必要とされる。これに対して、本発明の銅インクは、バインダー樹脂を添加しなくてよい。本実施形態では、銅インクは、バインダー樹脂が添加されない。 Binder resin is added to the conventional conductive paste and conductive ink for screen printing. Binder resins are required to adjust the rheological properties (viscoelasticity) of conductive pastes and the like to be suitable for screen printing. On the other hand, the copper ink of the present invention does not require the addition of a binder resin. In the present embodiment, the binder resin is not added to the copper ink.
　上記のように配合された銅インクにおいて、銅微粒子は、分散剤分子で表面が覆われるので、分散媒中で分散される。 In the copper ink blended as described above, the copper fine particles are dispersed in the dispersion medium because the surface is covered with the dispersant molecules.
　銅微粒子は、大気中に含まれる酸素によって最表面が酸化されるため、酸化銅から成る薄い表面酸化皮膜が形成される。一方、分散媒は、ヒドロキシ基を有する有機溶剤を含む。このため、銅インク中において、表面酸化被膜の酸化銅の酸素原子と、有機溶剤のヒドロキシ基の水素原子との間に水素結合が生じる。銅微粒子の粒径が小さいと、各銅微粒子における水素結合の影響が大きくなる。銅微粒子のメジアン径が１０ｎｍ以上１００ｎｍ以下のときに適度な水素結合が生じる。このような銅微粒子を含む銅インクをスクリーン印刷に用いた場合、銅微粒子と有機溶剤との間の水素結合により、スクリーン印刷に必要なレオロジー特性が得られる。このため、本発明の銅インクは、バインダー樹脂を添加しなくてよい。本実施形態では、銅インクは、バインダー樹脂が添加されない。 Since the outermost surface of copper fine particles is oxidized by oxygen contained in the atmosphere, a thin surface oxide film made of copper oxide is formed. On the other hand, the dispersion medium contains an organic solvent having a hydroxy group. Therefore, in the copper ink, a hydrogen bond is generated between the oxygen atom of the copper oxide of the surface oxide film and the hydrogen atom of the hydroxy group of the organic solvent. When the particle size of the copper fine particles is small, the influence of hydrogen bonds on each copper fine particle becomes large. Appropriate hydrogen bonds occur when the median diameter of the copper fine particles is 10 nm or more and 100 nm or less. When a copper ink containing such copper fine particles is used for screen printing, the hydrogen bonds between the copper fine particles and the organic solvent provide the rheological characteristics required for screen printing. Therefore, the copper ink of the present invention does not require the addition of a binder resin. In the present embodiment, the binder resin is not added to the copper ink.
　なお、本実施形態の変形例として、銅インクに微量のバインダー樹脂を添加してもよい。そのバインダー樹脂は、分散媒の有機溶剤に溶ける樹脂であり、銅インク全体に対して０．１重量％以上１重量％未満である。バインダー樹脂は、例えば、エチルセルロースの熱可塑性セルロースエーテルである。銅インクに微量のバインダー樹脂を添加することにより、銅インクを基材上に印刷する際に銅インクが流れにくくなり、バインダー樹脂を添加しない場合と比べて、銅インクの細い線を引けるようになる。バインダー樹脂の量を銅インク全体に対して０．１重量％未満とすることは可能であるが、バインダー樹脂を添加しない場合と比べて印刷時の効果があまり見られない。バインダー樹脂の量を１重量％以上にすることは不要であり、形成される導電膜の電気抵抗が高くなる。 As a modification of this embodiment, a small amount of binder resin may be added to the copper ink. The binder resin is a resin that is soluble in the organic solvent of the dispersion medium, and is 0.1% by weight or more and less than 1% by weight with respect to the entire copper ink. The binder resin is, for example, a thermoplastic cellulose ether of ethyl cellulose. By adding a small amount of binder resin to the copper ink, it becomes difficult for the copper ink to flow when printing the copper ink on the base material, so that fine lines of the copper ink can be drawn compared to the case where the binder resin is not added. Become. Although it is possible to make the amount of the binder resin less than 0.1% by weight based on the entire copper ink, the effect at the time of printing is not so much as compared with the case where the binder resin is not added. It is not necessary to increase the amount of the binder resin to 1% by weight or more, and the electric resistance of the conductive film to be formed increases.
　この銅インクを用いた導電膜形成方法を図１（ａ）（ｂ）を参照して説明する。この導電膜形成方法は、銅インクを用いて基材上に導電膜のパターンを形成する方法である。図１（ａ）に示すように、銅インクを用いてスクリーン印刷によって、銅インク膜１のパターンが基材２上に形成される。次に、その基材２上の銅インク膜１がギ酸雰囲気下で焼成される。焼成において、銅インク膜１中の分散媒が乾燥し、銅インク膜１中の銅微粒子１１が焼結し、図１（ｂ）に示すように、導電膜３が形成される。 A method for forming a conductive film using this copper ink will be described with reference to FIGS. 1 (a) and 1 (b). This conductive film forming method is a method of forming a conductive film pattern on a base material using copper ink. As shown in FIG. 1A, the pattern of the copper ink film 1 is formed on the base material 2 by screen printing using the copper ink. Next, the copper ink film 1 on the base material 2 is fired in a formic acid atmosphere. In the firing, the dispersion medium in the copper ink film 1 is dried, the copper fine particles 11 in the copper ink film 1 are sintered, and the conductive film 3 is formed as shown in FIG. 1 (b).
　すなわち、この導電膜形成方法は、銅インクを用いてスクリーン印刷によって銅インク膜１のパターンを基材２上に形成する工程と、その基材２上の銅インク膜１をギ酸雰囲気下で焼成してその基材２上に導電膜３を形成する工程とを有する。 That is, this conductive film forming method includes a step of forming a pattern of a copper ink film 1 on a base material 2 by screen printing using copper ink, and firing the copper ink film 1 on the base material 2 in a formic acid atmosphere. It has a step of forming a conductive film 3 on the base material 2.
　基材２は、絶縁物を成形したものであり、スクリーン印刷可能な表面を有し、例えば、フレキシブル基板又はリジッド基板である。 The base material 2 is a molded insulating material, has a screen-printable surface, and is, for example, a flexible substrate or a rigid substrate.
　ギ酸雰囲気下での銅インク膜１の焼成は、熱焼成であり、ギ酸リフロー装置を用いて行われる。ギ酸リフロー装置は、一般的には、ギ酸還元を利用したはんだリフローを行う装置である。本実施形態では、はんだリフローを行う装置をギ酸雰囲気下での銅インク膜１の焼成に用いる。 The firing of the copper ink film 1 in a formic acid atmosphere is thermal firing, and is performed using a formic acid reflow device. A formic acid reflow device is generally a device that performs solder reflow using formic acid reduction. In this embodiment, a device for performing solder reflow is used for firing the copper ink film 1 in a formic acid atmosphere.
　銅インク中に粒径が小さい銅微粒子１１を含むため、焼成に要する温度は低く、時間は短い。 Since the copper ink contains copper fine particles 11 having a small particle size, the temperature required for firing is low and the time is short.
　前述したように、銅インクは、粒径が小さい銅微粒子１１を含むので、その銅微粒子１１と有機溶剤との間の水素結合によって、スクリーン印刷に必要なレオロジー特性が得られ、バインダー樹脂を添加しなくてよい。銅インクにバインダー樹脂が含まれないか、含まれていても微量であるので、形成される導電膜３の電気抵抗が低くなる。 As described above, since the copper ink contains copper fine particles 11 having a small particle size, the rheological characteristics required for screen printing can be obtained by hydrogen bonding between the copper fine particles 11 and the organic solvent, and a binder resin is added. You don't have to. Since the copper ink does not contain the binder resin, or even if it contains the binder resin, the amount is very small, so that the electric resistance of the conductive film 3 to be formed becomes low.
　また、粒径が小さい銅微粒子１１によって、銅微粒子１１間の隙間が小さくなり、形成される導電膜３の電気抵抗がいっそう低くなる。 Further, the copper fine particles 11 having a small particle size reduce the gaps between the copper fine particles 11 and further reduce the electric resistance of the conductive film 3 formed.
　形成される導電膜３の体積抵抗率は、４～５μΩ・ｃｍ程度まで低減でき、スクリーン印刷を用いて形成された従来の導電膜の抵抗率の１／１０程度であり、バルク銅の抵抗率１．７μΩ・ｃｍ、めっき銅の抵抗率約２μΩ・ｃｍにかなり近い。粒径が小さい銅微粒子１１を用い、添加するバインダー樹脂の量を減らしただけでは、銅インクの焼成によって形成される導電膜３の電気抵抗は、ここまで低くならない。本願の発明者は、数多くの実験を行って、このような電気抵抗の低い導電膜３を形成する銅インク及び導電膜形成方法を開発した。 The volume resistivity of the formed conductive film 3 can be reduced to about 4 to 5 μΩ · cm, which is about 1/10 of the resistivity of the conventional conductive film formed by using screen printing, and the resistivity of bulk copper. It is 1.7 μΩ · cm, and the resistivity of plated copper is quite close to about 2 μΩ · cm. The electrical resistance of the conductive film 3 formed by firing the copper ink does not decrease to this extent simply by using the copper fine particles 11 having a small particle size and reducing the amount of the binder resin added. The inventor of the present application has conducted many experiments to develop a copper ink and a conductive film forming method for forming such a conductive film 3 having a low electric resistance.
　従来の導電性ペーストや導電性インクでは、分散剤が焼成時に分解されずにかなり残ることにより、形成された導電膜の電気抵抗が高くなる。本発明の銅インクは、ギ酸雰囲気下での焼成用であり、分散剤が高分子化合物であるので、ギ酸雰囲気下での焼成時、ギ酸によって分散剤の分解が促進され、形成される導電膜３の電気抵抗が低くなる。分散剤が塩基性基を有する高分子化合物である場合、分散剤の塩基性基がギ酸と反応するため、分散剤の分解がいっそう促進され、形成される導電膜３の電気抵抗が低くなる。 In the conventional conductive paste and conductive ink, the dispersant remains without being decomposed at the time of firing, so that the electric resistance of the formed conductive film becomes high. The copper ink of the present invention is for firing in a formic acid atmosphere, and since the dispersant is a polymer compound, the conductive film formed by promoting the decomposition of the dispersant by formic acid during firing in a formic acid atmosphere. The electrical resistance of 3 becomes low. When the dispersant is a polymer compound having a basic group, the basic group of the dispersant reacts with formic acid, so that the decomposition of the dispersant is further promoted and the electrical resistance of the formed conductive film 3 is lowered.
　この導電膜形成方法で作製する導電回路を図１（ｂ）を参照して説明する。導電回路４は、基材２と、導電膜３のパターンとを有する。その導電膜３のパターンは、上述した導電膜形成方法によって基材２上に形成される。本発明の銅インクとスクリーン印刷を用いることにより、基材２上に膜厚１０μｍ～４０μｍ程度の厚い導電膜３を形成することができ、導電膜３の電気抵抗を低くすることができる。 The conductive circuit produced by this conductive film forming method will be described with reference to FIG. 1 (b). The conductive circuit 4 has a base material 2 and a pattern of the conductive film 3. The pattern of the conductive film 3 is formed on the base material 2 by the above-described conductive film forming method. By using the copper ink of the present invention and screen printing, a thick conductive film 3 having a thickness of about 10 μm to 40 μm can be formed on the base material 2, and the electric resistance of the conductive film 3 can be lowered.
　本発明の実施例としての銅インク、及び比較のための銅インクを作り、その銅インクを用いて導電膜の形成を試みた。銅インクは以下の方法で作った。所定の濃度に測りとった分散媒と分散剤に、銅微粒子を徐々に添加しながら自転公転ミキサーにより攪拌した後、ディスパーやミルなどの分散機にて混合安定化した。基材には、０．５ｍｍ厚の無アルカリガラス（コーニング社製、商品名「Ｅａｇｌｅ　ＸＧ」）を切り出した板を用いた。そして、作った銅インクを基材にスクリーン印刷し、印刷した銅インク膜を焼成した。銅インク、焼成温度及び焼成時間等の条件を変えて、導電膜形成の可否、導電膜の膜厚及び体積抵抗率を評価した。 A copper ink as an example of the present invention and a copper ink for comparison were prepared, and an attempt was made to form a conductive film using the copper ink. Copper ink was made by the following method. Copper fine particles were gradually added to the dispersion medium and the dispersant measured to a predetermined concentration, and the mixture was stirred by a rotation / revolution mixer and then mixed and stabilized by a disperser such as a disper or a mill. As the base material, a plate obtained by cutting out 0.5 mm thick non-alkali glass (manufactured by Corning Inc., trade name "Eagle XG") was used. Then, the produced copper ink was screen-printed on the base material, and the printed copper ink film was fired. The feasibility of forming a conductive film, the film thickness of the conductive film, and the volume resistivity were evaluated by changing conditions such as copper ink, firing temperature, and firing time.
　先ず、銅インクを作った。銅微粒子として、メジアン径４０～５０ｎｍの小粒子と、メジアン径０．５μｍの球状粒子とを重量比７：３で混合して用いた（実施例２～１３及び比較例において同じ）。銅微粒子の濃度は、銅インク全体に対して（以下、重量％において同様）８５重量％とした。分散媒としてヒドロキシ基を有する有機溶剤（日本テルペン化学社製、商品名「テルソルブＭＴＰＨ」）及びヒドロキシ基及びアセチル基を有する有機溶剤（日本テルペン化学社製、商品名「テルソルブＴＨＡ－９０」）を混合して用いた（重量比１：１）。分散剤としてポリエステル（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－２１５２」）を用い、その濃度を３重量％とした。銅インクにバインダー樹脂を添加しなかった。次に、この銅インクを用いてスクリーン印刷によって基材上に銅インク膜を形成した。そして、その銅インク膜をギ酸リフロー装置で焼成した。焼成温度は３００℃、焼成時間は１０分とした。焼成後、導電膜が形成された。導電膜の膜厚は１６μｍ、体積抵抗率は５μΩ・ｃｍであった。 First, I made copper ink. As the copper fine particles, small particles having a median diameter of 40 to 50 nm and spherical particles having a median diameter of 0.5 μm were mixed and used at a weight ratio of 7: 3 (the same applies to Examples 2 to 13 and Comparative Examples). The concentration of the copper fine particles was set to 85% by weight with respect to the entire copper ink (hereinafter, the same in terms of weight%). An organic solvent having a hydroxy group (manufactured by Japan Terpene Chemical Co., Ltd., trade name "Tersolv MTPH") and an organic solvent having a hydroxy group and an acetyl group (manufactured by Japan Terpene Chemical Co., Ltd., trade name "Tersolv THA-90") are used as dispersion media. They were mixed and used (weight ratio 1: 1). Polyester (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -2152") was used as the dispersant, and the concentration thereof was set to 3% by weight. No binder resin was added to the copper ink. Next, a copper ink film was formed on the substrate by screen printing using this copper ink. Then, the copper ink film was fired by a formic acid reflow device. The firing temperature was 300 ° C. and the firing time was 10 minutes. After firing, a conductive film was formed. The film thickness of the conductive film was 16 μm, and the volume resistivity was 5 μΩ · cm.
　銅インク、焼成温度及び焼成時間を実施例１と同じにし、実施例１より厚い導電膜を形成した。導電膜の膜厚は２１μｍ、体積抵抗率は５μΩ・ｃｍであった。 The copper ink, firing temperature, and firing time were the same as in Example 1, and a thicker conductive film than in Example 1 was formed. The film thickness of the conductive film was 21 μm, and the volume resistivity was 5 μΩ · cm.
　銅インク、焼成温度及び焼成時間を実施例２と同じにし、実施例２より厚い導電膜を形成した。導電膜の膜厚は３８μｍ、体積抵抗率は５μΩ・ｃｍであった。 The copper ink, firing temperature, and firing time were the same as in Example 2, and a thicker conductive film than in Example 2 was formed. The film thickness of the conductive film was 38 μm, and the volume resistivity was 5 μΩ · cm.
　分散剤としてアルキルアンモニウム塩（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－９０７６」）を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分、焼成温度及び焼成時間は実施例３と同じにした。焼成後、導電膜が形成された。導電膜の膜厚は３９μｍ、体積抵抗率は１０μΩ・ｃｍであった。 An alkylammonium salt (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -9076") was used as a dispersant, and the concentration was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time in the copper ink were the same as in Example 3. After firing, a conductive film was formed. The film thickness of the conductive film was 39 μm, and the volume resistivity was 10 μΩ · cm.
　分散剤として塩基性基を有するブロック共重合物（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－２０１３」）を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分、焼成温度及び焼成時間は実施例４と同じにした。焼成後、導電膜が形成された。導電膜の膜厚は７μｍ、体積抵抗率は６μΩ・ｃｍであった。 A block copolymer having a basic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -2013") was used as a dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time in the copper ink were the same as in Example 4. After firing, a conductive film was formed. The film thickness of the conductive film was 7 μm, and the volume resistivity was 6 μΩ · cm.
　分散剤として塩基性基を有するブロック共重合物（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－２１５５」）を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分は実施例１と同じにした。焼成温度は実施例５より低い２５０℃、焼成時間は実施例５より長い３０分とした。焼成後、導電膜が形成された。導電膜の膜厚は３２μｍ、体積抵抗率は１０μΩ・ｃｍであった。 A block copolymer having a basic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -2155") was used as a dispersant, and the concentration was set to 3% by weight. The components of the copper ink other than the dispersant were the same as in Example 1. The firing temperature was 250 ° C., which was lower than that of Example 5, and the firing time was 30 minutes, which was longer than that of Example 5. After firing, a conductive film was formed. The film thickness of the conductive film was 32 μm, and the volume resistivity was 10 μΩ · cm.
　印刷する銅インク膜を厚くすると、その焼成が難しくなるので、形成される導電膜の体積抵抗率が大きくなることがある。しかし、導電膜の膜厚が増大するので、導電膜の電気抵抗は低くなる。 If the copper ink film to be printed is thickened, it becomes difficult to fire the film, so that the volume resistivity of the formed conductive film may increase. However, as the film thickness of the conductive film increases, the electrical resistance of the conductive film decreases.
　銅インク及び焼成温度は実施例６と同じにし、焼成時間を実施例６より長い６０分とした。導電膜の膜厚は２８μｍ、体積抵抗率は１０μΩ・ｃｍであった。 The copper ink and firing temperature were the same as in Example 6, and the firing time was 60 minutes, which was longer than in Example 6. The film thickness of the conductive film was 28 μm, and the volume resistivity was 10 μΩ · cm.
　銅インクを実施例６と同じにし、焼成温度及び焼成時間を実施例５と同じにした。導電膜の膜厚は４１μｍ、体積抵抗率は８μΩ・ｃｍであった。 The copper ink was the same as in Example 6, and the firing temperature and firing time were the same as in Example 5. The film thickness of the conductive film was 41 μm, and the volume resistivity was 8 μΩ · cm.
　銅インク、焼成温度及び焼成時間を実施例８と同じにし、実施例８より若干薄い導電膜を形成した。導電膜の膜厚は３０μｍ、体積抵抗率は７μΩ・ｃｍであった。 The copper ink, firing temperature, and firing time were the same as in Example 8, and a conductive film slightly thinner than in Example 8 was formed. The film thickness of the conductive film was 30 μm, and the volume resistivity was 7 μΩ · cm.
　銅インク、焼成時間を実施例９と同じにし、焼成温度を実施例９より高い３５０℃とし、実施例９より薄い導電膜を形成した。導電膜の膜厚は３μｍ、体積抵抗率は実施例９より低い３μΩ・ｃｍであった。 The copper ink and firing time were the same as in Example 9, the firing temperature was 350 ° C., which was higher than in Example 9, and a thinner conductive film than in Example 9 was formed. The film thickness of the conductive film was 3 μm, and the volume resistivity was 3 μΩ · cm, which was lower than that of Example 9.
　銅インク、焼成温度及び焼成時間を実施例１０と同じにし、実施例１０より厚い導電膜を形成した。導電膜の膜厚は２７μｍ、体積抵抗率は実施例１０より高い５μΩ・ｃｍであった。 The copper ink, firing temperature, and firing time were the same as in Example 10, and a thicker conductive film than in Example 10 was formed. The film thickness of the conductive film was 27 μm, and the volume resistivity was 5 μΩ · cm, which was higher than that of Example 10.
　銅インク、焼成時間を実施例１１と同じにし、焼成温度を実施例１１より低い３００℃とした。導電膜の膜厚は２８μｍ、体積抵抗率は実施例１１より高い７μΩ・ｃｍであった。 The copper ink and firing time were the same as in Example 11, and the firing temperature was set to 300 ° C., which was lower than that in Example 11. The film thickness of the conductive film was 28 μm, and the volume resistivity was 7 μΩ · cm, which was higher than that of Example 11.
　銅インク、焼成時間を実施例１２と同じにし、焼成温度を実施例１２より高い３５０℃とした。導電膜の膜厚は３２μｍ、体積抵抗率は実施例１２より低い５μΩ・ｃｍであった。 The copper ink and firing time were the same as in Example 12, and the firing temperature was 350 ° C., which was higher than in Example 12. The film thickness of the conductive film was 32 μm, and the volume resistivity was 5 μΩ · cm, which was lower than that of Example 12.
　銅インクの銅微粒子として、メジアン径４０～５０ｎｍの小粒子と、メジアン径２～３μｍのフレーク状粒子とを重量比７：３で混合して用いた（実施例１４～３１において同じ）。それ以外の銅インクの成分は、実施例１３と同じにした。焼成温度を実施例１３より低い３００℃とし、焼成時間を実施例１３と同じ１０分とした。焼成後、導電膜が形成された。導電膜の膜厚は実施例１３と同じ３２μｍ、体積抵抗率は実施例１３より高い８μΩ・ｃｍであった。 As the copper fine particles of the copper ink, small particles having a median diameter of 40 to 50 nm and flaky particles having a median diameter of 2 to 3 μm were mixed and used at a weight ratio of 7: 3 (the same applies to Examples 14 to 31). The other components of the copper ink were the same as in Example 13. The firing temperature was set to 300 ° C., which was lower than that of Example 13, and the firing time was set to 10 minutes, which was the same as that of Example 13. After firing, a conductive film was formed. The film thickness of the conductive film was 32 μm, which was the same as in Example 13, and the volume resistivity was 8 μΩ · cm, which was higher than that in Example 13.
　銅インク、焼成時間を実施例１４と同じにし、焼成温度を実施例１４より高い３５０℃とし、実施例１４より薄い導電膜を形成した。導電膜の膜厚は１０μｍ、体積抵抗率は５μΩ・ｃｍであった。 The copper ink and firing time were the same as in Example 14, the firing temperature was 350 ° C., which was higher than in Example 14, and a thinner conductive film than in Example 14 was formed. The film thickness of the conductive film was 10 μm, and the volume resistivity was 5 μΩ · cm.
　銅インク、焼成温度及び焼成時間を実施例１５と同じにし、実施例１５より厚い導電膜を形成した。導電膜の膜厚は３６μｍ、体積抵抗率は６μΩ・ｃｍであった。 The copper ink, firing temperature, and firing time were the same as in Example 15 to form a thicker conductive film than in Example 15. The film thickness of the conductive film was 36 μm, and the volume resistivity was 6 μΩ · cm.
　銅インク、焼成温度及び焼成時間を実施例１６と同じにした。導電膜の膜厚は３５μｍ、体積抵抗率は７μΩ・ｃｍであった。体積抵抗率は、実施例１６と比較して、ばらつきの範囲と推定される。 The copper ink, firing temperature, and firing time were the same as in Example 16. The film thickness of the conductive film was 35 μm, and the volume resistivity was 7 μΩ · cm. The volume resistivity is estimated to be in the range of variation as compared with Example 16.
　バインダー樹脂を銅インクに添加した。それ以外の銅インクの成分は実施例１４～１７と同じにした。具体的には、バインダー樹脂としてエチルセルロースの熱可塑性セルロースエーテル（ダウケミカル社製、商品名「エトセルＳＴＤ４」）を銅インクに０．０９重量％添加した。焼成温度は３００℃、焼成時間は１０分とした。焼成後、導電膜が形成された。導電膜の膜厚は３２μｍ、体積抵抗率は８μΩ・ｃｍであった。 Binder resin was added to the copper ink. The other components of the copper ink were the same as in Examples 14 to 17. Specifically, 0.09% by weight of ethyl cellulose thermoplastic cellulose ether (manufactured by Dow Chemical Co., Ltd., trade name "Etocell STD4") was added to the copper ink as a binder resin. The firing temperature was 300 ° C. and the firing time was 10 minutes. After firing, a conductive film was formed. The film thickness of the conductive film was 32 μm, and the volume resistivity was 8 μΩ · cm.
　銅インク（バインダー樹脂添加）、焼成時間を実施例１８と同じにした。焼成温度は３５０℃とした。導電膜の膜厚は１０μｍ、体積抵抗率は５μΩ・ｃｍであった。 Copper ink (binder resin added) and firing time were the same as in Example 18. The firing temperature was 350 ° C. The film thickness of the conductive film was 10 μm, and the volume resistivity was 5 μΩ · cm.
　銅インク（バインダー樹脂添加）、焼成温度及び焼成時間を実施例１９と同じにし、実施例１９より厚い導電膜を形成した。導電膜の膜厚は３６μｍ、体積抵抗率は６μΩ・ｃｍであった。 Copper ink (added binder resin), firing temperature and firing time were made the same as in Example 19 to form a thicker conductive film than in Example 19. The film thickness of the conductive film was 36 μm, and the volume resistivity was 6 μΩ · cm.
　銅インク（バインダー樹脂添加）、焼成温度及び焼成時間を実施例２０と同じにした。導電膜の膜厚は３５μｍ、体積抵抗率は７μΩ・ｃｍであった。体積抵抗率は、実施例２０と比較して、ばらつきの範囲と推定される。 Copper ink (added binder resin), firing temperature and firing time were the same as in Example 20. The film thickness of the conductive film was 35 μm, and the volume resistivity was 7 μΩ · cm. The volume resistivity is estimated to be in the range of variation as compared with Example 20.
　実施例２１より多くのバインダー樹脂を銅インクに添加した。それ以外の銅インクの成分は実施例２１と同じにした。具体的には、エチルセルロースの熱可塑性セルロースエーテルを銅インクに０．２１重量％添加した。焼成温度及び焼成時間は実施例２１と同じにした。導電膜の膜厚は３７μｍ、体積抵抗率は７μΩ・ｃｍであった。 More binder resin than in Example 21 was added to the copper ink. The other components of the copper ink were the same as in Example 21. Specifically, 0.21% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink. The firing temperature and firing time were the same as in Example 21. The film thickness of the conductive film was 37 μm, and the volume resistivity was 7 μΩ · cm.
　銅インク（バインダー樹脂添加）、焼成温度及び焼成時間を実施例２２と同じにした。導電膜の膜厚は３６μｍ、体積抵抗率は７μΩ・ｃｍであった。 Copper ink (added binder resin), firing temperature and firing time were the same as in Example 22. The film thickness of the conductive film was 36 μm, and the volume resistivity was 7 μΩ · cm.
　実施例２３より多くのバインダー樹脂を銅インクに添加した。それ以外の銅インクの成分は実施例２３と同じにした。具体的には、エチルセルロースの熱可塑性セルロースエーテルを銅インクに０．３０重量％添加した。焼成温度は２５０℃、焼成時間は１０分とした。導電膜の膜厚は６μｍ、体積抵抗率は６μΩ・ｃｍであった。 More binder resin than in Example 23 was added to the copper ink. The other components of the copper ink were the same as in Example 23. Specifically, 0.30% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink. The firing temperature was 250 ° C. and the firing time was 10 minutes. The film thickness of the conductive film was 6 μm, and the volume resistivity was 6 μΩ · cm.
　銅インク（バインダー樹脂添加）、焼成温度及び焼成時間を実施例２４と同じにし、実施例２４より厚い導電膜を形成した。導電膜の膜厚は４１μｍ、体積抵抗率は実施例２４より高い９μΩ・ｃｍであった。 Copper ink (added binder resin), firing temperature and firing time were the same as in Example 24, and a thicker conductive film than in Example 24 was formed. The film thickness of the conductive film was 41 μm, and the volume resistivity was 9 μΩ · cm, which was higher than that of Example 24.
　銅インク（バインダー樹脂添加）を実施例２４と同じにし、焼成温度を３５０℃、焼成時間を１０分とした。導電膜の膜厚は４μｍ、体積抵抗率は４μΩ・ｃｍであった。 The copper ink (added binder resin) was the same as in Example 24, the firing temperature was 350 ° C., and the firing time was 10 minutes. The film thickness of the conductive film was 4 μm, and the volume resistivity was 4 μΩ · cm.
　銅インク（バインダー樹脂添加）、焼成温度及び焼成時間を実施例２６と同じにし、実施例２６より厚い導電膜を形成した。導電膜の膜厚は３５μｍ、体積抵抗率は実施例２６より高い６μΩ・ｃｍであった。 Copper ink (added binder resin), firing temperature and firing time were the same as in Example 26, and a thicker conductive film than in Example 26 was formed. The film thickness of the conductive film was 35 μm, and the volume resistivity was 6 μΩ · cm, which was higher than that of Example 26.
　実施例２７より多くのバインダー樹脂を銅インクに添加した。それ以外の銅インクの成分は実施例２７と同じにした。具体的には、エチルセルロースの熱可塑性セルロースエーテルを銅インクに０．４３重量％添加した。焼成温度及び焼成時間は実施例２７と同じにした。導電膜の膜厚は３８μｍ、体積抵抗率は実施例２７より高い８μΩ・ｃｍであった。 More binder resin than in Example 27 was added to the copper ink. The other components of the copper ink were the same as in Example 27. Specifically, 0.43% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink. The firing temperature and firing time were the same as in Example 27. The film thickness of the conductive film was 38 μm, and the volume resistivity was 8 μΩ · cm, which was higher than that of Example 27.
　銅微粒子を銅インク全体に対して８０重量％とした。実施例２８より多くのバインダー樹脂を銅インクに添加した。それ以外の銅インクの成分は実施例２８と同じにした。具体的には、エチルセルロースの熱可塑性セルロースエーテルを銅インクに０．８０重量％添加した。焼成温度は３００℃、焼成時間は１０分とした。導電膜の膜厚は３２μｍ、体積抵抗率は８μΩ・ｃｍであった。 Copper fine particles were set to 80% by weight with respect to the entire copper ink. More binder resin than in Example 28 was added to the copper ink. The other components of the copper ink were the same as in Example 28. Specifically, 0.80% by weight of ethyl cellulose thermoplastic cellulose ether was added to the copper ink. The firing temperature was 300 ° C. and the firing time was 10 minutes. The film thickness of the conductive film was 32 μm, and the volume resistivity was 8 μΩ · cm.
　銅インク（バインダー樹脂添加）を実施例２９と同じにし、焼成温度を３５０℃、焼成時間を１０分とした。導電膜の膜厚は６μｍ、体積抵抗率は６μΩ・ｃｍであった。 The copper ink (added binder resin) was the same as in Example 29, the firing temperature was 350 ° C., and the firing time was 10 minutes. The film thickness of the conductive film was 6 μm, and the volume resistivity was 6 μΩ · cm.
　銅インク（バインダー樹脂添加）、焼成温度及び焼成時間を実施例３０と同じにし、実施例３０より厚い導電膜を形成した。導電膜の膜厚は３１μｍ、体積抵抗率は７μΩ・ｃｍであった。 Copper ink (added binder resin), firing temperature and firing time were the same as in Example 30, and a thicker conductive film than in Example 30 was formed. The film thickness of the conductive film was 31 μm, and the volume resistivity was 7 μΩ · cm.
　比較例では、分散剤として酸性基を有する化合物を用いた。 In the comparative example, a compound having an acidic group was used as the dispersant.
（比較例１）
　銅微粒子と分散媒は、実施例１と同じにした。分散剤として酸性基を有するコポリマー（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－１０２」）を用い、その濃度を３重量％とした。銅インクにバインダー樹脂を添加しなかった。次に、この銅インクを用いてスクリーン印刷によって基材上に銅インク膜を形成した。そして、その銅インク膜をギ酸リフロー装置で焼成した。焼成温度は３００℃、焼成時間は１０分とした。焼成後、形成された導電膜にクラックがあり、抵抗を測定できなかった。 (Comparative Example 1)
The copper fine particles and the dispersion medium were the same as in Example 1. A copolymer having an acidic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -102") was used as a dispersant, and the concentration thereof was set to 3% by weight. No binder resin was added to the copper ink. Next, a copper ink film was formed on the substrate by screen printing using this copper ink. Then, the copper ink film was fired by a formic acid reflow device. The firing temperature was 300 ° C. and the firing time was 10 minutes. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
（比較例２）
　分散剤として酸性基を有するポリマー塩（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－１０６」）を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分、焼成温度及び焼成時間は比較例１と同じにした。焼成後、形成された導電膜にクラックがあり、抵抗を測定できなかった。 (Comparative Example 2)
A polymer salt having an acidic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -106") was used as a dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
（比較例３）
　分散剤として酸性基を有するポリマー（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－１１１」）を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分、焼成温度及び焼成時間は比較例１と同じにした。焼成後、形成された導電膜にクラックがあり、抵抗を測定できなかった。 (Comparative Example 3)
A polymer having an acidic group (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -111") was used as a dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
（比較例４）
　分散剤として不飽和ポリカルボン酸ポリマー（ビックケミー社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－Ｐ１０５」）を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分、焼成温度及び焼成時間は比較例１と同じにした。焼成後、形成された導電膜にクラックがあり、抵抗を測定できなかった。 (Comparative Example 4)
An unsaturated polycarboxylic acid polymer (manufactured by Big Chemie, trade name "DISPERBYK (registered trademark) -P105") was used as a dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
（比較例５）
　分散剤としてホスホン酸（ドデシルホスホン酸（試薬））を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分、焼成温度及び焼成時間は比較例１と同じにした。焼成後、形成された導電膜にクラックがあり、抵抗を測定できなかった。 (Comparative Example 5)
Phosphonate (dodecylphosphonic acid (reagent)) was used as the dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
（比較例６）
　分散剤としてオレイン酸（試薬）を用い、その濃度を３重量％とした。銅インクにおける分散剤以外の成分、焼成温度及び焼成時間は比較例１と同じにした。焼成後、形成された導電膜にクラックがあり、抵抗を測定できなかった。 (Comparative Example 6)
Oleic acid (reagent) was used as the dispersant, and the concentration thereof was set to 3% by weight. The components other than the dispersant, the firing temperature, and the firing time of the copper ink were the same as in Comparative Example 1. After firing, there were cracks in the formed conductive film, and the resistance could not be measured.
　比較例では、分散剤が導電膜の形成を阻害したと考えられる。 In the comparative example, it is considered that the dispersant inhibited the formation of the conductive film.
　なお、本発明は、上記の実施形態の構成に限られず、発明の要旨を変更しない範囲で種々の変形が可能である。例えば、銅インク膜をギ酸雰囲気下で焼成してその基材上に導電膜を形成する工程に、ギ酸リフロー装置以外の焼成装置を用いてもよい。 The present invention is not limited to the configuration of the above embodiment, and various modifications can be made without changing the gist of the invention. For example, a firing device other than the formic acid reflow device may be used in the step of firing the copper ink film in a formic acid atmosphere to form a conductive film on the substrate.
１　銅インク膜
１１　銅微粒子
２　基材
３　導電膜 1 Copper ink film 11 Copper fine particles 2 Base material 3 Conductive

Claims (8)

  1. 　ギ酸雰囲気下での焼成用の銅インクであって、
    　銅微粒子と、前記銅微粒子を含有する分散媒と、前記銅微粒子を前記分散媒中で分散させる分散剤とを含有し、
    　前記銅微粒子は、メジアン径が１０ｎｍ以上１００ｎｍ以下のものを含み、
    　前記分散媒は、ヒドロキシ基を有する有機溶剤を含み、
    　前記分散剤は、高分子化合物であることを特徴とする銅インク。     Copper ink for firing in a formic acid atmosphere
    It contains copper fine particles, a dispersion medium containing the copper fine particles, and a dispersant for dispersing the copper fine particles in the dispersion medium.
    The copper fine particles include those having a median diameter of 10 nm or more and 100 nm or less.
    The dispersion medium contains an organic solvent having a hydroxy group and contains.
    The dispersant is a copper ink characterized by being a polymer compound.
  2. 　前記分散剤は、ポリエステルであることを特徴とする請求項１に記載の銅インク。 The copper ink according to claim 1, wherein the dispersant is polyester.
  3. 　前記分散剤は、塩基性基を有する高分子化合物であることを特徴とする請求項１に記載の銅インク。 The copper ink according to claim 1, wherein the dispersant is a polymer compound having a basic group.
  4. 　前記分散剤は、アルキルアンモニウム塩、又は塩基性基を有するブロック共重合物であることを特徴とする請求項３に記載の銅インク。 The copper ink according to claim 3, wherein the dispersant is an alkylammonium salt or a block copolymer having a basic group.
  5. 　バインダー樹脂が添加されないことを特徴とする請求項１乃至請求項４のいずれか一項に記載の銅インク。 The copper ink according to any one of claims 1 to 4, wherein no binder resin is added.
  6. 　バインダー樹脂が添加され、
    　前記バインダー樹脂は、前記有機溶剤に溶ける樹脂であり、銅インク全体に対して０．１重量％以上１重量％未満であることを特徴とする請求項３又は請求項４に記載の銅インク。     Binder resin is added,
    The copper ink according to claim 3 or 4, wherein the binder resin is a resin that is soluble in the organic solvent and is 0.1% by weight or more and less than 1% by weight with respect to the entire copper ink.
  7. 　前記バインダー樹脂は、エチルセルロースの熱可塑性セルロースエーテルであることを特徴とする請求項６に記載の銅インク。 The copper ink according to claim 6, wherein the binder resin is a thermoplastic cellulose ether of ethyl cellulose.
  8. 　基材上に導電膜のパターンを形成する導電膜形成方法であって、
    　請求項１乃至請求項７のいずれか一項に記載の銅インクを用いてスクリーン印刷によって銅インク膜のパターンを基材上に形成する工程と、
    　前記基材上の前記銅インク膜をギ酸雰囲気下で焼成してその基材上に導電膜を形成する工程とを有することを特徴とする導電膜形成方法。

          A conductive film forming method for forming a conductive film pattern on a substrate.
    A step of forming a pattern of a copper ink film on a substrate by screen printing using the copper ink according to any one of claims 1 to 7.
    A method for forming a conductive film, which comprises a step of firing the copper ink film on the base material in a formic acid atmosphere to form a conductive film on the base material.
PCT/JP2021/000997 2020-03-25 2021-01-14 Copper ink and method for forming electroconductive film WO2021192523A1 (en)

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JP2013175559A (en) * 2012-02-24 2013-09-05 Hitachi Chemical Co Ltd Composite layer composed of adhesive layer and wiring layer and adhesive layer forming ink for printing for forming the same
WO2017159611A1 (en) * 2016-03-15 2017-09-21 石原ケミカル株式会社 Fine copper particle dispersion liquid, electroconductive film formation method, and circuit board
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JP2013175559A (en) * 2012-02-24 2013-09-05 Hitachi Chemical Co Ltd Composite layer composed of adhesive layer and wiring layer and adhesive layer forming ink for printing for forming the same
WO2017159611A1 (en) * 2016-03-15 2017-09-21 石原ケミカル株式会社 Fine copper particle dispersion liquid, electroconductive film formation method, and circuit board
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