WO2023248485A1 - Copper ink, conductive film formation method, and rf tag - Google Patents

Copper ink, conductive film formation method, and rf tag Download PDF

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Publication number
WO2023248485A1
WO2023248485A1 PCT/JP2022/031645 JP2022031645W WO2023248485A1 WO 2023248485 A1 WO2023248485 A1 WO 2023248485A1 JP 2022031645 W JP2022031645 W JP 2022031645W WO 2023248485 A1 WO2023248485 A1 WO 2023248485A1
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Prior art keywords
copper
conductive film
fine particles
ink
dispersant
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PCT/JP2022/031645
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French (fr)
Japanese (ja)
Inventor
祐一 川戸
聡 南原
英俊 有村
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石原ケミカル株式会社
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Publication of WO2023248485A1 publication Critical patent/WO2023248485A1/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
    • 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
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/24—Electrically-conducting 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
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/09—Use of materials for the conductive, e.g. metallic pattern

Definitions

  • the present invention relates to a copper ink for forming a conductive film, a method for forming a conductive film using the copper ink, and an RF tag having the conductive film.
  • RFID radio frequency identification
  • Non-Patent Document 1 RFID (radio frequency identification) RF tags are used for product tagging.
  • RFID is a system that uses electromagnetic coupling to read data on RF tags.
  • JIS Z0667:2017 “Application of RFID to supply chain - Product tagging” in Non-Patent Document 1 corresponds to the international standard ISO17367:2013 "Supply chain applications of RFID-Product tagging”.
  • An RF tag has an antenna, wiring, and an IC chip on a resin film such as PET (polyethylene terephthalate).
  • the antenna and wiring are made of metal foil such as aluminum, and are formed on a resin film.
  • the manufacture of RF tags involves a process of etching metal foil, and processing of waste liquid generated during etching is costly. Furthermore, there has been a recent demand for a shift away from plastics. However, if the resin film of the RF tag is replaced with a paper base material, the metal foil on the paper base material cannot be etched.
  • the present invention solves the above problems, and aims to form a low-resistance conductive film on a paper base material.
  • the copper ink of the present invention is an ink for forming a conductive film, and includes copper fine particles, a liquid dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium, and the copper fine particles are copper particles having a median diameter of 60 nm or more and 110 nm or less, the concentration of the copper fine particles is 60% by weight or more based on the entire copper ink, and the dispersion medium contains an alcohol having a plurality of hydroxy groups.
  • the dispersant is a polymer compound having a phosphoric acid group or a salt thereof, and the concentration of the dispersant is 3% by weight or more and 6% by weight or less based on the weight of the copper fine particles. shall be.
  • the dispersion medium preferably contains an alcohol selected from the group consisting of 2-methyl 2,4-pentanediol and 3-methyl 1,3-butanediol.
  • the method for forming a conductive film of the present invention is a method for forming a conductive film on a paper base material, and includes a step of forming an ink film on a paper base material using the copper ink described above, and drying the ink film.
  • the method is characterized by comprising the steps of: forming a coated dry film made of fine copper particles on the paper base material; and photo-baking the coated dry film.
  • the RF tag of the present invention is an RFID RF tag, and includes at least a paper base material and an antenna on the paper base material, and the antenna is made of a conductive film formed by the above-described conductive film forming method. It is characterized by becoming.
  • the median diameter of the copper fine particles is 60 nm or more, a thick conductive film can be formed on the paper base material by photo-baking. Since the median diameter of the copper fine particles is 110 nm or less, a conductive film with low volume resistivity can be formed on the paper base material by photo-baking. Since the concentration of copper fine particles is 60% by weight or more based on the entire copper ink, a thick conductive film can be formed. Since the dispersion medium contains an alcohol having a plurality of hydroxy groups, hydrogen bonding with the surface of the copper fine particles provides the copper ink with viscosity and rheological properties (thixotropy) suitable for printing on paper substrates.
  • the concentration of the dispersant is 3% by weight or more based on the weight of copper, the stability of the copper ink is good. Since the concentration of the dispersant is 6% by weight or less, a conductive film with low volume resistivity can be formed. The conductive film formed is thick and has a low volume resistivity, so it has low resistance. Furthermore, since the dispersant has a phosphoric acid group and the concentration of the dispersant is 3% by weight or more, the durability of the conductive film in constant temperature and humidity tests is improved by preventing oxidation of copper by phosphorus. .
  • FIGS. 1A, 1B, and 1C are cross-sectional configuration diagrams chronologically showing the formation of a conductive film using copper ink according to an embodiment of the present invention.
  • a copper ink according to an embodiment of the present invention will be described. Copper ink is used to form the conductive film.
  • the copper ink contains copper fine particles, a liquid dispersion medium, and a dispersant.
  • the dispersant disperses copper fine particles in a dispersion medium.
  • the copper fine particles are copper particles and have a median diameter (D50) of 60 nm or more and 110 nm or less.
  • D50 median diameter
  • the particle size of the copper fine particles is extracted from an image taken by a scanning electron microscope (SEM image), and the median diameter is calculated from the particle size distribution. If the particle size of the copper fine particles is too small, the formed conductive film cannot be made thick. If the particle size is too large, the volume resistivity of the conductive film will increase.
  • the concentration of copper fine particles is 60% by weight or more based on the entire copper ink. If the concentration of copper fine particles is too low, the conductive film formed will be thin.
  • the concentration of copper fine particles is desirably 75% by weight or less.
  • the dispersion medium contains an alcohol having multiple hydroxy groups.
  • the outermost surface of the copper fine particles is oxidized by oxygen contained in the atmosphere, forming a thin surface oxide film made of copper oxide.
  • oxygen contained in the atmosphere forming a thin surface oxide film made of copper oxide.
  • hydrogen bonds occur between the oxygen atoms of the copper oxide in the surface oxide film of the copper fine particles and the hydrogen atoms of the hydroxyl groups of the alcohol. Therefore, alcohol having multiple hydroxy groups has excellent dispersibility of copper fine particles.
  • Alcohols having multiple hydroxy groups include, for example, 2-methyl 2,4-pentanediol (hexylene glycol), 3-methyl 1,3-butanediol (isoprene glycol), and 1,2-ethanediol (ethylene glycol). , propane-1,2-diol (propylene glycol), 1,5-pentanediol, 2,2'-oxydiethanol (diethylene glycol), triethylene glycol, 1,2,3-propanetriol (glycerin), and sorbitol. , but not limited to.
  • the dispersant is a polymer compound having a phosphoric acid group or a salt thereof.
  • a polymer is a molecule with a large molecular weight that has a structure made up of many repetitions of units that are derived substantially or conceptually from molecules with a small molecular weight (International Union of Pure and Applied Chemistry (IUPAC)). Since the surface of the copper fine particles is covered with dispersant molecules, they are dispersed in the dispersion medium.
  • the concentration of the dispersant is 3% by weight or more and 6% by weight or less based on the weight of copper. If the concentration of the dispersant is too low, the dispersibility of the dispersant will be insufficient and the stability of the copper ink will be poor. If the concentration is too high, dispersant residue will remain in the conductive film to be formed, increasing the volume resistivity of the conductive film.
  • the formed conductive film has improved durability in a constant temperature and humidity test.
  • TEM transmission electron microscopy
  • This conductive film forming method is a method of forming a conductive film on a paper base material.
  • an ink film 2 is formed on a paper base material 3 using a copper ink 1.
  • the ink film 2 is formed by a printing method.
  • copper ink is used as the printing ink, and a printing device applies the copper ink in a predetermined pattern onto the paper base material 3 to form an ink film 2 in the pattern.
  • the printing method is flexographic printing. Then, the ink film 2 is dried.
  • the coated dry film 4 made of copper fine particles is formed on the paper base material 3, as shown in FIG. 1(b). Then, the coated dry film 4 made of fine copper particles is irradiated with light, and the coated dry film 4 is photo-sintered.
  • the light source used for photo-baking is, for example, a xenon lamp. A laser device may be used as the light source.
  • the surface oxide film of the copper fine particles in the applied dry film 4 is removed by the energy of the light, and the copper fine particles are melted together to form a bulk. That is, as shown in FIG. 1(c), the applied and dried film 4 forms a conductive film 5 on the paper base material 3 by photo-baking. Note that the drying of the ink film 2 and the photo-baking of the applied dry film 4 may be performed at the same time by irradiation with light.
  • this conductive film forming method includes a step of forming an ink film 2 on a paper base material 3 using a copper ink 1, and a step of drying the ink film 2 to form a coated dry film 4 made of fine copper particles on the paper base material 3. and a step of photo-baking the applied dry film 4.
  • a copper ink having copper fine particles with a median diameter of 40 nm which is smaller than that of this embodiment, is used, a conductive film with a low volume resistivity can be formed, but the conductive film cannot be thickened.
  • the cause of the cracks is that if the particle size of the copper particles is small, the volumetric shrinkage rate when the ink film dries becomes large, and the path through which the dispersion medium is packed by the small copper particles and escapes as gas. is to disappear.
  • the inventor of the present application conducted numerous experiments and found that copper fine particles having a median diameter of 60 nm to 110 nm are suitable for forming a conductive film on a paper base material.
  • the viscosity of the copper ink decreases. This caused the copper ink to spread and sag during flexographic printing, making it necessary to increase the viscosity of the copper ink.
  • inks are thickened with additives such as resins and rheology control agents.
  • additives such as resins and rheology control agents.
  • the inventor of the present application has discovered that copper ink can be produced. If the dispersion medium is a monohydric alcohol, the viscosity of the copper ink will be insufficient.
  • the median diameter of the copper fine particles is 60 nm or more, a thick conductive film can be formed on the paper base material by photo-baking. Since the median diameter of the copper fine particles is 110 nm or less, a conductive film with low volume resistivity can be formed on the paper base material by photo-baking. Since the concentration of copper fine particles is 60% by weight or more based on the entire copper ink, a thick conductive film can be formed. Since the dispersion medium contains an alcohol having a plurality of hydroxy groups, hydrogen bonding with the surface of the copper fine particles provides the copper ink with viscosity and rheological properties (thixotropy) suitable for printing on paper substrates.
  • the concentration of the dispersant is 3% by weight or more based on the weight of copper, the stability of the copper ink is good. Since the concentration of the dispersant is 6% by weight or less, a conductive film with low volume resistivity can be formed. The conductive film formed is thick and has a low volume resistivity, so it has low resistance. Furthermore, since the dispersant has a phosphoric acid group and the concentration of the dispersant is 3% by weight or more, the durability of the conductive film in constant temperature and humidity tests is improved by preventing oxidation of copper by phosphorus. .
  • a coated and dried film with a thickness of 1 to 5 ⁇ m can be formed on a paper base material, and a coated and dried film with a thickness of about 1 to 2 ⁇ m (0.7 to 1.5 ⁇ m) can be formed on the paper base material.
  • a conductive film with a thickness of 8 ⁇ m) can be formed. Since the conductive film formed is thick and has a low volume resistivity, the conductive film has low resistance.
  • the RF tag 6 is an RFID RF tag.
  • the RF tag 6 of this embodiment includes at least a paper base material 3 and an antenna on the paper base material 3.
  • the antenna is made of a conductive film 5 formed by the conductive film forming method of this embodiment.
  • the antenna of the RF tag 6 is made of the conductive film 5 formed by the conductive film forming method of this embodiment.
  • the conductive film is thick and has a low volume resistivity, resulting in a low resistance antenna. Since this RF tag 6 has a low resistance antenna, sufficient signal strength can be obtained.
  • the RF tag 6 may be laminated. Note that an example of laminating an RF tag is described in the Japanese Industrial Standards (see Non-Patent Document 1).
  • a copper ink as an example of the present invention and a copper ink as a comparative example were prepared, and an experiment was conducted to form a conductive film on a paper base material using the copper ink.
  • Coated paper manufactured by Oji Paper Co., Ltd., product name "OK Top Coat + EF"("TopCoat” and “TOPKOTE” are registered trademarks
  • Copper ink was used.
  • a wiring test pattern (0.6 mm wide line) was printed on the paper base material using flexo printing.
  • the printed ink film was 2 to 5 ⁇ m thick.
  • the ink film was dried, and the coated dry film was The coated and dried film was photo-baked using a flash lamp with an energy of 4 J/cm 2 .
  • the resistance (wiring resistance) of the formed conductive film (line) with a measurement length of 37.8 mm was measured using a tester.
  • the cross-sectional area of the conductive film (line) was measured using a laser microscope.Then, the volume resistivity and average thickness of the conductive film were calculated from the resistance value, cross-sectional area, etc.
  • copper ink is transferred from the plate to the paper base.
  • the conductive film is not completely transferred to the material and is randomly split between the plate and the paper base material.For this reason, the cross-sectional shape of the conductive film that is formed is usually not smooth but has irregularities.
  • the average thickness of the conductive film is The thickness is the average thickness of the unevenness, that is, the thickness of the rectangle.
  • the formed conductive film (line) was evaluated by its wiring resistance.
  • the composition range of the copper ink in Examples will be explained.
  • the particle size (median diameter) of the copper fine particles was set to 60 to 110 nm.
  • the median diameter (D50) was calculated from the particle size frequency distribution of 100 or more fine copper particles randomly extracted from a 30,000 times magnified SEM image of the copper ink.
  • the concentration of the copper fine particles was 60 to 75% by weight (hereinafter the same applies to the weight percentage of the copper fine particles) based on the entire copper ink.
  • the dispersant had a phosphoric acid group.
  • the concentration of the dispersion medium was 3 to 6% by weight based on the weight of copper (hereinafter the same applies to the weight% of the dispersant).
  • the dispersion medium was an alcohol having multiple hydroxy groups.
  • the amount of dispersion medium is the balance in the copper ink.
  • Conductive films formed by photo-baking were evaluated by changing the composition of the copper ink. Note that, as described above, the cross-sectional area and wiring resistance of the conductive film are actually measured values, and the average thickness and volume resistivity are calculated values.
  • Copper fine particles with a median diameter of 80 nm were used in the copper ink (same in Examples 2 to 6 and Comparative Examples 1 and 3). The concentration of copper fine particles was 75% by weight.
  • a polymeric phosphate ester manufactured by BYK-Chemie, trade name "DISPERBYK (registered trademark)-102" was used as a dispersant. This dispersant is a polymer compound having a phosphoric acid group. The concentration of the dispersant was 4% by weight. 2-methyl 2,4-pentanediol (dihydric alcohol) was used as a dispersion medium.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 1.8 ⁇ m.
  • the volume resistivity was 5.2 ⁇ cm.
  • the cross-sectional area was 1100 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 1.8 ⁇ . This wiring resistance was the lowest among the examples.
  • the concentration of copper fine particles was 70% by weight, lower than in Example 1.
  • the concentration of the dispersant was 3% by weight, lower than in Example 1.
  • Other conditions were the same as in Example 1.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 1.3 ⁇ m, which was thinner than in Example 1.
  • the volume resistivity was 5.1 ⁇ cm, lower than in Example 1.
  • the cross-sectional area was 800 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 2.4 ⁇ , higher than in Example 1.
  • Example 1 Since the concentration of copper fine particles was lower than in Example 1, the average thickness of the conductive film was thinner and the wiring resistance was higher. Since the concentration of the dispersant was lower than in Example 1, the volume resistivity of the conductive film was lower, but the concentration of copper fine particles had a large influence on the wiring resistance.
  • the concentration of copper fine particles was set to 60% by weight, which is even lower than in Example 2. Other conditions were the same as in Example 2.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 0.7 ⁇ m, which was thinner than in Example 2.
  • the volume resistivity was 5.1 ⁇ cm, the same as in Example 1.
  • the cross-sectional area was 420 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 4.6 ⁇ , higher than in Example 2.
  • Example 2 Since the concentration of copper fine particles was lower than in Example 2, the average thickness of the conductive film was thinner and the wiring resistance was higher.
  • a polymeric phosphate ester (manufactured by BYK-Chemie, trade name "DISPERBYK (registered trademark)-111") was used as a dispersant.
  • This dispersant is a polymer compound having a phosphoric acid group.
  • the concentration of the dispersant was 4% by weight, which is higher than in Example 3.
  • Other conditions were the same as in Example 3.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 0.7 ⁇ m, the same as in Example 3.
  • the volume resistivity was 5.3 ⁇ cm, higher than that of Example 3.
  • the cross-sectional area was 420 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 4.8 ⁇ , higher than in Example 3.
  • Example 3 Since the concentration of the dispersant was higher than in Example 3, the volume resistivity of the conductive film was high, and the wiring resistance was high.
  • an alkylol ammonium salt of a copolymer having an acid group (manufactured by BYK-Chemie, trade name "DISPERBYK (registered trademark)-180") was used.
  • This dispersant is a salt of a polymer compound having a phosphoric acid group.
  • Other conditions were the same as in Example 4.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 0.8 ⁇ m, which was thicker than in Example 4.
  • the volume resistivity was 5.6 ⁇ cm, higher than that of Example 4.
  • the cross-sectional area was 450 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 4.7 ⁇ , which was slightly lower than in Example 4.
  • the dispersant may be a salt of a polymer compound having a phosphoric acid group.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 0.8 ⁇ m, the same as in Example 5.
  • the volume resistivity was 5.4 ⁇ cm, lower than that of Example 5.
  • the cross-sectional area was 450 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 4.5 ⁇ , which was slightly lower than in Example 5.
  • the dispersion medium in Example 6 has a plurality of hydroxy groups as in Examples 1 to 5. Although the dispersion medium in Example 6 had a different carbon skeleton from the dispersion medium in Examples 1 to 5, it could be used in the copper ink of the present invention.
  • the concentration of the dispersant was 4% by weight.
  • Other conditions were the same as in Example 2.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 1.5 ⁇ m, which was thicker than in Example 2.
  • the volume resistivity was 7.1 ⁇ cm, higher than that of Example 2.
  • the cross-sectional area was 900 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 3.0 ⁇ , higher than in Example 2.
  • the average thickness of the conductive film was thicker, and the volume resistivity of the conductive film was higher.
  • the concentration of copper fine particles was set to 60% by weight, lower than in Example 7. Other conditions were the same as in Example 7.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 1.1 ⁇ m, which was thinner than in Example 7.
  • the volume resistivity was 6.9 ⁇ cm, lower than that of Example 2.
  • the cross-sectional area was 650 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 4.0 ⁇ , higher than in Example 7.
  • Example 7 Since the concentration of copper fine particles was lower than in Example 7, the average thickness of the conductive film was thinner and the wiring resistance was higher.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 0.8 ⁇ m, which was thinner than in Example 8.
  • the volume resistivity was 5.0 ⁇ cm, lower than that of Example 8.
  • the cross-sectional area was 450 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 4.2 ⁇ , higher than in Example 8.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 1.2 ⁇ m, which was slightly thicker than in Example 8.
  • the volume resistivity was 6.1 ⁇ cm, lower than that of Example 8.
  • the cross-sectional area was 450 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 3.3 ⁇ , lower than in Example 8.
  • Example 8 Since the median diameter of the copper fine particles was smaller than in Example 8, the volume resistivity of the conductive film was lower than in Example 8.
  • the conductive films (line width 600 ⁇ m, length 37.8 mm) formed using the copper inks of Examples 1 to 10 have electrical resistances in the range of 1.8 ⁇ to 4.8 ⁇ , and are suitable for RF tag antennas. It had suitably low resistance (less than 10 ⁇ ).
  • Example 1 The concentration of copper fine particles was set to 40% by weight, lower than in Examples 1 to 10. Other conditions were the same as in Example 1.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 0.3 ⁇ m, which was thinner than in Examples 1 to 10.
  • the volume resistivity was 5.7 ⁇ cm.
  • the cross-sectional area was 200 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 10.8 ⁇ , higher than Examples 1 to 10.
  • the formed conductive film had cracks.
  • the wiring was broken.
  • Example 3 The concentration of the dispersant was 8% by weight, which is higher than in Examples 1-10. Other conditions were the same as in Example 3.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 0.6 ⁇ m.
  • the volume resistivity was 10.1 ⁇ cm, higher than Examples 1 to 10.
  • the cross-sectional area was 380 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 10.0 ⁇ , higher than in Examples 1 to 10.
  • the concentration of the dispersant was too high, the volume resistivity of the conductive film increased and the wiring resistance increased.
  • the formed conductive film had no cracks.
  • the average thickness of the conductive film was 1.7 ⁇ m.
  • the volume resistivity was 31.7 ⁇ cm, higher than Examples 1 to 10.
  • the cross-sectional area was 1000 ⁇ m2 .
  • the line width was 600 ⁇ m.
  • the wiring resistance was 12.0 ⁇ , higher than Examples 1 to 10.
  • the conductive films (line width 600 ⁇ m, length 37.8 mm) formed using the copper inks of Comparative Examples 1 to 4 were disconnected or had high resistance (10 ⁇ or more) unsuitable for RF tag antennas.
  • a conductive film (line) was formed on a paper base material in the same manner as in the above example, and the wiring resistance was measured before and after a constant temperature and humidity test.
  • the temperature of the constant temperature and humidity test was 85° C., the humidity was 85%, and the holding time was 264 hours.
  • a conductive film was formed using the same copper ink as in Example 4. That is, the median diameter of the copper fine particles is 80 nm, the concentration of the copper fine particles is 60% by weight, the dispersant is a polymeric phosphate ester, the concentration of the dispersant is 4% by weight, and the dispersion medium is 2-methyl 2,4-pentanediol. did. Then, a constant temperature and humidity test was conducted on the formed conductive film.
  • the wiring resistance of the conductive film before the constant temperature and humidity test was 4.8 ⁇ .
  • the wiring resistance after the constant temperature and humidity test was 9.6 ⁇ .
  • the resistance increase rate was 200%.
  • the conductive film was discolored only on the surface due to oxidation.
  • the concentration of the dispersant was 3% by weight, lower than in Example 11. Other conditions were the same as in Example 11.
  • the wiring resistance of the conductive film before the constant temperature and humidity test was 4.6 ⁇ .
  • the wiring resistance after the constant temperature and humidity test was 11.5 ⁇ .
  • the resistance increase rate was 250%.
  • the conductive film was discolored only on the surface due to oxidation.
  • Example 5 The concentration of the dispersant was 2% by weight, lower than in Example 12. Other conditions were the same as in Example 11.
  • the wiring resistance of the conductive film before the constant temperature and humidity test was 2.8 ⁇ .
  • the wiring resistance after the constant temperature and humidity test could not be measured.
  • the resistance increase rate was ⁇ . This conductive film could not withstand the constant temperature and humidity test.
  • the wiring resistance of the conductive film before the constant temperature and humidity test was 1.2 ⁇ .
  • the wiring resistance after the constant temperature and humidity test could not be measured.
  • the resistance increase rate was ⁇ . This conductive film could not withstand the constant temperature and humidity test.
  • the present invention is not limited to the configuration of the above-described embodiments, and various modifications can be made without changing the gist of the invention.
  • copper ink may be printed on a paper substrate using a printing method other than flexography.
  • the RF tag of the present invention is not limited to application to an RFID supply chain.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Dispersion Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Manufacturing & Machinery (AREA)
  • Inks, Pencil-Leads, Or Crayons (AREA)
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  • Manufacturing Of Electric Cables (AREA)

Abstract

In the present invention, a low-resistance conductive film is formed on a paper base material.　A copper ink according to the present invention comprises copper fine particles, a liquid dispersion medium, and a dispersant which disperses the copper fine particles in the dispersion medium. The copper fine particles are particles of copper having a median diameter of 60-110 nm. The concentration of copper fine particles is not less than 60 wt% with respect to the entirety of the copper ink. The dispersion medium contains an alcohol having a plurality of hydroxy groups. The dispersant is a polymer compound having a phosphate group, or a salt thereof. The concentration of the dispersant is 3-6 wt% with respect to the weight of the copper. The copper ink forms a conductive film of a paper base material via optical firing.

Description

銅インク、導電膜形成方法、及びＲＦタグCopper ink, conductive film forming method, and RF tag
　本発明は、導電膜を形成するための銅インク、その銅インクを用いた導電膜形成方法、及びその導電膜を有するＲＦタグに関する。 The present invention relates to a copper ink for forming a conductive film, a method for forming a conductive film using the copper ink, and an RF tag having the conductive film.
　製品タグ付けにＲＦＩＤ（radio frequency identification）のＲＦタグが用いられている（非特許文献１参照）。ＲＦＩＤは、電磁的結合を用いてＲＦタグのデータを読み取るシステムである。なお、非特許文献１の日本産業規格ＪＩＳ　Ｚ０６６７：２０１７「ＲＦＩＤのサプライチェーンへの適用－製品タグ付け」は、国際規格ＩＳＯ１７３６７：２０１３”Supply chain applications of RFID-Product tagging”に対応する。 RFID (radio frequency identification) RF tags are used for product tagging (see Non-Patent Document 1). RFID is a system that uses electromagnetic coupling to read data on RF tags. Note that the Japanese Industrial Standard JIS Z0667:2017 "Application of RFID to supply chain - Product tagging" in Non-Patent Document 1 corresponds to the international standard ISO17367:2013 "Supply chain applications of RFID-Product tagging".
　ＲＦタグは、ＰＥＴ（ポリエチレンテレフタラート）等の樹脂フィルムの上にアンテナ、配線、ＩＣチップを有する。そのアンテナ及び配線は、アルミ等の金属箔であり、樹脂フィルム上に形成される。ＲＦタグの製造は、金属箔をエッチングする工程を有し、エッチングで発生する廃液の処理にコストがかかる。さらに、最近、脱プラスチックが求められている。しかし、ＲＦタグの樹脂フィルムを紙基材に置き換えると、紙基材上の金属箔をエッチングできなくなる。 An RF tag has an antenna, wiring, and an IC chip on a resin film such as PET (polyethylene terephthalate). The antenna and wiring are made of metal foil such as aluminum, and are formed on a resin film. The manufacture of RF tags involves a process of etching metal foil, and processing of waste liquid generated during etching is costly. Furthermore, there has been a recent demand for a shift away from plastics. However, if the resin film of the RF tag is replaced with a paper base material, the metal foil on the paper base material cannot be etched.
　そこで、銅インクを用いてＲＦタグのアンテナ等を紙基材上に印刷することが考えられる。銅インクは、銅微粒子を含有し、焼成によって導電膜を形成する（例えば、特許文献１参照）。ＲＦタグの信号強度を上げるには、ＲＦタグのアンテナが低抵抗である必要がある。このため、銅インクを用いてアンテナを作るためには、銅インクの焼成によって厚く低体積抵抗率の導電膜を形成する必要がある。しかし、紙基材は、耐熱性が低いので、厚く低体積抵抗率の導電膜を焼成によって紙基材上に形成することは難しい。 Therefore, it is conceivable to print the antenna of the RF tag on the paper base material using copper ink. Copper ink contains copper fine particles and forms a conductive film by firing (see, for example, Patent Document 1). In order to increase the signal strength of the RF tag, the RF tag's antenna needs to have low resistance. Therefore, in order to make an antenna using copper ink, it is necessary to form a thick conductive film with low volume resistivity by firing the copper ink. However, since the paper base material has low heat resistance, it is difficult to form a thick conductive film with low volume resistivity on the paper base material by firing.
　また、紙基材に限らず、耐熱性が低い基材上に低抵抗の導電膜を形成することは困難である。 Furthermore, it is difficult to form a low-resistance conductive film on a substrate that has low heat resistance, not only a paper substrate.
特開２０２１－１５２１２５号公報JP 2021-152125 Publication
　本発明は、上記問題を解決するものであり、低抵抗の導電膜を紙基材上に形成することを目的とする。 The present invention solves the above problems, and aims to form a low-resistance conductive film on a paper base material.
　本発明の銅インクは、導電膜を形成するためのインクであって、銅微粒子と、液体の分散媒と、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６０ｎｍ以上かつ１１０ｎｍ以下の銅の粒子であり、前記銅微粒子の濃度は、銅インク全体に対して６０重量％以上であり、前記分散媒は、複数のヒドロキシ基を有するアルコールを含み、前記分散剤は、リン酸基を有する高分子化合物又はその塩であり、前記分散剤の濃度は、前記銅微粒子の重量に対して３重量％以上かつ６重量％以下であることを特徴とする。 The copper ink of the present invention is an ink for forming a conductive film, and includes copper fine particles, a liquid dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium, and the copper fine particles are copper particles having a median diameter of 60 nm or more and 110 nm or less, the concentration of the copper fine particles is 60% by weight or more based on the entire copper ink, and the dispersion medium contains an alcohol having a plurality of hydroxy groups. The dispersant is a polymer compound having a phosphoric acid group or a salt thereof, and the concentration of the dispersant is 3% by weight or more and 6% by weight or less based on the weight of the copper fine particles. shall be.
　この銅インクにおいて、前記分散媒は、２－メチル２，４－ペンタンジオール及び３－メチル１，３－ブタンジオールからなる群から選択されるアルコールを含むことが好ましい。 In this copper ink, the dispersion medium preferably contains an alcohol selected from the group consisting of 2-methyl 2,4-pentanediol and 3-methyl 1,3-butanediol.
　本発明の導電膜形成方法は、紙基材上に導電膜を形成する方法であって、前記の銅インクを用いてインク膜を紙基材上に形成する工程と、前記インク膜を乾燥して銅微粒子から成る塗布乾燥膜を前記紙基材上に形成する工程と、前記塗布乾燥膜を光焼成する工程とを有することを特徴とする。 The method for forming a conductive film of the present invention is a method for forming a conductive film on a paper base material, and includes a step of forming an ink film on a paper base material using the copper ink described above, and drying the ink film. The method is characterized by comprising the steps of: forming a coated dry film made of fine copper particles on the paper base material; and photo-baking the coated dry film.
　本発明のＲＦタグは、ＲＦＩＤのＲＦタグであって、少なくとも紙基材と、前記紙基材上のアンテナとを有し、前記アンテナは、前記の導電膜形成方法で形成された導電膜から成ることを特徴とする。 The RF tag of the present invention is an RFID RF tag, and includes at least a paper base material and an antenna on the paper base material, and the antenna is made of a conductive film formed by the above-described conductive film forming method. It is characterized by becoming.
　本発明の銅インクによれば、銅微粒子のメジアン径が６０ｎｍ以上であるので、光焼成により紙基材上に厚い導電膜を形成することができる。銅微粒子のメジアン径が１１０ｎｍ以下であるので、光焼成により紙基材上に低体積抵抗率の導電膜を形成することができる。銅微粒子の濃度が銅インク全体に対して６０重量％以上であるので、厚い導電膜を形成することができる。分散媒が複数のヒドロキシ基を有するアルコールを含むので、銅微粒子の表面との水素結合により、銅インクが紙基材への印刷に適した粘度及びレオロジー特性（チキソ性）になる。分散剤の濃度が銅重量に対して３重量％以上であるので、銅インクの安定性が良い。分散剤の濃度が６重量％以下であるので、低体積抵抗率の導電膜を形成することができる。形成される導電膜は、厚く、低体積抵抗率であるので、低抵抗となる。さらに、分散剤がリン酸基を有し、かつ、分散剤の濃度が３重量％以上であるので、リンが銅の酸化を防ぐことにより、恒温恒湿試験における導電膜の耐久性が向上する。 According to the copper ink of the present invention, since the median diameter of the copper fine particles is 60 nm or more, a thick conductive film can be formed on the paper base material by photo-baking. Since the median diameter of the copper fine particles is 110 nm or less, a conductive film with low volume resistivity can be formed on the paper base material by photo-baking. Since the concentration of copper fine particles is 60% by weight or more based on the entire copper ink, a thick conductive film can be formed. Since the dispersion medium contains an alcohol having a plurality of hydroxy groups, hydrogen bonding with the surface of the copper fine particles provides the copper ink with viscosity and rheological properties (thixotropy) suitable for printing on paper substrates. Since the concentration of the dispersant is 3% by weight or more based on the weight of copper, the stability of the copper ink is good. Since the concentration of the dispersant is 6% by weight or less, a conductive film with low volume resistivity can be formed. The conductive film formed is thick and has a low volume resistivity, so it has low resistance. Furthermore, since the dispersant has a phosphoric acid group and the concentration of the dispersant is 3% by weight or more, the durability of the conductive film in constant temperature and humidity tests is improved by preventing oxidation of copper by phosphorus. .
図１（ａ）（ｂ）（ｃ）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。FIGS. 1A, 1B, and 1C are cross-sectional configuration diagrams chronologically showing the formation of a conductive film using copper ink according to an embodiment of the present invention.
　本発明の一実施形態に係る銅インクについて説明する。銅インクは、導電膜を形成するために用いられる。銅インクは、銅微粒子と、液体の分散媒と、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。 A copper ink according to an embodiment of the present invention will be described. Copper ink is used to form the conductive film. The copper ink contains copper fine particles, a liquid dispersion medium, and a dispersant. The dispersant disperses copper fine particles in a dispersion medium.
　銅微粒子は、銅の粒子であり、メジアン径（Ｄ５０）が６０ｎｍ以上かつ１１０ｎｍ以下である。走査型電子顕微鏡による画像（ＳＥＭ画像）から銅微粒子の粒径が抽出され、その粒径分布からメジアン径が算出される。銅微粒子の粒子径が小さ過ぎると、形成される導電膜を厚くできない。粒子径が大き過ぎると、導電膜の体積抵抗率が高くなる。 The copper fine particles are copper particles and have a median diameter (D50) of 60 nm or more and 110 nm or less. The particle size of the copper fine particles is extracted from an image taken by a scanning electron microscope (SEM image), and the median diameter is calculated from the particle size distribution. If the particle size of the copper fine particles is too small, the formed conductive film cannot be made thick. If the particle size is too large, the volume resistivity of the conductive film will increase.
　銅微粒子の濃度は、銅インク全体に対して６０重量％以上である。銅微粒子の濃度が低過ぎると、形成される導電膜が薄くなる。銅微粒子の濃度は、７５重量％以下であることが望ましい。銅微粒子の濃度が高過ぎることによって銅インクの粘度が高くなると、印刷したインク膜の凹凸が低粘度の場合に比べて大きくなり、インク膜を乾燥して形成される塗布乾燥膜に５μｍより厚い部分が生じる。塗布乾燥膜の厚い部分は、表面と底部で光焼成時の焼結差が大きくなり、部分的に吹き飛ぶため、均一な導電膜を形成しない。 The concentration of copper fine particles is 60% by weight or more based on the entire copper ink. If the concentration of copper fine particles is too low, the conductive film formed will be thin. The concentration of copper fine particles is desirably 75% by weight or less. When the viscosity of the copper ink becomes high due to the concentration of copper fine particles being too high, the unevenness of the printed ink film becomes larger compared to when the viscosity is low, and the coated dry film formed by drying the ink film becomes thicker than 5 μm. Parts arise. In the thick part of the applied dry film, the difference in sintering between the surface and the bottom part during photo-baking becomes large, and parts of the film are blown off, so that a uniform conductive film is not formed.
　分散媒は、複数のヒドロキシ基を有するアルコールを含む。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、酸化銅から成る薄い表面酸化皮膜を形成する。銅インク中において、銅微粒子の表面酸化被膜の酸化銅の酸素原子と、アルコールのヒドロキシ基の水素原子との間に水素結合が生じる。このため、複数のヒドロキシ基を有するアルコールは、銅微粒子の分散性に優れる。 The dispersion medium contains an alcohol having multiple hydroxy groups. The outermost surface of the copper fine particles is oxidized by oxygen contained in the atmosphere, forming a thin surface oxide film made of copper oxide. In the copper ink, hydrogen bonds occur between the oxygen atoms of the copper oxide in the surface oxide film of the copper fine particles and the hydrogen atoms of the hydroxyl groups of the alcohol. Therefore, alcohol having multiple hydroxy groups has excellent dispersibility of copper fine particles.
　複数のヒドロキシ基を有するアルコールは、例えば、２－メチル２，４－ペンタンジオール（へキシレングリコール）、３－メチル１，３－ブタンジオール（イソプレングリコール）、１，２－エタンジオール（エチレングリコール）、プロパン－１，２－ジオール（プロピレングリコール）、１，５－ペンタンジオール、２，２‘－オキシジエタノール（ジエチレングリコール）、トリエチレングリコール、１，２，３－プロパントリオール（グリセリン）、ソルビトールであり、これらに限定されない。 Alcohols having multiple hydroxy groups include, for example, 2-methyl 2,4-pentanediol (hexylene glycol), 3-methyl 1,3-butanediol (isoprene glycol), and 1,2-ethanediol (ethylene glycol). , propane-1,2-diol (propylene glycol), 1,5-pentanediol, 2,2'-oxydiethanol (diethylene glycol), triethylene glycol, 1,2,3-propanetriol (glycerin), and sorbitol. , but not limited to.
　分散剤は、リン酸基を有する高分子化合物又はその塩である。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））。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。 The dispersant is a polymer compound having a phosphoric acid group or a salt thereof. A polymer is a molecule with a large molecular weight that has a structure made up of many repetitions of units that are derived substantially or conceptually from molecules with a small molecular weight (International Union of Pure and Applied Chemistry (IUPAC)). Since the surface of the copper fine particles is covered with dispersant molecules, they are dispersed in the dispersion medium.
　分散剤の濃度は、銅重量に対して３重量％以上かつ６重量％以下である。分散剤の濃度が低過ぎると、分散剤の分散性が不足し、銅インクの安定性が良くない。濃度が高過ぎると、形成される導電膜に分散剤残渣が残留し、導電膜の体積抵抗率が高くなる。 The concentration of the dispersant is 3% by weight or more and 6% by weight or less based on the weight of copper. If the concentration of the dispersant is too low, the dispersibility of the dispersant will be insufficient and the stability of the copper ink will be poor. If the concentration is too high, dispersant residue will remain in the conductive film to be formed, increasing the volume resistivity of the conductive film.
　分散剤がリン酸基を有し、かつ、その分散剤の濃度が３重量％以上の場合、形成される導電膜は、恒温恒湿試験における耐久性が向上する。これは、本願発明者による発見である。透過電子顕微鏡（ＴＥＭ）画像のエネルギー分散型Ｘ線分光法による分析では、形成された導電膜は、焼結された銅微粒子の周りにリンが残存している。そのリンが銅の酸化を防いでいる。 When the dispersant has a phosphoric acid group and the concentration of the dispersant is 3% by weight or more, the formed conductive film has improved durability in a constant temperature and humidity test. This is a discovery made by the inventor of the present application. Analysis of transmission electron microscopy (TEM) images by energy dispersive X-ray spectroscopy reveals that in the formed conductive film, phosphorus remains around the sintered copper fine particles. The phosphorus prevents copper from oxidizing.
　この銅インクを用いた導電膜形成方法を図１（ａ）～（ｃ）を参照して説明する。この導電膜形成方法は、紙基材上に導電膜を形成する方法である。図１（ａ）に示すように、銅インク１を用いてインク膜２が紙基材３上に形成される。インク膜２は、印刷法で形成される。印刷法では、銅インクが印刷用のインクとして用いられ、印刷装置によって紙基材３上に所定のパターンの銅インクが塗布され、そのパターンのインク膜２が形成される。本実施形態では、印刷方式は、フレキソ印刷である。そして、インク膜２が乾燥される。インク膜２の乾燥によって、図１（ｂ）に示すように、銅微粒子が紙基材３上に残り、銅微粒子から成る塗布乾燥膜４が紙基材３上に形成される。そして、銅微粒子から成る塗布乾燥膜４に光が照射され、塗布乾燥膜４が光焼成される。光焼成に用いられる光源は、例えば、キセノンランプである。光源にレーザー装置を用いてもよい。光のエネルギーによって、塗布乾燥膜４内の銅微粒子の表面酸化被膜が除去され、銅微粒子が互いに溶融してバルク化する。すなわち、図１（ｃ）に示すように、塗布乾燥膜４は、光焼成によって紙基材３上に導電膜５を形成する。なお、インク膜２の乾燥及び塗布乾燥膜４の光焼成を、光の照射によっていっぺんに行ってもよい。 A method of forming a conductive film using this copper ink will be explained with reference to FIGS. 1(a) to (c). This conductive film forming method is a method of forming a conductive film on a paper base material. As shown in FIG. 1(a), an ink film 2 is formed on a paper base material 3 using a copper ink 1. The ink film 2 is formed by a printing method. In the printing method, copper ink is used as the printing ink, and a printing device applies the copper ink in a predetermined pattern onto the paper base material 3 to form an ink film 2 in the pattern. In this embodiment, the printing method is flexographic printing. Then, the ink film 2 is dried. By drying the ink film 2, the copper fine particles remain on the paper base material 3, and a coated dry film 4 made of copper fine particles is formed on the paper base material 3, as shown in FIG. 1(b). Then, the coated dry film 4 made of fine copper particles is irradiated with light, and the coated dry film 4 is photo-sintered. The light source used for photo-baking is, for example, a xenon lamp. A laser device may be used as the light source. The surface oxide film of the copper fine particles in the applied dry film 4 is removed by the energy of the light, and the copper fine particles are melted together to form a bulk. That is, as shown in FIG. 1(c), the applied and dried film 4 forms a conductive film 5 on the paper base material 3 by photo-baking. Note that the drying of the ink film 2 and the photo-baking of the applied dry film 4 may be performed at the same time by irradiation with light.
　すなわち、この導電膜形成方法は、銅インク１を用いてインク膜２を紙基材３上に形成する工程と、インク膜２を乾燥して銅微粒子から成る塗布乾燥膜４を紙基材３上に形成する工程と、塗布乾燥膜４を光焼成する工程とを有する。 That is, this conductive film forming method includes a step of forming an ink film 2 on a paper base material 3 using a copper ink 1, and a step of drying the ink film 2 to form a coated dry film 4 made of fine copper particles on the paper base material 3. and a step of photo-baking the applied dry film 4.
　例えば、本実施形態よりも小粒径のメジアン径４０ｎｍの銅微粒子を有する銅インクを用いると、低体積抵抗率の導電膜を形成することができるが、導電膜を厚くすることができない。小粒径の銅微粒子を有する銅インクを用いて厚さ２μｍ以上の塗布乾燥膜を形成しようとすると、塗布乾燥膜にクラックが入るからである。そのクラックの原因は、銅微の粒径が小さいとインク膜の乾燥時の体積収縮率が大きくなること、及び、小粒径の銅微粒子によってパッキングされて分散媒がガスとして抜ける経路（パス）が無くなることである。本願の発明者は、数多くの実験を行い、メジアン径６０ｎｍ～１１０ｎｍの銅微粒子が紙基材上の導電膜の形成に好適であることを見出した。 For example, if a copper ink having copper fine particles with a median diameter of 40 nm, which is smaller than that of this embodiment, is used, a conductive film with a low volume resistivity can be formed, but the conductive film cannot be thickened. This is because if an attempt is made to form a coated dry film with a thickness of 2 μm or more using a copper ink having small copper particles, cracks will occur in the coated dry film. The cause of the cracks is that if the particle size of the copper particles is small, the volumetric shrinkage rate when the ink film dries becomes large, and the path through which the dispersion medium is packed by the small copper particles and escapes as gas. is to disappear. The inventor of the present application conducted numerous experiments and found that copper fine particles having a median diameter of 60 nm to 110 nm are suitable for forming a conductive film on a paper base material.
　しかし、銅微粒子の粒径を大きくすると、銅インクの粘度が低下する。それにより、フレキソ印刷で銅インクのぬれ広がりやだれることが発生したため、銅インクを増粘する必要が生じた。一般的に、インクは、樹脂やレオロジーコントロール剤などの添加剤で増粘する。しかし、有機物の添加剤は、その残渣が抵抗になって、導電膜の体積抵抗率を高くするので、銅インクに添加することは避けたい。銅微粒子の表面酸化被膜の酸化銅の酸素原子と、分散媒の複数のヒドロキシ基の水素原子との間の水素結合相互作用を利用することにより、紙基材への印刷に適した粘度を有する銅インクができることを本願の発明者が発見した。分散媒が一価アルコールであると、銅インクの粘度が不足する。 However, when the particle size of the copper fine particles is increased, the viscosity of the copper ink decreases. This caused the copper ink to spread and sag during flexographic printing, making it necessary to increase the viscosity of the copper ink. Generally, inks are thickened with additives such as resins and rheology control agents. However, it is desirable to avoid adding organic additives to the copper ink because their residue becomes resistive and increases the volume resistivity of the conductive film. It has a viscosity suitable for printing on paper base materials by utilizing the hydrogen bond interaction between the oxygen atoms of the copper oxide in the surface oxide film of the copper particles and the hydrogen atoms of multiple hydroxy groups in the dispersion medium. The inventor of the present application has discovered that copper ink can be produced. If the dispersion medium is a monohydric alcohol, the viscosity of the copper ink will be insufficient.
　以上、本実施形態の銅インクによれば、銅微粒子のメジアン径が６０ｎｍ以上であるので、光焼成により紙基材上に厚い導電膜を形成することができる。銅微粒子のメジアン径が１１０ｎｍ以下であるので、光焼成により紙基材上に低体積抵抗率の導電膜を形成することができる。銅微粒子の濃度が銅インク全体に対して６０重量％以上であるので、厚い導電膜を形成することができる。分散媒が複数のヒドロキシ基を有するアルコールを含むので、銅微粒子の表面との水素結合により、銅インクが紙基材への印刷に適した粘度及びレオロジー特性（チキソ性）になる。分散剤の濃度が銅重量に対して３重量％以上であるので、銅インクの安定性が良い。分散剤の濃度が６重量％以下であるので、低体積抵抗率の導電膜を形成することができる。形成される導電膜は、厚く、低体積抵抗率であるので、低抵抗となる。さらに、分散剤がリン酸基を有し、かつ、分散剤の濃度が３重量％以上であるので、リンが銅の酸化を防ぐことにより、恒温恒湿試験における導電膜の耐久性が向上する。 As described above, according to the copper ink of this embodiment, since the median diameter of the copper fine particles is 60 nm or more, a thick conductive film can be formed on the paper base material by photo-baking. Since the median diameter of the copper fine particles is 110 nm or less, a conductive film with low volume resistivity can be formed on the paper base material by photo-baking. Since the concentration of copper fine particles is 60% by weight or more based on the entire copper ink, a thick conductive film can be formed. Since the dispersion medium contains an alcohol having a plurality of hydroxy groups, hydrogen bonding with the surface of the copper fine particles provides the copper ink with viscosity and rheological properties (thixotropy) suitable for printing on paper substrates. Since the concentration of the dispersant is 3% by weight or more based on the weight of copper, the stability of the copper ink is good. Since the concentration of the dispersant is 6% by weight or less, a conductive film with low volume resistivity can be formed. The conductive film formed is thick and has a low volume resistivity, so it has low resistance. Furthermore, since the dispersant has a phosphoric acid group and the concentration of the dispersant is 3% by weight or more, the durability of the conductive film in constant temperature and humidity tests is improved by preventing oxidation of copper by phosphorus. .
　本実施形態の銅インクを用いることにより、紙基材上に１～５μｍの厚さの塗布乾燥膜を形成することができ、その紙基材上に約１～２μｍ（０．７～１．８μｍ）の厚さの導電膜を形成することができる。形成される導電膜が厚く、低体積抵抗率を有するので、その導電膜は低抵抗である。 By using the copper ink of this embodiment, a coated and dried film with a thickness of 1 to 5 μm can be formed on a paper base material, and a coated and dried film with a thickness of about 1 to 2 μm (0.7 to 1.5 μm) can be formed on the paper base material. A conductive film with a thickness of 8 μm) can be formed. Since the conductive film formed is thick and has a low volume resistivity, the conductive film has low resistance.
　この銅インクを用いて、紙基材を有するＲＦタグを作ることができる。図１（ｃ）を流用してそのＲＦタグについて説明する。ＲＦタグ６は、ＲＦＩＤのＲＦタグである。本実施形態のＲＦタグ６は、少なくとも紙基材３と、紙基材３上のアンテナとを有する。アンテナは、本実施形態の導電膜形成方法で形成された導電膜５から成る。 This copper ink can be used to make an RF tag with a paper base. The RF tag will be explained using FIG. 1(c). The RF tag 6 is an RFID RF tag. The RF tag 6 of this embodiment includes at least a paper base material 3 and an antenna on the paper base material 3. The antenna is made of a conductive film 5 formed by the conductive film forming method of this embodiment.
　このＲＦタグ６は、基材が紙であるので、環境にやさしい。ＲＦタグ６のアンテナは、本実施形態の導電膜形成方法で形成された導電膜５から成る。その導電膜が厚く、低体積抵抗率を有するので、アンテナが低抵抗になる。このＲＦタグ６は、アンテナが低抵抗であるので、十分な信号強度が得られる。 Since the base material of this RF tag 6 is paper, it is environmentally friendly. The antenna of the RF tag 6 is made of the conductive film 5 formed by the conductive film forming method of this embodiment. The conductive film is thick and has a low volume resistivity, resulting in a low resistance antenna. Since this RF tag 6 has a low resistance antenna, sufficient signal strength can be obtained.
　なお、ＲＦタグ６をラミネート加工してもよい。なお、ＲＦタグのラミネートの例が、日本産業規格に記載されている（非特許文献１参照）。 Note that the RF tag 6 may be laminated. Note that an example of laminating an RF tag is described in the Japanese Industrial Standards (see Non-Patent Document 1).
　本発明の実施例としての銅インク、及び比較例としての銅インクを作り、その銅インクを用いて紙基材上に導電膜を形成する実験を行った。 A copper ink as an example of the present invention and a copper ink as a comparative example were prepared, and an experiment was conducted to form a conductive film on a paper base material using the copper ink.
　共通の実験条件を説明する。紙基材として、コート紙（王子製紙株式会社（Oji PaperCo., Ltd.）製、商品名「ＯＫトップコート＋ＥＦ」（「トップコート」「TOPKOTE」は登録商標）を用いた。銅インクを用いて、フレキソ印刷にて配線テストパターン（０．６ｍｍ幅のライン）を紙基材上に印刷した。印刷したインク膜は、２～５μｍ厚であった。インク膜を乾燥し、塗布乾燥膜を形成した。フラッシュランプにて４Ｊ／ｃｍ２のエネルギーで塗布乾燥膜を光焼成した。形成された導電膜（ライン）の測定長３７．８ｍｍの抵抗（配線抵抗）をテスタで測定した。また、レーザー顕微鏡にて導電膜（ライン）の断面積を計測した。そして、抵抗値と断面積等から導電膜の体積抵抗率及び平均厚みを算出した。フレキソ印刷では、銅インクは、版から紙基材に完全には転写されず、版と紙基材にランダムに***する。このため、形成される導電膜の断面形状は、通常平滑でなく、凹凸を有する。導電膜の平均厚みは、その凹凸を平均化した厚み、すなわち長方形の厚みである。形成した導電膜（ライン）をその配線抵抗で評価した。 Describe common experimental conditions. Coated paper (manufactured by Oji Paper Co., Ltd., product name "OK Top Coat + EF"("TopCoat" and "TOPKOTE" are registered trademarks) was used as the paper base material. Copper ink was used. Then, a wiring test pattern (0.6 mm wide line) was printed on the paper base material using flexo printing.The printed ink film was 2 to 5 μm thick.The ink film was dried, and the coated dry film was The coated and dried film was photo-baked using a flash lamp with an energy of 4 J/cm 2 .The resistance (wiring resistance) of the formed conductive film (line) with a measurement length of 37.8 mm was measured using a tester. The cross-sectional area of the conductive film (line) was measured using a laser microscope.Then, the volume resistivity and average thickness of the conductive film were calculated from the resistance value, cross-sectional area, etc.In flexographic printing, copper ink is transferred from the plate to the paper base. The conductive film is not completely transferred to the material and is randomly split between the plate and the paper base material.For this reason, the cross-sectional shape of the conductive film that is formed is usually not smooth but has irregularities.The average thickness of the conductive film is The thickness is the average thickness of the unevenness, that is, the thickness of the rectangle.The formed conductive film (line) was evaluated by its wiring resistance.
　実施例における銅インクの組成範囲について説明する。銅微粒子の粒径（メジアン径）は、６０～１１０ｎｍとした。銅インクの３万倍のＳＥＭ画像から無作為に抽出した１００個以上の銅微粒子の粒径頻度分布からメジアン径（Ｄ５０）を算出した。銅微粒子の濃度は、銅インク全体に対して（以下、銅微粒子の重量％において同様）６０～７５重量％とした。分散剤は、リン酸基を有するものとした。分散媒の濃度は、銅重量に対して（以下、分散剤の重量％において同様）３～６重量％とした。分散媒は、複数のヒドロキシ基を有するアルコールとした。分散媒の量は、銅インクにおける残部である。 The composition range of the copper ink in Examples will be explained. The particle size (median diameter) of the copper fine particles was set to 60 to 110 nm. The median diameter (D50) was calculated from the particle size frequency distribution of 100 or more fine copper particles randomly extracted from a 30,000 times magnified SEM image of the copper ink. The concentration of the copper fine particles was 60 to 75% by weight (hereinafter the same applies to the weight percentage of the copper fine particles) based on the entire copper ink. The dispersant had a phosphoric acid group. The concentration of the dispersion medium was 3 to 6% by weight based on the weight of copper (hereinafter the same applies to the weight% of the dispersant). The dispersion medium was an alcohol having multiple hydroxy groups. The amount of dispersion medium is the balance in the copper ink.
　銅インクの組成を変えて、光焼成によって形成された導電膜（光焼成膜）を評価した。なお、前述したように、導電膜の断面積と配線抵抗は実測値であり、平均厚みと体積抵抗率は計算値である。 Conductive films formed by photo-baking (photo-baked films) were evaluated by changing the composition of the copper ink. Note that, as described above, the cross-sectional area and wiring resistance of the conductive film are actually measured values, and the average thickness and volume resistivity are calculated values.
　メジアン径８０ｎｍの銅微粒子を銅インクに用いた（実施例２～６及び比較例１、３において同じ）。銅微粒子の濃度は７５重量％とした。分散剤として高分子リン酸エステル（ビックケミー社（BYK-Chemie）製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－１０２」）を用いた。この分散剤は、リン酸基を有する高分子化合物である。分散剤の濃度は４重量％とした。分散媒として、２－メチル２，４－ペンタンジオール（二価アルコール）を用いた。 Copper fine particles with a median diameter of 80 nm were used in the copper ink (same in Examples 2 to 6 and Comparative Examples 1 and 3). The concentration of copper fine particles was 75% by weight. A polymeric phosphate ester (manufactured by BYK-Chemie, trade name "DISPERBYK (registered trademark)-102") was used as a dispersant. This dispersant is a polymer compound having a phosphoric acid group. The concentration of the dispersant was 4% by weight. 2-methyl 2,4-pentanediol (dihydric alcohol) was used as a dispersion medium.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは１．８μｍであった。体積抵抗率は５．２μΩｃｍであった。断面積は１１００μｍ２であった。線幅は６００μｍであった。配線抵抗は１．８Ωであった。この配線抵抗は、実施例の中で一番低かった。 The formed conductive film had no cracks. The average thickness of the conductive film was 1.8 μm. The volume resistivity was 5.2 μΩcm. The cross-sectional area was 1100 μm2 . The line width was 600 μm. The wiring resistance was 1.8Ω. This wiring resistance was the lowest among the examples.
　銅インクにおいて、銅微粒子の濃度は、実施例１より低い７０重量％とした。分散剤の濃度は、実施例１より低い３重量％とした。それ以外の条件は、実施例１と同じにした。 In the copper ink, the concentration of copper fine particles was 70% by weight, lower than in Example 1. The concentration of the dispersant was 3% by weight, lower than in Example 1. Other conditions were the same as in Example 1.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例１より薄い１．３μｍであった。体積抵抗率は、実施例１より低い５．１μΩｃｍであった。断面積は８００μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例１より高い２．４Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 1.3 μm, which was thinner than in Example 1. The volume resistivity was 5.1 μΩcm, lower than in Example 1. The cross-sectional area was 800 μm2 . The line width was 600 μm. The wiring resistance was 2.4Ω, higher than in Example 1.
　銅微粒子の濃度が実施例１より低かったため、導電膜の平均厚みが薄くなり、配線抵抗が高くなった。分散剤の濃度が実施例１より低かったため、導電膜の体積抵抗率が低くなったが、配線抵抗に対して銅微粒子の濃度の影響が大きかった。 Since the concentration of copper fine particles was lower than in Example 1, the average thickness of the conductive film was thinner and the wiring resistance was higher. Since the concentration of the dispersant was lower than in Example 1, the volume resistivity of the conductive film was lower, but the concentration of copper fine particles had a large influence on the wiring resistance.
　銅微粒子の濃度は、実施例２よりさらに低い６０重量％とした。それ以外の条件は、実施例２と同じにした。 The concentration of copper fine particles was set to 60% by weight, which is even lower than in Example 2. Other conditions were the same as in Example 2.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例２より薄い０．７μｍであった。体積抵抗率は、実施例１と同じ５．１μΩｃｍであった。断面積は４２０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例２より高い４．６Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 0.7 μm, which was thinner than in Example 2. The volume resistivity was 5.1 μΩcm, the same as in Example 1. The cross-sectional area was 420 μm2 . The line width was 600 μm. The wiring resistance was 4.6Ω, higher than in Example 2.
　銅微粒子の濃度が実施例２より低かったため、導電膜の平均厚みが薄くなり、配線抵抗が高くなった。 Since the concentration of copper fine particles was lower than in Example 2, the average thickness of the conductive film was thinner and the wiring resistance was higher.
　分散剤として高分子リン酸エステル（ビックケミー（BYK-Chemie）社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－１１１」）を用いた。この分散剤は、リン酸基を有する高分子化合物である。分散剤の濃度は、実施例３より高い４重量％とした。それ以外の条件は、実施例３と同じにした。 A polymeric phosphate ester (manufactured by BYK-Chemie, trade name "DISPERBYK (registered trademark)-111") was used as a dispersant. This dispersant is a polymer compound having a phosphoric acid group. The concentration of the dispersant was 4% by weight, which is higher than in Example 3. Other conditions were the same as in Example 3.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例３と同じ０．７μｍであった。体積抵抗率は、実施例３より高い５．３μΩｃｍであった。断面積は４２０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例３より高い４．８Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 0.7 μm, the same as in Example 3. The volume resistivity was 5.3 μΩcm, higher than that of Example 3. The cross-sectional area was 420 μm2 . The line width was 600 μm. The wiring resistance was 4.8Ω, higher than in Example 3.
　分散剤の濃度が実施例３より高かったため、導電膜の体積抵抗率が高くなり、配線抵抗が高くなった。 Since the concentration of the dispersant was higher than in Example 3, the volume resistivity of the conductive film was high, and the wiring resistance was high.
　分散剤として、酸基を有する共重合物のアルキロールアンモニウム塩（ビックケミー（BYK-Chemie）社製、商品名「ＤＩＳＰＥＲＢＹＫ（登録商標）－１８０」）を用いた。この分散剤は、リン酸基を有する高分子化合物の塩である。それ以外の条件は、実施例４と同じにした。 As a dispersant, an alkylol ammonium salt of a copolymer having an acid group (manufactured by BYK-Chemie, trade name "DISPERBYK (registered trademark)-180") was used. This dispersant is a salt of a polymer compound having a phosphoric acid group. Other conditions were the same as in Example 4.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例４より厚い０．８μｍであった。体積抵抗率は、実施例４より高い５．６μΩｃｍであった。断面積は４５０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例４より若干低い４．７Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 0.8 μm, which was thicker than in Example 4. The volume resistivity was 5.6 μΩcm, higher than that of Example 4. The cross-sectional area was 450 μm2 . The line width was 600 μm. The wiring resistance was 4.7Ω, which was slightly lower than in Example 4.
　本発明の銅インクにおいて、分散剤は、リン酸基を有する高分子化合物の塩であってもよいことがわかった。 It has been found that in the copper ink of the present invention, the dispersant may be a salt of a polymer compound having a phosphoric acid group.
　実施例１～３と同じ分散剤を用いた。分散媒として、３－メチル１，３－ブタンジオール（二価アルコール）を用いた。それ以外の条件は、実施例５と同じにした。 The same dispersant as in Examples 1 to 3 was used. 3-methyl 1,3-butanediol (dihydric alcohol) was used as a dispersion medium. Other conditions were the same as in Example 5.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例５と同じ０．８μｍであった。体積抵抗率は、実施例５より低い５．４μΩｃｍであった。断面積は４５０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例５より若干低い４．５Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 0.8 μm, the same as in Example 5. The volume resistivity was 5.4 μΩcm, lower than that of Example 5. The cross-sectional area was 450 μm2 . The line width was 600 μm. The wiring resistance was 4.5Ω, which was slightly lower than in Example 5.
　実施例６における分散媒は、実施例１～５と同様に、複数のヒドロキシ基を有する。実施例６における分散媒は、実施例１～５における分散媒とは炭素骨格が異なるが、本発明の銅インクに用いることができた。 The dispersion medium in Example 6 has a plurality of hydroxy groups as in Examples 1 to 5. Although the dispersion medium in Example 6 had a different carbon skeleton from the dispersion medium in Examples 1 to 5, it could be used in the copper ink of the present invention.
　実施例２より大きいメジアン径１１０ｎｍの銅微粒子を銅インクに用いた。分散剤の濃度は、４重量％とした。それ以外の条件は、実施例２と同じにした。 Copper fine particles with a median diameter of 110 nm, which was larger than that in Example 2, were used in the copper ink. The concentration of the dispersant was 4% by weight. Other conditions were the same as in Example 2.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例２より厚い１．５μｍであった。体積抵抗率は、実施例２より高い７．１μΩｃｍであった。断面積は９００μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例２より高い３．０Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 1.5 μm, which was thicker than in Example 2. The volume resistivity was 7.1 μΩcm, higher than that of Example 2. The cross-sectional area was 900 μm2 . The line width was 600 μm. The wiring resistance was 3.0Ω, higher than in Example 2.
　銅微粒子のメジアン径が実施例２より大きかったため、導電膜の平均厚みが厚くなり、導電膜の体積抵抗率が高くなった。 Since the median diameter of the copper fine particles was larger than in Example 2, the average thickness of the conductive film was thicker, and the volume resistivity of the conductive film was higher.
　銅微粒子の濃度は、実施例７より低い６０重量％とした。それ以外の条件は、実施例７と同じにした。 The concentration of copper fine particles was set to 60% by weight, lower than in Example 7. Other conditions were the same as in Example 7.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例７より薄い１．１μｍであった。体積抵抗率は、実施例２より低い６．９μΩｃｍであった。断面積は６５０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例７より高い４．０Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 1.1 μm, which was thinner than in Example 7. The volume resistivity was 6.9 μΩcm, lower than that of Example 2. The cross-sectional area was 650 μm2 . The line width was 600 μm. The wiring resistance was 4.0Ω, higher than in Example 7.
　銅微粒子の濃度が実施例７より低かったため、導電膜の平均厚みが薄くなり、配線抵抗が高くなった。 Since the concentration of copper fine particles was lower than in Example 7, the average thickness of the conductive film was thinner and the wiring resistance was higher.
　実施例１～８より小さいメジアン径６０ｎｍの銅微粒子を銅インクに用いた。メジアン径４０ｎｍの銅微粒子とメジアン径８０ｎｍの銅微粒子を１：１の重量比で混合することによってメジアン径６０ｎｍの銅微粒子とした。分散剤の濃度は、実施例８より高い６重量％とした。それ以外の条件は、実施例８と同じにした。 Copper fine particles with a median diameter of 60 nm, smaller than those in Examples 1 to 8, were used in the copper ink. Copper fine particles with a median diameter of 40 nm and copper fine particles with a median diameter of 80 nm were mixed at a weight ratio of 1:1 to obtain copper fine particles with a median diameter of 60 nm. The concentration of the dispersant was 6% by weight, which is higher than in Example 8. Other conditions were the same as in Example 8.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例８より薄い０．８μｍであった。体積抵抗率は、実施例８より低い５．０μΩｃｍであった。断面積は４５０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例８より高い４．２Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 0.8 μm, which was thinner than in Example 8. The volume resistivity was 5.0 μΩcm, lower than that of Example 8. The cross-sectional area was 450 μm2 . The line width was 600 μm. The wiring resistance was 4.2Ω, higher than in Example 8.
　銅微粒子のメジアン径が実施例１～８より小さかったため、導電膜の体積抵抗率が実施例１～８より低くなった。 Since the median diameter of the copper fine particles was smaller than in Examples 1 to 8, the volume resistivity of the conductive film was lower than in Examples 1 to 8.
　実施例８（１１０ｎｍ）より小さいメジアン径１００ｎｍの銅微粒子を銅インクに用いた。メジアン径４０ｎｍの銅微粒子とメジアン径１１０ｎｍの銅微粒子を１：４の重量比で混合することによってメジアン径１００ｎｍの銅微粒子とした。それ以外の条件は、実施例８と同じにした。 Copper fine particles with a median diameter of 100 nm, smaller than Example 8 (110 nm), were used in the copper ink. Copper fine particles with a median diameter of 40 nm and copper fine particles with a median diameter of 110 nm were mixed at a weight ratio of 1:4 to obtain copper fine particles with a median diameter of 100 nm. Other conditions were the same as in Example 8.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例８より若干厚い１．２μｍであった。体積抵抗率は、実施例８より低い６．１μΩｃｍであった。断面積は４５０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例８より低い３．３Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 1.2 μm, which was slightly thicker than in Example 8. The volume resistivity was 6.1 μΩcm, lower than that of Example 8. The cross-sectional area was 450 μm2 . The line width was 600 μm. The wiring resistance was 3.3Ω, lower than in Example 8.
　銅微粒子のメジアン径が実施例８より小さかったため、導電膜の体積抵抗率が実施例８より低くなった。 Since the median diameter of the copper fine particles was smaller than in Example 8, the volume resistivity of the conductive film was lower than in Example 8.
　実施例１～１０の銅インクを用いて形成された導電膜（線幅６００μｍ、長さ３７．８ｍｍ）は、１．８Ω～４．８Ωの範囲の電気抵抗を有し、ＲＦタグのアンテナに適した低抵抗（１０Ω未満）であった。 The conductive films (line width 600 μm, length 37.8 mm) formed using the copper inks of Examples 1 to 10 have electrical resistances in the range of 1.8 Ω to 4.8 Ω, and are suitable for RF tag antennas. It had suitably low resistance (less than 10Ω).
（比較例１）
　銅微粒子の濃度は、実施例１～１０より低い４０重量％とした。それ以外の条件は、実施例１と同じにした。 (Comparative example 1)
The concentration of copper fine particles was set to 40% by weight, lower than in Examples 1 to 10. Other conditions were the same as in Example 1.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは、実施例１～１０より薄い０．３μｍであった。体積抵抗率は５．７μΩｃｍであった。断面積は２００μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例１～１０より高い１０．８Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 0.3 μm, which was thinner than in Examples 1 to 10. The volume resistivity was 5.7 μΩcm. The cross-sectional area was 200 μm2 . The line width was 600 μm. The wiring resistance was 10.8Ω, higher than Examples 1 to 10.
　銅微粒子の濃度が低過ぎたため、導電膜の平均厚みが薄くなり、配線抵抗が高くなった。 Because the concentration of copper fine particles was too low, the average thickness of the conductive film became thin and the wiring resistance increased.
（比較例２）
　実施例１～１０より小さいメジアン径４０ｎｍの銅微粒子を銅インクに用いた。それ以外の条件は、実施例３と同じにした。 (Comparative example 2)
Copper fine particles with a median diameter of 40 nm, which is smaller than those in Examples 1 to 10, were used in the copper ink. Other conditions were the same as in Example 3.
　形成された導電膜は、クラックがあった。配線は、断線していた。 The formed conductive film had cracks. The wiring was broken.
　銅微粒子のメジアン径が小さ過ぎたため、導電膜にクラックが入った。 Because the median diameter of the copper particles was too small, cracks appeared in the conductive film.
（比較例３）
　分散剤の濃度は、実施例１～１０より高い８重量％とした。それ以外の条件は、実施例３と同じにした。 (Comparative example 3)
The concentration of the dispersant was 8% by weight, which is higher than in Examples 1-10. Other conditions were the same as in Example 3.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは０．６μｍであった。体積抵抗率は、実施例１～１０より高い１０．１μΩｃｍであった。断面積は３８０μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例１～１０より高い１０．０Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 0.6 μm. The volume resistivity was 10.1 μΩcm, higher than Examples 1 to 10. The cross-sectional area was 380 μm2 . The line width was 600 μm. The wiring resistance was 10.0Ω, higher than in Examples 1 to 10.
　分散剤の濃度が高過ぎたため、導電膜の体積抵抗率が高くなり、配線抵抗が高くなった。 Because the concentration of the dispersant was too high, the volume resistivity of the conductive film increased and the wiring resistance increased.
（比較例４）
　実施例１～１０より大きいメジアン径１５０ｎｍの銅微粒子を銅インクに用いた。それ以外の条件は、実施例３と同じにした。 (Comparative example 4)
Copper fine particles with a median diameter of 150 nm, which is larger than those in Examples 1 to 10, were used in the copper ink. Other conditions were the same as in Example 3.
　形成された導電膜は、クラックが無かった。導電膜の平均厚みは１．７μｍであった。体積抵抗率は、実施例１～１０より高い３１．７μΩｃｍであった。断面積は１０００μｍ２であった。線幅は６００μｍであった。配線抵抗は実施例１～１０より高い１２．０Ωであった。 The formed conductive film had no cracks. The average thickness of the conductive film was 1.7 μm. The volume resistivity was 31.7 μΩcm, higher than Examples 1 to 10. The cross-sectional area was 1000 μm2 . The line width was 600 μm. The wiring resistance was 12.0Ω, higher than Examples 1 to 10.
　銅微粒子のメジアン径が大き過ぎたため、導電膜の体積抵抗率が高くなり、配線抵抗が高くなった。 Because the median diameter of the copper fine particles was too large, the volume resistivity of the conductive film became high and the wiring resistance became high.
　比較例１～４の銅インクを用いて形成された導電膜（線幅６００μｍ、長さ３７．８ｍｍ）は、断線またはＲＦタグのアンテナに適さない高抵抗（１０Ω以上）であった。 The conductive films (line width 600 μm, length 37.8 mm) formed using the copper inks of Comparative Examples 1 to 4 were disconnected or had high resistance (10Ω or more) unsuitable for RF tag antennas.
　上述した実施例と同様に導電膜（ライン）を紙基材上に形成し、恒温恒湿試験の前後で配線抵抗を測定した。恒温恒湿試験の温度は８５℃、湿度は８５％、保持時間は２６４時間とした。 A conductive film (line) was formed on a paper base material in the same manner as in the above example, and the wiring resistance was measured before and after a constant temperature and humidity test. The temperature of the constant temperature and humidity test was 85° C., the humidity was 85%, and the holding time was 264 hours.
　実施例４と同じ銅インクを用いて導電膜を形成した。すなわち、銅微粒子のメジアン径は８０ｎｍ、銅微粒子の濃度は６０重量％、分散剤は高分子リン酸エステル、分散剤の濃度は４重量％、分散媒は２－メチル２，４－ペンタンジオールとした。そして、形成した導電膜について恒温恒湿試験を行った。 A conductive film was formed using the same copper ink as in Example 4. That is, the median diameter of the copper fine particles is 80 nm, the concentration of the copper fine particles is 60% by weight, the dispersant is a polymeric phosphate ester, the concentration of the dispersant is 4% by weight, and the dispersion medium is 2-methyl 2,4-pentanediol. did. Then, a constant temperature and humidity test was conducted on the formed conductive film.
　恒温恒湿試験前の導電膜の配線抵抗は４．８Ωであった。恒温恒湿試験後の配線抵抗は９．６Ωであった。抵抗上昇率は２００％であった。導電膜は、表面のみ酸化によって変色した。 The wiring resistance of the conductive film before the constant temperature and humidity test was 4.8Ω. The wiring resistance after the constant temperature and humidity test was 9.6Ω. The resistance increase rate was 200%. The conductive film was discolored only on the surface due to oxidation.
　分散剤の濃度は、実施例１１より低い３重量％とした。それ以外の条件は、実施例１１と同じにした。 The concentration of the dispersant was 3% by weight, lower than in Example 11. Other conditions were the same as in Example 11.
　恒温恒湿試験前の導電膜の配線抵抗は４．６Ωであった。恒温恒湿試験後の配線抵抗は１１．５Ωであった。抵抗上昇率は２５０％であった。導電膜は、表面のみ酸化によって変色した。 The wiring resistance of the conductive film before the constant temperature and humidity test was 4.6Ω. The wiring resistance after the constant temperature and humidity test was 11.5Ω. The resistance increase rate was 250%. The conductive film was discolored only on the surface due to oxidation.
（比較例５）
　分散剤の濃度は、実施例１２より低い２重量％とした。それ以外の条件は、実施例１１と同じにした。 (Comparative example 5)
The concentration of the dispersant was 2% by weight, lower than in Example 12. Other conditions were the same as in Example 11.
　恒温恒湿試験前の導電膜の配線抵抗は２．８Ωであった。恒温恒湿試験後の配線抵抗は測定不可であった。抵抗上昇率は∞であった。この導電膜は、恒温恒湿試験に耐えられなかった。 The wiring resistance of the conductive film before the constant temperature and humidity test was 2.8Ω. The wiring resistance after the constant temperature and humidity test could not be measured. The resistance increase rate was ∞. This conductive film could not withstand the constant temperature and humidity test.
（比較例６）
　分散剤の濃度は、比較例５より低い０．５重量％とした。それ以外の条件は、実施例１１と同じにした。 (Comparative example 6)
The concentration of the dispersant was 0.5% by weight, which is lower than that of Comparative Example 5. Other conditions were the same as in Example 11.
　恒温恒湿試験前の導電膜の配線抵抗は１．２Ωであった。恒温恒湿試験後の配線抵抗は測定不可であった。抵抗上昇率は∞であった。この導電膜は、恒温恒湿試験に耐えられなかった。 The wiring resistance of the conductive film before the constant temperature and humidity test was 1.2Ω. The wiring resistance after the constant temperature and humidity test could not be measured. The resistance increase rate was ∞. This conductive film could not withstand the constant temperature and humidity test.
　実施例１１、１２、及び比較例５、６によれば、銅インクの分散剤がリン酸基を有し、かつ、その分散剤の濃度が一定以上（３重量％以上）の場合、恒温恒湿試験における導電膜の耐久性が向上した。 According to Examples 11 and 12 and Comparative Examples 5 and 6, when the dispersant of the copper ink has a phosphoric acid group and the concentration of the dispersant is above a certain level (3% by weight or above), constant temperature The durability of the conductive film in wet tests has been improved.
　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、銅インクをフレキソ印刷以外の印刷方式で紙基材上に印刷してもよい。また、本発明のＲＦタグは、ＲＦＩＤのサプライチェーンへの適用に限定されない。 Note that the present invention is not limited to the configuration of the above-described embodiments, and various modifications can be made without changing the gist of the invention. For example, copper ink may be printed on a paper substrate using a printing method other than flexography. Further, the RF tag of the present invention is not limited to application to an RFID supply chain.
１　銅インク
２　インク膜
３　紙基材
４　塗布乾燥膜
５　導電膜
６　ＲＦタグ 1 Copper ink 2 Ink film 3 Paper base material 4 Coated dry film 5 Conductive film 6 RF tag

Claims (4)

  1. 　導電膜を形成するための銅インクであって、
    　銅微粒子と、液体の分散媒と、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６０ｎｍ以上かつ１１０ｎｍ以下の銅の粒子であり、
    　前記銅微粒子の濃度は、銅インク全体に対して６０重量％以上であり、
    　前記分散媒は、複数のヒドロキシ基を有するアルコールを含み、
    　前記分散剤は、リン酸基を有する高分子化合物又はその塩であり、
    　前記分散剤の濃度は、前記銅微粒子の重量に対して３重量％以上かつ６重量％以下であることを特徴とする銅インク。     A copper ink for forming a conductive film,
    Containing copper fine particles, a liquid dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium,
    The copper fine particles are copper particles with a median diameter of 60 nm or more and 110 nm or less,
    The concentration of the copper fine particles is 60% by weight or more based on the entire copper ink,
    The dispersion medium contains an alcohol having a plurality of hydroxy groups,
    The dispersant is a polymer compound having a phosphoric acid group or a salt thereof,
    A copper ink characterized in that the concentration of the dispersant is 3% by weight or more and 6% by weight or less based on the weight of the copper fine particles.
  2. 　前記分散媒は、２－メチル２，４－ペンタンジオール及び３－メチル１，３－ブタンジオールからなる群から選択されるアルコールを含む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 dispersion medium contains an alcohol selected from the group consisting of 2-methyl 2,4-pentanediol and 3-methyl 1,3-butanediol.
  3. 　紙基材上に導電膜を形成する導電膜形成方法であって、
    　請求項１又は請求項２に記載の銅インクを用いてインク膜を紙基材上に形成する工程と、
    　前記インク膜を乾燥して銅微粒子から成る塗布乾燥膜を前記紙基材上に形成する工程と、
    　前記塗布乾燥膜を光焼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 on a paper base material, the method comprising:
    forming an ink film on a paper base material using the copper ink according to claim 1 or claim 2;
    drying the ink film to form a coated dry film made of fine copper particles on the paper base material;
    A method for forming a conductive film, comprising the step of photo-baking the applied and dried film.
  4. 　ＲＦＩＤのＲＦタグであって、
    　少なくとも紙基材と、前記紙基材上のアンテナとを有し、
    　前記アンテナは、請求項３に記載の導電膜形成方法で形成された導電膜から成ることを特徴とするＲＦタグ。

          An RFID RF tag,
    comprising at least a paper base material and an antenna on the paper base material,
    4. An RF tag, wherein the antenna is made of a conductive film formed by the conductive film forming method according to claim 3.
PCT/JP2022/031645 2022-06-22 2022-08-23 Copper ink, conductive film formation method, and rf tag WO2023248485A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013104089A (en) * 2011-11-14 2013-05-30 Ishihara Chem Co Ltd Copper particle dispersion, conductive film formation method, and circuit board
JP2013105605A (en) * 2011-11-14 2013-05-30 Ishihara Chem Co Ltd Copper particulate dispersion liquid, conductive film forming method and circuit board
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
JP2014222611A (en) * 2013-05-14 2014-11-27 石原ケミカル株式会社 Copper fine particle dispersion liquid, conductive film forming method, and circuit board
WO2017057301A1 (en) * 2015-09-30 2017-04-06 住友電気工業株式会社 Coating liquid for forming electroconductive layer, and method for manufacturing electroconductive layer
JP2018147658A (en) * 2017-03-03 2018-09-20 三菱マテリアル株式会社 Conductive composition

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013104089A (en) * 2011-11-14 2013-05-30 Ishihara Chem Co Ltd Copper particle dispersion, conductive film formation method, and circuit board
JP2013105605A (en) * 2011-11-14 2013-05-30 Ishihara Chem Co Ltd Copper particulate dispersion liquid, conductive film forming method and circuit board
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
JP2014222611A (en) * 2013-05-14 2014-11-27 石原ケミカル株式会社 Copper fine particle dispersion liquid, conductive film forming method, and circuit board
WO2017057301A1 (en) * 2015-09-30 2017-04-06 住友電気工業株式会社 Coating liquid for forming electroconductive layer, and method for manufacturing electroconductive layer
JP2018147658A (en) * 2017-03-03 2018-09-20 三菱マテリアル株式会社 Conductive composition

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