JP2009209347A - Electrically-conductive ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrically-conductive circuit which is inexpensive and highly reliable and which causes no decrease in electrical conductivity even when bent in housing a flexible printed-wiring board compactly in the course of making cellular telephones, mobile personal computers, etc. lighter, thinner, shorter, and smaller. <P>SOLUTION: An electrically-conductive circuit is provided wherein a necessary pattern is printed with an electrically-conductive ink onto the bending part of a circuit consisting of a thin metal film by printing media such as screen printing, gravure printing, flexographic printing, and ink jet printing, and wherein an etching treatment is carried out. The electrically-conductive ink uses a phenoxy resin and rosin-based resin, the phenoxy resin consisting of a high-molecular-weight polyhydroxy polyether synthesized from bisphenol and epichlorohydrin, uses an electrically-conductive substance which is a flaky silver powder with a specific surface area of 0.3-4.0 m<SP>2</SP>/g and a 50% average particle size of 1-15 μm surface-treated with a fatty acid of less than 1 wt.% of the total amount of the electrically-conductive substance, and also uses a silicon-based and/or acrylic antifoaming agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive ink for manufacturing a printed circuit board for circuit formation. More specifically, the conductive ink is applied to a bent portion of a metal foil film having poor bending resistance when manufacturing a three-dimensional printed circuit board. The present invention relates to a conductive ink for a printed circuit board which forms an image by using an etching process and removes unnecessary metal foil to form a circuit with a bent portion reinforced.

In recent years, various electronic devices have been required to be smaller, thinner and lighter, and printed wiring boards constituting such electronic devices are also required to be smaller, thinner and highly integrated. Has reached. In addition to so-called rigid printed wiring boards using glass epoxy substrates or the like, various forms of printed wiring boards have been put into practical use. For example, a flexible printed wiring board (FPC), a multilayer printed wiring board, etc. are put into practical use. The flexible printed wiring board has a circuit pattern formed on the flexible printed wiring board having flexibility, and since it is thin, the space occupied by the printed wiring board can be reduced, or the housing is Widely used in electronic devices that can be bent.
In addition, a general flexible printed wiring board is formed by bonding a copper or aluminum foil to a base material such as a polyimide film or a polyester film or providing a conductive portion by vapor deposition plating, patterning using a resist, and performing an etching process. Circuit formation is performed.

  In recent years, it is necessary to efficiently use a limited space due to a demand for improving product performance of mobile phones and the like, and FPCs having a large area are accommodated in a small casing by bending and bending the FPC.

Here, when the metal foil is bent and bent, there is a problem that the metal part is broken and the resistance value is increased or the wire is broken. For example, in Japanese Patent Application Laid-Open No. 2007-242716, the bent part is reinforced with a metal plate such as brass interposed therebetween. Although the method is disclosed, there is a problem that the structure of the circuit is complicated and it is difficult to cope with the reduction in thickness and size.
JP 2007-242716 A

  Flexible printed wiring board that forms circuits by pasting copper or aluminum foil on a conventional substrate such as polyimide film or polyester film, or providing a conductive part by vapor deposition plating, patterning using a resist, and performing etching treatment However, there is a drawback in that the metal part is broken by bending and the performance and reliability as a circuit are impaired.

  The conductive ink of the present invention has very good adhesion to the surface of a metal foil such as copper and aluminum, and there is no damage to the dry film in an etching process immersed in an acid or alkaline aqueous solution during circuit formation. Since there is no moisture absorption due to moisture, it has very excellent performance in terms of reliability.

  That is, the present invention relates to a conductive ink containing a conductive substance and a binder component, wherein the binder component is composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin. The present invention relates to a conductive ink comprising a resin.

  The present invention also relates to the above conductive ink, wherein the binder component further comprises a rosin resin.

  Furthermore, the present invention provides a resin in which the rosin resin is one or more selected from rosin esters, rosin-modified phenol resins, rosin-modified maleic resins and rosin-modified xylene resins, and is based on the entire solid of the binder component. It is related with said electroconductive ink characterized by including 5 to 40 weight%.

Further, the present invention provides a specific surface area of 0.3 to 4.0 m ² / g, a tap density of ^{2 to 4} g / cm ³ , wherein the conductive material is surface-treated with a fatty acid having less than 1% by weight of the total amount of the conductive material. The present invention relates to the above conductive ink, wherein flaky silver powder having a 50% average particle diameter of 1 to 15 μm is used.

  Furthermore, the present invention is characterized in that the softening point of a phenoxy resin composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin is 70 to 90 ° C. The present invention relates to the above conductive ink.

  Further, the present invention relates to the above conductive ink, wherein the ratio of the conductive substance to the solid content in the binder component is 95% by weight / 5% to 70% by weight / 30% by weight.

  Furthermore, the present invention relates to a conductive ink characterized in that the component contains a silicon-based and / or acrylic antifoaming agent, and the contact angle between the dry film and purified water is 110 to 133 degrees. is there.

  Furthermore, the present invention relates to a conductive circuit characterized in that after the conductive ink is printed on a printed board material composed of a metal foil film and a film, a patterning process is performed by an etching process.

  The conductive ink obtained in the present invention is printed on the bent part of the circuit made of a metal thin film by printing the necessary pattern using screen printing, gravure printing, flexographic printing, ink jet printing, etc. In addition, it is possible to form a highly reliable circuit capable of suppressing an increase in resistance value even when bent, and withstanding long-term use. In particular, silicon and / or acrylic antifoaming agent is included in the components, and the contact angle between the dry film and purified water is 110 degrees to 133 degrees, so that etching and high temperature and high humidity resistance can be achieved even when the drying temperature is lowered. A circuit having excellent dimensional stability can be formed even when a material having poor heat resistance such as polyolefin is used as a base material and a polyester film is used as a base material.

  Hereinafter, the present invention will be described in more detail based on embodiments, but the present invention is not limited to these embodiments unless departing from the technical idea of the present invention.

  The conductive ink of the present invention comprises a conductive material, a phenoxy resin composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin, and a rosin resin.

  A phenoxy resin composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin contained in the conductive ink of the present invention is a component that acts as a binder of the conductive ink, It has excellent reliability as a conductive circuit forming material because of its excellent adhesion to foil, chemical resistance during etching, and high-temperature / high-humidity coating film properties.

  In addition, rosin-based resins have particularly high water resistance, and have excellent performance at high temperature and high humidity resistance.

  Furthermore, by using a phenoxy resin composed of polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 and rosin resin synthesized from bisphenol and epichlorohydrin as a binder, the dispersion fluidity of the conductive substance is improved. The stability as an ink is improved, the conductivity of the coating film is increased, and low resistance that cannot be obtained with other binder resins can be achieved by drying at a low temperature in a short time.

  Here, the molecular weight of a phenoxy resin composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin is 30,000 to 70,000, preferably 40,000 to 40,000. 70,000 is good.

  If the weight average molecular weight of the phenoxy resin is 30,000 or less, the chemical resistance at the time of etching treatment is poor, and if the weight average molecular weight of the phenoxy resin exceeds 70,000, synthesis of the resin becomes difficult.

  Here, the weight average molecular weight of the resin is a weight average molecular weight determined in terms of polystyrene by gel permeation chromatography using tetrahydroxyfuran as a solvent.

  Furthermore, the softening point of a phenoxy resin composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin is preferably 60 to 100 ° C. When the softening point of the phenoxy resin is lower than 60 ° C., if the resin is stored at a temperature equal to or higher than the softening point in a high-temperature / high-humidity test that is generally performed, the resin softens and causes problems such as disconnection. Further, when the softening point is higher than 100 ° C., the viscosity when ink is formed becomes high, the surface state of the printed matter becomes rough, appearance defects occur, and it is possible to add a solvent to make the viscosity suitable for printing. However, the solid content is lowered, and a stable and uniform dry film cannot be obtained, and the etching resistance and the high temperature and high humidity resistance are lowered.

On the other hand, the rosin resin used in the present invention is one or more resins selected from rosin ester, rosin modified phenolic resin, rosin modified maleic acid resin, and rosin modified xylene resin. These rosin resins are hydrophobic. Since the performance is high, for example, in a durability test at a temperature of 85 ° C. and a humidity of 85%, the corrosion of the metal foil film of the base material can be suppressed by suppressing the absorption and transmission of water vapor from the dried ink film.

1 to 40% by weight, preferably 5 to 35% by weight, is added to the solid content of the binder component.
When the blending ratio of the rosin resin is 5% by weight or less in the solid content of the binder component, the effect of improving the resistance to high temperature and high humidity cannot be obtained, and when 35% by weight or more is blended, the adhesion to the metal foil is inhibited.

  In the conductive ink of the present invention, other resins or precursors thereof compatible with the phenoxy resin and the rosin resin composed of a high molecular weight polyhydroxy polyether synthesized from bisphenol and epichlorohydrin can be contained. These serve to fix the conductive material to various substrates and maintain the performance as printing ink.

  The other resin or its precursor can be used in an amount of 0.1 to 20% by weight, preferably 1 to 10% by weight, in the solid content of the binder component of the conductive ink.

  Examples of other resins include polyurethane resin, polyester resin, alkyd resin, butyral resin, acetal resin, polyamide resin, acrylic resin, styrene-acrylic resin, styrene resin, nitrocellulose, benzylcellulose, styrene / maleic anhydride resin, polybutadiene Resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride / vinyl acetate resin, vinyl chloride / vinyl acetate / maleic acid resin, fluororesin, silicone resin, phenol resin, urea resin, melamine resin, benzoguanamine resin, ketone resin , One or more selected from chlorinated polyolefin resin, modified chlorinated polyolefin resin, chlorinated polyurethane resin, etc. may be used depending on the type of printing method, the type of substrate used, and the application of the circuit. it can.

  The conductive ink according to the present invention uses an appropriate amount of ester solvent, ketone solvent, glycol ether solvent, aliphatic solvent, aromatic solvent, alcohol solvent, water, etc., depending on the type of printing method, etc. Two or more types can be mixed and used.

  Examples of ester solvents include methyl acetate, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, (iso) amyl acetate, cyclohexyl acetate, ethyl lactate, and 3-methoxybutyl acetate. , Acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, methyl amyl ketone, isophorone, γ-butyl lactone, cyclohexanone and the like. The glycol ether solvents include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol mono n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol. Mono n-propyl ether, propylene glycol mono n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono n-propyl ether, and acetates of these monoethers, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, etc. Zia Kill ethers and the like.

  Examples of the aliphatic solvent include n-heptane, n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane, and examples of the aromatic solvent include toluene and xylene. Examples of the alcohol solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, cyclohexanol, 3-methoxybutanol, diacetone alcohol and the like. Other liquid media include dimethyl carbonate, ethyl methyl carbonate, and di-n-butyl carbonate.

  The conductive ink of the present invention may be used by blending a curing agent. The curing agent capable of reacting with a phenoxy resin composed of a high molecular weight polyhydroxypolyether synthesized from bisphenol and epichlorohydrin used in the conductive ink of the present invention is not limited in type, but it is fatty in view of adhesion, flex resistance, curability and the like. Amine polyamines, polyaminoamides, ketimines, aliphatic diamines, aromatic diamines, imidazoles, tertiary amines and other amine compounds, acid anhydride compounds, mercaptan compounds, phenol resins, amino resins, dicyandiamide, Lewis acid complex compounds, etc. If necessary, an appropriate amount can be used and a known catalyst or accelerator can be used in combination.

The conductive material used in the present invention was surface-treated with a fatty acid of less than 1% by weight of the total amount of the conductive material, specific surface area 0.3 to 4.0 m ² / g, tap density ^{2 to 4} g / cm ³ , 50 A silver powder having a% average particle diameter of 1 to 15 μm.

  As the silver powder, any shape such as flake shape, spherical shape, scale shape, plate shape, dendritic shape, foil shape and the like can be used, but the flake shape is preferable from the viewpoint of the conductivity and fluidity of the ink. Two or more kinds of silver powder can be mixed and used.

The flaky silver powder has a specific surface area of 0.3 to 4.0 m ² / g and a tap density of ^{2 to 4} g / g.
cm ³ and an average particle diameter of 1 to 15 μm are preferable. Silver powder having a specific surface area of 0.3 m ² / g or less and a tap density of ^{2 to 4} g / cm ³ has a shape close to a sphere, and there are few contacts between the silver powders, and good conductivity cannot be obtained. Further, when the specific surface area is 4.0 m ² / g, the wettability to the resin is poor,
The fluidity of the conductive ink becomes insufficient, and the printability is lowered. Further, even when the average particle size is 1 μm or less, the wettability to the resin is similarly inferior, so that the fluidity of the conductive ink becomes insufficient, and the printability is lowered. When the average particle size is 15 μm or more, silver powder tends to settle in a paste state, which causes a problem in ink stability.

  Here, the specific surface area of the conductive material can be obtained by the following formula (1) by adsorbing nitrogen gas on the powder surface with a flow-type specific surface area measuring device and the amount of adsorption / desorption of the nitrogen gas.

Formula (1)

  The tap density can be obtained from the following formula (2) by putting 100 g of powder in a graduated cylinder and tapping for 20 minutes using a tap density measuring device according to ISO3953.

Formula (2)

  Further, the 50% average particle size is obtained by calculating the volume flow rate distribution of particles from the diffraction intensity distribution generated when the laser beam is irradiated to the particles using a laser analysis flow rate distribution measuring device. Ask.

Further, the fatty acid to be subjected to the surface treatment of the conductive material used in the present invention is specifically formic acid, acetic acid, octylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and other saturated fatty acids, oleic acid, Examples thereof include unsaturated fatty acids such as linoleic acid and linolenic acid, tertiary fatty acids such as pivalic acid, neoheptanoic acid, neononanoic acid and neodecanoic acid, and dicarboxylic acids such as succinic acid and malonic acid. It is desirable that the fatty acid generated after decomposition is volatile. In this respect, saturated fatty acids having 1 to 18 carbon atoms in total and unsaturated fatty acids having 3 to 18 carbon atoms are preferably used. Among them, saturated fatty acids such as octylic acid, capric acid and lauric acid, and tertiary fatty acids such as neoheptanoic acid, neononanoic acid and neodecanoic acid have a large effect of improving conductivity, and the conductive film after the fatty acid produced after decomposition is cured. It is preferable because it does not remain inside. In this invention, fatty acid silver may be individual or may use 2 or more types together.

  On the other hand, the silicon-based and / or acrylic-based antifoaming agent used in the present invention is preferably localized on the surface of the conductive ink film, and makes the surface of the foam to be formed nonuniform, thereby suppressing the formation of foam. A defoaming agent having a defoaming effect or a defoaming agent having a defoaming action that locally breaks the surface of the formed foam and breaks the foam is good. One or more types of non-silicon type antifoaming agents such as emulsion type silicon type antifoaming agents and / or vinyl ethers, acrylic polymers, amides, metal soaps and the like can be used. These antifoaming agents can provide water repellency to the dry film by localizing on the surface of the dry film of the conductive ink. As a result, the drying temperature is low and the film strength is low. The alkali or acid aqueous solution and water vapor at high temperature and high humidity can be prevented from entering the conductive ink film, and their resistance is improved.

  The amount of these antifoaming agents is not particularly limited, but the contact angle between the dried film of the conductive ink and the purified water may be 110 degrees to 133 degrees. It is 1 to 3% by weight based on the total solid content weight of the conductive ink (100% by weight). When the contact angle between the dried film of the conductive ink and the purified water is less than 110 degrees, a good water repellency effect cannot be obtained, and the etching resistance during low temperature drying and the high temperature and high humidity resistance cannot be improved. In addition, when the contact angle between the dried film of the conductive ink and the purified water is larger than 133 degrees, the effect of improving the etching resistance and the high temperature and high humidity resistance during low temperature drying can be obtained. When ink or an adhesive is adhered, it causes repelling or poor adhesion.

  The contact angle between the dried film of the conductive ink and the purified water was measured using a DM700 contact angle meter manufactured by Kyowa Interface Science Co., Ltd., after dropping purified water and standing for 4800 msec.

  The conductive ink may include other conductive materials such as silver-plated copper, silver-copper composite, silver-copper alloy, amorphous copper, etc., inorganic powder coated with these metals, silver oxide, Metal oxides such as indium oxide, antimony oxide, zinc oxide, tin oxide, antimony-doped tin oxide, and indium-tin composite oxide, carbon black, graphite, and the like can be contained. These conductive materials may be used in combination of two or more.

  Further, the content of the conductive substance in the conductive ink is preferably 70 to 95% by weight based on the total solid content weight of the conductive ink (100% by weight), and preferably 75 to 92% by weight. Is more preferable. This is because when the content of the conductive material is less than 70% by weight, the conductivity is not sufficient, and when it exceeds 95% by weight, the printability and conductivity are lowered.

Finally, a conductive circuit formed using the conductive ink of the present invention will be described.
The conductive ink of the present invention can be used in a plastic group such as polyester film, polyester, polyethylene, polypropylene, cellophane, vinyl chloride, vinylidene chloride, polystyrene, vinyl alcohol, ethylene-vinyl alcohol, nylon, polyimide, polycarbonate, etc. Material or coated paper, uncoated paper, other, synthetic paper, polyethylene coated paper, impregnated paper, water-resistant processed paper, insulating processed paper, stretched paper, etc. on one or both sides, for example, gold, silver, copper , Platinum, palladium, rhodium, ruthenium, indium, nickel, aluminum, silicon, or two or more alloys and / or mixtures thereof or metal oxides, metal nitrides, metal halides, metal sulfides, metals A kind selected from carbides Alternatively, flexographic printing, gravure printing, gravure offset printing, offset printing on a circuit board formed by laminating and / or depositing and / or depositing and / or plating a thin film of a mixture of two or more of these and / or composites with an adhesive. Pattern printing using conventional printing methods such as screen printing, rotary screen printing, ink jet printing, etc., heat drying, and then etching with hydrochloric acid, copper chloride, sodium hydroxide aqueous solution to remove unnecessary metal thin film Therefore, even if it is bent or bent, it is possible to suppress an increase in resistance value and to form a conductive circuit with excellent reliability that can withstand long-term use at low cost.

  Moreover, in a portion where a load such as bending or bending is not applied as a circuit, the circuit can be formed by patterning with a general resist ink, and further, the conductive material of the present invention can be formed on a plastic base material or processed paper having no metal foil. The ink may be directly printed and patterned.

  EXAMPLES The present invention will be described in more detail with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In the examples, “part” represents “part by weight”, and “%” represents “% by weight”.

[Binder 1]
40 parts of Japan Epoxy Resin Phenoxy Resin JER1256 (weight average molecular weight 50,000, softening point 85 ° C.) was mixed with 60 parts of isophorone and heated and stirred at 60 ° C. to prepare a varnish-like binder 1.

[Binder 2]
Japan Epoxy Resin Epicoat 1010 (weight average molecular weight 5,500, softening point 85 ° C.) 40 parts were mixed with 60 parts of isophorone, and heated and stirred at 60 ° C. to prepare a varnish-like binder 2.

[Binder 3]
40 parts of Japan Epoxy Resin Phenoxy Resin JER4275 (weight average molecular weight 60,000, softening point 135 ° C.) was mixed with 60 parts of isophorone and heated and stirred at 60 ° C. to prepare a varnish-like binder 3.

[Binder 4]
40 parts of a vinyl chloride vinyl acetate copolymer resin sorbine ME (vinyl chloride, vinyl acetate, maleic acid copolymer) manufactured by Nissin Chemical Industry Co., Ltd. was mixed with 60 parts of isophorone and heated and stirred at 60 ° C. to prepare a varnish-like binder 4. .

[Binder 5]
40 parts of rosin ester resin Pencel A manufactured by Arakawa Chemical Co., Ltd. was mixed with 60 parts of isophorone and heated and stirred at 60 ° C. to prepare a varnish-like binder 5.

[Binder 6]
Rosin modified maleic acid resin Marquide No. 5 40 parts was mixed with 60 parts of isophorone and heated and stirred at 60 ° C. to prepare a varnish-like binder 6.

[Binder 7]
40 parts of rosin-modified phenolic resin Tamanol 351 manufactured by Arakawa Chemical Co., Ltd. was mixed with 60 parts of isophorone and heated and stirred at 60 ° C. to prepare a varnish-like binder 7.

[Silver powder A]
A flaky silver sill coat AgC-A (specific surface area 1.0 m ² / g, tap density 3.5 g / cm ³ , 50% average particle size 3 μm) manufactured by Fukuda Metal Foil Powder Industry was used as silver powder A.

[Silver powder B]
Spherical silver AG-5-7F (specific surface area 0.3 m ² / g, tap density 5.4 g / cm ³ , 50% average particle size 3 μm) manufactured by DOWA Electronics Co., Ltd. was used as silver powder B.

[Defoaming agent C]
The silicon-based antifoaming agent KP330 made of Shin-Etsu Silicone was used as antifoaming agent C.

[Antifoamer D]
The non-silicone antifoaming agent Dappo SN368 manufactured by San Nopco Co., Ltd. was designated as antifoaming agent D.

[Adjustment of conductive ink]
Silver powder, a binder, an antifoaming agent, and a solvent were mixed with a disper at a blending ratio shown in Table 1 to adjust the conductive ink, and the fluidity of the obtained conductive ink was measured by the following method.

[Production of conductive circuit]
A conductive ink described in Examples 1 to 4 and Comparative Examples 1 to 5 was screen-printed with a pattern of 20 mm × 40 mm on a conductive substrate obtained by bonding a 10 μm thick aluminum foil to a 50 μm thick PET film, and 100 After drying for 10 minutes in a box oven at ℃, immersed in a 1% -sodium hydroxide solution heated to 50 ℃ for 1 minute, and removed the aluminum foil other than the printed part as a conductive circuit, the blending ratio and physical property values are shown. It was published in 1.

  Further, Comparative Example 6 was obtained by attaching a 5 μm thick aluminum foil to a 50 μm thick PET film on which no conductive ink was printed.

[Measurement of resistivity]
A 80 mm × 50 mm pattern was printed on a 100 μm-thick PET film by screen printing, dried in a 100 ° C. box oven for 10 minutes, and then surface resistivity was measured by a four-probe method according to a measurement method according to JISK7194.

[Measurement of film thickness]
The film thickness of the printed matter was measured using an MH-15M type measuring instrument manufactured by Sendai Nikon Corporation.

[Evaluation of etching resistance]
A conductive ink described in Examples 1 to 4 and Comparative Examples 1 to 4 is screen-printed with a pattern of 20 mm × 40 mm on a conductive substrate obtained by bonding a 10 μm thick aluminum foil to a 50 μm thick PET film, and 150 C. and 100.degree. C. for 10 minutes after drying in a box oven, immersed in a 1% -sodium hydroxide solution heated to 50.degree. C. for 1 minute, and visually judged the state of the conductive circuit with the aluminum foil other than the printed part removed. In the case where the printed material was not damaged, it was marked as ◯, and the case where the printed material was damaged in any way such as peeling or deformation was marked as x.
[Bending resistance evaluation]
A conductive ink described in Examples 1 to 4 and Comparative Examples 1 to 4 is screen-printed with a pattern of 20 mm × 40 mm on a conductive substrate obtained by bonding a 10 μm thick aluminum foil to a 50 μm thick PET film, and 150 C. and 100.degree. C. for 10 minutes after drying in a box oven, immersed in a 1% -sodium hydroxide solution heated to 50.degree. C. for 1 minute, bent the conductive circuit from which the aluminum foil other than the printed part was removed from the center, 1 kg of The rate of change in resistance value (equation (3)) was measured when the load was applied again for 1 minute and then opened again.

Formula (3)

[High temperature and high humidity resistance evaluation]
A conductive ink described in Examples 1 to 4 and Comparative Examples 1 to 4 is screen-printed with a pattern of 20 mm × 40 mm on a conductive substrate obtained by bonding a 10 μm thick aluminum foil to a 50 μm thick PET film, and 150 The conductive circuit was dried for 10 minutes in a box oven at 100 ° C. and 100 ° C. and then immersed in a 1% -sodium hydroxide solution heated to 50 ° C. for 1 minute to remove the aluminum foil other than the printed part. The state after storage for 120 hours in a constant temperature and humidity oven was visually judged, and the case where the printed material was not damaged was evaluated as ◯, and the case where it was damaged in any way such as corrosion or peeling was evaluated as X.

  The measurement results are shown in Table 1.

[Examples 1 to 4]
A phenoxy resin composed of polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 and a rosin resin synthesized from bisphenol and epichlorohydrin as binders and using an antifoaming agent at 100 ° C. for 10 minutes under drying conditions. The obtained conductive circuit had a low resistance value, and further there was little change in the resistance value in the bending test, and good results were obtained in the etching resistance and high temperature and high humidity resistance tests.

[Comparative Example 1]
In a conductive circuit using an epoxy resin having a small weight average molecular weight of 5,500, the film was destroyed during etching.

[Comparative Example 2]
A conductive circuit using a phenoxy resin having a weight average molecular weight of 60,000 and a softening point of 135 ° C. had a thin film thickness, which was poor in the bending resistance and high temperature and high humidity resistance tests.

[Comparative Example 3]
A defect occurred in a high temperature and high humidity resistance test in which the phenoxy resin was changed to a vinyl chloride vinyl acetate copolymer resin.

[Comparative Example 4]
The conductive circuit changed to silver powder having a specific surface area of 0.3 m ² / g, a tap density of 5.4 g / cm ³ and a 50% average particle size of 3 μm had high surface resistivity, and good conductivity could not be obtained.

[Comparative Example 5]
A conductive circuit obtained under a drying condition of 100 ° C. for 10 minutes without using an antifoaming agent was poor in etching resistance, and a circuit pattern could not be produced.

[Comparative Example 6]
When a conductive substrate in which a 5 μm thick aluminum foil was bonded to a 50 μm thick PET film on which no conductive ink was printed was bent, the rate of change in resistance was clearly larger than that of a printed conductive circuit.

Claims (8)

  In a conductive ink containing a conductive substance and a binder component, the binder component comprises a phenoxy resin composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin. Conductive ink characterized by   The conductive ink according to claim 1, wherein the binder component further comprises a rosin resin.   The rosin resin is one or two or more resins selected from rosin ester, rosin-modified phenol resin, rosin-modified maleic acid resin and rosin-modified xylene resin, and 5 to 40% by weight based on the total solid content of the binder component The conductive ink according to claim 2, comprising: Conductive material was surface-treated with a fatty acid less than 1% by weight of the total amount of conductive material, specific surface area 0.3 to 4.0 m ² / g, tap density ^{2 to 4} g / cm ³ , 50% average particle size 1 The conductive ink according to any one of claims 1 to 3, wherein -15 µm of flaky silver powder is used.   The softening point of a phenoxy resin composed of a polyhydroxy polyether having a weight average molecular weight of 40,000 to 90,000 synthesized from bisphenol and epichlorohydrin is 70 to 90 ° C. Or a conductive ink.   6. The conductive ink according to claim 1, wherein the ratio of the conductive substance to the solid content in the binder component is 95 wt% / 5 wt% to 70 wt% / 30 wt%.   The conductive ink according to any one of claims 1 to 6, further comprising a silicon-based and / or acrylic-based antifoaming agent, wherein a contact angle between the dry film and the purified water is 110 degrees to 133 degrees.   8. A conductive circuit obtained by printing a conductive ink according to claim 1 on a printed board material comprising a metal foil film and a film, and then performing a patterning process by an etching process.