JP6519242B2 - Conductive paste for laser processing and use thereof - Google Patents

Description

  The present invention relates to a conductive paste for laser processing excellent in forming a wiring circuit, a laminate with a conductive pattern obtained using the conductive paste for laser processing, and a method of manufacturing the same.

  An etching method and a printing method are known as an electronic component, a thin film forming means for shielding an electromagnetic wave, or a forming means of a conductive circuit. The etching method is a method of obtaining a circuit pattern of a desired shape by removing a part of the metal film with an etching solution, but generally the process is complicated and the waste liquid treatment is required separately, so cost and There is a problem that loads on the environment. In addition, since the conductive circuit formed by the etching method is formed of a metal material such as aluminum or copper, there is a problem that it is weak against physical impact such as bending.

  Then, in order to solve these problems and to form a conductive circuit more inexpensively, a conductive paste attracts attention. By printing a conductive paste, a conductive circuit can be easily formed. Further, since realization of downsizing and weight reduction of the electronic parts, improvement of productivity and cost reduction can be expected, research and development on printable conductive inks are energetically made, and many proposals have been made.

Also, in recent years, information terminals such as smartphones and tablet-type terminals are becoming multifunctional and high definition of displays while maintaining their size, but in order to further improve these performances, electronic components should be used. Furthermore, it is necessary to mount at high density. For high-density mounting of electronic components, miniaturization of the electronic components themselves and miniaturization of wiring circuits are required.
For example, in a capacitive touch panel, lines / spaces of 100 μm or less (100 μm or less / 100 μm or less) (hereinafter abbreviated as “L / S”) are widely used, and further, smartphones and tablets Although L / S of 50 μm / 50 μm or less is strongly required due to multifunctionalization of mold terminals and the like and high definition of displays, in the printing method, it is difficult to further increase the definition.

Then, examination of the laser processing method (laser ablation method) which forms a wiring circuit by laser beam irradiation is performed. In the laser processing method, the conductive paste is formed on the insulating base material, and a portion of the conductive paste is removed from the insulating base material by laser light, so that the L / S, which is difficult in the printing method, is about 50 μm / 50 μm. Although a high definition wiring circuit can be formed, the market strongly demands an ultra high definition wiring circuit having an L / S of 30 μm / 30 μm or less.
Patent Document 1 discloses conductive particles, an inorganic filler, a resin binder, a surfactant, and a silane coupling agent as a conductive paste for forming an ablation process (hereinafter referred to as laser process) by laser irradiation. And conductive pastes comprising any of the organometallic compounds are disclosed.
Patent Document 2 discloses a conductive paste containing a binder resin having a number average molecular weight of 5,000 to 60,000 and a glass transition temperature of 60 to 100 ° C., a metal powder, and an organic solvent.

JP, 2014-2992, A WO 2014/013899

Conventional conductive pastes are inferior in laser processability of conductive films and are susceptible to laser irradiation conditions, and conductive circuit patterns are broken (hereinafter, also referred to as line skipping), and stable formation of fine wiring circuits is achieved. There was a problem of difficulty.
The present invention is a conductive paste for laser processing which is compatible with various printing methods and is used to form a fine electric circuit by a laser processing process, and is affected by the laser irradiation condition excellent in laser processability. It is an object of the present invention to provide a conductive paste for laser processing that is difficult to form.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining this invention so that the said subject might be solved, the present inventors discover that the said subject can be solved by using an organic solvent soluble laser beam absorber, and came to complete this invention.
That is, the present invention relates to a conductive paste for laser processing, which comprises a binder resin, conductive particles, an organic solvent, and an organic solvent-soluble laser light absorber which can be dissolved in the organic solvent.
The present invention also relates to a conductive sheet provided with a sheet-like substrate and a conductive film formed from the conductive paste for laser processing.
Furthermore, the present invention relates to a method for producing a circuit pattern, in which a conductive film on the conductive sheet is irradiated with a laser to remove a part of the conductive film to form a conductive circuit.
Furthermore, the present invention relates to an electronic device provided with a conductive circuit pattern formed from the conductive paste for laser processing.

  The present invention provides a conductive paste for laser processing excellent in laser processing stability, a cured product thereof, and a laminate, which are used for forming a fine electric circuit by a laser processing step after forming an eyebrow pattern by various printing methods. I was able to do that. The conductive paste for laser processing of the present invention is suitably used as a conductive paste for forming a fine conductive circuit formed in a frame of a touch screen panel or a fine metal mesh sheet having both transparency and low surface resistance. be able to.

It is a top view of the screen printing plate used by evaluation of laser processability. It is an enlarged view of a part of circuit pattern after laser processing.

The conductive paste for laser processing of the present invention contains a binder resin, conductive particles, and an organic solvent soluble laser absorber.
The organic solvent-soluble laser absorber preferably has an absorption peak in the wavelength range of 700 to 2000 nm.
In the present invention, "soluble in an organic solvent" means that 1 g of a laser absorber is dissolved in 100 g of the organic solvent used in the paste of the present invention at 23 ° C., and there is no undissolved matter visually. Say.
Examples of such organic solvent soluble laser absorbers include nigrosine. This nigrosine is a black azine condensation mixture as described in COLOR INDEX as CI SOLVENT BLACK 5 or CI SOLEVENTBLAC K7. This can be synthesized, for example, by oxidation and dehydration condensation of aniline, aniline hydrochloride and nitrobenzene at a reaction temperature of 160 to 180 ° C. in the presence of iron chloride.

  Commercial products of nigrosine include, for example, Spirit Black SB, Spirit Black AB, Spirit Black SA (above, CI SOLVENT BLACK 5); Nigrosine Base EE, Nigrosine Base EX, Nigrosine Base EX-BP (All are trade names, Oil Black S, Oil Black SF, Oil Black 109 (all trade names, manufactured by Orient Chemical Industries, Ltd.). (The above, C.I. SOLVENT BLACK 7).

The compounding amount of the organic solvent soluble laser absorber is not particularly limited, but from the viewpoints of sensitivity to laser beam, accuracy of pattern by ablation, developability, releasability and chemical resistance, binder resin, conductive particles and organic solvent soluble laser absorption It is preferable to mix | blend 0.1-20 mass% in a total of 100 mass% of an agent, and 0.5-10 mass% is more preferable.
Moreover, you may use together an organic type thing among the insoluble absorbers which have an absorption peak in the range of wavelength 700-2000 nm.

The conductive particles used in the present invention are, for example, metal powders such as gold, silver, copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum and platinum, and alloys thereof. And these composite powders.
Further, a nucleus and fine particles obtained by coating the surface of the nucleus with a substance different from the nucleus substance, specifically, for example, a silver-coated copper powder or the like in which copper is used as a nucleus and the surface is covered with silver Also, for example, powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, ITO (tin-doped indium oxide), AZO (aluminum-doped zinc oxide), and GZO (gallium-doped zinc oxide) And powders coated with these metal oxides. Among these, silver is preferable because it has high cost, high conductivity, and is difficult to oxidize, so that the change in electrical resistivity is small. The conductive particles may be used alone or in combination of two or more.

As the shape of the conductive particles, known shapes such as spherical, flake, dendritic, rod, and linear can be used.
The D50 average particle diameter of the conductive particles is preferably in the range of 0.1 to 5 μm, and more preferably in the range of 0.1 to 3 μm.
In addition, D50 average particle diameter of electroconductive particle measured the accumulation particle size (D50) of volume particle size distribution using Shimadzu Corp. make laser-diffraction particle size distribution measuring apparatus "SALD-3000".

  The conductive particles are preferably blended in an amount of 60 to 90% by mass, and more preferably 80 to 90% by mass, based on 100% by mass of the binder resin, the organic solvent soluble laser absorber and the conductive fine particles. Conductivity is further improved by becoming 60 mass% or more. In addition, by setting the content to 95% by mass or less, the conductive film further improves the adhesion to the substrate, and the mechanical strength is also improved.

The number average molecular weight of the binder resin in the present invention is preferably 10,000 to 50,000, and more preferably 20,000 to 40,000. When the number average molecular weight is 10,000 or more, the environmental reliability of the wiring circuit to be formed is improved, and particularly the heat and humidity resistance is further improved. Further, when the number average molecular weight is 50,000 or less, a suitable cohesive force can be obtained in the conductive film, so that ablation at the time of laser processing becomes easy, and a fine wiring circuit can be easily obtained.
The number average molecular weight is a value in terms of polystyrene measured by GPC (gel permeation chromatography). In addition, environmental reliability of the wiring circuit means that even if it is placed in an environment of 80 ° C, -40 ° C, and 60 ° C, 90% humidity for a long time, or after a cycle test of 85 ° C to -40 ° C. The adhesion of the conductive film to a substrate (for example, an ITO film) is less likely to deteriorate.

  Further, the binder resin preferably has a glass transition temperature (hereinafter referred to as Tg) of 5 to 100 ° C., and more preferably 10 to 95 ° C. When the Tg is 5 ° C. or more, the heat and moisture resistance of the wiring circuit is further improved. Further, when the Tg is 100 ° C. or less, the adhesion between the wiring circuit and the base material is further improved, and the laser processing becomes easy, so that it is easy to obtain a fine L / S. Tg is a numerical value measured by DSC (differential scanning calorimeter).

  When the binder resin simultaneously satisfies the above-mentioned number average molecular weight and the above-mentioned Tg, the reliability of the wiring circuit is further improved, and the laser processability is further improved.

The binder resin is, for example, polyester resin, urethane-modified polyester resin, epoxy-modified polyester resin, (meth) acrylic resin, styrene resin, styrene- (meth) acrylic resin, styrene-butadiene resin, epoxy resin, modified epoxy resin, phenoxy resin, Vinyl chloride-vinyl acetate copolymer, butyral resin, acetal resin, phenol resin, polycarbonate resin, polyether resin, polyurethane resin, polyurethane urea resin, polyurethane resin, polyamide resin, polyimide resin, polyamide imide resin, alkyd resin, polyolefin resin, fluorine resin , Ketone resin, benzoguanamine resin, melamine resin, urea resin, silicone resin, nitrocellulose, cellulose acetate butyrate (CAB) resin, cellulose acetate Propionate (CAP) resins, rosin, rosin esters, and maleic acid resins. Among them, the binder resin is a polyester resin, a polyurethane resin, a polyurethane urea resin from the viewpoint of adhesion to a substrate, for example, solubility in a solvent used in screen printing and mechanical strength of a coating film necessary for wiring circuits. It is preferable to be selected from the group consisting of and epoxy resins.
Binder resin can use together single or 2 types or more.

  The polyester resin preferably has at least one of a hydroxyl group and a carboxyl group. The polyester resin can be synthesized by a known synthesis method such as a reaction of a polybasic acid and a polyol or a transesterification reaction of a polybasic acid ester and a polyol or the like. Further, as a method for giving a carboxyl group to a polyester resin, known methods can be used. For example, after polymerizing a polyester resin, post-addition (ring-opening addition) of cyclic ester such as ε-caprolactone is carried out at 180 to 230 ° C. Examples thereof include a method of blocking and a method of adding an acid anhydride such as trimellitic anhydride and phthalic anhydride. Also, the polyester resin is preferably a saturated polyester.

The polybasic acid is preferably, for example, an aromatic dicarboxylic acid, a linear aliphatic dicarboxylic acid, a cyclic aliphatic dicarboxylic acid, etc., and a trifunctional or higher functional carboxylic acid. In addition, polybasic acid contains an acid anhydride group containing compound.
Examples of aromatic dicarboxylic acids include, but are not limited to, terephthalic acid and isophthalic acid. In addition, examples of linear aliphatic dicarboxylic acids include, but are not limited to, adipic acid, sebacic acid, and azelaic acid. In addition, examples of cyclic aliphatic dicarboxylic acids include 1,4-cyclohexanedicarboxylic acid, dicarboxylic acid hydrogenated bisphenol A, dimer acid, 4-methylhexahydrophthalic anhydride, and 3-methylhexahydrophthalic anhydride. Is not limited to these. Moreover, although trifunctional or more than trifunctional carboxylic acid is used, trimellitic anhydride, pyromellitic anhydride, etc. may be mentioned, but it is not limited thereto. Other carboxylic acids include, but are not limited to, unsaturated dicarboxylic acids such as fumaric acid, and sulfonic acid metal salt-containing dicarboxylic acids such as 5-sulfoisophthalic acid sodium salt.
The polybasic acids can be used alone or in combination of two or more.

The polyol is preferably a diol and a compound having three or more hydroxyl groups.
Examples of the diol include, but are not limited to, ethylene glycol, propylene glycol 1,4-butanediol, neopentyl glycol and the like.
Examples of the compound having three or more hydroxyl groups include, but are not limited to, tolmethylolpropane, glycerin, and pentaerythritol.
The polyols may be used alone or in combination of two or more.

  The said polyurethane resin is a compound which made the polyol, the diisocyanate, and the diol compound of the chain extender react, and has a hydroxyl group at the terminal. The polyurethane resin can extend the molecular chain using a chain extender. The chain extender is generally preferably a diol or the like. The polyurethane resin can be synthesized by a known synthesis method.

The polyol used for the synthesis of the polyurethane resin is preferably polyether polyol, polyester polyol, polycarbonate polyol, polybutadiene glycol and the like. The polyols can be used alone or in combination of two or more.
Polyether polyols are polymers such as ethylene oxide, propylene oxide, and tetrahydrofuran, and copolymers thereof.
The polyester polyol is an ester of the polyol described in the polyester resin and a polybasic acid.
The polycarbonate polyol is preferably 1) a compound obtained by reacting a diol or bisphenol with a carbonate, and 2) a compound obtained by reacting a diol or a bisphenol with phosgene in the presence of an alkali.
Examples of carbonates include, but are not limited to, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, and propylene carbonate.

  The diisocyanate is preferably an aromatic diisocyanate, an aliphatic diisocyanate, an alicyclic isocyanate or the like. Diisocyanates can be used alone or in combination of two or more.

The polyurethane urea resin is a compound obtained by reacting a polyol and a diisocyanate to synthesize a urethane prepolymer having an isocyanate group at an end, and further reacting with a polyamine. In addition, the polyurethaneurea resin can be reacted with a reaction terminator as needed to adjust the molecular weight. It is preferable to use the compound demonstrated by the said polyurethane resin as a polyol and diisocyanate. The polyamine is preferably a diamine.
The reaction terminator is preferably dialkylamine, monoalcohol or the like. The polyurethaneurea resin can be synthesized by a known synthesis method.

  The polyurethane resin and the polyurethane urea resin preferably have a carboxyl group in addition to the hydroxyl group. Specifically, there is a method of synthesis by replacing a part of the diol with a diol having a carboxyl group in the synthesis. The diol is preferably dimethylol propionic acid, dimethylol butanoic acid or the like.

  When the conductive paste contains a polyurethane resin or a polyurethane urea resin, the hardness of the conductive film to be formed is further improved.

A solvent can be used in the synthesis of the polyurethane resin or polyurethane urea resin.
Specifically, ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, aromatic solvents, carbonate solvents and the like are preferable.
Examples of ester solvents include, but are not limited to, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and dimethyl carbonate.
Examples of ketone solvents include, but are not limited to, acetone, methyl ethyl ketone, diisobutyl ketone, diisobutyl ketone, diacetone alcohol, isophorone, cyclohexanone and the like.
Examples of glycol ether solvents include monoethers such as ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, and ethylene glycol monobutyl ether, and acetates thereof; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether Propylene glycol monomethyl ether, propylene glycol monoethyl ether and the like, and acetic acid esters thereof; and the like, but not limited thereto.
Examples of aliphatic solvents include, but are not limited to, n-hexane, cyclohexane, methylcyclohexane, methylcyclohexane and the like.
The solvents may be used alone or in combination of two or more.

The said epoxy resin is a compound which has an epoxy group and a hydroxyl group, and can use a well-known compound. The epoxy resin is preferably a polyglycidyl ether obtained by reacting an aromatic diol represented by bisphenol A and bisphenol F with epichlorohydrin. It is also preferable to use a so-called phenoxy resin which is a high molecular weight epoxy resin as the epoxy resin.
Binder resin can use together single or 2 types or more.

  The binder resin is preferably blended with 4.9 to 20% by mass of the total 100% by mass of the conductive particles, the organic solvent soluble laser absorber and the binder resin, and more preferably 5.0 to 10% by mass. By becoming 5 mass% or more, the adhesiveness with the base material of a conductive film improves more, and mechanical strength also improves. In addition, when the content is 20% by mass or less, the conductivity is further improved.

  In the present invention, the dispersant is preferably used to disperse the conductive fine particles which are difficult to disperse in the conductive paste. In addition, when the conductive paste contains a dispersant, the binder resin and the conductive fine particles are easily mixed and the dispersibility is improved, so that the TI value becomes low, and the viscosity can be easily adjusted to the Newtonian. The conductive paste of the present invention has a low viscosity and a viscosity close to that of the Newtonian and therefore has good flowability. For example, a coating formed by screen printing has a smooth surface and a nonuniform thickness. Since it is difficult, the processability in laser processing is good, so that a wiring circuit with good linearity can be formed.

  The dispersant is preferably selected from the group consisting of resin type dispersants, surfactants, silane coupling agents, metal chelates and the like.

  The resin type dispersing agent is a dispersing agent of a polymer (resin) having an affinity site to be adsorbed to the conductive fine particles and a site having a high affinity to the binder resin. The said affinity site | part is a carboxyl group, a phosphoric acid group, a sulfonic acid group, a hydroxyl group, a maleic acid group, (primary, secondary, tertiary) amino group, an amide group, an alkyl ammonium salt, phosphate, polyamideamide etc. Can be mentioned. Moreover, a polyester unit, a polyether unit, a polyether ester unit, a polyacryl unit, a polyurethane unit etc. are mentioned as a site | part with high affinity to binder resin.

Resin type dispersants include, for example, polycarboxylic acid ester polyamides such as polyurethane and polyacrylate; polycarboxylic acid, polycarboxylic acid (partial) amine salt, polycarboxylic acid ammonium salt, polycarboxylic acid alkylamine salt, polysiloxane, long -Chain polyaminoamide phosphates, and hydroxyl group-containing polycarboxylic acid esters; amides synthesized by the reaction of poly (lower alkyleneimine) with polyesters having free carboxyl groups, and salts thereof, etc .;
Polyphosphoric acids (salts) such as polyesters, polyethers, polyester ethers, polyurethanes; polyphosphoric acids, polyphosphoric acids (partial) amine salts, polyphosphate ammonium salts, polyphosphate alkylamine salts etc .;
(Meth) acrylic acid-styrene copolymer, (meth) acrylic acid- (meth) acrylic acid ester copolymer, styrene-maleic acid copolymer, polyvinyl alcohol, polyvinyl pyrrolidone, vinyl chloride-vinyl acetate copolymer, Examples thereof include polyesters, modified polyacrylates, ethylene oxide / propylene oxide adducts, and fiber-based derivative resins.

The surfactant is preferably an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant.
Anionic surfactants include, for example, sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate, sodium dodecyl benzene sulfonate, and alkali salts of styrene-acrylic acid copolymer; sodium stearate, sodium alkyl naphthalene sulfonate, alkyl diphenyl ether Sodium disulfonate, monoethanolamine lauryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, monoethanolamine stearic acid, sodium stearate, sodium lauryl sulfate, and monoethanolamine polyoxyethylene alkyl ether of styrene-acrylic acid copolymer Examples include, but are not limited to, phosphoric acid and the like.
Examples of nonionic surfactants include polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene alkyl ether phosphate, polyoxyethylene sorbitan monostearate, polyethylene glycol monolaurate and the like. But not limited thereto.
Examples of cationic surfactants include, but are not limited to, alkyl quaternary ammonium salts and ethylene oxide adducts thereof.
Amphoteric surfactants include, but are not limited to, alkylpetines such as, for example, alkyl dimethylamino acetic acid acetate and alkyl imidazolines.

  The silane coupling agent is, for example, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycid Xypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane-3-methacryloxypropyl, methyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldi Ethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N ( 1,3-Dimethyl-butylidene), propylamine N-phenyl-3-aminopropyltrimethoxysilane, hydrochloride of N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane, 3-ureidopropyl Examples include triethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, and 3-isocyanatopropyltriethoxysilane. But not limited thereto.

  The metal chelate is a chelate compound (metal complex) in which a metal alcoside is reacted with a chelating agent such as β-diketone or ketoester (eg, ethyl acetoacetate). The metal chelate is preferably aluminum chelate, zirconium chelate, titanium chelate and the like.

Aluminum chelates are composed of aluminum and acetonate groups. Acetonate group such as acetyl acetonate _{group: -O-C (CH 3)} = CH, -CO (CH 3) and methyl acetoacetonate _{groups: -O-C (CH 3)} = CH-CO-O- CH ₃ and ethylacetoacetonate group: —O—C (CH ₃ ) = CH—CO—O—C ₂ H ₅ etc. may be mentioned. Among these, use of acetylacetonate group, methylacetoacetonate group and ethylacetoacetate group is preferable because the conductivity of the conductive film is further improved.
Aluminum chelates are, for example, ethyl acetoacetate aluminum diisopropionate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisopropiolate, aluminum tris (acetyl acetate), aluminum monoacetyl acetate bis (ethyl acetoacetate), aluminum Examples thereof include, but are not limited to, -di-n-butoxide monomethyl acetoacetate, aluminum diisobutoxide monomethyl acetoacetate, and aluminum di-sec-butoxide monomethyl acetoacetate. The aluminum chelate is preferably a compound having a formula weight of 200 to 420.

Zirconium chelates are composed of zirconium and acetonate groups. The acetonate group is preferably an acetylacetonate group and an ethylacetoacetate group.
Examples of the zirconium chelate include zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxy acetylacetonate bis (ethylacetoacetate), zirconium dibutoxybis (ethylacetoacetate), zirconium tetraacetylacetonate and the like. . The zirconium chelate is preferably a compound having a formula weight of 350 to 1,000.

The titanium chelate is preferably a titanium chelate and an alkoxy titanium which can be represented by (HOR ₁ O) ₂ Ti (OR ₂ ) ₂ or (H ₂ NR ₁ O) ₂ Ti (0R ₂ ) ₂ . R ₁ and R ₂ are alkyl groups.
Titanium chelates are, for example, di-i-propoxybis (acetylacetonato) titanium, di-n-ptoxybis (triethanolaminato) titanium, titanium-i-propoxy octylene glycolate, titanium stearate, titanium acetylacetonate And titanium tetraacetylacetonate, polytitanium acetylacetylacetonate, titanium octylene glycolate, titanium ethyl acetoacetate, titanium lactate, and titanium triethanol aminate. The titanium chelate is preferably a compound having a formula weight of 250 to 1,500.
The dispersant may be used alone or in combination of two or more.

  It is preferable to mix | blend 0.1-20 mass parts with respect to 100 mass parts which totaled binder resin and electroconductive fine particles, and, as for a dispersing agent, 0.1-15 mass% is more preferable. By the dispersing agent being 0.1 parts by mass or more, the dispersibility of the conductive fine particles is further improved. Moreover, the conductivity of a conductive film improves more because a dispersing agent becomes 20 weight or less.

The conductive paste for laser processing of the present invention may further contain a solvent. By blending the solvent, the dispersion of the conductive fine particles becomes easy, and it becomes easy to adjust the viscosity suitable for printing.
The solvent can be selected according to the type of the absorbent used and the solubility of the resin, the printing method, and the like. Specifically, as the solvent, ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, alicyclic solvents, aromatic solvents, alcohol solvents, water and the like are preferable.
As an ester solvent, what was illustrated as a solvent which can be used at the time of a synthesis | combination in polyurethane resin or polyurethane urea resin can be illustrated similarly. Furthermore, cyclic ester solvents such as ε-caprolactone and γ-butyrolactone can also be exemplified. As ketone solvents, glycol ether solvents and aliphatic solvents, those exemplified as solvents which can be used at the time of synthesis of polyurethane resin or polyurethane urea resin can be exemplified similarly.
Examples of the aromatic solvent include, but not limited to, toluene, xylene, tetralin and the like.
The solvents may be used alone or in combination of two or more.

  The solvent is about 5 to 50% by mass in the total of 100% by mass of the nonvolatile matter of the conductive paste and the solvent.

The conductive paste of the present invention can further contain a curing agent. The curing agent has a functional group capable of reacting with a functional group (for example, a hydroxyl group, a carboxyl group, etc.) of the binder resin, and improves the heat resistance, solvent resistance, chemical resistance, adhesion, etc. of the conductive film. be able to. The curing agent is preferably an isocyanate compound, an epoxy compound, an aziridine compound, an oxazoline compound, a carbodiimide compound, an amine compound, an acid anhydride group-containing compound, and the like.
Specifically, when the binder resin has a hydroxyl group, an isocyanate compound or the like is preferable. When the binder resin has a carboxyl group, isocyanate compounds, epoxy compounds, aziridine compounds, oxazoline compounds, carbodiimide compounds and the like are preferable. Furthermore, when a binder resin has an epoxy group, an amine compound, an acid anhydride group containing compound, etc. are preferable.

The isocyanate compound is preferably an aromatic polyisocyanate, an aliphatic polyisocyanate, an alicyclic polyisocyanate and the like.
Examples of the aromatic polyisocyanate include a trimethylolpropane adduct of tolylene diisocyanate, an isocyanurate of tolylene diisocyanate, and an oligomer of 4,4'-diphenylmethane diisocyanate.
Aliphatic polyisocyanates such as biuret of hexamethylene diisocyanate, isocyanurate of hexamethylene diisocyanate, trimethylolpropane adduct of hexamethylene diisocyanate, oligomer of hexamethylene diisocyanate, uretdione of hexamethylene diisocyanate, and tolylene diisocyanate The isocyanurate etc. of the copolymer which consists of hexamethylene diisocyanate etc. are mentioned.
The alicyclic polyisocyanate includes, for example, an isocyanurate of isophorone diisocyanate, an oligomer of isophorone diisocyanate and the like.
Also preferred is a blocked isocyanate obtained by blocking these compounds. The blocking agent is preferably, for example, ε-caprolactam, butanone oxime, phenol, an active methylene compound and the like.

  The epoxy compound is a compound having an epoxy group. The properties of epoxy compounds are liquid and solid. The epoxy compound is preferably an epoxy resin such as a glycidyl ether type epoxy resin, a glycidyl amine type epoxy resin, a glycidyl ester type epoxy resin, and a cyclic aliphatic (alicyclic type) epoxy resin.

  The glycidyl ether type epoxy resin is, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AD type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin And epoxy resin having biphenyl structure between cresol structure and cresol structure (manufactured by Nippon Kayaku Co., Ltd .: NC-3000 etc.), cresol novolak type epoxy resin, having dicyclopentadiene skeleton structure between cresol structure and cresol structure Epoxy resin (manufactured by Nippon Kayaku Co., Ltd .: XD-1000, etc.), α-naphthol novolac type epoxy resin, bisphenol A type novolac type epoxy resin, dicyclopentadiene type epoxy resin, Phenyl type epoxy resin, tris (glycidyloxy) methane, and tetrakis (glycidyloxyphenyl) ethane and the like.

  Examples of glycidyl amine type epoxy resins include tetraglycidyldiaminodiphenylmethane, triglycidyl paraaminophenol, triglycidyl metaaminophenol, and tetraglycidyl metaxylylene diamine.

Examples of glycidyl ester type epoxy resins include diglycidyl phthalate, diglycidyl hexahydrophthalate, and diglycidyl tetrahydrophthalate.

  Examples of cyclic aliphatic (alicyclic) epoxy resins include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate, and bis (epoxycyclohexyl) adipate.

  Among the curing agents used for the conductive paste of the present invention, as the aziridine compound, for example, trimethylolpropane-tri-β-aziridinyl propionate, tetramethylolmethane-tri-β-aziridinyl propionate, N, N-hexamethylene-1,6-bis-1-aziridinecarboxamide, 4,4-bis (ethyleneiminocarboxylamino) diphenylmethane and the like can be mentioned.

  Examples of the oxazoline compound include 2,2 ′-(1,3-phenylene) -bis (2-oxazoline) and the like.

  Examples of carbodiimide compounds include dicyclohexyl carbodiimide, and carbodilite (polycarbodiimide resin manufactured by Nisshinbo Co., Ltd.).

  Examples of the amine compound include diethylenetriamine, triethylenetetramine, tetraethylenepentamine and the like.

Examples of the acid anhydride group-containing compound include tetrahydrophthalic anhydride, dodecenyl succinic anhydride, methyl nadic anhydride, trimellitic anhydride, and pyromellitic anhydride.
The curing agents may be used alone or in combination of two or more.

  The curing agent is preferably blended in an amount of 0.5 to 20 parts by mass with respect to 100 parts by mass of the binder resin. When the curing agent is used within the above range, the adhesion of the conductive film and the heat resistance are further improved.

    The conductive paste of the present invention can be blended with additives such as a curing accelerator to accelerate the curing reaction. As the curing accelerator, dicyandiamide, tertiary amine compounds, phosphine compounds, imidazole compounds, carboxylic acid hydrazides, dialkylureas such as aliphatic or aromatic dimethylureas, acid anhydrides and the like can be used. In addition, the said additive is effective in hardening acceleration | stimulation of an epoxy resin.

Examples of tertiary amine compounds include triethylamine, benzyldimethylamine, 1,8-diazabicyclo (5.4.0) undecen-7, and 1,5-diazabicyclo (4.3.0) nonene-5.
The phosphine compounds include, for example, triphenyl phosphine, tributyl phosphine and the like.
The imidazole compounds are, for example, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-dimethylimidazole, 2-phenylimidazole, etc., and reaction thereof with an epoxy resin. And compounds which are insolubilized in a solvent, as well as latent curing accelerators having improved storage stability, such as a type in which these are encapsulated in microcapsules.

Examples of carboxylic acid hydrazides include succinic acid hydrazide and adipic acid hydrazide. Examples of the acid anhydride include tetrahydrophthalic anhydride, dodecenyl succinic anhydride, methyl nadic anhydride, trimellitic anhydride, and pyromellitic anhydride.
The additives may be used alone or in combination of two or more.

  It is preferable that the said additive mix | blends 0.1-30 mass parts with respect to 100 mass parts of binder resin.

  The conductive paste of the present invention may optionally contain a friction improver, an infrared absorber, an ultraviolet absorber, an aromatic, an antioxidant, an organic pigment, an inorganic pigment, an antifoamer, a plasticizer, a flame retardant, and a moisturizing agent. And the like.

The conductive paste of the present invention can be produced by blending the raw materials described in the upper part at a predetermined ratio and mixing them with a stirrer. As a stirrer, a known mixer such as a planetary mixer and a desper can be used. Further, conductive fine particles can be dispersed more finely by dispersing in addition to a stirrer. The dispersing machine may, for example, be a ball mill, a bead mill, or a 3-roll mill.
The conductive sheet of the present invention is provided with a sheet-like substrate and a conductive film formed from the conductive paste for laser processing. If one example of the manufacturing method of a conductive sheet is given, a conductive film can be formed by printing a conductive paste on a substrate, for example. The conductive film has a smooth surface and thus has good laser processability. The surface smoothness of the conductive film is preferably 0.3 μm or less, and more preferably 0.25 μm or less. The lower limit value of Ra is preferably 0 μm, but is actually about 0.1 μm because it is technically difficult in practice. When Ra is 0.3 μm or less, the unevenness of the surface is small, so that it is difficult for the laser light to be irregularly reflected and it becomes easy to form a circuit pattern having high straightness. In addition, Ra is an arithmetic mean height, and can be measured by a contact type surface shape roughness measuring device Talysurf 60 (manufactured by Ametec Co., Ltd.) or the like.

For example, screen printing, flexographic printing, offset printing, gravure printing, gravure offset printing and the like are preferable, and screen printing is more preferable. As the screen plate used for screen printing, it is preferable to use a fine mesh screen, particularly preferably a fine mesh screen of about 400 to 650 mesh, in order to correspond to the high definition of the conductive circuit pattern and the smoothness of the conductive film. . The open area of the screen at this time is preferably 20 to 50%. The screen wire diameter is preferably about 10 to 70 μm.
Moreover, it is preferable to perform a drying process after printing. The drying process includes known drying devices such as a hot air oven, an infrared oven, and a microwave oven, and a composite oven in which these are combined.

  The sheet-like substrate is not particularly limited, and, for example, polyimide film, polyparaphenylene terephthalamide film, polyether nitrile film, polyether sulfone film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film And polycarbonate films, polyvinyl chloride films, and polyacrylic films. Moreover, the ITO film which formed the ITO (tin dope indium oxide) layer on these films, and the ITO glass which formed the ITO layer on the glass plate are also mentioned. The substrate may also be an ITO ceramic in which an ITO layer is formed on a ceramic plate. The ITO layer does not have to be formed on the entire surface of the film or plate, and may be partially formed.

  The thickness of the sheet-like substrate is not particularly limited, but is about 50 to 350 μm, and more preferably 100 to 250 μm. By the thickness in the above range, mechanical properties, shape stability, dimensional stability, handling surface and the like of the substrate tend to be appropriate.

  3-30 micrometers is preferable normally, and, as for the thickness of a conductive film, 4-10 micrometers is more preferable. By setting the thickness to 3 to 30 μm, the influence of the laser light of the non-irradiated part is suppressed, and the adhesion to the substrate is further improved.

The manufacturing method of the wiring circuit using the conductive paste of this invention is demonstrated.
A first step of printing the conductive paste for laser processing of the present invention on a sheet-like substrate to form a conductive film,
Then, the conductive film is irradiated with a laser to remove a part of the conductive film, thereby forming a wiring circuit.

  The second step is a step of forming a wiring circuit having a desired L / S by irradiating the conductive film obtained in the first step with a laser beam. The portion of the conductive film irradiated with the laser light absorbs the laser energy and the temperature rapidly rises to several thousand degrees, and the portion melts and evaporates to become plasma instantly, and the conductive coating film Is believed to be eliminated.

The laser light preferably has a fundamental wave wavelength of 193 to 10600 nm. Specifically, excimer laser (wavelength of fundamental wave: 193 to 308 nm), YVO ₄ laser (wavelength of fundamental wave: 1064 nm), YAG laser (wavelength of fundamental wave: 1064 nm), fiber laser (wavelength of fundamental wave: 1060 nm) , CO ₂ lasers (wavelength of fundamental wave: 10600 nm), and semiconductor lasers.
In the present invention, YAG laser is particularly preferable because the damage to the substrate is small.

The output, scanning speed and frequency when using laser light may be any conditions that can remove the conductive film, and are not limited, but generally the output is 1 to 50 W, the scanning speed is 1,000 to 4 And 1000 mm / s, and the frequency is about 10 to 400 kHz.
In addition, scanning (irradiation) of laser light can be repeated plural times.

  The wiring circuit obtained by the above-mentioned manufacturing method can be used as a component of a touch panel whose visibility is important, since an ultra-high definition pattern with L / S of 30 μm / 30 μm or less can be easily obtained. Moreover, you may use for the use of a flat panel display and a solar cell.

  The electronic device of the present invention includes a wiring circuit formed using a conductive paste for laser processing. The electronic device is a mobile phone, a smartphone, or a tablet terminal. Examples include electronic devices provided with a touch panel display such as a laptop PC, an electronic book, and a car navigation. In addition, even without a display, it can be used without limitation in electronic devices and the like provided with a wiring circuit formed by laser processing, such as digital cameras, video cameras, CD / DVD players and the like.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples, but the present invention is not limited to the following examples. In addition, "part" means "mass part" and "%" means "mass%."

(Binder resin 1)
40 parts of JER 1256 (bisphenyl A type epoxy resin, number average molecular weight (Mn) 25,000, Tg 95 ° C, epoxy equivalent 7,500, hydroxyl value 190, manufactured by Mitsubishi Chemical Corporation) 30 parts isophorone, 30 parts γ-butyrolactone It melt | dissolved and obtained the binder resin solution (1) of 40% of a non volatile matter.

(Binder resin 2)
40 parts of JER 4250 (a mixture of bisphenyl A-type epoxy resin and bisphenol F-type epoxy resin, Mn 24,000, Tg 70 ° C., epoxy equivalent 8,500, hydroxyl value 180, Mitsubishi Chemical Co., Ltd.) 30 parts isophorone, 30 γ-butyrolactone The mixture was dissolved in a portion to obtain a binder resin solution (2) having a nonvolatile content of 40%.

(Binder resin 3)
40 parts of Byron 650 (polyester resin, Mn 23,000, Tg 10 ° C., hydroxyl number 5, acid number 1, acid number 1, manufactured by Toyobo Co., Ltd.) is dissolved in 30 parts of isophorone and 30 parts of γ-butyrolactone to obtain a binder resin solution with a nonvolatile content of 40% I got 3).

(Binder resin 4)
Polyester polyol synthesized from isophthalic acid and 3-methyl-1,5 pentanediol in a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet (Kuraray polyol P-2030, Mn2033, Kuraray Co., Ltd.) Charge 127.4 parts, 1.9 parts of dimethylolbutanoic acid, 15.9 parts of isophorone diisocyanate, 0.04 parts of dibutyltin dilaurate and 43 parts of diethylene glycol monoethyl ether acetate, and react at 90 ° C. for 5 hours under nitrogen stream I did. Subsequently, 102 parts of diethylene glycol monoethyl ether acetate was added to obtain a solution of a polyurethane resin having a Mn of 19,000, a Tg of 17 ° C., a hydroxyl value of 3, and an acid value of 5. 25 parts of isophorone was added to 100 parts of the polyurethane resin solution to obtain a binder resin solution (4) of polyurethane resin having a nonvolatile content of 40%.

(Binder resin 5)
A reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet pipe: 90.9 parts of P-2030, 1.5 parts of dimethylol butanoic acid, 17.1 parts of isophorone diisocyanate, 0.03 dibutyltin dilaurate Parts and 23 parts of diethylene glycol monoethyl ether acetate were charged and reacted at 90.degree. C. for 3 hours under a nitrogen stream. Then, 72 parts of diethylene glycol monoethyl ether acetate was added to obtain a urethane prepolymer solution having an isocyanate group. Next, a mixture of 3.18 parts of isophorone diamine, 0.36 parts of di-n-butylamine, 17.9 parts of diethylene glycol monoethyl ether, and 56.7 parts of diethylene glycol monoethyl ether acetate, the obtained urethane prepolymer having an isocyanate group obtained 204.5 parts of the solution is added, reacted at 50 ° C. for 3 hours, and reacted at 90 ° C. for 2 hours, and a binder of polyurethane urea resin having Mn 17,000, Tg 19 ° C., acid value 5 and nonvolatile content 40% Resin solution (5) was obtained.

  The Mn, Tg, epoxy equivalent, acid value and hydroxyl value of the binder resins 1 to 5 were determined according to the following method.

<Measurement of Number Average Molecular Weight (Mn)>
Device: GPC (gel permeation chromatography)
Model: Shodex GPC-101 manufactured by Showa Denko KK
Column: Showa Denko KK GPC KF-G + KF805L + KF803L + KF 802
Detector: Differential Refractive Index Detector Shodex RI-71 manufactured by Showa Denko KK
Eluent: THF
Flow rate: sample side: 1 mL / min, reference side: 0.5 mL / min Temperature: 40 ° C
Sample: 0.2% THF solution (100 μL injection)
Calibration curve: A calibration curve was prepared using 12 standard polystyrenes of the following molecular weight manufactured by Tosoh Corporation.
F128 (1.09 × 10 ⁶ ), F80 (7.06 × 10 ⁵ ), F40 (4.27 × 10 ⁵ ), F20 (1.90 × 10 ⁵ ), F10 (9.64 × 10 ⁴ ), F4 (3.79 × 10 ⁴ ), F2 1.81 × 10 ⁴ ), F1 (1.02 × 10 ⁴ ), A5000 (5.97 × 10 ³ ), A2500 (2.63 × 10 ³ ), A1000 (1.05 × 10 ³ ), A500 (5.0 × 10 ² ).
Baseline: Starting from the rising point of the first peak of the GPC curve, no peak was detected at a retention time of 25 minutes (molecular weight: 3,150), and this was used as the end point. Then, the molecular weight was calculated using a line connecting the two points as a baseline.

<Measurement of Tg>
Device: Differential Scanning Calorimeter DSC-220C manufactured by Seiko Instruments Inc.
Sample: about 10 mg (scale to 0.1 mg)
Temperature rising rate: 200 ° C. at 10 ° C./min Tg temperature: A straight line extending the baseline on the low temperature side to the high temperature side and a curve on the low temperature side of the melting peak drawn at the point where the slope is maximum It was the temperature at the intersection of the broken lines.

<Measurement of epoxy equivalent>
It measured based on JISK7236.
<Measurement of hydroxyl value and acid value>
It measured based on JISK 0070.

<Conductive particles>
Silver powder A: spherical silver powder (D50 particle size 1.6 μm, specific surface area 1.0 m ² / g)
Silver powder B: Aggregated silver powder (D50 particle size 0.9 μm, specific surface area 1.5 m ² / g)
<Conductive particle D50 particle size measurement>
The accumulated particle size (D50) of the volume particle size distribution was measured using a laser diffraction particle size distribution measuring apparatus "SALD-3000" manufactured by Shimadzu Corporation.

[Dispersant A] Aluminum chelate ALCH-90F (Aluminum ethyl acetoacetate diisopropionate, non volatile matter 90%, Kawaken Fine Chemical Co., Ltd.)
[Dispersing agent B] DISPERBYK-140 (resin type dispersing agent: ammonium salt having a carboxyl group, an amino group and a polyacrylic unit, acid value 73 KOHmg / g, amine value 76 KOHmg / g, non volatile matter 52%, manufactured by BIC Chemie Japan)
[Dispersing agent C] Hypermer KD-8 (Resin type dispersing agent: carboxyl group-containing fatty acid ester copolymer, acid value 33 KOH mg / g, non-volatile content 100% manufactured by Croda Japan)

<Laser light absorber>
[Absorbent A] Nigrosine Base EX (manufactured by Orient Chemical Industries, Ltd.)
[Absorbent B] Nigrosine Base EX-BP (manufactured by Orient Chemical Industries, Ltd.)
[Absorbent C] Oil Black 109 (manufactured by Chuo Synthetic Chemical Industry Co., Ltd.)
[Absorbent D] Carbon Black # 3030B (manufactured by Mitsubishi Chemical Corporation)
When 1 g of each of the absorbents A to C was added to 100 g (23 ° C.) of the organic solvent contained in each paste, it was rapidly dissolved, and no undissolved matter was observed. On the other hand, Absorbent D was similar but did not dissolve.

Example 1
Binder resin solution (1): 250 parts (including binder resin 1: 100 parts), dispersing agent A: 2.8 parts (nonvolatile content: including 2.5 parts), silver powder A: 391.5 parts, absorption A conductive paste was prepared by mixing 1.2 parts of agent C and 37 parts of diethylene glycol monobutyl ether acetate: 37 parts by a planetary mixer and then dispersing using a three-roll.

Examples 2 to 10, Comparative Examples 1 to 4
The conductive pastes of Examples 2 to 10 and Comparative Examples 1 to 4 are obtained in the same manner as Example 1, except that the resin solution, the silver powder, the dispersant, and the absorbent are mixed as shown in Table 1. It was adjusted.

[Create conductive sheet]
The conductive ink obtained on a corona-treated polyethylene terephthalate film (hereinafter referred to as PET film) having a thickness of 75 μm is screen printed in a pattern of 15 mm long × 30 mm wide, and dried in an oven at 135 ° C. for 30 minutes. A conductive sheet having a thickness of about 5 μm was obtained. In addition, the thickness of the electroconductive sheet was measured using MH-15M type | mold measuring device (made by Nikon Corporation).

<Measurement of surface roughness Ra>
The surface roughness Ra of the conductive film in the obtained conductive sheet was measured using a contact-type surface profile roughness tester Talysurf 60 (manufactured by Ametec Corporation), and analysis software “Taly Map Platinum ver. 5.0” ( It analyzed using Ametech company make).
The measurement conditions are as follows.
・ Measurement range: 5mm x 5mm
・ Number: 51 ・ Speed: 0.5 mm / s
In the analysis, parameters were calculated using data obtained by applying a 0.25 μm filter in a range of 4 mm × 4 mm to remove waviness.

[Evaluation of laser processing sensitivity]
The conductive paste is printed on an untreated PET film with a thickness of 75 μm using a high precision screen printer (SERIA, manufactured by Tokai Seiki Co., Ltd.), and dried for 30 minutes at 135 ° C. to a conductivity of about 6 μm in thickness A conductive sheet having a coating was obtained. As shown in FIG. 1, the screen printing plate used was a plate having four window frame pattern image portions each having a width of 6 mm, a length of 115 mm and a width of 65 mm in an area of 205 mm long and 340 mm wide. The printing conditions are as follows.

(Screen printing conditions)
Screen: Stainless steel plate 400 mesh, wire diameter 18 μm
Emulsion thickness: 10 μm
・ Screen frame: 650 × 550 mm
・ Squeegee angle: 70 °
・ Squeegee hardness: 80 °
Squeegee speed: 150 mm / sec Squeegee pressure: 15 kgf
・ Squeegee indentation: 1.5 mm
・ Clearance: 2.5 mm
・ Used solvent: ethylene glycol monobutyl ether acetate

Next, with respect to the corner portion of the window frame-like conductive film of the obtained conductive sheet, as shown in the enlarged view of FIG. 2, a vertical line (70 mm in length), a horizontal line (30 mm in length) and a corner Laser processing was performed for the purpose of forming a wiring pattern of 16 L / S of 20 μm / 20 μm. The laser processing conditions are as follows.
(Laser processing conditions)
-Laser processing machine: Suzhou Delphi Laser Co., LTD Ag Laser Etching System
Laser light: YAG laser (wavelength 1064 nm of fundamental wave)
・ Maximum output: 20W
・ Beam diameter: 20 μm
・ Frequency: 300kHz
・ Pulse width: 25 nm
・ Scanning speed: 2000 mm / s
・ Number of scans: 2 times

Space width: It evaluated by the following reference | standard in the laser output which can process 20 micrometers.
○: 25% or less of the maximum output.
Fair: 25% or more to 35% or less of the maximum output.
X: Over 35% of the maximum output.

<Line flyover evaluation>
When the laser was excessively irradiated at an output of 45%, the remaining state of the line was evaluated based on the following criteria.
○: The line remains.
Δ: The line is partially left.
X: The line hardly remains.

<Laser processing evaluation>
The conductive sheet was used to process at 25% of the maximum output. Images were taken using a digital microscope (manufactured by VHX-900 Keyence Corporation) in order to evaluate the degree of space width variation. Using the small-sized general-purpose image analyzer “LUZEX AP” (manufactured by Nireko Co., Ltd.), the photographed enlarged photograph was read for the width of the space where the conductive film was removed.
Arbitrary 8 spaces of the circuit pattern were selected, and a total of 3680 space spaces were measured at a total of 3 680 sites at 460 sites per one, and an average value and a standard deviation were determined.
The average value of the space width was determined based on the following criteria.
○: Space width is 18 to 22 μm on average. Good.
Δ: Space width is 16 to 17 μm on average, or 23 to 24 μm. There is no problem in practical use.
×: Space width is less than 16 μm or more than 24 μm. Not practical.

The linearity of the space (the degree of unevenness and the degree of unevenness at the boundary between the line portion 3 and the space portion 4 in FIG. 2) was evaluated by the standard deviation.
The linearity of the space was judged according to the following criteria.
○: standard deviation is 0 to 1.5 μm. Good.
Δ: Standard deviation is 1.6 to 2.4 μm. There is no problem in practical use.
X: Standard deviation is 2.5 micrometers or more. Not practical.
Tables 1 and 2 show the processing sensitivity, the line jump, the average space width, the space width evaluation and the space linearity evaluation.

   As is clear from Table 1, the conductive pastes of Examples 1 to 10 have high laser processing sensitivity and exhibit good laser processability without line loss.

  On the other hand, as shown in Table 2, since Comparative Examples 1 and 2 do not contain a soluble laser light absorbing agent, the laser processing sensitivity is low, and when the laser is excessively irradiated, the line fly tends to be deteriorated. While Comparative Examples 3 to 4 containing an insoluble one as a laser light absorber have excellent laser processing sensitivity, they are remarkably line-broken when the laser is excessively irradiated. In addition, the linearity of the space tends to decrease.

The conductive paste for laser processing according to the present invention has good laser processability and can provide a conductive sheet which is hard to break.
Moreover, the wiring circuit formed by laser processing using the conductive paste for laser processing which concerns on this invention can be used suitably, for example for touch-panel displays, such as a mobile telephone, a smart phone, a tablet terminal, a notebook PC.

1 Screen printing plate 2 Window frame pattern image area 3 Line area (L)
4 Space section (S)

Claims (10)

A binder resin, conductive particles may be dissolved in an organic solvent, and the organic solvent, seen containing an organic solvent-soluble laser absorbent, the organic solvent-soluble laser absorbent is nigrosine, laser machining a conductive paste. The organic solvent-soluble laser absorbent, a binder resin, within a total of 100 wt% of the conductive particles and organic solvent-soluble laser absorbent containing 0.1 to 20 mass%, conductivity for laser processing according to claim 1, wherein paste.   The conductive paste for laser processing according to claim 1 or 2, wherein the organic solvent-soluble laser light absorbent is a laser light absorbent having an absorption peak in a wavelength range of 700 to 2,000 nm. The electroconductive paste for laser processing of any one of Claims 1-3 in which an electroconductive particle contains a silver particle.   The conductive paste for laser processing according to any one of claims 1 to 4, wherein the binder resin has a number average molecular weight of 10,000 to 50,000 and a glass transition temperature of 5 to 100 ° C.   The conductive paste for laser processing according to any one of claims 1 to 5, wherein the binder resin is at least one selected from the group consisting of a polyester resin, a polyurethane resin, a polyurethane urea resin, and an epoxy resin.   A conductive sheet comprising a sheet-like substrate and a conductive film formed from the conductive paste for laser processing according to any one of claims 1 to 6.   8. The conductive sheet according to claim 7, wherein the surface roughness Ra of the conductive film is 0.1 to 0.3 [mu] m. A conductive paste for laser processing according to any one of claims 1 to 6 is printed on a sheet-like substrate to form a conductive film.
Then, the conductive film is irradiated with a laser to remove a part of the conductive film, thereby forming a wiring circuit. The electronic device provided with the circuit pattern formed from the electroconductive paste for laser processing of any one of Claims 1-6.