JP6094642B2 - Conductive paste for laser processing - Google Patents

Description

  The present invention relates to a conductive paste capable of producing a conductive film suitable for laser ablation and the like.

  Etching methods and printing methods are known as means for forming thin parts for electronic parts, electromagnetic wave shields, or means for forming wiring circuits. The etching method is a method of obtaining a circuit pattern having a desired shape by removing a part of the metal film with an etching solution. However, the process is generally complicated and a separate waste liquid treatment is required. There is a problem that takes. Moreover, since the wiring 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.

  Thus, in order to solve this problem and form a wiring circuit at a lower cost, conductive paste has attracted attention. By printing the conductive paste, the wiring circuit can be easily formed. Furthermore, since it can be expected that electronic parts are reduced in size and weight, productivity is improved, cost is reduced, and environmental burden is reduced, a method (printing method) for printing a conductive paste has become widespread.

  In addition, information terminals such as smartphones and tablet-type terminals are becoming multifunctional and maintaining high definition while maintaining their size. To further improve these performance, electronic components are further added. It is necessary to mount with high density. For high-density mounting of electronic components, miniaturization of the electronic component itself and miniaturization of the wiring circuit are required, and a high-definition wiring circuit formed by a conductive paste is also required. For example, in a capacitive touch panel, a line / space with a width of 100 μm or less (hereinafter abbreviated as “L / S”) is 100 μm or less / 100 μm or less, and moreover, smartphones and tablet terminals However, L / S is strongly required to be 50 μm / 50 μm or less due to multifunctional functions such as the above and high definition of the display. However, it is difficult to achieve further high definition by the printing method.

  Therefore, a laser processing method (also called a laser ablation method or a laser etching method) for forming a wiring circuit by laser light irradiation has been studied. In the laser processing method, a conductive coating is formed on an insulating substrate using a conductive paste, and a part thereof is removed with a laser beam, so that the L / S, which is difficult with the printing method, is about 50 μm / 50 μm. However, there is a strong demand from the market for an ultra-high-definition wiring circuit having an L / S of 30 μm / 30 μm or less.

In Patent Document 1, as a conductive paste for forming ablation processing (hereinafter also referred to as laser processing) by laser irradiation, conductive fine particles having an average particle diameter of 5 nm to 30 μm, an inorganic filler, and a resin binder, and A conductive paste containing any of a surfactant, a silane coupling agent, and an organometallic compound is disclosed.
Patent Document 2 discloses a conductive material 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., conductive particles having a D50 average particle diameter of 1 μm to 2 μm, and an organic solvent. A paste is disclosed.

JP 2014-29992 A WO2014 / 013899

  When forming high-definition wiring by laser irradiation, straight portions can be formed by low-energy laser ablation, whereas curved portions (non-linear portions) often require high-energy laser ablation. . Therefore, the conventional conductive paste uses conductive fine particles with an average particle diameter of 1 μm or more, so it is easy to form straight portions at low energy, but the formation of curved portions does not work well for laser ablation. There is a problem that it is difficult to form a simple wiring. On the other hand, when conductive fine particles having a small average particle diameter are used, a curved portion can be easily formed by high-energy laser ablation, but there is a problem in that disconnection is likely to occur because the amount of laser irradiation at the straight portion becomes excessive.

  An object of the present invention is to provide a conductive paste for laser processing that can form a fine wiring circuit by low-energy laser ablation and can form a conductive coating that is hardly broken by high-energy laser ablation.

The conductive paste for laser processing of the present invention comprises a conductive particle A having a D50 average particle size of 0.7 to 3 μm, a conductive particle B having a D50 average particle size of 0.1 to 0.6 μm, a binder resin, and a dispersion Agent,
The weight ratio of the conductive particles A and the conductive particles B is A / B = 95/5 to 30/70.

  According to the present invention, the conductive paste contains the conductive particles A having a D50 average particle size of 0.7 to 3 μm and the conductive particles B having a D50 average particle size of 0.1 to 0.6 μm. In the case of laser ablation at low energy, a fine wiring circuit can be formed due to the presence of the conductive particles B. On the other hand, in the case of laser ablation at high energy, damage to the wiring is minimized by the presence of the conductive particles A. In addition to this, an unexpected effect of improving the physical properties of the wiring circuit was obtained. Furthermore, conductivity was improved because a good conductive path could be formed by using conductive particles in combination.

  According to the present invention, it is possible to provide a conductive paste for laser processing that can form a fine wiring circuit by laser ablation with low energy and can form a conductive film that is hardly broken by laser ablation with high energy.

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

The conductive paste for laser processing of the present invention (hereinafter also referred to as a conductive paste) includes conductive particles A having a D50 average particle size of 0.7 to 3 μm and conductive properties having a D50 average particle size of 0.1 to 0.6 μm. Including particles B, a binder resin, and a dispersant;
The weight ratio of the conductive particles A and the conductive particles B is A / B = 95/5 to 30/70.

  The conductive paste for laser processing of the present invention preferably forms a conductive film by printing. Moreover, it is preferable that the conductive film forms a wiring circuit by laser processing. As another application, a conductive paste for laser processing may be directly printed on the wiring circuit shape. In this specification, laser processing is also referred to as laser ablation.

  In the present invention, the conductive particles include a conductive particle A having a D50 average particle size of 0.7 to 3 μm and a conductive particle B having a D50 average particle size of 0.1 to 0.6 μm. With respect to the role of the two conductive fine particles, the conductive particles B having a small average particle diameter can efficiently convert a low energy laser into heat, so that wiring formation with low energy is facilitated. In addition, since the conductive particles A having a large average particle diameter are relatively difficult to be ablated even by a high energy laser, disconnection of the wiring circuit hardly occurs.

  0.7-3 micrometers is preferable and, as for D50 average particle diameter of the electroconductive particle A, 0.8-2 micrometers is more preferable. Since the D50 average particle size is 0.7-3 μm, the impact on workability due to laser ablation at low energy can be minimized, and disconnection due to laser ablation at high energy can be suppressed. Improves.

  0.1-0.6 micrometer is preferable and, as for D50 average particle diameter of the electroconductive particle B, 0.2-0.6 micrometer is more preferable. When the D50 average particle diameter is 0.1 to 0.6 μm, the disadvantages of high energy laser ablation and low energy laser ablation are suppressed, and both laser processability and conductivity can be achieved. In addition, D50 average particle diameter measured the cumulative particle size (D50) of volume particle size distribution using the laser diffraction particle size distribution measuring apparatus "SALAD-3000" (made by Shimadzu Corp.).

The mixing ratio of the conductive particles A and the conductive particles B is preferably A / B = 95/5 to 30/70, more preferably 80/20 to 60/40 in terms of weight ratio. When the mixing ratio satisfies these numerical ranges, both conductivity and laser processability can be achieved at a higher level.
The two types of conductive particles may be mixed with the conductive particles A and the conductive particles B at the above ratio during paste production, or the particle size distribution of one type of conductive fine particles may be wide. As a result, fine particles satisfying the mixing ratio can be used.

The conductive particles A and B are made of, for example, gold, silver, copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, platinum and other metal fine particles, and alloys thereof. Can be mentioned.
Also preferred are nuclei and composite fine particles whose surfaces are coated with a substance different from the nuclei. The composite fine particles include, for example, silver-coated copper fine particles in which copper is used as a core and the surface thereof is coated with silver. For example, silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, ITO (tin-doped indium oxide) ), AZO (aluminum-doped zinc oxide), and fine particles of metal oxides such as GZO (gallium-doped zinc oxide), and fine particles whose surfaces are coated with these metal oxides.
Among these, silver is preferable because it is low in cost, has high electrical conductivity, and is difficult to oxidize, so that the change in volume resistivity is small. The conductive particles can be used alone or in combination of two or more.

  As the shape of the conductive particles, known shapes such as a spherical shape, a flake shape, a dendritic shape, a rod shape, and a linear shape can be used.

  The conductive particles A and B are added in a total amount of 60 to 95% by weight, more preferably 85 to 95% by weight, out of a total of 100% by weight of the binder resin and the conductive particles. Conductivity improves more by becoming 60 weight% or more. In addition, when the content is 95% by weight or less, the conductive film has more improved adhesion to the base material, and mechanical strength is also improved.

  The conductive paste for laser processing preferably forms a conductive film by a printing method, and more preferably forms a conductive film by a screen printing method. The conductive coating can form a desired wiring circuit by laser light irradiation.

  In the present invention, the binder resin preferably has a number average molecular weight of 10,000 to 50,000, more preferably 20,000 to 40,000. When the number average molecular weight is 10,000 or more, the environmental reliability of the formed wiring circuit is improved, and in particular, the heat and moisture resistance is further improved. Further, when the number average molecular weight is 50,000 or less, an appropriate cohesive force can be obtained in the conductive film, so that ablation during laser processing is facilitated and a high-definition wiring circuit is easily obtained. In addition, a number average molecular weight is a numerical value of polystyrene conversion measured by GPC (gel permeation chromatography).

  The binder resin preferably has a glass transition temperature (hereinafter referred to as Tg) of 5 to 100 ° C, more preferably 10 to 95 ° C. When Tg is 5 ° C. or higher, the moisture and heat resistance of the wiring circuit is further improved. Further, when Tg is 100 ° C. or lower, the adhesion between the wiring circuit and the substrate is further improved, and laser processing is facilitated, so that a fine L / S can be easily obtained. Tg is a numerical value measured by DSC (differential scanning calorimeter).

  When the binder resin satisfies the number average molecular weight and the Tg at the same time, 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, polyamide resin, polyimide resin, polyamideimide 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 these, the binder resin is polyester resin, polyurethane resin, polyurethane urea resin in terms of adhesion to a substrate, for example, solubility in a solvent used in screen printing, and mechanical strength of a coating film necessary for a wiring circuit. And epoxy resins are preferred.
Binder resins can be used alone or in combination of two 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 known reaction such as a reaction between a polybasic acid and a polyol or a transesterification reaction between a polybasic acid ester and a polyol. In addition, as a method for imparting a carboxyl group to a polyester resin, a known method can be used. For example, after polymerization of a polyester resin, a cyclic ester such as ε-caprolactone is post-added (ring-opening addition) at 180 to 230 ° C. Examples thereof include a method of blocking or a method of adding an acid anhydride such as trimellitic anhydride or phthalic anhydride. 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, or the like, or a trifunctional or higher functional carboxylic acid. The polybasic acid includes an acid anhydride group-containing compound.
Examples of the aromatic dicarboxylic acid include, but are not limited to, terephthalic acid and isophthalic acid. Examples of the linear aliphatic dicarboxylic acid include, but are not limited to, adipic acid, sebacic acid, and azelaic acid. Examples of the cycloaliphatic dicarboxylic acid include 1,4-cyclohexanedicarboxylic acid, dicarboxyloxy hydrogenated bisphenol A, dimer acid, 4-methylhexahydrophthalic anhydride, and 3-methylhexahydrophthalic anhydride. However, it is not limited to these. Examples of the tri- or higher functional carboxylic acid include, but are not limited to, trimellitic anhydride and pyromellitic anhydride. Other carboxylic acids include, but are not limited to, unsaturated dicarboxylic acids such as fumaric acid, sulfonic acid metal salt-containing dicarboxylic acids such as sodium 5-sulfoisophthalate, and the like.
Polybasic acids can be used alone or in combination of two or more.

The polyol is preferably a diol and a compound having 3 or more hydroxyl groups.
Examples of the diol include, but are not limited to, ethylene glycol, propylene glycol, 1,4-butanediol, and neopentyl glycol.
Examples of the compound having three or more hydroxyl groups include, but are not limited to, tolmethylolpropane, glycerin, and pentaerythritol.
Polyols can be used alone or in combination of two or more.

  The polyurethane resin is a compound having a hydroxyl group at the terminal, obtained by reacting a polyol, diisocyanate, and a chain extender diol compound. A polyurethane resin can extend a molecular chain using a chain extender. The chain extender is generally preferably a diol. The polyurethane resin can be synthesized by a known synthesis method.

Polyols used for the synthesis of the polyurethane resin are preferably polyether polyols, polyester polyols, polycarbonate polyols, and polybutadiene glycols. Polyols can be used alone or in combination of two or more.
The polyether polyol is a polymer such as ethylene oxide, propylene oxide, and tetrahydrofuran, and a copolymer thereof.
The polyester polyol is an ester of a polyol and a polybasic acid described in the polyester resin.
The polycarbonate polyol is preferably 1) a compound obtained by reacting a diol or bisphenol with a carbonic ester, and 2) a compound obtained by reacting a diol or bisphenol with phosgene in the presence of an alkali.
Examples of the carbonate ester 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. Diisocyanate can be used alone or in combination of two or more.

The polyurethane urea resin is a compound obtained by reacting a polyol and diisocyanate to synthesize a urethane prepolymer having an isocyanate group at a terminal and further reacting with a polyamine. In addition, the polyurethane urea resin can be reacted with a reaction terminator as necessary to adjust the molecular weight. As the polyol and diisocyanate, it is preferable to use the compounds described for the polyurethane resin. The polyamine is preferably a diamine.
The reaction terminator is preferably a dialkylamine, monoalcohol or the like. The polyurethane urea 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, a method of synthesizing by synthesizing a part of the diol with a diol having a carboxyl group at the time of synthesis can be mentioned. The diol is preferably dimethylolpropionic acid, dimethylolbutanoic 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 polyurethane resin or a polyurethane urea resin can use a solvent in the synthesis thereof.
Specifically, ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, aromatic solvents, carbonate solvents and the like are preferable.
Examples of the ester solvent include, but are not limited to, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and dimethyl carbonate.
Examples of the ketone solvent include, but are not limited to, acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanone.
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, but are not limited thereto.
Examples of the aliphatic solvent include, but are not limited to, n-hexane, cyclohexane, methylcyclohexane, methylcyclohexane, and the like.
The solvent can be used alone or in combination of two or more.

The epoxy resin is a compound having an epoxy group and a hydroxyl group, and a known compound can be used. The epoxy resin is preferably a polyglycidyl ether obtained by reacting an aromatic diol represented by bisphenol A and bisphenol F with epichlorohydrin. As the epoxy resin, it is also preferable to use a so-called phenoxy resin which is a polymer epoxy resin.
Binder resins can be used alone or in combination of two or more.

  The binder resin is preferably blended in an amount of 5 to 40% by weight, more preferably 5 to 15% by weight, out of a total of 100% by weight of the binder resin and conductive fine particles. By being 5 weight% or more, the adhesiveness with the base material of an electroconductive film improves more, and mechanical strength also improves. Moreover, electroconductivity improves more by becoming 40 weight% or less.

  The conductive paste of the present invention can further contain a curing agent. The curing agent has a plurality of functional groups capable of reacting with a reactive functional group (for example, a hydroxyl group or a carboxyl group) of the binder resin. When the curing agent is cured with the binder resin, it becomes easy to remove foreign matters generated during laser ablation by air blowing (air removability). In addition, the heat resistance, solvent resistance, chemical resistance, adhesion and the like of the conductive film are further improved. In addition, when the conductive coating is laser ablated, foreign matter is removed using an air blow to prevent short-circuiting to prevent the conductive coating from adhering to the substrate. It is common. The ease of removing foreign matter by this air blow is called air removability.

Preferred examples of the curing agent include isocyanate compounds, epoxy compounds, aziridine compounds, oxazoline compounds, carbodiimide compounds, amine compounds, imidazole compounds, dicyandiamide compounds, and acid anhydride group-containing compounds.
Specifically, when the binder resin has a hydroxyl group, an isocyanate compound or the like is preferable. Moreover, when a binder resin has a carboxyl group, an isocyanate compound, an epoxy compound, an aziridine compound, an oxazoline compound, a carbodiimide compound, etc. are preferable. Furthermore, when the binder resin has an epoxy group, an amine compound, an imidazole compound, a dicyandiamide compound, an acid anhydride group-containing compound, and the like are preferable.

Of the curing agents, the isocyanate compound is preferably aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate, or 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 include, for example, hexamethylene diisocyanate biuret, hexamethylene diisocyanate isocyanurate, hexamethylene diisocyanate trimethylolpropane adduct, hexamethylene diisocyanate oligomer, hexamethylene diisocyanate uretdione, and tolylene diisocyanate. Examples thereof include isocyanurate bodies of copolymers made of hexamethylene diisocyanate.
Examples of the alicyclic polyisocyanate include an isocyanurate of isophorone diisocyanate, an oligomer of isophorone diisocyanate, and the like.
Moreover, the blocked isocyanate which blocked these compounds is also preferable. As the blocking agent, for example, ε-caprolactam, butanone oxime, phenol, and an active methylene compound are preferable.

  Among the curing agents, the epoxy compound is a compound having an epoxy group. The properties of the epoxy compound include 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.

  Examples of glycidyl ether type epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AD type epoxy resins, cresol novolac type epoxy resins, phenol novolac type epoxy resins, and cresol novolak type epoxy resins. An epoxy resin having a biphenyl structure between the cresol structure and the cresol structure (Nippon Kayaku Co., Ltd .: NC-3000, etc.), a cresol novolac type epoxy resin having a dicyclopentadiene skeleton structure between the cresol structure and the cresol structure Epoxy resin (Nippon Kayaku Co., Ltd .: XD-1000, etc.), α-naphthol novolac epoxy resin, bisphenol A novolac epoxy resin, dicyclopentadiene epoxy resin, Phenyl type epoxy resin, tris (glycidyloxy) methane, and tetrakis (glycidyloxyphenyl) ethane and the like.

  Examples of the glycidylamine type epoxy resin include tetraglycidyldiaminodiphenylmethane, triglycidylparaaminophenol, triglycidylmetaaminophenol, and tetraglycidylmetaxylylenediamine.

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

  Examples of the cycloaliphatic (alicyclic) epoxy resin include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate and bis (epoxycyclohexyl) adipate.

  Among the curing agents, examples of the aziridine compound include trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N, N-hexamethylene-1, Examples include 6-bis-1-aziridinecarboxamide and 4,4-bis (ethyleneiminocarboxylamino) diphenylmethane.

  Among the curing agents, examples of the oxazoline compound include 2,2 ′-(1,3-phenylene) -bis (2-oxazoline).

  Examples of the carbodiimide compound among the curing agents include dicyclohexyl carbodiimide, carbodilite (Nisshinbo Co., Ltd., polycarbodiimide resin), and the like.

  Among the curing agents, examples of the amine compound include diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

  Among the curing agents, examples of imidazole compounds include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-dimethylimidazole, imidazole compounds such as 2-phenylimidazole, and the like. A latent curing agent with improved storage stability such as a type in which an imidazole compound and an epoxy resin are reacted to insolubilize in a solvent, or a type in which an imidazole compound is encapsulated in a microcapsule can be mentioned.

  Among the curing agents, examples of the dicyandiamide compound include dicyandiamide (DICY).

  Among the curing agents, examples of the acid anhydride group-containing compound include tetrahydrophthalic anhydride, dodecenyl succinic anhydride, methyl nadic anhydride, trimellitic anhydride, and pyromellitic anhydride.

  A hardening | curing agent can be used individually or in combination of 2 or more types.

  It is preferable to mix 0.5-20 weight part of hardening | curing agents with respect to 100 weight part of binder resin. When a hardening | curing agent is used within the said range, the adhesiveness with the base material of a conductive film and heat resistance will improve more.

  The conductive paste of the present invention can contain additives such as a curing accelerator in order to accelerate the curing reaction. As the curing accelerator, dicyandiamide, tertiary amine compound, phosphine compound, imidazole compound, carboxylic acid hydrazide, dialkylurea such as aliphatic or aromatic dimethylurea, acid anhydride and the like can be used. The curing accelerator is effective for promoting the curing of the epoxy resin.

Examples of the tertiary amine compound include triethylamine, benzyldimethylamine, 1,8-diazabicyclo (5.4.0) undecene-7, 1,5-diazabicyclo (4.3.0) nonene-5, and the like.
Examples of the phosphine compound include triphenylphosphine and tributylphosphine.
Examples of the carboxylic acid hydrazide include succinic acid hydrazide and adipic acid hydrazide. Examples of the acid anhydride include tetrahydrophthalic anhydride, dodecenyl succinic anhydride, methyl nadic anhydride, trimellitic anhydride, pyromellitic anhydride, and the like.
The additives can be used alone or in combination of two or more.

  The additive is preferably blended in an amount of 0.1 to 30 parts by weight with respect to 100 parts by weight of the binder resin.

  The conductive paste of the present invention includes a friction improver, an infrared absorber, an ultraviolet absorber, a fragrance, an antioxidant, an organic pigment, an inorganic pigment, an antifoaming agent, a plasticizer, a flame retardant, and a moisturizing agent as necessary. Agents and the like.

The conductive paste for laser processing of the present invention can further contain a laser sensitizer in order to improve laser processability. The laser sensitizer is preferably a dye, pigment, filler or the like having absorption at the wavelength of the laser beam, and more preferably carbon powder of the pigment.
Examples of the carbon powder include carbon black, furnace black, channel black, lamp black, acetylene black, ketjen black, carbon nanotube, and graphite. The laser sensitizer is preferably blended in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the total of the binder resin and the conductive fine particles.

  In the present invention, the dispersant is used to disperse conductive fine particles that 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 is lowered and the viscosity is easily adjusted to Newtonian. Since the conductive paste of the present invention has a low viscosity and a viscosity close to Newtonian, it has good fluidity. For example, a coating formed by screen printing has a smooth surface and a varying film thickness. Since it is difficult, the processability in laser processing is good. Therefore, a wiring circuit with good linearity can be formed.

  The dispersant is preferably a resin-type dispersant, a surfactant, a silane coupling agent, a metal chelate, or the like.

  The resin-type dispersant is a polymer (resin) dispersant having an affinity site (functional group site) adsorbed on conductive fine particles and a resin site having high affinity for the binder resin. Examples of the affinity site include a carboxyl group, a phosphate group, a sulfonate group, a hydroxyl group, a maleate group, a (primary, secondary, and tertiary) amino group, an amide group, an alkyl ammonium salt, a phosphate, and a polyamide amide. Is mentioned. Examples of the portion having high affinity for the binder resin include a polyester unit, a polyether unit, a polyether ester unit, a polyacryl unit, and a polyurethane unit.

Resin-type dispersants include, for example, polyurethanes and polycarboxylic acid ester polyamides such as polyacrylates; polycarboxylic acids, polycarboxylic acid (partial) amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid alkylamine salts, polysiloxanes, long A chain polyaminoamide phosphate, and a hydroxyl group-containing polycarboxylic acid ester; an amide synthesized by reaction of poly (lower alkyleneimine) with a polyester having a free carboxyl group, and a salt thereof;
Polyphosphoric acid (salt) such as polyester, polyether, polyester ether, polyurethane; polyphosphoric acid, polyphosphoric acid (partial) amine salt, polyphosphoric acid ammonium salt, polyphosphoric acid alkylamine salt, etc .;
(Meth) acrylic acid-styrene copolymer, (meth) acrylic acid- (meth) acrylic ester copolymer, styrene-maleic acid copolymer, polyvinyl alcohol, polyvinylpyrrolidone, vinyl chloride-vinyl acetate copolymer, Examples include polyester-based, modified polyacrylate-based, ethylene oxide / propylene oxide addition compounds, and fiber-based derivative resins.

The surfactant is preferably an anionic surfactant, a nonionic surfactant, a cationic surfactant, or an amphoteric surfactant.
Examples of the anionic surfactant include sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate, sodium dodecylbenzene sulfonate, and alkali salt of styrene-acrylic acid copolymer; sodium stearate, sodium alkylnaphthalene sulfonate, alkyl diphenyl ether Sodium disulfonate, monoethanolamine lauryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, monoethanolamine stearate, sodium stearate, sodium lauryl sulfate, and monoethanolamine polyoxyethylene alkyl ether of styrene-acrylic acid copolymer Examples include, but are not limited to, phosphoric acid ester.
Nonionic surfactants include, for example, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene alkyl ether phosphate ester, polyoxyethylene sorbitan monostearate, polyethylene glycol monolaurate, etc. However, it is not limited to these.
Cationic surfactants include, but are not limited to, alkyl quaternary ammonium salts and their ethylene oxide adducts.
Examples of amphoteric surfactants include, but are not limited to, alkyl petines such as alkyldimethylaminoacetic acid petine, and alkylimidazolines.

  Examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycid. Xylpropylmethyldiethoxysilane, 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, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyl Examples include triethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, and 3-isocyanatopropyltriethoxysilane. However, it is not limited to these.

  The metal chelate is a chelate compound (metal complex) obtained by reacting a metal alcoside with a chelating agent such as β-diketone or ketoester (for example, ethyl acetoacetate). The metal chelate is preferably an aluminum chelate, a zirconium chelate, a titanium chelate or the like.

Aluminum chelates are composed of aluminum and acetonate groups. The acetonate group is, for example, an acetylacetonate group: —O—C (CH ₃ ) ═CH, —CO (CH ₃ ), or a methyl acetoacetonate group: —O—C (CH ₃ ) ═CH—CO—O—. CH ₃ and ethyl acetoacetonate groups: —O—C (CH ₃ ) ═CH—CO—O—C ₂ H _{5 and the} like can be mentioned. Among these, it is preferable to use an acetylacetonate group, a methylacetoacetonate group, and an ethylacetoacetate group because the conductivity of the conductive coating is further improved.
Aluminum chelates include, for example, ethyl acetoacetate aluminum diisopropionate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum tris (acetyl acetate), aluminum monoacetyl acetate bis (ethyl acetoacetate), aluminum Examples include, but are not limited to, di-n-butoxide monomethyl acetoacetate, aluminum diisobutoxide monomethyl acetoacetate, aluminum di-sec-butoxide monomethyl acetoacetate, and the like. 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 or an ethylacetoacetate group.
Examples of the zirconium chelate include zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxyacetylacetonate 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 that 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 include, for example, di-i-propoxybis (acetylacetonato) titanium, di-n-ptoxybis (triethanolaminato) titanium, titanium-i-propoxyoctylene glycolate, titanium stearate, titanium acetylacetonate , Titanium tetraacetylacetonate, polytitanium acetylacetylacetonate, titanium octylene glycolate, titanium ethyl acetoacetate, titanium lactate, and titanium triethanolamate. The titanium chelate is preferably a compound having a formula weight of 250 to 1,500.
A dispersing agent can be used individually or in combination of 2 or more types.

  The dispersant is preferably blended in an amount of 0.1 to 20 parts by weight, more preferably 0.1 to 15 parts by weight, based on 100 parts by weight of the total amount of the binder resin and conductive fine particles. The dispersibility of electroconductive fine particles improves more because a dispersing agent will be 0.1 weight part or more. Moreover, the electroconductivity of a conductive film improves more because a dispersing agent will be 20 weight or less.

The conductive paste for laser processing of the present invention can further contain a solvent. By blending the solvent, the dispersion of the conductive fine particles is facilitated, and the viscosity suitable for printing can be easily adjusted.
The solvent can be selected depending on the solubility of the resin used, the type of printing method, and the like.
Specifically, ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, alicyclic solvents, aromatic solvents, alcohol solvents, water, and the like are preferable.
As the ester solvent, the solvent already described for the polyurethane resin or the polyurethane urea resin can be used. Other examples include cyclic ester solvents such as ε-caprolactone and γ-butyrolactone.
As the ketone solvent, glycol ether solvent, and aliphatic solvent, the solvents already described in the polyurethane resin or polyurethane urea resin can be used.
Examples of the aromatic solvent include, but are not limited to, toluene, xylene, tetralin and the like.
The solvent can be used alone or in combination of two or more.

  The solvent is about 5 to 50% by weight out of the total 100% by weight of the nonvolatile content of the conductive paste and the solvent.

  The viscosity of the conductive paste of the present invention is a numerical value measured using an E-type (cone plate type) viscometer and rotor # 7 (θ3 ° x R7.7 mm) at a temperature of 25 degrees and a rotational speed of 5 rpm. The thixo index (hereinafter referred to as TI value) is a numerical value obtained by dividing the viscosity at a rotation speed of 2 rpm at a temperature of 25 ° C. by the viscosity at a rotation speed of 20 rpm using a rotor # 7 in an E type viscometer. Each viscosity is a value 2 minutes after the start of measurement.

  The conventional conductive paste for screen printing has poor fluidity because the viscosity is adjusted to thixotropic properties to form a high-definition wiring circuit by printing, and is derived from the screen printing plate on the surface of the formed conductive film. Since the uneven shape remained, the variation in film thickness was large. When such a conductive film is subjected to laser processing for the purpose of, for example, L / S = 30 μm / 30 μm, it is difficult to laser ablate the part where the film is thick, and the film is likely to remain, whereas laser ablation is easy in the part where the film is thin As a result, the space width (S width) varies and a wiring circuit with low linearity is formed. On the other hand, since the conductive paste of the present invention has good fluidity because the viscosity is close to Newtonian, the formed conductive film has few irregularities. Since the conductive coating has little variation in thickness, for example, when laser processing is performed to form a wiring circuit of L / S = 30 μm / 30 μm, the conductive coating can be easily removed uniformly, so that the wiring with high linearity can be obtained. A circuit can be formed.

  The conductive paste of the present invention can be produced by blending the raw materials described above in a predetermined ratio and mixing with a stirrer. As the stirrer, a known apparatus such as a planetary mixer and a desper can be used. In addition to the stirrer, the conductive fine particles can be dispersed more finely by dispersing. Examples of the disperser include a ball mill, a bead mill, and a three roll.

  The laser processing sheet of the present invention includes a base material and a conductive coating containing a laser processing conductive paste. If an example of the manufacturing method of the sheet | seat for laser processing is given, the sheet | seat for laser processing provided with the electroconductive film can be manufactured by printing an electrically conductive paste on a base material, for example.

The printing is preferably, for example, screen printing, flexographic printing, offset printing, gravure printing, gravure offset printing, and more preferably screen printing. The screen plate used in the screen printing is preferably a fine mesh screen, particularly preferably a fine mesh screen of about 400 to 650 mesh, in order to cope with high definition of the wiring circuit pattern and smoothness of the conductive film. . At this time, the open area of the screen is preferably 20 to 50%. The screen wire diameter is preferably about 10 to 70 μm. It is preferable to perform a drying step after printing. Examples of the drying step include known drying apparatuses such as a hot air oven, an infrared oven, a microwave oven, and a composite oven in which these are combined.

  The substrate is, for example, polyimide film, polyparaphenylene terephthalamide film, polyether nitrile film, polyether sulfone film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polycarbonate film, polyvinyl chloride film, and A well-known film, such as a polyacryl film, is mentioned. 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. In addition, examples of the substrate include ITO ceramics in which an ITO layer is formed on a ceramic plate. The ITO layer does not need to be formed on the entire surface of the film or plate and may be formed partially.

  The thickness of the substrate is usually about 30 to 350 μm, and more preferably about 50 to 250 μm. The mechanical properties, shape stability, dimensional stability, handling surface and the like of the substrate are likely to be appropriate depending on the thickness within the above range.

  The thickness of the conductive coating is usually preferably about 3 to 30 μm and more preferably 4 to 10 μm. When the thickness is 3 to 30 μm, the non-irradiated portion of the laser beam is hardly affected by the laser beam, and the adhesion to the substrate is further improved.

A method of manufacturing a wiring circuit using a laser processing sheet will be described.
First, a wiring circuit can be formed by performing laser ablation on the conductive film of the produced laser processing sheet and removing a part of the conductive film.
In the manufacturing method, the conductive film is irradiated with laser light to form a wiring circuit having a desired L / S. The part of the conductive film irradiated with laser light absorbs the laser energy and the temperature rapidly rises to several thousand degrees, so that the part melts and evaporates, or instantly becomes plasma, and the conductive film becomes conductive. Is thought to be removed. If foreign matter derived from the conductive coating remains on the wiring circuit, it is removed by air blowing.

The laser beam preferably has a fundamental wavelength in the range 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 laser (wavelength of fundamental wave: 10600 nm), semiconductor laser, and the like.
In the present invention, a YAG laser is particularly preferable because it causes little damage to the substrate.

The output, scanning speed, and frequency when using the laser beam are not limited as long as the conductive film can be removed. Generally, the output is 1 to 50 W, and the scanning speed is 1,000 to 4. , 000 mm / s, and the frequency is about 10 to 400 kHz.
In addition, laser beam scanning (irradiation) can be repeated a plurality of times.

  The wiring circuit obtained by the above manufacturing method is preferably used as a constituent member of a touch panel in which visibility is important because an ultrahigh-definition pattern having an L / S of 30 μm / 30 μm or less is easily obtained. Moreover, you may use for uses, such as a flat panel display and a solar cell.

  The electronic apparatus of the present invention includes a wiring circuit formed using a conductive paste for laser processing. Examples of the electronic device include an electronic device including a touch panel display such as a mobile phone, a smartphone, a tablet terminal, a notebook PC, an electronic book, and a car navigation system. Further, even if there is no display, it can be used without limitation for an electronic device equipped with a wiring circuit formed by laser processing, such as a digital camera, a video camera, a CD / DVD player, and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to a following example. “Parts” means “parts by weight” and “%” means “% by weight”. Moreover, the compounding quantity in a table | surface is a weight part.

<Binder resin>
[Binder resin 1]
40 parts of JER1256 (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) in 30 parts of isophorone and 30 parts of γ-butyrolactone It melt | dissolved and the binder resin solution (1) of 40% of non volatile matters was obtained.

[Binder resin 2]
Byron 650 (polyester resin, Mn 23,000, Tg 10 ° C., hydroxyl value 5, acid value 1, manufactured by Toyobo Co., Ltd.) 40 parts was dissolved in isophorone 30 parts and γ-butyrolactone 30 parts, and a binder resin solution (non-volatile content 40%) 2) was obtained.

[Binder resin 3]
Polyester polyol synthesized with isophthalic acid and 3-methyl-1,5-pentanediol (Kuraray Polyol P-2030, Mn 2033, manufactured by Kuraray Co., Ltd.) in a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas introduction pipe 127.4 parts, dimethylolbutanoic acid 1.9 parts, isophorone diisocyanate 15.9 parts, dibutyltin dilaurate 0.04 parts and diethylene glycol monoethyl ether acetate 43 parts were charged and reacted at 90 ° C. for 5 hours under a nitrogen stream. I let you. Subsequently, 102 parts of diethylene glycol monoethyl ether acetate was added to obtain a polyurethane resin solution 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 a polyurethane resin solution to obtain a polyurethane resin binder resin solution (3) having a nonvolatile content of 40%.

[Binder resin 4]
In a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 90.9 parts of Kuraray polyol P-2030, 1.5 parts of dimethylolbutanoic acid, 17.1 parts of isophorone diisocyanate, dibutyltin dilaurate 0 0.03 part and 23 parts of diethylene glycol monoethyl ether acetate were charged and reacted at 90 ° C. for 3 hours under a nitrogen stream. Subsequently, 72 parts of diethylene glycol monoethyl ether acetate was added to obtain a urethane prepolymer solution having an isocyanate group. Next, a urethane prepolymer having an isocyanate group was added to a mixture of 3.18 parts of isophoronediamine, 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. After adding 204.5 parts of polymer solution and reacting at 50 ° C. for 3 hours, reacting at 90 ° C. for 2 hours, the polyurethane urea resin having Mn of 17,000, Tg of 19 ° C., acid value of 5 and nonvolatile content of 40% A binder resin solution (4) was obtained.

  The Mn, Tg, epoxy equivalent, acid value and hydroxyl value of the binder resins 1 to 4 were determined according to the following method.

<Measurement of number average molecular weight (Mn)>
Apparatus: GPC (gel permeation chromatography)
Model: Shodex GPC-101 manufactured by Showa Denko
Column: Showa Denko GPC KF-G + KF805L + KF803L + KF802
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 with the following molecular weights manufactured by Tosoh Corporation.
F128 (1.09 X10 ⁶ ), F80 (7.06 X10 ⁵ ), F40 (4.27 X10 ⁵ ), F20 (1.90 X10 ⁵ ), F10 (9.64 X10 ⁴ ), F4 (3.79 X10 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: The starting point of the first peak of the GPC curve was the starting point, and no peak was detected at a retention time of 25 minutes (molecular weight 3,150). The molecular weight was calculated using the line connecting both points as the baseline.

<Measurement of Tg>
・ Apparatus: Seiko Instruments' differential scanning calorimeter DSC-220C
-Sample: about 10 mg (weigh to 0.1 mg)
・ Temperature increase rate: Measured up to 200 ° C at 10 ° C / min. ・ Tg temperature: Draw at the point where the gradient is maximized on the low temperature side of the straight line and the melting peak on the low temperature side of the curve. It was set as the temperature of the intersection of a broken line.

<Measurement of epoxy equivalent>
It measured based on JISK7236.

<Measurement of hydroxyl value and acid value>
Measurement was performed in accordance with JIS K 0070.

<Conductive particles>
[Silver powder A] flaky silver powder (D50 average particle diameter 0.7 μm, tap density 4.5 g / cm ³ , specific surface area 2.3 m ² / g)

[Silver powder B] Flaky silver powder (D50 average particle size 0.8 μm, tap density 3.6 g / cm ³ , specific surface area 1.7 m ² / g)

[Silver powder C] Flaky silver powder (D50 average particle diameter 1.0 μm, tap density 3.8 g / cm ³ , specific surface area 1.3 m ² / g)

[Silver powder D] Spherical silver powder (D50 average particle diameter 1.4 μm, tap density 4.1 g / cm ³ , specific surface area 0.9 m ² / g)

[Silver powder E] Spherical silver powder (D50 average particle diameter 2.8 μm, tap density 4.8 g / cm ³ , specific surface area 0.4 m ² / g)

[Silver powder F] Flaky silver powder (D50 average particle diameter 4.0 μm, tap density 4.6 g / cm ³ , specific surface area 0.5 m ² / g)

[Silver powder a] Aggregated silver powder (D50 average particle diameter 0.2 μm, tap density 2.4 g / cm ³ , specific surface area 11.5 m ² / g)

[Silver powder b] Spherical silver powder (D50 average particle size 0.3 μm, tap density 2.5 g / cm ³ , specific surface area 4.0 m ² / g)

[Silver powder c] Flaky silver powder (D50 average particle diameter 0.6 μm, tap density 4.0 g / cm ³ , specific surface area 2.0 m ² / g)

<D50 average particle size measurement>
The cumulative particle size (D50) of the volume particle size distribution was measured using a laser diffraction particle size distribution analyzer “SALAD-3000” (manufactured by Shimadzu Corporation).

<Tap density>
Measured based on JIS Z 2512: 2006 method.

<BET specific surface area>
The value calculated by the following calculation formula from the surface area measured using the flow type specific surface area measuring device “Flowsorb II” (manufactured by Shimadzu Corporation) was defined and described as the specific surface area.
Specific surface area (m ² / g) = surface area (m ² ) / powder mass (g)

[Dispersant A] Aluminum chelate ALCH-90F (aluminum ethyl acetoacetate diisopropionate, non-volatile content 90%, manufactured by Kawaken Fine Chemical Co., Ltd.)

[Dispersant B] DISPERBYK-140 (resin-type dispersant: ammonium salt having carboxyl group, amino group and polyacryl unit, acid value 73 KOH mg / g, amine value 76 KOH mg / g, nonvolatile content 52%, manufactured by Big Chemie Japan)

[Dispersant C] Hypermer KD-8 (resin-type dispersant: carboxyl group-containing fatty acid ester copolymer, acid value 33 KOH mg / g, nonvolatile content 100%, manufactured by Croda Japan)

[Carbon Black A] Carbon black # 3030B (D50: 55nm, specific surface area 32m ² / g, oil absorption of 130 cm ^3/100 g, manufactured by Mitsubishi Chemical Corporation)

[Curing Agent A] Duranate MF-K60X (Block type hexamethylene diisocyanate curing agent, non-volatile content 60%, manufactured by Asahi Kasei Chemicals Corporation)

[Curing agent B] Amicure PN-23 (latent imidazole curing agent, non-volatile content 100%, manufactured by Ajinomoto Fine Techno Co., Ltd.)

[Curing agent C] Amicure PN-50 (latent imidazole curing agent, non-volatile content 100%, manufactured by Ajinomoto Fine Techno Co., Ltd.)

<Example 1>
Binder resin solution (1): 100 parts, Dispersant A: 2.5 parts, Silver powder C: 296 parts, Silver powder a: 74 parts, Diethylene glycol monobutyl ether acetate: 32 parts were mixed in a planetary mixer, Next, a conductive paste was prepared by dispersing using three rolls.
The obtained conductive paste contained about 90% by weight of silver powder and about 10% by weight of epoxy resin in the nonvolatile content.

<Examples 2 to 20, Comparative Examples 1 to 4>
Examples 2 to 20 and Comparative Example 1 were carried out in the same manner as in Example 1 except that the binder resin solution, silver powder, dispersant, carbon black and curing agent were changed to the blending ratios shown in Tables 1 and 2. ~ 4 conductive pastes were prepared. Carbon black was mixed with a binder resin solution, silver powder, a dispersant and a solvent, and dispersed using a three roll.

<Measurement of viscosity and TI value>
The viscosity and TI value of the obtained conductive paste were measured under the following conditions.
・ Viscometer: E-type viscometer TVE-25H (manufactured by Toki Sangyo Co., Ltd.)
Rotor: Cone rotor # 7 (θ3 ° x R7.7mm)
・ Measurement temperature: 25 ℃
・ Sample: 0.1 ml
-Viscosity measurement: The viscosity was 2 minutes at a rotation speed of 5 rpm.
-TI value measurement: Measured 2 minutes at 2 rpm and 2 minutes at 20 rpm TI value = (2 minutes at 2 rpm) / (2 minutes at 20 rpm)

[Creation of conductive sheet (for conductivity evaluation)]
The obtained conductive paste was screen-printed on a 75 μm thick polyethylene terephthalate film (hereinafter referred to as “PET film”) in a pattern shape of 15 mm in length × 30 mm in width, and dried in an oven at 135 ° C. for 30 minutes. A 5 μm conductive sheet was obtained.

<Measurement of film thickness>
The thickness of the conductive film in the obtained conductive sheet was measured using a MH-15M type measuring instrument (manufactured by Nikon Corporation).

<Surface resistivity>
The surface resistivity of the obtained conductive sheet was measured using a series 4 probe probe (ASP) of a Loresta GPMCP-T610 measuring machine (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) at 25 ° C. and a humidity of 50%. .

<Calculation of volume resistivity>
The volume resistivity of the conductive sheet was calculated by substituting the surface resistivity and film thickness measured by the above method into the following formulas.
Volume resistivity (Ω · cm) = (Surface resistivity: Ω / □) x (Film thickness: cm)
The evaluation criteria are as follows.
○: 100 μΩ · cm or less. Good.
Δ: More than 100 μΩ · cm and 500 Ω · cm or less. There is no problem in practical use.
×: Over 500 μΩ · cm. Not practical.

[Creation of conductive sheet (for laser workability evaluation)]
The conductive paste is printed on a 75 μm thick PET film using a high-precision screen printing apparatus (SERIA, manufactured by Tokai Seiki Co., Ltd.) and dried at 135 ° C. for 30 minutes to have a conductive film having a thickness of about 6 μm. A conductive sheet was obtained. As the screen printing plate, as shown in FIG. 1, a plate having four window frame image portions having a width of 6 mm, a length of 115 mm, and a width of 65 mm in an area of 205 mm in length and 340 mm in width was used. The printing conditions are as follows. In addition, the thickness of the obtained electroconductive sheet was measured using MH-15M type | mold measuring device (made by Nikon Corporation).

(Screen printing conditions)
Screen: Stainless steel plate 400 mesh, wire diameter 18 μm
・ Emulsion thickness: 10 μm
・ Screen frame: 650x550mm
・ Squeegee angle: 70 °
・ Squeegee hardness: 80 °
・ Squeegee speed: 150 mm / sec ・ Squeegee printing pressure: 15 kgf
・ Squeegee push: 1.5mm
・ Clearance: 2.5mm
・ Solvent used: Diethylene glycol monobutyl ether acetate

<Laser workability evaluation>
As shown in the enlarged view of FIG. 2, the conductive sheet is composed of a vertical line (length 70 mm), a horizontal line (length 30 mm), and a corner with respect to the corner of the window frame pattern-like conductive film of the obtained conductive sheet. Laser processing was performed for the purpose of forming 16 L / S wiring patterns of 20 μm / 20 μm. The laser workability was evaluated by three points: low energy workability, high energy resistance, and space linearity. The laser processing conditions are as follows.
(Laser processing conditions)
・ Laser processing machine: Ag Laser Etching System made by Suzhou Delphi Laser Co., LTD
・ Laser light: YAG laser (fundamental wavelength of 1064 nm)
・ Maximum output: 20W
・ Beam diameter: 20μm
・ Processing output: 10-60%
・ Frequency: 300 kHz
・ Pulse width: 25ns
・ Scanning speed: 2000mm / s
-Number of scans: 2 The machining output is the output (%) used in actual machining. Here, since the output used for processing is 10-60% of the maximum apparatus output of 20 W, it can be estimated as 2-12 W.

<Measurement of line width>
Using a conductive sheet after laser processing, a digital microscope (manufactured by VHX-900 Keyence) was used to evaluate the degree of variation in space width. The space width of the part from which the conductive coating was removed was read from the photographed enlarged photograph using a small general-purpose image analyzer “LUZEX AP” (manufactured by Nireco).
Arbitrary 8 spaces of the circuit pattern were selected, and the space width of 3680 locations in total, which was 460 locations, was measured, and the average value and standard deviation were obtained. The following laser workability evaluation was performed using this value.

1. Laser processability evaluation: low energy processability The low output processability was evaluated at the minimum output necessary for processing the space width to 20 μm.
The low energy workability was determined according to the following criteria.
○: Space width 20 μm Required processing output is 25% or less Good.
Δ: Space width 20 μm Required processing output exceeds 25% and 35% or less. There is no problem in practical use.
X: Space width 20 μm Required processing output exceeds 35%. Not practical.

2. Laser workability evaluation: high energy resistance High energy resistance was evaluated at the lowest output at which disconnection occurred.
High energy resistance was determined according to the following criteria.
○: Output is 50% or more when disconnection occurs. Good.
Δ: Output when disconnection occurs is 40% or more and less than 50%. There is no problem in practical use.
X: Output when disconnection occurs is less than 40%. Not practical.

3. Laser workability evaluation: Space linearity The linearity of the space (the jaggedness and the degree of unevenness at the boundary between the line portion 3 and the space portion 4 in FIG. 2) was evaluated with a standard deviation.
The linearity of the space was judged according to the following criteria.
○: Standard deviation is 0 to 1.5 μm. Good.
(Triangle | delta): A standard deviation is 1.6-2.4 micrometers. There is no problem in practical use.
X: Standard deviation is 2.5 μm or more. Not practical.

<Adhesion>
1. The adhesion was evaluated using an ITO laminated film and an ITO laminated etching film as a base material. The adhesion was evaluated by initial adhesion and adhesion after a time test.
The conductive paste obtained on the ITO layer of the ITO laminated film was screen-printed so that the film thickness after drying was 6 μm to form a pattern of 15 mm length × 30 mm width. Subsequently, the electroconductive sheet was obtained by making it dry in 135 degreeC oven for 30 minutes. Separately, a conductive sheet was obtained by printing a conductive paste on the surface of the ITO laminated etching film where the ITO layer and the PET film substrate were exposed in the same manner as described above. And the adhesiveness of the conductive film was evaluated using these conductive sheets.
-ITO laminated film: V150L-OFME (thickness: 175 μm, manufactured by Nitto Denko Corporation)
ITO laminated etching film: A film in which a part of the ITO laminated film is etched with hydrochloric acid to remove the ITO layer to expose the substrate (PET film).

Evaluation method Tape adhesion test: A tape adhesion test was performed in accordance with JIS K5600.
Put a total of 100 squares of 10 squares x 10 squares at intervals of 1 meter into the conductive paste on the ITO remaining part and ITO etched part, and use cellophane tape (25 mm wide, manufactured by Nichiban Co.) on the printing surface. After pasting, the cellophane tape was rapidly peeled by hand to evaluate the state of the remaining cells.
・ Evaluation criteria ○: No peeling (good)
Δ: Slightly chipped edges (no problem in practical use)
×: Peeling over 1 square is observed (not practical)

-Adhesiveness after time test After leaving the printed matter of the ITO laminated film and the ITO laminated etching film separately prepared by the above method in an atmosphere of 60 ° C and 90% for 240 hours, the adhesiveness was evaluated by the same method as above. did. Evaluation was performed according to the same evaluation criteria as described above.

2. Adhesion was evaluated using a polyimide film as the substrate.
On the polyimide film (Kapton 100H, 25 μm thickness, manufactured by Toray DuPont), the conductive paste was screen-printed so that the film thickness after drying was about 8 μm to form a pattern of 15 mm length × 30 mm width. Subsequently, the printed matter was obtained by drying in an oven at 180 ° C. for 30 minutes. The printed matter was used to evaluate the adhesion of the conductive coating.
Cellophane tape (25 mm width) was affixed on the conductive film of the printed matter, and the cellophane tape was rapidly peeled by hand to evaluate the adhesion.
○: No peeling at all (good)
Δ: Slight peeling (no problem in practical use)
X: Exfoliated entirely (not practical)

3. Using an ITO laminated etching film, the adhesion before and after laser processing was evaluated.
The conductive paste is printed on the surface of the ITO laminated etching film where the ITO layer and the PET film substrate are exposed using a high-precision screen printing apparatus (SERIA, manufactured by Tokai Seiki Co., Ltd.), A conductive sheet having a conductive film with a thickness of about 6 μm was obtained by drying at 135 ° C. for 30 minutes. The ITO laminated etching film used here is a film in which a part of V150L-OFME (thickness: 175 μm, manufactured by Nitto Denko Corporation) is etched with hydrochloric acid to remove the ITO layer and expose the substrate (PET film). It is. As the screen printing plate, as shown in FIG. 1, a plate having four window frame image portions having a width of 6 mm, a length of 115 mm, and a width of 65 mm in an area of 205 mm in length and 340 mm in width was used. As shown in the enlarged view of FIG. 2, 16 formed of a vertical line (length 70 mm), a horizontal line (length 30 mm), and a corner portion with respect to the corner portion of the window frame pattern-shaped conductive coating of the prepared conductive sheet 16. Laser processing was performed for the purpose of forming a wiring pattern having L / S of 20 μm / 20 μm. The printing conditions are the same as above, and the laser processing conditions are as follows. The printed matter was used to evaluate the adhesion of the conductive coating before and after laser irradiation. Cellophane tape (25 mm width) was affixed on the conductive film of the printed matter, and the cellophane tape was rapidly peeled by hand to evaluate the adhesion.
○: No peeling at all (good)
Δ: Slight peeling (no problem in practical use)
X: Exfoliated entirely (not practical)

(Laser processing conditions)
・ Laser processing machine: Ag Laser Etching System made by Suzhou Delphi Laser Co., LTD
・ Laser light: YAG laser (fundamental wavelength of 1064 nm)
・ Maximum output: 20W
・ Beam diameter: 20μm
・ Processing output: 25%
・ Frequency: 300 kHz
・ Pulse width: 25ns
・ Scanning speed: 2000mm / s
・ Number of scans: 2 times

<Air removal>
The obtained conductive sheet was subjected to laser processing in the same manner as described above and washed by air blow. The air blow cleaning conditions are as follows. Air removability was evaluated by the number of dust per unit area after the conductive sheet after laser processing was washed by air blow.
Air removability was determined according to the following criteria.
○: 10 / cm ² or less. Good.
Δ: More than 10 pieces / cm ² and not more than 20 pieces / cm ² . There is no problem in practical use.
×: More than 20 pieces / cm ² . Not practical.

(Air cleaning conditions)
・ Air cleaner: Air gun manufactured by ASONE ・ Cleaning time: 10 seconds

 From the results of Tables 1 and 2, the conductive pastes of Examples 1 to 20 exhibit good volume resistivity, laser workability, and adhesion to a substrate. Moreover, Examples 18-20 which added the hardening | curing agent further improved the adhesiveness to a polyimide film, and air removability. On the other hand, since the comparative example 1 does not contain the electroconductive particle B from the result of Table 3, low energy workability is bad and adhesiveness after a process is also bad. Moreover, since the comparative example 2 does not contain the electroconductive particle A, and does not contain the electroconductive particle A, an electroconductive path | pass is not formed, electroconductivity falls, and surface resistivity has the upper limit of a measurement. Since it exceeded, conductivity could not be measured. Moreover, although the comparative example 3 uses the silver powder from which D50 average particle diameter differs, since D50 average particle diameter of the electroconductive particle A is large, low energy workability is bad. Moreover, since the comparative example 4 does not use the dispersing agent, TI value is high and linearity is bad.

  The conductive paste for laser processing of the present invention can provide a conductive sheet having good laser processability, maintaining substrate adhesion, heat and humidity resistance and environmental reliability, and having good conductivity. Furthermore, the wiring circuit formed by laser processing using the conductive paste for laser processing of the present invention can be suitably used for touch panel displays such as mobile phones, smartphones, tablet terminals, and notebook PCs.

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

Claims (7)

Conductive particles A having a D50 average particle size of 0.7 to 3 μm, conductive particles B having a D50 average particle size of 0.1 to 0.6 μm, a number average molecular weight of 10,000 to 50,000 and a glass transition temperature of 5 A conductive paste for laser processing, comprising a binder resin at 100 ° C. and a dispersant.   The conductive paste for laser processing according to claim 1, wherein a weight ratio of the conductive particles A to the conductive particles B is A / B = 95/5 to 30/70.   Furthermore, the electrically conductive paste for laser processing of Claim 1 or 2 containing a hardening | curing agent.   Furthermore, the electrically conductive paste for laser processing of any one of Claims 1-3 containing a laser sensitizer.   The viscosity measured by using an E-type viscometer at a temperature of 25 ° C. and a rotor rotation speed of 5 rpm is 10 Pa · s to 150 Pa · s, and the thixo index is 1.2 to 2.4. The conductive paste for laser processing according to item 1.   The sheet | seat for laser processing provided with the base material and the electroconductive film containing the electroconductive paste for laser processing of any one of Claims 1-5.   A method for manufacturing a wiring circuit, comprising performing laser ablation on the conductive coating of the laser processing sheet according to claim 6 and removing a part of the conductive coating to form a wiring circuit.