JP5987930B2 - Conductive paste for laser etching, electrical circuit and touch panel - Google Patents

Description

  The present invention relates to a method for producing a conductive pattern capable of producing a conductive pattern having a high arrangement density in a planar direction, and a conductive paste that can be suitably used for this production method. The conductive pattern of the present invention can typically be used for electrode circuit wiring of a transparent touch panel.

  In recent years, electronic devices equipped with a transparent touch panel typified by a mobile phone, a notebook personal computer, an electronic book, and the like are rapidly increasing in performance and size. In order to improve the performance and miniaturization of these electronic devices, it is necessary to increase the density of the electrode circuit wiring that joins these electronic components in addition to the reduction in size, performance, and integration of the electronic components. It has been. As a transparent touch panel method, in addition to the resistive film method with a small number of electrode circuit wirings, the use of a capacitive method with a remarkably large number of electrode circuit wirings has been rapidly spreading in recent years. High density is strongly demanded. In addition, in order to make the display screen larger and due to demands on product design, there is a demand for a narrower frame portion on which the electrode circuit wiring is arranged. From this viewpoint, the density of the electrode circuit wiring is high. Is required. In order to satisfy the above requirements, there is a demand for a technique capable of performing higher-density arrangement of electrode circuit wiring than in the past.

  The arrangement density of the electrode circuit wiring in the frame part of the transparent touch panel of the resistive film type is about 200 μm (hereinafter abbreviated as L / S = 200/200 μm) in the width of the line and the space in the plane direction. Conventionally, this is formed by screen printing of a conductive paste. In the capacitive touch panel, the L / S requirement is about 100/100 μm or less, and there are cases where the L / S is required to be 50/50 μm or less. The situation is becoming difficult to deal with.

  As an example of a candidate electrode circuit wiring forming technique that replaces screen printing, a photolithography method can be given. If a photolithography method is used, it is possible to form a thin line having an L / S of 50/50 μm or less. However, there are also problems with photolithography. The most typical example of photolithography is a method using a photosensitive resist. Generally, a photosensitive resist is applied to a copper foil portion of a surface substrate on which a copper foil layer is formed, and a photomask or a laser beam is used. A desired pattern is exposed by a method such as direct drawing, the photosensitive resist is developed, and then a copper foil portion other than the desired pattern is dissolved and removed with a chemical to form a fine line pattern of the copper foil. For this reason, the environmental load by waste liquid processing is large, and also the process is complicated, and it has many problems including the viewpoint of production efficiency and the viewpoint of cost.

JP 2010-237573 A JP 2011-181338 A

  An object of the present invention is to provide a manufacturing method capable of manufacturing high-density electrode circuit wiring for a touch panel having an L / S of 50/50 μm or less, which is difficult to cope with by a screen printing method, at low cost and with low environmental load. There is to do. Moreover, it is providing the electrically conductive paste which can be used suitably for such a manufacturing method.

As a result of intensive studies on a manufacturing method for arranging electrode circuit wiring at a high density in the planar direction, the present inventors have found that a layer composed of a binder resin and conductive powder is formed on a substrate having a transparent conductive layer or a transparent conductive layer. The transparent conductive layer is formed on a substrate partially removed by etching, and a part of the transparent conductive layer is removed from the insulating substrate by laser light irradiation. It was found that a high-density electrode circuit wiring with a thickness of 50/50 μm or less can be produced. Moreover, the electroconductive paste suitable for forming the layer which consists of binder resin and electroconductive powder suitable for such a manufacturing method was discovered. That is, this invention consists of the following structures.
(1) It contains a binder resin (A) made of a thermoplastic resin, a metal powder (B) and an organic solvent (C), and the binder resin (A) has a number average molecular weight of 5,000 to 60,000. In addition, a thermoplastic resin having a glass transition temperature of 150 ° C. or less, and a center diameter (D50) of the metal powder (B) is 4 μm or less,
Touch panel circuit wiring with a L / S of 50/50 μm or less by laser etching processing on a substrate having a transparent conductive layer, or on a substrate having a transparent conductive layer and the transparent conductive layer partially removed by etching Conductive paste for laser etching process used to form in.
(2) The laser used for forming the circuit wiring of the touch panel according to (1), wherein the binder resin (A) is a thermoplastic resin having a glass transition temperature of 60 to 100 ° C. Conductive paste for etching process.
(3) The binder resin (A) is one or a mixture of two or more selected from the group consisting of a polyester resin, a polyurethane resin, an epoxy resin, a vinyl chloride resin, and a fiber derivative resin ( A conductive paste for laser etching used for forming the circuit wiring of the touch panel according to 1) or (2).
(4) the binder resin (A) is an acid value 50-300 equivalents / 10 ⁶ g one or two selected from the group consisting of polyester resin and an acid number of 50 to 300 polyurethane resin is equivalent / 10 ⁶ g is The conductive paste for laser etching used for forming the circuit wiring of the touch panel according to (1) or (2), which is a mixture of seeds or more.
(5) The conductive paste for laser etching used for forming the circuit wiring of the touch panel according to any one of (1) to (4), further comprising a laser light absorber (D) .
(6) A part of the conductive thin film formed from the conductive paste for laser etching according to any one of (1) to (5) is selected from a carbon dioxide gas laser, a YAG laser, a fiber laser, and a semiconductor laser. Of touch panel electric circuit having circuit wiring with L / S of 50/50 μm or less formed by irradiating laser beam to remove a part of the conductive thin film.
(7) The method for manufacturing an electric circuit for a touch panel according to (6), wherein the conductive thin film is formed on a transparent conductive layer.
(8) A method for manufacturing a touch panel including, as a constituent member, an electric circuit formed by the method for manufacturing an electric circuit according to any one of (6) to (7).
(9) A coating film is formed on a substrate using the conductive paste according to any one of (1) to (5), and then the coating film is dried, and then L / S is reduced by laser etching. A method of manufacturing a circuit wiring for a touch panel, comprising forming a circuit wiring of 50/50 μm or less.
(10) The method for producing a circuit wiring for a touch panel according to (9), wherein the film thickness after drying the coating film according to (9) is 3 μm or more and 30 μm or less.
(11) The method of manufacturing a circuit wiring for a touch panel according to any one of (9) to (10), wherein a scanning speed of laser light in the laser etching process is 1000 mm / s or more.
(12) The method for manufacturing a circuit wiring for a touch panel according to any one of (9) to (11), wherein the circuit wiring is formed on a base material having a transparent conductive layer.

  The conductive paste of the present invention is a conductive paste containing a binder resin (A) made of a thermoplastic resin, a metal powder (B) and an organic solvent (C). By taking such a configuration, laser etching is performed. It is possible to form a conductive thin film that is excellent in processing suitability and excellent in adhesion to the substrate at the initial stage and after a wet heat environment load even after laser etching. In addition, it is excellent in laser etching process suitability here, when peeling at least one part of an electroconductive thin film from a base material by laser etching process, and forming a thin wire | line about L / S = 30/30 micrometers 1) It refers to satisfying the three conditions of ensuring conduction between both ends of the fine wire, 2) ensuring insulation between adjacent fine wires, and 3) having a good fine wire shape. Moreover, since the conductive paste containing the laser light absorber (D) according to the embodiment of the present invention has higher sensitivity to laser light irradiation than the conductive paste not containing the laser light absorber (D), The laser scanning speed can be improved and the laser output can be reduced.

It is a schematic diagram showing the pattern which irradiates a laser beam to the laser etching process aptitude evaluation test piece used by the Example and comparative example of this invention. The white portion is irradiated with laser light, and the conductive thin film formed on the substrate is removed. The halftone dots are not irradiated with laser light. The unit of dimension display in the figure is mm.

<< Components constituting the conductive paste of the present invention >>
The conductive paste for laser etching according to the present invention contains a binder resin (A) made of a thermoplastic resin, a metal powder (B), and an organic solvent (C) as essential components.

<Binder resin (A)>
The type of binder resin (A) is not particularly limited as long as it is a thermoplastic resin. However, polyester resin, epoxy resin, phenoxy resin, polyamide resin, polyamideimide resin, polycarbonate resin, polyurethane resin, phenol resin, acrylic resin, polystyrene, styrene -Acrylic resin, styrene-butadiene copolymer, phenol resin, polyethylene resin, polycarbonate resin, phenol resin, alkyd resin, styrene-acrylic resin, styrene-butadiene copolymer resin, polysulfone resin, polyethersulfone resin, vinyl chloride -Vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer, polystyrene, silicone resin, fluorine resin, etc. can be mentioned, and these resins are used alone or as a mixture of two or more. Rukoto can. It is preferably one or a mixture of two or more selected from the group consisting of polyester resins, polyurethane resins, epoxy resins, vinyl chloride resins, and fiber derivative resins. Among these resins, a polyurethane resin containing a polyester resin and / or a polyester component as a copolymer component (hereinafter sometimes referred to as a polyester polyurethane resin) is preferable as the binder resin (A).

  One advantage of using a polyester resin as the binder resin (A) in the present invention is the high degree of freedom in molecular design. The dicarboxylic acid and glycol components constituting the polyester resin can be selected and the copolymerization component can be freely changed, and the functional group can be easily added in the molecular chain or at the molecular end. For this reason, the characteristics of the resin such as the glass transition temperature of the polyester resin to be obtained and the affinity with other components blended in the base material and the conductive paste can be appropriately adjusted.

  Examples of the dicarboxylic acid that can be used as a copolymer component of the polyester resin used as the binder resin (A) in the present invention include aromatics such as terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. Dicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, aliphatic dicarboxylic acid such as azelaic acid, dibasic acid having 12 to 28 carbon atoms such as dimer acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 2-methylhexahydrophthalic anhydride, dicarboxyhydrogenated bisphenol A, Dicarboxy hydrogenated bisphenol S, da Mer acid, hydrogenated dimer acid, hydrogenated naphthalenedicarboxylic acid, alicyclic dicarboxylic acids such as tricyclodecane acid, hydroxybenzoic acid, and hydroxycarboxylic acids such as lactic acid. Further, within the range not impairing the effects of the invention, trivalent or higher carboxylic acids such as trimellitic anhydride and pyromellitic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and / or 5-sulfoisophthalic acid sodium salt, etc. The sulfonic acid metal base-containing dicarboxylic acid may be used as a copolymerization component.

  Examples of polyols that can be used as a copolymer component of the polyester resin used as the binder resin (A) in the present invention include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, , 5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, Aliphatic diols such as 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,9-nonanediol, 1,10-decanediol, 1,4 -Cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedim Ethanol, and alicyclic diol and dimer diol. In addition, trivalent or higher polyols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, polyglycerin and the like may be used in combination as a copolymerization component as long as the effects of the invention are not impaired.

  The polyester resin used as the binder resin (A) in the present invention is an aromatic dicarboxylic acid among all acid components constituting the polyester resin from the viewpoints of durability such as strength, heat resistance, moisture resistance, and thermal shock resistance. The acid is preferably copolymerized in an amount of 60 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and particularly preferably 98 mol% or more. It is a preferred embodiment that the total acid component consists of an aromatic dicarboxylic acid. If the copolymerization ratio of the aromatic dicarboxylic acid component is too low, the glass transition temperature of the resulting polyester resin will be lower than 60 ° C., and the heat and humidity resistance and durability of the resulting conductive thin film will tend to be reduced.

  The polyester resin used as the binder resin (A) in the present invention is a main chain carbon among all polyols constituting the polyester resin from the viewpoint of durability such as strength, heat resistance, moisture resistance, and thermal shock resistance. The number of glycols having 4 or less is preferably 60 mol% or more, more preferably 80 mol% or more, and further preferably 95 mol% or more. When the copolymerization ratio of glycol having 4 or less carbon atoms in the main chain among all polyol components is too low, the glass transition temperature of the resulting polyurethane resin is lower than 60 ° C., and the resulting conductive thin film has heat and heat resistance and durability. Tend to decrease.

  It is also a preferred embodiment to use a polyurethane resin as the binder resin (A) in the present invention. As in the case of polyester resins, with regard to polyurethane resins, glass transition can be achieved by selecting appropriate components as copolymer components that make up polyurethane resins, and by adding functional groups in the molecular chain or at the molecular ends. Resin properties such as temperature and affinity with other components blended in the substrate and the conductive paste can be appropriately adjusted.

  The copolymer component of the polyurethane resin is not particularly limited, but is preferably a polyester polyurethane resin using a polyester polyol as a copolymer component from the viewpoint of freedom of design, heat and humidity resistance, and maintenance of durability. As a suitable example of the said polyester polyol, what is a polyol among the polyester resins which can be used as binder resin (A) in the above-mentioned this invention can be mentioned.

  The polyurethane resin used as the binder resin (A) in the present invention can be obtained, for example, by a reaction between a polyol and a polyisocyanate. The polyisocyanate that can be used as a copolymerization component of the polyurethane resin includes 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, m-phenylene diisocyanate. 3,3′-dimethoxy-4,4′-biphenylene diisocyanate, 2,6-naphthalene diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 4,4′-diphenylene diisocyanate, 4,4 '-Diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, m-xylene diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, tolu De be mentioned down diisocyanate, aromatic diisocyanates, may be any of aliphatic diisocyanates and alicyclic diisocyanates. Moreover, you may use together a trivalent or more isocyanate compound as a copolymerization component in the range which does not impair the effect of this invention.

  In the polyurethane resin used as the binder resin (A) in the present invention, a compound having a functional group capable of reacting with isocyanate can be copolymerized as necessary. The functional group capable of reacting with isocyanate is preferably a hydroxyl group or an amino group, and may have either one or both. Specific examples thereof include dimethylolbutanoic acid, dimethylolpropionic acid, 1,2-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 2,2- Dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,2- Dimethyl-3-hydroxypropyl-2 ′, 2′-dimethyl-3′-hydroxypropanoate, 2-normalbutyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3 -Propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 3-octyl-1,5-pentanediol , 3-phenyl-1,5-pentanediol, 2,5-dimethyl-3-sodiumsulfo-2,5-hexanediol, dimer diol (for example, PRIIPOL-2033 manufactured by Unikema International) Compounds having two hydroxyl groups, trimethylol ethane, trimethylol propane, glycerin, pentaerythritol, polyglycerin and other alcohols having three or more hydroxyl groups in one molecule, monoethanolamine, diethanolamine, triethanolamine 1 Amino alcohol having at least one hydroxyl group and amino group in its molecule, ethylenediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine 1,12-dodecandi Two amino groups in one molecule such as aliphatic diamines such as min, aromatic diamines such as metaxylene diamine, 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenyl ether, and 4,4′-diaminodiphenyl ether The compound which has is mentioned. The above-mentioned compound having a functional group capable of reacting with two or more isocyanates per molecule having a number average molecular weight of less than 1,000 may be used alone or in combination with a plurality of compounds without any problem.

  The number average molecular weight of the binder resin (A) in the present invention is not particularly limited, but the number average molecular weight is preferably 5,000 to 60,000. If the number average molecular weight is too low, it is not preferable in terms of durability and heat and humidity resistance of the formed conductive thin film. On the other hand, if the number average molecular weight is too high, the cohesive strength of the resin increases and the durability as a conductive thin film is improved, but the suitability for laser etching is significantly deteriorated.

  The glass transition temperature of the binder resin (A) in the present invention is preferably 60 ° C. or higher, and more preferably 65 ° C. or higher. If the glass transition temperature is low, the suitability for laser etching may be improved, but there is a risk that the reliability of wet heat environment as a conductive thin film may be reduced, and the manufacturing process and There is a risk that the reliability of the conductive thin film is lowered due to the migration of the paste-containing component to the contact partner side during use. On the other hand, the glass transition temperature of the binder resin (A) used in the present invention is preferably 150 ° C. or less, more preferably 120 ° C. or less in consideration of printability, adhesion, solubility, paste viscosity, laser etching processing suitability, and the like. Preferably, 100 degrees C or less is still more preferable.

  Although the acid value of binder resin (A) in this invention is not specifically limited, Adhesion with respect to a base material may be remarkably improved by having an acid value of a specific range. At the time of laser etching processing of the conductive thin film, the temperature around the laser irradiation site may increase and the adhesion between the conductive thin film and the substrate may decrease, but the binder resin (A) has an acid value in a specific range. By using the binder resin that has, it may be possible to suppress a decrease in adhesion. The acid value of the binder resin (A) is preferably 50 to 350 eq / ton, and more preferably 100 to 250 eq / ton. If the acid value is too low, the adhesion between the conductive thin film to be formed and the substrate tends to be low. On the other hand, if the acid value is too high, the water-absorbing property of the formed conductive thin film increases, and the hydrolysis of the binder resin may be promoted by the catalytic action of the carboxyl group. It tends to lead to a decline.

<Metal powder (B)>
The metal powder (B) used in the present invention is plated with noble metal powder such as silver powder, gold powder, platinum powder and palladium powder, base metal powder such as copper powder, nickel powder, aluminum powder and brass powder, or noble metal such as silver. Examples include alloyed base metal powders. These metal powders may be used alone or in combination. Among these, considering the conductivity, stability, cost, etc., the silver powder alone or the one mainly composed of silver powder is preferable.

  The shape of the metal powder (B) used in the present invention is not particularly limited. Examples of conventionally known metal powder shapes include flakes (flakes), spheres, dendrites (dendrites), and spherical primary particles described in JP-A-9-306240. There are three-dimensionally aggregated shapes (aggregate) and the like, and among these, it is preferable to use spherical, aggregated and flaky metal powders.

  The center diameter (D50) of the metal powder (B) used in the present invention is preferably 4 μm or less. By using the metal powder (B) having a center diameter of 4 μm or less, the thin line shape of the laser etching processed portion tends to be good. When a metal powder having a center diameter larger than 4 μm is used, the shape of the fine wire after laser etching is deteriorated, and as a result, the fine wires may come into contact with each other, possibly causing a short circuit. Furthermore, there is a possibility that the conductive thin film once peeled and removed by the laser etching process may adhere to the processing site again. The lower limit of the center diameter of the metal powder (B) is not particularly limited, but it is preferable that the center diameter is 80 nm or more because it tends to agglomerate when the particle diameter becomes fine and dispersion becomes difficult as a result. When the center diameter is smaller than 80 nm, the cohesive force of the metal powder increases, the laser etching processing suitability deteriorates, and it is not preferable from the viewpoint of cost.

  The central diameter (D50) is a particle diameter (μm) at which the cumulative value becomes 50% in the cumulative distribution curve (volume) obtained by some measurement method. In the present invention, the cumulative distribution curve is measured in the total reflection mode using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., MICROTRAC HRA).

  The content of the metal powder (B) is preferably 400 parts by mass or more with respect to 100 parts by mass of the thermoplastic resin (A) from the viewpoint that the conductivity of the formed conductive thin film is good. The above is more preferable. Further, the content of the component (B) is preferably 1,900 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin (A), from the viewpoint of good adhesion to the substrate. 230 parts by mass or less is more preferable.

<Organic solvent (C)>
The organic solvent (C) that can be used in the present invention is not particularly limited, but from the viewpoint of keeping the volatilization rate of the organic solvent within an appropriate range, the boiling point is preferably 100 ° C. or more and less than 300 ° C., more preferably. Has a boiling point of 150 ° C. or higher and lower than 280 ° C. The conductive paste of the present invention is typically prepared by dispersing a thermoplastic resin (A), a metal powder (B), an organic solvent (C) and other components as necessary with a three-roll mill or the like. In this case, if the boiling point of the organic solvent is too low, the solvent volatilizes during dispersion, and there is a concern that the ratio of components constituting the conductive paste changes. On the other hand, if the boiling point of the organic solvent is too high, a large amount of the solvent may remain in the coating film depending on the drying conditions, which may cause a decrease in the reliability of the coating film.

Moreover, as an organic solvent (C) which can be used for this invention, the thing in which a thermoplastic resin (A) is soluble and a metal powder (B) can be disperse | distributed favorably is preferable. Specific examples include ethyl diglycol acetate (EDGAC), butyl glycol acetate (BMGAC), butyl diglycol acetate (BDGAC), cyclohexanone, toluene, isophorone, γ-butyrolactone, benzyl alcohol, Exson Chemical's Solvesso 100, 150, 200, a mixture of dimethyl ester of propylene glycol monomethyl ether acetate, adipic acid, succinic acid and glutaric acid (for example, DBE manufactured by DuPont Co., Ltd.), terpionol, and the like. Among these, thermoplastic resins ( From the viewpoints of excellent solubility of the compounding component A), moderate solvent volatility during continuous printing, and good suitability for printing by a screen printing method, etc., EDGAC, BMGAC, BDGAC, and mixtures thereof Solvents are preferred.

  The content of the organic solvent (C) is preferably 5 parts by weight or more and 40 parts by weight or less, more preferably 10 parts by weight or more and 35 parts by weight or less with respect to 100 parts by weight of the total paste. . When the content of the organic solvent (C) is too high, the paste viscosity becomes too low, and the sagging tends to occur during fine line printing. On the other hand, if the content of the organic solvent (C) is too low, the viscosity as a paste becomes extremely high, and, for example, the screen printability when forming the conductive thin film is significantly reduced. The film thickness becomes thick and the laser etching processability may be reduced.

<Laser light absorber (D)>
You may mix | blend a laser beam absorber (D) with the electrically conductive paste of this invention. Here, the laser light absorber (D) is an additive having strong absorption at the wavelength of the laser light, and the laser light absorber (D) itself may be conductive or non-conductive. Good. For example, when a YAG laser having a fundamental wave wavelength of 1064 nm is used as a light source, a dye and / or pigment having strong absorption at a wavelength of 1064 nm can be used as the laser light absorber (D). By blending the laser light absorber (D), the conductive thin film of the present invention absorbs the laser light with high efficiency, and the volatilization and thermal decomposition of the binder resin (A) due to heat generation is promoted, and as a result, suitability for laser etching processing. Will improve.

  Among the laser light absorbers (D) that can be used in the present invention, examples of those having conductivity include carbon-based fillers such as carbon black and graphite powder. The compounding of the carbon-based filler has the effect of increasing the conductivity of the conductive thin film of the present invention. For example, since carbon black has an absorption wavelength in the vicinity of 1060 nm, it has a wavelength of 1064 nm such as YAG laser and fiber laser. When irradiated with laser light, the conductive thin film absorbs laser light with high efficiency, so the sensitivity to laser light irradiation increases, and it is good even when the scanning speed of laser irradiation is increased and / or when the laser light source is low power The effect that laser etching processing suitability can be obtained can be expected. As content of the said carbon type filler, it is preferable that it is 0.1-5 weight part with respect to 100 weight part of metal powder (B), and it is more preferable that it is 0.3-2 weight part. When the blending ratio of the carbon filler is too low, the effect of increasing the conductivity and the effect of increasing the sensitivity to laser light irradiation are small. On the other hand, when the blending ratio of the carbon-based filler is too high, the conductivity of the conductive thin film tends to be lowered, and further, the resin is adsorbed to the void portion of the carbon and the adhesion with the substrate is lowered. Dots may occur.

  Among the laser light absorbers (D) that can be used in the present invention, examples of non-conductive ones include conventionally known dyes, pigments, and infrared absorbers. More specifically, azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes, etc. Examples of the dyes and pigments include black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, and polymer-bonded pigments. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments , Quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, and inorganic pigments. Examples of infrared absorbers include NIR-IM1, which is a diimonium salt type infrared absorber, and NIR-AM1, an aminium salt type (both manufactured by Nagase ChemteX Corporation). These non-conductive laser light absorbers (D) are contained in an amount of 0.01 to 5 parts by weight, preferably 0.1 to 2 parts by weight. When the blending ratio of the non-conductive laser light absorber (D) is too low, the effect of increasing the sensitivity to laser light irradiation is small. When the blending ratio of the non-conductive laser light absorber (D) is too high, the conductivity of the conductive thin film may be lowered, and the color of the laser light absorber becomes remarkable, which is not preferable depending on the application. There is.

  The following inorganic substances can be added to the conductive paste of the present invention. Examples of inorganic substances include silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, diamond carbon lactam, and other carbides; boron nitride Various nitrides such as titanium nitride and zirconium nitride, various borides such as zirconium boride; various oxidations such as titanium oxide (titania), calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica and colloidal silica Products: various titanate compounds such as calcium titanate, magnesium titanate, strontium titanate; sulfides such as molybdenum disulfide; various fluorides such as magnesium fluoride and carbon fluoride; aluminum stearate, calcium stearate Um, zinc stearate, various metal soaps such as magnesium stearate and the like; may be used talc, bentonite, talc, calcium carbonate, bentonite, kaolin, glass fiber, mica, and the like. By adding these inorganic substances, it may be possible to improve printability and heat resistance, as well as mechanical properties and long-term durability. Among these, in the conductive paste of the present invention, silica is preferable from the viewpoint of imparting durability, printability, particularly screen printability.

  The conductive paste of the present invention includes a thixotropic agent, an antifoaming agent, a flame retardant, a tackifier, a hydrolysis inhibitor, a leveling agent, a plasticizer, an antioxidant, an ultraviolet absorber, a flame retardant, and a pigment. , Dyes can be blended. Furthermore, a carbodiimide, an epoxy, etc. can also be mix | blended suitably as a resin degradation inhibitor. These can be used alone or in combination.

<Curing agent (E)>
You may mix | blend the hardening | curing agent which can react with binder resin (A) in the electrically conductive paste of this invention to such an extent that the effect of this invention is not impaired. By adding a curing agent, there is a possibility that the curing temperature becomes high and the load of the production process may increase. However, it is expected that the heat and humidity resistance of the coating film can be improved by crosslinking caused by heat generated during coating film drying or laser etching. .

  The type of the curing agent capable of reacting with the binder resin (A) of the present invention is not limited, but an isocyanate compound is particularly preferable from the viewpoint of adhesion, flex resistance, curability, and the like. Furthermore, it is preferable to use those having an isocyanate group blocked as these isocyanate compounds because the storage stability is improved. Examples of curing agents other than isocyanate compounds include known compounds such as amino resins such as methylated melamine, butylated melamine, benzoguanamine, and urea resin, acid anhydrides, imidazoles, epoxy resins, and phenol resins. These curing agents can be used in combination with a known catalyst or accelerator selected according to the type. As a compounding quantity of a hardening | curing agent, it mix | blends to the grade which does not impair the effect of this invention, Although it does not restrict | limit in particular, It is 0.5-50 with respect to 100 mass parts of binder resin (A). A mass part is preferable, 1-30 mass parts is more preferable, and 2-20 mass parts is further more preferable.

  Examples of isocyanate compounds that can be blended in the conductive paste of the present invention include aromatic or aliphatic diisocyanates, trivalent or higher polyisocyanates, and any of low molecular compounds and polymer compounds may be used. For example, aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, aromatic diisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, isophorone diisocyanate, etc. Alicyclic diisocyanates, or trimers of these isocyanate compounds, and excess amounts of these isocyanate compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine Low molecular active hydrogen compounds such as Polyester polyols, polyether polyols, terminal isocyanate group-containing compounds obtained by reacting a polymeric active hydrogen compound such as polyamides and the like. Examples of the isocyanate group blocking agent include phenols such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol; oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime. Alcohols such as methanol, ethanol, propanol and butanol; halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol ; Lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propylolactam, and other aromatic amines, imides, acetylacetone, Seto acetate, active methylene compounds such as malonic acid ethyl ester, mercaptans, imines, imidazoles, ureas, diaryl compounds, sodium bisulfite, etc. can be mentioned. Of these, oximes, imidazoles, and amines are particularly preferable from the viewpoint of curability.

<< Physical Properties Required for the Conductive Paste of the Present Invention >>

  The conductive paste of the present invention preferably has an F value of 60 to 95%, more preferably 75 to 95%. The F value is a numerical value indicating the filler mass part with respect to 100 mass parts of the total solid content contained in the paste, and is represented by F value = (filler mass part / solid mass part) × 100. The filler mass part referred to here is the mass part of the conductive powder, and the solid mass part is a mass part of components other than the solvent, and includes all of the conductive powder, the binder resin, and other curing agents and additives. If the F value is too low, a conductive thin film showing good conductivity cannot be obtained. If the F value is too high, the adhesion between the conductive thin film and the substrate and / or the surface hardness of the conductive thin film tends to decrease. Yes, printability is inevitable. Here, the conductive powder refers to both the metal powder (B) and the conductive powder made of a nonmetal.

<< Method for Producing Conductive Paste of the Present Invention >>
As described above, the conductive paste of the present invention can be prepared by dispersing the thermoplastic resin (A), the metal powder (B), the organic solvent (C), and other components as necessary with a three roll or the like. it can. Here, an example of a more specific production procedure is shown. The thermoplastic resin (A) is first dissolved in the organic solvent (C). Thereafter, the metal powder (B) and additives as necessary are added, and preliminary dispersion is carried out with a double planetary, a dissolver, a planetary stirrer or the like. Then, it disperses | distributes with a 3 roll mill, and obtains an electrically conductive paste. The conductive paste thus obtained can be filtered if necessary. There is no problem even if the dispersion is performed using other dispersers such as a bead mill, a kneader, and an extruder.

<< Conductive Thin Film, Conductive Laminate and Production Method of the Present Invention >>
The conductive paste of the present invention is formed by applying or printing the conductive paste of the present invention on a substrate to form a coating film, and then evaporating the organic solvent (C) contained in the coating film and drying the coating film. Can be formed. The method for applying or printing the conductive paste on the substrate is not particularly limited, but printing by the screen printing method is simple in the process and the technology that is widely used in the industry for forming an electric circuit using the conductive paste It is preferable from the point. In addition, the conductive paste can be applied or printed on a portion slightly wider than the portion of the conductive thin film that is ultimately required as an electric circuit, reducing the load of the laser etching process and improving the efficiency of the electric circuit of the present invention. From the viewpoint of forming, it is preferable.

  As the base material to which the conductive paste of the present invention is applied, a material excellent in dimensional stability is preferably used. For example, a film made of a material having excellent flexibility such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, or polycarbonate can be used. Moreover, inorganic materials, such as glass, can also be used as a base material. The thickness of the substrate is not particularly limited, but is preferably 50 to 350 μm, and more preferably 100 to 250 μm from the viewpoint of mechanical properties, shape stability, handleability, and the like of the pattern forming material.

  Moreover, the adhesiveness of an electroconductive thin film and a base material can be improved by performing a physical process and / or a chemical process to the surface of the base material which apply | coats the electrically conductive paste of this invention. Examples of the physical treatment method include a sand blast method, a wet blast method in which a liquid containing fine particles is sprayed, a corona discharge treatment method, a plasma treatment method, an ultraviolet ray or vacuum ultraviolet ray irradiation treatment method, and the like. Examples of chemical treatment methods include strong acid treatment methods, strong alkali treatment methods, oxidizing agent treatment methods, and coupling agent treatment methods.

  Moreover, the said base material may have a transparent conductive layer. The conductive thin film of the present invention can be laminated on the transparent conductive layer. The material of the transparent conductive layer is not particularly limited, and examples thereof include an ITO film containing indium tin oxide as a main component. Further, the transparent conductive layer is not limited to the one formed on the entire surface of the base material, but can also be one obtained by removing a part of the transparent conductive layer by etching or the like.

  The step of evaporating the organic solvent (C) is preferably performed at room temperature and / or under heating. In the case of heating, since the conductivity, adhesion and surface hardness of the conductive thin film after drying are improved, the heating temperature is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and further preferably 110 ° C. or higher. Further, from the viewpoint of heat resistance of the underlying transparent conductive layer and energy saving in the production process, the heating temperature is preferably 150 ° C. or lower, more preferably 135 ° C. or lower, and further preferably 130 ° C. or lower. When the curing agent is blended in the conductive paste of the present invention, the curing reaction proceeds when the step of evaporating the organic solvent (C) is performed under heating.

  What is necessary is just to set the thickness of the electroconductive thin film of this invention to an appropriate thickness according to the use used. However, the thickness of the conductive thin film is preferably 3 μm or more and 30 μm or less, more preferably 5 μm from the viewpoint that the conductivity of the conductive thin film after drying is good and the suitability for laser etching processing is good. As mentioned above, it is 20 micrometers or less. If the conductive thin film is too thin, there is a possibility that desired conductivity as a circuit cannot be obtained. If the film thickness is too thick, an excessive amount of irradiation is required for laser etching, which may damage the substrate. In addition, when the film thickness varies greatly, the conductive thin film tends to be etched easily, and a short circuit between lines due to insufficient etching or disconnection due to excessive etching tends to occur. For this reason, it is better that the variation in film thickness is small.

<< Electric Circuit and Manufacturing Method of the Present Invention >>

  In the site where the laser beam is irradiated and absorbed, the energy of the laser beam is converted into heat, and thermal decomposition and / or volatilization occurs due to the temperature rise, and the irradiated site is peeled and removed. In order for the portion of the conductive thin film of the present invention irradiated with the laser light to be efficiently removed from the substrate, the conductive thin film of the present invention preferably has strong absorption at the wavelength of the irradiated laser light. Therefore, it is preferable to select a laser species having energy in a wavelength region where any of the components constituting the conductive thin film of the present invention has strong absorption.

  Common laser types include excimer laser (fundamental wavelength 193 to 308 nm), YAG laser (fundamental wave wavelength 1064 nm), fiber laser (fundamental wave wavelength 1060 nm), CO2 laser (fundamental wave wavelength). 10600 nm), semiconductor lasers, and the like. Basically, there is no problem even if any system and laser type of any wavelength are used. By selecting a laser species that matches the absorption wavelength region of any constituent of the conductive thin film and that can be irradiated with a wavelength that the substrate does not have strong absorption, the conductive thin film at the laser light irradiation site is selected. Can be efficiently removed, and damage to the substrate can be avoided. From such a viewpoint, the wavelength of the fundamental wave is preferably in the range of 532 to 10700 nm as the laser type to be irradiated. For example, when using as a base material a polyester film, a transparent conductive laminate in which an ITO layer is formed on a polyester film, or a laminate in which an ITO layer is formed on a polyester film and a part thereof is removed by etching It is particularly preferable to use a YAG laser or a fiber laser because the base material has no absorption at the wavelength of the fundamental wave and is difficult to damage the base material.

  The laser output and the Q modulation frequency are not particularly limited, but are adjusted so that the conductive thin film at the laser light irradiation site can be removed and the underlying substrate is not damaged. In general, the laser output is preferably adjusted as appropriate in the range of 0.5 to 100 W and the Q modulation frequency of 10 to 400 kHz. If the laser output is too low, removal of the conductive thin film tends to be insufficient, but such a tendency can be avoided to some extent by reducing the scanning speed of the laser or increasing the number of scans. If the laser output is too high, the portion where the conductive thin film is peeled off due to the diffusion of heat from the irradiated portion becomes extremely larger than the laser beam diameter, and the line width may be too thin or disconnected.

  The scanning speed of the laser beam is preferably as high as possible from the viewpoint of improving the production efficiency by reducing the tact time. Specifically, it is preferably 1000 mm / s or more, more preferably 1500 mm / s or more, and further preferably 2000 mm / s or more. It is. If the scanning speed is too slow, not only the production efficiency is lowered, but the conductive thin film and the substrate may be damaged by the thermal history. Although the upper limit of the processing speed is not particularly defined, if the scanning speed is too high, the removal of the conductive thin film at the laser light irradiation site may be incomplete and the circuit may be short-circuited. In addition, if the scanning speed is too high, it is inevitable that the scanning speed is reduced at the corner portion of the pattern to be formed as compared with the linear portion. There exists a possibility that the physical property of the electroconductive thin film around the site | part of the laser etching process of a site | part may fall notably.

  Laser beam scanning may be performed by either moving the laser beam projectile, moving the irradiated object irradiated with the laser beam, or combining both, and can be realized by using, for example, an XY stage. Further, the laser beam can be scanned by changing the irradiation direction of the laser beam using a galvanometer mirror or the like.

  The energy density per unit area can be increased by using a condensing lens (such as an achromatic lens) at the time of laser light irradiation. The advantage of this method is that the energy density per unit area can be increased compared to the case of using a mask, so laser etching can be performed at a high scanning speed even with a low-power laser oscillator. The point that becomes possible. When irradiating the focused laser beam to the conductive thin film, it is necessary to adjust the focal length. The focal length must be adjusted according to the film thickness applied to the substrate, but it can be adjusted so that the substrate is not damaged and the predetermined conductive thin film pattern can be removed and removed. preferable.

  It is one of the preferred embodiments that the scanning of the laser light is repeated a plurality of times in the same pattern. Even if there is an incompletely removed conductive thin film portion in the first scan, or even if the component constituting the removed conductive thin film is attached to the substrate again, the laser light irradiated portion is scanned multiple times. It is possible to completely remove the conductive thin film. The upper limit of the number of scans is not particularly limited. However, care must be taken because the periphery of the processed part may be damaged and discolored or the physical properties of the coating film may be deteriorated by receiving heat history multiple times. Of course, the smaller the number of scans, the better from the viewpoint of production efficiency.

  It is also a preferred embodiment that the laser beam scanning is not repeated a plurality of times in the same pattern. As long as the number of scans is small, the production efficiency is naturally excellent as long as the properties of the obtained conductive thin film, conductive laminate and electric circuit are not adversely affected.

<< Touch Panel of the Present Invention >>
The conductive thin film, conductive laminate and / or electric circuit of the present invention can be used as a constituent member of a touch panel. The touch panel may be a resistive film type or a capacitive type. Although it can be applied to any touch panel, the paste is suitable for forming a thin line, and therefore can be particularly suitably used for electrode wiring of a capacitive touch panel. In addition, as a base material which comprises the said touch panel, it is preferable to use the base material which has transparent conductive layers, such as an ITO film | membrane, or the base material from which they were partially removed by the etching.

  In order to describe the present invention in more detail, examples and comparative examples are given below, but the present invention is not limited to the examples. In addition, each measured value described in the Example and the comparative example was measured by the following method.

1. Number average molecular weight The sample resin was dissolved in tetrahydrofuran so that the resin concentration was about 0.5% by weight and filtered through a polytetrafluoroethylene membrane filter having a pore size of 0.5 μm to obtain a GPC measurement sample. GPC measurement of a resin sample using tetrahydrofuran as a mobile phase, a gel permeation chromatograph (GPC) Prominence manufactured by Shimadzu Corporation, and a differential refractometer (RI meter) as a detector at a column temperature of 30 ° C. and a flow rate of 1 ml / min. Was done. The number average molecular weight was a standard polystyrene equivalent value, and was calculated by omitting a portion corresponding to a molecular weight of less than 1000. Shodex KF-802, 804L, and 806L manufactured by Showa Denko KK were used as GPC columns.

2. Glass transition temperature (Tg)
5 mg of sample resin is put in an aluminum sample pan, sealed, and measured using a differential scanning calorimeter (DSC) DSC-220 manufactured by Seiko Instruments Inc. up to 200 ° C. at a temperature rising rate of 20 ° C./min. And the temperature at the intersection of the base line extension below the glass transition temperature and the tangent indicating the maximum slope at the transition.

3. Acid value 0.2 g of sample resin was precisely weighed and dissolved in 20 ml of chloroform. Subsequently, titration was performed with 0.01 N potassium hydroxide (ethanol solution) using a phenolphthalein solution as an indicator. The unit of the acid value was eq / ton, that is, the equivalent per 1 ton of the sample.

4). Resin Composition A sample resin was dissolved in chloroform-d, and a resin composition was determined by 1H-NMR analysis using a VARIAN 400 MHz-NMR apparatus.

5. Paste viscosity Viscosity was measured at a sample temperature of 25 ° C using a BH viscometer (manufactured by Toki Sangyo Co., Ltd.)
Measurements were performed at 20 rpm.

6). Storage stability of conductive paste The conductive paste was placed in a plastic container and sealed and stored at 40 ° C. for 1 month. 4. Viscosity measurement after storage and above 5. The test piece produced by the conductive laminate test piece was evaluated.
◯: There is no significant change in viscosity, and the initial specific resistance, pencil hardness and adhesion are maintained.
X: Either a significant increase in viscosity (more than twice the initial viscosity) or a significant decrease in viscosity (1/2 or less of the initial viscosity) and / or a decrease in specific resistance, pencil hardness and / or adhesion are observed. .

7). Preparation of conductive laminate test piece A 200-mesh polyester screen was used for each of a PET film (Lumirror S manufactured by Toray Industries, Inc.) and an ITO film (KH300 manufactured by Oike Kogyo Co., Ltd.) that had been annealed to a thickness of 100 μm. A conductive paste was printed by a screen printing method to form a solid coating pattern having a width of 25 mm and a length of 450 mm, and then heated at 120 ° C. for 30 minutes in a hot air circulation drying oven to obtain a conductive laminate test piece. . In addition, the coating thickness at the time of printing was adjusted so that a dry film thickness might be 6-10 micrometers.

8). Adhesiveness According to JIS K-5400-5-6: 1990 using the said electroconductive laminated body test piece, it evaluated by the peeling test using the cello tape (trademark) (made by Nichiban Co., Ltd.). However, the number of cuts in each direction of the lattice pattern was 11, and the cut interval was 1 mm. 100/100 indicates that there is no peeling and good adhesion, and 0/100 indicates that all are peeled off.

9. Specific Resistance The sheet resistance and film thickness of the conductive laminate test piece were measured, and the specific resistance was calculated. For the film thickness, a gauge stand ST-022 (manufactured by Ono Sokki Co., Ltd.) was used, and the thickness of the cured coating film was measured at five points with the thickness of the PET film as the zero point, and the average value was used. The sheet resistance was measured for four test pieces using MILLIOHMMETER 4338B (manufactured by HEWLETT PACKARD), and the average value was used. The range that can be detected by this milliohm meter is 1 × 10 −2 (Ω · cm) or less, and a specific resistance of 1 × 10 −2 (Ω · cm) or more is outside the measurement limit.

10. Pencil Hardness The conductive laminate test piece was placed on a 2 mm thick SUS304 plate, and the pencil hardness was measured according to JIS K 5600-5-4: 1999.

11 Moisture and heat resistance test:
The conductive laminate test piece was heated at 80 ° C. for 300 hours, then heated at 85 ° C. and 85% RH (relative humidity) for 300 hours, and then allowed to stand at room temperature for 24 hours, after which various evaluations were performed.

12 Evaluation of laser etching process suitability A conductive paste was printed and applied in a 2.5 × 10 cm rectangle on a polyester base material (Lumirror S (thickness: 100 μm) manufactured by Toray Industries, Inc.) by a screen printing method. A T400 stainless mesh (emulsion thickness 10 μm, wire diameter 23 μm (manufactured by Tokyo Process Service)) was used as a screen plate, and printing was performed at a squeegee speed of 150 mm / s. After the printing application, drying was performed at 120 ° C. for 30 minutes in a hot air circulation drying oven to obtain a conductive thin film. The paste was diluted and adjusted so that the film thickness was 5 to 12 μm. Next, laser etching processing was performed on the conductive thin film prepared by the above method to prepare a pattern having four straight portions with a length of 50 mm shown in FIG. 1 and used as a test piece for evaluating the suitability for laser etching processing. The laser etching process between the straight line portions was performed by scanning a laser beam having a beam diameter of 30 μm twice at a pitch of 60 μm. A fiber laser was used as the laser light source, and the Q modulation frequency was 200 kHz, the output was 10 W, and the scanning speed was 2700 mm / s.

  Evaluation items and measurement conditions are as follows.

(Laser etching processing width evaluation)
In the laser etching process suitability evaluation test piece, the line width of the portion where the conductive thin film was removed was measured. The measurement was performed using a laser microscope (Keyence VHX-1000), and the determination was made according to the following evaluation criteria.
○: The line width of the portion where the conductive thin film is removed is 28 to 32 μm.
Δ: The line width of the portion where the conductive thin film is removed is 24 to 27 μm or 33 to 36 μm.
X: The line width of the portion where the conductive thin film has been removed is 23 μm or less, or 37 μm or more

(Laser etching process suitability evaluation (1) Conductivity between both ends of fine wire)
In the laser etching process suitability evaluation test piece, the evaluation was made based on whether or not conduction between both ends of the thin wires 1b, 2b, 3b, and 4b was secured. Specifically, the presence / absence of conduction is confirmed by applying a tester between each of the terminals 1a and 1c, between the terminals 2a and 2c, between the terminals 3a and 3c, and between the terminals 4a and 4c. Judged by.
○: Conduction between both ends of the fine wire for all four fine wires. Δ: Conductivity between both ends of the thin wires for one of the four thin wires ×: Fine wires for all four thin wires No conduction between both ends (Laser etching process suitability evaluation (2) Insulation between adjacent thin wires)
The laser etching process suitability evaluation test piece was evaluated based on whether insulation between adjacent thin wires was ensured. Specifically, the presence / absence of conduction was confirmed by applying a tester between each of the terminals 1a and 2a, between the terminals 2a and 3a, and between the terminals 3a and 4a, and judged according to the following evaluation criteria.
○: All adjacent fine wires are insulated △: Some adjacent fine wires are insulated ×: All adjacent fine wires are not insulated

(Evaluation of residue at the site where the conductive thin film has been removed)
In the laser etching process suitability evaluation test piece, the site from which the conductive thin film was removed was observed with a laser microscope, and the presence or absence of residue was determined according to the following evaluation criteria.
○: There is no residue at the site where the conductive thin film has been removed.
Δ: There is some residue at the site where the conductive thin film has been removed.
X: Many residues are observed at the site where the conductive thin film has been removed.

(Evaluation of adhesion between conductive thin film and substrate after laser etching)
The adhesiveness to the substrate of the portion where the conductive thin film is sandwiched between the portions where the conductive thin film has been removed in the laser etching processing suitability evaluation test piece is measured with Cellotape (registered trademark) (Nichiban Co., Ltd.) The product was evaluated by a tape peeling test using This evaluation was performed immediately after 24 hours (initial stage) after the test piece was prepared, and after that, after further standing in a moist heat environment of 85 ° C. and 85% RH (relative humidity) for 120 hours and then at room temperature for 24 hours (moisture heat resistance) After the test).
○: No peeling. Δ: Partially peeled off. X: All peel.

Example of Resin Production Example of Polyester Resin P-1 In a reaction vessel equipped with a stirrer, a condenser, and a thermometer, 700 parts of terephthalic acid, 700 parts of isophthalic acid, 16.9 parts of trimellitic anhydride, 983 parts of ethylene glycol, 2 -154 parts of methyl-1,3-propanediol were charged, and the temperature was increased from 160 ° C to 230 ° C over 3 hours under a pressure of 2 atmospheres in a nitrogen atmosphere to carry out an esterification reaction. After releasing the pressure, 0.92 part of tetrabutyl titanate was added, and then the pressure inside the system was gradually reduced to 5 mmHg over 20 minutes, and then the pressure was reduced to 260 ° C. for 40 minutes under a vacuum of 0.3 mmHg or less. A condensation reaction was performed. Subsequently, it cooled to 220 degreeC under nitrogen stream, 50.6 parts of trimellitic anhydride was thrown in, and it reacted for 30 minutes, and obtained the polyester resin. The composition and physical properties of the obtained copolyester resin P-1 are shown in Table 1.

Manufacture example of polyester resin P-2-P-11 In the manufacture example of polyester resin P-1, the kind and compounding ratio of a monomer were changed, and polyester resin P-2-P-11 was manufactured. The composition and resin physical properties of the obtained copolyester resin are shown in Tables 1-2.

BPE-20F: Ethylene oxide adduct of bisphenol A (manufactured by Sanyo Chemical Industries)
BPX-11: Propylene oxide adduct of bisphenol A (Asahi Denka Co., Ltd.)

Production Example of Polyurethane Resin U-1 In a reaction vessel equipped with a stirrer, a condenser and a thermometer, 1000 parts of polyester resin P-7, 80 parts of neopentyl glycol (NPG), and 90 parts of dimethylolbutanoic acid (DMBA) are charged. Then, 1087 parts of ethyl diglycol acetate (EDGAC) was charged and dissolved at 85 ° C. Thereafter, 460 parts of 4,4′-diphenylmethane diisocyanate (MDI) was added and reacted at 85 ° C. for 2 hours, and then 0.5 part of dibutyltin dilaurate was added as a catalyst and reacted at 85 ° C. for another 4 hours. . Next, the solution was diluted with 1940 parts of EDGAC to obtain a solution of polyurethane resin U-1. The solid content concentration of the obtained polyurethane resin solution was 35% by mass. The resin solution thus obtained was dropped on a polypropylene film and spread using a stainless steel applicator to obtain a resin solution thin film. This was left in a hot air dryer adjusted to 120 ° C. for 3 hours to volatilize the solvent, and then the resin thin film was peeled off from the polypropylene film to obtain a film-like dry resin thin film. The thickness of the dry resin thin film was about 30 μm. Table 3 shows the evaluation results of various resin properties, using the dry resin thin film on the left as a sample resin of polyurethane resin U-1.

Production Examples of Polyurethane Resins U-2 to U-8 Polyurethane resins U-2 to U-8 are polyurethanes except that the polyester polyol, the compound having a group that reacts with isocyanate, and the polyisocyanate are replaced with those shown in Table 3. It manufactured by the method similar to the manufacture example of resin U-1. Table 3 shows the evaluation results of the physical properties of the polyurethane resins U-2 to U-8.

DMBA: dimethylol butanoic acid NPG: neopentyl glycol DMH: 2-butyl-2-ethyl-1,3-propanediol MDI: 4,4′-diphenylmethane diisocyanate IPDI: isophorone diisocyanate

Example 1
Kyoeisha Chemical Co., Ltd. 2860 parts (1000 parts in terms of solid part) of a solution in which polyester resin P-1 is dissolved in EDGAC so that the solid content concentration is 35% by mass, 7,888 parts of flaky silver powder 1 as a leveling agent 71 parts of MK Conk made, 30 parts of Disperbyk 130 made by Big Chemie Japan Co., Ltd. as a dispersant and 300 parts of EDGAC as a solvent were blended and dispersed by passing 3 times through a chilled three-roll kneader. Thereafter, the obtained conductive paste was printed in a predetermined pattern and then dried at 120 ° C. for 30 minutes to obtain a conductive thin film. The basic physical properties were measured using this conductive thin film, and then laser etching processing was examined. Table 4 shows the evaluation results of the paste, paste coating film, and laser etching processability.

Examples 2-13
Examples 2 to 17 were carried out by changing the resin and the composition of the conductive paste. The formulation and evaluation results of the conductive paste are shown in Tables 4 to 6. In the examples, good film properties could be obtained by heating at a relatively low temperature of 120 ° C. for 30 minutes in an oven at a relatively low temperature. Also, the adhesion to the ITO film and the adhesion after the wet heat environment test were good.

In Tables 4 to 7, the following binder resins, conductive powders, additives and solvents were used.
Binder resin PH-1: PKKH manufactured by InChem (phenoxy resin, number average molecular weight 14000, Tg = 71 ° C.)
Silver powder 1: flaky silver powder (D50: 2 μm)
Silver powder 2: Spherical silver powder (D50: 1 μm)
Carbon black: Tokai Carbon Co., Ltd. # 4400
Ketjen Black: Ketjen ECP600JD made by Lion Corporation
Graphite powder: Graphite BF manufactured by Chuetsu Graphite Co., Ltd.
Curing agent: MF-K60X manufactured by Asahi Kasei Chemicals Corporation
Curing catalyst: Kyodo Pharmaceutical Co., Ltd. KS1260
Leveling agent: Kyoeisha Chemical Co., Ltd. MK Conk Dispersant 1: Disperbyk130 manufactured by Big Chemie Japan Co., Ltd.
Dispersant 2: Disperbyk 2155 manufactured by Big Chemie Japan Co., Ltd.
Dispersant 3: Disperbyk180 manufactured by Big Chemie Japan Co., Ltd.
Additive 1: Silica R972 manufactured by Nippon Aerosil Co., Ltd.
Additive 2: NIR-AM1 manufactured by Nagase ChemteX Corporation
Additive 3: Light acrylate PE-3A (pentaerythritol triacrylate) manufactured by Kyoeisha Chemical Co., Ltd.
EDGAC: Ethyl diglycol acetate manufactured by Daicel Corp. BMGAC: Butyl glycol acetate manufactured by Daicel Corp. BDGAC: Butyl diglycol acetate manufactured by Daicel Corp. TPOL: Terpineol manufactured by Nippon Terpene Chemical Co., Ltd.

Comparative Example 1
Silver lauryl carboxylate (1000 g) and butylamine (480 g) were dissolved in toluene (10 L). Next, formic acid (150 g) was added dropwise, and the mixture was stirred at room temperature for 1.5 hours. When a large amount of methanol was added, an aggregate of silver nanoparticles precipitated and was decanted. After repeating the decantation three times, the precipitate was dried under reduced pressure. Next, 1000 g of the resulting precipitate (of which 920 g silver, 80 g silver carboxylate amine complex) was redispersed in 1860 g terpineol to obtain a conductive paste containing silver nanoparticles (silver powder 3). The obtained silver powder 3 had a particle diameter of about 10 nm from a transmission electron micrograph. The solid content concentration of the conductive paste was 35% by mass. Using the obtained conductive paste, a conductive laminate test piece and a laser etching processability evaluation test piece were prepared in the same manner as in the example, and the evaluation was performed in the same manner as in the example. The evaluation results are shown in Table 7. This electroconductive silver paste composition was remarkably inferior in initial coating film properties, in particular, poor in adhesion, and could not withstand practical use.

Comparative Example 2
Dodecylamine was dissolved in terpineol to obtain a solution having a solid content of 12% by weight. To 1000 parts of this solution (solid 120 parts by weight), silver powder 4 (spherical silver powder (D50 = 1 μm)) 8083 parts, and glass frit ((bismuth oxide (Bi 2 O 3)) pulverized with a bead mill to an average particle size of 1.5 μm. After adding 250 parts of glass powder (bismuth oxide content 80.0-99.9%) as a main component and mixing, this solution is dispersed with a three-roll mill, and glass frit-containing conductive material is obtained. Using the obtained conductive paste, a conductive laminate test piece and a laser etching processability evaluation test piece were prepared in the same manner as in the example, and evaluated in the same manner as in the example. The conductive silver paste composition has a remarkably inferior initial coating film property, particularly poor adhesion, and cannot be put into practical use. The coating process having a significantly wider width than the width of the laser beam irradiated in a wider range than the irradiated part was peeled off, and the predetermined line width could not be processed. Also, the adhesion of the thin wire after laser etching and the heat and humidity resistance were poor.

  The conductive paste for laser etching processing of the present invention provides a conductive thin film that is excellent in wet heat environment reliability while maintaining the suitability of laser etching processing and can maintain the durability of the coating film as a conductive thin film. For example, it is useful as a conductive paste used for a touch panel mounted on a mobile phone, a notebook computer, an electronic book, or the like.

1a, 2a, 3a, 4a: Terminals 1a, 2a, 3a, 4a
1b, 2b, 3b, 4b: Fine wires 1b, 2b, 3b, 4b
1c, 2c, 3c, 4c: Terminals 1c, 2c, 3c, 4c
5: Pattern formed on test piece for evaluating laser etching process suitability

Claims (12)

Binder resin (A) made of thermoplastic resin, metal powder (B) and organic solvent (C), the binder resin (A) has a number average molecular weight of 5,000 to 60,000, and It is a thermoplastic resin having a glass transition temperature of 150 ° C. or less, and the center diameter (D50) of the metal powder (B) is 4 μm or less,
Touch panel circuit wiring with a L / S of 50/50 μm or less by laser etching processing on a substrate having a transparent conductive layer, or on a substrate having a transparent conductive layer and the transparent conductive layer partially removed by etching Conductive paste for laser etching process used to form in. The laser binder used for forming the circuit wiring of the touch panel according to claim 1, wherein the binder resin (A) is a thermoplastic resin having a glass transition temperature of 60 to 100 ° C. Conductive paste.   The binder resin (A) is one or a mixture of two or more selected from the group consisting of a polyester resin, a polyurethane resin, an epoxy resin, a phenoxy resin, a vinyl chloride resin, and a fiber derivative resin. Item 3. A conductive paste for laser etching used for forming circuit wiring of a touch panel according to Item 1 or 2. The binder resin (A) is an acid value 50-300 one or more selected from the group consisting of polyurethane resins is equivalent / 10 ⁶ g polyester resin and an acid number of 50 to 300 equivalents / 10 ⁶ g is The conductive paste for laser etching used for forming the circuit wiring of the touch panel according to claim 1, wherein the conductive paste is a mixture.   Furthermore, a laser beam absorber (D) is contained, The electrically conductive paste for laser etching processing used in order to form the circuit wiring of the touchscreen in any one of Claims 1-4 characterized by the above-mentioned.   A laser beam selected from a carbon dioxide laser, a YAG laser, a fiber laser, and a semiconductor laser is irradiated to a part of the conductive thin film formed from the conductive paste for laser etching according to claim 1. A method for manufacturing an electric circuit for a touch panel having a circuit wiring having an L / S of 50/50 μm or less formed by removing a part of the conductive thin film.   The method for manufacturing an electric circuit for a touch panel according to claim 6, wherein the conductive thin film is formed on a transparent conductive layer.   The manufacturing method of the touch panel which contains the electric circuit formed by the manufacturing method of the electric circuit in any one of Claims 6-7 as a structural member.   A circuit having a L / S of 50/50 μm or less by laser etching after forming a coating film on a substrate using the conductive paste according to claim 1 and then drying the coating film A method of manufacturing a circuit wiring for a touch panel, wherein the wiring is formed.   The method for manufacturing a circuit wiring for a touch panel according to claim 9, wherein a film thickness after drying the coating film according to claim 9 is 3 μm or more and 30 μm or less.   The method for manufacturing a circuit wiring for a touch panel according to any one of claims 9 to 10, wherein a scanning speed of laser light in the laser etching process is 1000 mm / s or more.   The method for manufacturing a circuit wiring for a touch panel according to claim 9, wherein the circuit wiring is formed on a substrate having a transparent conductive layer.