JP6638393B2 - Conductive paste for laser etching, conductive thin film, conductive laminate - Google Patents

Description

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

  2. Description of the Related Art In recent years, electronic devices equipped with a transparent touch panel typified by a mobile phone, a notebook computer, an electronic book, and the like have been rapidly improving in performance and miniaturization. In order to improve the performance and miniaturization of these electronic devices, it is necessary to increase the density of electrode circuit wiring that connects these electronic components in addition to the miniaturization, higher performance, and higher integration of the electronic components to be mounted. Have been. In recent years, in addition to the resistive film method with a small number of electrode circuit wirings as a transparent touch panel method, the electrostatic capacitance method with a dramatic increase in the number of electrode circuit wirings has been rapidly spreading in recent years. There is a strong demand for higher density. Further, in order to make the display screen larger, there is a demand for a product design to make the frame portion where the electrode circuit wiring is arranged narrower, and from such a viewpoint, the high density of the electrode circuit wiring is required. Is required. In order to satisfy the above requirements, there is a demand for a technology capable of arranging the electrode circuit wiring at a higher density than in the related art.

  The arrangement density of the electrode circuit wiring in the frame portion of the transparent touch panel of the resistive film type is such that the width of the line and the space in the planar direction are each about 200 μm (hereinafter abbreviated as L / S = 200/200 μm) or more. This is conventionally 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 sometimes the L / S is required to be 50/50 μm or less. It is becoming a difficult situation to deal with.

  A photolithography method is an example of a candidate for an electrode circuit wiring forming technique replacing screen printing. If a photolithography method is used, it is possible to form a fine line having an L / S of 50/50 μm or less. However, the photolithography method also has a problem. The most typical example of the photolithography method is a method using a photosensitive resist. In general, a photosensitive resist is applied to a copper foil portion of a surface substrate having a copper foil layer formed thereon, and a photomask or laser light is applied. 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 burden on the environment due to waste liquid treatment is large, and the process is complicated.

  There is also a photolithography method that does not use a photosensitive resist. For example, in Patent Literatures 1 and 2, a dry coating film is formed using a conductive paste, and a laser beam is directly drawn on the dried coating film. There is disclosed a technique in which a portion irradiated with is fixed on a base material, an unirradiated portion is developed and removed, and a desired pattern is formed. With such a method, the process is simplified as compared with a general photolithography method because no photosensitive resist is used, but the photolithography method using a conventionally known photosensitive resist is Similarly, since the development process of the wet process is required, there is a problem of developing waste liquid treatment, and a high temperature of 400 ° C. or more is required in the firing process because glass frit and nano-sized silver powder are used as a component of the conductive paste. However, there is a problem that a large amount of energy is required, and there is a problem that a substrate that can be used is limited to a material that can withstand a firing step at a high temperature of 400 ° C. or higher. Furthermore, the process is complicated, and it must be said that the production efficiency is not suitable.

  Due to the above situation, a laser etching method disclosed in Patent Document 3 has attracted attention in recent years as an example of a candidate for an electrode circuit wiring forming technology replacing screen printing. If the laser etching method is used, it is sufficiently possible to form a thin line having an L / S of 50/50 μm or less. The laser etching method is a method of forming a layer consisting of a binder resin and conductive powder (hereinafter referred to as a conductive thin film) on an insulating substrate, and removing a part of the layer from the insulating substrate by laser light irradiation. That is.

However, the laser etching method also has a problem. Removal of the conductive thin film by irradiation with laser light generates a large amount of heat, which results in thermal deterioration of the conductive thin film and the base material. It may be damaged. As a method of suppressing thermal deterioration, it is conceivable to reduce the energy of the laser, but if the energy is too small, etching cannot be performed, short-circuits and burrs occur between the fine wires, which is not suitable for production efficiency. .

JP 2010-237573 A JP 2011-181338 A Japanese Patent Application No. 2012-161485

An object of the present invention is to provide a manufacturing method capable of realizing high-density electrode circuit wiring even under low energy laser conditions in order to minimize thermal degradation of a substrate and a conductive thin film due to laser etching. Another object of the present invention is to provide a conductive paste that can be suitably used in such a manufacturing method.

  The present inventors have conducted intensive studies on a manufacturing method of arranging electrode circuit wirings at high density in the plane direction, and found that a conductive material suitable for forming a layer made of a binder resin and a conductive powder suitable for a laser etching method at a low energy. Found the paste. That is, the present invention has the following configuration.

1. In a conductive paste for laser etching processing containing a binder resin (A) made of a thermoplastic resin, a metal powder (B) and an organic solvent (C), the binder resin (A) has a number average molecular weight of 5,000 to A conductive paste for laser etching, wherein the conductive paste is a thermoplastic resin having a glass transition temperature of less than 60 ° C.
2. 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 cellulose derivative resin. 1. 4. The conductive paste for laser etching according to item 1.
3. The binder resin (A) has an acid value of less than 50 equivalents / 10 ⁶ g. Or 2. 4. The conductive paste for laser etching according to item 1.
4. 1. The conductive paste is filtered. ~ 3. The conductive paste for laser etching according to any one of the above.
5. 1. ~ 4. A conductive thin film formed from the conductive paste for laser etching according to any one of the above.
6. 5. A conductive laminate, wherein the conductive thin film and the substrate are laminated.
7. 5. The substrate has a transparent conductive layer. 3. The conductive laminate according to 1.).
8. 5. 5. The conductive thin film according to the above, or Or 7. An electric circuit using the conductive laminate according to item 1.
9. 5. A wiring portion formed by irradiating a part of the conductive thin film according to the above with a laser beam selected from a carbon dioxide laser, a YAG laser, a fiber laser and a semiconductor laser to remove a part of the conductive thin film. An electric circuit having:
10. 8. The conductive thin film is formed on a transparent conductive layer. An electric circuit according to claim 1.
11. 8. -10. A touch panel including the electric circuit according to any one of the above as a constituent member.

  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), wherein the binder resin (A) has a number average molecular weight. It is a conductive paste characterized by being a thermoplastic resin having a glass transition temperature of 5,000 to 60,000 and a glass transition temperature of less than 60 ° C. A conductive thin film having excellent etching workability can be formed. Here, “excellent in laser etching process suitability” means that at least a part of the conductive thin film is peeled off from the base material by laser etching process to form a fine line of L / S = 20/20 μm. The following four conditions must be satisfied: conduction between both ends is ensured, 2) insulation between adjacent fine wires is ensured, 3) fine wire shape is good, and 4) substrate adhesion after laser etching is good. Point. In addition, by filtering the conductive paste according to the embodiment of the present invention, shear can be added to the aggregated silver powder and coarse particles can be removed, thereby exhibiting an effect of improving poor etching.

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

<< Components Constituting Conductive Paste of the Present Invention >>
The conductive paste for laser etching in the present invention is a conductive paste for laser etching containing a binder resin (A) made of a thermoplastic resin, a metal powder (B) and an organic solvent (C). A) contains, as an essential component, a thermoplastic resin having a number average molecular weight of 5,000 to 60,000 and a glass transition temperature of less than 60 ° C.

<Binder resin (A)>
The type of the binder resin (A) is not particularly limited as long as it is a thermoplastic resin, but a polyester resin, an epoxy resin, a phenoxy resin, a polyamide resin, a polyamideimide resin, a polycarbonate resin, a polyurethane resin, a phenol resin, an acrylic resin, polystyrene, and polystyrene -Acrylic resin, styrene-butadiene copolymer, phenolic resin, polyethylene-based resin, polycarbonate-based resin, phenolic resin, alkyd resin, styrene-acrylic resin, styrene-butadiene copolymerized resin, polysulfone resin, polyethersulfone resin, vinyl chloride -Vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer, polystyrene, silicone resin, fluororesin, etc., and these resins can be 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, phenoxy resins, vinyl chloride resins, and cellulose derivative resins. Among these resins, at least one of a polyester resin, a polyurethane resin containing a polyester component as a copolymer component (hereinafter sometimes referred to as a polyester polyurethane resin), and an epoxy resin is used as a binder resin ( More preferred as A).

  One of the advantages of using a polyester resin as the binder resin (A) in the present invention is a high degree of freedom in molecular design. The dicarboxylic acid and glycol components constituting the polyester resin can be selected and the copolymer components can be freely changed, and the functional groups can be easily provided in the molecular chain or at the molecular terminals. For this reason, the properties of the resin, such as the glass transition temperature of the obtained polyester resin and the affinity for other components blended in the base material and the conductive paste, can be appropriately adjusted.

  Examples of the dicarboxylic acid which can be used as a copolymer component of the polyester resin used as the binder resin (A) in the present invention include aromatic terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. Dicarboxylic acids, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, aliphatic dicarboxylic acids such as azelaic acid, dibasic acid and other dibasic acids having 12 to 28 carbon atoms, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 2-methylhexahydrophthalic anhydride, dicarboxy hydrogenated bisphenol A, Dicarboxy hydrogenated bisphenol S 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, as long as the effects of the invention are not impaired, trivalent or higher carboxylic acids such as trimellitic anhydride and pyromellitic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and / or sodium 5-sulfoisophthalate, etc. May be used in combination as a copolymerization component.

  Examples of the polyol 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, and 1,10-decanediol; -Cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol Ethanol, and alicyclic diol and dimer diol. Further, a trivalent or higher polyol such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, or polyglycerin may be used as a copolymer component within a range not to impair the effects of the invention.

  The polyester resin used as the binder resin (A) in the present invention is an aliphatic dicarboxylic acid among all the acid components constituting the polyester resin, from the viewpoints of adhesion, compatibility with other resins used in combination, and thermal shock resistance. Is preferably copolymerized in an amount of 10 mol% or more, more preferably 20 mol% or more, and still more preferably 30 mol% or more. If the copolymerization ratio of the aromatic dicarboxylic acid component is too high, the glass transition temperature of the obtained polyester resin becomes 60 ° C. or higher, and the storage stability is deteriorated due to the deterioration of the compatibility with the resin used in combination, and the straight line of the laser etching process is reduced. There is a possibility that a decrease in the properties and a decrease in the adhesion of the obtained conductive thin film after laser etching may occur.

  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 the polyester resin, the polyurethane resin also has a glass transition by selecting an appropriate component as a copolymerization component constituting the polyurethane resin and providing a functional group in a molecular chain or a molecular terminal. The properties of the resin, such as the temperature and the affinity with other components blended in the base material and the conductive paste, can be appropriately adjusted.

  The copolymerization component of the polyurethane resin is not particularly limited, but is preferably a polyester polyurethane resin using a polyester polyol as a copolymerization component from the viewpoints of design freedom, resistance to wet heat and durability. Preferable examples of the polyester polyol include those which are polyols among the polyester resins that can be used as the binder resin (A) in the present invention described above.

  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. Examples of the polyisocyanate that can be used as a copolymer component of the polyurethane resin include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 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, toluene De be mentioned down diisocyanate, aromatic diisocyanates, may be any of aliphatic diisocyanates and alicyclic diisocyanates. Further, a trivalent or higher isocyanate compound may be used as a copolymer component as long as the effects of the present invention are not impaired.

  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 needed. The functional group capable of reacting with the 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, and 2,2-butylene glycol. 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'-hydroxypropanate, 2-n-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, -Propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 3-octyl-1,5-pentanedio , 3-phenyl-1,5-pentanediol, 2,5-dimethyl-3-sodium sulfo-2,5-hexanediol, dimer diol (for example, PRIPOOL-2033 manufactured by Unichema International) in one molecule. Compounds having two hydroxyl groups, such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, polyglycerin, etc., alcohols having 3 or more hydroxyl groups in one molecule, monoethanolamine, diethanolamine, triethanolamine, etc. Amino alcohol having at least one hydroxyl group and amino group in a molecule, ethylenediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine , 1,12-dodecane Two amino groups in one molecule such as aliphatic diamines such as amines, metaxylenediamine, aromatic diamines such as 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylether, and 4,4'-diaminodiphenylether A compound having the following formula: The compound having a functional group capable of reacting with two or more isocyanates in one molecule having a number average molecular weight of less than 1,000 may be used alone or in combination of two or more without any problem.

Examples of the epoxy resin used as the binder resin (A) in the present invention include glycidyl ether types such as bisphenol A glycidyl ether, bisphenol S glycidyl ether, novolac glycidyl ether, and brominated bis, glycidyl hexahydrophthalate, and glycidyl dimer acid. Glycidyl ester types such as esters, triglycidyl isocyanurate, or 3,4 &#8722; alicyclic or aliphatic epoxides such as epoxycyclohexylmethyl carboxylate, epoxidized polybutadiene, and epoxidized soybean oil; They may be used or two or more of them may be used in combination. Among these, bisphenol A glycidyl ether is preferred from the viewpoint of durability of the coating film, and those having two or more glycidyl ether groups in one molecule are more preferred.

  The number average molecular weight of the binder resin (A) in the present invention is not particularly limited, but is preferably 5,000 to 60,000, more preferably 10,000 to 40,000. If the number average molecular weight is too low, the formed conductive thin film is not preferable in terms of durability and wet heat resistance. On the other hand, if the number average molecular weight is too high, the cohesive force 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 less than 60 ° C, more preferably 30 ° C or less. More preferably, it is 15 ° C. or lower. A lower glass transition temperature has the effect of increasing the surface smoothness of the silver coating and improving the sharpness of fine lines after laser etching. Further, since the silver coating film becomes more adhesive, high substrate adhesion can be realized as a result. The lower limit of the glass transition temperature of the binder resin (A) is not particularly limited, but is usually about -20 ° C or higher.

  The acid value of the binder resin (A) in the present invention is not particularly limited. However, if the acid value is too high, the water absorption of the formed conductive thin film becomes high, and hydrolysis of the binder resin is caused by a catalytic action of a carboxyl group. It may be accelerated and may lead to a decrease in the reliability of the conductive thin film. Hydrolysis is more remarkable when the glass transition temperature is low, and the glass transition temperature of the present application is disadvantageous from the viewpoint of hydrolysis. Therefore, by setting the acid value of the binder resin (A) to a low acid value, preferably less than 50 eq / ton, more preferably 30 eq / ton or less, the high reliability of the conductive thin film and the linearity and adhesion of the laser etching are improved. This has led to the realization of a conductive paste that has both properties.

<Metal powder (B)>
As the metal powder (B) used in the present invention, 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, and precious metal such as silver or the like can be used. An alloyed base metal powder, such as silver-coated copper powder, can be used. These metal powders may be used alone or in combination. Among these, silver powder alone or those mainly composed of silver powder are preferable in consideration of conductivity, stability, cost and the like.

  The shape of the metal powder (B) used in the present invention is not particularly limited. Examples of conventionally known metal powder shapes include flake-like (flake-like), spherical, dendritic (dendritic), and spherical primary particles described in JP-A-9-306240. There are three-dimensionally agglomerated shapes (agglomerated shapes) and the like. Among these, from the viewpoint of laser etching properties, it is preferable to use spherical, agglomerated and flaky metal powders, and more preferably flaky or spherical metal powders. is there.

  The center diameter (D50) of the metal powder (B) used in the present invention is preferably 4 μm or less. The use of metal powder (B) having a center diameter of 4 μm or less tends to improve the fine line shape of the laser-etched portion. When metal powder having a center diameter larger than 4 μm is used, the fine wire shape after the laser etching is deteriorated, and as a result, the fine wires may come into contact with each other to cause a short circuit. Furthermore, there is a possibility that the conductive thin film once peeled and removed by laser etching may adhere to the processed portion again. Although the lower limit of the center diameter of the metal powder (B) is not particularly limited, it is preferable that the center diameter is 80 nm or more because the aggregation is easy when the particle diameter is small and the dispersion becomes difficult as a result. If the center diameter is smaller than 80 nm, the cohesive force of the metal powder increases, which deteriorates the laser etching process aptitude, and is not preferable from the viewpoint of cost.

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

  The content of the metal powder (B) is preferably 400 parts by mass or more, and more preferably 560 parts by mass, based on 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 that adhesion to the substrate is good. It is more preferably at most part by mass.

<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 in an appropriate range, the boiling point is preferably 100 ° C or higher and less than 300 ° C, more preferably. Has a boiling point of 150 ° C. or more and less 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, if necessary, other components with a three-roll mill or the like. If the boiling point of the organic solvent is too low at that time, there is a concern that the solvent volatilizes during dispersion and the component ratio of 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, and there is a concern that the reliability of the coating film may be reduced.

  Further, as the organic solvent (C) that can be used in the present invention, those that are soluble in the thermoplastic resin (A) and capable of favorably dispersing the metal powder (B) are preferable. Specific examples include ethyl diglycol acetate (EDGAC), butyl glycol acetate (BMGAC), butyl diglycol acetate (BDGAC), cyclohexanone, toluene, isophorone, γ-butyrolactone, benzyl alcohol, and Exxon Chemical's Solvesso 100, 150, 200, propylene glycol monomethyl ether acetate, adipic acid, a mixture of dimethyl esters of succinic acid and glutaric acid (for example, DBE manufactured by DuPont Co., Ltd.), terpioneol and the like. Among these, thermoplastic resins ( EDGAC, BMGAC, BDGAC, and mixtures thereof, from the viewpoint of excellent solubility of the components of A), moderate solvent volatility during continuous printing, and good suitability for printing by a screen printing method or the like. 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 based on 100 parts by weight of the total paste. . If the content of the organic solvent (C) is too high, the viscosity of the paste becomes too low, and the thin line printing tends to cause sagging. On the other hand, when the content of the organic solvent (C) is too low, the viscosity of the paste becomes extremely high, and, for example, the screen printability when forming the conductive thin film is significantly reduced. In some cases, the film thickness is increased and the laser etching processability is reduced.

<Laser light absorber (D)>
The conductive paste of the present invention may contain a laser light absorber (D). 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 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 incorporating the laser light absorber (D), the conductive thin film of the present invention absorbs the laser light with high efficiency, and promotes the volatilization and thermal decomposition of the binder resin (A) due to heat generation. Is improved.

  Among the laser light absorbers (D) that can be used in the present invention, examples of conductive materials include carbon fillers such as carbon black and graphite powder. The compounding of the carbon-based filler also 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 near 1060 nm, a wavelength of 1064 nm such as a YAG laser or a fiber laser is used. By irradiating the laser light, the conductive thin film absorbs the laser light with high efficiency, so the sensitivity to the laser light irradiation is increased, and it is good even when the scanning speed of the laser irradiation is increased and / or the laser light source has a low output. The effect that laser etching processing suitability is obtained can be expected. The content of the carbon-based filler is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 2 parts by weight, based on 100 parts by weight of the metal powder (B). When the compounding ratio of the carbon-based filler is too low, the effect of increasing the conductivity and the effect of increasing the sensitivity to laser beam irradiation are small. On the other hand, when the compounding ratio of the carbon-based filler is too high, the conductivity of the conductive thin film tends to decrease, and further, the resin is adsorbed to the void portion of carbon, and the adhesion to the base material is reduced. Points may also 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 salt azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinone imine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes and the like 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-bound pigments. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelated azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments And quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, and inorganic pigments. Examples of the infrared absorber include NIR-IM1, which is a diimonium salt type infrared absorber, and NIR-AM1, which is an aminium salt type (both manufactured by Nagase ChemteX Corporation). It is preferable that the non-conductive laser light absorber (D) contains 0.01 to 5 parts by weight, preferably 0.1 to 2 parts by weight. If the compounding ratio of the non-conductive laser light absorber (D) is too low, the effect of increasing the sensitivity to laser light irradiation is small. If the compounding ratio of the non-conductive laser light absorber (D) is too high, the conductivity of the conductive thin film may be reduced, and the color tone of the laser light absorber becomes remarkable, which is not preferable for some applications. There is.

  The following inorganic substances can be added to the conductive paste of the present invention. Examples of inorganic substances include various carbides such as 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 the like; boron nitride , Titanium nitride, various nitrides such as zirconium nitride, various borides such as zirconium boride; titanium oxide (titania), calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica, fumed silica (for example, Japan Various oxides such as Aerosil) colloidal silica manufactured by Aerosil Co .; various titanate compounds such as calcium titanate, magnesium titanate and strontium titanate; sulfides such as molybdenum disulfide; each such as magnesium fluoride and carbon fluoride Fluoride; aluminum stearate, calcium stearate, 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 or 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. Above all, in the conductive paste of the present invention, fumed silica is preferred from the viewpoint of imparting durability and printability, particularly screen printability.

  In addition, 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. And a dye. Further, carbodiimide, epoxy, or the like can be appropriately compounded as a resin decomposition inhibitor. These can be used alone or in combination.

<Curing agent (E)>
The conductive paste of the present invention may contain a curing agent capable of reacting with the binder resin (A) to such an extent that the effects of the present invention are not impaired. By adding a curing agent, the curing temperature may increase and the load on the production process may increase, but improvement in the wet heat resistance of the coating film can be expected by crosslinking due to the heat generated at the time of coating drying or laser etching. .

  The curing agent capable of reacting with the binder resin (A) of the present invention is not particularly limited, but is preferably an isocyanate compound and / or an epoxy resin in view of adhesion, bending resistance, curability and the like. Further, with respect to the isocyanate compound, it is preferable to use a compound in which an isocyanate group is blocked, because storage stability is improved. Examples of the curing agent other than the isocyanate compound include known compounds such as methylated melamine, butylated melamine, benzoguanamine, amino resins such as urea resins, acid anhydrides, imidazoles, and phenol resins. These curing agents may be used in combination with a known catalyst or accelerator selected according to the type of the curing agent. The amount of the curing agent is such that the effect of the present invention is not impaired, and is not particularly limited, but is 0.5 to 50 parts by mass with respect to 100 parts by mass of the binder resin (A). A mass part is preferred, 1-30 mass parts is more preferred, and 2-20 mass parts is still more preferred.

  Examples of the isocyanate compound that can be blended in the conductive paste of the present invention include aromatic or aliphatic diisocyanate, trivalent or higher polyisocyanate, and may be either a low molecular compound or a high molecular compound. For example, aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, aromatic diisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, and isophorone diisocyanate. Alicyclic diisocyanates or trimers of these isocyanate compounds, and excess amounts of these isocyanate compounds and, for example, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine Etc. or low molecular active hydrogen compounds 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, methylethylketoxime, 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-propyrolactam and the like; and 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 preferred from the viewpoint of curability.

Epoxy compounds used as a curing agent in the present invention include, for example, glycidyl ether types such as bisphenol A glycidyl ether, bisphenol S glycidyl ether, novolac glycidyl ether, and brominated bis, glycidyl hexahydrophthalate, glycidyl dimer, and the like. Glycidyl ester type, triglycidyl isocyanurate, or 3,4 &#8722; alicyclic or aliphatic epoxides such as epoxycyclohexylmethyl carboxylate, epoxidized polybutadiene, epoxidized soybean oil, etc. Two or more kinds may be used in combination. Among these, bisphenol A glycidyl ether is most preferable from the viewpoint of curability, and among them, those having a molecular weight of less than 5,000 and having two or more glycidyl ether groups in one molecule are more preferable.

<< physical properties required of the conductive paste of the present invention >>
The viscosity of the conductive paste of the present invention is not particularly limited, and may be appropriately adjusted according to the method of forming a coating film. For example, when the conductive paste is applied to the base material by screen printing, the viscosity of the conductive paste at the printing temperature is preferably 100 dPa · s or more, more preferably 150 dPa · s or more. The upper limit is not particularly limited, but if the viscosity is too high, the thickness of the conductive thin film may be too large, and the suitability for laser etching may be reduced.

  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 a 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 term "parts by mass" as used herein refers to parts by mass of the conductive powder, and the term "parts by mass" refers to parts by mass 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 exhibiting good conductivity cannot be obtained, and 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, the printing performance is inevitably reduced. Here, the conductive powder refers to both the metal powder (B) and the conductive powder made of a non-metal.

<< Production method of 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 manufacturing procedure will be described. First, the thermoplastic resin (A) is dissolved in the organic solvent (C). Thereafter, the metal powder (B) and, if necessary, additives are added, and the dispersion is carried out with a double planetary, a dissolver, a planetary stirrer, or the like. Then, it is dispersed by a three-roll mill to obtain a conductive paste. The conductive paste thus obtained can be filtered if necessary. There is no problem even if the dispersion is performed using another dispersing machine, for example, a bead mill, a kneader, an extruder or the like.

<< The conductive thin film of the present invention, the conductive laminate and the method for producing them >>
The conductive thin film 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 base material is not particularly limited, but printing by a screen printing method is a simple process and a technique widely used in the industry of forming an electric circuit using the conductive paste. Is preferred. In addition, the conductive paste is applied or printed on a portion that is somewhat wider than the conductive thin film portion that is finally required as an electric circuit, thereby reducing the load of the laser etching process and efficiently using the electric circuit of the present invention. It is preferable from the viewpoint of formation.

  As the substrate on which the conductive paste of the present invention is applied, a material having excellent 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. In addition, an inorganic material such as glass can be used as the base material. Although the thickness of the substrate is not particularly limited, it is preferably from 50 to 350 μm, more preferably from 100 to 250 μm from the viewpoint of mechanical properties, shape stability, handleability and the like of the pattern forming material.

  In addition, by performing a physical treatment and / or a chemical treatment on the surface of the base material to which the conductive paste of the present invention is applied, the adhesion between the conductive thin film and the base material can be improved. Examples of the physical treatment method include a sand blast method, a wet blast method for spraying a liquid containing fine particles, a corona discharge treatment method, a plasma treatment method, and an ultraviolet or vacuum ultraviolet irradiation treatment method. Examples of the chemical treatment method include a strong acid treatment method, a strong alkali treatment method, an oxidizing agent treatment method, and a coupling agent treatment method.

  Further, the substrate may have a transparent conductive layer. The conductive thin film of the present invention can be laminated on a 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 and a silver nanowire film made of nano-sized linear silver. Further, the transparent conductive layer is not limited to one formed on the entire surface of the substrate, and may be one obtained by removing a part of the transparent conductive layer by etching or the like.

  The step of volatilizing the organic solvent (C) is preferably performed at normal temperature and / or under heating. When heating, the heating temperature is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, even more preferably 110 ° C. or higher, since the conductivity, adhesion and surface hardness of the conductive thin film after drying are improved. In addition, 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 conductive paste of the present invention contains a curing agent, if the step of evaporating the organic solvent (C) is performed under heating, the curing reaction proceeds.

  The thickness of the conductive thin film of the present invention may be set to an appropriate thickness according to the intended use. However, the thickness of the conductive thin film is preferably 3 μm or more and 30 μm or less, more preferably 4 μm, from the viewpoint that the conductivity of the conductive thin film after drying is good and the suitability for laser etching is good. As mentioned above, it is 20 μm or less, more preferably 4 μm or more and 10 μm or less. If the thickness of the conductive thin film is too small, desired conductivity as a circuit may not be obtained. If the film thickness is too large, the laser irradiation amount required for the laser etching processing becomes excessively necessary, which may damage the substrate. In addition, when the thickness variation is large, the easiness of etching of the conductive thin film varies, and short-circuiting between lines due to insufficient etching and disconnection due to excessive etching tend to occur. For this reason, the variation in the film thickness is preferably small.

  The surface roughness Ra of the conductive thin film of the present invention is preferably 0.7 μm or less, more preferably 0.5 μm or less. If the surface roughness Ra is too high, the edge of the conductive thin film is likely to be jagged at the etched end, and a short circuit between the lines or disconnection due to excessive etching may easily occur. Since the surface roughness Ra is strongly affected by the paste composition (particularly, the binder type and the silver powder type), the paste viscosity, and the screen printing conditions, it is necessary to control these by appropriately adjusting them.

<< Electric Circuit of the Present Invention and Manufacturing Method Thereof >>
The electric circuit of the present invention irradiates at least a part of the conductive thin film formed on the base material with the conductive paste of the present invention with laser light, and removes a part of the conductive thin film from the base material. This is an electric circuit having a wiring portion formed by the above. By adopting such an electric circuit forming method, the pattern forming step can be a dry process unlike the photolithography method, and no waste liquid containing a metal component is generated, so that waste liquid treatment or the like is not required, and it is environmentally friendly. It can be said that it is a process. In addition, since the process is simple, investment for the manufacturing equipment can be suppressed, and maintenance after the operation of the manufacturing equipment is easy. The method for forming the conductive thin film on the base material using the conductive paste is not particularly limited, but can be performed by printing or painting.

  The method for irradiating the laser beam is not particularly limited, but a laser etching apparatus which has been widely used in recent years, or a laser etching apparatus having further improved dimensional accuracy can be used. The laser etching processing apparatus can use the data produced by the image processing application software such as CAD as it is for laser processing, so that the production pattern can be easily switched. This can be cited as one of the advantages over the pattern formation by the conventional screen printing method.

  At the site where the laser beam is irradiated and absorbed, the energy of the laser beam is converted into heat, and the temperature rise causes thermal decomposition and / or volatilization, and the irradiated site is separated and removed. In order for the portion of the conductive thin film of the present invention irradiated with 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 in which any component constituting the conductive thin film of the present invention has strong absorption.

  Common laser types include excimer laser (fundamental wavelength is 193 to 308 nm), YAG laser (fundamental wavelength is 1064 nm), fiber laser (fundamental wavelength is 1060 nm), CO2 laser (fundamental wavelength) , 10600 nm), and a semiconductor laser. Basically, there is no problem with using any type of laser and any kind of laser. By selecting a laser type that can irradiate a wavelength that is consistent with the absorption wavelength range of any of the constituent components of the conductive thin film and that does not have strong absorption by the substrate, the conductive thin film at the laser light irradiation site 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 type of laser to be irradiated. When using a conductive thin film having a polyester layer structure as a substrate, or a thin film in which a portion of the conductive thin film having a polyester layer structure is removed by etching, using a YAG laser or a fiber laser, The substrate is particularly preferable in that the substrate has no absorption at the wavelength of the fundamental wave, so that the substrate is not easily damaged.

  The laser output and the frequency are not particularly limited, but are adjusted so that the conductive thin film at the laser beam irradiation site can be removed with an etching width of 10 to 50 μm and the base material as a base is not damaged. Generally, it is preferable that the laser output is appropriately adjusted within a range of 0.5 to 100 W, a frequency of 10 to 1000 kHz, and a pulse width of 1000 ns or less. If the laser output is too low, the conductive thin film tends to be insufficiently removed, 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 diffusion of heat from the irradiated portion becomes extremely larger than the laser beam diameter, and the line width may be too narrow or disconnected. In this regard, the laser output is preferably adjusted appropriately within a range of 0.5 to 20 W, a frequency of 10 to 800 kHz, and a pulse width of 800 ns or less, more preferably 0.5 to 12 W, a frequency of 10 to 600 kHz, and a pulse width of 600 ns. It is as follows.

  The scanning speed of the laser beam is preferably higher from the viewpoint of improving the production efficiency by reducing the tact time. Specifically, the scanning speed is preferably 1000 mm / s or more, more preferably 1500 mm / s or more, and still more preferably 2000 mm / s or more. It is. If the scanning speed is too slow, not only the production efficiency is reduced, but also the conductive thin film and the base material may be damaged by the heat history. The upper limit of the processing speed is not particularly defined, but if the scanning speed is too high, the removal of the conductive thin film at the laser beam irradiation site may be incomplete, and the circuit may be short-circuited. Further, if the scanning speed is too high, it is inevitable to reduce the scanning speed in the corner portion of the pattern to be formed as compared with the linear portion, so that the heat history of the corner portion becomes higher than that of the linear portion, and There is a possibility that the physical properties of the conductive thin film in the vicinity of the laser-etched portion of the portion may be significantly reduced.

  The scanning of the laser beam may be performed by moving the projectile of the laser beam, by moving the object to be irradiated with the laser beam, or by 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 galvanomirror or the like.

  The energy density per unit area can be increased by using a condenser lens (such as an achromatic lens) when irradiating laser light. The advantage of this method is that, since the energy density per unit area can be increased compared to the case where a mask is used, laser etching can be performed at a high scanning speed even with a laser oscillator having a small output. Is possible. When irradiating the condensed laser light to the conductive thin film, it is necessary to adjust the focal length. It is necessary to adjust the focal length in particular according to the film thickness applied to the substrate, but it is possible to adjust the focal length so as not to damage the substrate and to remove and remove a predetermined conductive thin film pattern. preferable.

  Repeating the scanning of the laser beam a plurality of times with the same pattern is one of preferred embodiments. Even if there is a part of the conductive thin film that is incompletely removed in the first scan, or even if the component constituting the removed conductive thin film adheres to the base material again, the laser light irradiation part may be used in a plurality of scans. Can be completely removed. The upper limit of the number of scans is not particularly limited, but care must be taken because the vicinity of the processed portion may be damaged, discolored, and deteriorate the properties of the coating film by receiving the thermal history a plurality of times. From the viewpoint of production efficiency, it is natural that the smaller the number of scans, the better.

  One of the preferred embodiments is that the scanning of the laser beam is not repeated a plurality of times with the same pattern. As long as the characteristics of the obtained conductive thin film, conductive laminate and electric circuit are not adversely affected, it is natural that the smaller the number of scans, the better the production efficiency.

  Since the conductive thin film of the present invention contains expensive conductive powder at a high concentration, it is included in the conductive thin film removed from the base material in consideration of the total cost required for manufacturing an electric circuit to be manufactured. It is important to collect and reuse the conductive powder. By providing a high-performance dust collector near the laser beam irradiation site and constructing a system for efficiently collecting conductive powder, a sufficiently profitable processing method can be achieved.

<<< 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 component of a touch panel. The touch panel may be of a resistive type or a capacitive type. Although the present paste can be applied to any of the touch panels, the paste is suitable for forming fine lines, and thus can be particularly suitably used for electrode wiring of a capacitive touch panel. In addition, it is preferable to use a substrate having a transparent conductive layer such as an ITO film or a silver nanowire film, or a substrate from which these are partially removed by etching, as a substrate constituting the touch panel.

  Examples and Comparative Examples will be given below to describe the present invention in further detail, but the present invention is not limited by the Examples. In addition, each measurement value described in the Examples and Comparative Examples was measured by the following method.

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

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

3. Acid value 0.2 g of the sample resin was precisely weighed and dissolved in 20 ml of chloroform. Next, 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 ton of the sample.

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

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

6. Storage Stability of Conductive Paste The conductive paste was placed in a plastic container, and the sealed one was stored at 40 ° C. for one month. After storage, measure the viscosity and 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 remarkable increase in viscosity (at least twice the initial viscosity) or a remarkable 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 Laminated Test Piece A 400-mesh stainless steel screen was used for each of a 100 μm-thick annealed PET film (Lumilar S manufactured by Toray Industries) and an ITO film (KH300 manufactured by Oike Industry Co., Ltd.). A conductive paste was printed by a screen printing method, a solid coating pattern having a width of 25 mm and a length of 450 mm was formed, and then heated at 130 ° C. for 30 minutes in a hot air circulating drying oven to obtain a conductive laminate test piece. . In addition, the coating thickness at the time of printing was adjusted so that the dry film thickness was 4 to 10 μm.

8. Adhesion The conductive laminate test piece was evaluated by a peel test using Cellotape (registered trademark) (manufactured by Nichiban Co., Ltd.) according to JIS K-5400-5-6: 1990. 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 was no peeling and the adhesion was good, and 0/100 indicates that all had peeled.

9. Specific Resistance The sheet resistance and the film thickness of the conductive laminate test piece were measured, and the specific resistance was calculated. The thickness of the cured film was measured at five points using a gauge stand ST-022 (manufactured by Ono Sokki Co., Ltd.), with the thickness of the PET film being zero, 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 or less (Ω · cm), and the specific resistance of 1 × 10 −2 (Ω · cm) or more is out of the measurement limit.

10. Pencil hardness A conductive laminate test piece was placed on a SUS304 plate having a thickness of 2 mm, 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 at 85 ° C. and 85% RH (relative humidity) for 300 hours, and then allowed to stand at room temperature for 24 hours.
12. Surface Roughness In the conductive laminate test piece 1, the surface roughness Ra was measured using a surface roughness meter (Handy Surf E-35B, manufactured by Tokyo Seimitsu Co., based on JIS-1994).

13. Evaluation of Suitability for Laser Etching Processing A conductive paste was printed and applied in a rectangular shape of 2.5 × 10 cm on a polyester substrate (Lumirror S (100 μm thick) manufactured by Toray Industries, Inc.) by a screen printing method. Printing was performed at a squeegee speed of 50 mm / s using a 400 stainless mesh (emulsion thickness: 10 μm, wire diameter: 18 μm (manufactured by Murakami), calendering) as a screen plate. After printing and application, drying was performed at 130 ° C. for 30 minutes in a hot-air circulation type drying furnace to obtain a conductive thin film. The paste was diluted and adjusted to have a thickness of 5 to 7 μm. Next, the conductive thin film formed by the above method was subjected to laser etching to form a pattern having four linear portions having a length of 50 mm as shown in FIG.

The laser etching between the lines was performed by scanning the laser light three times at a pitch of 40 μm (L / S = 20/20 μm). A YAG laser (wavelength: 1064 nm) is used as a laser light source, frequency 220 kHz, output 8 W, scanning speed 2800 mm / s, pulse width 75 ns (condition 1), frequency 500 kHz, output 8 W, scanning speed 2800 mm / s, pulse width 15 ns. (Condition 2) was performed on both sides. When the pulse energy was calculated by the following equation, the condition 1 was 36 μJ and the condition 2 was 16 μJ.
Pulse energy = output / frequency From this, it can be said that condition 2 is etching with lower energy than condition 1.

  Evaluation items and measurement conditions are as follows.

(Evaluation of laser etching width)
In the test piece for evaluating aptitude for laser etching, 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 was determined according to the following evaluation criteria.
；: Line width of the portion where the conductive thin film is removed is 18 to 22 μm
Δ: Line width of the portion where the conductive thin film has been removed is 14 to 17 μm or 23 to 26 μm
×: The line width of the portion where the conductive thin film has been removed is 13 μm or less, or 27 μm or more

(Laser etching suitability evaluation 1 Conductivity between both ends of fine wire)
The laser etching suitability evaluation test piece was evaluated based on whether conduction between both ends of the fine wire was secured. Specifically, a tester is applied to each of the terminals A1 and B1, between the terminals A2 and B2, between the terminals A3 and B3, and between the terminals A4 and B4 to check the presence or absence of continuity. Judged.
；: Conductivity is present between both ends of the thin wire for all four fine wires. △: No electrical conduction is provided between both ends of the fine wire for one to three of the four fine wires. No conduction between both ends (Laser etching suitability evaluation 2 Insulation between adjacent fine wires)
The laser etching suitability evaluation test piece was evaluated based on whether insulation between adjacent fine wires was ensured. Specifically, a tester was applied to each of the terminals A1 and A2, between the terminals A2 and A3, and between the terminals A3 and A4 to confirm the presence or absence of continuity, and the evaluation was made based on 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 the residue at the site where the conductive thin film has been removed)
In the laser etching suitability evaluation test piece, the portion where the conductive thin film was removed was observed with a laser microscope, and the presence or absence of the residue was determined according to the following evaluation criteria.
：: No residue is present at the portion where the conductive thin film has been removed.
Δ: There is some residue at the site where the conductive thin film has been removed.
×: 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 base material of the portion where the conductive thin film was sandwiched between the portions where the conductive thin film was removed in the laser etching suitability evaluation test piece was measured using Cellotape (registered trademark) (Nichiban Co., Ltd.) Was evaluated by a tape peeling test using the above method. This evaluation was performed immediately after 24 hours after the preparation of the test piece (initial stage) and then for 120 hours in a moist heat environment of 85 ° C. and 85% RH (relative humidity), and further after standing at room temperature for 24 hours (wet heat resistance After the test).
：: No peeling. Δ: Partially peeled off. X: All are peeled.

Production Example of Resin Production Example of Polyester Resin P-1 700 parts of terephthalic acid, 420 parts of isophthalic acid, 246 parts of adipic acid, 680 parts of ethylene glycol, 614 parts of neopentyl glycol in a reaction vessel equipped with a stirrer, a condenser, and a thermometer. , 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 the pressure was released, 0.92 parts of tetrabutyl titanate was charged, and then the pressure inside the system was gradually reduced. The pressure was reduced to 5 mmHg over 20 minutes, and the pressure was further reduced at 260 ° C for 40 minutes under a vacuum of 0.3 mmHg or less. A condensation reaction was performed to obtain a polyester resin. Table 1 shows the composition and physical properties of the obtained copolymerized polyester resin P-1.

Production Examples of Polyester Resins P-2 to P-6 Polyester resins P-2 to P-6 were produced by changing the types and blending ratios of monomers in the production examples of polyester resin P-1. Table 1 shows the composition and resin properties of the obtained copolyester resin.

Production Example of Polyurethane Resin U-1 In a reaction vessel equipped with a stirrer, a condenser and a thermometer, 1500 parts of polyester resin P-5, 1000 parts of P-6, 180 parts of neopentyl glycol (NPG), 1,6- After charging 50 parts of hexanediol (1,6HD), 2587 parts of ethyl diglycol acetate (EDGAC) were charged and dissolved at 85 ° C. Thereafter, 810 parts of 4,4′-diphenylmethane diisocyanate (MDI) was added, and the reaction was carried out at 85 ° C. for 2 hours. Then, 0.5 part of dibutyltin dilaurate was added as a catalyst, and the mixture was further reacted at 85 ° C. for 4 hours. . Then, the solution was diluted with 3440 parts of EDGAC to obtain a solution of polyurethane resin U-1. The solid content concentration of the obtained polyurethane resin solution was 37% by mass. The resin solution thus obtained was dropped on a polypropylene film and spread using a stainless steel applicator to obtain a thin film of the resin solution. This was allowed to stand in a hot-air dryer adjusted to 120 ° C. for 3 hours to evaporate 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 dried resin thin film was about 30 μm. Using the dry resin thin film on the left as a sample resin of polyurethane resin U-1, evaluation results of various resin properties are shown in Table 2.

Production Example of Polyurethane Resin U-2 Polyurethane resin U-2 was prepared in the same manner as the production example of polyurethane resin U-1, except that the polyester polyol, the compound having a group reactive with isocyanate, and the polyisocyanate were replaced with those shown in Table 2. It was manufactured in a similar manner. Table 2 shows the evaluation results of the physical properties of the polyurethane resin U-2.

DMBA: dimethylolbutanoic acid 1,6HD: 1,6-hexanediol NPG: neopentyl glycol MDI: 4,4'-diphenylmethanediisocyanate

Example 1
2381 parts (1000 parts in terms of solids) of a solution of polyester resin P-1 dissolved in EDGAC / BDGAC (7: 3) so that the solid concentration becomes 42% by mass, 9000 parts of flake silver powder 1, and curing agent 1 108 parts, 56 parts of leveling agent, 36 parts of Additive 1, 92 parts of EDGAC and 40 parts of BDGAC as a solvent, and the mixture was dispersed twice by passing through a chilled three-roll kneader. Then, a filtration filter of 500 mesh (stainless steel mesh filter (25 μm meridian, 30 μm opening)) was attached to a paste filter (PF320A manufactured by Protec), and the paste was filtered. Was printed in a predetermined pattern, and dried at 130 ° C. for 30 minutes to obtain a conductive thin film.The basic physical properties were measured using the conductive thin film, and then a laser etching process was examined. Table 3 shows the evaluation results of the coating film and the laser etching processability.

Examples 2 to 12, Comparative Examples 1 to 3
Examples 2 to 12 and Comparative Examples 1 to 3 were carried out by changing the resin and the composition of the conductive paste. Table 3 shows the composition of the conductive paste and the evaluation results. In the examples, good coating physical properties could be obtained by heating at a relatively low temperature of 130 ° C. for 30 minutes in an oven for a short time. The adhesion to the ITO film and the adhesion after the wet heat environment test were also good.

In Table 3, the following were used as the binder resin, the conductive powder, the additive, and the solvent.
Silver powder 1: Flaky silver powder (D50: 0.5 μm)
Silver powder 2: spherical silver powder (D50: 1 μm)
Carbon black: 4400 manufactured by Tokai Carbon Co., Ltd.
Ketchen Black: Ketchen ECP600JD made by Lion Corporation
Graphite powder: Graphite BF manufactured by Chuetsu Graphite Industry Co., Ltd.
Curing agent 1: MF-B60X manufactured by Asahi Kasei Chemicals Corporation
Curing agent 2: jER-828 manufactured by Mitsubishi Chemical
Curing catalyst: KS1260 manufactured by Kyodo Yakuhin Co., Ltd.
Leveling agent: MK Conc Kyoeisha Chemical Co., Ltd. Dispersant 1: Disperbyk2155 manufactured by Big Chemie Japan KK
Additive 1: Silica R972 manufactured by Nippon Aerosil Co., Ltd.
Additive 2: NIR-AM1 manufactured by Nagase ChemteX Corporation
EDGAC: Ethyl diglycol acetate manufactured by Daicel Corporation BDGAC: Butyl diglycol acetate manufactured by Daicel Corporation
DBE: a mixture of dimethyl esters of adipic acid, succinic acid and glutaric acid manufactured by DuPont

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

1a, 2a, 3a, 4a: Terminal A
1b, 2b, 3b, 4b: fine line B
1c, 2c, 3c, 4c: Terminal C

Claims (10)

In a conductive paste for laser etching containing a binder resin (A) made of a thermoplastic resin, a metal powder (B) and an organic solvent (C), the binder resin (A) is made of a polyester resin and a polyurethane resin is one or a mixture of two or more selected from the group, a number average molecular weight of 5,000 to 60,000, and a thermoplastic resin der glass transition temperature of less than 60 ° C. is, metal powder ( The content of B) is 400 parts by mass or more and 1,900 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin (A), and the content of the organic solvent (C) is 100 parts by mass of the total paste weight. 5 parts by weight or more 40, characterized in der Rukoto following parts laser etched conductive paste. 2. The conductive paste for laser etching according to claim 1 , wherein the binder resin (A) has an acid value of less than 50 equivalents / 10 ⁶ g. 3. The conductive paste for laser etching according to claim 1 or 2, wherein the conductive paste is filtered. Conductive thin film formed from a laser etched conductive paste according to any one of claims 1-3. A conductive laminate in which the conductive thin film according to claim 4 and a substrate are laminated. The conductive laminate according to claim 5 , wherein the substrate has a transparent conductive layer. An electric circuit comprising the conductive thin film according to claim 4 or the conductive laminate according to claim 5 or 6 . A part of the conductive thin film according to claim 4 is irradiated with a laser beam selected from a carbon dioxide laser, a YAG laser, a fiber laser and a semiconductor laser to remove the part of the conductive thin film. Electric circuit having a wiring portion. The electric circuit according to claim 8 , wherein the conductive thin film is formed on a transparent conductive layer. A touch panel including the electric circuit according to claim 7 as a constituent member.

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