JP7059240B2 - Conductive paste for laser etching, conductive thin film and conductive laminate - 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 the plane 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, the performance and miniaturization of electronic devices equipped with transparent touch panels such as mobile phones, notebook computers, and electronic books have been rapidly advancing. In order to improve the performance and miniaturization of these electronic devices, in addition to miniaturization, high performance, and improvement of the degree of integration of the mounted electronic components, it is required to increase the density of the electrode circuit wiring that joins these electronic components to each other. Has been done. In recent years, in addition to the resistance film method, which has a small number of electrode circuit wirings, as a transparent touch panel method, the capacitance method, which has a dramatically large number of electrode circuit wirings, has rapidly become widespread. There is a strong demand for higher density. In addition, in order to make the display screen larger and due to product design requirements, there is a demand to make the frame where the electrode circuit wiring is arranged narrower, and from this point of view, the high density of the electrode circuit wiring is also required. Is required. In order to satisfy the above requirements, there is a demand for a technique capable of arranging electrode circuit wiring at a higher density than before.

The arrangement density of the electrode circuit wiring in the frame portion of the resistance film type transparent touch panel is such that the width of the line and the space in the plane direction are each 200 μm (hereinafter, abbreviated as L / S = 200/200 μm) or more. It has been conventionally performed to form this by screen printing of a conductive paste. In the capacitive touch panel, the L / S requirement is about 100/100 μm or less, and in some cases, the L / S is required to be 50/50 μm or less. The situation is becoming difficult to deal with.

A photolithography method is an example of a candidate for an electrode circuit wiring forming technique that replaces screen printing. By using the photolithography method, it is sufficiently possible to form thin lines 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, and 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 laser light is used. A desired pattern is exposed by a method such as direct drawing, a 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 due to the waste liquid treatment is large, the process is complicated, and there are many problems from the viewpoint of production efficiency and cost.

In the photolithography method, there is also a method that does not use a photosensitive resist. For example, in Patent Documents 1 and 2, a dry coating film is formed by using a conductive paste, and a dry coating film is directly drawn on the dry coating film by using a laser beam. Disclosed is a technique for fixing an irradiated portion to a substrate, developing and removing an unirradiated portion, and forming a desired pattern. Compared with a general photolithography method, such a method simplifies the process because it does not use a photosensitive resist, but it is a photolithography method using a conventionally known photosensitive resist. Similarly, there is a problem of developing waste liquid treatment, and since glass frit or nano-sized silver powder is used as a component of the conductive paste, a high temperature of 400 ° C or higher is required in the firing process, which requires a large amount of energy. There is a problem that the substrate that can be used is limited to one that can withstand the firing process at a high temperature of 400 ° C. or higher. Furthermore, it must be said that the process is complicated and unsuitable for production efficiency.

Japanese Unexamined Patent Publication No. 2010-237573 Japanese Unexamined Patent Publication No. 2011-181338

An object of the present invention is to provide a manufacturing method capable of manufacturing high-density electrode circuit wiring having an L / S of 50/50 μm or less, which is difficult to handle by a screen printing method, at low cost and with a low environmental load. It is in. Another object of the present invention is to provide a conductive paste that can be suitably used for such a production method.

As a result of diligent studies on a manufacturing method for arranging electrode circuit wiring at high density in the plane direction, the present inventors have formed a layer composed of a binder resin and a conductive powder on an insulating base material, and a part of the layer is laser light. It has been found that by removing from the insulating substrate by irradiation, it is possible to manufacture a high-density electrode circuit wiring having an L / S of 50/50 μm or less, which is difficult to realize by the screen printing method. Further, they have found a conductive paste suitable for forming a layer composed of a binder resin and a conductive powder suitable for such a production method. That is, the invention of the present application has the following configuration.
(1) Binder resin (A), metal powder (B) and organic solvent (C) consisting of one or a mixture of two or more selected from the group consisting of polyurethane resin, phenoxy resin, vinyl chloride resin and fibrous derivative resin. The binder resin (A) is a thermoplastic resin having a number average molecular weight of 5,000 to 60,000 and a glass transition temperature of 60 to 100 ° C., and the organic solvent (C) . ) Has a boiling point of 100 ° C. or higher and lower than 300 ° C., and has a transparent conductive layer on the entire surface or a part of the electrode circuit wiring having a width of both the line and the space in the plane direction of 50 μm or less by laser etching. Used for forming on the transparent conductive layer of the base material, the line width in the plane direction is 25 to 31 μm and the space width in the plane direction is 25 by laser etching processing using a laser beam having a beam diameter of 30 μm. A conductive paste for laser etching that can form electrode circuit wiring with a thickness of ~ 31 μm.
(2) The conductive paste for laser etching processing according to (1), which further contains a laser light absorber (D).
(3) A conductive thin film formed from the conductive paste for laser etching processing according to any one of (1) to (2) above.
(4) A conductive laminate in which the conductive thin film according to (3) above and a base material having a transparent conductive layer on the entire surface or a part thereof are laminated.
(5) An electric circuit using the conductive thin film according to (3) or the conductive laminate according to (4).
(6) A part of the conductive thin film according to (3) is irradiated 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 a wiring portion formed by the laser.
(7) The electric circuit according to (6), wherein the conductive thin film is formed on a transparent conductive layer.
(8) A touch panel including the electric circuit according to any one of (6) to ( 7 ) 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), and by adopting such a configuration, laser etching is performed. It is possible to form a conductive thin film having excellent processability and excellent adhesion to the substrate at the initial stage and after being loaded with a moist heat environment even after laser etching. Here, "excellent in laser etching processing suitability" means that at least a part of the conductive thin film is peeled off from the substrate by laser etching processing to form a fine wire having an L / S = 30/30 μm 1). It means that the three conditions of 3) that the continuity between both ends of the thin film is secured, 2) the insulation between the adjacent thin wires is secured, and 3) the shape of the thin wire is good. Further, the conductive paste containing the laser light absorber (D) according to the embodiment of the present invention is more sensitive to laser light irradiation than the conductive paste not containing the laser light absorber (D). It also exerts an even better effect of improving the laser scanning speed and reducing the laser output.

It is a schematic diagram which shows the pattern which irradiates a laser beam to the laser etching processing aptitude evaluation test piece used in the Example and the comparative example of this invention. The white part is irradiated with laser light, and the conductive thin film formed on the substrate is removed. Laser light is not applied to the halftone dots. 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 processing in 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 the binder resin (A) is not particularly limited as long as it is a thermoplastic resin, but it is not particularly limited, but it is a polyester resin, a phenoxy resin, a polyamide resin, a polyamide imide resin, a polycarbonate resin, a polyurethane resin, a phenol resin, an acrylic resin, a polystyrene, or a 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, polyether sulfone resin, vinyl chloride-vinyl acetate Examples thereof include a copolymer resin, an ethylene-vinyl acetate copolymer, a polystyrene, a silicone resin, a fluororesin, and the like, and these resins can be used alone or as a mixture of two or more kinds. It is preferably one or a mixture of two or more selected from the group consisting of polyester resin, polyurethane resin, vinyl chloride resin, and fibrous derivative resin. Further, among these resins, a polyester resin and / or a polyurethane resin containing a polyester component as a copolymerization component (hereinafter, may be referred to as a polyester polyurethane resin) is preferable as the binder resin (A).

One of the advantages of using the 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 it is easy to add a functional group in the molecular chain or to the end of the molecule. Therefore, the characteristics of the resin such as the glass transition temperature of the obtained polyester resin and the affinity with the base material and other components blended in the conductive paste can be appropriately adjusted.

Examples of the dicarboxylic acid that can be used as a copolymerization component of the polyester resin used as the binder resin (A) in the present invention include aromatic acids 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-Methylhexahydrohydride phthalic acid, 3-methylhexahydrochloride phthalic acid, 2-methylhexahydrohydride phthalic acid, dicarboxyhydrogenated bisphenol A, Examples thereof include alicyclic dicarboxylic acids such as dicarboxyhydrogenated bisphenol S, dimer acid, hydrogenated dimer acid, hydrogenated naphthalenedicarboxylic acid and tricyclodecanedicarboxylic acid, and hydroxycarboxylic acids such as hydroxybenzoic acid and lactic acid. Further, as long as the effects of the present 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 5-sulfoisophthalic acid sodium salts and the like. Dicarboxylic acid containing a metal sulfonate metal base may be used in combination as a copolymerization component.

Examples of polyols that can be used as a copolymerization 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, and 1, , 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, 1,4 Examples thereof include alicyclic diols such as -cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, and dimerdiol. Further, a trivalent or higher-valent polyol such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, and polyglycerin 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 component among all acid components constituting the polyester resin from the viewpoints of strength, heat resistance, moisture resistance, durability such as heat impact resistance, and the like. 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 obtained polyester resin becomes lower than 60 ° C., and the moist heat resistance and durability of the obtained conductive thin film tend to decrease.

The polyester resin used as the binder resin (A) in the present invention is the carbon of the main chain among all the polyols constituting the polyester resin from the viewpoints of strength, heat resistance, moisture resistance, durability such as heat impact resistance, and the like. The amount of glycol having a number of 4 or less is preferably 60 mol% or more, more preferably 80 mol% or more, still more preferably 95 mol% or more. If the copolymerization ratio of the glycol having 4 or less carbon atoms in the main chain among all the polyol components is too low, the glass transition temperature of the obtained polyurethane resin becomes lower than 60 ° C., and the obtained conductive thin film has moisture resistance and durability. The sex tends 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 resin, for polyurethane resin, glass transition is performed by selecting an appropriate component as a copolymerization component constituting the polyurethane resin and by imparting a functional group in the molecular chain or to the end of the molecule. The characteristics of the resin such as the temperature and the affinity with the base material and other components blended in the conductive paste can be appropriately adjusted.

The copolymerization component of the polyurethane resin is also not particularly limited, but a polyester polyurethane resin using a polyester polyol as a copolymerization component is preferable from the viewpoint of design freedom, moisture and heat resistance, and maintenance of durability. As a preferable example of the polyester polyol, among the polyester resins that can be used as the binder resin (A) in the above-mentioned invention, those which are polyols can be mentioned.

The polyurethane resin used as the binder resin (A) in the present invention can be obtained, for example, by reacting a polyol with a polyisocyanate. Examples of the polyisocyanide that can be used as a copolymerization component of the polyurethane resin include 2,4-toluene diisocyanate, 2,6-toluene 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 '-Diisocyanide diphenyl ether, 1,5-naphthalenediocyanide, m-xylene diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, etc. It may be either. Further, as long as the effect of the present invention is not impaired, an isocyanate compound having a trivalent or higher valence may be used in combination as a copolymerization component.

The polyurethane resin used as the binder resin (A) in the present invention can be copolymerized with a compound having a functional group capable of reacting with isocyanate, if necessary. As the functional group capable of reacting with isocyanate, a hydroxyl group and an amino group are preferable, and those having either one or both may be used. 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-. 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'-hydroxypropanol, 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 Compounds having two hydroxyl groups in one molecule such as -3-sodiumsulfo-2,5-hexanediol, dimerdiol (for example, PRIPOOL-2033 manufactured by Unichema International), trimethylol ethane, trimethylol propane, glycerin , Pentaerythritol, polyglycerin and other alcohols having three or more hydroxyl groups in one molecule, monoethanolamine, diethanolamine, triethanolamine and other alcohols having one or more hydroxyl groups and amino groups in one molecule, ethylenediamine, Alibo diamines and metaxylenedamines such as 1,6-hexanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediol. Examples thereof include compounds having two amino groups in one molecule such as aromatic diamines such as 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether. The above-mentioned 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.

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 moisture heat resistance of the formed conductive thin film. On the other hand, if the number average molecular weight is too high, the cohesive force of the resin is increased and the durability as a conductive thin film is improved, but the suitability for laser etching processing is significantly deteriorated.

The glass transition temperature of the binder resin (A) in the present invention is preferably 60 ° C. or higher, more preferably 65 ° C. or higher. If the glass transition temperature is low, the suitability for laser etching processing may be improved, but the reliability of the moist heat environment as a conductive thin film may decrease, and the surface hardness may decrease due to the tackiness of the manufacturing process. / Or, during use, the paste-containing component may be transferred to the contact side, and the reliability of the conductive thin film may be lowered. On the other hand, the glass transition temperature of the binder resin (A) used in the present invention is preferably 150 ° C. or lower, more preferably 120 ° C. or lower, in consideration of printability, adhesion, solubility, paste viscosity, suitability for laser etching processing, and the like. It is preferably 100 ° C. or lower, and more preferably 100 ° C. or lower.

The acid value of the binder resin (A) in the present invention is not particularly limited, but having an acid value in a specific range may significantly improve the adhesion to the substrate. During the laser etching process of the conductive thin film, the temperature around the laser irradiation site may rise and the adhesion between the conductive thin film and the base material may decrease. By using the binder resin, it may be possible to suppress the decrease in adhesion. The acid value of the binder resin (A) is preferably 50 to 350 eq / ton, more preferably 100 to 250 eq / ton. If the acid value is too low, the adhesion between the formed conductive thin film and the substrate tends to be low. On the other hand, if the acid value is too high, the water absorption of the formed conductive thin film becomes high, and the hydrolysis of the binder resin may be promoted by the catalytic action of the carboxyl group, so that the reliability of the conductive thin film is high. It tends to lead to a decline.

<Metal powder (B)>
The metal powder (B) used in the present invention includes precious 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 noble metal such as silver. Examples thereof include alloyed base metal powders. These metal powders may be used alone or in combination. Among these, in consideration of conductivity, stability, cost and the like, silver powder alone or mainly 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 flake-like (flint-like), spherical, dendrite-like, and spherical primary particles described in JP-A-9-306240. There are three-dimensionally aggregated shapes (aggregated) and the like, and among these, it is preferable to use spherical, aggregated and flake-shaped 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 fine line shape of the laser-etched portion tends to be good. When a metal powder having a center diameter larger than 4 μm is used, the shape of the fine wires after the laser etching process deteriorates, and as a result, the fine wires may come into contact with each other, resulting in a short circuit. Furthermore, there is a possibility that the conductive thin film once peeled off and removed by laser etching processing will adhere to the processed portion 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 is easy to aggregate when the particle size is small and it becomes difficult to disperse 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 center diameter (D50) is a particle size (μm) at which the cumulative value is 50% in the cumulative distribution curve (volume) obtained by some measuring method. In the present invention, the cumulative distribution curve is measured in the total reflection mode using a laser diffraction / scattering type particle size distribution measuring device (MICROTRAC HRA manufactured by Nikkiso Co., Ltd.).

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), preferably 560 parts by mass, from the viewpoint of good conductivity of the formed conductive thin film. 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 the boiling point is preferably 100 ° C. or higher and lower than 300 ° C., more preferably, from the viewpoint of keeping the volatilization rate of the organic solvent in an appropriate range. 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, if necessary, other components with a three-roll mill or the like. At that time, if the boiling point of the organic solvent is too low, the solvent may volatilize during dispersion and the component ratio constituting the conductive paste may change. 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.

Further, as the organic solvent (C) that can be used in the present invention, it is preferable that the thermoplastic resin (A) is soluble and the metal powder (B) can be satisfactorily dispersed. Specific examples include ethyl diglycol acetate (EDGAC), butyl glycol acetate (BMGAC), butyl diglycol acetate (BDGAC), cyclohexanone, toluene, isophorone, γ-butyrolactone, benzyl alcohol, Solvento 100, 150 manufactured by Exxon Chemical Co., Ltd., 200, a mixture of dimethyl esters of propylene glycol monomethyl ether acetate, adipic acid, succinic acid and glutaric acid (for example, DBE manufactured by DuPont Co., Ltd.), tarpionale and the like can be mentioned. EDGAC, BMGAC, BDGAC and their mixed solvents are preferable from the viewpoint of excellent solubility of the compounding components of A), moderate solvent volatilization during continuous printing, and good suitability for printing by a screen printing method or the like. ..

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 weight of the paste. .. If the content of the organic solvent (C) is too high, the paste viscosity becomes too low, and there is a tendency that sagging is likely to occur during fine line printing. On the other hand, if 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 remarkably lowered, and the formed conductive thin film is formed. The film thickness may increase and the laser etching processability may decrease.

<Laser light absorber (D)>
The laser light absorber (D) may be blended in the conductive paste of the present 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 wavelength of the fundamental wave of 1064 nm is used as a light source, a dye and / or a pigment having a 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 are promoted, resulting in suitability for laser etching processing. Is improved.

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 formulation of a carbon-based filler also has the effect of enhancing 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 a YAG laser and a fiber laser. When irradiated with laser light, the conductive thin film absorbs the laser light with high efficiency, which increases the sensitivity to laser light irradiation, which is good even when the scanning speed of laser irradiation is increased and / or when the laser light source has a low output. The effect of obtaining laser etching processing suitability 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). If the blending ratio of the carbon-based 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, if the blending 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 the carbon, and the adhesion to the base material decreases. Points 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 salt 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 and the like. Examples of 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 other polymer-bound pigments. Specifically, insoluble azo pigments, azolake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments. , Kinoftalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, and inorganic pigments can be used. 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). These non-conductive laser light absorbers (D) are preferably contained in an amount of 0.01 to 5 parts by weight, preferably 0.1 to 2 parts by weight. If 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. If the blending ratio of the non-conductive laser light absorber (D) is too high, the conductivity of the conductive thin film may decrease, 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. 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 carbonate, and diamond carbon lactam; boron nitride. , Various nitrides such as titanium nitride and zirconium nitride, various borides such as zirconium borohydride; various oxidations such as titanium oxide (titania), calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica and colloidal silica. Products; Various titanium acid compounds such as calcium titanate, magnesium titanate, and strontium titanate; Sulfurized compounds such as molybdenum disulfide; Various fluorides such as magnesium fluoride and carbon fluoride; Aluminum stearate, calcium stearate, stearic acid Various metal soaps such as zinc and magnesium stearate; in addition, talc, bentonite, talc, calcium carbonate, bentonite, kaolin, glass fiber, mica and the like can be used. By adding these inorganic substances, it may be possible to improve printability, heat resistance, mechanical properties, and long-term durability. Above all, in the conductive paste of the present invention, silica is preferable from the viewpoint of imparting durability, printability, and particularly screen printability.

Further, the conductive paste of the present invention includes a thixo-imparting agent, a defoaming 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. Further, carbodiimide, epoxy and the like can be appropriately blended 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 the extent that the effect of the present invention is not impaired. By blending a curing agent, the curing temperature may increase and the load on the production process may increase, but it is expected that the moisture resistance of the coating film will be improved by cross-linking due to the heat generated during the drying of the coating film or laser etching. ..

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

Examples of the isocyanate compound that can be blended in the conductive paste of the present invention include aromatic or aliphatic diisocyanates, trivalent or higher polyisocyanates, and may be either low molecular weight compounds or high molecular weight compounds. For example, aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, aromatic diisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, hydride diphenylmethane diisocyanate, hydride xylylene diisocyanate, dimerate diisocyanate, isophorone diisocyanate and the like. Alicyclic diisocyanates, or trimerics 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. Examples thereof include terminal isocyanate group-containing compounds obtained by reacting with low-molecular-weight active hydrogen compounds such as, various polyester polyols, polyether polyols, and high-molecular-weight active hydrogen compounds of polyamides. 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, methylethylketooxime, and cyclohexanone oxime. Classes; alcohols such as methanol, ethanol, propanol and butanol; halogen-substituted alcohols such as ethylene chlorhydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol. Examples include lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propyrolactam, and other aromatic amines, imides, acetylacetones, acetoacetate esters, malonic acid ethyl esters, etc. Examples thereof include active methylene compounds, mercaptans, imines, imidazoles, ureas, diaryl compounds, sodium bisulfite and the like. Of these, oximes, imidazoles, and amines are particularly preferable because of their curability.

<< Physical characteristics required for 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 for forming the coating film. For example, when the conductive paste is applied to the substrate by screen printing, the viscosity of the conductive paste is preferably 100 dPa · s or more, more preferably 150 dPa · s or more at the printing temperature. The upper limit is not particularly limited, but if the viscosity is too high, the film thickness of the conductive thin film becomes too thick, and the laser etching process suitability may decrease.

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 parts by mass of the total solid content contained in the paste, and is represented by F value = (filler mass part / solid content mass part) × 100. The filler mass portion referred to here is a mass portion of the conductive powder, and the solid content mass portion is a mass portion of a component other than the solvent, and includes all 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, 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. Therefore, deterioration of printability is inevitable. Here, the conductive powder refers to both a metal powder (B) and a non-metal conductive powder.

<< 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, if necessary, other components with a three-roll or the like. can. Here, an example of a more specific manufacturing procedure is shown. First, the thermoplastic resin (A) is dissolved in the organic solvent (C). After that, the metal powder (B) and, if necessary, additives are added, and pre-dispersion is carried out with a double planetary, a dissolver, a planetary stirrer or the like. Then, it is dispersed with a three-roll mill to obtain a conductive paste. The conductive paste thus obtained can be filtered as needed. There is no problem in dispersing using other dispersers such as a bead mill, a kneader, and an extruder.

<< The conductive thin film of the present invention, the conductive laminate, and the method for producing these >>
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 volatilizing the organic solvent (C) contained in the coating film to dry the coating film. Can be formed. The method of applying or printing the conductive paste on the substrate is not particularly limited, but printing by the screen printing method is a technique widely used in the industry for forming an electric circuit using the conductive paste and the simplicity of the process. It is preferable from the viewpoint of. Further, the conductive paste can be applied or printed on a portion slightly wider than the conductive thin film portion finally required as an electric circuit to reduce the load of the laser etching process and efficiently obtain the electric circuit of the present invention. It is preferable from the viewpoint of forming.

As the base material to 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 mentioned. Further, an inorganic material such as glass can also be used as a base material. The thickness of the base material 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.

Further, by physically and / or chemically treating 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 sandblast method, a wet blast method for injecting a liquid containing fine particles, a corona discharge treatment method, a plasma treatment method, an ultraviolet ray or a vacuum ultraviolet irradiation treatment method, and the like. Further, as an example of the chemical treatment method, a strong acid treatment method, a strong alkali treatment method, an oxidizing agent treatment method, a coupling agent treatment method and the like can be mentioned.

Further, the 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, as the transparent conductive layer, not only the one formed on the entire surface of the base material but also the one in which a part of the transparent conductive layer is removed by etching or the like can be used.

The step of volatilizing the organic solvent (C) is preferably performed at room temperature and / or under heating. In the case of heating, the heating temperature is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 110 ° C. or higher, because the conductivity, adhesion and surface hardness of the dried conductive thin film are good. Further, from the viewpoint of heat resistance of the transparent conductive layer of the base and energy saving in the production process, the heating temperature is preferably 150 ° C. or lower, more preferably 135 ° C. or lower, still more 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 volatilizing the organic solvent (C) is performed under heating.

The thickness of the conductive thin film of the present invention may be set to an appropriate thickness according to the intended use. However, from the viewpoint of good conductivity of the conductive thin film after drying and good laser etching processing suitability, the film thickness of the conductive thin film is preferably 3 μm or more, 30 μm or less, and more preferably 5 μm. As mentioned above, it is 20 μm or less. If the film thickness of the conductive thin film is too thin, the desired conductivity as a circuit may not be obtained. If the film thickness is too thick, the irradiation amount required for the laser etching process becomes excessive, which may damage the substrate. Further, if the film thickness varies widely, the ease of etching of the conductive thin film varies, and short circuits between lines due to insufficient etching and disconnection due to excessive etching tend to occur easily. Therefore, it is better that the variation in film thickness is small.

<< The electric circuit of the present invention and its manufacturing method >>
In the electric circuit of the present invention, at least a part of the conductive thin film formed on the substrate by the conductive paste of the present invention is irradiated with laser light, and a part of the conductive thin film is removed from the substrate. It is an electric circuit having a wiring portion formed by the above. If such an electric circuit forming method is adopted, unlike the photolithography method, the pattern forming process can be a dry process, and no waste liquid containing a metal component is generated, so that waste liquid treatment 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 in manufacturing equipment can be suppressed, and maintenance after operation of manufacturing equipment is easy. The method of forming the conductive thin film on the substrate by the conductive paste is not particularly limited, but it can be performed by printing or painting.

The method of irradiating the laser beam is not particularly limited, but a laser etching processing device that has become widespread in recent years or a device with further improved dimensional accuracy can be used. Since the laser etching processing apparatus can use the data produced by image processing application software such as CAD as it is for laser processing, it is extremely easy to switch the manufacturing pattern. This can be mentioned as one of the advantages over the pattern formation in the conventional screen printing method.

In the portion 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 portion is peeled off and removed. In order to efficiently remove the portion of the conductive thin film of the present invention irradiated with the laser beam from the substrate, it is preferable that the conductive thin film of the present invention has strong absorption at the wavelength of the irradiation laser beam. Therefore, as the laser type, it is preferable to select a laser type 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 excima laser (wavelength of fundamental wave is 193 to 308 nm), YAG laser (wavelength of fundamental wave is 1064 nm), fiber laser (wavelength of fundamental wave is 1060 nm), CO2 laser (wavelength of fundamental wave). 10600nm), semiconductor lasers, etc., and basically there is no problem even if a laser type of any method and wavelength is used. By selecting a laser type that matches the absorption wavelength region of any of the constituents of the conductive thin film and can irradiate a wavelength at which the substrate does not have strong absorption, the conductive thin film at the laser beam irradiation site is selected. Can be efficiently removed and damage to the base material can be avoided. From this point of view, 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 a polyester film, a transparent conductive laminate having an ITO layer formed on a polyester film, or a laminate having an ITO layer formed on a polyester film and a part thereof removed by etching is used as a base material. , YAG laser or fiber laser is particularly preferable in that the substrate does not absorb the wavelength of the fundamental wave and therefore does not easily damage the substrate.

The laser output and the Q modulation frequency are not particularly limited, but are adjusted so that the conductive thin film at the laser beam irradiation site can be removed and the underlying substrate is not damaged. In general, it is preferable to appropriately adjust the laser output 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, the 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 scannings. 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 become too narrow or the wire may be broken.

The higher the scanning speed of the laser beam is, the better from the viewpoint of improving the production efficiency by reducing the tact time. Specifically, 1000 mm / s or more is preferable, 1500 mm / s or more is more preferable, and 2000 mm / s or more is more preferable. Is. If the scanning speed is too slow, not only the production efficiency is lowered, but also the conductive thin film and the substrate may be damaged by the thermal history. The upper limit of the processing speed is not particularly set, 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 fast, it is unavoidable to reduce the scanning speed at the corner portion of the formed pattern as compared with the straight portion, so that the thermal history of the corner portion becomes higher than that of the straight portion, and the corner Laser etching of the part The physical properties of the conductive thin film around the part may be significantly deteriorated.

The scanning of the laser beam may be performed by moving the projectile of the laser beam, moving the irradiated object irradiated with the laser beam, or a combination of both, and can be realized by using, for example, an XY stage. It is also possible to scan the laser beam by changing the irradiation direction of the laser beam using a galvano mirror or the like.

By using a condenser lens (achromatic lens or the like) when irradiating the laser beam, the energy density per unit area can be increased. 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 even a laser oscillator with a small output can perform laser etching at a high scanning speed. Is possible. When irradiating a conductive thin film with focused laser light, it is necessary to adjust the focal length. The focal length needs to be adjusted especially by the film thickness applied to the substrate, but it can be adjusted so as not to damage the substrate and to peel off / remove a predetermined conductive thin film pattern. preferable.

It is one of the preferred embodiments that the scanning of the laser beam is repeated a plurality of times in the same pattern. Even if there is a conductive thin film part that is incompletely removed in the first scan, or if the components that make up the removed conductive thin film adhere to the substrate again, the laser light irradiation part is detected in multiple scans. It is possible to completely remove the conductive thin film of. The upper limit of the number of scans is not particularly limited, but care must be taken because the area around the processed portion may be damaged, discolored, or the physical characteristics of the coating film deteriorate due to the heat history received multiple times. Further, from the viewpoint of production efficiency, it is natural that the smaller the number of scans is, the better.

It is also one of the preferred embodiments that the scanning of the laser beam is not repeated a plurality of times in 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 is, the better the production efficiency is.

Since the conductive thin film of the present invention contains an expensive conductive powder in 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 the electric circuit to be manufactured. It is important to collect and reuse the conductive powder. By installing a high-performance dust collector near the laser beam irradiation site and constructing a system that efficiently recovers the conductive powder, it is possible to make the processing method sufficiently profitable.

<< Touch panel of the present invention >>
The conductive thin film, the conductive laminate and / or the electric circuit of the present invention can be used as a component of a touch panel. The touch panel may be of a resistance film type or a capacitance type. Although it can be applied to any touch panel, since this paste is suitable for forming fine wires, it can be particularly preferably used for electrode wiring of a capacitive touch panel. As the base material constituting the touch panel, it is preferable to use a base material having a transparent conductive layer such as an ITO film, or a base material having some of them removed by etching.

Examples and comparative examples are given below to explain the present invention in more detail, but the present invention is not limited to the examples. The measured values described in Examples and Comparative Examples were measured by the following methods.

1. 1. The sample resin having a number average molecular weight was dissolved in tetrahydrofuran so that the resin concentration was about 0.5% by weight, and filtered through a membrane filter made of polytetrafluoride ethylene having a pore size of 0.5 μm to prepare 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 done. The number average molecular weight was calculated by using a standard polystyrene conversion value and omitting a portion corresponding to a molecular weight of less than 1000. As the GPC column, shodex KF-802, 804L, 806L manufactured by Showa Denko KK was used.

2. 2. Glass transition temperature (Tg)
5 mg of the sample resin was placed in an aluminum sample pan, sealed, and measured using a differential scanning calorimetry (DSC) DSC-220 manufactured by Seiko Instruments Co., Ltd. at a heating rate of 20 ° C / min up to 200 ° C. Then, it was determined by the temperature of the intersection of the extension line of the baseline below the glass transition temperature and the tangent line showing the maximum inclination at the transition part.

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

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

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 the conductive paste The conductive paste was placed in a plastic container and sealed at 40 ° C. for 1 month. Viscosity measurement after storage and 5. above. The test piece manufactured by the conductive laminated body test piece was evaluated.
◯: There is no significant change in viscosity, and the initial resistivity, 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 (less than 1/2 of the initial viscosity) and / or a decrease in resistivity, pencil hardness and / or adhesion is observed. ..

7. Preparation of Conductive Laminated Test Piece A 200-mesh polyester screen was used for each of the 100 μm-thick annealed PET film (Toray Industries, Inc. Lumirror S) and ITO film (Oike Kogyo Co., Ltd., KH300). A conductive paste was printed by a screen printing method to form a solid coating pattern with 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 type drying furnace to obtain a conductive laminate test piece. .. The coating thickness at the time of printing was adjusted so that the dry film thickness was 6 to 10 μm.

8. Adhesion The conductive laminate test piece was evaluated by a peeling test using cellophane tape (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 grid pattern was 11, and the cut interval was 1 mm. 100/100 indicates that there is no peeling and the adhesion is good, and 0/100 indicates that all have 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. As the film thickness, a gauge stand ST-022 (manufactured by Ono Sokki Co., Ltd.) was used, the thickness of the cured coating film was measured at 5 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 MILLIOHMMETER4338B (manufactured by Hewlett-Packard), and the average value thereof was used. The range that can be detected by this milliohm meter is 1 × 10 ⁻² (Ω · cm) or less, 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 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 left at room temperature for 24 hours, and then various evaluations were performed.

12. Evaluation of Laser Etching Appropriateness A conductive paste was printed and applied to a 2.5 × 10 cm rectangle on a polyester substrate (Toray Industries, Inc. Lumirror S (thickness 100 μm)) by a screen printing method. A T400 stainless mesh (emulsion thickness 10 μm, wire diameter 23 μm (manufactured by Tokyo Process Service Co., Ltd.)) was used as a screen plate, and printing was performed at a squeegee speed of 150 mm / s. After the printing was applied, it was dried at 120 ° C. for 30 minutes in a hot air circulation type 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, the conductive thin film prepared by the above method was subjected to laser etching processing to prepare a pattern having four linear portions having a length of 50 mm shown in FIG. 1 and used as a laser etching processing aptitude evaluation test piece. The laser etching process between the lines of the straight line portion 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.

The evaluation items and measurement conditions are as follows.

(Laser etching width evaluation)
In the laser etching processing aptitude 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 judgment was made according to the following evaluation criteria.
◯; The line width of the part where the conductive thin film was removed is 28 to 32 μm.
Δ; The line width of the portion where the conductive thin film was removed is 24-27 μm or 33-36 μm.
X; The line width of the part where the conductive thin film was removed is 23 μm or less, or 37 μm or more.

(Laser etching aptitude evaluation (1) Conductivity between both ends of thin wire)
In the laser etching processing aptitude evaluation test piece, evaluation was made based on whether conduction between both ends of the fine wires 1b, 2b, 3b, and 4b was secured. Specifically, a tester is applied to each of the terminals 1a-terminal 1c, the terminal 2a-terminal 2c, the terminal 3a-terminal 3c, and the terminal 4a-terminal 4c to check the presence or absence of continuity, and the following evaluation criteria are used. Judgment by.
○; There is continuity between both ends of the thin wire for all four thin wires Δ; There is no continuity between both ends of the thin wire for 1 to 3 of the four thin wires ×; There is no continuity between both ends (laser etching aptitude evaluation (2) insulation between adjacent fine wires)
In the laser etching process aptitude evaluation test piece, it was evaluated based on whether the insulation between the adjacent thin wires was secured. Specifically, the presence or absence of continuity was confirmed by applying a tester to each of the terminals 1a-terminal 2a, the terminal 2a-terminal 3a, and the terminal 3a-terminal 4a, and the determination was made according to the following evaluation criteria.
○; All adjacent thin wires are insulated △; Some adjacent thin wires are insulated ×; All adjacent thin wires are not insulated

(Evaluation of the residue at the site where the conductive thin film was removed)
In the laser etching process aptitude evaluation test piece, the portion from which the conductive thin film was removed was observed with a laser microscope, and the presence or absence of residue adhesion was determined according to the following evaluation criteria.
◯: There is no residue at the site where the conductive thin film was removed.
Δ: There is some residue in the portion where the conductive thin film is removed.
X: A large amount of residue is observed at the site where the conductive thin film has been removed.

(Evaluation of adhesion between conductive thin film and base material after laser etching)
Cellotape (registered trademark) (Nichiban Co., Ltd.) determines the adhesion of the part where the conductive thin film remains, which is sandwiched between the parts where the conductive thin film is removed in the laser etching aptitude evaluation test piece, to the substrate. It was evaluated by a tape peeling test using (manufactured by). This evaluation was carried out immediately after 24 hours after the preparation of the test piece (initial stage), and after that, it was allowed to stand in a moist heat environment at 85 ° C. and 85% RH (relative humidity) for 120 hours, and then left at room temperature for another 24 hours (moisture resistant heat resistance). After the test).
◯: There is no peeling. Δ: Partially peeled off. X: All peel off.

Example of resin production Example of production of polyester resin P-1 In a reaction vessel equipped with a stirrer, condenser, and 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 was charged, and the temperature was raised from 160 ° C. to 230 ° C. over 3 hours under a pressure of 2 atm in a nitrogen atmosphere to carry out an esterification reaction. After the pressure is released, 0.92 parts of tetrabutyl titanate is charged, then the pressure inside the system is gradually reduced, the pressure is reduced to 5 mmHg over 20 minutes, and the weight is further reduced to 5 mmHg under a vacuum of 0.3 mmHg or less at 260 ° C. for 40 minutes. A condensation reaction was carried out. Next, the mixture was cooled to 220 ° C. under a nitrogen stream, 50.6 parts of trimellitic anhydride was added, and the reaction was carried out for 30 minutes to obtain a polyester resin. The composition and physical properties of the obtained copolymerized polyester resin P-1 are shown in Table 1.

Production Examples of Polyester Resins P-2 to P-11 In the production examples of polyester resin P-1, the types and blending ratios of the monomers were changed to produce polyester resins P-2 to P-11. The composition and physical characteristics of the obtained copolymerized polyester resin are shown in Tables 1 and 2.

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

Production example of polyurethane resin U-1 1000 parts of polyester resin P-7, 80 parts of neopentyl glycol (NPG), and 90 parts of dimethylolbutanoic acid (DMBA) are put into a reaction vessel equipped with a stirrer, condenser, and thermometer. After that, 1087 parts of ethyl diglycol acetate (EDGAC) was charged and dissolved at 85 ° C. Then, 460 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 reaction was carried out at 85 ° C. for another 4 hours. .. Then, 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 onto a polypropylene film and spread using an applicator made of stainless steel 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 volatilize the solvent, and then the resin thin film was peeled off from the polypropylene film to obtain a film-shaped 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 the sample resin of the polyurethane resin U-1.

Production Examples of Polyurethane Resins U-2 to U-8 Polyurethane resins U-2 to U-8 are polyurethane except that polyester polyols, compounds having a group that reacts with isocyanates, and polyisocyanates are replaced with those shown in Table 3. It was produced by the same method as in the production example of the resin U-1. Table 3 shows the evaluation results of the resin physical properties of the polyurethane resins U-2 to U-8.

DMBA: Dimethylolbutanoic acid NPG: Neopentyl glycol DMH: 2-Butyl-2-ethyl-1,3-propanediol MDI: 4,4'-diphenylmethane diisocyanate IPDI: Isophorone diisocyanate

Example 1
2860 parts of a solution of polyester resin P-1 dissolved in EDGAC so that the solid content concentration is 35% by mass (1000 parts in terms of solid part), 7,888 parts of flake-like silver powder 1, and Kyoeisha Chemical Co., Ltd. as a leveling agent. 71 parts of MK Conch manufactured by MK, 30 parts of Disperbyk 130 manufactured by Big Chemy Japan Co., Ltd. as a dispersant, and 300 parts of EDGAC as a solvent were mixed and dispersed by passing through a chilled three-roll kneader three times. Then, the obtained conductive paste was printed on a predetermined pattern and 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, the paste coating film, and the laser etching processability.

Examples 2 to 8, Reference Examples 1 to 8
Examples 2 to 8 and Reference Examples 1 to 8 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 coating film physical characteristics could be obtained by heating at a relatively low temperature of 120 ° C. × 30 minutes in an oven for a short time. In addition, the adhesion to the ITO film and the adhesion after the moist heat environment test were also good.

In Tables 4 to 7, the following binder resins, conductive powders, additives and solvents were used.
Binder resin PH-1: InChem PKKH (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: # 4400 manufactured by Tokai Carbon Co., Ltd.
Ketjen Black: Ketjen ECP600JD manufactured by Lion Corporation
Graphite powder: Graphite BF manufactured by Chuetsu Graphite Industry Co., Ltd.
Hardener: MF-K60X manufactured by Asahi Kasei Chemicals Co., Ltd.
Curing catalyst: KS1260 manufactured by Kyodo Yakuhin Co., Ltd.
Leveling agent: Kyoeisha Chemical Co., Ltd. MK Conch Dispersant 1: Disperbyk 130 manufactured by Big Chemie Japan Co., Ltd.
Dispersant 2: Disperbyk2155 manufactured by Big Chemie Japan Co., Ltd.
Dispersant 3: Disperbyk 180 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 Co., Ltd. BMGAC: Butyl glycol acetate manufactured by Daicel Co., Ltd. BDGAC: Butyl diglycol acetate manufactured by Daicel Co., Ltd. TPOL: Tarpineol manufactured by Nippon Terpen Chemical Co., Ltd.

Comparative Example 1
Silver lauryl carboxylate (1000 g) and butylamine (480 g) were dissolved in toluene (10 L). Then, formic acid (150 g) was added dropwise, and the mixture was stirred as it was at room temperature for 1.5 hours. When a large amount of methanol was added, agglomerates of silver nanoparticles were precipitated, which was decanted. After repeating the decantation 3 times, the precipitate was dried under reduced pressure. Then, 1000 g of the obtained precipitate (of which 920 g of silver and 80 g of a silver carboxylate amine complex) was redistributed in 1860 g of tarpineol to obtain a conductive paste containing silver nanoparticles (silver powder 3). The obtained silver powder 3 had a particle size 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 aptitude evaluation test piece were prepared in the same manner as in Examples, and evaluated in the same manner as in Examples. The evaluation results are shown in Table 7. The present conductive silver paste composition was remarkably inferior in the physical characteristics of the initial coating film, particularly poor in adhesion, and could not be put into practical use.

Comparative Example 2
Dodecylamine was dissolved in tarpineol to prepare a solution having a solid content concentration of 12% by weight. A glass frit ((bismuth oxide (Bi ₂ )) obtained by crushing silver powder 4 (spherical silver powder (D50 = 1 μm) into 8083 parts with a bead mill so as to have an average particle size of 1.5 μm in 1000 parts (solid 120 parts by weight) of this solution). Add 250 parts of glass powder (bismuth oxide content 80.0-99.9%) containing O ₃ ) as the main component and continue mixing. After becoming uniform, disperse this solution with a three-roll mill to make the glass frit-containing conductive. A paste was prepared. Using the obtained conductive paste, a conductive laminate test piece and a laser etching process suitability evaluation test piece were prepared in the same manner as in the examples, and the evaluation results were evaluated in the same manner as in the examples. As shown in Table 7, the present conductive silver paste composition was remarkably inferior in the physical properties of the initial coating film, particularly poor in adhesion, and was not practically usable. In addition, the laser etching processability was remarkably inferior. In addition, it was not possible to process a predetermined line width because the coating film with a width significantly wider than the width of the laser beam irradiated in a wider range than the irradiation site was peeled off. The adhesion and moisture resistance of the part were also poor.

The conductive paste for laser etching processing of the present invention provides a conductive thin film capable of maintaining the suitability for laser etching processing, excellent reliability in a moist heat environment, and maintaining the durability of a 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 wire 1b, 2b, 3b, 4b
1c, 2c, 3c, 4c: Terminals 1c, 2c, 3c, 4c
5: Pattern formed on the laser etching aptitude evaluation test piece

Claims (8)

Contains binder resin (A), metal powder (B) and organic solvent (C) consisting of one or a mixture of two or more selected from the group consisting of polyurethane resin, phenoxy resin, vinyl chloride resin and fibrous derivative resin. The binder resin (A) is a thermoplastic resin having a number average molecular weight of 5,000 to 60,000 and a glass transition temperature of 60 to 100 ° C., and the organic solvent (C) has a boiling point. Is 100 ° C. or higher and lower than 300 ° C., and the width of the line and space in the plane direction is 50 μm or less by laser etching processing. Used for forming on the transparent conductive layer, the line width in the plane direction is 25 to 31 μm and the space width in the plane direction is 28 to 32 μm by laser etching processing using a laser beam having a beam diameter of 30 μm. A conductive paste for laser etching that can form certain electrode circuit wiring. The conductive paste for laser etching processing according to claim 1, further comprising a laser light absorber (D). A conductive thin film formed from the conductive paste for laser etching processing according to any one of claims 1 and 2. A conductive laminate in which the conductive thin film according to claim 3 and a base material having a transparent conductive layer on the entire surface or a part thereof are laminated. An electric circuit using the conductive thin film according to claim 3 or the conductive laminate according to claim 4. It is formed by irradiating a part of the conductive thin film according to claim 3 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 with a laser wiring part. The electric circuit according to claim 6, wherein the conductive thin film is formed on a transparent conductive layer. A touch panel including the electric circuit according to any one of claims 6 to 7 as a component.

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