JP6962179B2 - Method for manufacturing conductive paste and conductive pattern forming substrate - Google Patents

Description

The present invention relates to a conductive paste, a conductive pattern forming substrate using the conductive paste, a method for manufacturing the same, and a touch panel with electrodes.

In recent years, a touch panel has been widely used as an input means. The touch panel is composed of a display unit such as a liquid crystal panel and a touch panel sensor or the like that detects information input at a specific position. The touch panel method is roughly classified into a resistive film method, a capacitance method, an optical method, an electromagnetic induction method, an ultrasonic method, and the like, depending on the input position detection method. Among them, a capacitance type touch panel is widely used because of its optical brightness, excellent design, simple structure, and excellent functionality. The capacitance type touch panel sensor has a first electrode and a second electrode orthogonal to each other via an insulating layer, and a voltage is applied to the electrodes on the touch panel surface to generate capacitance when a conductor such as a finger touches the sensor. The contact position obtained by detecting the change is output as a signal. As the touch panel sensor used in the capacitance method, for example, a structure in which electrodes and external connection terminals are formed on a pair of opposing transparent substrates, or electrodes and external connection terminals are formed on both sides of one transparent substrate, respectively. The structure is known. As the wiring electrode used for the touch panel sensor, a transparent wiring electrode is generally used from the viewpoint of making the wiring electrode difficult to see. Wiring electrodes using materials are widespread, and finer patterns are required.

A touch panel sensor having a wiring electrode made of a metal material has a problem that the wiring electrode is visually recognized due to the metallic luster of the wiring electrode. As a method of making the wiring electrodes difficult to see, it is conceivable to suppress reflection by blackening the metal. As the metal blackening treatment liquid, for example, a hydrochloric acid solution in which tellurium is dissolved has been proposed (see, for example, Patent Document 1). Further, in order to reduce the reflectance of the conductive circuit pattern, a photosensitive conductive resin composition containing a black material has been proposed (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2006-23327 Japanese Unexamined Patent Publication No. 2014-170111

However, when the metal blackening technique described in Patent Document 1 is applied to a touch panel sensor, there is a problem that the conductivity of the wiring electrode is lowered due to the oxidation of the metal. Further, the techniques described in Patent Document 2 are that a pigment-based black material hinders contact between metal particles and lowers conductivity, and a dye-based black material has insufficient color development and sufficient metallic luster. There was a problem that it was difficult to suppress it. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conductive paste capable of forming a fine pattern that is difficult to see and exhibiting high conductivity.

In order to solve the above problems, the present invention mainly has the following configurations.
Conductive particles (A), compounds with unsaturated double bonds (B), photopolymerization initiators (C) and C.I. I. Solvent Black 3 (D) is contained, and the above-mentioned C.I. I. Solvent Black 3 (D) of the content of Ri is 0.5 to 15 parts by weight der respect to the conductive particles (A) 100 parts by weight of the conductive particles (A) is Ah with particles of silver Rushirubeden paste ..

According to the conductive paste of the present invention, it is possible to form a conductive pattern having a fine pattern that is difficult to see and has excellent conductivity.

It is a schematic diagram which shows the conductive pattern for evaluation of fine pattern processability, conductivity, visibility (difficulty to see) in an Example and a comparative example.

The conductive paste of the present invention comprises conductive particles (A), a compound having an unsaturated double bond (B), a photopolymerization initiator (C) and C.I. I. Solvent Black 3 contain (D), the conductive particles (A) is Ru Oh with particles of silver. The conductive pattern obtained by the conductive paste of the present invention is a composite of an organic component and an inorganic component, and the conductive particles (A) become conductive when they come into contact with each other due to curing shrinkage during heat curing. It is expressed. The compound (B) having an unsaturated double bond and the photopolymerization initiator (C) enable fine pattern formation using a photolithography method. Furthermore, C.I. I. The solvent black 3 (D) can suppress the reflection of the conductive pattern and make the conductive pattern less visible. Furthermore, among the black dyes, C.I. I. Since the solvent black 3 (D) does not easily inhibit the contact between the conductive particles (A) during heat curing, C.I. I. By selecting the solvent black 3 (D), the conductivity can be improved.

(Conductive particles (A))
"Conductivity" in the present invention means that the electrical resistivity at 20 ° C. is 500 μΩ · cm or less. Examples of the conductive particles (A) include particles such as gold, silver, copper, platinum, lead, tin, nickel, bismuth, zinc, palladium, aluminum, tungsten, molybdenum, chromium, titanium, indium, and alloys thereof. Can be mentioned. Two or more of these may be contained. Among these, gold, silver, copper, platinum, lead, tin, nickel, and aluminum particles are preferable, and silver particles are more preferable, from the viewpoint of further improving conductivity.

The primary particle size of the conductive particles (A) is preferably 0.1 μm or more from the viewpoint of further improving the fine pattern processability. On the other hand, the primary particle size of the conductive particles (A) is preferably 1.0 μm or less, more preferably 0.4 μm or less, from the viewpoint of further improving the conductivity. Here, the primary particle size of the conductive particles (A) means a number average value of the particle sizes of the primary particles of 100 randomly selected conductive particles (A). Conductive particles (A) were collected from the conductive paste, observed at a magnification of 25,000 using an electron microscope, and the major and minor diameters of 100 randomly selected primary particles of the conductive particles (A) were determined, respectively. The primary particle diameter of the conductive particles (A) can be calculated from the measured and average value of the primary particle diameter. As a method of collecting the conductive particles (A) from the conductive paste, for example, the resin component is dissolved with an organic solvent, the precipitated conductive particles (A) are recovered, and 10 at 70 ° C. using a box oven. A method of drying for a minute can be mentioned.

The content of the conductive particles (A) in the conductive paste of the present invention is preferably 60% by weight or more, more preferably 65% by weight or more, and 70% by weight or more in the total solid content from the viewpoint of further improving the conductivity. Is even more preferable. On the other hand, the content of the conductive particles (A) is preferably 95% by weight or less, more preferably 90% by weight or less, still more preferably 85% by weight or less, based on the total solid content, from the viewpoint of further improving the fine pattern processability. .. Here, the total solid content means all the constituent components excluding the solvent of the conductive paste.

(Compound (B) having an unsaturated double bond)
The compound (B) having an unsaturated double bond in the present invention is, for example, a reaction product of styrenes, an acrylic monomer, an acrylic polymer, a carboxyl compound having an unsaturated double bond and an epoxy compound. Examples thereof include epoxy carboxylate compounds and 1-vinyl-2-pyrrolidone. Two or more of these may be contained.

Examples of styrenes include styrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, α-methylstyrene, chloromethylstyrene, hydroxymethylstyrene and the like.

Examples of acrylic monomers include methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, iso-butyl acrylate, iso-propane acrylate, glycidyl acrylate, butoxytriethylene glycol acrylate, dicyclopentanyl acrylate, and dicyclopentanyl acrylate. Cyclopentenyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, isodexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methoxyethyl acrylate, methoxyethylene glycol acrylate, methoxydiethylene glycol acrylate, octafluororo Pentyl acrylate, phenoxyethyl acrylate, stearyl acrylate, trifluoroethyl acrylate, aminoethyl acrylate, phenyl acrylate, phenoxyethyl acrylate, 1-naphthyl acrylate, 2-naphthyl acrylate, thiophenol acrylate, benzyl mercaptan acrylate, allylated cyclohexyl diacrylate, Cyclohexyl methoxylated diacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, neopentyl glycol diacrylate, Propropylene glycol diacrylate, Polypropylene glycol diacrylate, Triglycerol diacrylate, Trimethylol propanetriacrylate, Ditrimethylol propanetetraacrylate, Dipentaerythritol monohydroxypentaacrylate, Dipentaerythritol hexaacrylate, acrylamide, N-methoxymethylacrylamide, N -Ethoxymethylacrylamide, Nn-butoxymethylacrylamide, N-isobutoxymethylacrylamide, acrylic acid adduct of ethylene glycol diglycidyl ether having a hydroxyl group in which the epoxy group is opened with unsaturated acid, diethylene glycol diglycidyl ether Acrylate adduct, Acrylate adduct of neopentyl glycol diglycidyl ether, Acrylate adduct of glycerin diglycidyl ether, Bisphenol A Epoxy acrylate monomers such as diglycidyl ether acrylic acid adduct, bisphenol F acrylic acid adduct, cresol novolac acrylic acid adduct, γ-acryloxypropyltrimethoxysilane and compounds in which their acrylic groups are replaced with methacrylic groups. And so on.

The acrylic polymer means a polymer or copolymer of a monomer containing an acrylic monomer. The acrylic polymer preferably has a carboxyl group, and a copolymer of the above-mentioned acrylic monomer and an unsaturated acid or an acid anhydride thereof is more preferable. Examples of unsaturated acids or acid anhydrides thereof include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetate and acid anhydrides thereof. The acid value of the acrylic copolymer can be adjusted by the copolymerization ratio of the unsaturated acid.

Examples of the epoxy compound that is a raw material of the epoxy carboxylate compound include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and tripropylene glycol diglycidyl ether. , Neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, bisphenol full orange glycidyl ether, biphenol diglycidyl ether, tetramethyl biphenol glycidyl ether , Glycidyl ethers such as trimethylolpropane triglycidyl ethers; alicyclic epoxy resins such as 3', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; glycidylamines such as tert-butylglycidylamines; glycidyl esters And so on. Examples of the carboxyl compound having an unsaturated double bond, which is a raw material for epoxy carboxylate, include (meth) acrylic acid, crotonic acid, cinnamic acid, and α-cyanocinnamic acid.

The compound (B) having an unsaturated double bond preferably has a urethane bond. Examples of the method for introducing a urethane bond into the compound (B) having an unsaturated double bond include a method in which a diisocyanate compound is reacted with these hydroxyl groups in the case of an acrylic polymer having a hydroxyl group or an epoxy carboxylate compound. Be done. Examples of the diisocyanate compound include hexamethylene diisocyanate, tetramethylxylylene diisocyanate, naphthalene-1,5-diisocyanate, tridendiisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, allylcyandiisocyanate, and norbornane diisocyanate. Two or more of these may be used.

The compound (B) having an unsaturated double bond preferably has a phenolic hydroxyl group. The acid value of the compound (B) having an unsaturated double bond is preferably 30 mgKOH / g or more from the viewpoint of solubility in a developing solution. On the other hand, the acid value of the compound (B) having an unsaturated double bond is preferably 250 mgKOH / g or less from the viewpoint of suppressing excessive dissolution of the unexposed portion. The acid value of the compound (B) having an unsaturated double bond can be measured according to JIS K 0070 (1992).

In the case of an acrylic polymer, for example, the acid value of the compound (B) having an unsaturated double bond can be adjusted to a desired range by the ratio of the unsaturated acid in the constituent components. In the case of the epoxy carbolate compound, it can be adjusted to a desired range by reacting with a polybasic acid anhydride. Examples of the polybasic acid anhydride include succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, itaconic anhydride, 3-methyltetrahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride, and anhydrous. Examples thereof include trimellitic acid and maleic anhydride.

Further, by reacting the carboxyl group of the above acrylic polymer or epoxy carboxylate compound with a compound having an unsaturated double bond such as glycidyl (meth) acrylate, the side chain is reactive unsaturated. A heavy bond can be introduced and the amount of reactive unsaturated double bond can be adjusted to the desired range depending on the proportion of the compound having the unsaturated double bond to be reacted.

(Photopolymerization Initiator (C))
Examples of the photopolymerization initiator (C) include benzophenone, methyl O-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone, and 4,4'-dichloro. Benzophenone derivatives such as benzophenone, 4-benzoyl-4'-methyldiphenylketone, fluorenone; pt-butyldichloroacetophenone, 4-azidobenzalacetophenone, acetophenone derivatives such as 2,2'-diethoxyacetophenone; thioxanthone, 2 -Thioxanthone derivatives such as methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone; benzyl derivatives such as benzyl, benzyl dimethyl ketal, benzyl-β-methoxyethyl acetal; benzoin such as benzoin, benzoin methyl ether, benzoin butyl ether Derivatives; 1,2-octanedione-1- [4- (phenylthio) -2- (O-benzoyloxime)], etanone-1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole- 3-Il] -1- (O-acetyloxime), 1-phenyl-1,2-butandion-2- (O-methoxycarbonyl) oxime, 1-phenyl-propandion-2- (O-ethoxycarbonyl) oxime , 1-Phenyl-propanedione-2- (O-benzoyl) oxime, 1,3-diphenyl-propanthrion-2- (O-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanthrion-2- ( Oxyme compounds such as O-benzoyl) oxime; 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2- Α-Hydroxyketone compounds such as methyl-1-propane-1-one; 2-methyl- (4-methylthiophenyl) -2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-one Α such as (4-morpholinophenyl) -butane-1-one, 2-dimethylamino-2- (4-methylbenzyl) -1- (4-morpholin-4-yl-phenyl) butane-1-one, etc. -Aminoalkylphenone compounds; phosphs such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Inoxide compounds; Aromatic sulfonyl chloride compounds such as naphthalene sulfonyl chloride and quinoline sulfonyl chloride; Anthracinone compounds such as anthraquinone, 2-t-butyl anthraquinone, 2-amyl anthraquinone and β-chloroanthraquinone; Antron compounds such as beron and methyleneanthron; 2,6-bis (p-azidobenzylene) cyclohexanone, 6-bis (p-azidobenzylene) -4-methylcyclohexanone, 2,6-bis (p-azidobenzylene) cyclohexanone, 6-Bis (p-azidobenzylidene) -4-methylcyclohexanone, N-phenylthioacridone, 4,4'-azobisisobutyronitrile, diphenyldisulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, four odors Examples thereof include carbonized carbon, tribromophenyl sulfone, and benzoyl peroxide. Two or more of these may be contained. Among these, oxime compounds having high photosensitivity are preferable.

The content of the photopolymerization initiator (C) in the conductive paste of the present invention is 0.05 weight by weight with respect to 100 parts by weight of the compound (B) having an unsaturated double bond from the viewpoint of sufficiently curing the exposed portion. More than parts are preferable, and 1.0 part by weight or more is more preferable. On the other hand, the content of the photopolymerization initiator (C) is preferably 30 parts by weight or less, more preferably 10 parts by weight or less, from the viewpoint of suppressing the wiring thickening due to high sensitivity.

C. I. Examples of Solven Black 3 (D) include Oil Black 803, Oil Black BS, Oil Black NO5, Oil Black HBB, Oil Black 860 (all manufactured by Orient Chemical Industry Co., Ltd.), and Neptun Black X60 (manufactured by BASF). , Fat Black HB01 (manufactured by Hext), Oil Color Black 141 (manufactured by Chuo Synthetic Chemical Co., Ltd.) and the like. Two or more of these may be contained.

C.I. in the conductive paste of the present invention. I. The content of the solvent black 3 (D) is preferably 0.5 parts by weight or more with respect to 100 parts by weight of the conductive particles (A) from the viewpoint of making it more difficult to see due to blackening. On the other hand, C.I. I. The content of Solvent Black 3 (D) is 100 parts by weight of the conductive particles (A) from the viewpoint of suppressing excessive light absorption in the upper part of the coating film of the conductive paste and further improving fine pattern processability and conductivity. On the other hand, 15 parts by weight or less is preferable, and 5 parts by weight or less is more preferable.

The conductive paste of the present invention preferably further contains a thermosetting resin. By containing the thermosetting resin, the adhesion to the substrate is improved, so that a finer wiring pattern can be formed. Examples of the thermosetting resin include epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, silicon resin, polyurethane and the like. Two or more of these may be contained. Among these, epoxy resin is preferable because it has higher substrate adhesion. Examples of the epoxy resin include ethylene glycol-modified epoxy resin, bisphenol A type epoxy resin, brominated epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, alicyclic epoxy resin, glycidylamine type epoxy resin, and glycidyl ether type. Examples thereof include epoxy resins and heterocyclic epoxy resins. The epoxy equivalent of the epoxy resin is preferably 500 g / equivalent or less from the viewpoint of further improving the pattern processability by improving the adhesion. On the other hand, the epoxy equivalent of the epoxy resin is preferably 150 g / equivalent or more from the viewpoint of suppressing a decrease in solubility of the unexposed portion due to heat curing. Here, the epoxy equivalent means the mass of an epoxy resin containing one equivalent of an epoxy group, and can be obtained by dividing the molecular weight obtained from the molecular structure by the number of epoxy groups contained in the structure. Molecular structure, determined by gel permeation chromatography (GPC), infrared spectroscopy (IR) analysis, proton nuclear magnetic resonance spectroscopy ⁽¹ H-NMR) analysis, the pyrolysis gas chromatography / mass (GC / MS) analysis, matrix-assisted It can be specified by selecting and analyzing an analysis method according to the structure from analysis methods such as laser desorption / ionization / time-of-flight mass analysis (MALDI / TOFMS), gas chromatography (GC) analysis, and CHN element analysis. can. When two or more kinds of epoxy resins are contained, it is preferable to contain one or more kinds of epoxy resins having an epoxy equivalent in the above range.

The content of the thermosetting resin in the conductive paste of the present invention is 1 weight per 100 parts by weight of the compound (B) having an unsaturated double bond from the viewpoint of further improving the fine pattern processability by improving the adhesion. More than 30 parts by weight is preferable, and 30 parts by weight or more is more preferable. On the other hand, the content of the thermosetting resin is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, from the viewpoint of suppressing a decrease in solubility of the unexposed portion due to heat curing.

The conductive paste of the present invention can further contain a sensitizer. Examples of the sensitizer include 2,4-diethylthioxanthone, isopropylthioxanthone, 2,3-bis (4-diethylaminobenzal) cyclopentanone, and 2,6-bis (4-dimethylaminobenzal) cyclohexanone, 2. , 6-bis (4-dimethylaminobenzal) -4-methylcyclohexanone, Michler ketone, 4,4-bis (diethylamino) benzophenone, 4,4-bis (dimethylamino) chalcone, 4,4-bis (diethylamino) chalcone , P-Dimethylaminocinnamylidene indanone, p-dimethylaminobenzylene indanone, 2- (p-dimethylaminophenylvinylene) isonaftthiazole, 1,3-bis (4-dimethylaminophenylvinylene) isonaftthiazole, 1,3-bis (4-dimethylaminobenzal) acetone, 1,3-carbonylbis (4-diethylaminobenzal) acetone, 3,3-carbonylbis (7-diethylaminocoumarin), N-phenyl-N-ethyl Examples thereof include ethanolamine, N-phenylethanolamine, N-tolyldiethanolamine, isoamyl dimethylaminobenzoate, isoamyl diethylaminobenzoate, 3-phenyl-5-benzoylthiotetrazole, 1-phenyl-5-ethoxycarbonylthiotetrazole and the like. Two or more of these may be contained.

The content of the sensitizer in the conductive paste of the present invention is preferably 0.05 parts by weight or more with respect to 100 parts by weight of the compound (B) having an unsaturated double bond from the viewpoint of improving the photosensitivity. On the other hand, the content of the sensitizer is preferably 10 parts by weight or less with respect to 100 parts by weight of the compound (B) having an unsaturated double bond from the viewpoint of suppressing the wiring thickening due to high sensitivity.

The conductive paste of the present invention can further contain a solvent. Examples of the solvent include N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone, dimethylsulfoxide, γ-butyrolactone, ethyl lactate, 1-methoxy-2-propanol. , 1-ethoxy-2-propanol, ethylene glycol mono-n-propyl ether, diacetone alcohol, tetrahydrofurfuryl alcohol, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether acetate (hereinafter , "DMEA"), diethylene glycol monobutyl ether, diethylene glycol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and the like. Two or more of these may be contained. The boiling point of the solvent is preferably 150 ° C. or higher. When the boiling point is 150 ° C. or higher, volatilization of the solvent is suppressed, and thickening of the conductive paste can be suppressed.

The conductive paste of the present invention is a non-photosensitive polymer, a plasticizer, a leveling agent, a surfactant, a silane coupling agent, a defoaming agent, a pigment, which does not have an unsaturated double bond, as long as the desired properties are not impaired. Etc. can be contained.

Examples of the non-photosensitive polymer include polyethylene terephthalate, a polyimide precursor, and a closed ring polyimide.

Examples of the plasticizer include dibutyl phthalate, dioctyl phthalate, polyethylene glycol, glycerin and the like.

Examples of the leveling agent include a special vinyl-based polymer and a special acrylic-based polymer.

Examples of the silane coupling agent include methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and vinyltri. Examples thereof include methoxysilane.

The conductive paste of the present invention comprises conductive particles (A), a compound having an unsaturated double bond (B), and a photopolymerization initiator (C) C.I. I. It can be obtained by mixing Solvent Black 3 (D) and, if necessary, a solvent or an additive. Examples of the mixing device include a disperser such as a three-roller mill, a ball mill, and a planetary ball mill, and a kneader.

The conductive pattern forming substrate of the present invention has a conductive pattern made of a cured product of the above-mentioned conductive paste. It is preferable to have a conductive pattern on the substrate.

Examples of the substrate include polyester film such as polyethylene terephthalate (PET), polyimide film, aramid film, epoxy resin substrate, polyetherimide resin substrate, polyetherketone resin substrate, polysulfone resin substrate, glass substrate, silicon wafer, alumina. Examples thereof include a substrate, an aluminum nitride substrate, a silicon carbide substrate, a decorative layer forming substrate, and an insulating layer forming substrate.

The thickness of the conductive pattern is preferably 5 μm or less, more preferably 3 μm or less, still more preferably 2 μm or less, from the viewpoint of forming finer conductive pattern wiring. On the other hand, from the viewpoint of further improving the conductivity, 0.1 μm or more is preferable, 0.2 μm or more is more preferable, and 0.3 μm or more is further preferable. The thickness of the conductive pattern can be measured using a stylus type profilometer such as "Surfcom" (registered trademark) 1400 (manufactured by Tokyo Seimitsu Co., Ltd.). More specifically, the thicknesses of three positions randomly selected from the conductive pattern were measured using a stylus type step meter (measurement length: 1 mm, scanning speed: 0.3 mm / sec), and they were measured. It can be obtained by calculating the average value of.

The reflectance of the conductive pattern at a wavelength of 550 nm is preferably 30% or less. By reducing the reflectance of visible light, it is possible to further suppress the light reflection of the conductive pattern and make the conductive pattern less visible. In the present invention, attention is paid to the reflectance at a wavelength of 550 nm as an index of the reflectance of visible light. By setting the reflectance at a wavelength of 550 nm to 30% or less, the conductive pattern can be made less visible. The reflectance can be measured using a reflectance meter (VSR-400: manufactured by Nippon Denshoku Kogyo Co., Ltd.) for a conductive pattern having a size of 0.1 mm square or more. The reflectance of the conductive pattern at a wavelength of 550 nm is determined by, for example, C.I. I. The content of the solvent black 3 (D) can be set to 30% or less by setting the content in the above-mentioned preferable range or the like.

The volume resistivity of the conductive pattern is preferably less than 100 μΩ · cm. By setting the volume resistivity to less than 100 μΩ · cm, the conductivity can be further improved and the touch sensitivity when used for a touch panel can be improved. Regarding the volume resistivity of the conductive pattern, the resistivity value of the linear conductive pattern was measured using a resistance measuring tester such as 2407A manufactured by BK Precision Co., Ltd., and the film thickness (μm) and line width of the measured conductive pattern were measured. (Μm) and the pattern length (μm) can be measured and calculated from the following formula (1).
Volume resistivity (μΩ · cm) = resistance value (Ω) × film thickness (μm) × line width (μm) × 100 / pattern length (μm) ... (1).

For the volume resistivity of the conductive pattern, for example, the content of the conductive particles (A) in the conductive paste is set to the above-mentioned preferable range, and the heating temperature in the method for manufacturing the conductive pattern-forming substrate is set to the above-mentioned preferable range. It can be made less than 100 μΩ · cm by such means.

The line width of the conductive pattern is preferably 1 μm or more, more preferably 1.5 μm or more, still more preferably 2 μm or more, from the viewpoint of further improving the conductivity. On the other hand, the line width of the conductive pattern is preferably 10 μm or less, preferably 7 μm or less, and even more preferably 6 μm or less from the viewpoint of making it more difficult to see.

Next, a method for manufacturing the conductive pattern forming substrate of the present invention will be described. It is preferable to apply the above-mentioned conductive paste on a substrate, expose it, develop it, and then heat it at a temperature of 100 to 250 ° C.

Examples of the method of applying the conductive paste include rotary coating using a spinner, spray coating, roll coating, screen printing, offset printing, gravure printing, letterpress printing, flexographic printing, blade coater, die coater, calendar coater, meniscus coater or Examples include application using a bar coater. Among these, screen printing is preferable because the surface flatness of the coating film of the conductive paste is excellent and the film thickness can be easily adjusted by selecting the screen plate.

When the conductive paste contains a solvent, it is preferable to dry the coating film to volatilize and remove the solvent. Examples of the drying method include heating and drying with an oven, an electromagnetic wave ultraviolet lamp, an infrared heater, a halogen heater, and the like, and vacuum drying. The drying temperature is preferably 50 to 130 ° C., and the drying time is preferably 1 minute to several hours.

It is preferable to expose the coating film or the dry film of the conductive paste by a photolithography method through an arbitrary pattern forming mask. The exposure light preferably emits light in an ultraviolet region that matches the absorption wavelength of the photopolymerization initiator (C) contained in the conductive paste composition, that is, in a wavelength region of 200 nm to 450 nm. Examples of the light source for obtaining such exposure light include mercury lamps, halogen lamps, xenon lamps, LED lamps, semiconductor lasers, KrF, ArF excimer lasers, and the like. Among these, the i-line (wavelength 365 nm) of the mercury lamp is preferable. ^{The exposure amount is preferably 50 mJ / cm 2} or more, and more preferably 200 mJ / cm ² or more in terms of wavelength 365 nm, from the viewpoint of solubility of the exposed part in the developing solution.

After the exposure, the unexposed portion is dissolved and removed by developing with a developing solution to obtain a desired pattern. Examples of the developing solution for alkaline development include inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, sodium metasilicate, and aqueous ammonia; 1 such as ethylamine and n-propylamine. Secondary amines; Secondary amines such as diethylamine and di-n-propylamine; Tertiary amines such as triethylamine and methyldiethylamine; Tetraalkylammonium hydroxides such as tetramethylammonium hydroxide (TMAH); Quadratic ammonium salts; alcohol amines such as triethanolamine, diethanolamine, monoethanolamine, dimethylaminoethanol, diethylaminoethanol; pyrrole, piperidine, 1,8-diazabicyclo [5,4,0] -7-undecene, 1, Examples thereof include an alkaline aqueous solution in which an alkaline substance such as an organic alkali such as 5-diazabicyclo [4,3,0] -5-nonane and cyclic amines such as morpholin is dissolved in water. One or more kinds of water-soluble organic solvents such as ethanol, γ-butyrolactone, dimethylformamide, N-methyl-2-pyrrolidone, and surfactants may be added thereto.

As a developing method, for example, a method of spraying a developer on the surface of the conductive paste coating film while allowing, rotating or transporting a substrate on which a conductive paste coating film is formed, or a method of spraying the conductive paste coating film into the developing solution. Examples thereof include a method of immersing and a method of applying ultrasonic waves while immersing a coating film of a conductive paste in a developing solution.

After development, rinsing treatment with a rinsing liquid may be performed. Examples of the rinsing solution include water; an aqueous solution of alcohols such as ethanol and isopropyl alcohol; and an aqueous solution of esters such as ethyl lactate and propylene glycol monomethyl ether acetate.

A conductive pattern can be obtained by heating the obtained pattern. The heating atmosphere, temperature and time can be appropriately set according to the composition of the conductive paste and the thickness of the coating film. In the present invention, it is preferable to heat in air. The heating temperature is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint of sufficiently advancing curing and further improving conductivity. On the other hand, from the viewpoint of heat resistance of the substrate, the heating temperature is preferably 200 ° C. or lower, more preferably 150 ° C. or lower. Examples of the heating device include the devices exemplified in the heating and drying of the coating film.

The conductive pattern forming substrate of the present invention can be suitably used for applications in which the conductive pattern is difficult to see. For example, a touch panel member, an electromagnetic shield member, a transparent LED light member, and the like can be mentioned. Above all, it can be suitably used as a touch panel member for which miniaturization and making the conductive pattern less visible are more highly required.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

The evaluation method in each example is as follows.

<Fine pattern workability>
The conductive pastes obtained from each Example and Comparative Example were applied onto a PET film so that the film thickness after drying was 2 μm, and dried in a drying oven at 100 ° C. for 10 minutes. ^{An exposure was made at an exposure amount of 500 mJ / cm 2} (wavelength 365 nm conversion) using an exposure apparatus (PEM-6M; manufactured by Union Optical Co., Ltd.) through a photomask having a mesh-shaped opening. The pitch of the mesh shape was set to 300 μm, and the mask opening width of the mesh portion was set to 7 types of 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, and 7.0 μm. .. The distance between the terminals was 20 mm, the width was 2 mm, and the pad portion was a 4 mm ² square. After the exposure, the mixture was spray-developed for 20 seconds using a _{0.1 wt% Na 2} CO _{3 aqueous solution, and rinsed with ultrapure water.} Then, it was heated in the drying of 140 degreeC for 120 minutes, and 7 kinds of conductive patterns having different line widths were obtained respectively. FIG. 1 shows a schematic view of a conductive pattern for evaluating fine pattern workability. The pad portions 1 were provided at both ends of the mesh portion, the distance between the terminals 2 was 20 mm, and the pad portion width 3 was 2 mm. The obtained conductive pattern was observed with an optical microscope, and the presence or absence of pattern peeling was observed. The fine pattern processability was evaluated according to the following evaluation criteria from the minimum mask opening width in which no pattern peeling was observed. 1 or more was accepted.
5: No pattern peeling when the mask opening width is 1.5 μm or more 4: No pattern peeling when the mask opening width is 2.0 μm or more 3: No pattern peeling when the mask opening width is 3.0 μm or more 2: Pattern when the mask opening width is 4.0 μm or more No peeling 1: No pattern peeling when the mask opening width is 5.0 μm or more 0: Pattern peeling when the mask opening width is 6.0 μm or more.

<Evaluation of conductivity>
Among the conductive patterns obtained by the above-mentioned evaluation method of fine pattern processability, the conductive pattern having the smallest mask opening width in which pattern peeling is not observed is used between terminals using a resistance measurement tester (2407A; manufactured by BK Precision Co., Ltd.). The resistance value was measured. Further, the thickness of the same conductive pattern was measured using a surface roughness shape measuring machine (“Surfcom” (registered trademark) 1400D; manufactured by Tokyo Seimitsu Co., Ltd.). Further, using an optical microscope, the same conductive pattern was magnified and observed at a magnification of 1000 times to measure the line width. The volume resistivity (μΩ · cm) was calculated according to the following formula (2), and the conductivity was evaluated according to the following evaluation criteria. 1 or more was accepted. However, Comparative Example 3 in which all the patterns were peeled off could not be evaluated.
Volume resistivity (μΩ · cm) = {resistance value (Ω) x film thickness (μm) x line width (μm) x pad width (μm)} / {distance between terminals (μm) / pitch (μm)} x 100 ... (2)
5: 50 μΩ ・ cm or less 4: 50 μΩ ・ cm or more and less than 60 μΩ ・ cm 3: 60 μΩ ・ cm or more and less than 70 μΩ ・ cm 2: 70 μΩ ・ cm or more and less than 80 μΩ ・ cm 1: 80 μΩ ・ cm or more and less than 100 μΩ ・ cm 0: 100 μΩ ・cm or more.

<Visibility (difficult to see) (visual)>
The conductive pattern forming substrate obtained by the above fine pattern processability evaluation method was placed on a black film, light was projected using a floodlight, and 10 people visually observed each from a position 30 cm away to form a mesh. Whether or not the electrode portion of the above was visible was evaluated according to the following evaluation criteria. 2 or more was passed. However, Comparative Example 3 in which all the patterns were peeled off could not be evaluated.
5:10 invisible 4: 8 or more and less than 10 invisible 3: 6 or more and less than 8 invisible 2: 4 or more and less than 6 invisible 1: 2 or more and less than 4 invisible Impossible 0: Less than 2 people cannot see.

<Visibility (difficult to see) (reflectance)>
The reflectance of the pad portion of the conductive pattern forming substrate obtained by the above fine pattern processability evaluation method was measured at a wavelength of 550 nm using a reflectance meter (VSR400: manufactured by Nippon Denshoku Kogyo Co., Ltd.). Evaluation was made according to the following evaluation criteria. 3 or more was passed.
Less than 5: 20% More than 4: 20% More than 25% less than 3: 25% more than 30% less than 2:30% More than 35% less than 1: 35% more than 40% less than 0: 40%.

The materials used in each example are as follows.
[Conductive particles (A)]
A-1: Silver particles with a primary particle size of 0.3 μm (electric resistivity at 20 ° C. of 3 μΩ · cm or less)
A-2: Silver particles with a primary particle size of 0.8 μm (electric resistivity at 20 ° C. of 3 μΩ · cm or less)
The primary particle diameter of the conductive particles was determined by observing the conductive particles at a magnification of 25,000 using an electron microscope, and determining the major axis and the minor axis of 100 randomly selected primary particles of the conductive particles, respectively. It was measured and the average value was taken as the primary particle size, and it was calculated from the number average value.

[Compound with unsaturated double bond (B)]
(Synthesis Example 1) Carboxyl Group-Containing Acrylic Copolymer (B-1)
150 g of diethylene glycol monoethyl ether acetate (hereinafter, “DMEA”) was charged in a reaction vessel having a nitrogen atmosphere, and the temperature was raised to 80 ° C. using an oil bath. To this, 20 g of ethyl acrylate (hereinafter, "EA"), 40 g of 2-ethylhexyl methacrylate (hereinafter, "2-EHMA"), 20 g of styrene (hereinafter, "St"), and 15 g of acrylic acid (hereinafter, "St"). "AA"), a mixture of 0.8 g 2,2-azobisisobutyronitrile and 10 g DMEA was added dropwise over 1 hour. After completion of the dropping, the polymerization reaction was further carried out by stirring at 80 ° C. for 6 hours. Then, 1 g of hydroquinone monomethyl ether was added to terminate the polymerization reaction. Subsequently, a mixture consisting of 5 g of glycidyl methacrylate (hereinafter, “GMA”), 1 g of triethylbenzeneammonium chloride and 10 g of DMEA was added dropwise over 0.5 hours. After completion of the dropping, the addition reaction was carried out by further stirring at 80 ° C. for 2 hours. Unreacted impurities were removed by purifying the obtained reaction solution with methanol, and the mixture was vacuum dried for 24 hours to copolymerize (based on mass): EA / 2-EHMA / St / GMA / AA = 20/40. A carboxyl group-containing acrylic copolymer of 20/5/15 was obtained. The acid value of the obtained copolymer was measured and found to be 103 mgKOH / g. The acid value was measured according to JIS K 0070 (1992).

[Photopolymerization Initiator (C)]
C-1: "IRGACURE" (registered trademark) 369 (manufactured by Ciba Japan Co., Ltd., α-aminoalkylphenone compound)
C-2 "IRGACURE" (registered trademark) OXE02 (Oxime compound manufactured by Ciba Japan Co., Ltd.)
[C. I. Solvent Black 3 (D)]
D-1: Oil Black (registered trademark) HBB (manufactured by Orient Chemical Industry Co., Ltd.)
D-2: Oil Black (registered trademark) 860 (manufactured by Orient Chemical Industry Co., Ltd.)
D-3: Neptun Black (registered trademark) X60 (manufactured by BASF)
[Epoxy resin]
E-1: "JER" (registered trademark) 828 (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 188)
E-2: "Adeka Resin" (registered trademark) EPR-4030 (manufactured by ADEKA Corporation, epoxy equivalent 380)
E'-3: "JER" (registered trademark) 1002 (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 650).

[Black material]
CB: Carbon Black # 240 (manufactured by Mitsubishi Chemical Corporation, average particle size 45 nm)
NH805: C.I. I. Solvent Black 5 NUBIAN BLACK (registered trademark) NH-805 (manufactured by Orient Chemical Industry Co., Ltd.)
[Example 1]
In a 100 mL clean bottle, 10.0 g of the compound having an unsaturated double bond (B-1), 0.50 g of the photopolymerization initiator (C-2), 0.24 g of C.I. I. Add Solvent Black 3 (D-1) and 5.0 g of DMEA, mix using a rotation-revolution vacuum mixer "Awatori Rentaro" (registered trademark) ARE-310 (manufactured by Shinky Co., Ltd.), and 15 A resin solution (solid content 68.2% by mass) of .74 g was obtained.

The obtained 15.74 g of the resin solution and 40.4 g of the conductive particles (A-1) were mixed and kneaded using a three-roller mill (EXAKT M-50; manufactured by EXAKT) to obtain 55.78 g. A conductive paste was obtained. Table 1 shows the composition of the conductive paste.

Using the obtained conductive paste, fine pattern processability, conductivity, visibility (difficult to see) (visual) and visibility (difficult to see) (reflectance) were evaluated by the above-mentioned methods. .. The fine pattern processability was "5" and the conductivity was "4", which were good. The visibility (difficult to see) (visual) and visibility (difficult to see) (reflectance) were all "2", but they were within the range in which they could be used without any problem. The evaluation results are shown in Table 2.

[Examples 2 to 14]
A conductive paste having the composition shown in Table 1 was prepared by the same method as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[Comparative Examples 1 to 5]
The conductive paste having the composition shown in Table 1 was produced by the same method as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[Comparative Example 6]
The photosensitive conductive paste having the composition shown in Table 1 was produced by the same method as in Example 1 to form a conductive pattern for each evaluation.

An aqueous solution of hydrochloric acid was prepared by adding 40 g of 36 mass% hydrochloric acid to 50 g of water. Then, 3 g of tellurium oxide was added to 90 g of this aqueous hydrochloric acid solution. After visually confirming that tellurium oxide was completely dissolved in the aqueous hydrochloric acid solution, 5 g of acetic acid was added to the aqueous hydrochloric acid solution, and water was further added to bring the total amount to 100 g to prepare a blackening solution. The substrate on which the conductive pattern was formed was immersed in the obtained blackening solution for 10 seconds to blacken the substrate to form a conductive pattern-forming substrate. The evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 2.

As shown in Table 2, the conductive patterns obtained by the conductive pastes of Examples 1 to 14 all have fine pattern processability, conductivity of "1" or more, visibility (difficult to see) (visual), and. The visibility (difficult to see) (reflectance) was "2" or higher, which was within the range in which it could be used without problems. On the other hand, the conductive patterns obtained by the conductive pastes of Comparative Examples 1 to 6 have fine pattern processability, conductivity, visibility (difficult to see) (visual) or visibility (difficult to see) (reflectance). Either was inadequate.

The conductive paste of the present invention can be suitably used as a member for a touch panel, which is required to be finer and the wiring electrodes to be less visible.

1 Pad part 2 Distance between terminals 3 Pad part width

Claims (8)

Conductive particles (A), compounds with unsaturated double bonds (B), photopolymerization initiators (C) and C.I. I. Solvent Black 3 (D) is contained, and the above-mentioned C.I. I. Solvent Black 3 (D) of the content of Ri is 0.5 to 15 parts by weight der respect to the conductive particles (A) 100 parts by weight of the conductive particles (A) is Ah with particles of silver Rushirubeden paste .. The conductive paste according to claim 1, further containing an epoxy resin (E) having an epoxy equivalent of 150 to 500 g / equivalent. The conductive paste according to claim 1 or 2, wherein the photopolymerization initiator (C) contains an oxime compound. The conductive paste according to any one of claims 1 to 3, wherein the primary particle diameter of the conductive particles (A) is 0.1 to 0.4 μm. A method for producing a conductive pattern-forming substrate, wherein the conductive paste according to any one of claims 1 to 4 is applied onto a substrate, exposed to light, developed, and then heated at a temperature of 100 to 250 ° C. to obtain a conductive pattern. The method for manufacturing a conductive pattern forming substrate according to claim 5, wherein the thickness of the conductive pattern is 2 μm or less. A conductive pattern forming substrate having a conductive pattern made of a cured product of the conductive paste according to any one of claims 1 to 4 on the substrate. The conductive pattern forming substrate according to claim 7, wherein the reflectance of the conductive pattern at a wavelength of 550 nm is 30% or less, and the volume resistivity is less than 100 μΩ · cm.

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