KR102208100B1 - Conductive paste, touch panel, and method for producing conductive pattern - Google Patents

Abstract

An object of the present invention is to provide a conductive paste capable of stably maintaining contact resistance even in environments such as high humidity, high heat, and capable of producing a fine conductive pattern with high connection reliability with a transparent electrode. The present invention contains a metal particle (A), a carbon particle (B), a compound having an unsaturated double bond (C), a photopolymerization initiator (D), and a solvent (E), and contains the metal for the carbon particle (B). A conductive paste having a mass ratio of particles (A) of 20 to 1900 is provided.

Description

Manufacturing method of conductive paste, touch panel, and conductive pattern {CONDUCTIVE PASTE, TOUCH PANEL, AND METHOD FOR PRODUCING CONDUCTIVE PATTERN}

The present invention relates to a method of manufacturing a conductive paste and a conductive pattern.

In recent years, a conductive paste in which a conductive filler is dispersed in an organic component has been developed that can produce a fine conductive pattern by a photolithography method (Patent Documents 1 and 2), and among them, connection reliability with transparent electrodes such as ITO is improved. A conductive paste characterized by being high has been developed (Patent Document 1).

International Publication No. 2013/108696 International Publication No. 2013/146107

However, in a conductive pattern such as a peripheral wiring of a touch panel manufactured using a conventional conductive paste, the electrical resistance generated on the contact surface between the conductive pattern and the transparent electrode such as ITO due to thermal stress such as high temperature or humidity change. It was a problem that this may increase.

Therefore, an object of the present invention is to provide a conductive paste capable of stably maintaining contact resistance even through environmental changes such as high humidity, high heat, and capable of producing a conductive pattern that is fine and has low specific resistance.

In order to solve the above problems, the present invention provides a method of manufacturing a conductive paste, a touch panel, and a conductive pattern described in the following (1) to (6).

(1) Metal particles (A), carbon particles (B), a compound having an unsaturated double bond (C), a photopolymerization initiator (D), and a solvent (E), and the metal for the carbon particles (B) A conductive paste in which the mass ratio of the particles (A) is 20 to 1900.

(2) The conductive paste according to (1), containing an oxime ester compound as the photopolymerization initiator (D).

(3) the volume average particle diameter of the metal particles (A) is 0.1 to 10 μm, and the volume average particle diameter of the primary particles of the carbon particles (B) is 0.005 to 0.5 μm, the above (1) or ( The conductive paste described in 2).

(4) The conductive paste according to any one of (1) to (3), wherein the acid value of the compound (C) having an unsaturated double bond is 30 to 250 mgKOH/g.

(5) A touch panel comprising a conductive pattern formed of the conductive paste according to any one of the above (1) to (4) and a transparent electrode made of ITO, and the transparent electrode and the conductive pattern are connected.

(6) A method for producing a conductive pattern, wherein the conductive paste according to any one of (1) to (4) is applied on a substrate, dried, exposed, and developed, and then cured at 100 to 300°C.

(Effects of the Invention)

According to the conductive paste of the present invention, an increase in contact resistance can be suppressed even through environmental changes such as high humidity, high heat, etc., and a fine conductive pattern with low specific resistance can be manufactured.

1 is a schematic diagram showing a light transmission pattern of a photomask used for specific resistance evaluation in Examples.
Fig. 2 is a schematic diagram showing a light-transmitting pattern of a photomask used for evaluation of the reliability of connection with ITO in Examples.

The conductive paste of the present invention contains metal particles (A), carbon particles (B), a compound having an unsaturated double bond (C), a photoinitiator (D), and a solvent (E), and contains the carbon particles (B). It is characterized in that the mass ratio of the metal particles (A) is 20 to 1900.

The conductive pattern obtained by the conductive paste of the present invention is made of a composite of an organic component and an inorganic component, and electrical conductivity is exhibited when metal particles (A) are brought into contact with each other due to curing shrinkage during curing.

The conductive paste of the present invention contains metal particles (A). The metal constituting the metal particles (A) is silver (hereinafter, ``Ag''), gold (hereinafter, ``Au''), copper, platinum, lead, tin, nickel, aluminum, tungsten, molybdenum, chromium, titanium or indium, or Although alloys of these metals are mentioned, Ag, Au, or copper is preferable from the viewpoint of conductivity, and Ag is more preferable from the viewpoint of cost and stability.

The inventors of the present invention repeated intensive examinations to obtain a desired conductive paste. And attention was paid to the carbon particle (B). Until now, it has been known to add carbon particles in order to increase the dispersibility of metal particles in a conductive paste or to adjust the conductivity. However, for that purpose, a considerable amount of carbon particles must be added, resulting in a decrease in conductivity, that is, an increase in specific resistance.

Therefore, the present inventors focused on the mass ratio of the metal particles (A) to the carbon particles (B). Further, further investigation was conducted, and it was found that by adding a small amount of carbon particles, the contact resistance can be stably maintained even through environmental changes such as high humidity, high heat, and the like. That is, the mass ratio of the metal particles (A) to the carbon particles (B) needs to be 20 to 1900, more preferably 30 to 1000.

If the mass ratio of the metal particles (A) is 1900 or less, the contact probability between the carbon particles (B) and the transparent electrode is improved, and the contact resistance between the manufactured conductive pattern and the transparent electrode is stably low even through environmental changes of high humidity and high heat. to be. On the other hand, when the mass ratio of the metal particles (A) is 20 or more, the probability of contact between the metal particles (A) is improved, and the specific resistance of the produced conductive pattern is sufficiently lowered.

The volume average particle diameter of the metal particles (A) is preferably 0.1 to 10 µm, more preferably 0.5 to 6 µm. When the volume average particle diameter is 0.1 µm or more, the probability of contact between the metal particles (A) in the curing step is improved, and the specific resistance and disconnection probability of the produced conductive pattern are lowered. In addition, in the exposure step, exposure light can smoothly pass through the coating film obtained by applying the conductive paste, thereby facilitating fine patterning. On the other hand, when the volume average particle diameter is 10 µm or less, the surface smoothness, pattern accuracy, and dimensional accuracy of the produced conductive pattern are improved. In addition, the volume average particle diameter of the metal particle (A) can be measured by the Coulter counter method.

The amount of the metal particles (A) added is preferably 60 to 95% by mass based on the total solid content in the conductive paste. When the addition amount to the total solid content is 60% by mass or more, the contact probability between the metal particles (A) during curing is improved, and the specific resistance and disconnection probability of the produced conductive pattern are lowered. On the other hand, when the addition amount to the total solid content is 95% by mass or less, exposure light in the exposure step can more smoothly pass through the coating film obtained by applying the conductive paste, thereby facilitating fine patterning. Here, the total solid content refers to all the constituent components of the conductive paste excluding the solvent.

The conductive paste of the present invention contains carbon particles (B). Here, the carbon particles refer to particles in which the proportion of carbon occupied by the entire particle is 50% by mass or more. Since the carbon particles contained in the conductive paste have particularly good wettability with ITO among the transparent electrodes, carbon particles collect at the interface between the conductive paste and ITO, and the number of contact points increases, thereby increasing the conductive path.Thus, through environmental changes such as high humidity, high heat, etc. Also, the effect of stably maintaining contact resistance is increased.

As the carbon particle (B), for example, MA77, 7, 8, 11, 100, 100R, 100S, 230, 14, 220 or 600 or #2650, 2600, 2350, 2300, 1000, 1000N, 980, 970, 960 , 950, 900, 850, 750B, 650B, 52, 47, 45, 45L, 44, 40, 32, 30, 30L, 25, 20, 10, 5, 95, 85, 260, 4000B, 3030B, 3050B, 3230B Or 3400B (above, all made by Mitsubishi Kagaku Corporation), Toka Black #8500/F, 8300/F, 7550SB/F, 7400, 7360SB, 7350/F, 7270SB, 7100F, 7050, 5500, 4500, 4400 , 4300, 3855, 3845 or 3800 (all above, all manufactured by Tokai Carbon Co., Ltd.), Asahi #78, 80, 70, 70L, 66, 65, 60HN, 60H, 60U, 60, 55, 50HG, 52, 51, 50U, 50, 35, 15HS, 15, 8 or Asahi F-200 or AX-015 or Asahi Thermal (above, all manufactured by Asahi Carbon Co., Ltd.) are mentioned.

The volume average particle diameter of the primary particles of the carbon particles (B) is preferably 0.005 to 0.5 µm. When the volume average particle diameter of the primary particles is 0.005 µm or more, dispersibility and dispersion stability in the conductive paste become higher, and generation of aggregates can be suppressed. On the other hand, when the volume average particle diameter of the primary particles exceeds 0.5 μm, the number of primary particles per certain mass decreases, and the contact probability with transparent electrodes such as ITO, silver nanowires, zinc oxide or tin oxide decreases, and the manufactured The contact resistance between the conductive pattern and the transparent electrode may increase. In addition, the volume average particle diameter of the primary particles of the carbon particles (B) is determined by observing 100 primary particles randomly selected using an electron microscope, measuring the maximum width of each primary particle, and It can be calculated by obtaining an average value.

The added amount of the carbon particles (B) is preferably 0.05 to 3% by mass, more preferably 0.1 to 2% by mass, based on the total solid content in the conductive paste. When the addition amount to the total solid content is 0.05% by mass or more, the contact probability between the carbon particles (B) and the transparent electrode is improved, and the contact resistance between the produced conductive pattern and the transparent electrode is stably lowered even in an environment of high humidity and high heat. On the other hand, when the addition amount to the total solid content is 3% by mass or less, exposure light can smoothly pass through the coating film obtained by applying the conductive paste in the exposure step, thereby facilitating fine patterning.

The conductive paste of the present invention contains the compound (C) having an unsaturated double bond. Examples of the compound (C) having an unsaturated double bond include styrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, α-methylstyrene, chloromethylstyrene or hydroxymethylstyrene, and acrylic A monomer, 1-vinyl-2-pyrrolidone, an acrylic copolymer, or an epoxy carboxylate compound.

As an acrylic monomer, for example, acrylic acid, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, iso-butyl acrylate, iso-propane acrylate, glycidyl acrylate, butoxy Triethylene glycol acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, isodexyl acrylate, isooctyl acrylate, Lauryl acrylate, 2-methoxyethyl acrylate, methoxyethylene glycol acrylate, methoxydiethylene glycol acrylate, octafluoropentyl acrylate, phenoxyethyl acrylate, stearyl acrylate, trifluoroethyl acrylic Acrylate, aminoethyl acrylate, phenyl acrylate, phenoxyethyl acrylate, 1-naphthyl acrylate, 2-naphthyl acrylate, thiophenol acrylate or benzyl mercaptan acrylate, allylated cyclohexyl diacrylate, Methoxylated cyclohexyl 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, propylene glycol diacrylate, polypropylene glycol diacrylate or triglycerol diacrylate, trimethylolpropane triacrylate, dimethylolpropane tetraacrylate, dipentaerythritol monohydroxy Pentaacrylate or dipentaerythritolhexaacrylate, acrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, Nn-butoxymethylacrylamide or N-isobutoxymethylacrylamide, epoxy group unsaturated acid Acrylic acid adduct of ethylene glycol diglycidyl ether having a hydroxyl group opened with a ring, acrylic acid adduct of diethylene glycol diglycidyl ether, acrylic acid adduct of neopentyl glycol diglycidyl ether, glycerin diglycidyl ether Epoxy acrylics such as acrylic acid adducts of, bisphenol A diglycidyl ether, acrylic acid adducts of bisphenol F, or cresol novolac acrylic acid adducts And compounds obtained by substituting yt monomer or γ-acryloxypropyltrimethoxysilane, or their acrylic groups with methacrylic groups.

The acrylic copolymer refers to a monomer to be used, that is, a copolymer containing an acrylic monomer in the copolymerization component.

The alkali-soluble acrylic copolymer having a carboxyl group is obtained by using an unsaturated acid such as an unsaturated carboxylic acid as a monomer. As an unsaturated acid, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetate, or these acid anhydrides are mentioned, for example. The acid value of the obtained acrylic copolymer can be adjusted by some of the unsaturated acids to be used.

Further, by reacting a carboxyl group of the acrylic copolymer with a compound having an unsaturated double bond such as glycidyl (meth)acrylate, an alkali-soluble acrylic copolymer having a reactive unsaturated double bond in the side chain is obtained.

The epoxy carboxylate compound refers to a compound capable of synthesizing an epoxy compound and a carboxyl compound having an unsaturated double bond as a starting material. Examples of the epoxy compound that can be a starting material include glycidyl ethers, alicyclic epoxy resins, glycidyl esters, glycidylamines, or epoxy resins, but more specifically, methylglyci Dyl ether, ethyl glycidyl ether, butyl glycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neo Pentyl glycol diglycidyl ether, bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, bisphenol fluorene diglycidyl ether , Biphenol diglycidyl ether, tetramethylbiphenol glycidyl ether, trimethylolpropane triglycidyl ether, 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate or tert -Butyl glycidylamine is mentioned. Further, examples of the carboxyl compound having an unsaturated double bond include (meth)acrylic acid, crotonic acid, cinnamic acid, or α-cyanocinic acid.

You may make an epoxy carboxylate compound and a polybasic acid anhydride react, and you may adjust the acid value of an epoxy carboxylate compound. Examples of the polybasic acid anhydride include succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydro phthalic anhydride, itaconic anhydride, 3-methyltetrahydro phthalic anhydride, 4-methylhexahydro phthalic anhydride, trimellitic anhydride or maleic anhydride Mountain.

The amount of reactive unsaturated double bonds of the epoxy carboxylate compound by reacting a carboxyl group of the epoxy carboxylate compound reacted with the polybasic acid anhydride and a compound having an unsaturated double bond such as glycidyl (meth)acrylate It doesn't matter if you adjust it.

Urethaneization may be performed by reacting the hydroxy group of the epoxy carboxylate compound with a diisocyanate compound. As a diisocyanate compound, for example, hexamethylene diisocyanate, tetramethylxylene diisocyanate, naphthalene-1,5-diisocyanate, tolidene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, allyl cyan diisocyanate, or norbo Nandiisocyanate is mentioned.

The acid value of the compound (C) having an unsaturated double bond is preferably 30 to 250 mgKOH/g in order to make alkali solubility suitable for conditions. If the acid value is less than 30 mgKOH/g, the solubility of the soluble portion may decrease. On the other hand, when the acid value exceeds 250 mgKOH/g, the allowable development width may be narrowed. In addition, the acid value of the compound (C) having an unsaturated double bond can be measured in accordance with JIS K 0070 (1992).

The conductive paste of the present invention contains a photoinitiator (D). As a photoinitiator (D), for example, 1,2-octanedione-1-[4-(phenylthio)-2-(O-benzoyloxime)], 2,4,6-trimethylbenzoyl-diphenyl-phos Pin oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, ethanone-1-[9-ethyl-6-2(2-methylbenzoyl)-9H-carbazol-3-yl]- 1-(O-acetyloxime), benzophenone, o-benzoylbenzoic acid methyl, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'- Dichlorobenzophenone, 4-benzoyl-4'-methyldiphenylketone, dibenzyl ketone, fluolenone, 2,2'-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydro Roxy-2-methylpropiophenone, pt-butyldichloroacetophenone, thioxanthone, 2-methyl thioxanthone, 2-chloro thioxanthone, 2-isopropyl thioxanthone, diethyl thioxanthone, benzyl, Benzyldimethylketal, benzyl-β-methoxyethylacetal, benzoin, benzoinmethylether, benzoinbutylether, anthraquinone, 2-t-butylanthraquinone, 2-amylanthraquinone, β-chloranthraquinone, an Tron, benzanthrone, dibenzosverone, methyleneanthrone, 4-azidebenzalacetophenone, 2,6-bis(p-azidebenzylidene)cyclohexanone, 6-bis(p-azidebenzylidene) )-4-methylcyclohexanone, 1-phenyl-1,2-butanedione-2-(O-methoxycarbonyl)oxime, 1-phenyl-propanedione-2-(O-ethoxycarbonyl)oxime , 1-phenyl-propanedione-2-(O-benzoyl)oxime, 1,3-diphenyl-propanetrione-2-(O-ethoxycarbonyl)oxime, 1-phenyl-3-ethoxy-propane Trione-2-(O-benzoyl)oxime, Michler's ketone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, naphthalenesulfonyl chloride, quinolinesulfonyl chloride , N-phenylthioacridone, 4,4'-azobisisobutylonitrile, diphenyldisulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, 2,4-diethylthioxanthone, A combination of a photoreducing dye such as isopropyl thioxanthone, carbon tetrabromide, tribromophenyl sulfone, benzoin peroxide, eosin or methylene blue, and a reducing agent such as ascorbic acid or triethanolamine, but high light sensitivity Oxim S Ter system compounds are preferred.

The amount of the photoinitiator (D) added is preferably 0.05 to 30 parts by mass per 100 parts by mass of the compound (C) having an unsaturated double bond. When the amount added to 100 parts by mass of the compound (C) having an unsaturated double bond is 0.05 parts by mass or more, the curing density of the exposed area increases, and the film remaining ratio after development can be increased. On the other hand, if the addition amount to 100 parts by mass of the compound (C) having an unsaturated double bond is 30 parts by mass or less, excessive light absorption by the photopolymerization initiator (D) on the top of the coating film obtained by applying the conductive paste is suppressed. . As a result, the decrease in adhesion to the substrate is suppressed due to the inverse tapered shape of the produced conductive pattern.

The conductive paste of the present invention may contain a sensitizer together with the photoinitiator (D).

As a sensitizer, for example, 2,4-diethyl thioxanthone, isopropyl thioxanthone, 2,3-bis(4-diethylaminobenzal)cyclopentanone, 2,6-bis(4-dimethylamino Benzal)cyclohexanone, 2,6-bis(4-dimethylaminobenzal)-4-methylcyclohexanone, Michler's ketone, 4,4-bis(diethylamino)benzophenone, 4,4-bis(dimethyl Amino) chalcone, 4,4-bis (diethylamino) chalcone, p-dimethylamino cinnamylidene indone, p-dimethylamino benzylidene indone, 2-(p-dimethylaminophenylvinylene) isonaphthothiazole , 1,3-bis(4-dimethylaminophenylvinylene)isonaphthothiazole, 1,3-bis(4-dimethylaminobenzal)acetone, 1,3-carbonylbis(4-diethylaminobenzal)acetone , 3,3-carbonylbis (7-diethylaminocoumarin), N-phenyl-N-ethylethanolamine, N-phenylethanolamine, N-tolyldiethanolamine, dimethylaminobenzoic acid isoamyl, diethylaminobenzoic acid Isoamyl, 3-phenyl-5-benzoylthiotetrazole or 1-phenyl-5-ethoxycarbonylthiotetrazole.

The amount of the sensitizer added is preferably 0.05 to 10 parts by mass per 100 parts by mass of the compound (C) having an unsaturated double bond. When the amount added to 100 parts by mass of the compound (C) having an unsaturated double bond is 0.05 parts by mass or more, the light sensitivity is improved. On the other hand, when the addition amount to 100 parts by mass of the compound (C) having an unsaturated double bond is 10 parts by mass or less, excessive light absorption on the top of the coating film obtained by applying the conductive paste is suppressed. As a result, the decrease in adhesion to the substrate due to the inverted tapered shape of the produced conductive pattern is suppressed.

The conductive paste of the present invention contains a solvent (E). As the solvent (E), for example, N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone, dimethyl sulfoxide, 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 monobutyl ether acetate, triethylene glycol dimethyl ether or 2 ,2,4,-trimethyl-1,3-pentanediol monoisobutylate may be mentioned, but a solvent having a boiling point of 150°C or higher is preferable. When the boiling point is 150°C or higher, the volatilization of the solvent (E) is suppressed, and the thickening of the conductive paste can be suppressed.

The conductive paste of the present invention may contain additives such as non-photosensitive polymers or plasticizers, leveling agents, surfactants, silane coupling agents, antifoaming agents or pigments that do not have an unsaturated double bond in the molecule as long as the desired properties are not impaired. none.

Examples of the non-photosensitive polymer include an epoxy resin, a novolac resin, a phenol resin, a polyimide precursor, or a cyclic polyimide thereof.

As a plasticizer, dibutyl phthalate, dioctyl phthalate, polyethylene glycol, or glycerin is mentioned, for example.

As the leveling agent, a special vinyl polymer or a special acrylic polymer can be mentioned, for example.

As the silane coupling agent, for example, methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, 3-methacryloxypropyltrimethoxysilane, and 3-glycidoxypropyltrime Oxysilane or vinyl trimethoxysilane.

The conductive paste of the present invention is manufactured using a dispersing machine or a kneader such as a three-stage roller, a ball mill, or a planetary ball mill.

The method for producing a conductive pattern of the present invention is characterized in that the conductive paste of the present invention is applied onto a substrate, dried, exposed, and developed, and then cured at 100 to 300°C.

A coating film is obtained by applying the conductive paste of the present invention on a substrate.

As a substrate to which the conductive paste of the present invention is applied, for example, a polyethylene terephthalate film (hereinafter, ``PET film''), a polyimide film, a polyester film, an aramid film, an epoxy resin substrate, a polyetherimide resin substrate, and a polyether A ketone resin substrate, a polysulfone resin substrate, a glass substrate, a silicon wafer, an alumina substrate, an aluminum nitride substrate, a silicon carbide substrate, a decorative layer forming substrate, or an insulating layer forming substrate may be mentioned.

As a method of applying the conductive paste of the present invention to a substrate, for example, spin coating using a spinner, spray coating, roll coating, screen printing or coating using a blade coater, die coater, calender coater, meniscus coater or bar coater. Can be mentioned. The film thickness of the resulting coating film may be appropriately determined according to the method of application or the total solid concentration or viscosity of the conductive paste, but the film thickness after drying is preferably 0.1 to 50 µm. In addition, the film thickness can be measured using a stylus type step meter such as Surfcom (registered trademark) 1400 (manufactured by Tokyo Seimitsu Co., Ltd.). More specifically, it can be calculated by measuring the film thicknesses at three randomly selected positions with a stylus type step meter (immediate length: 1 mm, scanning speed: 0.3 mm/sec), and calculating their average values.

The obtained coating film is dried and the solvent is volatilized. As a method of drying the coating film to volatilize and remove the solvent, for example, heat drying or vacuum drying using an oven, a hot plate, or infrared rays or the like can be mentioned. The heating temperature is preferably 50 to 180°C, and the heating time is preferably 1 minute to several hours.

The dried coating film is exposed through a photolithography method through an arbitrary pattern forming mask. As a light source for exposure, i-line (365 nm), h-line (405 nm), or g-line (436 nm) of a mercury lamp is preferable.

The coated film after exposure is developed using a developer, and the unexposed portion is dissolved and removed to obtain a desired pattern. As a developer for alkali development, for example, tetramethylammonium hydroxide, diethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylamine, methylamine, dimethyl Amine, dimethylaminoethyl acetate, dimethylaminoethanol, dimethylaminoethyl methacrylate, cyclohexylamine, ethylenediamine, or aqueous solutions of hexamethylenediamine are mentioned, but in these aqueous solutions, N-methyl-2-pyrrolidone, Polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide or γ-butyrolactone, alcohols such as methanol, ethanol or isopropanol, ethyl lactate or propylene glycol monomethyl ether acetate, etc. Ketones, such as esters, cyclopentanone, cyclohexanone, isobutyl ketone, or methyl isobutyl ketone, or surfactant may be added.

As a developer for performing organic development, for example, N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide A polar solvent such as seed or hexamethylphosphotriamide, or a mixed solution of these polar solvents and methanol, ethanol, isopropyl alcohol, xylene, water, methylcarbitol or ethylcarbitol.

As a method of development, for example, a method of spraying a developer onto the coated film surface while the substrate is standing or rotating, a method of immersing the substrate in the developer, or a method of applying ultrasonic waves while immersing the substrate in the developer.

The pattern obtained by development may be rinsed with a rinse liquid. Examples of the rinse solution include water or an aqueous solution in which an alcohol such as ethanol or isopropyl alcohol or an ester such as ethyl lactate or propylene glycol monomethyl ether acetate is added to water or water.

The obtained pattern is cured at 100 to 300°C. The curing temperature is preferably 120 to 180°C. When the curing temperature is less than 100° C., the volumetric shrinkage of the resin component does not increase, and the specific resistance does not sufficiently decrease. On the other hand, when the curing temperature exceeds 300°C, a conductive pattern cannot be produced on a material such as a substrate having low heat resistance.

As a method of curing the obtained pattern, for example, heat drying with an oven, inner oven or hot plate, heat drying with an ultraviolet lamp, an infrared heater, an electromagnetic wave such as a halogen heater or a xenon flash lamp, or heat drying with a microwave, or vacuum drying. Can be mentioned. By heating, the hardness of the laminated pattern to be produced increases, cracking or peeling due to contact with other members can be suppressed, and adhesion with the substrate can be improved.

The touch panel of the present invention includes a conductive pattern formed of the conductive paste of the present invention and a transparent electrode made of ITO, and the transparent electrode and the conductive pattern are connected.

The conductive pattern produced by using the conductive paste of the present invention is suitably used as peripheral wiring for a touch panel provided with a transparent electrode made of ITO. As described above, since the carbon particles contained in the conductive paste have particularly good wettability with ITO among the transparent electrodes, carbon particles are collected at the interface between the conductive paste and ITO, and the number of contact points increases to increase the conductive path, such as high humidity, high temperature, etc. This is because it increases the effect of stably maintaining contact resistance even through environmental changes.

As a method of a touch panel, a resistive film type, an optical type, an electromagnetic induction type, or a capacitive type can be mentioned, for example. In the capacitive touch panel, since particularly fine wiring is required, the conductive paste of the present invention is more suitably used.

In addition, in the capacitive touch panel, since it is necessary to transmit an electric signal from the transparent electrode to the IC chip, it is necessary that at least a part of the peripheral wiring is formed on the transparent electrode. As described above, the conductive pattern manufactured by using the conductive paste of the present invention is more suitably used because it has excellent connection reliability with ITO.

In a touch panel having a conductive pattern manufactured by the manufacturing method of the present invention as its peripheral wiring, and the peripheral wiring having a pitch of 50 μm or less (wire width + wiring width), the edge width can be made thinner, Area can be widened.

Example

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to these.

The evaluation methods used in each Example and Comparative Example are as follows.

<Evaluation method of patterning property>

The conductive paste was applied onto the PET film so that the film thickness after drying became 7 µm, and the obtained coated film was dried in a drying oven at 100°C for 5 minutes. A linear group, that is, a light-transmitting pattern, arranged in a certain line and space (hereinafter, ``L/S'') as one unit, and the dried coated film through a photomask each having 9 types of units with different L/S values. It exposed and developed to obtain 9 types of patterns with different L/S values, respectively. Thereafter, all of the obtained nine patterns were cured in a drying oven at 140° C. for 30 minutes to obtain nine types of conductive patterns with different L/S values. The L/S value of each unit of the photomask is 500/500, 250/250, 100/100, 50/50, 40/40, 30/30, 25/ for line width (㎛)/interval (㎛) 25, 20/20, 15/15. The obtained conductive pattern was observed with an optical microscope. There was no residue between patterns, and the conductive pattern with the minimum value of L/S without pattern peeling was confirmed. The L/S value was taken as the developable L/S value. What became over-developed and the pattern disappeared was made into "pattern flow".

In addition, for exposure, wire exposure was performed at an exposure amount of 150 mJ/cm 2 (in terms of wavelength 365 nm) using an exposure apparatus (PEM-6M; manufactured by Union Kogaku Co., Ltd.), and development was performed with a 0.2 mass% Na ₂ CO ₃ solution. After immersing the substrate for 30 seconds, rinse treatment with ultrapure water was performed.

<Method of evaluating specific resistance>

The conductive paste was applied onto the PET film so that the film thickness after drying became 7 µm, and the obtained coated film was dried in a drying oven at 100°C for 5 minutes. The dried coating film was exposed and developed through a photomask having a light-transmitting pattern (A) shown in FIG. 1 to obtain a pattern. Thereafter, the obtained pattern was cured in a drying oven at 140° C. for 30 minutes to obtain a conductive pattern for measuring specific resistance. The line width of the obtained conductive pattern was 0.400 mm, and the line length was 80 mm.

In addition, exposure and development conditions were the same as the method for evaluating the patterning property. Each end of the obtained conductive pattern for specific resistance measurement was connected with an ohmmeter to measure the resistance value, and the specific resistance was calculated based on the following equation (1). It was called "insulation" that no conduction was seen.

Resistivity = resistance value × film thickness × line width / line length… (One).

<Method of evaluating connection reliability with transparent electrodes>

On the transparent conductive film in which the transparent electrode was entirely formed on the PET film, the conductive paste was applied so that the film thickness after drying became 7 µm, and the obtained coating film was dried in a drying oven at 100°C for 5 minutes. The dried coating film was exposed and developed through a photomask having a light-transmitting pattern (A) shown in FIG. 2 to obtain a pattern. Thereafter, the obtained pattern was cured in a drying oven at 140° C. for 30 minutes to obtain a sample for evaluation of connection reliability with a transparent electrode. The line width of the conductive pattern in the obtained sample was 0.100 mm, the line-to-line was 5 mm, and the terminal portion was circular with a diameter of 2 mm.

The terminal part of the conductive pattern in the obtained sample was connected with a tester, the initial resistance value was measured, and then stored for 500 hours in a constant temperature and humidity tank (LU-113; SPEC Co., Ltd.) at 85°C and 85% RH. . Thereafter, the terminal portion of the conductive pattern in the pulled out sample was connected with a tester, the resistance value after storage was measured, and the resistance change rate was calculated based on the following equation (2). A calculated resistance change rate of 1.30 or less was determined as A, a value greater than 1.30 and 1.50 or less was determined as B, and a value greater than 1.50 was determined as C.

Resistance change rate = resistance value after storage (after 500 hours)/initial resistance value… (2).

In addition, the measured initial resistance value and the resistance value after storage are strictly obtained by adding the resistance value of the conductive pattern and the resistance value of the transparent electrode to the value of the contact resistance between the conductive pattern and the transparent electrode. However, since the resistance value of the conductive pattern and the resistance value of the transparent electrode are very small compared to the value of the contact resistance, it is possible to evaluate the rate of change of the contact resistance as the initial resistance value and the resistance value after storage.

Materials used in each Example and Comparative Example are as follows.

[Metal particle (A)]

Ag particles with a volume average particle diameter of 1.0㎛

Au particles having a volume average particle diameter of 1.0 μm.

[Carbon particle (B)]

Carbon particles having a volume average particle diameter of the primary particles of 0.05 µm (the ratio of carbon to the entire particle: 99% by mass).

[Compound (C) having an unsaturated double bond]

(Monomer)

Light acrylate BP-4EA (hereinafter, "BP-4EA"; manufactured by Kyoeisha Chemical Co., Ltd.)

(Synthesis Example 1: Compound (C-1))

Copolymerization ratio (mass basis): ethyl acrylate (hereinafter referred to as "EA")/methacrylic acid 2-ethylhexyl (hereinafter referred to as "2-EHMA")/styrene (hereinafter referred to as "St")/glycidyl methacrylate (Hereinafter "GMA") / acrylic acid (hereinafter "AA") = 20/40/20/5/15

150 g of DMEA was put into a reaction vessel in a nitrogen atmosphere, and the temperature was raised to 80°C using an oil bath. A mixture consisting of 20 g of EA, 40 g of 2-EHMA, 20 g of St, 15 g of AA, 0.8 g of 2,2'-azobisisobutylonitrile and 10 g of DMEA was added dropwise over 1 hour. After completion of the dropwise addition, the polymerization reaction was further carried out for 6 hours. After that, 1 g of hydroquinone monomethyl ether was added to stop the polymerization reaction. Then, a mixture consisting of 5 g of GMA, 1 g of triethylbenzylammonium chloride and 10 g of DMEA was added dropwise over 0.5 hours. After completion of the dropwise addition, an addition reaction was performed for another 2 hours. Unreacted impurities were removed by purifying the obtained reaction solution with methanol, and further, the compound (C-1) was obtained by vacuum drying for 24 hours. The acid value of the obtained compound (C-1) was 103 mgKOH/g.

(Synthesis Example 2: Compound (C-2))

Copolymerization ratio (mass basis): Ethylene oxide-modified bisphenol A diacrylate (FA-324A; Hitachi Kasei Kogyo Co., Ltd.)/EA/GMA/AA=60/25/10/5

150 g of DMEA was put into a reaction vessel in a nitrogen atmosphere, and the temperature was raised to 80°C using an oil bath. A mixture consisting of 60 g of ethylene oxide-modified bisphenol A diacrylate, 25 g of EA, 5 g of AA, 0.8 g of 2,2'-azobisisobutylonitrile and 10 g of DMEA was added dropwise over 1 hour. After completion of the dropwise addition, the polymerization reaction was further carried out for 6 hours. After that, 1 g of hydroquinone monomethyl ether was added to stop the polymerization reaction. Subsequently, a mixture consisting of 10 g of GMA, 1 g of triethylbenzylammonium chloride and 10 g of DMEA was added dropwise over 0.5 hours. After completion of the dropwise addition, an addition reaction was performed for another 2 hours. The resulting reaction solution was purified with methanol to remove unreacted impurities, and further vacuum-dried for 24 hours to obtain a compound (C-2) having a carboxyl group and an unsaturated double bond. The acid value of the obtained compound (C-2) was 1.4 mgKOH/g.

(Synthesis Example 3: Compound (C-3))

123 g of RE-310S (manufactured by Nihon Kayaku Co., Ltd.), 47 g of AA, 0.3 g of hydroquinone monomethyl ether and 0.5 g of triphenylphosphine were added to the reaction solution in a nitrogen atmosphere, and at a temperature of 98°C Compound (C-3) was obtained by reacting until the acid value of the reaction solution became 0.5 mgKOH/g or less. The acid value of the obtained compound (C-3) was 0.4 mgKOH/g.

(Synthesis Example 4: Compound (C-4))

In the reaction solution in a nitrogen atmosphere, 164 g of carbitol acetate, 287 g of EOCN-103S (manufactured by Nihon Kayaku Co., Ltd.), 96 g of AA, 2 g of 2,6-di-tert-butyl-p-cresol and 2 g of tree Phenylphosphine was added and reacted at a temperature of 98° C. until the acid value of the reaction solution became 0.5 mgKOH/g or less, thereby obtaining an epoxy carboxylate compound. Subsequently, 57 g of carbitol acetate and 67 g of tetrahydrophthalic anhydride were added to the reaction solution, followed by reaction at 95° C. for 4 hours to obtain compound (C-4). The acid value of the obtained compound (C-4) was 104 mgKOH/g.

(Synthesis Example 5: Compound (C-5))

In a reaction vessel in a nitrogen atmosphere, 123 g of RE-310S (manufactured by Nihon Kayaku Co., Ltd.), 47 g of AA, 0.3 g of hydroquinone monomethyl ether and 0.5 g of triphenylphosphine were added, and at a temperature of 98° C. The reaction was carried out until the acid value of the reaction solution became 0.5 mgKOH/g or less to obtain an epoxy carboxylate compound. Thereafter, 252 g of carbitol acetate, 89 g of 2,2-bis(dimethyrol)-propionic acid, 0.4 g of 2-methylhydroquinone and 47 g of spiro glycol were added to the reaction solution, and the temperature was raised to 45°C. To this solution, 162 g of trimethylhexamethylene diisocyanate was gradually added dropwise so that the reaction temperature did not exceed 65°C. After completion of the dropwise addition, the reaction temperature was raised to 80° C., and reacted for 6 hours until absorption in the vicinity of 2250 cm ^-1 disappeared by infrared absorption spectrometry to obtain compound (C-5). The acid value of the obtained compound (C-5) was 80.0 mgKOH/g.

(Synthesis Example 6: Compound (C-6))

In a reaction vessel in a nitrogen atmosphere, 300 g of Denacol EX-203 (manufactured by Nagase Chemtex Co., Ltd.) acrylic acid adduct (molecular weight: 368), 500 g of DMEA, 0.5 g of 2-methylhydroquinone and 200 g of 2,2 -Bis(hydroxymethyl)propionic acid was added, and the temperature was raised to 45°C. To this solution, 201.3 g of toluene diisocyanate was gradually added dropwise so that the reaction temperature did not exceed 50°C. After the dropwise addition, the reaction temperature was raised to 80° C., and the reaction was carried out for 6 hours until absorption in the vicinity of 2250 cm ^-1 disappeared by an infrared absorption spectrum measurement method. To this solution, 120 g of glycidyl methacrylate was added, the temperature was raised to 95°C, and reacted for 6 hours to obtain compound (C-6). The acid value of the obtained compound (C-6) was 83 mgKOH/g.

[Photopolymerization initiator (D)]

IRGACURE (registered trademark) OXE-01 (hereinafter referred to as ``OXE-01''; manufactured by Chiba Japan)

IRGACURE (registered trademark) 369 (hereinafter referred to as "IC-369"; manufactured by Chiba Japan Co., Ltd.).

[Solvent (E)]

DMEA (manufactured by Tokyo Kasei High School Co., Ltd.).

[Transparent electrode]

ITO film (manufactured by Nito Denko Co., Ltd.)

Silver nano wire film (manufactured by Hitachi Chemical Co., Ltd.).

(Example 1)

In a 100 mL clean bottle, 10.0 g of compound (C-1), 0.50 g of OXE-01, 5.0 g of DMEA, and 2.0 g of BP-4EA were put, and the rotating-orbital vacuum mixer "Awatori Rentaro" ARE-310 It mixed with (registered trademark; manufactured by Shinki Co., Ltd.) to obtain 17.5 g of a resin solution (solid content 71.4 mass%).

The obtained 17.5 g of resin solution, 85.0 g of Ag particles and 2.5 g of carbon particles (B) were mixed, and kneaded using a three-stage roller mill (EXAKT M-50; manufactured by EXAKT) to obtain 105.0 g of a conductive paste. .

Using the obtained conductive paste, the patterning property, specific resistance, and connection reliability with ITO of the conductive pattern were evaluated, respectively. The value of the developable L/S as an evaluation index of patterning property was 15/15 µm, and it was confirmed that a good patterning was performed. The specific resistance of the conductive pattern was 5.5×10 ^-5 Ωcm. The resistance change rate in the connection reliability evaluation with ITO was 1.03, and it was favorable.

(Examples 2 to 14)

The conductive paste of the composition shown in Table 1 was prepared in the same manner as in Example 1, and the results of evaluation in the same manner as in Example 1 are shown in Table 2.

(Comparative Examples 1 to 4)

The conductive paste of the composition shown in Table 1 was prepared in the same manner as in Example 1, and the results of evaluation in the same manner as in Example 1 are shown in Table 2.

In all of the conductive pastes of Examples 1 to 14, a conductive pattern excellent in patterning property, specific resistance, and connection reliability with ITO could be produced. On the other hand, in the conductive paste of Comparative Example 1, the connection reliability with ITO is lowered under high temperature and high humidity, and in the conductive pastes of Comparative Examples 2 and 4, a pattern flows during development, so that fine wiring cannot be manufactured, and the conductive paste of Comparative Example 3 The conductive pattern prepared by using did not show conductivity.

(Industrial availability)

The conductive paste of the present invention can be suitably used for manufacturing a conductive pattern such as peripheral wiring for a touch panel.

A: Light transmission pattern

Claims (6)

Metal particles (A),
Carbon particles (B),
Compound (C) having an unsaturated double bond,
Photopolymerization initiator (D), and
Contains a solvent (E),
The mass ratio of the metal particles (A) to the carbon particles (B) is 100 to 1900, the photopolymerization initiator (D) contains an oxime ester compound, and the acid value of the compound (C) having an unsaturated double bond A conductive paste for forming a conductive pattern for a touch panel having a transparent electrode of 30 to 250 mgKOH/g and made of ITO. The method of claim 1,
The volume average particle diameter of the metal particles (A) is 0.1 to 10 μm, and
The conductive paste, wherein the volume average particle diameter of the primary particles of the carbon particles (B) is 0.005 to 0.5 µm. delete A touch panel comprising a conductive pattern formed of the conductive paste according to claim 1 or 2, and a transparent electrode made of ITO, and the transparent electrode and the conductive pattern are connected. The method of claim 4,
The conductive pattern is a peripheral wiring of the touch panel, a touch panel. A method for producing a conductive pattern, wherein the conductive paste according to claim 1 or 2 is applied onto a substrate, dried, exposed, and developed, and then cured at 100 to 300°C.

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