CN111512398A - Conductive paste - Google Patents
Conductive paste Download PDFInfo
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- CN111512398A CN111512398A CN201980006714.4A CN201980006714A CN111512398A CN 111512398 A CN111512398 A CN 111512398A CN 201980006714 A CN201980006714 A CN 201980006714A CN 111512398 A CN111512398 A CN 111512398A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
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Abstract
Provided is a conductive paste having high suitability for forming fine wiring by a laser etching method, a micro-contact printing method, an inverse printing method, or the like. A conductive paste characterized in that a carboxyl group-containing urethane resin which is an addition polymerization reaction product of a diol compound having a bisphenol structure, a carboxyl group-containing dihydroxy compound, and an isocyanate compound is used as a binder resin in a conductive paste containing at least a conductive filler, an organic solvent, and the binder resin.
Description
Technical Field
The present invention has an object to provide a conductive paste which is suitably used for forming fine wiring formed in proximity to a transparent conductive film, which is used in a touch panel or the like, and which can be used for manufacturing electrode circuit wiring having high surface smoothness without any problem in forming a TFT substrate electrode in a printed electronics technology.
Background
In recent years, high performance and miniaturization of electronic devices including a transparent touch panel, such as a mobile phone, a notebook computer, and an electronic book, have been rapidly advanced. In order to achieve higher performance and smaller size of these electronic devices, electronic components mounted thereon are required to be smaller in size, higher in performance, and higher in integration, and further, electrode circuit wirings for interconnecting these electronic components are required to be more densely provided. In addition to the resistive film type in which the number of electrode circuit wirings is small, the capacitive type in which the number of electrode circuit wirings is dramatically increased has been rapidly spread in recent years as a transparent touch panel type, and from such a viewpoint, the density of the electrode circuit wirings is strongly required to be increased. In addition, in order to increase the display screen size and to meet the demand for a smaller frame portion in which electrode circuit wiring is arranged, the density of the electrode circuit wiring is also increased from the viewpoint of a desire for further reduction in size due to the demand for commercial design. In order to satisfy the above requirements, a technique capable of performing high-density arrangement better than conventional electrode circuit wiring is required.
The arrangement density of the electrode circuit wiring lines in the frame portion of the resistive transparent touch panel is about 200 μm (hereinafter, abbreviated as L/S — 200/200 μm) or more in the width of each line and pitch in the planar direction, and conventionally, it has been formed by screen printing of a conductive paste, and in the capacitive touch panel, L/S is required to be about 100/100 μm or less, and further, L/S is required to be 50/50 μm or less, and it is difficult to adapt to the electrode circuit wiring line forming technique by screen printing.
However, the most typical example of the photolithography method is a method using a photosensitive resist, and generally, a photosensitive resist is applied to a copper foil portion of a surface substrate on which a copper foil layer is formed, a desired pattern is exposed by a method such as photomask or direct drawing with laser, and the photosensitive resist is developed, and then the copper foil portion other than the desired pattern is dissolved and removed with a reagent to form a fine line pattern of the copper foil.
Patent document 1 discloses a pattern forming method including: a coating step of coating a slurry comprising an inorganic powder, a carboxyl group-containing resin, a glass frit, and a solvent on a substrate; a drying step of drying the applied slurry to form a dried coating film; a laser irradiation step of drawing a pattern on the dried coating film by laser irradiation; and a developing step of developing the pattern with an alkali solution. This proposal differs from general lithography in that patterning is performed by removing a resin component in a paste resin component with a laser beam, but cannot be said to solve the drawbacks of the conventional lithography in that cleaning with an alkali solution is required.
Patent document 2 discloses a conductive pattern forming method including: a coating step of coating a slurry containing an AlN powder, a glass frit and a solvent on a substrate; a drying step of drying the applied slurry to form a dried coating film; a laser drawing step of drawing a conductive pattern on the dried coating film by irradiation with a laser beam; and a developing step of removing the non-irradiated portion of the laser beam in the dried coating film using a developing solution. This invention is similar to the above-described technique in that a laser is used for patterning, and cannot be said to be a technique for eliminating the drawbacks of the conventional photolithography in that cleaning is necessary.
In recent years, a technique for manufacturing an active element such as a transistor by printing has been realized in printed electronics. In such applications, uniformity of film thickness and reduction in film thickness are required together with fine wiring. In the printing technique, a reverse printing method, a micro-contact printing method, a screen offset printing method, an ink jet offset printing method, a pad printing method, and the like are being applied, instead of the conventional screen printing or gravure printing, and the conventional conductive material is hardly applied to such a new printing method.
Documents of the prior art
Patent document
Patent document 1: japanese patent application laid-open No. 2010-237573
Patent document 2: japanese patent laid-open publication No. 2011-181338
Disclosure of Invention
Problems to be solved by the invention
The present invention aims to provide a conductive paste suitable for forming fine wiring formed close to a transparent conductive film used in a touch panel or the like, and to provide a conductive paste which can produce electrode circuit wiring having high surface smoothness without any problem when forming a TFT base electrode, and further to provide a conductive paste which is widely suitable for a novel printing technique for use in a printed electronics technique.
The present inventors intensively studied a conductive paste in which an electrode circuit wiring having high surface smoothness is disposed, and as a result, found a conductive paste suitable for forming a conductive film. That is, the present invention includes the following configurations.
[1] A conductive paste comprising at least a conductive filler, an organic solvent and a binder resin, wherein a carboxyl group-containing urethane resin is used as the binder resin,
the carboxyl group-containing polyurethane resin is an addition polymerization reaction product of a diol compound having a bisphenol structure, a carboxyl group-containing dihydroxy compound, and an isocyanate compound.
[2] The conductive paste according to item [1], wherein the content of the organic solvent is 5 to 100 parts by mass with respect to 100 parts by mass of the conductive filler, and the content of the binder resin is 5 to 25 parts by mass with respect to 100 parts by mass of the conductive filler.
[3] The conductive paste according to [1] or [2], wherein the diol compound having a bisphenol structure is an alkylene oxide adduct of bisphenol A.
[4] The conductive paste according to any one of [1] to [3], wherein the molecular weight of the diol compound having a bisphenol structure is 500 or less.
[5] The conductive paste according to any one of [1] to [4], characterized in that the conductive filler is a metal powder having a median particle diameter D50 of 0.8 μm or more and less than 2.0 μm as measured by a laser diffraction method.
Effects of the invention
The conductive paste of the present invention is a substance: by using a carboxyl group-containing urethane resin containing a diol compound having a bisphenol structure in the skeleton as an adhesive resin, a conductive film having excellent adhesion to a substrate after a wet heat test can be formed by using a coating film formed by screen printing having a small surface roughness Ra, specifically, Ra of 0.4 μm or less.
Detailed Description
The conductive paste of the present invention contains a binder resin, a conductive filler and an organic solvent as essential components.
< adhesive resin >
As the adhesive resin in the present invention, a carboxyl group-containing polyurethane resin obtained by addition polymerization of a diol compound having a bisphenol structure, a carboxyl group-containing dihydroxy compound, and an isocyanate compound is used.
The adhesive resin of the present invention preferably has a number average molecular weight of 3,000 to 100,000 and an acid value of 20 to 500 meq/kg.
As the diol compound having a bisphenol structure in the present invention, bisphenol A, bisphenol F, bisphenol S, an alkylene oxide adduct of bisphenol A, an alkylene oxide adduct of bisphenol F, an alkylene oxide adduct of bisphenol S, a mixture or a polycondensate of these compounds can be used.
In the present invention, bisphenol A/F copolymer type, bisphenol S type, and bisphenol A/S copolymer type can be used. Among them, from the viewpoint of the adhesion of the substrate and the flexibility of the obtained coating film, and further from the viewpoint of the transferability via a blanket in a printing technique including reverse printing, microcontact printing, and other offset printing steps, it is preferable to use an alkylene oxide adduct of bisphenol a.
The acid value of the adhesive resin in the present invention is preferably 20 meq/kg or more and 500 meq/kg or less, and more preferably 30 meq/kg or more and 200 meq/kg or less. The acid value in the organic component increases the adhesion to the substrate, particularly after the wet heat test, but if it is too high, hydrolysis of the organic component may be promoted, and the conductivity and the adhesion to the substrate may be impaired. In addition, it is possible that the migration resistance is also adversely affected.
In order to keep the acid value of the adhesive resin within a predetermined range, a carboxyl group-containing dihydroxy compound is used.
Examples of the dihydroxy compound having a carboxyl group include 2, 2-dimethylolpropionic acid, 2-dimethylolbutyric acid, bicine, and bicine.
Examples of the isocyanate compound include 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, p-phenylene diisocyanate, 4 ' -diphenylmethane diisocyanate, m-phenylene diisocyanate, 3 ' -dimethoxy-4, 4 ' -biphenyl diisocyanate, 2, 6-naphthalene diisocyanate, 3 ' -dimethyl-4, 4 ' -biphenyl diisocyanate, 4 ' -diphenylene diisocyanate, 4 ' -diisocyanatodiphenyl ether, 1, 5-naphthalene diisocyanate, m-xylylene diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate.
The content ratio of each of the diol compound having a bisphenol structure, the dihydroxy compound having a carboxyl group, and the isocyanate compound is preferably: the amount of the carboxyl group-containing dihydroxy compound and the amount of the isocyanate compound are 3 to 10 parts by mass and 60 to 80 parts by mass, respectively, per 100 parts by mass of the diol compound having a bisphenol structure. By setting the range, effects of adhesion and heat resistance can be obtained.
The molecular weight of the diol compound having a bisphenol structure is preferably 500 or less, more preferably 400 or less, and still more preferably 350 or less. The lower limit is not particularly limited, but is preferably 200 or more, more preferably 300 or more, and still more preferably 300 or more. By setting the concentration of the urethane group within the above range, the effect of excellent adhesion can be obtained.
The content of the adhesive resin is preferably 5 to 25 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the conductive filler. When the amount is within the above range, the conductivity and the adhesion to the substrate are improved.
In the present invention, other resins may be mixed as an auxiliary binder resin. The type of the binder resin is preferably a thermoplastic resin, and is not particularly limited, and examples thereof include polyester resins, epoxy resins, phenoxy resins, polyamide resins, polyamideimide resins, polycarbonate resins, polyurethane resins, phenol resins, acrylic resins, polystyrene, styrene-acrylic resins, styrene-butadiene copolymers, phenol resins, polyethylene resins, polycarbonate resins, phenol resins, alkyd resins, styrene-acrylic resins, styrene-butadiene copolymer resins, polysulfone resins, polyethersulfone resins, vinyl chloride-vinyl acetate copolymer resins, ethylene-vinyl acetate copolymer resins, polystyrene, silicone resins, fluorine resins, and the like, and these resins may be used alone or as a mixture of 2 or more kinds. Preferably 1 or 2 or more selected from the group consisting of polyester resin, polyurethane resin, epoxy resin, phenoxy resin, vinyl chloride resin, and cellulose derivative resin.
The number average molecular weight of the adhesive resin in the present invention is not particularly limited, and is preferably 3,000 to 100,000, and more preferably 8000 to 50000. When the number average molecular weight is too low, the resulting conductive film is not preferable in terms of durability and moist heat resistance. On the other hand, if the number average molecular weight is too high, the cohesive force of the resin increases, and the durability and the like as a conductive film are improved, but the surface smoothness may be significantly deteriorated.
The glass transition temperature of the adhesive resin in the present invention is preferably 60 ℃ or higher, and more preferably 65 ℃ or higher. If the glass transition temperature is low, the reliability of the conductive film after wet heating may be lowered, and the viscosity may cause the migration of the paste-containing component to the contact side during use due to the reduction of the induced surface hardness, thereby lowering the reliability of the conductive film. On the other hand, the glass transition temperature of the adhesive resin is preferably 150 ℃ or lower, more preferably 120 ℃ or lower, and further preferably 100 ℃ or lower, in view of printability, adhesiveness, solubility, and paste viscosity.
< conductive Filler >
As the conductive filler in the present invention, metal powder, carbon-based particles, inorganic or organic particles coated with a metal, a conductive polymer, a mixed material containing a conductive polymer, or the like can be used. The conductive filler mainly used in the present invention is metal powder. As the metal powder, noble metals such as gold, silver, platinum, rhodium and ruthenium, base metals such as copper, nickel and aluminum, noble metal-coated base metal particles such as silver-coated copper powder and silver-coated nickel powder, and alloy powders such as brass, bronze, cupronickel, phosphor bronze, monel, invar, nickel silver and silver copper alloy can be used.
Usually, the metal powder most used as the conductive paste is silver powder, and silver powder can be also preferably used in the present invention. The shape of the silver powder used in the present invention is not particularly limited. Examples of the conventionally known shape include a flaky (scaly), spherical, dendritic (dendritic), and a shape in which 1-time spherical particles are aggregated in a 3-dimensional state (aggregated state) as described in japanese patent laid-open No. 9-306240.
The silver powder used in the present invention preferably has a median particle diameter (D50) of 0.6 μm or more. More preferably 0.8 μm or more. In addition, a preferred upper limit of the median diameter is less than 2.0. mu.m. More preferably 1.5 μm or less, and still more preferably 1 μm or less. When the median diameter is out of the predetermined range, a conductive path cannot be formed satisfactorily, and the conductivity may be deteriorated. Further, if the particle diameter is too small, the particles tend to aggregate, and as a result, dispersion may become difficult. If the amount exceeds the upper limit, the smoothness of the printed coating film may be reduced.
The median diameter (D50) in the present invention is determined from a cumulative particle size distribution measured in a total reflection mode using a laser diffraction scattering particle size distribution measuring apparatus (MICROTRAC HRA, manufactured by japan ltd.).
The tap density of the silver powder used in the present invention is preferably 2.0g/cm3The above. When the tap density is low, the silver filling degree in the coating film becomes low, and as a result, the surface smoothness becomes poor. The upper limit of the tap density is not particularly limited, but is preferably 9.0g/cm3More preferably 7.5g/cm3More preferably 5.5g/cm3。
< organic solvent >
The organic solvent that can be used in the present invention is not particularly limited, and the boiling point is preferably 100 ℃ or more and less than 300 ℃, more preferably 150 ℃ or more and less than 280 ℃ from the viewpoint of maintaining the volatilization rate of the organic solvent in an appropriate range. The conductive paste of the present invention is typically prepared by dispersing the thermoplastic resin, silver powder, organic solvent, and other components as needed, using a three-roll mill or the like, but in this case, if the boiling point of the organic solvent is too low, the solvent volatilizes during dispersion, and the ratio of the components constituting the conductive paste may change. On the other hand, if the boiling point of the organic solvent is too high, a large amount of the solvent may remain in the coating film depending on the drying conditions, and the reliability of the coating film may be lowered.
In addition, as the organic solvent that can be used in the present invention, it is preferable that the binder is a soluble organic solvent that can well disperse the conductive filler. Specific examples thereof include diethylene glycol ethyl ether acetate (EDGAC), ethylene glycol butyl ether acetate (BMGAC), diethylene glycol butyl ether acetate (BDGAC), cyclohexanone, toluene, isophorone, γ -butyrolactone, benzyl alcohol, a mixture of Solvesso100, 150, 200 manufactured by exxon chemical, propylene glycol monomethyl ether acetate, adipic acid, succinic acid, and dimethyl ester of glutaric acid (for example, DBE manufactured by dupont), terpineol, and the like.
The content of the organic solvent is preferably 5 to 100 parts by mass, and more preferably 10 to 50 parts by mass, based on 100 parts by mass of the conductive filler. If the content of the organic solvent is too high, the viscosity of the paste becomes too low, and sagging tends to occur during fine line printing. On the other hand, if the content of the organic solvent is too low, the viscosity of the paste becomes extremely high, and the screen printing property may be significantly reduced when forming a conductive film.
In the conductive paste of the present invention, a carbon-based filler may be added. Examples of the carbon-based filler include carbon black, graphite powder, ketjen black, carbon nanotubes, graphene, fullerene, and carbon nanohorns. The content of the carbon-based filler is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 2 parts by weight, based on 100 parts by weight of the silver powder.
The following inorganic substances may be added to the conductive paste of the present invention. As the inorganic substance, various carbides such as silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, diamond carbon lactam, and the like; various nitrides such as boron nitride, titanium nitride, and zirconium nitride, and various borides such as zirconium boride; various oxides such as titanium oxide (titania), calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica, fumed silica (for example, Aerosil manufactured by Aerosil corporation of japan), colloidal silica, and the like; various titanic acid compounds such as calcium titanate, magnesium titanate, and strontium titanate; sulfides such as molybdenum disulfide; various fluorides such as magnesium fluoride and carbon fluoride; various metal soaps such as aluminum stearate, calcium stearate, zinc stearate, and magnesium stearate; further, talc, bentonite, talc, calcium carbonate, bentonite, kaolin, glass fiber, mica, and the like can be used. By adding these inorganic substances, printability and heat resistance can be improved, and further, mechanical properties and long-term durability can be improved. Among these, fumed silica is preferable in the conductive paste of the present invention from the viewpoint of imparting durability and printability, particularly screen printability.
The conductive paste of the present invention may contain, as additives, a dispersant, a surface conditioner, an antifoaming agent, and a rheology control agent. Further, carbodiimide, epoxy resin, or the like may be appropriately mixed. These may be used alone or in combination. These substances are sometimes added to the slurry to change the rheology of the slurry and improve the surface smoothness.
As the dispersant, a known dispersant can be used. Further, there may be mentioned monocarboxylic acids such as lauric acid, myristic acid, palmitic acid, maltonic acid and stearic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and 2, 6-naphthalenedicarboxylic acid, dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid and azelaic acid, dicarboxylic acids having 12 to 28 carbon atoms such as maleic acid and dimer acid, alicyclic dicarboxylic acids such as 1, 4-cyclohexanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid, 1, 2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 2-methylhexahydrophthalic anhydride, dicarboxyhydrobisphenol A, dicarboxyhydrobisphenol S, dimer acid, hydrogenated naphthalenedicarboxylic acid and tricyclodecanedicarboxylic acid, alicyclic dicarboxylic acids such as dicarboxylic acid, Hydroxycarboxylic acids such as hydroxybenzoic acid and lactic acid. Further, there may be mentioned tribasic or higher carboxylic acids such as trimellitic anhydride and pyromellitic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and carboxylic diols such as dimethylolbutyric acid and dimethylolpropionic acid.
In the present invention, among these, aliphatic monocarboxylic acids and aliphatic dicarboxylic acids which are solid at 25 ℃ are preferably used as the dispersant. Specifically, dicarboxylic acids such as lauric acid, myristic acid, palmitic acid, maltobionic acid, stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, and azelaic acid, and maleic acid can be exemplified.
In the present invention, among these solid fatty acids, a compound having a melting point at 60 to 150 ℃ is preferable as the dispersant. Such a dispersant is precipitated while the solvent is volatilized under the temperature condition at the time of curing the slurry, but at the same time, it liquefies by itself reaching the melting point, and exerts an effect of smoothing the cured film of the slurry.
As other surface conditioner, defoaming agent, leveling agent, and rheology control agent in the present invention, known additives used in ink or slurry may be used as needed.
< curing agent >
In the conductive paste of the present invention, a curing agent capable of reacting with the adhesive resin may be mixed to such an extent that the effects of the present invention are not impaired. When a curing agent is mixed, the curing temperature is increased, and the load on the production process may increase, but the moist heat resistance of the coating film is expected to be improved by crosslinking due to heat generated during drying of the coating film.
The type of the curing agent that can react with the adhesive resin of the present invention is not limited, but an isocyanate compound and/or an epoxy resin is particularly preferable in view of adhesion, bending resistance, curability, and the like. Further, it is preferable to use an isocyanate compound in which an isocyanate group is blocked because storage stability is improved. Examples of the curing agent other than the isocyanate compound include known compounds such as amino resins such as methylated melamine, butylated melamine, benzoguanamine and urea resins, acid anhydrides, imidazoles and phenol resins. These curing agents may be used in combination with a known catalyst or accelerator selected according to the kind thereof. The amount of the curing agent to be mixed is not particularly limited as long as the effects of the present invention are not impaired, but is preferably 0.5 to 50 parts by mass, more preferably 1 to 30 parts by mass, and still more preferably 2 to 20 parts by mass, based on 100 parts by mass of the adhesive resin.
Examples of the isocyanate compound which can be mixed with the conductive paste of the present invention include aromatic or aliphatic diisocyanates, polyisocyanates having a valence of 3 or more, and any of low molecular weight compounds and high molecular weight compounds, for example, aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, aromatic diisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, dimer acid diisocyanate and isophorone diisocyanate, or trimers of these isocyanate compounds, as well as compounds containing a terminal isocyanate group obtained by reacting an excess amount of these isocyanate compounds with low molecular active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine and triethanolamine, or various polyester polyols, polyether polyols and polyamide active hydrogen compounds, as well as blocking agents for isocyanate groups such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, chlorocresol, chloroxylenol, chloroketoxime, aromatic lactams such as chlorobutanol, ketoxime, and the like, and.
Examples of the epoxy compound used as the curing agent in the present invention include glycidyl ether types such as bisphenol a glycidyl ether, bisphenol S glycidyl ether, novolac glycidyl ether, and brominated bis, glycidyl ester types such as glycidyl hexahydrophthalate and dimer acid glycidyl ester, triglycidyl isocyanurate, and alicyclic or aliphatic epoxides such as 3, 4-epoxycyclohexylmethyl carboxylate, epoxidized polybutadiene, and epoxidized soybean oil, and one kind may be used alone, or two or more kinds may be used in combination. Among these, bisphenol a glycidyl ethers are most preferable from the viewpoint of curability, and among these, bisphenol a glycidyl ethers having a molecular weight of less than 3000 and 2 or more glycidyl ether groups in one molecule are more preferable.
The viscosity of the conductive paste of the present invention is not particularly limited, and may be appropriately adjusted according to the method of forming the coating film. For example, when the conductive paste is applied to a substrate by screen printing, the viscosity of the conductive paste is preferably 100 dpas or more, and more preferably 150 dpas or more, in terms of the printing temperature. The upper limit is not particularly limited, but if the viscosity is too high, the surface smoothness may be reduced.
The conductive paste of the present invention preferably has an F value of 60 to 95%, more preferably 75 to 95%, wherein the F value is a value representing a mass part of the filler per 100 mass parts of the total solid content contained in the paste, (mass part of the filler per mass part of the solid content) × 100. the mass part of the filler herein refers to a mass part of the conductive filler, and the mass part of the solid content refers to a mass part of the component other than the solvent, including all of the conductive filler, the organic component, the other curing agent and the additive.
The conductive paste of the invention is prepared from ISO 1524: the dispersity of Grind Gage described in 2013 should be 10 μm or less. When the dispersion degree exceeds this range, abnormal protrusions are increased on the surface of the conductive film obtained from the slurry, and the definition of fine lines by laser etching is deteriorated.
As described above, the conductive paste of the present invention can be prepared by dispersing the organic component, silver powder, organic solvent, and other components as necessary using a three-roll mill or the like. Here, a more specific example of the manufacturing procedure is shown. The adhesive resin is first dissolved in an organic solvent. Thereafter, silver powder, a dispersant, and other additives added as needed are added, and the mixture is dispersed by a double planetary mixer, a dissolver, a planetary mixer, or the like. Then, the mixture was dispersed by a three-roll mill to obtain a conductive paste. The conductive paste thus obtained may be filtered as necessary. There is no problem in dispersing using other dispersing machines such as a bead mill, a kneader, an extruder, etc.
In the present invention, it is preferable to use a dispersant which is solid at 25 ℃ and to mix a solvent solution in which silver powder and a binder resin are dispersed and a dispersant.
In the present invention, the materials are mixed and dispersed and then filtered. The mesh of the filter for filtering the conductive paste is not particularly limited, but is preferably a filter of 25 μm or less, more preferably 20 μm or less, and most preferably 15 μm or less. When a filter having a mesh of more than 25 μm is used, it is impossible to remove the non-dispersed matter, coarse particles, foreign matter, etc. of the conductive powder, and short-circuiting occurs between the fine lines after etching, resulting in deterioration of the yield.
On the other hand, the mesh is preferably 1 μm or more, and if it is made finer than this value, the filtration rate is significantly reduced depending on the particle diameter of the silver powder, and the filter is finally clogged. As a result, the filter replacement times increase, and the production efficiency significantly decreases.
The conductive film of the present invention can be formed by forming a coating film by applying or printing the conductive paste of the present invention on a substrate, and then drying the coating film by volatilizing an organic solvent contained in the coating film. The method of applying or printing the conductive paste on the substrate is not particularly limited, and the method can be applied to all printing methods such as gravure printing, offset printing, relief printing, ink jet printing, reverse printing, microcontact printing, and the like, but printing by a screen printing method is particularly preferable in terms of the ease of the process and the technique which is becoming popular in the industry of forming circuits using conductive paste.
The step of volatilizing the organic solvent is preferably performed at normal temperature and/or under heating. The heating temperature is preferably 80 ℃ or higher, more preferably 100 ℃ or higher, and still more preferably 110 ℃ or higher, because the dried conductive film has good conductivity, adhesiveness, and surface hardness. From the viewpoint of heat resistance of the transparent conductive layer of the base and energy saving in the production process, the heating temperature is preferably 150 ℃ or lower, more preferably 135 ℃ or lower, and still more preferably 130 ℃ or lower. When the conductive paste of the present invention is mixed with a curing agent, a curing reaction proceeds when the step of volatilizing the organic solvent is performed under heating.
The thickness of the conductive film of the present invention may be set to an appropriate thickness according to the application. However, from the viewpoint of satisfactory conductivity of the conductive film after drying, the thickness of the conductive film is preferably 0.5 μm or more and 30 μm or less, more preferably 0.8 μm or more and 20 μm or less, still more preferably 1.2 μm or more and 10 μm or less, and still more preferably 1.6 μm or more and 7 μm or less. If the thickness of the conductive film is too thin, desired conductivity as a circuit may not be obtained. Further, since the thickness of the conductive film affects the line width formed by laser etching and the line width, it is preferable not to increase the thickness more than necessary particularly when fine wiring is required.
The surface roughness Ra of the conductive film of the present invention is required to be 0.40 μm or less. If the surface roughness Ra is too high, scattering of laser light becomes significant in the laser etching process, and the definition (edge linearity) of a thin line is reduced.
In the present invention, the conductive fine wiring having a line width of 100 μm or less and a line width of 100 μm or less can be formed by laser etching. In the present invention, the width between lines of the conductive fine wiring is preferably 50 μm or less, and the width between lines may be 4 times or less the thickness of the conductive film. In the present invention, the conductive fine wiring may have a line width of 35 μm or less and a line width of 3.5 times or less the thickness of the conductive film.
Examples
In order to explain the present invention in more detail, the following examples and comparative examples are given, but the present invention is not limited to the examples at all. The measurement values described in examples and comparative examples were measured by the following methods.
< number average molecular weight >
A sample resin was dissolved in tetrahydrofuran to give a resin concentration of about 0.5% by weight, and the solution was filtered through a polytetrafluoroethylene membrane filter having a pore diameter of 0.5. mu.m, to obtain a GPC measurement sample, GPC measurement of the resin sample was performed at a column temperature of 30 ℃ and a flow rate of 1 ml/min using tetrahydrofuran as a mobile phase and a Gel Permeation Chromatograph (GPC) protocol manufactured by Shimadzu corporation and a differential Refractometer (RI) as a detector, and a fraction corresponding to a molecular weight of less than 1000 was subtracted from a standard polystyrene conversion value, and Shodex KF-802, 804L, and 806L, manufactured by Showa Denko K.K., were used as GPC columns.
< acid number >
0.2g of a sample resin was accurately weighed and dissolved in 20ml of chloroform. Next, titration was performed with 0.01N potassium hydroxide (ethanol solution) using phenolphthalein solution as an indicator. The unit of the acid value is eq./106g, i.e. as equivalents per 1 metric ton (metric ton) of sample.
< glass transition temperature (Tg) >
5mg of the sample resin was sealed in an aluminum sample pan, and measured at a temperature rise rate of 20 ℃/min to 200 ℃ using a Differential Scanning Calorimeter (DSC) DSC-220 manufactured by Seiko instruments, and the temperature was determined from the temperature of the intersection of the extension line of the base line at a temperature not higher than the glass transition temperature and the tangent line indicating the maximum inclination of the transition part.
< dispersity >
According to ISO 1524: 2013 using a Grind gauge (Grind Gage).
< production of conductive laminate test piece 1 >
A conductive paste was printed on an annealed PET film (L umiror S, manufactured by Toray corporation) having a thickness of 100 μm by a screen printing method using a 400-mesh stainless steel wire net to form a full-coating pattern having a width of 25mm and a length of 45mm, and then heated at 130 ℃ for 30 minutes in a hot air circulation type drying oven to obtain a conductive laminate test piece, and the coating thickness at the time of printing was adjusted so that the dry film thickness became 5 to 10 μm.
< adhesion >
Using the above conductive laminate test piece 1, the thickness of the conductive laminate was measured in accordance with JIS K-5400-5-6: 1990, evaluation was carried out by a peel test using a transparent adhesive tape (registered trademark) (manufactured by Nichiban corporation). However, the number of cuts in each direction of the lattice pattern was 11, and the cutting interval was 1 mm. 100/100 shows no peeling and good adhesion, 0/100 shows that peeling was totally occurred.
< Damp Heat test >
The samples were exposed to a high-temperature and high-humidity chamber adjusted to 85 ℃ and 85% RH1 atmosphere for 240 hours, and left to stand in a room in a standard state for 24 hours or more, and then subjected to a adhesion test to evaluate the test as a moist heat test.
< resistivity >
The film resistance and the film thickness of the conductive laminate test piece 1 were measured, and the resistivity was calculated by measuring the thickness of the cured coating film at 5 points using a film thickness measuring instrument manufactured by kojiu tester, and measuring the thickness of the cured coating film at 5 points, and using the average value thereof, the film resistance was measured by holding the long sides of the test piece having a width of 25mm and a length of 45mm between electrodes having a width of 10mm as measurement ranges, measuring 4 test pieces using a 4-probe resistance measuring instrument, a milliohm meter 4338B (manufactured by HEW L ETT PACKARD), measuring the resistance value of a square pattern having a width of 25mm × 25mm, and using the average value thereof.
< surface roughness >
In the conductive laminate test piece 1, the surface roughness Ra was measured using a surface roughness meter (HANDYSURF E-35B, manufactured by Tokyo Kogyo Co., Ltd., calculated according to JIS-1994).
< laser etching Property >
A conductive paste is printed and coated on ITO of a polyester substrate on which an ITO film is formed by a screen printing method into a rectangular shape of 2.5 × 10cm by using screen printing, and after the printing and coating, the conductive paste is dried at 120 ℃ for 30 minutes by a hot air circulation type drying furnace to obtain a conductive film, wherein the surface roughness R of the ITO is 0.3 [ mu ] m, the film thickness is 4 to 6 [ mu ] m by adjusting the printing conditions, and the conductive film produced by the above method is subjected to laser etching to draw the line width/line width shown below, and the presence or absence of fine wiring is confirmed by microscopic observation, the presence or absence of conduction, and line-to-line short circuit according to each set line width/line width, and when the wiring portion having a length of 100mm or more is conducted, and when the line width having a length of 100mm or more is not electrically short-circuited, it is determined that fine wiring is formed.
The document is × that enables processing in a region wider than the line width/line width of 40 μm/40 μm, △ that enables processing from the line width/line width of 40 μm/40 μm to the line width/line width of 20 μm/20 μm, ○ that enables processing at the line width/line width of 20 μm/20 μm or less, and ◎ that enables processing at the line width/line width of 15 μm/15 μm.
The YAG laser is used as the laser beam, and the minimum diameter of the beam is adjusted to be not more than half the width of each line. Further, the presence or absence of wiring and the presence or absence of short-circuiting between wires were confirmed by using a tester with an applied voltage of 1.5V.
< micro-contact printability >
A diluted conductive paste was applied on a PDMS plate, and a printing pressure was applied to form a fine pattern of 5 μm, wherein the pattern was represented by × when the pattern was broken, ○ when the pattern was not broken, and ◎ when the pattern was not broken and the line width was within. + -. 20% of the design value, and the presence or absence of wiring and short-circuiting between the lines were confirmed by using a tester with an applied voltage of 1.5V.
< synthetic example >
< polyurethane resin 1 >
(Synthesis of polyester resin)
Charging into autoclave equipped with thermometer and stirrer
97 parts by weight of dimethyl terephthalate
Isophthalic acid dimethyl ester 97 parts by weight
Ethylene glycol 61 parts by weight
Propylene glycol 75 parts by weight
25 parts by weight of 1, 4-cyclohexanediol
Tetrabutoxy titanate 0.1 part by weight
Heating at 180-230 ℃ for 120 minutes to perform ester exchange reaction. Subsequently, the reaction system was heated to 250 ℃ and the reaction was continued for 60 minutes under a system pressure of 1 to 10mmHg, whereby a copolyester resin (A1) was obtained. The composition of the obtained copolyester resin (A1) was analyzed by NMR as follows:
as the acid component, are
50 mol% of terephthalic acid
50 mol% of isophthalic acid
As the alcohol component, are
Ethylene glycol 45 mol%
Propylene glycol 45 mol%
1, 4-cyclohexanediol 10 mol%
The weight average molecular weight was 3500.
100 parts by mass of the obtained copolyester (a1), DMBA: 5.3 parts by mass, EDGAC: 174 parts, after dissolution, HDI: 31.6 parts, MDI: 36.8 parts, dibutyltin dilaurate as catalyst: 0.03 part by weight, and reacted at 95 ℃ for 6 hours. Then, with EDGAC: 152 parts, BDGAC: the solution was diluted by 81 parts to obtain a solution of a urethane resin 1.
< polyurethane resin 2-4 >
In a reaction vessel equipped with a stirrer, a condenser and a thermometer, an ethylene oxide adduct of bisphenol a: 100 parts by mass, DMBA: 5.3 parts by mass of a solvent dissolved in EDGAC: 174 parts are added with HDI: 31.6 parts, MDI: 36.8 parts, dibutyltin dilaurate as catalyst: 0.03 part by weight, and reacted at 95 ℃ for 6 hours. Then, with EDGAC: 152 parts, BDGAC: the solution was diluted by 81 parts to obtain a solution of a urethane resin 2.
The solid content concentration of the obtained polyurethane resin solution was 35 mass%. The resin solution thus obtained was dropped on a polypropylene film, applied by a coater made of stainless steel, allowed to stand in a hot air dryer adjusted to 120 ℃ for 3 hours to evaporate the solvent for drying, and then the dried resin film was peeled off from the polypropylene film to obtain a film-like dried resin film which was used for measuring an acid value and the like.
The raw materials were modified in the same manner as described below to obtain adhesive resin solutions shown in table 1.
[ example 1]
2857 parts (1000 parts in terms of solid content) of a solution of the polyurethane resin 2 shown in Table 1,
18700 parts of flake silver powder,
65 portions of curing agent,
5 parts of curing catalyst,
400 portions of ion trapping agent,
25 parts of carbon black,
15 portions of dispersant,
Further, 2100 parts of EDGAC and 900 parts of BDGAC were mixed as a solvent, and the mixture was passed through a three-roll mill twice to disperse the mixture, then a 635 mesh (stainless steel mesh filter (mesh 20 μm)) filter was attached to a slurry filter to filter the slurry, and then the obtained conductive slurry was printed in a predetermined pattern and dried at 130 ℃ × 30 for 30 minutes to obtain a conductive film.
[ Table 1]
Table 1 specifically shows the following.
Bis-A-EO: ethylene oxide adduct of bisphenol A molecular weight 316
Bis-F-EO: ethylene oxide adduct molecular weight 288 of bisphenol F
Bis-S-EO: ethylene oxide adduct molecular weight 456 of bisphenol S
DMBA: dimethylolbutanoic acid
EDGAC: diethylene glycol monoethyl ether acetate made from Dacellosolve, Inc
HDI: 1, 6-hexamethylene diisocyanate
MDI: 4, 4' -diphenylmethane diisocyanate
Examples 2 to 10 comparative example 1
The results of examples 2 to 10 and comparative example 1, in which the resin and formulation of the conductive paste were changed, are shown in table 2, in the examples, good coating film physical properties were obtained by heating in a relatively low temperature and short time such as in an oven at 130 ℃ for × 30 minutes, and the adhesion to an ITO film and the adhesion after a hot and humid environment test were also good.
[ Table 2]
Table 2 specifically shows the following.
Silver powder 1: flake silver powder (D50: 1.5 μm, tap density 3.7 g/cm)3)
Silver powder 2: spherical silver powder (D50; 0.8 μm, tap density 5.3 g/cm)3)
Silver powder 3: nano silver powder (D50; 600nm)
Silicon dioxide: product #300 of Nippon Aerosil corporation
An ion scavenger: IXE-100 manufactured by Toyo Synthesis Co., Ltd
Carbon black: keqin manufactured by lion king corporation ECP600JD
Curing agent: BI-7960 Baxenden
Curing catalyst: KS-1260, a product of Co., Ltd
Leveling agent: km コンク Kyoeisha chemical Co
Dispersant 1: disperbyk2155 manufactured by BYK Japan KK K.K
Dispersant 2: malonic acid
EDGAC: diethylene glycol monoethyl ether acetate made from Dacellosolve, Inc
BDGAC: diethylene glycol monobutyl ether acetate made from Dacellosolve of Kyowa Kabushiki Kaisha
Industrial applicability
As described above, the conductive paste of the present invention has a high degree of dispersion, and the conductive film obtained from the paste of the present invention has good laser etching properties, and can be effectively used as a member for an input/output interface such as a touch panel by combining with a conductive thin film such as ITO. Further, the present invention can be suitably used for wiring layers such as a printed TFT which require fine wiring.
Claims (5)
1. A conductive paste comprising at least a conductive filler, an organic solvent and a binder resin, wherein a carboxyl group-containing urethane resin is used as the binder resin,
the carboxyl group-containing polyurethane resin is an addition polymerization reaction product of a diol compound having a bisphenol structure, a carboxyl group-containing dihydroxy compound, and an isocyanate compound.
2. The electroconductive paste according to claim 1, wherein the content of the organic solvent is 5 to 100 parts by mass with respect to 100 parts by mass of the electroconductive filler, and the content of the binder resin is 5 to 25 parts by mass with respect to 100 parts by mass of the electroconductive filler.
3. The electroconductive paste according to claim 1 or claim 2, wherein said diol compound having a bisphenol structure is an alkylene oxide adduct of bisphenol a.
4. The electroconductive paste according to any one of claims 1 to 3, wherein the molecular weight of the diol compound having a bisphenol structure is 500 or less.
5. The electroconductive paste according to any one of claims 1 to 4, wherein the electroconductive filler is a metal powder having a median particle diameter D50 of 0.8 μm or more and less than 2.0 μm as measured by a laser diffraction method.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| JP2018-076799 | 2018-04-12 | ||
| JP2018076799 | 2018-04-12 | ||
| PCT/JP2019/015065 WO2019198624A1 (en) | 2018-04-12 | 2019-04-05 | Conductive paste |
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| Publication Number | Publication Date |
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| CN111512398A true CN111512398A (en) | 2020-08-07 |
| CN111512398B CN111512398B (en) | 2022-09-30 |
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| JP (1) | JP7331840B2 (en) |
| CN (1) | CN111512398B (en) |
| TW (1) | TWI810274B (en) |
| WO (1) | WO2019198624A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115662676A (en) * | 2022-04-26 | 2023-01-31 | 广东江玻玻璃科技有限公司 | Conductive paste and preparation method and application thereof |
| CN115947924A (en) * | 2022-09-30 | 2023-04-11 | 江苏华大新材料有限公司 | Polyurethane adhesive for conductive aluminum paste and preparation method and application thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| EP4279549A4 (en) * | 2021-01-14 | 2024-12-18 | Namics Corporation | ELECTRICALLY CONDUCTIVE COMPOSITION, ELECTRICALLY CONDUCTIVE PASTE, ELECTRICAL CIRCUIT, FLEXIBLE ELECTRICAL CIRCUIT OBJECT AND METHOD FOR PRODUCING A MOULDED BODY |
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| JP2007231057A (en) * | 2006-02-28 | 2007-09-13 | Sanyo Chem Ind Ltd | Polyurethane resin emulsion |
| CN104379696A (en) * | 2012-06-29 | 2015-02-25 | 大自达电线股份有限公司 | Conductive adhesive composition, conductive adhesive film, bonding method, and circuit board |
| CN104488040A (en) * | 2012-07-20 | 2015-04-01 | 东洋纺株式会社 | Conductive paste for laser etching, conductive thin film, and conductive laminate |
| CN106415735A (en) * | 2014-01-22 | 2017-02-15 | 东洋纺株式会社 | Conductive paste for laser etching, conductive thin film and conductive laminate |
| JP2017160354A (en) * | 2016-03-10 | 2017-09-14 | 株式会社Adeka | Aqueous polyurethane resin composition, and coating material using the composition |
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2019
- 2019-04-05 CN CN201980006714.4A patent/CN111512398B/en active Active
- 2019-04-05 JP JP2020513236A patent/JP7331840B2/en active Active
- 2019-04-05 WO PCT/JP2019/015065 patent/WO2019198624A1/en active Application Filing
- 2019-04-09 TW TW108112244A patent/TWI810274B/en active
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| JP2007231057A (en) * | 2006-02-28 | 2007-09-13 | Sanyo Chem Ind Ltd | Polyurethane resin emulsion |
| CN104379696A (en) * | 2012-06-29 | 2015-02-25 | 大自达电线股份有限公司 | Conductive adhesive composition, conductive adhesive film, bonding method, and circuit board |
| CN106947409A (en) * | 2012-06-29 | 2017-07-14 | 大自达电线股份有限公司 | Conductive adhesive composition, conductive adhesive film, adhesive method and circuit base plate |
| CN104488040A (en) * | 2012-07-20 | 2015-04-01 | 东洋纺株式会社 | Conductive paste for laser etching, conductive thin film, and conductive laminate |
| CN106415735A (en) * | 2014-01-22 | 2017-02-15 | 东洋纺株式会社 | Conductive paste for laser etching, conductive thin film and conductive laminate |
| JP2017160354A (en) * | 2016-03-10 | 2017-09-14 | 株式会社Adeka | Aqueous polyurethane resin composition, and coating material using the composition |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115662676A (en) * | 2022-04-26 | 2023-01-31 | 广东江玻玻璃科技有限公司 | Conductive paste and preparation method and application thereof |
| CN115662676B (en) * | 2022-04-26 | 2024-06-11 | 广东江玻玻璃科技有限公司 | Conductive paste and preparation method and application thereof |
| CN115947924A (en) * | 2022-09-30 | 2023-04-11 | 江苏华大新材料有限公司 | Polyurethane adhesive for conductive aluminum paste and preparation method and application thereof |
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| WO2019198624A1 (en) | 2019-10-17 |
| TW201943820A (en) | 2019-11-16 |
| JPWO2019198624A1 (en) | 2021-04-15 |
| JP7331840B2 (en) | 2023-08-23 |
| TWI810274B (en) | 2023-08-01 |
| CN111512398B (en) | 2022-09-30 |
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