WO2017170496A1 - Malleable conductive paste and method for producing curved printed circuit board - Google Patents

Abstract

[Problem] To provide a malleable conductive paste that can be used to obtain a curved printed circuit board by thermal deformation after being printed and cured on a thermoplastic substrate. [Solution] A malleable conductive paste containing: a binder resin (A) comprising a thermoplastic resin; a conductive powder (B); and an organic solvent (C), wherein the organic solvent (C) is a glycol ether solvent and/or an alcohol solvent. The obtained paste is printed on a substrate comprising a thermoplastic resin, whereafter a curved printed wiring board is obtained by a thermal deformation process.

Description

Expandable conductive paste and method for producing curved printed wiring board

The present invention relates to a display panel and an operation panel for home appliances, a mobile phone, a portable information device, a three-dimensional circuit sheet used for a switch part of an automobile interior part, a curved printed wiring board, and a spreadability for a three-dimensional circuit part. The present invention relates to a conductive paste and a manufacturing method thereof.

With the recent miniaturization and high performance of electric devices, there is an increasing demand for circuit sheets and printed boards having a three-dimensional three-dimensional structure, and three-dimensional molded products having an electric circuit formed on the surface. Circuit sheets and three-dimensional molded products having such an electric circuit include a circuit pattern (electric circuit) formed on an insulating base made of synthetic resin by electrolytic plating and then processed into a three-dimensional shape by press molding or the like. Are known. In addition, as in Patent Document 1, a part of a three-dimensional molded product provided with a resist layer and a conductive layer is covered with a mask, and a circuit pattern is provided on the surface by exposure, development, and etching, or as in Patent Document 2. A circuit pattern is provided on the surface of a three-dimensional molded product by injecting molten synthetic resin into a mold in which a laminate formed by laminating a circuit pattern and an adhesive layer on a synthetic resin film is set. ing.

Japanese Patent Laid-Open No. 9-319068 JP 2001-36240 A

However, the method of providing a circuit pattern on the surface of an insulating base material or molded product by plating or etching has a problem that harmful waste liquid is generated in the plating or etching process, which adversely affects the environment. . In addition, in the method of injecting synthetic resin into a mold in which a laminated body having a circuit pattern is set, the circuit pattern after molding can follow the deformation of the laminated body, and the circuit pattern is cracked and peeled off. There is a problem that gets worse.

An object of the present invention is to solve the problems of the above-described conventional circuit sheet and printed board having a three-dimensional shape, and a three-dimensional molded product, and a process in which a laminate having a circuit pattern is deformed and molded by heat and pressure. Is to provide a spreadable conductive paste in which the circuit pattern is not cracked or peeled off.

As a result of intensive studies to achieve this object, the present inventor has found that the above-mentioned problems can be solved by the following means, and has reached the present invention.
The first invention of the present invention has the following configuration.
[1] In a conductive paste containing a binder resin (A) made of a thermoplastic resin, a conductive powder (B) and an organic solvent (C), the organic solvent (C) is a glycol ether solvent or / and an alcohol type. A spreadable conductive paste characterized by being a solvent.
[2] The spreadable conductive paste according to [1], wherein the boiling point of the organic solvent (C) is in the range of 100 to 300 ° C.
[3] The spreadable conductive paste according to [1] or [2], wherein the second solvent includes a solvent having a slower evaporation rate than the organic solvent (C) and containing a hydroxyl group.
[4] The binder resin (A) is one or more selected from the group consisting of a polyester resin, a polyurethane resin, an epoxy resin, a phenoxy resin, a vinyl chloride resin, a fiber derivative resin, a polyvinyl acetal resin, and an acrylic resin. The spreadable conductive paste according to any one of [1] to [3], which is a mixture of
[5] The glass transition temperature of the binder resin (A) is 30 ° C. or higher, and the number average molecular weight is in the range of 3000 to 150,000, according to any one of [1] to [4] A spreadable conductive paste.
[6] A method for producing a curved printed wiring board, comprising a step of thermally deforming a plastic substrate after printing the spreadable conductive paste according to any one of [1] to [5] on a plastic substrate.

The second aspect of the present invention has the following configuration.
[7] In the conductive paste containing the binder resin (A) made of a thermoplastic resin, the conductive powder (B), the organic solvent (C) and the carbon black powder (D), the F value is 75 to 95%. A spreadable conductive paste characterized by that.
[8] The binder resin (A) is one or more selected from the group consisting of a polyester resin, a polyurethane resin, an epoxy resin, a phenoxy resin, a vinyl chloride resin, a fiber derivative resin, a polyvinyl acetal resin, and an acrylic resin. The spreadable conductive paste according to [7], which is a mixture of
[9] The spreadable conductive material according to [7] or [8], wherein the binder resin (A) has a glass transition temperature of 20 ° C. or higher and a number average molecular weight in the range of 3000 to 150,000. paste.
[10] The extensible conductive paste according to any one of [7] to [9], wherein the organic solvent (C) is a glycol ether solvent or / and an alcohol solvent.
[11] The spreadable conductive paste according to any one of [7] to [10], wherein the boiling point of the organic solvent (C) is in the range of 100 to 300 ° C.
[12] The extensible conductivity according to any one of [7] to [11], wherein the second solvent includes a solvent having a slower evaporation rate than the organic solvent (C) and containing a hydroxyl group. Sex paste.
[13] A method for producing a curved printed wiring board, comprising a step of thermally deforming a plastic substrate after printing the spreadable conductive paste according to any one of [7] to [12] on a plastic substrate.

The third aspect of the present invention has the following configuration.
[14] A spreadable conductive paste containing a binder resin (A) made of a thermoplastic resin, a conductive powder (B), an organic solvent (C) and a curing agent (E), wherein the binder resin (A) is a polyester. Resin, polyurethane resin, epoxy resin, phenoxy resin, vinyl chloride resin, fiber derivative resin, polyvinyl acetal resin, one kind selected from the group consisting of acrylic resin, or a mixture of two or more kinds, and the curing agent (E) Is a spreadable conductive paste characterized in that is a blocked isocyanate or an epoxy compound or both.
[15] The spreadable conductive paste according to [14], wherein the organic solvent (C) is a glycol ether solvent or / and an alcohol solvent.
[16] The spreadable conductive paste according to [14] or [15], wherein the boiling point of the organic solvent (C) is in the range of 100 to 300 ° C.
[17] The extensible conductivity according to any one of [14] to [16], wherein the second solvent includes a solvent having a slower evaporation rate than the organic solvent (C) and containing a hydroxyl group. Sex paste.
[18] The spreadable conductive material according to any one of [14] to [17], wherein the curing agent (E) is at least one block isocyanate selected from a burette type, a trimmer type, and an adduct type. Sex paste.
[19] The spreadable conductive paste according to any one of [14] to [18], wherein the curing agent (E) is a glycerol type epoxy resin.
[20] The glass transition temperature of the binder resin (A) is 30 ° C. or higher, and the number average molecular weight is in the range of 3000 to 150,000, according to any one of [14] to [19] A spreadable conductive paste.
[21] A method for producing a curved printed wiring board, comprising a step of thermally deforming a plastic substrate after printing the spreadable conductive paste according to any one of [14] to [20] on a plastic substrate.

Furthermore, the present invention preferably has the following configuration.
[22] The spreadable conductive paste according to any one of [1] to [4], wherein the binder resin (A) is a phenoxy resin.
[23] On a substrate made of a thermoplastic resin and having a non-developable surface shape, a binder resin (A) made of a phenoxy resin, a conductive powder (B), and a burette type block isocyanate, an adduct type block isocyanate, and a trimer type block A curved printed wiring board having an electrical wiring composed of a cured product of a conductive resin composition containing one or more curing agents (D) selected from isocyanates.
[24] The curved printed wiring board according to [23], wherein the substrate made of a thermoplastic resin and having a non-developable shape is a polycarbonate resin or a polyester resin.

Furthermore, the present invention preferably has the following configuration.
[25] The spreadable conductive paste according to [7] to [12], wherein the binder resin (A) is a phenoxy resin.
[26] A conductive resin composition comprising a binder resin (A) made of a phenoxy resin, a conductive powder (B), and a carbon black powder (D) on a non-developable surface substrate made of a thermoplastic resin. A curved printed wiring board characterized by having an electrical wiring made of a cured product.
[27] The curved printed wiring board according to [26], wherein the substrate made of a thermoplastic resin and having a non-expandable surface shape is a polycarbonate resin or a polyester resin.
[28] The cured product of the conductive resin composition is a binder resin (A) made of a phenoxy resin, a conductive powder (B), and a carbon black powder (D), a burette type block isocyanate, an adduct type block isocyanate, and a trimer. The curved printed wiring board according to [26] or [27], which is a cured product of a conductive resin composition containing one or more curing agents (E) selected from type-block isocyanates.

Furthermore, the present invention preferably has the following configuration.
[29] The spreadable conductive paste according to [14] to [20], wherein the binder resin (A) is a phenoxy resin.
[30] A binder resin (A) made of a phenoxy resin, a conductive powder (B), and a burette type block isocyanate, an adduct type block isocyanate, and a trimer type block on a non-developable surface substrate made of a thermoplastic resin. A curved printed wiring board having an electrical wiring composed of a cured product of a conductive resin composition containing one or more curing agents (E) selected from isocyanates.
[31] The curved printed wiring board according to [30], wherein the substrate made of a thermoplastic resin and having a non-developable surface shape is a polycarbonate resin or a polyester resin.

The present invention relates to a spreadable conductive paste used for manufacturing a curved printed wiring board by thermally deforming a plastic substrate after printing on the plastic substrate. In particular, a heat-deformable plastic substrate is often used as a base material for a curved printed wiring board. Many plastic materials having such thermoplasticity and heat deformability have low resistance to organic solvents. One conductive paste contains a binder resin, and an organic solvent is usually used to liquefy and dissolve the binder resin at the same time. Therefore, when a conductive paste containing an organic solvent is inadvertently printed on a plastic substrate that can be thermally deformed, the plastic substrate surface melts due to the contact between the solvent component contained in the conductive paste and the plastic substrate. Unnecessary deformation may occur, or micro cracks may occur at the contact site, causing problems such as a decrease in mechanical strength of the substrate.

The conductive paste of the present invention does not cause such a problem even in a plastic substrate having poor solvent resistance, such as an acrylic material, a polycarbonate material, and a vinyl chloride material, and has excellent adhesion to a base material. Even when the material is thermally deformed, the conductive layer formed of the conductive paste sufficiently follows the deformation, and has an excellent effect of being excellent in electrical characteristics even after the deformation.

As the binder of the conductive paste, a thermosetting resin is often used. This is because the curing shrinkage accompanying the heat curing promotes direct contact between the conductive particles, and it is easy to obtain advantages in terms of electrical characteristics in order to form a relatively tough cured coating film. However, in the first invention of the present invention, the thermoplastic resin is used for the binder because it is an object to be thermally deformed in a later process, but surprisingly, excellent electrical characteristics as well as the thermosetting resin are used. Can be obtained. This is considered to be due to the effect that the solvent component of the present invention exerts the same effect on the thermoplastic resin as the curing process of the thermosetting resin in the drying curing process.

In the second invention of the present invention, the thermoplastic resin is used for the binder because it is an object of heat deformation in the subsequent process, but surprisingly, excellent electrical characteristics are obtained in the same manner as the thermosetting resin. be able to. This is because the carbon black added to the conductive paste in the present invention not only relieves the influence of the organic solvent on the base material, but also in the formation of a coating film, as if it is as if it were a filler in a powder reinforced plastic. Considered. As a result, in the spreadable conductive paste of the present invention, a conductive coating film having excellent mechanical properties and electrical properties can be obtained even after thermal deformation as if a thermosetting resin was used while using a thermoplastic resin.

In the third invention of the present invention, by using a resin that has been provided with thermosetting properties by using a specific curing agent in a resin that is originally thermoplastic, good electrical characteristics and reliability are achieved. Cured coating film that can maintain good physical properties even after deformation, and the conductive layer can sufficiently follow the deformation even if the substrate is thermally deformed in a later step. Can be obtained. In the combination of the curing agent component and the resin component of the present invention, the binder resin and the curing agent react to form a crosslinked structure in the drying and curing process, and the crosslinked portion is flexible in the temperature range where the substrate is thermally deformed. This is considered to be due to maintaining sufficient crosslinkability while maintaining a crosslinked state, and returning to a strong crosslinked body in a cooled state after deformation.

Hereinafter, the spreadable conductive paste according to an embodiment of the present invention will be described. In the present invention, a binder resin (A) made of a thermoplastic resin, a conductive powder (B) and an organic solvent (C), carbon black (D), and a curing agent (E) are used.

<Binder resin (A)>
The binder resin (A) contained in the spreadable conductive paste of the present invention needs to contain a resin having flexibility and three-dimensional formability as a main component.
The type of the binder resin (A) is not particularly limited as long as it is a thermoplastic resin, but is not limited to polyester resin, epoxy resin, phenoxy resin, polyamide resin, polyamideimide resin, polycarbonate resin, polyurethane resin, phenol resin, polyvinyl acetal resin, acrylic resin. , Polystyrene, styrene-acrylic resin, styrene-butadiene copolymer, phenol resin, polyethylene resin, polycarbonate resin, phenol resin, alkyd resin, styrene-acrylic resin, styrene-butadiene copolymer resin, polysulfone resin, polyethersulfone Resin, vinyl chloride-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer, polystyrene, silicone resin, fluorine-based resin and the like. As a mixture of more, it can be used. It is preferably one or a mixture of two or more selected from the group consisting of polyester resins, polyurethane resins, epoxy resins, phenoxy resins, vinyl chloride resins, fiber derivative resins, butyral resins, and acrylic resins. Among these resins, phenoxy resin and / or urethane resin and / or acrylic resin and / or polyvinyl acetal resin are preferable as the binder resin (A).

As one of the advantages of using a phenoxy resin and / or a urethane resin and / or an acrylic resin and / or a polyvinyl acetal resin as the binder resin (A) in the present invention, compared with other binder resins, Examples thereof include good solubility in a wide range of solvents such as alcohol solvents and good adhesion to various substrates. Ketone solvents and ester solvents widely used in conductive pastes may cause damage depending on the type of substrate, which may cause poor appearance and spreadability of printed circuits.

In the present invention, the phenoxy resin is a polyhydroxy polyether synthesized from bisphenols and epichlorohydrin and having a molecular weight of 3,000 to 150,000. Examples of the phenoxy resin used as the binder resin (A) in the present invention include bisphenol A type, bisphenol A / F copolymer type, bisphenol S type, and bisphenol A / S copolymer type. Among these, bisphenol A type is preferable from the viewpoint of substrate adhesion.

In the present invention, the urethane resin is a polymer having a urethane bond and having a molecular weight of 3,000 to 150,000.

In the present invention, the acrylic resin is a resin obtained by radical polymerization reaction by adding a polymerization initiator or heat to a radical polymerizable monomer such as an acrylic ester or methacrylic ester, and has a molecular weight of 3,000 to 150, 000.

In the present invention, the polyvinyl acetal resin is a resin obtained by acetalizing or butyralizing polyvinyl alcohol and having a molecular weight of 3,000 to 150,000.

The number average molecular weight of the binder resin (A) in the present invention is not particularly limited, but the number average molecular weight is preferably 3,000 to 150,000. More preferably, it is in the range of 7,000 to 140,000, and still more preferably in the range of 10,000 to 130,000. If the number average molecular weight is too low, it is not preferable in terms of durability and heat and humidity resistance of the formed conductive thin film. On the other hand, if the number average molecular weight is too high, the cohesive force of the resin is increased and the durability as a conductive thin film is improved, but the viscosity of the spreadable conductive paste is increased, which is not preferable in practical use.

In the first invention and the third invention in the present invention, the glass transition temperature of the binder resin (A) is preferably 30 ° C. or higher, and more preferably 40 ° C. or higher. If the glass transition temperature is low, the surface hardness of the silver coating film may decrease.
In the second invention of the present invention, the glass transition temperature of the binder resin (A) is preferably 15 ° C. or higher, and more preferably 20 ° C. or higher. If the glass transition temperature is low, the surface hardness of the silver coating film may decrease.

<Conductive powder (B)>
As the conductive powder (B) used in the present invention, it is plated with noble metal powder such as silver powder, gold powder, platinum powder and palladium powder, base metal powder such as copper powder, nickel powder, aluminum powder and brass powder, and noble metal such as silver. Alternatively, alloyed base metal powder can be used. These metal powders may be used alone or in combination. Among these, considering the conductivity, stability, cost, etc., the silver powder alone or the one mainly composed of silver powder is preferable. Further, as the conductive powder (B), for example, a non-metallic powder such as carbon black powder can be used.

The shape of the conductive powder (B) used in the present invention is not particularly limited. Examples of conventionally known metal powder shapes include flakes (flakes), spheres, dendrites (dendrites), and spherical primary particles described in JP-A-9-306240. There are three-dimensionally aggregated shapes (aggregate) and the like, and among these, it is preferable to use spherical, aggregated and flaky metal powders.

The center diameter (D50) of the conductive powder (B) used in the present invention is preferably 4 μm or less. By using the metal powder (B) having a center diameter of 4 μm or less, the printed shape of the thin line tends to be good. When a metal powder having a center diameter larger than 4 μm is used, the printed fine line shape is deteriorated, and as a result, the fine lines may come into contact with each other, possibly causing a short circuit. The lower limit of the central diameter of the conductive powder (B) is not particularly limited, but it is preferable that the central diameter is 80 nm or more because it tends to agglomerate when the particle diameter is small and dispersion becomes difficult as a result. When the center diameter is smaller than 80 nm, the cohesive force of the conductive powder increases, the printing suitability and the storage stability of the spreadable conductive paste deteriorate, and it is not preferable from the viewpoint of cost.

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

The content of the conductive powder (B) is preferably 400 parts by mass or more with respect to 100 parts by mass of the thermoplastic resin (A) from the viewpoint that the conductivity of the formed conductive thin film is good. Part or more is more preferable. Further, the content of the component (B) is preferably 1,900 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin (A), from the viewpoint of good adhesion to the base material, Less than the mass part is more preferable.

<Organic solvent (C)>
The organic solvent (C) that can be used in the present invention is preferably a glycol ether solvent or / and an alcohol solvent. Since the glycol ether solvent and / or alcohol solvent hardly damages the resin film that can be three-dimensionally formed as a printing substrate, the obtained conductive thin film can exhibit good spreadability. When a solvent that does not contain these structures is used, the resin film that can be three-dimensionally molded may be damaged by the solvent, and the resulting conductive thin film base is weak, which is good. There may be cases where spreadability cannot be obtained.

Glycol ether solvents include diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, ethylene glycol monophenyl. Ether, diethylene glycol isopropyl methyl ether, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, propylene glycol monomethyl Ether, polyethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, but tripropylene glycol dimethyl ether, without limitation. Among these, dipropylene glycol monomethyl is excellent in solubility of the components of the thermoplastic resin (A), has a suitable solvent volatility during continuous printing, and has good suitability for printing by a screen printing method or the like. Ether, tripropylene glycol dimethyl ether and mixed solvents thereof are particularly preferred.

Examples of alcohol solvents include solvents having an OH group. Examples include butanol, cyclohexanol, methylcyclohexanol, heptanol, texanol, butyl cellosolve, ethylene glycol, propylene glycol, butanediol, 3-methoxy-3-methyl-1 -Butanol and the like, but not limited thereto. Among these, 3-methoxy- is superior in that it has excellent solubility in the components of the thermoplastic resin (A), has an appropriate solvent volatility during continuous printing, and is suitable for printing by a screen printing method or the like. 3-methyl-1-butanol is particularly preferred.

In addition, an organic solvent other than the organic solvent (C) can be used in combination as long as the effects of the present invention are not impaired. Examples of organic solvents that can be used in combination include ethyl diglycol acetate (EDGAC), butyl glycol acetate (BMGAC), butyl diglycol acetate (BDGAC), cyclohexanone, toluene, isophorone, γ-butyrolactone, benzyl alcohol, and Exson Chemical's Solvesso Examples thereof include, but are not limited to, 100, 150, 200, propylene glycol monomethyl ether acetate, adipic acid, a mixture of succinic acid and dimethyl ester of glutaric acid (for example, DBE manufactured by DuPont Co., Ltd.), and tarpione.

The boiling point of the organic solvent (C) that can be used in the present invention is not particularly limited, but the boiling point is preferably 100 ° C. or more and less than 300 ° C. from the viewpoint of keeping the volatilization rate of the organic solvent in an appropriate range. The boiling point is preferably 150 ° C. or higher and lower than 280 ° C. The conductive paste of the present invention is typically prepared by dispersing a thermoplastic resin (A), a conductive powder (B), an organic solvent (C) and other components as necessary with a three-roll mill or the like. However, if the boiling point of the organic solvent is too low at that time, the solvent volatilizes during dispersion, and there is a concern that the ratio of components constituting the conductive paste changes. On the other hand, if the boiling point of the organic solvent is too high, a large amount of the solvent may remain in the coating film depending on the drying conditions, and there is a concern that the conductivity of the coating film deteriorates and the reliability decreases.

The content of the organic solvent (C) is preferably 5 parts by weight or more and 40 parts by weight or less, more preferably 10 parts by weight or more and 35 parts by weight or less with respect to 100 parts by weight of the total paste. . When the content of the organic solvent (C) is too high, the paste viscosity becomes too low, and the sagging tends to occur during fine line printing. On the other hand, when the content of the organic solvent (C) is too low, the viscosity as a paste becomes extremely high, and for example, when the conductive thin film is formed, for example, screen printability may be significantly lowered.

The spreadable conductive paste of the present invention preferably contains a solvent containing a hydroxyl group having a slower evaporation rate than the first solvent as the second solvent. Since the solvent containing a hydroxyl group acts as a reducing agent, the resistance value of the circuit obtained from the spreadable conductive paste can be lowered. By selecting the second solvent having a slower evaporation rate than the first solvent, the second solvent remains in the coating film for a long period of time in the drying process after printing the spreadable conductive paste, and the reduction The effect as an agent is easily exhibited.

The following inorganic substances can be added to the spreadable conductive paste of the present invention. Examples of inorganic substances include 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 other carbides; boron nitride Various nitrides such as titanium nitride and zirconium nitride, various borides such as zirconium boride; various oxidations such as titanium oxide (titania), calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica and colloidal silica Products: various titanate compounds such as calcium titanate, magnesium titanate, strontium titanate; sulfides such as molybdenum disulfide; various fluorides such as magnesium fluoride and carbon fluoride; aluminum stearate, calcium stearate Um, zinc stearate, various metal soaps such as magnesium stearate and the like; may be used talc, bentonite, talc, calcium carbonate, bentonite, kaolin, glass fiber, mica or the like. By adding these inorganic substances, it may be possible to improve printability and heat resistance, as well as mechanical properties and long-term durability. Among them, in the spreadable conductive paste of the present invention, silica is preferable from the viewpoint of imparting durability, printability, particularly screen printability.

The spreadable conductive paste of the present invention includes a thixotropic agent, an antifoaming agent, a flame retardant, a tackifier, a hydrolysis inhibitor, a leveling agent, a plasticizer, an antioxidant, an ultraviolet absorber, a flame retardant, Pigments and dyes can be blended. Furthermore, a carbodiimide, an epoxy, etc. can also be mix | blended suitably as a resin degradation inhibitor. These can be used alone or in combination.

<Carbon black powder (D)>
In 2nd invention in this invention, it is preferable to add carbon black powder (D) in addition to electroconductive powder (B). By adding carbon black powder, the toughness of the coating film is increased, and the spreadability of the coating film in a high temperature environment can be increased. The addition of carbon black has a function of alleviating damage to the printing equipment due to the organic solvent contained in the conductive paste.
In the present invention, carbon black is a general term for carbon-based fine particles. As the carbon particles in the present invention, graphite powder, activated carbon powder, scaly graphite powder, acetylene black, ketjen black, fullerene, single-walled carbon nanotube, multi-walled carbon nanotube, carbon nanocone, and the like can be used. In the present invention, preferably used carbon-based particles are graphite powder, scaly graphite powder, activated carbon powder, and ketjen black. In the present invention, it is further preferable to use carbon-based particles having a BET specific surface area of 1000 m 2 / g or more.

The addition amount of carbon black powder is preferably in the range of 0.3 to 3.5% by weight with respect to the total amount of conductive powder (B). A range of 0.5 to 3.0% by weight is more preferred, and a range of 0.7 to 2.5% by weight is most preferred. When the addition amount is less than 0.3% by weight, the effect of increasing the toughness of the coating film is hardly expressed, and the coating film has poor spreadability. On the other hand, if the amount added exceeds 3.5% by weight, good conductive performance may not be obtained.

In the first and second inventions of the present invention, the spreadable conductive paste of the present invention may be blended with a curing agent capable of reacting with the binder resin (A) to such an extent that the effects of the present invention are not impaired. Good. By adding a curing agent, there is a possibility that the curing temperature becomes high and the load of the production process is increased, but it is expected that the wet heat resistance of the coating film can be improved by crosslinking by heat generated when the coating film is dried. In the third invention of the present invention, a curing agent is used to impart thermosetting properties to the binder resin.

<Curing agent (E)>
The type of the curing agent (E) that can be used in the present invention is not particularly limited, but an isocyanate compound and an epoxy compound are particularly preferable in view of adhesion, flex resistance, curability, and the like. Furthermore, it is more preferable to use a blocked isocyanate group as these isocyanate compounds, since the storage stability is improved. Examples of curing agents other than isocyanate compounds and epoxy compounds include amino compounds such as methylated melamine, butylated melamine, benzoguanamine, and urea resin, and known compounds such as acid anhydrides, imidazoles, epoxy resins, and phenol resins. These curing agents can be used in combination with a known catalyst or accelerator selected according to the type. The blending amount of the curing agent is preferably 0.5 to 50 parts by mass, more preferably 1 to 30 parts by mass, and further preferably 2 to 20 parts by mass with respect to 100 parts by mass of the binder resin (A).

Examples of the isocyanate compound that can be blended in the spreadable conductive paste of the present invention include aromatic or aliphatic diisocyanates, trivalent or higher polyisocyanates, and any of low molecular compounds and high molecular compounds may be used. For example, aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, aromatic diisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, isophorone diisocyanate, etc. Alicyclic diisocyanates, or trimers of these isocyanate compounds, and excess amounts of these isocyanate compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine Low molecular active hydrogen compounds such as Polyester polyols, polyether polyols, terminal isocyanate group-containing compounds obtained by reacting a polymeric active hydrogen compound such as polyamides and the like. Examples of the isocyanate group blocking agent include phenols such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol; oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime. Alcohols such as methanol, ethanol, propanol and butanol; halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol ; Lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propylolactam, and the like, as well as aromatic amines, imides, acetylacetone, Seto acetate, active methylene compounds such as malonic acid ethyl ester, mercaptans, imines, imidazoles, ureas, diaryl compounds, sodium bisulfite, etc. can be mentioned. Of these, oximes, imidazoles, and amines are particularly preferable from the viewpoint of curability.

In the present invention, it is preferable to use at least one block isocyanate selected from a burette type, a trimmer type, and an adduct type as the curing agent (E). In particular, when a burette type is used, an excellent cured coating film in which physical properties and spreadability of the cured product are compatible can be obtained.

As the burette type blocked isocyanate, product number 7960 in which aliphatic isocyanate is blocked with dimethylpyrazole, product number 7961 (both manufactured by Baxenden), product number 7991 (made by Baxenden) blocked with dimethylpyrazole and diethyl malonate, Examples include DURANATE 24A-100 block type, DURANATE 22A-75P block type, DURANATE 21S-75E block type (all manufactured by Asahi Kasei Corporation), and the like.

Examples of the trimer type blocked isocyanate include water-based product number AquaBI200, product number AquaBI220 (both manufactured by Baxenden), product number 7951 obtained by blocking aliphatic isocyanate with dimethylpyrazole, product number 7982 (both manufactured by Baxenden), dimethylpyrazole, Examples thereof include part number 7990 and part number 7992 (both manufactured by Baxenden) and the like blocked with diethyl malonate.

Examples of adduct type block isocyanate include DURANATE P301-75E block type, DURANATE E402-80B block type, DURANATE E405-70B block type, DURANATE AE700-100 block type (all manufactured by Asahi Kasei Corporation).

Examples of the epoxy compound that can be blended in the spreadable conductive paste of the present invention include aromatic or aliphatic diglycidyl ether, trivalent or higher polyglycidyl ether, and any of low molecular compounds and high molecular compounds. But you can. For example, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol Examples thereof include diglycidyl ether, hydrogenated bisphenol type diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

In the present invention, when an epoxy compound is used as the curing agent (E), it is preferable to use an aliphatic epoxy compound in terms of spreadability. A particularly preferred epoxy compound is a glycerol type epoxy resin.

<< Physical Properties Required for the Expandable Conductive Paste of the Present Invention >>
The viscosity of the spreadable conductive paste of the present invention is not particularly limited, and may be appropriately adjusted according to the method for forming the coating film. For example, when the spreadable conductive paste is applied to the base material by screen printing, the viscosity of the spreadable conductive paste is preferably 100 dPa · s or more, more preferably 150 dPa · s or more at the printing temperature. The upper limit is not particularly limited, but if the viscosity is too high, screen printability may be deteriorated.

The spreadable conductive paste of the present invention preferably has an F value of 60 to 95%, more preferably 75 to 95%. The F value is a numerical value indicating the filler mass part with respect to 100 mass parts of the total solid content contained in the paste, and is represented by F value = (filler mass part / solid mass part) × 100. The filler mass part referred to here is the mass part of the conductive powder, and the solid mass part is a mass part of components other than the solvent, and includes all of the conductive powder, the binder resin, and other curing agents and additives. If the F value is too low, a conductive thin film showing good conductivity cannot be obtained. If the F value is too high, the adhesion between the conductive thin film and the substrate and / or the surface hardness of the conductive thin film tends to decrease. Yes, printability is inevitable. Here, the conductive powder refers to both metal powder and non-metal conductive powder.

<< Method for Producing the Expandable Conductive Paste of the Present Invention >>
The spreadable conductive paste of the present invention is prepared by dispersing the thermoplastic resin (A), the conductive powder (B), the organic solvent (C) and other components as necessary with a three-roll as described above. be able to. Here, an example of a more specific production procedure is shown. The thermoplastic resin (A) is first dissolved in the organic solvent (C). Thereafter, the conductive powder (B) and additives as necessary are added, and dispersion is carried out with a double planetary, a dissolver, a planetary stirrer or the like. Then, it disperses | distributes with a 3 roll mill, and obtains an electrically conductive paste. The conductive paste thus obtained can be filtered if necessary. There is no problem even if the dispersion is performed using other dispersers such as a bead mill, a kneader, and an extruder.

<< Conductive Thin Film, Conductive Laminate and Production Method of the Present Invention >>
The spreadable conductive paste of the present invention forms a coating film that becomes a circuit pattern on a resin film that can be three-dimensionally formed by a simple method such as printing, and then volatilizes the organic solvent (C) contained in the coating film. The conductive thin film of the present invention can be formed by drying the coating film. The resin film that can be three-dimensionally formed can be a flat sheet that can be three-dimensionally formed before being formed into a three-dimensional shape. The resin film may be a light-transmitting resin film such as a colorless transparent film or a colored translucent film, or a light-impermeable resin film. Various resin films excellent in flexibility can be used as the resin film, and examples thereof include polyester, polycarbonate, polyethylene, polypropylene, polyamide, and thermoplastic elastomer resin films. . Especially, since both transparency and moldability are favorable, it is preferable to use a polycarbonate film, a polycarbonate / polybutyl terephthalate alloy film, or a polyethylene terephthalate film. The thickness of the film or sheet is not particularly limited, but about 20 to 9000 μm can be used, and a thickness of 50 to 500 μm is preferable. If the film thickness is thinner than a predetermined range, the film may be curled when a circuit pattern is printed or the film may be damaged during molding. Moreover, if the film or sheet thickness exceeds a predetermined range, the moldability of the film may be lowered.

The method of applying or printing the spreadable conductive paste of the present invention on a substrate to form a coating film and applying or printing the spreadable conductive paste on the substrate is not particularly limited, but printing by a screen printing method Is preferable because it is a technique that is widely used in the industry for forming an electric circuit by using a simple process and a spreadable conductive paste.

Examples of the three-dimensional forming method include, but are not limited to, vacuum forming, press forming, and hydroforming forming.

As the resin film base material capable of three-dimensional molding to which the spreadable conductive paste of the present invention is applied, a three-dimensional moldable material that is excellent in dimensional stability and can be easily deformed and molded at a high temperature is preferably used. For example, a film made of a material having excellent flexibility such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, or polycarbonate can be used. The thickness of the substrate is not particularly limited, but is preferably 50 to 500 μm. 100 to 250 μm is more preferable from the viewpoint of mechanical properties, shape stability, or handleability of the pattern forming material.

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

The step of evaporating the organic solvent (C) is preferably performed at room temperature and / or under heating. In the case of heating, since the conductivity, adhesion and surface hardness of the conductive thin film after drying are improved, the heating temperature is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and further preferably 110 ° C. or higher. Further, from the viewpoint of heat resistance of the underlying transparent conductive layer and energy saving in the production process, the heating temperature is preferably 150 ° C. or lower, more preferably 135 ° C. or lower, and further preferably 130 ° C. or lower. When the curing agent is blended in the conductive paste of the present invention, the curing reaction proceeds when the step of evaporating the organic solvent (C) is performed under heating.

The thickness of the conductive thin film of the present invention may be set to an appropriate thickness according to the application used. However, from the viewpoint that the conductivity of the conductive thin film after drying is good, the thickness of the conductive thin film is preferably 3 μm or more and 100 μm or less, more preferably 4 μm or more and 80 μm or less. If the conductive thin film is too thin, there is a possibility that desired conductivity as a circuit cannot be obtained. If the film thickness is too thick, the solvent needs to be heated at a high temperature for a long time to volatilize the solvent, and the resin film that can be three-dimensionally formed as a printing substrate may be damaged.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, this invention is not limited to the following embodiment. Unless otherwise specified, “parts” in the examples means “parts by weight”.

The conductive paste in the present invention was evaluated by the following method.
1. Preparation of conductive laminate test piece Polycarbonate (PC) film with a thickness of 400 μm (FE-2000 manufactured by Mitsubishi Gas Chemical Co., Ltd.) or Polyester (PET) film with a thickness of 100 μm (Lumirror S100 manufactured by Toray Industries, Inc.) Then, a conductive paste was printed by a screen printing method using a 150 mesh polyester screen plate and dried in a hot air circulation type drying furnace at 130 ° C. for 30 minutes to form a coating film. The coating thickness at the time of printing was adjusted so that the dry film thickness was 10 to 30 μm. Thereafter, a conductive laminate test piece having a width of 1 mm and a length of 100 mm having a terminal portion having a width of 5 mm and a length of 5 mm on both sides for the specific resistance measurement shown below, and a width of 15 mm and a length of 110 mm for adhesion measurement. A conductive laminate test piece was produced.

2. The circuit resistance and film thickness of the conductive laminate test piece produced on the PC film or PET film with specific resistance 1 were measured, and the specific resistance was calculated. For the film thickness, a gauge stand ST-022 (manufactured by Ono Sokki Co., Ltd.) was used, and the thickness of the cured coating film was measured at two points on the left and right terminals using the film thickness as the zero point.
The circuit resistance was measured for three test pieces using a HIOKI RM3544 resistance measuring device, and the average value was used.

3. Using a cellulosette (registered trademark) (manufactured by Nichiban Co., Ltd.) according to JIS K-5400-5-6: 1990, using a conductive laminate test piece produced on a PC film or PET film with adhesion 1 It was evaluated by testing. However, the number of cuts in each direction of the lattice pattern was 11, and the cut interval was 1 mm. 100/100 indicates that there is no peeling and good adhesion, and 0/100 indicates that all are peeled off.

4). The following method evaluated the presence or absence of the chemical attack to the PC base material of the electroconductive laminated body test piece produced on the PC film or PET film by the chemical attack 1. Observation was performed at a magnification of 100 using an optical microscope (VHX-1000 manufactured by Keyence), and judgment was made based on the presence or absence of traces due to curing shrinkage of the coating film. When a trace remained around the coating film, it was marked as x.

5. Evaporation rate The evaporation rate at 130 degrees for the solvents used in the examples and comparative examples was measured using the differential thermal and thermogravimetric simultaneous measurement device (TG-DTA: TA-60, DTG-60 manufactured by Shimadzu) under the following conditions. Then, the change in weight (TG) from the start of measurement to the end of the test was measured, and the average (N = 3) was taken as the evaporation rate at 130 degrees.
<TG-DTA measurement conditions>
Sample amount: 40mg
Initial temperature: 30 degrees Measurement conditions Heating rate 40 ℃ / min Hold temperature 130 degrees Hold time 30min
The evaporation rate of the solvent used is shown in Table 1.

6). The spreadability evaluation was performed by the following measuring method. Using an autograph AG-X plus manufactured by Shimadzu as a measurement sample, a conductive laminate test piece with a width of 1 mm and a length of 100 mm having a terminal part with a width of 5 mm and a length of 5 mm on both sides prepared for specific resistance measurement was used. Both ends of the measurement sample were chucked. At this time, the interval between both chucks was set to 12 cm, and the chuck portion was set to be outside the terminal portion of the measurement sample. Then, pulling is performed in the longitudinal direction of the measurement sample until the conductive laminate test piece is 10%, 20%, 40%, and 80% of the chuck interval at a speed of 25 mm / min in an atmosphere of 140 ° C. went. (The initial chuck interval is 100, and the state extended to 110 is 10%.)
Thereafter, observation was performed at a magnification of 100 using an optical microscope (VHX-1000 manufactured by Keyence), and the presence or absence of cracking / peeling of the coating film was confirmed. The case where the coating film was not cracked or peeled off was rated as “◯”, and the case where the coating film was cracked or peeled off was rated as “X”. Further, the rate of change in circuit resistance was measured, and those having a rate of change of 300% or less were evaluated as ◯, those exceeding 300%, Δ being 1000% or less, and those exceeding 1000% as x.

7). Moisture and heat resistance test:
A conductive laminate test piece produced on a PC film or a PET film for the purpose of evaluating specific resistance and adhesion was allowed to stand at 85 ° C. and 85% RH (relative humidity) for 120 hours, and then taken out. Then, after leaving at room temperature for 24 hours, various evaluations were performed.

<Example 1>
500 parts of phenoxy resin PKHC manufactured by InChem as the resin binder (A) (including 400 parts of dipropylene glycol monomethyl ether as the organic solvent (C)), and flaky silver powder (D50 = 3) as the conductive powder (B) 1.5 μm), 10 parts of carbon, 10 parts of propylene glycol as the second solvent, and 30 parts of ethyl diglycol acetate as the other organic solvent, and passed twice through a chilled three-roll kneader. And dispersed. Thereafter, the obtained conductive paste was printed in a predetermined pattern on a PET substrate and a PC substrate, respectively, and then dried with a hot air dryer at 130 ° C. for 30 minutes to obtain a conductive thin film. Then, using this electroconductive thin film, basic physical properties, such as a specific resistance and adhesiveness, were measured and evaluated. Tables 2-1 and 2-2 show the evaluation results of paste and paste coating film, conductivity, chemical attack, and spreadability.

<Examples 2 to 10>
Examples 2 to 13 were carried out by changing the resin and formulation of the conductive paste. The formulation and evaluation results of the conductive paste are shown in Tables 2-1 and 2-2. In the examples, good coating properties and evaluation without chemical attack could be obtained. It was also confirmed that the conductivity of the binder resin (A) -1 to which the organic solvent (E) was added was improved compared to the unadded product.

In Table 2-1, Table 2-2, the following binder resin, conductive powder, organic solvent, carbon, and other compounds were used.
Binder resin A (1): Phenoxy resin PKHC manufactured by InChem (weight average molecular weight: 43,000 Glass transition temperature: 67 ° C)
Binder resin A (2): Phenoxy resin InChme PKHH (weight average molecular weight: 57,000, glass transition temperature: 70 ° C),
Binder resin A (3): Acrylic resin Kyoeisha Chemical Oricox KC-7000 (weight average molecular weight: 30.000 Glass transition temperature: 56 ° C)
Binder resin A (4): Polyester resin (obtained from the present applicant) Byron GK890 (weight average molecular weight: 17.000 glass transition temperature: 20 ° C)
Binder resin A (5): Polyvinyl acetal resin BM-5 manufactured by Sekisui Chemical Co., Ltd. (weight average molecular weight: 53,000 Glass transition temperature: 67 ° C)
Binder resin A (6): Polyurethane resin Desmocoll 500 (weight average molecular weight: 97,000, glass transition temperature: 47 ° C) manufactured by Sumitomo Bayer
Conductive powder B (1): flaky silver powder (D50: 3.5 μm)
Conductive powder B (2): Spherical silver powder (D50: 1.4 μm)
Organic solvent C (1): Dipropylene glycol monomethyl ether (Hisolv DPM) manufactured by Toho Chemical Co., Ltd.
Organic solvent C (2): 3-methoxy-3-methyl-1-butanol (Solfit) manufactured by Kuraray Co., Ltd.
Second organic solvent (1): Propylene glycol (industrial propylene glycol) manufactured by Adeka Corporation
Second organic solvent (2): Sankyo Chemical Co., Ltd. 1,3 butanediol (1,3 butyl glycol)
Other organic solvents (1): Ethyl diglycol acetate (EDGAC) manufactured by Daicel Corporation
Other organic solvent (2): Diacetone alcohol manufactured by Sankyo Chemical Co., Ltd. Other organic solvent (3): Dibasic acid ester (DBE) manufactured by INVISTA
Carbon black powder: Ketjen black made by Lion (ECP-600JP)
Curing agent: Bullet type blocked isocyanate manufactured by Vaxenden (part number 7960)
Curing catalyst: Kyodo Pharmaceutical Co., Ltd. KS1260
Dispersant: Disperbyk193 from Big Chemie
Additive: BYK-410 made by Big Chemie

<Comparative Example 1>
A silver paste was prepared in the same manner as in Example 1 except that 100% of EDGAC was used as an organic solvent, and the obtained conductive paste was printed on a PC substrate in a predetermined pattern, followed by hot air at 130 ° C. for 30 minutes. It dried with the dryer and obtained the electroconductive thin film. Thereafter, basic physical properties such as specific resistance and adhesion were measured and evaluated. The evaluation results of the paste and paste coating film are shown in Tables 2-1 and 2-2.

<Comparative example 2>
A silver paste was prepared in the same manner as in Comparative Example 1 using the components and blends shown in Tables 2-1 and 2-2, and a coating film was prepared using a PC film as a base material. The same was done. The evaluation results are shown in Tables 2-1 and 2-2.

From Examples 1 to 10 and Comparative Examples 1 and 2, it can be seen that the spreadable conductive paste of the present invention has good spreadability, good adhesion to the substrate, and excellent conductivity. .

<Application Example 1>
Using a spreadable conductive paste obtained in Example 1 on a polycarbonate (PC) film (Mitsubishi Gas Chemical Co., Ltd. FE-2000) having a thickness of 400 μm, a predetermined circuit pattern was formed, and a dry film thickness was 15 μm ± 3 μm. Was printed and dried under predetermined conditions. Next, the obtained polycarbonate film with a circuit pattern was subjected to curved surface processing with a hemispherical male / female mold having a diameter of 30 mm. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of curved surfaces was similarly evaluated using the spreadable conductive pastes obtained in Examples 2 to 10. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.
<Application Example 2>
In Application Example 1, instead of the polycarbonate (PC) film, a readily molded polyester film “Soft Shine” (manufactured by Toyobo Co., Ltd.) with a thickness of 188 μm was used, and the same operation was performed in the same manner, and a three-dimensional curved printed wiring board. Got. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of curved surfaces was similarly evaluated using the spreadable conductive pastes obtained in Examples 2 to 10. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.
<Application Example 3>
In Application Example 1, instead of the polycarbonate (PC) film, a 125 μm thick polyethylene naphthalate “Teonex” (manufactured by Teijin DuPont Co., Ltd.) was used, and the same operation was performed in the same manner to obtain a three-dimensional curved printed wiring. I got a plate. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of curved surfaces was similarly evaluated using the spreadable conductive pastes obtained in Examples 2 to 10. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.

<Example 11>
500 parts of phenoxy resin PKHC manufactured by InChem as the resin binder (A) (including 400 parts of dipropylene glycol monomethyl ether as the organic solvent (C)), and flaky silver powder (D50 = 3) as the conductive powder (B) 0.5 μm), 10 parts of carbon black, 10 parts of propylene glycol as the second solvent, and 30 parts of ethyl diglycol acetate as the other organic solvent were blended twice in a chilled three-roll kneader. Distributed through. Thereafter, the obtained conductive paste was printed in a predetermined pattern on a PET substrate and a PC substrate, respectively, and then dried with a hot air dryer at 130 ° C. for 30 minutes to obtain a conductive thin film. Then, using this electroconductive thin film, basic physical properties, such as a specific resistance and adhesiveness, were measured and evaluated. Tables 3-1 and 3-2 show the evaluation results of paste and paste coating film, conductivity, chemical attack, and spreadability.

<Examples 12 to 18>
Examples 12 to 18 were carried out by changing the resin and formulation of the conductive paste. The formulation and evaluation results of the conductive paste are shown in Tables 3-1 and 3-2. In the examples, good coating properties and evaluation without chemical attack could be obtained.
In Table 3-1, Table 3-2, the following binder resin, conductive powder, organic solvent, carbon, and other compounds were used.
Binder resin A (1): Phenoxy resin PKHC manufactured by InChem (weight average molecular weight: 43,000 Glass transition temperature: 67 ° C)
Binder resin A (2): Phenoxy resin InChme PKHH (weight average molecular weight: 57,000, glass transition temperature: 70 ° C),
Binder resin A (3): Acrylic resin Kyoeisha Chemical Oricox KC-7000 (weight average molecular weight: 30.000 Glass transition temperature: 56 ° C)
Binder resin A (4): Polyester resin (Toyobo Co., Ltd.) Byron GK890 (weight average molecular weight: 17.000 glass transition temperature: 20 ° C)
Binder resin A (5): Polyvinyl acetal resin BM-5 manufactured by Sekisui Chemical Co., Ltd. (weight average molecular weight: 53,000 Glass transition temperature: 67 ° C)
Binder resin A (6): Polyurethane resin Desmocoll 500 (weight average molecular weight: 97,000, glass transition temperature: 47 ° C) manufactured by Sumitomo Bayer
Conductive powder B (1): flaky silver powder (D50: 3.5 μm)
Conductive powder B (2): Spherical silver powder (D50: 1.4 μm)
Organic solvent C (1): Dipropylene glycol monomethyl ether (Hisolv DPM) manufactured by Toho Chemical Co., Ltd.
Organic solvent C (2): 3-methoxy-3-methyl-1-butanol (Solfit) manufactured by Kuraray Co., Ltd.
Organic solvent C (3): Sankyo Chemical Co., Ltd. 1,3 butanediol (1,3 butyl glycol)
Other organic solvents (1): Ethyl diglycol acetate (EDGAC) manufactured by Daicel Corporation
Other organic solvent (2): Diacetone alcohol manufactured by Sankyo Chemical Co., Ltd. Other organic solvent (3): Dibasic acid ester (DBE) manufactured by INVISTA
Carbon black powder: Ketjen black made by Lion (ECP-600JP)
Curing agent: Burette type blocked isocyanate, manufactured by Vaxenden (Part No. 7960)
Curing catalyst: Kyodo Pharmaceutical Co., Ltd. KS1260
Dispersant: Disperbyk193 from Big Chemie
Additive: BYK-410 made by Big Chemie

<Comparative Example 11>
A silver paste was prepared in the same manner as in Example 1 except that carbon black powder was not used as the paste composition, and the obtained conductive paste was printed on a PC substrate in a predetermined pattern, and then heated at 130 ° C. for 30 minutes. It dried with the dryer and obtained the electroconductive thin film. Thereafter, basic physical properties such as specific resistance and adhesion were measured and evaluated. The evaluation results of the paste and the paste coating film are shown in Tables 3-1 and 3-2.

<Comparative Examples 12-14>
A silver paste was prepared in the same manner as in Comparative Example 1 with the components and blends shown in Tables 3-1 and 3-2, and a coating film was prepared using a PC film as a base material. The same was done. The evaluation results are shown in Tables 3-1 and 3-2.

From Examples 11 to 18 and Comparative Examples 11 to 14, it can be seen that the spreadable conductive paste of the present invention has good spreadability, good adhesion to the substrate, and excellent conductivity. .

<Application Example 11>
Using a spreadable conductive paste obtained in Example 1 on a polycarbonate (PC) film (Mitsubishi Gas Chemical Co., Ltd. FE-2000) having a thickness of 400 μm, a predetermined circuit pattern was formed, and a dry film thickness was 15 μm ± 3 μm. Was printed and dried under predetermined conditions. Next, the obtained polycarbonate film with a circuit pattern was subjected to curved surface processing with a hemispherical male / female mold having a diameter of 30 mm. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of curved surfaces was similarly evaluated using the spreadable conductive pastes obtained in Examples 12 to 18. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.

<Application Example 12>
In Application Example 11, instead of the polycarbonate (PC) film, a readily molded polyester film “Soft Shine” (manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm was used, and the same operation was carried out in the same manner to obtain a three-dimensional curved printed wiring board. Got. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of curved surfaces was similarly evaluated using the spreadable conductive pastes obtained in Examples 12 to 18. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.

<Application Example 13>
In Application Example 11, instead of the polycarbonate (PC) film, a 125 μm thick polyethylene naphthalate “Teonex” (manufactured by Teijin DuPont Co., Ltd.) was used, and the same operation was carried out in the same manner to obtain a three-dimensional curved printed wiring. I got a plate. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of curved surfaces was similarly evaluated using the spreadable conductive pastes obtained in Examples 12 to 18. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.

<Example 21>
500 parts of phenoxy resin PKHC manufactured by InChem as the resin binder (A) (including 400 parts of dipropylene glycol monomethyl ether as the organic solvent (C)), and flaky silver powder (D50 = 3) as the conductive powder (B) 1.5 μm), 15 parts of bullet type isocyanate block 7960 (Baxenden) as curing agent (E), 2 parts of KS1260 as curing catalyst, 10 parts of carbon black powder, propylene glycol as second solvent 10 parts and 20 parts of ethyl diglycol acetate as other organic solvent were mixed and dispersed twice by passing through a chilled three-roll kneader. Thereafter, the obtained conductive paste was printed in a predetermined pattern on a PE film and a PC film, respectively, and then dried with a hot air dryer at 130 ° C. for 30 minutes to obtain a conductive thin film. Then, using this electroconductive thin film, physical properties, such as a specific resistance and adhesiveness, were measured and evaluated. The evaluation results are shown in Tables 4-1 and 4-2.

<Examples 22 to 30>
Examples 22 to 30 were carried out by changing the resin and the composition of the conductive paste. The formulation and evaluation results of the conductive paste are shown in Tables 4-1 and 4-2. In the examples, good coating properties and evaluation without chemical attack could be obtained.

In Table 4-1, Table 4-2, the following binder resin, conductive powder, organic solvent, carbon, and other compounds were used.
Binder resin A (1): Phenoxy resin PKHC manufactured by InChem (weight average molecular weight: 43,000 Glass transition temperature: 67 ° C)
Binder resin A (2): Phenoxy resin InChme PKHH (weight average molecular weight: 57,000, glass transition temperature: 70 ° C),
Binder resin A (3): Acrylic resin Kyoeisha Chemical Oricox KC-7000 (weight average molecular weight: 30.000 Glass transition temperature: 56 ° C)
Binder resin A (4): Polyester resin (Toyobo Co., Ltd.) Byron GK890 (weight average molecular weight: 17.000 glass transition temperature: 20 ° C)
Binder resin A (5): Polyvinyl acetal resin BM-5 manufactured by Sekisui Chemical Co., Ltd. (weight average molecular weight: 53,000 Glass transition temperature: 67 ° C)
Binder resin A (6): Polyvinyl acetal resin Sekisui Chemical Co., Ltd. BH-6 (weight average molecular weight: 92,000 Glass transition temperature: 67 ° C)
Binder resin A (7): Polyurethane resin Desmocoll 500 (weight average molecular weight: 97,000, glass transition temperature: 47 ° C) manufactured by Sumitomo Bayer
Conductive powder B (1): flaky silver powder (D50: 3.5 μm)
Conductive powder B (2): Spherical silver powder (D50: 1.4 μm)
Organic solvent C (1): Dipropylene glycol monomethyl ether (Hisolv DPM) manufactured by Toho Chemical Co., Ltd.
Organic solvent C (2): 3-methoxy-3-methyl-1-butanol (Solfit) manufactured by Kuraray Co., Ltd.
Second organic solvent (1): Propylene glycol (industrial propylene glycol) manufactured by Adeka Corporation
Second organic solvent (2): Sankyo Chemical Co., Ltd. 1,3 butanediol (1,3 butyl glycol)
Other organic solvents (1): Ethyl diglycol acetate (EDGAC) manufactured by Daicel Corporation
Other organic solvent (2): Diacetone alcohol manufactured by Sankyo Chemical Co., Ltd. Other organic solvent (3): Dibasic acid ester (DBE) manufactured by INVISTA
Carbon black powder (1): Ketjen black made by Lion (ECP-600JP)
Curing agent D (1): Bullet type blocked isocyanate product No. 7960 (Baxenden)
Curing agent D (2): Adduct type blocked isocyanate DURANATE E402-B80B (manufactured by Asahi Kasei Corporation)
Curing agent D (3): Epoxy compound EX-314 manufactured by Nagase ChemteX Corporation
Curing catalyst: Kyodo Pharmaceutical Co., Ltd. KS1260
Dispersant: Disperbyk193 from Big Chemie
Additive: BYK-410 made by Big Chemie

<Comparative Examples 21 and 22>
A silver paste was prepared in the same manner as in the examples with the components and blends shown in Tables 4-1 and 4-2, and a coating film was prepared using a PC film and a PET film as a base material. The same was done. The evaluation results are shown in Tables 2-1 and 2-2.

From Examples 21 to 30 and Comparative Examples 21 to 22, it can be seen that the spreadable conductive paste of the present invention has good spreadability, good adhesion to the substrate, and excellent conductivity. .

<Application Example 21>
Using a spreadable conductive paste obtained in Example 1 on a polycarbonate (PC) film (Mitsubishi Gas Chemical Co., Ltd. FE-2000) having a thickness of 400 μm, a predetermined circuit pattern was formed, and a dry film thickness was 15 μm ± 3 μm. Was printed and dried under predetermined conditions. Next, the obtained polycarbonate film with a circuit pattern was subjected to curved surface processing with a hemispherical male / female mold having a diameter of 30 mm. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of the curved surface was similarly evaluated using the spreadable conductive paste obtained in Examples 22 to 30. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.

<Application Example 22>
In Application Example 21, in place of the polycarbonate (PC) film, an easily molded polyester film “Soft Shine” (manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm was used, and the same operation was carried out in the same manner to obtain a three-dimensional curved printed wiring board. Got. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of the curved surface was similarly evaluated using the spreadable conductive paste obtained in Examples 22 to 30. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.

<Application Example 23>
In Application Example 21, instead of polycarbonate (PC) film, a 125 μm thick polyethylene naphthalate “Teonex” (manufactured by Teijin DuPont Co., Ltd.) was used, and the same operation was carried out in the same manner to obtain a three-dimensional curved printed wiring. I got a plate. There was no disconnection in the obtained circuit pattern, and no conduction failure occurred.
Similarly, the workability of the curved surface was similarly evaluated using the spreadable conductive paste obtained in Examples 22 to 30. As a result, any spreadable paste did not cause cracks or poor conduction, and had practically sufficient electrical characteristics as a three-dimensional curved printed wiring board.

 

The spreadable conductive paste of the present invention is a circuit sheet or printed circuit board having a three-dimensional structure because the circuit pattern is not cracked or peeled even in a process in which a laminate having a circuit pattern is deformed or molded by heat or pressure. It is useful as a three-dimensional molded product having an electric circuit formed on the surface.

Claims (21)

1. In the conductive paste containing the binder resin (A) made of a thermoplastic resin, the conductive powder (B), and the organic solvent (C), the organic solvent (C) is a glycol ether solvent or / and an alcohol solvent. A spreadable conductive paste characterized by that.
2. The spreadable conductive paste according to claim 1, wherein the boiling point of the organic solvent (C) is in the range of 100 to 300 ° C.
3. 3. The spreadable conductive paste according to claim 1 or 2, wherein the second solvent includes a solvent having a slower evaporation rate than the organic solvent (C) and containing a hydroxyl group.
4. The binder resin (A) is one or a mixture of two or more selected from the group consisting of a polyester resin, a polyurethane resin, an epoxy resin, a phenoxy resin, a vinyl chloride resin, a fiber derivative resin, a polyvinyl acetal resin, and an acrylic resin. The spreadable conductive paste according to any one of claims 1 to 3, wherein the spreadable conductive paste is provided.
5. The spreadable conductive paste according to any one of claims 1 to 4, wherein the binder resin (A) has a glass transition temperature of 30 ° C or higher and a number average molecular weight in the range of 3000 to 150,000.
6. A method for producing a curved printed wiring board, comprising: a step of thermally deforming a plastic substrate after printing the spreadable conductive paste according to any one of claims 1 to 5 on a plastic substrate.
7. A conductive paste containing a thermoplastic resin binder resin (A), conductive powder (B), organic solvent (C) and carbon black powder (D) has an F value of 75 to 95%. A spreadable conductive paste.
8. The binder resin (A) is one or a mixture of two or more selected from the group consisting of a polyester resin, a polyurethane resin, an epoxy resin, a phenoxy resin, a vinyl chloride resin, a fiber derivative resin, a polyvinyl acetal resin, and an acrylic resin. 8. The spreadable conductive paste according to claim 7, wherein the spreadable conductive paste is provided.
9. The spreadable conductive paste according to claim 7 or 8, wherein the binder resin (A) has a glass transition temperature of 20 ° C or higher and a number average molecular weight in the range of 3000 to 150,000.
10. The spreadable conductive paste according to any one of claims 7 to 9, wherein the organic solvent (C) is a glycol ether solvent or / and an alcohol solvent.
11. The spreadable conductive paste according to any one of claims 7 to 10, wherein the boiling point of the organic solvent (C) is in the range of 100 to 300 ° C.
12. The spreadable conductive paste according to any one of claims 7 to 11, comprising a solvent having a slower evaporation rate than the organic solvent (C) and containing a hydroxyl group as the second solvent.
13. A method for producing a curved printed wiring board, comprising the step of thermally deforming a plastic substrate after printing the spreadable conductive paste according to any one of claims 7 to 12 on a plastic substrate.
14. In a spreadable conductive paste containing a binder resin (A), a conductive powder (B), an organic solvent (C), and a curing agent (E) made of a thermoplastic resin, the binder resin (A) is a polyester resin or polyurethane. One or more selected from the group consisting of resin, epoxy resin, phenoxy resin, vinyl chloride resin, fiber derivative resin, polyvinyl acetal resin, acrylic resin, and the curing agent (E) is blocked isocyanate or A spreadable conductive paste characterized by being either or both of an epoxy compound.
15. The spreadable conductive paste according to claim 14, wherein the organic solvent (C) is a glycol ether solvent or / and an alcohol solvent.
16. The spreadable conductive paste according to claim 14 or 15, wherein the boiling point of the organic solvent (C) is in the range of 100 to 300 ° C.
17. The spreadable conductive paste according to any one of claims 14 to 16, wherein the second solvent includes a solvent having a slower evaporation rate than the organic solvent (C) and containing a hydroxyl group.
18. The spreadable conductive paste according to any one of claims 14 to 17, wherein the curing agent (E) is at least one block isocyanate selected from a burette type, a trimmer type, and an adduct type.
19. The spreadable conductive paste according to any one of claims 14 to 18, wherein the curing agent (E) is a glycerol type epoxy resin.
20. The spreadable conductive paste according to any one of claims 14 to 19, wherein the binder resin (A) has a glass transition temperature of 30 ° C or higher and a number average molecular weight in the range of 3000 to 150,000.
21. 21. A method of manufacturing a curved printed wiring board, comprising a step of thermally deforming a plastic substrate after printing the spreadable conductive paste according to claim 14 on a plastic substrate.