KR102311273B1 - Conductive copper powder based oil paste for improved long term stability and manufacturing method thereof - Google Patents

Abstract

The present invention relates to oil paste based on conductive copper powder having improved long term stability, and a method for manufacturing the same. The present invention provides copper-based oil paste and a method for manufacturing the same, which manufacture copper powder-based oil paste by treating a surface of copper powder with a vinyl imidazole polymer in order to prevent oxidation of the copper powder and provide thermal stability and long term stability, mixing the treated copper powder complex with an oil binder containing a solvent and an additive, so that the copper powder-based oil paste can replace conventional conductive metal paste and can be applied to fields of electronic circuit elements, semiconductor elements, flexible electrical and electronic elements, and wearable electrical and electronic elements.

Description

Conductive copper powder based oil paste for improved long term stability and manufacturing method thereof

The present invention relates to a conductive copper powder-based oil-based paste with improved long-term stability and a method for manufacturing the same. More specifically, in order to provide long-term stability while maintaining the electrical conductivity of the copper powder-based oil-based paste, the surface of the copper powder etched with citric acid is treated with an imidazole polymer, and the copper powder with the corrosion-preventing layer is treated with a solvent and additives. Provided are a copper powder-based oil-based paste and a method for manufacturing the same, which can be used to replace the conventional conductive metal paste and to be applied to low-cost uses by mixing with an oil-based binder to prepare a conductive copper powder oil-based paste.

Conductive copper powder-based oil-based paste is prepared by dispersing various types of copper powder in an oil-based binder resin dissolved in a solvent, and consists of copper powder coated with a corrosion protection layer, solvent, oil-based binder, and additives.

Silver powder-based conductive paste is a representative conductive metal paste and is used in various electrical and electronic material fields, but is limited in price compared to other metal powder-based pastes. On the other hand, copper powder-based conductive paste has a low price and similar conductivity As a result, the field of application is increasing.

In order to manufacture a copper powder-based conductive paste having excellent conductivity, a corrosion protection layer should be formed on the surface of the copper powder, and the oxidation-prevented copper powder should be uniformly distributed in the binder resin containing the solvent and additives. In the case of the conventional copper powder-based conductive paste, there was a problem of oxidation through a portion having a low degree of dispersibility in the binder resin during mixing.

Therefore, as a method of preventing oxidation of copper, a method of forming a corrosion-preventing coating layer by surface treatment of copper powder has been proposed, and among them, various imidazole compounds are a representative corrosion inhibitor. The imidazole compound used as a surface treatment agent for copper powder is 2-alkylimidazole, 2-alkylbenzimidazole, 2-arylimidazole, and 2-aralkylimidazole. When zero is used, oxidation of the surface of the copper powder can be effectively prevented, but during high temperature heat treatment, the surface of the copper powder is oxidized and the conductivity of the conductive paste is lowered. On the other hand, in the present specification, when the surface of the copper powder is coated using an imidazole polymer, which is a high-molecular corrosion inhibitor, excellent heat resistance properties are exhibited even in a high-temperature heat treatment process.

In the case of copper paste, the copper density is 8.96 g/cm ³ at room temperature, which is relatively heavy compared to the oil-based binder, so copper powder may re-agglomerate in the paste during paste preparation. In addition, when the copper paste is to be used after being stored for a long time, there is a problem in that time and inconvenience are caused due to the redispersion process due to the non-homogeneity of the product. Therefore, the long-term stability of the copper-based conductive paste by long-term storage is strongly required in the practical application stage of the copper paste.

Korea Patent No. 1555753 specifies a method for manufacturing a corrosion-resistant copper paste in a single process, the surface treatment of copper powder must be performed under an inert atmosphere, and polystyrene sulfonate, an aqueous binder, is introduced to make a copper powder-based aqueous paste Although a method for manufacturing a copper powder has been proposed, it has a disadvantage in that it cannot secure the water resistance and long-term stability of the copper powder aqueous paste.

In addition, Korea Patent No. 1906767 specifies a method for manufacturing a copper powder-based conductive paste by coating a cross-linked surface treatment agent on copper powder that has been simultaneously surface-treated with an aqueous hydrochloric acid solution and an aqueous phosphoric acid solution, and applying an aqueous binder and an oil-based binder, have. In the case of this copper powder-based oil-based paste, a cellulose-based binder (ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, etc.) was used as an oil-based binder, but the cross-linked imidazole-silane copolymer coated on the copper powder surface and an oil-based binder were used. There was a problem in that the long-term stability of the copper powder oil-based paste could not be secured because the binder gradually caused a condensation reaction over time to cause the oil-based paste to gel.

Accordingly, there is an urgent need to develop a method capable of easily manufacturing a copper powder-based oil-based paste having excellent mechanical properties, electrical conductivity, and heat resistance while being able to solve the limitations of the long-term stability of the method.

In particular, after coating the surface of copper powder using imidazole polymer to form an anti-corrosion layer of copper, various copper powder bases that suppress gelation caused by condensation with oil-based binders, improve long-term stability, and maintain uniform conductivity There is a strong need for a manufacturing method that can be applied to a conductive oil-based paste.

Prior art literature

(Patent Document 0001) Korean Patent No. 1555753

(Patent Document 0002) Korean Patent No. 1906767

It is an object of the present invention to solve the problems of the prior art at once by introducing an imidazole polymer on the surface of copper powder to form a coating layer for corrosion prevention, and a copper powder in which a corrosion prevention layer is formed on an oil-based binder resin in which a solvent and an additive are mixed. It is intended to prepare a conductive copper powder-based oil-based paste having long-term stability by dispersing it.

After numerous experiments and in-depth research, the present inventor introduced an oil-based paste based on conductive copper powder with improved long-term stability, that is, an imidazole polymer, as an anti-corrosion layer of copper powder, and an additive dissolved in a solvent. A conductive copper powder-based oil-based paste with improved long-term stability was prepared by dispersing copper powder with a corrosion-resistant layer in the introduced oil-based binder resin.

An object of the present invention is to introduce an imidazole polymer to copper powder to form a coating layer for corrosion protection and to prepare a copper powder-based oil-based paste with improved long-term stability.

The method for manufacturing an oil-based paste based on conductive copper powder according to the present invention,

(a) preparing an imidazole polymer that is radically polymerized using an imidazole monomer represented by the following Chemical Formula 1 and an initiator;

(b) preparing an imidazole polymer-copper composite in which the imidazole polymer of (a) is introduced into a copper powder surface-treated with an aqueous citric acid solution; and,

(c) preparing an oil-based paste based on conductive copper powder, characterized in that the imidazole polymer-copper composite of (b) includes a solvent, an oil-based binder, and an additive using a paste mixer.

[Formula 1]

Here, X represents a vinyl group (vinyl), an allyl group (allyl), a vinylbenzyl group (vinylbenzyl), and an alkenyl group (alkenyl), Y is a hydrogen atom (H), a methyl group (-CH ₃ ), an ethyl group (-CH ₂ CH ₃ ), a propyl group (-CH ₂ CH ₂ CH ₃ ), a butyl group (-CH ₂ CH ₂ CH ₂ CH ₃ ), a pentyl group (-CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), and a hexyl group (-CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ) is represented.

Unless otherwise specified in the present specification, numerical ranges such as time, temperature, content, size, etc. mean a range capable of optimizing the manufacturing method of the present invention.

The method for producing a copper-based oil-based paste with improved long-term stability according to the present invention is a completely new method compared to the previously reported oil-based binder-based copper paste, and an imidazole polymer for corrosion prevention is coated on the surface of copper powder etched with citric acid. to prepare an imidazole polymer-copper composite, and mixing the imidazole polymer-copper composite with an oil-based binder including a solvent and an additive to prepare an oil-based paste based on conductive copper powder with improved corrosion resistance and long-term stability.

In addition, the copper powder-based oil-based paste prepared in the present invention is a conductive copper paste that does not require heat treatment and curing process at all, and uses copper powder with relatively good price competitiveness and is a copper paste with corrosion resistance and long-term stability. It has the characteristics of being able to mass-produce. Compared to the conventional imidazole-vinylsilane copolymer, which is a corrosion inhibitor, the imidazole polymer prepared in the present invention has a simple process step in terms of polymerization process, and thus has the advantage of low manufacturing cost in terms of economy. When oil-based copper paste with improved long-term stability is commercialized, it is expected to strengthen international competitiveness due to localization in the domestic conductive metal paste industry, which is mainly dependent on imports, and to increase price competitiveness, increase exports, increase productivity, and reduce costs. In addition, by using a copper powder-based oil-based paste with improved long-term stability as a conductive ink solution for printing, it is easily applied as an electrode material on a variety of printed boards, and then a conductive copper paste electrode having the shape and size required for the product is manufactured to produce an electronic circuit device. , semiconductor devices, flexible electrical and electronic devices, and wearable electrical and electronic devices can be applied.

1 is a flowchart illustrating a method for manufacturing a copper powder-based oil paste according to an embodiment of the present invention.
2 is a diagram schematically illustrating a cross-sectional structure of an imidazole polymer-copper composite prepared by putting an imidazole polymer in copper powder surface-treated with an aqueous citric acid solution according to an embodiment of the present invention.

In the present invention, it was attempted to prepare a copper powder-based oil-based paste with improved corrosion resistance and long-term stability using various imidazole polymers. The monomer used when preparing the imidazole polymer in step (a) is an imidazole compound represented by the following formula (1).

[Formula 1]

Here, Chemical Formula 1 represents a polymerizable imidazole compound, X represents a vinyl group, an allyl group, a vinylbenzyl group, and an alkenyl group, and is a polymerizable functional group, and Y is Hydrogen atom (H), methyl group (-CH), ethyl group (-CH ₂ CH ₃ ), propyl group (-CH ₂ CH ₂ CH ₃ ), butyl group (-CH ₂ CH ₂ CH ₂ CH ₃ ), pentyl group ( —CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), and a hexyl group (—CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ).

In the case of the monomer used for preparing the imidazole polymer, which is a coating agent for corrosion protection, vinylimidazole is preferably used, but is not limited thereto. The conductive copper powder-based oil-based paste and its manufacturing method specified in the subsequent steps are applicable to all of the above-mentioned various imidazole polymers.

Polymer materials generally have a higher molecular weight than organic compounds and have excellent mechanical properties, so they can be used in applications requiring high strength and heat resistance. Accordingly, the present inventors radically polymerized the imidazole monomer in order to solve the gelation phenomenon of the copper powder-based oil-based paste and use it as a coating agent for corrosion prevention of copper powder. In addition, numerous studies were conducted to prepare an optimal oil-based binder and imidazole polymer that maintains heat resistance and high conductivity in order to improve long-term stability in copper powder-based oil-based paste, and the optimal reaction conditions were found and started.

The oil-based binder suitable for use in the low-temperature quick-drying paste of the present invention is a first monomer unit consisting of styrene and alpha-methylstyrene, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. A copolymer comprising at least one substance in each monomer unit selected from monomers consisting of two monomer units and a third monomer unit consisting of acrylic acid, methacrylic acid and hydroxyethyl methacrylate is used.

The imidazole-silane copolymer, which is a conventionally used coating agent for preventing corrosion of copper powder, provided oxidation prevention and thermal stability of copper paste when treated on the surface of copper powder. The copper paste prepared by applying the imidazole-silane copolymer as a corrosion inhibitor to the novel oil-based binder system of the present invention is excellent in oxidation inhibition and heat resistance, but when stored for a long time, it prevents gelation in the copper powder-based oil paste over time. As a result, the copper oil paste itself is solidified and the original function of the copper powder-based conductive oil paste is lost.

Such a phenomenon causes the copper paste prepared by the imidazole-silane copolymer, which is an anticorrosion coating agent to be treated to protect the surface of the copper powder, and the oil-based binder and gelation reaction over time to harden. To describe the above phenomenon in detail, the methoxy group, 2-methoxyethoxy group, and ethoxy group of the silane compound present in the imidazole-silane copolymer form a hydroxyl group (-OH) by a hydrolysis reaction. , the newly formed hydroxyl group chemically bonds with the organic binder through a condensation reaction over time to decrease the fluidity of the copper powder-based oil paste, and ultimately change to a solid state.

Therefore, in this patent, when a new imidazole polymer in which a silane compound forming a hydroxyl group is removed from an imidazole-silane copolymer previously used as a coating for corrosion prevention of copper powder is applied, the long-term stability problem of the copper powder oil-based paste presented above is applied. could be resolved at once.

In addition, since the oil-based binder of the present invention was developed for copper paste, which has excellent low-temperature and quick-drying properties, water resistance, heat resistance, and long-term stability of copper powder-based oil-based paste, it is better to use the imidazole polymer alone than to use the imidazole-silane copolymer. In the field of practical application, excellent physical properties of copper powder-based oil-based paste were exhibited. In addition, the imidazole polymer has a simpler manufacturing step in terms of polymerization process and is economical compared to imidazole-silane copolymer, which is a corrosion inhibitor used in the past. It has the advantage of low manufacturing cost.

In the case of radical polymerization of the imidazole monomer in step (a), the initiator concentration is preferably 0.6 to 5 parts by weight based on 100 parts by weight of the imidazole monomer. In the vinylimidazole polymer, the nitrogen atom present in the imidazole ring has a lone pair of electrons and forms a complex with the copper atom present on the surface of the powder to inhibit oxidation of the copper powder and provide heat resistance. When the initiator concentration is lower than 0.6 parts by weight relative to 100 parts by weight of the imidazole monomer during radical polymerization of the imidazole monomer, the degree of polymerization of the imidazole polymer is high and the viscosity is high when applied as an oil-based binder, so that the flowability of the oil-based binder is poor. When the concentration of the initiator exceeds 5 parts by weight based on 100 parts by weight of the imidazole monomer, the polymerization degree of the imidazole polymer is lowered, and when applied as an oil-based binder, the viscosity is low, which causes layer separation of the copper-based oil-based paste, making it difficult to maintain the shape.

In the case of radical polymerization of the imidazole monomer in step (a), the polymerization time is preferably 6 to 36 hours. When an imidazole polymer is formed by introducing a radical polymerization method when preparing the polymer, it is possible to overcome the limitation of the gelation phenomenon of the oily paste caused by the imidazole-silane copolymer, which has been used as an anticorrosion coating agent for copper powder. . When the radical polymerization time is less than 6 hours, the degree of polymerization of the imidazole polymer is low, and a portion of the imidazole monomer is present in the reactor. When the radical polymerization time exceeds 36 hours, the polymerization degree of the imidazole polymer is increased, and thus the surface coating of the copper powder is not easy.

In the case of radical polymerization of the imidazole monomer in step (a), the polymerization temperature is preferably 60 to 90 degrees Celsius.

When the radical polymerization temperature is less than 60 degrees Celsius, the polymerization rate of the imidazole compound is too slow, which is not economical in terms of manufacturing the imidazole polymer. is difficult to control, and the polymerization degree increases in a short time and causes an accelerated reaction, making it difficult to prepare an oil-based binder for copper-based oil-based paste.

The copper powder used in step (b) is preferably in the form of flakes having an average particle diameter of 0.1 to 20 micrometers, but is not limited thereto.

In step (b), a method of coating the copper powder with an imidazole polymer, which is a coating agent for preventing corrosion, after acid treatment of the copper powder with an aqueous citric acid solution is presented. This is intended to coat the imidazole polymer on the surface of copper particles on which the copper-citric acid chelate is formed in order to effectively bind various imidazole polymers to the citric acid-treated copper surface.

Currently, about 100,000 kinds of chemicals are distributed in the chemical industry, and among them, hazardous chemicals take a long time to decompose and have very high persistence, so they are harmful to human health and the environment. It is classified as a prohibited substance and an accident preparation substance. Hazardous substance solutions include strong acid solutions such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, and hydrofluoric acid, strong alkaline solutions such as caustic soda and potassium hydroxide, highly toxic organic solvents, and petrochemical fuels. The hazardous chemicals cause environmental problems during disposal after use in the manufacturing industry, and in recent years, serious restrictions on actual field use from the viewpoint of various environmental regulations are followed, and manufacturers are avoiding practical use.

In the conventional copper surface treatment method, hydrochloric acid, phosphoric acid and perchloric acid were mainly used for the purpose of removing the oxide layer. In the case of hydrochloric acid, phosphoric acid and perchloric acid used for the above purpose, as strong acids classified as hazardous chemicals, industries in the relevant field face serious regulations due to environmental problems when disposing of actual on-site waste liquid. In addition, the economic burden due to the waste liquid treatment of the strong acid aqueous solution is high, and in recent years, the use of the above substances tends to be avoided. In particular, hydrochloric acid is a class 3 hazardous substance and causes skin burns, headaches, and coughs, and has side effects such as damage to the respiratory mucosa when inhaling a large amount of high-concentration hydrogen chloride gas.

On the other hand, citric acid is classified as an existing chemical according to the chemical information system, so it has the advantage of being easy to use as a chemical that is processed for product production by industries. The citric acid is a white solid crystal, a weak organic acid, is ionized as one of the carboxylic acids and acts as a trivalent anion. It is an excellent chelating agent and is used to dissolve the metal surface by binding to the metal to easily remove the rust and oxide layer.

When the aqueous hydrochloric acid solution and the phosphoric acid aqueous solution used in the conventional copper surface treatment method were simultaneously treated on the copper powder surface, the copper surface was etched and copper-phosphate was formed during the process. In the case of the present invention, when the surface of the copper powder is treated using the citric acid aqueous solution alone, the copper surface oxide film can be removed through the etching process and the copper-citric acid chelate can be formed at the same time, so that the efficiency and simplicity of the surface treatment process can be obtained.

Therefore, in this patent, after removing the oxide film on the copper surface and forming a copper-citric acid chelate using an aqueous citric acid solution alone, the imidazole polymer, which is a coating agent for corrosion prevention, is treated on the copper surface from which the oxide film has been removed step by step to achieve the target performance of the present invention. could achieve

The concentration of the aqueous solution of citric acid added for surface treatment of copper powder in step (b) is preferably 0.3 to 40 parts by weight relative to 100 parts by weight of distilled water as a solvent.

When the concentration of the aqueous citric acid solution is less than 0.3 parts by weight relative to 100 parts by weight of distilled water, the surface treatment concentration of the copper powder is low and the etching rate of the oxide layer present on the surface of the copper powder is slow, so that the copper surface treatment time is required for a long time. The efficiency is low, and when the concentration of the citric acid aqueous solution is 40 parts by weight or more relative to 100 parts by weight of distilled water, the rapid etching reaction with the copper surface causes the loss of copper powder in a short time beyond the removal of the oxide layer of the copper powder and the crystallization of citric acid in the aqueous solution There is a disadvantage of this precipitation.

The volume of the aqueous citric acid solution added for surface treatment of the copper powder in step (b) is preferably 50 to 1000 milliliters based on 100 grams of the copper powder.

If the amount is less than 50 milliliters per 100 grams of copper powder, the amount of citric acid aqueous solution introduced is small, so the surface etching of the copper powder does not proceed efficiently, and the oxide layer remains on the copper surface, reducing the conductivity of the copper powder oil paste, and exceeding 1000 milliliters In this case, there is a problem in that the surface of the copper powder is etched excessively in a short time, causing weight loss of the copper powder.

It is preferable that the imidazole polymer in step (b) is 0.1 to 10 parts by weight based on 100 parts by weight of the copper powder.

When the imidazole polymer is less than 0.1 based on 100 parts by weight of the copper powder, the coating content is insufficient to impart corrosion resistance and heat resistance to the copper powder, and when it exceeds 10 based on 100 parts by weight of the copper powder, the imidazole polymer on the surface of the copper powder of the coating layer is excessively increased, resulting in an increase in the ratio of the non-conductive layer, resulting in a decrease in the electrical conductivity of the copper-based conductive paste.

The kind of solvent used when preparing the copper powder oil-based paste in step (c) is preferably an organic solvent, but is not particularly limited. When preparing a copper powder oil-based paste suitable for low-temperature quick-drying paste use, the organic solvents are ketone compounds such as acetone, methyl ethyl ketone, 2-pentanone, cyclopentanone, cyclohexanone, methylcyclohexanone, ionone, and methylionone. , methyl oxide, isophorone, diacetyl, acetylacetone, acetonylacetone, diacetyl alcohol, acetolcarbinol, carbon, menthone, acetophenone, and methylacetophenone. In addition, ethanol, propanol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, There are cyclopentanol, cyclohexanol, and methylcyclohexanol. It is not limited to primary alkyl alcohol, and it is possible to use secondary alcohol type, tertiary alcohol type and alkanediol, alcohol compounds having a cyclic structure. .

In step (c), the amount of the organic solvent is preferably 10 to 200 parts by weight based on 100 parts by weight of the oil-based binder. When the organic solvent is less than 10 parts by weight based on 100 parts by weight of the oil-based binder, the viscosity of the conductive paste is too high, so that the coating property is poor when the copper-based oil-based paste is applied. Since the viscosity of the oil-based paste is too low, a smearing phenomenon is caused during coating, so that it is not easy to form a film of the paste.

The binder used to prepare the conductive paste in step (c) is preferably an oil-based binder, but the type of binder used is not particularly limited.

When preparing a copper powder oil-based paste suitable for low-temperature quick-drying paste use, the oil-based binder is a copolymer including all of the first, second, and third monomer units, and each unit of the first, second, and third monomers is styrene and alpha-methylstyrene. A first monomer unit consisting of, a second monomer unit consisting of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate, and a second monomer unit consisting of acrylic acid, methacrylic acid, and hydroxyethyl methacrylate It is preferably a copolymer comprising at least one substance selected from 3 monomer units.

As for the oil-based binder of the copper paste, the copolymer to which the monomer having a short side chain length is introduced exhibits higher adhesion than the copolymer to which the monomer having a long side chain length is introduced. In addition, the oil-based binder of the copper paste exhibits superior properties in terms of peel strength and shear strength than that of a monomer having a short side chain length compared to a monomer having a long side chain length. Therefore, as the content of styrene, alpha-methylstyrene, methyl methacrylate, ethyl acrylate, and ethyl methacrylate in the oil-based binder increases, the adhesion and strength of the copper paste are improved. Butyl acrylate, butyl methacrylate, and hydroxyethyl methacrylate with a long monomer chain give flexibility to the copper paste, and acrylic acid, methacrylic acid and hydroxyethyl methacrylate improve the adhesion of the copper paste. serves to make

In the case of radical polymerization of the oil-based binder in step (c), the concentration of the initiator is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the monomer for the binder.

When the initiator concentration during radical polymerization of the oil-based binder is lower than 0.1 parts by weight relative to 100 parts by weight of the monomer for the binder, the polymerization degree of the oil-based binder polymer is high, and when applied as a copper powder-based oil-based paste, the viscosity of the paste is high, resulting in poor flowability of the paste. do. When the initiator concentration exceeds 10 parts by weight based on 100 parts by weight of the monomer for binder, the polymerization degree of the oil-based binder polymer is lowered, and when applied as a copper powder-based oil-based paste, the viscosity of the paste is low, causing layer separation of the paste, resulting in a homogeneous oil-based paste form difficult to maintain

In the case of radical polymerization of the oil-based binder in step (c), the polymerization time is preferably 12 to 48 hours.

In the case of an imidazole-silane copolymer previously used as a surface treatment agent for copper powder, a hydroxyl group is formed in the silane copolymer through a hydrolysis reaction. It causes a step-by-step side reaction, and ultimately the oil-based paste hardens due to gelation.

In the case of the present patent, when a polymer is prepared by radical polymerization of an oil-based binder, the anticorrosion coating agent is imidazole using imidazole monomer without a silane compound alone in order to remove the hydroxyl group present in the silane compound. The polymer was prepared. Therefore, an oil-based paste was prepared by mixing copper powder treated with a silane compound-free corrosion inhibitor with an oil-based binder. could do it The polymerization time during radical polymerization of the copolymer for binder is preferably 12 to 48 hours. When the radical polymerization time is less than 12 hours, the polymerization degree of the polymer for the oil-based binder is low, and some of the monomers for the oil-based binder are present in the polymerization reactor. Therefore, when a low-viscosity oil-based binder is applied to a copper powder surface-coated with an imidazole polymer, an oil-based paste is not effectively formed, and phenomena such as layer separation of the oil-based paste, reduced conductivity, and reduced heat resistance are caused. When the radical polymerization time exceeds 48 hours, the polymerization degree of the polymer for the binder increases, so that when a high-viscosity oil-based binder is introduced into the copper powder, the dispersibility of the copper powder surface-treated with the imidazole polymer in the oil-based paste is not good.

In the case of radical polymerization of the oil-based binder in step (c), the polymerization temperature is preferably 50 to 80 degrees Celsius.

When the radical polymerization temperature is less than 50 degrees Celsius, the polymerization degree of the polymer for the binder is low, so when a low-viscosity oil-based binder is applied, layer separation of the copper powder-based oil-based paste occurs. It is difficult to prepare an oil-based binder suitable for a copper-based oil-based paste because the polymerization rate of the monomers present in the copolymer is high, the polymerization degree is increased, and it is difficult to control the polymerization reaction due to the accelerated reaction of the polymer.

When preparing the copper powder-based oil-based paste, the amount of the oil-based binder is preferably 2 to 50 parts by weight based on 100 parts by weight of the copper powder. When the oil-based binder is less than 2 based on 100 parts by weight of the copper powder, the amount of the oil-based binder in the copper paste is insufficient to sufficiently cover the copper powder particles, and the dispersion of the oil-based paste is not easy due to aggregation between the copper powders. When the oil-based paste is coated, the coating film properties and film adhesion are deteriorated. When the oil-based binder exceeds 50 parts by weight relative to 100 parts by weight of the copper powder, the content of the oil-based binder in the copper paste is excessive, preventing mutual contact between the copper powder particles and causing deterioration of mechanical properties and conductivity of the copper powder-based oil-based paste will do

Preferably, the additive in step (c) further comprises at least one additive selected from a dispersing agent, a pattern forming agent, an antifoaming agent, a thickener, and a leveling agent.

In step (c), the dispersant is preferably any one of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant. The dispersant imparts the function of uniformly presenting the copper powder without agglomeration in the binder when manufacturing the copper powder-based oil-based paste. Among these dispersants, cationic surfactants include alkylamine salts and quaternary ammonium salts, and anionic surfactants include polycarboxylates, polyoxyalkylaryl phosphate esters and salts, alkenylsuccinates, and alkylbenzenesulfonates. , alkylnaphthalenesulfonate, alkanesulfonate, salt of naphthalenesulfonic acid formalin condensate, and fatty acid salt. Nonionic surfactants include polyoxyethylene derivatives, polyoxyalkylene ethers, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyalkylene alkylamines, poly There are oxyethylene hydrogenated castor oil, alkyl alkanamide, and sorbitan fatty acid ester. Amphoteric surfactants include alkylamine oxide and alkylbetaine. Products marketed as dispersants include DISPERBYK-102, DISPERBYK-103, DISPERBYK-107 DISPERBYK-108, DISPERBYK-109, DISPERBYK-110, DISPERBYK-111, DISPERBYK-112, DISPERBYK-115, DISPERBYK-118, DISPERBYK-130 , DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DISPERBYK-160, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-170 -171, DISPERBYK-174, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2008, DISPERBYK-2009, DISPERBYK-2013, DISPERBYK-2022, DISPERBYK-2025, DISPERBYK-2026, DISPERBYK-2050, DISPERBYK-2055, DISPERBYK-2117 , DISPERBYK-2118, DISPERBYK-2163, DISPERBYK-2164, DISPERBYK-2200, DISPERBYK-2205 (BYK Chemie), etc., and these may be used alone or in combination of two or more.

In step (c), the pattern forming agent increases the dispersion of the copper powder in the binder when preparing the copper powder-based oil-based paste, thereby optimizing the viscosity and imparting slip property,

Even after the paste is fired, it gives the function of forming a smooth surface of the copper paste. The pattern forming agent includes a surfactant having an acidic group such as a carboxyl group (-COOH) or a sulfonic acid group (-SO ₃ H) and a surfactant not having an acidic group. Representative pattern forming agents include polycarboxylic acid-type polymer surfactants, polyoxy Ethylene sulfate ester salt is used. Products marketed as a pattern forming agent include DISPERBYK-180, DISPERBYK-2150, BYK-W990, BYK-W995, BYK-W996, BYK-W9010 (BYK Chemie), etc. can be used by

In step (c), the antifoaming agent removes surface air bubbles formed when copper powder is dispersed in a binder to prepare a copper powder-based oil-based paste and provides a function of releasing trapped air. As an antifoaming agent, silicone-based polymer materials and silicone-based organic materials are mainly used, and there are also non-silicone-based materials. Silicone-based anti-foaming agent has excellent emulsification state and shows excellent anti-foaming and anti-foaming power even in a small amount. Silicone-based organic materials do not cause product changes even when stored for a long period of time, have excellent dispersibility in water, have good removal effect when washing with water, and have excellent defoaming and anti-foaming effects even in high-temperature, high-pressure dyeing and other processes of textiles. Non-silicone-based anti-foaming agent is an anti-foaming agent containing polyalkylene glycol derivatives as a main component, and exhibits excellent foam suppression and foaming properties. Products marketed as defoaming agents include BYK-051N, BYK-052N, BYK-054, BYK-067A, BYK-072, BYK-077, BYK-081, BYK-085, BYK-088, BYK-141, BYK- 354, BYK-392, BYK-A 530, BYK-A535, BYK-A555, BYK-A560 (by BYK Chemie), etc. may be mentioned, and these may be used alone or in combination of two or more.

In step (c), the thickener is preferably any one of a synthetic high molecular compound, a semi-synthetic high molecular compound, and a natural high molecular compound. A thickener is a high molecular compound used for the purpose of enhancing the viscosity of a copper powder-based oil-based binder. In the case of a synthetic polymer compound, carboxyl vinyl polymer obtained by polymerizing acrylic acid is typical. In this case, even a small amount of the synthetic polymer compound is used. It has the characteristic of realizing high viscosity. In the case of semi-synthetic polymers, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose and ethyl cellulose are representative compounds. In addition, in the case of natural polymer compounds, gelatin, rosin, collagen, guar gum, gentan gum, and gum arabic are used. BERMOCOLL EBS 351 FQ, BERMOCOLL EBS 411 FQ, BERMOCOLL EBS 431 FQ, BERMOCOLL EBS 451 FQ, BERMOCOLL EBS 481 FQ, BERMOCOLL EHM 100, BERMOCOLL EHM 100ED, BERMOCOLL EHM 100ED, BERMOCOLL EHM 200 and BERMOCOLL EHM 300, BERMOCOLL EHM 500, and BERMOCOLL EM 7000 (Nouryon), and these may be used alone or in combination of two or more.

In step (c), the leveling agent is preferably any one of alkyl polyacrylate, polyalkyl vinyl ether, cellulose acetate butyrate, dimethyl polysiloxane, methylphenyl polysiloxane, organic modified polysiloxane, fluorine-based surfactant, and anionic copolymer. The leveling agent is a compound added to suppress a phenomenon in which the miscibility of the copper powder particles and the paste composition decreases due to the surface tension of the copper paste composition, and to reduce product defects due to the non-uniformity of the copper paste coating film. In the drying process of the copper paste, the leveling agent is an additive that aligns the surface tension of the paste to prevent the formation of color stains or craters because it is oriented to the surface of the coating film. BYK-300, BYK-306, BYK-307, BYK-310, BYK-313, BYK-315N, BYK-320, BYK-322, BYK-325, BYK-326, BYK- 333, BYK-337, BYK-370, BYK-371, BYK-377, BYK-378, BYK-381, BYK-3550, BYK-3700, BYK-3701 (BYK Chemie), and the like, and these are single Or 2 or more types may be mixed and used.

In step (c), the content of each of the dispersant, the pattern forming agent, the defoaming agent, the thickener, and the leveling agent is preferably 0.001 to 10 parts by weight based on 100 parts by weight of the copper powder. When the content of each of the dispersant, the pattern former, the defoaming agent, the thickener, and the leveling agent is less than 0.001 based on 100 parts by weight of the copper powder, the content of the additive in the copper powder-based oil-based paste is too low, so that it cannot function as an additive. In addition, when the content of each of the dispersant, the pattern former, the defoaming agent, the thickener, and the leveling agent is 10 parts by weight or more relative to 100 parts by weight of the copper powder, the content of the additive present in the copper powder-based oil paste is excessive. There is a problem in that the coating film adhesion and coating film properties of the copper powder-based oil paste are lowered by lowering the intrinsic properties.

The method for preparing the copper powder-based oil-based paste is not particularly limited, and the copper powder-based oil-based paste can be prepared by mixing the above components and uniformly mixing them with a mixing means such as a paste mixer, a stirrer, a kneader, or a mill.

The paste mixer uses centrifugal force, centripetal force, and friction force generated by simultaneously rotating and revolving the container in which the high-viscosity material is put, enabling rapid and rapid stirring, dispersion, defoaming, and degassing of the material. There are characteristics that do not have A paste mixer is used as a method of mixing a surface-treated copper powder and an oil-based binder mixed with additives when manufacturing a copper powder-based oil-based paste.

When mixing the paste in step (c), the stirring time is preferably 10 seconds to 10 minutes. In addition, the stirring speed when mixing the paste in step (c) is preferably 200 to 2000 rpm. When the paste mixing agitation speed is out of the exemplified range or the mixing time exceeds 10 minutes, the electrical conductivity of the finally formed copper powder-based oil-based paste is lower than that of the other cases.

The present invention is characterized by comprising a surface-treated copper powder, a solvent, an oil-based binder, and an additive. Disclosed is a configuration for implementing an oil-based paste based on copper powder with improved long-term stability through a combination of various solvents, oil-based binders, and additives.

Advantages and features of the present invention, as well as techniques for achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms.

Hereinafter, the configuration and effect of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a flowchart illustrating a method of manufacturing a copper paste according to an embodiment of the present invention. An imidazole monomer and an initiator are added to polymerize the imidazole polymer (S100). The copper powder is put in an aqueous solution of citric acid and stirred (S110) to prepare a copper powder (S120) in which citric acid is chelated on the surface. The prepared imidazole polymer is added to the surface-treated copper powder (S130) to prepare an imidazole polymer-copper composite (S140). The imidazole polymer-copper composite is mixed with an oil-based binder and additives dissolved in a solvent (S150) to prepare a copper-based conductive oil-based paste (S160).

2 is an imidazole polymer-copper composite 130 by putting an imidazole polymer after surface treatment 120 with an aqueous citric acid solution to the copper powder 110 according to an embodiment of the present invention, and the imidazole polymer-copper composite is a diagram schematically illustrating the cross-sectional structure of a copper-based conductive oil-based paste prepared by mixing an oil-based binder and a solvent 140 containing an additive.

The copper powder-based oil-based paste of the present invention may be prepared by mixing an oil-based binder, a solvent and additives into an imidazole polymer-copper composite in which an imidazole polymer is introduced into copper powder, and then using a paste mixer to prepare a copper paste. The prepared copper paste may be manufactured in various conductive patterns through a printing method such as screen printing, roll-to-roll process, offset printing, or the like. The copper powder-based conductive pattern is excellent in water resistance, thermal stability, impact resistance, printing workability, pot life, etc. It can be applied to various fields of electric and electronic devices. For example, electrode material, sensor transducer, electromagnetic shielding material, touch panel electrode material, smartphone electrode material, solar cell front electrode, PDP panel electrode, RFID tag antenna, capacitive touch panel circuit, PCB paste through hole, etc. This is possible. The copper paste of the present invention can be applied to a wearable electric and electronic device, a flexible battery and electronic material, a transparent screen material, a smart glasses material, a smart watch material, a wireless sensor electrode material, a wrist wear band device material, and the like.

If this new concept of copper paste is developed as a product, various expected effects such as strengthening international competitiveness for the domestic conductive paste industry, cost reduction, productivity increase, and cost reduction due to energy saving are expected.

In addition, in the case of the conventional copper-based conductive paste, patterning is performed only on non-flexible materials such as metal substrates due to weak coating film properties and film adhesion. The copper powder-based oil-based paste of the present invention uses an imidazole polymer as a corrosion inhibitor and has a characteristic composition including a solvent, an oil-based binder and an additive. It shows the improved physical properties that can be achieved. In the present invention, it was intended to realize a copper-based conductive paste that can be applied to various electronic circuit devices, semiconductor devices, flexible electrical and electronic devices, and wearable electrical and electronic devices because it meets the requirements for conductive oil-based paste and secures long-term stability.

The present invention may be better understood by the following examples, which are for illustrative purposes of the present invention and are not intended to limit the scope of protection defined by the appended claims.

Hereinafter, the present invention will be described in more detail through Examples of the present invention, through which the content and advantageous effects of the present invention can be understood in more detail. However, this is provided only for the purpose of explanation in order to further clarify the technical spirit of the present invention, and the scope of the present invention is not limited thereto.

Examples 1-3 and Comparative Example 1 (Preparation of conductive copper powder oil-based paste with improved long-term stability)

In this Example and Comparative Example, the conductive copper particles were in the form of flakes having an average particle diameter of 9 micrometers, an organic polymer copolymer was used as the binder resin, and cyclohexanone was used as the solvent.

The imidazole polymer, which is a corrosion inhibitor of copper powder, was prepared as follows. A vinylimidazole polymer was prepared by adding 1.5 parts by weight of azobisisobutyronitrile as an initiator to the vinylimidazole monomer based on 100 parts by weight of the monomer. At this time, the concentration of the monomer and the initiator in the mixed solution consisting of the monomer and the initiator was 5.3 mol/liter and 0.045 mol/liter, respectively. And the conditions for adding azobisisobutyronitrile (AIBN) were 68 degrees Celsius of inert gas conditions. The oil-based binder for the preparation of the conductive copper powder oil-based paste was prepared as follows. The organic polymer copolymer was prepared by adding 1.5 parts by weight of azobisisobutyronitrile (AIBN) as an initiator to styrene, methyl methacrylate, butyl acrylate, and hydroxyethyl methacrylate monomers based on 100 parts by weight of the monomer. . During radical polymerization of the oil-based binder, azobisisobutyronitrile (AIBN) was used as a polymerization initiator, and cyclohexanone was used as a polymerization solvent. The polymerization time was 24 hours, and the polymerization temperature was 64 degrees Celsius. 100 grams of copper powder was prepared by treatment with 120 milliliters of aqueous citric acid solution. Then, 4 parts by weight of vinylimidazole polymer based on 100 parts by weight of copper powder was added and stirred for 30 minutes to prepare an imidazole polymer-copper composite. A copper powder-based oil-based paste was prepared by introducing and mixing 8 grams of cyclohexanone as a solvent and 8 grams of an organic polymer copolymer as a binder resin to 100 grams of the prepared imidazole polymer-copper composite. The long-term stability of the copper powder-based paste was evaluated using the copper-based oil-based paste prepared as described above, and the results are shown in Table 1 below. (Each ingredient is in grams)

Ingredients

Example 1
Example 2
Example 3
Comparative Example 1 vinylimidazole 21.0 21.0 21.0 21.0 Vinyltrimethoxysilane 0.7 1.4 2.1 ---- divinylbenzene 1.12 1.12 1.12 ---- isopropyl
Alcohol 62.8 62.8 62.8 62.8 initiator 0.224 0.224 0.224 0.224 surface treated
copper powder 100 100 100 100 planetary binder
(including solvent) 16 16 16 16 paste
long-term stability error error error Good

In the case of Example 1, crosslinking is introduced into the imidazole-silane copolymer, but the content of the vinylsilane compound in the copolymer is relatively low, so that the copolymer can be dissolved in ethanol, a solvent for treating the surface of copper powder. , the formation of the copolymer-copper composite is excellent. When the copper powder surface-treated with the imidazole-silane copolymer is mixed with an oil-based binder to produce a copper paste, dispersibility and flowability of the paste are excellent at the beginning, but when one month has elapsed since the oil-based paste was prepared, the copper paste The long-term stability of the copper powder-based oil-based paste was poor because it changed from a gel state to a solid state. This phenomenon caused the imidazole-silane copolymer, which is a corrosion inhibitor treated to protect the surface of the copper powder, to harden the copper paste by the gelation reaction with the oil-based binder. The solidification phenomenon of this copper powder-based oil-based paste is due to hydrolysis, the hydroxyl group of the silane present in the imidazole-silane copolymer binds with the oil-based binder over time to reduce the fluidity of the copper paste, ultimately reducing the copper powder-based oil-based paste. Let the paste turn into a solid state.

On the other hand, in Comparative Example 1, the imidazole polymer-copper composite was formed in a good state when the imidazole polymer was coated with the copper powder in a state where the silane compound present in the imidazole-silane copolymer was excluded, and crosslinking was not introduced at all. , the imidazole polymer was well soluble in ethanol, a solvent for treating the copper powder surface. When the copper powder surface-treated with the imidazole polymer was mixed with an oil-based binder, dispersibility and flowability of the paste were excellent in the initial stage of manufacturing the copper paste. Even after one month, the copper paste did not show any gelation phenomenon, The long-term stability of the copper powder-based oil-based paste was very good because it did not change into a solid state.

In the case of Example 2, crosslinking was introduced into the imidazole-silane copolymer, and the content of the vinyl silane compound was doubled compared to Example 1, but the imidazole-silane copolymer was dissolved in ethanol, a solvent for treating the copper surface. It was easily melted and the copolymer-copper composite was formed in an excellent state. When the copper powder surface-treated with the imidazole-silane copolymer was mixed with an oil-based binder to prepare copper paste, dispersibility and flowability of the paste were good at the beginning, but after one month, the copper paste passed the gel state and was in a solid state. It was found that the long-term stability of the copper powder-based oil-based paste was poor. This is because the content of vinylsilane present in the imidazole-silane copolymer is doubled compared to Example 1, and the hydroxyl group of the vinylsilane present in the imidazole-silane copolymer is also doubled, and as time goes by, the oily Through the condensation reaction with the binder, the gelation phenomenon is accelerated, ultimately reducing the fluidity of the copper powder-based oil paste and changing it to a solid state.

In the case of Example 3, the content of vinylsilane present in the imidazole-silane copolymer increased three times compared to Example 1, but it was easily dissolved in ethanol, a solvent for treating the copper surface with the imidazole-silane copolymer. and the formation of the copolymer-copper composite was excellent. When the copper powder surface-treated with the imidazole-silane copolymer is mixed with an oil-based binder to produce copper paste, dispersibility and flowability of the paste are excellent at the beginning, but when one month has elapsed, the presence of the imidazole-silane copolymer The increased hydroxyl group of the vinylsilane accelerates the gelation phenomenon due to the condensation reaction with the organic binder over time. Ultimately, the copper powder-based oil paste changes from the gel state to the solid state, resulting in long-term stability of the copper powder-based oil paste. was found to be very poor. As a result, it was found that the presence and content of the silane compound present in the imidazole-vinylsilane copolymer directly affects the long-term stability of the organic paste.

Examples 1 to 6 and Comparative Example 1 (Evaluation of the performance of copper paste according to the type of additive)

In this Example and Comparative Example, the conductive copper particles were in the form of copper flakes having an average particle diameter of 9 micrometers, an oil-based polymer copolymer was used as the binder resin, and cyclohexanone was used as the solvent.

The manufacturing method of the imidazole polymer, the citric acid treatment method of copper powder, and the polymer-copper composite manufacturing method by introducing the vinylimidazole polymer to the copper powder surface are the same as the manufacturing method of the conductive copper powder oil paste with improved long-term stability. did. In addition, BYK Chemie's DISPERBYK-111 was used as a dispersing agent used as an additive, BYK Chemie's DISPERBYK-2150 was used as a pattern forming agent, BYK Chemie's BYK-066N was used as an antifoaming agent, and the thickener was Co., Ltd. Chemicon's BERMOCOLL EBS 451 FQ was used, and BYK Chemie's BYK-381 was used as a leveling agent.

First, a certain amount of additives such as a dispersing agent, pattern forming agent, defoaming agent, thickener and leveling agent were added to a mixed solution of the oil-based polymer copolymer and the solvent cyclohexanone and mixed by hand mixing. Surface treatment on an oil-based binder containing solvent and additives A copper powder-based oil-based paste was prepared using a paste mixer by introducing the copper composite. After applying the prepared conductive oil-based paste, it was dried at room temperature and used as a copper-based conductive paste sample.

After applying the copper powder-based oil-based paste prepared as described above on the cover glass, dispersibility, coating film adhesion, and coating film properties were evaluated. After evaluation, the results are shown in Table 2 below. (Each ingredient is in grams)

Ingredients

Example 1
Example 2
Example 3
Example 4
Example 5
Example 6
Comparative Example 1 Surface-treated copper powder 300 300 300 300 300 300 300 planetary binder 24 24 24 24 24 24 24 menstruum 24 24 24 24 24 24 24 dispersant 6 ---- 6 6 6 6 ---- pattern forming agent 0.6 0.6 ---- 0.6 0.6 0.6 ---- antifoam 0.6 0.6 0.6 ---- 0.6 0.6 ---- thickener 0.6 0.6 0.6 0.6 ---- 0.6 ---- leveling agent 0.6 0.6 0.6 0.6 0.6 ---- ---- dispersibility Good error error Good Good Good error film adhesion 100/100 100/100 100/100 error error 100/100 error film properties Good Good Good error error error error long-term stability Good Good Good Good Good Good Good

As can be seen from the above results, in the case of Example 1, a sample was prepared by introducing all of the additives, such as a dispersant, a pattern forming agent, an antifoaming agent, a thickener, and a leveling agent, into the copper paste, and dispersibility, coating film properties, coating film adhesion, and long-term stability It can be seen that the copper paste exhibits the best characteristics when considering the overall aspect.

In the case of Example 2, the pattern forming agent, the antifoaming agent, the thickener, and the leveling agent, which are additives, were introduced, but the dispersing agent DISPERBYK-111 was not added, so the copper paste exhibited poor dispersibility. In addition, coating film adhesion, coating film properties, and long-term stability showed excellent copper paste characteristics.

In the case of Example 3, a dispersing agent, an antifoaming agent, a thickener, and a leveling agent, which are additives, were introduced into the copper paste, but DISPERBYK-2150, a pattern forming agent, was not added. It was found that when the pattern forming agent was not added to the copper paste, the dispersibility of the copper paste was poor. The coating film adhesion, coating film properties, and long-term stability of the copper paste showed excellent properties. According to these results, it was found that in the present invention, the pattern forming agent has an important effect on the dispersion characteristics of the copper paste.

In the case of Example 4, the dispersing agent, the pattern forming agent, the thickener, and the leveling agent, which are additives, were introduced into the copper paste, but the antifoaming agent BYK-066N was not added. When the antifoaming agent was not added to the organic binder, the overall properties of the copper paste were excellent and good, but the coating film adhesion and the coating film properties of the copper paste were poor.

In the case of Example 5, a dispersing agent, a pattern forming agent, an antifoaming agent, and a leveling agent, which are additives, were added to the copper paste, but a thickener was not added. If BERMOCOLL EBS 451 FQ, a thickener, was not added to the copper paste, the overall properties of the copper paste film were good, but the viscosity of the paste was not smoothly controlled, so the dispersion of copper powder in the copper paste was not uniform. It exhibited poor physical properties.

In the case of Example 6, the dispersing agent, pattern forming agent, defoaming agent, and thickener, which are additives, were added to the copper paste, but BYK-381, a leveling agent, was not added. In this case, the overall properties of the copper paste film were good, but the coating film properties showed poor properties.

On the other hand, in the case of Comparative Example 1, the introduction of the dispersant, the pattern forming agent, the defoaming agent, the thickener, and the leveling agent used in the above Examples were all omitted, and the manufacturing method was prepared in the same manner as the above method. When the additive was not added to the copper paste, it was found that the copper paste had poor dispersibility, coating film adhesion, and coating film physical properties. On the other hand, long-term stability showed excellent copper paste properties.

As a result, the poor performance of Comparative Example 1 is at a level that makes it impossible to commercialize a copper powder-based oil-based paste, and many improvements are needed for practical use. However, it can be seen that the long-term stability of the copper powder oil paste does not depend on the presence or absence of additives added to the copper paste, but depends on the composition of the imidazole polymer, which is a corrosion inhibitor introduced to the surface of the copper powder, and the properties of the organic binder. In the present invention, the composition of various solvents, oil-based binders and additives is included without being limited to the examples disclosed in Table 2 above.

Dispersibility was determined by examining the microstructure of the paste through a microscope lens after coating copper paste on a glass surface of 7.5 cm X 2.5 cm.

Coating film adhesion was evaluated by ASTM D3359 using 3M Scotch tape 600 as a cross cut test.

The physical properties of the coating film were observed through a microscope lens after copper paste was coated on the glass surface of 7.5 cm X 2.5 cm. It was evaluated by judging the presence or absence of unevenness and the presence or absence of a coating film on the surface of the copper paste.

For long-term stability, the prepared copper paste was placed in a polyethylene container with a diameter of 4 cm and a height of 6 cm and stored at 23 degrees Celsius and 50% humidity. After one month, the state of the copper paste was visually confirmed and evaluated according to the following criteria.

Good: No separation of copper paste, no sedimentation of copper powder, smooth

kept as is.

Insufficient: sedimentation of copper powder was not confirmed, but separation of copper paste was

Confirmed.

Poor: The copper powder is settling, or the copper paste is gelled.

there was.

In the above, the present invention has been described in detail with reference to the described embodiments, but those of ordinary skill in the art to which the present invention pertains may make various substitutions, additions and modifications within the scope not departing from the technical spirit described above. As a matter of course, it should be understood that such modified embodiments also fall within the protection scope of the present invention as defined by the appended claims below.

100: copper powder based oily paste
110: copper powder
120: copper-citric acid chelate film
130: imidazole polymer layer
140: oil-based binder containing solvent and additives

Claims (29)

(a) preparing an imidazole polymer that is radically polymerized using an imidazole monomer represented by the following Chemical Formula 1 and an initiator;
(b) preparing a polymer-copper composite in which the imidazole polymer of (a) is introduced into a copper powder surface-treated with an aqueous citric acid solution; and,
(c) Method for producing an oil-based paste based on conductive copper powder, characterized in that the polymer-copper composite of (b) contains a solvent, an oil-based binder, and an additive, and a paste mixer is used
[Formula 1]

Here, X represents a vinyl group (vinyl), an allyl group (allyl), a vinylbenzyl group (vinylbenzyl), and an alkenyl group (alkenyl), Y is a hydrogen atom (H), a methyl group (-CH ₃ ), an ethyl group (-CH ₂ CH ₃ ), a propyl group (-CH ₂ CH ₂ CH ₃ ), a butyl group (-CH ₂ CH ₂ CH ₂ CH ₃ ), a pentyl group (-CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), and a hexyl group (-CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ) is represented.
The method of claim 1, wherein the initiator concentration during radical polymerization of the imidazole monomer represented by Formula 1 in (a) is 0.6 to 5 parts by weight based on 100 parts by weight of the imidazole monomer.
The method according to claim 1, wherein the polymerization time during radical polymerization of the imidazole monomer represented by Formula 1 in (a) is 6 to 36 hours.
The method according to claim 1, wherein a polymerization temperature of the imidazole monomer represented by Formula 1 in (a) is 60 to 90 degrees during radical polymerization.
The method of claim 1, wherein the copper powder of (b) is in the form of flakes having an average particle diameter of 0.1 to 20 micrometers.
The method of claim 1, wherein the imidazole polymer added of (b) is introduced after surface treatment of copper powder with an aqueous citric acid solution.
The method of claim 1, wherein the concentration of the added aqueous solution of citric acid in (b) is 0.3 to 40 parts by weight based on 100 parts by weight of distilled water as a solvent.
The method according to claim 1, wherein the volume of the added aqueous solution of citric acid in (b) is 50 to 1000 milliliters based on 100 grams of copper powder.
The method of claim 1, wherein the imidazole polymer of (b) is 0.1 to 10 parts by weight based on 100 parts by weight of the copper powder.
The method according to claim 1, wherein the solvent of (c) is an organic solvent.
11. The method of claim 10, wherein the organic solvent is acetone, methyl ethyl ketone, 2-pentanone, cyclopentanone, cyclohexanone, methylcyclohexanone, ionone, methylionone, mesityl oxide, isophorone, diacetyl, Acetylacetone, acetonylacetone, diacetyl alcohol, acetolcarbinol, carbonyl, menthone, acetophenone, methylacetophenone, ethanol, propanol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, Decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, secondary alcohol type, tertiary alcohol type and alkanediol, cyclic structure Conductive copper powder-based oil paste manufacturing method comprising at least one material selected from the group consisting of alcohol compounds
11. The method of claim 10, wherein the organic solvent is used in an amount of 10 to 200 parts by weight based on 100 parts by weight of the oil-based binder.
According to claim 1, wherein the oil-based binder of (c) is a copolymer including all of the first, second, and third monomer units, and each unit of the first, second, and third monomers is a first In the monomer unit, the second monomer unit consisting of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate, and the third monomer unit consisting of acrylic acid, methacrylic acid, and hydroxyethyl methacrylate Method for producing an oily paste based on conductive copper powder, characterized in that it is a copolymer comprising one or more selected substances
14. The method of claim 13, wherein the concentration of the initiator during radical polymerization of the oil-based binder is 0.1 to 10 parts by weight based on 100 parts by weight of the monomer for the binder.
14. The method of claim 13, wherein the polymerization time during radical polymerization of the oil-based binder is 12 to 48 hours.
14. The method of claim 13, wherein the polymerization temperature during radical polymerization of the oil-based binder is 50 to 80 degrees Celsius.
14. The method of claim 13, wherein the oil-based binder is used in an amount of 2 to 50 parts by weight based on 100 parts by weight of the copper powder.
The method of claim 1, wherein the additive of (c) further comprises at least one additive selected from a dispersant, a pattern former, an antifoaming agent, a thickener, and a leveling agent.
The dispersant according to claim 18, wherein the dispersing agent is an alkylamine salt, a quaternary ammonium salt, a polycarboxylate, a phosphate ester of polyoxyalkylaryl and a salt thereof, an alkenyl succinate, an alkylbenzenesulfonate, an alkylnaphthalenesulfonate, an alkanesulfone Acid salt of naphthalenesulfonic acid formalin condensate, fatty acid salt, polyoxyethylene derivative, polyoxyalkylene ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, poly Conductive copper powder-based oily paste preparation comprising at least one material selected from the group consisting of oxyalkylenealkylamine, polyoxyethylene hydrogenated castor oil, alkylalkanamide, sorbitan fatty acid ester, alkylamine oxide, and alkylbetaine Way
The method of claim 18, wherein the pattern forming agent comprises at least one material selected from the group consisting of polycarboxylic acid-type polymer surfactants and polyoxyethylene sulfate ester salts.
The method of claim 18, wherein the antifoaming agent comprises at least one material selected from the group consisting of a silicone-based polymer material, a silicone-based organic material, and a polyalkylene glycol-based derivative.
The method of claim 18, wherein the thickener comprises at least one material selected from the group consisting of carboxyl vinyl polymer, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, gelatin, rosin, collagen, guar gum, gentan gum, and gum arabic. Conductive copper powder-based oil-based paste manufacturing method characterized by
The method of claim 18, wherein the leveling agent is at least one selected from the group consisting of alkyl polyacrylate, polyalkylvinyl ether, cellulose, acetate butyrate, dimethylpolysiloxane, methylphenylpolysiloxane, organomodified polysiloxane, fluorine-based surfactant, and anionic copolymer. Conductive copper powder-based oil-based paste manufacturing method comprising a material
The method according to claim 18, wherein the content of each of the dispersing agent, the pattern forming agent, the defoaming agent, the thickener, and the leveling agent is 0.001 to 10 parts by weight based on 100 parts by weight of the copper powder.
The method of claim 1, wherein the stirring time for mixing the paste in (c) is 10 seconds to 10 minutes.
The method of claim 1, wherein the stirring speed is 200 to 2000 rpm when mixing the paste in (c).
27. A conductive copper powder-based oil-based paste prepared by the method according to any one of claims 1 to 26.
A device comprising a conductive copper powder-based oil paste manufactured by the manufacturing method according to any one of claims 1 to 26
The device according to claim 28, wherein the device comprises an oil-based paste based on conductive copper powder, characterized in that the device is an electronic circuit device, a semiconductor device, a flexible electrical/electronic device, and a wearable electrical/electronic device.

Images