TWI567756B - A conductive paste composition for forming conductive thin film on a flexible substrate and a method for producing the same - Google Patents

Description

Conductive paste composition for flexible substrate and preparation method thereof

The present invention relates to a conductive paste composition for a flexible substrate for forming a conductive film and a method of producing the same.

In the conductive paste used in the conventional soft material, in the case of using the silver powder as the conductive filler, in order to improve the conductivity, a plate-like shape in which the surface contact is formed is mainly used as compared with the spherical shape in which the dots are formed. In the case of a plate-like silver powder based on conventional physical processing of a conventional conductive paste, primary particles (spherical or agglomerated) are prepared in the process of preparing a powder, and then a secondary plate-like form is prepared. The process of forming the plates in a physical manner is performed. However, according to the morphology of the particles prepared for the first time, in the process of forming a plate shape in a secondary physical manner, unevenness of particles and generation of pores in the particles may be generated, whereby the coating film may be lowered when the electrode is formed. The unevenness and compactness have a bad influence on the conductivity.

On the other hand, Korean Patent Application No. 10-0756853 discloses a method of preparing silver particles by a liquid phase reduction method. Therefore, although this method is used, in order to solve The paste composition using the plate-like silver powder prepared by the chemical liquid phase reduction method was completed.

The present specification refers to a plurality of comparative documents and patent documents as a whole, and cites references to the above-mentioned comparative documents and patent documents. The disclosures of the cited documents and patents are hereby incorporated by reference in its entirety in its entirety in its entirety in the extent of the disclosure of the disclosure of the present disclosure.

It is an object of the present invention to provide a composition comprising a first platy silver powder by means of a chemical liquid phase reduction method and a process for the preparation thereof.

Another object of the present invention is to provide a flexible substrate in which a conductive film is formed from the above paste composition.

Further objects and advantages of the present invention will become more apparent from the following description of the appended claims.

Various specific examples described in the present invention are described with reference to the accompanying drawings. In the following description, various specific details, such as specific forms, compositions, and procedures, are described for the complete understanding of the present invention. However, specific specific examples can be implemented by excluding one or more of such special details, or can be carried out together with other known methods and modes. In the other examples, well-known processes and preparation techniques are not described in detail, and are not described in detail. The reference to the entire specification of "a specific example" or "specific example" means a specific feature, a form, and a The composition or characteristics are included in one or more specific examples of the present invention. Therefore, the state in which "a specific example" or "specific example" is expressed in various positions throughout the specification is not necessarily the same specific example of the invention. Additionally, particular features, forms, compositions or characteristics may be combined in any of the more specific embodiments using any suitable method.

In one embodiment, a method of preparing a paste composition, the method for preparing a paste composition, comprising the steps of: preparing a first plate-shaped silver powder by reducing silver from a silver compound solution; and 1 to 30% by weight of the above a first plate-shaped silver powder, 20 to 89% by weight of a second plate-shaped silver powder of pulverized metallic silver, and 10 to 50% by weight of a polyester binder and a solvent of a glycol ether, an ester and an acetate series One or more solvents are mixed in an amount of 5 to 20% by weight to prepare a paste composition. In the above specific examples, there is provided a method for preparing a paste composition by adding and reducing a first plate-shaped polyvinylpyrrolidone (PVP) and a palladium (Pd) compound, which provides a weight ratio of the silver compound to the polyvinylpyrrolidone of 1:1 or even A method for preparing a paste composition of 1:2, which provides a method for preparing a paste composition further comprising 0.1 to 1% by weight of an additive, which provides a weight ratio of the first plate-shaped silver powder to the second plate-like silver powder of 1 a method of preparing a paste composition of from 4 to 1:20, wherein the solvent is selected from the group consisting of butyl carbitol, butyl carbitol acetate, butyl cellosolve acetate, butyl cellosolve, ethyl carbitol, One or more methods of preparing a paste composition in the group of ethyl carbitol acetate, ethyl cellosolve, cellosolve acetate, ester alcohol (Texanol) and terpineol, providing a first plate shape The silver powder has an average particle diameter of 1.0 to 10 μm for preparing a paste composition, and provides a polyester binder having a molecular weight of 9000 to 10,000, or a polyester binder having a viscosity of 10,000 to 30,000 cps. A method of preparing a paste composition.

In a specific example, the second plate-shaped silver powder containing 1 to 30% by weight of the first plate-shaped silver powder, 20 to 89% by weight of the pulverized metallic silver, and 10 to 50% by weight of the polyester binder are provided. In the paste composition, the first plate-shaped silver powder is formed by reducing silver from a silver compound solution in one or more solvents of 5 to 20% by weight of a glycol ether, an ester, and an acetate series solvent. In the above specific examples, a paste composition further comprising 0.1 to 1% by weight of an additive is provided, and a paste having a weight ratio of the first plate-shaped silver powder to the second plate-like silver powder of 1:4 to 1:20 is provided. The composition provides a solvent selected from the group consisting of butyl carbitol, butyl carbitol acetate, butyl cellosolve acetate, butyl cellosolve, ethyl carbitol, ethyl carbitol acetate, ethyl a combination of one or more pastes in the group of cellosolve, cellosolve acetate, ester alcohol and terpineol, providing a paste composition having an average particle diameter of 1.0 to 10 μm of the first plate-shaped silver powder, and providing a poly The ester binder has a molecular weight of 9000 to 10000, or a polyester binder having a viscosity of 10,000 to 30,000 cps.

In a specific example, a flexible substrate of a conductive film formed of the above composition is provided.

In a specific example, the silver powder prepared by the chemical liquid phase reduction method may have a plate shape, and the average particle diameter may be in the range of 1.0 to 10 μm or 4 to 6 μm. The length-to-minor axis ratio (D/T) = 25, that is, the diameter is 25 times the thickness. However, although the silver powder which is physically processed by the above-described conventional method is also in the form of a plate, the average particle diameter may be in the range of 1.0 to 20 μm or 6.0 to 8.0 μm.

In a specific example, the total content of the silver powder is 50 to 90% by weight or 70. ~80% by weight. However, in the case of containing less than 50% by weight of silver powder, since the volume occupied by the silver powder in the entire volume on the printed pattern is small, the filling rate can be lowered and the packaging is poor, eventually affecting the conductivity. On the contrary, in the case where more than 90% by weight is contained, the dispersibility can be lowered at the time of dispersion due to an excessive increase in the viscosity of the paste composition, and the printability and levelling can be affected when a printed pattern is formed. It is difficult to form a pattern, and the strength and adhesion of the coating film are lowered because the content of the binder for binding the conductive powder is small.

In the silver powder of a specific example, in the case of the plate-like silver powder prepared by the chemical reduction method, the above-mentioned plate shape is contained in an amount of 1.0 to 30% by weight or 1.0 to 20% by weight based on the total weight of the entire silver powder. Silver powder. If the content of the addition is increased, the economical efficiency is slightly lowered due to an increase in the preparation cost, and when the added content is too small, the uniformity and compactness of the coating film are deteriorated, and the conductivity can be poor. influences.

In a specific example, the binder is selected in consideration of the adhesive strength of the adhesive, heat treatment conditions, fluidity, and the like. Although not limited thereto, polyester (one-liquid type) or epoxy (two-liquid type) is used. The polyester binder is a saturated polyester type, and the resin solid component is dissolved in a compound solvent of an ester, and is used in a condition of a solid content of 10 to 50% by weight, a molecular weight of 9000 to 10,000, and a viscosity of 20,000 cps. When polyethylene terephthalate (PET) is mainly used for a flexible printed circuit board such as a touch panel or an antenna, the adhesion and affinity of the above-mentioned binder to the substrate are excellent. In other specific examples, the epoxy adhesive is a bisphenol A (solvent free) type having a molecular weight of 350 to 380, a viscosity of 13,000 cps, and curing with an amino group. The agents are mixed together and used as a binder. The resin solid content of the above binder may be 5 to 15% by weight or 6 to 13% by weight. When the resin solid content of the above-mentioned binder is 5% by weight or less, since the amount of the resin surrounding the conductive filler is small, the dispersibility may be lowered, and the adhesion to the adhesive may be weakened, and the binder may be used. When the resin solid content is 15% by weight or more, there is a problem that the smoothness of the coating film on the printed pattern is lowered due to poor conductivity or increased viscosity.

In a specific example, the organic solvent is selected in consideration of the viscosity, fluidity, printability of the paste composition, and compatibility with the resin in the vehicle (resin + solvent), etc. It is not limited thereto, but has a solvent of a glycol ether, an ester, and an acetate series, and a solvent having a boiling point of 120 to 250 ° C is used. When the boiling point is 120 ° C or lower, the dispersibility can be lowered when dispersed by a three-roll mill, and when the printing is performed, the plate drying phenomenon due to drying can occur. When the boiling point is 250 ° C or more, when pattern heat treatment is performed after printing, drying failure may be caused. As these solvents, for example, butyl carbitol, butyl carbitol acetate, butyl cellosolve acetate, butyl cellosolve, ethyl carbitol, ethyl carbitol acetate, ethyl group can be used. A single solvent or a mixed solvent in the group of cellosolve, cellosolve acetate, ester alcohol, and terpineol. At this time, the glycol ether solvent possesses both an ester group and a hydroxyl group in one molecule. Due to this structure, the solvent is excellent in solubility to resins and other organic compounds, and is easily mixed with other organic solvents, compared with other solvents. It has a low volatility and a high boiling point, and is excellent in dryness and printability when paste printing is performed. As an example, butyl carbitol acetate can be used.

In a specific example, for the dispersibility, storage stability, rheology, and printability of the paste in the composition of the conductive paste, functionalities such as a dispersant, an antifoaming agent, and a rheology modifier may be used. additive. An additive in the range of 0.1 to 1% by weight is used with respect to 100% by weight of the paste. In this case, when the amount of the additive is 0.1% by weight or less, it is difficult to provide the above characteristics, and when the amount of the additive is 1% by weight or more, the physical properties such as conductivity may be lowered.

In a specific example, the dispersing agent in the functional additive may be selected from the group consisting of polyaminomethanol ethyl esters, polypropylenes, fatty acids, and phosphates. For example, Disperbky-110 which is a depolymerized phosphate dispersant can be used. 0.1 to 3% by weight of a dispersant may be used, and in the case of using less than 0.1% by weight of a dispersant, there may be a problem that the dispersion effect is insufficient, and in the case where more than 3% by weight of a dispersant is used, it may occur to obtain The problem of low physical properties of the paste composition.

In a specific example, the thixotropic agent in the above functional additive may use a modified urea solution, cerium oxide, and a clay type additive. For example, a byk-410 of a modified urea solution type can be used. The thixotropic agent may be used in an amount of 0.1 to 2% by weight, and in the case where less than 0.1% by weight of the thixotropic agent is used, there is a problem that the thixotropic property of the paste cannot be imparted, and in the case where more than 2% by weight of the thixotropic agent is used, It can cause the stabilization of the bubble, the poorness of the leveling property, and the poor handling of the coating.

In one embodiment, the conductive paste has a viscosity of 10,000 to 60000 cps or 10,000 to 30,000 cps. The method of viscosity adjustment or the like can be applied to various printing methods depending on the situation.

The term "liquid phase reduction method" as used in the present invention, as a step in the preparation of particles, directly produces flake particles, and the solvent in the preparation is ethanol, and the form and physical processing method of the reducing agent and the additive exist. difference. In a specific example, although the method of directly preparing the slab-like image by the liquid phase reduction method is more advantageous than the physical processing method in terms of surface uniformity and density of the process and the particle itself, the solvent and the like are prepared from the preparation. In terms of high production cost and a recovery ratio of particles after synthesis of less than 50%, there is a difference in economical work with a particle recovery rate of 95% or more.

The term "physical processing method" as used in the present invention is not limited thereto, but means that the particles are physically plated by a processing device such as a ball mill or an attrition mill. method. At this time, the processing method depends on the form of the solvent, the reducing agent, and the additive, and a process of producing a monodisperse spherical or agglomerated particle by a chemical liquid phase reduction method may be performed before the above processing.

The conductive paste of the present invention achieves uniformity and compactness of the coating film as compared with the conventional paste, and can improve conductivity, and improve dispersibility, printability, and substrate adhesion. Therefore, due to the advantages of the low-temperature heat treatment process, a variety of printed patterns can be realized in various fields of electronic materials, particularly in the field of soft materials.

Figure 1 is a scanning electron of a plate-shaped silver powder prepared by a chemical liquid phase reduction method. Microscope (SEM) photo.

2 is a particle size analysis of a platy silver powder prepared by a chemical liquid phase reduction method.

Fig. 3 is an X-ray diffraction (XRD) analysis of a plate-like silver powder prepared by a chemical liquid phase reduction method.

4 is a scanning electron micrograph of a slab-shaped silver powder based on physical processing.

Figure 5 is a particle size analysis of a slab-shaped silver powder based on physical processing.

Hereinafter, the present invention will be described in more detail by way of examples. The present invention is only intended to be more specific to the invention, and it is obvious to those skilled in the art that the scope of the invention is not limited by the scope of the invention.

Example 1

Preparation and confirmation of platy silver powder based on chemical liquid phase reduction

Dissolve silver nitrate (AgNO ₃ ) in water and ethanol, make AgNO ₃ a concentration of 0.03M, and add ammonium hydroxide (NH ₄ OH) and polyvinylpyrrolidone to the AgNO ₃ solution and completely dissolve, so that NH ₄ OH becomes 0.2. The concentration of M is such that polyvinylpyrrolidone becomes PVP(g)/AgNO ₃ (g) = 1, and then, Pd which is a seed crystal is added to completely dissolve in a manner of using PdCl ₂ to have a concentration of 5 × 10 ^-5 M. AgNO ₃ solution. Thereafter, H ₂ O ₂ as a reducing agent was gradually added to the AgNO ₃ solution so that the concentration became 0.13 M, and then a plate-shaped silver powder was prepared by stirring for 120 minutes. The plate-shaped silver powder was separated by a centrifugal separator, washed with water and alcohol, and then dried at a temperature of about 50 ° C for 12 hours, and a plate-like silver powder was obtained.

The obtained plate-like silver powder was confirmed by an electron microscope, and a plate shape having a size of about 5 μm (see Fig. 1) was confirmed, and the crystallinity was silver (Ag) (see Fig. 3).

Example 2

Comparison of characteristics of paste compositions containing platy silver powder

Comparative example 1

65% by weight of physical processing-based platy silver powder, 24% by weight of polyester binder, 10% by weight of butyl carbitol acetate, and 1% by weight of additive as a paste composition ratio, first time After the revolutionary agitator was uniformly mixed, the second time, the three roller mills were used for tendering and dispersion four times. The dispersed paste composition is finally obtained after the filtration process. The paste composition was screen-printed on a polyester film (PET) using SUS #250, and subjected to a heat treatment at 130 ° C for 30 minutes in an air circulation type hot air blower, using a 4-point probe apparatus and a scanning electron microscope. The electrical properties and other physical properties were evaluated.

Comparative example 2

Except that an epoxy binder was used instead of the polyester binder of Comparative Example 1 as a binder, it was carried out in the same manner as in Comparative Example 1, and evaluation of the paste composition was also performed in the same manner.

Comparative example 3

75% by weight of physical processing-based platy silver powder, 15% by weight of polyester binder, 9.5% by weight of butyl carbitol acetate, 0.5% by weight of additive as a paste combination ratio, first time After the revolutionary agitator was uniformly mixed, the second time, the three roller mills were used for tendering and dispersion four times. The dispersed paste composition is finally obtained after the filtration process. The paste composition was screen-printed on a polyester film using SUS #250, and subjected to heat treatment at 130 ° C for 30 minutes in an air circulation type hot air blower, and evaluated by a 4-point probe apparatus and a scanning electron microscope. Electrical properties and other physical properties.

Manufacturing example 1

In addition to 71.25 wt% of physically processed platy-shaped silver powder (95 wt% of total silver powder content), 3.75 wt% of slab-shaped silver powder based on liquid phase reduction method (silver) in 75 wt% of silver powder Except for the mixed powder of 5% by weight of the total content of the powder, it was carried out in the same manner as in Comparative Example 3, and evaluation of the paste composition was also performed in the same manner.

Manufacturing Example 2

In addition to using 75.5% by weight of the physically processed platy silver powder (90% by weight of the total silver powder), 7.5% by weight of the plate-like silver powder based on the liquid phase reduction method (75% by weight) Except for the mixed powder of 10% by weight of the total content of the powder, it was carried out in the same manner as in Comparative Example 3, and evaluation of the paste composition was also performed in the same manner.

Manufacturing Example 3

In addition to using 60% by weight of the physically processed platy silver powder (80% by weight of the total silver content) and 15% by weight of the liquid phase reduction-based platy silver powder (silver) in 75 wt% of the silver powder Except for the mixed powder of 20% by weight of the total content of the powder, it was carried out in the same manner as in Comparative Example 3, and evaluation of the paste composition was also performed in the same manner.

Manufacturing Example 4

In addition to using 52.5 wt% of physically processed platy-shaped silver powder (70 wt% of total silver powder content), 22.5 wt% of a mixture of slab-shaped silver powders based on liquid phase reduction in 75 wt% of silver powder Except for the powder, it was carried out in the same manner as in Comparative Example 3, and evaluation of the paste composition was also performed in the same manner.

Manufacturing Example 5

In addition to using 45% by weight of the physically processed platy-shaped silver powder (60% by weight of the total silver powder), 30% by weight of the plate-like silver powder based on the liquid phase reduction method (silver) Except for the mixed powder of 40% by weight of the total content of the powder, it was carried out in the same manner as in Comparative Example 3, and evaluation of the paste composition was also performed in the same manner.

The evaluation results of Comparative Examples 1 to 3 and Production Examples 1 to 5 above are shown in Table 1 below.

^* Ratio of slab-shaped silver powder based on liquid phase reduction method to slab-shaped silver powder based on physical processing

At this time, the surface resistance of the surface of the printed pattern was measured by a 4-point probe method using a surface resistance measuring instrument (CMT-SR2000N), and the thickness of the printed pattern was measured by a scanning electron microscope to measure the cross section of the coating film. The measured surface resistance value was calculated by measuring the thickness of the coating film.

Measurement of coating hardness of the coating film The pencil core having the size, shape, and hardness specified by the method based on KS D 6711 (coating pencil hardness measurement method) was inspected and evaluated by the naked eye, under a load condition of 1 kg. When the surface of the film is applied by pressing, there is a trace on the surface of the above coating film or resistance to a certain defect.

The adhesion measurement was evaluated in such a manner that the surface of the printed pattern was prepared to be 1 mm by a cross cutter using a cross cut test based on the KS M ISO 2409 (coating tightness test method) method. Interval cross After 100 cells of the shape, the amount of the cells in the pattern was observed under the illumination magnifying glass by sticking and tearing off the prescribed tape.

The viscosity measurement was performed using a Brookfield Rotary Viscometer (LVDV-II+PRO) and evaluated using a plurality of spins specified at a measurement temperature of 25 °C.

The specific embodiments of the present invention have been described in detail above, and the specific embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto. Therefore, the scope of the invention is to be determined by the scope of the invention and its equivalents.

Claims (13)

A method for preparing a paste composition, comprising: adding polyvinylpyrrolidone and a palladium compound to a silver compound solution; and reducing silver from the silver compound solution to prepare a first plate-shaped silver powder, wherein the silver compound and the polyethylene The pyrrolidone weight ratio is 1:1 to 1:2; and 1 to 30% by weight of the first plate-shaped silver powder, 20 to 89% by weight of the second plate-shaped silver powder of the pulverized metal silver, and 10~ 50% by weight of the polyester binder is mixed with 5 to 20% by weight of one or more solvents in the glycol ether, ester and acetate series solvents to prepare a paste composition. The method of preparing a paste composition according to claim 1, wherein the additive further comprises 0.1 to 2% by weight. The method of preparing a paste composition according to claim 1, wherein the weight ratio of the first platy silver powder to the second platy silver powder is 1:3 to 1:20. The method for preparing a paste composition according to claim 1, wherein the solvent is selected from the group consisting of butyl carbitol, butyl carbitol acetate, butyl cellosolve acetate, butyl cellosolve, and ethyl card. One or more of the group consisting of alcohol, ethyl carbitol acetate, ethyl cellosolve, cellosolve acetate, ester alcohol (Texanol), and terpineol. The method of preparing a paste composition according to claim 1, wherein the first plate-shaped silver powder has an average particle diameter of 1.0 to 10 μm. The method for preparing a paste composition according to claim 1, wherein the polyester binder has a molecular weight of 9000 to 10,000, or the polyester binder has a viscosity of 10,000 to 30,000 cps. A paste composition comprising 1 to 30% by weight of a first plate-shaped silver powder, 20 to 89% by weight of a second plate-shaped silver powder of pulverized metallic silver, and 10 to 50% by weight of a polyester The first plate-shaped silver powder is a silver compound solution to which polyvinylpyrrolidone and a palladium compound are added in one or more solvents of 5 to 20% by weight of a glycol ether, an ester and an acetate series solvent. It is formed by reducing silver, wherein the weight ratio of the silver compound to the polyvinylpyrrolidone is 1:1 to 1:2. The paste composition of claim 7, which further comprises 0.12% by weight of an additive. The paste composition according to claim 7, wherein the weight ratio of the first plate-shaped silver powder to the second plate-shaped silver powder is 1:3 to 1:20. The paste composition of claim 7, wherein the solvent is selected from the group consisting of butyl carbitol, butyl carbitol acetate, butyl cellosolve acetate, and butyl. One or more of the group consisting of cellosolve, ethyl carbitol, ethyl carbitol acetate, ethyl cellosolve, cellosolve acetate, ester alcohol (Texanol), and terpineol. The paste composition according to claim 7, wherein the first plate-shaped silver powder has an average particle diameter of 1.0 to 10 μm. The paste composition according to claim 7, wherein the polyester binder has a molecular weight of 9000 to 10,000, or the polyester binder has a viscosity of 10,000 to 30,000 cps. A flexible substrate characterized by forming a conductive film from the composition according to any one of claims 7 to 12.