JP6247015B2 - Polymer type conductive paste and method for producing electrode using polymer type conductive paste - Google Patents

Description

  The present invention relates to a polymer-type conductive paste that can form a desired dark electrode.

  In recent years, polymer-type conductive pastes have been widely used to form these circuits or electrodes in various electronic devices including touch panel circuits or electrodes, electrodes for defogger, terminal electrodes, and the like. The polymer-type conductive paste can form a circuit or an electrode at a lower temperature than a fired-type conductive paste containing an inorganic substance such as glass frit. For this reason, it can be suitably applied to, for example, a resin substrate having low heat resistance. An electrode having excellent low resistance can also be formed. Furthermore, since it is excellent also in flexibility and lightness, use of a polymer-type conductive paste is promising (Patent Document 1).

JP 2009-176728 A

  In recent years, in addition to the above-described viewpoints, a further improved polymer type conductive paste has been demanded from the viewpoints of decorativeness and visibility on appearance. In particular, there is a need for a technique that is excellent in low resistance and efficiently manufactures dark-colored electrodes. The above-mentioned patent document does not describe realizing both low resistance and dark color.

  Accordingly, the present invention provides a polymer-type conductive paste having a low resistance value and capable of forming a dark-colored electrode, and a method for producing an electrode using the polymer conductive paste.

  The present invention relates to a polymer-type conductive paste containing conductive powder, a thermoplastic binder resin, and an organic solvent. In this polymer type conductive paste, the conductive powder is substantially composed of silver powder, and the silver powder has an average particle diameter (D50) of more than 0.1 μm and not more than 10 μm, and is flaky or irregular. Or a first silver powder having a shape selected from a combination thereof, and a second silver powder having an average particle diameter (D50) of more than 50 nm and not more than 100 nm and having a spherical shape, The weight ratio of the powder to the first silver powder (second silver powder / first silver powder) is more than 10/90 and less than 50/50.

  The present invention is characterized in that the weight ratio of the conductive powder to the binder resin (conductive powder / binder resin) is 90/10 to 97/3. Furthermore, the organic solvent is dipropylene glycol methyl ether.

  The present invention includes a method for manufacturing an electrode. The electrode manufacturing method includes applying a polymer-type conductive paste on a substrate and heating at 100 to 200 ° C., wherein the polymer-type conductive paste includes a conductive powder, a thermoplastic binder resin, and an organic solvent. And the conductive powder is substantially composed of silver powder, and the silver powder has an average particle diameter (D50) of more than 0.1 μm and not more than 10 μm, and is formed from flakes, amorphous, or a combination thereof A first silver powder having a selected shape; and a second silver powder having an average particle diameter (D50) of more than 50 nm and not more than 100 nm and having a spherical shape, the second silver powder and the first The weight ratio with the silver powder (second silver powder / first silver powder) is more than 10/90 and less than 50/50.

  The polymer-type conductive paste of the present invention can provide an electrode having both characteristics of being excellent in low resistance and having a dark color.

It is a figure which shows the electrode pattern for measuring the various physical properties of the electrode using the polymer type electrically conductive paste of this invention.

  The first of the present invention relates to a polymer-type conductive paste. The second of the present invention relates to an electrode manufacturing method using this polymer type conductive paste. The present invention provides an electrode that exhibits satisfactory results in both low resistance and darkening characteristics by combining a plurality of conductive powders having specific average particle diameters (D50) in different ranges in a polymer-type conductive paste. Based on the finding that can be provided.

(A) Polymer-type conductive paste In one embodiment, the polymer-type conductive paste of the present invention contains a conductive powder, a thermoplastic binder resin, and an organic solvent, and optionally contains additional components.

  Below, each component of the polymer type electrically conductive paste of this invention is demonstrated.

(I) Conductive powder The polymer-type conductive paste of the present invention contains a conductive powder. In the present invention, the conductive powder substantially consists of silver powder. In the present specification, “substantially composed of silver powder” may include other conductive powders other than silver powder as long as the low resistance characteristics and hue of the electrode according to the present invention are not adversely affected. Means that. In one embodiment, the other conductive powder is gold (Au), platinum (Pt), nickel (Ni), aluminum (Al), or the like. The polymer-type conductive paste of the present invention can contain these other conductive powders in an amount that does not adversely affect the low resistance characteristics and hue of the electrode. In one embodiment, the polymer-type conductive paste of the present invention may include 0 to 30% by weight of the other conductive powder based on the total amount of conductive powder.

  In one embodiment of the present invention, the conductive powder is a silver powder, and the silver powder contains a first silver powder and a second silver powder. Hereinafter, the first silver powder and the second silver powder will be described.

(A) First silver powder The first silver powder has an average particle diameter (D50) of more than 0.1 μm and not more than 10 μm. Those having an average particle size (D50) of less than 0.1 μm tend to be difficult to manufacture and difficult to obtain in practice. On the other hand, when the average particle size (D50) exceeds 10 μm, the line resolution may be affected.

  In the present specification, the average particle diameter (D50) of the silver powder is a value obtained by measurement using Particle Size Analyer (Laser diffraction analysis machine X-100, manufactured by Microtrac).

  The first silver powder is flake-shaped silver powder, irregular-shaped silver powder, or a mixture thereof. Here, “flake-shaped silver powder” refers to a silver powder having an average major axis L / average thickness T of one silver particle having an aspect ratio of 3 or more. In one embodiment, the aspect ratio is 3 to 40 from the viewpoint of lowering the resistance of the electrode to be formed, and 5 to 30 in a further aspect. In addition, “indefinite shape silver powder” means that the shape of one silver particle is neither a spherical shape nor a flake shape, and the ratio of the average value of the major axis to the minor axis (major axis / minor axis) exceeds 1 and is 10 or less. Refers to silver powder. These numerical values can be obtained, for example, by direct measurement using a scanning electron microscope (SEM).

  In this embodiment, resistance reduction is efficiently achieved by using the silver powder of flake shape, indefinite shape, or a mixture thereof. In the present specification, “resistance” refers to “lateral resistance (lateral resistance)”, and is a value obtained by measuring by applying probes to both ends of a conductor (line) formed as an electrode. Specific measurement methods are described in the examples of this specification.

  Examples of the flake-shaped silver powder include silver powder having shapes such as “rod-like” and “plate-like” in addition to “flaky”. In one embodiment, the shape of the flakes is practically preferable because a better and more stable low resistance value is relatively easily obtained and the manufacture and availability are relatively easy.

(B) Second silver powder In one embodiment of the present invention, the second silver powder has an average particle diameter (D50) of more than 50 nm and not more than 100 nm, and has a spherical shape. When the average particle diameter (D50) is 50 nm or less, the resistance value of the obtained conductor may increase. On the other hand, if the average particle diameter (D50) exceeds 100 nm, it may be difficult to obtain a dark-colored electrode.

  In this specification, the “spherical shape” of silver powder is a set of spherical surfaces in which the shape of the silver powder is constant from a specific fixed point in space, and a set of internal points. , Refers to consisting of. In addition, since it is substantially impossible to manufacture only such a spherical silver powder (true spherical silver powder), in this specification, the “spherical” silver powder includes the spherical shape. Silver powder (true spherical silver powder) and silver powder having irregularities on a spherical surface (that is, “substantially spherical silver powder”) that can be regarded as equivalent to this based on the common general knowledge in the art. Is included.

(C) Silver powder weight ratio (second silver powder / first silver powder)
In one embodiment, the weight ratio of the second silver powder to the first silver powder (second silver powder / first silver powder) in the polymer-type conductive paste is more than 10/90 and less than 50/50. is there. In another embodiment, the weight ratio (second silver powder / first silver powder) is 20/80 to 40/60. When the weight ratio of the first and second silver powders satisfies this numerical range, an electrode having both suitable low resistance and dark color characteristics can be obtained.

(D) Content of conductive powder In one embodiment, the content of the conductive powder in the polymer-type conductive paste is 99% by weight to 70% by weight based on the solid content of the polymer-type conductive paste. In another embodiment, the content of the conductive powder in the polymer-type conductive paste is 98% by weight to 85% by weight based on the solid content of the polymer-type conductive paste.

(II) Binder Resin The polymer type conductive paste of the present invention contains a binder resin. In one embodiment, the binder resin is a thermoplastic resin. Examples of the thermoplastic resin include aliphatic thermoplastic resins such as polyvinyl butyral, polyacetoacetal, polyacrylic acid, and polyvinylidene fluoride, and aromatic thermoplastic resins such as phenoxy resin. Among these, polyacetoacetal (acetoacetal resin) is preferable as one embodiment from the viewpoint of viscosity retention and the like. As another embodiment, a phenoxy resin is preferable from the viewpoint of transparency, flexibility, impact resistance, adhesion, mechanical properties, and the like. Specific examples of these thermoplastic resins are SLECK KS-3Z and KS-5Z manufactured by Sekisui Chemical Co., Ltd. The weight average molecular weight of this thermoplastic resin can mention 100,000-150,000 as one embodiment.

  In one embodiment, the weight ratio of the conductive powder to the binder resin (conductive powder / binder resin) in the polymer-type conductive paste is 90/10 to 97/3. In another embodiment, the weight ratio is from 91/9 to 95/5. If the weight ratio exceeds 97/3, the resulting conductor film may become brittle. On the other hand, if the weight ratio is less than 90/10, the resistivity of the obtained conductor may increase.

  In one embodiment, the content of the binder resin in the polymer-type conductive paste is 1% by weight to 20% by weight based on the total weight of the polymer-type conductive paste. In another embodiment, the content of the binder resin in the polymer type conductive paste is 2% by weight to 10% by weight based on the total weight of the polymer type conductive paste.

(III) Organic solvent The polymer-type conductive paste of the present invention contains an organic solvent. Conductive powder, binder resin, and optional additional components (see (IV) below) are dissolved or dispersed in this organic solvent. In one embodiment, the organic solvent includes ethylene glycol monomethyl ether, dipropylene glycol methyl ether, propylene glycol monomethyl ether acetate, methyl propanol acetate, 1-methoxy-2-propanol acetate, methyl cellosolve acetate, butyl propionate, Primary amyl acetate, hexyl acetate, cellosolve acetate, pentyl propionate, diethylene oxalate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl isoamyl ketone, methyl n-amyl ketone, cyclohexanone, diacetone alcohol, diisobutyl ketone, N-methylpyrrolidone, butyrolactone, isophorone, methyl n-isopropyl ketone, ethyl acetate Terpenes such as α- terpineol or β- terpineol, kerosene, dibutylphthalate, butyl carbitol, butyl carbitol acetate, hexylene glycol, etc. butyrolactone, but not limited thereto. A mixture of one or more organic solvents can be used to meet the desired requirements such as the desired viscosity and volatility. A volatile liquid may be included in the organic solvent to facilitate rapid curing after attachment to the substrate.

  In one embodiment, the content of the organic solvent is 10 to 60% by weight based on the total weight of the polymer-type conductive paste. In another embodiment, the content of the organic solvent is 30 to 50% by weight based on the total weight of the polymer-type conductive paste.

(IV) Additional Components The polymer-type conductive paste of the present invention can optionally contain additional components. In one embodiment, the polymer-type conductive paste can contain additional components to improve its properties. Examples of such additional components include a silane coupling agent and a thixotropic agent.

(V) Preparation of Polymer Type Conductive Paste In the polymer type conductive paste of the present invention, the above components are usually mixed by mechanical mixing using a planetary mixer, and then dispersed by a three roll mill. Thus, it can be formed as a paste having a consistency and rheology suitable for printing.

(B) Manufacturing method of electrode This invention includes the manufacturing method of the electrode using the above-mentioned polymer type electrically conductive paste. In one embodiment, the method for producing an electrode of the present invention includes a step of applying the polymer-type conductive paste obtained as described above on a substrate, and heating and drying at a predetermined temperature.

  The substrate is not particularly limited, and includes various base materials such as glass base materials, polymer base materials such as polycarbonate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyimide. The coating method is not particularly limited, and examples thereof include screen printing, coating printing with a blade, drawing printing with a dispenser, gravure (offset) printing, stamping printing, and the like. In one embodiment, the heating and drying temperatures are 100 ° C. to 200 ° C., and an appropriate heating temperature is appropriately selected in consideration of the heat resistance temperature of the base material to be applied. In addition, when the temperature of heating and drying exceeds 200 degreeC, sintering of fine silver powder may start and a dark color may be lost.

  In the manufacturing method of the electrode of the present invention, in one embodiment, the heating temperature is 80 ° C. to 200 ° C., and the heating time is 10 minutes to 60 minutes. In another embodiment, the heating temperature is from 100C to 150C.

  Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples.

(Examples 1-5 and Comparative Examples 1-12)
Preparation of Polymer Type Conductive Paste As shown in Table 1, the conductive powder, binder resin, and organic solvent were mixed thoroughly using a roll mill with the composition shown in Table 1, and polymer types of Examples 1 to 5 A conductive paste was prepared. In addition, conductive powder, binder resin, and organic solvent as shown in Table 2-1 and Table 2-2 were mixed thoroughly with a composition shown in these tables using a roll mill, and Comparative Examples 1-12. A polymer type conductive paste was prepared.

  In addition, the following were used for the silver powder, binder resin, and solvent of Table 1 and Table 2-1 to Table 2-2.

1st silver powder (flakes): Ferro and Technic 1st silver powder (indefinite shape): DuPont 2nd silver powder (spherical shape): Ferro

Cuprous oxide (Cu ₂ O): manufactured by Furukawa Chemicals Copper oxide (CuO): manufactured by Furukawa Chemicals

Binder resin 1: Phenoxy resin (Inchem, PKHH)
Binder resin 2: Acetoacetal resin (manufactured by Sekisui Chemical Co., Ltd., KS-5Z)

  Organic solvent 1: Dipropylene glycol methyl ether (DowChemical)

(VI) Production of electrodes, measurement of physical properties and evaluation (a) Measurement of resistance value The polymer type conductive paste of each composition described above was applied on a glass substrate by the following procedure.

  First, the glass substrate 100 of width 75mm x length 50mm was prepared (refer FIG. 1). On the prepared glass substrate 100, the pastes having the compositions shown in Table 1 (Examples) and the pastes having the compositions shown in Tables 2-1 to 2-2 (Comparative Examples) shown in FIG. The electrode pattern 110 was formed by coating each so as to draw.

  In addition, application | coating of the polymer type electrically conductive paste on a board | substrate was performed as follows. First, a plastic film having an electrode pattern-shaped cutout was attached to the glass substrate surface. Next, the polymer-type conductive paste was applied with a blade after a plastic film was attached. Then, the said plastic film was removed and the paste coating film | membrane of the electrode pattern shape shown in FIG. 1 on the board | substrate was obtained. Here, the applied pattern shape had a width of 4 mm, a length of 274 mm, and a thickness of 20 μm. Then, each board | substrate with which the paste was apply | coated to the electrode pattern shape was heated and dried in 120 degreeC for 30 minutes for every board | substrate in the oven, and the electrode pattern was hardened. Thereby, each sample of Examples 1-5 and Comparative Examples 1-12 in which the electrode was formed on the glass substrate was obtained. For each sample obtained as described above, a probe was applied to both ends of the electrode formed on the glass substrate, and the resistance value was measured. The results are shown in Table 1. In addition, if the resistance value (μΩ · cm) of the electrode to be measured is less than 40 μΩ · cm, it is evaluated that there is no practical problem.

(B) Measurement and Evaluation of Hue (Blackness) Next, the blackness (L value) was measured as follows for each sample electrode obtained above. The results are shown in Table 1 and Tables 2-1 to 2-2.

  About each sample, the blackness at the time of observing from the surface in which the electrode pattern of a glass substrate was not formed was determined. The blackness was determined by measuring the L * value using a color meter (Konica Minolta Color Reader CR10). L * represents brightness. When the L * value is 100, pure white is indicated, and when the L * value is 0, pure black is indicated. Here, a standard white plate was used for calibration. When the measured blackness (L * value) is 65 or less, it is evaluated that the level is sufficiently dark.

(C) Results The polymer-type conductive paste of the present invention was able to form an electrode that satisfies both a sufficiently low resistance value and a sufficient blackness as compared with the comparative example. In particular, when conductive particles having a specific average particle diameter and shape defined in the present invention were used, a conductor satisfying both the characteristics of low resistance and darkening could be obtained.

On the other hand, a mode in which a paste outside the range of the polymer-type conductive paste of the present invention, for example, carbon black, CuO, Cu ₂ O, or the like is substantially contained (these correspond to Comparative Examples 9 to 11), It was shown that the resistance value was increased.

100 Substrate 110 Electrode pattern

Claims (3)

Including silver powder, thermoplastic binder resin, and organic solvent,
The silver powder has a mean particle diameter (D50) of more than 0.1 μm and not more than 10 μm, a first silver powder having a shape selected from flakes, amorphous or combinations thereof, and more than 50 nm; A second silver powder having an average particle diameter (D50) of 100 nm or less and having a spherical shape, and a weight ratio of the second silver powder to the first silver powder (second silver powder / first silver powder). ) Ri is 25 / 75-35 / 65 der, polymeric said silver powder, the weight ratio of the binder resin (silver powder / binder resin) is characterized 90 / 10-97 / 3 der Rukoto Conductive paste.   The polymer type conductive paste according to claim 1, wherein the organic solvent is dipropylene glycol methyl ether. This is a method for producing an electrode having a blackness (L * value) of 65 or less measured with a Konica Minolta Color Reader CR10, which comprises applying a polymer-type conductive paste on a substrate and heating at 100 to 200 ° C. The polymer-type conductive paste includes silver powder, a thermoplastic binder resin, and an organic solvent,
The silver powder has a mean particle diameter (D50) of more than 0.1 μm and not more than 10 μm, a first silver powder having a shape selected from flakes, amorphous or combinations thereof, and more than 50 nm; A second silver powder having an average particle diameter (D50) of 100 nm or less and having a spherical shape, and a weight ratio of the second silver powder to the first silver powder (second silver powder / first silver powder). ) is Ri 25 / 75-35 / 65 der, the silver powder, the weight ratio of the binder resin (silver powder / binder resin) is characterized 90 / 10-97 / 3 der Rukoto, electrode How to manufacture.

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