conductive components

Abstract

To provide a conductive composition that maintains high adhesion while keeping resistivity. [Solution] The conductive composition according to this disclosure contains silver particles, a thermoplastic resin, and an organic solvent, wherein the thermoplastic resin contains 13-25 wt% hydroxyl groups and 2-6.5 wt% acetal groups, and the molar amount of the hydroxyl groups relative to the specific surface area of ​​the silver particles is 1 × 10⁻⁶ 9 ~1 × 10 10 That is the case.

Description

Technical Field

[0001] The present disclosure relates to a conductive composition. <000||>

Background Art

[0002] A technique for forming a conductive pattern of an electrode constituting an electronic device using a conductive composition is known. For example, Patent Document 1 discloses a technique using a conductive composition to which a binder is added.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors have found the following problems regarding the conductive composition. When preparing a conductive composition by adding a binder based on the technique disclosed in Patent Document 1, it is necessary to mix a large amount of binder to enhance the adhesion to the substrate. However, when the amount of binder increases, the amount of organic matter in the conductive composition decreases, making it difficult to lower the resistivity.

[0005] [[ID=||]]

Means for Solving the Problems

[0006] One aspect for achieving the above object is a conductive composition comprising e silver particles, a thermoplastic resin, and an organic solvent, The thermoplastic resin contains 13-25 wt% hydroxyl groups and 2-6.5 wt% acetal groups, and the molar amount of the hydroxyl groups relative to the specific surface area of ​​the silver particles is 1 × 10⁻⁶ 9 ~1 × 10 10 That is the case. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a conductive composition that maintains high adhesion while maintaining resistivity. [Brief explanation of the drawing]

[0008] [Figure 1] This graph shows the relationship between viscosity and resistivity of a conductive composition. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described in detail below with reference to the drawings. For ease of understanding, the scale of the parts in the drawings may differ from that of the actual parts. In this specification, the "~" indicating a numerical range includes the numbers written before and after it as the lower and upper limits. In numerical ranges described in stages in this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In addition, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples.

[0010] The conductive composition according to this embodiment is a paste-like composition that functions as an electrode after being printed on a substrate and then sintered. The conductive composition according to this embodiment contains silver particles, a thermoplastic resin, and an organic solvent. Figure 1 is a graph showing the relationship between the viscosity and resistivity of the conductive composition. The asterisks in Figure 1 represent the conductive composition according to this disclosure, and the circles represent conductive compositions according to existing technology. As shown in Figure 1, generally, the viscosity and resistivity of the conductive composition are proportional. From the viewpoint of ease of printing, the viscosity of the conductive composition is preferably 50 Pa·s or more per 10 seconds. The conductive composition according to this disclosure has a viscosity above a predetermined level while exhibiting a resistivity below a predetermined level.

[0011] <Silver particles> Silver particles are used to impart conductivity to conductive patterns formed by conductive compositions. Silver particles are particles whose main component is silver. The "main component" refers to the component with the highest content in the silver particles, which is usually 50% by mass or more, preferably 70% by mass or more. The particle size of the silver particles is not particularly limited, but for example, the average particle size may be 0.6 to 1.0 μm. Here, the "average particle size" is the value measured by a particle size analyzer. Examples of particle size analyzers include the "MT3300" manufactured by Microtrac-Bell Co., Ltd. The particle shape of the silver particles is not particularly limited, and various shapes such as spherical, flake-shaped, and dentite-shaped particles can be used.

[0012] <Thermoplastic resin> Thermoplastic resins are used as binders to impart printability and to remain after the conductive composition is applied, dried, and cured, thereby obtaining good physical properties such as adhesion, flexibility, and hardness of the conductive pattern to the substrate. Thermoplastic resins contain 13-25 wt% hydroxyl groups and 2-6.5 wt% acetal groups. An example of a thermoplastic resin having such properties is polyvinyl butyral.

[0013] By using a thermoplastic resin with the characteristics described above, the acetal and hydroxyl groups of the thermoplastic resin interact with the surface of the silver particles, and the hydroxyl groups interact with the surface of the substrate, thus enabling strong adhesion with just one type of thermoplastic resin. Because thermoplastic resins with the characteristics described above have a high amount of functional groups, a small amount of addition is sufficient to produce the desired effect. Furthermore, by modifying the properties of the thermoplastic resin as described above, the dispersibility of the silver particles in organic solvents can also be ensured, making it possible to adjust the viscosity to a printable level.

[0014] Thermoplastic resins interact with metal surfaces, so it is necessary to adjust the amount of functional groups to an appropriate level relative to the specific surface area of ​​the contained particles. Specifically, if the specific surface area of ​​the silver particles is A, and the molar amount of hydroxyl groups in the thermoplastic resin is B, then A (A / B) relative to B is 1 × 10⁻⁶ 9 ~1 × 10 10 The mixture is adjusted to achieve this. By making this adjustment, sufficient adhesion to the substrate can be obtained by adding a small amount of thermoplastic resin. Because the amount of thermoplastic resin added is small, the conductive pattern formed using the conductive composition according to this embodiment has low resistance.

[0015] <Organic solvents> Organic solvents are used to impart good printability. Such organic solvents can be any solvent that can dissolve the thermoplastic resin without chemical reaction. Specifically, examples include toluene, xylene, ethyl acetate, butyl acetate, methanol, ethanol, isopropyl alcohol, isobutyl alcohol, 1-butanol, diacetone alcohol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, terpineol, methyl ethyl ketone, carbitol, carbitol acetate, butyl carbitol, texanol, etc. These can be used individually or in mixtures of two or more.

[0016] <Preparation and sintering of conductive compositions> The conductive composition according to this embodiment is adjusted by kneading silver particles, a thermoplastic resin, and an organic solvent by an existing kneading method. Examples of the kneading method include a method of stirring using a planetary mixer, a rotation-revolution mixer, etc., and then kneading with a three-roll mill or the like. The adjusted conductive composition is sintered after being printed on a substrate. The sintering method is not particularly limited, and may be a continuous process or a batch process. Examples of the heating temperature profile in the sintering process include raising the temperature from room temperature to 120°C at a rate of about 10°C / min, then holding at 120°C for 2 hours, and cooling at a rate of 2°C / sec or more.

Examples

[0017] Hereinafter, this embodiment will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0018] <Preparation of Conductive Composition> The conductive composition was adjusted in the amounts shown in Table 1 below. In Examples 1 to 4 and Comparative Examples 1 to 5, polyvinyl butyral resin was used as the thermoplastic resin, and in Comparative Example 6, an epoxy resin was used. In Examples 1 to 4 and Comparative Examples 1 to 6, silver powder with an average particle size of 0.66 μm produced by a chemical reduction method was used so that it accounted for 66 wt% of the total amount of the conductive composition. The average particle size of the silver powder is the value measured by a particle size distribution meter. The particle size distribution meter used was "MT3300" manufactured by Microtrac Bell Co., Ltd. In addition, nanoparticles produced by the manufacturing method disclosed in Japanese Patent Application No. 2022-034974 and from which impurities were removed were used so that they accounted for 16 wt% of the total amount of the conductive composition. The silver powder and the nanoparticles were combined, and the silver particle concentration in the conductive composition was 82 wt%. As the organic solvent, 2,2,4-trimethylpentane-1,3-diol monoisobutyrate (Texanol) was used.

[0019] <Evaluation Method> (Coating and Sintering Evaluation) A paste-like conductive composition was applied to the surface of a thoroughly cleaned resin substrate using a 15mm x 15mm, 100mm thick metal mask. Sintering was performed in a dryer at a predetermined temperature (120°C) for 2 hours. The film thickness after firing was measured using a micrometer. Volume resistivity was measured using a resistivity meter (Nitto Seiko Analytech Loresta-GX MCP-T70, PSP probe MCP-TP06P RMH112). The solid content was determined from the change in mass before and after sintering. Density was calculated from the measured weight, the dimensions of the metal mask (15mm x 15mm), and the volume obtained from the film thickness. Three samples were prepared for each temperature condition, and the average value calculated from the obtained measurements is recorded. A volume resistivity of 20 μohm·cm or less was evaluated as good, and anything outside this range was evaluated as poor.

[0020] (Evaluation of printable viscosity) If the viscosity of the paste-like conductive composition was 50 Pa·s or higher, the printable viscosity was evaluated as good; otherwise, it was evaluated as poor.

[0021] (Evaluation of the proportion of hydroxyl groups and acetal groups) Measurements were taken in accordance with JIS K 6728.

[0022] (Adhesion to the substrate) The test was conducted using the cross-cut method specified in JIS K 5600-5-6. If the tape peel test results with PET (polyethylene terephthalate) substrates and PC (polycarbonate) substrates were satisfactory, the adhesion to the resin substrate was evaluated as good; otherwise, it was evaluated as poor.

[0023] [Table 1]

[0024] As shown in Table 1, Examples 1-4 exhibited good printable viscosity, volume resistivity, and adhesion to the resin substrate. On the other hand, Comparative Examples 1-6 showed poor performance in at least one of the following: printable viscosity, volume resistivity, and adhesion to the resin substrate. This confirms that the conductive composition according to this embodiment achieves both good adhesion and low resistivity.

[0025] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from its spirit.

Claims

[Claim 1] A conductive composition, It contains silver particles, thermoplastic resin, and an organic solvent. The thermoplastic resin contains 13 to 25 wt% hydroxyl groups and 2 to 6.5 wt% acetal groups, and the molar amount of the hydroxyl groups relative to the specific surface area of ​​the silver particles is 1 × 10⁻⁶ ９ ~1 x 10 １０ That is, Conductive composition.

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