JP6999468B2 - Conductive film forming agent - Google Patents

Description

The present invention relates to a conductive film forming agent and a conductive film formed by using the same.

As a conductive film forming agent for forming a conductive film in an electromagnetic wave shield or an electronic component, there is a demand for a conductive film forming agent that can be used in a coating method having excellent mass productivity such as a spray method and an inkjet method and has excellent storage stability. There is.

Conventionally, for example, in Patent Document 1, as a conductive film forming agent suitable for the inkjet method, an alkane having 8 or less carbon atoms, isoparaffin and / or liquid paraffin, and metal nanoparticles having a particle diameter of 100 nm or less composed of a metal and an organic substance are used. A metal nanoparticle dispersion liquid containing the above is disclosed. In Patent Document 1, good coatability is obtained by containing a specific alcan, but since the metal nanoparticles used have a small particle size of 100 nm or less, the surface energy becomes very large and aggregation is likely to occur. , There is a concern that the storage stability of the metal nanoparticle dispersion will decrease.

Patent Document 2 discloses an inorganic particle film forming agent suitable for a spray method and having good storage stability. Patent Document 2 discloses that an inorganic particle film forming agent having excellent sprayability and storage stability can be obtained by containing an aqueous dispersion of cellulose fibers and water as a dispersion medium.

In order to form a conductive film having excellent conductivity, it is preferable to use silver powder as a metal powder (that is, a conductive powder), but the silver powder is generally surface-treated with a fatty acid as a hydrophobic treatment at the time of production. Since it has a low affinity with water, it is difficult to apply it to a technique using water as a dispersion medium as described in Patent Document 2.

Japanese Unexamined Patent Publication No. 2010-196150 Japanese Unexamined Patent Publication No. 2016-17161

It is an object of the present invention to provide a conductive film forming agent which is excellent in coating film forming property such as sprayability and storage stability and can form a conductive film having good conductivity.

The conductive film forming agent according to the embodiment of the present invention contains the following components (A) to (C).
(A) Silver powder and / or silver-coated powder (B) Cellulose nanofiber (C) Organic solvent The conductive film according to the present embodiment is formed by applying the conductive film forming agent.

The conductive film forming agent according to the embodiment of the present invention is excellent in coating film forming property such as sprayability and storage stability, and can form a conductive film having good conductivity.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The conductive film forming agent according to the present embodiment contains (A) silver powder and / or silver-coated powder, (B) cellulose nanofibers, and (C) an organic solvent, and the organic solvent is used as a dispersion medium. It is a dispersion liquid in which silver powder and / or silver-coated powder and cellulose nanofibers are dispersed. According to the present embodiment, by using an organic solvent as the dispersion medium, silver powder and / or silver-coated powder can be used as the metal powder, and therefore good conductivity can be imparted. In addition, by containing cellulose nanofibers, thixotropic properties (thixotropy) can be imparted to the conductive film forming agent, which enhances fluidity during application such as spraying to improve coating film forming properties and storage stability. Can be enhanced.

[(A) component]
As the component (A), either one or both of silver powder (that is, silver powder) and silver-coated powder is used. The specific composition of the silver powder and / or the silver-coated powder is not particularly limited, and various silver powders and silver-coated powders generally used as a conductive film forming agent can be used. The shape is not particularly limited, and various shapes such as a spherical shape and a flake shape can be mentioned, but a flake shape is preferable because the specific resistance is low.

The silver-coated powder is a powder whose surface is coated with silver, for example, silver-coated metal powder such as silver-coated copper powder, silver-coated nickel powder, and silver-coated aluminum powder, silver-coated glass powder, silver-coated resin powder, and the like. Can be mentioned.

As the silver powder and / or the silver-coated powder, a hydrophobizing treatment, for example, a surface-treated one with a fatty acid may be used.

The particle size of the silver powder and / or the silver-coated powder of the component (A) is not particularly limited, but from the viewpoint of imparting excellent conductivity, the 50% average particle size (D50) is 100 nm or more, that is, 0.1 μm or more. Some are preferred. D50 may be 0.1 to 20 μm, 1 to 10 μm, or 2 to 5 μm.

Here, D50 can be measured by a laser diffraction method. For example, 0.3 g of metal powder is weighed in a 50 ml beaker, 30 ml of isopropyl alcohol is added, and then the mixture is treated with an ultrasonic washer (USM-1 manufactured by AS ONE Co., Ltd.) for 5 minutes to disperse the microtrack particle size distribution measuring device. (9320-HRA X-100 manufactured by Nikkiso Co., Ltd.) can be used to measure D50.

The content of the silver powder and / or the silver-coated powder of the component (A) is not particularly limited, but the component (A) with respect to the total content of the component (A) and the component (B) in the conductive film forming agent is 100% by mass. The content of the above is preferably in the range of 80 to 98% by mass, more preferably 85 to 98% by mass, and further preferably 90 to 98% by mass. When it is 85% by mass or more, the specific resistance can be made smaller, and when it is 98% by mass or less, the sprayability can be improved.

[(B) component]
The cellulose nanofiber of the component (B) is a cellulose fiber having a fiber diameter of nanometer level. The number average fiber diameter of the cellulose nanofibers is not particularly limited, and may be, for example, 3 to 800 nm, 3 to 400 nm, 3 to 100 nm, or 3 to 30 nm.

The number average fiber diameter of the cellulose nanofibers can be measured as follows. That is, a cellulose nanofiber dispersion having a solid content of 0.05 to 0.1% by mass (for example, a methanol dispersion in Production Example 1 described later and an N-methylpyrrolidone dispersion in Production Example 2) is prepared. The dispersion is cast onto a hydrophilicized carbon film-coated grid to obtain a transmission electron microscope (TEM) observation sample. The observation sample may be negatively stained with, for example, a 2 mass% uranyl nitrate aqueous solution. Then, observation is performed using an electron microscope image at a magnification of 5000 times, 10000 times, or 50,000 times depending on the size of the constituent fibers. At that time, an axis having an arbitrary vertical and horizontal image width is assumed in the obtained image, and the sample and observation conditions (magnification, etc.) are adjusted so that 20 or more fibers intersect the axis. Then, after obtaining an observation image satisfying this condition, two random axes are drawn vertically and horizontally for each image, and the fiber diameters of the fibers intersecting the axes are visually read. In this way, images of at least three non-overlapping surface portions are taken with an electron microscope and the value of the fiber diameter of the fibers intersecting each of the two axes is read (hence, at least 20 fibers × 2 × 3 = 120). Information on the fiber diameter of the book can be obtained). The arithmetic mean of the fiber diameters thus obtained is defined as the number average fiber diameter.

As the cellulose nanofibers, those having a cellulose type I crystal structure are used. The fact that the cellulose constituting the cellulose nanofibers has an I-type crystal structure means that, for example, in the diffraction profile obtained by wide-angle X-ray diffraction image measurement, 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 °. It can be identified by having typical peaks at the two positions of.

As the cellulose nanofibers, anion-modified cellulose nanofibers in which an anionic group is introduced into a glucose unit in a cellulose molecule are preferably used. Examples of the anionic group include at least one selected from the group consisting of a carboxyl group, a phosphoric acid group, a sulfonic acid group, and a sulfate group. As used herein, a carboxyl group is a concept that includes not only an acid type (-COOH) but also a salt type, that is, a carboxylic acid base (-COOX, where X is a cation forming a salt with a carboxylic acid). Similarly, the phosphoric acid group, the sulfonic acid group, and the sulfuric acid group are concepts that include not only the acid type but also the salt type.

In one embodiment, the carboxyl group is preferred as the anion group. Examples of cellulose nanofibers containing a carboxyl group include oxidized cellulose nanofibers formed by oxidizing the hydroxyl group of a glucose unit in a cellulose molecule and carboxymethylated cellulose formed by carboxymethylating a hydroxyl group of a glucose unit in a cellulose molecule. Examples include nanofibers.

Examples of the oxidized cellulose nanofibers according to the preferred embodiment include those in which the hydroxyl group at the C6 position of the glucose unit in the cellulose molecule is selectively oxidized and modified to a carboxyl group. Oxidized cellulose nanofibers are obtained by oxidizing natural cellulose such as wood pulp with an oxidizer in the presence of an N-oxyl compound and defibrating (refining) the fibers. As the N-oxyl compound, a compound having a nitroxy radical generally used as an oxidation catalyst is used, for example, a piperidine nitroxy oxy radical, and particularly 2,2,6,6-tetramethylpiperidinooxy radical (TEMPO). ) Or 4-acetamide-TEMPO is preferred. Cellulose nanofibers oxidized by TEMPO are generally referred to as TEMPO-oxidized cellulose nanofibers, and can also be used in this embodiment. The cellulose oxide nanofibers may have an aldehyde group or a ketone group together with the carboxyl group.

The amount of the anion group in the cellulose nanofiber is not particularly limited, and may be, for example, 0.05 to 3.0 mmol / g or 0.5 to 2.5 mmol / g. For the amount of anionic group, for example, in the case of carboxyl group, 60 mL of 0.5 to 1% by mass slurry was prepared from a cellulose sample whose dry mass was precisely weighed, and the pH was adjusted to about 2.5 with a 0.1 M aqueous hydrochloric acid solution. After that, a 0.05 M aqueous solution of sodium hydroxide was added dropwise, the electric conductivity was measured, and the pH was continued until the pH reached about 11, and the hydroxide consumed in the neutralization step of the weak acid in which the change in the electric conductivity was gradual. It can be obtained from the amount of sodium (V) according to the following formula. The phosphoric acid group can also be measured by the same electric conductivity measurement. Other anion groups may also be measured by a known method.
Anion group amount (mmol / g) = V (mL) x [0.05 / cellulose sample mass (g)]

Cellulose nanofibers may be obtained by performing a defibration treatment. The defibration treatment may be carried out after the anion group is introduced, or may be carried out before the introduction. As the defibration treatment, for example, a homomixer under high-speed rotation, a high-pressure homogenizer, an ultrasonic dispersion processing machine, a beater, a disc type refiner, a conical type refiner, a double disc type refiner, a grinder and the like can be used.

When blending cellulose nanofibers with a conductive film forming agent, it is preferable to use a cellulose nanofiber dispersion dispersed in a dispersion medium other than water. Examples of the dispersion medium other than water include various organic solvents, for example, alcohol solvents such as methanol, ethanol and 2-propanol, and amides such as N-methylpyrrolidone, N, N-dimethylformamide and N, N-dimethylacetamide. The system solvent is preferable from the viewpoint of dispersibility of the cellulose nanofibers. Since these dispersion media are blended with the cellulose nanofibers in the conductive film forming agent by adding the cellulose nanofiber dispersion to the conductive film forming agent, they are mixed with a part or all of the organic solvent which is the component (C). Become.

In order to obtain a cellulose nanofiber dispersion using an organic solvent as a dispersion medium, acid-type anionic groups such as carboxyl groups are neutralized with polyetheramine in anion-modified cellulose nanofibers such as oxidized cellulose nanofibers. It is preferable, and the dispersibility in an organic solvent can be improved.

The content of the cellulose nanofibers of the component (B) is not particularly limited, but the content of the component (B) with respect to the total content of the components (A) and the component (B) in the conductive film forming agent is 100% by mass. It is preferably in the range of 2 to 20% by mass, more preferably 2 to 15% by mass, and may be 2 to 10% by mass.

[(C) component]
The organic solvent of the component (C) functions as a dispersion medium for the components (A) and (B) in the conductive film forming agent.

The organic solvent is not particularly limited, and is, for example, methanol, ethanol, 2-propanol, isobutyl alcohol, 1-butanol, terpineol, diacetone alcohol, methyl cellosolve, ethyl cellosolve, carbitol, ethylene glycol monobutyl ether, propylene glycol monomethyl. Alcohol-based solvents such as ether, propylene glycol monoethyl ether, ethylene glycol, glycerin, etc .; hydrocarbon solvents such as toluene, xylene, petroleum hydrocarbons; ethyl acetate, butyl acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate , Ester-based solvents such as propylene glycol monomethyl ether acetate and carbitol acetate; Ketone-based solvents such as acetone and methyl ethyl ketone; Ether-based solvents such as ethylene glycol dimethyl ether, 1,4-dioxane and tetrahydrofuran; N-methylpyrrolidone, N, N -Amid-based solvents such as dimethylformamide and N, N-dimethylacetamide can be mentioned, and these can be used alone or in combination of two or more. Among these, alcohol-based solvents and / or amide-based solvents are preferable.

The content of the organic solvent of the component (C) is not particularly limited, and is, for example, 30 to 30 parts by mass when the total content of the components (A) and (B) in the conductive film forming agent is 100 parts by mass. It may be 500 parts by mass or 50 to 400 parts by mass.

It is preferable that the conductive film forming agent according to the present embodiment substantially does not contain water as a dispersion medium. That is, in the conductive film forming agent according to the present embodiment, the dispersion medium is substantially composed of only an organic solvent, so that even if the silver powder and / or the silver-coated powder of the component (A) is hydrophobized. , The dispersibility can be improved. In the present specification, the fact that the conductive film forming agent does not contain water substantially means that the conductive film forming agent does not contain water or even if it contains water, the total amount of the dispersion medium is 100% by mass. It means that the amount of water is less than 10% by mass, more preferably less than 5% by mass, still more preferably less than 1% by mass.

[Conducting film forming agent]
In addition to the above components (A) to (C), the conductive film forming agent according to the present embodiment includes, for example, a binder resin, a curing agent, a colorant, a metal dispersant, as long as the effects of the present embodiment are not impaired. Various additives such as defoaming agents, leveling agents, antioxidants, ultraviolet absorbers, coupling agents, fillers, and viscosity modifiers may be blended.

The method for producing the conductive film forming agent according to the present embodiment is not particularly limited, and a method known in the field of the conductive film forming agent can be preferably used. For example, a method of blending each of the above-mentioned components in a predetermined blending ratio and mixing using a known mixer can be mentioned. At that time, it is preferable that the cellulose nanofibers of the component (B) are added as a cellulose nanofiber dispersion using an organic solvent as a dispersion medium as described above.

The viscosity of the conductive film forming agent according to the present embodiment is not particularly limited, and for example, the viscosity at 25 ° C. may be 50 Pa · s or less, or 20 Pa · s or less. From the viewpoint of sprayability, the smaller the viscosity, the more preferable. Here, the viscosity of the conductive film forming agent is obtained by measuring the viscosity (η1 rpm) at 1 rpm rotation (slip speed 2s-1) at 25 ° C. using an E-type viscometer.

[Use of conductive film forming agent]
The conductive film forming agent according to this embodiment is used for forming a conductive film. Specifically, it can be used for forming a conductive film in an electromagnetic wave shield and forming a conductive film (for example, wiring) in various electronic components.

In one embodiment, a conductive film can be formed on a substrate by applying a conductive film forming agent on the substrate and curing the conductive film forming agent.

Examples of the coating method include a spray method and an inkjet method, and a spray method is preferable. That is, the conductive film forming agent according to a preferred embodiment is a conductive film forming agent for spraying, which is used to form a conductive film by spraying.

Examples of the base material include a glass substrate, a ceramic substrate (alumina substrate, etc.), a flexible substrate (PET film, etc.), and the like.

The coating film formed on the substrate can be cured by, for example, drying at 60 to 150 ° C. for 1 to 60 minutes and then firing at a low temperature of 100 to 250 ° C. for 1 to 60 minutes to form a conductive film. be able to.

The specific resistance (volume resistivity) of the conductive film formed by the conductive film forming agent according to the present embodiment is not particularly limited, but is preferably 1 × 10 ^-3 Ω · cm or less, and is preferably 1 × 10 ^-6 . It may be ~ 1 × 10 ^-4 Ω · cm.

[effect]
In the conductive film forming agent according to the present embodiment, the dispersibility of the silver powder and / or the silver-coated powder is good because the organic solvent is used as the dispersion medium. Further, by containing the cellulose nanofibers, the conductive film forming agent has high ticking property, so that it is possible to achieve both coating film forming property such as spraying property and storage stability, and it has good conductivity. A conductive film can be formed.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

The evaluation method of the conductive film forming agent is as follows.

[Dispersity]
The conductive film forming agent immediately after the preparation was allowed to stand and the state was visually confirmed, and the case where the metal powder did not settle was evaluated as “◯”, and the case where the metal powder settled was evaluated as “x”.

[Sprayability]
Only the conductive film forming agents having a dispersibility of "○" were evaluated. A conductive film forming agent was put into a spray (nozzle type Z-75-1-1 manufactured by Mitani Valve Co., Ltd.), and the nozzle was pressed with a constant pressure to spray. Then, the sprayability was compared by using water as a positive control and a 1% by mass xanthan gum aqueous solution as a negative control. That is, the one that could be sprayed like water with a feeling of use similar to that of water was marked with "○", and the one that could be sprayed only partially with a feeling of use similar to that of a 1% by mass xanthan gum aqueous solution (direct irradiation). Those that were sprayed) and those that could not be sprayed were evaluated as "x".

[Storage stability]
Only the conductive film forming agents having a dispersibility of "○" were evaluated. The conductive film forming agent was allowed to stand at 25 ° C. overnight. The change in the state of the conductive film forming agent was visually confirmed, and the case where the metal powder did not settle was evaluated as “◯”, and the time when the metal powder settled was evaluated as “x”.

[TI value]
Only the conductive film forming agents having a dispersibility of "○" were evaluated. The viscosity of the conductive film forming agent was measured at 25 ° C. using an E-type viscometer (TV-22 type viscometer cone plate type manufactured by Toki Sangyo Co., Ltd.). The viscosity (η1 rpm) at 1 rpm rotation (slip speed 2s-1) and the viscosity (η10 rpm) at 10 rpm rotation (slip speed 20s-1) are measured, and the former is divided by the latter to obtain the TI value (η1 rpm / η10 rpm). Was calculated.

[Specific resistance]
Only the conductive film forming agents having dispersibility, sprayability and storage stability of "○" were evaluated. A conductive film forming agent was applied to a glass substrate in a rectangular shape of 10 mm × 26 mm with a thickness of 100 to 200 μm, and heated in a hot air dryer at 150 ° C. for 10 minutes and in a hot air dryer at 200 ° C. for 60 minutes. A conductive film was formed. The film thickness of the formed conductive film is measured by a surface roughness meter (Surfcom 480A manufactured by Tokyo Precision Co., Ltd.), and the electrical resistance at room temperature (25 ° C) is measured by an electrical resistance measuring device (low resistivity meter manufactured by Mitsubishi Chemical Analytics Co., Ltd.). It was measured by Loresta GP, four-terminal four-probe method), and the specific resistance (volume resistivity) was calculated and evaluated based on the film thickness, electrical resistance, and aspect ratio of the conductive film.

[Production Example 1: Preparation of CNF Dispersion 1]
To 2 g of coniferous tree pulp, 150 ml of water, 0.25 g of sodium bromide, and 0.025 g of 2,2,6,6-tetramethylpiperidinooxy radical (TEMPO) were added, and the mixture was sufficiently stirred and dispersed, and then 13 mass by mass. % Sodium hypochlorite aqueous solution (cooxidant) was added to 1.0 g of the above pulp so that the amount of sodium hypochlorite was 12.0 mmol / g, and the reaction was started. Since the pH decreases as the reaction progresses, the reaction was carried out while dropping a 0.5 N sodium hydroxide aqueous solution so as to maintain the pH at 10 to 11 until no change in pH was observed (reaction time: 120 minutes). .. After completion of the reaction, solid-liquid separation was performed with a centrifuge, and pure water was added to adjust the solid content concentration to 4% by mass. Then, the pH of the slurry was adjusted to 10 with a 24 mass% NaOH aqueous solution. The temperature of the slurry was set to 30 ° C., 0.2 mmol / g of sodium borohydride was added to the cellulose fibers, and the mixture was reacted for 2 hours for reduction treatment. After the reaction, 0.1N hydrochloric acid was added for neutralization, and then filtration and washing with water were repeated for purification to obtain modified cellulose fibers. Methanol was added to the modified cellulose fiber and filtered, and the washing with methanol was repeated to replace the water contained in the modified cellulose fiber with methanol. Then, methanol and an equal amount of polyetheramine (PO / EO-based monoamine, JEFFAMINE M-2070, manufactured by HUNTSMAN) equal to the amount of carboxyl groups of the modified cellulose fiber are added to make the cellulose fiber concentration 2.5% by mass. It was diluted so as to be the same, and treated once with a high-pressure homogenizer (manufactured by Sugino Machine Limited, Starburst) at a pressure of 100 MPa to obtain a gel-like composition (CNF dispersion 1).

The obtained CNF dispersion 1 is a 2.5% by mass dispersion of TEMPO oxidized cellulose nanofibers using methanol as a dispersion medium, and the content of the carboxyl group of the cellulose nanofibers is 2.1 mmol / g, and the number average fiber. It had a diameter of 4 nm and had an I-type crystal structure.

[Production Example 2: Preparation of CNF Dispersion 2]
To 2 g of coniferous pulp, 150 ml of water, 0.25 g of sodium bromide, and 0.025 g of TEMPO were added, and the mixture was sufficiently stirred and dispersed. Sodium hypochlorite was added to 0 g so that the amount of sodium hypochlorite was 12.0 mmol / g, and the reaction was started. Since the pH decreases as the reaction progresses, the reaction was carried out while dropping a 0.5 N sodium hydroxide aqueous solution so as to maintain the pH at 10 to 11 until no change in pH was observed (reaction time: 120 minutes, Reaction temperature: 40 ° C.). After completion of the reaction, 0.1N hydrochloric acid was added for neutralization, filtration and washing with water were repeated for purification, and pure water was added to adjust the solid content concentration to 4% by mass. Then, the pH of the slurry was adjusted to 10 with a 24 mass% NaOH aqueous solution. The temperature of the slurry was set to 30 ° C., 0.2 mmol / g of sodium borohydride was added to the cellulose fibers, and the mixture was reacted for 2 hours for reduction treatment. After the reaction, 0.1N hydrochloric acid was added for neutralization, and then filtration and washing with water were repeated for purification to obtain modified cellulose fibers. N-Methylpyrrolidone (NMP) was added to the modified cellulose fiber and filtered, and NMP washing was repeated to replace the water contained in the modified cellulose fiber with NMP. After that, NMP, 3/4 equal amount of polyether amine (JEFFAMIN M-2005, manufactured by HUNTSMAN) and 1/4 equal amount of polyether amine (JEFFAMINE M-2070, HUNTSMAN) of the amount of carboxyl group of the modified cellulose fiber. Is added to dilute the cellulose fiber concentration to 9.0% by mass, and the mixture is treated once with a high-pressure homogenizer (manufactured by Sugino Machine Limited, Starburst) at a pressure of 100 MPa to form a gel-like composition (CNF). Dispersion 2) was obtained.

The obtained CNF dispersion 2 is a 9.0 mass% dispersion of TEMPO oxidized cellulose nanofibers using NMP as a dispersion medium, and the content of the carboxyl group of the cellulose nanofibers is 1.8 mmol / g, and the number average fiber. It had a diameter of 4 nm and had an I-type crystal structure.

[Comparative Production Example 1: Preparation of CNF Dispersion 3]
To 2 g of coniferous pulp, 150 ml of water, 0.25 g of sodium bromide, and 0.025 g of TEMPO were added, and the mixture was sufficiently stirred and dispersed. Sodium hypochlorite was added to 0 g so that the amount of sodium hypochlorite was 12 mmol / g, and the reaction was started. Since the pH decreases as the reaction progresses, a 0.5 N aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 to 11, and the reaction was carried out until no change in pH was observed (reaction time: 120 minutes). ). After completion of the reaction, 0.1N hydrochloric acid was added for neutralization, and then filtration and washing with water were repeated for purification to obtain cellulose fibers having an oxidized fiber surface. Next, pure water was added to the cellulose fibers to dilute them to 2% by mass, and the mixture was treated once with a high-pressure homogenizer (manufactured by Sanwa Engineering Co., Ltd., H11) at a pressure of 100 MPa to obtain a gel-like composition (CNF dispersion). 3) was manufactured.

The obtained CNF dispersion 3 is a 2.0% by mass dispersion of TEMPO oxidized cellulose nanofibers using water as a dispersion medium, and the content of the carboxyl group of the cellulose nanofibers is 2.1 mmol / g, and the number average fiber. It had a diameter of 4 nm and had an I-type crystal structure.

[Example 1: Preparation of conductive film forming agent]
Flake-shaped silver powder (trade name: Silcoat AgC-A, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., specific surface area 0.6 to 0.9 m ² / g, 50% average particle diameter 4.65 μm) 0.95 parts by mass And 2.00 parts by mass of CNF dispersion 1 (2.5% by mass dispersion of TEMPO oxidized cellulose nanofibers using methanol as a dispersion medium) obtained in Production Example 1 was measured in a glass container and rotated and revolved. Mixing was carried out at 1500 rpm for 5 minutes using a mixer (V-mini300 manufactured by EME) to obtain a conductive film forming agent according to Example 1.

In the conductive film forming agent of Example 1, the mixing ratio of the silver powder and the cellulose nanofibers (each content in the solid content) is 95% by mass of the silver powder and 5% by mass of the cellulose nanofibers.

[Example 2, Comparative Examples 1 to 7]
A conductive film forming agent was prepared in the same manner as in Example 1 except that the types and blending amounts of each component were as shown in Table 1 below. In both the conductive film forming agents of Examples 2 and Comparative Examples 1 to 7, the mixing ratio of the silver powder and the cellulose nanofibers or the binder resin in the solid content was 95% by mass of the silver powder and 5% by mass of the cellulose nanofibers or the binder resin. Met.

The binder resins 1 and 2 in the table are as follows.
-Binder resin 1: Epoxy resin, trade name: ADEKA Resin EP-4901E, manufactured by ADEKA Corporation-Binder resin 2: ethyl cellulose, trade name: ethyl cellulose viscosity: 80-120 cps (5% solution, 25 ° C), manufactured by Nacalai Tesque

The obtained conductive film forming agents of Examples 1 and 2 and Comparative Examples 1 to 7 were evaluated for dispersibility, sprayability, storage stability, TI value, and specific resistance. The results are shown in Table 1. In Comparative Examples 1, 3 and 7, since a conductive film forming agent having good dispersibility could not be obtained, evaluation other than dispersibility was impossible.

As is clear from Table 1, the conductive film forming agents of Examples 1 and 2 containing cellulose nanofibers using an organic solvent as a dispersion medium have excellent dispersibility of silver powder and high thixophilicity (TI). It had good storage stability and could be spray-applied. Further, the conductive film obtained from the conductive film forming agent had low resistivity and showed good conductivity.

On the other hand, in Comparative Examples 1 and 3 in which the cellulose nanofibers in Examples 1 and 2 were replaced with the binder resin 1 (epoxy resin), the dispersion was poor and the silver powder settled. Since the conductive film forming agents of Comparative Examples 1 and 3 had a considerably lower viscosity than Examples 1 and 2, when the amount of the organic solvent was reduced as in Comparative Examples 2 and 4 in order to increase the viscosity, the dispersibility was increased. And although the storage stability was improved, the sprayability was not good.

In Comparative Examples 5 and 6 in which ethyl cellulose soluble in an organic solvent was used instead of the cellulose nanofibers, the silver powder could be dispersed, but the sprayability or storage stability was inferior, and the sprayability and storage stability were poor. Could not be compatible.

Further, when the aqueous dispersion of cellulose nanofibers was used as in Comparative Example 7, the dispersibility of the silver powder deteriorated.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments, omissions, replacements, changes, etc. thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

Claims (6)

A conductive film forming agent containing the following components (A) to (C), wherein the component (A) and the component (B) are dispersed in the component (C) .
(A) Silver powder and / or silver-coated powder (B) Cellulose nanofibers (C) Organic solvent The conductive film forming agent according to claim 1, wherein the component (A) is a silver powder having a 50% average particle diameter of 100 nm or more and / or a silver-coated powder. A conductive film forming agent containing the following components (A) to (C) and substantially free of water as a dispersion medium.
(A) Silver powder and / or silver-coated powder
(B) Cellulose nanofibers
(C) Organic solvent It contains the following components (A) to (C), and is characterized in that the content of the component (A) is 70 to 98% by mass with respect to the total content of the components (A) and (B) of 100% by weight. A conductive film forming agent.
(A) Silver powder and / or silver-coated powder
(B) Cellulose nanofibers
(C) Organic solvent The conductive film forming agent according to any one of claims 1 to 4, which is used for spraying. A conductive film formed by applying the conductive film forming agent according to any one of claims 1 to 5.