Conductive material composition and method for forming a conductive film

Abstract

To provide a conductive material composition for forming a conductive film having high conductivity and high transparency.SOLUTION: A conductive material composition contains: (A) metal nanowires; (B) a resin whose main chain is to be decomposed by an acid, heat, or both; and (C) a solvent.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a conductive material composition, a conductive film, and a method for forming a highly transparent, highly conductive conductive film. [Background technology]

[0002] In recent years, the market for highly transparent conductive films has continued to expand with the spread of organic EL displays and touch panels.

[0003] Indium tin oxide films (ITO) are widely used as transparent electrodes (Patent Document 1).

[0004] Non-contact touch panels require transparent electrodes with higher conductivity than ITO, and silver nanowires are being considered as a candidate for this purpose (Patent Document 2).

[0005] Early silver nanowire production employed a template method. Templates included carbon nanotubes, porous silica and alumina, surfactants, and block copolymers, but these methods suffered from long reaction times and low silver nanowire productivity.

[0006] A method has been proposed in which nanowires are grown by adding surfactants such as polyvinylpyrrolidone in water or ethylene glycol and reducing them with silver nitrate (Non-Patent Literature 1). This method is highly productive and has made it possible to mass-produce silver nanowires.

[0007] When a substrate coated with silver nanowires is heated to approximately 250°C, the silver nanowires melt and fuse together, suppressing the degradation of conductivity even when the substrate expands or contracts (Non-Patent Literature 2). The flash annealing method, which heats only the silver nanowires with very short light irradiation, suppresses the rise in temperature of the substrate and can melt silver nanowires on a polyurethane film that is flexible but has a heat resistance lower than 250°C (Non-Patent Literature 3). Furthermore, Non-Patent Literature 4 discloses the self-assembly of silver nanowires.

[0008] When applying silver nanowire ink composed only of a solvent and silver nanowires, the distribution of the silver nanowires may become non-uniform. If the distribution of the silver nanowires is non-uniform, spots may occur in transparency and conductivity, and the performance of the devices using this may be degraded.

[0009] Furthermore, when heating for fusion of silver nanowires with each other after applying silver nanowire ink composed only of a solvent and silver nanowires, the silver nanowires may break before fusion. Particularly, when the density of the silver nanowires is low or the diameter of the silver nanowires is thin, there is no support due to contact between the wires, and due to insufficient strength of the wires themselves, they seem to break due to air vibration at high temperatures. To form a conductive film with high transparency, the concentration of silver nanowires is lowered or silver nanowires with a small diameter are used, but it is necessary to fuse the silver nanowires without breaking them.

[0010] To uniformly apply silver nanowires or to prevent silver nanowires from breaking during heating, a method of adding a resin as a component of the silver nanoink can be mentioned. For example, Non-Patent Document 5 describes a technique related to the synthesis of silver nanostructures in the presence of polyvinylpyrrolidone. By containing a resin, the film after coating is flattened, and the resin can support the silver nanowires and prevent the silver nanowires from breaking. However, the addition of an insulating resin leads to a decrease in conductivity. Therefore, the development of an ink for forming a uniform and highly conductive silver nanowire layer is required.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0012] [Non-Patent Document 1] Yugang Sun et al., "Crystalline Silver Nanowires by Soft Solution Processing", Nano letters, Vol. 2, (2002), No. 2, p. 165-168 [Non-Patent Document 2] Natsuki Komoda et al., "Evaluation of Conductivity of Silver Nanowire Printed Wiring," Proceedings of the 26th Spring Conference of the Japan Society for Electronics Packaging, 9D-04, (2012), p. 318. [Non-Patent Document 3] Yang Yang et al., "Facile fabrication of stretchable Ag nanowire / polyurethane electrodes using high intensity pulsed light", Nano Research, 9 (2), (2016), p. 401-414 [Non-Patent Document 4] Y. Gao et al., "Synthesis, characterization and self-assembly of silver nanowires", Chemical Physics Letters, 380, (2003), p. 146-149 [Non-Patent Document 5] Masaharu Tsuji et al., "Effects of chain length of polyvinylpyrrolidone for the synthesis of silver nanostructures by a microwave-polyol method", Materials Letters, 60, (2006), p. 834-838 [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention was made to solve the above problems and aims to provide a conductive material composition for forming a highly conductive and highly transparent conductive film, a highly conductive and highly transparent conductive film, and a method for forming a highly conductive and highly transparent conductive film. [Means for solving the problem]

[0014] To solve the above problems, the present invention provides: (A) Metal nanowires and (B) A resin whose main chain decomposes due to either acid and / or heat, (C) Solvent and The present invention provides a conductive material composition characterized by containing the following:

[0015] Such conductive material compositions enable the low-cost production of uniform, highly transparent, and highly conductive films.

[0016] It is preferable that the resin (B) contains repeating units having an acetal structure represented by the following general formula (1). [ka] (In the formula, R 1 (where is a hydrogen atom, or a saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms, which may be substituted. W is a saturated or unsaturated divalent organic group having 2 to 30 carbon atoms.)

[0017] Such a conductive material composition can exhibit appropriate decomposability and fluidity.

[0018] Furthermore, it is particularly preferable that the resin (B) is a compound represented by any of the following general formulas (1a) to (1c). [ka] (In the formula, R 1a This is an alkyl group having 1 to 4 carbon atoms. aR is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, and may have an ether bond. b1 Each of these is independent of -W a -OH, or a monovalent organic group having 1 to 30 carbon atoms, either saturated or unsaturated. 1c R is a hydrogen atom, or an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 4 to 20 carbon atoms, which may be substituted. c1 Each of these is independently an alkyl group having 1 to 4 carbon atoms, or -W a It is -OH. n represents the average number of repeating units, ranging from 3 to 2,000.

[0019] Such conductive material compositions can exhibit even more appropriate decomposability and fluidity.

[0020] Furthermore, it may also contain a photoacid generator or a thermoacid generator.

[0021] If the product contains a photoacid generator or a thermoacid generator, the decomposition temperature of resin (B) can be lowered.

[0022] Furthermore, in the present invention, a conductive film formed on a substrate, The present invention provides a conductive film characterized in that the resin (B) component of the conductive material composition of the present invention, coated on the substrate, is decomposed and / or removed by either acid and / or heat, or both.

[0023] Such conductive films can be highly transparent and highly conductive.

[0024] Furthermore, the present invention provides a method for forming a conductive film, characterized by coating a substrate with the conductive material composition of the present invention, and then decomposing and / or removing the resin (B) component by either acid and / or heat, or both, to form a conductive film.

[0025] This method of forming conductive films allows for the production of uniform, highly transparent, and highly conductive films at a low cost. [Effects of the Invention]

[0026] As described above, the conductive material composition of the present invention makes it possible to manufacture a uniform, highly transparent, and highly conductive film at low cost.

[0027] Furthermore, the conductive film of the present invention can be made highly transparent and highly conductive.

[0028] Furthermore, the conductive film formation method of the present invention makes it possible to manufacture a uniform, highly transparent, and highly conductive film at low cost. [Brief explanation of the drawing]

[0029] [Figure 1] This is a cross-sectional view of a coating film obtained by applying an example of the conductive material composition of the present invention onto a substrate. [Figure 2] This is a cross-sectional view of a conductive film obtained by decomposing and removing the resin in the coating film shown in Figure 1 using either acid, heat, or both. [Figure 3] This shows the thermal decomposition data (DTA) of resin B1 used in Examples 1-3 in air. [Figure 4] This is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Example 1 onto a quartz wafer and baking it on a hot plate at 220°C for 10 minutes. [Figure 5] This is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Example 1 onto a quartz wafer and baking it on a hot plate at 250°C for 10 minutes. [Figure 6] This is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Comparative Example 1 onto a quartz wafer and baking it on a hot plate at 250°C for 10 minutes. [Figure 7] This is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Comparative Example 2 onto a quartz wafer and baking it on a hot plate at 250°C for 10 minutes. [Modes for carrying out the invention]

[0030] As mentioned above, there was a need for the development of uniform, highly transparent, and highly conductive thin-film conductive films.

[0031] As a result of diligent research into the above-mentioned problems, the present inventors have discovered that a conductive material composition comprising metal nanowires, a resin whose main chain decomposes upon either acid and / or heat, and a solvent, allows for the formation of a uniform layer of metal nanowires during coating due to the presence of the resin, and the decomposition and evaporation of the insulating resin by acid and / or heat allows for the formation of a highly transparent and highly conductive metal nanowire layer (conductive film), thus completing the present invention.

[0032] In other words, the present invention is (A) Metal nanowires and (B) A resin whose main chain decomposes due to either acid and / or heat, (C) Solvent and This is a conductive material composition characterized by containing [a specific substance].

[0033] Furthermore, the present invention relates to a conductive film formed on a substrate, The conductive film is characterized in that the resin (B) component of the conductive material composition of the present invention coated on the substrate is decomposed and / or removed by either acid and / or heat, or both.

[0034] Furthermore, the present invention is a method for forming a conductive film, characterized by coating a substrate with the conductive material composition of the present invention, and decomposing and / or removing the resin (B) component by either acid and / or heat, or both, to form a conductive film.

[0035] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0036] [Conductive material composition] The conductive material composition of the present invention is (A) Metal nanowires and (B) A resin whose main chain decomposes due to either acid and / or heat, (C) Solvent and Includes.

[0037] By using such a conductive material composition, a uniform metal nanowire layer coating can be formed during coating due to the presence of resin (B). Furthermore, since the insulating resin (B) can be decomposed and / or removed by acid and / or heat, the high-resistance resin (B) can be eliminated from the coating by applying heat to the coating or by generating acid in the coating. This makes it possible to obtain a conductive film (metal nanowire layer) that does not contain resin (B), i.e., a highly conductive film. The metal nanowires contained in the obtained conductive film have a diameter at the nanoscale, and therefore can transmit visible light. Thus, the obtained conductive film can be highly transparent.

[0038] Furthermore, because this conductive film is flexible, it can be applied to flexible touch sensors, displays, and lighting. Its stretchability also makes it suitable for use in biosensors such as bioelectrodes that can be attached to the body.

[0039] The components of the conductive material composition of the present invention will be described in more detail below.

[0040] [(A) Metal nanowires] The diameter of the metal nanowire, which is component (A), can be, for example, 1 to 200 nm, and its length can be in the range of 0.5 to 500 μm. When preparing the conductive material composition of the present invention, it is preferable to use the metal nanowire (A) in a form dispersed in water or a lower alcohol.

[0041] (A) The metal species of the metal nanowire is not particularly limited, but silver is preferred, and gold, copper, and cobalt can also be used. Furthermore, (A) the metal nanowire may be made of silver alone, or an alloy of silver with gold, platinum, copper, or cobalt.

[0042] [(B) Resin] The resin as the component (B) is a resin (degradable polymer) whose main chain is decomposed by either or both of an acid and heat.

[0043] As a preferred form of the above resin (B), those containing a repeating unit having an acetal structure represented by the following general formula (1) can be mentioned. [Chemical formula] (In the formula, R 1 is a hydrogen atom or a saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms which may be substituted. W is a saturated or unsaturated divalent organic group having 2 to 30 carbon atoms.)

[0044] And, as a more preferred form of the above component (B), compounds represented by the following general formulas (1a) to (1c) (hereinafter, sometimes referred to as "degradable polymers (1a) to (1c)") can be mentioned. [Chemical formula] (In the above general formulas (1a) to (1c), R 1a is an alkyl group having 1 to 4 carbon atoms. W a is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms and may have an ether bond. R b1 are each independently -W a -OH or a saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms which may be substituted. R 1c is a hydrogen atom or an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 4 to 20 carbon atoms which may be substituted. R c1 are each independently an alkyl group having 1 to 4 carbon atoms or -W a -OH. n represents the average number of repeating units and is 3 to 2,000, preferably 3 to 500.)

[0045] The presence of the chain-like acetal structure represented by the above general formula (1) or (1a) to (1c) is effective in imparting appropriate degradability and fluidity to the resin (B). Furthermore, since it decomposes into highly volatile low-molecular-weight compounds after decomposition, it does not remain in large quantities on the conductive film, thus minimizing deterioration of the conductive film's conductivity.

[0046] In the above general formula (1), R 1 This is a hydrogen atom, or a monovalent organic group having 1 to 30 carbon atoms, which may be substituted, either saturated or unsaturated.

[0047] Herein, in the present invention, "organic group" means a group containing at least one carbon atom, and may further contain a hydrogen atom, as well as a nitrogen atom, oxygen atom, sulfur atom, silicon atom, halogen atom, etc.

[0048] R 1 It can be a single type, or multiple types can be mixed together. 1 More specifically, examples include hydrogen atoms, methyl groups, ethyl groups, vinyl groups, 2,2,2-trifluoroethyl groups, propyl groups, isopropyl groups, allyl groups, 1-propenyl groups, isopropenyl groups, butyl groups, s-butyl groups, t-butyl groups, isobutyl groups, pentyl groups, cyclopentyl groups, hexyl groups, cyclohexyl groups, cyclohexenyl groups, decyl groups, dodecyl groups, eicosyl groups, norbornyl groups, adamantyl groups, phenyl groups, toluyl groups, xylyl groups, naphthyl groups, phenantrenyl groups, anthracenyl groups, benzyl groups, fluorenyl groups, naphthylmethyl groups, norbornyl groups, triacontyl groups, 2-furanyl groups, and 2-tetrahydrofuranyl groups.

[0049] In the general formula (1) above, W is a saturated or unsaturated divalent organic group having 2 to 30 carbon atoms. W may be a single entity or a mixture of multiple types. More specifically, examples of W include ethylene, propylene, butylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, decamethylene, dodecamethylene, eicosamethylene, triacontamethylene, cyclopentanediyl, cyclohexanediyl, dimethylcyclohexanediyl, 2-butene-1,4-diyl, 2,4-hexadiene-1,6-diyl, 3-oxapentane-1,5-diyl, 3,6-dioxaoctane-1,8-diyl, 3,6,9-trioxaundecane-1,11-diyl, phenylene, xylyl, naphthalenediyl, dimethylnaphthalenediyl, and adamantanediyl.

[0050] In the above general formulas (1a) and (1b), R 1a R is an alkyl group having 1 to 4 carbon atoms. 1a It can be a single type, or multiple types can be mixed together. 1a More specifically, examples include methyl group, ethyl group, propyl group, isopropyl group, butyl group, s-butyl group, t-butyl group, and isobutyl group.

[0051] In the above general formulas (1a) to (1c), W a This is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, and may have an ether bond. a It may be a single type, or multiple types may be mixed together. a More specifically, examples include the tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, decamethylene group, cyclopentanediyl group, cyclohexanediyl group, dimethylcyclohexanediyl group, 2-butene-1,4-diyl group, 2,4-hexadiene-1,6-diyl group, 3-oxapentane-1,5-diyl group, 3,6-dioxaoctane-1,8-diyl group, 3,6,9-trioxaundecane-1,11-diyl group, phenylene group, xylyl group, and adamantanediyl group.

[0052] In the general formula (1b) above, R b1 Each of these is independent of -W a It is either an -OH group or a substituted, saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms. More specifically, examples of substituted, saturated or unsaturated monovalent organic groups having 1 to 30 carbon atoms include the methyl group, ethyl group, vinyl group, 2,2,2-trifluoroethyl group, propyl group, isopropyl group, allyl group, 1-propenyl group, isopropenyl group, butyl group, s-butyl group, t-butyl group, isobutyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, cyclohexenyl group, decyl group, dodecyl group, eicosanyl group, norbornyl group, adamantyl group, phenyl group, toluyl group, xylyl group, naphthyl group, phenantrenyl group, anthracenyl group, benzyl group, fluorenyl group, naphthylmethyl group, norbornyl group, eicosanyl group, triacontyl group, 2-furanyl group, and 2-tetrahydrofuranyl group.

[0053] In the above general formula (1c), R 1c R is a hydrogen atom, or an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 4 to 20 carbon atoms, which may be substituted. 1c It can be a single type, or multiple types can be mixed together. 1c More specifically, examples include hydrogen atoms, phenyl groups, toluyl groups, xylyl groups, naphthyl groups, phenantrenyl groups, anthracenyl groups, 2-furanyl groups, and anisyl groups.

[0054] In the above general formula (1c), R c1 Each of these is independently an alkyl group having 1 to 4 carbon atoms, or a -Wa-OH group. More specifically, examples of alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, and isobutyl groups.

[0055] n represents the average number of repeating units, which is between 3 and 2000, preferably between 3 and 500, and more preferably between 5 and 300.

[0056] When the above resin (B) contains repeating units having an acetal structure represented by the above general formula (1), it may have only a single repeating unit or it may have a combination of two or more repeating units.

[0057] More specifically, the following are examples of repeating units having the acetal structure shown in the general formula (1) above, but are not limited to these. [ka]

[0058] The following are some, but are not limited to, examples of compounds represented by the general formula (1a) above. In the formula below, n is the same as above. [ka]

[0059] More specifically, the following compounds can be given as examples of compounds represented by the above general formula (1b), but are not limited to these. In the formula below, n is the same as above. [ka]

[0060] The following are some, but are not limited to, examples of compounds represented by the general formula (1c) above. In the formula below, n is the same as above. [ka]

[0061] R 1 , R 1a , R b1 , R 1c , R c1 , W and W aBy selecting the structure, the properties of resin (B), such as the thermal decomposition temperature, weight loss rate during heating, and fluidity, can be adjusted as needed, and consequently, the properties of the conductive material composition can be adjusted.

[0062] In particular, the degradable polymers (1a) to (1c) have excellent fluidity, and R 1a and W a By selecting the appropriate structure, it is easily possible to achieve a weight loss rate of 70% by mass or more during heating. Decomposable polymers (1a) and (1b) are preferred because they have low thermal decomposition temperatures, which in turn further suppresses the decrease in the etching resistance of the conductive film material. Pyrodecomposable polymer (1c) is also preferred because it may act as a crosslinking agent, which further expands the range of property adjustment for the conductive film material.

[0063] The weight-average molecular weight of resin (B) is preferably 300 to 200,000, more preferably 300 to 50,000, and even more preferably 500 to 40,000. The average number of repeating units is preferably 3 to 2,000, and even more preferably 3 to 500. If the weight-average molecular weight is 300 or higher, the decrease in the blending effect due to volatilization, etc., can be suppressed, and a sufficient blending effect can be obtained. Furthermore, if the weight-average molecular weight is 200,000 or lower, the fluidity will not deteriorate, and the embedding / planarization characteristics will be excellent.

[0064] A degradable polymer having the structure represented by the above general formula (1) or (1a) can be manufactured by selecting the most suitable method depending on the structure. Taking the degradable polymer (1a) as an example, it can be manufactured by selecting from, for example, the following three methods. The degradable polymer (1) can also be manufactured by a similar method. However, the manufacturing method of the degradable polymer used in the present invention is not limited to these.

[0065] [ka] (In the formula, R 1a This is an alkyl group having 1 to 4 carbon atoms. a(where n is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, and may have an ether bond. n represents the average number of repeating units, ranging from 3 to 2,000.)

[0066] The above reaction is, as an elementary reaction, a general acetal formation reaction catalyzed by an acid. This elementary reaction proceeds repeatedly to ultimately yield a polymer. In the above reaction, the optimal amount of diol compound (6) to diether compound (5) is 0.5 to 2 moles of (6) per 1 mole of (5), and is particularly preferably 0.8 to 1.2 moles. In the above reaction, the optimal amount of diol compound (6) to t-butyl ether compound (7) is preferably 0.5 to 2 moles of (6) per 1 mole of (7), and is particularly preferably 0.8 to 1.2 moles.

[0067] The above acetalization reaction can be carried out by mixing each raw material with an acid catalyst in or without a solvent, and then cooling or heating. When a solvent is used in the reaction, the solvent can be selected from aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene, xylene, trimethylbenzene, and methylnaphthalene; ethers such as diethyl ether, dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and tetrahydrofuran; ketones such as acetone and 2-butanone; alcohols such as t-butyl alcohol and t-amyl alcohol; esters such as ethyl acetate, propylene glycol monomethyl ether acetate, and γ-butyrolactone; nitriles such as acetonitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; and halogenated hydrocarbons such as o-dichlorobenzene, methylene chloride, and 1,2-dichloroethane, and can be used individually or in combination of two or more.

[0068] Various inorganic or organic acids can be used as acid catalysts in the reaction. Specifically, examples of acid catalysts include hydrochloric acid, nitric acid, sulfuric acid, formic acid, oxalic acid, acetic acid, methanesulfonic acid, camphorsulfonic acid, tosylic acid, trifluoromethanesulfonic acid, cation exchange resins, sodium bisulfate, and pyridinium p-toluenesulfonate. The amount of these acid catalysts used is 1 × 10⁻⁶ per 1 mole of total raw materials. -5 ~5×10 -1 Moles are preferred.

[0069] The reaction temperature is preferably -20°C to 100°C, and more preferably 0°C to 80°C. If a solvent is used, it is preferable to limit the temperature to around the boiling point of the solvent. If the reaction temperature is above -20°C, the reaction proceeds smoothly, and if it is below 100°C, side reactions such as the decomposition of the product can be suppressed. The reaction time for the above reaction is preferably determined by tracking the progress of the reaction using thin-layer chromatography, liquid chromatography, gel filtration chromatography, etc., in order to improve the yield, but it is usually around 0.5 to 200 hours. After the reaction is completed, the target product, the degradable polymer (1a), can be obtained by conventional aqueous work-up and / or filtration of insoluble components.

[0070] The resulting biodegradable polymer (1a) can be purified by conventional methods such as liquid-liquid separation, crystallization, vacuum concentration, dialysis, and ultrafiltration, depending on its properties, if necessary. Furthermore, the metal content can be reduced by passing it through a commercially available demetallation filter, if required.

[0071] The reaction can be carried out by, for example, charging all the raw materials, acid catalyst, and solvent together as needed; adding each raw material or raw material solution individually or mixed dropwise into the presence of the catalyst; or passing a mixed raw material or mixed raw material solution through a column packed with a solid acid catalyst. Molecular weight can be adjusted by, for example, controlling the reaction time; controlling the amount of acid catalyst; controlling the addition / adjusting the content of polymerization inhibitors such as water / alcohol / basic compounds; controlling the raw material charging ratio when using two types of raw materials; or controlling by combining several of these methods.

[0072] The raw material compounds represented by the above general formulas (5) to (8) may be used individually or in combination of two or more types. The raw material compounds represented by the above general formulas (5), (7), and (8) may be unstable in the presence of oxygen, light, moisture, etc., and in such cases, the reaction is preferably carried out under an inert atmosphere such as nitrogen and in the absence of light.

[0073] In the case of the aforementioned degradable polymers (1b) and (1c), they can be specifically produced by selecting from, for example, the following two methods. The same method can also be used to produce the aforementioned degradable polymer (1). However, the methods for producing the degradable polymers used in the present invention are not limited to these.

[0074] [ka] (In the formula, R is R 1a or R 1c That is. R' is R b1 or R c1 That is. W a R is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, and may have an ether bond. b1 Each of these is independent of -W a -OH, or a monovalent organic group having 1 to 30 carbon atoms, either saturated or unsaturated. 1cR is a hydrogen atom, or an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 4 to 20 carbon atoms, which may be substituted. c1 Each of these is independently an alkyl group having 1 to 4 carbon atoms, or a -Wa-OH group. n represents the average number of repeating units, ranging from 3 to 2,000.

[0075] The above reaction is, as an elementary reaction, a general acetal formation reaction catalyzed by an acid. This elementary reaction proceeds repeatedly to ultimately yield a polymer. In the above reaction, the optimal amount of diol compound (6) to aldehyde compound (9) is 0.5 to 2 moles of (6) per mole of (9), and is particularly preferably 0.8 to 1.2 moles. In the above reaction, the optimal amount of diol compound (6) to acetal compound (10) is 0.5 to 2 moles of (6) per mole of (10), and is particularly preferably 0.8 to 1.2 moles.

[0076] The above acetalization reaction can be carried out by mixing each raw material with an acid catalyst in or without a solvent, and then cooling or heating. When a solvent is used in the reaction, the solvent can be selected from aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene, xylene, trimethylbenzene, and methylnaphthalene; ethers such as diethyl ether, dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and tetrahydrofuran; ketones such as acetone and 2-butanone; alcohols such as t-butyl alcohol and t-amyl alcohol; esters such as ethyl acetate, propylene glycol monomethyl ether acetate, and γ-butyrolactone; nitriles such as acetonitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; and halogenated hydrocarbons such as o-dichlorobenzene, methylene chloride, and 1,2-dichloroethane, and can be used individually or in combination of two or more.

[0077] Various inorganic and organic acids can be used as acid catalysts in the reaction. Specifically, examples of acid catalysts include hydrochloric acid, nitric acid, sulfuric acid, formic acid, oxalic acid, acetic acid, methanesulfonic acid, camphorsulfonic acid, tosylic acid, trifluoromethanesulfonic acid, cation exchange resins, sodium bisulfate, and pyridinium p-toluenesulfonate. The amount of these acid catalysts used is 1 × 10⁻⁶ per mole of total raw materials. -5 ~5×10 -1 Moles are preferred.

[0078] The reaction temperature is preferably 0°C to 250°C, and more preferably 20°C to 200°C. If a solvent is used, it is preferable to limit the temperature to around the boiling point of the solvent. If the reaction temperature is above 0°C, the reaction proceeds smoothly, and if it is below 250°C, side reactions such as the decomposition of the product can be suppressed. The reaction time for the above reaction is preferably determined by tracking the progress of the reaction using thin-layer chromatography, liquid chromatography, gel filtration chromatography, etc., in order to improve the yield, but it is usually around 0.5 to 200 hours. After the reaction is completed, the target product, the degradable polymer (1"), i.e., the degradable polymer (1b) or (1c), can be obtained by conventional aqueous work-up and / or filtration of insoluble components.

[0079] The resulting biodegradable polymer (1") can be purified, if necessary, by conventional methods such as liquid-liquid separation, crystallization, vacuum concentration, dialysis, or ultrafiltration, depending on its properties. Furthermore, if necessary, the metal content can be reduced by passing it through a commercially available demetallation filter.

[0080] The reaction can be carried out by, for example, charging each raw material, acid catalyst, and solvent together as needed; adding each raw material or raw material solution individually or mixed dropwise in the presence of the catalyst; or passing a mixed raw material or mixed raw material solution through a column packed with a solid acid catalyst. It is preferable to carry out the reaction while distilling off the water or alcohol produced by the reaction to improve the reaction rate. Molecular weight can be adjusted by, for example, controlling by reaction time, controlling by the amount of acid catalyst, controlling by adding / adjusting the content of polymerization inhibitors such as water / alcohol / basic compounds, controlling by the raw material charging ratio, or by a combination of these methods.

[0081] The amount of resin (B) is preferably such that the amount of metal nanowire (A) in the conductive material composition is in the range of 5 to 1000 parts by mass per 100 parts by mass of resin (B).

[0082] [(C) Solvent] Furthermore, the conductive material composition of the present invention contains a solvent as component (C). Specifically, the solvent (C) may include water, heavy water, alcohols such as methanol, ethanol, propanol, and butanol, polyhydric aliphatic alcohols such as ethylene glycol, propylene glycol, 1,3-propanediol, dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, D-glucose, D-glucitol, isoprene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl glycol, dialkyl ethers, ethylene glycol monoalkyl ethers, ethylene glycol dialkyl ethers, propylene glycol monoalkyl ethers, propylene glycol dialkyl ethers, polyethylene glycol dialkyl ethers, and polypropylene glycol dialkyl ethers. Chain ethers such as chol dialkyl ethers, cyclic ether compounds such as dioxane and tetrahydrofuran, cyclohexanone, methyl amyl ketone, ethyl acetate, butanediol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, butanediol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, t-butyl propionate, propylene glycol mono-t-butyl ether acetate, γ-butyrolactone, N-methyl-2-pyrrolidone, N,N'-dimethylformamide, N,Examples include, but are not limited to, polar solvents such as N'-dimethylacetamide, dimethyl sulfoxide, and hexamethylene phosphortriamide; carbonate compounds such as ethylene carbonate and propylene carbonate; heterocyclic compounds such as 3-methyl-2-oxazolidinone; nitrile compounds such as acetonitrile, glutaronitrile, methoxyacetonitrile, propionitrile, and benzonitrile; and mixtures thereof.

[0083] Furthermore, the amount of solvent added is preferably in the range of 10 to 50,000 parts by mass per 100 parts by mass of resin (B).

[0084] [Other ingredients] The conductive material composition of the present invention may also contain components other than those listed above (A) to (C). The other components other than those listed above (A) to (C) will be described in detail below.

[0085] (Surfactants) In the present invention, surfactants may be added to improve the wettability of the conductive material composition to a workpiece such as a substrate. Examples of such surfactants include various nonionic, cationic, and anionic surfactants. Specifically, examples include nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene carboxylic acid esters, sorbitan esters, and polyoxyethylene sorbitan esters; cationic surfactants such as alkyltrimethylammonium chloride and alkylbenzylammonium chloride; anionic surfactants such as alkyl or alkylallyl sulfates, alkyl or alkylallyl sulfonates, and dialkyl sulfosuccinates; and amphoteric surfactants such as amino acid type and betaine type.

[0086] When a surfactant is added, the amount added is preferably in the range of 5 to 1000 parts by mass per 100 parts by mass of resin (B).

[0087] (Acid generator) (B) Resins whose main chain decomposes due to either acid and / or heat allow for main chain decomposition at low temperatures in the presence of acid. Acids can be added as part of the composition, but it is preferable that the composition does not contain acid, as this can suppress the progression of decomposition of resin component (B) during storage of the composition. Instead, it is preferable to add an acid generator that is neutral and becomes acidic when exposed to light or heat, i.e., a photoacid generator or a thermoacid generator.

[0088] Examples of acid generating agents include neutralized salts of ammonium salts, pyridinium salts, sulfonium salts, iodonium salts, phosphonium salts, diazonium salts, etc., sulfonyldiazomethane, N-sulfonyloxiimide, oxime-O-sulfonates, and the like. Specific examples of acid generating agents are described, for example, in paragraphs

[0122] to

[0142] of Japanese Patent Publication No. 2008-111103. These can be used individually or in combination of two or more.

[0089] When an acid generator is included, the amount is preferably 0.1 to 50 parts by mass per 100 parts by mass of resin (B).

[0090] As described above, the conductive material composition of the present invention can be formed into a film by methods such as spin coating, roll coating, flow coating, dip coating, spray coating, and doctor coating. Furthermore, it can also be patterned by methods such as screen printing, gravure printing, flexographic printing, and inkjet printing.

[0091] Figure 1 schematically shows a cross-sectional view of a coating obtained by applying an example of the conductive material composition of the present invention to a substrate.

[0092] A conductive material composition coating 10 is applied (coated) onto a substrate 20. The conductive material composition coating 10 contains metal nanowires (A) 11, resin (B) 12, and a solvent (not shown). Resin (B) 12 is a resin whose main chain decomposes upon exposure to either acid and / or heat. By applying either acid and / or heat to the resin (B) 12 in such a conductive material composition coating 10, the resin (B) 12 can be decomposed and removed from the coating 10.

[0093] As explained above, the presence of resin (B) 12 allows for the formation of a uniform layer of metal nanowires (A) 11 during coating of the composition, and the decomposition and evaporation of the insulating resin (B) 12 by acid and / or heat allows for the formation of a highly transparent and highly conductive conductive film 30 of metal nanowires (A) 11, as shown in Figure 2.

[0094] <Conductive film> The conductive film 30 shown in Figure 2 is an example of the conductive film of the present invention. That is, the conductive film 30 of the present invention is a conductive film 30 formed on a substrate 20. This conductive film 30 is obtained by decomposing and / or removing the resin (B) component of the conductive material composition of the present invention, which is coated on the substrate 20 as shown in Figure 1, by either acid and / or heat, or both.

[0095] <Method for manufacturing conductive films> Furthermore, the present invention provides a method for forming a conductive film, characterized by coating a substrate with the conductive material composition of the present invention, and then decomposing and / or removing the resin (B) component by either acid and / or heat, or both, to form a conductive film.

[0096] In this method, for example, the conductive material composition of the present invention can be applied to a substrate, and then the resin (B) can be decomposed and evaporated by heat and / or acid to form a conductive film of silver nanowires.

[0097] Heating can be done, for example, by using a hot plate or oven, or by irradiation with infrared, near-infrared, visible light, ultraviolet light, microwaves, or electromagnetic waves, and can be continuous waves or instantaneous flash waves.

[0098] If the thermal decomposition temperature of resin (B) is in the range of 200-300°C, and if the resin (B) is to be decomposed by heating, then heating within this range is necessary. If the substrate is a high heat-resistant substrate such as glass, quartz, silicon, or polyimide, heating to 200-300°C in a hot plate or oven is possible. In the case of stretchable substrates such as polyurethane, which have low heat resistance, thermal deformation of the substrate can be suppressed by selectively heating only the metal nanowires using the flash annealing method.

[0099] When the acid generator described above is added to the conductive material composition, the decomposition temperature of resin (B) is lowered by the acid generated by the decomposition of the acid generator. For example, if the acid generator contains trifluoromethanesulfonic acid, the thermal decomposition temperature can be reduced to 100°C or below.

[0100] For a conductive film to possess properties such as flexibility and stretchability, it is preferable for the metal nanowires to be fused together. Heating to approximately 250°C is necessary for the fusion of metal nanowires. [Examples]

[0101] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0102] For each conductive material solution in the examples and comparative examples, silver nanowire solution 1 was an aqueous solution containing Sigma-Aldrich silver nanowires with an average diameter of 20 nm and an average length of 10 μm at a concentration of 5 mg / mL, and silver nanowire solution 2 was an aqueous solution containing Sigma-Aldrich silver nanowires with an average diameter of 60 nm and an average length of 40 μm at a concentration of 5 mg / mL.

[0103] The average diameter and length of the silver nanowires are based on catalog values ​​from Sigma-Aldrich.

[0104] Furthermore, the following resins (degradable polymers) B1 to B3 were synthesized using the synthesis method described in Japanese Patent Publication No. 2015-149384. The structural formulas and molecular weights of resins B1 to B3 are shown below. Resins B1 to B3 were used as 20% by mass isopropyl alcohol solutions of each resin.

[0105] The Mw and Mw / Mn values ​​for each resin were confirmed using GPC (solvent: THF, standard: polystyrene). The average repeating unit number n was determined from the Mw value.

[0106] [ka] B1:Mw=5,200, Mw / Mn=2.64, n=34

[0107] [ka] B2: Mw 3,900, Mw / Mn 2.34, n=26

[0108] [ka] B3: Mw 6,400, Mw / Mn 2.53, n=20

[0109] Figure 3 shows the thermal decomposition data (DTA) of resin B1 in air. From the thermal decomposition data shown in Figure 3, it was found that the decomposition start temperature of resin B1 was 221.5°C and the decomposition end temperature was 246°C.

[0110] In each example and each comparative example, one of the resins B1 to B3, a solvent, a surfactant, and an additive were added to the silver nanowire solution 1 or 2 to prepare the conductive material solution for each example and the composition for each comparative example listed in Table 1.

[0111] The surfactants and additives listed in Table 1 are as follows:

[0112] Fluoroalkylnonionic surfactant FS-31 (manufactured by DuPont)

[0113] Acid generator 1: Triphenylsulfonium chloride Acid Generator 2: Triphenylsulfonium Methanesulfonic Acid Acid Generator 3: Triethylammonium trifluoromethanesulfonic acid Acid generator 4: 4-fluoropyridinium trifluoromethanesulfonic acid

[0114] In Comparative Example 2, the following resin was used. Polyvinylpyrrolidone: PVP Mw=3.2, Mw / Mn=2.20

[0115] [Table 1]

[0116] Each conductive material composition from the examples and comparative examples listed in Table 1 was applied to a synthetic quartz wafer, and baked on a hot plate at the temperatures listed in Table 1 to remove the resin in the composition by decomposition and evaporation, thereby obtaining the conductive film for each example. In Examples 4 and 5, before baking, the irradiation power was 10 mW / cm². 2 The device was irradiated with light from a low-pressure mercury lamp for 60 seconds.

[0117] The surface resistivity of the conductive film after baking was measured and observed using an electron microscope as shown in Figures 4-7.

[0118] Figure 4 is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Example 1 onto a quartz wafer and baking it on a hot plate at 220°C for 10 minutes. As shown in the DTA data in Figure 3, at this temperature, resin B1 remains black without decomposing.

[0119] Figure 5 is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Example 1 onto a quartz wafer and baking it on a hot plate at 250°C for 10 minutes. As shown in the DTA data in Figure 3, at this temperature, resin B1 decomposes and disappears, and white silver nanowires appear.

[0120] Figure 6 is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Comparative Example 1 onto a quartz wafer and baking it on a hot plate at 250°C for 10 minutes. In this image, the silver nanowires are broken.

[0121] Figure 7 is a 10,000x electron microscope image of the film surface obtained by coating the conductive material composition of Comparative Example 2 onto a quartz wafer and baking it on a hot plate at 250°C for 10 minutes. In this image, the base resin remains black.

[0122] Table 1 shows that a substrate coated with the thermally or acidically decomposable polymer-containing silver nanowire dispersion of the present invention forms a highly conductive film by decomposing and removing resin B1 by heating, as shown in Figure 5 of Example 1. Similarly, Examples 2 to 7 were also able to form highly conductive films. Furthermore, the conductive films of Examples 1 to 7 were uniform and exhibited high transparency.

[0123] On the other hand, in Comparative Example 1, which used a silver nanowire dispersion without thermal or acid-degradable polymers, the silver nanowires broke upon heating, resulting in low conductivity, as shown in Figure 6. Furthermore, in the case of a silver nanowire dispersion composition with conventional polyvinylpyrrolidone, which does not decompose with heat or acid, the silver nanowires did not break after heating, as shown in Figure 7 and Comparative Example 2, but polyvinylpyrrolidone remained, resulting in low conductivity.

[0124] This specification includes the following embodiments: [1] A conductive material composition characterized by comprising (A) metal nanowires, (B) a resin whose main chain decomposes upon either an acid and / or heat, and (C) a solvent. [2] The conductive material composition according to [1], characterized in that the resin (B) contains repeating units having an acetal structure represented by the following general formula (1). [ka] (In the formula, R 1 (where is a hydrogen atom, or a saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms, which may be substituted. W is a saturated or unsaturated divalent organic group having 2 to 30 carbon atoms.) [3] The conductive material composition according to [1] or [2], characterized in that the resin (B) is a compound represented by any of the following general formulas (1a) to (1c). [ka] (In the formula, R 1a This is an alkyl group having 1 to 4 carbon atoms. a R is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, and may have an ether bond. b1 Each of these is independent of -W a -OH, or a monovalent organic group having 1 to 30 carbon atoms, either saturated or unsaturated. 1c R is a hydrogen atom, or an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 4 to 20 carbon atoms, which may be substituted. c1 Each of these is independently an alkyl group having 1 to 4 carbon atoms, or -W a It is -OH. n represents the average number of repeating units, ranging from 3 to 2,000. [4] The conductive material composition according to any one of [1] to [3], further characterized by containing a photoacid generator or a thermoacid generator. [5] A conductive film formed on a substrate, characterized in that the resin (B) component of the conductive material composition described in any of [1] to [4] coated on the substrate is decomposed and / or removed by either acid and / or heat, or both. [6] A method for forming a conductive film, characterized by coating a substrate with a conductive material composition described in any of [1] to [4], and decomposing and / or removing the resin (B) component by either an acid and / or heat, or both, to form a conductive film.

[0125] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0126] 10...Coating film of conductive material composition, 11...Metal nanowire, 12...Resin, 20...Substrate, 30...Conductive film.

Claims

1. (A) Metal nanowires and (B) Resins whose main chain decomposes due to either acid and / or heat, (C) Solvent and It includes, A conductive material composition characterized in that the resin (B) is a compound represented by any of the following general formulas (1a) to (1c). 【Chemistry 2】 (In the formula, R1a is an alkyl group having 1 to 4 carbon atoms. Wa is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, which may have an ether bond. Rb1 is independently -Wa-OH or a saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms, which may be substituted. R1c is a hydrogen atom, or an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 4 to 20 carbon atoms, which may be substituted. Rc1 is independently an alkyl group having 1 to 4 carbon atoms, or -Wa-OH. n represents the average number of repeating units, which is between 3 and 2,000.)

2. Furthermore, the conductive material composition according to claim 1 is characterized in that it contains a photoacid generator or a thermoacid generator.

3. A method for forming a conductive film, characterized by coating a substrate with the conductive material composition described in claim 1 or claim 2, and then decomposing and / or removing the resin (B) component by either acid and / or heat, or both, to form a conductive film.

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