Method for producing silver chloride particles

Abstract

To provide a method for producing a silver chloride particle which hardly forms secondary particles in the formation into a paste, and consequently hardly forms a silver chloride particle with a large diameter in the paste.SOLUTION: A method for producing a silver chloride particle comprises depositing a silver chloride particle by a liquid reaction between an ammine complex of silver and chloride ions. A dispersant is added before and / or after the deposition of the silver chloride particle. The silver chloride particle produced by the production method may have a cumulative 50% particle diameter D50 of 8 μm or more and 25 μm or less in the cumulative particle size distribution from the small particle diameter side in the volume-based particle diameter distribution obtained by wet measurement by a laser diffraction / scattering method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a silver chloride-containing paste used for forming conductors such as electrodes and wiring, and to silver chloride particles that are the raw material for this silver chloride-containing paste. [Background technology]

[0002] A paste containing silver chloride particles (also referred to as "silver chloride-containing paste" in this specification) is used as a raw material for forming electrodes and wiring, for example, a bioelectrode. For example, Patent Document 1 discloses a conductive composition containing an elastomer, silver powder, and silver chloride particles, the silver powder being surface-treated, the silver powder having an average primary particle size of 1.0 μm or less, an apparent porosity of 50 to 95%, and a cumulative 95% particle size (D95 particle size) in the particle size distribution of the secondary particles of the silver powder and silver chloride particles in the conductive composition being 3.0 to 25.0 μm.

[0003] Furthermore, the silver chloride-containing paste can be used in a wide range of fields, including medicine, as a photocatalyst, based on the excellent photochemical properties of silver chloride and silver (see, for example, Patent Document 2). Patent Document 2 discloses a method for producing nanoaggregates in which the shape and structure of the nanoaggregates formed are changed by the reaction molar ratio of silver nitrate and hydrochloric acid, and discloses that when the reaction molar ratio of silver nitrate and hydrochloric acid is 1:2-1:30, silver chloride nanocubes with a size of 50-2000 nm are formed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-55918 A [Patent Document 2] Korean Patent No. 10-1209175 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of stabilizing the characteristics of a member using the silver chloride-containing paste, such as an electrode, it is preferable that the silver chloride particles contained in the paste are dispersed as uniformly as possible. Therefore, it has been considered preferable to reduce the primary particle size of the silver chloride particles contained in the silver chloride-containing paste.

[0006] The present invention aims to provide a method for producing silver chloride particles that are used, for example, to prepare a silver chloride-containing paste that is a raw material for electrodes and wiring, and that have good dispersibility when made into a silver chloride-containing paste. It is also an object of the present invention to provide silver chloride particles that have good dispersibility when made into a silver chloride-containing paste, and a silver chloride-containing paste that contains such silver chloride particles. [Means for solving the problem]

[0007] In order to solve such problems, one embodiment of the present invention provides a method for producing silver chloride particles, which comprises precipitating silver chloride particles by a liquid reaction between a silver ammine complex and chloride ions, and is characterized in that a dispersant is added before or after the precipitation of the silver chloride particles, or both.

[0008] By employing such a production method, it is possible to obtain silver chloride particles which have a relatively large primary particle size and which are less prone to aggregation.

[0009] In the above-mentioned production method, the silver ammine complex may be formed by reacting silver nitrate with ammonia.

[0010] In the above production method, the dispersant is preferably an anionic surfactant.

[0011] In the above-mentioned production method, it may be preferable that the chlorine source which provides the chloride ions contains hydrochloric acid.

[0012] In another aspect, the present invention provides silver chloride particles characterized in that a cumulative 50% particle diameter D50 in a cumulative particle size distribution (in this specification, "cumulative particle size distribution" is used in this sense unless otherwise specified) from the small particle size side in a volume-based particle size distribution (in this specification, "cumulative particle size distribution" is used in this sense unless otherwise specified) obtained by wet measurement using a laser diffraction / scattering method is 8 μm or more and 25 μm or less.

[0013] Such silver chloride particles are less likely to aggregate because they contain a small proportion of silver chloride particles having a small primary particle size and a large coagulating force, and as a result, coarse particles are less likely to be generated.

[0014] In the above silver chloride particles, it may be preferable that the cumulative 10% particle diameter D10, the cumulative 90% particle diameter D90, and the cumulative 50% particle diameter D50 in the cumulative particle size distribution satisfy the following formula (1). (D90-D10) / D50≦2.2 (1)

[0015] In some cases, it may be preferable for the above silver chloride particles to have a frequency particle size Dm of 10 μm or more in the volume-based particle size distribution.

[0016] In the above silver chloride particles, it is sometimes preferable that the cumulative 50% particle diameter D50 and the most frequent particle diameter Dm in the volume-based particle diameter distribution satisfy the following formula (2). Dm / D50≦1.7 (2)

[0017] In the volume-based particle size distribution of the above silver chloride particles, the frequency distribution value Ps of a sub-peak, which is a peak located on the smaller particle size side than the most frequent particle size Dm, satisfies the following formula (3) with the frequency distribution value Pm at the most frequent particle size Dm. Ps≦Pm×0.6 (3)

[0018] The method for producing the silver chloride particles may be for producing the silver chloride particles described above.

[0019] In another aspect, the present invention provides a silver chloride-containing paste comprising the above-mentioned silver chloride particles and a vehicle. The silver chloride-containing paste may further contain conductive particles, and the conductive particles may contain silver powder. Effect of the Invention

[0020] According to the present invention, there is provided a method for producing silver chloride particles that is less likely to produce silver chloride particles having an excessively large secondary particle size. Also, according to the present invention, there are provided silver chloride particles that exhibit good dispersibility when made into a silver chloride-containing paste, and a silver chloride-containing paste containing such silver chloride particles. [Brief description of the drawings]

[0021] [Figure 1] 1 is a graph showing the volume-based particle size distribution of silver chloride particles of Example 1 and Comparative Example 1. [Diagram 2] 1 is a graph showing the volume-based cumulative particle size distribution of silver chloride particles of Example 1 and Comparative Example 1. [Diagram 3] FIG. 2 is a diagram showing an observation image (500x) of the silver chloride particles of Example 1. [Figure 4] FIG. 2 is a diagram showing an observation image (2000x) of the silver chloride particles of Example 1. [Diagram 5] FIG. 2 is a diagram showing an observation image (10,000 times) of the silver chloride particles of Example 1. [Figure 6] FIG. 2 is a diagram showing an observed image (magnification: 500 times) of silver chloride particles in Comparative Example 1. [Figure 7] FIG. 2 is a diagram showing an observed image (2000x) of silver chloride particles in Comparative Example 1. [Figure 8] FIG. 2 is a diagram showing an observed image (10,000 times) of silver chloride particles in Comparative Example 1. [Figure 9] 2 is a graph showing the volume-based particle size distribution of the silver chloride particles of Example 22. [Figure 10] 2 is a graph showing the cumulative particle size distribution by volume for the silver chloride particles of Example 22. [Figure 11]FIG. 2 is a diagram showing an observation image (10,000 times) of silver chloride particles of Example 22. [Figure 12A] FIG. 1 is a diagram showing the measurement results of the shape of a wiring pattern (wiring pattern 1, measurement point 2) based on Example 1. [Figure 12B] FIG. 23 is a diagram showing the measurement results of the shape of a wiring pattern (wiring pattern 1, measurement point 2) based on Example 21. [Figure 12C] FIG. 13 is a diagram showing the measurement results of the shape of a wiring pattern (wiring pattern 2, measurement location 1) based on Comparative Example 1. [Figure 13A] FIG. 13 is a diagram showing the measurement results of the shape of the wiring pattern (wiring pattern 2, measurement point 4) based on Example 1. [Figure 13B] FIG. 23 is a diagram showing the measurement results of the shape of the wiring pattern (wiring pattern 1, measurement point 4) based on Example 21. [Figure 13C] FIG. 13 is a diagram showing the measurement results of the shape of a wiring pattern (wiring pattern 1, measurement point 5) based on Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described. In the silver chloride particles according to one embodiment of the present invention, the cumulative 50% particle diameter D50 in the cumulative particle size distribution from the small particle diameter side in the volume-based particle diameter distribution obtained by wet measurement using a laser diffraction / scattering method is 8 μm or more and 25 μm or less. By having the cumulative 50% particle diameter D50 of 8 μm or more and 25 μm or less, the proportion of silver chloride particles having a small primary particle diameter and a large cohesive force is reduced, and as a result, coarse secondary particles are less likely to be generated. From the viewpoint of more stably reducing the proportion of silver chloride particles having a small primary particle diameter, it may be more preferable that the cumulative 50% particle diameter D50 is 20 μm or less.

[0023] In the silver chloride particles according to this embodiment, it may be preferable that the cumulative 10% particle diameter D10, the cumulative 90% particle diameter D90, and the cumulative 50% particle diameter D50 in the cumulative particle size distribution satisfy the following formula (1). (D90-D10) / D50≦2.2 (1)

[0024] The left side of the above formula (1) indicates the degree of steepness of the rise of the cumulative particle size distribution, and the smaller the value of the left side, the steeper the rise and the narrower the distribution width of the particle size distribution. Since it is preferable that the distribution of silver chloride particles is as narrow as possible from the viewpoint of the quality stability of the silver chloride-containing paste (prevention of coarse secondary particles), it may be more preferable that the left side of the above formula (1) is 2.0 or less, and particularly preferably 1.5 or less.

[0025] The silver chloride particles according to this embodiment may preferably have a modal particle diameter Dm of 10 μm or more. When the modal particle diameter Dm is 10 μm or more, the amount of silver chloride having a small primary particle diameter is relatively small, and the quality stability of the silver chloride-containing paste is excellent. The upper limit of the modal particle diameter Dm is not particularly limited, but may preferably be 35 μm or less, and more preferably be 30 μm or less.

[0026] The cumulative 50% particle diameter D50 and the most frequent particle diameter Dm of the volume-based particle diameter distribution may satisfy the following formula (1). 1.0 <Dm / D50≦1.7 (1)

[0027] The cumulative 50% particle diameter D50 is the particle diameter at which the cumulative value from the small diameter side of the particle volume is equal to the cumulative value from the large diameter side in the volume-based particle diameter distribution. On the other hand, the most frequent particle diameter Dm is the particle diameter at which the maximum peak of the volume-based particle diameter distribution is located.

[0028] By making the particle size ratio (Dm / D50) 1.7 or less, the sub-peak located on the smaller diameter side of the maximum peak is less likely to become apparent, and the proportion of silver particles with small primary particle sizes is small. Therefore, large secondary particles are less likely to be generated in a silver chloride-containing paste containing such silver chloride particles. From this viewpoint, Dm / D50 may be preferably 1.6 or less, more preferably 1.5 or less, even more preferably 1.4 or less, and particularly preferably 1.3 or less.

[0029] The lower limit of Dm / D50 is not particularly limited. Dm / D50 being less than 1.0 means that the most frequent particle diameter Dm is located on the smaller diameter side than the cumulative 50% particle diameter D50. Therefore, from the viewpoint of more stably reducing the proportion of silver chloride particles having a small primary particle diameter, Dm / D50 may be preferably 0.5 or more, more preferably 0.6 or more, even more preferably 0.7 or more, and particularly preferably 0.8 or more.

[0030] In the silver chloride particles according to this embodiment, in the volume-based particle size distribution, it may be preferable that the frequency distribution value Ps of a sub-peak, which is a peak located on the smaller particle size side than the most frequent particle diameter Dm, and the frequency distribution value Pm at the most frequent particle diameter Dm satisfy the following formula (3). Ps≦Pm×0.6 (3)

[0031] As shown in the examples below, silver chloride particles with a primary particle size of about 10 μm or more are unlikely to form coarse secondary particles when made into a silver chloride-containing paste, but silver chloride particles with a primary particle size of 6 μm or less are likely to form coarse secondary particles. Therefore, silver chloride particles having a particle size distribution in which the most frequent particle size Dm is 10 μm or more are preferable as raw materials for silver chloride-containing pastes, but depending on the manufacturing method of silver chloride particles, silver chloride particles having a most frequent particle size Dm of 10 μm or more but a double-peak particle size distribution with a sub-peak on the smaller diameter side than the most frequent particle size Dm may be obtained, rather than a single-peak particle size distribution in which only the most frequent particle size Dm is a peak. Even in such a case, it is preferable that the frequency distribution value Ps of the sub-peak is sufficiently lower than the frequency distribution value Pm of the peak (main peak) that gives the most frequent particle size Dm, and specifically, as shown in the above formula (3), it is preferable that Ps / Pm is 0.6 or less.

[0032] A simple measure for controlling the proportion of silver chloride particles having a primary particle size of 6 μm or less is the ratio (P10 / P3) of the frequency distribution value P3 having a particle size of about 3 μm to the frequency distribution value P10 having a particle size of about 10 μm in the volumetric particle size distribution. From the viewpoint of reducing the proportion of silver chloride particles having a primary particle size of 6 μm or less, this ratio (P10 / P3) is preferably 3 or more, more preferably 5 or more, even more preferably 6 or more, and particularly preferably 7 or more.

[0033] Since the silver chloride particles according to this embodiment have a relatively large primary particle size, when the powder state is observed under a scanning electron microscope at a magnification of 10,000 times with a field of view of 9 μm × 13 μm, the number of silver chloride particles that can be observed in their entirety without overlapping tends to be less than 10.

[0034] Next, a method for producing silver chloride particles according to one embodiment of the present invention will be described. The silver chloride particles produced by the method according to this embodiment may have the characteristics of the silver chloride particles according to the present embodiment described above, and are unlikely to produce coarse secondary particles, so that the silver chloride-containing paste containing such silver chloride particles has excellent quality.

[0035] The manufacturing method according to the present embodiment includes precipitating silver chloride particles by a liquid reaction between a silver ammine complex and chloride ions. The solvent of the reaction liquid is generally water, but is not limited thereto. The silver ammine complex may be prepared by any method. As a non-limiting example, the silver ammine complex may be produced by a reaction between silver nitrate and ammonia.

[0036] The substance that supplies chloride ions to the reaction solution, i.e., the chlorine source, is not limited. Examples of the chlorine source include hydrochloric acid and chlorides, such as sodium chloride and potassium chloride. When the chlorine source is hydrochloric acid, it does not contain alkali metal ions such as sodium and potassium, so it is suitable for use in electronic materials.

[0037] The reaction in liquid between the silver ammine complex and chloride ions may occur by supplying chloride ions (chlorine source) to a liquid containing a silver ammine complex, or the silver ammine complex may be supplied to a liquid containing chloride ions. The supply form is not limited. For example, when the chlorine source is hydrochloric acid, a liquid containing hydrochloric acid may be supplied to the liquid containing the silver ammine complex. For example, when sodium chloride is the chlorine source, sodium chloride may be supplied as a solid or as a sodium chloride solution to the liquid containing the silver ammine complex.

[0038] The quantitative relationship between the silver ammine complex and the chloride ions is not limited. It is preferable to supply chloride ions in a molar amount equal to or greater than the molar amount of silver so that the total amount of silver becomes silver chloride. When the silver ammine complex is generated from a silver salt such as silver nitrate and ammonia, it is preferable to supply ammonia in a molar amount twice or more the molar amount of silver so that the total amount of silver becomes an ammine complex.

[0039] In the manufacturing method according to the present embodiment, a dispersant is added before or after precipitation of silver chloride particles, or both. Adding a dispersant makes it difficult for primary particles to aggregate. Here, "before precipitation of silver chloride particles" refers to a stage before the in-liquid reaction between a silver ammine complex and chloride ions is initiated, and the dispersant may be present in the liquid containing the silver ammine complex before chloride ions are supplied, or the dispersant may be present in the liquid containing chloride ions before the silver ammine complex is supplied.

[0040] A surfactant may be used as the dispersant, and the dispersant is preferably an anionic surfactant. Specific examples of anionic surfactants include fatty acid surfactants based on higher fatty acids having 6 or more carbon atoms; linear alkylbenzene surfactants such as linear alkylbenzene sulfonates; higher alcohol surfactants such as alkyl sulfates and alkyl ether sulfates based on higher alcohols having 12 or more carbon atoms; paraffin surfactants such as sodium alkylsulfonate; and polycarboxylic acid surfactants based on polyacrylic acid, acrylic acid-phthalic acid copolymers, and acrylic acid-sulfonic acid monomer copolymers. Of these, for polycarboxylic acid surfactants, it may be preferable to use a weight average molecular weight in the range of 5,000 to 500,000, and it may be more preferable to use a weight average molecular weight in the range of 10,000 to 200,000.

[0041] The amount of the dispersant to be supplied is not particularly limited, and may be in the range of 0.1 to 10%, preferably 0.5 to 5%, based on the mass of the silver chloride particles to be produced.

[0042] From the viewpoint of properly performing the function of the dispersant (preventing the generation of coarse particles), it is preferable to supply the dispersant before and after the precipitation of silver chloride. In this case, the supply balance is arbitrary, and one specific example is to supply an equal amount before and after the precipitation.

[0043] By employing the production method according to this embodiment, it may be possible to easily obtain the silver chloride particles according to this embodiment.

[0044] The silver chloride thus obtained is filtered and washed, and the filtered product is dried to obtain the desired silver chloride particles. The silver chloride particles obtained by drying the filtered product may be pulverized to improve handling. Even if this pulverization is performed, the silver chloride particles formed have a large particle size at the primary particle level, so the quality stability of the silver chloride-containing paste is not affected.

[0045] Next, a silver chloride-containing paste according to one embodiment of the present invention will be described. The silver chloride-containing paste according to this embodiment contains the silver chloride particles according to the above-described embodiment or the silver chloride particles produced by the method for producing silver chloride particles according to the above-described embodiment, and further contains a vehicle.

[0046] The type of vehicle contained in the silver chloride-containing paste according to this embodiment is not particularly limited, and various solvents known in the field of paste compositions can be suitably used.

[0047] Specifically, for example, glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; acetate esters of these glycol ethers (a specific example of which is 2-(2-butoxyethoxy)ethyl acetate); esters such as dibasic acid esters (DBE), 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate; ketones such as cyclohexanone and isophorone; monoterpene alcohols such as terpineol and hydrogenated terpineol; acetate esters of these monoterpene alcohols; γ-butyrolactone; limonene; and the like. Only one of these substances may be used, or two or more of them may be used in appropriate combination.

[0048] When the silver chloride-containing paste according to this embodiment is used for creating a pattern by screen printing, the vehicle preferably contains a substance whose boiling point is 200° C. or higher. It is preferable that the vehicle is a high-boiling point solvent. Although there is no particular limitation on such high-boiling point solvent, specific examples include diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and terpineol. Only one of these substances may be used, or two or more of them may be used in appropriate combination.

[0049] The silver chloride-containing paste according to the present embodiment may further contain conductive particles. Examples of conductive particles include metal particles such as silver powder, copper powder, and silver-coated copper powder, and carbon particles such as acetylene black, graphite powder, and Ketchan black. When used as a bioelectrode, the conductive particles are preferably silver powder or silver-coated copper powder.

[0050] The size of the conductive particles is not particularly limited, but from the viewpoint of the shape stability of the pattern (e.g., printed pattern) created from the paste, it may be preferable that the cumulative 50% particle diameter D50 is 15 μm or less. The shape of the conductive particles is not limited, and the conductive particles may be any of spherical, scaly, and irregular shapes, or the conductive particles may be a mixture of these.

[0051] The silver chloride-containing paste according to this embodiment may further contain a binder resin. The binder resin may be required to have heat resistance, that is, to be a heat-resistant resin. Specific examples of heat-resistant resins include cellulose-based resins, fluororesins, polyimide resins, polyamideimide resins, polyesterimide resins, polyester resins, polyethersulfone resins, polyetherketone resins, polyetheretherketone resins, polybenzimidazole resins, polybenzoxazole resins, polyphenylene sulfide resins, bismaleimide resins, epoxy resins, phenolic resins, and phenoxy resins. Only one of these heat-resistant resins may be used, or two or more of them may be used in appropriate combination.

[0052] The silver chloride-containing paste according to this embodiment may further contain a curable component. An example of such a curable component is an epoxy resin. Specific examples of epoxy resins include bisphenol-type epoxy resins (A-type, F-type, AD-type, etc.), phenol and cresol-type epoxy resins (novolac-type, etc.), polyol glycidyl ether-type epoxy resins, polyacid glycidyl ester-type epoxy resins, polyamine glycidyl amine-type epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Only one of these epoxy resins may be used, or two or more of them may be used in appropriate combination.

[0053] When the silver chloride-containing paste according to the present embodiment contains a curing component, it is preferable that a curing agent is further contained.Specific examples of the curing agent when the silver chloride-containing paste according to the present embodiment contains an epoxy resin as a curing component include acid anhydrides such as phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and succinic anhydride; imidazoles such as imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecyl imidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-aminoethyl-2-methylimidazole, 1-methylimidazole, and 2-ethylimidazole; dimethyloctylamine, dimethyldecylamine, dimethyl Tertiary amines such as laurylamine, dimethylmyristylamine, dimethylpalmitylamine, dimethylstearylamine, dimethylbehenylamine, dilaurylmonoethylamine, methyldideethylamine, methyldioleylamine, triallylamine, triisopropanolamine, triethylamine, 3-(dibutylamino)propylamine, tri-n-octylamine, 2,4,6-trisdimethylaminomethylphenol, triethanolamine, methyldiethanolamine, and diazabicycloundecene; Lewis acids containing boron fluoride such as boron trifluoride ethyl ether, boron trifluoride phenol, boron trifluoride piperidine, boron trifluoride acetate, boron trifluoride monoethylamine, boron trifluoride triethanolamine, and boron trifluoride monoethanolamine, or compounds thereof. These compounds may be used alone or in combination of two or more.

[0054] The silver chloride-containing paste according to this embodiment may further contain various additives known in the field of paste compositions.Specific examples of such additives include antioxidants, ultraviolet absorbers, colorants, defoamers, viscosity adjusters, etc.The amount of these additives added is appropriately set within the range in which the silver chloride-containing paste according to this embodiment can perform its original function.

[0055] The above-described embodiments are described for the purpose of facilitating understanding of the present invention, and are not described for the purpose of limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0056] For example, the silver particles according to the present embodiment may be produced without employing the production method according to the present embodiment. As a specific example of such a production method, silver chloride particles that satisfy the above conditions may be obtained by using a particle size selection means such as classification for silver chloride particles produced by a very common production method for silver chloride particles (for example, neutralization of silver nitrate with hydrochloric acid). When using a particle size selection means, it may be preferable to select silver chloride particles with a particle size of about 6 μm or more as a rough guideline. EXAMPLES

[0057] The effects of the present invention will be described below based on examples, but the present invention is not limited to these.

[0058] Example 1 20.0 g of silver nitrate crystals were dissolved in 23 g of pure water, and 18.0 g of 25% ammonia water was added to obtain a solution containing a silver ammine complex (silver-containing solution). 1.27 g of a dispersant made of polyacrylic acid (weight average molecular weight 25,000) was added to the silver-containing solution, and then 41.5 g of 12% hydrochloric acid was added to perform a neutralization reaction and a precipitation reaction of silver chloride to obtain a silver chloride-containing liquid. 1.27 g of polyacrylic acid (weight average molecular weight 25,000) was added to the silver chloride-containing liquid, and then the liquid was filtered, the filtered product was washed with 400 g of pure water, and then 40 g of ethanol was added to replace the pure water contained in the filtered product. The filtered product was dried at a drying temperature of 60°C for 14 hours to obtain silver chloride particles.

[0059] The resulting silver chloride particles were measured in a wet state using a laser diffraction / scattering method (equipment used: Shimadzu Corporation's "SALD-7100") to obtain a volumetric particle size distribution. In addition, the dried silver chloride particles were observed using a scanning electron microscope (JEOL Ltd.'s "JCM-5700").

[0060] A silver chloride-containing paste was prepared by mixing 2.0 g of the above silver chloride particles, 2.0 g of spherical silver powder ("KT058" manufactured by Toyo Kagaku Co., Ltd., cumulative 50% particle diameter D50: 2.1 μm), and 1.5 g of a mixture of 95% 2-(2-butoxyethoxy)ethyl acetate and 5% ethyl cellulose (100 cps) as a vehicle. A pattern with a width of 1 mm was created by printing using the obtained silver chloride-containing paste. The shape of the created pattern was measured using a surface roughness shape measuring device ("SURFCOM TOUCH 50" manufactured by Tokyo Seimitsu Co., Ltd.).

[0061] The details of the pattern shape measurement were as follows. Four grooves measuring 4 cm in length and 1 mm in width were printed on a glass substrate using tape or seal, and a paste containing silver chloride was applied to each groove, which was then flattened with a spatula to create four wiring patterns. The substrate was then heated in a 150°C dryer for more than an hour.

[0062] Of the four wiring patterns obtained, two were randomly selected that had no fading (wiring pattern 1, wiring pattern 2). Each wiring pattern was visually inspected and the three locations with the greatest irregularities were selected, designated as measurement points 1 to 3. Two locations on the same pattern that were visually flat were also selected, designated as measurement points 4 and 5. Surface roughness was measured in the short direction (cross-sectional direction) of the wiring pattern for these five measurement points, and the arithmetic mean height Pa and maximum cross-sectional height Pt were calculated from the obtained cross-sectional curve.

[0063] Comparative Example 1 Silver chloride particles were obtained in the same manner as in Example 1, except that the silver-containing solution was prepared without adding aqueous ammonia. The obtained silver chloride particles were subjected to the same measurements and observations as in Example 1. In addition, a silver chloride-containing paste was prepared in the same manner as in Example 1, and a wiring pattern with a width of 1 mm was created by printing using this paste, and the shape of the wiring pattern was measured in the same manner as in Example 1.

[0064] (Examples 2 to 22) From the viewpoint of confirming the reproducibility of the production method, silver chloride particles were produced by the same production method as in Example 1, and measurements and observations were carried out in the same manner as in Example 1. In Examples 10 to 22, silver chloride particles were produced on a scale 1000 times or more larger than that of Example 1. Among these, a silver chloride-containing paste was prepared using the silver chloride particles of Example 21 in the same manner as in Example 1, and the shape of the wiring pattern was measured.

[0065] (particle size distribution) The volume-based particle size distribution and cumulative particle size distribution of the silver chloride particles of Example 1 are shown in Table 1. In Table 1, silver chloride particles with a particle size in the range of more than 0 μm and less than 0.064 μm were not measured, so they are omitted. The same applies to particles with a particle size in the range of more than 57.648 μm and less than 300 μm.

[0066] [Table 1]

[0067] The volume-based particle size distribution and cumulative particle size distribution of the silver chloride particles of Comparative Example 1 are shown in Table 2. In Table 2, "Omitted" is used in the same sense as in Table 1.

[0068] [Table 2]

[0069] The distributions in Tables 1 and 2 are graphed in Figures 1 and 2.

[0070] 1, the volume-based particle size distribution of the silver chloride particles of Example 1 differed fundamentally from the volume-based particle size distribution of the silver chloride particles of Comparative Example 1. The silver chloride particles of Example 1 had a single-peak distribution with a peak at approximately 10 μm.

[0071] Regarding the particle size distribution of the silver chloride particles in Example 1, the ratio (P10 / P3) of the frequency distribution value P3 at a particle size of about 3 μm to the frequency distribution value P10 at a particle size of about 10 μm was calculated as follows. Since the frequency distribution value at a particle size of 10 μm was not measured in Table 1, the average value of the frequency distribution value at a particle size of 9 μm (P9) and the frequency distribution value at a particle size of 11 μm (P11) was taken as P10. The P10 / P3 calculated in this way was 6.4 (=(7.984+9.562) / 5.605), which is more than 6.

[0072] On the other hand, the silver chloride particles of Comparative Example 1 had a double-peak distribution with a main peak at just over 10 μm and a sub-peak on the smaller diameter side than the main peak. From Table 2, the particle size at which the main peak was located (the most frequent particle size Dm) was 13.614 μm, and the frequency distribution value Pm at this time was 10.179%. The particle size at which the sub-peak was located was 3.215 μm, and the frequency distribution value Ps at this time was 5.065%. Therefore, Ps / Pm was 0.50, which did not satisfy the above formula (3). When P10 / P3 was calculated in the same manner as in Example 1, it was 2.2, which was less than 3.

[0073] Reflecting such a difference in the basic tendency of particle size distribution, the cumulative particle size distribution of the silver chloride particles of Comparative Example 1 had a more gradual rise than that of the silver chloride particles of Example 1.

[0074] In order to further quantitatively evaluate the tendency of the particle size distribution, the cumulative 10% particle diameter D10, cumulative 90% particle diameter D90, cumulative 50% particle diameter D50 and most frequent particle diameter Dm were determined for the silver chloride particles of Examples 1 to 22 and Comparative Example 1, and (D90-D10) / D50 and Dm / D50 were calculated from these values. The results are shown in Table 3.

[0075] [Table 3]

[0076] As shown in Table 3, the silver chloride particles of Examples 1 to 22 satisfied both the above formula (1) and the above formula (2), but the silver chloride particles of Comparative Example 1 did not satisfy either the above formula (1) or the above formula (2).

[0077] 3 to 5 are images (500x, 2000x, 10000x) of the silver chloride particles of Example 1. FIG. 6 to FIG. 8 are images (500x, 2000x, 10000x) of the silver chloride particles of Comparative Example 1. By comparing these images, it was confirmed that the silver chloride particles of Example 1 have a larger primary particle size than the silver chloride particles of Comparative Example 1. In particular, from FIG. 6 and FIG. 7, it was confirmed that the silver chloride particles of Comparative Example 1 have secondary particles having a size of 50 μm or more, which are formed by agglomeration of primary particles. Such coarse secondary particles remain even when the silver chloride particles are made into a paste, and reduce the quality stability of the silver chloride-containing paste.

[0078] The silver chloride particles of Example 22 are a scaled-up product of Example 1. FIG. 9 is a graph showing the volume-based particle size distribution of the silver chloride particles of Example 22, FIG. 10 is a graph showing the volume-based cumulative particle size distribution of the silver chloride particles of Example 22, and FIG. 11 is a diagram showing an observation image (10,000 times) of the silver chloride particles of Example 22. As shown in FIG. 11, the silver chloride particles of Example 22 have a primary particle size equal to or greater than that of the silver chloride particles of Example 1, and as shown in FIG. 9 and FIG. 10, they have a sharper (narrower) distribution than those of Example 1. This point can also be confirmed by comparing (D90-D10) / D50 in Table 3. That is, (D90-D10) / D50 in Example 1 was 1.96, which was almost 2, but in Example 22 it was 1.2, and the uniformity of the particle size of the silver chloride particles was improved.

[0079] The measurement results of the shape of the wiring pattern are shown in Tables 4 and 5. Table 4 shows the arithmetic mean height Pa (JIS B0601:2001) of the cross-sectional curve, and Table 5 shows the maximum cross-sectional height Pt (JIS B0601:2001) of the cross-sectional curve. The units of the numbers showing the measurement results in the tables are all μm. For both the arithmetic mean height Pa and the maximum cross-sectional height Pt, all the average values ​​were Comparative Example 1>Example 1>Example 21. This tendency was also observed for the average values ​​of measurement points 1 to 3 with large irregularities and the average values ​​of measurement points 4 and 5 with small irregularities and flatness.

[0080] [Table 4]

[0081] [Table 5]

[0082] Specific examples of the measurement results of the wiring pattern are shown in Figures 12A to 13C. Figures 12A to 12C show the measurement results of a measurement point with large unevenness, and Figures 13A to 13C show the measurement results of a flat measurement point with small unevenness. As shown in Tables 4 and 5 and Figures 12A to 13C, the wiring pattern formed from the silver chloride-containing paste using the silver chloride particles of Comparative Example 1 had higher average values ​​of cross-sectional curve parameters (arithmetic mean height Pa) and (maximum cross-sectional height Pt) than the wiring patterns formed from the silver chloride-containing paste using the silver chloride particles of Example 1 and the silver chloride particles of Example 21 (about 1.5 to 2 times). The reason why the numerical value of the shape parameter of the wiring pattern of Comparative Example 1 was larger is thought to be because the silver chloride-containing paste prepared using the silver chloride particles of Comparative Example 1 contained a relatively large number of coarse particles.

[0083] (Examples 23 to 24, Comparative Example 2) Silver chloride particles were produced by the same production method as in Example 1, except that the conditions for adding the dispersant were changed as follows. Example 23: No dispersant added to silver-containing solution Example 24: No dispersant added to silver chloride-containing liquid Comparative Example 2: No dispersant added to the silver-containing solution, and no dispersant added to the silver chloride-containing liquid

[0084] The appearance of the obtained silver chloride particles was visually confirmed. In Examples 23 and 24, the amount of coarse secondary particles increased compared to the silver chloride particles of Example 1, but the particles were equivalent to those of Example 1 by pulverization. In contrast, in Comparative Example 2, the obtained silver chloride was substantially agglomerated rather than particulate, and even after pulverization, the particles contained coarser particles than those of Examples 23 and 24.

[0085] (Example 25 to Example 27) Silver chloride particles were produced by the same production method as in Example 1, except that the type of dispersant was changed as follows. Example 25: Polyoxyethylene sorbitan monolaurate (Tokyo Chemical Industry Co., Ltd. "Twin 20") Example 26: Benzethonium chloride Example 27: Stearic Acid

[0086] The appearance of the obtained silver chloride particles was confirmed by visual observation. In Examples 25 and 26, the amount of coarse secondary particles increased compared to the silver chloride particles of Example 1, but the particles were pulverized to the same size as those of Example 1. The silver chloride particles of Example 27 were in a powder form, and the cumulative 50% particle diameter D50 was 5.8 μm.

Claims

1. 1. A method for producing silver chloride particles, comprising: precipitating silver chloride particles by a liquid reaction between a silver ammine complex and chloride ions, reacting silver nitrate with ammonia to form an ammine complex of said silver to obtain a silver-containing solution; adding an anionic surfactant as a dispersant to the silver-containing solution, and then precipitating the silver chloride particles; (excluding the case where the pH of the silver-containing solution before adding the chloride ions is 7.5 or less).

2. 2. The method for producing silver chloride grains according to claim 1, wherein the chlorine source that provides the chloride ions comprises hydrochloric acid.

3. 2. The method for producing silver chloride particles for forming a conductor according to claim 1, wherein the cumulative 50% particle diameter D50 in the cumulative particle size distribution from the small particle diameter side in the volume-based particle size distribution obtained by wet measurement using a laser diffraction / scattering method is 8 μm or more and 25 μm or less.

4. 4. The method for producing silver chloride particles for forming an electric conductor according to claim 1, wherein a cumulative 10% particle diameter D10, a cumulative 90% particle diameter D90, and a cumulative 50% particle diameter D50 in the cumulative particle size distribution satisfy the following formula (1): (D90-D10) / D50≦2.2 (1)

5. 4. The method for producing silver chloride particles for forming an electric conductor according to claim 1, wherein the most frequent particle diameter Dm of the volume-based particle diameter distribution is 10 μm or more.

6. 4. The method for producing silver chloride particles for forming an electric conductor according to claim 1, wherein the cumulative 50% particle diameter D50 and the most frequent particle diameter Dm of the volume-based particle diameter distribution satisfy the following formula (2): Dm / D50≦1.7 (2)

7. 4. The method for producing silver chloride particles for forming a conductor according to claim 1, wherein in the volume-based particle size distribution, a frequency distribution value Ps of a sub-peak, which is a peak located on the smaller particle size side than the most frequent particle diameter Dm, and a frequency distribution value Pm at the most frequent particle diameter Dm satisfy the following formula (3): Ps≦Pm×0.6 (3)

Images