Silver powder and resin-cured conductive paste

Abstract

The purpose of this invention is to provide a silver powder that imparts excellent volume resistivity and fine-line printability to conductive pastes. This invention provides a silver powder with a cumulative 50% diameter D50 based on laser diffraction volume reference of 0.1 μm or more and 1.0 μm or less, wherein the ratio of D50 to the BET diameter DBET is 1.3 or less, and the shrinkage rate at 200°C in thermomechanical analysis is 1% or more.

Description

Technical Field

[0001] The present invention relates to a silver powder, a method for manufacturing the silver powder, a silver powder manufacturing apparatus, and a resin-curable conductive paste. Prior Art

[0002] Previously, in order to form electrodes or wirings of electronic components by a printing method or the like, a conductive paste prepared by blending a solvent, a resin, a dispersant, etc. in metal powders such as silver powder was used.

[0003] In recent years, heterojunction (HJT) type solar cells have attracted attention. In HJT type solar cells and the like, generally, a resin-curable conductive paste containing silver powder is calcined and cured at a relatively low temperature of about 200°C in an atmospheric environment to form an electrode or a conductor pattern.

[0004] For example, in Patent Document 1, silver fine particles having an average particle diameter (D SEM) of 30 nm to 100 nm and a tapped density of 3.0 g / cm 3 or more obtained by a prescribed manufacturing method are proposed, and it is described that the silver fine particles are used in a resin-curable conductive paste or the like. [Prior Art Documents] [Patent Documents]

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-159805 Summary of the Invention

[0006] [Problems to be Solved by the Invention]

[0007] Here, if the calcination temperature when forming an electrode or a conductor pattern or the like is lowered to, for example, 150°C to 200°C, there may be a problem of an increase in volume resistivity. Therefore, it is desirable that the conductive paste containing silver powder can suppress an increase in volume resistivity even when the calcination temperature is lowered.

[0008] In addition, in recent years, electrodes or conductor patterns or the like are being miniaturized. Therefore, when forming an electrode or a conductor pattern or the like using a conductive paste containing silver powder, it is desirable that the conductive paste is less likely to break even when printed with a finer line width than before and is also less likely to break after calcination, that is, it has excellent fine line printability.

[0009] Therefore, an object of the present invention is to provide a silver powder and a method for manufacturing the same, which can impart excellent volume resistivity and fine line printability even when calcined at a low temperature when made into a conductive paste. In addition, an object of the present invention is to provide a silver powder manufacturing apparatus capable of manufacturing the silver powder. In addition, an object of the present invention is to provide a resin-cured conductive paste that has excellent volume resistivity and fine line printability even when calcined at a low temperature. [Means for Solving the Problems]

[0010] The inventors of the present invention have repeatedly conducted intensive studies to solve the above problems, and as a result, the inventors of the present invention have completed the present invention described below.

[0011] That is, the main structure of the present invention for solving the above problems is as follows.

[0012] [1] A silver powder, wherein the cumulative 50% diameter D50 based on the volume standard by laser diffraction method is 0.1 μm or more and 1.0 μm or less, the ratio of the D50 to the Brunauer-Emmett-Teller (BET) diameter DBET is 1.3 or less, and the shrinkage rate at 200 °C in thermomechanical analysis is 1% or more.

[0013] [2] The silver powder according to [1], wherein the shrinkage rate at 150 °C in thermomechanical analysis is 0.6% or more.

[0014] [3] The silver powder according to [1] or [2], wherein the BET specific surface area is 0.90 m2 / g or more and 2.50 m2 / g or less.

[0015] [4] The silver powder according to any one of [1] to [3], which is used for a resin-cured conductive paste.

[0016] [5] A method for manufacturing silver powder, wherein a silver-containing solution is made to flow in a flow path, a pH adjuster is added to the flow path at a pH adjuster addition position in the middle of the flow path, a complexing agent is added to the flow path at a complexing agent addition position downstream of the pH adjuster addition position, a hydrazine-based reducing agent is added to the flow path at a reducing agent addition position downstream of the complexing agent addition position, and silver powder is reduced and precipitated in the flow path.

[0017] [6] The method for producing silver powder according to [5], wherein the time required for the silver-containing solution to flow from the complexing agent addition position to the reducing agent addition position is 0.1 second or more and 10 seconds or less.

[0018] [7] The method for producing silver powder according to [5] or [6], wherein a surface treatment agent is added to the flow path between the complexing agent addition position and the reducing agent addition position, or on the downstream side of the reducing agent addition position.

[0019] [8] A silver powder production apparatus that adds a pH adjuster, a complexing agent, and a hydrazine-based reducing agent as a reducing agent to a silver-containing solution to cause silver powder to precipitate by reduction. The silver powder production apparatus has a pipe that forms a flow path of the silver-containing solution, a pH adjuster addition part and a complexing agent addition part connected to the pipe, and a reducing agent addition part connected to the pipe on the downstream side of the nitric acid addition part and the complexing agent addition part.

[0020] [9] A resin-curing type conductive paste containing the silver powder according to any one of [1] to [3]. [Advantages of the Invention]

[0021] According to the present invention, there can be provided silver powder that can impart excellent volume resistivity and fine line printability even when calcined at a low temperature when made into a conductive paste, a method for producing the silver powder, a silver powder production apparatus capable of producing such silver powder, and a resin-curing type conductive paste having excellent volume resistivity and fine line printability even when calcined at a low temperature. Brief Explanation of the Drawings

[0022] FIG. 1 is an external perspective view of an example of a silver powder production apparatus. FIG. 2A is a cross-sectional view perpendicular to the flow path of the silver complex solution at the center position of the reducing agent supply pipe of the reducing agent addition member of the silver powder production apparatus of the present invention. FIG. 2B is a cross-sectional view taken along line A-A of FIG. 2A in the horizontal direction of the flow path of the silver complex solution. FIG. 2C is a cross-sectional view taken along line B-B of FIG. 2A in the horizontal direction of the flow path of the silver complex solution. FIG. 3 is a graph showing the results of thermomechanical analysis of the silver powder obtained in Examples 1 to 8 and Comparative Examples 1 and 2. FIG. 4 is a graph magnifying a part of the graph of FIG. 3. Figure 5 is a SEM photograph (20,000 times magnification) of the silver powder of Example 1. Figure 6 is a SEM photograph (20,000 times magnification) of the silver powder of Example 2. Figure 7 is a SEM photograph (20,000 times magnification) of the silver powder of Example 3. Figure 8 is a SEM photograph (20,000 times magnification) of the silver powder of Example 4. Figure 9 is a SEM photograph (20,000 times magnification) of the silver powder of Example 5. Figure 10 is a SEM photograph (20,000 times magnification) of the silver powder of Example 6. Figure 11 is a SEM photograph (20,000 times magnification) of the silver powder of Example 7. Figure 12 is a SEM photograph (20,000 times magnification) of the silver powder of Example 8. Figure 13 is a SEM photograph (20,000 times magnification) of the silver powder of Comparative Example 1. Figure 14 is a SEM photograph (20,000 times magnification) of the silver powder of Comparative Example 2. Embodiment

[0023] (Terms and Measurement Methods) First, before describing the embodiments, the terms and measurement methods in this specification will be described.

[0024] <Shrinkage Rate of Silver Powder> The measurement of the shrinkage rate of the silver powder is carried out as follows. First, 0.3 g of silver powder was weighed. Then, the silver powder was put into a specified mold with a diameter of 5 mmϕ, and using a press machine, it was compacted for 1 minute with a load of 50 kg to produce a cylindrical measurement specimen. This measurement specimen was placed in the specimen holder of a Thermomechanical Analysis (TMA) device (Thermo plus EVO 2 series TMA8311), and a load of 98 mN was applied by a measurement probe. The temperature was raised from room temperature (25°C ± 5°C) to 900°C at a heating rate of 10°C per minute, and the thermomechanical analysis (TMA) of the measurement specimen was carried out. The "shrinkage rate at 200°C in the thermomechanical analysis" and the "shrinkage rate at 150°C in the thermomechanical analysis" were calculated respectively by the following formulas (1) and (2). Shrinkage rate at 200°C in the thermomechanical analysis (%) = (L RT - L 200) / L RT × 100…(1) Shrinkage rate (%) at 150 °C in thermomechanical analysis = (L RT - L 150) / L RT×100…(2) Here, L RT is the length (mm) in the axial direction of the cylindrical measurement specimen at room temperature (25 °C ± 5 °C). L 200 is the length (mm) in the axial direction of the cylindrical measurement specimen at a temperature of 200 °C. L 150 is the length (mm) in the axial direction of the cylindrical measurement specimen at a temperature of 150 °C.

[0025] <BET specific surface area> In this specification, the "BET specific surface area" is measured using Macsorb HM-model 1210 (manufactured by MOUNTECH Co., Ltd.) by the BET one-point method based on nitrogen adsorption. Furthermore, for the measurement of the BET specific surface area, the sample weight is set to 3.0 g, a N 2 / He (30 / 70) mixed gas is used, the gas flow rate is set to 25 mL / min, and the degassing conditions before measurement are set to 60 °C for 10 minutes.

[0026] <True density measurement> Silver powder is filled in a 10 cc platinum crucible, and the mass of the filled silver powder is precisely measured. Then, using a dry automatic density meter (manufactured by Micromeritics, device name: AccuPyc II 1340), the volume of the silver powder after mass measurement is measured by the constant volume expansion method (the "pycnometer method" in the Japanese Pharmacopoeia), and the density is calculated. Furthermore, in the measurement of the true density, the measurement is performed in such a way that the density includes the closed voids inside the silver particles that are not connected to the outside.

[0027] <BET diameter D BET> The BET diameter D BET (hereinafter sometimes simply referred to as "D BET") (unit: μm) is the particle diameter obtained by converting the BET specific surface area (unit: m 2 / g) and the true density (unit: g / cm 3) measured by the BET one-point method, and is obtained by the following formula (3). D BET = 6 / (BET specific surface area × true density)…(3)

[0028] <Average primary particle diameter D SEM> The average primary particle diameter DSEM (hereinafter sometimes simply referred to as "DSEM") is determined by measuring the equivalent circle diameter (Heywood diameter) of 100 or more arbitrary silver particles in the image obtained by a scanning electron microscope (SEM) for silver powder, and calculating the average value. For DSEM, for example, an image taken at 10,000 times magnification can be used, and image shape measurement software such as Mac-View (manufactured by MOUNTECH Co., Ltd.) can be used to obtain it.

[0029] <Particle size distribution> In this specification, the cumulative 10% particle diameter D10, cumulative 50% particle diameter D50, and cumulative 90% particle diameter D90 of silver powder based on volume are measured by a laser diffraction-scattering particle size distribution measuring device (manufactured by Microtrac Bel Co., Ltd., Microtrac MT-3300 EXII). At the time of measurement, 0.1 g of the sample (silver powder) is added to 40 mL of isopropyl alcohol (IPA) and dispersed. When dispersing, an ultrasonic homogenizer (manufactured by Nippon Seiki Co., Ltd., device name: US-150T; 19.5 kHz, chip front diameter 18 mm) is used. The dispersion time is set to 2 minutes. The dispersed sample is supplied to the said device, and the particle size distribution is obtained by the attached analysis software. Furthermore, hereinafter, the cumulative 10% particle diameter D10, cumulative 50% particle diameter D50, and cumulative 90% particle diameter D90 based on volume based on the laser diffraction method may be sometimes simply referred to as "D10", "D50", and "D90", respectively.

[0030] <Ratio of D50 to DBET (D50 / DBET)> Silver powder sometimes becomes a state where each particle is not completely separated and multiple particles are aggregated. In the measurement of the particle size based on the laser diffraction method, the particle size of the aggregated particles in the aggregated state is measured. On the other hand, the BET single point method is a method of measuring the specific surface area using the amount of gas adsorbed on the particles, and the BET diameter obtained by converting according to this specific surface area represents the particle size (particle diameter) when the measured particles are assumed to be spherical. In the case of a state with less aggregation and close to a monodisperse state, the value of the ratio (D50 / DBET) tends to be close to 1.

[0031] <Ignition loss value (Ig-loss)> In this specification, the so-called "ignition loss (Ig-loss) value" represents the change in mass when heated from room temperature to 800°C. Specifically, it becomes an index of the amount of components other than silver in the silver powder, and becomes an index indicating the amount of residual components in the silver powder, such as the amount of treatment agents or additives used in the manufacturing process of the silver powder. Moreover, in this specification, the "ignition loss (Ig-loss) value" is obtained by precisely weighing (weighing value: w1) a silver powder sample, placing it in a magnetic crucible, heating it to 800°C, then maintaining it at 800°C for 30 minutes as a time sufficient to fully reach a constant weight, then cooling and weighing again (weighing value: w2), and calculating from "ignition loss (Ig-loss) value (mass%) = (w1 - w2) / w1 × 100".

[0032] <Quantification of surface treatment agent> In this specification, for example, when the surface treatment agent of the silver powder is a fatty acid, the content of the fatty acid is measured according to the quantitative analysis method of fatty acids described in Japanese Patent No. 5622543. Specifically, first, after dissolving the silver powder with nitric acid, an organic solvent (n-hexane) is mixed, and after extracting all the surface treatment agents into the organic solvent phase, a specified amount of the organic solvent phase is separated, the solvent is evaporated to dryness to leave a solid (the surface treatment agent that has not evaporated and solidified), and for the remaining solid, the carbon amount is measured by a carbon-sulfur analyzer, and thus calculated.

[0033] For example, when the surface treatment agent is determined to be stearic acid and there is no carbon source other than stearic acid in the silver powder, the measurement method of the stearic acid content is as described in the said publication.

[0034] In addition, in this specification, for example, when the surface treatment agent of the silver powder is benzotriazole, the content of the benzotriazole is measured according to the quantitative analysis method of benzotriazole and benzotriazole salts described in Japanese Patent No. 5523153. Specifically, it is obtained by the following method: First, the silver powder is washed with an aqueous hydrochloric acid solution, and the washing solution is quantitatively analyzed by spectrophotometry.

[0035] Furthermore, the type of the surface treatment agent can be determined by qualitative analysis of the surface treatment agent that volatilizes when the silver powder is heated, based on gas chromatography.

[0036] <Microcrystal diameter> The microcrystal diameter Dx was determined using an X-ray diffraction device (SmartLab manufactured by Rigaku Corporation), and calculated by the Scherrer formula (Dhkl=Kλ / βcosθ). Here, in the Scherrer formula, Dhkl represents the size of the microcrystal diameter (the size of the microcrystal in the direction perpendicular to hkl) (unit: nm), λ represents the wavelength of the X-ray used (0.15405 nm when using a Cu target), β represents the broadening of the diffracted ray caused by the microcrystal size (rad) (expressed using the half value width), θ represents the Bragg angle of the diffraction angle (rad) (the angle when the incident angle and the reflection angle are equal, using the angle at the peak), and K represents the Scherrer constant (K = 0.94). Furthermore, the peak data of the (111) plane of the Miller indices can also be used in the calculation.

[0037] (Silver powder) Regarding the silver powder of the present invention, the volume-based D50 based on the laser diffraction method is 0.1 μm or more and 1.0 μm or less, the ratio of D50 to DBET (D50 / DBET) is 1.3 or less, and the shrinkage rate at 200°C in the thermomechanical analysis is 1% or more. For silver powder as described above, even when calcined at a low temperature (150°C to 200°C) in a conductive paste, excellent volume resistivity can be imparted. It is speculated that the reason is that silver powder with a D50 / DBET of 1.3 or less and in a state close to monodispersion has a shrinkage rate of a specified ratio or more at 200°C. Thus, compared with silver powder with a small shrinkage rate at 200°C in an electrode or conductor pattern obtained by using a conductive paste containing the silver powder, a good conductive network can be formed between silver particles during calcination. Furthermore, in this specification, the case where the volume resistivity and the disconnection rate are small even when calcined at a low temperature (150°C to 200°C) is also described as "having low-temperature calcination property". In addition, for silver powder as described above, excellent fine-line printability can be imparted to the conductive paste. It is speculated that the reason is that by setting D50 within a specified range, the deterioration of the fine-line printability caused by a large particle size and the excessive increase in the viscosity of the conductive paste containing the silver powder can be effectively suppressed.

[0038] The shrinkage rate at 200°C in the thermomechanical analysis is 1.0% or more, preferably 1.1% or more, more preferably 1.3% or more. If the shrinkage rate at 200°C in the thermomechanical analysis is 1.0% or more, the low-temperature calcination property can be improved. On the other hand, D50 / D BET is 1.3 or less, so the shrinkage rate does not exceed 5.0%. The shrinkage rate at 200°C in thermomechanical analysis is preferably 5.0% or less, more preferably 3.0% or less.

[0039] The shrinkage rate at 150°C in thermomechanical analysis is preferably 0.6% or more, more preferably 0.7% or more, and even more preferably 0.8% or more. If the shrinkage rate at 150°C in thermomechanical analysis is 0.6% or more, the low-temperature sinterability can be obtained more effectively. On the other hand, the shrinkage rate at 150°C in thermomechanical analysis is preferably 3.0% or less, more preferably 1.5% or less, and even preferably 1.3% or less. In addition, for the conductive film obtained by firing the resin-cured conductive paste using the silver powder of the present invention at a low temperature, when obtaining high conductivity is emphasized, the shrinkage rate at 150°C in the thermomechanical analysis of the present invention can be set to 1.05% or more and 1.5% or less, and further can be set to 1.05% or more and 1.4% or less.

[0040] D50 / D BET is preferably 1.3 or less, more preferably 1.27 or less, and even more preferably 1.20 or less. If D50 / D BET is 1.3 or less, excellent dispersibility can be obtained, so excellent fine line printability can be imparted. Furthermore, D50 / D BET is mostly 1.0 or more, but sometimes it is less than 1.0 as in this embodiment. In such a case, the value of D50 / D BET is preferably set to 0.8 or more.

[0041] D50 is 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.25 μm or more, and even preferably 0.35 μm or more, and is 1.0 μm or less, preferably 0.9 μm or less, more preferably 0.8 μm or less. If D50 is within the above range, the fine line printability of the conductive paste can be improved. In addition, for the conductive film obtained by firing the resin-cured conductive paste using the silver powder of the present invention at a low temperature, when obtaining high conductivity is emphasized, D50 of the silver powder of the present invention can be set to 0.1 μm or more and 0.5 μm or less, and further can be set to 0.2 μm or more and 0.4 μm or less.

[0042] D10 is preferably 0.05 μm or more, more preferably 0.10 μm or more, preferably 0.40 μm or less, and more preferably 0.35 μm or less. If D10 is within the above range, the fine line printability of the conductive paste can be improved.

[0043] D90 is preferably 0.5 μm or more, more preferably 0.55 μm or more, still more preferably 0.6 μm or more, preferably 1.2 μm or less, more preferably 1.1 μm or less, still more preferably 1.0 μm or less. If D90 is within the above range, the fine line printability of the conductive paste can be improved. Further, in the case of emphasizing obtaining high conductivity for a conductive film obtained by calcining a resin-cured conductive paste using the silver powder of the present invention at a low temperature, D90 of the silver powder of the present invention can be set to 0.5 μm or more and 0.9 μm or less, and can be further set to 0.55 μm or more and 0.85 μm or less.

[0044] DBET is preferably 0.22 μm or more, more preferably 0.25 μm or more, still more preferably 0.28 μm or more, particularly preferably 0.30 μm or more. Further, DBET is preferably 0.68 μm or less, more preferably 0.61 μm or less, still more preferably 0.58 μm or less. If DBET is within the above range, the fine line printability of the conductive paste can be improved.

[0045] The BET specific surface area is preferably 0.90 m2 / g or more, more preferably 1.00 m2 / g or more, still more preferably 1.05 m2 / g or more, preferably 2.50 m2 / g or less, more preferably 2.25 m2 / g or less, still more preferably 2.00 m2 / g or less, still more preferably 1.80 m2 / g or less. If the BET specific surface area is 0.90 m2 / g or more, appropriate particle activity can be obtained, which is advantageous in terms of the volume resistivity of a wiring pattern formed by using a conductive paste even in calcination at a low temperature. In addition, it is easy to cope with high density and the like. On the other hand, if the BET specific surface area is 2.50 m2 / g or less, it is advantageous in terms of the ease of handling of the paste when producing the conductive paste. Further, in the case of emphasizing obtaining high conductivity for a conductive film obtained by calcining a resin-cured conductive paste using the silver powder of the present invention at a low temperature, the specific surface area of the silver powder of the present invention can be set to 1.35 m2 / g or more and 2.50 m2 / g or less, and can be further set to 1.40 m2 / g or more and 2.50 m2 / g or less.

[0046] Here, the true density of silver is 10.49 g / cm3, but the true density of the silver powder of the present invention is preferably 9.7 g / cm3 or more, more preferably 9.8 g / cm3 or more, still more preferably 9.9 g / cm3 or more, and preferably 10.49 g / cm3 or less. In addition, when high conductivity is emphasized for the conductive film obtained by calcining the resin-curable conductive paste using the silver powder of the present invention at a low temperature, the bulk density of the silver powder of the present invention can be set to 9.7 g / cm3 or more and 9.95 g / cm3 or less, and further can be set to 9.7 g / cm3 or more and 9.9 g / cm3 or less.

[0047] DSEM is preferably 0.10 μm or more, more preferably 0.20 μm or more, still more preferably 0.25 μm or more, and even more preferably 0.35 μm or more, and preferably 1.00 μm or less, more preferably 0.90 μm or less, and even more preferably 0.80 μm or less. If DSEM is within the above range, the fine line printability of the conductive paste can be improved. In addition, when high conductivity is emphasized for the conductive film obtained by calcining the resin-curable conductive paste using the silver powder of the present invention at a low temperature, DSEM of the silver powder of the present invention can be set to 0.10 μm or more and 0.4 μm or less, and further can be set to 0.15 μm or more and 0.35 μm or less.

[0048] The ignition loss (Ig-loss) value is preferably 0.3 mass% or more, more preferably 0.35 mass% or more. In addition, it is preferably 1.2 mass% or less, more preferably 1.1 mass% or less, and still more preferably 0.8 mass% or less. If the ignition loss value is 0.3 mass% or more, the aggregation of silver powders can be suppressed and the dispersibility can be improved. On the other hand, if the ignition loss value is 1.2 mass% or less, the deterioration of the resistance value caused by excessive impurities can be prevented. In addition, when high conductivity is emphasized for the conductive film obtained by calcining the resin-type conductive paste using the silver powder of the present invention at a low temperature, the ignition loss value of the silver powder of the present invention can be set to 0.65 mass% or more and 1.2 mass% or less, and further can be set to 0.70 mass% or more and 1.2 mass% or less.

[0049] The crystallite diameter is preferably 25 nm or more, more preferably 30 nm or more, or can be 30 nm or more, still more preferably 32 nm or more, or can be 32 nm or more, and preferably 38 nm or less.

[0050] Here, the silver powder of the present invention preferably contains a surface treatment agent. If the silver powder contains a surface treatment agent, the dispersibility of the silver powder can be improved. Furthermore, specific examples of the surface treatment agent will be described in the section "Method for Producing Silver Powder" described later.

[0051] Here, the silver powder of the present invention preferably contains a surface treatment agent. If the silver powder contains a surface treatment agent, the dispersibility of the silver powder can be improved. Furthermore, specific examples of the surface treatment agent will be described in the section "Method for Producing Silver Powder" described later.

[0052] The silver powder of the present invention is not particularly limited and can be used in conductive pastes such as resin-curing type conductive pastes or sintering type conductive pastes. However, when the silver powder of the present invention is made into a conductive paste, it has excellent volume resistivity and fine line printability even when calcined at a low temperature. Therefore, it can be preferably used in resin-curing type conductive pastes.

[0053] (Method for Producing Silver Powder) The method for producing the silver powder of the present invention (hereinafter sometimes simply referred to as the "production method") includes: flowing a solution containing silver in a flow path, adding a pH adjuster to the flow path at a pH adjuster addition position in the middle of the flow path, adding a complexing agent to the flow path at a complexing agent addition position downstream of the pH adjuster addition position, adding a hydrazine-based reducing agent to the flow path at a reducing agent addition position downstream of the complexing agent addition position, and reducing and precipitating silver powder in the flow path. If it is the method as described above, silver powder that can impart excellent volume resistivity and fine line printability to a conductive paste even when calcined at a low temperature can be obtained. In addition, if it is the production method of the present invention, the silver powder of the present invention can be obtained. Furthermore, in the production method of the present invention, by continuously supplying a solution containing silver, a pH adjuster, a complexing agent, and a hydrazine-based reducing agent in sequence and quantitatively mixing these, the formation rate of the silver complex and the reduction precipitation rate of the silver powder can be kept constant, and thus silver powder of a specified amount can be obtained quantitatively and continuously.

[0054] The solution containing silver is a solution that reacts with a complexing agent to form a silver complex, and a solution containing a silver salt can be used. For example, aqueous solutions of silver nitrate, silver chloride, silver formate, silver oxalate, silver sulfate, etc. can be cited. In terms of ease of acquisition and other aspects, an aqueous solution of silver nitrate is preferred.

[0055] From the perspective of economy, the silver concentration in the silver-containing solution is preferably 0.01 mol / L or more, more preferably 0.05 mol / L or more, and even more preferably 0.10 mol / L or more. On the other hand, from the aspect of ensuring the interparticle distance of the particles after reduction precipitation and suppressing aggregation, the silver concentration in the silver-containing solution is preferably 0.5 mol / L or less, more preferably 0.3 mol / L or less.

[0056] The flow rate in this embodiment is a value obtained by filling the inside of the tube with liquid and dividing the flow rate of the solution by the cross-sectional area of the tube. In addition, the elapsed time between specific positions is obtained by dividing the length between the positions by the flow rate. From the aspect of productivity and forming monodisperse particles, the flow rate of the silver-containing solution is preferably 0.45 m / s or more, more preferably 0.65 m / s or more, and even more preferably 1.00 m / s or more. In addition, from the aspect of suppressing aggregation and forming monodisperse particles, it is preferably 3.20 m / s or less, more preferably 2.70 m / s or less, and even more preferably 2.00 m / s or less.

[0057] In the manufacturing method of the present invention, the silver-containing solution is made to flow in the flow path, and a pH adjuster is added to the flow path at the pH adjuster addition position in the middle of the flow path, thereby adjusting the pH of the silver-containing solution. Thereby, the particle diameter of the silver powder can be effectively adjusted. As the pH adjuster, general alkaline and acidic pH adjusters such as sodium hydroxide, potassium hydroxide, sodium carbonate, and nitric acid can be used. Furthermore, the pH adjuster is usually added to the flow path in the state of an aqueous solution of the pH adjuster. The addition amount of the pH adjuster is appropriately adjusted according to the particle diameter of the silver powder to be manufactured.

[0058] In the manufacturing method of the present invention, a silver complex is formed by adding a complexing agent to the flow path at the complexing agent addition position further downstream than the pH adjuster addition position. Furthermore, the complexing agent is usually added to the flow path in the state of an aqueous solution of the complexing agent.

[0059] Examples of the complexing agent include ammonia, ammonium salts, citric acid, acetic acid, etc., and ammonia is preferably used among them. Ammonia can be added in the form of aqueous ammonia. For example, when aqueous ammonia is added as the complexing agent, a silver-ammonia complex is formed. The silver-ammonia complex can be easily reduced by hydrazine, so it is preferable.

[0060] From an economic perspective, the concentration of ammonia water is preferably 0.35 mol / L or more, more preferably 0.50 mol / L or more, preferably 16.2 mol / L or less, more preferably 15.1 mol / L or less, and still more preferably 10.0 mol / L or less.

[0061] The addition amount of ammonia relative to 1 mol of silver is preferably 2.10 mol or more, more preferably 2.20 mol or more. On the other hand, the addition amount of ammonia relative to 1 mol of silver is preferably 10.00 mol or less, more preferably 8.00 mol or less.

[0062] The flow rate of the complexing agent added at the complexing agent addition position is preferably 0.40 m / s or more, more preferably 0.60 m / s or more, still more preferably 1.00 m / s or more, preferably 3.20 m / s or less, more preferably 2.70 m / s or less, and still more preferably 2.00 m / s or less.

[0063] Even when using a complexing agent other than ammonia, considering the amount of the complexing agent relative to the amount of silver required for forming the complex, the concentration, addition amount, and flow rate can be set based on the above.

[0064] In the manufacturing method of the present invention, a hydrazine-based reducing agent is added to the flow path at the reducing agent addition position downstream of the complexing agent addition position to precipitate silver powder by reduction. Furthermore, as the hydrazine-based reducing agent in the present invention, there are hydrazine, hydrazine hydrate, carbohydrazide, hydrazine sulfate, phenylhydrazine, etc. Preferably, they are hydrazine and carbohydrazide, and more preferably hydrazine. By using hydrazine, silver powder with a desired particle size can be stably obtained. Usually, the hydrazine-based reducing agent is added to the flow path in an aqueous solution state.

[0065] From the perspective of a uniform reduction reaction, the concentration of hydrazine in the hydrazine aqueous solution is preferably 0.025 mol / L or more, more preferably 0.05 mol / L or more, still more preferably 0.10 mol / L or more, preferably 3.3 mol / L or less, more preferably 2.0 mol / L or less, and still more preferably 1.0 mol / L or less. In addition, from the perspective of a uniform reduction reaction, the concentration of the hydrazine-based reducing agent in the hydrazine-based reducing agent aqueous solution is preferably 0.025 mol / L or more, more preferably 0.05 mol / L or more, still more preferably 0.10 mol / L or more, preferably 3.3 mol / L or less, more preferably 2.0 mol / L or less, and still more preferably 1.0 mol / L or less.

[0066] The addition amount of hydrazine relative to 1 mole of silver is preferably such that substantially no unreacted silver is produced, preferably 0.26 mole or more, more preferably 0.28 mole or more. On the other hand, in order not to add a reducing agent more than necessary, the addition amount of hydrazine relative to 1 mole of silver is preferably 0.88 mole or less, more preferably 0.75 mole or less, and still more preferably 0.50 mole or less. In addition, the addition amount of the hydrazine-based reducing agent relative to 1 mole of silver is preferably such that substantially no unreacted silver is produced, preferably 0.26 mole or more, more preferably 0.28 mole or more. On the other hand, in order not to add a reducing agent more than necessary, the addition amount of the hydrazine-based reducing agent relative to 1 mole of silver is preferably 0.88 mole or less, more preferably 0.75 mole or less, and still more preferably 0.50 mole or less.

[0067] In the manufacturing method of the present invention, from the viewpoint of productivity, the flow rate of the silver complex solution before adding the reducing agent to the flow path is preferably 0.50 m / sec or more, more preferably 0.75 m / sec or more, and still more preferably 1.0 m / sec or more. In addition, from the viewpoint of suppressing aggregation and forming monodisperse particles, it is preferably 3.5 m / sec or less, more preferably 3.0 m / sec or less, and still more preferably 2.0 m / sec or less.

[0068] The flow rate of the reducing agent when adding the reducing agent to the flow path is preferably 0.5 times or more, more preferably 0.8 times or more, relative to the flow rate of the silver complex solution before the reducing agent. In addition, from the viewpoint of suppressing the liquid flow to the pipe wall surface from becoming large and the mixing efficiency from decreasing, it is preferably 2.5 times or less, more preferably 2.0 times or less, and still more preferably 1.5 times or less.

[0069] In the manufacturing method of the present invention, in order to add the hydrazine-based reducing agent at the place where the silver complex is formed, the time required for the solution containing silver to flow from the complexing agent addition position to the reducing agent addition position (the elapsed time obtained by dividing the length from the complexing agent addition position to the reducing agent addition position by the flow rate of the silver complex solution before adding the reducing agent) is preferably 0.1 second or more, more preferably 0.5 second or more. On the other hand, if the elapsed time after forming the complex becomes long, there is a risk that the stability of the silver complex becomes high and the reduction reaction is not easily carried out. Therefore, in order to preferably maintain the freshness of the silver complex when adding the reducing agent, the elapsed time is preferably within 10.0 seconds, more preferably within 5.0 seconds.

[0070] In the manufacturing method of the present invention, a surface treatment agent can be added to the flow path between the complexing agent addition position and the reducing agent addition position, or on the downstream side of the reducing agent addition position. The addition of the surface treatment agent is advantageous in suppressing the aggregation of the reduced and precipitated silver powder. Preferably, the addition is carried out at a time point between the complexing agent addition position and the reducing agent addition position.

[0071] Examples of the surface treatment agent include: fatty acids, fatty acid salts, surfactants, organometals, chelating agents, protective colloids, etc. The surface treatment agent can be used in an amount of 0.3% by mass or more and 1.3% by mass or less based on the silver in the silver-containing solution. The surface treatment agent can be used in the form of an emulsion, a solution, or the like.

[0072] (1) Fatty acids Examples of the fatty acid include: propionic acid, octanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, acrylic acid, oleic acid, linoleic acid, arachidonic acid, ricinoleic acid, etc.

[0073] (2) Fatty acid salts Examples of the fatty acid salt include metal salts of the fatty acids described in (1) above. Examples of the metal include: lithium, sodium, potassium, barium, magnesium, calcium, aluminum, iron, cobalt, manganese, lead, zinc, tin, strontium, zirconium, silver, copper, etc.

[0074] (3) Surfactants Examples of the surfactant include: anionic surfactants such as alkylbenzene sulfonates, polyoxyethylene alkyl ether phosphates, etc.; cationic surfactants such as aliphatic quaternary ammonium salts, etc.; amphoteric surfactants such as imidazolium betaines, etc.; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, etc.

[0075] Examples of the organometal include: zirconium tributoxide acetylacetonate, magnesium citrate, diethylzinc, dibutyltin oxide, dimethylzinc, zirconium tetra-n-butoxide, triethylindium, triethylgallium, trimethylindium, trimethylgallium, monobutyltin oxide, tetraisocyanate silane, tetramethylsilane, tetramethoxysilane, monomethyltriisocyanate silane, silane coupling agent, titanate coupling agent, aluminum coupling agent, etc.

[0076] (5) Chelating agents Examples of the chelating agent-forming agent include imidazole, oxazole, thiazole, selenazole, pyrazole, isoxazole, isothiazole, 1H-1,2,3-triazole, 2H-1,2,3-triazole, 1H-1,2,4-triazole, 4H-1,2,4-triazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 1H-1,2,3,4-tetrazole, 1,2,3,4-oxatriazole, 1,2,3,4-thiatriazole, 2H-1,2,3,4-tetrazole, 1,2,3,5-oxatriazole, 1,2,3,5-thiatriazole, indazole, benzimidazole, benzotriazole, etc., and salts of these chelating agent-forming agents, polycarboxylic acids typified by dicarboxylic acids such as succinic acid, malonic acid, glutaric acid, and adipic acid.

[0077] (6) Protective colloid Examples of the protective colloid include peptides, gelatin, albumin, gum arabic, protalbinic acid, lysalbinic acid, glue, etc.

[0078] As the surface treatment agent, from the viewpoint of the ease of modification of the silver particle surface, (1) fatty acids are preferred, and stearic acid is more preferred. (1) Fatty acids are preferably in the form of an emulsion, and examples thereof include stearic acid emulsion.

[0079] In the production method of the present invention, from the viewpoint of the reactivity of the reduction reaction, the temperature of the silver complex solution before adding the reducing agent is preferably 20°C or higher, more preferably 30°C or higher. On the other hand, from the viewpoint of operability, the temperature of the liquid flowing in the flow path is preferably 65°C or lower, more preferably 60°C or lower.

[0080] In the production method of the present invention, a stirrer can also be used to apply a helical rotation in the axial direction of the flow path to perform liquid mixing.

[0081] In the production method of the present invention, silver powder can be obtained by discharging the liquid containing the silver powder precipitated by reduction (hereinafter also referred to as "liquid containing silver powder") outside the flow path and recovering it. Furthermore, the liquid containing silver powder is usually obtained in the state of a slurry or a dispersion.

[0082] In terms of predicting the end of the reduction reaction, the time from adding the reducing agent to discharging the liquid containing silver powder outside the flow path is preferably 1 second or more, more preferably 2 seconds or more. On the other hand, in terms of suppressing deposition on the piping, the time from adding the reducing agent to discharging the liquid containing silver powder outside the flow path is preferably 10 seconds or less, more preferably 5 seconds or less.

[0083] By filtering and washing with water the liquid containing silver powder discharged outside the flow path, a filter cake in the form of a lump containing silver powder and water and having almost no fluidity can be obtained. By drying the filter cake using a dryer such as a forced circulation type atmospheric dryer, a vacuum dryer, or a fluidized bed dryer, the silver powder of the present invention can be obtained. By replacing the water in the filter cake with a lower alcohol or the like, the drying can be accelerated. Dry crushing treatment, surface smoothing treatment, etc. can be performed on the filter cake. The dry crushing treatment can be performed using, for example, a sample mill, a mixer, a coffee grinder, a multi-functional stirrer, etc. In addition, the surface smoothing treatment can be performed by mechanically colliding particles with each other using a high-speed stirrer. Thereafter, aggregates of silver powder having a particle size larger than a specified particle size can also be removed by classification treatment. Furthermore, an integrated device (such as a drymeister or a micron dryer manufactured by Hosokawa Micron Corporation) that can dry, crush, and classify the filter cake can also be used for drying, crushing, and classification.

[0084] (Silver powder manufacturing apparatus) The silver powder manufacturing apparatus of the present invention adds a pH adjuster, a complexing agent, and a hydrazine-based reducing agent as a reducing agent to a silver-containing solution to precipitate silver powder by reduction. The silver powder manufacturing apparatus has a pipe forming a flow path for the silver-containing solution, a pH adjuster addition part and a complexing agent addition part connected to the pipe, and a reducing agent addition part connected to the pipe on the downstream side of the nitric acid addition part and the complexing agent addition part. It is also preferably provided with a surface treatment agent addition part on the downstream side of the nitric acid addition part and the complexing agent addition part and near the reducing agent addition part. Hereinafter, with reference to the drawings, an example of a silver powder manufacturing apparatus that can be used in the manufacturing method of the present invention will be described.

[0085] FIG. 1 is an external perspective view of an example of a silver powder manufacturing apparatus. In FIG. 1, the silver powder manufacturing apparatus 1 includes: a tube 2 through which a solution containing silver flows; a pH adjuster supply tube 7 that supplies a pH adjuster; a complexing agent supply tube 6 that is located downstream of the pH adjuster supply tube 7 and supplies a complexing agent; a surface treatment agent supply tube 5 that is located downstream of the complexing agent supply tube 6 and supplies a surface treatment agent; and a reducing agent addition member 10 that is located downstream of the surface treatment agent supply tube 5 and supplies a hydrazine-based reducing agent as a reducing agent. A reducing agent supply tube 4a and a reducing agent supply tube 4b are eccentrically connected to the reducing agent addition member 10. The silver powder manufacturing apparatus 1 of FIG. 1 includes the surface treatment agent supply tube 5 between the complexing agent supply tube 6 and the reducing agent addition member 10, but the surface treatment agent supply tube 5 may also be disposed on the downstream side of the reducing agent addition member 10.

[0086] The pH adjuster addition section, the complexing agent addition section, and the surface treatment agent addition section may each be a Y-shaped pipe or a T-shaped pipe, and may be a second pipe connected in the middle of the pipe forming the flow path of the solution containing silver, so that the flow path of the solution containing silver merges with the flow path of the second pipe. Alternatively, the pH adjuster addition section, the complexing agent addition section, and the surface treatment agent addition section may each be a coaxial double pipe.

[0087] Regarding the reducing agent, when the reducing agent is added to the flow path from one direction, it takes time for the reducing agent to reach the side opposite to the addition point, and there is a risk of deviation in the concentration of the reducing agent at the reducing agent addition position. Therefore, when using a Y-shaped tube or a T-shaped tube to bring the silver complex solution into contact with and mix with the reducing agent at the confluence section, there is also a risk of concentration deviation for the same reason. In addition, when the reducing agent is added at the central position of the flow path through a coaxial double tube, the reducing agent is added in parallel with the flow of the silver complex solution. Therefore, it takes time before the silver complex solution and the reducing agent are mixed, and in the coaxial double tube, the flow velocity at the center of the tube is relatively fast, and the flow velocity near the wall surface becomes relatively slow. Therefore, the growth of particles is likely to be uneven.

[0088] The addition of the reducing agent is preferably performed in two or more directions with respect to the flow path, more preferably in four or more directions, and particularly preferably in all directions from the outer periphery of the flow path. The addition of the reducing agent to the flow path can be performed in multiple directions according to the number and shape of the orifices described orally.

[0089] Preferably, the plurality of directions form angles of 75 degrees or more and 105 degrees or less with the flow path, respectively. Adding the reducing agent substantially perpendicularly to the flow path is advantageous for rapidly mixing the silver complex solution and the reducing agent. More preferably, the angle with respect to the flow path is 80 degrees or more and 100 degrees or less. The so-called "with respect to the flow path" can also be referred to as "with respect to the axial direction of the tube through which the silver complex solution flows".

[0090] When the silver powder manufacturing apparatus of the present invention is used, silver powder capable of imparting excellent low-temperature heatability and fine line printability to the conductive paste can be obtained.

[0091] FIG. 2A is a cross-sectional view perpendicular to the flow path of the silver complex solution at the central positions of the reducing agent supply pipes 4a and 4b of the reducing agent addition member 10 of FIG. 1. FIG. 2B is a cross-sectional view of the flow path of the silver complex solution and the horizontal direction, and is a cross-sectional view taken along line A-A of FIG. 2A. FIG. 2C is a cross-sectional view of the flow path of the silver complex solution and the horizontal direction, and is a cross-sectional view taken along line B-B of FIG. 2A.

[0092] In FIG. 2A, a gap 13 is provided along the outer periphery of the tube 2 serving as the flow path of the silver complex solution, and the gap 13 is connected to the inside of the tubes of the reducing agent supply pipe 4a and the reducing agent supply pipe 4b. As shown in FIG. 2C, which is a cross-sectional view taken along line B-B of FIG. 2A, the downstream side of the flow path of the silver complex solution in the gap 13 is connected to a slit portion 12 having an opening 11 along the radially outer side of the inner periphery of the tube 2. Moreover, as shown in FIG. 2B, which is a cross-sectional view taken along line A-A of FIG. 2A, when the reducing agent flows into the gap 13 from the inside of the tube of the reducing agent supply pipe 4a and the inside of the tube of the reducing agent supply pipe 4b, the reducing agent reaches the slit portion 12 through the gap 13, and the reducing agent enters the tube 2 substantially perpendicularly (for example, 75 degrees or more and 105 degrees or less) from the opening 11 of the slit portion 12 and from the entire circumference of the tube 2, and is added to the silver complex solution. Here, the angle at which the reducing agent enters with respect to the flow path of the silver complex solution is the angle at which the axial direction of the tube 2 intersects the opening direction of the opening 11 through which the reducing agent enters the tube 2. The opening direction can be regarded as the direction along the wall surface near the opening of the slit portion 12 as shown in FIG. 2B.

[0093] According to the flow rate of the reducing agent flowing in the reducing agent supply pipe 4a and the reducing agent supply pipe 4b and the size of the total area of the openings 11, the flow rate of the reducing agent when the reducing agent is added to the flow path of the silver complex solution can be controlled. By controlling the flow rate of the reducing agent within the above range, the reaction between the silver complex and the reducing agent can be carried out rapidly, and thereby, silver powder with a sharp width of particle size distribution can be obtained.

[0094] The width of the opening 11 in the slit portion 12 in FIGS. 2B and 2C is referred to as the slit width. In order to reduce the size of the total area of the opening 11, the slit width is preferably narrower than the diameter of the reducing agent supply pipe. The addition of the reducing agent can be performed from multiple directions with respect to the flow path. As the shape of the gap 13 and the slit portion 12 that can form a slit width narrower than the diameter of the reducing agent supply pipe, it is not limited to the structures in FIGS. 2A to 2C, and various deformations can be made. In addition, it is also possible to make a deformation such that the opening 11 of the slit portion 12 is not provided around the entire circumference of the pipe 2 but is provided as a plurality of through holes or the like.

[0095] The number of reducing agent supply pipes for flowing the reducing agent into the reducing agent addition member 10 is preferably one or more, and more preferably two or more. When there are two or more reducing agent supply pipes, the flow paths of the reducing agent connected to the opening 11 from the reducing agent supply pipes can be facing each other or eccentric. In FIGS. 2A to 2C, the reducing agent supply pipe 4a and the reducing agent supply pipe 4b are connected to be eccentric with respect to the center of the pipe 2, and the flow paths of the reducing agent supply pipe 4a and the reducing agent supply pipe 4b are connected to the slit portion 12 having the opening 11. When connecting a plurality of reducing agent supply pipes, if at least two reducing agent supply pipes are eccentric to each other, the reducing agent can be made to flow into the opening 11 of the slit portion 12 while rotating the outer circumference of the flow path (pipe 2) of the silver complex solution in one direction. When the reducing agent rotates on the outer circumference of the flow path of the silver complex solution, the flow rate of the reducing agent toward the opening 11 can also be adjusted by changing the cross-sectional area of the flow path (gap 13 or slit portion 12) of the reducing agent.

[0096] (Resin-curable conductive paste) The resin-curable conductive paste of the present invention contains the silver powder of the present invention. Among the metal powders contained in the resin-curable conductive paste, the proportion of the silver powder of the present invention in the total amount of the metal powders is preferably 20% to 100%. As the metal powder other than the silver powder of the present invention, it is also preferable to contain silver powder having a particle size (D50) larger than that of the silver powder of the present invention. Since the resin-curable conductive paste of the present invention contains the silver powder of the present invention, it has excellent volume resistivity and fine line printability. Furthermore, the resin-curable conductive paste of the present invention generally contains the silver powder, resin, and solvent of the present invention. In addition, the resin-curable conductive paste of the present invention can also optionally further contain components other than the silver powder, resin, and solvent (hereinafter sometimes referred to as "other components").

[0097] The resin is not particularly limited and examples thereof include epoxy resin, acrylic resin, polyester resin, polyimide resin, polyurethane resin, phenoxy resin, silicone resin, and ethyl cellulose. These may be used alone or in combination at any ratio of two or more.

[0098] The solvent is not particularly limited and examples thereof include terpene alcohols such as terpineol, butyl carbitol, ester alcohols, glycols such as ethylene glycol and diethylene glycol, and glycerol; ester solvents such as butyl carbitol acetate and ethyl acetate; and hydrocarbon solvents such as toluene, xylene, and cyclohexane. These may be used alone or in combination at any ratio of two or more.

[0099] Examples of other components include dispersants, surfactants, viscosity modifiers, lubricants, and the like.

[0100] The method for producing the resin-cured conductive paste is not particularly limited, and examples thereof include a method of mixing the silver powder, organic binder, solvent, and any other components of the present invention. The mixing method is not particularly limited, and for example, a rotation-revolution type stirrer, ultrasonic dispersion, a disperser, a three-roll mill, a ball mill, a bead mill, a twin-screw kneader, or the like can be used.

[0101] The resin-cured conductive paste of the present invention can be applied to a substrate by printing such as screen printing, offset printing, and photolithography, or dipping to form a coating film. The coating film can also be formed into a specified pattern shape by photolithography using a resist.

[0102] The conductive film can be formed by heating the coating film to cure it. The heat curing can be carried out in an atmospheric environment or in a non-oxidizing environment such as nitrogen.

[0103] Even when calcined at a low temperature, the resin-cured conductive paste of the present invention is excellent in volume resistivity and fine line printability, and thus can be preferably used for manufacturing a heterojunction (HJT) type solar cell or the like in which an electrode or a conductor pattern is formed by heating at a relatively low temperature. [Examples]

[0104] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited by any of the following examples. Furthermore, the BET specific surface area, true density, BET diameter D BET, average primary particle diameter D SEM, particle size distribution, ignition loss (Ig-loss) value, quantification of the surface treatment agent, crystallite diameter, and shrinkage rate of the silver powder (at 200 °C and 150 °C) are measured or calculated by the methods described above.

[0105] (Example 1) Silver powder was produced using the silver powder production apparatus 1 shown in FIGS. 1 and 2A to 2C. An aqueous silver nitrate solution of 0.160 mol / L was introduced into the tube 2 (inner diameter 20 mm) at a liquid temperature of 50 °C at a flow rate of 23.35 L / min, and an aqueous nitric acid solution of 0.024 mol / L was introduced from the pH adjuster supply tube 7 (inner diameter 6 mm) as a coaxial double tube at a flow rate of 2.13 L / min to adjust the pH. An aqueous ammonia solution of 4.500 mol / L as a complexing agent was introduced from the complexing agent supply tube 6 (inner diameter 6 mm) as a coaxial double tube at a flow rate of 2.33 L / min to form a silver ammonia complex in the tube 2. A surface treatment agent (0.10 mass% Selosol 920 (manufactured by Chukyo Yushi Co., Ltd., containing 15.5 wt% stearic acid)) was introduced from the surface treatment agent supply tube 5 (inner diameter 6 mm) upstream of the reducing agent addition member 10 at a flow rate of 2.19 L / min. The amount of the aqueous silver nitrate solution was such that the silver concentration in the total liquid volume after adding the pH adjuster, complexing agent, reducing agent, and surface treatment agent became 0.115 mol / L. An aqueous hydrazine solution of 0.50 mol / L as a reducing agent was introduced at a flow rate of 2.55 L / min over the entire circumference of the slit portion 12 (slit width 0.44 mm, inner diameter of the tube 20.6 mm) of the reducing agent addition member 10 to precipitate silver powder. The flow rate of the reducing agent entering from the slit portion with a slit width of 0.44 mm was 1.49 m / s, and the flow rate of the silver ammonia complex immediately before adding the reducing agent at the inner diameter of the tube 20.6 mm at the position where the reducing agent entered was 1.50 m / s. The ratio of the flow rate of the complex to the flow rate of the reducing agent (complex flow rate / reducing agent flow rate) was 1.01. The operation time of the silver powder production apparatus (the time from the start of introducing the reducing agent into the silver ammonia complex until the stop after the flow of the silver ammonia complex into which the surface treatment agent was introduced became stable) was set to 616 seconds. Furthermore, the slurry generated before the flow of the silver ammonia complex into which the surface treatment agent was introduced became stable was received by another container and not used in the steps after solid-liquid separation. In the above, it is 0.5 seconds from the inlet of the silver nitrate aqueous solution flow path to the nitric acid aqueous solution addition position, 0.5 seconds from the nitric acid aqueous solution addition position to the ammonia water addition position, 2.12 seconds (2.1 m) from the ammonia water addition position to the hydrazine aqueous solution addition position, and 0.12 seconds from the surface treatment agent addition position to the hydrazine aqueous solution addition position. That is, the temperature of the silver ammonia complex aqueous solution located before the hydrazine aqueous solution addition position is 47.2 °C.

[0106] The slurry containing silver powder is discharged from pipe 2. The time from the hydrazine aqueous solution addition position to the discharge is about 2 seconds. The slurry containing silver powder after the reduction reaction is stabilized is recovered, and the solid obtained by solid-liquid separation with pure water is washed to remove impurities in the solid. The end point of this washing can be judged according to the conductivity of the water after washing. Wash until the conductivity becomes 0.5 mS / m or less, and then dry to obtain 3.8 kg of silver powder.

[0107] For the silver powder obtained in the above, a sample mill (manufactured by Kyori Riko Co., Ltd., SK-M10) is used, 120 g of silver powder is loaded, and it is crushed twice within 90 seconds to obtain the silver powder of Example 1. The measurement results and the like of the silver powder of Example 1 are shown in Table 3. In addition, the thermomechanical analysis curve of the silver powder of Example 1 is shown in Figure 3, the curve after magnifying a part (0 °C to 250 °C) of the curve of Figure 3 is shown in Figure 4, and the SEM photograph (20,000 times) is shown in Figure 5.

[0108] (Example 2) A 0.153 mol / L silver nitrate aqueous solution is introduced into pipe 2 (inner diameter 20 mm) at a liquid temperature of 50 °C at a flow rate of 23.35 L / min. A 0.008 mol / L nitric acid aqueous solution is introduced from the pH adjuster supply pipe 7 (inner diameter 6 mm) as a coaxial double pipe at a flow rate of 3.15 L / min to adjust the pH. A 4.919 mol / L ammonia aqueous solution is introduced from the complexing agent supply pipe 6 (inner diameter 6 mm) as a coaxial double pipe at a flow rate of 2.33 L / min to form a silver ammonia complex in pipe 2. A surface treatment agent (0.10 mass% Selosol 920 (manufactured by Chukyo Yushi Co., Ltd., containing 15.5 wt% stearic acid)) is introduced from the surface treatment agent supply pipe 5 (inner diameter 6 mm) upstream of the reducing agent addition member 10 at a flow rate of 2.19 L / min. The amount of the silver nitrate aqueous solution is such that the silver concentration in the total liquid volume after adding the pH adjuster, complexing agent, reducing agent, and surface treatment agent becomes 0.106 mol / L. An aqueous hydrazine solution with a concentration of 0.478 mol / L was introduced at a flow rate of 2.55 L / min over the entire circumference of the slit portion (slit width: 0.44 mm, inner pipe diameter: 20.6 mm) of the self-reducing agent addition member 10 to precipitate silver powder. The flow rate of the reducing agent entering from the slit portion with a slit width of 0.44 mm was 1.49 m / s, and the flow rate of the silver ammonia complex immediately before the addition of the reducing agent at the position where the inner pipe diameter of pipe 2 was 20.6 mm at the entrance of the reducing agent was 1.55 m / s (calculated based on the total value of the flow rates of the silver nitrate aqueous solution, nitric acid aqueous solution, and ammonia aqueous solution). The ratio of the flow rate of the complex to the flow rate of the reducing agent (complex flow rate / reducing agent flow rate) was 1.04. The operation time of the silver powder manufacturing apparatus (the time from the start of introducing the reducing agent into the silver ammonia complex until the stop after the flow of the silver ammonia complex introduced with the surface treatment agent became stable) was set to 115 seconds. Furthermore, the slurry generated before the flow of the silver ammonia complex introduced with the surface treatment agent became stable was received by another container and not used in the steps after solid-liquid separation. In the above, from the inlet of the silver nitrate aqueous solution flow path to the nitric acid aqueous solution addition position was 0.5 seconds, from the nitric acid aqueous solution addition position to the ammonia aqueous solution addition position was 0.48 seconds, from the ammonia aqueous solution addition position to the hydrazine aqueous solution addition position was 2.05 seconds (2.1 m), from the surface treatment agent addition position to the hydrazine aqueous solution addition position was 0.12 seconds, and the temperature of the silver ammonia complex solution immediately before the hydrazine aqueous solution addition position was 46.6°C.

[0109] The slurry containing silver powder was discharged from pipe 2. The time from the hydrazine aqueous solution addition position to the discharge was approximately 2 seconds. The slurry containing silver powder after the reduction reaction was stabilized was recovered, and the solid obtained by solid-liquid separation was washed with pure water to remove impurities in the solid. The end point of this washing could be judged based on the conductivity of the water after washing. Washing was performed until the conductivity became 0.5 mS / m or less, and drying was carried out to obtain 0.55 kg of silver powder.

[0110] Furthermore, the silver powder obtained in Example 2 was subjected to the same pulverization treatment as in Example 1. The measurement results and the like of the silver powder of Example 2 are shown in Table 3. In addition, the thermomechanical analysis curve diagrams of the silver powder of Example 2 are shown in Figures 3 and 4. The SEM photographs (20,000 times) are shown in Figure 6.

[0111] (Example 3) An aqueous silver nitrate solution with a concentration of 0.160 mol / L is introduced into tube 2 (inner diameter 20 mm) at a flow rate of 23.35 L / min at a liquid temperature of 50°C. An aqueous nitric acid solution with a concentration of 0.024 mol / L is introduced from the pH adjuster supply tube 7 (inner diameter 6 mm) of the coaxial double tube at a flow rate of 2.13 L / min to adjust the pH. An aqueous ammonia solution with a concentration of 4.436 mol / L is introduced from the complexing agent supply tube 6 (inner diameter 6 mm) of the coaxial double tube at a flow rate of 2.33 L / min to form a silver ammonia complex in tube 2. From the surface treatment agent supply tube 5 (inner diameter 6 mm) upstream of the reducing agent addition member 10, a surface treatment agent (0.10 mass% Selosol 920 (manufactured by Chukyo Yushi Co., Ltd., containing 15.5 wt% stearic acid)) is introduced at a flow rate of 2.19 L / min. The amount of the aqueous silver nitrate solution is such that the silver concentration in the total liquid volume after adding the pH adjuster, complexing agent, reducing agent, and surface treatment agent becomes 0.115 mol / L. An aqueous hydrazine solution with a concentration of 0.50 mol / L is introduced at a flow rate of 2.55 L / min around the entire circumference of the slit portion (slit width 0.44 mm, inner diameter of the tube 20.6 mm) of the reducing agent addition member 10 to precipitate silver powder. The flow rate of the reducing agent entering from the slit portion with a slit width of 0.44 mm is 1.49 m / s, and the flow rate of the silver ammonia complex immediately before adding the reducing agent at the inner diameter of tube 2 at the position where the reducing agent enters is 1.50 m / s (calculated based on the total value of the flow rates of the aqueous silver nitrate solution, aqueous nitric acid solution, and aqueous ammonia solution). The ratio of the flow rate of the complex to the flow rate of the reducing agent (complex flow rate / reducing agent flow rate) is 1.01. The operation time of the silver powder manufacturing apparatus (the time from the start of introducing the reducing agent into the silver ammonia complex until the stop after the flow of the silver ammonia complex into which the surface treatment agent has been introduced has stabilized) is set to 617 seconds. Furthermore, the slurry generated before the flow of the silver ammonia complex into which the surface treatment agent has been introduced has stabilized is received by another container and not used in the steps after solid-liquid separation. In the above, it is 0.5 seconds from the inlet of the flow path of the aqueous silver nitrate solution to the nitric acid aqueous solution addition position, 0.5 seconds from the nitric acid aqueous solution addition position to the ammonia aqueous solution addition position, 2.12 seconds (2.1 m) from the ammonia aqueous solution addition position to the hydrazine aqueous solution addition position, 0.12 seconds from the surface treatment agent addition position to the hydrazine aqueous solution addition position, and the temperature of the silver ammonia complex solution immediately before the hydrazine aqueous solution addition position is 47.4°C.

[0112] The slurry containing silver powder is discharged from the self-pipe 2. The time from the addition position of the hydrazine aqueous solution to the discharge is about 2 seconds. The slurry containing silver powder after the reduction reaction is stabilized is recovered, and the solid obtained by solid-liquid separation using pure water is washed to remove impurities in the solid. The end point of this washing can be judged according to the conductivity of the water after washing. Wash until the conductivity becomes 0.5 mS / m or less, and then dry to obtain 3.6 kg of silver powder.

[0113] Furthermore, the silver powder obtained in Example 3 is subjected to the same pulverization treatment as in Example 1. The measurement results and the like of the silver powder of Example 3 are shown in Table 3. In addition, the graphs of the thermomechanical analysis of the silver powder of Example 3 are shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 7.

[0114] (Example 4) A 0.160 mol / L silver nitrate aqueous solution is introduced into pipe 2 (inner diameter 20 mm) at a flow rate of 27.24 L / min at a liquid temperature of 50°C. A 0.024 mol / L nitric acid aqueous solution is introduced from the pH adjuster supply pipe 7 (inner diameter 6 mm) as a coaxial double pipe at a flow rate of 2.49 L / min to adjust the pH. A 4.436 mol / L ammonia aqueous solution is introduced from the complexing agent supply pipe 6 (inner diameter 6 mm) as a coaxial double pipe at a flow rate of 2.72 L / min to form a silver ammonia complex in pipe 2. From the surface treatment agent supply pipe 5 (inner diameter 6 mm) upstream of the reducing agent addition member 10, a surface treatment agent (0.10 mass% Selosol 920 (manufactured by Chukyo Yushi Co., Ltd., containing 15.5 wt% stearic acid)) is introduced at a flow rate of 2.55 L / min. The amount of the silver nitrate aqueous solution is such that the silver concentration in the total liquid volume after adding the pH adjuster, complexing agent, reducing agent, and surface treatment agent becomes 0.115 mol / L. A 0.50 mol / L hydrazine aqueous solution is introduced at a flow rate of 2.97 L / min around the entire circumference of the slit portion (slit width 0.44 mm, inner diameter of the pipe 20.6 mm) of the reducing agent addition member 10 to precipitate silver powder. The flow rate of the reducing agent entering from the slit portion with a slit width of 0.44 mm is 1.74 m / s, and the flow rate of the silver ammonia complex immediately before adding the reducing agent at the inner diameter of the pipe 20.6 mm at the position where the reducing agent enters is 1.75 m / s. The ratio of the flow rate of the complex to the flow rate of the reducing agent (flow rate of the complex / flow rate of the reducing agent) is 1.01. The operation time of the silver powder manufacturing apparatus (the time from the start to the stop after the flow of the silver ammonia complex introduced with the surface treatment agent has stabilized, until the reducing agent is introduced into the silver ammonia complex) was set to 568 seconds. Furthermore, the slurry generated before the flow of the silver ammonia complex introduced with the surface treatment agent has stabilized is received by another container and not supplied to the steps after solid-liquid separation. In the above, from the inlet of the silver nitrate aqueous solution flow path to the nitric acid aqueous solution addition position is 0.43 seconds, from the nitric acid aqueous solution addition position to the ammonia aqueous solution addition position is 0.43 seconds, from the ammonia aqueous solution addition position to the hydrazine aqueous solution addition position is 1.82 seconds (2.1 m), from the surface treatment agent addition position to the hydrazine aqueous solution addition position is 0.10 seconds, that is, the temperature of the silver ammonia complex solution located before the hydrazine aqueous solution addition position is 47.3 °C.

[0115] The slurry containing silver powder is discharged from pipe 2. The time from the hydrazine aqueous solution addition position to the discharge is about 1.7 seconds. The silver powder-containing slurry after the reduction reaction has stabilized is recovered, and the solid obtained by solid-liquid separation is washed with pure water to remove impurities in the solid. The end point of this washing can be judged based on the conductivity of the water after washing. Wash until the conductivity becomes 0.5 mS / m or less, and then dry to obtain 3.2 kg of silver powder.

[0116] Furthermore, the silver powder obtained in Example 4 was subjected to the same pulverization treatment as in Example 1. The measurement results and the like of the silver powder of Example 4 are shown in Table 3. In addition, the thermomechanical analysis curve diagrams of the silver powder of Example 4 are shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 8.

[0117] (Example 5) A 0.070 mol / L silver nitrate aqueous solution was introduced into pipe 2 (inner diameter 20 mm) at a liquid temperature of 50 °C at a flow rate of 23.35 L / min. A 0.016 mol / L sodium carbonate aqueous solution was introduced from the pH adjuster supply pipe 7 (inner diameter 6 mm) as a coaxial double pipe at a flow rate of 2.13 L / min to adjust the pH. 3.773 mol / L ammonia water as a complexing agent was introduced from the complexing agent supply pipe 6 (inner diameter 6 mm) as a coaxial double pipe at a flow rate of 2.33 L / min to generate a silver ammonia complex in pipe 2. From the upstream of the surface treatment agent supply pipe 5 (inner diameter 6 mm) of the self-reducing agent adding member 10, a surface treatment agent with a stearic acid concentration of 0.08% by mass (Selosol 920 (manufactured by Chukyo Yushi Co., Ltd., containing 15.5 wt% stearic acid)) was introduced at a flow rate of 2.19 L / min. The amount of the silver nitrate aqueous solution was such that the silver concentration in the total liquid volume after adding the pH adjuster, complexing agent, reducing agent, and surface treatment agent became 0.050 mol / L. An aqueous solution of carbohydrazide with a concentration of 0.240 mol / L as a reducing agent was introduced at a flow rate of 2.55 L / min around the entire circumference of the slit portion 12 (slit width 0.44 mm, inner diameter of the pipe 20.6 mm) of the self-reducing agent adding member 10 to precipitate silver powder. The flow rate of the reducing agent entering from the slit portion with a slit width of 0.44 mm was 1.49 m / s, the flow rate of the silver ammonia complex immediately before adding the reducing agent at the position where the inner diameter of the pipe 2 was 20.6 mm at the position where the reducing agent entered was 1.50 m / s, and the ratio of the flow rate of the complex to the flow rate of the reducing agent (flow rate of the complex / flow rate of the reducing agent) was 1.01. The operation time of the silver powder manufacturing apparatus (the time from the start of introducing the reducing agent into the silver ammonia complex until the stop after the flow of the silver ammonia complex into which the surface treatment agent was introduced became stable) was set to 83 seconds. Furthermore, the slurry generated before the flow of the silver ammonia complex into which the surface treatment agent was introduced became stable was received by another container and not supplied to the steps after solid-liquid separation. In the above, it was 0.5 seconds from the inlet of the silver nitrate aqueous solution flow path to the sodium carbonate aqueous solution addition position, 0.5 seconds from the sodium carbonate aqueous solution addition position to the ammonia water addition position, 2.12 seconds (2.1 m) from the ammonia water addition position to the carbohydrazide aqueous solution addition position, 0.12 seconds from the surface treatment agent addition position to the carbohydrazide aqueous solution addition position, and the temperature of the silver ammonia complex aqueous solution immediately before the carbohydrazide aqueous solution addition position was 46.5°C.

[0118] The slurry containing silver powder was discharged from the pipe 2. The time from the carbohydrazide aqueous solution addition position to the discharge was about 2 seconds. The slurry containing silver powder after the reduction reaction was stabilized was recovered, and the solid matter obtained by solid-liquid separation was washed with pure water to remove the impurities in the solid matter. The end point of this washing could be judged based on the conductivity of the water after washing, and the washing was carried out until the conductivity became 0.5 mS / m or less, and then dried to obtain 0.24 kg of silver powder.

[0119] Furthermore, the silver powder obtained in Example 5 was subjected to the same pulverization treatment as in Example 1. The measurement results of the silver powder of Example 5 and the like are shown in Table 3. In addition, the graphs of the thermomechanical analysis of the silver powder of Example 5 are shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 9.

[0120] (Example 6) The concentration of ammonia water as a complexing agent was set to 3.144 mol / L, and the operation time was set to 85 seconds. Except for this, the silver powder of Example 6 was obtained in the same manner as in Example 5. The obtained silver powder was 0.25 kg. Furthermore, the silver powder obtained in Example 6 was subjected to the same pulverization treatment as in Example 1. The measurement results of the silver powder of Example 6 and the like are shown in Table 3. In addition, the graphs of the thermomechanical analysis of the silver powder of Example 6 are shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 10.

[0121] (Example 7) The concentration of ammonia water as a complexing agent was set to 3.041 mol / L, and the operation time was set to 84 seconds. Except for this, the silver powder of Example 7 was obtained in the same manner as in Example 5. The obtained silver powder was 0.25 kg. Furthermore, the silver powder obtained in Example 7 was subjected to the same pulverization treatment as in Example 1. The measurement results of the silver powder of Example 7 and the like are shown in Table 3. In addition, the graphs of the thermomechanical analysis of the silver powder of Example 7 are shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 11.

[0122] (Example 8) The concentration of ammonia water as a complexing agent was set to 2.728 mol / L, and the operation time was set to 84 seconds. Except for this, the silver powder of Example 8 was obtained in the same manner as in Example 5. The obtained silver powder was 0.25 kg. Furthermore, the silver powder obtained in Example 8 was subjected to the same pulverization treatment as in Example 1. The measurement results of the silver powder of Example 8 and the like are shown in Table 3. In addition, the graphs of the thermomechanical analysis of the silver powder of Example 8 are shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 12.

[0123] (Comparative Example 1) To an aqueous silver nitrate solution containing 40.99 g (0.38 mol) of silver and having a mass of 3233.4 g, 124.65 g of industrial ammonia water with a concentration of 28 mass% (equivalent to 5.4 molar equivalents of ammonia relative to 1 mol of silver) was added to obtain an aqueous solution of a silver ammonia complex. To the aqueous solution of the silver ammonia complex, 2.28 g of an aqueous sodium hydroxide solution with a concentration of 20 mass% was added. After adjusting the liquid temperature to 25 °C, while stirring, 111.17 g of an aqueous hydrazine solution with a concentration of 7.3 mass% was added to obtain a slurry containing silver particles. Further, 12.69 g of a 1.55 mass% stearic acid emulsion was added to the obtained slurry containing silver particles and stirred. Then, the stirring was stopped to allow the silver particles to settle, and the liquid after the silver particles had settled was filtered, washed with water until the conductivity of the liquid after passing water became 0.5 mS / m or less, and dried under vacuum at 73 °C.

[0124] For the silver powder obtained by repeating the silver powder production three times, using a sample mill (manufactured by Kyoritsu Riko Co., Ltd., SK-M10), 120 g of silver powder was loaded and disintegrated twice within 90 seconds to obtain the silver powder of Comparative Example 1.

[0125] The measurement results and the like of the silver powder of Comparative Example 1 are shown in Table 3. In addition, the thermomechanical analysis curve of the silver powder of Comparative Example 1 is shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 13.

[0126] (Comparative Example 2) To an aqueous silver nitrate solution containing 45.32 g (0.42 mol) of silver and having a mass of 3374.7 g, 3.3 g of a 60 mass% nitric acid aqueous solution was added, and then 76.5 g of industrial ammonia water with a concentration of 28 mass% (equivalent to 3 molar equivalents of ammonia relative to 1 mol of silver) was added to obtain an aqueous solution of a silver ammonia complex. The liquid temperature of the aqueous solution of the silver ammonia complex was adjusted to 35 °C. Then, while stirring, 20.57 g of a 1.1 mass% aqueous sodium benzotriazole solution as an azole (0.5 mass% of sodium benzotriazole was added relative to silver) was added to obtain a first liquid. Then, 142.7 g of an aqueous hydrazine hydrate solution with a concentration of 5.6 mass% was added to the first liquid as a reducing agent to obtain a slurry containing silver fine particles as a second liquid. Further, 17.54 g of a 1.55 mass% stearic acid emulsion was added relative to the second liquid and stirred. Then, the stirring was stopped to allow the silver particles to settle, and the liquid after the silver particles had settled was filtered, washed with water until the conductivity of the liquid after passing water became 0.5 mS / m or less, and dried under vacuum at 73 °C.

[0127] For the silver powder obtained by repeating the silver powder manufacturing process three times, 120 g of silver powder was loaded into a sample mill (manufactured by Kyoryoku Riko Co., Ltd., SK-M10) and disintegrated twice within 90 seconds to obtain the silver powder of Comparative Example 2.

[0128] The measurement results and the like of the silver powder of Comparative Example 2 are shown in Table 3. In addition, the graphs of the thermomechanical analysis of the silver powder of Comparative Example 1 are shown in FIGS. 3 and 4. The SEM photograph (20,000 times) is shown in FIG. 14.

[0129] Tables 1 and 2 show the manufacturing conditions in Examples 1 to 8 and Comparative Examples 1 and 2.

[0130] [Table 1] Manufacturing method Silver nitrate aqueous solution (Silver-containing solution) pH adjuster Ammonia water (Complexing agent) Stearic acid (Surface treatment agent) Reducing agent Concentration [mol / L] Flow rate [L / min] Type Concentration [mol / L] Flow rate [L / min] Concentration [mol / L] Flow rate [L / min] Concentration [wt%] Flow rate [L / min] Type Concentration [mol / L] Flow rate [L / min] Example 1 Continuous type 0.160 23.35 Nitric acid 0.024 2.13 4.500 2.33 0.0155 2.19 Hydrazine 0.500 2.55 2 Continuous 0.153 23.35 Nitric acid 0.008 3.15 4.919 2.33 0.0155 2.19 Hydrazine 0.478 2.55 3 Continuous 0.160 23.35 Nitric acid 0.024 2.13 4.436 2.33 0.0155 2.19 Hydrazine 0.500 2.55 4 Continuous 0.160 27.24 Nitric acid 0.024 2.49 4.436 2.72 0.0155 2.55 Hydrazine 0.500 2.97 5 Continuous 0.070 23.35 Sodium carbonate 0.016 2.13 3.773 2.33 0.0804 2.19 Carbohydrazide 0.240 2.55 6 Continuous 0.070 23.35 Sodium carbonate 0.016 2.13 3.144 2.33 0.0804 2.19 Carbohydrazide 0.240 2.55 7 Continuous 0.070 23.35 Sodium carbonate 0.016 2.13 3.041 2.33 0.0804 2.19 Carbohydrazide 0.240 2.55 8 Continuous 0.070 23.35 Sodium carbonate 0.016 2.13 2.728 2.33 0.0804 2.19 Carbohydrazide 0.240 2.55 Comparative Example 1 Batch - - - - - - - - - - - - 2 Batch - - - - - - - - - - - -

[0131] [Table 2] Manufacturing Method Silver Concentration in the Total Liquid Volume after Adding pH Adjusting Agent, Complexing Agent, Reducing Agent, and Surface Treatment Agent [mol / L] Complexing Agent Flow Rate [m / s] Reducing Agent Flow Rate [m / s] Complexing Agent Flow Rate / Reducing Agent Flow Rate Operating Time [seconds] The Obtained Silver Powder [kg] Example 1 Continuous 0.115 1.50 1.49 1.01 616 3.8 2 Continuous 0.106 1.55 1.49 1.04 115 0.55 3 Continuous 0.115 1.50 1.49 1.01 617 3.6 4 Continuous 0.115 1.75 1.74 1.01 568 3.2 5 Continuous 0.050 1.50 1.49 1.01 83 0.24 6 Continuous 0.050 1.50 1.49 1.01 85 0.25 7 Continuous 0.050 1.50 1.49 1.01 84 0.25 8 Continuous 0.050 1.50 1.49 1.01 84 0.25 Comparative Example 1 Batch - - - - - - 2 Batch - - - - - -

[0132] [Table 3] BET Specific surface area [m2 / g] True density [g / cm3] D BET [μm] D SEM [μm] Particle size distribution D50 / D BET Ig-loss [%] Content of surface treatment agent [mass%] Crystallite diameter Thermal shrinkage rate [%] D10 [μm] D50 [μm] D90 [μm] Dx [nm] 150 °C 200 °C Example 1 1.16 9.99 0.52 0.45 0.22 0.57 0.99 1.10 0.62 0.480 38 0.89 1.32 2 1.30 10.02 0.46 0.41 0.22 0.54 0.92 1.17 0.58 0.450 34 1.03 1.81 3 1.12 10.01 0.54 0.51 0.24 0.63 1.13 1.18 0.58 0.470 35 0.68 1.02 4 1.17 9.97 0.51 0.59 0.26 0.62 1.04 1.21 0.63 0.520 35 0.74 1.11 5 1.72 9.84 0.34 0.23 0.13 0.31 0.65 0.91 0.93 0.710 30 1.07 2.23 6 2.02 9.81 0.29 0.19 0.12 0.27 0.59 0.93 0.94 0.730 29 1.21 2.38 7 1.81 9.80 0.32 0.21 0.12 0.27 0.57 0.86 1.01 0.810 27 1.36 2.48 8 2.49 9.73 0.23 0.18 0.12 0.26 0.60 1.12 1.03 0.880 28 1.06 2.67 Comparative Example 1 1.04 10.07 0.57 0.51 0.313 0.83 1.50 1.45 0.52 0.440 45 0.50 0.88 2 1.78 9.93 0.34 0.40 0.153 0.47 0.93 1.39 0.71 0.540 38 0.54 0.91

[0133] (Evaluation of Paste) <Wire Breakage Rate and Volume Resistivity> First, a resin-cured conductive paste was prepared using the silver powders obtained in Example 1, Example 5, Example 7, Comparative Example 1, and Comparative Example 2. Specifically, the silver powder as the evaluation object was mixed with AG-5-54F (D50: 2.9 μm, BET: 0.21 m2 / g, TAP: 6.1 g / cm3) manufactured by DOWA-ELECTRONICS, which was used as a filler together with the silver powder as the evaluation object, in a mass ratio of 5:5 to obtain a mixed silver powder. Then, 91.92 parts by mass of the mixed silver powder, 3.87 parts by mass of a first epoxy resin (EP4901E manufactured by ADEKA), 0.97 parts by mass of a second epoxy resin (JER1009 manufactured by Mitsubishi Chemical), 0.24 parts by mass of a curing agent (boron trifluoride monoethylamine complex manufactured by Wako Pure Chemical Industries), and 3.00 parts by mass of a solvent (BCA: butoxyethoxyethyl acetate) were taken and put into a non-propeller self-rotating and revolving stirring and defoaming device (VMX-N360 manufactured by EME Co., Ltd.). After stirring and mixing at 1200 rpm for 30 seconds, a three-roll mill (80S manufactured by EXAKT) was used to knead the mixture by passing it through the nip from 100 μm to 20 μm to obtain a resin-cured conductive paste before viscosity adjustment. Further, a required amount of BCA was added to the resin-cured conductive paste before viscosity adjustment to obtain a conductive paste after viscosity adjustment with a viscosity adjusted to 300 Pa·s. The viscosity adjustment of the resin-cured conductive paste was carried out by successively adding a small amount of BCA to the resin-cured conductive paste before viscosity adjustment and measuring the viscosity successively. Using the obtained resin-cured conductive paste, 10 resin-cured conductive pastes with wire widths (designed widths) of 15 μm, 17 μm, 19 μm, and 21 μm were respectively produced by a screen printing plate (#480 mesh) as the evaluation objects. The squeegee speed during printing was set to 350 mm / second, and printing was carried out twice. Subsequently, it was dried at 150°C for 10 minutes by using an air circulation dryer, and then heated at 200°C for 30 minutes to be cured to form a linear conductive film (wiring). The disconnection rate and volume resistivity of the obtained conductive film were measured. Bring the measurement terminals into contact with both ends of the conductive film, and measure the line resistance (Ω) using a digital multimeter (manufactured by ADC Co., Ltd.). The value of the line resistance is set as the average value of 20 line patterns (printed twice × 10 patterns) (excluding those regarded as open circuits as described later). Furthermore, the open circuit rate is defined as the ratio of the number of line patterns with open circuits observed among all 20 line patterns when a very high value of 100 kΩ or more is regarded as an open circuit during the line resistance measurement. In addition, use a laser microscope (manufactured by KEYENCE Corporation, VK-X1000) to measure the shape in the line width direction at 10 locations (printed twice × 5 locations), and calculate the average value of the cross-sectional area of the wiring. Based on the measured value of the line resistance and the cross-sectional area, calculate the volume resistivity represented by the following formula (4). Volume resistivity [Ω·cm] = Line resistance [Ω] × Cross-sectional area [cm²] ÷ Line length [cm]…(4) Calculate the volume resistivity (Ω·cm) for line widths (designed widths) of 15 μm and 19 μm. Furthermore, in the measurement of the line resistance, the line length (designed length) is set to 150 mm.

[0134] [Table 4] Volume resistivity [Ω·cm] Open circuit rate [%] Line width 15 μm 19 μm 15 μm 17 μm 19 μm 21 μm Example 1 7.7 7.8 0 10 0 0 Example 5 7.3 7.2 - 0 0 0 Example 7 7.1 7.4 0 0 0 0 Comparative Example 1 8.4 8.0 20 25 0 0 Comparative Example 2 8.1 8.7 0 0 10 0

[0135] As is clear from Table 4, it can be seen that: for the silver powder of this example where the cumulative 50% diameter D50 based on the volume standard by the laser diffraction method is 0.1 μm or more and 1.0 μm or less, the ratio of D50 to DBET is 1.3 or less, and the shrinkage rate at 200°C in the thermomechanical analysis is 1% or more, when calcined at a low temperature of 200°C, the volume resistivity and disconnection rate in the fine wire are low, and thus excellent volume resistivity and fine wire printability can be imparted to the conductive paste. [Industrial Applicability]

[0136] According to the present invention, there can be provided a silver powder, a method for manufacturing the silver powder, a silver powder manufacturing apparatus capable of manufacturing such silver powder, and a resin-cured conductive paste that have excellent volume resistivity and fine wire printability even when calcined at a low temperature, in the case of forming a conductive paste.

[0137] 1: Silver powder manufacturing apparatus 2: Tube 4a: Reducing agent supply tube 4b: Reducing agent supply tube 5: Surface treatment agent supply tube 6: Complexing agent supply tube 7: pH adjuster supply tube 10: Reducing agent addition member 11: Opening 12: Slit portion 13: Gap

Claims

1. A silver powder having a cumulative 50% diameter D50 based on laser diffraction volume reference of 0.1 μm or more and 1.0 μm or less, wherein the ratio of D50 to Buerter diameter DBET is 0.8 or more and 1.3 or less, and a shrinkage rate of 1% or more and 5.0% or less at 200°C in thermomechanical analysis.

2. The silver powder as described in claim 1, wherein, The shrinkage rate at 150°C in thermomechanical analysis is over 0.6%.

3. The silver powder as described in claim 1, wherein, The specific surface area of ​​the Buerter is above 0.90 m2 / g and below 2.50 m2 / g.

4. The silver powder as described in any one of claims 1 to 3, used in a resin-cured conductive paste.

5. A resin-cured conductive paste comprising silver powder as described in any one of claims 1 to 3.

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