Fine silver particle dispersion, fine silver particles, and method for producing same

Abstract

Provided are a fine silver particle dispersion which exhibits low temperature sinterability and in which fine silver particles are uniformly dispersed in a variety of solvents (and especially highly polar solvents); fine silver particles that exhibit low temperature sinterability and excellent dispersion stability in a variety of solvents (and especially highly polar solvents); a dispersion obtained using the fine silver particles; and a method for producing same. The fine silver particle dispersion is characterized by containing fine silver particles, a short chain amine having 5 or fewer carbon atoms, and a highly polar solvent and in that the partition coefficient (log P) of the short chain amine is 1.0 to 1.4.

Claims

1. A fine silver particle dispersion, which comprises fine silver particles, a short chain amine having 5 or less carbon atoms and a highly polar solvent, wherein a partition coefficient log P of the short chain amine is 1.0 to 1.4 and wherein the short amine is an alkoxyamine.

2. The fine silver particle dispersion according to claim 1, which further comprises a dispersant having an acid value for dispersing the fine silver particles.

3. The fine silver particle dispersion according to claim 1, which further comprises a protective dispersant having an acid value.

4. The fine silver particle dispersion according to claim 1, wherein the highly polar solvent is an alcohol having 1 to 6 carbon atoms.

5. The fine silver particle dispersion according to claim 1, wherein the highly polar solvent is methanol, ethanol, isopropyl alcohol or n-propyl alcohol.

6. The fine silver particle dispersion according to claim 2, wherein the acid value of the dispersant is 5 to 200.

7. The fine silver particle dispersion according to claim 2, wherein the dispersant has a functional group derived from a phosphoric acid.

8. The fine silver particle dispersion according to claim 3, wherein the acid value of the protective dispersant is 5 to 200.

9. The fine silver particle dispersion according to claim 3, wherein the protective dispersant has a functional group derived from a phosphoric acid.

10. A composition for bonding, which comprises the fine silver particle dispersion according to claim 1.

11. A fine silver particle, which comprises an alkoxyamine having 5 or less carbon atoms which is adhered to at least a part of the surface of the particle, and a partition coefficient log P of the alkoxyamine is 1.0 to 1.4.

12. A composition for bonding, which comprises the fine silver particle according to claim 11.

13. A method for producing a fine silver particle, which comprises a first step for preparing a mixed liquid of a silver compound which is decomposed by reduction to produce a metal silver, and a short chain amine having a partition coefficient log P of 1.0 to 1.4, a second step for reducing the silver compound in the mixed liquid to produce a fine silver particle where a short chain amine having 5 or less carbon atoms which is adhered to at least a part of the surface of the particle, and a third step for adding and mixing a dispersant having an acid value for dispersing the fine silver particles.

14. The method for producing a fine silver particle according to claim 13, wherein the short chain amine is added in an amount of 2 mol or more relative to 1 mol of the metal silver in the first step.

Description

EXAMPLE

Example 1

(1) 200 ml of toluene (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) and 11 g of butylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 1.0) were mixed and sufficiently stirred with a magnetic stirrer (molar ratio of the added amine being 2.5 to the silver). While stirring, 10 g of silver nitrate (special grade chemicals manufactured by Toyo Chemical Industrial Co., Ltd.) was added into this mixture, and after the silver nitrate was dissolved, 10 g of DISPERBYK-2090 and 10 g of hexanoic acid (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) were added.

(2) A 0.02 g/ml of sodium borohydride solution prepared by adding 1 g of sodium borohydride (manufactured by Wako Pure Chemical Industries, Ltd.) into 50 ml of ion-exchanged water was instilled into this mixture, and a liquid containing silver particles was obtained. After stirring for one hour, 200 ml of methanol (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the silver particles were agglomerated and precipitated. In addition, after the silver particles were completely precipitated with centrifugal separation, toluene and methanol, which are supernatants, were removed and excess organic substances were removed, and approximately 6 g of the silver particles 1 were obtained. To the obtained fine silver particles, the following dispersion stability, reducibility, volume resistivity, and organic component measurement were evaluated, and the obtained results are shown in Table 1. The dispersing medium was 2-pentanol.

(3) [Evaluation Tests]

(4) (1) Dispersing Property

(5) The fine silver particles 1 obtained as described above was dispersed in an appropriate solvent and was set stationary in a container, and one day later at room temperature, dispersing property of the dispersion liquid was evaluated by visually observing whether or not there was any precipitation and conditions of the supernatants. A case when any precipitation was hardly confirmed at the bottom of the container was evaluated as ; a case when a small amount precipitation was confirmed was evaluated as ; and a case when there was obviously a difference between upper side and a bottom side of the container and precipitation was clearly confirmed was evaluated as x.

(6) (2) Reducibility

(7) The dispersion as described above was diluted 100-fold into a dispersion medium and the resulting state was visually evaluated. A case when particles were dispersed was evaluated as ; a case when agglomeration or silver mirror was partially observed was evaluated as ; and a case when agglomeration and precipitation was generated was evaluated as x.

(8) (3) Volume Resistivity

(9) A coating was formed by applying the dispersion obtained as mentioned above onto a glass slide with a brush; the silver colloidal dispersion liquid 1 was sintered by heating and baking under conditions at 120 C. for 30 minutes in a gear oven; and an conductive coating was formed. Volume resistivity of this coating was measured using a direct-current precision measuring instrument Portable Precision Double Bridge 2769 manufactured by Yokogawa Meters & Instruments Corporation. Specifically, based upon a formula below, volume resistivity was converted from in-measuring terminal distance and thickness of an conductive coating. A case when the volume resistivity was 20 .Math.cm or less was evaluated as and another case when it exceeded 20 .Math.cm was evaluated as x.
(Volume resistivity v)=(Resistance value R)(Coating width W)(Coating thickness t)/(Distance between terminals L)Equation:
(4) Organic Component Measurement

(10) Content of the organic component contained in the dispersion obtained as mentioned above was measured using a thermogravimetric method. Specifically, solid content of the dispersion was heated at 10 C./min of rate of temperature increase, and the content of the organic component was identified as a weight reduction at room temperature to 500 C.

Example 2

(11) 200 ml of toluene (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) and 13.4 g of 3-methoxypropylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 0.5) were mixed and sufficiently stirred with a magnetic stirrer (molar ratio of the added amine being 2.5 to the silver). While stirring, 10 g of silver nitrate (special grade chemicals manufactured by Toyo Chemical Industrial Co., Ltd.) was added into this mixture, and after the silver nitrate was dissolved, 10 g of DISPERBYK-111 and 10 g of hexanoic acid (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) were added. A 0.02 g/ml of sodium borohydride solution prepared by adding 1 g of sodium borohydride (manufactured by Wako Pure Chemical Industries, Ltd.) into 50 ml of ion-exchanged water was instilled into this mixture, and a liquid containing silver particles was obtained. After stirring for one hour, 200 ml of methanol (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the silver particles were agglomerated and precipitated. In addition, after the silver particles were completely precipitated with centrifugal separation, toluene and methanol, which are supernatants, were removed and excess organic substances were removed, and approximately 6 g of the silver particles 2 were obtained. The dispersing medium was isobutanol. The obtained fine silver particles 2 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 3

(12) 8.9 g of 3-methoxypropylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 0.5) and 0.3 g of DISPERBYK-111 of a polymer dispersant were mixed and sufficiently stirred with a magnetic stirrer to prepare an amine mixture (molar ratio of the added amine being 10 to the silver). Next, 3.0 g of silver oxalate was added while stirring. After adding the silver oxalate, the silver oxalate was converted to a viscous white substance by continuing the stirring at room temperature, the stirring was finished at the time when the change was terminated in view of appearance (first step).

(13) The thus obtained mixture was transferred to an oil bath, and stirred with heating at 120 C. Just after the stirring, a reaction started with generation of carbon dioxide, and thereafter, the stirring was continued until the generation of the carbon dioxide was terminated to obtain a suspension where the fine silver particles were suspended in the amine mixture (second step).

(14) Next, in order to displace the dispersing medium of the suspension, after adding 10 mL of a mixed solvent of methanol/water and stirring, the fine silver particles were separated by precipitating with a centrifugal treatment, and 10 mL of a mixed solvent of methanol/water was added again, and then subjected to stirring and separating with the centrifugal treatment to obtain fine silver particle 3. The dispersing medium was isobutanol. The obtained fine silver particles 3 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 4

(15) Fine silver particles 4 were obtained in the same manner as in Example 3 except that 0.4 g of DISPERBYK-190 was introduced instead of DISPERBYK-111. The dispersing medium was ethanol. The obtained fine silver particles 4 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 5

(16) Fine silver particles 5 were obtained in the same manner as in Example 3 except that 0.3 g of DISPERBYK-102 was introduced instead of DISPERBYK-111. The dispersing medium was ethanol. The obtained fine silver particles 5 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 6

(17) Fine silver particles 6 were obtained in the same manner as in Example 4 except that 7.3 g of butylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 1.0) (molar ratio of the added amine being 10 to the silver) instead of 3-methoxypropylamine. The dispersing medium was hexanol. The obtained fine silver particles 6 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 7

(18) Fine silver particles 7 were obtained in the same manner as in Example 4 except that 7.5 g of 2-methoxyethylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 3, log P: 0.9) (molar ratio of the added amine being 10 to the silver) instead of 3-methoxypropylamine. The dispersing medium was ethanol. The obtained fine silver particles 7 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 8

(19) 3.6 g of butylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 1.0), 4.5 g of 3-methoxypropylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 0.5) and 0.25 g of DISPERBYK-102 of a polymer dispersant were mixed and sufficiently stirred with a magnetic stirrer to prepare an amine mixture (molar ratio of the added amine being 10 to the silver). Next, 3.0 g of silver oxalate was added while stirring. After adding the silver oxalate, the silver oxalate was converted to a viscous white substance by continuing the stirring at room temperature, the stirring was finished at the time when the change was terminated in view of appearance (first step). In the second step and the later, the same procedures as in Example 3 were repeated to obtain fine silver particles 8. The dispersing medium was ethanol. The obtained fine silver particles 8 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 9

(20) Fine silver particles 9 were obtained in the same manner as in Example 7 except that 0.3 g of TEGO Dispers655 (manufactured by Evonik Co., Ltd.) was used instead of DISPERBYK-102. The dispersing medium was ethanol. The obtained fine silver particles 9 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Example 10

(21) Fine silver particles 10 were obtained in the same manner as in Example 7 except that 0.3 g of Dispalon DA-375 (manufactured by Kusumoto Chemicals, Ltd.) was used instead of DISPERBYK-102. The dispersing medium was isobutanol. The obtained fine silver particles 10 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Example 11

(22) Fine silver particles 11 were obtained in the same manner as in Example 4 except that 7.3 g of butylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 1.0) (molar ratio of the added amine being 10 to the silver) instead of 3-methoxypropylamine. The dispersing medium was ethanol. The obtained fine silver particles 11 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Example 12

(23) 1.1 g of 2-methoxyethylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 3, log P: 0.9) and 0.3 g of DISPERBYK-102 of a polymer dispersant were mixed and sufficiently stirred with a magnetic stirrer to prepare an amine mixture (molar ratio of the added amine being 1.5 to the silver). Next, 3.0 g of silver oxalate was added while stirring. After adding the silver oxalate, the silver oxalate was converted to a viscous white substance by continuing the stirring at room temperature, the stirring was finished at the time when the change was terminated in view of appearance (first step). In the second step and the later, the same procedures as in Example 3 were repeated to obtain fine silver particles 12. The dispersing medium was ethanol. The obtained fine silver particles 12 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Example 13

(24) 2.7 g of 3-methoxypropylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 0.5) and 0.3 g of DISPERBYK-102 of a polymer dispersant were mixed and sufficiently stirred with a magnetic stirrer to prepare an amine mixture (molar ratio of the added amine being 3 to the silver). Next, 3.0 g of silver oxalate was added while stirring. After adding the silver oxalate, the silver oxalate was converted to a viscous white substance by continuing the stirring at room temperature, the stirring was finished at the time when the change was terminated in view of appearance (first step). In the second step and the later, the same procedures as in Example 3 were repeated to obtain fine silver particles 13. The dispersing medium was ethanol. The obtained fine silver particles 13 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Example 14

(25) 200 ml of toluene (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) and 11 g of butylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 1.0) were mixed and sufficiently stirred with a magnetic stirrer (molar ratio of the added amine being 2.5 to the silver). While stirring, 10 g of silver nitrate (special grade chemicals manufactured by Toyo Chemical Industrial Co., Ltd.) was added into this mixture, and after the silver nitrate was dissolved, 10 g of DISPERBYK-2090 and 10 g of hexanoic acid (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) were added. Thereto a 0.02 g/ml of sodium borohydride solution prepared by adding 1 g of sodium borohydride (manufactured by Wako Pure Chemical Industries, Ltd.) into 50 ml of ion-exchanged water was instilled into this mixture, and a liquid containing fine silver particles was obtained. After stirring for one hour, 200 ml of methanol (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the silver particles were agglomerated and precipitated. In addition, after the fine silver particles were completely precipitated with centrifugal separation, toluene and methanol, which are supernatants, were removed and excess organic substances were removed, and added 9.8 g of 2-pentanol containing 0.2 g of SOLSPERSE41000 (manufactured by The Lubrizol Corporation) to obtain a fine silver particle dispersion 1. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Example 15

(26) 200 ml of toluene (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) and 13.4 g of 3-methoxypropylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 0.5) were mixed and sufficiently stirred with a magnetic stirrer (molar ratio of the added amine being 2.5 to the silver). While stirring, 10 g of silver nitrate (special grade chemicals manufactured by Toyo Chemical Industrial Co., Ltd.) was added into this mixture, and after the silver nitrate was dissolved, 10 g of DISPERBYK-111 and 10 g of hexanoic acid (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) were added. Thereto a 0.02 g/ml of sodium borohydride solution prepared by adding 1 g of sodium borohydride (manufactured by Wako Pure Chemical Industries, Ltd.) into 50 ml of ion-exchanged water was instilled into this mixture, and a liquid containing fine silver particles was obtained. After stirring for one hour, 200 ml of methanol (special grade chemicals manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the silver particles were agglomerated and precipitated. In addition, after the fine silver particles were completely precipitated with centrifugal separation, toluene and methanol, which are supernatants, were removed and excess organic substances were removed, and added 9.5 g of isobutanol containing 0.5 g of SOLSPERSE190 (manufactured by The Lubrizol Corporation) to obtain a fine silver particle dispersion 2. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Example 16

(27) 8.9 g of 3-methoxypropylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 4, log P: 0.5) and 0.3 g of DISPERBYK-111 of a polymer dispersant were mixed and sufficiently stirred with a magnetic stirrer to prepare an amine mixture (molar ratio of the added amine being 5 to the silver). Next, 3.0 g of silver oxalate was added while stirring. After adding the silver oxalate, the silver oxalate was converted to a viscous white substance by continuing the stirring at room temperature, the stirring was finished at the time when the change was terminated in view of appearance (first step).

(28) The thus obtained mixture was transferred to an oil bath, and stirred with heating at 120 C. Just after the stirring, a reaction started with generation of carbon dioxide, and thereafter, the stirring was continued until the generation of the carbon dioxide was terminated to obtain a suspension where the fine silver particles were suspended in the amine mixture (second step).

(29) Next, in order to displace the dispersing medium of the suspension, after adding 10 mL of a mixed solvent of methanol/water and stirring, the fine silver particles were separated by precipitating with a centrifugal treatment, and 10 mL of a mixed solvent of methanol/water was added again, and after subjected to stirring and separating with the centrifugal treatment, added 3.0 g of isobutanol containing 0.06 g of SOLSPERSE41000 (manufactured by The Lubrizol Corporation) to obtain a fine silver particle dispersion 3. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Example 17

(30) A fine silver particle dispersion 4 was obtained in the same manner as in Example 16 except that 0.3 g of DISPERBYK-102 was introduced instead of DISPERBYK-111. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Example 18

(31) A fine silver particle dispersion 5 was obtained in the same manner as in Example 17 except that 7.5 g of 2-methoxyethylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 3, log P: 0.9) (molar ratio of the added amine being 5 to the silver) instead of 3-methoxypropylamine, 0.3 g of TEGO Dispers655 (manufactured by Evonik Co., Ltd.) was used instead of DISPERBYK-102, the amount of SOLSPERSE41000 was 0.08 g, and methanol was used instead of ethanol. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Com. Example 1

(32) Fine silver particles 14 were obtained in the same manner as in Example 6 except that 7.4 g of 1,3-propanediamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 3, log P: 1.4) (molar ratio of the added amine being 10 to the silver) instead of 3-methoxypropylamine. The dispersing medium was isobutanol. The obtained fine silver particles 14 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Com. Example 2

(33) Fine silver particles 15 were obtained in the same manner as in Example 8 except that 5.5 g of pentylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 5, log P: 1.5) (molar ratio of the added amine being 10 to the silver) instead of butylamine. The dispersing medium was ethanol. The obtained fine silver particles 15 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Com. Example 3

(34) Fine silver particles 16 were obtained in the same manner as in Example 11 except that 10.1 g of hexylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 6, log P: 2.1) (molar ratio of the added amine being 10 to the silver) instead of 3-methoxypropylamine. The dispersing medium was ethanol. The obtained fine silver particles 16 were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2.

Com. Example 4

(35) A comparative fine silver particle dispersion 1 was obtained in the same manner as in Example 17 except that 7.4 g of 1,3-propanediamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 3, log P: 1.4) (molar ratio of the added amine being 5 to the silver) instead of 3-methoxypropylamine. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Com. Example 5

(36) A comparative fine silver particle dispersion 2 was obtained in the same manner as in Example 14 except that 13.0 g of pentylamine (first class grade chemicals manufactured by Wako Pure Chemical Industries, Ltd., number of carbon atoms: 5, log P: 1.5) (molar ratio of the added amine being 2.5 to the silver) instead of butylamine. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Com. Example 6

(37) A comparative fine silver particle dispersion 3 was obtained in the same manner as in Example 17 except that SOLSPERSE41000 was not added. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Com. Example 7

(38) A comparative fine silver particle dispersion 4 was obtained in the same manner as in Example 17 except that SOLSPERSE41000 was added at the synthesis of the fine silver particles. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Com. Example 8

(39) A comparative fine silver particle dispersion 5 was obtained in the same manner as in Example 16 except that SOLSPERSE41000 was not added. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

Com. Example 9

(40) A comparative fine silver particle dispersion 6 was obtained in the same manner as in Example 16 except that SOLSPERSE41000 was added at the synthesis of the fine silver particles. The dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3.

(41) TABLE-US-00001 TABLE 1 Ex.1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Short Butylamine chain (logP 1.0) amine Pentylamine (logP 1.5) 1,3-Propanediamine (logP 1.4) 2-Methoxyethylamine (logP 0.9) 3-Methoxypropylamine (logP 0.5) Polymer DISPERBYK-102 dispersant DISPERBYK-190 DISPERBYK-2090 DISPERBYK-111 TEGO Dispers655 DISPARLON DA-375 Fine silver particle 1 2 3 4 5 6 7 8 Dispersing property Solvent 2- Iso- Iso- Eth- Eth- Hex- Eth- Eth- Pentanol butanol butanol anol anol anol anol anol Reducibility Volume resistivity 11 15 11 13 8 13 9 12 cm Weight Room temperature 5 5 4 3 3 3 3 3 loss to 200 C. (%) 200 to 500 C. 5 7 5 5 3 5 3 4 Total 10 12 9 8 6 8 6 7

(42) TABLE-US-00002 TABLE 2 Com. Com. Com. Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 1 Ex. 2 Ex. 3 Short Butylamine chain (logP 1.0) amine Pentylamine (logP 1.5) 1,3-Propanediamine (logP 1.4) 2-Methoxyethylamine (logP 0.9) 3-Methoxypropylamine (logP 0.5) Polymer DISPERBYK-102 dispersant DISPERBYK-190 DISPERBYK-2090 DISPERBYK-111 TEGO Dispers655 DISPARLON DA-375 Fine silver particle 9 10 11 12 13 14 15 16 Dispersing property x x x Solvent Eth- Iso- Ace- Eth- Eth- Iso- Eth- Eth- anol butanol tone anol anol butanol anol anal Reducibility x x x x Volume resistivity 9 17 19 20 18 Cannot Cannot Cannot cm evalu- evalu- evalu- ated ated ated Weight Room temperature 3 4 4 3 4 3 3 3 loss to 200 C. (%) 200 to 500 C. 3 5 4 4 4 4 4 5 Total 6 9 8 8 8 7 7 8

(43) TABLE-US-00003 TABLE 3 Example Comparative Example 14 15 16 17 18 4 5 6 7 8 9 Short Butylamine chain (logP 1.0) amine Pentylamine (logP 1.5) 1,3-Propanediamine (logP 1.4) 2-Methoxyethylamine (logP 0.9) 3-Methoxypropylamine (logP 0.5) Polymer DISPERBYK-2090 dispersant DISPERBYK-111 DISPERBYK-102 TEGO Dispers655 SOLSPERSE4100 Late SOLSPERSE4100 Addition DISPARLON DA-375 Solvent Methanol Ethanol Isobutanol 2-Pentanol Evaluation Dispersing property x x Oto Oto Oto Oto Reducibility x x (just after) Reducibility x x x x (1 week after stability) Volume resistivity 11 15 12 10 15 Cannot Cannot 8 12 11 18 @ 120 C. evaluate evaluate Weight Room 5 3 5 3 4 3 3 3 3 5 5 loss temperature (%) to 200 C. 200 to 500 C. 5 5 5 4 5 5 5 4 6 4 5 Total 10 8 10 7 9 8 8 7 9 9 10 Overall x x x x x x
[Evaluation of Various Dispersing Properties]

(44) The same evaluation of dispersing property as in Example 1 and a yield measurement were conducted by dispersing the fine silver particles 6 obtained in the same manner as in Example 5, and the results are shown in Table 4. The Yield is calculated by dividing the recovered amount of silver by the initial amount of silver.

(45) TABLE-US-00004 TABLE 4 Iso- propyl Used colloid Evaluation Hexane Toluene Acetone Hexanol alcohol Fine silver Dispersing particle 5 property Yield (%) 40 85 69 98 98

(46) From the results shown Table 1 and Table 4, it has been proved that, according to the present invention, good dispersing property can be obtained with respect to the high polar solvent. From Examples 12 to 13, it is more suitable that the short chain amine is added in an amount of 2 mol or more relative to 1 mol of the silver in the first step. Further, from the results shown in Table 2, it has been proved that the used of the partition coefficient log P is suitable within the scope of from 1.0 to 1.4. As shown in Comparative Example 1, when the log P is 1.0 or less, a dispersible particle cannot be prepared. As shown in Comparative Examples 2 and 3, when the amine having the log P of more than 1.4 is present in the system, the dispersing property to the high polar solvent is extremely lowered. These results show that in order to obtain the fine silver particle having a good dispersing property to the high polar solvent, the partition coefficient log P is 1.0 to 1.4. In the following Table 5, acid values and kinds of adsorbing group of the used dispersants are shown.

(47) TABLE-US-00005 TABLE 5 Effective Acid Amine component value value Adsorbing Dispersant (%) mgKOH/g mgKOH/g group DISPERBYK-102 99 102 Phosphoric acid DISPERBYK-190 40 10 Comb-type carboxylic acid DISPERBYK-2090 81 61 Star-type carboxylic acid DISPERBYK-111 95 129 Phosphoric acid TEGO Dispers655 99 190 Phosphoric acid DISPARLON 99 14 Phosphoric DA-375 acid

(48) From the results shown in Table 3, it has been found that the fine particle dispersion of the present invention is excellent in all evaluations of the dispersing property, the reducibility, the volume resistivity, and the weight loss. To the contrary, from Comparative Examples 4 and 5, if the log P is not within the determined range, the dispersion is inferior in the dispersing property and the reducibility to the solvent. Further, from the results of Comparative Example 6, even though the dispersing property and the reducibility (just after) are good, it has been found that the dispersion is inferior in the reducibility (1 week after stability) (namely, potentially lack in dispersing stability). Furthermore, according to Comparative Example 7, when the dispersant is added only at the synthesis of the fine silver particles, it has been found that the dispersion is inferior in the reducibility (1 week after stability).