WO2022137886A1 - Silver nano-wire production method - Google Patents
Silver nano-wire production method Download PDFInfo
- Publication number
- WO2022137886A1 WO2022137886A1 PCT/JP2021/041880 JP2021041880W WO2022137886A1 WO 2022137886 A1 WO2022137886 A1 WO 2022137886A1 JP 2021041880 W JP2021041880 W JP 2021041880W WO 2022137886 A1 WO2022137886 A1 WO 2022137886A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- reaction
- silver nanowires
- temperature
- silver
- cooling
- Prior art date
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- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims abstract description 145
- 239000002042 Silver nanowire Substances 0.000 title claims abstract description 131
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 34
- 238000006243 chemical reaction Methods 0.000 claims abstract description 118
- 238000001816 cooling Methods 0.000 claims abstract description 89
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 56
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 55
- 238000000034 method Methods 0.000 claims abstract description 27
- 229920005862 polyol Polymers 0.000 claims abstract description 21
- 150000003077 polyols Chemical class 0.000 claims abstract description 21
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 8
- 238000009835 boiling Methods 0.000 claims description 24
- 229910052751 metal Inorganic materials 0.000 claims description 24
- 239000002184 metal Substances 0.000 claims description 24
- 239000007788 liquid Substances 0.000 claims description 21
- 239000002904 solvent Substances 0.000 claims description 21
- 239000012295 chemical reaction liquid Substances 0.000 claims description 7
- 239000003507 refrigerant Substances 0.000 claims description 4
- 230000001629 suppression Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 72
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 34
- 239000010408 film Substances 0.000 description 16
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 15
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 14
- 239000003795 chemical substances by application Substances 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 13
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 12
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 12
- 229910052709 silver Inorganic materials 0.000 description 12
- 239000004332 silver Substances 0.000 description 12
- 238000003756 stirring Methods 0.000 description 11
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- -1 for example Substances 0.000 description 9
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- SOIFLUNRINLCBN-UHFFFAOYSA-N ammonium thiocyanate Chemical compound [NH4+].[S-]C#N SOIFLUNRINLCBN-UHFFFAOYSA-N 0.000 description 6
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- 239000002609 medium Substances 0.000 description 6
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- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- SJWFXCIHNDVPSH-UHFFFAOYSA-N octan-2-ol Chemical compound CCCCCCC(C)O SJWFXCIHNDVPSH-UHFFFAOYSA-N 0.000 description 2
- XCOHAFVJQZPUKF-UHFFFAOYSA-M octyltrimethylammonium bromide Chemical compound [Br-].CCCCCCCC[N+](C)(C)C XCOHAFVJQZPUKF-UHFFFAOYSA-M 0.000 description 2
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- NDVLTYZPCACLMA-UHFFFAOYSA-N silver oxide Chemical compound [O-2].[Ag+].[Ag+] NDVLTYZPCACLMA-UHFFFAOYSA-N 0.000 description 2
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Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/054—Nanosized particles
- B22F1/0547—Nanofibres or nanotubes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2301/00—Metallic composition of the powder or its coating
- B22F2301/25—Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
- B22F2301/255—Silver or gold
Definitions
- the present invention relates to a method for manufacturing silver nanowires.
- silver nanowires have been attracting attention as a raw material for highly transparent and highly conductive thin films that can replace the ITO (indium tin oxide) film used for transparent electrodes such as touch panels.
- Such silver nanowires are generally produced by a so-called polyol reduction method in which a silver compound is heated in the presence of a polyol such as polyvinylpyrrolidone and ethylene glycol (Patent Document 1, Non-Patent Document 1).
- High transparency is required for the transparent conductive film used for touch panels and the like.
- the so-called polyol reduction method used in the production of silver nanowires is generally performed under heating.
- the reaction is carried out at a high temperature of around 150 ° C., the reaction is completed relatively quickly (Patent Document 2).
- the reaction temperature is high, it is possible that the silver source remaining in the reaction system further reacts with residual heat during cooling from the reaction temperature to room temperature, and the diameter of the silver nanowire may increase.
- the cooling rate is expected to be even slower, and the effect of residual heat during cooling is expected to be large.
- an object of the present invention is to provide a method for producing silver nanowires, which is highly productive and can suppress an increase in diameter during cooling of the reaction solution after the reaction is completed.
- the present invention includes the following embodiments.
- a method for producing silver nanowires which comprises a step of cooling at a cooling rate of a minute or more.
- a solvent having a boiling point of 40 ° C. or lower and a boiling point equal to or higher than the reaction temperature at the time of synthesizing silver nanowires is added to the reaction solution over 30 minutes to cool the reaction.
- the method for manufacturing silver nanowires according to any one.
- the present invention it is possible to suppress an increase in diameter due to residual heat after synthesizing silver nanowires and to produce a desired fine silver nanowire.
- embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described.
- the method for producing silver nanowires according to the present embodiment is a step of synthesizing silver nanowires at a temperature of 120 to 170 ° C. by a polyol reduction method, and a reaction solution temperature after completion of silver nanowire synthesis from the temperature at the end of reaction. It is characterized by comprising a step of cooling to 80 ° C. at an average cooling rate of ⁇ 0.50 ° C./min or more.
- "at the end of the reaction” means that silver nanowires are synthesized by a polyol reduction method under a predetermined temperature condition and heated at a predetermined temperature of a heat source at the time of synthesis (in the examples described later, an oil bath is predetermined).
- the cooling rate of "average ⁇ 0.50 ° C./min or more" means that the absolute value of the cooling rate (speed of temperature decrease [° C./min]) is 0.50 or more on average.
- the reaction solution the reaction solvent used for the synthesis and the liquid containing the generated silver nanowires, etc.
- the silver source remaining in the reaction solution due to the residual heat during cooling can suppress the increase in the diameter of silver nanowires.
- the present inventor has found that the diameter of the silver nanowires hardly increases when the reaction solution temperature drops to 80 ° C. Therefore, it is possible to suppress an increase in the diameter of the silver nanowires by increasing the cooling rate until the reaction solution temperature is set to 80 ° C.
- This cooling rate has an average of ⁇ 0.50 ° C./min or higher, preferably ⁇ 0.60 ° C./min or higher, and more preferably ⁇ 0.70 ° C./min or higher. If the cooling rate is smaller than ⁇ 0.50 ° C./min on average, the diameter of the silver nanowires will greatly increase due to the residual heat during cooling even after the reaction is completed. Even when the cooling rate up to 80 ° C. is not constant, if the average cooling rate is within the above range, the effect of suppressing the increase in diameter is recognized. If the increase in the average diameter of the silver nanowires after cooling the reaction solution temperature to 80 ° C.
- the cooling rate is preferably less than -10.00 ° C / min, more preferably less than ⁇ 8.00 ° C / min.
- the reaction liquid cooling method after the reaction is not particularly limited as long as it is a cooling method having a cooling rate higher than the above.
- a method of cooling the reaction vessel with a gas at the time of cooling a method of cooling by contacting with a liquid refrigerant, a method of blowing air toward the reaction vessel to be air-cooled, and the like can be mentioned.
- the temperature of the liquid refrigerant and the temperature of the blown air are preferably 40 ° C. or lower, more preferably 35 ° C. or lower, and even more preferably 30 ° C. or lower. If the temperature exceeds 40 ° C, the effect of increasing the cooling rate becomes small.
- a cooling method having a cooling rate higher than the above there is also a method of adding a solvent having a temperature of 40 ° C. or lower into the reaction solution after the reaction is completed.
- the boiling point of the solvent is set to be equal to or higher than the reaction temperature at the time of synthesizing silver nanowires so as not to suddenly boil at the temperature at the time of charging. Specifically, it is preferably 170 ° C. or higher, more preferably 175 ° C. or higher, and even more preferably 180 ° C. or higher.
- the solvent is preferably added to the liquid over 30 minutes, more preferably 40 minutes or more, still more preferably 50 minutes or more.
- the amount of the solvent to be added is suppressed to about 1/5 of the reaction liquid amount at most.
- adding a large amount of solvent at once puts a load on the synthetic container due to a sudden temperature change. It is not preferable because it may cause problems such as the presence of. Further, if the amount of the solvent added at one time is small, the cooling effect becomes insufficient.
- the solvent may be, for example, 2-octanol (boiling point: 179 ° C.), 2-ethylhexanol (boiling point: 187 ° C.), 2-butoxyethanol (boiling point: 171 ° C.), benzyl alcohol (boiling point: 200 ° C.), acetphenone (boiling point: 187 ° C.).
- 1,3-propanediol (boiling point: 214 °C), diethylene glycol (boiling point: 245 °C), triethylene glycol (boiling point: 288 °C), dipropylene glycol (boiling point: 232 °C), 1,2-butanediol (Boiling point: 194 ° C), 1,3-butanediol (boiling point: 207 ° C), 1,4-butanediol (boiling point: 228 ° C), 2-methyl-1,3-propanediol (boiling point: 214 ° C), Examples thereof include polyols such as glycerin (boiling point: 290 ° C.).
- the solvent is preferably at least one selected from the group consisting of these.
- Polyols are preferable from the viewpoint of compatibility with polyols used as a reaction solvent and a reducing agent, and dihydric alcohols are more preferable from the viewpoint of not having a high viscosity, and among them, ethylene glycol and propylene glycol are economical. More preferred.
- the liquid heat medium (oil bath in the examples described later) used at the time of synthesis after the completion of silver nanowire synthesis (reaction) has a high thermal conductivity, for example, 100 W / m ⁇ K or more.
- a method of throwing a metal plate (aluminum, copper, duralumin, etc.) that is partly in contact with air and blowing air at 40 ° C or lower toward the part of the metal plate that is in contact with air. ..
- the cooling rate of the liquid heat medium is improved by using a metal having high thermal conductivity.
- the metal used for the metal plate is not particularly limited, but aluminum is particularly preferable from the viewpoint of workability and economy.
- cooling methods may be implemented in combination. Especially in the reaction vessel for mass production machines, it is considered that the cooling effect is limited by only one method due to the increase in the internal capacity. It is preferable to combine two or three of the above cooling methods as needed.
- air at room temperature (40 ° C.) or lower is blown toward the reaction vessel and / or at room temperature (40 ° C.) or lower.
- examples thereof include a method of dropping the polyol until the reaction liquid temperature becomes a predetermined temperature (for example, 80 ° C.) or less.
- the reaction solution temperature during the production (synthesis) of silver nanowires is 120 ° C to 170 ° C, preferably 130 to 165 ° C, more preferably 140 to 160 ° C. If the temperature is lower than 120 ° C, it takes a long time to complete the growth process of silver nanowires, and the productivity is poor. If the temperature exceeds 170 ° C, the heat medium that can be used during manufacturing is limited and the versatility is lowered.
- silver nanowires of the present invention As the method for producing silver nanowires of the present invention, a known polyol (Poly-ol) reduction method is used. Silver nanowires can be synthesized by reducing silver nitrate in the presence of poly-N-vinylpyrrolidone (see Chem. Matter., 2002, 14, 4736).
- the production method previously disclosed by the applicant in WO2017 / 057326 that is, a first solution containing an ionic derivative (containing a polyol as a solvent) is kept at the above temperature and is added to the first solution.
- the molar ratio with and (the number of moles of the metal atom of the metal salt supplied per minute / the total number of moles of the halogen atom of the ionic derivative) is preferably less than 10, preferably 1 or less, more preferably 0.22.
- the molar ratio of the total number of moles of halogen atoms of the ionic derivative in the first solution to the number of moles of metal atoms of the metal salt (number of moles of metal atoms of the metal salt / ionic derivative) is as follows.
- a (co) polymer containing a monomer unit derived from N-vinylpyrrolidone as a structure-determining agent is supplied in the first solution or the second solution. You can apply the method of putting it in at least one of them.
- the reaction pressure is normal pressure (atmospheric pressure).
- the reaction solvent used in the above-mentioned polyol reduction method is polyols used as reducing agents, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1 , 2-Butanediol, 1,3-Butanediol, 1,4-Butanediol, 2-Methyl-1,3-Propylenediol, glycerin, etc., and be at least one selected from the group consisting of these. Is preferable.
- the reaction solution after the synthesis reaction contains silver nanoparticles produced as a by-product in addition to the ionic derivative used for the synthesis, the structure-defining agent, and the reaction solvent together with the target silver nanowire.
- the silver nanowire obtained by synthesis is metallic silver having a diameter on the order of nanometers, and is a conductive material having a linear shape (including silver nanotubes in the shape of a hollow tube). Further, it is preferable that the metallic silver of the silver nanowire does not contain a metal oxide in terms of conductive performance, but if air oxidation is unavoidable, a silver oxide may be contained in a part (at least a part of the surface). ..
- the length (diameter) of the silver nanowire in the minor axis direction is preferably 5 nm or more and 90 nm or less on average, more preferably 10 nm or more and 85 nm or less on average, and the length in the major axis direction is preferably 1 ⁇ m or more and 100 ⁇ m or less on average, more preferably. Is 5 ⁇ m or more and 95 ⁇ m or less on average.
- the term "silver nanowire” means that the aspect ratio represented by a / b exceeds 5 when the length in the major axis direction is a and the length (diameter) in the minor axis direction is b. It means, and it is preferable that it is 10 or more.
- the “silver nanoparticles” means particles having an aspect ratio of 5 or less, which are by-produced by synthesis, excluding the above-mentioned “silver nanoparticles”.
- the above-mentioned ionic derivative is a component that contributes to the growth of metal wires, and can be applied as long as it is a compound that can be dissolved in a solvent to dissociate halogen ions, and quaternary ammonium salt halides and metal halides are suitable. ..
- the halogen ion is preferably at least one of chlorine ion, bromine ion and iodine ion, and more preferably contains a compound capable of dissociating chlorine ion.
- a quaternary alkylammonium salt having a total number of carbon atoms in the molecule of 4 to 20 (four alkyl groups are bonded to the nitrogen atom of the quaternary ammonium salt, and each alkyl group is
- the same or different halides are preferred, for example quaternary ammonium such as tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, octyltrimethylammonium chloride, hexadecyltrimethylammonium chloride.
- Examples thereof include chlorides and quaternary ammonium bromides such as tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, octyltrimethylammonium bromide and hexadecyltrimethylammonium bromide. Any one of these may be used alone or in combination of two or more. Further, a quaternary ammonium hydroxide reacted with hydrogen chloride, hydrogen bromide or hydrogen iodide to form an ammonium salt can be used.
- hydrogen chloride hydrogen bromide, hydrogen iodide
- they may be neutralized using their aqueous solution in a polyol solvent, and water or excess water or excess can be obtained by heating after neutralization. Hydrogen halide can also be distilled off.
- a halide of a quaternary alkylammonium salt having a total molecular weight of 4 to 16 carbon atoms is more preferable in terms of solubility and usage efficiency, and the longest alkyl chain attached to a nitrogen atom has a carbon atom number.
- a halide of a quaternary alkylammonium salt having a molecular weight of 12 or less, more preferably 8 or less, is more preferable in terms of efficiency of use because the molecular weight is not so large.
- tetramethylammonium chloride tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, Octyltrimethylammonium chloride and octyltrimethylammonium bromide are particularly preferred.
- metal halogen compound examples include alkali metal halides, alkaline earth metal halides, and metal halides of Groups 3 to 12 of the Long Periodic Table.
- alkali metal halides include alkali metal chlorides such as lithium chloride, sodium chloride and potassium chloride, alkali metal bromides such as lithium bromide, sodium bromide and potassium bromide, lithium iodide, sodium iodide and potassium iodide. Examples thereof include alkali metal iodide.
- alkaline earth metal halide include magnesium chloride, magnesium bromide, and calcium chloride.
- Group 3 to Group 12 metal halides in the Long Periodic Table include ferric chloride, ferric chloride, ferric bromide, and ferric bromide. Any one of these may be used alone or in combination of two or more.
- a compound that dissociates chloride ions for wire formation.
- a compound that dissociates chloride ions in order to obtain a wire having a small diameter, it is preferable to use a compound that dissociates chloride ions, and at least one of a compound that dissociates bromine ions and a compound that dissociates iodine ions in combination.
- the molar ratio of A) / (B) is preferably 2 to 8, more preferably 3 to 6.
- the structure-defining agent used for synthesis is a compound having a function of one-dimensionally defining the growth direction of metal particles at the time of synthesis, and the ratio of metal nanowires formed in the particle forming step by using the structure-defining agent. Can be enhanced.
- the structure-determining agent preferentially or selectively adsorbs to a specific crystal plane of the target particle and controls the growth direction by suppressing the growth of the adsorption plane. This growth direction can be controlled by adding a structure-defining agent to the polyols and adsorbing them on the surface of the silver nanowires to be produced.
- the structure-determining agent a structure-determining agent having a weight average molecular weight of more than 1000 is preferable, a structure-determining agent having a weight average molecular weight of 2000 or more is more preferable, and a structure-determining agent having a weight average molecular weight of 10,000 or more is further preferable.
- the weight average molecular weight of the structural regulator is preferably 1.5 million or less, more preferably 1 million or less, and even more preferably 500,000 or less.
- the type of the structural regulator include poly-N-vinylpyrrolidone (PVP), a 1: 1 copolymer of N-vinylpyrrolidone and vinyl acetate, and the like.
- the structure-defining agent has the effect of controlling the wire-like growth of silver nanowires during the synthesis of silver nanowires and preventing the aggregated silver nanowires produced.
- the by-produced silver nanoparticles are contained in addition to the ionic derivative, the structure-defining agent, and the solvent used for the synthesis together with the target silver nanowire. It is possible to prepare a conductive ink containing silver nanowires by performing a known purification step of silver nanowires according to the above.
- Synthesis Example 1 Production of silver nanowires 667 g of propylene glycol (manufactured by AGC Co., Ltd.) is weighed in a 1 L plastic container, and 22.5 g (0.13 mol) of silver nitrate (manufactured by Toyo Kagaku Kogyo Co., Ltd.) is added as a metal salt to block light at room temperature. A silver nitrate solution (second solution) was prepared by stirring underneath for 2 hours.
- Sokalan (registered trademark) K90) was charged and completely dissolved by stirring at 150 ° C. for 1 hour using an oil bath as a heat medium at a rotation speed of 200 rpm to obtain a first solution.
- the silver nitrate solution (second solution) prepared above was connected to a metering pump and dropped onto the first solution at a temperature of 150 ° C. over 2.5 hours to synthesize silver nanowires. After the dropping was completed, heating and stirring were continued for another 30 minutes to complete the reaction. At the end of the reaction, heating of the heat source (heating of the oil bath) was stopped.
- Example 1 After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in Synthesis Example 1 except that the flask was taken out from the oil bath and cooled (air-cooled). Similar to Synthesis Example 1, the solution (reaction solution) immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. .. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The average cooling rate is the difference (T-80) ° C. between the temperature T (° C.) at the end of the reaction and 80 ° C. divided by the time t (minutes) required from immediately after the end of the reaction to 80 ° C. ((T-80). / T) Calculated by. The same applies to the other examples and comparative examples. The results are shown in Table 2.
- Example 2 After the reaction of Synthesis Example 1 was completed, the flask was taken out from the oil bath, and was further cooled by blowing air toward the flask with a small fan (Yamazen Corporation, 15 cm mini desktop fan DS-A151). Similarly, a silver nanowire was manufactured. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
- Example 3 After the reaction of Synthesis Example 1 was completed, the flask was immersed in an oil bath in which heating was stopped, and 500 g of propylene glycol at 25 ° C. was added dropwise at a rate of 9.0 g / min to cool the flask, which was the same as the method of Synthesis Example 1.
- Manufactured silver nanowires As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
- Example 4 After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in Synthesis Example 1 except that the solution in the flask was transferred to another 2L SUS container and cooled at room temperature. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
- Example 5 Silver nanowires were produced in the same manner as in Example 1 except that the temperature at which the first solution was prepared and the temperature at which the silver nitrate solution (second solution) was dropped into the first solution was changed to 170 ° C.
- the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
- Example 6 Silver nanowires were produced in the same manner as in Example 2 except that the temperature at which the first solution was prepared and the temperature at which the silver nitrate solution (second solution) was dropped into the first solution was changed to 170 ° C.
- the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
- Example 7 After the reaction of Synthesis Example 1 is completed, the flask is immersed in an oil bath with an aluminum heat sink (length 300 mm ⁇ width 40 mm ⁇ thickness 8 mm metal plate) immersed in the oil bath while being immersed in the oil bath in which heating is stopped. In the oil bath between the flask and the installation position of the fan, immerse the two heat sinks in the oil bath by a vertical length of 150 mm so that the surfaces of the two heat sinks face the fan (150 mm is exposed from the oil surface).
- an aluminum heat sink length 300 mm ⁇ width 40 mm ⁇ thickness 8 mm metal plate
- a silver nanowire was produced in the same manner as in the method of Synthesis Example 1 except that the oil was cooled.
- the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
- Examples 1 to 7 having an average cooling rate of ⁇ 0.50 ° C./min or more it was confirmed that the difference in the diameter of the silver nanowires immediately after the reaction was completed and after cooling to 80 ° C. was 1 nm or less, and the diameter hardly increased. rice field.
- Comparative Examples 1 to 3 having an average cooling rate of less than ⁇ 0.50 ° C./min the difference in the diameter of the silver nanowires immediately after the reaction was completed and after cooling to 80 ° C. was larger than 1 nm, and the cooling rate was particularly slow in Comparative Example 1. The diameter increased by 2 nm or more, and the correlation between the cooling rate and the increase in diameter was confirmed.
- Example 8 evaluation of transparent conductive film
- transparent conductive films were prepared and evaluated using the silver nanowires of Example 4 and Comparative Example 1. The following purification operations were performed on the silver nanowire reaction solutions of Example 4 and Comparative Example 1, respectively.
- PFA perfluoroalkoxyethylene-tetrafluoroethylene copolymer
- the opening and closing of the permeation valve was adjusted so that the permeation rate of the filtrate was about 10 g / min, and 100 g of ion-exchanged water was added to the system by backwashing every 100 g of the filtrate (solvent retention rate 95%). Backwash pressure 0.15 MPa).
- the solvent added to the system by backwashing was changed from ion-exchanged water to ethanol, and cross-flow filtration (second filtration) was continued at a filtration differential pressure of 0.03 MPa.
- Cross-flow filtration was terminated when an additional 2800 g of filtrate was obtained.
- the silver concentration is determined using the Forhardt method. Weigh about 1 g of the sample into a beaker and add 4 mL of nitric acid (1 + 1) and 20 mL of pure water. Cover the beaker with a watch glass and heat it to 150 ° C. on a hot plate to dissolve the solids. After confirming the dissolution, stop heating and allow to cool, then wash the inner surface of the watch glass and the wall surface of the beaker with pure water to make the liquid volume about 50 mL.
- the silver concentration is determined according to the following formula.
- Silver concentration (mass%) ⁇ (V ⁇ c) ⁇ 107.9 / 1000 ⁇ / m m: Sample weight (g) V: Amount of ammonium thiocyanate aqueous solution consumed for titration to the end point (mL) c: Concentration of aqueous solution of ammonium thiocyanate (0.01 mol / L)
- ammonium iron sulfate (III) 3% nitric acid acidity
- a mixture of 5.17 g of ammonium iron sulfate (III), 170 g of pure water and 2.00 g of nitric acid was used.
- As the 0.01 mol / L ammonium thiocyanate aqueous solution pure water was added to 38.06 mg of ammonium thiocyanate to prepare a total volume of 50 mL.
- PNVA poly-N-vinylacetamide
- GE191-103 manufactured by Showa Denko KK, homopolymer (10% by mass aqueous solution of weight average molecular weight 900,000 (catalog value))
- PNVA poly-N-vinylacetamide
- GE191-103 manufactured by Showa Denko KK, homopolymer (10% by mass aqueous solution of weight average molecular weight 900,000 (catalog value)
- the mixing amount was adjusted so as to be a dispersion medium), and each ink was obtained.
- Each of the above silver nanowire inks was used as a supporting base material plasma-treated at a printing speed of 500 mm / sec using a coating machine 70F0 manufactured by Imoto Seisakusho Co., Ltd. and a bar coater having a wet film thickness of about 15 ⁇ m. It was applied to a COP (cycloolefin polymer) supporting substrate (film substrate, ZF-14 manufactured by Zeon Corporation) having a size of 21 cm ⁇ 30 cm. Then, it was dried at 80 ° C. for 1 minute with a hot air dryer (ETAC HS350 manufactured by Kusumoto Kasei Co., Ltd.) to form a transparent conductive film having a transparent conductive layer.
- COP cycloolefin polymer
- ⁇ Plasma treatment of supporting substrate (film substrate)> The plasma treatment as the surface treatment of the film substrate was carried out for 20 seconds at an output of 1 kW under a nitrogen gas atmosphere using a plasma treatment device (AP-T03 manufactured by Sekisui Chemical Co., Ltd.).
- the sheet resistance (surface resistivity) of the obtained transparent conductive film was measured by Loresta-GP manufactured by Mitsubishi Chemical Analytech. Further, as the optical characteristics of the transparent conductive film, the total light transmittance, haze and b * were measured by a spectroscopic color / haze meter COH7700 manufactured by Nippon Denshoku Kogyo Co., Ltd. The reference for measuring the optical characteristics was measured using air. The results are shown in Table 3.
- the transparent conductive film using the silver nanowires synthesized in Example 4 has a low haze despite having the same surface resistivity. , High transparency was confirmed.
Abstract
[Problem] To provide a silver nano-wire production method having high production capability and allowing for suppression of an increase in diameter during cooling that follows completion of reaction. [Solution] This silver nano-wire production method is characterized by comprising the step of synthesizing a silver nano-wire at a temperature of 120 to 170°C by the polyol reduction method, and the step of cooling, after the end of the silver nano wire synthesis, the reaction solution temperature from the temperature at the time of the end of the reaction to 80°C at a cooling speed of -0.50°C/minute or faster on average.
Description
本発明は、銀ナノワイヤーの製造方法に関する。
The present invention relates to a method for manufacturing silver nanowires.
タッチパネル等の透明電極に使用されるＩＴＯ（酸化インジウムスズ）膜の代替となる高透明性・高導電性薄膜の原料として、銀ナノワイヤーが近年注目されている。斯かる銀ナノワイヤーは、一般に、ポリビニルピロリドンとエチレングリコール等のポリオールの存在下に銀化合物を加熱する、いわゆるポリオール還元法によって製造されている（特許文献１、非特許文献１）。
In recent years, silver nanowires have been attracting attention as a raw material for highly transparent and highly conductive thin films that can replace the ITO (indium tin oxide) film used for transparent electrodes such as touch panels. Such silver nanowires are generally produced by a so-called polyol reduction method in which a silver compound is heated in the presence of a polyol such as polyvinylpyrrolidone and ethylene glycol (Patent Document 1, Non-Patent Document 1).
タッチパネル等に使用される透明導電膜には高い透明性が要求される。銀ナノワイヤーを原料とする透明導電膜において高い透明性を実現するためには、できるだけ細く、かつ長い銀ナノワイヤーを用いることが望ましい。
High transparency is required for the transparent conductive film used for touch panels and the like. In order to realize high transparency in a transparent conductive film made of silver nanowires, it is desirable to use silver nanowires as thin and long as possible.
銀ナノワイヤーの製造に用いられる、いわゆるポリオール還元法は一般に加熱下で行われる。１５０℃前後の高い温度で反応すると、反応は比較的早く完結する（特許文献２）。しかしながら、反応温度が高いがゆえに、反応温度から室温まで冷却する間に、反応系中に残存する銀源が余熱でさらに反応し、銀ナノワイヤー径が増大する可能性が考えられる。特に大型の反応釜で製造した場合、冷却速度はさらに遅くなり、冷却時の余熱の影響は大きいと予想される。
The so-called polyol reduction method used in the production of silver nanowires is generally performed under heating. When the reaction is carried out at a high temperature of around 150 ° C., the reaction is completed relatively quickly (Patent Document 2). However, since the reaction temperature is high, it is possible that the silver source remaining in the reaction system further reacts with residual heat during cooling from the reaction temperature to room temperature, and the diameter of the silver nanowire may increase. Especially when manufactured in a large reaction kettle, the cooling rate is expected to be even slower, and the effect of residual heat during cooling is expected to be large.
一方、１００℃以下で反応させた場合は反応温度からの冷却中に銀ナノワイヤー径が増大する懸念は小さいが、銀ナノワイヤーの合成（成長）に非常に時間がかかり生産効率が低いことが問題である（特許文献３）。
On the other hand, when the reaction is carried out at 100 ° C. or lower, there is little concern that the diameter of the silver nanowires will increase during cooling from the reaction temperature, but the synthesis (growth) of the silver nanowires takes a very long time and the production efficiency is low. This is a problem (Patent Document 3).
したがって、本発明の目的は、生産性が高く、かつ反応終了後の反応液の冷却中に径の増大を抑制することが可能な銀ナノワイヤーの製造方法を提供することにある。
Therefore, an object of the present invention is to provide a method for producing silver nanowires, which is highly productive and can suppress an increase in diameter during cooling of the reaction solution after the reaction is completed.
上記目的を達成するために、本発明者らが検討した結果、銀ナノワイヤー反応終了時の温度から８０℃までの反応液の冷却速度を調整すると、冷却中の銀ナノワイヤー径の増加を抑制できる効果があることを見出した。すなわち、本発明は、以下の実施態様を含む。
As a result of studies by the present inventors in order to achieve the above object, when the cooling rate of the reaction solution is adjusted from the temperature at the end of the silver nanowire reaction to 80 ° C., the increase in the diameter of the silver nanowire during cooling is suppressed. I found that there is an effect that can be done. That is, the present invention includes the following embodiments.
［１］銀ナノワイヤーを１２０～１７０℃の温度でポリオール還元法により合成する工程と、銀ナノワイヤー合成終了後、反応液温度を反応終了時の温度から８０℃まで平均－０．５０℃／分以上の冷却速度で冷却する工程と、を含むことを特徴とする銀ナノワイヤーの製造方法。
[1] The step of synthesizing silver nanowires at a temperature of 120 to 170 ° C. by the polyol reduction method, and after the completion of silver nanowire synthesis, the reaction solution temperature is averaged to −0.50 ° C./80 ° C. from the temperature at the end of the reaction to 80 ° C. A method for producing silver nanowires, which comprises a step of cooling at a cooling rate of a minute or more.
［２］前記冷却速度が－１０．００℃／分未満である、［１］に記載の銀ナノワイヤーの製造方法。
[2] The method for producing silver nanowires according to [1], wherein the cooling rate is less than -10.00 ° C./min.
［３］銀ナノワイヤー合成終了後、反応液温度を反応終了時の温度から８０℃まで冷却する冷却時間が１４０分以内である、［１］又は［２］に記載の銀ナノワイヤーの製造方法。
[3] The method for producing silver nanowires according to [1] or [2], wherein the cooling time for cooling the reaction solution temperature from the temperature at the end of the reaction to 80 ° C. after the completion of the synthesis of silver nanowires is within 140 minutes. ..
［４］反応終了直後の銀ナノワイヤーの平均径に対する８０℃まで冷却後の銀ナノワイヤーの平均径の増分が、１ｎｍ以下である、［１］～［３］のいずれか一に記載の銀ナノワイヤーの製造方法。
[4] The silver according to any one of [1] to [3], wherein the increase in the average diameter of the silver nanowires after cooling to 80 ° C. with respect to the average diameter of the silver nanowires immediately after the reaction is completed is 1 nm or less. Nanowire manufacturing method.
［５］冷却時に反応容器を気体で冷却（空冷）、または４０℃以下の液体冷媒と接触させることで冷却する、［１］～［４］のいずれか一に記載の銀ナノワイヤーの製造方法。
[5] The method for producing a silver nanowire according to any one of [1] to [4], wherein the reaction vessel is cooled by gas (air cooling) at the time of cooling or by contacting with a liquid refrigerant having a temperature of 40 ° C. or lower. ..
［６］冷却時に４０℃以下の空気を反応容器に向かって送風することで冷却する、［１］～［５］のいずれか一に記載の銀ナノワイヤーの製造方法。
[6] The method for producing silver nanowires according to any one of [1] to [5], wherein the silver nanowires are cooled by blowing air at 40 ° C. or lower toward the reaction vessel during cooling.
［７］反応終了後、４０℃以下、かつ沸点が銀ナノワイヤー合成時の反応温度以上の溶剤を３０分以上かけて反応液中に投入することで冷却する、［１］～［６］のいずれか一に記載の銀ナノワイヤーの製造方法。
[7] After the reaction is completed, a solvent having a boiling point of 40 ° C. or lower and a boiling point equal to or higher than the reaction temperature at the time of synthesizing silver nanowires is added to the reaction solution over 30 minutes to cool the reaction. The method for manufacturing silver nanowires according to any one.
［８］冷却時に投入する前記溶剤がポリオールである、［７］に記載の銀ナノワイヤーの製造方法。
[8] The method for producing silver nanowires according to [7], wherein the solvent added during cooling is a polyol.
［９］銀ナノワイヤー合成終了後、合成時に使用した液体熱媒に金属板を一部が空気に触れるように投入し、４０℃以下の空気を金属板の空気に触れている部分に向かって送風することで冷却する、［１］～［４］のいずれか一に記載の銀ナノワイヤーの製造方法。
[9] After the synthesis of silver nanowires is completed, a metal plate is put into the liquid heat medium used at the time of synthesis so that a part of the metal plate comes into contact with air, and air at 40 ° C. or lower is directed toward the part of the metal plate that is in contact with air. The method for producing a silver nanowire according to any one of [1] to [4], which is cooled by blowing air.
本発明によれば、銀ナノワイヤー合成後の余熱による径の増大を抑制し、所望の細い銀ナノワイヤーを製造することができる。
According to the present invention, it is possible to suppress an increase in diameter due to residual heat after synthesizing silver nanowires and to produce a desired fine silver nanowire.
以下、本発明を実施するための形態（以下、実施形態という）を説明する。
Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described.
本実施形態にかかる銀ナノワイヤーの製造方法は、銀ナノワイヤーを１２０～１７０℃の温度でポリオール還元法により合成する工程と、銀ナノワイヤー合成終了後、反応液温度を反応終了時の温度から８０℃まで平均－０．５０℃／分以上の冷却速度で冷却する工程と、を含むことを特徴とする。本明細書において、「反応終了時」とは、銀ナノワイヤーをポリオール還元法で所定の温度条件で合成し、合成時の熱源の所定温度での加熱（後述の実施例では、オイルバスを所定温度とするための加温）を停止した時点を意味する。また、冷却速度が「平均－０．５０℃／分以上」とは、冷却速度（温度が低下する速さ[ ℃／分]）の絶対値が平均０．５０以上であることを意味する。
The method for producing silver nanowires according to the present embodiment is a step of synthesizing silver nanowires at a temperature of 120 to 170 ° C. by a polyol reduction method, and a reaction solution temperature after completion of silver nanowire synthesis from the temperature at the end of reaction. It is characterized by comprising a step of cooling to 80 ° C. at an average cooling rate of −0.50 ° C./min or more. In the present specification, "at the end of the reaction" means that silver nanowires are synthesized by a polyol reduction method under a predetermined temperature condition and heated at a predetermined temperature of a heat source at the time of synthesis (in the examples described later, an oil bath is predetermined). It means the time when the heating to make the temperature is stopped. Further, the cooling rate of "average −0.50 ° C./min or more" means that the absolute value of the cooling rate (speed of temperature decrease [° C./min]) is 0.50 or more on average.
上記の通り銀ナノワイヤー合成後の反応液（合成に使用した反応溶媒及び生成した銀ナノワイヤー等を含む液体）の冷却速度を速めることにより、冷却中の余熱で反応液中に残存する銀源が銀ナノワイヤーの径を増大させることを抑制することができる。後述の実施例、比較例の結果より、本発明者は反応液温度が８０℃まで下がると、銀ナノワイヤーの径が殆ど増大しないことを見出した。よって、反応液温度を８０℃とするまでの冷却速度を速めることで銀ナノワイヤーの径増大を抑制することができる。この冷却速度は平均－０．５０℃／分以上であり、－０．６０℃／分以上であることが好ましく、－０．７０℃／分以上であることがより好ましい。冷却速度が平均－０．５０℃／分より小さいと反応終了後も冷却中の余熱により銀ナノワイヤーの径は大きく増大する。反応液温度が８０℃までの冷却速度が一定でない場合でも平均冷却速度が上記範囲内であれば径の増大を抑制する効果が認められる。反応終了直後の銀ナノワイヤーの平均径に対する反応液温度を８０℃まで冷却後の銀ナノワイヤーの平均径の増分が１ｎｍ以下であれば径の増大抑制効果は十分発揮されたと判断できる。なお、径の増大抑制効果は冷却速度が大きいほど高いが、冷却速度が大き過ぎると、例えば反応容器がガラス製である場合急激な温度変化による罅の発生（破損）が起こることがあり、また、反応液の増粘により銀ナノワイヤーが破損する可能性がある。そのため、冷却速度は－１０．００℃／分未満とすることが好ましく、－８．００℃／分未満とすることがより好ましい。
As described above, by increasing the cooling rate of the reaction solution (the reaction solvent used for the synthesis and the liquid containing the generated silver nanowires, etc.) after the synthesis of silver nanowires, the silver source remaining in the reaction solution due to the residual heat during cooling. Can suppress the increase in the diameter of silver nanowires. From the results of Examples and Comparative Examples described later, the present inventor has found that the diameter of the silver nanowires hardly increases when the reaction solution temperature drops to 80 ° C. Therefore, it is possible to suppress an increase in the diameter of the silver nanowires by increasing the cooling rate until the reaction solution temperature is set to 80 ° C. This cooling rate has an average of −0.50 ° C./min or higher, preferably −0.60 ° C./min or higher, and more preferably −0.70 ° C./min or higher. If the cooling rate is smaller than −0.50 ° C./min on average, the diameter of the silver nanowires will greatly increase due to the residual heat during cooling even after the reaction is completed. Even when the cooling rate up to 80 ° C. is not constant, if the average cooling rate is within the above range, the effect of suppressing the increase in diameter is recognized. If the increase in the average diameter of the silver nanowires after cooling the reaction solution temperature to 80 ° C. with respect to the average diameter of the silver nanowires immediately after the completion of the reaction is 1 nm or less, it can be judged that the effect of suppressing the increase in diameter is sufficiently exhibited. The effect of suppressing the increase in diameter is higher as the cooling rate is higher, but if the cooling rate is too high, for example, if the reaction vessel is made of glass, cracks may occur (damage) due to a sudden temperature change, and the reaction vessel may be damaged. , The thickening of the reaction solution may damage the silver nanowires. Therefore, the cooling rate is preferably less than -10.00 ° C / min, more preferably less than −8.00 ° C / min.
反応後の反応液冷却方法は上記冷却速度以上となる冷却方法であれば特に制限されない。例えば冷却時に反応容器を気体で冷却する所謂空冷や液体冷媒と接触させることで冷却する方法、空冷する反応容器に向かって空気を送風する方法等が挙げられる。液体冷媒の温度や送風する空気の温度は４０℃以下であることが好ましく、３５℃以下であることがより好ましく、３０℃以下であることがさらに好ましい。４０℃超であると冷却速度を上げる効果は小さくなる。
The reaction liquid cooling method after the reaction is not particularly limited as long as it is a cooling method having a cooling rate higher than the above. For example, a method of cooling the reaction vessel with a gas at the time of cooling, a method of cooling by contacting with a liquid refrigerant, a method of blowing air toward the reaction vessel to be air-cooled, and the like can be mentioned. The temperature of the liquid refrigerant and the temperature of the blown air are preferably 40 ° C. or lower, more preferably 35 ° C. or lower, and even more preferably 30 ° C. or lower. If the temperature exceeds 40 ° C, the effect of increasing the cooling rate becomes small.
上記冷却速度以上となる冷却方法としては、反応終了後４０℃以下の溶剤を反応液中に投入する方法も挙げられる。溶剤は、投入時の温度で突沸しないように、沸点が銀ナノワイヤー合成時の反応温度以上とする。具体的には、１７０℃以上であることが好ましく、１７５℃以上であることがより好ましく、１８０℃以上であることがさらに好ましい。また、溶剤は液中に３０分以上かけて投入するのが好ましく、４０分以上がより好ましく、５０分以上がさらに好ましい。投入する溶剤量にもよるが、投入時間が３０分未満であると冷却効果は不十分であり、投入停止後の冷却速度は小さく、銀ナノワイヤー径の増大を抑制することが困難となる。後工程として必要な反応液の精製工程の効率を考慮すると、投入する溶剤量は多くても反応液量の１／５程度に抑えることが好ましい。使用する銀ナノワイヤーの合成容器の材質にもよるが、一度にまとめて大量の溶剤を投入することは急激な温度変化に伴い合成容器に負荷がかかり、例えばガラス容器を使用した場合には罅が入る等の不具合が発生する可能性があるため好ましくない。また、一度に投入する溶剤量が少ないと、冷却効果は不十分となる。
As a cooling method having a cooling rate higher than the above, there is also a method of adding a solvent having a temperature of 40 ° C. or lower into the reaction solution after the reaction is completed. The boiling point of the solvent is set to be equal to or higher than the reaction temperature at the time of synthesizing silver nanowires so as not to suddenly boil at the temperature at the time of charging. Specifically, it is preferably 170 ° C. or higher, more preferably 175 ° C. or higher, and even more preferably 180 ° C. or higher. Further, the solvent is preferably added to the liquid over 30 minutes, more preferably 40 minutes or more, still more preferably 50 minutes or more. Although it depends on the amount of the solvent to be charged, if the charging time is less than 30 minutes, the cooling effect is insufficient, the cooling rate after the charging is stopped is small, and it becomes difficult to suppress the increase in the diameter of the silver nanowire. Considering the efficiency of the reaction liquid purification step required as a subsequent step, it is preferable that the amount of the solvent to be added is suppressed to about 1/5 of the reaction liquid amount at most. Although it depends on the material of the synthetic container of silver nanowires used, adding a large amount of solvent at once puts a load on the synthetic container due to a sudden temperature change. It is not preferable because it may cause problems such as the presence of. Further, if the amount of the solvent added at one time is small, the cooling effect becomes insufficient.
上記溶剤は、例えば２－オクタノール（沸点：１７９℃）、２－エチルヘキサノール（沸点：１８７℃）、２－ブトキシエタノール（沸点：１７１℃）、ベンジルアルコール（沸点：２００℃）、アセトフェノン（沸点：２０２℃）、ジエチレングリコールモノメチルエーテル（沸点：１９３℃）、ジエチレングリコールモノブチルエーテル（沸点：２３１℃）等の高沸点溶媒や、例えばエチレングリコール（沸点：１９７℃）、１，２－プロピレングリコール（沸点：１８８℃）、１，３－プロパンジオール（沸点：２１４℃）、ジエチレングリコール（沸点：２４５℃）、トリエチレングリコール（沸点：２８８℃）、ジプロピレングリコール（沸点：２３２℃）、１，２－ブタンジオール（沸点：１９４℃）、１，３－ブタンジオール（沸点：２０７℃）、１，４－ブタンジオール（沸点：２２８℃）、２－メチル－１，３－プロパンジオール（沸点：２１４℃）、グリセリン（沸点：２９０℃）等のポリオール類が挙げられる。上記溶剤は、これらからなる群より選択される少なくとも一種であることが好ましい。反応溶媒かつ還元剤として使用されるポリオール類との相溶性の観点からポリオール類が好ましく、高粘度にならないという観点で２価アルコールがより好ましく、その中でもエチレングリコール、プロピレングリコールが経済性の点でさらに好ましい。
The solvent may be, for example, 2-octanol (boiling point: 179 ° C.), 2-ethylhexanol (boiling point: 187 ° C.), 2-butoxyethanol (boiling point: 171 ° C.), benzyl alcohol (boiling point: 200 ° C.), acetphenone (boiling point: 187 ° C.). 202 ° C.), diethylene glycol monomethyl ether (boiling point: 193 ° C.), diethylene glycol monobutyl ether (boiling point: 231 ° C.) and other high boiling point solvents, such as ethylene glycol (boiling point: 197 ° C.), 1,2-propylene glycol (boiling point: 188 ° C.). ℃), 1,3-propanediol (boiling point: 214 ℃), diethylene glycol (boiling point: 245 ℃), triethylene glycol (boiling point: 288 ℃), dipropylene glycol (boiling point: 232 ℃), 1,2-butanediol (Boiling point: 194 ° C), 1,3-butanediol (boiling point: 207 ° C), 1,4-butanediol (boiling point: 228 ° C), 2-methyl-1,3-propanediol (boiling point: 214 ° C), Examples thereof include polyols such as glycerin (boiling point: 290 ° C.). The solvent is preferably at least one selected from the group consisting of these. Polyols are preferable from the viewpoint of compatibility with polyols used as a reaction solvent and a reducing agent, and dihydric alcohols are more preferable from the viewpoint of not having a high viscosity, and among them, ethylene glycol and propylene glycol are economical. More preferred.
さらに上記冷却速度以上となる冷却方法として、銀ナノワイヤー合成（反応）終了後合成時に使用した液体熱媒（後述の実施例ではオイルバス）に熱伝導率が高い、例えば１００Ｗ／ｍ・Ｋ以上である金属板（アルミニウム、銅、ジュラルミン等）を一部が空気に触れるように投入し、４０℃以下の空気を金属板の空気に触れている部分に向かって送風する方法も挙げることができる。熱伝導率が高い金属を使用することで液体熱媒の冷却速度が向上する。金属板に用いる金属は特に制限はないが、加工性、経済性の観点でアルミニウムが特に好ましい。
Further, as a cooling method having a cooling rate higher than the above, the liquid heat medium (oil bath in the examples described later) used at the time of synthesis after the completion of silver nanowire synthesis (reaction) has a high thermal conductivity, for example, 100 W / m · K or more. There is also a method of throwing a metal plate (aluminum, copper, duralumin, etc.) that is partly in contact with air and blowing air at 40 ° C or lower toward the part of the metal plate that is in contact with air. .. The cooling rate of the liquid heat medium is improved by using a metal having high thermal conductivity. The metal used for the metal plate is not particularly limited, but aluminum is particularly preferable from the viewpoint of workability and economy.
これらの冷却方法は組み合わせて実施してもよい。特に量産機用の反応容器では内容量の増加に伴い、一つの方法だけでは冷却効果には限界があると考えられる。必要に応じて上記冷却方法を２つまたは３つ組み合わせることが好ましい。一例として、反応終了直後に反応容器と合成時に使用した液体熱媒との接触を避けた後、室温（４０℃）以下の空気を反応容器に向かって送風及び／又は室温（４０℃）以下のポリオールを反応液温が所定温度（例えば８０℃）以下となるまで滴下する方法などが挙げられる。
These cooling methods may be implemented in combination. Especially in the reaction vessel for mass production machines, it is considered that the cooling effect is limited by only one method due to the increase in the internal capacity. It is preferable to combine two or three of the above cooling methods as needed. As an example, after avoiding contact between the reaction vessel and the liquid heat medium used at the time of synthesis immediately after the reaction is completed, air at room temperature (40 ° C.) or lower is blown toward the reaction vessel and / or at room temperature (40 ° C.) or lower. Examples thereof include a method of dropping the polyol until the reaction liquid temperature becomes a predetermined temperature (for example, 80 ° C.) or less.
銀ナノワイヤー製造（合成）時の反応液温度は１２０℃～１７０℃であるが、１３０～１６５℃が好ましく、１４０～１６０℃がより好ましい。１２０℃未満では銀ナノワイヤーの成長工程完結までに長時間を要し、生産性が乏しく、１７０℃超では製造時に使用できる熱媒が制限され汎用性が低くなる。
The reaction solution temperature during the production (synthesis) of silver nanowires is 120 ° C to 170 ° C, preferably 130 to 165 ° C, more preferably 140 to 160 ° C. If the temperature is lower than 120 ° C, it takes a long time to complete the growth process of silver nanowires, and the productivity is poor. If the temperature exceeds 170 ° C, the heat medium that can be used during manufacturing is limited and the versatility is lowered.
本発明の銀ナノワイヤーの製造方法には、公知のポリオール（Ｐｏｌｙ－ｏｌ）還元法を用いる。ポリ－Ｎ－ビニルピロリドン存在下で硝酸銀を還元することによって銀ナノワイヤーを合成することができる（Ｃｈｅｍ．Ｍａｔｅｒ．，２００２，１４，４７３６参照）。好ましくは、本出願人が先にＷＯ２０１７／０５７３２６にて開示している製造方法、すなわち、イオン性誘導体を含む第一溶液（溶媒としてポリオールを含む）を上記温度に保ち、上記第一溶液に、金属塩（硝酸銀）を含む第二溶液（溶媒としてポリオールを含む）を、上記第一溶液中のイオン性誘導体のハロゲン原子の総モル数と１分間に供給される金属塩の金属原子のモル数とのモル比（１分間に供給される金属塩の金属原子のモル数／イオン性誘導体のハロゲン原子の総モル数）が１０より小さくなるように、好ましくは１以下、より好ましくは０．２２以下となるように、かつ、上記第一溶液中のイオン性誘導体のハロゲン原子の総モル数と金属塩の金属原子のモル数とのモル比（金属塩の金属原子のモル数／イオン性誘導体のハロゲン原子の総モル数）が１０より小さくなるように供給し、構造規定剤として、Ｎ－ビニルピロリドンに由来するモノマー単位を含む（共）重合体を上記第一溶液または上記第二溶液の少なくとも一方に入れておく方法を適用することができる。反応圧力は常圧（大気圧）である。
As the method for producing silver nanowires of the present invention, a known polyol (Poly-ol) reduction method is used. Silver nanowires can be synthesized by reducing silver nitrate in the presence of poly-N-vinylpyrrolidone (see Chem. Matter., 2002, 14, 4736). Preferably, the production method previously disclosed by the applicant in WO2017 / 057326, that is, a first solution containing an ionic derivative (containing a polyol as a solvent) is kept at the above temperature and is added to the first solution. The total number of moles of halogen atoms of the ionic derivative in the first solution and the number of moles of metal atoms of the metal salt supplied in one minute in a second solution containing a metal salt (silver nitrate) (containing a polyol as a solvent). The molar ratio with and (the number of moles of the metal atom of the metal salt supplied per minute / the total number of moles of the halogen atom of the ionic derivative) is preferably less than 10, preferably 1 or less, more preferably 0.22. The molar ratio of the total number of moles of halogen atoms of the ionic derivative in the first solution to the number of moles of metal atoms of the metal salt (number of moles of metal atoms of the metal salt / ionic derivative) is as follows. A (co) polymer containing a monomer unit derived from N-vinylpyrrolidone as a structure-determining agent is supplied in the first solution or the second solution. You can apply the method of putting it in at least one of them. The reaction pressure is normal pressure (atmospheric pressure).
上記ポリオール還元法で使用される反応溶媒は、還元剤として使用されるポリオール類、例えばエチレングリコール、１，２－プロピレングリコール、１，３－プロピレングリコール、ジエチレングリコール、トリエチレングリコール、ジプロピレングリコール、１，２－ブタンジオール、１，３－ブタンジオール、１，４－ブタンジオール、２－メチル－１，３－プロパンジオール、グリセリン等が挙げられ、これらからなる群より選択される少なくとも一種であることが好ましい。高粘度にならないという観点で２価アルコールがより好ましく、その中でもエチレングリコール、プロピレングリコールが経済性の点でさらに好ましい。合成反応後の反応液には、目的とする銀ナノワイヤーとともに合成に使用したイオン性誘導体、構造規定剤、反応溶媒以外に、副生した銀ナノ粒子が含まれる。
The reaction solvent used in the above-mentioned polyol reduction method is polyols used as reducing agents, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1 , 2-Butanediol, 1,3-Butanediol, 1,4-Butanediol, 2-Methyl-1,3-Propylenediol, glycerin, etc., and be at least one selected from the group consisting of these. Is preferable. Dihydric alcohols are more preferable from the viewpoint of not having a high viscosity, and ethylene glycol and propylene glycol are further preferable from the viewpoint of economic efficiency. The reaction solution after the synthesis reaction contains silver nanoparticles produced as a by-product in addition to the ionic derivative used for the synthesis, the structure-defining agent, and the reaction solvent together with the target silver nanowire.
合成で得られる銀ナノワイヤーは、径がナノメーターオーダーのサイズを有する金属銀であり、線状（中空のチューブ状である銀ナノチューブを含む）の形状を有する導電性材料である。また、銀ナノワイヤーの金属銀は導電性能の点では金属酸化物を含まないほうが好ましいが、空気酸化が避けられない場合には一部（表面の少なくとも一部）に銀酸化物を含んでもよい。上記銀ナノワイヤーの短軸方向の長さ（径）は好ましくは平均５ｎｍ以上９０ｎｍ以下、より好ましくは平均１０ｎｍ以上８５ｎｍ以下、かつ長軸方向の長さは好ましくは平均１μｍ以上１００μｍ以下、より好ましくは平均５μｍ以上９５μｍ以下である。本明細書において「銀ナノワイヤー」とは、長軸方向の長さをａ、短軸方向の長さ（径）をｂとするとき、ａ／ｂで表されるアスペクト比が５を超えるものを意味し、１０以上であることが好ましい。また、本明細書において「銀ナノ粒子」とは、アスペクト比が５以下である、合成により副生する、上記「銀ナノワイヤー」を除いた粒子状のものを意味する。
The silver nanowire obtained by synthesis is metallic silver having a diameter on the order of nanometers, and is a conductive material having a linear shape (including silver nanotubes in the shape of a hollow tube). Further, it is preferable that the metallic silver of the silver nanowire does not contain a metal oxide in terms of conductive performance, but if air oxidation is unavoidable, a silver oxide may be contained in a part (at least a part of the surface). .. The length (diameter) of the silver nanowire in the minor axis direction is preferably 5 nm or more and 90 nm or less on average, more preferably 10 nm or more and 85 nm or less on average, and the length in the major axis direction is preferably 1 μm or more and 100 μm or less on average, more preferably. Is 5 μm or more and 95 μm or less on average. As used herein, the term "silver nanowire" means that the aspect ratio represented by a / b exceeds 5 when the length in the major axis direction is a and the length (diameter) in the minor axis direction is b. It means, and it is preferable that it is 10 or more. Further, in the present specification, the “silver nanoparticles” means particles having an aspect ratio of 5 or less, which are by-produced by synthesis, excluding the above-mentioned “silver nanoparticles”.
上記イオン性誘導体は、金属のワイヤーの生長に寄与する成分であり、溶媒に溶解してハロゲンイオンを解離できる化合物であれば適用でき、４級アンモニウム塩のハロゲン化物、金属ハロゲン化物が好適である。ハロゲンイオンとしては塩素イオン、臭素イオン、ヨウ素イオンの少なくとも一つであることが好ましく、塩素イオンを解離できる化合物を含むことがより好ましい。
The above-mentioned ionic derivative is a component that contributes to the growth of metal wires, and can be applied as long as it is a compound that can be dissolved in a solvent to dissociate halogen ions, and quaternary ammonium salt halides and metal halides are suitable. .. The halogen ion is preferably at least one of chlorine ion, bromine ion and iodine ion, and more preferably contains a compound capable of dissociating chlorine ion.
４級アンモニウム塩のハロゲン化物としては、分子内の総炭素原子数が４～２０の４級アルキルアンモニウム塩（４級アンモニウム塩の窒素原子に４つのアルキル基が結合しており、各アルキル基は同一でも異なっていても良い）のハロゲン化物が好ましく、例えば、塩化テトラメチルアンモニウム、塩化テトラエチルアンモニウム、塩化テトラプロピルアンモニウム、塩化テトラブチルアンモニウム、塩化オクチルトリメチルアンモニウム、塩化ヘキサデシルトリメチルアンモニウム等の４級アンモニウム塩化物や、臭化テトラメチルアンモニウム、臭化テトラエチルアンモニウム、臭化テトラプロピルアンモニウム、臭化テトラブチルアンモニウム、臭化オクチルトリメチルアンモニウム、臭化ヘキサデシルトリメチルアンモニウム等の４級アンモニウム臭化物等が挙げられる。これらのいずれかを単独で使用しても２種類以上を組み合わせて使用してもよい。また、４級アンモニウムヒドロキシドと塩化水素、臭化水素、ヨウ化水素を反応させてアンモニウム塩にしたものを使用することができる。これら（塩化水素、臭化水素、ヨウ化水素）は室温で気体状態であるので、ポリオール溶媒中でそれらの水溶液を用いて中和しても良く、中和後に加熱することにより水や余分なハロゲン化水素を留去することもできる。
As the halide of the quaternary ammonium salt, a quaternary alkylammonium salt having a total number of carbon atoms in the molecule of 4 to 20 (four alkyl groups are bonded to the nitrogen atom of the quaternary ammonium salt, and each alkyl group is The same or different halides are preferred, for example quaternary ammonium such as tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, octyltrimethylammonium chloride, hexadecyltrimethylammonium chloride. Examples thereof include chlorides and quaternary ammonium bromides such as tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, octyltrimethylammonium bromide and hexadecyltrimethylammonium bromide. Any one of these may be used alone or in combination of two or more. Further, a quaternary ammonium hydroxide reacted with hydrogen chloride, hydrogen bromide or hydrogen iodide to form an ammonium salt can be used. Since these (hydrogen chloride, hydrogen bromide, hydrogen iodide) are in a gaseous state at room temperature, they may be neutralized using their aqueous solution in a polyol solvent, and water or excess water or excess can be obtained by heating after neutralization. Hydrogen halide can also be distilled off.
これらの中でも、分子内の総炭素原子数が４～１６の４級アルキルアンモニウム塩のハロゲン化物が溶解性や使用効率の点でより好ましく、窒素原子に付くアルキル鎖で最も長いもので炭素原子数が１２以下のもの、更に好ましくは８以下である４級アルキルアンモニウム塩のハロゲン化物が特に分子量がそれほど大きくならず、使用効率の点でさらに好ましい。得られるワイヤー形状の観点から、塩化テトラメチルアンモニウム、臭化テトラメチルアンモニウム、塩化テトラエチルアンモニウム、臭化テトラエチルアンモニウム、塩化テトラプロピルアンモニウム、臭化テトラプロピルアンモニウム、塩化テトラブチルアンモニウム、臭化テトラブチルアンモニウム、塩化オクチルトリメチルアンモニウム、臭化オクチルトリメチルアンモニウムが特に好ましい。
Among these, a halide of a quaternary alkylammonium salt having a total molecular weight of 4 to 16 carbon atoms is more preferable in terms of solubility and usage efficiency, and the longest alkyl chain attached to a nitrogen atom has a carbon atom number. A halide of a quaternary alkylammonium salt having a molecular weight of 12 or less, more preferably 8 or less, is more preferable in terms of efficiency of use because the molecular weight is not so large. From the viewpoint of the obtained wire shape, tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, Octyltrimethylammonium chloride and octyltrimethylammonium bromide are particularly preferred.
金属ハロゲン化合物としては、アルカリ金属ハロゲン化物、アルカリ土類金属ハロゲン化物、長周期律表の第３族から第１２族の金属ハロゲン化物が挙げられる。
Examples of the metal halogen compound include alkali metal halides, alkaline earth metal halides, and metal halides of Groups 3 to 12 of the Long Periodic Table.
アルカリ金属ハロゲン化物としては、塩化リチウム、塩化ナトリウム、塩化カリウムなどのアルカリ金属塩化物、臭化リチウム、臭化ナトリウム、臭化カリウムなどのアルカリ金属臭化物、ヨウ化リチウム、ヨウ化ナトリウム、ヨウ化カリウムなどのアルカリ金属ヨウ化物などが挙げられる。アルカリ土類金属ハロゲン化物としては、塩化マグネシウム、臭化マグネシウム、塩化カルシウムが挙げられる。長周期律表の第３族から第１２族の金属ハロゲン化物としては、塩化第二鉄、塩化第二銅、臭化第二鉄、臭化第二銅が挙げられる。これらのいずれかを単独で使用しても２種類以上を組み合わせて使用してもよい。
Examples of alkali metal halides include alkali metal chlorides such as lithium chloride, sodium chloride and potassium chloride, alkali metal bromides such as lithium bromide, sodium bromide and potassium bromide, lithium iodide, sodium iodide and potassium iodide. Examples thereof include alkali metal iodide. Examples of the alkaline earth metal halide include magnesium chloride, magnesium bromide, and calcium chloride. Examples of Group 3 to Group 12 metal halides in the Long Periodic Table include ferric chloride, ferric chloride, ferric bromide, and ferric bromide. Any one of these may be used alone or in combination of two or more.
これらの中でも塩素イオンを解離する化合物を含むことが特にワイヤーの生成に好ましい。また、細い径のワイヤーを得るためには塩素イオンを解離する化合物と、臭素イオンを解離する化合物及びヨウ素イオンを解離する化合物の少なくとも一方と、を併用することが好ましい。塩素イオンを解離する化合物の塩素原子の総モル数を（Ａ）、臭素イオンを解離する化合物の臭素原子及びヨウ素イオンを解離する化合物のヨウ素原子の総モル数を（Ｂ）とした場合、（Ａ）／（Ｂ）のモル比が大きくなるとワイヤー径が太くなり、小さくなるとワイヤー径は細くなるものの小さくなり過ぎると球状粉の副生率が高くなる傾向がある。したがって、（Ａ）／（Ｂ）のモル比は、２～８が好ましく、３～６がより好ましい。
Among these, it is particularly preferable to contain a compound that dissociates chloride ions for wire formation. Further, in order to obtain a wire having a small diameter, it is preferable to use a compound that dissociates chloride ions, and at least one of a compound that dissociates bromine ions and a compound that dissociates iodine ions in combination. When the total number of moles of chlorine atoms of the compound that dissociates chlorine ions is (A) and the total number of moles of bromine atoms of the compound that dissociates bromine ions and the number of iodine atoms of the compound that dissociates iodine ions is (B), When the molar ratio of A) / (B) becomes large, the wire diameter becomes large, and when it becomes small, the wire diameter becomes small, but when it becomes too small, the by-product rate of spherical powder tends to increase. Therefore, the molar ratio of (A) / (B) is preferably 2 to 8, more preferably 3 to 6.
合成に使用される構造規定剤は、合成時に金属粒子の成長方向を一次元に規定する機能を有する化合物であり、構造規定剤を用いることによって、粒子形成工程において形成される金属ナノワイヤーの比率を高めることができる。多くの場合、構造規定剤は、対象となる粒子の特定の結晶面に優先的あるいは選択的に吸着して、吸着面の成長を抑制することによって成長方位を制御する。この成長方位の制御は、ポリオール類中に構造規定剤を添加しておき、生成する銀ナノワイヤーの表面に吸着させることにより行うことができる。この構造規定剤としては、重量平均分子量が１０００より大きい構造規定剤が好ましく、２０００以上の構造規定剤がより好ましく、１００００以上の構造規定剤がさらに好ましい。一方、構造規定剤の重量平均分子量が大きすぎると、銀ナノワイヤーが凝集する可能性が高くなる。従って、上記構造規定剤の重量平均分子量は１５０万以下が好ましく、１００万以下がより好ましく、５０万以下が更に好ましい。上記構造規定剤の種類としては、例えばポリ－Ｎ－ビニルピロリドン（ＰＶＰ）、Ｎ－ビニルピロリドンと酢酸ビニルの１：１共重合体等が挙げられる。
The structure-defining agent used for synthesis is a compound having a function of one-dimensionally defining the growth direction of metal particles at the time of synthesis, and the ratio of metal nanowires formed in the particle forming step by using the structure-defining agent. Can be enhanced. In many cases, the structure-determining agent preferentially or selectively adsorbs to a specific crystal plane of the target particle and controls the growth direction by suppressing the growth of the adsorption plane. This growth direction can be controlled by adding a structure-defining agent to the polyols and adsorbing them on the surface of the silver nanowires to be produced. As the structure-determining agent, a structure-determining agent having a weight average molecular weight of more than 1000 is preferable, a structure-determining agent having a weight average molecular weight of 2000 or more is more preferable, and a structure-determining agent having a weight average molecular weight of 10,000 or more is further preferable. On the other hand, if the weight average molecular weight of the structure defining agent is too large, there is a high possibility that silver nanowires will aggregate. Therefore, the weight average molecular weight of the structural regulator is preferably 1.5 million or less, more preferably 1 million or less, and even more preferably 500,000 or less. Examples of the type of the structural regulator include poly-N-vinylpyrrolidone (PVP), a 1: 1 copolymer of N-vinylpyrrolidone and vinyl acetate, and the like.
構造規定剤は、上記の通り銀ナノワイヤー合成時の銀ナノワイヤーのワイヤー状の成長を制御するとともに、生成した銀ナノワイヤー同士の凝集を防止する作用も有する。
As described above, the structure-defining agent has the effect of controlling the wire-like growth of silver nanowires during the synthesis of silver nanowires and preventing the aggregated silver nanowires produced.
前述の通り銀ナノワイヤーの合成反応後は、目的とする銀ナノワイヤーとともに合成に使用したイオン性誘導体、構造規定剤、溶媒以外に、副生した銀ナノ粒子が含まれるので、合成反応後目的に応じた公知の銀ナノワイヤーの精製工程を行い、銀ナノワイヤーを含む導電性インクの調製等を行うことができる。
As described above, after the synthesis reaction of the silver nanowire, the by-produced silver nanoparticles are contained in addition to the ionic derivative, the structure-defining agent, and the solvent used for the synthesis together with the target silver nanowire. It is possible to prepare a conductive ink containing silver nanowires by performing a known purification step of silver nanowires according to the above.
以下、実施例を挙げて本発明を詳細に説明するが、本発明はこれら実施例に限定されるものではない。
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
合成例１ 銀ナノワイヤーの製造
１Ｌポリ容器にプロピレングリコール６６７ｇ（ＡＧＣ株式会社製）を秤量し、金属塩として硝酸銀２２．５ｇ（０．１３ｍｏｌ）（東洋化学工業株式会社製）を加えて室温遮光下で２時間撹拌することで硝酸銀溶液（第二溶液）を調製した。 Synthesis Example 1 Production of silver nanowires 667 g of propylene glycol (manufactured by AGC Co., Ltd.) is weighed in a 1 L plastic container, and 22.5 g (0.13 mol) of silver nitrate (manufactured by Toyo Kagaku Kogyo Co., Ltd.) is added as a metal salt to block light at room temperature. A silver nitrate solution (second solution) was prepared by stirring underneath for 2 hours.
１Ｌポリ容器にプロピレングリコール６６７ｇ（ＡＧＣ株式会社製）を秤量し、金属塩として硝酸銀２２．５ｇ（０．１３ｍｏｌ）（東洋化学工業株式会社製）を加えて室温遮光下で２時間撹拌することで硝酸銀溶液（第二溶液）を調製した。 Synthesis Example 1 Production of silver nanowires 667 g of propylene glycol (manufactured by AGC Co., Ltd.) is weighed in a 1 L plastic container, and 22.5 g (0.13 mol) of silver nitrate (manufactured by Toyo Kagaku Kogyo Co., Ltd.) is added as a metal salt to block light at room temperature. A silver nitrate solution (second solution) was prepared by stirring underneath for 2 hours.
メカニカルスターラー、定量ポンプ、還流管、温度計、窒素ガス導入管を備えた５Ｌ四つ口セパラブルフラスコに、窒素ガス雰囲気下、プロピレングリコール３０００ｇ、イオン性誘導体としての塩化カリウム０．３６ｇ（４．８ｍｍｏｌ）（富士フイルム和光純薬株式会社製）および臭化ナトリウム０．１２ｇ（１．２ｍｍｏｌ）（マナック株式会社製）、構造規定剤としてポリビニルピロリドンＫ－９０（ＰＶＰ）７２．１ｇ（ＢＡＳＦ社製、Ｓｏｋａｌａｎ（登録商標）Ｋ９０）を仕込み、２００ｒｐｍの回転数でオイルバスを熱媒として、１５０℃にて１時間撹拌することで完全に溶解させ、第一溶液を得た。先に調製した硝酸銀溶液（第二溶液）を定量ポンプに接続し、上記第一溶液へ温度１５０℃にて２．５時間かけて滴下することで銀ナノワイヤーを合成した。滴下終了後さらに３０分加熱撹拌を継続し反応を終了した。反応終了時に熱源の加熱（オイルバスの加温）を停止した。
In a 5L four-port separable flask equipped with a mechanical stirrer, a metering pump, a recirculation tube, a thermometer, and a nitrogen gas introduction tube, 3000 g of propylene glycol and 0.36 g of potassium chloride as an ionic derivative under a nitrogen gas atmosphere (4. 8 mmol) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and sodium bromide 0.12 g (1.2 mmol) (manufactured by Manac Co., Ltd.), and polyvinylpyrrolidone K-90 (PVP) 72.1 g (manufactured by BASF) as a structural regulator. , Sokalan (registered trademark) K90) was charged and completely dissolved by stirring at 150 ° C. for 1 hour using an oil bath as a heat medium at a rotation speed of 200 rpm to obtain a first solution. The silver nitrate solution (second solution) prepared above was connected to a metering pump and dropped onto the first solution at a temperature of 150 ° C. over 2.5 hours to synthesize silver nanowires. After the dropping was completed, heating and stirring were continued for another 30 minutes to complete the reaction. At the end of the reaction, heating of the heat source (heating of the oil bath) was stopped.
反応終了直後およびフラスコをオイルバスに浸漬させたまま冷却中の反応液の温度（反応液温度）が１２０℃、１００℃、８０℃、室温（２５℃）時点でサンプリングを行い、各温度で得られた任意の１００本の銀ナノワイヤーの寸法（径）をＳＥＭ（日本電子株式会社製 ＪＳＭ－７０００Ｆ）を用いて計測しその相加平均値を求めた。結果を表１に示す。なお、冷却中、フラスコは加熱を停止したオイルバスに浸漬させたままであった。また、反応液の冷却速度は、後述する比較例１と同等である。
Sampling was performed immediately after the reaction was completed and when the temperature of the reaction solution (reaction solution temperature) during cooling while the flask was immersed in the oil bath was 120 ° C., 100 ° C., 80 ° C., and room temperature (25 ° C.), and obtained at each temperature. The dimensions (diameter) of any 100 silver nanowires obtained were measured using SEM (JSM-7000F manufactured by JEOL Ltd.), and the additive average value was obtained. The results are shown in Table 1. During cooling, the flask remained immersed in an oil bath in which heating was stopped. Further, the cooling rate of the reaction solution is the same as that of Comparative Example 1 described later.
表１の結果より、反応液を８０℃まで冷却すれば銀ナノワイヤーの径はそれ以上殆ど増大しないことが分かった。以降、８０℃時点の銀ナノワイヤー径は室温まで冷却した最終溶液の径と同等であると判断する。反応液温度が高い期間（時間）が長いほど銀ナノワイヤー径の増加は大きくなると考えられるので、合成終了時の反応液温度（１４０℃～１７０℃）から１２０℃まで、特に１３０℃までの冷却に要する時間を極力短くすることが好ましい。
From the results in Table 1, it was found that the diameter of the silver nanowires hardly increased when the reaction solution was cooled to 80 ° C. Hereinafter, it is judged that the diameter of the silver nanowire at 80 ° C. is equivalent to the diameter of the final solution cooled to room temperature. It is considered that the longer the period (time) when the reaction solution temperature is high, the larger the increase in the silver nanowire diameter is. Therefore, cooling from the reaction solution temperature (140 ° C. to 170 ° C.) at the end of the synthesis to 120 ° C., especially to 130 ° C. It is preferable to shorten the time required for the operation as much as possible.
実施例１
合成例１の反応終了後、フラスコをオイルバスから取り出して冷却（空冷）した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液（反応液）をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。平均冷却速度は反応終了時点の温度Ｔ（℃）と８０℃との差（Ｔ－８０）℃を、反応終了直後から８０℃までに要した時間ｔ（分）で割る（（Ｔ－８０）／ｔ）ことにより算出した。他の実施例、比較例も同様である。それらの結果を表２に示した。 Example 1
After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in Synthesis Example 1 except that the flask was taken out from the oil bath and cooled (air-cooled). Similar to Synthesis Example 1, the solution (reaction solution) immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. .. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The average cooling rate is the difference (T-80) ° C. between the temperature T (° C.) at the end of the reaction and 80 ° C. divided by the time t (minutes) required from immediately after the end of the reaction to 80 ° C. ((T-80). / T) Calculated by. The same applies to the other examples and comparative examples. The results are shown in Table 2.
合成例１の反応終了後、フラスコをオイルバスから取り出して冷却（空冷）した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液（反応液）をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。平均冷却速度は反応終了時点の温度Ｔ（℃）と８０℃との差（Ｔ－８０）℃を、反応終了直後から８０℃までに要した時間ｔ（分）で割る（（Ｔ－８０）／ｔ）ことにより算出した。他の実施例、比較例も同様である。それらの結果を表２に示した。 Example 1
After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in Synthesis Example 1 except that the flask was taken out from the oil bath and cooled (air-cooled). Similar to Synthesis Example 1, the solution (reaction solution) immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. .. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The average cooling rate is the difference (T-80) ° C. between the temperature T (° C.) at the end of the reaction and 80 ° C. divided by the time t (minutes) required from immediately after the end of the reaction to 80 ° C. ((T-80). / T) Calculated by. The same applies to the other examples and comparative examples. The results are shown in Table 2.
実施例２
合成例１の反応終了後、フラスコをオイルバスから取り出し、さらに小型扇風機（株式会社山善製、１５ｃｍミニ卓上扇ＤＳ－Ａ１５１）でフラスコに向かって送風して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 2
After the reaction of Synthesis Example 1 was completed, the flask was taken out from the oil bath, and was further cooled by blowing air toward the flask with a small fan (Yamazen Corporation, 15 cm mini desktop fan DS-A151). Similarly, a silver nanowire was manufactured. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
合成例１の反応終了後、フラスコをオイルバスから取り出し、さらに小型扇風機（株式会社山善製、１５ｃｍミニ卓上扇ＤＳ－Ａ１５１）でフラスコに向かって送風して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 2
After the reaction of Synthesis Example 1 was completed, the flask was taken out from the oil bath, and was further cooled by blowing air toward the flask with a small fan (Yamazen Corporation, 15 cm mini desktop fan DS-A151). Similarly, a silver nanowire was manufactured. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
実施例３
合成例１の反応終了後、フラスコは加熱を停止したオイルバスに浸漬させたまま２５℃のプロピレングリコール５００ｇを９．０ｇ／分の速度で滴下して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 3
After the reaction of Synthesis Example 1 was completed, the flask was immersed in an oil bath in which heating was stopped, and 500 g of propylene glycol at 25 ° C. was added dropwise at a rate of 9.0 g / min to cool the flask, which was the same as the method of Synthesis Example 1. Manufactured silver nanowires. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
合成例１の反応終了後、フラスコは加熱を停止したオイルバスに浸漬させたまま２５℃のプロピレングリコール５００ｇを９．０ｇ／分の速度で滴下して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 3
After the reaction of Synthesis Example 1 was completed, the flask was immersed in an oil bath in which heating was stopped, and 500 g of propylene glycol at 25 ° C. was added dropwise at a rate of 9.0 g / min to cool the flask, which was the same as the method of Synthesis Example 1. Manufactured silver nanowires. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
実施例４
合成例１の反応終了後、フラスコ内の溶液を別の２Ｌ ＳＵＳ製容器に移し変えて室温中冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 4
After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in Synthesis Example 1 except that the solution in the flask was transferred to another 2L SUS container and cooled at room temperature. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
合成例１の反応終了後、フラスコ内の溶液を別の２Ｌ ＳＵＳ製容器に移し変えて室温中冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 4
After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in Synthesis Example 1 except that the solution in the flask was transferred to another 2L SUS container and cooled at room temperature. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
実施例５
第一溶液の調製および硝酸銀溶液（第二溶液）を第一溶液へ滴下する時の温度を１７０℃に変更した以外は実施例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 5
Silver nanowires were produced in the same manner as in Example 1 except that the temperature at which the first solution was prepared and the temperature at which the silver nitrate solution (second solution) was dropped into the first solution was changed to 170 ° C. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
第一溶液の調製および硝酸銀溶液（第二溶液）を第一溶液へ滴下する時の温度を１７０℃に変更した以外は実施例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 5
Silver nanowires were produced in the same manner as in Example 1 except that the temperature at which the first solution was prepared and the temperature at which the silver nitrate solution (second solution) was dropped into the first solution was changed to 170 ° C. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
実施例６
第一溶液の調製および硝酸銀溶液（第二溶液）を第一溶液へ滴下する時の温度を１７０℃に変更した以外は実施例２の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 6
Silver nanowires were produced in the same manner as in Example 2 except that the temperature at which the first solution was prepared and the temperature at which the silver nitrate solution (second solution) was dropped into the first solution was changed to 170 ° C. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
第一溶液の調製および硝酸銀溶液（第二溶液）を第一溶液へ滴下する時の温度を１７０℃に変更した以外は実施例２の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 6
Silver nanowires were produced in the same manner as in Example 2 except that the temperature at which the first solution was prepared and the temperature at which the silver nitrate solution (second solution) was dropped into the first solution was changed to 170 ° C. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
実施例７
合成例１の反応終了後、フラスコは加熱を停止したオイルバスに浸漬させたままオイルバス内にアルミニウム製ヒートシンク（縦３００ｍｍ×横４０ｍｍ×厚さ８ｍｍの金属板）を、オイルバスに浸漬されているフラスコと扇風機の設置位置との間のオイルバス内に、２枚のヒートシンクの表面が扇風機と対向するように、それぞれ縦の長さ１５０ｍｍだけオイルバス内に浸漬（１５０ｍｍがオイル表面より露出して空気に触れ）させるようにクランプで並べて固定し、オイルバス外１５０ｍｍの部分（空気に触れている部分）に向かって小型扇風機（株式会社山善製、１５ｃｍミニ卓上扇ＤＳ－Ａ１５１）で送風して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 7
After the reaction of Synthesis Example 1 is completed, the flask is immersed in an oil bath with an aluminum heat sink (length 300 mm ×width 40 mm × thickness 8 mm metal plate) immersed in the oil bath while being immersed in the oil bath in which heating is stopped. In the oil bath between the flask and the installation position of the fan, immerse the two heat sinks in the oil bath by a vertical length of 150 mm so that the surfaces of the two heat sinks face the fan (150 mm is exposed from the oil surface). Fix them side by side with a clamp so that they come into contact with the air), and blow air toward the part 150 mm outside the oil bath (the part that comes in contact with the air) with a small fan (Yamazen Co., Ltd., 15 cm mini tabletop fan DS-A151). A silver nanowire was produced in the same manner as in the method of Synthesis Example 1 except that the oil was cooled. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
合成例１の反応終了後、フラスコは加熱を停止したオイルバスに浸漬させたままオイルバス内にアルミニウム製ヒートシンク（縦３００ｍｍ×横４０ｍｍ×厚さ８ｍｍの金属板）を、オイルバスに浸漬されているフラスコと扇風機の設置位置との間のオイルバス内に、２枚のヒートシンクの表面が扇風機と対向するように、それぞれ縦の長さ１５０ｍｍだけオイルバス内に浸漬（１５０ｍｍがオイル表面より露出して空気に触れ）させるようにクランプで並べて固定し、オイルバス外１５０ｍｍの部分（空気に触れている部分）に向かって小型扇風機（株式会社山善製、１５ｃｍミニ卓上扇ＤＳ－Ａ１５１）で送風して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Example 7
After the reaction of Synthesis Example 1 is completed, the flask is immersed in an oil bath with an aluminum heat sink (length 300 mm ×
比較例１
合成例１の反応終了後、合成例１と同様にフラスコをオイルバスに浸漬させたまま冷却して銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Comparative Example 1
After the reaction of Synthesis Example 1 was completed, the flask was cooled while being immersed in an oil bath in the same manner as in Synthesis Example 1 to produce silver nanowires. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
合成例１の反応終了後、合成例１と同様にフラスコをオイルバスに浸漬させたまま冷却して銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Comparative Example 1
After the reaction of Synthesis Example 1 was completed, the flask was cooled while being immersed in an oil bath in the same manner as in Synthesis Example 1 to produce silver nanowires. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
比較例２
合成例１の反応終了後、フラスコはオイルバスに浸漬させたまま銀ナノワイヤー溶液中に直接窒素ガスを０．３Ｌ／分の速度でバブリングさせ冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Comparative Example 2
After the reaction of Synthesis Example 1 was completed, the flask was cooled by bubbling nitrogen gas directly into the silver nanowire solution at a rate of 0.3 L / min while being immersed in the oil bath, but the silver was the same as the method of Synthesis Example 1. Manufactured nanowires. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
合成例１の反応終了後、フラスコはオイルバスに浸漬させたまま銀ナノワイヤー溶液中に直接窒素ガスを０．３Ｌ／分の速度でバブリングさせ冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Comparative Example 2
After the reaction of Synthesis Example 1 was completed, the flask was cooled by bubbling nitrogen gas directly into the silver nanowire solution at a rate of 0.3 L / min while being immersed in the oil bath, but the silver was the same as the method of Synthesis Example 1. Manufactured nanowires. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
比較例３
合成例１の反応終了後、フラスコはオイルバスに浸漬させたまま５００ｇのプロピレングリコールを全量約１０秒で投入して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Comparative Example 3
After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in the method of Synthesis Example 1 except that the flask was cooled by adding 500 g of propylene glycol in an oil bath in a total amount of about 10 seconds. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
合成例１の反応終了後、フラスコはオイルバスに浸漬させたまま５００ｇのプロピレングリコールを全量約１０秒で投入して冷却した以外は合成例１の方法と同様に銀ナノワイヤーを製造した。合成例１同様、反応終了直後および８０℃まで冷却した溶液をサンプリングし、得られた任意の１００本の銀ナノワイヤーの寸法（径）を測定しその相加平均値を求めた。また反応終了直後から８０℃までの反応液の平均冷却速度を求めた。それらの結果を表２に示した。 Comparative Example 3
After the reaction of Synthesis Example 1 was completed, silver nanowires were produced in the same manner as in the method of Synthesis Example 1 except that the flask was cooled by adding 500 g of propylene glycol in an oil bath in a total amount of about 10 seconds. As in Synthesis Example 1, the solution immediately after the reaction was completed and cooled to 80 ° C. was sampled, the dimensions (diameter) of any 100 silver nanowires obtained were measured, and the arithmetic mean value was obtained. Further, the average cooling rate of the reaction solution from immediately after the completion of the reaction to 80 ° C. was determined. The results are shown in Table 2.
平均冷却速度が－０．５０℃／分以上の実施例１～７では反応終了直後と８０℃まで冷却後の銀ナノワイヤー径の差が１ｎｍ以下でほとんど径が増大していないことが確認できた。一方、平均冷却速度が－０．５０℃／分未満の比較例１～３では反応終了直後と８０℃まで冷却後の銀ナノワイヤー径の差が１ｎｍより大きく、特に冷却速度が遅い比較例１では２ｎｍ以上径が増大し、冷却速度と径の増分の相関が確認された。実施例１～７、比較例１～３における銀ナノワイヤー合成後の反応液温度冷却プロファイルを図１に示した。これらの結果から勾配が大きく（冷却速度が速く）、８０℃までの冷却を１４０分以内にすることが好ましく、１３０℃までの冷却を３０分以内にすることがより好ましいことが示唆される。
In Examples 1 to 7 having an average cooling rate of −0.50 ° C./min or more, it was confirmed that the difference in the diameter of the silver nanowires immediately after the reaction was completed and after cooling to 80 ° C. was 1 nm or less, and the diameter hardly increased. rice field. On the other hand, in Comparative Examples 1 to 3 having an average cooling rate of less than −0.50 ° C./min, the difference in the diameter of the silver nanowires immediately after the reaction was completed and after cooling to 80 ° C. was larger than 1 nm, and the cooling rate was particularly slow in Comparative Example 1. The diameter increased by 2 nm or more, and the correlation between the cooling rate and the increase in diameter was confirmed. The reaction liquid temperature cooling profile after the synthesis of silver nanowires in Examples 1 to 7 and Comparative Examples 1 to 3 is shown in FIG. These results suggest that the gradient is large (cooling rate is fast), cooling to 80 ° C. is preferably within 140 minutes, and cooling to 130 ° C. is more preferably within 30 minutes.
実施例８（透明導電フィルム評価）
本発明で得られた銀ナノワイヤーの透明導電膜における光学特性への寄与を確認するため、実施例４と比較例１の銀ナノワイヤーを用いて透明導電フィルムの作製、評価を実施した。実施例４および比較例１の銀ナノワイヤー反応液に対し、それぞれ以下の精製操作を行った。 Example 8 (evaluation of transparent conductive film)
In order to confirm the contribution of the silver nanowires obtained in the present invention to the optical properties of the transparent conductive film, transparent conductive films were prepared and evaluated using the silver nanowires of Example 4 and Comparative Example 1. The following purification operations were performed on the silver nanowire reaction solutions of Example 4 and Comparative Example 1, respectively.
本発明で得られた銀ナノワイヤーの透明導電膜における光学特性への寄与を確認するため、実施例４と比較例１の銀ナノワイヤーを用いて透明導電フィルムの作製、評価を実施した。実施例４および比較例１の銀ナノワイヤー反応液に対し、それぞれ以下の精製操作を行った。 Example 8 (evaluation of transparent conductive film)
In order to confirm the contribution of the silver nanowires obtained in the present invention to the optical properties of the transparent conductive film, transparent conductive films were prepared and evaluated using the silver nanowires of Example 4 and Comparative Example 1. The following purification operations were performed on the silver nanowire reaction solutions of Example 4 and Comparative Example 1, respectively.
＜銀ナノワイヤー反応液の精製＞
得られた銀ナノワイヤー反応液のうち３．５ｋｇを５ＬのＰＦＡ（パーフルオロアルコキシエチレン－テトラフルオロエチレン共重合体）コートＳＵＳ容器に入れ、メカニカルスターラーを用いて１５０ｒｐｍにて攪拌しながら酢酸ブチル（富士フイルム和光純薬株式会社製）３．６ｋｇを１０分かけて添加した。１０分攪拌を継続した後、撹拌を止め１０分静置することで上澄み液と沈殿物とを分離させた。その後、デカンテーション操作により上澄みを５．９ｋｇ除去した。 <Purification of silver nanowire reaction solution>
3.5 kg of the obtained silver nanowire reaction solution was placed in a 5 L PFA (perfluoroalkoxyethylene-tetrafluoroethylene copolymer) coated SUS container, and butyl acetate (butyl acetate) was stirred at 150 rpm using a mechanical stirrer. Fujifilm Wako Pure Chemical Industries, Ltd.) 3.6 kg was added over 10 minutes. After continuing stirring for 10 minutes, stirring was stopped and the mixture was allowed to stand for 10 minutes to separate the supernatant and the precipitate. Then, 5.9 kg of the supernatant was removed by a decantation operation.
得られた銀ナノワイヤー反応液のうち３．５ｋｇを５ＬのＰＦＡ（パーフルオロアルコキシエチレン－テトラフルオロエチレン共重合体）コートＳＵＳ容器に入れ、メカニカルスターラーを用いて１５０ｒｐｍにて攪拌しながら酢酸ブチル（富士フイルム和光純薬株式会社製）３．６ｋｇを１０分かけて添加した。１０分攪拌を継続した後、撹拌を止め１０分静置することで上澄み液と沈殿物とを分離させた。その後、デカンテーション操作により上澄みを５．９ｋｇ除去した。 <Purification of silver nanowire reaction solution>
3.5 kg of the obtained silver nanowire reaction solution was placed in a 5 L PFA (perfluoroalkoxyethylene-tetrafluoroethylene copolymer) coated SUS container, and butyl acetate (butyl acetate) was stirred at 150 rpm using a mechanical stirrer. Fujifilm Wako Pure Chemical Industries, Ltd.) 3.6 kg was added over 10 minutes. After continuing stirring for 10 minutes, stirring was stopped and the mixture was allowed to stand for 10 minutes to separate the supernatant and the precipitate. Then, 5.9 kg of the supernatant was removed by a decantation operation.
沈殿を含む残液にイオン交換水０．８ｋｇを添加し、１０分攪拌を継続して沈殿を分散させた後、アセトン（富士フイルム和光純薬株式会社製）２．８ｋｇを１０分かけて添加した。１０分攪拌を継続した後、撹拌を止め１０分静置することで上澄み液と沈殿物とを分離させた。その後、デカンテーション操作により上澄みを全液量の７０％（２．５ｋｇ）除去した。イオン交換水０．８ｋｇ添加以降の操作を１１回繰り返すことで副生したナノ粒子を除去した。
Add 0.8 kg of ion-exchanged water to the residual liquid containing the precipitate, continue stirring for 10 minutes to disperse the precipitate, and then add 2.8 kg of acetone (manufactured by Wako Pure Chemical Industries, Ltd.) over 10 minutes. did. After continuing stirring for 10 minutes, stirring was stopped and the mixture was allowed to stand for 10 minutes to separate the supernatant and the precipitate. Then, 70% (2.5 kg) of the total amount of the supernatant was removed by a decantation operation. The by-produced nanoparticles were removed by repeating the operation after the addition of 0.8 kg of ion-exchanged water 11 times.
沈殿を含む残液にアセトン３．０ｋｇを添加し、５分攪拌を継続した後、撹拌を止め５分静置することで上澄み液と沈殿物とを分離させた。その後、デカンテーション操作により上澄みを全液量の７０％（２．９ｋｇ）除去した。沈殿を含む残液を３Ｌポリ容器に移液し、イオン交換水を内液が２．１ｋｇとなるまで加えて振盪撹拌することで完全に分散させた。
3.0 kg of acetone was added to the residual liquid containing the precipitate, and after continuing stirring for 5 minutes, stirring was stopped and the mixture was allowed to stand for 5 minutes to separate the supernatant liquid and the precipitate. Then, 70% (2.9 kg) of the total amount of the supernatant was removed by a decantation operation. The residual liquid containing the precipitate was transferred to a 3 L plastic container, ion-exchanged water was added until the internal liquid became 2.1 kg, and the mixture was completely dispersed by shaking and stirring.
得られた銀ナノワイヤー水分散液２．１ｋｇを卓上小型試験機（日本ガイシ株式会社製、セラミック膜フィルター セフィルト使用、膜面積０．０６ｍ２、孔径２．０μｍ、寸法Φ３０ｍｍ×２５０ｍｍ）に流し入れ、循環流速４Ｌ／ｍｉｎ、分散液温度２５℃、ろ過差圧０．０２ＭＰａにてクロスフロー濾過（第一ろ過）を実施した。ろ液の透過速度がおよそ１０ｇ／ｍｉｎとなるように透過バルブの開閉を調整し、ろ液が１００ｇ得られる（溶媒保持率９５％）毎にイオン交換水１００ｇを逆洗により系に加えた（逆洗圧力０．１５ＭＰａ）。ろ液が合計５６００ｇ得られた段階で、逆洗により系に加える溶媒をイオン交換水からエタノールに変え、ろ過差圧０．０３ＭＰａにてクロスフロー濾過（第二ろ過）を継続した。ろ液がさらに２８００ｇ得られた段階でクロスフロー濾過を終了した。
Pour 2.1 kg of the obtained silver nanowire aqueous dispersion into a small desktop testing machine (manufactured by Nippon Gaishi Co., Ltd., using ceramic membrane filter Sepilt, membrane area 0.06 m 2 , pore diameter 2.0 μm, dimensions Φ30 mm × 250 mm). Cross-flow filtration (first filtration) was performed at a circulation flow rate of 4 L / min, a dispersion temperature of 25 ° C., and a filtration differential pressure of 0.02 MPa. The opening and closing of the permeation valve was adjusted so that the permeation rate of the filtrate was about 10 g / min, and 100 g of ion-exchanged water was added to the system by backwashing every 100 g of the filtrate (solvent retention rate 95%). Backwash pressure 0.15 MPa). When a total of 5600 g of filtrate was obtained, the solvent added to the system by backwashing was changed from ion-exchanged water to ethanol, and cross-flow filtration (second filtration) was continued at a filtration differential pressure of 0.03 MPa. Cross-flow filtration was terminated when an additional 2800 g of filtrate was obtained.
クロスフロー濾過後の分散液を３５５メッシュのナイロンフィルターに通し凝集物を除去することで銀ナノワイヤー精製液（分散媒：水／エタノール＝１９／８１（質量比））を１．６ｋｇ取得した。銀ナノワイヤー精製液に含まれる銀濃度は０．６３質量％であった。銀濃度の測定方法は以下の通りである。
1.6 kg of silver nanowire purified liquid (dispersion medium: water / ethanol = 19/81 (mass ratio)) was obtained by passing the dispersion liquid after cross-flow filtration through a 355 mesh nylon filter to remove aggregates. The silver concentration contained in the silver nanowire purified liquid was 0.63% by mass. The method for measuring the silver concentration is as follows.
銀濃度はフォルハルト法を用いて決定する。試料をビーカーに約１ｇ秤量し、硝酸（１＋１）４ｍＬおよび純水２０ｍＬを添加する。ビーカーを時計皿で覆い、ホットプレート上で１５０℃に加熱し固形分を溶解させる。溶解を確認後、加熱を止めて放冷し、時計皿内面とビーカー壁面を純水で洗い込み液量を約５０ｍＬとする。この溶液に硝酸（１＋１）５ｍＬと硫酸アンモニウム鉄（III）（３％硝酸酸性）３ｍＬを加え、０．０１ｍｏｌ／Ｌチオシアン酸アンモニウム水溶液で滴定する。このとき、溶液が無色から淡茶に着色した点を終点とする。
滴定結果に基づいて、下記式に従い銀濃度を求める。
銀濃度（質量％）＝｛（Ｖ×ｃ）×１０７．９／１０００｝／ｍ
ｍ：試料の重量（ｇ）
Ｖ：終点までの滴定に消費したチオシアン酸アンモニウム水溶液の量（ｍＬ）
ｃ：チオシアン酸アンモニウム水溶液の濃度（０．０１ｍｏｌ／Ｌ） The silver concentration is determined using the Forhardt method. Weigh about 1 g of the sample into a beaker and add 4 mL of nitric acid (1 + 1) and 20 mL of pure water. Cover the beaker with a watch glass and heat it to 150 ° C. on a hot plate to dissolve the solids. After confirming the dissolution, stop heating and allow to cool, then wash the inner surface of the watch glass and the wall surface of the beaker with pure water to make the liquid volume about 50 mL. To this solution, add 5 mL of nitric acid (1 + 1) and 3 mL of ammonium iron (III) sulfate (3% acidic nitrate), and titrate with a 0.01 mol / L ammonium thiocyanate aqueous solution. At this time, the end point is the point where the solution is colored from colorless to light brown.
Based on the titration result, the silver concentration is determined according to the following formula.
Silver concentration (mass%) = {(V × c) × 107.9 / 1000} / m
m: Sample weight (g)
V: Amount of ammonium thiocyanate aqueous solution consumed for titration to the end point (mL)
c: Concentration of aqueous solution of ammonium thiocyanate (0.01 mol / L)
滴定結果に基づいて、下記式に従い銀濃度を求める。
銀濃度（質量％）＝｛（Ｖ×ｃ）×１０７．９／１０００｝／ｍ
ｍ：試料の重量（ｇ）
Ｖ：終点までの滴定に消費したチオシアン酸アンモニウム水溶液の量（ｍＬ）
ｃ：チオシアン酸アンモニウム水溶液の濃度（０．０１ｍｏｌ／Ｌ） The silver concentration is determined using the Forhardt method. Weigh about 1 g of the sample into a beaker and add 4 mL of nitric acid (1 + 1) and 20 mL of pure water. Cover the beaker with a watch glass and heat it to 150 ° C. on a hot plate to dissolve the solids. After confirming the dissolution, stop heating and allow to cool, then wash the inner surface of the watch glass and the wall surface of the beaker with pure water to make the liquid volume about 50 mL. To this solution, add 5 mL of nitric acid (1 + 1) and 3 mL of ammonium iron (III) sulfate (3% acidic nitrate), and titrate with a 0.01 mol / L ammonium thiocyanate aqueous solution. At this time, the end point is the point where the solution is colored from colorless to light brown.
Based on the titration result, the silver concentration is determined according to the following formula.
Silver concentration (mass%) = {(V × c) × 107.9 / 1000} / m
m: Sample weight (g)
V: Amount of ammonium thiocyanate aqueous solution consumed for titration to the end point (mL)
c: Concentration of aqueous solution of ammonium thiocyanate (0.01 mol / L)
硝酸（１＋１）、硫酸アンモニウム鉄（III）、チオシアン酸アンモニウムは、いずれも富士フイルム和光純薬株式会社製の試薬を用いた。硫酸アンモニウム鉄（III）（３％硝酸酸性）は、硫酸アンモニウム鉄（III）５．１７ｇ、純水１７０ｇおよび硝酸２．００ｇを混合して調製したものを用いた。０．０１ｍｏｌ／Ｌチオシアン酸アンモニウム水溶液は、チオシアン酸アンモニウム３８．０６ｍｇに純水を加え、全量５０ｍＬに調製したものを用いた。
Nitric acid (1 + 1), ammonium iron (III) sulfate, and ammonium thiocyanate all used reagents manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. As the ammonium iron sulfate (III) (3% nitric acid acidity), a mixture of 5.17 g of ammonium iron sulfate (III), 170 g of pure water and 2.00 g of nitric acid was used. As the 0.01 mol / L ammonium thiocyanate aqueous solution, pure water was added to 38.06 mg of ammonium thiocyanate to prepare a total volume of 50 mL.
＜銀ナノワイヤーインク化＞
得られた銀ナノワイヤー精製液を用いて銀ナノワイヤーインクを作製した。バインダー樹脂源として、ポリ－Ｎ－ビニルアセトアミド（ＰＮＶＡ（登録商標））（昭和電工株式会社製ＧＥ１９１－１０３、ホモポリマー（重量平均分子量９０万（カタログ値））の１０質量％水溶液）を用いた。 <Silver nanowire ink>
A silver nanowire ink was produced using the obtained silver nanowire purified liquid. As a binder resin source, poly-N-vinylacetamide (PNVA (registered trademark)) (GE191-103 manufactured by Showa Denko KK, homopolymer (10% by mass aqueous solution of weight average molecular weight 900,000 (catalog value))) was used. ..
得られた銀ナノワイヤー精製液を用いて銀ナノワイヤーインクを作製した。バインダー樹脂源として、ポリ－Ｎ－ビニルアセトアミド（ＰＮＶＡ（登録商標））（昭和電工株式会社製ＧＥ１９１－１０３、ホモポリマー（重量平均分子量９０万（カタログ値））の１０質量％水溶液）を用いた。 <Silver nanowire ink>
A silver nanowire ink was produced using the obtained silver nanowire purified liquid. As a binder resin source, poly-N-vinylacetamide (PNVA (registered trademark)) (GE191-103 manufactured by Showa Denko KK, homopolymer (10% by mass aqueous solution of weight average molecular weight 900,000 (catalog value))) was used. ..
蓋付きの容器に、上記で得られた銀ナノワイヤー精製液５．４１ｇ、上記ＰＮＶＡの１０質量％水溶液０．３５ｇ、水（Ｈ２Ｏ）０．６６ｇ、メタノール（ＭｅＯＨ）３．００ｇ、エタノール（ＥｔＯＨ）３．６４ｇ、プロピレングリコールモノメチルエーテル（ＰＧＭＥ）６．４０ｇ、プロピレングリコール（ＰＧ）０．６０ｇを添加して、蓋をしたのち、自転公転攪拌機で混合した。混合組成は水（Ｈ２Ｏ）：メタノール（ＭｅＯＨ）：エタノール（ＥｔＯＨ）：プロピレングリコールモノメチルエーテル（ＰＧＭＥ）：プロピレングリコール（ＰＧ）[質量比]＝１０：１５：４０：３２：３、全混合物の総量に対し、ＰＮＶＡ水溶液から供給されるＰＮＶＡ成分の量：０．１８質量％、銀ナノワイヤーによって供給される金属銀の量が０．１７質量％（残部９９．６５質量％が上記組成の分散媒）となるように混合量を調整し各インクを得た。
In a container with a lid, 5.41 g of the silver nanowire purified solution obtained above, 0.35 g of a 10 mass% aqueous solution of PNVA, 0.66 g of water ( H2O ), 3.00 g of methanol (MeOH), ethanol. 3.64 g of (EtOH), 6.40 g of propylene glycol monomethyl ether (PGME), and 0.60 g of propylene glycol (PG) were added, covered, and then mixed with a rotating and revolving stirrer. The mixed composition is water (H 2 O): methanol (MeOH): ethanol (EtOH): propylene glycol monomethyl ether (PGME): propylene glycol (PG) [mass ratio] = 10: 15: 40: 32: 3, total mixture The amount of PNVA component supplied from the PNVA aqueous solution: 0.18% by mass, and the amount of metallic silver supplied by the silver nanowire is 0.17% by mass (the balance of 99.65% by mass is the above composition). The mixing amount was adjusted so as to be a dispersion medium), and each ink was obtained.
＜透明導電フィルムの製造＞
上記各銀ナノワイヤーインクを、株式会社井元製作所製塗工機７０Ｆ０を用い、ウエット膜厚が約１５μｍとなるバーコーターを使用して、印刷速度５００ｍｍ／ｓｅｃで、プラズマ処理した支持基材としての２１ｃｍ×３０ｃｍのサイズのＣＯＰ（シクロオレフィンポリマー）支持基材（フィルム基板、ＺＦ－１４ 日本ゼオン株式会社製）に塗布した。その後、熱風乾燥機（楠本化成株式会社製 ＥＴＡＣ ＨＳ３５０）により８０℃で１分間、乾燥させ、透明導電層を有する透明導電フィルムを形成した。 <Manufacturing of transparent conductive film>
Each of the above silver nanowire inks was used as a supporting base material plasma-treated at a printing speed of 500 mm / sec using a coating machine 70F0 manufactured by Imoto Seisakusho Co., Ltd. and a bar coater having a wet film thickness of about 15 μm. It was applied to a COP (cycloolefin polymer) supporting substrate (film substrate, ZF-14 manufactured by Zeon Corporation) having a size of 21 cm × 30 cm. Then, it was dried at 80 ° C. for 1 minute with a hot air dryer (ETAC HS350 manufactured by Kusumoto Kasei Co., Ltd.) to form a transparent conductive film having a transparent conductive layer.
上記各銀ナノワイヤーインクを、株式会社井元製作所製塗工機７０Ｆ０を用い、ウエット膜厚が約１５μｍとなるバーコーターを使用して、印刷速度５００ｍｍ／ｓｅｃで、プラズマ処理した支持基材としての２１ｃｍ×３０ｃｍのサイズのＣＯＰ（シクロオレフィンポリマー）支持基材（フィルム基板、ＺＦ－１４ 日本ゼオン株式会社製）に塗布した。その後、熱風乾燥機（楠本化成株式会社製 ＥＴＡＣ ＨＳ３５０）により８０℃で１分間、乾燥させ、透明導電層を有する透明導電フィルムを形成した。 <Manufacturing of transparent conductive film>
Each of the above silver nanowire inks was used as a supporting base material plasma-treated at a printing speed of 500 mm / sec using a coating machine 70F0 manufactured by Imoto Seisakusho Co., Ltd. and a bar coater having a wet film thickness of about 15 μm. It was applied to a COP (cycloolefin polymer) supporting substrate (film substrate, ZF-14 manufactured by Zeon Corporation) having a size of 21 cm × 30 cm. Then, it was dried at 80 ° C. for 1 minute with a hot air dryer (ETAC HS350 manufactured by Kusumoto Kasei Co., Ltd.) to form a transparent conductive film having a transparent conductive layer.
＜支持基材（フィルム基板）のプラズマ処理＞
フィルム基板の表面処理としてのプラズマ処理は、プラズマ処理装置（積水化学工業株式会社製 ＡＰ－Ｔ０３）を用いて窒素ガス雰囲気下、出力１ｋＷで２０秒間行った。 <Plasma treatment of supporting substrate (film substrate)>
The plasma treatment as the surface treatment of the film substrate was carried out for 20 seconds at an output of 1 kW under a nitrogen gas atmosphere using a plasma treatment device (AP-T03 manufactured by Sekisui Chemical Co., Ltd.).
フィルム基板の表面処理としてのプラズマ処理は、プラズマ処理装置（積水化学工業株式会社製 ＡＰ－Ｔ０３）を用いて窒素ガス雰囲気下、出力１ｋＷで２０秒間行った。 <Plasma treatment of supporting substrate (film substrate)>
The plasma treatment as the surface treatment of the film substrate was carried out for 20 seconds at an output of 1 kW under a nitrogen gas atmosphere using a plasma treatment device (AP-T03 manufactured by Sekisui Chemical Co., Ltd.).
＜シート抵抗・光学特性＞
得られた透明導電フィルムのシート抵抗（表面抵抗率）を、三菱化学アナリテック社製 Ｌｏｒｅｓｔａ－ＧＰにより測定した。また、透明導電フィルムの光学特性として、全光線透過率、ヘーズおよびｂ＊を、日本電色工業社製、分光色彩・ヘーズメーターＣＯＨ７７００により測定した。光学特性測定のリファレンスは空気を用いて測定を行った。結果を表３に示す。 <Sheet resistance / optical characteristics>
The sheet resistance (surface resistivity) of the obtained transparent conductive film was measured by Loresta-GP manufactured by Mitsubishi Chemical Analytech. Further, as the optical characteristics of the transparent conductive film, the total light transmittance, haze and b * were measured by a spectroscopic color / haze meter COH7700 manufactured by Nippon Denshoku Kogyo Co., Ltd. The reference for measuring the optical characteristics was measured using air. The results are shown in Table 3.
得られた透明導電フィルムのシート抵抗（表面抵抗率）を、三菱化学アナリテック社製 Ｌｏｒｅｓｔａ－ＧＰにより測定した。また、透明導電フィルムの光学特性として、全光線透過率、ヘーズおよびｂ＊を、日本電色工業社製、分光色彩・ヘーズメーターＣＯＨ７７００により測定した。光学特性測定のリファレンスは空気を用いて測定を行った。結果を表３に示す。 <Sheet resistance / optical characteristics>
The sheet resistance (surface resistivity) of the obtained transparent conductive film was measured by Loresta-GP manufactured by Mitsubishi Chemical Analytech. Further, as the optical characteristics of the transparent conductive film, the total light transmittance, haze and b * were measured by a spectroscopic color / haze meter COH7700 manufactured by Nippon Denshoku Kogyo Co., Ltd. The reference for measuring the optical characteristics was measured using air. The results are shown in Table 3.
比較例１で合成した銀ナノワイヤーを用いた透明導電フィルムに対して、実施例４で合成した銀ナノワイヤーを用いた透明導電フィルムは同程度の表面抵抗率であるにもかかわらずヘーズが低く、高い透明性が確認された。
Compared to the transparent conductive film using the silver nanowires synthesized in Comparative Example 1, the transparent conductive film using the silver nanowires synthesized in Example 4 has a low haze despite having the same surface resistivity. , High transparency was confirmed.
Compared to the transparent conductive film using the silver nanowires synthesized in Comparative Example 1, the transparent conductive film using the silver nanowires synthesized in Example 4 has a low haze despite having the same surface resistivity. , High transparency was confirmed.
Claims (9)
- 銀ナノワイヤーを１２０～１７０℃の温度でポリオール還元法により合成する工程と、銀ナノワイヤー合成終了後、反応液温度を反応終了時の温度から８０℃まで平均－０．５０℃／分以上の冷却速度で冷却する工程と、を含むことを特徴とする銀ナノワイヤーの製造方法。 The step of synthesizing silver nanowires at a temperature of 120 to 170 ° C. by the polyol reduction method and the reaction liquid temperature after completion of silver nanowire synthesis from the temperature at the end of the reaction to 80 ° C. on average -0.50 ° C./min or more. A method for producing silver nanowires, which comprises a step of cooling at a cooling rate.
- 前記冷却速度が－１０．００℃／分未満である、請求項１に記載の銀ナノワイヤーの製造方法。 The method for producing silver nanowires according to claim 1, wherein the cooling rate is less than -10.00 ° C./min.
- 銀ナノワイヤー合成終了後、反応液温度を反応終了時の温度から８０℃まで冷却する冷却時間が１４０分以内である、請求項１又は２に記載の銀ナノワイヤーの製造方法。 The method for producing silver nanowires according to claim 1 or 2, wherein after the completion of silver nanowire synthesis, the cooling time for cooling the reaction solution temperature from the temperature at the end of the reaction to 80 ° C. is within 140 minutes.
- 反応終了直後の銀ナノワイヤーの平均径に対する８０℃まで冷却後の銀ナノワイヤーの平均径の増分が１ｎｍ以下である、請求項１～３のいずれか一項に記載の銀ナノワイヤーの製造方法。 The method for producing silver nanowires according to any one of claims 1 to 3, wherein the increase in the average diameter of the silver nanowires after cooling to 80 ° C. with respect to the average diameter of the silver nanowires immediately after the completion of the reaction is 1 nm or less. ..
- 冷却時に反応容器を気体で冷却（空冷）、または４０℃以下の液体冷媒と接触させることで冷却する、請求項１～４のいずれか一項に記載の銀ナノワイヤーの製造方法。 The method for producing a silver nanowire according to any one of claims 1 to 4, wherein the reaction vessel is cooled by gas (air cooling) at the time of cooling, or by contacting with a liquid refrigerant having a temperature of 40 ° C. or lower.
- 冷却時に４０℃以下の空気を反応容器に向かって送風することで冷却する、請求項１～５のいずれか一項に記載の銀ナノワイヤーの製造方法。 The method for producing silver nanowires according to any one of claims 1 to 5, wherein air at 40 ° C. or lower is blown toward the reaction vessel to cool the product.
- 反応終了後、４０℃以下、かつ沸点が銀ナノワイヤー合成時の反応温度以上の溶剤を３０分以上かけて反応液中に投入することで冷却する、請求項１～６のいずれか一項に記載の銀ナノワイヤーの製造方法。 According to any one of claims 1 to 6, after the reaction is completed, a solvent having a boiling point of 40 ° C. or lower and a boiling point equal to or higher than the reaction temperature at the time of synthesizing silver nanowires is poured into the reaction solution over 30 minutes or more to cool the reaction solution. The method for manufacturing silver nanowires described.
- 冷却時に投入する前記溶剤がポリオールである、請求項７に記載の銀ナノワイヤーの製造方法。 The method for producing silver nanowires according to claim 7, wherein the solvent added during cooling is a polyol.
- 銀ナノワイヤー合成終了後、合成時に使用した液体熱媒に金属板を一部が空気に触れるように投入し、４０℃以下の空気を金属板の空気に触れている部分に向かって送風することで冷却する、請求項１～４のいずれか一項に記載の銀ナノワイヤーの製造方法。
After the synthesis of silver nanowires is completed, a metal plate is put into the liquid heat medium used at the time of synthesis so that a part of it comes into contact with air, and air at 40 ° C or lower is blown toward the part of the metal plate that is in contact with air. The method for producing a silver nanowire according to any one of claims 1 to 4, which is cooled by.
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| JP2016166402A (en) * | 2014-10-28 | 2016-09-15 | ダウ グローバル テクノロジーズ エルエルシー | Method for manufacturing silver nanowire |
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| CN105086630A (en) * | 2015-08-18 | 2015-11-25 | Tcl集团股份有限公司 | Preparation methods of silver nanowires for conductive ink and silver nanowire electrode |
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