KR20200060012A - Silver nano wire ink manufacturing method - Google Patents

Abstract

The present invention relates to a silver nano-wire ink manufacturing method and, more specifically, to a silver nano-wire manufacturing method, which suppresses the formation of silver nanoparticles, and is improved to increase an output of silver nano-wires according to smooth dispersion, that is, a yield by minimizing the phenomenon of aggregation during the production of the silver nano-wires. The silver nano-wires manufactured by the manufacturing method are recovered, dispersed in an NMP solution, and precipitated, and a thermoplastic polyurethane binder is mixed and stirred in the precipitate to manufacture an ink.

Description

Silver nano wire ink manufacturing method

The present invention relates to a method of manufacturing a silver nanowire ink, and more particularly, to a silver nanowire ink prepared by dispersing the silver nanowires using a polar solvent and then precipitating the mixture by adding a binder and a solvent to the precipitate.

Metal nanowires include silver, copper, and platinum, but the typical material is silver nanowires.

Silver nanowires have been studied in many schools, research institutes, and companies since their release in 2002, and the most active research field is conductive materials used in transparent electrodes.

Silver nanowires generally have a diameter of 30 to 300 nm and a length of 5 to 100 um to spread on a transparent film with a thin film and have electrical conductivity, and visible light becomes a transparent conductive film that is transmitted.

In addition, silver nanowires are developed as flexible electrodes coated on polyurethane films or silicones, and are also developed as conductive cloths coated on fabrics.

The silver nano wire network has the advantage of being excellent in electrical conductivity, not oxidizing in the air, not easily broken by repeated bending, and excellent in heat transfer performance, but it has not been found to be suitable for practical use because it cannot find a suitable application.

The main reason is that the price is high, but it is also the reason that commercialization is delayed because it does not give convenience or advantage of use beyond the expensive price.

Then, the silver nano-wire is prepared by dissolving the silver compound in a polyol solvent such as ethylene glycol to precipitate a linear metallic silver by using the reducing power of the solvent polyol in the presence of a halogen compound and a protective agent PVP (polyvinylpyrrolidone). The method of prescribing is known as stated in the [Prior Art Document] described below.

However, these methods have a disadvantage in that the formation amount of silver nanoparticles is large, and as a result, the production of silver nanowires, i.e., yields, has been deteriorated due to precipitation during the production of silver nanowires and aggregation and re-dispersion.

US Patent Publication No. 2005-0056118 (2005.03.17.), 'Methods of nanostructure formation and shape selection' United States Published Patent US 2008-0003130 (2008.01.03.), 'Methods for production of silver nanostructures' Domestic Publication No. 10-2016-0129895 (2016.11.09.), 'Method of manufacturing silver nanowire and silver nanowire and ink using the same' Domestic registered patent No. 10-1693486 (2017.01.02.), 'Coating solution composition including silver nanowire, conductive thin film using the same and method for manufacturing the same'

The present invention was created to solve the above-mentioned problems in consideration of various problems in the prior art, and suppresses the formation of silver nanoparticles, thereby minimizing the agglomeration during the production of silver nanowires, thereby reducing the silver nanowires according to the smooth dispersion. A method of manufacturing a silver nanowire ink for producing silver ink by mixing and stirring a thermoplastic polyurethane binder in a precipitate by dispersing and separating the silver nanowire produced by the improved silver nanowire manufacturing method to increase the yield, that is, the yield. It is to provide.

The present invention is a means for achieving the above object,

It provides a method of manufacturing a silver nanowire ink in which silver nanowires are dispersed in an NMP solution, precipitated, and mixed with a precipitate to mix and stir a thermoplastic polyurethane binder with ink.

The silver nano wire,

A reducing solution preparation step for producing a reducing solution using a polyol and an antifoaming agent; A reaction solution preparation step of adding a capping agent, a surfactant, and a catalyst to the reduced solution to make a reaction solution; A silver source preparation step of preparing a silver source solution by dissolving silver nitrate in a solvent; Synthesizing the silver nanowires by performing a silver nanowire generation step of making a silver nanowire by injecting the prepared silver source solution into the reaction solution at a constant rate,

After the injection of the silver source solution is completed in the silver nanowire generation step, the precipitate is spontaneously spontaneously cooled, and a recovery step of centrifuging the precipitate to recover the silver nanowire; it is characterized in that the silver nanowire recovered by performing.

At this time, the polyol is also characterized in that it is one or a combination of two or more of ethylene glycol, glycerol, diethylene glycol, propylene glycol, dipropylene glycol as a solvent.

In addition, the anti-foaming agent is characterized by using any one of solvent NMP (N-Methyl-2-pyrrolidone), cetyl alcohol (Cetyl alcohol), stearyl alcohol (stearyl alcohol).

In addition, the reducing liquid preparation step includes a first process of mixing ethylene glycol and glycerol in a volume ratio of 7: 3; A second process of adding 10-20% by volume of an antifoaming agent to the mixed solution mixed in the first process; It is also characterized by the fact that it consists of a third process that produces a reducing solution by heating the mixed solution made through the second process to 120 ° C.

In addition, the reaction solution preparation step includes a first step of introducing a capping agent into the reducing solution 300-400 g based on 10 l of the reducing solution; A second step in which 15-40 g of a surfactant is added to the reducing solution in which the capping agent is added after the first step, based on 10 liters of the reducing solution; A third step in which 0.05-0.2 g of a catalyst is added to the reducing solution containing the surfactant after the second step, based on 10 liters of the reducing solution; It is also characterized by including a third step; a fourth step of stirring to heat the mixture to 150-160 ° C. so that all the additives are dissolved by stirring.

In addition, the silver source preparation step is a step of preheating to 60 ° C. after dissolving silver nitrate serving as a silver source in ethylene glycol in a weight ratio of 1: 6; The step of generating silver nanowires is a step of injecting the prepared silver source liquid into the reaction solution at a constant rate for 30 minutes to generate silver nanowires.

In addition, the present invention is 40 to 60% by weight of silver nanowires produced by the above method; Also provided is a silver nanowire ink characterized in that it is composed of 8-12% by weight of the binder and the remaining solvent.

At this time, the binder is also characterized by being TPU (thermoplastic polyurethane).

In addition, a polar solvent mixed with alcohols or water is used as the solvent; The alcohol is one of acetone, ethanol, and methanol, and the polar solvent mixed with water is also characterized by being NMP.

In addition, the silver nanowire and the TPU form a weight ratio of 4: 1-6: 1, and the NMP is also characterized by being specified to contain more than 200% of the TPU.

In addition, the polyimide, novolak resin, acrylic, cellulose, methacrylic, styrene, and vinyl acetate resins are added to the TPU in an amount of 5-10 weights to further increase the bending and folding characteristics of the TPU. It is also characterized by adding more parts.

In addition, butyl carbitol, terpinol, cocosol, methyl silicate, xylene, 1,4-butanediamine (BDA), ether, glycol ether, acetate, texanol, pine oil, green oil, butyl carbitol acetate in the TPU Another feature is that 5-10 parts by weight is added to 100 parts by weight of TPU to prevent drying when ink is printed.

In addition, the present invention is a step of printing a pattern using a silver nanowire ink composed of 40-60% by weight of a silver nanowire, 8-12% by weight of a binder, and the remaining solvent after placing a 100 mesh screen print mask on the base fabric for printing; Drying the pattern printed base cloth at a temperature of 130-150 ° C; Also provided is a method of manufacturing a flexible electrode using silver nanowire ink, comprising: insulating the nanowire wire exposed after drying with a hot melt film.

At this time, the base fabric is also characterized by using a TPU fabric or a fabric coated with a certain thickness of TPU.

In addition, the pattern printing uses a pattern for separating the 'c'-shaped heating wire into several; The TPU component is contained in the hot melt film, but the TPU content in the hot melt film is also characterized by maintaining 5-10 parts by weight relative to 100 parts by weight of the hot melt.

According to the present invention, the following effects can be obtained.

First, it is possible to increase the yield of the silver nano-wire by suppressing the generation of particles when synthesizing the silver nano-wire.

Second, it is possible to make a silver nanowire ink that is flexible and has excellent electrical conductivity.

Third, it can be commercialized as a heating element that has excellent washing fastness and good electrical conductivity by utilizing it as a flexible electrode.

Fourth, it can be used as a stretch sensor by printing on tight clothing such as tights.

Fifth, it can be used as a wire by replacing the conductive polymer.

1 is an explanatory view of a silver nanowire manufacturing process according to the present invention.
2 is an explanatory diagram of a preparation step of a reducing solution of the method for manufacturing a silver nanowire according to the present invention.
3 is an explanatory diagram of the reaction solution preparation step of the method of manufacturing a silver nanowire according to the present invention.
4 is an explanatory diagram of a method of manufacturing a silver nanowire ink according to the present invention.
5 is an explanatory diagram of a method for recovering silver nanowires according to the present invention.
6 is an explanatory diagram of a method for manufacturing a flexible electrode using silver nanowire ink according to the present invention.
7 is an exemplary view of a flexible electrode pattern according to the present invention.
8 is an exemplary view of attaching electric wires to the flexible electrode pattern according to the present invention.
9 is an exemplary view of a heat test of a flexible electrode pattern according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

Prior to the description of the present invention, the following specific structures or functional descriptions are merely exemplified for the purpose of illustrating the embodiments according to the concept of the present invention, and the embodiments according to the concept of the present invention may be implemented in various forms, It should not be construed as being limited to the embodiments described herein.

In addition, embodiments according to the concept of the present invention can be applied to various changes and may have various forms, so specific embodiments will be illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments according to the concept of the present invention to a specific disclosure form, and it should be understood that it includes all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

1 is an explanatory view of a silver nanowire manufacturing process according to the present invention.

First, a method of manufacturing a silver nanowire according to the present invention will be described with reference to FIG. 1. The production of silver nanowires can be considered as a method of synthesizing silver nanowires.

The synthesis of silver nanowires is accomplished by heating silver nitrate to a constant temperature using a reducing polyol as a solvent.

At this time, the polyol may be ethylene glycol, glycerol, diethylene glycol, propylene glycol, dipropylene glycol, etc. as a solvent, and is used as a reducing agent.

In addition, silver nitrate, silver acetate, silver oxide, silver chloride, and the like may be used as the silver source, but silver nitrate is most preferable when considering solubility and cost for the polyol as a solvent.

Here, the present invention is to suppress the production of silver nanoparticles, which are impurities, through control of the reaction rate, and for this purpose, a capping agent and a halogen compound may be further added, and the reduction temperature may be further increased.

More specifically, a method of manufacturing silver nanowires according to the present invention will be described with reference to FIG. 1.

A reducing solution preparation step (S10) for producing a reducing solution using a polyol and an antifoaming agent; A reaction solution preparation step (S20) of adding a capping agent, a surfactant, and a catalyst to the reduced solution to make a reaction solution; A silver source preparation step (S30) in which silver nitrate is dissolved in a solvent to make a silver source solution; Includes a silver nano-wire generation step (S40) to make a silver nano-wire by injecting the prepared silver source solution at a constant rate into the reaction solution.

When the injection of the silver source solution is completed in the silver nanowire generation step (S40), the reaction vessel is naturally precipitated while cooling for a predetermined time, and the silver nanowire recovery step (S50) of recovering the silver nanowire by centrifuging the precipitate; Includes.

2 is an explanatory diagram of a preparation step of a reducing solution of the method for manufacturing a silver nanowire according to the present invention.

The reducing liquid preparation step (S10) will be described with reference to FIG. 2.

Here, the reducing solution preparation step (S10) comprises: a first process (S11) of mixing ethylene glycol and glycerol in a volume ratio of 7: 3; A second process (S12) in which 10-20% by volume of an antifoaming agent is added to the mixed solution mixed in the first process (S11); It consists of a third process (S13) to create a reducing solution by heating the mixed solution made through the second process (S12) to 120 ℃.

At this time, the reason for mixing the ethylene glycol and glycerol in a volume ratio of 7: 3 in the first step (S11), because the glycerol has a high boiling point, it is possible to reduce the amount of vaporization, so the same effect can be achieved even if a small amount is used. Because it can.

In addition, the antifoaming agent used in the second process (S12) reduces the bubbles generated by the capping agent described later using alcohols having a high vaporization point to smoothly release nitric acid gas, thereby reducing the generation of silver nanoparticles while reducing the generation of silver nanoparticles. To increase the yield of.

As such an antifoaming agent, any one of a solvent, N-Methyl-2-pyrrolidone (NMP), Cetyl alcohol, and stearyl alcohol is used.

In addition, the reason for raising the mixed solution to 120 ° C. in the third process (S13) is to increase the reduction ability while promoting the generation of the reaction solution.

3 is an explanatory diagram of the reaction solution preparation step of the method of manufacturing a silver nanowire according to the present invention.

The reaction solution preparation step will be described with reference to FIG. 3.

On the other hand, the reaction solution preparation step (S20), the first step (S21) for introducing a capping agent in the reducing solution 300-400g based on 10L of the reducing solution; A second step (S22) in which 15-40 g of a surfactant is added to the reducing solution in which the capping agent is added after the first step (S21) based on 10L of the reducing solution; A third step (S23) in which 0.05-0.2 g of a catalyst is added to the reducing solution to which the surfactant is added after the second step (S22) based on 10 L of the reducing solution; And a third step (S23) followed by stirring to heat the mixture to 150-160 ° C. so that all of the additives are dissolved, thereby forming a reaction solution.

At this time, the capping agent used in the first step (S21) is to maintain the dispersibility into a liquid medium while suppressing growth to grow to an appropriate size by wrapping the surface of a nanomaterial, that is, a silver nanowire, produced through a reduction reaction. will be.

The capping agent may be polyvinyl pinolidone or polyvinyl pinolidone copolymer or polyvinyl acetate.

In addition, the surfactant used in the second step (S22) prevents the length of the silver nanowires from becoming longer and induces them to have an appropriate length, and when excessively supplied, the short silver nanowires and silver nanoparticles are promoted. It should be added in a limited amount.

As such a surfactant, any one of Cocamide DEA, Cocamide TEA, and Cocamide MEA can be used.

In addition, the catalyst used in the third step (S23) is a material containing a soluble halogen element such as AgCl, KBr, NaCl, and becomes a seed for silver nanowire production.

And, the silver source preparation step (S30) is a step of pre-heating to 60 ° C. after dissolving silver nitrate serving as a silver source in ethylene glycol in a weight ratio of 1: 6.

At this time, the reason for preheating is to promote reduction by increasing reactivity.

In addition, the silver nanowire generation step (S40) is a step of generating a silver nanowire by injecting the prepared silver source liquid into the reaction solution at a constant rate for 30 minutes.

Here, maintaining the injection rate at 30 minutes is twice as fast as the conventional injection rate. Unlike the injection method that is dropped from the top, the method is adopted in which the pipe is completely immersed to the bottom of the reaction solution. That is, it is a method of injecting a silver source liquid from the bottom of the reaction solution to accelerate diffusion after injection. Therefore, it is possible to increase the injection speed.

In the case of the conventional top injection type, bubbles are formed at the top, which causes a decrease in the reaction rate and a rapid increase in the amount of silver nanoparticles as impurities.

However, in the case of the present invention, since it is injected while being defoamed in a immersed state, there is almost no foaming, so that formation of silver nanoparticles, which are impurities, is significantly reduced, and the reaction rate is relatively high.

However, if the injection speed is too fast, the silver nanowire generation rate is too fast, which may result in a large diameter, and at the injection rate that is too slow for more than 4 hours, aggregation occurs between the silver nanowires, causing sedimentation despite stirring. , It is particularly important to maintain the above conditions, since the silver nanowires precipitated as a result of this aggregation cannot be redispersed and must be discarded.

In addition, the appropriate injection amount is until the silver source solution corresponds to 23% by volume based on the reaction solution. For example, when the reaction solution is 1 liter, it means that the silver sauce solution is divided into 30 minutes and injected at a constant rate so that the final amount to be injected at a constant rate is 230 milliliters.

As described above, the method of manufacturing silver nanowires according to the present invention is closely related to the amount of silver nanowires produced according to the content of the antifoaming agent and surfactant added during production, and the production of silver nanoparticles as impurities. Let's take a look.

[Example 1] Confirmation of the appropriateness of the antifoaming agent

In order to confirm the production change of the silver nanowire according to the amount of the antifoaming agent, an example outside the appropriate range and the range was compared with each other through [Comparative Example 1,2] of the following description.

Here, NMP was used as an antifoaming agent.

For example, a reducing solution of 7 L of ethylene glycol, 3 L of glycerol, and 1.4 L of NMP (N-Methyl-2-pyrrolidone) is heated while stirring at 120 ° C. Subsequently, 350 g of polyvinylpinolidone, 20 g of cocamide DEA and 0.1 g of NaCl were added to the reducing solution, and the mixture was stirred until all dissolved. Thereafter, when all of them are dissolved, the reaction solution is raised to 150 to 160 ° C. Then, 500 g of silver nitrate is dissolved in 3 L of ethylene glycol at 60 ° C. and then injected into the reaction solution at a constant rate over 30 minutes.

The silver nanowire produced in this way was as shown in the electron micrograph below.

As a result of the confirmation, the average diameter of the silver nanowire was 100 nm and the average length was 6.5 µm, and the generation of silver nanoparticles was suppressed more than before (however, it can be further suppressed by reducing the pressure), and the silver nanowires were straight to improve electric conductivity. It was confirmed that it is advantageous.

[Comparative Example 1]

The same as in Example 1, but the content of NMP was 0.6L, which was sufficiently lower than the scope of the present invention, and the electron micrograph of the silver nanowire thus produced was as follows.

As a result of the confirmation, it was confirmed that the length of the silver nanowire was shortened to 4 µm or less, and that many short nanoparticles, such as particles, were formed.

This is expected to occur because nitrate gas and vaporized polyol solution and bubbles by polyvinyl pinolidone are continuously generated and remain, thereby slowing the release of nitric acid gas. It is inferred to reduce the length of and silver particles to generate a large amount of particles.

[Comparative Example 2]

The same procedure as in Example 1, but the content of NMP was 3L and was added excessively more than the scope of the present invention, and the electron micrograph of the silver nanowire thus produced was as follows.

As a result of the check, it was confirmed that excessively adding NMP interferes with the reduction reaction and causes a problem of producing silver nanowires in bold. That is, NMP is an amide-based solvent without reducing power and is well mixed with the polyol solution to reduce the reducing power of the polyol solution. Therefore, when NMP is added excessively, part of the silver nitrate cannot be reduced and the reduction cannot be performed smoothly with the phenomenon of remaining. It was confirmed that the thickness increased significantly and the silver nanoparticles increased at the same time.

Therefore, it is very important in the present invention to precisely control the reduction reaction of silver nitrate by limiting the amount of the antifoaming agent such as NMP to a specific range.

The management of these ingredients is not limited to silk defoamers.

[Example 2] Check whether the surfactant is appropriate

In order to confirm the production change of silver nanowires according to the amount of the surfactant used, an appropriate range and an example outside the range were compared with each other through [Comparative Examples 3 and 4] in the following description.

Here, as the surfactant, cocamide DEA was used.

For example, in the same manner as in Example 1, the surfactant cocaramide DEA was changed only by adding 27.5 g, which is an intermediate value in an appropriate range.

The silver nanowire thus produced was roughly the same as the electron micrograph below and the photo of Example 1 described above.

[Comparative Example 3]

For comparison, the same procedure as in Example 2 was performed, and silver nanowires were produced without adding cocarmide DEA, which is a surfactant.

The silver nanowire produced in this way was as shown in the electron micrograph below.

As a result of the confirmation, although silver nanowires were well formed, the length was several tens of µm, which was much longer than desired, which is advantageous for transparent electrode production, but is not good because it does not obtain a uniform dispersion liquid during the production of silver nanowire ink.

[Comparative Example 4]

For comparison, the same procedure as in Example 2 was performed, but the excess of surfactant, cocarmide DEA, was added at 120 g to generate silver nanowires.

The silver nanowire produced in this way was as shown in the electron micrograph below.

As a result of the confirmation, it was confirmed that the amount of silver nanowire production was significantly reduced, the thickness of the silver nanowire was thickened, and the particles were significantly increased. This seems to be because cocamide DEA has excessively blocked the role of the capping agent.

On the other hand, nitric acid gas is generated in the process of reducing silver nitrate. If the nitric acid gas is released quickly, the amount of silver nanowire production can be increased. That is, when the internal pressure of the reactor is lowered, the release of nitric acid gas can be accelerated as much as possible, so that the production of silver nanowires can be increased while suppressing silver nanoparticles without using an antifoaming agent.

In this way, in order to confirm the relationship between the internal pressure of the reactor and the amount of silver nanowires produced, a test was conducted by dividing the case of depressurization without defoamer and the case of no decompression.

[Example 3] Decompression effect when no antifoaming agent was used

Proceeding in the same manner as in Example 1, without using an antifoaming agent, a pan was placed in a reactor before injection of the silver nitrate solution, and then dropped to 950 mbar at normal pressure (1014 mbar) and then the silver nitrate solution was injected.

As a result, silver nanoparticles having an average diameter of 80-150 nm and an average length of 5-15 µm were significantly increased while silver nanoparticles were suppressed as in the following electron micrograph.

[Comparative Example 5]

In order to compare the effect of reduced pressure, the same procedure as in Example 3 was carried out, but the pressure was maintained at normal pressure.

As a result, as shown in the following electron micrograph, the generation of silver nanoparticles increases and the production of silver nanowires decreases relatively.

In addition, in order to confirm whether silver nanoparticles are generated according to the injection position of the silver nitrate solution, the lower injection type according to the present invention and the conventional upper injection type were compared.

[Example 4]

In the same manner as in Example 1, when the silver nitrate solution was injected, the reaction solution was injected at 1/5 or less of the height of the reaction solution.

As a result of the injection, it was confirmed that silver nanoparticle generation was significantly reduced as in the following electron micrograph.

[Comparative Example 6]

The same procedure as in Example 1, but as a result of injecting the silver nitrate solution in a dropping manner at a height of 10 cm from the surface of the reaction solution, it was confirmed that a large amount of silver nanoparticles was formed as follows.

Through this comparison, it was confirmed that the method of injecting the silver nitrate solution was also closely related to the production of silver nanowires.

As described above, when silver nanowire synthesis is completed by injecting a silver source solution at a constant rate using the lower injection method of the reaction vessel, the reaction vessel is naturally precipitated while cooling for 4 hours or more, and the precipitate is centrifuged to recover the silver nanowire.

On the other hand, the silver nanowires thus synthesized can be produced with silver nanowire ink after being recovered.

The silver nanowire ink according to the present invention is composed of 40-60% by weight of the silver nanowires prepared according to the above-described silver nanowire manufacturing method, 8-12% by weight of the binder, and the remaining solvent.

In this case, the binder may be TPU (thermoplastic polyurethane), and a polar solvent mixed with alcohol or water may be used as the solvent.

Here, TPU is a material that is soluble in a solvent while being stretched well, such as rubber, and thus has the property of maintaining performance even when folded or crumpled, so it is the most suitable binder for ink. In addition, alcohols may be acetone, ethanol, methanol, and the like, and the polar solvent mixed with water is preferably NMP described above.

This is because NMP has a very good dispersibility and can maintain the best recovery rate.

In addition, for the production of stable silver nanowire ink, the silver nanowire and the TPU may have a weight ratio of 4: 1-6: 1, and NMP may be specified to be contained in 200% or more of the TPU.

In addition, in the present invention, polyimide, novolak resin, acrylic, cellulose, methacrylic, styrene, and vinyl acetate resins are added to 100 parts by weight of TPU to increase the bending and folding characteristics of TPU. -10 parts by weight can be added.

In addition, in order to prevent drying when printing the ink, butylcarbitol, terpinol, cocosol, methyl silicate, xylene, 1,4-butanediamine (BDA), ether, glycol ether, acetate, tec in the TPU 5-10 parts by weight may be added to 100 parts by weight of TPU, one selected from acidol, pine oil, green tea oil, and butyl carbitol acetate.

Then, a method of manufacturing such a silver nanowire ink will be described in detail.

4 is an explanatory diagram of a method of manufacturing a silver nanowire ink according to the present invention.

Silver nano wire ink manufacturing method according to the present invention,

Injecting silver nitrate into the reaction solution to recover the silver nanowires (S50); Dispersing the recovered silver nanowires in NMP, which is a polar solvent (S60); A filtering step (S70) of filtering the dispersion to filter grains that are difficult to ink; Separating the filtered solution for 2 hours or more to obtain a precipitate (S80); It consists of; adding a binder and a solvent to the precipitate and mixing and stirring to make ink (S90).

Here, the silver nanowire to be obtained through the recovery step (S50) has an average diameter of a suitable silver nanowire targeted at 80-150nm, an average length of 5-15㎛ (ratio of diameter and length is between 1: 50-1: 200) It is important that the production of silver nanowires is performed so that a large amount of silver nanowires having the desired properties are produced.

At this time, the reason for limiting the average diameter and the average length of the silver nanowires as described above is that the electrical conductivity deteriorates when it is less than that, and when it is more than that, the warpage property becomes large and clumps, so that dispersion is difficult. If you do, you will not be able to withstand bending.

In addition, the smaller the diameter, the shorter the length, so the shorter the length, the lower the electrical conductivity, and is not useful because it cannot withstand folding.

Therefore, the most preferable diameter and length are as shown in the electron micrograph below.

5 is an explanatory diagram of a silver nanowire recovery method according to the present invention.

Then, the recovery step (S50) will be described.

The recovery step (S50) is a silver nitrate solution is reacted while being injected, a precipitation process (S51) of cooling and cooling to 30 ° C. or less while allowing natural reaction by cooling at least 4 hours after completion of the injection of a reaction tube in which silver nanowires are formed; Discarding the suspended upper water and recovering the precipitate (S52); It consists of; centrifuging the recovered precipitate (S53);

In addition, the dispersing step (S60) is a step of dispersing the recovered silver nanowires in NMP, which is a polar solvent, both of which are finely chopped to several hundreds of micrometers through a high-speed mixer of 2000-3600rpm in a mixed state at a weight ratio of 1: 1. It involves crushing and dispersing the particles so that they are not visible through the ultrasonic disperser or rotating mixer.

In addition, the filtering step (S70) is a step in which the dispersion solution is passed through a 50 mesh filter to filter out only the grains having a size that is difficult to ink and to obtain only a portion having a good dispersion state.

In addition, the step of obtaining the precipitate (S80) is a step of separating a portion having a good dispersion state for 2 hours or more into a clear supernatant and a precipitate, and the supernatant is collected and reused during the next dispersion. Used as a composition.

At this time, silver has a specific gravity of 9, so it is possible to settle even at a small size.

In addition, the step of making ink (S90) is a step of mixing and stirring to have the silver nanowire ink composition described above using the recovered precipitate, that is, a silver nanowire, a binder, and a solvent to make ink.

On the other hand, the present invention also provides a method of making a flexible electrode using the silver nanowire ink thus manufactured.

6 is an explanatory diagram of a method for manufacturing a flexible electrode using silver nanowire ink according to the present invention.

The method for manufacturing a flexible electrode according to the present invention comprises the steps of placing a screen print mask of 100 mesh on a base cloth for printing and printing a pattern using silver nanowire ink (S110); Drying the pattern printed base cloth at a temperature of 130-150 ° C. (S120); Attaching a wire to the electrode portion of the silver nanowire pattern (S130); And covering the exposed silver nanowires after drying with a hot melt film (S140).

At this time, the base fabric is preferably a TPU cloth or a cloth coated with a certain thickness of TPU.

This is because TPU is used as a binder for silver nanowire ink, so that the properties of the folded product can be sufficiently maintained while exerting strong adhesion to each other.

In addition, the reason for drying by increasing the drying temperature as described above after pattern printing is to induce the completion of dispersion for a very small amount of finely dispersed matter.

In addition, the pattern printing is preferably a pattern consisting of several 'c' shaped heating wires.

This is to facilitate the attachment of the wire by collecting the electrode parts to one side, and also to minimize the amount of use of the electrode parts.

In addition, the reason for dividing the heating wire into multiple ones is to prevent this, because when a single heating wire is formed, the current is concentrated to the rest in case of partial damage, and overheating and burns may occur.

In addition, it is preferable that the TPU component is contained in the hot melt film so as to improve adhesion and maintain bending characteristics even when covering the silver nanowire heating wire exposed with the hot melt film for insulation. In this case, the TPU content included in the hot melt film is preferably maintained at 5-10 parts by weight relative to 100 parts by weight of the hot melt.

7 is an exemplary view of a flexible electrode pattern according to the present invention.

An example of the pattern configuration of the flexible electrode configured as described above is as illustrated in FIG. 7. As illustrated in FIG. 7, a “c” -shaped pattern is formed in a plurality of hot wire arrays at regular intervals, and both ends are integrated into electrode portions.

8 is an exemplary view of attaching electric wires to the flexible electrode pattern according to the present invention.

The wire attachment step was specially made because the wires are also thick and inflexible when using ordinary wires, and there is a problem in that they cannot be washed.

The wire material is a twisted pair of 7 strands of silver-plated copper wire. This is because the stranded wire is resistant to bending, and the reason for using the silver-plated copper wire is to prevent corrosion by water that may be penetrated during washing and to minimize contact resistance with silver nanowires. As shown in Fig. 8, the contact area is maximized by attaching stranded wires of 7 strands of silver-plated copper wire to each electrode portion of the pattern.

9 is an exemplary view of a photo of a heating test of a flexible electrode pattern according to the present invention.

In addition, an example in which heat was generated by supplying electricity of 5V and 2A to a flexible electrode after bonding a 300um cloth to the printed surface as an insulating layer is shown in FIG. 9. As shown in FIG. 9, it was confirmed that heat spreads and maintains an even heating state.

The electric wire is a method of facing the coated surface of a polyester cloth that has become a waterproof coating such as PU (polyurethane-based, acrylic-based, and polysiloxane-based) and placing the electric wire therebetween and attaching it with adhesive. It is recommended to use a waterproof coating polyester cloth with a thickness of about 100um.

The contact between the silver nanowire printed electrode and the electric wire portion is generally bonded through an eyelet, but in the present invention, the silver nanowire electrode is printed linearly and the silver-plated copper wire is laid linearly to maximize the contact area to increase the contact stability. (Heat wires, electrodes, and wires have the most defects at the junction.)

The laminated structure is produced in the order of polyester fabric-PU waterproof coating-silver nanowire printing-silver plated copper wire-adhesive containing TPU-PU waterproof coating-polyester fabric. Laminated silver nanowire printing surface and silver-plated copper wire are zigzag-stitched along the wire arrangement direction from the outside to prevent falling into frequent washing. The number of washable times increases more than 2 times depending on whether the lock is sewn.

The wire and connector connections are secured using gold-plated rivets. It is a general gold-plated rivet for the purpose of preventing corrosion by washing and reducing contact resistance.

On the other hand, in order to check the elasticity of the flexible electrode, a silver nanowire ink was coated on a TPU film to a thickness of 10 μm, dried, and cut into a length of 10 cm and a width of 3 cm.

At this time, the initial resistance was 10 ohms.

In this state, when stretched 150% in the longitudinal direction, the resistance rose to 300 ohms, and the film returned to its original state when the pulling force was subtracted.

Thus, by confirming that the resistance is changed by stretching, it was confirmed that the applicability as an electrode while being a stretch sensor that senses movement by attaching it to clothing or a joint of a body.

In addition to this, the present invention can be used for products requiring a thin heating element, such as a heating jacket, a heating vest, a heating waistband, a heating bag, a heating knee protector, a heating insole, a heating neck warmer, heating gloves, heating underwear, heating pants, etc. There will be.

Claims (8)

Preparing a reaction solution by adding a capping agent, a surfactant, and a catalyst to a reducing solution using a polyol and an antifoaming agent, and injecting a silver source solution into the reaction solution at a constant rate to synthesize silver nanowires;
After the completion of the injection of the silver source liquid in the synthesis step of the silver nano-wire, and spontaneously precipitated while cooling, and recovering the silver nano-wire by centrifuging the precipitate;
Dispersing the recovered silver nanowires in polar solvent, NMP;
A filtering step of filtering the dispersion to filter grains that are difficult to ink;
Sedimenting the filtered solution for 2 hours or more to obtain a precipitate;
Adding a binder and a solvent to the precipitate and mixing and stirring to make ink;
Silver nano-wire ink manufacturing method, characterized in that consisting of.
The method according to claim 1,
The silver nano-wire synthesis step,
A reducing solution preparation step for producing a reducing solution using a polyol and an antifoaming agent;
A reaction solution preparation step of adding a capping agent, a surfactant and a catalyst to the reduced solution to make a reaction solution;
A silver source preparation step of preparing a silver source solution by dissolving silver nitrate in a solvent;
A silver nanowire generation step of injecting the prepared silver source solution into the reaction solution at a constant rate to make a silver nanowire;
Silver nano-wire ink manufacturing method comprising a.
The method according to claim 1,
A sample of a predetermined amount of silver nanowires recovered after the centrifugation or sedimentation before centrifugation in the recovery step is inspected with an electron microscope to make ink when the silver nanowires have an average diameter of 90 to 150 nm and an average length of 5 to 15 um. A method of manufacturing a silver nanowire ink, further comprising an inspection step of determining that it is suitable for the silver nanowire composition.
The method according to claim 1,
The binder used in the making of the ink is a silver nanowire ink manufacturing method, characterized in that TPU (thermoplastic polyurethane).
The method according to claim 1,
As a solvent used in the making of the ink, a polar solvent mixed with alcohol or water is used; The alcohols are one of acetone, ethanol, and methanol, and the polar solvent mixed with water is NMP.
The method according to claim 1,
The step of making the ink,
The silver nano-wire and the binder TPU is 4: 1-6: a weight ratio of the silver nanowire ink manufacturing method, characterized in that characterized in that the solvent containing NMP 200% or more of the TPU.
The method according to claim 6,
5-10 parts by weight of polyimide, novolak resin, acrylic, cellulose-based, methacryl-based, styrene-based, and vinyl acetate-based resins are added to the TPU to 100 parts by weight of the TPU to further increase the bending and folding characteristics of the TPU. Silver nanowire ink manufacturing method characterized in that added.
The method according to claim 6,
The TPU is selected from butyl carbitol, terpinol, cocosol, methyl silicate, xylene, 1,4-butanediamine (BDA), ether, glycol ether, acetate, texanol, pine oil, green tea oil, and butyl carbitol acetate. A method of manufacturing silver nanowire ink, characterized in that, by adding 5-10 parts by weight to 100 parts by weight of TPU, one is prevented from drying out when printing ink.

Images