KR20060004162A - Preparation method of highly concentrated aqueous metal nano sol printable on hydrophobic substrate by inkjet method - Google Patents

Abstract

The present invention relates to a method for producing a partially hydrophobic inkjet-based high concentration metal nano sol, and more particularly, to a polymer-metal salt complex by adding a polymer electrolyte to an aqueous metal salt solution, and then treating the same with a reducing agent to prepare a metal nano sol. The polymer electrolyte may include an acryl-based repeating unit, an acrylate-based repeating unit combined with polyethylene glycol, and an acrylamide repeating unit, a main chain into which a hydrophilic part and a hydrophobic part are introduced together, and the main chain. By using a graft copolymer in which a hydrophilic polymer side chain is bonded to a part of, the particle size of the resulting metal nano sol is smaller than 100 nm, uniform and inkjet technique is directly applied to the hydrophobic substrate. Aqueous, Highly Concentrated Metal Nanoparticles for Partially Hydrophobic Inkjet Printing The present invention relates to a method of manufacturing the same.

Polymer electrolyte, metal nano sol, hydrophobic substrate

Description

Preparation method of highly concentrated aqueous metal nano sol printable on hydrophobic substrate by inkjet method             

1 is a transmission electron microscope (TEM) photograph of a silver (Ag) nano sol powder prepared according to Example 7 of the present invention.

Figure 2 (a) is an optical photomicrograph of a silver nano sol prepared according to Comparative Example 1 of the present invention directly printed on the ITO substrate by the inkjet method, (b) is a silver nano sol prepared according to Example 7 Photograph printed directly on ITO substrate by inkjet technique.

The present invention relates to a method for producing a partially hydrophobic inkjet-based high concentration metal nano sol, and more particularly, to a polymer-metal salt complex by adding a polymer electrolyte to an aqueous metal salt solution, and then treating the same with a reducing agent to prepare a metal nano sol. In the above, the polymer electrolyte includes an acryl-based repeating unit, an acrylate-based repeating unit combined with polyethylene glycol, and an acrylamide repeating unit, a main chain into which a hydrophilic part and a hydrophobic part are introduced together, and the main chain By using a graft copolymer in which a hydrophilic polymer side chain is bonded to a part of, the particle size of the resulting metal nano sol is smaller than 100 nm, uniform and inkjet technique is directly applied to the hydrophobic substrate. Aqueous, Highly Concentrated Metal Nanoparticles for Partially Hydrophobic Inkjet Printing It relates to a method for preparing a sol.

In general, in order to effectively transmit visible light generated from a phosphor in a flat panel display plasma display panel (PDP), a transparent electrode and a low resistance bus electrode for transmitting a signal to the transparent electrode are required.

Representative methods that have been put to practical use as a method for forming bus electrodes among the electrodes include screen printing of Ag electrodes, photolithography patterning of Ag electrodes, or photoetching of Cr / Cu / Cr electrodes. Although the photosensitive electrode paste manufactured by the photolithography method which is currently used most among the above methods has an excellent resolution when forming a fine pattern, it still takes a long time in the manufacturing process due to printing, exposure, drying and developing processes. It has a disadvantage.

Accordingly, there is a need for a new pattern formation technology using a new technique, which is improved in terms of manufacturing process and cost, compared to the photolithography method.

Currently, as the fine pattern forming technology, a solution or a suspension is added to several tens of pL (pico) through screen printing, a photolithography method that enables the formation of a small line width, and a micronozzle. The inkjet method of spraying a droplet of liter) to form fine lines or dots of several tens of micrometers in width is used.

Comparing the inkjet technique with the screen printing or photolithography method, the following advantages are specifically mentioned. First, no mask for forming fine lines is necessary. Second, it is not affected by the size of the substrate to be printed. Third, the printing time is short and the process is simple. Fourth, it is an eco-friendly process with little waste, and consumes less material.

In other words, the current position of the inkjet technique lies between screen printing and photolithography methods in terms of manufacturing cost and resolution, and is expected to serve as a bridge between nano and micro fields, and may partially replace these two technologies. It is expected.

Therefore, the recent movement of the inkjet technique in the production of electrodes in all flat panel display fields, such as liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), field emission displays (FEDs), etc. It is actively underway.

In order to apply the inkjet technique to the display manufacturing process, it is very important to diversify inkjet ink materials and control the wettability of the substrate to be printed. In view of the diversification of the inkjet ink material, not only a metal nano sol having dispersion stability and uniformly sized particles is required for stable inkjet injection, but also for the connectivity and high conductivity of the electrode after formation and sintering of fine lines High concentrations of metal nano sol are required.

At present, the method for producing the metal nanoparticles is known as a physical method such as a gas phase method and a chemical synthesis method using a liquid phase reaction. There is a prior art.

However, it would be more useful to employ a method of improving the production efficiency of high concentration of metal nanosol by using a relatively simple synthesis device as an environmentally friendly aqueous solution chemical method, rather than using an expensive device such as using a laser. It is feed.

When preparing metal nanoparticles by chemical method, control of particle size and particle size distribution is an important requirement, and most suitable surfactants (anti-agglomerating agent or Dispersing agent).

Many researches have been conducted in relation to the preparation method of the metal powder using such a surfactant, and Korea Patent Publication No. 2002-0022168, 2001-0070070, 2000-0012423, 2000-0011546, etc. Several inventions have been filed and published.

However, when the metal nanoparticles are prepared using the surfactant as described above, the smaller the size of the metal nanoparticles to be prepared, the exponentially increasing the amount of the surfactant to be used to prevent the growth and aggregation of the particles. . Therefore, there is a disadvantage that simply by using a surfactant can not control the concentration of the metal nanoparticles above a certain concentration.

In order to overcome the above-mentioned drawbacks, the chemical manufacturing method of the metal nanoparticles was improved to reduce the metal ions in the metal salt solution with a suitable reducing agent, and then a surfactant was added to the surface of the metal particles to be reduced to adsorb the surface. By inhibiting particle growth, it is possible to produce fine metal particles without using an excessive amount of surfactant.

MEANS TO SOLVE THE PROBLEM The present inventor adds a polymer electrolyte to a metal salt aqueous solution, forms a polymer-metal ion complex, and then processes it with a reducing agent to produce high concentration metal particles of fine and uniform size without aggregation or sedimentation of the metal particles. Application No. 2003-0015923 has been proposed.

The metal nano sol prepared by the above method has a contact angle characteristic similar to that of distilled water. In this case, the contact angle is generally a measure of the wettability of the solid surface, and is measured by mostly fixed water droplets, and a low contact angle indicates high wettability and a high contact angle indicates low wettability. The wettability of the water-based metal nano sol to the glass substrate has almost the same characteristics as distilled water.

However, the wettability of distilled water and silver nano sol on hydrophobic substrates such as pure ITO substrates is very different from the wettability on glass substrates. For example, the contact angles measured for glass of distilled water and silver nano sol are as low as 27.1 ° and 21.6 °, whereas the contact angles are large at 82.7 ° and 66.1 ° on pure ITO substrates.

That is, the aqueous metal nano sol manufactured by the method proposed to date has a strong hydrophilicity, so it is difficult to print directly due to low wettability to an ITO substrate having high hydrophobicity, and formation of fine lines used for electrodes such as flat panel displays. Is an impossible situation at all.

Accordingly, the present inventors have made an effort to find a method that can be directly printed on a hydrophobic substrate. As a result, an acrylic repeating unit is used as a polymer electrolyte used when producing a fine and uniform metal nano sol using a complex formation effect between a polymer electrolyte and a metal ion. And a main chain including a acrylate repeating unit and an acrylamide repeating unit bonded to polyethylene glycol, a main chain into which a hydrophilic part and a hydrophobic part are introduced, and a polymer side chain having a high hydrophilicity on a part of the main chain. By using a graft copolymer having a chain bonded thereto, hydrophobicity can be imparted to the aqueous high-concentration metal nano sol, which has a poor hydrophilicity and poor wettability with a hydrophobic substrate, thereby completing the present invention.

Accordingly, an object of the present invention is to provide a method for producing a partially hydrophobized inkjet-based high-concentration metal nano sol capable of directly printing a hydrophobic substrate to form fine lines.

The present invention is a method for preparing a metal nano-sol by adding a polymer electrolyte to a metal salt aqueous solution to form a polymer-metal salt complex and then treating it with a reducing agent, wherein the polymer electrolyte is an acrylic repeating unit as shown in the following formula (1) And a method for producing a partially hydrophobized inkjet-based high concentration metal nano sol using a graft copolymer comprising an acrylate repeating unit and an acrylamide repeating unit structure.

In Chemical Formula 1; R ₁ is H or CH ₃ , R ₂ is H or cation selected from ammonium, sodium, potassium, n is an integer from 5 to 40, x is 0.3 to 0.7, y is 0.3 to 0.7, z is It is 0-0.1, and x + y + z = 1.

In the present invention, the polymer electrolyte is added to an aqueous metal salt solution to form a polymer-metal salt complex and then treated with a reducing agent to prepare a metal nano sol. As the polymer electrolyte, an acryl-based repeating unit and an acrylate-based repeating unit of polyethylene glycol are combined. A graft copolymer comprising a main chain including a unit and an acrylamide repeating unit and having a hydrophilic part and a hydrophobic part introduced therein, and a hydrophilic polymer side chain bonded to a part of the main chain. By using, the particle size of the produced metal nano sol is small and uniform to 100 nm or less, and it is possible to print directly on the hydrophobic substrate by inkjet technique, so that it is possible to form a fine line of the partially hydrophobized inkjet aqueous high concentration metal nano sol. It relates to a manufacturing method.

Referring to the present invention in more detail as follows.

Prior to the detailed description of the present invention, although briefly mentioned in the related art, a method for preparing a metal nano sol proposed by the present inventor will be described in detail in order to help the present invention.

That is, in the production of metal nanoparticles by adding a reducing agent to the aqueous metal salt solution, when a polymer electrolyte as shown in Formula 2 is used, the metal ions to be reduced are substituted for each structural unit of each polymer electrolyte, thereby Since the growth of particles is suppressed from the reduction process, smaller metal particles can be produced as compared with the use of general surfactants. Moreover, since the polymer electrolyte has a large number of functional groups capable of substituting metal ions in one electrolyte, general surfactants Compared with the use of very small amounts, it is possible to effectively control the aggregation and growth of the particles, which enables the preparation of small, uniform, high concentration metal nano sol having a particle size of 100 nm or less.

However, the metal nano sol prepared using the polymer electrolyte as described above is very hydrophilic and is very suitable for coating and micropatterns on hydrophilic surfaces such as glass substrates, but it is desired to form fine lines on hydrophobic substrates using inkjet techniques. The wettability of the prepared water-based metal nano sol is not good with the hydrophobic substrate, so direct printing is impossible.

Thus, in the present invention, the polymer electrolyte is used as a graft copolymer in which the type and amount of each chain is changed to have a hydrophobic part and a hydrophilic part at the same time. have.

Comparing the polymer electrolyte used to prepare the metal colloid with the polymer electrolyte which is the graft copolymer used in the present invention, the conventional polymer electrolyte is a copolymer based on polyethylene and polyacrylic acid. The repeating unit and acrylamide repeating unit are graft copolymerized. In addition, the hydrophobic acrylate-based repeating unit has polyethyleneglycols as a hydrophilic side chain, each repeating unit may include ammonium, sodium, calcium, and the like. As a result, the polymer electrolyte of the present invention including the repeating unit includes a main chain having a hydrophilic portion and a hydrophobic portion and a side chain having strong hydrophilicity.

As a specific example of the preparation of the polymer electrolyte used in the present invention, methoxy polyethylene glycol (MPEG) is prepared by addition polymerization of methanol and ethylene oxide in the presence of a catalyst, and esterification of the MPEG and methacrylic acid to terminate the MPEG. After preparing methoxy polyethylene glycol methacrylate (MPEGMA) containing acrylic acid, and finally using a polycarboxylic acid polymer electrolyte prepared by copolymerizing the MPEGMA with an acrylic repeating unit selected from acrylic acid, amine ester, phenyl ester, etc. do. The preparation method of the polymer electrolyte is shown in Scheme 1 below.

The polymer electrolyte used in the present invention prepared as described above may be represented by the following formula (1).

[Formula 1]

In Chemical Formula 1; R ₁ is H or CH ₃ , R ₂ is H or cation selected from ammonium, sodium, potassium, n is an integer from 5 to 40, x is 0.3 to 0.7, y is 0.3 to 0.7, z is It is 0-0.1, and x + y + z = 1.

As described above, the main chain chain of the polymer containing an acryl repeating unit has a carboxyl group at its end and is easily attached to the inorganic particles during nucleation of the colloid. The side chain chain of polyethylene glycol, which has a very high water solubility, increases hydrophilicity in aqueous solution and has a long polymer. By increasing the steric phenomena by the chain to stabilize the growth of the particles it is possible to produce a stable high concentration of metal nano sol.

The manufacturing method of the high concentration metal nano sol according to the present invention is as follows. First, a soluble metal salt is added to distilled water to prepare an aqueous metal salt solution. The polymer electrolyte is added to the aqueous metal salt solution and stirred to form a polymer-metal salt complex. Then, a reducing agent is added to the polymer-metal salt complex-containing solution to reduce metal ions to obtain a metal particle solution.

Looking at each component used in the manufacturing method of the present invention described above is as follows.

The metal salt is a soluble salt of a metal ion selected from silver (Ag), copper (Cu), nickel (Ni), gold (Au), palladium (Pd) and platinum (Pt), and includes nitrates, sulfates, carbonates or Soluble metal salts that are soluble in water, such as chloride, are used. Specifically, silver nitrate (AgNO ₃ ), copper nitrate (Cu (NO ₃ ) ₂ ), nickel nitrate (Ni (NO ₃ ) ₂ ), and gold hydrochloride (AuCl ₃ ) , Platinum hydrochloride (PtCl ₂ , PtCl ₄ ) and the like can be used.

As the reducing agent, NaBH ₄ , LiAlBH ₄ , hydrazine, hydrazine hydrate, formaldehyde, or the like may be used. The reducing agent uses 0.1 to 1.5 equivalents with respect to 0.1 equivalent of the metal salt to be reduced. If the amount of the reducing agent is less than 0.1 equivalent, there may be a problem that the metal salt may not be reduced by 100%. It is undesirable because it is wasted.

As the polymer electrolyte, the above-described ones may be used, and may vary depending on the degree of polymerization of the polymer, but in general, it is preferable to add 10 to 150 parts by weight based on 1 part by weight of the metal salt. If the amount of the polymer electrolyte is less than 10 parts by weight, the fixing effect of the metal ions is remarkably decreased, so that the metal ions are freely present in the solution, and the agglomeration occurs in the reduction process, so that the effect of adding the electrolyte is halved. If the portion is exceeded, there is a problem that the solution gels due to a decrease in solubility.

According to the production method of the present invention as described above, it is possible to prepare a high concentration metal nano sol having a particle size of 100 nm or less, and also to prepare a high concentration solution of 10% by weight or more, as well as a low concentration solution in the concentration of the metal particle solution. have. In addition, it was confirmed that the metal particles solution of high concentration prepared by the method of the present invention did not easily aggregate or settle even after being left for a long time.

The present invention as described above will be described in more detail based on the following examples, but the present invention is not limited by the following examples.

Synthesis Example 1 Synthesis of Polymer Electrolyte

Substitute oxygen by using nitrogen in an autoclave equipped with a thermometer and a stirrer, add 32 parts by weight of methanol, 0.2 parts by weight of sodium hydroxide as a catalyst, and inject ethylene oxide while raising the temperature to 70 to 155 °. The reaction was carried out to prepare methoxy polyethylene glycol (MPEG) in which 9 mol of ethylene oxide was added to methanol.

Into a glass reactor equipped with a thermometer, a stirrer, a product water separator, and a reflux condenser, 1300 parts by weight of phase MPEG 9 mol, 650 parts by weight of methacrylic acid, 800 parts by weight of benzene and 10 parts by weight of sulfuric acid with a catalyst and 0.5 part by weight of hydroquinone as a polymerization inhibitor were added. While stirring at 400 rpm, the reaction temperature was raised to 90 °, which was an esterification reaction.

After confirming the degree of ester reaction by distillation of the desired product water and liquid chromatography, the reaction was terminated to prepare 9 moles of MPEGMA, followed by removing the solvent used in the reaction, followed by washing and neutralizing the acid catalyst.

1300 parts by weight of distilled water was added to 1300 parts by weight of 9 moles of MPEGMA prepared above, and the mixture was stirred well. Separately, 300 parts by weight of methacrylic acid as an acrylic monomer and 10 parts by weight of ammonium persulfate as a polymerization initiator were dissolved in distilled water. After dropping for 2 hours, the reaction was terminated by maintaining the reaction temperature for 3 hours after completion of dropping, and a predetermined amount of sodium hydroxide was added thereto to obtain a polycarboxylic acid-based polymer electrolyte maintained at neutral pH.

The calculated HLB of the obtained polycarboxylic acid-based polymer electrolyte was 11.4, the weight average molecular weight was 32400, and the polymer concentration in the aqueous solution was 40%.

Synthesis Examples 2 to 13: Synthesis of Polymer Electrolyte

A polymer electrolyte was prepared under the same conditions as in Synthesis Example 1, and in order to change the structure of the main chain and the side chain in preparing the polycarboxylic acid polymer electrolyte, the type of MPEGMA chain, the type of acrylic monomer, By changing the amount of use as shown in Table 1 to prepare a polycarboxylic acid-based polymer electrolyte.

The concentration of the polymer in the HLB, the weight average molecular weight and the aqueous solution of the polycarboxylic acid-based polymer electrolyte obtained in Synthesis Examples 2 to 13 are shown in Table 1 below.

Examples 1-9 and Comparative Examples 1-6: Preparation of High Concentration Metal Nano Sols

After dissolving silver nitrate in distilled water with a soluble silver salt, the polymer electrolyte was dispersed and stirred for 1 hour to form a polymer-silver nitrate complex in which silver ions were substituted in the polymer electrolyte functional group. Separately, a reducing agent solution was prepared by dissolving an equivalent amount of NaBH ₄ required to reduce the silver nitrate in distilled water. The silver-Ag ions were reduced by slowly dropwise adding the reducing agent solution prepared above while strongly stirring the solution containing the polymer-silver nitrate. After the reduction reaction, the solution appeared dark black, and when diluted, the solution appeared light yellow. The silver particle solution containing the silver particles thus prepared was analyzed by particle size analyzer and transmission electron microscope (TEM). The amount of each component used in preparing the silver nano sol and the size of the prepared silver nano particles are shown in Table 2 below.

As shown in Table 2 above, according to the method of the present invention, it is possible to produce uniform silver particles having an ultrafine size of 100 nm or less, fix the concentration of the silver salt to 15.7% by weight and change the structure of the main chain of the polymer electrolyte. As a result of the preparation of the silver nano sol, it was confirmed that the silver particles of 20 to 100 nm size were prepared even in the ultra high concentration of 10 wt%, and synthesized the silver nano sol regardless of the main chain of the polymer electrolyte. .

The silver nano sol prepared according to Examples 1 to 9 and Comparative Examples 1 to 6 was prepared at a concentration of 10%, and the results of forming fine lines on the ITO substrate using the inkjet method are shown in Table 3 below.

As shown in Table 3, in Comparative Examples 1 to 3, dots were formed without forming a fine line (refer to FIG. 2 (a)). However, high concentrations using a partially hydrophobized polymer electrolyte as in Examples 1 to 9 were used. In the case of using a silver nano sol, it was very easy to form fine lines (see FIG. 2 (b)).

 As described above, in the present invention, a polymer-metal salt complex is formed by adding a main chain in which a hydrophilic part and a hydrophobic part are introduced together with a polymer electrolyte prepared by substituting a part of the main chain with a hydrophilic polymer in an aqueous solution in which a metal salt is dissolved. By controlling the particle growth and aggregation during the reduction of ions, it is possible to prepare ultra-sized uniform metal particles of 100 nm or less in a high concentration solution, and also partially hydrophobic to introduce a printable metal directly on the hydrophobic substrate by inkjet technique. Nano sol can be prepared.

Metal nano sol prepared by the manufacturing method according to the present invention is expected to be very useful for electrode materials for display.

Claims (6)

In the method of preparing a metal nano-sol by adding a polymer electrolyte to the aqueous metal salt solution to form a polymer-metal salt complex and then treating it with a reducing agent, As the polymer electrolyte, a partially hydrophobized inkjet for graft copolymer comprising an acryl repeating unit, an acrylate repeating unit, and an acrylamide repeating unit structure as shown in Chemical Formula 1 is used. Process for preparing aqueous high concentration metal nano sol: [Formula 1]

In Chemical Formula 1; R ₁ is H or CH ₃ , R ₂ is H or cation selected from ammonium, sodium, potassium, n is an integer from 5 to 40, x is 0.3 to 0.7, y is 0.3 to 0.7, z is It is 0-0.1, and x + y + z = 1. The method of claim 1, wherein the aqueous metal salt solution is nitrate, sulfate, carbonate or salt of a metal ion selected from silver (Ag), copper (Cu), nickel (Ni), gold (Au), palladium (Pd) and platinum (Pt). A method for producing a partially hydrophobic inkjet water-based high concentration metal nano sol, wherein chloride is dissolved. The method of claim 1, wherein the reducing agent is selected from NaBH ₄ , LiAlBH ₄ , hydrazine, hydrazine hydrate, and formaldehyde. 4. The method of claim 1 or 3, wherein the reducing agent is used in an amount of 0.1 to 1.5 equivalents based on 0.1 equivalents of the metal salt. The method of claim 1, wherein the polymer electrolyte is used in an amount of 10 to 150 parts by weight based on 1 part by weight of the metal salt. The method of claim 1, wherein the produced metal nano sol has a size of 100 nm or less.

Images