KR101991676B1 - Conductive ink composition for forming transparent electrode - Google Patents

Abstract

The present invention relates to a conductive ink composition for forming a transparent electrode. Specifically, the conductive ink composition for forming a transparent electrode according to the present invention has excellent electrical conductivity and visible light transmittance since it forms a conductive network with metal nanowires and complements disconnection of a metal sol, Since it acts as a protective layer for preventing corrosion and oxidation of the metal nanowire, it is not necessary to use a separate antioxidant or a protective layer and it is possible to ensure the environmental resistance of the transparent electrode to be manufactured.

Description

TECHNICAL FIELD [0001] The present invention relates to a conductive ink composition for forming a transparent electrode,

The present invention relates to a conductive ink composition for forming a transparent electrode.

The transparent electrode means an electrode which is transparent to a visible light region (wavelength of 380-780 nm) and has a high electric conductivity, which is obtained by condensing atoms, molecules or ions on a transparent glass substrate or a thin polymer substrate by a physicochemical method. More specifically, the transparent electrode means a thin film having a light transmittance of about 80% or more and a sheet resistance of 500 Ω / □ or less.

 In order to be used as a transparent electrode material, a material having excellent electrical and optical characteristics and etching properties is required. Indium tin oxide (ITO) has been widely used as a material developed to date. However, since ITO is mainly composed of indium, which is an expensive rare metal, a transparent electrode material that can replace the ITO is required.

There is an attempt to use a thin film of gold, silver or copper as a transparent electrode by sputtering a metal such as gold, silver or copper. However, this has a problem that the electrical conductivity is excellent, but the light transmittance in the visible light region is low and the adhesion with the lower substrate is poor.

In addition, the ZnO thin film is a low-cost material, but its electrical conductivity is lower than that of ITO, and the ATO thin film containing a small amount of Sb added to SnO ₂ is not etched and has a problem of high sintering temperature.

In addition, although a method of forming an oxide film using sol-gel synthesis is also used, there is still a problem that a high-temperature process with a low electrical conductivity and a firing temperature exceeding 350 ° C. is required.

In addition, there is a method of manufacturing transparent electrode by preparing oxide of ZnO, ITO, IZO or the like as nano-sized particles and using it to prepare ink or paste, but it is difficult to manufacture nano-sized oxide and relatively high temperature process There is a problem.

In recent years, attempts have been made to apply metal nanowires to transparent electrodes.

In conductive ink for transparent electrode, metal nanowires serve to secure electrical conductivity by forming a network when transparent electrodes are formed. As the metal nanowire network is densely formed, the electrical conductivity of the transparent electrode is improved, but the visible light transmittance is lowered and an excessive cost is required. In addition, even if a conductive network is formed by a metal nanowire, a disconnection of a network is inevitably generated, and an empty space between the networks remains as a nonconductive region having no conductivity. In addition, metal nanowires are nanostructured, and their activity is stronger than that of conventional materials. Therefore, they tend to oxidize and corrode when exposed to air without a protective layer. In particular, silver nanowires have high conductivity and are transparent in the visible light region, but they are known to increase resistance by about 15-20% due to oxidation and corrosion in the atmosphere. To prevent this, a separate antioxidant or a plurality of protective layers There is a problem in that it is necessary to use.

In order to solve the above-described problems, the present invention provides an organic electroluminescent display device which exhibits excellent electrical conductivity and visible light transmittance, does not require a separate antioxidant or a protective layer for preventing corrosion and oxidation of metal nanowires, And a conductive ink composition for a transparent electrode.

It is another object of the present invention to provide a method of forming a transparent electrode using the composition and a transparent electrode manufactured by the method.

In order to achieve the above object,

A) a) a metal precursor; b) a metal sol comprising a solvent; And

B) metal wire

And a conductive ink composition for forming a transparent electrode.

Also, the present invention provides a method for producing a conductive transparent electrode, which comprises applying the conductive ink composition for forming a transparent electrode to a substrate, followed by drying and firing, and a conductive transparent electrode produced by the method.

According to the present invention, the conductive ink composition for forming a transparent electrode including the metal sol and the metal nanowire forms a conductive network with the metal nanowire, complements the disconnection of the metal sol-gel network and fills the void space, Respectively. In addition, since the metal sol functions as a protective layer for preventing corrosion and oxidation of the metal nanowire, a separate antioxidant or a protective layer is not required and the environmental resistance of the transparent electrode to be manufactured can be ensured.

1 is a conceptual view showing an embodiment of a transparent electrode formed according to the present invention.
2 is a scanning electron microscope enlarged view of a transparent electrode formed according to the present invention.
3 is a visible light transmittance of the transparent electrode formed according to the present invention.
[Description of Symbols]
11: metal nanowire
12: metal sol

The conductive ink composition for forming a transparent electrode of the present invention

A) a) a metal precursor; b) a metal sol comprising a solvent; And

B) metal wire

And a control unit.

The metal sol according to the present invention can be prepared at room temperature and atmospheric pressure. Since the metal content of the metal sol can be controlled within the range of the solubility of the metal precursor, it is possible to control the metal concentration as well as control the viscosity and the firing temperature. In addition, when a conductive ink composition for forming a transparent electrode is mixed with a metal nanowire, a strong acid or a strong base is not used, so that the metal nanowire is not damaged.

The metal sol usable in the present invention serves to improve the electrical conductivity of the entire coating by complementing the disconnection of the network without damaging the metal nanowires and filling the void space between the networks with the conductive metal coating. It also prevents oxidation of the metal nanowires and serves as a protective layer to prevent wear. In particular, it prevents permeation of substances that can corrode metal nanowires such as moisture, oxygen, sulfur, etc., as well as improves the adhesion between the metal nanowires and the lower substrate.

The metal of the metal precursor a) which can be used for the metal sol is not particularly limited, but is preferably a Group I element such as gold, silver, copper, aluminum, nickel, tin, palladium, platinum, zinc, iron, indium, magnesium, At least one metal selected from the group consisting of zinc, aluminum, tin, iron, copper and silver is preferably used. It is better to use at least one.

The metal precursor may be at least one inorganic salt selected from the group consisting of nitrate, acetate, acetylacetonate, silicate, phosphate, and mixtures thereof, preferably acetic acid salt, acetylacetone salt or silicate .

The metal precursor is preferably used in an amount of 3 to 20% by weight based on the total weight of the metal sol. When the metal precursor is used in an amount of less than 3 wt%, it can not form a dense metal coating layer and can not act as a protective layer of metal nanowires. When the content is more than 20% by weight, the stability of the metal sol is lowered, and the metal precursor is precipitated, or the calcination temperature is required to be 300 ° C or more, and the calcination time is 30 minutes or more. .

The solvent used for dissolving the metal precursor in the present invention may be water, methanol, ethanol, propanol, isopropanol, isopropyl acetate, butanol, 2-butanol, octanol, 2-ethylhexanol, pentanol, Ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, Glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, 2-propane Diacetyl, acetyl acetone, 1,2-diacetyl ethane, dimethyl carbonate, diethyl carbonate, pro At least one solvent selected from the group consisting of methanol, ethanol, propanol, isopropanol, isopropanol, n-butanol, isopropanol, n-butanol, Preferably, acetylacetone alone or a mixed solvent containing the same may be used. It is preferable to select the solvent in consideration of the dissolving power to the metal precursor, the viscosity control of the ink, the formation of a smooth thin film, and the mixing with the metal nanowire. And more preferably, the content of the solvent in the metal sol of the present invention is 80-97 wt%.

When two or more kinds of solvents are mixed and used, the mixing ratio of the solvents is preferably 0.2 to 0.8 parts by weight based on 1 part by weight of the main solvent. The main solvent may be selected from one of the solvents listed above, and at least one solvent other than the solvent used as the main solvent may be used as an auxiliary solvent. Solvent Mixing Ratio When the mixing ratio is within the above range, effects such as ease of viscosity control, increase in solubility of the metal precursor, and control of the firing temperature of the conductive ink can be obtained.

For example, there is a problem that terpineol or nonanol has a high viscosity and a high boiling point, thereby increasing the firing temperature of the conductive ink. When methanol, ethanol or the like is used as an auxiliary solvent within the above range, the viscosity is lowered and the boiling point is lowered, so that the firing temperature of the conductive ink can be controlled. However, when the content of methanol and ethanol is out of the above range, the viscosity and the firing temperature lowering effect can not be expected. On the other hand, when the content of methanol and ethanol is excessively added, the proper viscosity of the conductive ink can not be maintained, . Further, diacetyl, acetylacetone, dimethyl carbonate or ethylene glycol is a solvent having a relatively good solubility with respect to a metal precursor, and addition of methanol, ethanol, isopropanol or the like as an additional solvent has an effect of drastically increasing solubility in a metal precursor It is suitable for making high-concentration metal sol, but if it is out of the range, the effect is reduced.

The metal sol according to the present invention can be prepared by dissolving the metal precursor in the solvent under normal temperature and normal pressure conditions.

More specifically, the metal sol can be prepared by using an inorganic salt of a metal as a metal precursor, preferably a metal acetate, an acetylacetone salt or a silicate, and using acetylacetone or a mixed solvent containing the same as a solvent, And the metal precursor is simply dissolved in an appropriate solvent, so that the production method is simple. In addition, since the metal content of the metal sol can be controlled within the range of the solubility of the metal precursor, a metal sol having a high concentration can be produced at a low concentration as well as a dense metal coat can be formed. Also, there is no damage to the metal nanowires because no strong acid or strong bases are used.

The metal of the metal nanowire B) which can be used in the present invention is not particularly limited, but is preferably a metal of Group I, such as gold, silver, copper, aluminum, nickel, tin, palladium, platinum, zinc, iron, indium, It is preferable to use at least one metal selected from the group consisting of Group IIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, Group IIIA, It is better to use one or more metals. The metal nanowires preferably have a diameter of 20 to 120 nm and a length of 5 to 60 μm.

The metal nanowires are preferably contained in an amount of 0.25 to 4 parts by weight based on 1 part by weight of the metal precursor contained in the metal sol. When the metal nanowire is used in an amount of less than 0.25 parts by weight, the metal nanowire is difficult to form a network due to difficulty in forming a network, and when the content exceeds 4 parts by weight, the metal nanowire forms a network The substrate is blurred, which is undesirable because it causes a decrease in visible light transmittance.

The metal nanowires are preferably dispersed in a dispersion, and the dispersion may be a solvent used for preparing the metal sol. For example, a dispersion medium-metal nanowire dispersed in a dispersion medium is mixed with the metal sol by mixing a metal precursor and a solvent to produce a metal sol, wherein a part of the solvent is used as a dispersion medium of the metal nanowire to form a conductive ink composition And the content of each component in the conductive ink composition for forming the final transparent electrode can be controlled within the range described above.

The conductive ink composition for forming a transparent electrode according to the present invention may contain, in addition to the metal sol and the metal nanowire, additives commonly used in the art if necessary.

The conductive ink composition for forming a transparent electrode according to the present invention preferably has a pH range of 6 to 9. When the pH is less than 6, the metal nanowires can be oxidized in the solution by an acid atmosphere, and even when the pH is more than 9, the metal nanowires may oxidize, cut or dissolve.

The present invention also provides a method of manufacturing a conductive transparent electrode, which comprises applying the conductive ink composition for forming a transparent electrode to a substrate and firing the conductive ink composition, and a transparent electrode produced by the method.

The conductive ink composition for forming a transparent electrode according to the present invention may be applied to various printing processes commonly used in the art, for example, gravure off-set printing, gravure direct printing, For example, a glass substrate, a polyimide film, a polyimide film, a polyimide film, a polyimide film, a polyimide film, a polyimide film, a polyimide film, (PI) substrate, a polyethylene terephthalate (PET) substrate, and the like, and the thickness is preferably adjusted appropriately according to the application.

The electrode thus prepared can be fired according to a firing method commonly used in the art, and the firing conditions can be appropriately controlled according to the characteristics of the substrate and the composition, , And is preferably baked at 80 ° C to 250 ° C.

The transparent electrode according to the present invention can be advantageously applied to electrodes such as a liquid crystal display, a plasma display, a touch panel, an electroluminescent device, a thin film solar cell, a dye sensitized solar cell, and an inorganic crystalline solar cell.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Examples 1 to 14: Preparation of conductive ink for transparent electrode

Metal precursors and solvents were mixed at room temperature and normal pressure according to the ingredients and contents shown in Table 1 below to prepare metal sols, and nanowire dispersions were mixed to prepare conductive inks for transparent electrodes. At this time, as the metal nanowire dispersion, a silver nanowire dispersion in which silver nanowires were dispersed in isoppanol at a concentration of 0.8 wt% was used.

Unit (g) Metal precursor 1 Metal precursor 2 Metal precursor 3 Main solvent Minor solvent 1 Minor solvent 2 Example 1 Zn AcAc 0.3 AcAc 6 Example 2 Zn AcAc 2 AcAc 6 EtOH 3 Example 3 Zn AcAc 1.5 AcAc 5 MtOH 2 Example 4 Zn AcAc 0.8 EtOH 5 AcAc 2 Example 5 Zn AcAc 0.8 EtOH 5 AcAc One IPAC One Example 6 Zn AcAc 0.8 Fe AcAc 0.01 EtOH 5 AcAc One IPAC One Example 7 Zn AcAc 0.8 Cu AcAc 0.05 EtOH 5 AcAc One IPAC One Example 8 Zn AcAc 0.8 Cu AcAc 0.05 Fe AcAc 0.01 EtOH 5 AcAc One IPAC One Example 9 Zn AcAc 0.8 EtOH 5 AcAc One IPA One Example 10 Zn AcAc 0.8 Fe AcAc 0.01 EtOH 5 AcAc One IPA One Example 11 Zn AcAc 0.8 Cu AcAc 0.05 EtOH 5 AcAc One IPA One Example 12 Zn AcAc 0.8 Cu AcAc 0.05 Fe AcAc 0.01 EtOH 5 AcAc One IPA One Example 13 Zn AcAc 1.8 AcAc 6 IPA 2 Example 14 Zn Ac 0.5 AcAc 6 Example 15 Zn Ac 0.5 MtOH 6 Example 16 Zn Ac 1.5 MtOH 12 AcAc 4 Example 17 Zn Ac One EtOH 10 IPA 2 MtOH One Example 18 Zn AcAc 1.5 Cu AcAc 0.05 AcAc 6 EtOH 4 Example 19 Zn AcAc 1.5 Cu AcAc 0.05 Sn AcAc 0.05 AcAc 6 EtOH 4 Example 20 Zn AcAc 1.5 Cu AcAc 0.05 Fe AcAc 0.01 AcAc 6 EtOH 4 Example 21 Zn AcAc 1.5 Cu AcAc 0.05 AcAc 6 MtOH 3 Example 22 Zn AcAc 1.5 Cu AcAc 0.05 AcAc 15 IPA 4 Example 23 Zn AcAc One Sn AcAc 0.1 EtOH 12 AcAc 4 Example 24 Zn AcAc One Al AcAc 0.01 AcAc 11 IPA 2.4 Example 25 Zn AcAc 1.5 Fe AcAc 0.02 AcAc 5 MtOH 3 Example 26 Zn AcAc One Zn Ac 0.1 AcAc 5 MtOH 3 Example 27 Zn AcAc One Zn Ac 0.1 AcAc 5 EtOH 3 Example 28 Zn AcAc 1.5 Ag Ac 0.01 AcAc 15 MtOH 10 Example 29 Zn AcAc 1.5 Ag AcAc 0.01 AcAc 5 EtOH 3.5

In the above Table 1, Zn AcAc is zinc acetylacetonate, Cu AcAc is copper acetylacetonate, Sn AcAc is acetylacetonate tin, Al AcAc is aluminum acetylacetonate, Fe AcAc is acetylacetonate iron, Zn Ac is zinc acetate, Ag Ac represents acetic acid, Ag AcAc represents acetylacetonic acid, AcAc represents acetylacetone, and IPA represents isopropanol.

Test Example 1

The visible light transmittance and conductivity of the conductive ink for transparent electrode prepared in Examples 1 to 14 were measured to evaluate the environmental resistance.

Specifically, after cleaning the glass substrate to remove foreign matter such as organic matters, the conductive inks for transparent electrodes of Examples 1 to 14 were applied to the glass substrate, respectively. After the application, heat treatment was performed at 200 占 폚 for 10 minutes.

The visible light transmittance was measured using a Agilent Cary 4000 UV-Visible Spectrophotometer in a wavelength range of 400 nm to 800 nm, and the conductivity was measured by measuring the sheet resistance with a conductive 4-point measuring instrument. At a temperature of 85 ° C and a humidity of 85% The environmental resistance was evaluated by measuring the time during which the sheet resistance did not change. The results are shown in Table 2 and FIG.

Light transmittance (%) Sheet resistance (Ω / □) Environmental evaluation (hr) Example 1 97.51 187 240 Example 2 98.85 255 360 Example 3 97.37 242 360 Example 4 98.54 210 360 Example 5 98.07 195 320 Example 6 97.15 182 296 Example 7 97.59 157 344 Example 8 97.37 175 344 Example 9 98.72 207 380 Example 10 96.42 215 296 Example 11 97.47 190 320 Example 12 98.02 205 320 Example 13 98.46 250 360 Example 14 97.91 196 264 Example 15 98.11 198 216 Example 16 97.67 220 216 Example 17 97.88 205 320 Example 18 96.79 237 192 Example 19 97.63 245 264 Example 20 96.27 200 288 Example 21 96.25 225 192 Example 22 97.14 230 192 Example 23 96.24 478 240 Example 24 96.79 493 240 Example 25 96.33 250 144 Example 26 96.53 395 192 Example 27 97.26 403 192 Example 28 94.34 207 216 Example 29 93.77 264 216

As shown in Table 2 and FIG. 3, according to the present invention, a transparent electrode manufactured using an ink composition containing metal nanowires and a metal sol has excellent light transmittance of 93% or more and a sheet resistance of 500 Ω / □ or less.

Further, since the metal sol acts as a protective layer of the metal nanowire and exhibits excellent environmental resistance, no separate antioxidant or protective layer is required.

Claims (12)

A) a) a metal precursor; And b) a metal sol comprising a solvent; And
B) a metal nanowire;
wherein the pH of the conductive ink composition is from 6 to 9. The method according to claim 1,
A) a) 3 to 20% by weight of a metal precursor; And b) from 80 to 97% by weight of a solvent; And
B) 0.25 to 4 parts by weight of metal nanowires based on 1 part by weight of the metal precursor contained in the metal sol;
Wherein the conductive ink composition for forming a transparent electrode is a conductive ink composition for forming a transparent electrode. The method according to claim 1,
Wherein the metal of the metal precursor is at least one metal selected from the group consisting of Group I, IIA, IIIA, IVA, and VIII B metals. The method of claim 3,
Wherein the metal is at least one metal selected from the group consisting of zinc, aluminum, tin, iron, copper and silver. The method according to claim 1,
Wherein the metal precursor is at least one inorganic salt selected from the group consisting of nitrate, acetate, acetylacetonate, silicate, phosphate, and mixtures thereof. 6. The method of claim 5,
Wherein the metal precursor is an acetate salt, an acetylacetone salt, or a silicate. The method according to claim 1,
Wherein the solvent is selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, isopropyl acetate, butanol, 2-butanol, octanol, 2-ethylhexanol, pentanol, benzyl alcohol, hexanol, Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, 2-propanone, diacetyl, acetylacetone, Diacetyl ethane, dimethyl carbonate, diethyl carbonate, propylene glycol methyl ether acetate, 2-methoxyethyl Wherein the solvent is at least one solvent selected from the group consisting of citrate, propylene glycol monomethyl ether, N-methyl-2-pyrrolidone, N-methylacetamide and mixtures thereof. 8. The method of claim 7,
Wherein the solvent is a mixed solvent of two or more kinds, and 0.2 to 0.8 parts by weight of a minor solvent is mixed based on 1 part by weight of the main solvent. delete 9. A method for producing a conductive transparent electrode, comprising applying a conductive ink composition for forming a transparent electrode according to any one of claims 1 to 8 on a substrate, followed by drying and firing. 11. The method of claim 10,
Wherein the firing is performed at 80 to 250 ° C. A conductive transparent electrode produced by the manufacturing method according to claim 10.

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