KR102024647B1 - Solution type ITO including inorganic ligand and Method of fabricating the same - Google Patents

Abstract

The present invention is ITO particles; Solution ITO surrounding the ITO particles and comprising an iodine-containing inorganic ligand is provided.

Description

Solution type ITO having an inorganic ligand and a method for producing the same {Solution type ITO including inorganic ligand and Method of fabricating the same}

The present invention relates to ITO particles, and more particularly, to a solution type ITO comprising an iodine-containing inorganic ligand and a method for producing the same.

As the society enters the information age, the display field for processing and displaying a large amount of information has been rapidly developed. In response, a liquid crystal display device (LCD) and an organic light emitting diode display device ( Various flat panel display devices such as organic light emitting diode display devices (OELD) have been developed and are in the spotlight.

For example, the liquid crystal display device is driven by using the optical anisotropy and polarization of the liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal. Accordingly, if the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light is refracted in the molecular arrangement direction of the liquid crystal due to optical anisotropy to express image information.

Currently, an active matrix liquid crystal display device (AM-LCD: abbreviated as an active matrix LCD, abbreviated as a liquid crystal display device) in which a thin film transistor and pixel electrodes connected to the thin film transistor are arranged in a matrix manner has the best resolution and video performance. It is attracting attention.

The liquid crystal display includes a color filter substrate having a common electrode, an array substrate having pixel electrodes, and a liquid crystal layer interposed between the two substrates. The liquid crystal is driven by an electric field formed between the common electrode and the pixel electrode.

That is, the liquid crystal display requires a pixel electrode and a common electrode for driving the liquid crystal layer, and they are mainly formed of indium-tin-oxide (ITO), which is a transparent conductive material.

The ITO layer is formed by using a sputter device, and the pixel electrode or the like is formed by patterning the ITO layer by using a photolithography process.

However, the sputter apparatus is very expensive and the process is complicated, which has disadvantages in terms of production efficiency and manufacturing cost.

Recently, to solve this problem, a solution type ITO has been developed. Conventional solution type ITO has a form in which an organic ligand surrounds the ITO particles. For example, a solution type ITO has been proposed in which the ITO particles are surrounded by an organic ligand such as myristic acid.

However, the solution-type ITO containing the organic ligand in this way has a low conductivity because the distance between the ITO particles is increased by the bulky organic ligand. In addition, a high firing temperature of 500 ° C. or higher is required to obtain the required conductivity. In addition, since the solution type ITO having an organic ligand requires a non-polar solvent, solvent selection is limited.

Recently, plastic substrates having flexible characteristics have been used in place of glass substrates. If a pixel electrode or the like is formed using a solution type ITO requiring such a high firing temperature, the flexible substrate may be damaged.

The present invention seeks to solve the problem of low conductivity and high firing temperature caused by the solution type ITO comprising an organic ligand.

In order to solve the above problems, the present invention is ITO particles; Solution ITO surrounding the ITO particles and comprising an iodine-containing inorganic ligand is provided.

In the solution type ITO of the present invention, the iodine-containing inorganic ligand is characterized by being I ^- or BI ₃ .

In another aspect, the present invention comprises the steps of mixing the ITO particles, the molecule containing the inorganic ligand and the solution containing the first polar solvent to form an inorganic ligand substituted ITO particles; Phase separating the ITO particles substituted with the inorganic ligand; It provides a method for producing a solution type ITO comprising the step of dispersing the phase separated inorganic ligand substituted ITO particles in a second polar solvent.

In the method for producing a solution-type ITO of the present invention, the inorganic ligand is I ⁻ and the first polar solvent is ammonia water or sodium hydroxide aqueous solution.

In the solution-type ITO preparation method of the present invention, the inorganic ligand is BI ₃ and the first polar solvent is dimethylformamide.

In the method for producing a solution type ITO of the present invention, the second polar solvent is ethanol.

In the solution-type ITO manufacturing method of the present invention, after the phase separation of the inorganic ligand-substituted ITO particles, before the step of dispersing the ITO particles substituted with the phase-separated inorganic ligand in a polar solvent, the phase separation And separating the ITO particles substituted with the inorganic ligand, followed by phase separation including toluene and the second polar solvent.

Solution-type ITO of the present invention includes an inorganic ligand surrounding the ITO particles, thereby reducing the distance between the ITO particles and improving the conductivity characteristics.

In addition, since the conductive properties are improved even at a low firing temperature, the flexible display device may be formed by being applied to a plastic substrate.

In addition, since the polar solvent is used, the degree of freedom for selecting the solvent can be increased.

1 is a schematic perspective view of a solution type ITO according to an embodiment of the present invention.
2 is an FTIR spectrum of a solution type ITO according to an embodiment of the present invention.
3 is a schematic cross-sectional view of a liquid crystal display device to which a solution type ITO according to the present invention is applied.

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

Solution-type ITO according to an embodiment of the present invention includes ITO particles and an inorganic ligand surrounding the ITO particles. In addition, by including a dispersion solvent in which the ITO particles surrounded by the inorganic ligand is dispersed, the ITO layer is formed by a solution process.

That is, referring to FIG. 1, which is a schematic perspective view of a solution-type ITO according to an embodiment of the present invention, the solution-type ITO 100 includes an ITO particle 102 and an inorganic ligand 104 surrounding the ITO particle 102. It includes. The solution-type ITO 100 is dispersed in a solvent to form an ITO electrode by a solution process.

The solution type ITO 100 is obtained by replacing the inorganic ligand 104 with the inorganic ligand in the ITO particles 102 surrounded by the inorganic ligand 104 surrounded by the organic ligand.

In this case, the inorganic ligand 104 may be an iodine (I) -containing ligand. For example, the inorganic ligand 104 may be I ⁻ or BI ₃ . I ^- ligands are substituted with organic ligands of the ITO particles to surround the ITO particles by electrostatic interaction, BI ₃ The ligand is substituted with the organic ligand of the ITO particles to have a structure surrounding the ITO particles by van der Waals interaction.

Since these inorganic ligands are shorter in length than organic ligands, the distance between ITO particles in the formed ITO electrode is reduced. Therefore, it is possible to form an ITO electrode having a low sheet resistance by a low temperature process, and has an advantage applicable to a flexible substrate such as plastic.

The solution-type ITO according to the present invention is synthesized by mixing the solution in which the iodine salt is dissolved with the ITO particles, replacing the iodine-containing inorganic ligand in the ITO particles, and dispersing the precipitated ITO particles in the solvent.

Hereinafter, specific synthesis examples will be described.

Synthesis Example 1

1) Hexane solution containing ITO particles (20 mg / mL) and ammonia-ethanol solution containing potassium iodide (KI) were mixed at room temperature.

2) The mixture was phase separated by centrifuge.

3) The precipitated ITO particles were mixed with 3 mL of toluene and 3 mL of ethanol at room temperature, and then separated by centrifugation.

4) The precipitated nanocrystals were dispersed in ethanol to synthesize a solution type ITO.

Synthesis Example 2

1) Hexane solution (20mg / mL) containing ITO particles and dimethylformamide (DMF) solution containing boron triiodide (BI3) were mixed at room temperature.

2) The mixture was phase separated by centrifuge.

3) The precipitated nanocrystals were mixed with 3 mL of toluene and 3 mL of DMF and then separated by centrifugation.

4) The precipitated nanocrystals were dispersed in ethanol to synthesize a solution type ITO.

In the above synthesis example, the ITO particles are dissolved in hexane which is an apolar solvent including an organic ligand. In the case of ITO particles, when the organic ligand is bound, the uniformity of the particles is improved. However, bare ITO particles may be used in which the organic ligand is not substituted.

The organic ligand of the ITO particles was replaced with an inorganic ligand by mixing the ITO particles with a solution containing KI, such as ammonia solution, which is a polar solution. Of course, if the ITO particles do not contain an organic ligand, the inorganic ligand is directly bonded to the ITO particles.

Ammonia water serves to improve the yield by lowering the PH value, ammonia water or sodium hydroxide (NaOH) solution may be used instead of ammonia-ethanol solution. The ITO particles substituted with inorganic ligands are then phase separated and dispersed in a polar solvent such as ethanol to give a solution type ITO.

Here, ethanol is a weakly acidic solvent, and proton deprotonation occurs on the surface of ITO nanocrystals (NP) by ethanol. Thereby, the organic ligand which adhered to the surface of an ITO nanocrystal is removed efficiently.

In addition, under ammonia water solution conditions, due to the high electronegativity of the nitrogen atoms, chemical modifications occur on the surface of the ITO nanocrystals (NP). As a result, electrons move and reduction occurs. In addition, dimethylformamide (DMF) stabilizes the unstable ITO nanocrystals when the inorganic ligand is substituted.

On the other hand, step 3) in the synthesis examples 1 and 2 described above is to effectively remove the organic ligand of the ITO particles, which can be omitted.

The FTIR spectrum of the solution type ITO having I-inorganic ligand obtained by Synthesis Example 1 described above is shown in FIG. 2.

Empty reduce the graph (B) of the ITO particles having a peak inorganic ligands in the ^{first wavelength-1} wavelength and 3000cm ^- As shown in Figure 2, 1500cm shown in the graph (A) of the ITO particles having the conventional organic ligand It can be seen. That is, in the solution type ITO of the present invention, it can be confirmed that the organic ligand is substituted with the inorganic ligand.

A solution type ITO having an organic ligand of myristic acid and an inorganic ligand according to the present invention, that is, a solution type ITO having an I ^- inorganic ligand and a BI ₃ inorganic ligand, are respectively coated to a thickness of about 300 nm and then annealed at 150 ° C After the sheet resistance was measured, it is shown in Table 1 below.

Organic ITO BI ₃ ITO I ^- ITO Sheet resistance (kΩ / sq) Not measurable 842.3 375.4

As can be seen from Table 1, after annealing at 150 ° C., the organic ITO layer was too high to measure the sheet resistance. However, the sheet resistance of 300-850 kΩ / sq of the ITO layer using the solution type ITO of this invention was measured.

That is, when a flexible substrate such as plastic is used, an ITO layer having a small sheet resistance can be formed even at a low process temperature. This is an organic ligand of the ITO particles BI ₃ Or because the distance between the ITO particles was reduced by substitution with an inorganic ligand such as I ⁻ .

3 is a schematic cross-sectional view of an array substrate for a liquid crystal display device to which a solution type ITO according to the present invention is applied.

As shown in FIG. 3, a gate line (not shown) is formed along the first direction on the substrate 101, and the gate electrode 112 connected to the gate line is formed in each pixel area P. have.

A gate insulating layer 116 made of an inorganic insulating material is formed on the gate line and the gate electrode 112. The inorganic insulating material may be silicon oxide or silicon nitride.

On the gate insulating layer 116, an active layer 120a made of pure amorphous silicon and an ohmic contact layer 120b formed on the active layer 120a and exposing the center of the active layer 120a and made of impurity amorphous silicon. Is formed. The active layer 120a and the ohmic contact layer 120b form a semiconductor layer 120.

A source electrode 132 and a drain electrode 134 are formed on the semiconductor layer 120 to expose the center of the active layer 120a to be spaced apart from each other.

The semiconductor layer 120, the source electrode 132, and the drain electrode 134 including the gate electrode 112, the gate insulating layer 116, the active layer 120a, and the ohmic contact layer 120b. Is a thin film transistor (Tr).

In addition, a data line 130 extending along the second direction is formed on the gate insulating layer 116 to define the pixel region P by crossing the gate line 110. The data line 130 extends from the source electrode 134 of the thin film transistor Tr.

The first passivation layer 140 is formed to cover the thin film transistor Tr and the data line 130. The first protective layer 140 may be made of an organic insulating material such as benzocyclobutene (BCB) or photo acryl or an inorganic insulating material such as silicon oxide or silicon nitride.

The common electrode 150 made of a transparent conductive material is formed on the first protective layer 140. The common electrode 150 has a plate shape covering the entire display area including the plurality of pixel areas P. Referring to FIG.

The second passivation layer 160 is formed to cover the common electrode 150. The second protective layer 160 may be made of an organic insulating material such as benzocyclobutene (BCB) or photo acryl or an inorganic insulating material such as silicon oxide or silicon nitride. A drain contact hole 162 exposing the drain electrode 134 of the thin film transistor Tr is formed in the second passivation layer 160 and the first passivation layer 140.

The pixel electrode 170 made of a transparent conductive material is formed on the second protective layer 160. The pixel electrode 170 is connected to the drain electrode 134 of the thin film transistor Tr through the drain contact hole 162.

The pixel electrode 170 has a plate shape corresponding to each pixel area P and has a plurality of openings 172. The pixel electrode 170 overlaps the common electrode 150 with the second passivation layer 160 interposed therebetween, and a fringe between the pixel electrode 170 and the common electrode 150 by applying a voltage. Will form a field. A liquid crystal display device including such an array substrate is called a fringe field type liquid crystal display device.

In the array substrate having the above-described structure, the common electrode 150 and the pixel electrode 170 cover the pixel region except for the opening 172 of the pixel electrode 170. Therefore, the common electrode 150 and the pixel electrode 170 should have transparent characteristics.

To this end, each of the common electrode 150 and the pixel electrode 170 is made of a transparent conductive material such as ITO, as described above, the deposition of the ITO layer by the conventional sputtering is expensive and the process of deposition equipment is complicated Therefore, there are disadvantages in terms of production efficiency and manufacturing cost.

In addition, in the case of the solution type ITO having a conventional organic ligand, since the ITO layer can be formed by the coating process, it is advantageous in terms of production efficiency and manufacturing cost compared to the case of using a sputter, but because it requires a high firing temperature, There is a limitation in the application of the same flexible substrate.

However, when the common electrode 150 and the pixel electrode 170 are formed by using the solution type ITO having an inorganic ligand as in the present invention, the production efficiency is higher than that of the stuffer method because the common electrode 150 and the pixel electrode 170 are formed by a coating process. And in terms of manufacturing cost.

In addition, since the inorganic ligand is small in size, it has a sheet resistance lower than that of a solution type ITO having a conventional organic ligand even at a low firing temperature. Therefore, a flexible substrate such as plastic can be applied.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and changes to the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

100: solution type ITO 102: ITO particles
104: inorganic ligand

Claims (7)

ITO particles;
Iodine-containing inorganic ligands surrounding the ITO particles
Solution type ITO comprising a.
The method of claim 1,
The iodine-containing inorganic ligand is solution ITO, characterized in that I ^- or BI ₃ .
Mixing the ITO particles, a molecule containing an inorganic ligand, and a solution containing a first polar solvent to form an ITO particle substituted with an inorganic ligand;
Phase separating the ITO particles substituted with the inorganic ligand;
Dispersing the phase separated inorganic ligand-substituted ITO particles in a second polar solvent
Method for producing a solution type ITO comprising a.
The method of claim 3, wherein
The inorganic ligand is I ⁻ and the first polar solvent is aqueous ammonia or sodium hydroxide aqueous solution.
The method of claim 3, wherein
Wherein said inorganic ligand is BI ₃ and said first polar solvent is dimethylformamide.
The method according to claim 4 or 5,
And said second polar solvent is ethanol.
The method of claim 3, wherein
After the phase separation of the inorganic ligand-substituted ITO particles, before the step of dispersing the phase-separated inorganic ligand-substituted ITO particles in a polar solvent,
And separating the phase separated inorganic ligand-substituted ITO particles with toluene and the second polar solvent, followed by phase separation.

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