KR960011171B1 - Method of manufacturing liquid crystal display contained with indium tin oxide - Google Patents

Abstract

The process that forms transparent conductive film onto a glass substrate by dipping method comprises the steps of : preparing a solution in which a molar ratio of Sn : Sb of 1 : 0.01-0.2 is measured and dissolved to alcohol followed by adding acetic acid to adjust pH 1 below; dipping the pre-treated glass substrate in the solution, holding up the substrate at the rate of 20-30 cm/min, drying in 5 mins. and then dip-coating 1-5 times repeatedly; drying the coated glass substrate in oven at a temperature of 55-110 deg.C for about 1.5 - 2 hrs.; plasticizing the glass substrate in furnace at a temperature of 450-550 deg.C for 5 min.- 2 hrs.; and cooling slowly the substrate at the rate of 20 deg.C/min.

Description

Method of manufacturing tin oxide transparent conductive film containing antimony

Figure 1 schematically shows the manufacturing process of the present invention.

2 is a graph showing the relationship between time and temperature during drying and heat treatment during the manufacturing process of the present invention.

3 is a perspective view of an apparatus for measuring electrical resistance of a transparent conductive film.

The present invention relates to a method for forming a transparent conductive film using antimony oxide and tin oxide, and more particularly, antimony is added in the form of a dopant using a dipping method by a sol-gel method. The present invention relates to a method for producing a transparent conductive film that is not only excellent in effect as a transparent thin film but also economically easy in producing a tin oxide antimony film.

In general, the transparent conductive film is used in places where an electrical shielding function is required as well as transparent electrodes such as liquid crystal display devices (LCDs) and various display devices, or glass free of merchandise shelves, and a method of forming such a conductive thin film is generally used. Five methods are known.

The first is vacuum deposition by evaporation. This method takes advantage of the fact that when the temperature of a solid material is sufficiently raised, the solid material evaporates and is condensed on a low temperature substrate in a vacuum atmosphere to form a thin film. The distance of 10 ~ 50cm and the degree of vacuum should be about 10 ^-5 Torr or less so that the vaporized vapor can reach the substrate.

Korean Patent No. 26766 (Samsung Electric Co., Ltd.) discloses a method of forming a low resistance high transmittance transparent conductive film on a substrate using the vacuum deposition method described above. That is, after mixing indium oxide and tin oxide in a predetermined mole% (addition ratio of tin oxide; 5-10 mole%) and compressing them to form a tablet of a predetermined shape, the initial oxygen partial pressure is 4 × 10 ^-4 Torr. Provided is a method of forming an indium tin oxide (ITO) transparent conductive film by installing in a vacuum chamber and depositing on a glass substrate previously heated to 250 to 400 ° C.

Second is the spray method using a metal salt solution. This is a method of spraying a solution of 100 g of InCl ₃ -5H ₂ O, 10 ml of HCl, 50 ml of water, and a small amount of SnCl ₄ into an electric furnace heated to about 450 to 650 ° C. to form a transparent film on the substrate.

The third is chemical vapor deposition (CVD), and the material to be deposited is vaporized and decomposed by heat or reacted with other gases or vapors and deposited on the substrate. The process of forming a stable film by pyrolysis is called pyrolysis, and the organometallic compound is decomposed at a temperature lower than 600 degrees, and the metal halide compound is decomposed at 600 degrees or more to form a metal film.

The fourth method is sputtering, in which plasma is formed by a voltage applied to two electrodes, gas ions formed by ionization of an inert gas collide with a cathode, and a target material is sputtered to form a film on a substrate.

Fifth, the solution coating method or the sol-gel method is applied to the substrate by dipping method or rotating method, sol, which is a highly reactive solution, and the dry gel film is fixed as the hydroxyl group on the surface of the substrate reacts with the alkoxide of the doze. And forming a solid oxide film by heat treatment.

Which one of the methods of forming the transparent conductive film as described above should be determined in consideration of the purpose of use, use, productivity, economics, and physical properties.

In general, vacuum deposition and chemical vapor deposition require high vacuum and high temperature, which leads to high manufacturing costs and difficulty in controlling gas phase reactions. In sputtering, the substrate temperature must be kept high and high voltage, There is a drawback that the high vacuum is required and the manufacturing cost is high and the continuous process is difficult.

In addition, all of the above-described spraying methods together with these methods cannot accommodate the large capacity when it is necessary to form a transparent conductive film with a large area, and it is uneconomical since the fixings do not proceed at normal temperature and pressure.

Therefore, the present invention is relatively simple and economical process with the advantage of being able to accommodate such a capacity and to facilitate a high homogeneity and thickness control, in order to form a transparent conductive film of a large area used for display shelves of goods, etc. The sol-gel method is adopted, and the immersion method that can simultaneously process both sides of the glass at room temperature and atmospheric pressure is used.

On the other hand, as the transparent conductive film forming material to be applied to the glass surface, SnO ₂ , SnO ₂ -Sb, SnO ₂ -F, InO ₃ -Sn, In ₂ O ₃ , ZnO and the like are known. In particular, In ₂ O ₃ -Sn (ITO) Membranes have been widely used regardless of the various methods described above.

Examples of using an indium tin oxide film using the sol-gel method include Korean Patent Application No. 79-625 (Gaz. No. 83-478) given to Hidachi Seisakusho Co., Ltd. and Application No. 93-7820 of the present applicant.

However, since indium is not a common element on the earth, the unit price is high, so it is difficult to accommodate the use of a large area although the low resistance, conductivity and permeability are excellent. Indium is inexpensive, in particular, since the amount of solution to be prepared reaches a considerable level when the conductive film is formed using the sol-gel method.

Therefore, an object of the present invention is to provide a method for producing a transparent thin film which is excellent in conductivity and low in cost with low resistance, using antimony as an additive and tin as a substitute for a conventional indium tin oxide film.

In the present invention, the antimony is adopted as a transparent conductive film forming material because the resistance value is considered in addition to the economics. The principle of antimony lowering the resistance of the transparent conductive film to about 300 Ω to maintain electrical conductivity is as follows.

In other words, when the antimony chloride-added tin chloride solution is applied to glass according to the preparation method of the present invention and subjected to drying and calcining heat treatment, it is combined with oxygen to take the form of an oxide, wherein antimony is used as a dopant in the crystal structure of tin oxide. It appears to have been added. In other words, when antimony ions replace tin ions in the tin oxide crystals, effective charges occur due to differences in valence of tin and antimony, and free electrons move freely in the crystal structure with respect to the excess charges. Is formed, which lowers the electrical resistance of the conductive film.

The ratio of tin and antimony depends on the temperature of the heat treatment, and an addition ratio of 1: 0.01 to 0.2 is generally suitable.

Hereinafter, the method for manufacturing a transparent conductive film of the present invention will be described in more detail for each process.

1. Pretreatment of glass substrate

In order to uniformly apply the solution to the glass substrate during coating, the glass substrate is referred to as a solution in which NaOH is saturated with dichromic acid solution and alcohol.

Many ions or molecules are adsorbed on the surface of the glass substrate, and these adsorbates not only cause staining when the solution is applied to the glass substrate, but also diffuse into the coating layer during heat treatment and act as an impurity. Reduces the conductivity and light transmittance of the.

Therefore, in the present invention, the glass immersed in the dichromic acid solution to remove the metal ions adsorbed on the glass surface, at this time, the organic components remaining unremoved are completely removed with an alcohol solution saturated with NaOH again to obtain a more excellent transparent conductive film. .

By using the above dichromate solution, the glass substrate can be efficiently pretreated without the need for a vacuum chamber. The pre-treated glass substrate is dried and stored in a dust-free chamber.

2. Preparation of Transparent Conductive Film Formation Solution

SnCl ₂ · xH ₂ O and SbCl ₃ is quantified in a fixed ratio, dissolved in alcohol and acetic acid is added so that the pH of the solution is about 1, and the concentration of the solution is 0.1M.

In preparing the solution, the temperature is kept constant at room temperature (about 20 ° C.) and the humidity is kept constant.

The ratio of tin to antimony is 1: 0.01 to 0.2, and preferably 1: 0.05. This ratio depends on the heat treatment temperature of the transparent conductive film, and as the heat treatment temperature is lowered, the composition ratio for obtaining the lowest electric resistance value is smaller, that is, the direction of the addition of antimony is decreased, and when the heat treatment temperature is increased, Conversely, the lowest resistance value is obtained when the amount of antimony added is increased.

Adjusting the pH by adding acetic acid in the above process is to prevent the cloudiness caused by dissolving only with alcohol and to completely dissolve the solute to make a clear solution. In addition, acetic acid can eliminate the whitening phenomenon as the film thickness increases when it is necessary to make the film thickness very low in order to reduce sheet resistance very much.

3. Immersion and Application

The prepared solution is applied to a glass substrate prepared by washing and pretreatment using a dipping machine. When the solution is applied, the glass substrate is lifted at a speed of 20 to 30 cm / min, and the glass substrate is lifted and repeated 1 to 5 times to adjust the thickness of the film after drying for 5 minutes. At this time, the drying time between immersion and immersion is alternately 5 minutes and 30 minutes.

4. Drying

After application of the solution, the glass substrate is first dried for about 1 hour in an oven at about 55 to 65 ° C, and secondly dried for 30 minutes in an oven at about 95 to 110 ° C.

The drying temperature is divided into two and subjected to two drying steps, because the dry state of the solution applied to the glass surface determines the surface strength and transparency of the final product. That is, if the temperature is kept too high from the beginning during drying, cracks occur in the coating film formed in a gel form along with the drying of the solution, and the strength of the film after heat treatment is drastically lowered. In addition, the solution is rapidly evaporated when the product is dried at a high temperature without undergoing the first drying at 55 to 65 ° C., thereby decreasing the adhesion of the gelled film.

Therefore, in the preparation method of the present invention, first, by evaporating a volatile solvent such as alcohol in the first step of 55 ~ 65 ℃, and inducing a gelation reaction through a second drying process of 95 ~ 110 ℃, effective evaporation of the applied solution And it is excellent in the strength of the transparent conductive coating film which is the final product.

In addition, it is necessary to adjust the drying time appropriately, about 1 hour is preferable at 55-65 ° C. If the drying is too long, the coating film may be contaminated, and at about 95-110 ° C, about 30 minutes suitable for inducing gelation is preferable. If the drying time at 95 to 110 ° C. is too long, the film strength after heat treatment may be greatly reduced.

5. Plastic Heat Treatment

The dried glass substrate is placed in a furnace at 450 to 550 ° C. and heat treated for 5 minutes to 2 hours.

The drying process and the heat treatment process are shown in a graph as shown in FIG.

6. Cooling

The glass substrate applied through the above process is cooled slowly while lowering to a temperature of 20 ° C. per minute.

The manufacturing process described above is shown in FIG.

The electrical conductivity of the transparent conductive film completed through such a process, that is, a method of measuring electrical resistance is shown in FIG. 3.

The silver electrode 1 is applied to both ends of an area of 1 cm x 1 cm on the heat-treated glass substrate 2, and then the resistance is measured.

The on-electrode is obtained by coating silver at both ends of the conductive film-coated glass by screen printing and then heat-treating (200 ° C.) for 30 minutes in an electric oven. After the terminal is installed in the silver electrode, resistance generated on the surface is measured by using a digital multi-meter (DMM).

Such a measuring method is characterized in that the change of the electrical resistance can be immediately read in accordance with the change in the thickness or the composition of the film. Even when the product is actually manufactured, as shown in FIG. 3, electrodes are formed at both ends of the glass to allow current to flow, so that the quality of the product can be predicted immediately.

Since the electrical resistance of the Sb ₂ O ₃ -SnO ₂ transparent conductive film formed through the above-described manufacturing method has a relatively low resistance value such as 300-1000Ω, the present invention provides a low production cost and an economical manufacturing method.

In the present invention, the principle that the solution of tin and antimony is gelated on the glass substrate is that the highly reactive alkoxide (M-OR) is partially hydrated by water and it is combined with other alkoxide to polymerize. As it is polymerized, it grows into a colloidal form, and each colloidal particle combines with each other to form a network with a network structure.

In addition, the form of the polymerization is changed depending on the acidic or basic reaction conditions of the hydration reaction, the shape of the gel after drying depending on the state of these molecules. Acidic conditions are advantageous for the formation of the conductive thin film, and basic conditions are favorable for the synthesis of the narrow gel powder.

Examples according to the present invention are as follows, these examples are provided only to assist in understanding the present invention, the present invention is not limited to these examples.

Example 1

11.28 g of SnCl ₂ · 2H ₂ O and 0.5703 g of SbCl ₃ were added to 400 ml of ethyl alcohol so that the ratio of tin and antimony was 1: 0.5, and 110 ml of acetic acid solution was added thereto, followed by stirring for 1 hour. In this process, 10 ml of the solution will evaporate.

As the pH of the solution goes below 1, the solution turns transparent in suspension. In preparing the solution, the temperature (20 ° C.) and the humidity were kept constant.

The glass substrate was immersed in a dichromic acid solution to remove metal ions, immersed in a solution saturated with NaOH in alcohol for about 12 hours, then taken out, washed clean in flowing distilled water, and stored in a chamber free of dust.

After the pretreatment was completed, the glass substrate was sufficiently immersed in the above solution and was pulled up at a speed of 25 cm / min using a motor driving device.

It was dried in air for 5 minutes and this dipping and drying process was repeated twice.

Next, after 1-hour drying in an oven at 60 ° C, secondary drying was performed for 30 minutes in an oven at 100 ° C. The dried glass substrates were put into a furnace at 450 to 550 ° C. and heat-treated for 1 hour, and cooled to about 20 ° C. per minute.

As a result, a transparent film was obtained. In order to know its efficiency, the resistance was measured to obtain a resistance value of 374Ω.

Example 2

A solution was prepared in the same manner as Example 1, in which 11.28 g of SnCl ₂ · 2H ₂ O and 1.141 g of SbCl ₃ were used so that the ratio of tin and antimony was 1: 0.1.

The rest of the process was carried out as in Example 1 to obtain a resistance value of 548Ω.

When the transparent conductive film of the present invention is applied to glass, to find out what conditions can be expected to prevent the effect of condensation, the temperature deviation between the inside and the outside of the glass experiments as shown in the following table results, the present invention It was found that the conductive conductive film of was better in preventing condensation than ordinary glass.

The above experimental result is because the present invention adopts a constant ratio of antimony and tin as the raw material of the transparent conductive film and lowers the resistance value to 300 to 1000 Ω, thereby providing a method of obtaining excellent thermal conductivity effect even with low power consumption.

In addition, the transparent conductive film according to the present invention has not only the above-described effects but also excellent optical properties of 95% or more of visible light transmittance.

As described above, the present invention provides a method of forming a transparent conductive film on a large area of glass by applying a solution containing antimony to tin on the surface of the glass, and applying a transparent and rigid conductive film through a second drying process. It will provide a method of manufacturing efficiently.

Claims (4)

In the method of forming a transparent conductive film on a glass substrate by the immersion method, tin chloride and antimony chloride are dissolved in alcohol with a molar ratio of Sn: Sb of 1: 0.01 to 0.2, and then acetic acid is added to adjust the pH to 1 or less. Solution manufacturing process; A dip coating process in which the pre-treated glass substrate is immersed in the solution, lifted at a speed of 20 to 30 cm / min, dried for 5 minutes, and then repeated 1 to 5 times of the immersion operation; A drying step of drying the coated glass substrate in an oven at 55-110 ° C. for about 1 hour and a half to 2 hours; A heat treatment step of baking the glass substrate in a furnace at 450 to 550 ° C. for 5 minutes to 2 hours; And a slow cooling step of cooling the glass substrate at a rate of 20 ° C. per minute. The method for manufacturing a transparent conductive film according to claim 1, wherein the molar ratio of SnSb is 1: 0.05. The method of claim 1, wherein the glass substrate is pretreated by dipping in a dichromic acid solution to remove metal ions, and then immersing in NaOH-saturated alcohol in a solution to remove the remaining organic components. According to claim 1, wherein the glass substrate subjected to the immersion coating step is first dried for 50 to 70 minutes in an oven at 55 ~ 65 ℃ and secondary drying for 20 to 40 minutes in an oven at 95 ~ 110 ℃ Method for producing a transparent conductive film, characterized in that.