KR20030085739A - Conductive black-colored coating composition for shielding electromagnetic waves, method for forming coating film using the same and the coating film - Google Patents

Abstract

PURPOSE: A conductive black-coloring coating solution composition for screening the electromagnetic wave, a preparation method of a coating film using the composition and a coating film prepared by the method are provided, to reduce the reflectivity and to improve the contrast. CONSTITUTION: The conductive black-coloring coating solution composition comprises 2-25 wt% of polyethylene dioxythiophene whose solid content is 1.2-1.5 wt%; 1-32 wt% of Ag-Au sol whose solid content is 0.4-2.0 wt%; 0.1-5 wt% of an alkoxysilane; 1-15 wt% of titanium nitride; 30-80 wt% of an alcohol solvent of C1-C7; and 0.1-10 wt% of an amide-based solvent. Preferably the titanium nitride is the water-dispersed or alcohol-dispersed titanium nitride whose solid content is 2-4 wt%, and its surface is treated with silicate; the polyethylene dioxythiophene is doped with polystyrene sulfonate; and the alkoxysilane is tetraalkoxysilane (Si(OR)4, wherein R is methyl or ethyl), alkyltrialkoxysilane (RSi(OR)3, wherein R is methyl or ethyl) or 3-glycidyloxypropyltrimethoxysilane.

Description

Conductive black-colored coating liquid composition for electromagnetic shielding, a method for manufacturing a coating film using the same and a coating film thereof TECHNICAL FIELD

The present invention relates to a conductive black colored coating liquid composition for electromagnetic shielding having AR (antireflective) and contrast enhancement properties, and more specifically, polyethylene dioxythiophene in a mixed solvent of an alcohol solvent and an amide solvent. : PEDT), Ag-Au sol, alkoxysilane, and conductive black coloring coating liquid composition for electromagnetic shielding prepared by dispersing water dispersion or alcohol dispersing titanium nitride, a method for producing a coating film using the same, and a coating film thereof.

Commonly used conductive polymer compounds include polyaniline, polypyrrol, polythiophene, and the like. These compounds have been attracting attention as synthetic metals for a long time because they are easy to polymerize and have excellent electrical conductivity, and have been proposed for their application as various conductive materials such as electromagnetic wave materials, secondary battery electrodes and transparent electrodes. Only a few examples have actually been commercialized due to problems such as difficulty in phase, thermal and atmospheric stability and poor UV stability.

Therefore, efforts to solve the above problems of the existing conductive polymers have been continued, and recently, polyethylene dioxythiophene (PEDT), an alcohol-soluble polythiophene-based conductive polymer, has been noted as a new conductive material. (See US Pat. No. 5,035,926 and US Pat. No. 5,391,472). In these patents, polyethylenedioxythiophene is not only soluble in polyaniline-based, polypyrrole-based, but also other conventional conductive polymers such as polythiophene-based. Therefore, it has been proposed that it can be used as a conductive coating material of the external exposed areas which was almost impossible to apply. Particularly, since the film exhibits excellent transmittance when a thin film is formed, polyethylene dioxythiophene is coated on a transparent substrate such as a cathode ray tube (CRT) glass surface, a transparent plastic surface (for example, a panel or a film), and an electromagnetic wave. It has been proposed that it can be used as a conductive coating such as a shielding material and an antistatic material.

Meanwhile, the metal oxide-based inorganic ITO (indiumtinoxide) thin film and PEDT thin film containing high refractive index (formerly Korean Patent Publication No. 2000-040197), which are conventionally used as an electromagnetic shielding coating material for CRT outer glass, have high conductivity and Although it has an AR (antireflective) function that exhibits a reflectance of less than%, and has excellent coating properties such as very high transmittance (more than 98%), it is not suitable as a coating material for color plane CRT, which has recently been in the spotlight. It has been pointed out. The reason for this is that recent outer surface glass for color plane CRT has a transmittance of 83% or more, so that the contrast of a flat CRT screen is reduced when a conventional high permeability inorganic ITO thin film or PEDT thin film coating containing high refractive index is coated. Because. Therefore, in recent years, black colored coating liquids having low transmittance have been used for the outer glass of the color flat CRT. Most coating solutions developed for this purpose are used in the form of carbon black dispersed in a transparent conductive solution, and representative examples are black colored coating solutions in which carbon powder is dispersed in ATO (antimonytinoxide) sol and silica sol (see US Patent 5,681,885). However, in the case of the coating solution in which the carbon black is dispersed, the color of dark black or brown black is expressed, so that the appearance color characteristics are not excellent, and the sense of quality is deteriorated, and as the non-conductive colorant is used, the film surface resistance is 10 ^10. As high as ˜10 ¹¹ Ω / □, it can be used only for antistatic but has a disadvantage that it cannot be used for electromagnetic shielding.

The present invention is to solve the problems of the prior art as described above, by using a water dispersion or alcohol dispersion titanium nitride as a color pigment to reduce the transmittance of the coating film to improve the contrast of the color flat CRT, further extinction coefficient (extinction By adding Ag-Au sol having a large coefficient, it is possible to form a high refractive index layer necessary for AR properties, in combination with the silicate layer, to show an excellent AR effect, and at the same time to properly combine the conductive polymer and Ag-Au sol. It is an object of the present invention to provide a conductive black colored coating liquid composition which can be used for electromagnetic shielding (surface resistance ≤ 1 × 10 ⁵ Pa / □) by significantly lowering the resistance.

That is, the first aspect of the present invention provides a conductive black colored coating liquid composition for electromagnetic shielding comprising:

(a) polyethylenedioxythiophene (PEDT);

(b) Ag-Au sol;

(c) alkoxysilanes;

(d) titanium nitride;

(e) alcohol solvents having 1 to 7 carbon atoms; And

(f) amide solvents.

A second aspect of the present invention provides a method of manufacturing a conductive black colored coating film for electromagnetic shielding comprising the following steps:

(i) polishing the CRT outer glass with CeO ₂ , followed by washing with ethanol and drying;

(ii) spin coating or spray coating the coating liquid composition on the CRT outer glass surface and drying to form a first coating layer;

(iii) spin coating or spray coating silica sol as a secondary coating solution on the first coating layer and drying to form a second coating layer; And

(iv) curing the coating film by drying the first and second coating layers at 150 to 200 ° C. for about 30 minutes to 1 hour.

The third aspect of the present invention is a conductive black for electromagnetic shielding having the characteristics of reflectance 0.01 ~ 0.8%, surface resistance 1 × 10 ⁵ Ω / □ or less, transmittance 50% ~ 80%, and hardness 4H ~ 9H produced by the above method It provides a coloring coating film.

Hereinafter, the coating liquid composition of the present invention will be described in more detail.

In the present invention, the conductive polymer used for the purpose of imparting conductivity to the coating liquid composition is a water-soluble polyethylene dioxythiophene (PEDT), which is a kind of polythiophene-based polymer, and the PEDT used in the present invention has a molecular weight in the range of 500 to 50000. Polystyrene sulfonate (PSS) is doped as a dopant, and it is well soluble in water, and has excellent heat resistance, moisture resistance, and UV stability (hereinafter referred to as PEDT dopant, that is, PSS doped state) Means PEDT). In preparing the coating solution of the present invention, the PEDT is added in the form of an aqueous solution. Since the aqueous solution of PEDT is well mixed with a solvent having a high dielectric constant such as water and / or an alcohol and / or an amide solvent, it can be easily coated by diluting with these solvents. Excellent transparency compared to phosphorus polyaniline and polypyrrole.

The coating solution composition of the present invention contains 2 to 25% by weight of the aqueous PEDT solution (solid content of 1.2 to 1.5% by weight). If the aqueous solution of PEDT is used in less than 2% by weight, there is a problem of exceeding the commercially available minimum conductivity value of the conductive thin film, the surface resistance of 10 ⁸ Ω / □, when using more than 25% by weight of the conductivity is excellent However, PEDT and the highly refractive inorganic sol described later are not suitable for CRT outer glass coating requiring a high uniform thin film because the gelling in the coating liquid and the economical efficiency are inferior.

Ag-Au sol used for the purpose of increasing the refractive index of the conductive polymer thin film transparent film in the present invention is a state in which the Ag fine particles coated with Au is dispersed in a mixed solvent of water and ethanol, the solid content in the dispersion 0.4-2.0 wt%. Such Ag-Au sol is commercially available, and a representative example thereof is CKR-102NH-CH1 manufactured by Sumitomo Metal Mining. Ag-Au sol is commonly used in electromagnetic wave shielding coatings because of its high conductivity, and has a high extinction coefficient in spite of its low refractive index. There is.

The coating liquid composition of the present invention contains 1 to 32% by weight of the Ag-Au sol (solid content of 0.4 to 2.0% by weight). If the Ag-Au sol is used in less than 1% by weight in the preparation of the coating solution of the present invention, the desired high refractive film cannot be produced in the present invention, and the AR effect does not appear. If the content is more than 32% by weight, the refractive index of the film is very excellent. However, it is not commercially suitable because of increased manufacturing cost and low economic feasibility.

In the present invention, as the alkoxysilane used for the purpose of improving the adhesion to the CRT outer glass and the hardness of the coating film, tetraalkoxysilane [Si (OR ^' ) ₄ ] (R ^' = methyl or ethyl), alkyltrialkoxy Silane [RSi (OR ^' ) ₃ ] (R = methyl; R ^' = methyl or ethyl), or 3-glycidyloxypropyl trimethoxysilan (hereinafter referred to as GPTMS) can be used. Such alkoxysilane reacts with water contained in the aqueous solution of PEDT or additionally added water in the preparation of the coating solution composition of the present invention to undergo a hydrolysis reaction and a condensation reaction, followed by silica sol (-SiO ₂ -SiO _2- ) or alkylsilica sol. After (R-SiO ₂ -SiO _2- ) is formed, an organic-inorganic hybrid with PEDT is formed. The silica sol forms a polysilicate crystal when the coating liquid composition including the same is coated with a thin film and then thermally cured. The polysilicate crystal has adhesiveness with the CRT outer glass and increases the film hardness of the coating film. Done.

The coating liquid composition of the present invention contains 0.1 to 5% by weight of the alkoxysilane. When the content of the alkoxysilane is less than 0.1% by weight, hardness of 4H or more cannot be achieved, whereas when the content of the alkoxysilane is higher than 5% by weight, the hardness increases, but the amount of polysilicate that adversely affects the conductivity becomes excessive, so that the additional conductivity Even with the addition of the enhancer, it is not possible to achieve a surface resistance of 1 × 10 ⁵ Ω / □ or less, which is a target of the electromagnetic wave shielding level.

In the present invention, as the color pigment, a water dispersion or an alcohol dispersed titanium nitride having a solid content of 2 to 4% by weight is used, and the titanium nitride is preferably treated with a silicate surface. The reason is that titanium nitride surface-treated with silicate does not increase resistance even though it is a non-conductive material, and has a bluish black color to enhance the appearance of the coating. to be. In addition, silicate surface-treated titanium nitride maintains a stable dispersion state in water or alcohol, so appearance defects due to the radial pattern of the coating film which is frequently used when carbon black is used as a pigment even when used in high content Almost no, very low transmittance can be achieved while maintaining good appearance characteristics.

The aqueous dispersion or alcohol-dispersed titanium nitride used in the present invention may be prepared by dispersing the titanium nitride particles in a solvent by milling using an appropriate polymer dispersant and a surfactant, and may be purchased and used commercially. . Representative examples of commercially available titanium nitride include Sumitomo Metal Mining's TPD-N, TPD4N-1 and TPD4N-2, all of which are treated with silicate on the surface of titanium nitride particles. -N is an alcohol dispersion product with a solid content of 2%, TPD4N-1 is an alcohol dispersion product with a solid content 4%, and TPD4N-2 is an aqueous dispersion product with a solid content 4%.

In the preparation of the coating solution of the present invention, the amount of the titanium nitride dispersion (solid content 2 to 4 wt%) is 1 to 15 wt%. If the amount of the titanium nitride dispersion is out of the above range, not only the permeability (50 to 80%) targeted by the present invention can be achieved, but also the precipitation and staining of the pigment occur, resulting in an excellent black color. You won't be able to get it.

In the present invention, a mixed solvent of an alcohol solvent and an amide solvent is necessarily used as a solvent for dispersing the above components to prepare a coating solution composition. The reason is that when only the alcohol solvent is used alone, the conductivity of the coating film tends to be very low, which is undesirable. On the other hand, when the alcohol solvent and the amide solvent are jointly used, the conductivity of the coating film is improved, and sufficient film conductivity (surface resistance ≤ 1 × 10 ⁵ Ω / □) desired by the present invention even when the PEDT conductive polymer solution is used less. ) Is much more economical and extremely low in the probability of occurrence of problems such as gelation caused by the use of a large amount of conductive polymers, which is highly desirable in terms of long-term stability of the coating solution.

Alcohol solvents usable in the present invention include methanol, ethanol, isopropanol, propanol, 1-butanol, 2-butanol, 2-methoxy ethanol (hereinafter referred to as MC), 2-ethoxy ethanol (hereinafter referred to as EC) Alcohols having 1 to 7 carbon atoms, such as 2-isopropoxy ethanol, 2-butoxy ethanol, diacetone alcohol (hereinafter referred to as DAA) and propylene glycol monomethyl ether (hereinafter referred to as PGM) Since methanol is the best in terms of dispersibility, it is preferable to use methanol alone, or to mix one or more kinds of methanol and other alcohol solvents, but use a mixed alcohol containing 50% by weight or more of methanol.

On the other hand, the amide solvent can be used in the present invention formamide (FA: formamide), N-methylformamide (MFA: N-methylformamide), N, N- dimethylformamide (DMF: N, N-dimethylformamide), acet Amide (AA: acetamide), N-methylacetamide ( NMAA : N-methylacetamide), N, N-dimethylacetamide (DMA: N-, N-dimethylacetamide), N-methylpropionamide (MPA: N-methylpropion amide ), N-methylpyrrolidone (NMP: N-methylpyrrolidone) and the like, any one of these may be used alone, or two or more may be used in combination. The amide solvents are commonly characterized by having an amide group [—N (R) —C═O] (R = alkyl group) in the molecule.

According to the present invention, it is preferable to use an alcohol solvent corresponding to 30 to 80% by weight of the coating liquid composition and an amide solvent corresponding to 0.1 to 10% by weight of the coating liquid composition. If the amide solvent is used at less than 0.1% by weight, sufficient conductivity desired by the present invention cannot be achieved. On the other hand, the use of more than 10% by weight can achieve the desired degree of conductivity in the present invention, but such amide-based solvents have a high boiling point and when used in excess, a trace amount even after high temperature baking at 150 ° C. or higher in the coating film manufacturing process. Many of the undesirable phenomena, such as remaining, cause delay in subsequent processes such as secondary coating and adversely affect long-term stability of the coating film.

In the coating liquid composition of the present invention, an aqueous solvent, alkoxysilane, Ag-AU sol, an amide solvent, and a color pigment are sequentially added to the container having a predetermined capacity by adding an aqueous solution of PEDT conductive polymer and vigorously stirring. It is manufactured by stirring enough for about 6 hours. At this time, even if the addition order of each component is mixed to show the desired physical properties in the present invention, when added and mixed in the above order is the best in terms of solubility and dispersibility, it is effective in producing a high uniform coating film.

Hereinafter, a step-by-step description of the method for forming a coating film on the CRT outer glass using the coating liquid composition of the present invention as follows:

i) The CRT outer glass is polished with CeO ₂ , then washed with ethanol and dried.

ii) The coating liquid composition of the present invention prepared as described above is spin-coated or spray-coated on the surface of the CRT outer glass prepared in step i) and dried to form a first coating layer. When spin coating, the proper rotation speed is 80 ~ 150rpm and the time is 80 ~ 150 seconds.

iii) spin coating or spray coating a secondary coating solution to be described later on the first coating layer and dried to form a second coating layer. When spin coating, the proper rotation speed is 80 ~ 150rpm and the time is 80 ~ 150 seconds.

iv) Finally, to form a hard film, it is dried for 30 minutes to 1 hour at 150 ~ 200 ℃.

The secondary coating solution means a silica (SiO ₂ ) sol having a solid content of 0.85%, and such silica sol is 90 to 95% by weight of an alcohol solvent, tetraalkoxysilane or alkyltrialkoxysilane 1 in a container of a predetermined capacity. It is prepared by sequentially adding 0.5% to 3% by weight of nitric acid solution at a concentration of 5% by weight, 2% to 5% of pure water and 1%, and stirring for 10 to 60 minutes, and the weight average molecular weight of the solution is 1000 to 1,500. The types of alcohol solvent, tetraalkoxysilane and alkyltrialkoxysilane used in the preparation of the secondary coating solution are the same as those used in the preparation of the coating solution composition of the present invention.

The coating film of the present invention prepared as described above has a reflectance of 0.01 to 0.8%, surface resistance of 1 × 10 ⁵ Ω / □ or less, preferably 1 × 10 ³ Ω / □ or less, transmittance of 50% to 80% The hardness is 4H to 9H and has AR (antireflective) and contrast enhancement characteristics.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Preparation Examples 1 to 5 and Comparative Preparation Example 1 Preparation of Primary Coating Liquid

Baytron P 4071 (solid content 1.3% by weight) of Bayer was used as the aqueous solution of PEDT conductive polymer in this preparation example and the comparative manufacturing example, and Ag-Au solo was CKR-102NH of SUMITOMO METAL MINING -CH1 (solid content 0.4, 0.8 or 1.4%) was used. All alcohol solvents, amide solvents, and alkoxysilanes, TEOS (tetraethoxysilane) and GPTMS (3-glycidyloxypropyl trimethoxy silane) were all used as Aldrich Co. without special purification, and as color pigments SUMITOMO TPD-N (solid content 2%, alcohol dispersion), TPD4N-1 (solid content 4%, alcohol dispersion), or TPD4N-2 (solid content 4%, aqueous dispersion) from METAL MINING was used without dilution.

A coating liquid composition was prepared according to the composition shown in Table 1 using the above-described components, but the alcoholic solvent, alkoxysilane, Ag-Au sol was first added to the aqueous solution of PEDT conductive polymer in a 1 L glass container and stirred vigorously. , An amide solvent, and an aqueous dispersion or an alcohol dispersed color pigment were added in sequence, and then sufficiently stirred at room temperature for about 5 hours to prepare a coating solution composition of the present invention.

Composition of Coating Solution (wt%) Preparation Example 1 PEDT (aq) / Ag-Au Sol (1.4%) / MeOH / PGM / DAA / FA / TEOS / GPTMS (12 / 2.5 / 67.5 / 5/5/1 / 0.5 / 0.5) TPD4N-2 (4%, aq ) = 6% Preparation Example 2 PEDT (aq) / Ag-Au Sol (1.4%) / MeOH / PGM / DAA / FA / TEOS / GPTMS (6/24 / 55.6 / 5/5/1 / 0.2 / 0.2) TPD4N-1 (4%, alcohol ) = 3% Preparation Example 3 PEDT (aq) / Ag-Au Sol (0.4%) / MeOH / EC / DAA / NMAA / TEOS / GPTMS (6 / 2.5 / 67.6 / 7.5 / 5/1 / 0.2 / 0.2) TPD-N (2%, alcohol ) = 10% Preparation Example 4 PEDT (aq) / Ag-Au Sol (1.4%) / MeOH / 1BuOH / DAA / NMAA / FA / TEOS (10/12 / 62.5 / 5/5/1/1 / 0.5) TPD4N-1 (4%, alcohol ) = 3% Preparation Example 5 PEDT (aq) / Ag-Au Sol (1.4%) / MeOH / 1BuOH / DAA / NMAA / FA / TEOS (25/12 / 47.5 / 5/5/1/1 / 0.5) TPD4N-2 (4%, aq ) = 3% Comparative Production Example 1 PEDT (aq) / Ag-Au Sol / MeOH / 1BuOH / DAA / NMAA / FA / TEOS (25/0 /59.5/ 5/5/1/1 / 0.5) TPD4N-2 (4%, aq) = 3%

Preparation Example 6 Preparation of Secondary Coating Liquid

In order to confirm the AR effect of the coating film, a secondary coating film should be formed by using silica sol as a second coating solution on the first coating film formed using the coating solution prepared from Preparation Examples 1 to 5 and Comparative Preparation Example 1. To prepare the required silica sol, 57 g of ethanol as an alcohol solvent, 20 g of methyl silicate as alkoxysilane, 15 g of pure water, and 8 g of nitric acid solution at 1% concentration were sequentially added to a container having a predetermined capacity, and stirred for about 1 hour, followed by ethanol. Was diluted to prepare a SiO ₂ sol (hereinafter referred to as CII-AR solution) having a solid content of 0.85%.

Examples 1 to 5 and Comparative Example 1: Preparation and evaluation of the coating film

Each of the coating liquid compositions prepared in Preparation Examples 1 to 5 and Comparative Preparation Example 1 was washed with acid, and then spin coated and dried on the surface of the dried glass plate to form a first coating layer. At this time, the rotational speed was 150 rpm, and the coating time was 80 seconds. The CII AR solution obtained from Preparation Example 6 was coated on the first coating layer thus formed by spin coating and then dried to form a second coating layer. At this time, the rotational speed was 150 rpm, and the coating time was 80 seconds. Finally, it was dried for about 30 minutes at 180 ℃ to form a hard film. The thickness of the dried coating film was about 50-400 nm in total for both 1 and 2 layers.

The physical properties of the coating film formed as described above were evaluated by surface resistance per unit area using Loresta (4-point probe) manufactured by Mitsubishi Chemical in the case of conductivity, and the transmittance was measured at 550 nm using a UV-visible spectrometer. Transmittance was evaluated, reflectance was measured using DARSA PRO 5000, the film hardness was measured using a pencil hardness meter. The film uniformity was evaluated visually, and the evaluation criteria were classified as good or bad. If the state of the coating film was uneven due to gelation or the gelation remained in the coating film, the film was evaluated as bad. Evaluation results are shown in Table 2 below.

Properties of Coating Film Surface resistance (Ω / □) Permeability (T%) reflectivity(%) Film hardness Uniformity Example 1 5K * 57 0.71 9 Good Example 2 1.1K 59 0.03 7 Good Example 3 25K 62 0.88 7 Good Example 4 9K 62 0.74 8 Good Example 5 0.8K 53 0.22 8 Good Comparative Example 1 1.0 53 3.88 8 Good

^* K = 1000

As described in detail above, when the coating liquid composition of the present invention is used for the outer glass coating of the cathode ray tube (CRT) for flat display, it is possible to obtain an electromagnetic shielding coating film having low reflectance and excellent conductivity and contrast.

Claims (11)

Conductive black coloring coating liquid composition for electromagnetic shielding comprising: (a) polyethylenedioxythiophene (PEDT); (b) Ag-Au sol; (c) alkoxysilanes; (d) titanium nitride; (e) alcohol solvents having 1 to 7 carbon atoms; And (f) amide solvents. The coating solution composition of claim 1 comprising: (a) 2 to 25% by weight aqueous solution of polyethylene dioxythiophene (PEDT) having a solid content of 1.2 to 1.5% by weight; (b) 1 to 32% by weight of Ag-Au sol having a solid content of 0.4 to 2.0% by weight; (c) 0.1-5% by weight of alkoxysilane; (d) 1-15% by weight aqueous dispersion or alcohol-dispersed titanium nitride having a solid content of 2-4% by weight; (e) 30 to 80% by weight of an alcohol solvent having 1 to 7 carbon atoms; And (f) 0.1 to 10% by weight of an amide solvent. The coating liquid composition according to claim 1 or 2, wherein the PEDT is doped with polystyrenesulfonate (PSS). 3. The alkoxysilane according to claim 1 or 2, wherein the alkoxysilane is tetraalkoxysilane [Si (OR ^' ) ₄ ] (R ^' = methyl or ethyl), alkyltrialkoxysilane [RSi (OR ^' ) ₃ ] (R = methyl R ^' = methyl or ethyl), or 3-glycidyloxypropyl trimethoxysilane. The coating liquid composition according to claim 1 or 2, wherein the surface of the titanium nitride is treated with silicate. The alcoholic solvent according to claim 1 or 2, wherein the alcohol solvent is methanol alone or ethanol, isopropanol, propanol, 1-butanol, 2-butanol, 2-methoxy ethanol, 2-ethoxy ethanol, 2-isopropoxy ethanol. , A mixed alcohol of at least one alcohol selected from the group consisting of 2-butoxy ethanol, diacetone alcohol and propylene glycol monomethyl ether and methanol, the mixed alcohol comprising at least 50% by weight of methanol Coating liquid composition. The amide solvent according to claim 1 or 2, wherein the amide solvent is formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N Coating liquid composition, characterized in that at least one member selected from the group consisting of -methyl propionamide and N-methylpyrrolidone. Method for producing a conductive black colored coating film for electromagnetic shielding comprising the following steps: (i) polishing the CRT outer glass with CeO ₂ , followed by washing with ethanol and drying; (ii) spin coating or spray coating the coating liquid composition of any one of claims 1 to 7 on the CRT outer glass surface and drying to form a first coating layer; (iii) spin coating or spray coating silica sol as a secondary coating solution on the first coating layer and drying to form a second coating layer; And (iv) curing the coating film by drying the first and second coating layers at 150 to 200 ° C. for about 30 minutes to 1 hour. 9. The method according to claim 8, wherein the silica sol of step (iii) is a silica sol having a weight average molecular weight of 1000 to 1,500 and a SiO ₂ solids content of 0.85 wt%. The method of claim 8, wherein the spin coating of the steps (ii) and (iii) is carried out for 80 to 150 seconds at a speed of 80 ~ 150rpm. A conductive black colored coating film for electromagnetic shielding having the properties of a reflectance of 0.01 to 0.8%, a surface resistance of 1 × 10 ⁵ Ω / □, a transmittance of 50% to 80%, and a hardness of 4H to 9H prepared by the method of claim 8. .