KR20030079264A - Compositions for coating layer and method for preparing the same - Google Patents

Abstract

PURPOSE: Provided is a coating composition for forming a coating layer of an image display device, which has excellent safety and stability against water. The method for producing the coating composition is also provided. CONSTITUTION: The coating composition for forming a coating layer of an image display device comprises a metal alkoxide having the formula of M(OR)n, wherein M is one or more elements selected from the group consisting of alkali metals, alkaline earth metals, transition metals and rare earth metals, R is a C1-C15 alkyl, and n is 1 to 6, which is determined according to M; an organic compound containing an element having a non-shared electron pair; and water. The coating composition is produced by reacting the metal alkoxide and the organic compound in an organic solvent and then adding an excessive amount of water.

Description

Composition for forming coating film and manufacturing method therefor {COMPOSITIONS FOR COATING LAYER AND METHOD FOR PREPARING THE SAME}

The present invention relates to a composition for forming a coating film, and more particularly, to a composition for forming a coating film having excellent stability to water.

1 is a diagram schematically showing a cross section of a cathode ray tube which is the dominant type of a modern information display. The cathode ray tube has a structure in which a metal back layer 40 is formed on a fluorescent surface on which a fluorescent film 30 is formed between the black matrices 20 on the panel 10. Among the light emitted from the fluorescent surface of the cathode ray tube, the light visible to the human eye can be classified into two types. That is, the light L1 caused by the light emission of the phosphor due to the collision with the electron beam and the light of the external light source in the environment in which the CRT is used are the light L2 and L3 reflected from the surface of the fluorescent surface of the cathode ray tube. The light reflected from the surface of the cathode ray tube reflected by the external light source is divided into two again, one is light (L2) reflected from the outer surface of the panel 10, and the other is passed through the panel 10 It is light (L3) reflected from the inner surface of the panel and the interface of the phosphor. Such external light forms an afterimage on the entire surface of the panel, and the image due to the light emission of the fluorescent film 30 is superimposed to reduce the contrast.

Therefore, in order to improve the contrast of the cathode ray tube, it is possible to minimize the reflection of external light from the surface and the inner surface of the cathode ray tube panel and to absorb a relatively large amount of side bands near 575 nm of the red phosphor. Coatings for this purpose have been concentrated mainly on the outer surface coating of the cathode ray tube. In such an outer coating, a method of forming a multilayer film mainly made of a transparent oxide material was used. In this method, a plurality of transparent oxide layers having different refractive indices are coated on the outer surface of the panel of the cathode ray tube and the thickness of the coating film is adjusted to reduce the external reflection by the optical interference phenomenon. However, the above methods attempt to improve contrast by reducing the reflection of the outer surface of the cathode ray tube, but there is a problem in that the reflection of light generated at the interface between the inner surface of the panel and the phosphor is not reduced.

In order to solve this problem, US Pat. Nos. 4,019,905, 4,132,919, and 5,627429 disclose a method for forming an intermediate layer containing a pigment capable of absorbing light in a specific wavelength band between an inner surface of a panel and a fluorescent film. US Patent Nos. 5,068,568 and 5,179,318 disclose a method of utilizing an optical interference phenomenon by alternately stacking a low refractive index layer and a high refractive index layer between an inner surface of a panel and a fluorescent film.

However, the use of such conventional inorganic pigments has the advantage of excellent chemical or physical durability. However, since the absorption wavelength of the pigment depends on the properties of the material, it is necessary to mix several pigments to obtain a desired color. have. In addition, the transmittance absorption spectrum of the pigment also causes a problem that the color becomes turbid because the absorption band is wide.

As a method for solving such a problem, coating compositions in which metal fine particles having a size of several hundreds to several hundred nanometers are dispersed in a dielectric matrix such as silica are widely used. The nano-sized metal particles can absorb light of a specific wavelength between emission peaks of the phosphor while the conductive electrons on the particle surface resonate with respect to an electric field applied from the outside. This phenomenon is referred to as Surface Plasmon Resonance (SPR) phenomenon on the surface of metal particles (J. Opt. Soc. Am. B vol. 3, No. 12 / Dec. 1986, pp 1647-1655).

Nano-size metal particles regularly distributed in the dielectric matrix have a characteristic of strongly absorbing visible light of a specific wavelength due to surface plasmon resonance, and the maximum absorption wavelength thereof depends on the refractive index of the dielectric matrix surrounding the metal particles. Change accordingly. By using these characteristics, it is used as a coating for surface treatment of various apparatuses, a display, or an optical filter.

In the conventional coating method, a coating composition prepared by dissolving a dielectric matrix precursor (metal alkoxide or metal salt) and a metal particulate precursor (metal salt) in a solvent by a wet method using a sol-gel method is coated on a panel substrate.

When the metal alkoxide is used as the dielectric matrix precursor, the metal alkoxide is added to a flammable organic solvent such as alcohol to prepare a coating liquid for forming a metal oxide matrix of the coating film in order to secure the stability of the coating liquid. The coating film prepared therefrom has a very good quality, but when the metal alkoxide coating liquid is in contact with water or water, the alkoxide may be hydrolyzed to produce a precipitate or lose its original properties. In addition, since an organic solvent having a high flammability is used, an explosion-proof facility is required, which causes additional cost.

In addition, when the metal salt is used as the dielectric matrix precursor, water is used instead of the flammable organic solvent, so there is no problem of fire or additional equipment, but the quality of the prepared coating film is lower than that of the coating film made of the metal alkoxide coating solution. When water is used in the process, there is a problem in that the final coating film is easily redissolved and the coating film is damaged. Therefore, there is an urgent need for a coating composition that is safe during operation in manufacturing a coating film for improving contrast of an image display device and excellent in water stability.

The present invention is to solve the above problems of the prior art, an object of the present invention is to provide a coating composition of an image display apparatus excellent in safety and stability to water.

Another object of the present invention is to provide a method for preparing a stable coating composition.

Another object of the present invention is to provide an image display apparatus in which a coating film formed from the coating composition is applied to an inner surface, an outer surface, or both of the panels.

1 is a partially enlarged cross-sectional view schematically showing the fluorescent surface structure of a cathode ray tube.

2 is a view showing the deposition test results of the coating film prepared according to the Examples and Comparative Examples of the present invention.

3 is a view showing an absorption spectrum of the coating film according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: panel

20: black matrix

30: fluorescent film

In the present invention, M (OR) _n (M is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals and rare earth elements, R is an alkyl group having 1 to 15 carbon atoms, n is A metal alkoxide represented by 1 to 6 and determined according to M; An organic compound containing an element having an unshared electron pair; And it provides a coating composition comprising water.

The present invention also relates to M (OR) _n (M is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals and rare earth elements, R is an alkyl group having 1 to 15 carbon atoms, n is 1 to 6 and to M It provides a method for producing a coating composition comprising the step of reacting an organic compound containing a metal alkoxide and an element having a non-covalent electron pair in the organic solvent, and adding an excess water thereto.

The present invention also provides an image display apparatus having improved contrast, including a coating film formed by coating and drying the coating composition on an inner surface, an outer surface, or both of the panel.

Hereinafter, the present invention will be described in more detail.

The coating composition of the present invention is an aqueous solvent-based coating liquid which improves the stability of the metal alkoxide by adding a metal alkoxide to water and using an organic compound additive for improving the stability of the metal alkoxide to water.

The metal alkoxide used in the coating composition of the present invention is M (OR) _n wherein M is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals and rare earth elements, R is an alkyl group having 1 to 15 carbon atoms, n is 1 to 6 and depends on M. Specific examples of the metal alkoxide include tetraethyl orthosilicate, titanium tetraisopropoxide, 3-aminopropyltriethoxysilane, aluminum 2-butoxide, zirconium butoxide and the like.

The metal alkoxide is added in an amount of 0.1 to 5% by weight based on the coating composition. If the added amount is less than 0.1% by weight, the thickness of the coating film is too thin, so that absorption occurs only a little, and if it exceeds 5% by weight, the thickness of the coating film is too thick, which is not preferable because there is a problem that a crack occurs.

The organic compound added to improve the stability of the metal alkoxide to water is an organic compound containing an element having a lone pair of electrons. The non-covalent electron pairs coordinate with the metal of the metal alkoxide to form a stable complex to prevent the metal alkoxide from hydrolyzing and settling and to be stably present in water. In addition, the metal alkoxide / organic compound complex may be re-dissolved in water during the slurry process to form a coating film can improve the uniformity of the coating film.

O, N, P, etc. are examples of the element having the lone pair, and examples of the compound containing these elements include alcohol amines such as triethanolamine and diethanolamine, and acetylacetone.

The organic compound is preferably used in an amount of 0.2 to 0.8 mol, and more preferably 0.5 to 0.7 mol, with respect to 1 mol of the metal alkoxide. If the molar ratio of the organic compound / metal alkoxide is less than 0.2, the metal alkoxide is polycondensed, so that a large amount of precipitation occurs, and if it exceeds 0.8, the metal alkoxide / organic complex complex has a problem of re-dissolving.

The coating composition of the present invention may further include an organic solvent to further improve the quality of the coating film. Examples of the organic solvent include methanol, ethanol, isopropyl alcohol, butanol, or a mixture thereof.

The organic solvent is preferably added in an amount of 10 to 80% by weight based on the coating composition. If the amount is less than 10% by weight, it is difficult to produce a high quality thin film and there is almost no effect of addition. If the amount is more than 80% by weight, the content of water is too small, which is not preferable.

The content of water contained in the coating composition may be easily determined in consideration of film forming properties, but the content of water present in the final coating composition is preferably 60 to 70% by weight.

According to a preferred embodiment of the present invention, the coating composition of the present invention is M (OR) _n (M is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals and rare earth elements, R is 1 to 15 carbon atoms An organic compound comprising an alkyl group, n is 1 to 6 and is determined according to M), and an organic compound comprising an element having an unshared electron pair and an unshared electron pair are reacted in an organic solvent and prepared by adding an excess of water thereto. When precipitation occurs during the preparation of the coating composition, a stable waterborne coating composition may be obtained by performing a grinding and dispersing process.

In addition, the coating composition of the present invention may further include a metal salt as a metal fine particle precursor to form a coating film capable of improving the contrast of the image display device. Nanosized metal particles dispersed in a metal oxide dielectric matrix, such as silica, titania, zirconia, alumina, formed from a metal alkoxide precursor, emit luminescent peaks of the phosphor as the conductive electrons on the particle surface resonate with an externally applied electric field It can exhibit surface plasmon resonance phenomena that absorb visible light of a certain wavelength in between. Herein, the metal fine particles are preferably " nanosizes " having a size of several nm to several hundred nm, that is, 1 nm or more and less than 1 μm, more preferably 10 to 50 nm. Such metal fine particles can improve contrast without lowering luminance by absorbing side bands of phosphors of an image display device such as a cathode ray tube by surface plasmon resonance absorption.

As the metal salt that can be used as the metal particulate precursor, salts of transition metals, alkali metals, alkaline earth metals, or mixtures thereof can be used. Examples of specific metals include Au, Ag, Pd, Pt, Cu, Ni, Co, Rh, Rb, Sb, Sn, Zn, Zr, Se, Cr, Al, Ti, Ge, Fe, W, Pb or mixtures thereof Etc., of which Au, Ag, Pd, Pt or mixtures thereof are preferable because they strongly absorb light in the visible region. The metal salt can be used as long as it can be dissolved in water or an organic solvent, and examples thereof include halides, nitrates or sulfonates. For example, in the case of gold, HAuCl ₄ , NaAuCl ₄ , AuCl ₃ , AgNO _3, etc. may be preferably used.

The metal salt used as the metal particulate precursor is added in an amount of 0.001 to 10% by weight based on the coating composition. When the added amount is less than 0.001% by weight, the absorption strength of the pigment is weak and the contrast enhancement effect is small. When the addition amount is more than 10% by weight, the metal fine particles which are not impregnated or adsorbed to the metal oxide are not preferable.

The coating composition of the present invention may be coated on a substrate to be coated by a sol-gel method and then heat-treated to obtain a metal oxide coating film. The heat treatment step is preferably carried out at 200 to 600 ℃.

In the case of the coating composition further comprising a metal fine particle precursor, the metal fine particles may be present in the metal oxide coating layer to selectively absorb light having a specific wavelength by inducing an SPR phenomenon.

For example, when the metal oxide is silica (SiO ₂ ) (refractive index: 1.46) and the metal fine particles are silver (Ag), gold (Au), or copper (Cu), the coating film selectively absorbs light of 410 nm, 530 nm, and 580 nm. . In this case, the absorption wavelength can be shifted to a long wavelength by mixing a second metal oxide such as alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), and the like, having high refractive index, with silica, which is a first metal oxide. The intensity and intensity of absorption peaks can be controlled by adjusting the type and content of metal fine particles.

The coating film of the present invention is applicable as a coating film for improving contrast of various image display devices such as flat panel displays (FPDs) such as cathode ray tubes or liquid crystal displays, plasma display panels, or various decorative colored coating films.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

<Example 1>

₄ g of titanium tetraisopropoxide (Ti (OC ₃ H ₇ ) ₄ ) and 16 g of isopropyl alcohol were added thereto, and 0.6265 g of acetylacetone was added thereto, followed by strong stirring. As the stirring progressed, the solution turned a clear yellow color. After stirring for about 2 hours, 46 g of water was dropped and vigorously stirred for 24 hours. As the stirring progressed, a white precipitate was observed, but the solution remained stable. After stirring, 100 g of zirconia beads were added, and the resultant was shaken for 6 hours using a paint shaker to obtain a stable coating solution of yellow milky color. Water was added to the coating solution as a diluting solvent so that 70% by weight of water was present in the final coating solution. This coating solution was added dropwise to a glass substrate and spun for 2 minutes at about 230 rpm with a spin coater to obtain a transparent titania gel film. This gel film was heat-treated at 500 ° C. to obtain a crystallized titania coating film.

<Example 2>

9.73 g of zirconium n-butoxide and 39 g of ethanol were added thereto, and then 1.12 g of acetylacetone was added thereto, followed by strong stirring. As the stirring progressed, the solution turned a clear yellow color. After stirring for about 2 hours, 115 g of water was dropped and vigorously stirred for 24 hours. As the drip proceeded, water and zirconium n-butoxide reacted to cause polycondensation to increase the viscosity, but after the peak of the polycondensation reaction, the viscosity decreased again due to the added water. After stirring, a milky translucent stable coating solution was obtained. Water was added to the coating solution as a diluting solvent so that 70% by weight of water was present in the final coating solution. This coating solution was added dropwise to a glass substrate and spun for 2 minutes at about 230 rpm with a spin coater to obtain a transparent zirconia gel film. This gel film was heat-treated at 500 ° C. to obtain a crystallized zirconia coating film.

<Example 3>

Ethanol was added as a diluting solvent, except that 50 wt% of the water was added to the final coating solution.

<Example 4>

Ethanol was added as a diluting solvent, except that 50 wt% of the water was added to the final coating solution.

Example 5

9.73 g of zirconium n-butoxide and 39 g of ethanol were added thereto, and then 1.12 g of acetylacetone was added thereto, followed by vigorous stirring. As the stirring progressed, the solution turned a clear yellow color. After stirring for about 2 hours, 115 g of water was dropped and vigorously stirred for 24 hours. As the drip proceeded, water and zirconium n-butoxide reacted to cause polycondensation to increase the viscosity, but after the peak of the polycondensation reaction, the viscosity decreased again due to the added water. After stirring, a milky translucent stable zirconium precursor solution was obtained. 21 g of water and 20 g of ethanol were added and mixed with 10 g of the solution, followed by vigorous stirring. After about 10 minutes, 0.4 g of a gold nanoparticle solution (20% solids) was added to the above solution, followed by vigorous stirring to prepare a coating solution. This coating solution was added dropwise to a glass substrate and spun for 2 minutes at about 230 rpm with a spin coater to obtain a transparent zirconia gel film. This gel film was heat-treated at 500 ° C. to obtain a crystallized zirconia coating film.

Comparative Example 1

3 g of titanium isopropoxide (Ti (OC ₃ H ₇ ) ₄ ) was added to 100 g of isopropyl alcohol and stirred vigorously for 10 minutes to prepare a yellow coating solution in which titanium isopropoxide was completely dissolved. A coating film was obtained in the same manner as in Example 1 above.

Comparative Example 2

A coating film was obtained in the same manner as in Example 1 except that 3 g of zirconium oxychloride was added to 100 g of water to prepare a coating solution.

Glass substrates with a coating film formed according to Examples 1 to 5 and Comparative Examples 1 and 2 were dipped in water to test stability against water. The results of Example 4 and Comparative Example 2 are shown in FIG. 2. As shown in FIG. 2, the coating film of Example 4 is not dissolved even after deposition, but the coating film of Comparative Example 2 can be seen that the coating film of the portion deposited in water is dissolved and removed. From this it can be seen that the coating film of the present invention is more stable in water than the coating film formed by the existing method.

3 is a graph showing the transmittance of the coating film of Example 5. It can be seen that the coating film of Example 5 shows strong absorption at about 580 nm. This is due to a resonance absorption phenomenon (SPR) that absorbs light of a certain wavelength by the metal particles added to the coating film.

Since the coating composition of the present invention is a water-based solvent-based coating composition, there is no risk of fire, and since the metal alkoxide is used as the metal oxide matrix precursor, the wettability and coating property of the coating film are remarkably excellent as compared with the case of using a metal salt. In addition, the coating film made of the coating composition of the present invention is very stable even in a subsequent process such as washing with water and can easily form a multi-layer film by re-coating the solvent-based coating liquid.

Claims (12)

In the composition for forming a coating film of an image display device, M (OR) _n (M is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals and rare earth elements, R is an alkyl group having 1 to 15 carbon atoms, n is 1 to 6 and is determined by M) Metal alkoxides represented; An organic compound containing an element having an unshared electron pair; And Coating composition comprising water. The coating composition of claim 1, wherein the metal alkoxide is present at 0.1 to 5 weight percent. The coating composition of claim 1, wherein the element having an unshared electron pair is selected from the group consisting of O, N, and P. 7. The coating composition of claim 1, wherein the organic compound including an element having an unshared electron pair is at least one compound selected from the group consisting of alcoholamine, acetylacetone, and mixtures thereof. The coating composition of claim 1, wherein the organic compound including an element having an unshared electron pair is used in an amount of 0.2 to 0.8 moles based on 1 mole of a metal alkoxide. The coating composition of claim 5, wherein the organic compound including an element having an unshared electron pair is used in an amount of 0.5 to 0.7 moles based on 1 mole of the metal alkoxide. The coating composition of claim 1, wherein the coating composition further comprises an organic solvent. The coating composition of claim 1, wherein the coating composition further comprises a metal salt as the metal particulate precursor. In the method for producing a composition for forming a coating film of an image display device, M (OR) _n (M is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals and rare earth elements, R is an alkyl group having 1 to 15 carbon atoms, n is 1 to 6 and is determined by M) A method for producing a coating composition comprising the step of reacting an organic compound comprising a metal alkoxide and an element having an unshared electron pair in an organic solvent, and adding excess water thereto. 10. The method according to claim 9, wherein said manufacturing method further comprises a grinding and dispersing process. An image display apparatus comprising a coating film formed by applying and drying the coating composition of claim 1 to a panel. An image display apparatus according to claim 11, wherein the image display apparatus is a cathode ray tube or a flat panel display.