JPH05234538A - Antireflection and antistatic coatings particularly for cathode-ray tube and its manufacture - Google Patents

Abstract

PURPOSE: To provide antireflectioon and antistatic layers which are simply manufactured having good reproducibility and which are not subject to rapid deterioration due to damage and to erosion or contamination due to moisture. CONSTITUTION: This coating is made in the form of a double layer comprising an antiglare layer 6 and an antireflection layer 4 on a substrate 2, particularly on a display screen of a cathode-ray tube. The antistatic layer made of silicon dioxide containing at least one kind of conductive gold oxide is formed from an alcohol solution of alkoxyl silane compound. The antiglar layer 6 made of lithium silicate is formed from underwater sol of lithium oxide stabilized silicon dioxide. If desired, both layers may be reversed, in this case, the conductive gold oxide is blended in lithium silicate when necessary.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an antireflection and antistatic coating on a substrate having a double layer consisting of a layer of silicon dioxide and an antiglare layer. The present invention also provides
The present invention relates to a cathode ray tube having an antireflection and antistatic coating consisting of a layer of silicon dioxide and an antiglare layer. The invention further comprises a double layer consisting of an antistatic layer and an antiglare layer, the antistatic layer being provided with a suspension of at least one electrically conductive metal oxide in an alcoholic solution of an alkoxysilane compound and subsequently at high temperature. The invention relates to a method for producing an antireflection and antiglare layer coating on a substrate, which forms a layer of a mixture of silicon dioxide and at least one electrically conductive metal by treatment with. The invention also relates to a method for producing an antireflection and antistatic coating on a substrate having a double layer consisting of a layer of silicon dioxide and an antiglare layer.

[0002]

Anti-reflection coatings are used on other optical elements, such as display screens of display devices, light source containers and windows, to reduce reflection losses of light and suppress interfering reflections of images. It The coating as described above is used especially for reducing specular reflection (antiglare effect). Antistatic coatings are used, for example, on the display screen of display devices. Such layers are sufficiently conductive to ensure that high static voltages present on the outer surface of the device can be removed within seconds. Therefore, when the user touches the screen, the user is prevented from receiving an unpleasant shock or adsorbing dust around the user.

US Pat. No. 4,945,282 describes a screen with an antireflective and antistatic coating having a double layer of a layer of silicon dioxide and an antireflective layer. The silicon dioxide layer is an antistatic layer which comprises, for example, a transparent conductive metal oxide and is between the substrate and the antireflection layer and has a thickness of 5 to 50 nm. The antireflective layer described above also comprises silicon dioxide particles containing silicon dioxide and having a diameter of 10 to 1000 nm. If desired, the functions of both layers can be combined into a single layer. The aforementioned U.S. patents also describe methods of making antireflective and antistatic coatings. Both layers are made by providing a solution of an alkoxysilane compound followed by a high temperature treatment to form silicon dioxide. For the production of the antistatic layer, a conductive metal oxide such as tin oxide, indium oxide or antimony oxide is suspended in an alcohol solution of an alkoxysilane compound. For the production of antireflection layers, silicon dioxide particles are suspended in an alcohol solution of an alkoxysilane compound.

A disadvantage of this known method of making antireflection and antistatic coatings is that the coating uses an alcoholic solution of a reactive and inherently unstable alkoxysilane compound. This solution is sensitive to moisture and has a limited shelf life. Since the structure of the layer thus produced depends, inter alia, on the extent of hydrolysis and polymerization of the alkoxysilane compound and the viscosity of the solution, the reproducibility of the results leaves much to be desired. .. This is important for antireflective layers, where the microstructure significantly affects the optical properties, and less so for much thicker antistatic layers. Another drawback of the known method is that it is formed by the use of organic solvents which require many safety precautions when used in large quantities. Moreover, the coatings produced by the known method are mechanically weak due to the discrete presence of silicon dioxide in the surface layer.

[0005]

The object of the invention is, inter alia, to obtain an antireflection and antistatic coating on a substrate which can be produced in a simple and reproducible manner. In this regard, the present invention is directed to safe starting materials with long-term shelf life. Another object of the present invention is to obtain a mechanically strong layer with stable properties which are not subject to rapid deterioration due to damage, the action of moisture or contamination. Yet another object of the present invention is to provide a simple and reliable method of obtaining such antireflective and antistatic coatings. In this regard, the present invention
The aim is to minimize the use of organic solvents.

[0006]

The object of obtaining a substrate having an antireflection and antistatic coating, in particular a cathode ray tube with a display screen, is the reflection consisting of a double layer of a layer of silicon dioxide and an antiglare layer as described at the outset. This is accomplished in the antistatic and antistatic coatings by having the antiglare layer consist of lithium oxide.

In a preferred embodiment of the present invention, the layer of silicon dioxide is an antistatic layer containing at least one conductive metal oxide. A suitable transparent conductive metal oxide is tin oxide,
Indium oxide, antimony oxide and mixtures thereof. Other materials known per se, such as hygroscopic materials and metals and metal compounds, especially palladium compounds, may be used instead to provide the charge layer with the required conductivity.

According to a first embodiment of the invention, a layer of silicon dioxide is located between the substrate and the layer of lithium silicate.
If desired, materials may be added to the layer to modify its optical, mechanical or other properties. For example, dyes can be used to affect the light transmission properties.
It is preferred that the silicon dioxide layer contains at least one dye. This is preferable to adding the dye to the lithium silicate layer because incorporation of the dye into such a layer is less durable.

In a second embodiment, in which, compared to the first embodiment, the layers are provided in reflective order, the lithium silicate layer is located between the substrate and silicon dioxide. The third one, in which the antiglare and antistatic functions are combined into a single layer
In one embodiment, the layer of lithium silicate is an antistatic layer comprising at least one conductive metal oxide, which layer is located between the substrate and the layer of silicon dioxide. The conductive metal oxide used, or other material which imparts conductivity if desired, can be the same material used in the layer of silicon dioxide in the previous two embodiments. .. In this third embodiment, the layer of silicon dioxide serves to ensure that the material added to the layer of lithium silicate is permanently incorporated therein.

If it is desired to include additive materials such as one or more dyes in the second or third embodiments of the coating of the present invention, this dye is optionally added to each of the layers. You can In particular, at least one of the bilayers contains a dye. The dye is permanently incorporated into the layer of silicon dioxide and the layer of lithium oxide in these embodiments is coated with a layer of silicon dioxide, which again ensures a stable coating.

If desired, the substrate with the coating according to the invention can additionally be provided with an antireflection layer which is known per se in order to reduce the total specular and diffuse reflection. For this purpose, for example, a layer of magnesium fluoride having a low refractive index can be provided as the outermost layer or alternatively a stack of layers having a high and a low refractive index can be used.

If desired, the index of refraction can also be altered by adding a dopant to the coating of the present invention, especially the silicon dioxide layer. A stack of layers suitable for reducing total internal reflection is, for example, a first antistatic layer of silicon dioxide (refractive index 1.7) additionally doped with titanium dioxide and a second layer of titanium dioxide (refractive index 2.1). , Made by a method similar to the method of manufacturing the silicon dioxide layer) and having an outermost antiglare layer of lithium silicate (refractive index 1.43). The thickness of each layer is 100 to 150 nm.

The purpose of obtaining an antireflection and antistatic coating is to have a double layer consisting of an antistatic layer and an antiglare layer, the antistatic layer being at least one conductive metal oxide in an alcoholic solution of an alkoxysilane compound. In the method for producing an antireflection and antiglare layer coating on a substrate, which comprises providing a suspension of and subsequently forming a layer of a mixture of silicon dioxide and at least one conductive metal by treatment at high temperature, the antiglare layer comprises: This is accomplished by providing a sol of lithium oxide-stabilized silicon dioxide in water, followed by treatment at high pressure to form a layer of lithium silicate. Corresponding to the first two embodiments of the invention, the antistatic layer and the antiglare layer can be provided in any desired order on the substrate, for example on the display screen of a cathode ray tube.

Along with the above-mentioned third embodiment of the coating of the invention, another method of the invention is characterized in that the antiglare layer with antistatic effect is stabilized with lithium oxide. A suspension of at least one metal oxide in a sol of silicon dioxide in water is provided and subsequently treated at high temperature to form a layer of a mixture of lithium silicate and at least one metal oxide, followed by an alkoxysilane compound. Of an alcoholic solution and subsequently formed at high temperature by forming a layer of silicon dioxide.

According to the invention, US Pat. No. 4,945,
A layer of silicon dioxide is used which can be made by the method described in 282. According to the invention, this layer is
Used as an antistatic layer or a protective layer. For both applications it is possible to use relatively thin layers with a thickness below 200 nm, preferably between 5 and 50 nm. Therefore, the required amounts of reactive and thus unstable alkoxysilane compounds and organic solvents are limited compared to prior art methods. According to the invention, a layer of lithium silicate is used for the antiglare layer, this layer of lithium silicate does not contain discrete particles,
Therefore, it exhibits high mechanical strength. US Patent Specification No.
No. 3,940,511 describes an antireflection layer of lithium silicate and a method for producing the same, which layer contains color correction means such as soot and dyes, but according to the research that led to the present invention,
It has been found that, without some measures, such layers are not suitable for permanent incorporation of conductive metal oxides or dyes. The method of the present invention combines the advantages of both known techniques or minimizes the drawbacks of each technique.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to embodiments of the drawings. Example 1 FIG. 1 shows a substrate 2 having an antireflective and antistatic coating according to the invention, which coating comprises an antistatic layer 4 of silicon dioxide with at least one conductive metal oxide and an antiglare layer of lithium silicate. It consists of six.

Such a coating was produced according to the present invention in the following manner. The display screen of the cathode ray tube was thoroughly cleaned, after which the first antistatic layer was applied by spin coating, the material of this coating being 2% by weight of tetraethylorthosilicate Si (O 2
C ₂ H ₅ ) ₄ in ethanol, which contains 1% by weight of tin oxide SnO ₂ and antimony oxide 1: 0.15.
The mixture was dispersed as a conductive material. If desired, the coating material contains a dye, for example 0.2% by weight rhodamine B. The size of the metal oxide particles and dyes present in the suspension is smaller than 50 nm to prevent light scattering. This layer was dried at 60 ° C. and had a thickness in the range between 50 and 100 nm.

A second antiglare layer was then applied by spin coating. The material of this coating is 2 by weight
% Solid component and a sol of lithium oxide stabilized silicon dioxide in water with a molar ratio of SiO ₂ : Li ₂ O of 8: 1. The thickness of this layer was approximately 1000 nm. Next, both layers
It was cured by treatment for 30 minutes at a temperature of 160 ° C., in which the first layer was converted to silicon dioxide and the second layer was converted to lithium silicate. Finally, the display screen was washed with running water and dried.

The display screen thus obtained was sufficiently conductive and antistatic. Scattered reflections at the expense of specular reflections help to prevent disturbing images of external light sources, for example on the display screen.

Instead of the tetraethylorthosilicate mentioned above, it is also possible to use alkoxysilane compounds of the type Si (OR) ₄ known per se. In this case R is 1
Preferred alkyl groups have from 5 to 5 carbon atoms. For example, methanol can alternatively be used as the solvent. A certain amount of water with, for example, an inorganic acid may be added to the solution to enhance the conversion to silicon dioxide. Suitable compositions are described, for example, in U.S. Pat.No. 4,945,282, in which U.S. Pat.No. Oxides are also mentioned. Instead of metal oxides it is also possible to use compounds of, for example, palladium, platinum or gold to obtain conductivity (see US Pat. No. 4,563,612). Suitable compounds for the sol of lithium oxide-stabilized silicon dioxide in water are described in US Pat.
940,511 and 4,563,612.

EXAMPLE 2 FIG. 4 shows a partially cutaway perspective view of a cathode ray tube known per se with a glass container 31 having a display window 32, a cone 33 and a neck 34. An electron gun 35 for generating an electron beam 36 is provided in the neck. The electron beam 36 is focused on a display screen 37 to form a target spot 38. The electron beam 36 is deflected by a deflection coil system 39 in two mutually orthogonal directions xy across the display screen 37. Fluorescent layer is display screen 37
It is above. The outside of the display window 32 is provided with an antireflection and antistatic coating made as described in Example 1.

EXAMPLE 3 FIG. 2 shows a substrate 12 having an antireflective and antistatic coating according to another embodiment of the present invention, the coating comprising an antiglare layer 16 of lithium silicate and at least one conductive gold oxide. And an antistatic layer 14 of silicon dioxide containing the same. Such a coating was made using the materials and methods of Example 1 except that the order of applying the layers was reversed. After providing the first layer of lithium oxide stabilized silicon dioxide sol, this layer was dried at 60 ° C. After applying the second layer containing the alkoxysilane compound, both layers were annealed at a temperature of 160 ° C. for 30 minutes, after which the display screen was washed with running water and dried.
The results obtained were the same as those described in Example 1.

EXAMPLE 4 FIG. 3 shows a substrate 22 having an antireflective and antistatic coating according to yet another embodiment of the present invention, which coating is a lithium silicate coating containing at least one conductive gold oxide. Antiglare and antistatic layer 26 and protective layer of silicon dioxide
And a double layer having 28 and. Such a coating was made by using the materials and methods according to Example 3 except that the gold oxide was suspended in a sol of lithium oxide stabilized silicon dioxide in water instead of an alcoholic solution of an alkoxysilane compound. .. The amount used, the work process and the result were the same as in Example 3. According to the invention, an effective coating is produced in a simple and reproducible way, which coating is suitable for cathode ray tube display screens and has good anti-glare and antistatic properties as well as various environmental influences such as moisture and mechanical damage. Showed sufficient resistance to.

[Brief description of drawings]

1 is a schematic cross-sectional view of a first embodiment of a substrate having a coating of the present invention,

FIG. 2 is a schematic cross-sectional view of a second embodiment of a substrate having a coating of the present invention,

FIG. 3 is a schematic cross-sectional view of a third embodiment of a substrate having a coating of the present invention,

FIG. 4 is a partially cutaway perspective view of an embodiment of the cathode ray tube of the present invention,

[Explanation of symbols]

 2,12,22 Substrate 4,14 Antistatic layer 6,16 Antiglare layer 26 Antiglare and antistatic layer 28 Protective layer 32 Display window 40 Reflective and antistatic coating

 ─────────────────────────────────────────────────── ───Continued from the front page (72) Inventor Adrinus Leonardus Herald Us van den Eden Netherlands 5621 Beer Ainde Ven Frühne Wautzwech 1 (72) Inventor Jürgen Paul Albert Bermeim Beck Netherlands 5621 Bein Ain Fenflue Nevautzwech 1 (72) Inventor Henrix Arnordus Antonius Katers Netherlands 5621 Beer Aindow Fenflu Nevautzwech 1

Claims (10)

[Claims] 1. An antireflection and antistatic coating on a substrate having a double layer consisting of a layer of silicon dioxide and an antiglare layer, characterized in that the antiglare layer consists of lithium silicate. .. 2. The coating of claim 1, wherein the layer of silicon dioxide is an antiglare layer containing at least one conductive metal oxide. 3. The coating of claim 2, wherein the layer of silicon dioxide is located between the substrate and the layer of lithium silicate. 4. The coating of claim 3 wherein the silicon dioxide layer comprises at least one dye. 5. The coating of claim 2, wherein the layer of lithium silicate is located between the substrate and silicon dioxide. 6. The coating of claim 1, wherein the layer of lithium silicate is an antistatic layer containing at least one conductive metal oxide, the layer being located between the substrate and silicon dioxide. 7. A coating according to claim 5 or 6 wherein at least one of the bilayers comprises a dye. 8. A cathode ray tube having an antireflection and antistatic coating comprising a layer of silicon dioxide and an antiglare layer, wherein the antiglare layer is made of lithium silicate. 9. A double layer comprising an antistatic layer and an antiglare layer, wherein the antistatic layer is provided with a suspension of at least one conductive metal oxide in an alcohol solution of an alkoxysilane compound and subsequently at high temperature. In the method for producing an antireflection and antistatic layer coating on a substrate, wherein a layer of a mixture of silicon dioxide and at least one conductive metal is formed by the treatment with the antiglare layer, the antiglare layer is a sol of lithium oxide stabilized silicon dioxide in water. And subsequently forming a layer of lithium silicate by treatment at elevated temperature to form an antireflective and antistatic coating on a substrate. 10. A method of forming an antireflective and antistatic coating on a substrate having a bilayer consisting of a layer of silicon dioxide and an antiglare layer, the method comprising at least one metal oxide in a sol of lithium oxide stabilized silicon dioxide in water. Suspended in water and subsequently treated at high temperature to form a layer of a mixture of lithium silicate and at least one metal oxide, and then an alcoholic solution of an alkoxysilane compound is provided and subsequently treated by high temperature treatment. A method of making an antireflection and antistatic coating on a substrate, which comprises forming a layer of silicon.