Reflection preventing painted layer

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to an antireflection coating layer on a substrate, wherein the coating layer has a refractive index gradient such that the refractive index decreases in the direction from the surface of the substrate to the outer surface of the coating layer. The layer consists of gel.

【0002】

The present invention is also related to a cathode ray tube comprising a display window with an antireflection coating layer.

【0003】

The present invention is further related to a method of producing an antireflection coating layer on a substrate, and the coating layer has a refractive index such that the refractive index decreases in the direction from the surface of the substrate to the outer surface of the coating layer. It has a slope and the coating layer consists of a gel formed by the reaction of the alcoholate starting material with water.

【0004】

[Conventional technology]

Anti-reflective coating layers are used, for example, to reduce the loss of reflected light across and to suppress disturbing reflections in the image, such as the display screen of a display device, the protective plate of a solar condenser, or a light source. Used for envelopes or other optical elements such as lenses and windows.

【0005】

U.S. Patent Specification No. US 4837809 describes how to make an antireflection layer. The reaction of the alcoholate starting material with water produces various solutions with gel particles, and the solutions represent the graded particle size. A continuous layer of solution with increasing particle size is applied to the substrate and dried. The layer thus produced is porous and exhibits particle size and pore size that increase in the direction from the substrate surface to the outer surface of the layer. As a result of the increasing average density within the layer, there is a considerable decrease in the index of refraction. Alcolates, such as methoxy and ethoxy compounds of silicon, titanium and aluminum, are used as starting materials and the optical properties of the layers can be modified by impurities.

【0006】

The drawback of this known anti-reflective layer is that it is porous and therefore mechanically weak. This drawback is also caused by other methods that prevent the substrate surface from reflecting, for example, when the substrate is roughened by etching. Another drawback of this known method is the need to use many different solutions that are applied one after another to the surface and each requires a drying step. Such a method is not suitable to be carried out as a continuous method with many steps.

【0007】

[Problems to be Solved by the Invention]

In particular, it is an object of the present invention to provide a mechanically strong antireflection layer having high scratch resistance and low sensitivity to the action of moisture. A particular object of the present invention is to provide a cathode ray tube provided with such an improved antireflection layer. Another object of the present invention is to provide a simple and effective method for producing an antireflection layer, which method must be suitable to be carried out as a continuous method as much as possible.

【0008】

[Means for solving problems]

According to the present invention, these objects are achieved by an antireflection coating layer as described at the beginning, the coating layer is a sealed layer, and the degree of cross-bonding of the gel material is such that the coating is applied from the substrate surface. It increases in the direction towards the outer surface of the layer. As a result of the increased degree of cross-coupling in the gel material, the degree of order and the packing density in the material decrease, resulting in a decrease in the index of refraction. The expression "sealed layer" here means that the layer is non-porous or nearly non-porous, as opposed to the known anti-reflective layer according to US Pat. No. 6,4837809. Should be interpreted.

【0009】

In a preferred embodiment of the anti-prevention coating layer according to the present invention, the coating layer consists of adjacent particles whose dimensions decrease in the direction from the substrate surface to the outer surface of the coating layer. By using such a layer, the remaining specular reflection is partially converted to diffuse reflection (anti-glare effect), which prevents, for example, an external light source on the display screen from interfering with the image. Therefore, it is important for application to display devices.

【0010】

Suitable gel materials for use in layers with a gradient index are, for example, M (OR)._xIt can be produced by the form alcoholate, where M is a metal atom such as Si, Al, Ti, R is a group of alkyl groups with 1-5 carbon atoms, and x is a metal atom. For valence, see US Patent Specification US 4837809. In certain embodiments of the invention, the antireflection coating layer is made of silica gel, which may contain impurities if necessary. The use of silica gel, which can be produced by using alkoxysilane as a starting material, provides a mechanically strong, temperature resistant layer with a low index of refraction. Within the scope of the present invention, the optical and many properties of the antireflection layer can be affected by the use of impurities, see, for example, US Pat. No. 6,4837809. Oxides of both chromium and / or aluminum can be used to affect the transfer properties of the layer. Metal molecules can be used to affect the conductivity of a layer, so that the layer can have an antistatic effect.

【0011】

An object of the present invention to provide a cathode line tube with an improved antireflection coating layer is that the coating layer is made of a non-porous gel and the degree of cross-bonding of the gel material is from the surface of the display window. The coating layer increases in the direction toward the outer surface of the coating layer, and as a result, the coating layer has a refractive index inclination such that the refractive index decreases in the direction from the surface of the display window to the outer surface of the coating layer. Achieved by having.

【0012】

According to the present invention, an object of providing a method for producing an antireflection coating layer on a substrate is achieved by a method as described at the beginning, in which an organic solution of an alcoholate starting material is applied onto the substrate. During the formation of the gel, the reaction conditions are such that the degree of cross-bonding of the gel material is from the surface of the substrate to the outside of the coating layer. It is varied in such a way that a porous gel that increases in the direction towards the surface is formed. Short chain alcohols, such as methanol and ethanol, or ketones can be used as solvents in organic solutions, also see US Pat. No. 6,4837809.

【0013】

A layer with a regularly fluctuating index of refraction and a layer with low porosity and thus a low degree of light scattering are formed by subdividing the organic solution of the alcoholate starting material, preferably using ultrasonic energy supply. The mist is obtained according to a method in which the coating layer is brought into contact with the surface of the substrate to which it is applied.

【0014】

In a preferred embodiment of the method according to the invention, an increase in the degree of cross-bonding is obtained by increasing the temperature during the formation of the gel. At relatively low temperatures, linear chains are formed during the reaction with water, resulting in the formation of regular and fine-grained structures with high density and high index of refraction. At relatively high temperatures, a greater degree of cross-coupling occurs, which results in a fine-grained structure with low density and low index of refraction. An additional effect is that at relatively high temperatures there is little coalescence of fog droplets, and they dry more rapidly, thus forming smaller particles on the outside of the antireflection layer. Such layers have a particularly effective anti-reflective and anti-glare effect.

【0015】

The degree of cross-bonding of the gel can also be affected by a variety of other methods. An increase in the degree of cross-bonding can be obtained by increasing the degree of acidity during gel formation. Irregular networks are formed in alkaline media, whereas linear chains are formed in acid media, as at low temperatures. An increase in the degree of cross-bonding can instead be obtained by reducing the concentration of the alcohol starting material in the organic solution, and as a side effect it determines the particle size (after drying of the water droplets). Decreases in the direction of the outer surface of the antireflection layer. An increase in the degree of cross-bonding can also be achieved by using an alcoholate starting material with an increased degree of hydrolysis, and the properties of the material used in the process can be changed continuously or in small steps. A suitable starting material is the formula Si (OR)_4-p(OH)_pAlkoxysilane, where R is, for example, a methyl group or an ethyl group, and p has a value of 0 to 4. The degree of increase in hydrolysis is consistent with the increased value of p.

【0016】

An additional advantage of the use of a mechanically strong antireflection layer according to the present invention is the substrate on which it is located, as essentially described in EPO Publication No. EP-A1-0294830. Formed by the fact that it has the effect of strengthening. Thanks to that, for example in the case of cathode ray tubes, thinner display screens can be used, which results in glass savings and 10-15% weight reduction.

【0017】

[Example]

Now, let us explain the present invention in more detail with reference to the drawings and typical examples.

【0018】

Typical Example 1 FIG. 1 schematically shows an apparatus for carrying out the method according to the present invention. Starting materials for the production of the antireflection layer are supplied via tube 2 from a storage container (not shown) and the amount of each starting material can be controlled individually. The supply pipe 2 carries the liquid starting material by dropping into the atomizer 4 provided with the ultrasonic element 6. The transport gas can be supplied via a separate pipe 8 and the transport gas can be used to transport the fog to be formed into the deposition chamber 12 via the transport pipe 10. In the deposition chamber, the substrate 14 to be painted placed on the heating plate 16 is brought into contact with the mist.

【0019】

In this typical example, an alcohol solution of alkoxysilane and water with a small amount of hydrochloric acid were used as starting materials. The composition of this alcohol solution is Si (OC)₂H₅) (OH)₃It consisted of ethanol with an alkoxysilane, where the molar ratio between ethanol and alkoxysilane was 13: 1. A small amount of acid, such as hydrochloric acid or nitric acid, may be added to the water to catalyze the hydrolysis, see US Pat. No. 6,4837809. According to this example, 10^-3A solution containing M nitric acid was used. The ratio between the amount of water and the alcohol solution was chosen so that 4 mol of water was given to 1 mol of alkoxysilane.

【0020】

A polished glass plate was used as the substrate. The glass had a refractive index of 1.52 and a reflection of 4.2% at a wavelength of 550 nm. The substrate was brought into contact with the fog as described above for 20 minutes, during which the temperature of the substrate gradually increased from an initial value of 23 ° C to a final value of 55 ° C. The layer was then fired at a temperature of 150 ° C for 30 minutes. An antireflection layer with a thickness of 300 nm was provided. This layer thickness can be influenced as needed by varying the duration of deposition, by varying the concentration of materials used, and by adjusting the gas and fog streams, respectively.

【0021】

The outer surface of this antireflection layer had a refractive index of about 1.36. The reflexes were less than 1.0%, some of which were in the form of diffuse reflexes. FIG. 2 shows a schematic cross-sectional view of the substrate 20 having the antireflection layer 22. In the layer, adjacent particles 28 can be recognized and the size of the particles is reduced in the direction from the polished substrate surface 24 to the outer surface 26.

【0022】

FIG. 3 shows the reflection R as a function of the wavelength of light measured on the front surface of the glass plate (a) without the antireflection layer and the glass plate (b) having the antireflection layer as described above.

【0023】

If necessary, the substrate surface may be pretreated to ensure that the mist deposits on the surface as a continuous layer and not in the form of large droplets. For this purpose, essentially known methods can be used to make the substrate hydrophilic or hydrophobic, depending on the composition and hydrophilic / hydrophobic properties of the material to be applied.

【0024】

Typical Example 2 FIG. 4 schematically shows a cathode ray tube having a glass envelope 31 which is essentially known, and the cathode ray tube includes a display window 32, a cone portion 33, and a neck portion 34. An electron gun 35 for generating an electron beam 36 is housed in the neck. The electron beam 36 is focused on point 38 on the display screen 37. The display screen is provided on the inside of the display window 32. The electron beam 36 is deflected across the display screen 37 in two mutually perpendicular directions xy by the deflection coil system 39. A layer of material (phosphorus) that emits cold light is present on the display screen 37. The display window 32 is provided with an antireflection layer 40 on the outside, and the antireflection layer is manufactured as described in a typical Example 1.

【0025】

Typical Example 3 This method was performed as described in Typical Example 1 by the difference that the temperature was kept constant at a value of 30 ° C. During the deposition process, the degree of acidity of the water added is 10^-3M to 10^-4It was reduced to M in small steps, thus gradually reducing the density of the layers produced. Again, there was a clear reduction in reflections on the surface.

【0026】

Typical Example 4 This method was performed as described in Typical Example 1 by the difference that the temperature was kept constant at a value of 30 ° C. During the deposition process, the alcohol solution used was gradually diluted with ethanol, and the ratio between ethanol and alkoxysilane was gradually changed from 10: 1 to 25: 1. The reflection was clearly reduced, and the structure of the antireflection layer was the same as shown in FIG.

【0027】

Typical Example 5 This method was performed as described in Typical Example 1 by the difference that the temperature was kept constant at a value of 30 ° C. Increased hydrolysis by varying the amount of water added during the deposition process, one after the other, from the initial value of 1: 1 to the final value of 4: 1 expressed as the molar ratio of water to alkoxysilane. Alkoxysilanes with a certain degree of susceptibility were used. Thus, the reflection in the manufactured layers was less than 1.0%.

[Simple explanation of drawings]

[Figure 1]

An apparatus suitable for carrying out the method according to the present invention is shown graphically.

[Figure 2]

FIG. 6 is a schematic cross-sectional view of a substrate having an antireflection coating layer according to the present invention.

[Fig. 3]

It is a graph which shows reflection R as a function of wavelength λ.

[Fig. 4]

It is a partially cut-out perspective view of an Example of a cathode ray tube according to the present invention.

[Explanation of symbols]

2 Supply pipe 4 nebulizer 6 Ultrasonic element 8 Independent pipe 10 Transport pipe 12 Sedimentary chamber 14 board 16 Hot plate 20 board 22 Anti-reflective layer 24 Polished substrate surface 26 outer surface 28 Adjacent particles 31 glass envelope 32 Display window 33 Cone part 34 neck 35 electron gun 36 electron beam 37 Display screen 38 points 39 Deflection coil system 40 Anti-reflective layer R reflection λ wavelength