JPH04334852A - Anti-reflection coating forming method for display device - Google Patents

Abstract

PURPOSE:To prevent resolution from being deteriorated by suppressing a reflection factor due to dispersion in film thickness to be fairly increased even if a film is formed by a simple method insufficient for film thickness control, and concurrently reducing diffusion effect caused by irregularities on the outermost layer. CONSTITUTION:In an anti-reflection coating forming method for a display device multi-layer optical films 17 and 18 each of which has more than two layers different in refraction factor, are formed on the outer surface of a glass substrate 10 for a display screen, particulates of SiO2 10 to 1000nm in size are laminated on the outermost surface of the multi-layer optical film, and the outermost layer of the multi-layer optical film is corroded via the laminated particulates of SiO2, so that the surface of the outermost layer is thereby formed into a surface having an irregular pitch of 10 to 1000nm, and also having an irregular surface of 50 to 100nm.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Field of Industrial Application] This invention relates to a method for forming an anti-reflection film on a display device, and particularly when forming an anti-reflection film on the outer surface of a glass substrate of a display surface such as a cathode ray tube on which a phosphor screen is formed. The present invention relates to an effective method for forming an anti-reflection film.

0003

[Prior Art] Generally, in a cathode ray tube, a phosphor screen is formed on the inner surface of a face plate (glass base) made of glass with a smooth outer surface, and the electron beam emitted from the electron gun is deflected by the magnetic field generated by the deflection yoke. By deflecting and scanning the phosphor screen horizontally and vertically,
The device is configured to display an image on the phosphor screen and view the image from the outside through the face plate. Therefore, if the outer surface of the face plate is smooth, the reflection of external light on this outer surface overlaps with the image, significantly deteriorating the quality of the image viewed from the outside through the face plate.

[0004] Conventionally, therefore, there are cathode ray tubes in which anti-reflection treatment is applied to the outer surface of the face plate in order to prevent this image deterioration.

This antireflection treatment method includes (a)
A method of sandblasting by spraying an abrasive onto the outer surface of the glass substrate to make it uneven, or a method of etching with hydrofluoric acid to form unevenness (b) Ethyl silicate is applied to the outer surface of the glass substrate which has been preheated to 50 to 60°C. (Si(OR)4)
A method of spraying an alcohol solution of (R: alkyl group) to form a film, then vaporizing the alcohol component to form an uneven film, and firing this uneven film (c) SiO2 or Mg on the outer surface of the glass substrate F
2 A method in which a dispersion of fine particles such as 2 is dispersed in an alcoholic solution of ethyl silicate is applied and then baked to form an uneven film (d) A method in which a multilayered film is formed by vapor deposition (e)
There is a method of forming a multilayer film on the outer surface of a glass substrate by a sol-gel method using a dispersion in which oxide fine particles are dispersed in an alcohol solution of ethyl silicate or a metal alkoxide solution.

Among these methods, method (a) of forming unevenness by sandblasting or corrosion is a method of directly forming unevenness on the outer surface of the face plate.
There are many problems such as the impossibility of regenerating cathode ray tube bulbs and the tendency for dirt to adhere to them.

On the other hand, in the method (b) of spraying an alcoholic solution of ethyl silicate, the bulb can be regenerated and the antireflection film can be formed relatively easily.

However, these methods (a) and (b) both involve forming an uneven surface or an uneven film on the outer surface of the glass substrate, and using the unevenness to diffuse external light and prevent reflection. Because the unevenness simultaneously diffuses the displayed image,
There is a problem that resolution deteriorates.

The method (c) of applying a dispersion in which fine particles such as SiO2 and MgF2 are dispersed in an alcoholic solution of ethyl silicate is described in Japanese Patent Application Laid-open No. 76001/1983.
Publication No., JP-A-1-154444, JP-A-1-1
54445, Japanese Patent Application Laid-Open No. 175601/1994, and one example is Japanese Patent Application Laid-Open No. 1-154
To explain the anti-reflection film disclosed in Publication No. 444, as shown in FIG. It is formed by applying it to the external surface of the body using a spin coating method and then firing it.

[0010] Therefore, this antireflection film is made of SiO
2 Consists of fine particles 1 and a SiO2 thin film 2 that binds the fine particles 1, and has a slightly lower refractive index of 1.47 compared to 1.52 of the glass substrate 3, so the reflectance is slightly lower due to interference effects. However, it can be said that the anti-reflection effect of the anti-reflection film itself is almost negligible, and the anti-reflection effect of this anti-reflection film is due to the continuous change in volume ratio between air and thin film due to the uneven structure of the coated surface by the SiO2 fine particles 1. This achieves low reflection characteristics.

However, this antireflection film is made of SiO2
The light diffusion effect by the fine particles 1 is large, and there is also a slight diffusion effect by the unevenness, which deteriorates the resolution. In order to reduce this deterioration in resolution, it is effective to reduce the diameter of the SiO2 fine particles 1 and smoothen the SiO2 thin film 2; If this is done, the reflection characteristics will deteriorate.

[0012] Furthermore, in order to achieve low reflectance, S
It is necessary to increase the content of i O2 fine particles 1 and increase the degree of unevenness, but in this case, the antireflection film tends to have a microporous structure, and Si O2 fine particles - Si
The bonding force between the O2 thin films becomes weaker, and the wear resistance deteriorates significantly.

[0013] In other words, the anti-reflection film that uses SiO2 fine particles to prevent reflection due to the interference effect as described above has the following properties:
There are problems with resolution and wear resistance.

As an example of the multilayer vapor deposited film formed by vapor deposition (d), FIG.
TiO2 +Pr with F2 and refractive index n2 = 2.06
6 O11 is alternately deposited to form four layers of deposited films 5a and 5b.
, 6a, 6b is shown. The film thickness d of this multilayer deposited film is 930 angstroms for the first layer 5a, 1270 angstroms for the second layer 6a, and 1270 angstroms for the third layer 5b.
is 290 angstroms, and the fourth layer 6b is 140 angstroms.

[0015] When such a multilayer vapor deposited film is used, the specular reflectance can be reduced to 0.1 or less due to the interference effect. However, when this multilayer vapor deposition film is applied to large-scale cathode ray tubes with large screens, it requires large-scale equipment and has the problem of increasing manufacturing costs.

In the sol-gel method (e), desired oxide fine particles are mixed with an alcoholic solution of ethyl silicate or Ti
, Sn or the like is dispersed in a metal alkoxide solution and applied to the outer surface of a glass substrate by a method such as a spray, spin, dip, or roll method, and then baked.

The multilayer film formed by this method has the same effect as the multilayer vapor deposited film described above, but the film structure consists of oxide fine particles with a high or low refractive index and a refractive index n=1.46.
The refractive index of the film itself is higher in the case of low refractive index oxide fine particles than that of high refractive index or low refractive index oxide fine particles. In the case of oxide fine particles, the refractive index is low, and the refractive index changes depending on the content of the oxide fine particles.

In general, a multilayer film with low reflection characteristics has a low refraction that satisfies n×d=λ/4, where n is the refractive index, d is the film thickness, and λ is the center wavelength in the visible range (550 nm). It is formed by combining a high refractive index film and a high refractive index film.

For example, in the case of a multilayer film with a two-layer structure, the first upper layer is formed by using a dispersion in which Mg F2 fine particles (n=1.38) having the lowest refractive index are dispersed in an alcoholic solution of ethyl silicate. If it is formed, the refractive index of the film in this case is limited to 1.40, so in order to achieve low reflection characteristics, the refractive index of this upper layer must be set to the maximum of 1.40.
In this case, the refractive index of the lower second layer must be 1.73. When forming a multilayer film using the sol-gel method in this way, the refractive index of the low refractive index film is 1.40 or more, so the refractive index of the high refractive index film must be 1.70 or more. In order to obtain the desired refractive index, the content of fine particles must be increased. As a result, SiO2 in the film
Bonding (bonding between fine particles and SiO2) is reduced, and wear resistance is significantly deteriorated. In order to improve this wear resistance, high temperature firing of 500° C. or higher is required, which is accompanied by manufacturing difficulties. Especially in the case of metal alkoxides, 50
Although a desired refractive film can be obtained by firing at a high temperature of 0° C. or higher, the wear resistance is still low.

[0020] Regarding this sol-gel method, the case of a two-layer film has been described, but in terms of reflection characteristics, by using more layers, the reflectance can be lowered and the low reflection range can be widened. .

However, as mentioned above, this sol-gel method has problems with reflection characteristics and wear resistance, and furthermore, it is difficult to control the film thickness to be uniform for large cathode ray tubes with large screens. However, in order to improve these problems, there is a problem in that the cost of equipment etc. tends to be high.

[0022]

[Problems to be Solved by the Invention] As mentioned above, conventional methods for forming an antireflection film for display devices include (a) a method of directly forming unevenness on a glass substrate by sandblasting or corrosion, and (b) a method of forming an unevenness on a glass substrate directly. Method of forming an uneven film using an alcohol solution, (c) SiO2 or MgF
A method of forming an uneven film using a dispersion in which fine particles such as 2 are dispersed in an alcohol solution of ethyl silicate, (
There are various methods such as (d) forming a multilayer film by vapor deposition and (e) forming a multilayer film by sol-gel method, but each method has problems with bulb regeneration, resolution, reflection characteristics, wear resistance, etc. There is.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to relatively easily form an antireflection film that has a low reflectance and a wide range of low reflections, and causes almost no deterioration in the resolution of a display screen. The purpose is to make it possible.

[Configuration of the invention]

[0025]

[Means for Solving the Problems] A method for forming an antireflection film for a display device includes a step of forming the antireflection film on the outer surface of a glass substrate of a display surface as a multilayer optical film having two or more layers having different refractive indexes. , 10 to 1 on the outermost layer surface of the multilayer optical film.
The process of laminating 000 nm SiO2 fine particles and corroding the outermost layer of the multilayer optical film with 1% or less hydrofluoric acid or ammonium fluoride through the laminated SiO2 fine particles. The outer layer was formed by a step of making the surface of the outer layer an uneven surface with an uneven pitch of 10 to 1000 nm and an uneven surface roughness of 50 to 100 nm, and then a step of removing SiO2 fine particles laminated on the uneven surface.

[0026]

[Function] When an antireflection film is formed by the above method, the refractive index of the outermost layer can be lowered to a value that cannot be achieved with ordinary optical media by continuously changing the volume ratio of air and the outermost layer. An antireflection film having low reflectance and a broadband reflection spectrum can be obtained. As a result, even if the film is formed using a simple film formation method with insufficient film thickness control due to its broadband reflection spectrum, the increase in reflectance due to variations in film thickness can be suppressed to a small level. Further, since the irregularities of the outermost layer are very fine, the diffusion effect due to the irregularities can be reduced and resolution deterioration can be prevented.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the drawings.

FIG. 1 shows a color picture tube according to one embodiment. This color picture tube has an envelope consisting of a glass panel (glass base) 10 and a funnel 11 integrally joined to the panel 10. On the inner surface of the panel 10, dot-shaped or striped three-color fluorescent A phosphor screen 12 made of a body layer is formed, and a shadow mask 13 is mounted inside the phosphor screen 12, facing the phosphor screen 12. Further, an electron gun 15 is disposed within the neck 14 of the funnel 11. The three electron beams emitted from the electron gun 15 are deflected by a magnetic field generated by a deflection yoke (not shown) attached to the outside of the funnel 11, and the phosphor screen 12 is scanned horizontally and vertically. , is formed to display a color image on this phosphor screen 12, and the glass panel 10 serves as the base of the display surface.

In this color picture tube, an antireflection film 16 is further formed on the outer surface of the panel 10. As shown in FIG. 2, this antireflection film 16 has a laminated structure of two upper and lower layers 17 and 18, and is made of a high refractive index oxide with an average particle size of less than 50 nm, such as TiO2, SnO2.
, a lower layer (second layer) 17 with a film thickness of λ/4n in which fine particles such as In 2 O 3 are bound with Sn O 2 , an uneven pitch P of 100 to 1000 nm, and a surface roughness h of 50 to 10
SnO2 with an uneven surface of 0 nm and a maximum film thickness of λ/4n
and an upper layer (first layer) 18 consisting of.

This antireflection film 16 is formed by the process shown in FIG. 3(a).

That is, the glass substrate 10 shown in (b)
The outer surface is cleaned with an alkaline detergent such as cerium oxide or NaOH aqueous solution to remove dirt and activate the outer surface. Then, preheat the outer surface to 20 to 40°C. In this case, if the temperature of the outer surface is below 20°C, the evaporation of the alcohol component of the liquid applied afterwards will be delayed.
Liquid may accumulate around the area. If the temperature exceeds 40° C., the evaporation rate is too fast, the film becomes thick, and interference colors become noticeable.

Next, on the outer surface of the preheated glass substrate 10, TiO2, SiO2, In2 having an average particle size of less than 50 nm is added to an alcoholic solution of ethylsilicate.
A dispersion liquid in which fine particles of high refractive index oxide such as O3 are stably dispersed is applied by a spin method, and then
C. to form an ethyl silicate film 21 containing high refractive index oxide fine particles 20 and having a thickness of λ/4n for forming the lower layer, as shown in FIG. in this case,
In order to make the film thickness λ/4n as the lower layer, it is necessary to add 1 to 3% of high refractive index oxide fine particles to the alcohol solution of ethyl silicate. Even if the rotation speed of glass substrate 1 is slowed down,
It becomes difficult to control the film thickness/refractive index over the entire surface. Moreover, when it exceeds 3%, the wettability of the dispersion liquid to the outer surface of the glass substrate 10 becomes poor, and radial uneven coating tends to occur.

Next, an alcohol solution of ethyl silicate is applied by a spin method onto the ethyl silicate film 21 heated to 30 to 40°C, and then heated to 40 to 40°C.
Dry at 60°C to form a chill silicate film 22 to form an upper layer with a maximum thickness of λ/4n, as shown in (d).
form. In this case, the alcohol solution of ethyl silicate to be applied is a 1-3% solution in order to obtain an upper layer with a thickness of λ/4n.

[0034] Next, on this ethyl silicate film 22, an alcohol dispersion in which SnO2 fine particles of 10 to 1000 nm are stably dispersed is applied by a spin method, and then dried at 40 to 60°C. As shown in e), S adheres to the ethyl silicate film 22 in point contact.
A layer of i O2 fine particles 23 is formed.

Next, the ethyl silicate film 22 on which the layer of the SiO2 fine particles 23 is laminated is immersed in a less than 1% hydrofluoric acid or ammonium fluoride aqueous solution to
Ethyl silicate film 22 from the gap between O2 fine particles 23
corrodes the surface of In this way, when less than 1% of hydrofluoric acid or ammonium fluoride aqueous solution is used, corrosion can be stably controlled only by time. As a result, due to the stacking of the SiO2 fine particles with a diameter of 10 to 1000 nm, the ethyl silicate film 2
The surface of No. 2 has an uneven pitch of 100 to 1000 nm and a roughness of 5.
An uneven surface 24 of 0 to 100 nm is formed.

[0036] Thereafter, the SiO2 fine particles 23 laminated on the ethyl silicate film 22 and the hydrofluoric acid or ammonium fluoride remaining on the ethyl silicate film 22 are removed by washing with water or hot water, and the water is drained. , the ethyl silicate films 21 and 22 are decomposed by firing at a temperature of 200° C. or higher, and the surface roughness shown in FIG. 2 is 50 to 10.
An upper layer 18 made of SiO2 having a maximum film thickness of λ/4n and having an uneven surface with an uneven pitch of 100 to 1000 nm, and a film thickness λ of SiO2 fine particles bonded with SiO2.
/4n lower layer 17 and a multilayer structure anti-reflection film 16
shall be.

The antireflection film 16 formed in this way is
SiO2
The refractive index decreases to about 1.35, compared to 1.46 for a smooth film made of Therefore, the lower layer 17 has a refractive index of 1.5 from the regular reflectance of the two layers in combination with the upper layer 18.
5 to 1.70, and the film thickness λ/4n should be formed to be 80 to 90 nm. Antireflection film 1 with such a refractive index
6, when the refractive index is 1.55, the average particle size is 10 μm
By applying a dispersion liquid with a weight composition ratio of SiO2 particles/SiO2 of 1.5 using SiO2 fine particles of using the Si
It is obtained by applying a dispersion having a weight composition ratio of O2 fine particles/SiO2 of 0.5.

FIG. 3 shows that high refractive index oxide fine particles are made of SiO2 by the above method, and the SiO2 fine particles/
The lower layer 17 was formed with a weight composition ratio of SiO2 of 15, and the upper layer 18 had a surface roughness of 50 nm and an uneven pitch of 2000.
Each wavelength and specular reflectance R(x) of the anti-reflection film 16 in nm
Indicates the relationship between Curve 25a is the regular reflectance when the incident angle θ of the measurement light on the antireflection film is 0°, and curve 25b is 30°.

In general, this antireflection film had a broadband reflection spectrum, exhibited good reflection characteristics with a regular reflectance of about 0.6%, and showed almost no deterioration in resolution. In addition, because the final firing is performed at a temperature of 200°C or higher,
A film with sufficient strength and wear resistance could be obtained. Furthermore, due to the fine uneven structure on the surface of the upper layer 18, the reflection characteristics due to changes in film thickness (errors) are smaller than when the upper layer is a smooth film, so it can be formed even with a relatively simple film formation method using the sol-gel method. can. In this regard, FIG. 5 shows calculated values of variations in the luminous reflectance R(lum) as a function of the refractive index n1 of the upper layer when the film thickness of the lower layer 17 or the upper layer 18 deviates from the design value 26 by 10%.

In the above embodiment, SiO2 fine particles were used as the high refractive index oxide fine particles in the lower layer, but as the high refractive index oxide fine particles in the lower layer, SnO2, In2
When transparent conductive oxide fine particles such as O3 are used, an antistatic effect as well as an antireflection effect can be obtained.

Furthermore, in order to further lower the refractive index of the lower layer, Mg F2 fine particles are added to reduce the Mg F2
A layer in which fine particles are bound with SiO2 may be used.

Although the above embodiment describes the case where an antireflection film is formed on the outer surface of a panel of a color picture tube, the method for forming an antireflection film of the present invention can be applied to the formation of an antireflection film on other display devices. It can also be applied to

[0043]

Effects of the Invention The antireflection coating for a display device is formed by forming a multilayer optical film of two or more layers with different refractive indexes on the outer surface of a glass substrate of the display surface, and forming a multilayer optical film with a refractive index of 10 to 100 on the outermost layer surface of the multilayer optical film.
0 nm SiO2 fine particles are laminated, and the outermost layer of the multilayer optical film is corroded through the laminated SiO2 fine particles, so that the surface of the outermost layer has an uneven pitch of 10 to 1000n.
When the surface has an uneven surface with a roughness of 50 to 100 nm, the refractive index of the outermost layer decreases to a value that cannot be achieved with ordinary optical media due to a continuous change in the volume ratio of air and the outermost layer. It is possible to obtain an antireflection film having high reflectance and a broadband reflection spectrum. As a result, even if the film is formed using a simple film formation method with insufficient film thickness control, the increase in reflectance due to film thickness variations can be suppressed to a small degree, and since the unevenness of the outermost layer is extremely fine, , it is possible to reduce the diffusion effect due to unevenness and prevent resolution deterioration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a color picture tube according to an embodiment of the present invention.

FIG. 2 is a diagram showing the structure of an antireflection film formed on the outer surface of the panel.

[Fig. 3] Fig. 3(a) is a process diagram showing a method for forming an antireflection film on the outer surface of the panel, and Figs. 3(b) to 3(f) are each a method for forming an antireflection film shown corresponding to the process diagram. FIG.

FIG. 4 is a diagram showing the relationship between wavelength and regular reflectance of the antireflection film.

FIG. 5 is a diagram showing variations in the luminous reflectance of an antireflection film as a function of the refractive index of the outermost layer.

[Figure 6] S in the conventional alcohol solution of ethyl silicate
It is a figure which shows the structure of the antireflection film formed with the dispersion liquid which disperse|distributed iO2.

FIG. 7 is a diagram showing the structure of a conventional multilayer deposited film.

[Explanation of symbols]

10...Panel 12...phosphor screen 15...electron gun 16...Anti-reflection film 17...Lower layer (second layer) 17... Upper layer (first layer) 20...High refractive index oxide fine particles 21...Ethyl silicate film 22...Ethyl silicate film 23...Si O2 fine particles

Claims (1)

[Claims] 1. A step of forming a multilayer optical film having two or more layers with different refractive indexes on the outer surface of a glass substrate of a display surface, and a step of forming a 10 to 1000 nm Si layer on the outermost layer surface of the multilayer optical film.
The step of stacking O2 fine particles and the stacked Si
corroding the outermost layer of the multilayer optical film with 1% or less hydrofluoric acid or ammonium fluoride through O2 fine particles;
The surface of the outermost layer of this multilayer optical film has an uneven pitch of 10 to 100.
0 nm, and a step of forming an uneven surface with an uneven surface roughness of 50 to 100 nm, and a step of removing the SiO2 fine particles laminated on the uneven surface after forming the uneven surface. A method for forming an anti-reflection film.