JPH01319224A - Cathode-ray tube with fluorescent screen and formation of fluorescent screen - Google Patents

Abstract

PURPOSE:To improve intensity deterioration by coating a metal oxide selected from a group of indium and tin on the surface of phosphor grains constituting a fluorescent screen. CONSTITUTION:A coagulant is added to a binder solution dispersed with phos phor grains, the phosphor grains are sedimentation-coated on a substrate, the coagulant is made of an electrolyte containing metal ions selected from a group of zinc, indium and tin which can be solved in the binder solution and can easily become an oxide in the heat treatment process of a paint film. Zinc oxide ZnO, indium oxide In2O3, or tin oxide SnO2 is formed. ZnO, In2O3 and SnO2 are a material with electric conductivity and have a function to reduce the electrification on the surface of phosphors when electrons are radiated with high density to phosphors. When a high-density electron beam is radiated to a fluorescent screen, the intensity deterioration of the fluorescent screen can be improved by several - tens %, the life of a cathode-ray tube can be greatly improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cathode ray tube having a phosphor film and a method for forming the phosphor film used therein, and particularly to a cathode ray tube having a phosphor film that is not easily deteriorated by electron beam irradiation. The present invention relates to a suitable fluorescent film and a method for forming the same.

[Conventional technology]

As a typical technique for forming conventional fluorescent films, phosphor powder is dispersed in water glass, and a salt containing barium ions, such as barium acetate or barium nitrate, is added as a flocculant to gel the water glass. A so-called sedimentation coating method is known in which a phosphor is coagulated and precipitated onto a substrate. In addition,
As related to the formation of this type of fluorescent film, for example, Proceedings of the 1960 Four Electrical Engineers of Japan Federation Conference, Lecture No. 1161
can be mentioned.

[Problem to be solved by the invention]

In the coating method described above, alkali metal ions and barium ions contained in water glass remain on the fluorescent film, which is one of the factors that cause deterioration of the fluorescent film. In particular, barium compounds as aggregates become barium oxide through heat treatment in the final phosphor film formation process, and in the case of a cathode ray tube, for example, this has an adverse effect on the phosphor film while scanning the phosphor screen with an electron beam. and cause brightness deterioration. Barium compounds have certainly been widely used because they have the excellent feature of being able to form fine-grained fluorescent coatings as agglomerating substances.

However, there are few examples in which reviews have been made from the standpoint of reducing luminance deterioration of fluorescent films.

In particular, in recent projection-type cathode ray tubes that emit electron beams with an energy density more than 100 times higher than that of ordinary cathode ray tubes, the combination of water glass and barium ions is one of the factors that degrades the brightness of the phosphor film. It turned out that it was.

The present inventor conducted various experiments to find a flocculant other than a barium compound that is effective in improving the brightness deterioration of a phosphor film, and found that flocculants containing specific metal ions. We obtained knowledge that the agent has excellent properties.

Moreover, these metal ions become oxides during heat treatment in the final phosphor film formation process, and since these metal oxides have conductivity, they reduce the charging caused by electron beam irradiation on the phosphor surface and prevent brightness deterioration. We obtained knowledge that it is effective.

The present invention has been made based on the above findings, and its purpose is to solve the above-mentioned problem of improving brightness deterioration.The first purpose is to provide a cathode ray tube having an improved fluorescent film. A second purpose is to provide an improved method for forming a fluorescent film for use therein.

[Means to solve the problem]

The first object is to provide a cathode ray tube equipped with an electron beam deflection means formed by forming a phosphor film on a face plate, in which the surface of phosphor particles constituting the phosphor film is made of a material selected from the group consisting of indium and tin. This is achieved by a cathode ray tube having a fluorescent film characterized in that it is coated with at least one metal oxide.

The second object is to add a flocculant to a binder solution in which phosphor particles are dispersed, and when dispersing the phosphor particles onto a substrate in a sedimentation chamber, the flocculant is dissolved in the binder solution, and is achieved by a method for forming a fluorescent film, characterized in that the electrolyte is comprised of an electrolyte containing at least one metal ion selected from the group consisting of zinc, indium, and tin, which can easily become oxides during the heat treatment process of the coating film. Ru.

Examples of the electrolytes containing zinc ions include zinc acetate Zn(C)(a COO)i *zinc nitrate Zn(No,
), etc., zinc oxide, Zn
Substances that can be converted to O are preferred.

The same applies to electrolytes containing indium ions, such as indium nitrate I n (N 03)3, and the same applies to electrolytes containing tin ions.
For example, potassium stannate Km(Sn(OH)) is preferable.These electrolytes can of course be used alone, or may be used in combination by replacing a portion of each with the other electrolyte.Binder As the solution, any well-known solution can be used as long as it has the effect of binding the phosphor particles together during subsequent film formation, and water glass, which has been widely used in the past, is a typical example. It can be said that it is a thing.

[Effect]

Since zinc ions are divalent ions like barium ions, it seems that both have almost the same ability to coagulate water glass. However, as the number of charges of ions increases, the ability to aggregate them generally increases. It was found that ions remaining in the coated fluorescent film are involved in the deterioration of the brightness of the fluorescent film. That is, in the conventional film coated using barium ions, barium oxide BaO is formed by heat treatment performed in the cathode ray tube manufacturing process, but according to the present invention, zinc oxide Zn○, indium oxide In, O,...
Tin oxide 5no2 will be formed. ZnO,I
n2O and Sno are substances that have electrical conductivity,
When the phosphor is irradiated with electrons at high density, it has the effect of reducing the charge on the phosphor surface.

One of the factors that causes luminance deterioration of a fluorescent film is the ease with which it is charged, and reducing charging is effective in reducing luminance deterioration.

〔Example〕

Example 1 0.15 g of terbium-activated indium borate InBO:Tb phosphor was weighed out and coated by precipitation onto a substrate set at the bottom of a cylinder with a diameter of 46 mm.

The compositions of the phosphor suspension, sedimentation flocculant liquid, etc. are as follows.

(1) Phosphor suspension: 0.15g of phosphor, 45ml of pure water
2 (2) Water glass (potassium silicate) 11%, 15
mQ (3) Sedimentation flocculant liquid: 125 mQ of pure water.

15 mQ of 0.87% zinc acetate aqueous solution For comparison, a composition of 15 mQ of barium acetate aqueous solution was also prepared instead of the zinc acetate in (3) above as a conventional sedimentation flocculant containing barium ions.

As the substrate, a stainless steel plate and a quartz plate were used. The phosphor suspension and water glass were mixed and immediately poured into the sedimentation flocculant solution to settle the phosphor onto the substrate.

After the supernatant liquid became almost transparent, the water was drained and it was dried. When a quartz plate was used as the substrate, heat treatment was performed at 800° C. for 1 hour in air.

In order to evaluate the brightness deterioration of the fluorescent film prepared in this way, a special evaluation device was used for irradiation with high-density electron beams for 10 minutes at an accelerating voltage of 20 kV, a current of 150 μA, and 2 rasters of 5×5 rays. Forced deterioration was performed. As a measure of deterioration, we took the ratio of brightness before and after high-density irradiation, that is, the brightness maintenance rate. In the case of stainless steel substrate, B am
While the film coated with * (comparative example) had a brightness maintenance rate of 0.72, that of the film using Zn''+ of the present invention had a brightness maintenance rate of 0.72.
It showed 89. This is an increase of 23.6% over the comparative example.

On the other hand, for each heat-treated sample using a quartz plate as a substrate, III (comparative example) coated with B am + had a brightness maintenance factor of 0.82, and that of the film using Zn''+ of the present invention 1.00, which showed no deterioration at all in this evaluation test.In this case, it was 22.0% higher than the comparative example.Figure 1 shows the deterioration of the fluorescent film of the comparative example and the present invention. Curve 1 is for the comparative example, and curve 2 is for the present invention. Discontinuous points A and B after 10 minutes are the points at which irradiation was stopped for a while, cooled, and then irradiated again. In both cases, the brightness was less likely to deteriorate when Zn'' was used than when Ba''+ was used.

Example 2゜Green phosphor Y, AQ, 0.2: Tb'' and Zn, 5in
4: Example 1 regarding the phosphor mixed with Mn''+
A fluorescent film was prepared using the coating method described in . A glass plate with a tin oxide conductive film formed on its surface was used as the substrate. As a result of forced deterioration under the same irradiation conditions as in Example 1, the luminance maintenance rate of the film of the comparative example coated with Ba'' + ions was 0.
68, whereas the membrane of the present invention using z n2 + ions was 0.92, which was less likely to deteriorate. This example is 35.3% higher than the comparative example.

In this example as well, it can be seen that the fluorescent film coated using Zn''+ ions is less likely to deteriorate than the film produced by the conventional method.

Examples 3 to 7 Several commercially available phosphors were subjected to the same coating and evaluation methods as in Example 1.

The same glass as in Example 2 was used for the substrate. A comparison of deterioration (difference in brightness maintenance rate) is shown in Table 1 below.

In Table 1, the values in parentheses further assume that the current value is 300μA,
These are the results when the forced deterioration test was continued for 10 minutes.

The degree of improvement in deterioration of the phosphors listed here differs depending on the coating method, but in all examples, the film of the present invention coated using z n* + ions showed a higher degree of deterioration than the comparative example. It can be seen that is small.

Example 8 In place of the zinc acetate used in Example 1 above, indium nitrate I n (N 0a)a, potassium stannate, (Sn
(OH), 1 and a mixture of the two (1:1 mixture)
The luminance deterioration of the fluorescent films coated by preparing three types of solutions and using them as water glass flocculants was improved by 5 to 10% compared to the film coated using Ba''+ as a comparative example.

Therefore, like Zn''+ ions, if water glass is agglomerated with an electrolyte containing trivalent indium or tetravalent tin (divalent is acceptable, but tetravalent is preferable), a film with a small degree of brightness deterioration can be formed. I can do it.

Example 9゜ One part 5 mQ of the aqueous solution of dumbbell acetate of Example 1 above was replaced with indium nitrate, the same was replaced with potassium stannate, and indium nitrate and potassium stannate were mixed at 1:1.
Three types of fluorescent films were prepared using the liquid mixed in Example 1, and a fluorescent film was formed using the same method as in Example 1, and a forced deterioration test was conducted under the same conditions. The characteristics were shown.

Example 10 Terbium-activated indium borate InB◯: 1.3 g of Tb phosphor was deposited and coated on a 6-inch projection cathode ray tube. The compositions of the phosphor suspension and flocculant solution are as follows.

Phosphor 1 suspension: Phosphor L3g, pure water 180mQ.

11% water glass' (potassium silicate) 60m! I.

Flocculant solution: Pure water 500mQ.

0.87% zinc acetate aqueous solution 60rnQ A flocculant solution was previously injected from the neck of the projection tube, and the phosphor suspension was quickly poured in to precipitate the phosphor. Subsequent steps were performed by well-known projection tube manufacturing processes.

FIG. 2 shows a partial cross-sectional schematic diagram of the projection type cathode ray tube manufactured in this manner. In the same figure, 2
1 is face plate glass, 22 is fluorescent film, 23 is A
24 represents a neck tube, and 25 represents an electron gun. The fluorescent film 22 is made of Sin produced by coagulation of water glass.
, is applied to the face plate 21 as a binder, and AQl[23 is further vapor-deposited. Note that the electron beam deflection means is omitted from the drawing.

The life test was performed at an accelerating voltage of 30 kV and a current of 500 μA.

Continuous irradiation was performed over a 5-inch area.

As a measure of brightness deterioration, we took the ratio of the brightness after irradiation for a certain period of time to the initial brightness, that is, the brightness maintenance rate. 2000
The brightness maintenance factor after time irradiation was 0.85 for the projection tube coated using Ba ions in the conventional method, whereas the projection tube of this example was excellent at 0.85.

Therefore, in this example as well, the effect of improving deterioration when coating using Zn ions is large.

〔Effect of the invention〕

According to the present invention, when the phosphor film is irradiated with high-density electron beams, the luminance deterioration of the phosphor film can be improved by several percent to several tens of percent, which has the effect of greatly improving the life of the cathode ray tube.

[Brief explanation of the drawing]

FIG. 1 is a characteristic curve diagram showing the temporal change in luminance of the phosphor film under electron beam irradiation and the luminance after cooling in Example 1 of the present invention, and FIG. 2 is a partial cross section of the projection type cathode ray tube in Example 10. A schematic diagram is shown. 1... Fluorescent film coated using Ba"+ ions 2...
・Fluorescent film 21 coated using Zn"" ions...Face plate 22...Fluorescent film 23...AQ vapor deposited film attorney Junnosuke Nakamura Opening time during electron beam q and p irradiation) 'i , t A1%, Rashi*#Glaze 11 Bow-rate. Dit db hl ≦: i-change a. Figure 1 Figure 2

Claims (1)

[Claims] 1. In a cathode ray tube equipped with an electron beam deflection means formed by forming a phosphor film on a face plate, a material selected from the group consisting of indium and tin is applied to the surface of phosphor particles constituting the phosphor film. 1. A cathode ray tube having a fluorescent film coated with at least one metal oxide. 2. When an aggregating agent is added to a binder solution in which phosphor particles are dispersed and the phosphor particles are precipitated and coated on a substrate, the aggregating agent is dissolved in the binder solution and is easily applied during the heat treatment process of the coating film. 1. A method for forming a fluorescent film, comprising an electrolyte containing at least one metal ion selected from the group consisting of zinc, indium, and tin, which can be turned into oxides. 3. The binder solution consists of a water glass solution, and
3. The method for forming a fluorescent film according to claim 2, wherein the flocculant comprises a water-soluble electrolyte.