JPH01122544A - Formation of fluorescent screen for cathode-ray tube - Google Patents

Abstract

PURPOSE:To reduce the brightness deterioration due to the electron beam radiation by using a mixed liquid containing the acetate or nitrate of Al as an electrolyte at the time of forming a fluorescent screen. CONSTITUTION:In forming the fluorescent screen of a cathode-ray tube by the precipitation coating method, a mixed liquid 0.02-0.5wt.% containing the acetate or nitrate of Al as an electrolyte for the total liquid quantity of water glass aqueous solution, phosphor suspension, and pure water is used. For conditions of precipitation coating, the preset quantity of electrolyte is solved in the pure water, the preset quantity of water glass and phosphor suspension is poured in the solution, it is left as it is, then the supernatant liquid is removed, and it is dried.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a phosphor film suitable for projection cathode ray tubes and the like, which exhibits little brightness deterioration even when exposed to strong electron beam irradiation for a long period of time.

[Conventional technology]

The precipitation coating method, which has been widely used to form fluorescent films in cathode ray tubes since the days of black-and-white tubes up to the recent monochrome projection tubes of each of the 3JM colors, conventionally involves electrolyzing barium salts such as barium acetate and barium nitrate. It is used as a substance to gel water glass (an aqueous solution of potassium silicate glass, etc.), coagulates and precipitates the phosphor suspended in the liquid, and deposits it on the inner surface of the panel glass, forming a supernatant liquid. is removed, dried, and attached to form a fluorescent film.

As a factor for brightness deterioration due to electron beam irradiation of a phosphor screen by such a sedimentation coating method, known documents such as Proceedings of the 1961 Electrical Engineering Society Federation Conference Lecture No. 1161 describe water glass or alkaline components in water glass. has been pointed out.

[Problem that the invention seeks to solve]

As mentioned above, water glass has traditionally been cited as one of the causes of brightness deterioration (life span) due to electron beam irradiation of fluorescent films using the precipitation coating method, but electrolytes have not been considered or are considered to be the direct cause. It has been said that this should not be done (see the above document).

However, in cathode ray tubes such as projection cathode ray tubes, which operate with electron beams with a current density several tens of times higher than that of picture tubes used in conventional television broadcasting receivers, The brightness deterioration of fluorescent films has become an important problem, and it is necessary to newly consider and take countermeasures against this factor.

The present invention is directed to the use of cathode ray tubes that exhibit little luminance deterioration even when exposed to extremely high current density electron beam irradiation, such as the phosphor film produced by the sedimentation coating method for projection tubes used in the above-mentioned projection type television receivers. An object of the present invention is to provide a method for forming a fluorescent film.

[Means for solving problems]

In order to solve the above problems, in the present invention, in the step of forming a fluorescent film of a cathode ray tube by a known sedimentation coating method, the total amount of water glass solution, phosphor suspension, and pure water is It was decided to use a mixed solution containing 0.02 to 0.5% of aluminum acetate or nitrate as an electrolyte.

[Function] The present inventors experimentally investigated the relationship between electrolytic substances and the brightness deterioration of a precipitated fluorescent film due to electron beam irradiation.

As a result, barium salt electrolytes such as barium acetate and barium nitrate, which are conventionally used for boat fishing, are relatively susceptible to brightness deterioration when exposed to high current density electron beam irradiation; A new fact has been discovered that aluminum salt electrolytes such as acetate or nitrate have the effect of significantly reducing and suppressing brightness deterioration.

The basis for achieving the present invention will be explained below using experimental results.

The conditions for precipitation coating are as follows: a predetermined amount of electrolyte
The usual method involves dissolving the solution in pure water, injecting a predetermined amount of water glass (potassium silicate aqueous solution) and a phosphor suspension into the solution, allowing it to stand for 10 minutes, removing the supernatant liquid, and drying. The conditions were used. However, the amount of electrolyte and the amount of water glass are
The optimal values for obtaining a high-quality fluorescent film were studied and determined in advance.

In addition, the test piece (
Using a non-Browning glass substrate coated with a fluorescent film), we conducted a forced acceleration test using a special electron beam irradiation device, and created a 7-type projection cathode ray tube.
Two methods were used: a life test under normal operating conditions; and a life test under normal operating conditions.

The results of forced tests on fluorescent films formed using various electrolytes are shown in Table 1 below. The irradiation conditions in this case are shown in Table 1. Luminance maintenance rate for electron beam irradiation Accelerating voltage 20 kV, beam current 150 μA, 5 x 5 mm2 raster, irradiation for 10 minutes. The brightness deterioration evaluation shows the relative brightness ratio before and after as the brightness maintenance rate.

From the experimental results shown in Table 1, aluminum salt electrolytes such as aluminum acetate and nitrate have a better brightness maintenance rate than conventional electrolytes (barium salts) and other electrolytes. I discovered that it is good. Also,
It was also found that there was no significant difference between the types of water glass (potassium-based and sodium-based).

Based on these experimental results, in order to confirm this effect and realize a cathode ray tube with less brightness deterioration,
Real ball evaluation was performed using a Type 7 projection tube.

〔Example〕

Example] Bulb used: Type 7 projection tube bulb Fluorescent substance used: InBO3: Tb phosphor input amount: i
, 5g/pure water...560d Aluminum acetate...2.0g 11% water glass aqueous solution...60d Phosphor suspension...100cd Pure water...80d Prepare Each of the above solutions is injected into the valve according to a predetermined procedure, and after being allowed to stand for 10 minutes, the supernatant liquid is drained and dried. Thereafter, a 7-type projection tube is manufactured through the usual process. The projection tube produced in this way was subjected to the above-mentioned life test, and the relative brightness ratio of the pre-irradiation (initial) brightness to the operating time was determined. The results are shown by curve A in FIG.

Example 2 Bulb used: Type 7 projection tube bulb Phosphor used: InBOa: Amount of Tb phosphor added:
1.5H/Pure water...56'OcJ Aluminum nitrate...0,3g ■1% water glass solution...60cn? Phosphor suspension/
...100cn? Pure water...80. ffl is prepared, and in the same manner as in Example 1, a type 7 projection tube is manufactured through the usual process after sedimentation coating. This projection tube was subjected to a life test under the same conditions as in Example 1. The results are shown by curve B in FIG.

In order to clarify the effects of these embodiments, curve C in FIG. 1 shows the results of a life test of a reference projection tube manufactured using a conventional conventional method, that is, using barium acetate as an electrolyte.

From FIG. 1, it can be clearly seen that both Example 1-12 have the effect that the luminance deterioration is smaller than that of the reference example using the conventional method.

The concentration of the electrolyte in the above examples is about 0.25% in Example 1 and 0.04% in Example 2 with respect to the total liquid volume, but it is considered that the concentration of the electrolyte is about 0.25% in Example 1 and 0.04% in Example 2. Preliminary experiments have confirmed that the appropriate amount to obtain electrolyte is 0.02 to 0.5% (that is, below 0.02%, there is no effect of electrolyte addition, and above 0.5%, it is still not effective). membrane becomes impossible).

Further, the electrolyte is not limited to aluminum acetate or aluminum nitrate, and similar effects can be obtained by using other aluminum acetates or nitrates.

〔Effect of the invention〕

As explained above, according to the present invention, luminance deterioration due to electron beam irradiation can be reduced by 40% or more, and a cathode ray tube with excellent luminance life can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the life test results of the projection tube according to Example 1.2 and the reference side tube according to the conventional method. Banquet-fi! 4th monk of the 11th pipe

Claims (1)

[Claims] 1. In the step of forming a fluorescent film for a cathode ray tube by a precipitation coating method, 0.02 to 0.5% by weight of aluminum is added to the total amount of water glass solution, phosphor suspension, and pure water. A method for forming a fluorescent film for a cathode ray tube, characterized in that a mixed solution containing acetate or nitrate as an electrolyte is used.