JPH0339557B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a fluorescent display tube using a ZnO:Zn phosphor as _{a phosphor} . This invention relates to an improvement of a fluorescent display tube that prevents deterioration. [Prior art] The fluorescent surface of the fluorescent display tube contains ZnO:Zn, which emits a bright bluish-green color when struck by an electron beam of 100 V or less.
Fluorescent materials are mainly used. This phosphor has a low emission threshold voltage and can provide sufficient luminance at about 10V, so it is currently widely used as a phosphor in fluorescent display tubes. By the way, in general, the brightness and emission efficiency of phosphors vary greatly depending on their surface conditions, and if the phosphor surface is contaminated with various substances, the phosphor itself will lose its original properties. Unable to bring out full performance. ZnO used in fluorescent display tubes:
The same goes for Zn phosphors; brightness and emission efficiency decrease due to various contaminations received during the fluorescent display tube manufacturing process.
Alternatively, the heat resistance (change in brightness when the tube is turned on after being left in a high temperature environment) after being made into a tube may be significantly deteriorated in some cases. To improve this point, conventionally, ZnO:Zn
Mix WO ₈ powder into the phosphor, as shown in Figure 1.
The surface of the WO ₈ powder particles 20 has a getter action for contaminants or a decomposition action for CO ₂ gas, etc.
There was a method to prevent contaminants from adhering to the surface of the ZnO:Zn phosphor 10 as much as possible, but in this case, since the particle size of the WO ₈ powder particles 20 mixed with the phosphor was 5 μm or less, the following method was used: It had such drawbacks. 1 ZnO: Since the Zn phosphor particle diameter and the WO ₈ particle diameter are approximately the same level, when a fluorescent surface is formed with this mixture, the fluorophore exposed to the electron irradiation field seen from the cathode side is The surface area of the photon particles is reduced due to the mixed WO ₈ particles, the effective light emitting area is reduced, and the light emission brightness is reduced. 2. ZnO: If the WO ₈ particle size is smaller than the Zn phosphor particle size, the surface of the phosphor is covered with WO ₈ powder, which reduces the effective light emitting area and significantly reduces the luminance. [Object and structure of the invention] In view of the above points, the present invention has been made to eliminate such drawbacks, and the gist thereof is to:
ZnO: The particle size of the WO ₈ powder mixed with the Zn phosphor is 2 to 30 times the phosphor particle size (approximately 3 μm),
It is characterized by the use of WO ₈ powder containing these large particles. That is, the present invention contained WO ₈ powder with a particle size of 2 to 30 times the average particle size of the ZnO:Zn phosphor.
WO ₈ powder and ZnO:Zn phosphor are mixed and a fluorescent surface is formed using a printing method. According to the present invention, as shown in _FIG .
is considerably larger than the particles of ZnO:Zn phosphor 11, the particles of this phosphor 11 are WO ₈ particles 21
The surface of the WO ₈ particles 21 is almost shielded by the particles of the ZnO:Zn phosphor 11. Therefore _, the ZnO:Zn phosphor surface appears in the electron irradiation field seen from the cathode, and there is no WO ₈ powder surface, which is a non-luminescent substance, so there is no reduction in luminance. ZnO on WO ₈ particles:
The Zn phosphor emits sufficient light without charging up at all. Here, WO ₈ powder with such a particle size distribution was used because it has various particle size distributions.
WO ₈ powder and ZnO:Zn phosphor were mixed to form a fluorescent display tube after _forming a fluorescent surface, and the luminescent properties were measured. , found that the luminous efficiency was high, and published WO ₈
This is because it has been found that the relationship between the particle size and the ZnO:Zn particle size greatly affects the luminance.
This is because if the WO ₈ powder particles are 5 μm or less, the brightness will be 20 to 30% lower than the fluorescent surface of the present invention, and if they are larger than 90 μm, screen printing will be impossible and the formation of a fluorescent surface will not be possible. Further, the mixing amount of WO ₈ powder with respect to the ZnO:Zn phosphor was preferably in the range of 5 to 25 wt%. Table 1 below shows the brightness, luminous efficiency, and slump rate of each fluorescent surface after being left at high temperatures with respect to the mixing amount. (This test uses harsher conditions than normal conditions to see the difference in slump rate.)

〔Example〕

ZnO with an average particle size of 2.4 μm: 5 to 80 μm for Zn phosphor
A phosphor paste was prepared by mixing 20 wt% of WO ₈ powder containing 70% of particles of M and kneading it with a printing binder. Next, using a screen with a coarse mesh diameter, fluorescent surface printing was performed in a predetermined shape, and a display tube was completed through the fluorescent display tube manufacturing process. After tube formation,
When measuring the luminescent characteristics of a fluorescent display tube, we found that
Brighter than a fluorescent surface that does not contain any WO ₈ powder.
Both luminous efficiency has been improved by 32 to 40%, and the slump rate after being left at high temperatures is -10 to -26% compared to the previous model.
It was significantly improved to around 3%. Also, WO ₈
Fluorescent surfaces prepared by mixing ZnO:Zn phosphors with particle diameters almost the same level had a lower brightness than conventional ones and could not be used. [Effects of the Invention] As explained above, the present invention provides a fluorescent display tube.
On the ZnO:Zn phosphor surface, WO ₈ powder containing WO ₈ powder with a larger particle size than the particles of the ZnO:Zn phosphor is mixed with the ZnO:Zn phosphor, and this mixture is used in the printing method. By forming a fluorescent surface,
Since the ZnO:Zn phosphor is attached to the surface of the WO ₈ particles, the phosphor surface is exposed to the electron irradiation field seen from the cathode, and there is no non-light emitting area due to the WO ₈ particles. Therefore, there is no reduction in brightness. In addition, since it contains large-particle WO ₈ powder, the amount of binder used during fluorescent surface printing can be reduced, which has the effect of reducing contamination caused by binder combustion on the surface of the fluorescent material. .

[Brief explanation of drawings]

Figure 1 is a schematic illustration of a conventional fluorescent surface;
The figure is a schematic illustration of a fluorescent surface according to the invention. 11...ZnO: Zn phosphor, 21...WO ₈ particles.

Claims (1)

[Claims] 1. In the ZnO:Zn fluorescent surface of the fluorescent display tube,
A WO ₈ powder containing WO ₈ powder with a particle diameter 2 to 30 times the average particle diameter of the ZnO:Zn phosphor is mixed with a ZnO:Zn phosphor, and this mixture is used to fluoresce by printing. A fluorescent display tube characterized by forming a light surface. 2 WO ₈ powder is 5-25wt for ZnO:Zn phosphor
The fluorescent display tube according to claim 1, characterized in that the fluorescent display tube is mixed in a range of %.