JP2002025481A - Fluorescent display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the life time of the fluorescent display device longer and reduce image persistence of the display section. SOLUTION: The fluorescent substance membrane 5 of the fluorescent display device is composed of a ZnO phosphor, having a silica volume of 370-1,000 μg/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent display device using a phosphor containing ZnO (zinc oxide) as a main component (hereinafter referred to as ZnO phosphor).

[0002]

2. Description of the Related Art Conventionally, a fluorescent display tube, which is one of electronic display devices, is often used as a display component of a dashboard of an audio device or an automobile. The fluorescent display tube comprises an anode with a phosphor attached thereto and a cathode provided above and separated from the anode in a vacuum vessel, and the electrons emitted from the cathode collide with the phosphor. This is to obtain emitted light. Generally, a triode type in which a grid for controlling the flow of electrons is provided between the cathode and the anode to selectively emit light from the phosphor is adopted.

[0003] In such a fluorescent display tube, a low-speed electron-beam-excited light-emitting phosphor capable of obtaining a practical luminance with an acceleration voltage of about several tens of volts is used. A representative example of this type of phosphor is a ZnO phosphor that emits green light. This Z
The nO phosphor is usually coated with silica. Thereby, it is possible to prevent the ZnO phosphor from being oxidized in the heating step of manufacturing the fluorescent display tube, thereby preventing the emission characteristics from deteriorating. Conventionally, in order to obtain an initial luminance higher than a predetermined value, ZnO
The amount of silica added to the phosphor was limited to 350 μg / g or less. Here, “350 μg / g” means that 350 μg of silica is present per 1 g of ZnO phosphor after silica addition. Hereinafter, it is similarly described.

[0004]

However, such Z
Although the nO phosphor has a high initial luminance, it tends to deteriorate with time due to electron beam irradiation. Therefore, there is a problem that the life of the fluorescent display tube using the ZnO phosphor is shortened. In addition, since the brightness of the illuminated portion is significantly lower than that of the non-illuminated portion, there is a problem in that, when the fixed pattern display is performed for a long time, burn-in occurs in the display portion. This burn-in is a phenomenon in which, when a fixed pattern is lit for a long time and another pattern is displayed, the lit portion becomes dark.

The present invention has been made to solve such a problem, and an object thereof is to extend the life of a fluorescent display device such as a fluorescent display tube. Another object is to reduce burn-in of the display unit of the fluorescent display device.

[0006]

In order to achieve the above object, according to the present invention, a phosphor film of a fluorescent display device is made of a ZnO phosphor having an amount of silica of 370 to 1000 μg / g. As a result, deterioration of the phosphor film with time due to electron beam irradiation can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the fluorescent display device of the present invention will be described in detail with reference to the drawings. Figure 1
1 is a cross-sectional view illustrating a configuration of a direct-view type flat fluorescent display tube according to an embodiment of the present invention. As shown in FIG. 1, a wiring layer 2 having a predetermined pattern is formed on a glass substrate 1, and an insulating layer 3 having a through hole 3A is formed on the wiring layer 2. On the surface of the insulating layer 3, an anode 4 having a predetermined pattern electrically connected to the wiring layer 2 through a through hole 3A is formed. The surface of the anode 4 has a silica content of 370 to 1000 μg /
g of ZnO phosphor is adhered.
The phosphor film 5 constitutes a display section of a fluorescent display tube.

A grid 6 is arranged above the phosphor film 5 at a distance, and a filament-shaped cathode 7 is arranged above the grid 6. This cathode 7
Is obtained by adhering an electron-emitting substance to an ultrafine wire of tungsten. A translucent face glass 9 is arranged above the cathode 7, and the face glass 9 is held at a predetermined height from the glass substrate 1 by a frame-shaped side wall 8. The glass substrate 1, the side walls 8, and the face glass 9 are sealed with a frit glass 10 having a low melting point, and the inside is 10 ^-3.
A vacuum container maintained at a degree of vacuum of 10 to 10 ^-5 Pa is formed. Further, a plurality of leads (not shown) are provided through the contact portion between the side wall 8 and the glass substrate 1, and an electric signal is externally applied to the cathode 7, the grid 6, and the anode 4 by these leads. You. A positive voltage of several hundred volts or less is applied to the anode 4 as an electron acceleration voltage.

A predetermined voltage is applied to the cathode 7 to 650
When heated to about ° C., thermoelectrons are emitted from the electron-emitting substance. At this time, when a voltage higher than that of the cathode 7 is applied to the grid 6 while a positive voltage is applied to the anode 4, electrons emitted from the cathode 7 are accelerated, and a part of the electrons passes through the grid 6 and passes through the anode 4. Collides with the phosphor film 5 attached to the substrate. The phosphor film 5 is irradiated with the electron beam.
Is excited to emit light, and the light is transmitted through the face glass 9 and emitted to the outside. A voltage lower than that of the cathode 7 is applied to the grid 6 or the anode 4
By applying a negative voltage to the phosphor film 5, it is possible to prevent electrons from entering the phosphor film 5.

However, when electrons collide with the ZnO phosphor, the impact may damage the surface of the ZnO phosphor. On the other hand, the silica added to the ZnO phosphor has an effect of preventing electrons incident on the phosphor film 5 from destroying the surface of the ZnO phosphor. By adding / g of silica, the deterioration of the ZnO phosphor over time due to electron beam irradiation can be reduced. This extends the life of the phosphor film 5 made of the ZnO phosphor, so that the life of the entire fluorescent display tube is prolonged. Further, even if the fixed pattern is turned on for a long time, deterioration of the portion is reduced, so that burn-in of the display portion can be reduced.

Next, the experimental results for the fluorescent display tube shown in FIG. 1 will be described. First, the phosphor film 5 of the fluorescent display tube was formed in the following procedure. First, a predetermined amount of silica was added to the ZnO phosphor, and the amount of silica was 0 μg / g and 230 μg / g.
g, 370 μg / g, 550 μg / g, 910 μg / g
g, 1500 μg / g ZnO phosphor. Next, ethyl cellulose dissolved in butyl carbitol acetate was added to these ZnO phosphors to prepare a phosphor paste. Next, these phosphor pastes were applied on a carbon anode (anode 4) by a screen printing method. After drying these, the phosphor film 5 was formed by firing at a temperature of about 500 ° C. in the air.

In each fluorescent display tube using the phosphor film 5 thus formed, 25
The initial luminance when a voltage _VA of V, 60 V, and 100 V was applied and the luminance after lighting for a predetermined time were measured. FIG.
It is a graph which shows this measurement result. Here, FIG.
Is a graph showing the initial luminance of each fluorescent display tube, the horizontal axis is the amount of silica in the ZnO phosphor (μg / g), and the vertical axis is the initial luminance (%) based on the case where no silica was added. is there. Reference numerals 11, 12, and 13 denote anode voltage _VA = 2, respectively.
It shows the initial luminance at 5V, 60V, and 100V. From this figure, it can be seen that when the amount of silica exceeds 1000 μg / g, the initial luminance is significantly reduced. When the anode voltage V _A = 100 V, the amount of silica is 37
When it is set to 0.550 μg / g, the initial luminance is increased.

FIG. 2B is a graph showing the rate of change in luminance after each fluorescent display tube has been turned on for a predetermined time. The horizontal axis is Zn.
The amount of silica in the O phosphor (μg / g), and the vertical axis represents the luminance change rate (%) based on the respective initial luminance. 21,
Reference numeral 22 denotes a luminance change rate after lighting for 2000 hours with the anode voltage _{VA set} to 25 V and 60 V, respectively.
Reference numeral 23 denotes a luminance change rate after lighting for 800 hours with the anode voltage _{VA set} to 100V. From this figure, it can be seen that when the amount of silica is less than 370 μg / g, the luminance significantly decreases after lighting for a predetermined period of time, so that the luminance change is large. Considering the above experimental results, Zn
By adjusting the amount of silica in the O phosphor within the range of 370 to 1000 μg / g, the change in luminance with time is small,
In addition, it can be said that a bright fluorescent display tube can be realized. In particular, when the anode voltage V _A = 100 V, very good characteristics can be obtained.

Although the present invention has been described above with reference to a direct-view type flat fluorescent display tube as an example, it goes without saying that the present invention can be applied to a transmission type flat fluorescent display tube. Further, a fluorescent display device having an acceleration voltage (corresponding to the anode voltage _VA in the fluorescent display tube shown in FIG. 1) of several hundred volts or less, for example, an FED
(Field Emissin Display).

[0015]

As described above, in the fluorescent display device of the present invention, the phosphor film has a silica content of 370 to 1000 μg /
By using g ZnO phosphor, it is possible to reduce deterioration of the phosphor film with time due to electron beam irradiation. As a result, the life of the fluorescent display device can be extended, and burn-in of the display unit can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a direct-view type flat fluorescent display tube according to an embodiment of the present invention.

FIG. 2 is a graph showing an experimental result of the fluorescent display tube shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Wiring layer, 3 ... Insulating layer, 3A ... Through hole, 4 ... Anode, 5 ... Phosphor film, 6 ... Grid, 7 ... Cathode, 8 ... Side wall, 9 ... Face glass, 1
0: frit glass.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yutaka Miura 700 Wada, Ueno-cho, Ise-shi, Mie F-term (reference) in Ise Electronics Industry Co., Ltd. 4H001 CC05 XA08 XA30 5C036 EE01 EF02 EF05 EG36 EH13 EH22

Claims (1)

[Claims] 1. A fluorescent display device comprising: an anode formed on a substrate and having a phosphor film attached thereto; a cathode provided at a distance above the anode; and a vacuum container containing the anode and the cathode. In the above phosphor film, the amount of silica is 370 to 1000 μg / g.
A fluorescent display device comprising: a ZnO phosphor according to any one of claims 1 to 3.