JPS617561A - Electric discharge lamp for displayer - Google Patents

Abstract

PURPOSE:To display clear images by making the luminance of the central area of a diaplay screen higher than that of its peripheral area by using an anode which has an annular shape extending along the inner surface of the glass tube and installing the anode inside the display screen. CONSTITUTION:When a cathode 7 is preheated by feeding a current, electrons are emitted from the preheated cathode 7 into a glass tube 3. The thus emitted electrons are then drawn by an anode 9 installed in the opposite end of a glass tube 3 and move in it, thereby initiating electric discarge between the cathode 7 and the anode 9. The thus initiated electric discharge forms a positive column connecting the cathode 7 and the anode 9 in the glass tube 3. Then ultraviolet raus emitted from the positive column excite a phosphor film 12 formed on the inner surface of the glass tube 3 to emit visible rays which are then irradiated outside the lamp through a convex lens 4. Since the anode 9 has an annular shape extending along the inner surface of the glass tube 3, the positive column becomes adjacent to the phosphor film 12 near the anode 9. Consequently, the phosphor is actively excited and optical emission with high luminance is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a discharge lamp for a display element used, for example, as a light source for a color image display or apparatus.

[Technical background of the invention]

This type of light source is C, which emits monochromatic light of red, green, and blue.
A combination of RT and color light bulbs was common, but as an alternative to these light sources, for example,
As shown in Publication No. 6-189357, the luminous efficiency is increased by concentrating luminescence only in the direction necessary for display.
Fluorescent lamps with a so-called single-end structure are known.

[Problems with background technology]

However, the present inventors manufactured fluorescent lamps with the above-mentioned configuration, and conducted various tests by arranging a large number of these lamps on the same plane and actually lighting them. found that the brightness was insufficient and that the brightness at the center of the display surface was relatively low compared to the surrounding area.

Therefore, in addition to insufficient brightness, it has become clear that images tend to become unclear because the light from adjacent fluorescent lamps interferes with each other.

[Purpose of the invention]

The present invention was made in view of these circumstances.
To provide a discharge lamp for a display element, which can increase the brightness at the center of a display surface compared to the surrounding area, and can also increase the brightness over the entire display surface to display clear images.

[Summary of the invention]

That is, in order to achieve the above object, the present invention is characterized in that the anode located inside the display surface is formed in an annular shape along the inner circumferential wall surface of the glass tube.

[Embodiments of the invention]

The present invention will be explained below based on one embodiment shown in the drawings.

FIG. 3 shows a large display screen that is used, for example, by being built into a scoreboard at a baseball field or stadium, or into the wall of a building.
Thousands to tens of thousands of display element discharge lamps 2 are densely arranged. Details of the display element discharge lamp 2 are shown in FIG. 1. That is, 3 is a straight glass tube, and one end opening of this glass tube 3 is closed by a convex lens 4, and the outer peripheral surface of this convex lens 4 forms a display surface 4a. The opening at the other end of the glass tube 3 is sealed by a glass stem 5, and lead wires 6, 6 are passed through the glass stem 5 and sealed.

A preheated cathode 7 made of a filament coil is connected between the tip portions led out into the glass tube 3. A support line 8 which also serves as a power supply line is penetrated and sealed in the glass stem 5, and the tip of the support line 8 extends in the tube axis direction within the glass tube 3 and is located near the convex lens 4. In addition,
This support wire 8 is inserted into a glass insulating tube 8a so as not to cause short-circuit discharge between the support wire 8 and the preheated cathode 7.

An annular anode 9 (anode) according to the present invention is supported at the tip of this support 118 in an electrically connected state. The anode 9 is along the inner peripheral wall surface of the glass tube 3.
In addition, it is formed in a thin annular shape with a circular opening 10 in the center, and is held coaxially with respect to the glass tube 3, with its outer circumferential surface being close to the inner circumferential wall surface of the glass tube 3. . Further, on the inner peripheral wall surface of the glass tube 3 on the side of the preheated cathode 7, a light reflecting film 11 made of, for example, an alumina coating film is adhered, and a phosphor coating [912 The phosphor coating 12 extends to one end of the glass tube 3 on the convex lens 4 side and covers the outside of the anode 9.

In the case of this embodiment, the distance X from the end surface of the anode 9 on the convex lens 4 side to the tip edge of the phosphor cover m12 on the display surface 4a side is defined to be 5 m or less.

Further, a cap member 13 is attached to the other end of the glass tube 3, and the lead wires 6, 6 and the support wire 8 are connected to three cap bottles 14 protruding from the cap member 13. are connected to each other.

Note that a predetermined amount of mercury and an inert gas are sealed inside the glass tube 3.

Such display element discharge lamps 2... are closely arranged on the screen tote 7 with the display surface 4a facing the display direction, and the cap bins 14... are connected to a lighting device (not shown). Connected to power supply via.

When starting the display element discharge lamp 2 having such a configuration, when a current is passed through the preheated cathode 1 to preheat it, electrons are emitted from the preheated cathode 7 into the glass tube 3.
The emitted electrons are attracted to the anode 9 on the opposite side and move within the glass tube 3, thereby starting a discharge between the two electrodes. With the start of this discharge, a positive column connecting the preheated cathode 7 and the anode 9 is formed in the glass tube 3, and the ultraviolet rays emitted from this positive column cause a phosphor coating on the inner peripheral wall of the glass tube 3. 12 is excited and emits visible light,
This visible light is irradiated outward through the convex lens 4.

In this case, since the anode 9 is formed in an annular shape along the inner circumferential wall surface of the glass tube 3, the positive light column on the l1tiQ side is close to the phosphor coating 12, so that the phosphor is actively excited. This is done to obtain high-brightness light emission. That is, FIG. 4 shows the results of various changes in the ring ratio of the anode 9 to the inner diameter of the glass tube 3 expressed as d/D, where D is the inner diameter of the glass tube 3 and d is the outer diameter of the anode 9. Display surface 4
The luminous intensity on a is shown. From this figure 4, the ring ratio is 1
．． It can be seen that the closer the luminous intensity is to 0, that is, the closer the outer peripheral surface of the anode 9 is to the phosphor coating 12 on the inner surface of the glass tube 3, the higher the luminous intensity in the display direction. This is because the outer circumferential surface of the anode 9 and the inner circumferential surface of the glass tube 3 are close to each other, so that the positive column passes close to the phosphor coating 12 in the vicinity of the display surface 4a, and therefore the luminous intensity in the display direction is Display surface 4 has a major influence on
This shows that the phosphor near a is actively excited.

In addition, because the present inventors formed the anode 9 in an annular shape, the display surface 4a was tilted at a certain angle (15° in the case of this embodiment) with respect to the tube axis 01-01 of the glass tube 3. Experiments were conducted to examine how the central brightness on the display surface 4a changes when viewed from above. In this experiment, the ring ratio of the anode 9 was varied, and the width 1 of the anode 9 was set to 3.5 and 7M at each ring ratio.
The brightness at the center of the display surface 4a was measured by changing the brightness.

Figure 5 shows the results, and the diameter of the anode 9 is large,
It is also recognized that the narrower the width of the anode 9, the higher the brightness at the center of the display surface 4a. This means that the anode 9
If the width of the opening 10 is narrowed or the diameter of the opening 10 is increased,
This is thought to be due to the fact that when the display surface 4a is viewed from the above direction, the shadow of the anode 9 moves less to the center of the display surface 4a. Therefore, light is guided to the display surface 4a through the opening 10 not only when the display surface 4a is viewed from the front, but also when viewed from a direction inclined at a certain angle with respect to the tube axis 0l-Of. Therefore, the brightness at the center of the display surface 4a is relatively high compared to the surrounding area. Therefore, in combination with the increased brightness of the display surface 4a, clear and high quality images can be displayed.

Furthermore, according to the experiments conducted by the present inventors, as shown in FIG.
It has been found that when the distance X to the tip edge on the anode 9 side exceeds 5#l111, the luminous intensity on the display surface 4a tends to decrease rapidly. That is, the larger the distance X is, the closer the phosphor coating 1 is to the convex lens 4.
It is thought that this is because 2 moves away from the positive column, the excitation becomes insufficient, and it no longer contributes to light emission. Therefore, it was concluded that it is desirable to suppress the distance X to 5Il1m or less.

Furthermore, the present inventors investigated the relationship between the surface area of the anode 9 and the life of the discharge lamp 2. In other words, in a typical fluorescent lamp, if the area of the anode 9 is too small, it will not be able to support the lamp current, and as a result, the temperature of the anode 9 will become too high and the electron emitting material will evaporate and scatter, causing blackening. However, the same can be said for the discharge lamp 2 having the configuration described in 1 above, and according to experiments conducted by the present inventors, as shown in FIG. It has been found that when the surface area of the anode 9 is less than 2 cd, the brightness maintenance rate after 5000 hours sharply decreases. Furthermore, the same thing was confirmed for lamps with lamp currents of 200,771 A or less. Therefore, in order to satisfy the desired lifespan, it was concluded that it is desirable to ensure the surface area of the anode 9 to be at least 2 ci, although it depends on the diameter, overall length, and output of the glass tube 3.

In the above-mentioned example, the phosphor coating was applied to almost the entire inner peripheral wall surface of the glass tube, but in some cases, the phosphor coating was applied only to the vicinity of the anode, and other parts were exposed to light. A reflective film may be used, or a phosphor film may be applied to the inner wall surface of the lens.

Further, the anode is not limited to a ring shape that is continuous in the circumferential direction, but may have a shape in which a part of the anode is separated along the circumferential direction.

〔Effect of the invention〕

According to the present invention described in detail above, since the anode is formed in an annular shape along the inner peripheral wall surface of the glass tube, the positive light column on the anode side is close to the phosphor coating, and therefore the phosphor is excited. The process is active and produces high-brightness light. Moreover, since the inside of the anode is open, there is nothing in the center of the display surface side of the glass tube that blocks the light guided to the display surface. Of course, even when viewed from a direction tilted at a certain angle with respect to the tube axis, the brightness at the center of the display surface is relatively high compared to the surrounding area, which has the advantage of displaying clear, high-quality images. .

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is a sectional view of a discharge lamp for a display element, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a schematic configuration of a display screen. 4 to 7 are characteristic diagrams, respectively. 3... Glass tube, 4a... Display surface, 7... Preheated cathode, 9... Anode, 12... Phosphor coating, 13...
・Cap part/material.

Claims (2)

[Claims] (1) A glass tube whose both ends are closed and whose one end closed surface is a translucent display surface, an anode provided within one end of the glass tube on the display surface side, and the other end of the glass tube. A preheated cathode provided in the section, a phosphor coating attached to at least the inner circumferential wall surface of the glass tube on the display surface side, and a phosphor coating provided at the other end of the glass tube and electrically connected to the anode and preheated cathode. In the discharge lamp for a display element, which is used for lighting with the display surface of the glass tube facing the display direction, the anode is formed in an annular shape along the inner peripheral wall surface of the glass tube. A discharge lamp for a display element, which is characterized by: (2) The distance X along the tube axis direction from the end surface of the anode on the display surface side to the tip edge of the phosphor coating on the display surface side is 5 mm.
Claim No. 1 (1) characterized by the following:
) A discharge lamp for display elements as described in item 2.