JPH021801Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fluorescent display tube used as a light source for light-receiving liquid crystal displays, electromic displays, and the like.

Currently, liquid crystal displays are widely used in the fields of watches, calculators, and measuring instruments. As is well known, a liquid crystal display is a light-receiving type display element, and therefore has the disadvantage that it is very easy to see in bright places, but it is difficult to see in dark places. In the fields of watches, calculators, and measuring instruments mentioned above, it is widely used because it can be driven with low voltage and low power consumption, which is a characteristic of liquid crystal displays.
In other fields, such as automobiles, home appliances, and monitoring boards, there are dissatisfaction with liquid crystal displays in terms of display clarity, and fluorescent display tubes, plasma displays, and light-emitting diodes are currently used.
However, if we take the example of a fluorescent display tube developed for use in automobiles, it has been praised as an extremely excellent display element for driving at night, but on the other hand, it can interfere with driving during the day. There is a problem.

It is easy to imagine that by stacking a light-receiving type display and a light-emitting type display, a display that can be used both day and night can be realized.
As a specific example, this can be realized by using a light-emitting type display as a surface light source and placing it behind a light-receiving type display. As mentioned above, the disadvantage of the LCD display being lack of clarity,
This can be compensated for by using a surface light source. In particular, the twisted nematic mode using color polarizing plates, which will be put into practical use in the future, or the
Guest-host mode color LCD displays with added color dyes require a surface light source to produce the vivid colors that are the lifeblood of the display. Surface light sources currently under consideration include those that combine a fluorescent lamp with a light guide plate or a light diffuser plate;
Three types have been proposed: electroluminescent and fluorescent display tubes.

Among these, fluorescent display tubes are superior to fluorescent lamps in terms of operating voltage life, and superior to electroluminescent lamps in terms of operating voltage, illuminance, and color tone, so they are the best when comprehensively evaluated. ing. Fluorescent display tubes can change the emission color depending on the type of phosphor, and since the emission spectrum is relatively broad, the color tone can be controlled using a filter. Therefore, in combination with the absorption spectrum of a color liquid crystal display, a highly visible display element can be obtained. When a fluorescent display tube is used as a surface light source, the anode electrode is a single flat plate, and the entire surface of the flat plate is coated with phosphor, so that electrons emitted from the cathode collide with the phosphor, producing surface light emission. do.
Since the space factor of the fluorescent display tube, that is, the ratio between the light emitting area and the external area of the fluorescent display tube, is small, when the display area of the liquid crystal display and the light emitting area of the fluorescent display tube are matched, the external dimensions of the liquid crystal display There is a problem in that the external dimensions of the fluorescent display tube are larger than those of the fluorescent display tube. Furthermore, when looking at the light emitting surface of a fluorescent display tube, it is not necessarily a uniform surface light emission, but some uneven light emission can be seen.

An object of the present invention is to provide a uniform surface light source that has external dimensions comparable to or smaller than those of a liquid crystal display, and that emits light evenly.

According to the present invention, in a fluorescent display tube in which thermionic electrons emitted from a cathode filament collide with one or more anode patterns in which a phosphor is coated on an insulating substrate, the phosphor emits light. A fluorescent display tube is obtained which is characterized in that a semi-transparent light diffusing film is formed on the surface of a cover plate which is one of the constituent elements of the optical display tube.

Hereinafter, the present invention will be explained in detail with reference to Examples.
FIG. 1 shows a schematic sectional view of an embodiment of a fluorescent display tube used to explain the present invention. An anode electrode 2 on which a phosphor layer 3 is formed is placed on a back plate 1. The anode electrode is a single flat plate for surface emission. Electrons emitted from the filament 5 are accelerated and controlled by the grid lattice 4,
It collides with a phosphor and emits light. The cover plate 6 is
It has a shape as shown in FIG. 1, and is fitted with a back plate through a frit glass 7 to form a vacuum container for the fluorescent display tube. Although not shown in FIG. 1, a transparent electrode is provided on the inner surface of the cover plate in order to prevent static electricity and to obtain uniform light emission, and the electrode is set at the same potential as the filament or grid. A semi-transparent light diffusing film 8 is formed on the cover plate 6. As the light diffusion film, for example, an alumina film obtained by vacuum-depositing aluminum and then firing it in an oxygen atmosphere is used. The film thickness is about 1000 Å to make it semi-transparent. The light-diffusing film may be a cover glass coated with a resin containing light-scattering particles such as alumina particles or magnesium oxide.

Since the light emitted by the phosphor is diffused by the surface of the cover plate, it is possible to illuminate a wider area than the light emitting area of the phosphor. When zinc oxide is used as a slow electron beam excited phosphor, the phosphor has a white body color, so it acts as a reflector, and therefore the light emitted by the phosphor is absorbed by the light diffusing film. Although the light is partially reflected back, it is reflected again by the phosphor layer, so the loss of light amount due to the provision of the light diffusion film does not pose a problem. On the other hand, a portion of the light that passes through the liquid crystal display from the outside is reflected by the light diffusion film, and the remaining light that passes through the light diffusion film is reflected by the phosphor layer and returns, so in a bright environment, A fluorescent display tube can be used as a reflector. In this case, even if the coating area of the phosphor layer is smaller than the display area of the liquid crystal display, it can sufficiently function as a reflector.

According to the embodiment described above, since the light is diffused by the light diffusion film on the top surface of the cover glass, the fluorescent display tube of this embodiment has the same light emitting area as the conventional surface light source fluorescent display tube. It can illuminate a wide area. Furthermore, for light incident from the outside, a highly efficient reflector can be obtained by combining a light diffusing film and a phosphor film.

In the above-mentioned embodiment, the anode electrode was used as a single plate, but even if it is divided into multiple pieces and emitted light,
Since light is diffused by the light diffusing film on the cover plate surface, it can be used as a surface light source. in this case,
Since the light emitting area can be made smaller than when a single plate is used, there is an advantage that power consumption can be reduced.

The present invention has been described above using examples, but the semi-transparent light diffusion film in the examples is only one example, and the type of light diffusion film is not limited. Further, the configuration and structure inside the vacuum container of the fluorescent display tube used in the examples does not limit the scope of the present invention. Further, in the schematic cross-sectional view of the embodiment, lead terminals of each electrode of the anode grit filament are omitted.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a fluorescent display tube according to an embodiment used to explain the present invention. 1... Back plate, 2... Plate electrode,
3... Fluorescent layer, 4... Grid electrode, 5... Filament electrode, 6... Cover plate, 7...
Fritted glass, 8...Light diffusion film.

Claims (1)

[Scope of utility model registration request] A component of a fluorescent display tube in which thermionic electrons emitted from a cathode filament collide with one or more anode patterns in which a fluorescent material is coated on an insulating substrate to cause the fluorescent material to emit light. A fluorescent display tube characterized in that a semi-transparent light diffusing film is formed on the surface of a cover plate.