JPH0213874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum fluorescent tube for a light source in a facsimile transmitter for illuminating a document and performing photoelectric conversion.

In general, a vacuum fluorescent tube is a vacuum tube made up of a substrate and a front envelope, in which electrons emitted from a cathode impinge on a phosphor layer attached to the surface of an anode. This takes advantage of the phenomenon in which layers emit light. In other words, it is a light source that applies the principle of a conventional fluorescent display tube.

This vacuum fluorescent tube emits light extremely brightly with relatively low power consumption, can provide high illuminance on the surface of non-illuminated objects, has a flat light source shape and has an excellent space factor, and has the advantages of It has superior features such as a much longer lifespan than light sources such as incandescent and fluorescent lamps. Therefore, utilizing these features, it is being considered as a light source for back lights of non-luminous display devices, such as liquid crystal display devices, facsimile transmitters, copying machines, and the like.

Fluorescent lamps have often been used as light sources for conventional facsimile transmitters. However, unlike ordinary fluorescent lights for the bottom of a house, this fluorescent light is a special fluorescent light designed to provide high illuminance.
There is a problem in terms of lifespan, in that the period during which the required high illuminance can be maintained is short.

Therefore, as mentioned above, the use of vacuum fluorescent tubes, which are light sources that apply the principles of fluorescent display tubes, is being considered.

Conventional vacuum fluorescent tubes include a flat tube type shown in FIG. 1 and a round tube type shown in FIG. 2. The flat tube type vacuum fluorescent tube A is made by depositing silver paste on the glass substrate 1 by screen printing method, or by depositing metal such as Al, Au, Ag, etc. by vapor deposition method, sputtering method, etc. An anode conductor 2 is formed. Therefore, the anode conductor 2 is in close contact with the substrate 1. A slit portion 3 to which the anode conductor 2 is not attached is formed approximately at the center of the anode conductor 2. A phosphor layer 4 is deposited on the upper surface of the anode conductor 2 by a printing method, an electrodeposition method, a precipitation method, or the like to form an anode 5. Therefore, the substrate 1, anode conductor 2, and phosphor layer 4 are laminated and integrated. Furthermore, a filament-shaped cathode 6 is provided in a stretched manner facing the phosphor layer 4 . Then, a flat-bottom boat-shaped front enclosure 7 is sealed onto the substrate 1 so as to cover the electrodes and the like. The substrate 1 and the front enclosure 7 form a vacuum container.
The inside of this vacuum container is evacuated from an exhaust pipe (not shown) to bring the inside of the container into a vacuum state. A lens system 8 is disposed below the slit 3 of the vacuum fluorescent tube A so that the light emitted from the phosphor layer 4 is reflected on the document surface, and the reflected light is transmitted through the slit 3 and focused. .
The light collected by this lens 8 is photoelectrically converted by a sensor 9 into an electrical signal.

Further, the vacuum fluorescent tube B of the round tube type shown in FIG. , a slit 3 is provided at the bottom. Further, a mesh-like grid 6a, a lens system 8, and a filament-like cathode 6 are arranged in the surrounding air 1a. Therefore, the vacuum fluorescent tube B has a complicated structure and is expensive to manufacture, and when the vacuum fluorescent tube B reaches the end of its life, it must be replaced along with the lens system, which increases the cost of replacement.

Regardless of the type of conventional vacuum fluorescent tube, the anode conductor 2 is closely fixed directly to the glass envelope 1a, and the phosphor layer 4 is adhered to the top surface of the anode conductor 2. It has an integrated structure. Therefore, when current flows to the anode and the phosphor layer 4 emits light, it generates heat, which is stored in the glass envelope with poor thermal conductivity, and the phosphor layer 4
However, there was a problem in that the temperature gradually rose with the temperature of the envelope, and the brightness decreased due to the temperature quenching characteristics of the phosphor.

Figure 3 shows how the substrate temperature and the brightness of the phosphor layer 4 change over time when a voltage is applied to the facsimile light source shown in Figure 1 to emit light. This is a graph showing changes in substrate temperature and brightness of the phosphor layer when a voltage of 100V is applied and 1.8V is applied to the cathode to generate light. This figure is a graph in which the left vertical axis shows the substrate temperature, the right vertical axis shows the brightness of the phosphor layer 4, and the horizontal axis shows the elapsed time.

The brightness immediately after applying the anode voltage is approximately 8000 (ft
-L) Yes. The substrate temperature at that time is about 32°C, but after that, the heat generated by the phosphor layer is stored in the substrate, so it rapidly rises to about 70°C after about 10 minutes. However, after that, the temperature leveled off at around 70℃. On the other hand, the brightness was initially 8000 (ft-L), but as the substrate temperature rose, the brightness suddenly decreased. Approximately 6400 (ft-L) after about 10 minutes
After 30 minutes, descend to
I descended to around 6300 (ft-L). When 32 minutes had passed after applying the anode voltage, air was sent to the substrate 1 to air-cool it, and the substrate temperature dropped from 70℃ to about 50℃, and then stabilized at about 50℃, so it was further air-cooled. By increasing the wind strength, the substrate temperature further decreased to about 45°C. When air cooling was stopped after 40 minutes, the substrate temperature began to rise. On the other hand, the brightness of the phosphor layer is determined by the fundamental temperature of 70℃.
When the temperature of the substrate started to decrease from 100°C to 45°C, the brightness increased to a maximum of 7100 (ft-L). When air cooling was stopped, the brightness began to decrease again.

From the graph of this experimental data, it can be seen that there is a certain correlation between the substrate temperature and brightness of vacuum fluorescent tubes. This relationship is consistent with the temperature quenching property of the phosphor. In other words, the luminance of the phosphor decreases as the temperature of the phosphor increases. Considering the above two points, when the phosphor layer 4 of the vacuum fluorescent tube starts emitting light, it also generates heat, and the heat passes through the anode conductor 2 and accumulates in the glass substrate 1, which has poor thermal conductivity, and the phosphor layer 4 The temperature of No. 4 will also rise. Therefore, the brightness also decreases due to the temperature quenching characteristics of the phosphor. It has also been found that when the substrate 1 is cooled, the substrate temperature decreases, the temperature of the phosphor layer 4 decreases, temperature quenching is prevented, brightness increases, and luminous efficiency improves.

With conventional vacuum fluorescent tubes, the above phenomenon occurs, and the luminous efficiency drops significantly, to 1/3 to 1/4 of the normal value.
There was a problem with the extent. When the luminous efficiency decreases, the brightness also decreases, and therefore the illuminance on the document surface also decreases, and power consumption also increases.

Furthermore, when the substrate temperature rises, the substrate 1 expands due to thermal expansion because it is in close contact with the anode conductor 2, but the flat-bottomed front envelope 7 is separated from the anode conductor, so the temperature does not rise as much as the substrate 1. do not have. Therefore, the vacuum fluorescent tube A is warped in its length direction.
Then, the distance between the filament-shaped cathode 6 and the phosphor layer 4 of the anode 5 changes partially, and the light emission in the middle portion in the length direction becomes weaker. Furthermore, since the distance between the document surface and the phosphor layer 4 varies depending on the location, there is a problem in that illuminance unevenness occurs on the document surface.

Furthermore, in the case of a light source for a facsimile transmitter, it is necessary to focus the light onto a line on a certain document on the light source to increase the illuminance on the surface of the document and to obtain uniform illuminance. However, in the conventional vacuum fluorescent tube, since the anode conductor 2 is disposed on the flat substrate 1 as shown in FIG. The document 10 on the front envelope 7 is irradiated evenly. However, the required document surface 10a is the front envelope 7 facing the slit 3.
It is only on the straight line above. However, if the light is focused only on the original surface 10a, the illuminance on the original surface 10a will be higher even if the luminance is the same.

The present invention has been made in view of the above-mentioned problems, and in order to improve heat dissipation of the anode conductor, it is formed of a metal plate, lowers the temperature of the phosphor layer, increases luminous efficiency, and improves the heat dissipation of the anode conductor. The conductor is formed into a concave groove shape with a chevron-shaped or semicircular cross section, and the emitted light from the phosphor layer placed on the surface is focused on a predetermined line on the document, increasing the brightness of the phosphor layer and uneven illuminance. It is an object of the present invention to provide a vacuum fluorescent tube for a facsimile light source that has a long life and can be made uniform and high in quality without any damage.

In order to achieve the object of the present invention, the present invention has an anode consisting of an anode conductor disposed in a vacuum container and a phosphor layer deposited on the surface of the anode conductor, and an anode disposed facing the anode. In a vacuum fluorescent tube for a facsimile light source consisting of a cathode and a cathode, the anode conductor is a metal plate with a slit provided inside the vacuum vessel, and the end of this metal plate is extended outside the vacuum vessel.
It is characterized in that the extended portion is a cooling portion that is in contact with the outside air.

EMBODIMENT OF THE INVENTION Hereinafter, the vacuum fluorescent tube for light sources of this invention will be explained with reference to the embodiments shown in the drawings.

FIG. 4 is a longitudinal sectional view showing a first embodiment of a vacuum fluorescent tube for a facsimile light source according to the present invention.

The vacuum fluorescent tube for a facsimile light source of the present invention has a horizontally long rectangular shape, and the horizontal length is about 10 times the vertical length, but the structure is the same around the center, so the structure is the same. Parts have been omitted.

Reference numeral 11 denotes a glass translucent insulating substrate, and a front enclosure 12 consisting of a side plate 12a and a translucent front plate 12b is sealed on the outer edge of this substrate 11 to form a vacuum container. An anode conductor 13 made of a metal plate is arranged in this vacuum container. The metal forming this anode conductor 13 is, for example, 42% Ni and Cr.
There is a 426 alloy whose main component is 6% Fe and the balance is Fe. The expansion coefficient of this 426 alloy is approximately equal to the expansion coefficient of glass, which is the material of the vacuum container. In addition to 426 alloy, 13Cr alloy and 18Cr alloy Fe−
Ni alloys have similar expansion coefficients. Further, a slit 13a is formed in the anode conductor 13 in the longitudinal direction near the center thereof, and its vertical cross section is shaped like a pair of mountains facing each other with the slit 13a in between. The width of this slit 13a needs to be at least the width of the document 14. Further, the end of the anode conductor 13 extends continuously to the outside of the vacuum vessel. In the case of this first embodiment, as shown in the figure, the groove extends to the long side of the rectangular vacuum container. This extended portion serves as a cooling portion 13b that is in contact with the outside air. Furthermore, this anode conductor 13 is connected to the side plate 12 of the front enclosure 12.
It extends from between a and the substrate 11. Side plate 12
There is a small hole 1 in the anode conductor 13 near the intersection with a.
A large number of holes 3c are provided, and the substrate 1 is inserted into the small holes 13c.
1 and the front envelope 12 are filled with a sealing material 15, which has high strength and can be airtightly sealed without leakage.

On the upper surface of the anode conductor 13 and through the slit 13
A phosphor layer 1 is disposed on the inclined surface 13c facing each other with a
6 is deposited by a screen printing method, electrodeposition method, etc. to form an anode 17. Further, a filament-shaped cathode 18 is stretched on a cathode support 19 so as to face this inclined surface 13c. The gas in the vacuum container in which the electrodes are disposed in this way is exhausted from an exhaust pipe (not shown) and hermetically sealed to maintain the interior in a high vacuum state. Also, the cathode support 19 and the anode conductor 1
3, and an external terminal 20 is provided. Also, a condenser lens 2 is placed below the slit 13a outside the vacuum fluorescent tube.
1 is disposed, and further a sensor 22 is disposed below this condensing lens 21.

Since this embodiment has the structure as explained above, the anode conductor 13 and the cathode 18 are connected from the external terminal.
When a voltage is applied to the cathode 18, electrons are emitted from the cathode 18, and the electrons impinge on the phosphor layer 16 on the anode conductor 13, causing the phosphor layer 16 to emit light. The emitted light is focused on the document surface 14a, which is the part of the document 14 to be transmitted, as shown by the dotted line in FIG.
The light is reflected by the document surface 14a, passes through the slit 13a, is focused by the condenser lens 21, and is photoelectrically converted by the sensor 22. When the phosphor layer 16 emits light, it generates heat, which is conducted to the anode conductor 13 made of a metal plate with good thermal conductivity. Since the continuous portion of the anode conductor 13 constitutes a cooling section 13b outside the vacuum vessel, the heat conducted to the anode conductor 13 is cooled and radiated by a cooling process such as wind in this cooling section 13b. Therefore, the heat generated by the phosphor layer 16 can be radiated through the anode conductor 13, and the temperature of the phosphor layer 16 can be lowered. Therefore, temperature quenching of the phosphor layer 16 can be prevented, light emission efficiency can be improved, and brightness can be increased.

Furthermore, since the structure has the inclined surfaces 13c facing each other with the slit 13a in between, the light emitted from the phosphor layer 16 is focused on the document surface 14a, and the illuminance on the document surface 14a can be increased. . Furthermore, since the contact area between the anode conductor 13 and the substrate 11 is small, the rate of conduction to the vacuum vessel is reduced. Therefore, the temperature of the substrate 11 does not rise;
Since the temperature difference between the front plate 12b and the substrate 11 is small, it is possible to prevent the vacuum container from warping due to the difference in thermal expansion between the two.

FIG. 5 is a longitudinal sectional view of a second embodiment of the invention.

In this embodiment, the metal plate of the anode conductor 13 is formed into a groove having a semicircular concave cross section as shown in the figure, and a slit 13a is provided in the bottom of the concave groove in the longitudinal direction. There is. That is, a slit 13a is formed at the bottom of the semi-cylindrical anode conductor 13.
A phosphor layer 16 is adhered to the inner wall of the semi-cylindrical anode conductor 13. Anode conductor 1
3 is the longitudinal side plate 12a of the vacuum container.
The cooling portion 13b extends outside the vacuum vessel from between the front plate 12b and the front plate 12b. Therefore, the anode conductor 13
The vicinity of the bottom portion is in contact with the substrate 11, and the flat portion other than the semi-cylindrical portion is in contact with the front plate 12b. Since the phosphor layer is in contact with both surfaces, even if the phosphor layer generates heat, the heat is conducted through the anode conductor 13 and cooled and dissipated in the cooling section 13b, but some of it is transferred to the front plate 12b and the substrate 11. It also conducts to both sides.
Therefore, instead of only the substrate 11 expanding due to thermal expansion as in the first embodiment, the front plate 12b and the substrate 1
1 expands due to thermal expansion, the phenomenon of warping can be prevented.

Further, the original surface 1 of the original 14 to be copied is located near the center of the circumferential curvature of the anode conductor 13 having a semicircular cross section.
Since the anode rod 13 is blended so that 4a is placed, the phosphor layer 1 formed on the anode conductor 13 is
All of the light emitted from No. 6 is focused on the document surface 14a. Therefore, even if the brightness is the same, the original surface 14
It is possible to increase the illuminance at point a. The light reflected from the document surface 14a passes through the slit 13a, is focused by a condensing lens, and is photoelectrically converted by the sensor 22. Moreover, the end of the anode conductor 13 is
As in other embodiments, the substrate 11 and the side plate 12a
It is also possible to extend from between.

The present invention is not limited to the embodiments and drawings described above, and may be implemented with various modifications without departing from the gist of the present invention.

For example, the shape of the anode conductor may be any shape other than a mountain shape or a semicircular shape as long as it has an inclined surface that can focus light on a certain location.

The shape of the cooling part 13b may also be modified to a shape that increases the heat dissipation area, a shape that allows air to pass through easily, etc., instead of a simple plate shape.

As explained above, in the present invention, the anode conductor is composed of a metal plate with good thermal conductivity, and the end portion thereof is extended outside the vacuum vessel and a cooling section is disposed there. This has the effect of reducing heat generation, thereby preventing temperature quenching, increasing luminous efficiency, and maintaining high-intensity luminescence.

Furthermore, since the anode conductor is configured to have an inclined surface such as a mountain shape or a semi-cylindrical shape that can condense the emitted light, the emitted light from the phosphor layer of the anode can be focused on the document surface, making it possible to increase the illuminance on the document surface. There are some effects that can be achieved.

In addition, the heat generated in the phosphor layer is transmitted through the anode conductor and cooled by a cooling section outside the vacuum container, so no heat is stored in the substrate. This prevents the substrate from warping due to thermal expansion, and the document surface This has the effect of preventing uneven illuminance.

Furthermore, since the vacuum fluorescent tube of the present invention is a light source with a condensing lens provided outside the vacuum fluorescent tube, it not only simplifies the structure of the vacuum fluorescent tube and reduces manufacturing costs, but also shortens the lifespan of the vacuum fluorescent tube. It is easy to replace just the vacuum fluorescent tube even when it burns.
This exchange also has the effect of allowing it to be used as a light source.

[Brief explanation of drawings]

1 and 2 are vertical cross-sectional views of conventional vacuum fluorescent tubes for facsimile light sources, FIG. 3 is a graph showing the relationship between substrate temperature, brightness, and elapsed time, and FIG. 4 is a graph showing the relationship between substrate temperature, brightness, and elapsed time.
FIG. 5 is a vertical cross-sectional view showing one embodiment of a vacuum fluorescent tube for facsimile light source according to the present invention. FIG. 5 is a vertical cross-sectional view showing another embodiment of the present invention. 11... Substrate, 12... Front enclosure, 13... Anode conductor, 13a... Slit, 13b... Cooling section,
13c... Inclined surface, 16... Phosphor layer, 17...
Anode, 18... cathode.

Claims (1)

[Claims] 1. An anode consisting of an anode conductor disposed in a box-shaped vacuum container and a phosphor layer coated on its surface, a slit provided in this anode, and a cathode disposed facing the anode. In a vacuum fluorescent tube for a facsimile light source, the anode conductor has a slit in the center and has inclined surfaces facing each other across the slit and having a phosphor layer coated on the surface. 1. A vacuum fluorescent tube for a facsimile light source, characterized in that the tube is made of a metal plate, an end of the metal plate extends outside the vacuum container, and the extended portion serves as a cooling part in contact with the outside air.