JPH0519257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum fluorescent tube for a light source used in a light source such as a light source for a facsimile, a light source for a copying machine, a light source for a backlight of a liquid crystal, and the like.

In general, a vacuum fluorescent tube is a fluorescent display tube in which electrons emitted from a cathode placed in a vacuum container kept in a vacuum collide with a phosphor coated on the surface of an anode, causing the phosphor to emit light. It uses the principle of This vacuum fluorescent tube is extremely bright and can provide high illuminance with relatively low power consumption, and has a flat light source with a good space factor.
Furthermore, it has features such as a much longer lifespan than conventional light sources such as incandescent bulbs and fluorescent lamps.
It is being considered for use as a backlight for liquid crystal display devices, a light source for facsimile transmitters, a light source for copying machines, etc.

Fluorescent lamps have often been used as light sources for conventional facsimile transmitters and copying machines, but they have the following drawbacks.

(1) Fluorescent lamps can maintain high illumination for a short period of time, so they must be replaced frequently, which increases maintenance costs.

(2) Manufacturing costs are high due to special fluorescent lamps that increase illuminance.

(3) Because electrodes are provided at both ends of a fluorescent lamp, a decrease in brightness cannot be avoided, and in order to obtain uniform illuminance, the lamp must be large. This makes the space factor worse.

(4) Fluorescent lamps require a lighting device.

(5) Fluorescent lamps are gas discharge tubes, so they tend to generate noise.

Due to the above-mentioned drawbacks, there are problems in that maintenance using a fluorescent lamp as a light source is troublesome and the size of the device cannot be avoided.

Therefore, the present applicant has devised and filed an application for a vacuum fluorescent tube, which is a light source that utilizes the principles of conventional fluorescent display tubes. A case in which the vacuum fluorescent tube of this prior application is used as a light source for a facsimile transmitter is shown in FIGS. 1, 2, and 2.

FIG. 1 is a plan view of a light source for a facsimile transmitter, and FIG. 2 is an enlarged sectional view of the main parts.

1 is a vacuum container for a vacuum fluorescent tube. This vacuum container 1 is formed into a box-shaped structure including a substrate 1a made of insulating glass, a side plate 1b standing upright around the substrate 1, and a front plate 1c facing the substrate 1a on the side plate 1b. The inside of the vacuum container is sealed and sealed in a high vacuum state. An anode conductor 2 made of a thin Al film is adhered to the surface of the substrate 1a made of glass. A slit 3 is formed in the longitudinal direction approximately at the center of the anode conductor 2, and the Al anode conductor is removed from this portion. A phosphor layer 4 is deposited on the surface of the anode conductor 2. The anode conductor 2 and the phosphor layer 4 constitute an anode. Further, a filament-shaped cathode 5 is provided in a stretched manner facing the phosphor layer 4 . External terminals 6 and 7 electrically connected to the anode conductor 2 and the cathode 5
is placed through the vacuum vessel. Therefore, when used as a light source, the external terminal 6
When an anode voltage is applied to the anode conductor 2 through the external terminal 7 and a cathode voltage is applied to the cathode 5 through the external terminal 7, the heater of the cathode 5 heats up and thermionic electrons are emitted from the surface of the cathode 5, which are attracted to the anode and emit fluorescence. It collides with the body and causes the phosphor to emit light. The emitted light illuminates the document surface 8 through the translucent front plate 1c, passes through the slit 3, is collected by the lens 9a, and is photoelectrically converted by the sensor 9b.

FIG. 3 shows a backlight light source for a liquid crystal display device. This light source is also a substrate 1 made of glass.
A box-shaped vacuum container 1 is constituted by a, a side plate 1b, and a front plate 1c. On this glass substrate 1a
An anode conductor 2 made of an Al thin film is provided, and the anode conductor 2 is
A phosphor layer 4 is formed almost entirely on the surface. The anode conductor 2 and the phosphor layer 4 constitute an anode. A filament-shaped cathode 5 is disposed facing this phosphor layer 4 .

When used as a backlight, the anode voltage is applied to the anode conductor 2 through the external terminal.
When a cathode voltage is applied to the cathode 5, electrons emitted from the cathode collide with the phosphor layer 4, causing the phosphor to emit light. The emitted light passes through the translucent front plate 1.
Irradiate through C.

The inside of the vacuum container is maintained at a high vacuum state.

Figure 4 is a graph of preliminary experiment data showing how the substrate temperature and brightness change over time when voltage is applied to the facsimile light source shown in Figures 1 and 2 to illuminate it. be. It is a graph in which the left vertical axis shows the substrate temperature, the right vertical axis shows the brightness of the light source, and the horizontal axis shows the elapsed time.

The substrate temperature when the anode voltage is turned on is 32℃
However, as soon as the light was turned on, the board temperature rose to about 70 degrees Celsius after 10 minutes, and then remained almost flat. On the other hand, the initial brightness is 8000ft−
Although the temperature is around L, the brightness decreases as the substrate temperature increases. After about 10 minutes, it descends to 6,400 ft-L, and then gradually descends to 6,300 ft-L after 30 minutes.
I fell to the lowest rank. After about 32 minutes, air was sent to the board to cool it down, and the board temperature dropped to about 50℃.
From around 34 minutes, the rate of decrease becomes slow and the board temperature is
The temperature leveled off, so from around the 37th minute, the air cooling wind strength was further increased, and the temperature dropped further to 45℃. When air cooling was stopped after 40 minutes, the temperature of the board began to rise again. On the other hand, the brightness began to rise as the board temperature began to drop, and as the temperature dropped further, the brightness increased further, reaching a maximum of about 7100ft-L. When I stopped air cooling, the brightness started to drop again.

The data from this preliminary experiment shows that there is a correlation between the substrate temperature and brightness of vacuum fluorescent tubes. That is, it was found that lowering the temperature of the phosphor layer by lowering the substrate temperature increases the brightness and improves the luminous efficiency.

In any conventional vacuum fluorescent tube, the anode, which is composed of the anode conductor 2 made of an Al thin film and the phosphor layer 4 adhered to the surface of the anode conductor 2 made of an Al thin film and the phosphor layer 4 deposited on the surface of the anode conductor 2, is placed on the glass substrate 1a in any light source. When an anode current is passed through the anode conductor 2 and a cathode current is passed through the cathode 5, the anode conductor 2
The upper phosphor layer 4 emits light and generates heat. Since the substrate 1a is made of glass, heat dissipation is poor, so this heat is stored in the phosphor itself, raising the temperature of the phosphor layer 4 and significantly reducing the luminous efficiency to 1/3 to 1/4 of the normal value. Become. When the luminous efficiency decreases, the brightness decreases, the illuminance on the document surface decreases, and the power consumption increases.

Furthermore, the heat generated by the phosphor layer is also stored in the glass substrate 1a, increasing the substrate temperature. For that purpose, the board 1
Since a expands at a larger rate than the front plate 1c, a phenomenon of warpage occurs in the length direction of the vacuum fluorescent tube. Therefore, the distance between the filament-shaped cathode and the anode changes, and the light emission in the longitudinally intermediate portion of the glass substrate 1a becomes weaker.Furthermore, the distance between the document surface and the phosphor layer varies depending on the location, so that the document There was also the problem of uneven illumination across the surface. Back lights also have the problem of uneven brightness and low brightness.

The present invention has been made in view of the above problems, and aims to lower the temperature of the phosphor, increase luminous efficiency, and increase brightness by improving the heat dissipation of the substrate on which the anode is disposed. It is an object of the present invention to provide a vacuum fluorescent tube for a light source that is capable of providing stable illumination and has a long life by preventing uneven illuminance due to warping.

In order to achieve the object of the present invention, the structure of the present invention is such that a box-shaped vacuum container is formed by a substrate, a side plate erected around the substrate, and a front plate facing the substrate, and the interior of the vacuum container is In a vacuum fluorescent tube, in which at least a phosphor and a cathode are disposed, and the electrons emitted from the cathode collide with the phosphor to emit light, at least the substrate of the side plate and the substrate of the components of the vacuum vessel is made of a conductive metal. formed of a board,
The present invention is characterized in that a phosphor is directly deposited on the inner surface of this conductive metal plate to form an anode. below,
DESCRIPTION OF THE PREFERRED EMBODIMENTS A vacuum fluorescent tube for a light source according to the present invention will be explained with reference to embodiments shown in the drawings.

The first embodiment shown in FIG. 5 is a light source for a backlight. The vacuum container of this light source is composed of a front container 10 made of glass and a substrate 11 made of a metal plate, and the inside of the vacuum container is maintained in a vacuum. The front container 10 includes a front plate 1 made of translucent glass.
A frame body made of a glass side plate 10b is fixed around the periphery of 0a. This front container 10
Since it is heated during the manufacturing process, it is not limited to glass, but may also be made of translucent ceramic or the like as long as it has heat resistance of about 300 to 500°C and translucency that allows light to pass through.

The substrate 11 must be made of a metal material with good thermal conductivity and must have an expansion coefficient approximately equal to the coefficient of expansion of glass, which is the material of the front container 10 . This example is a case where a conductive metal plate is used as the substrate material, and an example of the metal is 42% Ni, 6% Cr,
The rest is 426 alloy, which has Fe as its main component. 426
In addition to alloys, Cr alloys, 18Cr alloys, Fe-Ni alloys, etc. may also be used. These alloys have approximately the same coefficient of expansion as glass. Since the alloy has electrical conductivity, there is no need to provide an anode conductor as in the conventional method, and the metal substrate 11 acts as an anode conductor as shown in FIG. 5, and the phosphor layer 14 is directly applied to the substrate 11. Adhesion is formed by a printing method or the like. and front container 10
A filament-shaped cathode 15 is disposed inside. After the metal substrate 11 and the glass front container 10 are sealed with a glass sealing material R, the inside of the vacuum container is maintained in a high vacuum state by exhausting air from an exhaust pipe (not shown). Further, external terminals 16 are provided connected to the metal substrate 11.

The structure of this embodiment is as explained above.
1 is made of a metal plate, which is one of the highly thermally conductive materials,
Since the phosphor layer 14 is directly formed on this metal plate, the heat generated by the phosphor layer 14 is quickly conducted to the metal substrate 11. The back surface of the metal substrate 11 is exposed on the outside of the vacuum container, and by cooling this portion, the temperature of the substrate 11 can be lowered. As the temperature of the substrate 11 decreases, the heat generated by the phosphor layer 14 is conducted to the substrate 11, and the substrate 11 is cooled from the back surface, so that the temperature of the phosphor layer 14 can be lowered. Therefore, temperature quenching of the phosphor layer 14 can be prevented, light emission efficiency can be improved, and brightness can be increased.

The second embodiment shown in FIG. 6 is a light source for a facsimile transmitter. This vacuum container is made up of a metal substrate 11 and a glass front container 10, as in the first embodiment, and the front container 10 has a translucent glass front plate 10a and is fixed around the front plate 10a. It is composed of four glass side plates 10b. The substrate 11 is made of 426 alloy, 13Cr alloy,
It is made of a metal plate made of a highly thermally conductive material such as 18Cr alloy or Fe-Ni alloy, which has a coefficient of thermal expansion almost equal to that of glass. A plurality of auxiliary embossments are arranged in the length direction of the metal substrate 11 to reinforce the mechanical strength of the substrate 11. Also, a through hole 13 is provided in the longitudinal direction of the substrate 11.
is bored to form a slit, and a translucent glass plate is sealed on the back side of the through hole 13 with a glass sealing material to provide a translucent window portion 12. A portion of the metal substrate 11 forms an external terminal 16 and extends outside the vacuum vessel. Inside the metal substrate 11, the substrate 11 is directly used as an anode conductor, and a phosphor layer 14 is formed on the surface of this substrate 11.
A filament-shaped cathode 15 is provided facing the phosphor layer 14. The external terminal of the cathode 15 is connected to the conductive metal substrate 1.
1 and extend to the outside of the vacuum container. The front container 10 and the metal substrate 11 are hermetically sealed and the inside is evacuated.

Although this light source for facsimile is constructed as described above, the method of use is the same as that of the conventional example shown in FIG. 2, so the explanation will be omitted. In this case as well, the heat generated by the phosphor layer 14 is conducted to the metal substrate 11 and the substrate 11 is cooled from the back side, thereby lowering the temperature of the phosphor 14 and preventing temperature quenching of the phosphor, resulting in high luminous efficiency and brightness. Since a high light source can be obtained, the illuminance on the document surface can be increased, which is an excellent effect. Also, since warping due to temperature changes can be prevented, uneven illuminance can be reduced.

The third embodiment shown in FIG. 7 is an example in which the metal substrate 11 is composed of a substrate 11a and at least two of four side plates 11b facing each other. The substrate 11 may be formed in a U-shape consisting of two sides, the substrate 11a and a side plate 11b, or in a box shape, consisting of the substrate 11a and four side plates. Therefore, in the former case, the front container 10 has a U-shape consisting of a front plate 10a and part of a side plate 11b, and in the latter case, it is composed of only the front plate 10a.
Similar to the second embodiment, a transparent window portion 12 is formed by forming a through hole in the longitudinal direction near the center of the substrate 11a and sealing a transparent glass plate to the back surface of the hole. be. A phosphor 14 is deposited on the bottom surface of this substrate 11, and a filament cathode 15 is placed facing the phosphor.
A rack is installed. Thereafter, the glass front container 10 and the metal substrate 11 are sealed with a sealing material. In this embodiment, since the substrate 11 is integrally formed with at least a part of the side plate 11b, the area in contact with the outside air is large, and the cooling effect is greater.
Since the shape is U-shaped or box-shaped, the strength is high and deformation can be prevented even if no embossing is provided.

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 substrate may be made of BeO, Al ₂ O ₃ ,
It also includes composite materials of high thermal conductivity materials such as MgO and metals.

As explained above, the present invention has the substrate, which is a part of the vacuum container, made of a metal plate made of a highly thermally conductive material. , the temperature of the anode phosphor can be lowered. Therefore, the temperature of the phosphor can be lowered and temperature quenching can be prevented, which has the effect of improving luminous efficiency and maintaining high-intensity luminescence. Further, when the light source of the present invention is used for a fax transmitter, it is possible to increase the illuminance on the surface of the document and to extend the life of the document.

Furthermore, since it is possible to prevent the substrate and the vacuum fluorescent tube from warping due to thermal expansion of the substrate, it is possible to prevent uneven illuminance on the document surface.

In addition, since a conductive metal is used as the substrate material, the phosphor layer can be directly provided on the substrate without providing an anode conductor, making it possible to omit processes and simplify the structure by omitting parts. have an effect.

[Brief explanation of drawings]

Figure 1 is a plan view of a conventional fax light source.
Fig. 2 is an explanatory cross-sectional view of the main part of a conventional fax light source, Fig. 3 is a vertical cross-sectional view of a conventional backlight light source, and Fig. 4 shows the relationship between substrate temperature, brightness, and elapsed time. 5 is a vertical sectional view of an embodiment of the backlight light source of the present invention, FIG. 6 is a longitudinal sectional view of an embodiment of the fax light source of the present invention, and FIG. 7 is a longitudinal sectional view of an embodiment of the fax light source of the present invention. FIG. 10...Front container, 10a...Front plate, 10b
... Side plate, 11 ... Substrate (anode), 12 ... Transparent window section, 13 ... Slit, 14 ... Phosphor layer, 15 ... Cathode.

Claims (1)

[Claims] 1. A box-shaped vacuum container is formed by a substrate, a side plate standing around the substrate, and a front plate facing the substrate, and at least a phosphor and a cathode are disposed within this vacuum container. In a vacuum fluorescent tube that emits light by colliding electrons emitted from the cathode with a phosphor, at least the substrate of the side plate and substrate of the components of the vacuum container is formed of a conductive metal plate. A vacuum fluorescent tube for a light source, characterized in that a phosphor is directly deposited on the inner surface of a plate to constitute an anode. 2. The conductive metal plate constituting the substrate is made of 426 alloy, 13Cr alloy, 18Cr alloy, Fe-
The vacuum fluorescent tube for a light source according to claim 1, which is made of a metal such as a Ni alloy. 3. The vacuum fluorescent tube for a light source according to claim 1 or 2, wherein a light-transmitting window is provided on the substrate and a phosphor is coated on the substrate excluding the light-transmitting window. 4. The vacuum fluorescent tube for a light source according to claim 3, wherein the light-transmitting window portion is provided with a lid hermetically sealed with a light-transmitting material. 5. Claim 1, 2 or 3, wherein a plurality of embossings are arranged on a part of the substrate.
Vacuum fluorescent tube for light source as described in section.