JPH05205671A - Fluorescent display tube - Google Patents

Abstract

PURPOSE:To generate the proper cooling of a hot cathode filament and lessen the ineffective display part of a fluorescent character display tube by forming a support from inorganic dielectric substance. CONSTITUTION:An inorganic dielectric substance is used to construct a support 7, whose coefficient of thermal expansion is determined relating to that of a flat plate form base body consisting of a back board 1 and a face glass 11, ranging 40-100X10<-7>/ deg.C at 25-500 deg.C. Therefore, the thermal expansion of the back board 1 or face glass 11 is made similar to that of the support 7. The heat from a hot cathode filament 5 is diffused by the support 7 properly, and the filament 5 is located accurately at a specified level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent display tube, and more particularly, to a flat type fluorescent display tube used in digital watches, calculators and the like.

[0002]

2. Description of the Related Art FIG. 1 shows a cross section of a flat fluorescent display tube which is generally used today. As is clear from FIG. 1, the fluorescent display tube has a front glass 1 that constitutes a flat substrate.
It is configured by sandwiching a narrow spacer 12 between the back plate 1 and the back plate 1. The front glass 11, the rear plate 1, and the spacer 12 are airtightly fixed by frit glass. As a result, an airtight vacuum container surrounded by the front glass 11, the back plate 1 and the spacer 12 is formed. A getter 9 for maintaining a high vacuum is provided inside the vacuum container, and an exhaust hole 10 is further provided in the spacer 12 or the back plate 1. Exhaust hole 10 (not shown)
An exhaust pipe is connected to the vacuum container, and the vacuum container is sealed by chipping off the exhaust pipe or by a seal lid. On the inner surface of the back plate 1 forming the vacuum container, a plurality of anodes 2 having phosphors 3 on the surface are attached by printing or the like. There is also a type in which these phosphors 3 are formed on the front glass 11, but since the contents of the description are the same, the following description will be given based on FIG. The phosphor 3 receives the electrons attracted by the anode 2 and emits light. Further on the inner surface of the back plate 1, these anodes 2
And the support 7 provided so as to have a predetermined height at a position such that the phosphor 3 is sandwiched between itself and the support 7.
It is fixed by a fixed end 6 provided at the end of the.
The hot cathode filament 5 that provides the electrons necessary for the light emission of the phosphor 3 is supported by the pair of supports 7, and is thus suspended from the anode 2 or the like so as to have a predetermined height. It is possible to omit the support 7 by providing a mechanism for determining the height in the spring 8 part, but it is understood as an essential element for suspending the hot cathode filament 5 in an accurate position. One end of the hot cathode filament 5 is fixed to the fixed end 6 of the one support 7, and the remaining one end is fixed to the spring 8 provided on the side surface of the other support 7. By fixing at least one end of the hot cathode filament 5 to the spring 8 in this manner, the hot cathode filament 5 is held in a substantially straight line even if it expands and contracts due to thermal expansion. This also means that the hot cathode filament 5 slides on the support 7. Generally, in such a fluorescent display tube, a control grid 4 is often provided between the hot cathode filament 5 and the anode 2 to form a triode vacuum tube structure. The control grid 4 has a function of spreading the electrons from the hot cathode filament 5 in the width direction and accelerating the electrons, and is formed of a mesh-shaped thin metal plate.

[0003]

In the fluorescent display tube having the above-mentioned configuration, the support 7 has a function of appropriately dissipating the heat generated by the hot cathode filament 5. If the temperature of the hot cathode filament 5 is too high, the life of the hot cathode filament 5 will be shortened and other components will be adversely affected. On the other hand, if it is too low, the amount of electrons emitted from the hot cathode filament 5 decreases, so that the phosphor cannot have sufficient brightness and the fluorescent display tube has many invalid display portions. Normally, the temperature of the hot cathode filament 5 is 80
Around 0 ° C is considered appropriate. Therefore, when the temperature of the hot cathode filament 5 becomes higher than this temperature, it is preferable to cool it appropriately.

Although there are various cooling mechanisms, since the hot cathode filament 5 is arranged in the vacuum container, the effect cannot be obtained by cooling by convection. The same applies to radiation. Under such circumstances, cooling by heat conduction is generally used. The cooling by the heat conduction is also performed by the spring 8 and the like, but it is considered that the support 7 plays an important role in this cooling.

At present, the support 7 is made of metal for easy production. However, since the heat conduction and heat dissipation of the metal are too large for cooling the hot cathode filament 5, the fact is that proper cooling is not performed.
The support 7 has a function of accurately suspending the hot cathode filament 5 at a predetermined height in addition to the function of dissipating heat as described above. However, even in this case, when the support body 7 is made of metal as described above, the wear of the support body 7 due to the sliding of the hot cathode filament 5 is severe, and therefore the hot cathode filament 5 is placed at a predetermined position. It will be difficult to hold.

The present invention has been made in view of these problems of the prior art, and is intended to further enhance the above-mentioned function by forming the support with a better material. Furthermore, by forming the support with an appropriate material, it is possible to appropriately cool the hot cathode filament by this support to reduce the ineffective display portion of the fluorescent display tube, and also to increase the abrasion of the support. Therefore, it is intended to facilitate that the hot cathode filament is accurately suspended at a predetermined position for a long period of time.

[0007]

According to the present invention, in a fluorescent display tube having a hot cathode filament suspended at a position and / or height through a support, the support is a flat substrate. There is provided a fluorescent display tube formed of an inorganic dielectric material having a thermal expansion coefficient close to that of.

[0008] Also, according to the present invention, the fluorescent display tube described above, a glass plate flat base body is made of a soft or hard glass, the support is 25 to 500 ° C at 40 to 100 × 10 ^- Provided is a fluorescent display tube having a coefficient of thermal expansion in the range of ⁷ / ° C. Furthermore, according to the present invention, in the above fluorescent display tube, the inorganic dielectric material is 0.02 cal / (cm · sec · ° at 25 ° C.
C) A fluorescent display tube having the following thermal conductivity is provided.

Further, according to the present invention, there is provided a fluorescent display tube as described above, wherein at least a contact surface between the support and the hot cathode filament is made of a ceramic containing zirconia as a main component. Alternatively, there is provided a fluorescent display tube in which the support is made of crystallized glass or mixed glass with ceramics.

[0010]

SUMMARY OF THE INVENTION According to one aspect of the invention, the support is composed of an inorganic dielectric. This is because when a conductive material is used, undesired heat dissipation is performed via electrons, and
This is because when an organic substance is used, an undesired gas is released when the support is fixed. The fixing of the support is carried out by a thermal process, more specifically by heating at 400 ° C to 600 ° C. At this time, it is necessary to approximate the thermal expansion between the support and the fixing surface. If they are too different, at least one of them will break during cooling.
Therefore, the support needs to be formed of an inorganic dielectric material having a coefficient of thermal expansion similar to that of the flat substrate. For example, this is the glass thermal expansion coefficient of the front glass constituting the front surface of a flat plate substrate, that is, 90 × 10 ⁻⁷ / ° C which is the thermal expansion coefficient of soft glass and 50 × 10 ⁻ which is the thermal expansion coefficient of hard glass. Determined to approximate ⁷ / ° C. For this reason, in one embodiment of the present invention, the thermal expansion coefficient of the support is 40 to 10 at 25 to 500 ° C.
It was determined to be 0 × 10 ⁻⁷ / ° C. By using the support as described above, it is possible to provide a more appropriate support with less heat dissipation than the conventional one.

In order to further enhance the heat dissipation function of this support, it is preferable to reduce the thermal conductivity. In one form of the support according to the present invention, the thermal conductivity of the support is small,
Specifically, 0.02 cal at least at 25 ° C
/ (Cm · sec · ° C) or less It is preferably 0.01 cal / (cm · sec · ° C). Materials that satisfy such requirements include zirconia-based ceramics, various oxide glasses, and glass composites.

The heat conduction of the support can also be reduced by making the support thin and porous. In the case of such a form, the support preferably has high mechanical strength. Under such circumstances, in another form of the support of the present invention, the support is formed of crystallized glass or mixed glass with ceramics, instead of glass alone. The support has the function of accurately suspending the hot cathode filament at a predetermined height, in addition to the above heat dissipation function. By the way, since the hot cathode filament slides on the upper portion of the support during heating or cooling, at least the contact portion between the support and the hot cathode filament is required to have a material having good abrasion resistance. .. In the present invention, a ceramic containing zirconia as a main component is used as a material satisfying such requirements. Since such a material is also excellent in mechanical strength and toughness, the contact area with the filament can be reduced, and the contact surface can be made smooth.

[0013]

The present invention will be described with reference to FIG. An inorganic dielectric is used for the support 7 according to the present invention. When an organic substance is used, gas is released in the heat step for connecting the support 7 and the back plate 1, and when a conductive material is used, undesired heat dissipation is performed via electrons. is there. The coefficient of thermal expansion of the support 7 is determined in consideration of the coefficient of thermal expansion of the flat substrate formed by the back plate 1 and the front glass 11. The support 7 may be fixed on the surface of the back plate 1 as shown in FIG. 1, or alternatively the front glass 11
May be fixed to. Fixing is performed by heating at 400 ° C to 600 ° C. In the case of fixing by such heating, if the coefficient of thermal expansion of the flat substrate and the coefficient of thermal expansion of the support 7 are too different, at least one of them may be damaged when they are cooled. Therefore, it is necessary to approximate the thermal expansion of these flat bases, that is, the thermal expansion of the back plate 1 or the front glass 11 to the thermal expansion of the support 7. Usually, soft glass or hard glass is used for the front glass 11. The coefficient of thermal expansion of these glasses is 90 × 10 ⁻⁷ / ° for soft glass.
C, which is 50 × 10 ⁻⁷ / ° C for hard glass. In one embodiment of the present invention, the coefficient of thermal expansion of the support 7 is
From the coefficient of thermal expansion of these glasses, the range of ± 10 × 10 ⁻⁷ / ° C was considered appropriate, and was set to 40 to 100 × 10 ⁻⁷ / ° C. Examples of inorganic dielectric materials that satisfy these conditions include various ceramics such as alumina, mullite, zirconia, and forsterite, various glasses, and composites thereof.

In order to further enhance the heat dissipation function of the support 7 used in the fluorescent display tube, the smaller the value of the thermal conductivity, the better. The thermal conductivity of conventionally used metals such as stainless steel is about 0.02c at 25 ° C.
It was al / (cm · sec · ° C). The thermal conductivity is preferably 0.01 cal / (cm · sec · ° C) or less. As a material of the support 7 which satisfies such thermal conductivity, there are ceramics containing zirconia as a main component and various oxide glasses or glass composites.

The heat conduction can be reduced by making the shape of the support 7 as thin as possible or making it porous. When the support 7 has such a form, the support 7 preferably has high mechanical strength. For this reason, it is preferable to use a glass material alone as the material of the support body 7,
It is considered preferable to use it in combination with crystallized glass or other ceramics.

The support 7 has a function of appropriately dissipating the heat from the hot cathode filament 5 as described above, and a function of accurately positioning the hot cathode filament 5 at a predetermined height. Since the hot cathode filament 5 slides on the upper portion of the support 7 during heating or cooling, at least a contact portion between the hot cathode filament 5 and the support 7 in the support 7 is made of a material having good abrasion resistance. It is desired to be used. As such a material, a ceramic containing zirconia as a main component is preferable. Since this also has excellent mechanical strength and toughness, the contact area with the filament can be reduced.
Furthermore, since the contact surface can be made smooth, heat conduction can be reduced. Various types of structural ceramics are used for this zirconia-based ceramic, and the main ones are stabilized or partially stabilized zirconia stabilized with yttria, or a composite of these and alumina. is there.

For reference, the present invention will be described below using more detailed numerical values and the like. In the examples described below, soda glass for windows was used for forming the front glass 11, the rear glass 1, the spacers 12, and the like. However, for the hot cathode filament 5, tungsten having a core wire system of 15 μm was used. The support 7 was a round bar having a diameter of 1 mm and was fixed to the rear glass 1 using glass. The display temperature part of the hot cathode filament 5 was 830 ° C., and the length of the hot cathode filament 5 from the support 7 to 750 ° was defined as the cooling length, and this cooling length was measured. Furthermore, 1 hot cathode filament
After being turned on and off 000 times, the depth of wear of the support 7 by the hot cathode filament 5 was measured.

First, as the material of the support 7, zirconia stabilized with 2 mol% of yttria was used. In this case, the thermal expansion of the support 7 is 92 × 10 ⁻⁷ / ° C,
The thermal conductivity is 0.004 cal / (cm · sec · °
It became C). The cooling length was 6 mm, and the wear depth was too small to be measured. Next, as the material of the support 7, forsterite 55 wt%, SiO ₂ —B ₂ O ₃
-Al ₂ O ₃ -ZnO glass 45 wt% at 900 ° C
The composite that was fired at was used. In this case, the thermal expansion of the support 7 is 88 × 10 ⁻⁷ / ° C, and the thermal conductivity is 0.
It was 01 cal / (cm · sec · ° C). The cooling length was 7 mm and the wear depth was about 10 μm.

In contrast to these examples according to the present invention, when a metal is used as the support material as in the conventional case, for example, as the material of the support 7, Ni 42 wt% and Cr 6 wt% F are used.
When an e-alloy is used, the thermal expansion of the support 7 is 93 ×
10 ^-7 / ° C and thermal conductivity is 0.035cal
/ (Cm · sec · ° C). The cooling length was 9 mm and the wear depth was about 50 μm.

[0020]

According to the present invention, the invalid display portion due to the cooling portion of the filament can be reduced, so that the fluorescent display tube can be formed compactly, and the filament can be accurately positioned at a predetermined position for a long period of time. It will be easy. It is considered that the technique used in the present invention can be applied to fluorescent display tubes having various configurations, because the steps of forming the support and assembling the support are not complicated compared with the conventional ones.

[Brief description of drawings]

FIG. 1 is a general configuration diagram of a flat-panel fluorescent display tube.

[Explanation of symbols]

 1 Back Plate 2 Cathode 3 Phosphor 4 Controlling Grid 5 Hot Cathode Filament 6 Fixed End 7 Support 8 Spring 9 Getter 10 Exhaust Hole 11 Front Glass Plate 12 Spacer

Claims (5)

[Claims] 1. A fluorescent display tube comprising a hot cathode filament suspended at a position and / or height via a support, wherein the support is a thermal expansion of a flat plate-shaped substrate constituting the fluorescent display tube. A fluorescent display tube characterized by being formed of an inorganic dielectric material having a thermal expansion coefficient close to that of the coefficient. 2. The fluorescent display tube according to claim 1, wherein the flat substrate is a glass plate formed of soft or hard glass, and the support is 40 to 100 × 10 ^{−7 at} 25 to 500 ° C. A fluorescent display tube having a coefficient of thermal expansion in the range of / ° C. 3. The fluorescent display tube according to claim 1, wherein the inorganic dielectric material is 0.02 cal / 25 ° C.
A fluorescent display tube having a thermal conductivity of (cm · sec · ° C) or less. 4. The fluorescent display tube according to claim 1, wherein at least a contact surface between the support and the hot cathode filament in the support is formed of a ceramic containing zirconia as a main component. 5. The fluorescent display tube according to claim 1, wherein the support is made of crystallized glass or mixed glass with ceramics.