KR20010069555A - Line-type cathode for Flat Panel Display - Google Patents

Abstract

PURPOSE: A line-type cathode of a flat display is provided to maintain the temperature around the filament by providing a heating device on both ends of the filament and to prevent the irregularity of fluorescent luminance by adjusting the temperatures on the both ends differently. CONSTITUTION: In the line-type cathode of a flat display, when the first filament(30) needs a heating, the power source is connected to the fixing support(20) and the elastic support(21) supporting the first filament(30). Simultaneously, the elastic element on both ends of the second filament are also connected to the power source for heating. The first filament(30) can maintain a constant temperature by adjusting the voltages given to the both ends of the second filament(40), matching the temperatures at the centers of the two filaments(30,40).

Description

Line-type cathode for flat panel display

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cathodes used in flat panel displays, and more particularly, to line-type cathodes used in various flat panel displays that excite phosphors by accelerating thermo-electrons emitted from heated filament cathodes. It is about.

In general, various types of flat panel displays using hot electrons, such as vacuum fluorescence displays (VFDs), employ a line-shaped filament cathode as an electron emission source. That is, a line filament, which is made of a material such as glass and maintained in a sealed structure (hereinafter referred to as an envelope) that maintains a vacuum state, is supported by a supporting means to emit hot electrons when voltage is applied. The side is provided with an accelerating electrode for addressing the emitted electrons and a fluorescent film of various patterns to perform a function as an information display device such as numbers or graphics.

The reason why the filament in the form of a line is used as a cathode in a flat panel display using hot electrons is that, unlike CRT (Cathode Ray Tube), which is commonly referred to as a CRT, it is not necessary to consider the electron deflection distance that increases the thickness of the envelope. That is, since both ends of the line filament are installed corresponding to both ends of the fluorescent film, electrons can be supplied to all pixels (hereinafter, referred to as pixels) of the fluorescent film without a separate deflection device.

However, such a linear cathode has a problem in that low temperature zones are formed at both ends of the filament due to heat transfer due to the temperature difference between the envelope of the room temperature and the heated filament. Since the electron emission amount is sensitive to the temperature change until the saturation region, the fluorescent film corresponding to the low temperature zone is significantly lowered in brightness than other points, resulting in severe brightness imbalance of the fluorescent film.

As an alternative to this problem, in the case of VFD, a method of not forming a fluorescent film at a point corresponding to a low temperature region is currently employed, which causes the front glass substrate and the back glass to form an envelope compared to the area of the fluorescent film. It was true that the area of the rear glass substrate was relatively large, causing unnecessary material loss. In addition, such a low temperature zone is increased as the length of the filament increases, which is an obstacle in constructing a large screen display.

On the other hand, in general, VFD is driven by applying a positive potential to the anode with respect to the cathode, that is, the filament. When heating the filament by applying a DC voltage between both ends of the filament, the filament's cathode side and The potential difference between the anodes becomes larger than the potential difference between the anode side of the filament and the anode, resulting in uneven luminance of the fluorescent film. As the length of the filament increases, a higher voltage must be applied between both ends of the filament, and thus the potential difference becomes even more severe. This phenomenon is another obstacle in forming a large-screen display by employing a line filament as a cathode.

Although, in order to solve such a problem, the current VFD applies an AC voltage between both ends of the filament or employs a heat dissipating filament, but there is a problem in that a large cost is required for the device or the circuit configuration.

The present invention has been made to solve the above problems, and the object of the present invention is to prevent the occurrence of low temperature zones on the filament by providing a heat generating means at both ends of the filament to prevent heat transfer on the filament.

Another object of the present invention is to prevent the unbalance of the luminance of the fluorescent film generated when the direct current voltage is applied between the both ends of the filament by allowing the temperature at both ends of the filament to be set differently.

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a side cross-sectional view briefly showing the configuration of a conventional VFD employing a line filament as a cathode.

2 is a perspective view illustrating an example of a heating pattern when a voltage is applied between both ends of a conventional line filament.

3 is a perspective view illustrating an example of a heating pattern when voltage is applied to both ends of the line-type cathode according to the preferred embodiment of the present invention.

4 is a cross-sectional view schematically showing a state in which the second filament in thermal contact with the first filament is supported by the U-shaped elastic member according to the present invention.

<Description of main reference numerals in the drawings>

4: grid 5: fluorescent film 6: anode

10: envelope 20: fixed support 21: elastic support

30: first filament 40: second filament 45: elastic member

In order to achieve the above object, the line-type cathode according to the present invention includes: a fixed supporter installed on one side of an envelope in which a vacuum state is maintained; An elastic supporter opposed to the fixed supporter and installed; A first filament having one end attached to the fixed supporter and the other end attached to the elastic supporter; And heating means provided to supply heat to both ends of the first filament.

Preferably the heat generating means, the second filament in contact with the first filament; And support means for supporting both ends of the second filament.

The support means is preferably composed of a U-shaped elastic member to effectively absorb the thermal expansion of the second filament in a narrow space.

The linear cathode of the present invention prevents the formation of low temperature zones at both ends of the first filament through the above components.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 1 is a view showing the configuration of a VFD employing a conventional line filament cathode. As shown in the drawings, conventionally, through the fixing body 2 and the elastic body 3 in the envelope 10 consisting of a front glass substrate 10a, a side glass substrate 10b and a back glass substrate 10c. The cathode was configured to support both ends of the filament 1 and to emit electrons by heating the filament 1 by applying a predetermined voltage to both ends of the linear filament 1. In addition, hot electrons emitted by applying a negative potential to the cathode with respect to the anode 6 on which the grid 4 and the fluorescent film 5 which are acceleration / control electrodes are formed pass through the grid 4 and are formed on the anode 6. A mechanism for causing the fluorescent film 5 to emit light was adopted.

However, as shown in FIG. 2, which shows the heat generation pattern of the filament 1, the cathode having the above structure causes a problem in that the temperature distribution on the filament 1 is uneven. That is, heat transfer is performed from the high temperature filament 1 to the fixed body 2, the elastic body 3, and the envelope 10 at room temperature, and as a result, a heating pattern in which the low temperature zones A are formed at both ends of the filament 1. Will appear. In the drawings, the same reference numerals as those of FIG. 1 indicate the same members, and the slender portions on the filaments 1 indicate relatively low temperatures.

Since the low temperature zone (A) is significantly lower in temperature than other points on the filament (1), the amount of electron emission is also very small, and if the fluorescent film is located at the point opposite to the low temperature zone (A), serious luminance imbalance occurs. do.

The linear cathode according to the present invention is to solve the above problem, and as a preferred embodiment is configured as shown in FIG. Referring to the drawings, the cathode of the present invention comprises: a first filament 30; And heating means installed at both ends of the first filament 30 to supply heat.

The first filament 30 is a wire-shaped metal body, and preferably a tungsten wire having a higher melting point than other metal materials. In addition, the diameter of the wire is preferably configured to be very fine, for example, a few microns (μm) so as to reduce power consumption and do not interfere with the phosphor emission. In addition, a thin film of barium (Ba), strontium (Sr) and calcium (Ca) oxide is preferably coated on the outer circumferential surface of the first filament 30 so as to lower the work function. .

Both ends of the first filament 30 are supported by being preferably welded to the fixed supporter 20 and the elastic supporter 21. In this case, the reason for employing the elastic supporter 21 having elasticity as the supporter facing the fixed supporter 20 is that the first filament 30 is provided by providing tension when the length of the first filament 30 is expanded due to the high temperature. This is to maintain the tension.

Both ends of the first filament 30 as described above is provided with a heating means. The heat generating means may be a member or apparatus of various forms as various means for generating heat to supply heat energy to both ends of the first filament 30 so that heat does not occur on the first filament 30. . As a preferred embodiment, as shown in Fig. 3, the second filament 40; Support means for supporting both ends of the second filament 40 may be employed.

The second filament 40 supplies heat to an end portion of the first filament 30 when its center portion is in contact with the end portion of the first filament 30 and is heated. At this time, the voltage source for applying a voltage across the second filament 40, the voltage source is applied to the first filament 30 to be independent from the portion where the first filament 30 and the second filament 40 is in contact It is desirable to prevent the distribution of the current to occur.

The support means for supporting both ends of the second filament 40 may provide a tension to maintain the tensioned state of the second filament 40 and at the same time as a means for functioning as an electrode can be configured in various forms. For example, structures such as the fixed supporter 20 and the elastic supporter 21 supporting the first filament 30 may be employed. In addition, preferably, U-shaped elastic member 45 may be employed to efficiently utilize a narrow space as shown in the figure.

U-shaped elastic member 45 is an elastic body provided at each end of each of the second filament 40, as shown in Figure 4, by applying an external force to support the second filament 40 in a state slightly open top The tension is provided to the second filament 40 through the restoring force generated at this time. Here, when a plurality of first filaments 30 are provided at intervals of a few millimeters (mm) and a plurality of second filaments 40 are correspondingly provided, one U-shaped elastic member 45 may have two second filaments ( 40) can be supported at the same time, so that the narrow space can be effectively used. Here, when the polarity is applied to the U-shaped elastic member 45 to apply a voltage to the plurality of second filaments 40, the anode (+) and the cathode (-) alternately as shown in FIG. Of course, it must be authorized.

Next, an operation example of the line-type cathode including the above components will be described. According to the present invention, when the first filament 30 is to be heated, a power supply terminal must be connected to the fixed support 20 and the elastic support 21 supporting the first filament 30. In addition, at the same time, the second filament 40 is heated by connecting a power supply terminal to the elastic member 45 at both ends of the second filament 40. At this time, the voltage between the both ends of the second filament 40 is adjusted. (40) When the temperature of the center portion and the temperature of the center portion of the first filament 30 are set to coincide with each other, heat transfer does not occur on the first filament 30, thereby achieving a uniform temperature distribution.

In the line-type cathode according to the present invention, since the low-temperature zone is not formed on the first filament 30 in the same principle as described above, the fixing support 20 fixes the fluorescent film 5 regardless of the length of the first filament 30. It is possible to form close to the elastic support 21.

On the other hand, the linear cathode of the present invention by setting the temperature of the second filament 40, each one provided on each side of the first filament 30 different from each other by varying the temperature on both sides of the first filament (30) It is possible to apply a DC voltage to 30. That is, when the direct current voltage is applied to both ends of the first filament 30 as described above, the potential difference of each point on the first filament 30 with respect to the grid 4 or the anode 6 is formed to be different from each other. The fluorescent film 5 corresponding to the small point has a lower luminance than the other point. At this time, if the temperature of the second filament 40 with a small potential difference is further increased, the amount of electron emission increases, so that the luminance imbalance of the fluorescent film 5 is corrected.

In the above, preferred embodiments of the present invention have been described with reference to the accompanying drawings. Herein, the terms or words used in the present specification and claims should not be interpreted as being limited to the ordinary or dictionary meanings, and the inventors properly define the concept of terms in order to explain their own invention in the best way. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

In the linear cathode according to the present invention, since the low temperature zone is not formed at both ends of the filament when the wire filament is heated, the electron emission amount at each point on the filament has a uniform value within a small error range, thereby causing a problem of unbalance in luminance of the fluorescent film. There is an effect that can be solved.

In addition, since the filament having a uniform temperature distribution is obtained regardless of the length of the wire, the present invention has an effect of significantly widening the area of the fluorescent film. Furthermore, it is expected that this effect can be very usefully employed as an electronic room application in constructing a low-cost, large-screen flat panel display.

On the other hand, when the line-type cathode according to the present invention is applied to a conventional VFD, so-called 'unused area' disappears, so that the problem of wasting waste can be eliminated, and since the DC drive is possible, the conventional AC power supply device There is an effect that can reduce the accompanying costs for.

Claims (3)

A fixed supporter 20 installed at one side of the envelope 10 in which the vacuum state is maintained; An elastic supporter 21 opposed to the fixed supporter 20 and installed on the other side; A first filament 30 having one end attached to the fixed supporter 20 and the other end attached to the elastic supporter 21; And And a heat generating means provided to supply heat to both ends of the first filament (30). The method of claim 1, The heat generating means may include a second filament 40 in contact with the first filament 30; And And a supporting means for supporting both ends of the second filament (40). The method of claim 2, The support means is a linear cathode, characterized in that the U-shaped elastic member (45).