JPH07161303A - Indirectly heated cathode for cathode-ray tube - Google Patents

Abstract

PURPOSE:To improve heat efficiency and to reduce a size by applying a thermionic emission material on an electron emitting cathode metal part which is heated to raise its own temperature by penetrating stimulation of an electron. CONSTITUTION:A strong electric field is generated in a tip needle part of an electrode 11 and electron emission is generated because of the potential difference impressed between the needle electrode 11 and a cathode 2. This electron collides against the cathode 2 in plus potential in comparison with the electrode 11, so that the cathode 2 is heated and its temperature is raised. The shape and the potential of an electron reflecting electrode 12 are selected so that, in this process, the electrons emitted toward the outer side beyond a metal part 22 for electron emission of the cathode 2 are 0801, to the inside by means of the electron reflecting electrode 12 in minus potential in comparison with the potential of the electrode 11, and ail. the electrons effectively collide against the metal part 22 on which a thermionic emission material 23 is applied. In this way, an indirect heated cathode type cathode structure having good heat efficiency can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indirectly heated cathode structure for a cathode ray tube.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing the structure of an indirectly heated cathode for a cathode ray tube which has been generally used in the past.
Reference numeral 1 is a heater, 2 is a cathode, which is composed of a cathode sleeve 21, a cathode sleeve top 22 made of a metal for electron emission, a thermionic emission material 23, and a sleeve holding mechanism 24. Reference numeral 3 is an electron flow rate control electrode commonly called G1 electrode, and 4 is an electron flow accelerating electrode commonly called G2 electrode.

Next, the operation will be described. By energizing and heating the heater 1 inserted in the cathode 2, the cathode sleeve 21 is heated, and the thermionic emissive material 23 can stably radiate thermoelectrons on the cathode sleeve top 22. Temperature, that is, usually heated up to about 800 ° C,
Thermionic emission material 23 emits thermionic electrons, and G
An electric field formed by the first electrode 3 and the G2 electrode 4 causes an electron beam flow of a predetermined flow rate.

[0004]

Since the conventional indirectly heated cathode is constructed as described above, it is originally sufficient to heat only the thermionic emission portion to a predetermined temperature. The heat efficiency was extremely poor because heating was applied to parts other than the radiating part. In order to improve thermal efficiency, conventionally, the structure of the cathode part is designed to be as small as possible so that the heat radiation loss is as small as possible. For example, heater 1
The heat generation point of (1) is made as small as possible, the heat transfer to the cathode sleeve 21 is made efficient, and the heat loss due to conduction from the cathode support 24 is reduced.

However, in order to reduce the heat-generating portion of the heater 1, a heater material having a thin core wire must be used. Therefore, there is a problem in reliability such as disconnection during use, and there is a limit to thinning. was there. Further, the heater 1 needs to be coated with alumina or the like in order to electrically insulate it from the cathode sleeve 21, which also makes it impossible to design the heating portion of the heater to be smaller than a certain extent.
On the other hand, in order to efficiently capture the heat generated by the heater 1 in the cathode sleeve 21, the length of the cathode sleeve 21 could not be shortened to a certain extent or more. Further, the heat conduction loss to the heater support due to the heat conduction of the heater 1 itself cannot be ignored.

Due to the above-mentioned limiting conditions, the most efficient one among those generally used in the conventional cathode structure has the following structural dimensions. G1 electrode hole diameter: 0.4 mm Cathode sleeve diameter: 1.5 mm Cathode sleeve length: 3 mm In the cathode having such a structure, the thermal efficiency of the heater, that is, the heater. The power efficiency can be estimated to be less than 1%.

The present invention has been made to solve the above problems, and improves the thermal efficiency of the indirectly heated cathode, that is, the efficiency of heating power of the indirectly heated cathode, and reduces the size of the cathode structure. As a result, it is intended to reduce the total length of the cathode ray tube itself.

[0008]

The indirectly heated cathode for a cathode ray tube according to the present invention accelerates the emitted electrons from the electron emitting means and causes them to collide with the electron emitting cathode metal portion for heating and heating. The thermoelectron emitting material adhered to the metal part is heated. The electron emission means is composed of a field emission needle electrode. Further, between the field emission type needle-shaped electrode and the electron emission cathode metal portion, an electron reflection electrode is provided so that the electrons emitted from the needle-shaped electrode can effectively strike the electron emission cathode metal portion. It is provided. Further, the electron emitting means is constituted by an assembly of field emission type needle electrodes. Also,
A gate electrode for controlling the amount of field electron emission is provided on each needle electrode of the assembly of field emission type needle electrodes. Further, the electron emission density of the field emission type needle-shaped electrode assembly is changed between the central portion and the peripheral portion of the assembly.

[0009]

In the indirectly heated cathode according to the present invention, electrons are emitted from the field emission type needle-shaped electrode, and the electrons are projected onto the electron emission metal part to heat and raise the temperature of the electron emission metal part. Thermions are emitted from the thermionic emission material deposited on the part. Electron emission by field emission requires little electric power and is advantageous in efficiency.

[0010]

【Example】

Example 1. The present invention will be described below with reference to examples. Figure 1
In the figure, 11 is a field emission type needle electrode, 12 is, for example, a cylindrical electron reflection electrode, 2 is a cathode, and includes an electron emission metal part 22, a thermoelectron emission material 23, and a cathode holding mechanism 24. 3 is a G1 electrode and 4 is a G2 electrode.

Next, the operation will be described. Due to the potential difference applied between the needle-shaped electrode 11 and the cathode 2, a strong electric field is generated at the tip needle-shaped portion of the needle-shaped electrode 11, and electron emission is generated. The electrons collide with the cathode 2 having a positive potential from the needle-shaped electrode 11 and become thermal energy, heating the cathode 2 to raise its temperature.
At this time, the electrons emitted outward from the electron emission metal portion 22 of the cathode 2 are bent inward by the electron reflection electrode 12 having a potential lower than the potential of the needle-shaped electrode 11, and the electron emission metal portion 22. The shape of the electron reflection electrode 12 and its potential are selected so that all the electrons effectively collide with.

In such a structure, unlike the conventional cathode structure, there is no heat conduction loss from the heater itself and radiant heat loss from the cathode sleeve, and an indirectly heated cathode structure with good thermal efficiency can be obtained. it can. Furthermore, the projecting density distribution of the projecting electrons can be easily realized by selecting the shape and potential of the electron reflecting electrode 12 so that the temperature distribution of the metal part 22 for electron emission has a predetermined value.

Example 2. FIG. 2 shows another embodiment of the present invention. In this embodiment, an aggregate 111 of needle-like electrodes is used as a source of electrons that are made to strike the cathode 2. The aggregate 111 of needle-like electrodes is called a field emission array (FEA) in the academic field of vacuum microelectronics, and is introduced in the following document, for example. IVOR BODIE, "PHYSICAL CONS
IDERATION IN VACCUM MICROE
LECTRONICS DEVICES "(IEEE TRANSACTIONS ON EE
CTRONDEVICES, VOL. 36, NO. 1
1, NOV. 1989, PP2641-2644).

FIG. 3 is a sectional view showing the basic structure of one element in the FEA. In FIG. 3, 51 is a metal base electrode, 52 is a cathode tip (needle electrode), 53 is a first insulator, 54 is a metal gate electrode, 55 is a second insulator, and 56.
Indicates a metal anode (corresponding to the metal 22 for electron emission). Generally, the tip of the cathode tip 52 has a radius of 0.
A sharp electric field is sharpened to less than 01 μm, and a strong electric field is generated at the tip of the cathode tip 52 by the potential applied to the metal anode 56 arranged at a distance of several μm or less, and electrons are emitted. The amount of emitted electrons can be controlled by the metal gate electrode 54 which is normally arranged at a distance of 1 μm or less.

As described above, since one element in the FEA has an extremely fine structure, it is possible to reduce the operating voltage, damage to the chip due to ion sputtering, and use in a relatively low vacuum, and it is stable. The emission current can be obtained. Further, the FEA is such that 10 ⁴ or more such elements are integrated per 1 cm ² . Since the FEA integrates a large number of chips, it has a high degree of redundancy, and even if there are defective ones among a large number of chips, the overall effect is small.

When such FEA is applied to the present invention, it is most preferable that the metal anode 56 is the metal part 22 for direct electron emission. However, if there is a problem in FEA manufacturing, another metal plate is used once. After being configured, it may be bonded to the electron emitting metal portion 22.

Generally, since the FEA is manufactured by using the semiconductor integrated circuit manufacturing technique, it is easy to manufacture the FEA by changing the field electron emission density between the central part and the peripheral part of the assembly. On the indirectly heated cathode surface, the tendency that the temperature tends to lower in the peripheral portion than in the central portion can be made uniform by changing the distribution of the projecting electron flow rate.

By applying the above FEA to the present invention, the following characteristics can be obtained. 1) A stable field emission electron flow can be obtained. 2) By changing the potential of the metal gate electrode 54,
The cathode temperature can be changed easily. 3) The entire cathode structure can be made extremely small. 4) The temperature distribution of the electron emitting metal portion 22 can be arbitrarily changed in design by changing the integrated distribution of the elements in design.

[0019]

As described above, according to the present invention, since the indirectly heated cathode for a cathode ray tube is heated to a high temperature by the impact stimulus of accelerated electrons, it can be compared with the conventional one using a heater for heating. The heating power for the indirectly heated cathode can be reduced.

Further, by adopting the field emission type cathode as the source of the electrons for the impact stimulation, the efficiency of the heating power of the indirectly heated cathode can be further enhanced.

In addition, an electrode for reflecting electrons is installed between the projecting portions of the field emission section, and the field-emitted electrons are effectively emitted to the cathode section, thereby heating power of the indirectly heated cathode. It can be reduced.

Further, by using an assembly of fine needle-shaped cathodes, the field emission cathode can be made redundant and the field emission characteristics can be stabilized because of its fine structure.

Further, the temperature of the indirectly heated cathode can be easily controlled by providing each of the fine needle electrodes with a gate electrode for controlling the amount of field electron emission.

Further, the electron emission density of the assembly of fine needle-shaped electrodes can be changed between the central portion and the peripheral portion of the assembly to design the temperature distribution of the indirectly heated cathode to a desired value.

Further, by adopting the fine needle-shaped cathode, the structure itself of the indirectly heated cathode can be downsized, the total length of the electron gun for the cathode ray tube can be shortened, and the total length of the cathode ray tube itself can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic line sectional view showing a first embodiment of the present invention.

FIG. 2 is a schematic line sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing the structure of one element of the FEA used in the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a conventional indirectly heated cathode.

[Explanation of symbols]

 2 Cathode 22 Electron Emission Metal Part 23 Thermionic Emissive Material 24 Cathode Holding Mechanism 11 Field Emission Needle Electrode 111 Field Emission Needle Electrode Assembly 12 Electron Reflection Electrode 51 Metal Base Electrode 52 Cathode Chip 53 First Insulator 54 Metal Gate Electrode 55 Second Insulator 56 Metal Anode

Claims (6)

[Claims] 1. An electron emission means, an electron emission cathode metal part for accelerating the emitted electron, and being heated to a temperature by a collision stimulus of the electron, and attached to the electron emission cathode metal part. An indirectly heated cathode for a cathode ray tube, comprising: 2. The indirectly heated cathode for a cathode ray tube according to claim 1, wherein the electron emitting means is adapted to obtain electrons for impact stimulation by a field emission type needle electrode. 3. Electrons between the field emission type needle-shaped electrode and the electron emission cathode metal portion so that the electrons emitted from the needle-shaped electrode effectively strike the electron emission cathode metal portion. The indirectly heated cathode for a cathode ray tube according to claim 2, wherein a reflective electrode is provided. 4. The indirectly heated type for a cathode ray tube according to claim 1, wherein the electron emitting means is adapted to obtain electrons for impact stimulation by an assembly of field emission type needle electrodes. cathode. 5. The indirectly heated cathode for a cathode ray tube according to claim 4, wherein each of the field emission needle electrodes is provided with a gate electrode for controlling the amount of field electron emission. 6. The cathode ray tube according to claim 4, wherein the electron emission density of the assembly of field emission type needle-shaped electrodes is changed between the central part and the peripheral part of the assembly. Indirect heating type cathode.