JP2788234B2 - Electron emission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electron-emitting device, and more particularly, to a stable operation of a cold-cathode-type electron-emitting device (hereinafter, a cold-cathode-type electron-emitting device is referred to as an electron-emitting device). The present invention relates to an electron emission device capable of performing the following. [Prior Art] Conventional electron-emitting devices include those using avalanche breakdown of a PN junction, those that inject electrons into a P layer by applying a forward bias to the PN junction, and those that are thin. A device having a structure in which an insulating layer is sandwiched between metals (MIM type), and a surface conduction type device and the like have been proposed. FIG. 5 (A) shows a case where a forward bias is applied to the PN junction and P
FIG. 5B is a schematic explanatory view of an electron-emitting device in which electrons are injected into a layer, and FIG. 5B is a graph showing a schematic current-voltage characteristic. In FIG. 7A, when a forward bias voltage V is applied to the PN junction, a forward current I as shown in FIG.
Flows, and electrons injected from the N layer into the P layer are emitted from the surface of the P layer into a vacuum. Cesium Cs or the like is applied to the surface of the P layer to lower the work function and increase the amount of emitted electrons. FIG. 6 is a schematic configuration diagram of a MIM type electron-emitting device, and FIG. 7 is a schematic configuration diagram of a surface conduction electron-emitting device. The MIM type electron-emitting device has a structure in which a metal electrode 1, an insulating layer 2, and a thin metal electrode 3 are stacked, and electrons are emitted from the thin electrode 3 side by applying a voltage between the electrodes 1 and 3. . In the surface conduction electron-emitting device, electrodes 5 and 6 are formed on an insulating substrate 4, and a rough high-resistance thin film 7 is formed between them. Then, by applying a voltage between the electrodes 5 and 6, electrons are emitted from the surface of the high-resistance thin film 7. [Problems to be Solved by the Invention] In an electron-emitting device using such an electron-emitting device,
Electron emission control, particularly ON / OFF control, can be performed by a driving voltage applied to the electron-emitting device or an acceleration voltage applied to the acceleration electrode. However, the conventional electron-emitting device has a problem that the current flowing through the electron-emitting device fluctuates due to the influence of external temperature or the like. An object of the present invention is to provide an electron emission device capable of stably driving an electron emission element in view of the above-mentioned problems of the related art. [Means for Solving the Problems] The above-mentioned problem is caused by an electron-emitting device in which a driving current is applied to drive an electron-emitting device, electrons are emitted from the electron-emitting device into a vacuum, and a current is generated by the emitted electrons. According to the present invention, there is provided an electron emission device having a current holding means for holding the driving current constant. [Operation] According to the present invention, by providing current holding means in a circuit for driving an electron-emitting device, the current flowing through the electron-emitting device is kept constant to perform constant current driving, thereby preventing current fluctuation due to external temperature or the like. , For stably driving the electron-emitting device. If the electron emission device of the present invention is provided with current control means for controlling the current flowing through the electron emission element by an external signal, the current can be controlled by the external signal, and the electron emission amount of the electron emission element can be controlled. Becomes Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of a first embodiment of the electron emission device of the present invention. As shown in the figure, the present embodiment is an electron emission device that performs voltage division by resistors R ₁ and R ₂ and applies a bias to a constant current by applying the voltage to the base of a transistor Q. In this case, the driving current I of the electron-emitting device (MEB in the figure)
₀ is set by the resistors R ₁ , R ₂ , R ₃ , the applied voltage V ₁ , the base voltage V _{BE of the} transistor Q, and the like, and has the relationship shown in the following equation. In this case it is possible to reduce the effect of the temperature coefficient, etc. by making integral with the transistor Q a resistor R _3. In this embodiment, the current holding means is a resistor.
R ₁ , R ₂ , R ₃ and the transistor Q. FIG. 2 is a circuit diagram of a second embodiment of the electron-emitting device according to the present invention. This embodiment is an electron emission device using a current mirror type constant current circuit, which is an improvement of the temperature coefficient of the first embodiment. As shown in the drawing, connecting the collector of the transistor Q ₁ which is short-circuited base and collector to the base of the transistor Q _2, and connects the emitter of the transistor Q _1, the transistor Q ₂ emitter of the transistor Q ₁ biased by applying a base-emitter forward voltage drop in the transistor Q _2. When a current I through the resistor R, is diverted to the base and collector of the transistor Q _1, is biased to the collector current I _D is approximately equal to the current I, the base voltage V _BE
Occurs. The base voltage V _BE is引加to the base of the transistor Q _2, biased constant current is performed. That current I ₀ flowing through the electron-emitting devices (in the drawing MEB) is related represented by the following formula. If V ₁ ≫V _BE at this time, the temperature change of V _BE is reduced, and I ₀
Can be stabilized. In this embodiment, the current holding means is a resistor R and transistors Q ₁ and Q ₂ . The above-described electron-emitting device performs a constant-current operation of the electron-emitting device. However, the constant-current operation can be controlled by an external signal. FIG. 3 is a circuit diagram showing an embodiment of the electron emission device of the present invention controlled by an external signal, and FIG. 4 is a characteristic diagram showing its transfer characteristics. As shown in FIG. 3, and the transistors Q _3, Q ₄ are provided symmetrically in the present embodiment, the transistor Q ₃
The collector current I _C1 flowing through and the drive current I ₀ flowing through the electron-emitting device (MEB in the figure) are controlled by external signal voltages V _B1 and V _B2 , and the current flowing out of the transistors Q ₃ and Q ₄ is controlled by a constant current circuit. It is kept at a constant current value (I ₁ = I _{0 +} I _C1 ). The electron emission device of the present embodiment has a configuration of a differential amplifier, and has a relationship expressed by the following equation between the external signal voltages V _B1 and V _B2 and the collector currents I _C1 and I _C2 of the transistors Q ₃ and Q _4. There is. k: Boltzmann constant, T: absolute temperature, q: electron charge At this time, I _C1 = αI _E1 and I _C2 = αI _E2 . (I _E1 , I _E2 : Emitter Currents of Transistors Q ₃ and Q ₄ ) When the relationship of the above equations is illustrated, a characteristic diagram as shown in FIG. 4 is obtained. As shown in the figure, the differential input voltage ratio (V _B1
−V _B2 ) (About 100mV, T: absolute temperature, q: electron charge)
That is Then, there is a relation that the collector current I _C1 or I _C2 is constant. That is, the electron-emitting device of the present embodiment shown in FIG. 3 is (V _B1 -V _B2) <- unless keep the 4kT / q can constant current driving of the electron-emitting device. Current at this time is determined only by the constant current source I _1, not affected by the temperature change of the Q _3, Q _4. When −4 kT / q <(V _B1 −V _B2 ) <4 Tk / q, the drive current I ₀ of the electron-emitting device can be controlled by the value of the external signal voltage difference V _B1 −V _B2 . When (V _B1 −V _B2 )> 4 / q, the drive current I ₀ of the electron-emitting device can be cut off. In addition,
In this embodiment, the power source current supply means for providing a voltage V ^+, the first current control means transistors Q4, the second current control means transistors Q3, the constant current source is a constant current which holds the current I ₁ at a constant Means a circuit. Further, the transistor Q4 as the first current control means and the transistor Q3 as the second current control means become current control means for controlling the current flowing through the electron-emitting device by an external signal. [Effects of the Invention] As described above in detail, according to the electron emission device of the present invention, current fluctuation due to external temperature or the like can be prevented, and the electron emission element can be driven stably. In addition, the peripheral circuits can be protected, and the reliability of the electron emission device can be greatly improved. If the electron emission device of the present invention is provided with current control means for controlling the current flowing through the electron emission element by an external signal, the current can be controlled by the external signal, and the electron emission amount of the electron emission element can be controlled. It becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a first embodiment of the electron-emitting device according to the present invention. FIG. 2 is a circuit diagram of a second embodiment of the electron-emitting device according to the present invention. FIG. 3 is a circuit diagram showing one embodiment of the electron emission device of the present invention controlled by an external signal. FIG. 4 is a characteristic diagram showing a transfer characteristic of the electron emission device. FIG. 5A is a schematic explanatory view of an electron-emitting device in which a forward bias is applied to the PN junction to inject electrons into the P layer, and FIG. -It is a graph which shows a voltage characteristic. FIG. 6 is a schematic configuration diagram of a MIM type electron-emitting device, and FIG. 7 is a schematic configuration diagram of a surface conduction electron-emitting device. _{V 1, V 2, V +} , V - ...... applied voltage _{I c, I c1, I c2} ...... collector current I ₀ ...... drive current _{R, R 1, R 2,} R 3 ...... resistor V _B1, V _B2 ...... external signal voltage Q, Q _1, Q ₂ ...... transistor

Continuing on the front page (72) Inventor Akira Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masao Suga 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masahiko Okunuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-51-242464 (JP, A) Jiko 50-501414 (JP, Y1) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01J 1/30, 9/02

Claims (1)

(57) [Claims] Driving a driving current to drive the cold cathode type electron-emitting device,
An electron emission device in which electrons are emitted from the cold cathode type electron emission device into a vacuum to flow a current due to the emitted electrons, wherein the electron emission device has current holding means for holding the driving current constant. 2. 2. The cold cathode type electron emitting device according to claim 1, wherein said cold cathode type electron emitting device is a PN junction type cold cathode type electron emitting device.
Item 3. The electron emission device according to Item 1. 3. 2. The electron emission device according to claim 1, wherein said cold cathode type electron emitting device is a MIM type cold cathode type electron emitting device. 4. 2. The electron-emitting device according to claim 1, wherein the cold-cathode electron-emitting device is a surface-conduction-type cold-cathode electron-emitting device.