JPH0424819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a light-emitting electron tube that can be used, for example, as a compact and highly efficient light source for illumination.

(Background technology) As a light source for illumination, fluorescent lamps that combine low-pressure mercury vapor deposition discharge and a phosphor have been used because of their high efficiency.
It has been widely used since ancient times. However, since such fluorescent lamps utilize light emission (ultraviolet radiation) from the positive column, they generally have the disadvantage of requiring a longer tube length and larger size in order to achieve high efficiency.

Furthermore, there is a light emission method based on a completely different principle from the above-mentioned light emission principle, that is, electronic excitation. This was put into practical use as a cathode ray tube (hereinafter referred to as CRT).
It has been widely used in televisions etc. since ancient times. As shown in Fig. 1, this method uses a vacuum inside an outer tube 1, accelerates electrons e emitted from a thermionic emissive cathode (electron gun) 2 using a high-voltage electric field, and causes them to directly pass through a lattice anode 3. The phosphor (electron beam excitation type) is collided with and excited by the phosphor 4, but this excitation conversion efficiency is poor and high voltage and considerable distance are required to accelerate the electrons, resulting in a large size. It is unsuitable as a light source for illumination. In the figure, 5 is a deflection magnetic field device, 6 is an acceleration DC power supply, and 7 is a resistor.

Furthermore, as shown in FIG. 2, a system has recently been proposed that combines the above-mentioned CRT system with a gas discharge system (Japanese Patent Application Laid-open No. 130364/1983). In this method, instead of creating a complete vacuum inside the transparent outer tube 11 as in the CRT method described above, a low vacuum is created in which mercury vapor exists on the order of several mTorr, and mercury vapor is emitted from the thermionic cathode (electron gun) 12. The electron e is accelerated by applying an electric field as in the above CRT method, and
By forming the anode 13 into a mesh-like or lattice-like structure, most of the electrons are allowed to pass through and collide with an ultraviolet emitting gas such as mercury vapor in the back space 14 to excite the mercury and emit ultraviolet rays. This is a method in which a light body (ultraviolet excitation type) 15 is applied and excited to perform desired visible light conversion.
In addition, in the figure, 16 is an acceleration DC power supply, and 17 is a resistor.

This method requires that the space for collision with mercury after passing through the anode is sufficiently large compared to the space for electron acceleration;
By applying appropriate kinetic energy to the mercury and electrons, the probability of excitation of mercury becomes extremely high, and the overall visible light emission efficiency is improved compared to the conventional CRT method. Therefore, the accelerating electric field and accelerating space are
It is reported that it is smaller than the CRT method.

However, such a method requires a sufficient amount of space behind it, which leaves the drawback that the arc tube becomes large as a result.

(Object of the Invention) The present invention has been made in view of the above points, and its object is to provide a light-emitting electron tube that is extremely compact in size and yet provides sufficient luminous efficiency.

(Disclosure of the Invention) The present invention arranges a cathode symmetrically with respect to a mesh-shaped anode, thereby causing electrons to vibrate back and forth with respect to the anode, dramatically increasing the probability of collision with a radiation gas such as mercury. The present invention provides a light-emitting electron tube that has an extremely compact configuration compared to other conventional methods and is capable of highly efficient radiation (light emission).

The present invention will be explained in detail below. FIG. 3 is a conceptual diagram showing the basic configuration of the present invention. Inside the outer tube 21, which is airtightly formed of a material that transmits desired radiation (light emission), such as transparent glass, there is a pair of cathodes 22, 23 and an anode 24 are disposed, and at least one of the two cathodes 22, 23 (the left cathode 22 in the figure) is an electron-emitting cathode (currently heated by a direct current or alternating current power supply (not shown), and heated to a desired temperature). (e.g., a thermionic barium oxide coated tungsten filament coil similar to those used in conventional fluorescent lamps).
The anode 24 is disposed approximately midway between the cathodes 22 and 23, and is formed into a rough mesh or lattice shape (hereinafter referred to as a mesh anode). Furthermore, a low pressure (10 ^-2 to ^{10 -4} Torr level) radiation gas such as vaporized mercury that irradiates ultraviolet rays or visible radiation is sealed within the outer tube 21 . A positive DC voltage is applied between the anode 24 and the pair of cathodes 22 and 23 via a resistor 25 to the DC power supply 2.
6 and 27.

Therefore, the magnitude of the DC voltage accelerates the thermoelectrons e emitted from one cathode 22, and
The beam is formed into a beam shape to reach the anode 24, and after passing through the anode 24, it is decelerated, and the speed is set to zero just before reaching the other cathode 23.

Next, the operation will be explained. First, when the first cathode 22, that is, the electron-emitting hot cathode 22 emits thermoelectrons e, the thermoelectrons e are accelerated because a positive electric field is applied between it and the anode 24. Since the anode 24 has a rough mesh or lattice shape,
Most of the thermoelectrons e directly pass through the anode 24 and enter the deceleration electric field region formed by the anode 24 and the second cathode 23. Here, the thermoelectron e is decelerated, stalls just before the second cathode 23, and has a speed of 0. Then, from now on, due to the positive electric field applied between the anode 24 and the second cathode 23, it is accelerated in the opposite direction to the above direction, reaches the anode 24 again, and passes through the anode 24. Thereafter, since the anode 24 and the first cathode 22 form a decelerating electric field in the same manner as described above, the thermoelectrons e are decelerated, reversed again just before the first cathode 22, and head toward the anode 24. Thereafter, this operation is repeated, and the thermoelectrons e vibrate electrically around the anode 24.

Thus, as in the embodiment shown in FIG.
The airtight space formed by 1 is filled with mercury, and the outer tube 2
When a phosphor 28 such as calcium halophosphate is coated on the inner surface of the tube, a part of the mercury becomes a gas with a vapor pressure corresponding to the coldest temperature of the tube wall, so the inside of the tube exists as a gas close to several mTorr at room temperature. ing. now,
The voltage and dimensional relationship between the anode 24 and both cathodes 22 and 23 are determined by the average kinetic energy of the electrons e.
If designed to be about 5 eV, the electrons will efficiently move the gaseous mercury atoms to the 6 ³ P ₁ resonance excitation level (approximately 4.9 eV high level). Such excitation immediately emits ultraviolet light of 254 nm, which is converted into visible light by the phosphor 28 coated on the inner surface of the outer tube 21 and emitted.

In addition, in order to cause electron movement and excitation collision with a high probability, the electron energy E corresponding to the necessary excitation energy of the gas to be emitted (radiated) is
The accelerating voltage and distance between the electrodes should be designed to obtain the average value as shown by the solid line in the figure, the anode structure should be designed to minimize the trapping of accelerated electrons to the anode, and the electrons after passing through the anode should be It is important to design the voltage and distance between the electrodes so that the speed is decelerated to v=0 (indicated by the broken line in FIG. 5) and reversed just before the cathode.

A specific example will be explained based on FIG. 1 pair of cathodes 2
2 and 23 are both composed of thermionic emissive filaments, which are heated by an external auxiliary power source (not shown) and are configured to be able to sufficiently emit electrons of about 1 A. Anode 24 and both cathodes 2
The distance between 2 and 23 is about 1 to several cm, and the voltage applied between the two poles is about 10V. The radiation gas sealed in the outer tube 1 contains several to 10 mg of mercury.
The coldest temperature inside the pipe is between 10 and 60°C, and if necessary, a rare gas of 0.1 Torr or less is filled.

With the above settings, the emitted electrons will average 1~
The energy is about 10eV, which excites mercury and generates 254n.
It can efficiently emit ultraviolet rays of m (equivalent to about 4.9 eV) or ultraviolet rays of 185 nm (equivalent to about 6.7 eV).

The gas to be emitted may be a partial metal vapor such as the above-mentioned mercury or a full gas such as argon. Alternatively, ultraviolet light or the like may be emitted directly without using a phosphor. In short, a pair of cathodes are arranged in the airtight space formed by the outer tube, at least one of which is a thermionic emissive cathode, and a mesh-shaped anode is arranged approximately in the middle of the two cathodes. To be there. The voltage and distance between the anode and cathode are set so that electrons emitted from one cathode continue reciprocating motion through the anode.

In the above airtight space, the gas to be radiated (light-emitted) is at an extremely low pressure level (at a level where losses due to elastic collisions of electrons and ionization collisions are relatively negligible with respect to the overall input. In the case of mercury, it is within a few mTorr). ) is enclosed.

Next, the scope in which the present invention can be effectively implemented will be explained.

First, the distance between the electrodes (between the anode and the cathode) is 10
If it is more than cm, the overall size becomes too large, and the diffusion loss of accelerated electrons to the wall surface of the outer tube increases, resulting in a relative limitation of the effective light emission (ultraviolet radiation) range, which is disadvantageous in practice. Moreover, if it is less than 0.5 cm, it is difficult to construct the anode and cathode, and it is also difficult to make the electric field uniform, making it impractical. Therefore, the distance between the electrodes is 0.5~
10cm is preferable.

Next, the voltage applied between the anode and the cathode is preferably 5 to 20V. In order to obtain the desired ultraviolet light (254 nm) using mercury, it is optimal to accelerate the electrons to around 5 eV, and as mentioned above, if the distance between the electrodes is 0.5 to 10 cm,
In order to provide energy of about 5 eV each during this time, a voltage of about 5 V is required. If we assume that the conversion efficiency is approximately 50% taking into consideration electron collision loss and scattering loss, it is practically desirable to apply twice the voltage of 10V, and if we further consider the distribution, the optimal range is 5 to 20V. . Note that below 5V, there is an increased possibility that the desired electron energy cannot be achieved due to collision loss with mercury gas, etc. Above 20V, the electron energy is too strong, and the space and electron density to obtain around 5eV are relatively reduced. However, the radiation efficiency decreases.

Finally, the coldest temperature on the inner surface of the outer tube during operation is
Assuming the ambient temperature is 25°C, a temperature of 25 to 100°C is desirable.
As is well known, mercury gas most efficiently emits ultraviolet light at 254 nm at a temperature of approximately 40° C. and a vapor pressure of approximately 5×10 ⁻³ Torr. As the temperature rises higher than this, the emission shifts to a longer wavelength spectrum, and conversely, as the temperature becomes lower, the emission shifts to a shorter wavelength spectrum. Therefore, when converting mercury ultraviolet to near ultraviolet radiation into visible light through a phosphor to obtain a highly efficient illumination light source, it is necessary to use 200 to 400n.
m range (specifically applicable spectrum is 254nm,
It can be said that the highest ultraviolet emissivity of wavelengths (297 nm, 313 nm, 365 nm, 366 nm) is approximately 25 to 100°C. twenty five
At temperatures below .degree. C., the efficiency decreases and the vapor pressure of mercury itself becomes extremely small, resulting in a decrease in the absolute radiation intensity itself. Moreover, at temperatures above 100°C, the radiation efficiency of ultraviolet radiation decreases significantly, and radiation becomes visible radiation itself.

(Effects of the Invention) As described above, the present invention includes a pair of cathodes, at least one of which has thermionic emissivity, arranged symmetrically with respect to a mesh-like anode, and which allows electrons to move back and forth between the two cathodes. By continuing to do so, the probability of collision with the radiated gas in the airtight space can be dramatically increased. Therefore, it is possible to provide a light emitting electron tube that can obtain efficient radiation despite its compact configuration.

[Brief explanation of drawings]

Figures 1 and 2 are simplified diagrams showing conventional examples;
The figure is a conceptual diagram showing the basic configuration of the present invention, FIG. 4 is a simplified diagram showing one embodiment of the present invention, and FIG. 5 is a diagram showing the state of movement and energy state of electrons according to the present invention.

Claims (1)

[Scope of Claims] 1. An outer tube in which a low-pressure radiation gas (10 ^-2 to ^{10 -4} Torr level) is sealed and is transparent to radiation; and an outer tube disposed at substantially both ends of the outer tube. An electron tube consisting of a pair of cathodes, at least one of which has thermionic emissivity, and a rough mesh-shaped anode disposed approximately midway between the two cathodes, the distance between the anode and cathode being 0.5 to 10 cm. A light-emitting electron tube characterized in that a DC voltage of 5 to 20 V is applied between the anode and both cathodes. 2 The main gas of the above radiation gas is vaporized mercury, and the coldest temperature of the outer tube during operation is 25~25°C when the ambient temperature is 25°C.
The light-emitting electron tube according to claim 1, wherein the temperature is 100° C. and an ultraviolet-excited visible conversion phosphor is coated on the inner surface of the outer tube.