Electric lamp and discharge devices: systems – Miscellaneous systems
Reexamination Certificate
2001-02-05
2003-01-21
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Miscellaneous systems
C313S524000, C313S525000, C313S542000, C313S543000, C250S395000
Reexamination Certificate
active
06509701
ABSTRACT:
FIELD OF USE
Light sources are broadly used in the industry. In particular, vacuum ultraviolet radiation is used to etch resists in microelectronics, to desinfect spent materials, tools and equipment in medicine. Visible light sources of various spectrum are the illumination devices and information displays of different kind. Some of the most frequently used methods and related devices to generate optical radiation are the gas discharge light sources. For example, luminescent lamps are broadly used which are generating visible light. These lamps are based on the gas discharge in a noble gas at low pressure which is admixed with mercury which radiation is converted by a phosphor into visible light. Same principle is also used to produce plasma displays where the same type of discharge, though without mercury and at a higher gas pressure, is employed. Such broad use makes it important to build an effective compact visible light source.
PRIOR ART
Methods to generate optical radiation which are used in e.g. fluorescent gas discharge lamps of low pressure are known [Rokhlin G. N. Discharge light sources, Energoatomizdat, 1991, p.392]. These methods though being effective still possess a number of shortcomings which can not be excluded, for example, environments pollution with mercury possible if the lamp is broken.
Method to generate optical radiation and devices based thereupon are known where electrons emitted from a cathode are accelerated in the vacuum gap due to voltage applied to it and then generate optical radiation of cathode rays phosphor [Dobretsov L. N., Gamaiunova M. V. (<<Emittion electronics>>, Moscow, Nauka, 1966, p.245]. Main shortcoming of light sources based on this methods is a low effectiveness of cathode rays luminescence, especially at low voltage.
Method is also known comprising generation of electrons and generation of radiation from a gas discharge gap and a device to do the same which further comprise a chamber filled with the light emitting gas, and at least two electrodes, cathode and anode, placed in front of each other and at least one of which is made to be transparent for radiation [Dispalys ed. by J. Pankov, Moscow, Mir, 1982, pp.123-126]. Optical radiation is generated as a result of gas excitation in the discharge. Shortcoming of this method and device implementing it is a low effectiveness of conversion of electrical power into optical radiation.
SUMMARY OF THE INVENTION
Effectiveness of conversion of electrical power into optical radiation at lower voltage is the main purpose of the present invention.
The suggested method to produce an optical radiation comprises forming of an electron beam due to emission of them from a cathode surface and generation of radiation due to acceleration of electrons in the gas gap by an electric field applied between the cathode and anode up to the energy higher than excitation threshold of emitting energy levels of gas, but which is lower than self sustained discharge breakdown voltage, i.e. applied voltage is lower than a value when the gas ionization becomes an important factor leading to certain restrictions connected with presence of ions in the gas gap: surplus power losses inherent to the formed then electrode layers and shorter life of the light source because of bombardment of cathode with high-energy ions. Technically, ionization can be avoided, for example, due to a selection of voltage less than ionization potential of the gas, i.e. the electrons generation and acceleration in the gas gap is provided by a voltage which is less than I/e, where I is ionization potential of atoms or molecules of gas, e is an electron charge.
The device to generate an optical radiation comprises a chamber filled with a light emitting gas, for example, any noble gas, and at least two electrodes, cathode and anode, placed in front of each other and at least one of which is made to be transparent for radiation. Gas pressure is determined by a selection of a gap between the electrodes which should be about the electron energy relaxation length.
Radiation produced due to excitation of gas particles can escape through the transparent electrodes or converted into radiation of another spectral range via excitation of emitting states of phosphor. Phosphor can be placed both on the interior and external electrode surfaces including transparent parts of the electrodes, and it can be deposited in the form of RGB triads covering every particular point. Cathode can be made as a photocathode, thermocathode or autoemission cathode. Autoemission cathode can be made as a cold emission film cathode comprising a substrate coated with a diamond-carbon or carbon film emitter of electrons. For the purpose of additional control of the current at least one grid can be placed between the anode and cathode.
Autoemitting film cathode can be made in the form of parallel strips which width d is determined from a condition Ed=U where E is a strength of electrical field near the cathode strips surface which is sufficient to enable the needed autoemission, and spacing between the strips equals or exceed the width of interelectrode gap L determined from a condition of its equality to electron energy relaxation length what is selected by varying the gas pressure and voltage applied to the electrodes U which shall be lower than I/e where I is ionization potential of atoms or molecules of gas, e is an electron charge.
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Parol, N.V. et al., Znakosinteziryjuschie indikatory i ikh primenenie. Moscow, Radio i svyaz, pp. 9-13. (To follow).
Rokhlin, G.N., Discharge Light Sources, Energoatomizdat, 1991, p.392. (Enclosed).
Dobretsov, L.N. et al., Emittion electronics, Moscow, Nauka, 1966, p. 245 (Enclosed).
Display, ed. by J. Pankov, Moscow, Mir, 1982, pp. 123-126. (enclosed).
Ivanov Vladimir Vitalievich
Mankelevich Jury Alexandrovich
Rakhimov Alexandr Tursunovich
Rakhimova Tatiyana Viktorovna
Suetin Nikolai Vladislavovich
Collard & Roe P.C.
Tran Thuy Vinh
Wong Don
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