Description

A NEW ELECTRODELESS UV LAMP

Technical Field

[1] The present invention relates to an improved microwave ultraviolet (UV) generating device (lamp) which substitutes trivalent zirconium ion or tetravalent lanthanum ion with high emission characteristic at 240nm through 270nm for mercury and is driven by an electrodeless discharging method using a microwave electric field to achieve high efficiency, high output power and semipermanent durability. Background Art

[2] A conventional UV generating technique sets a discharge electrode in a transparent glass tube, evacuates the glass tube, injects vaporized mercury into the glass tube, seals up the glass tube, ionizes the mercury vapor filled in the glass tube according to a discharge current generated from electrons emitted caused by a DC electric field or low-frequency AC electric field such that the intrinsic spectrum of mercury is emitted and uses the intrinsic spectrum.

[3] The quantity of emission of UV rays as well as emitted spectrum of an ionized gas filled in a UV lamp are determined according to the type of the ionized gas, and it is very important to find a material having wider UV distribution and larger quantity of emission. The line spectrum of currently used monovalent mercury is included in UV, visible ray and infrared ray (IR) regions and 117 lines exist in the range of lOOnm to 2000nm. Lines arranged in the order of intensity include 253.6536nm (luminance: 15000), 435.8335 (luminance: 4000), 365.0518nm (luminance: 2800), 1013.975 (luminance: 2000), 404.6559 (luminance: 1800), 296.7278 (luminance: 1200), 546.0731 (luminance: 1100), 184.950 (luminance: 1000), 256.369 (luminance: 400), and 434.749 (luminance: 400). Here, the principal UV wavelength is spectrum of 253.6536nm which corresponds to 37.3% of the overall spectrum intensity.

[4] A conventional UV lamp is constructed in such a manner that electrodes are attached to both sides of the inside of a tube such that a discharge current flows between the electrodes and ionized gas existing on the discharge current path is excited to emit the spectrum of the ionized gas. In the event of discharge, the electrodes are heated to emit hot electrodes, and thus the metal constituting the electrodes is vaporized and deposited on the wall of the tube to reduce the quantity of light and damage the electrodes and the lamp is dead. The dead lamp is discarded and mercury vapor generated during the discarding process affects environment.

[5] Furthermore, to improve the output power of the UV lamp, the quantity of current flowing through the electrodes should be increased. This becomes a primary factor of

reducing the durability of the electrodes and the chief obstacle in manufacturing a high-power lamp.

[6] Accordingly, an electrodeless lamp having no filament or no discharge electrode is being developed in order to improve the durability and output power of the lamp. The principle of the electrodeless lamp is that electrons reciprocate in a high-frequency AC electric field in which the direction of the electric field is continuously reversed and collide with gas molecules to emit spectrum according to the gas.

[7] That is, gas molecules in a lamp tube located in a high-density high-frequency electric field are excited to generate discharge, and thus a high frequency is applied to a vacuum tube from the outside without forming electrodes in the vacuum tube to emit light with continuous spectrum according to gas characteristic in the lamp tube. This lamp tube is increasingly used as a visible ray lamp because it has high emission efficiency and long durability.

[8] Electric energy is applied to the electrodeless lamp using a high-frequency method that applies several hundred KHz to several MHz and a microwave discharge method that applies several GHz.

[9] A conventional electrodeless lamp using a high frequency condenses the high frequency into the lamp through inductive coupling or capacitive coupling in order to apply the high frequency to the lamp tube and requires an oscillator for supplying high frequency power to the lamp. Accordingly, the conventional electrodeless lamp is expensive, complicated and difficult to generate high output power.

[10] On the other hand, the microwave discharge method arranges a lamp tube in a resonant cavity such that microwave discharge occurs in the lamp tube, and thus the microwave discharge method is economical and easy to generate high output power. Disclosure of Invention Technical Problem

[11] Accordingly, the present invention has been made in an effort to solve the above- mentioned problems including low output power, short durability and mercury contamination occurring in the conventional art, and a primary object of the present invention is to provide a method of manufacturing a discharge lamp filled with zirconium and lanthanum, a microwave generator for turning on the discharge lamp, and a method and components for injecting a generated microwave field into a lamp tube.

[12] Zirconium ions or lanthanum ions filled in the lamp tube are excited by microwave field of 2.54GHz and hundreds to thousands of watts obtained by oscillating the zirconium ions or lanthanum ions in a microwave generator corresponding to a microwave oscillating element to generate UV rays from a zirconium lamp having

262.057 lnm (luminance: 10,000,000) as a principal wavelength and high UV intensity in that range of 220nm to 270nm and a lanthanum lamp having 259.750nm (luminance: 95,000) as a principal wavelength.

[13] The attached drawings for illustrating preferred embodiments of the present invention are referred to in order to gain a sufficient understanding of the present invention, the merits thereof, and the objectives accomplished by the implementation of the present invention. Technical Solution

[14] To accomplish the object of the present invention, there is provided an electrodeless

UV lamp having no mercury, which comprises a microwave generator; a waveguide guiding and transmitting microwaves generated from the microwave generator to a resonant mode and having an opening formed at one side of an electromagnetic wave fracture point of an electric field face or a magnetic field face; an electrodeless UV lamp tube filled with zirconium or lanthanum ion gas and sealed and having a distal end sealably bonded to the opening of the waveguide; and a microwave resonant cavity internally including the lamp tube, and adapted to transmit light and block microwaves.

[15] The electrodeless UV lamp of the present invention can include a single lamp tube and a single set of a microwave generator and a waveguide (FIG. 2) or include a plurality of lamp tubes and two sets of a microwave generator and a waveguide (FIG. 3). When the UV lamp includes the plurality of lamp tubes, the waveguide has a plurality of openings respectively corresponding to the lamp tubes. When the UV lamp includes the two sets of a microwave generator and a waveguide, voltages applied to the two microwave generators may have a phase difference of 180°therebetween.

[16] In the present invention, the lamp tube is a cylindrical tube having a diameter in the range of 10mm to 30mm and a length in the range of 200mm to 2000mm, which is made of fused silica, and can be manufactured through a process of injecting zirconium iodide or lanthanum iodide of lmg to 5mg per 1 cm of the lamp tube into the lamp tube, evacuating the lamp tube to 10 Torr to 10 Torr, filling the lamp tube with argon gas to 10 Torr, sealing up the lamp tube, putting the lamp tube into an electric field furnace with a microwave emission strength of at least 5W/cm and performing melting and evaporation. Although the upper limit of the field strength is not described, the upper limit is meaningless because the field strength is a lower limit for applying a temperature of higher than the evaporation point for evaporating a solid.

Advantageous Effects

[17] The durability of the UV lamp according to the present invention remarkably increases because there is no factor of reducing the durability due to electrode deterioration so as to decrease mercury pollution caused by lamp waste and achieve envi-

ronmental effect. [18] Furthermore, according to the lamp of the present invention, damage of waveguide is reduced to maintain radiation of light while minimizing a loss of microwave energy. [19] Moreover, the zirconium UV lamp using a microwave discharge method according to a preferred embodiment of the present invention can distribute microwaves generated by a single microwave generator that emits microwaves with high output power to install/use a plurality of lamp tubes, and thus a UV emission portion can be dispersed.

Brief Description of the Drawings [20] Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: [21] FIG. 1 illustrates UV spectra of zirconium ion and lanthanum ion using microwave discharge used in the present invention for comparison with UV characteristic of mercury; [22] FIG. 2 is a perspective view showing a configuration of a zirconium UV lamp using microwave discharge; and [23] FIG. 3 illustrates a configuration of a UV lamp according to another embodiment of the present invention.

Best Mode for Carrying Out the Invention [24] The principle of generating an electrodeless short wavelength UV rays using microwave according to a preferred embodiment of the present invention is explained in detail with reference to the attached drawings. [25] FIG. 1 shows graphs representing spectrum intensities and wavelengths of mercury, zirconium and lanthanum in UV region. Referring to FIG. 1, the spectra of zirconium and lanthanum are superior to the spectrum of mercury used in prior arts in UV region. [26] In FIG. 1, the horizontal axis represents wavelength and the vertical axis represent photon emission intensity and the spectra of mercury, lanthanum and zirconium in UV region are sequentially illustrated from the top to bottom. It can be known from FIG. 1 that a remarkable emission spectrum difference exists among the materials (Reference:

NIST; National Institutes of standards and technology). [27] In the present invention, the lamp tube is an electrodeless UV lamp tube filled with zirconium or lanthanum ion gas instead of mercury. [28] It is desirable that the lamp tube 10 uses a material that transmits more than 90% of wavelength of 260nm (for example, fused silica) and has a cylindrical shape with a diameter in the range of 10mm to 30mm and a length in the range of 200mm to

2000mm. The lamp tube 10 is manufactured through a process of injecting zirconium iodide or lanthanum iodide of lmg to 5mg per lcm of the lamp tube 10 into the lamp

tube 10, evacuating the lamp tube to 10 Torr to 10 Torr, filling the lamp tube 10 with argon gas to 10 Torr, sealing up the lamp tube 10, putting the lamp tube into an

3 electric field furnace with microwave field strength of minimum 5W/cm and performing melting/evaporation.

[29] The manufactured lamp tube 10 is set in a resonant cavity 40 and the resonant cavity

40 is mounted on a waveguide 20 to which a microwave generator 30 is attached. One side or the overall face of the resonant cavity 40 including the UV lamp tube 10 is covered with a conductive shielding material 80 to prevent electromagnetic wave leakage and transmit only light and sealed with a material (for example, fused silica glass) that transmits UV rays well (refer to FIGS. 2 and 3). The shielding material 80 can use a perforated plate having small holes or a metal mesh and can be a lath having a grating aperture of 1.5mm to 2.5mm or a metal net with 8 to 20 mesh.

[30] In the present invention, various devices, for example, magnetron, klystron and traveling-wave tube, can be selected as the microwave generator 30. The frequency of microwave generated by the microwave generator can be determined as 900MH, 2.45GHz or 5.3GHz according to the type of ion injected into the lamp tube, luminous intensity, the standard of waveguide, etc. In the following embodiment, magnetron with 2.45GHz is selected.

[31] A cooling tool for heat-radiating the microwave generator 30 of the electrodeless UV generating device using microwave according to a preferred embodiment of the present invention can be set outside the microwave generator and have an appropriate structure.

[32] In the present invention, the waveguide guides microwave generated by the microwave generator to a resonant mode and transmits the microwave to the lamp tube.

[33] The length of a single wave in the waveguide 20 is determined according to the width of a magnetic field face and the length is determined for resonance in the microwave generator 30 having a fixed oscillating frequency. Accordingly, a waveguide in an appropriate standard can be applied according to wavelength characteristic of microwave. When it is difficult to manufacture the waveguide such that the length of the waveguide is suited to the resonant mode, a tuner is inserted or an iris 70 is set in the waveguide such that resonance occurs.

[34] The standard of the waveguide 20 is determined such that microwave resonates in

TE0,ln mode. Here, n is a length corresponding to half wavelength of microwave of 2450MHz and corresponds to 7cm to 9cm in the present invention. The waveguide 20 for TEOl 1 resonance has a width in the range of 72mm to 120mm and a height corresponding to half of the width and is manufactured using a conductor.

[35] In the present embodiment, a microwave transmission line uses the waveguide 20

having TMOl mode characteristic and a rectangular cross section of 72mm to 120mm x 30mm to 45mm.

[36] The microwave generated by the microwave generator 30 is injected into the resonant cavity 40 in TMOl 1 mode in which the lamp tube 10 is set and the material filled in the lamp tube 10 resonates to the microwave injected into the resonant cavity 40 and is repeatedly changed between an excited state and a ground state to emit the intrinsic spectrum thereof (UV rays).

[37] FIG. 2 is a perspective view showing a configuration of a lamp including a single lamp tube, a single microwave generator, a waveguide and a resonant cavity partially integrated with the waveguide according to a preferred embodiment of the present invention.

[38] As shown in FIG. 2, the microwave generator 30 is attached to one end of the waveguide 20 and extended to the resonant cavity 40 having the same size as the waveguide (that is, an opening of the waveguide corresponds to the cross section of the resonant cavity). One side or the overall face of the waveguide is opened for light and shielded from electromagnetic waves.

[39] FIG. 3 is a perspective view showing a configuration of a lamp (composite lamp) including a plurality of lamps tubes, two microwave generators and two waveguides according to a preferred embodiment of the present invention.

[40] The lamp has a structure in which the waveguides 20 and the microwave generators

30 are attached to both ends of the lamp tubes 10 respectively included in the resonant cavities 40. Slots (openings) having a length in the range of 50mm to 70mm and a width in the range of 5mm to 10mm are formed at fracture points of electromagnetic wave in the waveguides 20 in which the electromagnetic wave is transmitted in TEOl mode and the ends of the lamp tubes respectively correspond to the slots. In this structure, the two microwave generators 30 (oscillating elements) alternately oscillate electromagnetic waves.

[41] A power supply of the microwave generator uses a method of performing half- wave voltage-multiplication rectification on the secondary side of a high-voltage transformer to supply a minus voltage of several volts to a filament of the magnetron 30, and thus the microwave generator oscillates only for half wavelength of power current. Accordingly, it is possible to apply two microwave voltages to a single lamp by making phases of single-phase voltages respectively applied to the two microwave generators different from each other. Consequently, the lamp can be provided with double power.

[42] It is also possible to attach a single waveguide and a single microwave generator to the lamp. In this case, lamp power will be 50% of the power of the lamp including two waveguides and two microwave generators.

[43] The operation of the UV lamp using microwaves according to the present invention,

constructed as above, is explained.

[44] Microwaves generated from the microwave generator 30 resonate in the waveguide

20 and maintain a specific field distribution. When the material filled in the elec- trodeless lamp 10 arranged along the length direction of the waveguide 20 is excited by the microwaves and has energy of higher than a predetermined level, outer electrons of zirconium or lanthanum filled in the UV lamp 10 escape from the orbit of atom and generate UV rays while returning to the ground state.

[45] Although one side of the waveguide 20 is formed as a UV transmitting face in a preferred embodiment of the present invention, the present invention is not limited thereto and two sides or three sides of the waveguide can be formed as the UV transmitting face, which is included in the present invention.

[46] It is desirable that a support 25 for supporting the UV lamp 10 is made of Teflon that does not absorb microwaves in order to restrain microwave energy consumption, improve insulation characteristic and prevent heat radiation caused by microwaves. Industrial Applicability

[47] The lamp according to the present invention can maintain radiation of light while minimizing loss of microwave energy. In addition, the durability of UV lamp can be remarkably increased to reduce environmental pollution caused by lamp waste.