ES2402160A2 - Cold cathode fluorescent lamp for illumination - Google Patents

Abstract

Provided is a cold cathode fluorescent lamp (CCFL) that can be used as an illumination light source. The CCFL includes a cold cathode electrode disposed at each end of a glass tube, a fluorescent layer being formed on an inner surface of the glass tube 17. Each of the cold cathode electrodes includes a base metal 7 connected to the front ends of lead wires 9a, 9b for connection with a power source. A helical wire coil 3 is formed by helically winding a tungsten or tungsten-alloy wire around a cup shape (Fig. 1), the helical wire coil 3 being connected to the base metal 7 in a manner such that the helical wire coil 3 is erected in a length direction of the glass tube. An emitter coated coil is inserted in the helical wire coil about the end of the coil and is coated with an emitter material such as cesium oxide, barium oxide, strontium calcium oxide, carbon nanotubes etc for inducing emission of electrons.

Description

COLD CATHODE FLUORESCENT LAMP FOR LIGHTING

CROSS REFERENCE TO RELATED APPLICATIONS

This United States non-provisional patent application claims the

5 priority, according to 35 U.S.C. § 119, of the Korean patent application number 10-2011-0069236, filed on July 13, 2011, the content of which is incorporated herein in its entirety by reference.

BACKGROUND

10 The content of the present specification refers to a cold cathode fluorescent lamp (CCFL) for lighting and, more specifically, to a long-lasting and high efficiency CCFL which has a better tube current, optical efficiency, luminosity and duration for use as a light source of illumination, in addition to its conventional use as a backlight for

15 a liquid crystal display, a facsimile scanning light source, a copier's eraser lamp, etc.

In the related art, cold cathode fluorescent lamps (CCFL) are used as light sources such as backlights of liquid crystal displays, facsimile scan light sources and eraser lamps 20 of copiers, it being possible to achieve levels of brightness required in such devices by applying in the CCFL a tube current of only about 4 to 4 mA. Such a CCFL includes cup-shaped electrodes disposed at both ends of a glass tube and a fluorescent layer formed by applying a fluorescent material 25 on the inner surface of the glass tube. The glass tube is filled with a rare gas, such as neon gas, argon gas and xenon gas, together with a small amount of mercury, and the glass tube is sealed. If a high voltage is applied to the cup-shaped electrodes arranged on both sides of the glass tube, a small number of electrons ionize the rare gas 30 sealed in the glass tube and secondary electrons are emitted from the

cup-shaped electrodes as the rare ionized gas collides with the cup-shaped electrodes (this is called light discharge). The secondary electrons collide with the mercury and, consequently, the mercury emits ultraviolet rays towards the fluorescent layer formed on the inner surface of the glass tube. In this way, the fluorescent material of the fluorescent layer emits visible light. At that time, a tube current of approximately 4 mA to 5 mA circulates through the glass tube. However, a tube current of 10 mA or greater is necessary to increase the brightness of the CCFL to a level necessary for illumination.

In the related technique, the electrodes of a CCFL are cup-shaped to increase the inner surfaces of the electrodes necessary for the emission of electrons. In addition, such electrodes are mainly formed by nickel (Ni), since nickel (Ni) has a relatively low melting point and can be easily machined in the desired shape, such as a cup shape. However, nickel (Ni) or nickel alloys have a high working function and a high spray coefficient. For this reason, cup-shaped electrodes are made of an Nb-Ni alloy or a Y-Ni alloy to increase the spray resistance of cup-shaped electrodes. However, the duration of such cup-shaped electrodes is reduced, due to the spraying that occurs if a tube current of 10 mA or greater is applied to the electrodes. Spraying causes excessive heat generation in the electrodes and greatly reduces light efficiency. In addition, because a spray layer is formed on the inner surface of the glass tube due to spraying, it is difficult to achieve a level of brightness necessary for illumination if the electrodes are sprayed. That is, nickel (Ni) or nickel alloy electrodes are not suitable for a CCFL having a tube current of 5 mA or greater and, therefore, it is difficult to use a CCFL that includes nickel or electrode electrodes. cup-shaped nickel alloy as a source of lighting light.

In addition, because electrodes are preferred in the related art

Having a large surface area, the size of the electrodes increases excessively. The large electrodes take up a lot of space in the glass tubes and, therefore, the space for the positive columns is reduced, reducing light efficiency and energy efficiency. Therefore, it is difficult to use CCFL as illumination light sources.

SUMMARY

The objective of the present invention is to overcome the aforementioned limitations that occur when using a cold cathode fluorescent lamp (CCFL) as a source of illumination light. For this reason, an objective of the present invention is to provide a lighting CCFL that includes cold cathode electrodes that can be easily shaped into a cup using tungsten or tungsten alloy with a reduced spray coefficient and a function of reduced work

Another objective of the present invention is to disclose a lighting CCFL that includes short electrodes but capable of emitting very bright light.

Another objective of the present invention is to provide a lighting CCFL in which it is possible to easily install two conductor cables for compatibility with a socket for a conventional hot cathode fluorescent lamp.

Another objective of the present invention is to disclose a lighting CCFL that requires a reduced discharge maintenance voltage, so that it is possible to increase the duration of the electrodes.

Another objective of the present invention is to disclose a lighting CCFL having a structure in which it is possible to carry out a coating with an emitter and easily retain it.

Embodiments of the present invention disclose a CCFL for illumination, including the CCFL cold cathode electrodes, in which each of the cold cathode electrodes includes: a base metal connected to front ends of conductive cables for connection to a power supply; a coil of helical cable formed by helically winding a tungsten or tungsten alloy cable around a cup shape, the coil of coil cable being connected to the base metal so that the coil of coil cable is held up in the direction of the length of the glass tube; and a coil coated with emitter introduced into the coil of helical cable and coated with an emitter to induce the emission of electrons.

In some embodiments, the lead wires connected to the base metal can be two and can be electrically disconnected from each other in the base metal.

In other embodiments, the emitter-coated coil may be formed by forming a thinner tungsten thinner cable than the helical cable coil and by coating the thin wire with at least one emitter selected from cesium oxide, barium oxide, strontium calcium oxide , yttrium oxide and magnesium oxide.

In other additional embodiments, the emitter-coated coil may be formed by winding a thinner tungsten thinner cable than the helical cable coil in a thin coil, winding the thin coil in a helical shape and coating the thin coil with at least one emitter selected from cesium oxide, barium oxide, calcium strontium oxide, yttrium oxide and magnesium oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to improve the understanding of the invention and are incorporated herein and constitute part thereof. The drawings show illustrative embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a perspective view showing a coil coated with emitter according to the present invention;

FIG. 2 is an exploded perspective view showing a cold cathode electrode according to the present invention;

FIG. 3 is a perspective view showing the cold cathode electrode according to the present invention;

FIG. 4 is a partial perspective view showing the cold cathode electrode sealed in a glass tube according to the present invention; Y

FIG. 5 is a partial section showing a cold cathode fluorescent lamp (CCFL) for lighting according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Illustrative embodiments will be described in more detail below, with reference to the accompanying drawings.

Referring to FIGS. 4 and 5, a cold cathode fluorescent lamp (CCFL) is shown for use as a lighting lamp. The CCFL includes a pair of cold cathode electrodes 1 disposed at both ends of a glass tube 17 and the inner surface of the glass tube 17 is coated with a fluorescent layer. The cold cathode electrodes 1 have a reduced spray coefficient, a reduced activation voltage and a reduced discharge maintenance voltage, but can emit a large number of electrons. In the CCFL, the fluorescent layer is formed on the inner surface of the glass tube 17 using a fluorescent material and the cold cathode electrodes 1 are arranged at both ends of the glass tube 17 facing each other. If a high voltage is alternatively applied to the cold cathode electrodes 1, electrons are emitted from the cold cathode electrodes 1. The cold cathode electrodes 1 of the present invention have a satisfactory spray resistance, a reduced discharge activation voltage and a reduced discharge maintenance voltage, so that the tube current can be increased to 10 mA or more to emit A lot of electrons for lighting purposes. Therefore, the CCFL of the present invention can be used as a source of illumination light.

Next, an emitter-coated coil 21 that constitutes a characteristic element of the present invention will be described, referring to FIG. one.

As shown in FIG. 1, the emitter-coated coil 21 of the present invention has a structure suitable for applying a powder emitter 5 on the emitter-coated coil 21 and retaining the emitter 5 applied. According to an illustrative embodiment shown in FIG. 1, a thin cable coil 19 is formed by a thin tungsten cable (for example, with a diameter of 0.02 mm to 0.05 mm) that is thinner than a coil 3 of helical cable (see FIG. 2 ) arranged around the coil 21 coated with emitter, then the coil 19 of thin wire is wound in a helical shape to form the coil 21 coated with emitter. The emitter 5 includes at least cesium oxide, barium oxide, strontium calcium oxide, yttrium oxide or magnesium oxide in powder form. In the present invention, the emitter 5 is made of a material that has a reduced working function to emit electrons easily. If a material has a reduced work function, the material can emit electrons easily. That is, the material can be easily downloaded. It is possible to use carbon nanotubes to easily apply the emitter 5. In this case, it is possible to prepare a coating material by dispersing the carbon nanotubes in water and isopropyl alcohol, while facilitating the dispersion of the carbon nanotubes with dodecylbenzenesulfonate. sodium (a surfactant). Thanks to the aforementioned structure of the emitter-coated coil 21, it is possible to increase the total length of the emitter-coated coil 21 compared to the size of the emitter-coated coil 21 and, therefore, it is possible to emit electrons in a small space to cause a tube current of 10 mA or higher.

In addition, it is possible to apply the emitter 5 easily and densely in spaces between turns close to each other of a thin wire of the thin wire coil 19. Also, the emitter 5 can be stably retained in the thin wire coil 19 for a prolonged period of time, therefore it is possible to increase the duration of the cold cathode electrodes 1.

The emitter-coated coil 21 may be formed by winding a thin linear tungsten or tungsten alloy cable (for example, with a diameter of 0.02 mm to 0.05 mm) thinner than the coil 3 of the helical cable, in instead of forming the coil 21 coated with emitter using the thin cable coil 19. The thin wire may be coated with an emitter that includes at least cesium oxide, barium oxide, strontium calcium oxide, yttrium oxide or magnesium oxide. However, in this case, it may be difficult to coat the thin cable with the transmitter and that the transmitter cannot be retained for a prolonged period of time compared to the case of using the thin cable coil 19.

FIGS. 2 and 3 show coil coil 3, which is another characteristic element of the present invention. The coil 3 of helical cable is formed by helically winding a tungsten or tungsten alloy cable (with a diameter of 0.2 mm to 0.5 mm) around a cup shape. The coil 3 of helical cable is connected to a base metal 7 so that the coil 3 of the helical cable is raised in the direction of the length of the glass tube 17. In each of the cold cathode electrodes 1 of the present invention, the base metal 7 is connected to conductive cables 9a and 9b connected to a power source. Dumet cables or Kovar cables are used as conductive cables 9a and 9b. The conductive cables 9a and 9b are perpendicular to the base metal 7. The coil 3 of the helical cable is erected in the base metal 7 in a direction opposite to the conductive cables 9a and 9b. In the present invention, thanks to the base metal 7, it is possible to use two conductor cables. Therefore, it is possible to use a conventional fluorescent lamp socket with the CCFL of the present invention. Both ends of the coil 3 of the helical cable are firmly fixed to the base metal 7, so that the coil 3 of the helical cable can be raised in the direction of the length of the glass tube 17 and the conductor cables 9a and 9b (cables Dumet or Kovar) can easily be connected to coil coil 3 through the base metal 7. Therefore, the base metal 7 is made of a material that can be welded to the coil 3 of the helical cable and to the conductor cables 9a and 9b. The base metal 7 may have a bar or bead shape. If the base metal 7 is made of tungsten or a tungsten alloy, it may not be possible to weld the base metal 7 to the coil 3 of helical cable made of tungsten or tungsten alloy, due to the high point of tungsten fusion. Therefore, the base metal 7 may be nickel or a nickel alloy. The coil 3 of the helical cable is electrically connected to one side of the base metal 7 by spot welding. The two conductor cables 9a and 9b are connected to the base metal 7 in a state in which the conductor cables 9a and 9b are electrically disconnected from each other. The conductive cables 9a and 9b extend in a direction opposite to the coil 3 of the helical cable and are connected to an external power supply.

As shown in FIG. 2, both ends of the coil cable 3 can extend towards the base metal 7 so that one or both ends of the coil 3 coil extend from the upper side of the coil 3 coil to the metal 7 of base, through the coil 3 of helical cable, and the coil 21 coated with emitter can be introduced in the coil 3 of helical cable, around the end of the coil 3 of helical cable. In this case, it is possible that the coil 21 coated with emitter is not separated from the coil 3 of the helical cable. One end of the coil 21 coated with emitter may be welded to the base metal 7 or not welded to the base metal 7. Referring to FIGS. 2 and 3, a coil 21 coated with emitter is arranged in the coil 3 of helical cable. However, it is possible to arrange another coil coated with emitter in the coil 21 coated with emitter, or to arrange two or more coils coated with emitter in the coil 3 of helical cable very close to each other. Therefore, the cold cathode electrodes 1 can emit a large number of electrons even if a reduced voltage is applied to the cold cathode electrodes 1 and, thus, it is possible to achieve the level of luminosity necessary for lighting without reducing the Size of a positive column.

As shown in FIGS. 3 and 4, the conductive cables 9a and 9b are connected to a glass foot 11 by a method of glass bead formation, and the glass foot 11 is connected to the glass tube 17. In the method of glass bead formation, the conductive cables 9a and 9b of the cold cathode electrode 1 and a gas injection conduit 15 are inserted into the glass foot 11 and an upper part of the glass foot 11 is fused to fix the conductive cables 9a and 9b and the glass injection conduit 15. After carrying out the method of forming glass beads, the glass beads remain in connected parts. In this way, it is possible to easily seal the spaces between the glass tube 17 and the conductive cables 9a and 9b of the cold cathode electrode 1.

It is difficult to produce a cup-shaped electrode using tungsten or a tungsten alloy, since tungsten or tungsten alloys cannot be easily machined in the desired shapes through a plastic forming process. However, it is easy to produce tungsten or tungsten alloy cables through a stretching process and wind the tungsten or tungsten alloy cables into coils. It is possible to produce a cup-shaped electrode that has a reduced spray coefficient and a reduced working function by stacking such coils with different diameters in multiple stages. The present invention has been proposed based on this aspect.

That is, according to the present invention, because the coil 3 of the helical cable is made of tungsten or tungsten alloy with a reduced spray coefficient and a reduced working function, it is possible to increase the duration of the CCFL and it is possible start a discharge with a reduced activation voltage. In addition, because the coil 21 coated with emitter is arranged in the coil 3 of the helical cable, it is possible to maintain a level of discharge (electron emission) necessary for lighting (10 mA or more) with a reduced voltage in a state stationary after initial activation.

As shown in FIGS. 4 and 5, if a voltage is applied alternatively to the cold cathode electrodes 1 of the CCFL, electrons are emitted from the cold cathode electrodes 1, by an electric field formed by the voltage. That is, because electrons are emitted through an electric field, no heat is necessary for the emission of electrons. Initially, a small amount of electrons that remain in the glass tube 17 collide with the cold cathode electrodes 1 and, thus, electrons are emitted from the cold cathode electrodes 1. The electrons emitted from the cold cathode electrodes 1 collide again with the cold cathode electrodes 1. In this way, the discharge (electron emission) continues. During the discharge, the electrons that move towards an anode collide with the mercury disposed in the glass tube 17 and, thus, ultraviolet rays are emitted from the mercury to the fluorescent layer of the glass tube 17. Next, the fluorescent layer is optically excited and emits visible light. Because electrons can be easily emitted in the CCFL of the present invention, the CCFL can have high brightness and long duration. In the present invention, the cold cathode electrodes 1 are made of tungsten (W), having a high melting point compared to the working function. Because tungsten (W) is difficult to machine, cold cathode electrodes 1 are formed by stretching tungsten wires and winding tungsten wires into helical coils. Electrons can be emitted from helical coils. As described above, if an electrode is constituted by a densely wound helical tungsten coil having a sufficient diameter and by an emitter-coated coil disposed in the coil, the electrode may have an electron emission surface more larger than that of a corresponding cup-shaped electrode. In a lighting lamp, an energy of 10 eV or higher is necessary for electrons to collide with an electrode. Therefore, it may be necessary to form the electrodes of a lighting CCFL using tungsten (W). In addition, the electrode may be shaped in a helical manner to increase the electrode emission surface of the electrode. However, even if the tungsten electrode has a helical shape, the electrode may need a high discharge maintenance voltage and emit a small amount of electrons. Therefore, according to the present invention, a coil of coil cable is made of tungsten and a coil coated with emitter is arranged in the coil of coil cable, so that it is possible to achieve a tube current necessary for lighting of 10 mA or higher, while maintaining the discharge maintenance voltage at a reduced level.

As described above, according to the present invention, because the CCFL electrodes are made of tungsten or a tungsten alloy and have a double coil structure, the electrodes can have a high spray resistance even when The tube current is 10 mA or higher, and the CCFL can emit very bright light thanks to the reduced tungsten work function. In addition, the electrodes can emit a sufficient amount of electrons even if the electrodes have short lengths. Also, because the base metal is disposed between the coil of helical cable and the conductor cables, the conductor cables can be easily installed for compatibility with a socket for a conventional hot cathode fluorescent lamp. In addition, because the emitter-coated coil is used as an internal coil, it is possible to emit secondary electrons with a reduced voltage and, therefore, it is possible to reduce the discharge maintenance voltage to increase the duration of the electrodes. In addition, because the inner coil is formed by winding a thin tungsten coil in a helical shape and coating the thin coil wound helically with an emitter, it is possible to easily carry out the coating with the emitter and hold it stably in The inner coil.

Claims (4)

1. Cold cathode fluorescent lamp (CCFL) for lighting comprising cold cathode electrodes arranged at both ends of a glass tube, a fluorescent layer being formed on the inner surface of the glass tube, in which each of the cold cathode electrodes comprises: a base metal connected to front ends of conductive cables for connection to a power source; a coil of helical cable formed by helically winding a tungsten or tungsten alloy cable around a cup shape, the coil of coil cable being connected to the base metal so that the coil of coil cable is held up in the direction of the length of the glass tube; Y a coil coated with emitter introduced into the coil of helical cable and coated with an emitter to induce the emission of electrons.

2.

 CCFL according to claim 1, wherein the conductive cables connected to the base metal are two and electrically disconnected from each other in the base metal.

3.

 CCFL according to claim 1, wherein both ends of the helical cable coil extend towards the base metal such that one end of both ends of the helical cable coil extends from an upper side of the helical cable coil towards the base metal, through the coil of coil cable,

wherein the coil coated with emitter is arranged around the end of the coil of coil cable.

Four.

 CCFL according to claim 1, wherein the emitter-coated coil is formed by winding a thinner tungsten cable that is thinner than

the coil of helical cable in a thin coil, winding the thin coil in a helical shape and coating the thin coil with at least one emitter selected from cesium oxide, barium oxide, strontium calcium oxide, yttrium oxide and magnesium oxide . Fig. 1 Fig 2 Fig. 3 Fig. 4 Fig. 5