JP2003317665A - Cold-cathode discharge tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to narrow down a diameter of a sealing tube while securing a luminous efficiency and to lead out a lead wire without a space unduly taken. <P>SOLUTION: It is so constructed that a glass sealing tube 1 with a phosphor 2 coated on the inside face and rare gas sealed inside is formed into a flat tube with a radial-direction cross section almost oval, of which, a short-plate bracket 4 is integrally combined to one sealing end in a form extended toward an axis direction, a pair of outer electrodes 5 are fitted for a whole length along the axis direction on the outside face, and lead wires 7 are connected to the both electrodes 5 at the part of tie bracket 4. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode discharge tube used as a light source such as a backlight of a liquid crystal display. 2. Description of the Related Art In a liquid crystal display of a notebook computer or a small facsimile, a cold cathode discharge tube is widely used as a light source of a backlight or the like. A conventional cold cathode discharge tube of this type has a configuration in which electrodes are disposed at both ends of a glass envelope tube having a straight cylindrical shape, for example, and mercury and a rare gas are sealed therein. In recent years, along with the miniaturization of the apparatus, there has been a strong demand for shortening or reducing the diameter of the discharge tube while securing an effective length. As described above, electrodes are arranged at both ends. In such a configuration, the diameter is inevitably increased by this electrode. Further, since the light emitting arc is generated between the two electrodes, there is also a dissatisfaction point that the effective length becomes shorter than the entire length of the sealing tube by the amount of the electrodes. Particularly, the above-mentioned demand for the reduction of the diameter is extremely strong, and a thickness of 2.0 mm to 1.6 mm is required. However, it is difficult to realize this in the above-described configuration in which the electrodes are arranged at both ends. Furthermore, since the electrodes are arranged in the both ends, the lead wires are led out from both ends, and the whole length of the lead wire becomes unnecessary. Therefore, instead of the above-described internal electrodes, a configuration has been developed in which a pair of external electrodes are provided in a strip shape along the axial direction on the outer surface of the envelope tube so as to face each other. Here, when a voltage is applied to both external electrodes, the gas sealed in the envelope tube is ionized, whereby the envelope tube itself functions as a capacitor, and a high-frequency discharge is performed in the radial direction. However, even with this external electrode structure, the diameter of the envelope tube is limited to 4 mm to 5 mm. If the diameter is less than 4 mm, the luminous efficiency is inferior and a sufficient amount of light cannot be obtained. Further, in the case of the external electrode structure, each lead wire projects outward in the radial direction of the envelope tube. Therefore, even if the diameter of the envelope tube is reduced, the lead wire and An extra space is required for the solder connection portion between the lead wire and the external electrode, which is against the overall miniaturization. SUMMARY OF THE INVENTION Accordingly, the present invention has been developed to solve the above-mentioned disadvantages and disadvantages of the conventional technique. Can be derived without occupying extra space. [0008] In order to solve the above-mentioned problems, a cold cathode discharge tube of the present invention comprises a glass envelope tube in which a phosphor is coated on the inner surface and a rare gas is sealed inside. A cross section in the radial direction is formed into a flat tube having a substantially elliptical shape, and a short plate-shaped bracket is integrally connected to one of the sealing ends so as to extend in the axial direction, on the outer surface of the glass envelope tube, The configuration is characterized in that a pair of external electrodes are provided over the entire length along the axial direction up to the bracket, and lead wires are respectively connected to both electrodes at this bracket portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A glass envelope tube 1 is a straight cylindrical tube having an outer diameter of 4.0 mm or more and having a length of about 100 to 500 mm selected depending on the application, and having a substantially radial cross section. It is configured to be squashed flat so as to have an oval shape. Prior to the crushing operation, the phosphor 2 is applied to the inner surface of the straight cylindrical tube in a film form. This phosphor 2
Dissolve a small amount of a binder such as nitrocellulose in an organic solvent such as butyl acetate or deionized water to make a highly viscous solution, mix a fluorescent material into this solution, and add a small amount of a binder Then, the aperture 3 which is cut off along the axial direction to form a slit-shaped opening is formed. The above-mentioned straight cylindrical tube before applying the phosphor 2 is a so-called thick object having an outer diameter of 4.0 mm or more and an inner diameter of 3.4 mm or more.
In addition to freely controlling the film thickness, the aperture 3 can be formed very easily. The crushing process is performed by placing the straight cylindrical tube in an electric furnace set at a melting temperature and crushing the tube with a predetermined jig. The outer diameter thickness and width are set according to the purpose of use. For example, processing from 3.0 mm to about 1.6 mm is possible. In this crushing process, the straight cylindrical tube is set and arranged so that the aperture 3 is located on one side edge of the crushed glass envelope tube 1 which is a narrow short side surface. Will do. A rare gas such as xenon, a mixture of xenon and neon, and a mixture of xenon and argon are sealed inside the glass envelope tube 1, and both ends of the glass envelope tube 1 are sealed. At this time, a short plate-shaped bracket 4 is integrally connected to the one sealing end in a form extending in the axial direction. Next, on the outer surface of the glass envelope tube 1, a pair of electrodes 5a and 5b are provided in a strip shape over substantially the entire length along the axial direction, and further continue to the bracket 4 at one sealing end. That is, one electrode 5a extends from one wide major surface to a narrow minor surface and one surface of the bracket 4,
The other electrode 5b is arranged only on the other wide long-diameter surface and over the other surface of the bracket 4, and no electrode is provided on the narrow short-diameter side surface on which the aperture 3 is formed. A light-emitting window 6 is formed on one side edge of the tube 1 along the axial direction. The external electrode 5 is provided in a strip shape along the axial direction on the outer surface of the glass envelope tube 1 by applying a conductive silver paint or sticking an aluminum foil cut into a strip with a predetermined width. However, there is also a means for applying a conductive paint to a predetermined outer surface using a squeegee and baking it in an electric furnace by silk screen printing. In the bracket 4 which is one end of the glass envelope tube 1, the respective core wires 8 of the two lead wires 7 are connected to the two electrodes 5a and 5b, respectively, and are fixed to the solder 9, and the two electrodes 5a and 5b are fixed. In order to prevent external discharge from occurring between them, the entire outer surface is covered with an insulating film such as a hessian tube (not shown). Since the bracket 4 has a short plate shape,
First, the work of fixing the solder 9 to the core wire 8 is extremely simple and reliable, and the lead wire 7 and the solder 9 portion protrude greatly from the narrow short-diameter interval D range of the glass envelope tube 1. Not even. Now, in the above-described configuration, the glass envelope tube 1 in which the rare gas is sealed has a flat and sufficiently small thickness width in the short diameter direction. On the inner surface of the narrow minor diameter side surface, an aperture 3 that is formed by cutting a part of the phosphor 2 along the axial direction to form a slit-shaped opening is formed, and a light emitting window 6 is formed on the outer surface. I have. Then, when a voltage is applied to both external electrodes 6,
When the gas sealed in the envelope tube 1 is ionized, high-frequency discharge is performed in the radial direction by passing through the aperture 3 and the light-emitting window 6 and efficiently radiated to the outside as direct light and indirect light. Since this light emission is reflected only on the inner surface and only from the aperture 3 portion, it has directivity, and emits line light toward the outside only in one major diameter direction of the flat envelope tube 1 (illustration shown). (A direction in the example). It should be noted that considerable directivity and luminous efficiency can be obtained only by forming the light emitting window 6 without forming the aperture 3 in the phosphor 2. Also, aperture 3 and / or
Alternatively, a part of the above-mentioned one electrode 5a is covered on the narrow short side surface opposite to the light emitting window 6, so that a part of the emission of the high frequency discharge is reflected by the inner surface of the one electrode 5a. Then, since the light is radiated to the outside as indirect light (arrow B), the luminance further increases. As described above, according to the present invention, by forming the glass envelope tube to be flat, the thickness width in the minor diameter direction for emitting line light to the outside is sufficiently reduced. Therefore, it is extremely effective as a light source such as a backlight for a thin liquid crystal display which is requested, and the thickness width in the short diameter direction can be freely selected at the stage of flattening the glass envelope tube, and furthermore, the glass envelope is sealed. Since the body tube is flat, it is easy to attach external electrodes. Also, a short plate-shaped bracket is integrally connected to one sealing end of the glass sealed tube so as to extend in the axial direction, and a pair of external electrodes are provided extending to respective surfaces of the bracket. First, the connection of the lead wire can be made only at one end of the glass envelope tube, and the solder portion for connecting and fixing the external electrode and the lead wire does not protrude in the radial direction. The length can be kept to a minimum size so that it does not become unnecessarily long as a whole,
In addition, since the inner electrode structure is not used, the ratio of the effective light emission length to the total length of the glass envelope tube is large, and since there is no blackening in both ends, the effective length can be maintained. Can be expected. Although the lead wire does not protrude to the side in the radial direction in spite of the external electrode structure, the advantages of the flat structure of the glass envelope tube can be fully utilized. The cold-cathode discharge tube has many excellent functions and effects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view along the axial direction of a cold cathode discharge tube of the present invention. FIG. 2 is a sectional view taken along a radial direction of the cold cathode discharge tube of the present invention. FIG. 3 is a perspective view of the cold cathode discharge tube of the present invention. [Description of Signs] 1; glass envelope tube, 2; phosphor, 3; aperture, 4;
Bracket, 5; electrode, 6; light emitting window, 7; lead wire,
8; core wire, 9; solder.

Claims (1)

Claims: 1. A glass envelope tube (1) in which a phosphor (2) is coated on an inner surface and a rare gas is sealed therein, is formed into a flat shape having a substantially elliptical cross section in a radial direction. A short plate-shaped bracket (4) is integrally connected to one of the sealing ends in a form extending in the axial direction while being formed on the tube, and is attached to the outer surface of the glass envelope tube (1).
A pair of external electrodes (5) are provided over substantially the entire length along the axial direction up to the bracket (4), and lead wires (7) are connected to both electrodes (5) at the bracket (4). Cold cathode discharge tube.