JP2006085983A - External electrode discharge lamp and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an external electrode discharge lamp without thermal distortion of ends of a glass vessel covered with an external electrode. <P>SOLUTION: The discharge lamp comprises a tubular glass vessel 2 with a phosphor layer 5 on its inner wall 4, enclosing gas including at least mercury in the inside space 6, and external electrodes 3 formed on both ends in the longer direction of the glass vessel to cover the outer surfaces and end surfaces of the both ends. The both ends of the glass tube 2 are air-proofed without any sealing components. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an external electrode type discharge lamp in which electrodes are provided at both ends of a glass tube and a method for manufacturing the same.

  With the widespread use of liquid crystal televisions, the demand for high-brightness liquid crystal panels continues to increase. In a liquid crystal panel that requires high luminance, a direct type backlight unit using an external electrode type discharge lamp as a light source is often used for the following reasons. That is, when a cold cathode discharge lamp that is generalized in the same manner as the external electrode type discharge lamp is used as the light source for the backlight, the same number of ballast capacitors as the number of lamps are required. Therefore, when the number of lamps increases with the increase in brightness, the number of ballast capacitors also increases accordingly, resulting in an increase in size and cost of the power supply unit. On the other hand, in the external electrode type discharge lamp, the glass tube itself functions as a ballast capacitor (capacitance). Therefore, theoretically, a ballast capacitor is unnecessary, and it is not necessary to prepare at least as many ballast capacitors as the number of lamps.

  Next, an outline of an external electrode type discharge lamp using a mixed gas containing mercury as a discharge medium will be described. This type of external electrode type discharge lamp has a glass container in which a phosphor layer is formed on the inner surface and both ends are hermetically sealed with bead glass, and two external electrodes provided on the outer surface of the glass container. . A mixed gas containing mercury is sealed in the internal space of the glass container, and when an AC voltage is applied to the external electrode, dielectric barrier discharge using the wall surface of the glass container as a dielectric occurs. Then, the phosphor layer formed on the inner surface of the glass container is excited by ultraviolet rays generated by the dielectric barrier discharge, and light is generated. Here, a stable discharge is realized when the distance between the two external electrodes is as far as possible. Therefore, conventionally, an external electrode has been formed by winding a strip-shaped metal foil around the outer peripheral surface of both ends of the glass container. In other words, only a part of the outer peripheral surface of the glass container was covered with the external electrode, and both end surfaces were exposed.

  In the conventional external electrode type discharge lamp having the above-described structure, light leaks from both end faces of the glass container not covered with the external electrode, or the adhesion between the external electrode and the glass container is weakened due to deterioration over time. There was a problem that the electrode peeled off.

  Therefore, Patent Document 1 discloses a technique for forming an external electrode by solder dipping. Specifically, both ends of a glass container filled with a mixed gas as a discharge medium are immersed in a molten solder tank in which an ultrasonic vibrator is installed, and plating is performed while applying ultrasonic vibration to the molten solder. A technique for forming external electrodes at both ends of a container is disclosed. According to this technique, external electrodes are also formed on both end faces of the glass container. FIG. 4 shows a cross-sectional view of an external electrode type discharge lamp 31 in which an external electrode 30 is formed by the method described in Patent Document 1. In the figure, reference numeral 33 denotes a glass container, reference numeral 34 denotes a bead glass that hermetically seals both ends of the glass container 33, and reference numeral 35 denotes a phosphor layer.

As described above, if the external electrode is formed by plating, solder dip, or the like, both end surfaces of the glass container are covered with the external electrode, so that light leakage from the end surface is prevented. Also, inconveniences such as peeling of the external electrode are avoided.
JP 2004-146351 A

  However, the conventional external electrode type discharge lamp has the following problems. That is, when the lamp is lit, current flows through the end of the glass container covered with the external electrode to generate heat, and the generated heat propagates through the wall surface of the glass container to the bead glass. At this time, the bead glass is only partially welded to the inner surface of the glass container, and the bead glass is not materially integrated with the glass container. Therefore, when thermal distortion occurs at the end of the glass container that is sealed with bead glass, a crack occurs in the glass container. In addition, the residual stress at the time of sealing this edge part with bead glass exists in the edge part of a glass container, and this residual stress also contributes to a crack generation. As shown in FIG. 5, when the external electrode 30 that covers up to the end surface of the glass container 33 is formed by plating, solder dip, or the like, the external electrode 30 is positioned very close to the bead glass 34. In addition, a current also flows in the bead glass 34 itself, and the bead glass 34 itself generates heat. Therefore, the thermal strain is further increased, and the occurrence rate of cracks 36 is increased.

  An object of the present invention is to solve the above-mentioned problems by hermetically sealing both ends of a glass container constituting an external electrode type discharge lamp without using bead glass.

  In the external electrode type discharge lamp of the present invention, both ends of the glass container provided with the external electrode are hermetically sealed without using any sealing member. Therefore, even if current flows through the end portion of the glass container covered with the external electrode and heat is generated, thermal distortion does not occur. In particular, when the end surface of a glass container whose end is sealed with bead glass is covered with an external electrode, the bead glass itself generates heat, and a large thermal strain is generated at the end of the glass container. However, in the external electrode type discharge lamp of the present invention in which the end portion of the glass container is not sealed with a sealing member such as bead glass, there is no room for occurrence of a phenomenon such as heat generation of the bead glass.

  According to the manufacturing method of the external electrode type discharge lamp of the present invention, the external electrode type discharge lamp of the present invention having the above advantages can be mass-produced at low cost.

  In the external electrode type discharge lamp of the present invention and the external electrode type discharge lamp manufactured by the manufacturing method of the present invention, thermal distortion occurs at the end of the glass container covered with the external electrode, and this is caused by the thermal distortion. There is no inconvenience that the glass container is cracked.

  Hereinafter, an example of an embodiment of the external electrode type discharge lamp of the present invention will be described. As shown in FIG. 1, an external electrode type discharge lamp 1 of this example applies a voltage to a tubular glass container 2, external electrodes 3 formed at both longitudinal ends of the glass container 2, and the external electrode 3. And at least lead wires (not shown).

  A phosphor layer 5 is formed on the inner surface 4 of the glass container 2 along the longitudinal direction of the glass container 5. The material for forming the phosphor layer 5 (phosphor) can be arbitrarily selected from known or novel phosphors. For example, among the phosphors preferably used in fluorescent lamps utilizing mercury discharge, such as Y2O3: Eu which is a red phosphor, LaPO3: Ce, Tb which is a green phosphor, and BaMgAl10O17: Eu which is a blue phosphor. From this, a suitable phosphor can be selected. Moreover, the fluorescent substance layer 5 may consist of a kind of fluorescent substance, or may consist of 2 or more types of mixed fluorescent substance.

  A mixed gas containing at least mercury is sealed in the internal space 6 of the glass container 2 as a discharge medium. The interior space 6 is depressurized to a predetermined pressure. The gas species constituting the mixed gas can be arbitrarily selected. For example, one or more suitable gases can be selected from neon gas, argon gas, krypton gas, and the like.

  Both ends of the glass container 2 are hermetically sealed by a diameter reducing process in which the diameter is reduced and the glass tube is heated and softened while being melted. In other words, the bead glass is hermetically sealed without using any sealing member. The diameter reduction processing will be described in detail later.

  The external electrode 3 is composed of a conductor layer formed so as to cover the outer peripheral surface and end surfaces of both ends of the glass container 2. This conductor layer is formed on both ends of the glass container 2 using a plating method or a solder dipping method. The conductive material forming the external electrode 3 (conductor layer) can be arbitrarily selected from known or novel conductive materials. In addition, the external electrode 3 can be formed of a kind of conductive material, or the external electrode 3 can be formed of an alloy made of two or more kinds of conductive materials.

  In addition, the bulging part 7 which arose by the diameter reduction process at the time of manufacture exists in the both end surfaces of the glass container 2 shown in FIG. The bulging portion 7 can be recessed inside the glass container 2 as shown in FIG. Moreover, the bulging part 7 can be removed and the end surface of the glass container 2 can also be finished flat. However, even if the end surface of the glass container 2 is bulged, recessed, or flat, there is no substantial influence on the operational effects of the present invention. That is, the present invention is essentially characterized in that both ends of the glass container 2 are hermetically sealed without using bead glass or other sealing members.

The external electrode type discharge lamp 1 shown in FIG. 1 can be manufactured by the following process, for example.
(1) As shown in FIG. 3A, a phosphor layer 21 having a predetermined length L is formed on the inner surface of a glass tube 20 that is longer than the glass container 2 shown in FIG. The method for forming the phosphor layer 21 is the same as that of the prior art. In the following description, the portion where the phosphor layer 5 is formed is referred to as “phosphor layer forming portion 22” as necessary.
(2) As shown in FIG. 3B, the glass tube 20 is subjected to diameter reduction processing at a portion outside the longitudinal end of the phosphor layer forming portion 22, and the glass tube 20 is melted and melted. The part is hermetically sealed. In FIG. 3B, among the longitudinal ends of the glass tube 20, the end portion on the lower side in the drawing is hermetically sealed. In the following description, the end of the glass tube 20 hermetically sealed by this process is referred to as “non-exhaust side end” as necessary. Further, the end opposite to the non-exhaust side end is referred to as “exhaust side end” as necessary. In the diameter reduction process, one or both chucks are moved away from each other while heating and softening the desired position while holding both outer sides of the desired position of the glass tube with a chuck or the like. Means a process of reducing the diameter of the heated portion or finally fusing it. When reducing the diameter, the glass tube may be rotated in the circumferential direction as necessary.
(3) As shown in FIG. 3C, the diameter of the glass tube 20 is reduced by reducing the diameter of the glass tube 20 at a portion outside the end of the phosphor layer forming portion 21 on the exhaust side end side. A diameter portion 23 is formed.
(4) As shown in FIG. 3D, mercury pellets 24 are introduced into the glass tube 20 from the exhaust side end of the glass tube 20. The mercury pellet 24 is obtained by sandwiching mercury inside a folded metal plate. In order to prevent the charged mercury pellet 24 from passing through the reduced diameter portion 23 and entering the phosphor layer forming portion 22, in the step (3), the glass tube is made to the extent that the mercury pellet 24 cannot pass. Keep the diameter of 20 down.
(5) As shown in FIG. 3E, the exhaust gas side end of the glass tube 20 is deformed to confine the mercury pellet 24 in the glass tube 20. Here, it is necessary and sufficient that the mercury pellet 24 does not come out of the glass tube 20. Therefore, the shape of the exhaust-side end portion after deformation may be any shape. Thereafter, the air in the phosphor layer forming part 22 is exhausted from the exhaust side end of the glass tube 20, and the inside of the phosphor layer forming part 22 is depressurized to a predetermined pressure. Subsequently, a neon / argon mixed gas containing neon as a main component is filled into the phosphor layer forming portion 22 from the exhaust side end of the glass tube 20.
(7) As shown in FIG. 3F, the mercury pellet 24 is heated by high frequency induction from the outside of the glass tube 20 to deposit mercury, and the mercury is filled into the phosphor layer forming portion 22.
(8) As shown in FIG. 3G, the reduced diameter portion 23 of the glass tube 20 is subjected to diameter reduction processing to melt the glass tube 20 and the melted end portion is hermetically sealed. Through the steps so far, the glass container 2 shown in FIG. 1 is formed.
(9) As shown in FIG. 3H, the conductor layer 25 is formed by attaching a molten conductive material to both ends of the glass container 2 by a plating method or a solder dipping method. By this process, the external electrode 3 shown in FIG. 1 is formed. Thereafter, the external electrode type discharge lamp 1 shown in FIG. 1 is completed through a step of connecting a lead wire for applying a voltage to the external electrode 3.

It is sectional drawing which shows an example of embodiment of the external electrode type discharge lamp of this invention. It is a partial expanded sectional view which shows the other example of embodiment of the external electrode type discharge lamp of this invention. It is explanatory drawing which shows 1 process of the manufacturing method of the external electrode type discharge lamp of this invention. It is explanatory drawing which shows the process following the process shown to FIG. 3A. It is explanatory drawing which shows the process following the process shown to FIG. 3B. It is explanatory drawing which shows the process following the process shown to FIG. 3D. It is explanatory drawing which shows the process following the process shown to FIG. 3D. It is explanatory drawing which shows the process following the process shown to FIG. 3E. It is explanatory drawing which shows the process following the process shown to FIG. 3F. It is explanatory drawing which shows the process following the process shown to FIG. 3G. It is sectional drawing which shows an example of the conventional external electrode type discharge lamp. It is a partial expanded sectional view which shows the edge part of the conventional external electrode type discharge lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 External electrode type discharge lamp 2 Glass container 3 External electrode 4 Inner surface 5 Phosphor layer 6 Internal space 7 A bulging part 20 Glass tube 21 Phosphor layer 22 Phosphor layer formation part 23 Reduced diameter part 24 Mercury pellet 25 Conductor layer

Claims (5)

  An external electrode type having a tubular glass container in which a phosphor layer is formed on the inner surface and a gas containing at least mercury is sealed in the inner space, and external electrodes provided on outer surfaces at both longitudinal ends of the glass container An external electrode type discharge lamp, wherein both ends of the glass tube are hermetically sealed without using any sealing member.   2. The external electrode type discharge lamp according to claim 1, wherein an outer peripheral surface and both end surfaces of both end portions in the longitudinal direction of the glass container are covered with the external electrode.   The external electrode type discharge lamp according to claim 1 or 2, wherein the external electrode is a conductor layer formed by adhering a molten conductive material to an outer surface of the glass container. External electrode type having a tubular glass container in which a phosphor layer is formed on the inner surface and a gas containing at least mercury is sealed in the inner space, and external electrodes provided on outer surfaces at both ends in the longitudinal direction of the glass container A method for manufacturing a discharge lamp, comprising:
While heating the desired position of the glass tube, the diameter of the heated portion is gradually reduced by pulling both outer sides of the heated portion relatively away from each other, and finally blown out, thereby fusing A method for manufacturing an external electrode type discharge lamp, comprising a step of hermetically sealing an end of a glass tube. A method of manufacturing an external electrode type discharge lamp according to claim 4,
Forming a phosphor layer on the inner surface of the glass tube;
A step of forming a reduced diameter portion by sealing one end of the glass tube in an airtight manner and then reducing the diameter of the glass tube at a desired position between the other end of the glass tube and the end of the phosphor layer. When,
Introducing mercury pellets having a size that cannot pass through the reduced diameter portion from the other end of the unsealed glass tube into the glass tube;
A method of manufacturing an external electrode type discharge lamp, further comprising a step of heating the mercury pellet from the outside of the glass tube and filling the glass tube with mercury.

Images