JP2004335370A - Cold-cathode tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold-cathode tube to materialize a longer life. <P>SOLUTION: A sealed wire material 3 connected to an inner lead 4 and an electrode part 5 while airtightly penetrating inside and outside through the tube end part 1a of a glass tube 1 is formed into two layers. Heat of the electrode part 5 is made to efficiently conduct to an outer lead 6 and a wire 8 in the outside of the tube, by forming the outer layer 31 by a kovar, and by forming the inner layer 32 by a heat conducting wire of copper, beryllium, or aluminum having higher thermal conductivity than the outer layer 31. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cold cathode tube used as a backlight of a liquid crystal display device or the like.
[0002]
[Prior art]
A cold-cathode tube generally used as a backlight of a liquid crystal display device has a sealing wire rod which penetrates the tube end of the glass tube in a gas-tight manner in the vicinity of the electrode, and an inner lead provided at the inner end of the tube. And an electrode part, and an outer lead provided at an outer end of the tube (for example, see Patent Document 1). Such a cold cathode tube has already achieved a long life of 30,000 to 50,000 hours (for example, see Non-Patent Document 1).
[0003]
[Patent Document 1]
JP-A-8-241693 (pages 4 to 5, FIG. 2)
[Non-patent document 1]
Seiichiro Fujioka, "Long Life High Efficiency Cold Cathode Fluorescent Lamp", Monthly Display, August 1999, pp. 82-84.
[Problems to be solved by the invention]
In order to further extend the life of the cold cathode tube as described above, for example, it is conceivable to add a protective film of a phosphor, change an electrode shape, control the amount of mercury, change a glass composition, and the like. However, all of these require considerable capital investment and development investment, and are not practically effective measures.
[0005]
In view of the above conventional problems, an object of the present invention is to provide a cold-cathode tube that can easily achieve a longer life.
[0006]
[Means for Solving the Problems]
The cold-cathode tube of the present invention is provided with a glass tube having a light-emitting layer on the inner surface, and a tube end portion of the glass tube penetrating the inside and outside of the glass tube in an airtight manner. A sealing wire including a high heat conduction wire, an inner lead and an electrode portion provided inside the glass tube and connected to one end of the sealing wire, and the sealing wire outside the glass tube. And an outer lead connected to an external electric wire.
The cold cathode tube configured as described above has a simple structure in which the sealing wire is multi-layered and a heat conducting wire is provided, so that the heat generated in the electrode portion transfers the heat conducting wire of the sealing wire from the inner lead. This leads to efficient conduction to the outer leads, and from the outer leads to the electric wires connected to the outer leads. Therefore, it is possible to sufficiently secure the amount of heat absorption and the amount of heat radiation to the electrode portion, and it is possible to prevent the electrode portion from overheating. As a result, the life of the cold cathode tube can be further extended.
[0007]
In the cold cathode tube, the outer layer of the sealing wire is preferably made of a metal material having a coefficient of thermal expansion equivalent to that of the sealing portion of the glass tube.
In this case, even if thermal expansion or contraction occurs, a gap cannot be formed between the sealing portion and the sealing portion. Therefore, it is possible to prevent a situation in which the sealing ability is impaired and the lighting cannot be performed.
[0008]
Further, in the cold cathode tube, the sealing wire preferably has a diameter of 0.8 mm or more.
In this case, the diameter of the heat conducting wire can be ensured accordingly. In addition, the overall sealing wire contributes to further improvement in thermal conductivity. Therefore, overheating of the electrode portion can be prevented more reliably.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a sectional view of a cold cathode tube according to an embodiment of the present invention. This cold-cathode tube is used for various devices such as a direct-type backlight or a sidelight-type backlight of a liquid crystal display device, a shokasten for viewing an X-ray photograph, a backlighting device for a signboard, and a lighting box for viewing a negative of a photograph. Is done.
In FIG. 1, the cold-cathode tube includes a glass tube 1 having a light-emitting layer 2 on an inner surface, a sealing wire 3 penetrating inside and outside a tube end 1a of the glass tube 1, and a sealing member inside the glass tube 1. An inner lead 4 and an electrode portion 5 are provided at one end of the wire 3, and an outer lead 6 is provided outside the glass tube 1 and is provided at the other end of the sealing wire 3. The outside of the sealing wire 3 is covered with a glass bead 7, whereby the sealing wire 3 is hermetically sealed to the glass tube 1.
[0010]
The outer lead 6, the sealing wire 3, and the inner lead 4 are all cylindrical, and have respective outer diameters of, for example, 0.35 mm, 0.8 mm, and 1.0 mm. The inner lead 4 and the outer lead 6 are made of nickel wire, and are butt-welded (end-face welding) to the left and right ends of the sealing wire 3. The electrode portion 5 is a nickel sleeve, which is externally inserted into the inner lead 4 and welded.
[0011]
FIG. 2 is an enlarged view of the left end side of the cold cathode tube of FIG. 1, showing a state in which the sealing wire 3 is shown in cross section and the outer lead 6 is connected to an external electric wire 8. In addition, although the electric wire 8 is omitted in the middle, it is sufficiently longer than the outer lead 6.
In the figure, the sealing wire 3 has a two-layer structure, and the cylindrical outer layer 31 is made of Kovar (an alloy of nickel, cobalt, and iron) having the same thermal expansion coefficient as that of the glass bead 7. Due to the presence of such an outer layer 31, even if thermal expansion or contraction occurs, there is no gap between the outer layer 31 and the glass bead 7. Therefore, it is possible to prevent a situation in which the sealing ability is impaired and the lighting cannot be performed. On the other hand, the cylindrical inner layer 32 is made of a metal material, such as copper, beryllium, or aluminum, having a higher thermal conductivity than the outer layer 31 and has a role as a “heat conducting wire”.
[0012]
The core wire 8a of the electric wire 8 and the outer lead 6 are connected to each other by a terminal 9 formed by caulking a single metal or alloy having a high thermal conductivity such as copper, beryllium, or aluminum instead of soldering. Thereby, a higher thermal conductivity than soldering can be ensured at the connection portion by the terminal 9. In addition, the connection portion has a higher tensile strength at a high temperature than in the case of soldering. Therefore, even if a tensile force acts on the connection portion that has become hot for some reason, it is possible to prevent the occurrence of connection failure.
[0013]
In the cold-cathode tube configured as described above, heat generated in the electrode portion 5 is conducted from the inner lead 4 to the inner layer 32 of the sealing wire 3. Here, the heat quickly reaches the left end by the inner layer 32 having a high thermal conductivity, and is efficiently conducted to the outer lead 6. Although the thermal conductivity is lower than that of the inner layer 32, the outer layer 31 also contributes to heat transfer from the inner lead 4 to the outer lead 6 by heat conduction. The heat conducted to the outer leads 6 is further conducted to the core wire (copper wire) 8a. At this time, the thermal conductivity from the outer lead 6 to the core wire 8a is ensured by the terminal 9 having a high thermal conductivity. Thus, the heat of the electrode portion 5 is efficiently carried out of the glass tube 1 and is absorbed by the outer lead 6, the terminal 9, and the core wire 8a. The heat absorbed by the core wire 8a is radiated from the entire electric wire 8 via the coating. The electric wire 8 has a good thermal conductivity of the copper core wire 8a, and is sufficiently longer than the outer lead 6, so that its volume and surface area are correspondingly large. Therefore, sufficient heat absorption and heat dissipation can be ensured. The outer leads 6, the terminals 9, and the exposed surfaces of the core wires 8a also radiate heat to the surrounding air.
[0014]
As described above, with a simple structure in which the sealing wire 3 is multi-layered and a heat conduction wire is simply provided, heat transfer to the outside of the tube can be promoted, and heat absorption and heat dissipation by the electric wire can be utilized. In addition, overheating of the electrode unit 5 can be prevented. Therefore, promotion of blackening of the tube end due to overheating can be suppressed. Thereby, the life of the cold cathode fluorescent lamp can be further extended as compared with the conventional product.
[0015]
Further, the diameter of the above-mentioned sealing wire 3 is 0.8 mm (conventionally 0.6 mm), but by this, the diameter of the inner layer 32 as a heat conducting wire can be appropriately secured. Further, the entire sealing wire 3 also contributes to the improvement of the thermal conductivity. Therefore, in combination with the existence of the inner layer 32 as a heat conducting wire, it contributes to the temperature reduction of the electrode portion 5.
[0016]
FIG. 3 shows a conventional cold-cathode tube using a sealing wire made of Kovar having a diameter of 0.6 mm and the cold-cathode tube of the present embodiment in a state in which 12 lamps are installed in a housing of a direct-type backlight. It is a graph of a temperature comparison. The temperature was measured at four positions: near the high-voltage electrode, near the low-voltage electrode, at the center of the lamp, and in the atmosphere in the housing. The left side of the bar graph is the conventional cold cathode tube, and the right side is the cold cathode tube of the present embodiment. As is clear from the graph, the temperature of the cold cathode tube of the present embodiment is lower in the vicinity of the high-voltage side electrode and in the vicinity of the low-voltage side electrode than in the conventional cold cathode tube.
[0017]
FIG. 4 is a graph comparing the temperature, the central luminance of the single tube, and the luminance per power consumption of the conventional cold cathode tube and the cold cathode tube of the present embodiment in a single tube (one lamp). The left side of the bar graph shows the vicinity of the high voltage side electrode, the center shows the vicinity of the low voltage side electrode, and the right side shows the center of the lamp. As is clear from the graph, the cold-cathode tube according to the present embodiment has a lower temperature near the high-voltage side electrode and near the low-voltage side electrode than the conventional cold-cathode tube, and has a higher single-tube central luminance. . On the other hand, the luminance per power consumption hardly changes.
From the above two graphs, it can be seen that the cold cathode tube of the present embodiment can lower the temperature of the electrode portion and is a bright lamp as compared with the conventional cold cathode tube.
[0018]
In the above embodiment, the diameter of the sealing wire 3 is preferably 0.8 mm or more because the larger the diameter, the easier it is to secure the thermal conductivity. However, even if it is less than 0.8 mm (for example, 0.6 mm), a certain effect of preventing overheating of the electrode portion 5 can be obtained due to the presence of the inner layer 32 as a heat conducting wire.
In the above embodiment, the sealing wire 3 has a two-layer structure, but may have a multilayer structure of three or more layers. In this case, the outer layer (outermost layer) is Kovar, and at least one of the inner layers is a heat conducting wire.
In the above embodiment, Kovar is used as the material of the outer layer 31. However, the material is not limited to this, and any metal material having a coefficient of thermal expansion equivalent to that of the glass bead 7, which is the sealing portion of the glass tube 1, may be used. In the case of tungsten glass (BFW), tungsten (W) is preferred.
[0019]
【The invention's effect】
According to the cold cathode tube of the present invention configured as described above, the heat generated in the electrode portion is transferred from the inner lead to the sealing wire by a simple structure in which the sealing wire is provided in multiple layers and the heat conduction wire is provided. The heat is efficiently transmitted to the outer lead through the heat conduction wire, and from the outer lead to the electric wire connected to the outer lead. Therefore, it is possible to sufficiently secure the amount of heat absorption and the amount of heat radiation to the electrode portion, and it is possible to prevent the electrode portion from overheating. As a result, the life of the cold cathode tube can be further extended.
[Brief description of the drawings]
FIG. 1 is a sectional view of a cold cathode tube according to an embodiment of the present invention.
2 is an enlarged view of a left end side of the cold cathode tube of FIG. 1, showing a sealing wire in a cross section, and showing a state where an outer lead is connected to an external electric wire.
FIG. 3 shows a conventional cold-cathode tube using a sealing wire made of Kovar having a diameter of 0.6 mm and the cold-cathode tube of the present embodiment in a state in which 12 lamps are installed in a housing of a direct-type backlight. It is a graph of a temperature comparison.
FIG. 4 is a graph comparing the temperature, the central luminance of a single tube, and the luminance per power consumption of a single tube (one lamp) with a conventional cold cathode tube and the cold cathode tube of the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Glass tube 1a Tube end part 2 Light emitting layer 3 Sealing wire 4 Inner lead 5 Electrode part 6 Outer lead 7 Glass bead (sealing part)
8 Electric wire 31 Outer layer 32 Inner layer (heat conduction wire)

Claims (3)

A glass tube having a light-emitting layer on the inner surface,
A sealing wire including a heat conducting wire having a higher thermal conductivity than the outer layer in the inner layer, which is provided in a manner that the tube end of the glass tube penetrates the inside and outside of the tube in an airtight manner,
An inner lead and an electrode portion which are provided inside the glass tube and are connected to one end of the sealing wire,
An outer lead, which is provided outside the glass tube and is connected to the other end of the sealing wire and connected to an external electric wire, is provided. The cold cathode tube according to claim 1, wherein the outer layer of the sealing wire is made of a metal material having a coefficient of thermal expansion equivalent to that of the sealing portion of the glass tube. The cold cathode tube according to claim 1, wherein the sealing wire has a diameter of 0.8 mm or more.

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