JP2007179835A - Cold cathode discharge lamp and backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold cathode discharge lamp and a backlight unit which is capable of having greater safety by including a structure for stopping a flowing current when an excessive current flows. <P>SOLUTION: The cold cathode discharge lamp includes: an electrode consisting of an electrode body and a lead 24; a glass bulb 21 which seals the lead 24 at an end portion with the electrode body contained inside; and a power supply terminal 30 which is arranged on the outside of the end of the glass bulb 21 and electrically connected to the lead 24. Therein the lead 24 and the power supply terminal 30 are disposed with keeping them away from each other and electrically joined with a solder 45, and an ozone prevention structure is formed, which prevents ozone from being generated by discharging caused between the lead 24 and the power supply terminal 30 when the solder 45 is melted during lamp lighting. Further, as the ozone prevention structure, it comprises: insulating members 43, 44a, 44b for sealing the vicinity of the joint part of the lead 24 and the power supply terminal 30; and a rosin 46 for covering the joint part of the lead 24 and the power supply terminal 30 by using the solder 45. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cold cathode discharge lamp in which a power supply terminal is disposed on the outer periphery of an end portion of a glass bulb and a backlight unit including the same as a light source.

As shown in FIG. 9, there is a cold cathode discharge lamp 100 in which a power supply terminal 110 having a metal cap 111 fixed with solder 112 is provided at an end of a glass bulb 101 (Patent Document 1). Since the power supply terminal 110 is electrically connected to the lead wire 103 of the electrode body 102 by the solder 113, the end of the cold cathode discharge lamp 100 is fitted into a lamp holder (not shown) of a lighting device such as a backlight unit. As a result, the cold cathode discharge lamp 100 can be fixed to the lighting device, and the cold cathode discharge lamp 100 and the lighting circuit of the lighting device can be electrically connected. Therefore, when the cold cathode discharge lamp 100 is attached to the lighting device, it is not necessary to solder the lead wire 104 to the lighting circuit, so that the attachment is easier than a cold cathode discharge lamp without the power supply terminal 110. It is.
Japanese Patent Laid-Open No. 9-17329

  By the way, overcurrent may flow through the cold cathode discharge lamp 100 due to, for example, the end of the life of the cold cathode discharge lamp or an abnormality in the lighting circuit. If an overcurrent continues to flow through the cold cathode discharge lamp 100, there is a concern about problems such as melting of the electrode, so it is necessary to stop the overcurrent. In view of this, some conventional devices have a structure in which energization is stopped in the lighting circuit when an overcurrent flows.

However, from the viewpoint of further safety improvement, in addition to the energization stop structure in the lighting circuit described above, there is an increasing demand for a cold cathode discharge lamp that additionally includes a structure for stopping energization when an overcurrent flows.
In view of the above-described points, an object of the present invention is to provide a cold cathode discharge lamp and a backlight unit that have a structure that stops energization when an overcurrent flows and has high safety.

The inventors of the present invention have repeatedly studied the configuration of a cold cathode discharge lamp that stops energization of the cold cathode discharge lamp when an overcurrent flows. As a result, the lead wire and the inner surface of the power supply terminal are arranged at a distance, and the gap between the lead wire and the power supply terminal is joined by solder that is melted by heat generated when an overcurrent flows. I came up with a composition.
Therefore, a cold cathode discharge lamp according to the present invention includes an electrode composed of an electrode body and a lead wire, a glass bulb formed by sealing the lead wire at an end with the electrode body housed therein, A cold cathode discharge lamp comprising a power supply terminal disposed outside an end portion of the glass bulb, wherein the lead wire and the power supply terminal are disposed at a distance and are electrically joined by solder. The solder is melted by Joule heat when an overcurrent flows.

In the above configuration, the lead wires and the power supply terminals arranged at a distance are joined by solder. Therefore, when an overcurrent flows, the solder is melted, the lead wire and the power supply terminal are electrically insulated, and energization is stopped. Thereby, the safety of the cold cathode discharge lamp can be improved.
Further, in the above, it is desirable that an ozone prevention structure for preventing generation of ozone due to discharge between the lead wire and the power supply terminal when the solder is melted is desirable.

  If a high voltage is applied from the lighting circuit to the power supply terminal in a state where the solder is melted and a gap is generated between the lead wire and the power supply terminal, corona discharge is generated between the lead wire and the power supply terminal. The inventors have confirmed that ozone having strong oxidizing power is generated from oxygen in the air by this discharge. Cold cathode discharge lamps are used as a light source for backlight units, and many members made of resin are used in the backlight units, and there is a concern that these resin members may be discolored by ozone. Need to prevent. In the above configuration, since the ozone prevention structure is provided, generation of ozone due to discharge between the lead wire and the power supply terminal can be prevented.

Here, it is preferable that the ozone prevention structure includes an insulating member that seals a space in the vicinity of a joint portion between the lead wire and the power supply terminal by the solder.
In the above configuration, since the space near the joint between the lead wire and the power supply terminal is sealed by the insulating member, even if discharge occurs between the lead wire and the power supply terminal, there is an effect that ozone is not generated. It is done.

Here, it is preferable that the ozone prevention structure includes a rosin that covers the solder joint between the lead wire and the power supply terminal.
As a result, when the solder is melted, the solder is split and covered with rosin. Since rosin has insulating properties, no discharge occurs. Therefore, with this structure, the occurrence of discharge in the space can be prevented, and consequently the generation of ozone can be prevented.

The ozone prevention structure is configured such that when the lead wire and the power supply terminal are joined by the solder and the solder is melted, the lead wire and the power supply terminal are disposed at a distance of 6 mm or more in the discharge space. It is good also as composition which has. The “discharge space” refers to a space between two objects in which an insulating member or the like is not provided.
By the present inventors, if there is more than 6 mm between the lead wire and the power supply terminal in the discharge space, even if a voltage for lighting the cold cathode discharge lamp is applied to the power supply terminal, It has been found that ozone is not generated because no discharge occurs between them.

Here, the inner surface of the power supply terminal is preferably covered with an insulating film.
Even if the distance between the lead wire and the power supply terminal is not 6 mm or more, the lead wire and the power supply terminal can be insulated by applying an insulating film to the power supply terminal, so the diameter of the power supply terminal can be reduced. Therefore, it is possible to reduce the size of the cold cathode discharge lamp.
A backlight unit according to the present invention includes any one of the cold cathode discharge lamps described above as a light source. Since the cold cathode discharge lamp is provided as a light source, a highly safe backlight unit can be provided.

Hereinafter, a cold cathode discharge lamp and a backlight unit according to an embodiment of the present invention will be described with reference to the drawings.
<Configuration of backlight unit>
First, the configuration of the backlight unit according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic perspective view showing a configuration of a backlight unit 1 for a liquid crystal display having an aspect ratio of 16: 9 according to the present embodiment. In the figure, a part of the front panel 16 is cut away to show the internal structure.

As shown in FIG. 1, the backlight unit 1 includes a plurality of cold cathode discharge lamps (hereinafter referred to as “lamps”) 20, a housing 10 that has openings and accommodates these lamps 20, And a front panel 16 covering the opening of the housing 10.
The housing 10 is made of, for example, polyethylene terephthalate (PET) resin, and a reflective surface is formed by depositing a metal such as silver on the inner surface 11 thereof.

The lamps 20 have a straight tube shape, and in the present embodiment, 14 lamps 20 are arranged in the casing 10 in a direct manner. The configuration of the lamp 20 will be described later.
FIG. 2 is a diagram for explaining a mounting state of the lamp in the housing. As shown in FIG. 2, a set of lamp holders 12 is arranged on the inner surface 11 of the housing 10 at a position corresponding to the mounting position of each cold cathode discharge lamp 20. Each lamp holder 12 is formed by bending a copper alloy or aluminum plate material such as phosphor bronze, for example, and connects the pair of sandwiching pieces 12a and 12b to the sandwiching pieces 12a and 12b at the lower edge. It consists of a connecting piece 12c. The sandwiching pieces 12a and 12b are provided with recesses that match the outer shape of the cold cathode discharge lamp 20, and by inserting the cold cathode discharge lamp 20 into the recesses, the sandwiching pieces 12a and 12b are cooled by the leaf spring action of the sandwiching pieces 12a and 12b. The cathode discharge lamp 20 is held by the lamp holder 12 and the lamp holder 12 and the power supply terminal 30 are electrically connected. Electric power is supplied to the lamp 20 attached to the backlight unit 1 from the lighting circuit (not shown) of the backlight unit 1 via the lamp holder 12.

Further, an insulating plate 17 made of polycarbonate that insulates the lamp holder 12 and the housing 10 is disposed between the lamp holder 12 and the housing 10. As a result, each lamp holder 12 has an independent potential, a voltage is applied to each lamp 20, and discharge is started for each lamp.
Returning to FIG. 1, the opening of the housing 10 is sealed with a translucent front panel 16 formed by laminating a diffusion plate 13 made of polycarbonate resin, a diffusion sheet 14 and a lens sheet 15 made of acrylic resin. .

The diffusion plate 13 and the diffusion sheet 14 in the front panel 16 scatter and diffuse the light emitted from the lamp 20, and the lens sheet 15 arranges the light in the normal direction of the sheet 15, Thus, the light emitted from the lamp 20 is configured to irradiate the front uniformly over the entire surface (light emitting surface) of the front panel 16.
In the above description, the backlight unit is of the direct type, but it may be of a so-called edge light type.

<Lamp configuration>
FIG. 3 is a partially broken perspective view showing a cold cathode discharge lamp according to an embodiment of the present invention, and FIG. 4 is an enlarged sectional view showing one end portion of the cold cathode discharge lamp. The lamp 20 is used as a light source of the backlight unit 1, and includes a glass bulb 21, a pair of hollow electrodes 22 sealed at both ends of the glass bulb 21, and outside the both ends of the glass bulb 21. And a power supply terminal 30 provided.

The glass bulb 21 is obtained by processing a glass tube made of borosilicate glass (SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —K ₂ O—TiO ₂ ) and has a total length of 730 mm.
The glass bulb 21 has an annular cross section, an outer diameter of 4 mm, an inner diameter of 3 mm, and a wall thickness of 0.5 mm. The maximum width of the sealing portion in the tube axis direction of the glass bulb 21 is 2 mm, and the hollow electrode 22 is sealed.

The configuration of the glass bulb 21 is not limited to the above configuration. However, in order to make the cold cathode discharge lamp 20 elongated, it is desirable that the glass bulb 21 has a small diameter and a thin wall. Therefore, in general, the outer diameter of the glass bulb 21 is 1.8 mm (inner diameter 1.4 mm) to It is preferably 6.0 mm (inner diameter: 5.0 mm).
A phosphor layer 29 is formed on the inner surface of the glass bulb 21. The phosphor layer 29 is made of, for example, a red rare earth (Y ₂ O ₃ : Eu), a green phosphor (LaPO ₄ : Ce, Tb), and a blue phosphor (BaMg ₂ Al ₁₆ O ₂₇ : Eu, Mn). It is made of a phosphor. The glass bulb 21 is filled with, for example, about 1200 μg of mercury and about 8 kPa (20 ° C.) neon / argon mixed gas (Ne 95% + Ar 5%) as a rare gas.

The configuration of the phosphor layer 29, mercury, and rare gas is not limited to the above configuration. For example, a neon / krypton mixed gas (Ne 95% + Kr 5%) may be enclosed as a rare gas. When a neon / krypton mixed gas is used as the rare gas, lamp startability is improved, and the cold cathode discharge lamp 20 can be lit at a low voltage.
The hollow electrode 22 includes an electrode body 23 and a lead wire 24 and is sealed to a sealing portion of the glass bulb 21.

The electrode body 23 is made of nickel (Ni) and has a bottomed cylindrical shape. In addition, the electrode main body 23 is not limited to nickel, For example, it is possible to make it from niobium (Nb), a tantalum (Ta), or molybdenum (Mo).
The electrode body 23 has a total length of 5.2 mm, an outer diameter of 2.7 mm, an inner diameter of 2.3 mm, and a wall thickness of 0.2 mm. The hollow electrode 22 is disposed so that the tube axis of the electrode main body 23 and the tube axis of the glass bulb 21 are substantially coincident with each other, and the distance between the outer peripheral surface of the electrode main body 23 and the inner surface of the glass bulb 21 is set as follows. Is substantially uniform over the entire outer periphery of the.

  The distance between the outer peripheral surface of the electrode body 23 and the inner surface of the glass bulb 21 is specifically 0.15 mm. When the interval is narrow in this way, discharge does not enter the interval and discharge occurs only inside the hollow electrode 22. Therefore, the sputtered material scattered by the discharge is less likely to adhere to the inner surface of the glass bulb 21, and the cold cathode discharge lamp 20 has a long life. On the other hand, since the discharge does not go to the lead wire 24 side, the lead wire 24 is hardly heated by the discharge.

In addition, although the space | interval of the outer peripheral surface of the electrode main body 23 and the inner surface of the glass bulb 21 does not necessarily need to be 0.15 mm, it may be 0.2 mm or less in order to prevent discharge from entering the space. preferable.
The lead wire 24 has a feature of being linear. The lead wire 24 is a connection between an internal lead wire 25 made of tungsten (W) and an external lead wire 26 made of nickel that easily adheres to solder or the like, and a joint surface between the internal lead wire 25 and the external lead wire 26. However, it is substantially flush with the outer surface of the glass bulb 21. That is, the internal lead wire 25 is located inside the outer surface of the glass bulb 21, and the external lead wire 26 is located outside the outer surface of the glass bulb 21.

The internal lead wire 25 has a substantially circular cross section, a total length of 3 mm, and a wire diameter of 0.8 mm. The internal lead wire 25 has an end portion on the external lead wire 26 side sealed to the sealing portion of the glass bulb 21, and an end portion opposite to the external lead wire 26 side is the outer surface of the bottom portion of the electrode body 23. It is joined to the approximate center by welding.
The external lead wire 26 protrudes from the outer surface of the glass bulb 21 toward the tube axis direction, and is electrically connected to the power supply terminal 30 via a lead wire 41 and a solder body 45 (see FIG. 5A) described later. It is connected. The external lead wire 26 has a total length of 1 mm to 10 mm, for example, 2 mm, and the axial center of the external lead wire 26 and the tube axis of the glass bulb 21 substantially coincide with each other. The external lead wire 26 has a substantially circular cross section, and the wire diameter is 0.6 mm, which is narrower than the internal lead wire 25.

Hereinafter, the power supply terminal according to each embodiment will be described.
<First Embodiment>
(Lamp configuration)
First, the configuration of the power supply terminal according to the first embodiment will be described with reference to FIG. FIG. 5A is an enlarged view of the end of the cold cathode discharge lamp.

The power supply terminal 30 includes a metal cap 31 and a terminal lead wire 32.
The metal cap 31 has a bottomed cylindrical shape and is made of an iron-nickel alloy. A hole 31a into which the terminal lead wire 32 is inserted is formed at the bottom.
The terminal lead wire 32 is a nickel wire having a wire diameter of 0.6 mm. One end of the terminal lead wire 32 is inserted into the hole 31a of the metal cap 31 and fixed by welding.

The glass bulb 21 is inserted into the metal cap 31 from the open end to the middle. The external lead wire 26 of the glass bulb 21 and the terminal lead wire 32 are electrically connected by a lead wire 41 and a solder body 45.
The lead wire 41 is a nickel wire having a wire diameter of 0.6 mm.
The solder body 45 is made of solder and has a wire diameter of 0.6 mm. The solder composition of the solder body 45 is, for example, Sn: 96.5%, Ag: 3.0%, Au: 0.5%, and the melting point is about 220 ° C.

The terminal lead wire 32 and the lead wire 41 are arranged on the tube axis of the glass bulb at a predetermined distance so as to face the end surfaces. The lead wire 41 and the terminal lead wire 32 are electrically connected by a solder body 45. The solder body and the axes of the lead wires 41 and 32 are substantially on the same straight line.
In this embodiment, there are two ozone prevention structures for preventing the generation of ozone.

  The first ozone prevention structure includes an insulating case 43 and insulating resins 44a and 44b. The insulating case 43 is made of ceramic and has a cylindrical shape. The insulating resins 44a and 44b are made of, for example, an epoxy resin. The space in the vicinity of the joint is sealed with the insulating case 43 and insulating resins 44a and 44b that seal between the opening of the insulating case and the lead wires 41 and 42.

The second ozone prevention structure includes a rosin 46 that covers a joint portion of the terminal lead wire 32 and the lead wire 41 by the solder body 45.
(Lamp operation)
Next, the operation of the cold cathode discharge lamp according to the first embodiment will be described. FIG. 5A is a diagram illustrating a state before an overcurrent flows, and FIG. 5B is a diagram illustrating a state after an overcurrent flows. It is known that the lamp current in a normal state is about 5 mA, but an overcurrent that is about 1.5 times or more that in a normal state flows in an abnormal state.

In FIG. 5A, when an overcurrent flows through the lamp, the solder body 45 is melted by Joule heat.
When the solder body 45 is melted, as shown in FIG. 5B, the solder body 45 is melted and cut into solder 45a and solder 45b. The divided solder 45a and solder 45b are covered with rosin 46, respectively. Since the rosin 46 is insulative, the lead wire 41 and the terminal lead wire 32 are electrically insulated. Even if a voltage is applied to the metal cap 31 in this state, the overcurrent stops because the metal cap 31 and the lead wire 41 are electrically insulated.

  Further, since the solders 45a and 45b are respectively covered with the insulating rosin 46, no discharge occurs, so that generation of ozone is prevented. Even if the solder 45a and 45b are not covered by the rosin 46 and a discharge occurs between the solders 45a and 45b, the space near the joint is sealed by the insulating case 43 and the insulating resins 44a and 44b. Therefore, since oxygen in the atmosphere does not change to ozone due to discharge, generation of ozone is prevented.

(Lamp manufacturing method)
Next, a manufacturing method of the cold cathode discharge lamp according to the present embodiment will be described. The method for manufacturing the lamp 20 according to the present embodiment is characterized by the method for forming the power supply terminal 30. Since the formation method of the phosphor layer 29, the glass bulb 21 and the like is in accordance with a known technique, description thereof will be omitted, and the formation method of the feeding terminal 30 will be described in detail below.

According to a known method in advance, a phosphor layer 29 is formed on the inner wall, and a glass bulb 21 in which a pair of electrodes 22 are sealed with mercury and buffer rare gas sealed therein is formed.
A metal cap 31, a terminal lead wire 32, a lead wire 41, a solder body 45, a rosin 46, an insulating case 43, an epoxy resin, and a glass bulb 21 are prepared.
First, the lead wire 41 and the terminal lead wire 32 are joined by the solder body 45. At this time, the lead wires 41, the solder bodies 45, and the terminal lead wires 32 are aligned in a straight line. Next, rosin 46 is applied to the joint portion by the solder body 45, and the joint portion is covered with the rosin 46. This lead wire structure is inserted into the insulating case 43, and the lead wire 41 and the terminal lead wire 32 are sealed with insulating resins 44a and 44b made of an epoxy resin to seal the space near the joint. Thereby, a joined structure is obtained.

  Next, the lead wire 41 of the joint structure is welded to the external lead wire 26. Specifically, in a state where the end face of the external lead wire 26 and the end face of the lead wire 41 are in contact with each other, the high-power laser is irradiated to the external lead wire 26 for a short time, and the external lead wire 26 is generated by the heat generated at this time. And the lead wire 41 are welded. During laser irradiation, the root portion of the lead wire 41, the insulating case 43, and the like are cooled to keep the solder body 45 from melting.

  Further, the joining structure and the glass bulb end are inserted into the metal cap 31. In the metal cap 31, a hole 31a is formed in the center of the bottom portion to engage the tip of the terminal lead wire 32 of the joint structure. At this time, the distal end portion of the terminal lead wire 32 of the joint structure is inserted into the hole 31a in the bottom portion of the metal cap 31, and is electrically connected by welding. During welding, the joining structure is cooled and the solder body 45 is not melted. Thereby, the cold cathode discharge lamp 20 according to the present embodiment is obtained.

<Second Embodiment>
(Lamp configuration)
A configuration of the power supply terminal according to the second embodiment will be described. The second embodiment is different from the first embodiment in the configuration of the power supply terminal, and the other parts are the same. Therefore, the description of the portion excluding the power supply terminal is omitted.

Fig.6 (a) is an expanded sectional view which shows the structure of a feed terminal. The power supply terminal 50 includes a metal cap 51 and an insulating film 52.
The metal cap 51 has a bottomed cylindrical shape having an opening at one end, and a semicircular hole 53 is formed at the bottom.
The glass bulb 21 is directly inserted from the opening end of the metal cap 51 to the middle. An insulating film 52 made of, for example, an epoxy resin or a phenol resin is attached to the inner surface of the metal cap 51 where the glass bulb 21 is not inserted. However, the insulating film 52 is not deposited on the inner surface of the metal cap (conductive portion 51a) in the region facing the end face of the external lead wire 26.

The distance between the end face of the external lead wire 26 and the conductive portion 51a of the metal cap 51 is 6 mm or more, for example, 8 mm. The external lead wire 26 and the conductive portion 51 a of the metal cap 51 are joined and electrically connected by a linear solder body 60.
The solder body 60 has a wire diameter of 0.6 mm, and its composition is, for example, Sn: 96.5%, Ag: 3%, Cu: 0.5%, and the melting point is about 220 ° C.

(Lamp operation)
Next, the operation of the cold cathode discharge lamp according to the second embodiment will be described. FIG. 6A is a diagram showing a state before an overcurrent flows, and FIG. 6B is a diagram showing a state after an overcurrent flows.
In FIG. 6A, when an overcurrent flows through the lamp, the solder body 60 is melted by Joule heat. Then, as shown in FIG. 6B, the melted solder falls into the metal cap due to gravity, the electrical connection between the external lead wire 26 and the conductive portion 51a of the metal cap 51 is cut, and the energization is stopped. Therefore, the safety of the lamp can be improved.

In addition, when the distance between the external lead wire 26 and the metal cap 51 is 6 mm or more in the discharge space, the present inventors can apply a voltage for lighting the cold cathode discharge lamp to the metal cap 51. It has been found that since no discharge occurs between the external lead wire 26 and the metal cap 51, no ozone is generated.
In FIG. 6B, the region of the metal cap 51 that is covered with the insulating film 52 is spatially insulated from the external lead wire 26, and the metal cap 51 is covered with the insulating film 52. Since the conductive portion 51a that has not been separated is 6 mm or more away from the external lead wire 26 in the discharge space, even if a peak voltage (about 2 kV) is applied to the metal cap 51, the external lead wire 26 and the conductive portion 51a. Corona discharge does not occur between Therefore, since ozone is not generated from oxygen in the atmosphere, generation of ozone can be prevented.

(Lamp manufacturing method)
Next, a manufacturing method of the cold cathode discharge lamp according to the second embodiment will be described. The manufacturing method of the cold cathode discharge lamp according to the present embodiment is characterized by a method of forming a power supply terminal. Since the formation method of the glass bulb 21 is in accordance with a known technique, the description thereof will be omitted, and the formation method of the power supply terminal 50 will be described in detail below.

According to a known method in advance, a glass bulb 21 is formed in which a phosphor layer is formed on the inner wall and mercury and a buffering rare gas are sealed inside to seal a pair of electrodes.
Next, the metal cap 51 is manufactured. A metal cap 51 is obtained by forming a cylindrical body having a bottom made of a nickel-iron alloy and forming a semicircular hole 53 in the bottom of the cylindrical body. Then, an insulating film 53 made of epoxy resin or phenol resin is applied to a predetermined area on the inner surface of the metal cap 51.

  Subsequently, the external lead wire 26 of the glass bulb 21 and the solder body 60 are electrically connected by, for example, heating and melting a part of the solder body 60. At this time, the external lead wire 26 and the solder body 60 are connected so that the axial centers thereof are on the same straight line. Then, the end portion of the glass bulb 21 is inserted from the opening end of the metal cap 51, and the solder body 60 and the conductive portion 51a of the metal cap 51 are electrically melted by heating, for example, a part of the solder body 60. Connecting. As described above, the cold cathode discharge lamp according to the second embodiment can be obtained.

<Modification>
As described above, the present invention has been described based on the embodiments. However, the content of the present invention is not limited to the specific examples shown in the above-described embodiments. For example, the following modifications are possible. Can think.
(1) In the first embodiment, as shown in FIG. 5A, the joint portion with the solder 45 is covered with the rosin 46, and the space near the joint portion is formed in the insulating case 43 and the insulating resins 44a and 44b. In the above description, the configuration including the structure to be sealed is described. However, a configuration including any one of the above-described covering structure with rosin and the sealing structure with the insulating case 43 or the like may be used.

In the case of a configuration including only the covering structure with the rosin 46, when an overcurrent flows through the lamp 20, the molten solder is split into two and the energization is stopped. Furthermore, since the split molten solders 45a and 45b are respectively covered with the insulating rosin 46, no discharge is generated between the solders 45a and 45b, thereby preventing generation of ozone.
In the case of a configuration including only the sealing case 43 and the sealing structure made of the insulating resins 44a and 44b, when an overcurrent flows through the lamp 20, the solder body 45 melts and falls into the insulating case 43, and the terminal lead wire 32 and the lead The line 41 is insulated and the energization is stopped. Here, even if a high voltage is applied to the metal cap 31 and corona discharge occurs between the terminal lead wire 32 and the lead wire 41, this space is sealed, and oxygen is continuously supplied from the atmosphere to continue. Therefore, ozone is not generated.

  (2) In the first embodiment, the configuration in which the metal cap 31 and the terminal lead wire 32 are electrically connected by welding has been described. However, as shown in FIG. 7, the metal cap 70 and the terminal lead wire are connected. 71 may be electrically connected by a solder 72 applied to the inner surface of the metal cap 70. In order to prevent the external lead wire 26 and the lead wire 41 and the metal cap 70 from being electrically connected via the solder 72, a space is formed in the vicinity of the external lead wire 26 and the lead wire 41 so that the soldering can be performed. It is necessary not to fill with 72.

The composition of the solder 72 is Sn: 99.3%, Cu + Ni: 0.7%, and the melting point is 230 ° C. higher than that of the solder body 45.
In the configuration as shown in FIG. 7, since the solder 72 is in contact with the end face of the glass bulb 21, the heat transferred from the electrode 22 to the sealing portion of the glass bulb 21 is transmitted to the metal cap 70 via the solder 72. Therefore, the heat dissipation efficiency of the lamp is improved.

Further, the terminal lead wire 71 and the metal cap 70 are electrically joined by the solder 72, and there is no need to weld the terminal lead wire 71 and the metal cap 70 as in the first embodiment. Is simplified.
(3) In the second embodiment, as shown in FIG. 6A, the metal cap 51 has a substantially cylindrical shape in appearance, but is not limited to this.

FIG. 8 is a diagram showing a modification of the metal cap in the second embodiment. The metal cap 81 has a cylindrical shape from the opening end to the position where the end of the glass bulb 21 is inserted, but in the region corresponding to the end of the glass bulb 21 from the end to the bottom of the metal cap 81. The lower part when the lamp is disposed is concave.
As a result, the distance between the conductive portion 81 a of the metal cap 81 and the solder 62 that has melted and dropped into the recess of the metal cap 81 is increased. Therefore, even when a high voltage is applied to the metal cap 81, there is an advantage that corona discharge is less likely to occur between the conductive portion 81a and the molten solder 62.

  (4) The structure of the power feeding terminal described in each embodiment may be provided at the end of at least one glass bulb 21. That is, it may be provided at both ends of the glass bulb 21 or may be provided only at one end.

  The present invention can be widely applied to cold cathode discharge lamps and backlight units. Moreover, since the present invention can provide a cold cathode discharge lamp with high safety, its industrial utility value is extremely high.

It is a schematic perspective view which shows the structure of the backlight unit 1 for liquid crystal displays of the aspect ratio 16: 9 which concerns on this Embodiment. It is a figure for demonstrating the attachment state of the lamp | ramp in a housing | casing. 1 is a partially broken perspective view showing a cold cathode discharge lamp according to an embodiment of the present invention. It is an expanded sectional view which shows the one end part of a cold cathode discharge lamp. FIG. 5A is an enlarged view of an end of the cold cathode discharge lamp according to the first embodiment, and FIG. 5A is a diagram showing a state before an overcurrent flows, and FIG. It is a figure which shows the state after flowing. FIG. 6A is an enlarged view of an end portion of a cold cathode discharge lamp according to a second embodiment, and FIG. 6A is a diagram illustrating a state before an overcurrent flows, and FIG. It is a figure which shows the state after flowing. It is a figure which shows the modification of the cold cathode discharge lamp which concerns on 1st Embodiment. It is a figure which shows the modification of the cold cathode discharge lamp which concerns on 2nd Embodiment. It is an expanded sectional view which shows the one end part of the cold cathode discharge lamp of a conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight unit 10 Case 12 Lamp holder 20 Cold cathode discharge lamp 21 Glass bulb 22 Electrode 23 Electrode main body 26 External lead wire 30 Power supply terminal 31 Metal cap 32 Terminal lead wire 43 Insulating case 44a, 44b Insulating resin 45 Solder 46 Rosin

Claims (7)

An electrode composed of an electrode main body and a lead wire, a glass bulb formed by sealing the lead wire at the end with the electrode main body housed therein, and a power supply disposed outside the end of the glass bulb A cold cathode discharge lamp comprising a terminal,
The lead wire and the power supply terminal are arranged at a distance and are electrically joined by solder,
The cold cathode discharge lamp, wherein the solder is melted by Joule heat when an overcurrent flows. The cold cathode discharge lamp according to claim 1, further comprising an ozone prevention structure that prevents generation of ozone due to discharge between the lead wire and the power supply terminal when the solder is melted. The cold cathode discharge lamp according to claim 2, wherein the ozone prevention structure includes an insulating member that seals a space in the vicinity of the solder joint between the lead wire and the power supply terminal. 4. The cold cathode discharge lamp according to claim 2, wherein the ozone prevention structure includes a rosin that covers the solder joint between the lead wire and the power supply terminal. 5. In the ozone prevention structure, when the lead wire and the power supply terminal are joined by the solder, and the solder is melted, the lead wire and the power supply terminal are disposed at a distance of 6 mm or more in the discharge space. The cold cathode discharge lamp according to claim 2, wherein: The cold cathode discharge lamp according to claim 5, wherein an inner surface of the power supply terminal is covered with an insulating film.   A backlight unit comprising the cold cathode discharge lamp according to any one of claims 1 to 6 as a light source.

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