JP3293815B2 - Cold cathode low pressure discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-tube cold-cathode low-pressure discharge lamp, and more particularly to a high-performance cold-cathode low-pressure discharge lamp having a small size and a long life.

[0002]

2. Description of the Related Art With the spread of liquid crystal display devices such as liquid crystal displays, word processors, personal computers, etc., higher performance, more functions, smaller size, and longer life are required. In response to such demands, a cold cathode low-pressure discharge lamp (cold cathode fluorescent lamp) as a light source for a backlight is inevitably required to be improved in performance and the like.

FIGS. 6 (a) and 6 (b) show a schematic configuration of a cold cathode low-pressure discharge lamp conventionally used as a backlight light source. FIG. 6 (a) is an overall sectional view, FIG. 6B is an enlarged cross-sectional view of the sealed cold cathode. Fig. 6 (a),
In (b), reference numeral 1 denotes a glass tube (glass bulb) in which a phosphor layer 2 that emits light when stimulated by ultraviolet rays is provided on an inner wall surface and encloses a rare gas or a mixed system of a rare gas and mercury.
Reference numerals 3 and 3 'denote pairs of metallic cylindrical cold cathodes (discharge electrodes) sealed at both ends of the glass tube 1, respectively. Here, the glass tube 1 has an outer diameter of about 1.2 to 3.0 mm and a length of 50 to 5 mm.
The glass tube 1 has a diameter of, for example, 0.5 to
2.0 mg extent of mercury and 8 to 20 kPa of about rare gas is enclosed as a discharge medium.

In the configuration shown in FIGS. 6 (a) and 6 (b), the cylindrical cold cathodes 3, 3 'have, for example, an inner diameter of 0.2 to 1.0.
This is a bottomed cylindrical cup (sleeve) made of nickel having a thickness of about 0.1 mm, a wall thickness of about 0.1 to 0.2 mm, and a length of about 2 to 4 mm. While being fixed and electrically connected, the glass tube 1 is formed of power supply leads 4 and 4 ′ which are sealed and led out at the end of the glass tube 1. That is, the cold cathodes 3, 3 'are connected via the power supply leads 4, 4'.
Then, a required voltage is applied to make the cold cathodes 3, 3 'function as discharge electrodes.

[0005] Here, the closed-end cylindrical cup means a closed-end cylindrical body having an opening at one end (in this case, a power supply lead wire is welded to the outer bottom surface of the bottomed cylindrical body). One end of the tubular body is opened and the power supply lead wire is inserted and fixed to the other end side, so that the leading end surface of the power supply lead wire may form a bottom surface.

The cold cathode low-pressure discharge lamp of this type is provided with the cold cathode 3, 3 by the ions in the initial plasma generated by energizing the cold cathodes 3, 3 'via the power supply leads 4, 4'. Secondary electrons are emitted from 3 ', discharge starts in the glass tube 1, and the discharge is maintained. And
Ultraviolet rays are radiated by resonance transition of the rare gas or mercury excited by the discharge energy, and the ultraviolet rays are
The light is converted into visible light by the phosphor layer 2 formed on the inner wall surface, and functions as a cold-cathode low-pressure discharge lamp.

[0007] In order to improve the performance of cold cathode low-pressure discharge lamps equipped with this type of bottomed cylindrical cold cathodes 3, 3 ',
For example, JP-A-3-184252, JP-A-9-82275, JP-A-10-21876, JP-A-10-69887, JP-A-10-188888, and various means have been proposed. I have.

[0008]

However, with the trend toward thinner, lighter, and higher performance devices such as liquid crystal displays and scanners, cold cathode low-pressure discharge devices used as backlight light sources and reading light sources have been developed. Electric lamps are also required to have even smaller capillaries, lighter weight, longer life, and higher brightness.
Here, in order to reduce the size of the cold cathode low-pressure discharge lamp, it is necessary to reduce the diameter of the metallic cylindrical cold cathodes 3 and 3 ′ sealed in the glass tube 1.

However, reducing the diameter of the cylindrical cold cathodes 3, 3 '
In order to reduce the surface area of the cylindrical cold cathodes 3, 3 ', spattering of the cylindrical cold cathodes 3, 3' due to ion collision during lighting is likely to become severe. Then, the material of the cylindrical cold cathode 3, 3 'scattered by the sputtering is combined with mercury in the glass tube 1 and the consumption of pure mercury which contributes to the discharge progresses, so that the lighting life is shortened. There is a problem of doing. The lighting life required for the backlight of the liquid crystal display is at least about 10,000 hours.

The inventor of the present invention has further studied the structure of the cylindrical cold cathodes 3, 3 ', whose rear end is sealed and bottomed, in consideration of the above-mentioned problem of the reduction of the lighting life. The phenomenon was found. That is, a metal cylindrical cold cathode is
If the inner diameter is less than 0.8 mm, the entire inner wall surface of the cylindrical cold cathodes 3, 3 'is not sputtered uniformly, but a partial area is preferentially sputtered locally, and It has been found that the cathode is cut off from the middle and the tip opening side falls off.

First, a glass tube 1 provided with a phosphor layer 2 on the inner wall surface has an outer diameter of 2.0 mm, an inner diameter of 1.6 mm, a length of 220 mm, an enclosed discharge medium (neon-argon-mercury) of 8 kPa, and a rear end side. Nine types of cold-cathode low-pressure discharge lamps are prepared, in which the cylindrical cold cathodes 3, 3 'sealed by inserting the power supply leads 4, 4' are sealed. Here, the cylindrical cold cathodes 3, 3 'have a wall thickness of 0.1 m.
m, inner diameter 0.4 to 1.4 mm, length of cavity (length between the front end surface of power supply lead wire and the front end opening) is 3 mm.

Next, each of the cold cathode low-pressure discharge lamps was cooled to room temperature (25
C) and the lamp current was 6 mA, and the operating life of each of the cold cathode low-pressure discharge lamps was tested and evaluated from the phenomenon that the tubular cold cathodes 3, 3 'were cut off by sputtering and the tip opening side dropped off. . FIG. 7 is a characteristic diagram showing the result of the test evaluation, that is, the relationship between the inner diameter of the cylindrical cold cathode and the lighting time until the end of the cold cathode drops off.

Here, the drop of the tip of the cylindrical cold cathode 3 causes a sharp decrease in the area of the cylindrical cold cathode, while the current density (electrode area / lamb current) of the cylindrical cold cathode 3 greatly increases. However, since the temperature of the electrode portion is increased, there is a possibility that peripheral members may be melted or burnt out. Such a phenomenon suddenly occurs when the inner diameter of the metal tubular member constituting the tubular cold cathode 3 is less than 0.8 mm with a boundary of about 0.8 mm, and is 0.8 mm or more (for example, when the inner diameter is About 0.9mm or
In the case of 1.4 mm), the inner wall surface of the cylindrical cold cathode was almost uniformly sputtered over the entire area, and no drop off of the tip was observed even after 15,000 hours of lighting.

FIGS. 8 (a), 8 (b) and 8 (c) are enlarged sectional views schematically showing the progress of local sputtering in the cylindrical cold cathodes 3, 3 '. FIG. 8A shows a state at the time of initial lighting, and FIG. 8B shows a state at a lighting time of 3000 to 5000 hours from the front end face of the power supply lead wire 4 toward the opening end face side of the cylindrical cold cathode 3. Within a range of about 1.5 mm, the inner wall surface of the cylindrical cold cathode 3 violently causes a sputtering phenomenon, and the wall thickness is reduced. Fig. 8 (c) shows the lighting 5000 to 1000
In the state at time 0, the cylindrical cold cathode 3 is divided in the above-mentioned local sputtering progress region, and its tip falls off.

Although the drop of the tip of the cylindrical cold cathode due to the local sputtering can be slightly suppressed by reducing the lamp current, the required brightness cannot be obtained. Further, it is conceivable to suppress spattering by increasing the filling gas. However, there is a problem in that the lamp voltage increases, resulting in an increase in power consumption.

In order to solve the local spattering problem in the cylindrical cold cathode having an inner diameter of less than 8 mm in which the discharge region side is opened and the rear end side is sealed (closed), the rear end sealing (blocking) of the cylindrical cold cathode is prevented. ) It has been found that the local spattering problem can be prevented or avoided by cutting out a part of the side wall adjacent to the inner bottom surface. In other words, in the case of a cylindrical cold cathode with an inner diameter of less than 0.8 mm that is open on the discharge area side and substantially sealed / closed on the rear end side, for example, one or more holes or slits are formed in the side wall area within 2 mm from the inner bottom surface. It was confirmed that when the formed configuration was adopted, the lighting life was comparable to that of a cylindrical cold cathode with an inner diameter of 0.8 mm or more.

Here, it is considered that the local spattering problem can be prevented or avoided when a part of the side wall region adjacent to the inner bottom surface of the cylindrical cold cathode is cut off, for the following reasons. That is, the discharge medium (mercury vapor or the like) sealed in the glass tube 1 not only serves to generate ultraviolet light or visible light by the discharge, but also cools due to the collision of electrons and ions with the cold cathode during the discharge. There is an effect of blocking the sputtering of the cathode constituent material and returning the sputtered cold cathode constituent material back to the cold cathode surface (reverse diffusion phenomenon).

However, when the rear end of the cylindrical cold cathode is sealed (closed), when the inner diameter of the cylindrical cold cathode is reduced to 0.8 mm or less, mercury vapor enters the bottom of the hollow portion of the cylindrical cold cathode. (Supply) becomes difficult, and the above-mentioned reverse diffusion phenomenon becomes difficult to work. On the other hand, when a part of the side wall region adjacent to the inner bottom surface of the cylindrical cold cathode is cut off, mercury vapor enters (supplies) to the cavity bottom surface side easily through the cutout portion. It is considered that local spattering on the inner wall surface of the hollow portion of the cylindrical cold cathode can be prevented or avoided.

The present invention has been made based on the above findings, and an object of the present invention is to provide a thin-tube cold-cathode low-pressure discharge lamp capable of making a backlight unit thinner, lighter, brighter, and longer in life. And

[0020]

A first aspect of the present invention is a glass tube provided with a phosphor layer on an inner wall surface and enclosing a rare gas or a mixture of a rare gas and mercury, and at least one of the glass tubes. Metal inner diameter 0.8mm sealed at one end
In a cold cathode low-pressure discharge lamp comprising less than a cylindrical cold cathode, the cylindrical cold cathode has a bottomed shape in which the discharge region side is open, and forms a cavity from the inner bottom wall surface to the open end, and at least This is a cold cathode low pressure discharge lamp characterized in that a part of the side wall within 2 mm from the inner bottom wall is notched.

According to a second aspect of the present invention, in the cold cathode low pressure discharge lamp according to the first aspect, a part of the cylindrical cold cathode side wall has a notch.
It is characterized by at least one hole or slit.

According to a third aspect of the present invention, in the cold cathode low-pressure discharge lamp according to the first or second aspect, the total area of the partially cut-out region of the side wall within 2 mm from the inner bottom wall of the cylindrical cold cathode is reduced.
0.02 to 0.4 mm ² .

According to a fourth aspect of the present invention, in the cold cathode low pressure discharge lamp according to any one of the first to third aspects, the side wall thickness of the cylindrical cold cathode is 0.05 to 0.2 mm.

According to a fifth aspect of the present invention, in the cold cathode low-pressure discharge lamp according to any one of the first to fourth aspects, the cylindrical cold cathode is selected from the group consisting of nickel, stainless steel, molybdenum, tantalum and tungsten. It is characterized by being made of one kind of metal.

That is, the present invention provides a cold-cathode low-pressure discharge lamp in which a rare gas or a mixed system of mercury and a rare gas is sealed in an arc tube and a metal cylindrical cold cathode is sealed at least at one end. It consists of a bottomed cylindrical cup made of nickel, for example, with an open end face of the cold cathode facing the discharge area. A part of the side wall adjacent to the inner bottom wall surface (within 2 mm) of the bottomed cylindrical cup is perforated and slit-shaped. The main point is that the cutout is provided.

In the first to fifth aspects of the present invention, the glass tube has an outer diameter of about 1.2 to 3.0 mm and a length of about 40 to 500 mm, and a rare gas such as argon, neon, xenon, or krypton is contained in the glass tube. Alternatively, a discharge medium such as a mixed system of these rare gases and mercury is sealed. Here, inclusion of rare gas about 8 to 20 kPa, enclosed amount of mercury is 0.5 to 3.5 mg extent.

The bottomed cylindrical cold cathode is made of one kind of metal selected from the group consisting of, for example, nickel, stainless steel, molybdenum, tantalum and tungsten, and has, for example, an inner diameter of less than 0.2 to 0.8 mm and a thickness of 0.05 to 0.05. About 0.2mm, length 2
About 4 mm. The bottomed cylindrical cold cathode generally has a configuration in which it is sealed opposite to both ends of the glass tube, but the configuration of an external electrode lamp in which one of the opposed electrodes is arranged on the outer peripheral surface of the glass tube. Can also be taken.

The bottomed cylindrical cold cathode (bottomed cylindrical cup) has a structure having a bottomed cylindrical body with one end opened (in this case, the outer bottom wall surface of the bottomed cylindrical body is used for power supply). The lead wire is connected by welding, etc.), and one end of the tubular body is opened and the power supply lead wire is inserted and fixed to the other end, so that the structure where the front end surface of the power supply lead wire forms the bottom surface is there. The structure of the cylindrical cold cathode is generally a cylindrical shape, but may be a polygonal cylindrical shape such as a square or hexagon other than the cylindrical shape. In short, the shortest part of the center diameter (inner diameter) may be used. Either case may be used as long as it is less than 0.8 mm.

Further, the means for partially cutting off the side wall of the cylindrical cold cathode includes, for example, perforation of a hole and formation of a slit. These may be plural or a combination of a hole and a slit. . However, in each case, the side wall portion adjacent to the inner bottom wall surface (within 2 mm) of the bottomed cylindrical cup is set so that at least a part thereof is notched.

For example, a slit may be formed in the bottomed cylindrical cup from the center or the opening at the front end or from the rear end to the center. The starting point must be the side wall adjacent to the inner bottom wall (within 2 mm). The total area of the notch (notch area) adjacent to the inner bottom wall (within 2 mm) is:
0.02 to 0.4 mm when the bottomed cylindrical cold cathode has the above dimensions
^{About 2} is preferred.

According to the first to fifth aspects of the present invention, the inner diameter is 0.8 mm.
In the configuration of the hollow cold cathode, the mercury vapor is easily supplied to the inner bottom surface side of the hollow cold cathode portion during lighting, through the cutout region of the side wall portion adjacent to the inner bottom surface of the hollow, and the cavity is easily cooled. Local spattering on the inner bottom surface side of the cold cathode is suppressed. In other words, the breakage of the hollow cold cathode due to local sputtering and the falling off of the tip are easily prevented, and the required discharge function is maintained and exhibited for a long period of time.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. 1, 2, 3, 4, and 5. FIG.

Embodiment 1 FIG. 1 is a cross-sectional view showing, on an enlarged scale, the main components of a cold-cathode low-pressure discharge lamp according to this embodiment. That is, a phosphor layer 5 that emits light when stimulated by ultraviolet rays is provided on the inner wall surface, and an outer diameter that encapsulates rare gas (neon and argon) and mercury.
A glass tube 6 made of borosilicate glass having a diameter of 1.6 mm, an inner diameter of 1.2 mm (wall thickness 0.2 mm) and a length of 220 mm, and a pair of bottomed cylindrical cold cathodes sealed at both ends of the glass tube 6 (discharge Electrodes 7).

Here, the bottomed cylindrical cold cathode 7 has an outer diameter of 0.9 m.
A nickel-made cylindrical sleeve having a diameter of 0.7 mm, an inner diameter of 0.7 mm and a length of 4 mm is provided with a power supply lead wire (a Kovar wire having an outer diameter of less than 0.5 mm) on the rear end side (with respect to the discharge region) of the cylindrical sleeve 7. 8) is inserted, fixed and joined by caulking or drawing of the bottomed cylindrical cold cathode 7, and the other end of the power supply lead wire 8 is sealed and led out of the glass tube 6. Also,
The cylindrical cold cathode 7 has a hollow portion with a length of about 3 mm, and a hole 9 having a hole diameter of 0.1 mm ² is formed on a side wall portion within 2 mm from the inner bottom surface (the end surface of the power supply lead wire 8). ing.

The cold-cathode low-pressure discharge lamp having the above-mentioned structure was used at room temperature of 25 ° C.
The lamp was turned on under the condition of a lamp current of 6 mA, and a life test was performed. Also, 150
Even after turning on for 00 hours, the cylindrical cold cathode 7 did not fall off. Further, after the end of the life test, the cold cathode low-pressure discharge lamp was broken, and the state of the inner wall surface of the cylindrical cold cathode 7 was observed. As a result, it was confirmed that sputtering was performed substantially uniformly on the whole.

In this embodiment, the outer diameter of the bottomed cylindrical cold cathode 7 is 0.4 to 0.8 mm, the inner diameter is 0.2 to 0.6 mm, and
Similar effects were obtained when the size of the hole formed in the side wall portion within 2 mm was changed. The inner diameter is 0.7mm
If there is enough space in the electrode area, the hole diameter can be set to about 0.4 mm2, which facilitates hole forming. Further, the shape of the hole may be any of a circle, a triangle, and a square.

Embodiment 2 In the case of Embodiment 1 described above, the bottomed cylindrical cold cathode 7 is
A cold-cathode low-pressure discharge lamp constructed under the same conditions as in Example 1 except that a 0.7 mm-thick, 0.1 mm-thick, 0.1 mm-thick nickel bottomed cylindrical cup was used at room temperature of 25 ° C. and a lamp current of 6 mA It turned on under the conditions described above, and a life test was performed. As a result, it functioned as a high-luminance and stable light source. Further, even after lighting for 12000 hours, the tubular cold cathode 7 did not fall off.

Embodiment 3 FIG. 2 is an enlarged sectional view showing the configuration of a main part of a cold cathode low-pressure discharge lamp according to this embodiment. That is, a phosphor layer 5 that emits light when stimulated by ultraviolet rays is provided on the inner wall surface, and an outer diameter that encapsulates rare gas (neon and argon) and mercury.
A glass tube 6 made of borosilicate glass having a diameter of 1.2 mm, an inner diameter of 0.9 mm (wall thickness 0.15 mm) and a length of 220 mm, and a pair of bottomed cylindrical cold cathodes respectively sealed at both ends of the glass tube 6 (discharge Electrodes 7).

Here, the bottomed cylindrical cold cathode 7 has an outer diameter of 0.6 m.
This is a molybdenum-bottomed cylindrical cup with an inner diameter of 0.4 mm and a cavity length of 2.5 mm, and a power supply lead wire (tungsten wire with an outer diameter of 0.3 mm) on the outer bottom wall of the cup. 8
Is welded and fixed, and the other end of the power supply lead wire 8 is sealed and led out of the glass tube 6. Further, a hole 9 having a hole diameter of 0.02 mm ² is formed on a side wall portion within 2 mm from the inner bottom surface of the bottomed cylindrical cup forming the cold cathode 7.

The cold-cathode low-pressure discharge lamp having the above-described structure was used at a room temperature of 25 ° C.
When the lamp was turned on under the condition of a lamp current of 6 mA and a life test was performed, it functioned as a high-intensity and stable light source.
Even after the lighting for a long time, the cold cathode 7 did not fall off. Further, after the end of the life test, the cold cathode low-pressure discharge lamp was broken, and the state of the inner wall surface of the cold cathode 7 was observed. As a result, it was confirmed that sputtering was performed almost uniformly as a whole.

In this embodiment, the bottomed cylindrical cold cathode 7 has an outer diameter of 0.4 to 0.7 mm, an inner diameter of 0.2 to 0.5 mm, and
Similar effects were obtained when the size of the hole formed in the side wall portion within 2 mm was changed. The inner diameter is 0.5mm
If there is enough electrode area, the hole diameter can be set to about 0.1 mm ² , which facilitates hole forming. Further, the shape of the hole may be any of a circle, a triangle, and a square.

Embodiment 4 FIG. 3 is a perspective side view showing, on an enlarged scale, the main components of a cold-cathode low-pressure discharge lamp according to this embodiment. That is, the phosphor layer 5 that emits light when stimulated by ultraviolet rays is provided on the inner wall surface,
1.6mm in outer diameter, 1.2mm in inner diameter (0.2mm in wall thickness), and 220mm in length to enclose rare gases (neon and argon) and mercury
It comprises a glass tube 6 made of borosilicate glass of mm and a pair of bottomed cylindrical cold cathodes (discharge electrodes) 7 respectively sealed at both ends of the glass tube 6.

Here, the bottomed cylindrical cold cathode 7 has an outer diameter of 0.9.
This is a cylindrical sleeve made of nickel with a diameter of 0.7 mm, an inner diameter of 0.7 mm, and a length of 4 mm. A power supply lead wire (a Kovar wire with an outer diameter of less than 0.5 mm) is provided on the rear end side (with respect to the discharge area) of the cylindrical sleeve.
The other end of the power supply lead wire 8 is sealed and led out of the glass tube 6 by inserting the distal end portion of the lead wire 8 and fixing and joining it by caulking or drawing of the bottomed cylindrical cold cathode 7. The cylindrical cold cathode 7 has a hollow portion of about 3 mm in length, and its tip reaches the side wall within 2 mm from the inner bottom surface (the tip end of the power supply lead wire 8). A slit 9 'having a notch area of 0.1 mm ² within a range of 2 mm from the bottom surface is formed.

FIG. 4 is a perspective side view showing, on an enlarged scale, the main components of a cold cathode low-pressure discharge lamp according to a modification of this embodiment. This modified example is configured under the same conditions except that the slit 9 ′ having a notch of 0.1 mm ² in the bottomed cylindrical cold cathode 7 is formed on the tip insertion side of the power supply lead wire 8.

Each cold cathode low-pressure discharge lamp having the above configuration
The lamp was turned on under the conditions of ° C and a lamp current of 6 mA, and a life test was performed. Also,
Even after lighting for 15000 hours, the cold cathode 7 did not fall off. Further, after the end of the life test, the cold cathode low-pressure discharge lamp was broken, and the state of the inner wall surface of the cold cathode 7 was observed. As a result, it was confirmed that sputtering was performed almost uniformly as a whole.

Embodiment 5 FIG. 5 is a perspective side view showing, on an enlarged scale, the main components of a cold cathode low-pressure discharge lamp according to this embodiment. That is, the inner wall surface is provided with a phosphor layer 5 that emits light when stimulated by ultraviolet rays, and has an outer diameter of 1.2 mm, an inner diameter of 0.9 mm (thickness of 0.15 mm), and a length for enclosing a rare gas (neon and argon) and mercury. But
It comprises a glass tube 6 made of borosilicate glass of 220 mm, and a pair of bottomed cylindrical cold cathodes (discharge electrodes) 7 respectively sealed at both ends of the glass tube 6.

Here, the bottomed cylindrical cold cathode 7 has an outer diameter of 0.6 m.
This is a molybdenum-bottomed cylindrical cup with an inner diameter of 0.4 mm and a cavity length of 2.5 mm, and a power supply lead wire (tungsten wire with an outer diameter of 0.3 mm) on the outer bottom wall of the cup. 8
Is welded and fixed, and the other end of the power supply lead wire 8 is sealed and led out of the glass tube 6. Further, a slit 9 'having a notch width of 0.02 mm ² extending to the outer bottom surface is provided on a side wall portion within 2 mm from the inner bottom surface of the bottomed cylindrical cup forming the cylindrical cold cathode 7.
Is formed.

The cold-cathode low-pressure discharge lamp having the above-mentioned structure was used at a room temperature of 25 ° C.
When the lamp was turned on under the condition of a lamp current of 6 mA and a life test was performed, it functioned as a high-intensity and stable light source.
Even after the lighting for a time, the tubular cold cathode 7 did not fall off. Further, after the end of the life test, the cold cathode low-pressure discharge lamp was broken, and the state of the inner wall surface of the cylindrical cold cathode 7 was observed. As a result, it was confirmed that sputtering was performed substantially uniformly on the whole.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. For example, the dimensions such as the length and diameter of the glass tube forming the arc tube, the distance between the discharge electrodes, the dimensions of the discharge electrodes,
It is also possible to appropriately change and set the shape and the like.

[0050]

As can be seen from the above description, according to the cold-cathode low-pressure discharge lamp of the present invention in which the structure of the discharge electrode is devised, the local sputtering of the hollow inner wall of the bottomed cylindrical cold cathode is performed. Is prevented, and the life of the bottomed cylindrical cold cathode is greatly extended, so that a small-sized, long-life cold cathode low-pressure discharge lamp can be provided. That is, it is possible to provide a cold-cathode low-pressure discharge lamp suitable for a backlight of a liquid crystal display device which is required to have a small size, high luminance, and a long life.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view illustrating a configuration of a main part of a cold cathode low-pressure discharge lamp according to a first embodiment.

FIG. 2 is an enlarged cross-sectional view showing a configuration of a main part of a cold cathode low-pressure discharge lamp according to a second embodiment.

FIG. 3 is a perspective side view showing, on an enlarged scale, a main part configuration of a cold-cathode low-pressure discharge lamp according to a third embodiment.

FIG. 4 is a perspective side view showing, on an enlarged scale, a main part configuration of a cold-cathode low-pressure discharge lamp according to a modification of the third embodiment.

FIG. 5 is a perspective side view showing, in an enlarged manner, a main part configuration of a cold cathode low-pressure discharge lamp according to a fourth embodiment.

6A and 6B show a main part configuration of a conventional cold-cathode low-pressure discharge lamp, in which FIG. 6A is a cross-sectional view showing the entire structure, and FIG. 6B is an enlarged cross-sectional view showing the main part structure.

FIG. 7 is a characteristic diagram showing an example of the relationship between the inner diameter of a metal cylindrical cup forming the cold cathode of the cold cathode low-pressure discharge lamp and the lighting life.

8 (a), 8 (b) and 8 (c) are cross-sectional views schematically showing a state in which a local spattering phenomenon occurs inside the hollow of the cylindrical cold cathode with the lighting time of the cold cathode low pressure discharge lamp. .

[Explanation of symbols]

 1, 6 glass tube 2, 5 phosphor layer 3, 3 ', 7 tubular cold cathode (discharge electrode) 4, 4', 8 power supply lead wire 9, 9 ' Chipping (hole, slit)

Claims (5)

(57) [Claims] A glass tube provided with a phosphor layer on an inner wall surface and enclosing a rare gas or a mixture of a rare gas and mercury, and a metal inner diameter of 0.8 sealed at at least one end of the glass tube. In a cold cathode low-pressure discharge lamp comprising a cylindrical cold cathode of less than mm, the cylindrical cold cathode has a bottomed shape in which the discharge region side is open, and forms a cavity from the inner bottom wall surface to the opening end, A cold-cathode low-pressure discharge lamp characterized in that at least a part of a side wall portion within 2 mm from an inner bottom wall surface is notched. 2. The cold-cathode low-pressure discharge lamp according to claim 1, wherein the notch in the cylindrical cold-cathode side wall has at least one hole or slit. 3. The cylindrical cold cathode according to claim 1, wherein the total area of the partially cutout region of the side wall portion within 2 mm from the inner bottom wall surface is 0.02 to 0.4 mm ² . Cold cathode low pressure discharge lamp. 4. The cold-cathode low-pressure discharge lamp according to claim 1, wherein the cylindrical cold cathode has a side wall thickness of 0.05 to 0.2 mm. 5. The cylindrical cold cathode is made of one type of metal selected from the group consisting of nickel, stainless steel, molybdenum, tantalum and tungsten. Cold cathode low pressure discharge lamp.