JP2001076668A - Cold-cathode fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold-cathode fluorescent lamp which allows a backlight unit to be lowered in profile, reduced in weight, and enhanced in brightness, having low power consumption, having high luminous efficiency, and having a long service life. SOLUTION: This cold-cathode fluorescent lamp is equipped with a glass tube 5, having a phosphor layer 6 on its inner wall surface and filled with a rare gas, and a pair of cold cathodes 7, 7' sealed in both end parts of the glass tube 5. The cold cathodes 7, 7' have cylindrical metal cups 7a, 7a' with their opposed surfaces opened and emitter layers 7b, 7b' provided on inner wall surfaces of the cylindrical cups 7a, 7a', The diameters 7c, 7c' of the opposed openings in the cylindrical metal cups 7a, 7a' are reduced to half their inside diameters.

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 fluorescent lamp, and more particularly to a long-life, low-power cold-cathode fluorescent lamp.

[0002]

2. Description of the Related Art In liquid crystal display devices such as personal computers, word processors and liquid crystal televisions, for example, a cold cathode fluorescent lamp (cold cathode low pressure discharge lamp) is generally used as a light source for a liquid crystal backlight. Fig. 4 (a),
(b) is an enlarged view of a main part configuration of a cold cathode fluorescent lamp used as a light source for a liquid crystal backlight,
(a) is a longitudinal sectional view, (b) is a transverse sectional view taken along line aa of (a).

In FIGS. 4 (a) and 4 (b), reference numeral 1 denotes a glass tube 1 provided on its inner wall surface with a phosphor layer 2 which emits light when stimulated by ultraviolet rays and containing a rare gas. 3, 3 'are a pair of cold cathodes respectively sealed at both ends of the glass tube 1, and 4, 4' are connected to the cold cathodes 3, 3 'to supply required electric power from outside the glass tube 1. This is the introduction line.

Here, the cold cathodes 3, 3 'are provided with emitter layers 3b, 3b' on the inner and outer wall surfaces of cylindrical bodies 3a, 3a 'made of Ni-based metal, and impart electron emission properties to save power. Or high performance. And these cylindrical bodies 3a,
3a 'has an opening at the facing surface, and the other end thereof is inserted (fitted) with the end of the introduction wire 4, 4' sealed and introduced into the end of the glass tube 1, and is electrically and mechanically welded. Is connected and held to function as a discharge electrode.

[0005] This type of cold cathode fluorescent lamp has a
When the cold cathodes 3 and 3 'are energized via 4', discharge is started to emit ultraviolet rays, and the ultraviolet rays are converted into visible light by the phosphor layer 2 to function as a light source. By the way, when this kind of cold cathode fluorescent lamp is operated (lighted) at a low current of, for example, 10 mA or less, the cylindrical bodies 3a, 3a forming the cold cathodes 3, 3 '
Emitters 3b and 3b 'provided on the inner and outer wall surfaces of 3a' are used for emitting electrons from cold cathodes 3 and 3 '.

However, the emitters 3b, 3b 'provided on the inner and outer wall surfaces of the cylindrical bodies 3a, 3a' and contributing to the emission of electrons are gradually scattered during lighting and are deposited on the surface of the phosphor layer 2, so that blackening or blackening occurs. This leads to a significant consumption of mercury. That is, the emitters provided on the inner and outer wall surfaces of the cylindrical bodies 3a, 3a 'forming the cold cathodes 3, 3' tend to be easily scattered, and the life of the cold cathode fluorescent lamp is impaired.

[0007]

As described above, with regard to the cold cathode fluorescent lamps described above, thin, light, high brightness, and long life of the backlight unit are regarded as important trends in the market. As for the light source (cold-cathode fluorescent lamp) to be incorporated, not only weight reduction and downsizing, but also longer life and higher luminous efficiency are desired.

[0008] In response to such demands, for example, attempts have been made to improve the fluorescent material, to study the filling gas, and to improve the structure of the cold cathode. Among these remedies, the structure of the cold cathode has a large effect on the amount of power and the life, and so various remedies have been proposed (JP-A-4-58449, JP-A-6-1302, JP-A-8-102285).

[0009] However, it is practically satisfactory.
There has not yet been provided a cold-cathode fluorescent lamp that is lightweight, compact, has a long life, has low power, and has high luminous efficiency.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to make a backlight unit thinner, lighter, have higher brightness, etc., and it is a low-power, high-luminance, long-life cold-cathode fluorescent lamp. The purpose is to provide.

[0011]

According to the first aspect of the present invention, there is provided a glass tube provided with a phosphor layer on an inner wall surface and containing a rare gas, and a pair of cold tubes sealed at both ends of the glass tube. A cold cathode fluorescent lamp comprising a cathode, wherein the cold cathode has a metal cylindrical cup having an opening on an opposite surface, and an emitter layer provided on an inner wall surface of the cylindrical cup, and The opposite opening diameter of the cylindrical cup made of
A cold cathode fluorescent lamp characterized in that the diameter is reduced to less than 1/2 inner diameter. According to a second aspect of the present invention, in the cold cathode fluorescent lamp according to the first aspect, the cylindrical cup is made of a Ni-based cup.

That is, in the cold cathode fluorescent lamp according to the first and second aspects of the present invention, a pair of cold cathodes sealed at both ends are provided.
A cylindrical cup having an open surface facing each other was provided, an emitter layer was provided on at least the inner wall surface (inner peripheral surface) of the cylindrical cup, and the diameter of the opposed opening was reduced to about 1/2 to 1/5. The main point is to adopt the configuration. In the invention according to claims 1 and 2, the glass tube forming the arc tube generally has an outer diameter of about 2 to 4 mm, a wall thickness of about 0.2 to 0.6 mm, and a length of about 50 to 500 mm. The phosphor layer is usually formed of a phosphor used in this type of fluorescent lamp. Further, the metal cylindrical cup forming the cold cathode is formed by using a Ni-based metal such as Ni or Ni alloy, or the like as a material.

The dimensions and structure are generally about 0.6 to 1.0 mm in inner diameter and about 2 to 3 mm in length, and the facing end faces need to be locally reduced in diameter. In other words, only the facing end face openings are stepwise (non-continuous slope)
The diameter must be reduced to 1/2 or less. Here, if the stepwise diameter reduction of the end face opening is not less than 1/2 of the inner diameter other than the end face (the lower limit is about 1/5), the required long life cannot be achieved.

The connection of the cylindrical cup to the lead-in wire is mechanically and electrically joined by a fitting type by welding the fitting connection portion. In addition, the sealing and arrangement of the cylindrical cup in the glass tube is generally concentric with the glass tube.

In the invention according to the first and second aspects, the emitter layer provided on at least the inner wall surface of the metal cylindrical cup forming the cold cathode is an emitter used for a cold cathode fluorescent lamp, for example, an alkaline earth such as barium oxide. Examples thereof include oxides of a class of metals and borides of rare earth elements such as lanthanum boride.

According to the first and second aspects of the present invention, since the cold cathode is configured as described above, the scattering (evaporation) of the emitter from the inner wall surface of the metal cylindrical cup during lighting is suppressed or suppressed at the opening end face. Be captured. Therefore, the adhesion of the emitter to the surface of the phosphor film formed on the inner wall surface of the arc tube is prevented and reduced, and with the prevention of the scattering and adhesion of the emitter, the consumption of mercury during lighting is greatly suppressed. Longer life is achieved.

Since the emitter is scattered (evaporated) from the cold cathode during the lighting operation, it is performed around the tip of the cold cathode (the opposite end face side). The effect of reducing the amount of scattering is important.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment will be described with reference to FIGS. 1 (a), 1 (b), 2 and 3. FIG.

FIGS. 1 (a) and 1 (b) are enlarged views of a configuration example of a main part of a cold cathode fluorescent lamp. FIG. 1 (a) is a longitudinal sectional view, and FIG.
(a) It is a cross-sectional view along the AA line.

In FIGS. 1 (a) and 1 (b), reference numeral 5 denotes a phosphor layer 6 provided on the inner wall surface which emits light when stimulated by ultraviolet rays, and has an outer diameter of 3.0 mm, an inner diameter of 2.0 mm, and a length, which seals a rare gas. 220mm
The glass tubes 7, 7 'are a pair of cold cathodes sealed at both ends of the glass tube 5 via lead wires 8, 8', respectively. Here, the cold cathodes 7, 7 'have, for example, an inner diameter of 0.
8 mm, 2.8 mm long cylindrical cups 7a, 7a 'made of Ni, and the thickness formed on the inner wall surfaces of the cylindrical cups 7a, 7a'.
It is composed of emitter layers 7b and 7b 'of about 10 .mu.m.

The cylindrical cups 7a, 7a 'have leading ends of the lead wires 8, 8' inserted at one end thereof and are mechanically and electrically connected by welding or the like, while the other ends facing each other are provided. The side has a configuration in which the diameter is reduced stepwise by 7c, 7c '. In other words, the other ends facing each other are bent at substantially right angles, and compared to the inner diameters of the original cylindrical cups 7a and 7a '.
Reduced diameter 7c to 1/2 (Example 1) or 1/4 (Example 2)
7c '.

On the other hand, the emitter layers 7b and 7b 'formed on the inner wall surfaces of the cylindrical cups 7a and 7a' are mainly composed of, for example, at least one of barium oxide and a boride of a rare earth element. In this configuration example, the thicknesses of the emitter layers 7b and 7b 'are provided on the inner wall surfaces of the cylindrical cups 7a and 7a' to be substantially uniform, respectively. It may not be provided, and may be provided on the outer wall surface in addition to the inner wall surface.

[0023] Here, the emitter layer 7b composed mainly of borides of barium oxide or a rare earth element, 7b 'are prepared for example BaO, the _{YB 6, GdB 6, LaB 6} , CeB 6 fine powder slurry, such as, This can be formed by flowing, drying and sintering at least on the inner wall surfaces of the cylindrical cups 7a and 7a '.

As a comparative example, in the configuration of the cold cathode fluorescent lamp, the reduced diameters 7c and 7c 'of the cylindrical cups 7a and 7a' are not performed (conventional example), or the reduced diameters 7c of the cylindrical cups 7a and 7a 'are reduced. , 7c 'was changed to 3/4 (reference example), and a cold cathode fluorescent lamp was constructed under the same conditions. A lighting test was performed on each of the cold cathode fluorescent lamps of the above Examples and Comparative Examples at a room temperature and a lamp current of 5 mA. The cathode drop voltage was about 100 V r · m · s, and the luminous efficiency was the same. Of the cold-cathode fluorescent lamp.

On the other hand, when the mercury consumption (mg) after lighting for 5000 hours under the above lighting conditions was obtained, the result shown in FIG. 3 was obtained. The amount of mercury consumption (mg) after lighting for 5000 hours was obtained by heating the blackened portion of the fluorescent lamp and measuring the mercury content of the blackened portion by a reduction vaporization method.

Similarly, under the above-mentioned lighting conditions, an invalid emission length (mm) was evaluated after a test for 5000 hours, and the result shown in FIG. 4 was obtained. The test evaluation of the invalid emission length (mm) was performed based on the distance 6.5 mm between the sealing end of the cold cathode fluorescent lamp and the tip of the electrode. As can be seen from the lighting test, the cold cathode fluorescent lamp according to the example has a reduced mercury consumption during lighting, and accordingly has a longer life and a higher performance (low power consumption, etc.). In addition, the reduction of the invalid light emission length (mm) during lighting means that the longer effective light emission length is maintained.

That is, as described above, by reducing the diameter of the opening end of the cylindrical cup to 1/2 or less, the emitter on the inner wall surface of the cylindrical cup can be used more efficiently (scattering and scattering).
Evaporation is suppressed). With the improvement of the utilization efficiency, the so-called blackening phenomenon is reduced, while the life of the lamp itself is extended,
In addition, an effective light emitting source can be achieved while being made compact.

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 outer diameter, thickness, and length of the glass tube, or the outer diameter, thickness, and length of the cylindrical cup, the thickness, material, and forming method of the emitter layer can be appropriately selected.

[0029]

According to the first and second aspects of the present invention, the adhesion of the emitter to the surface of the phosphor film formed on the inner wall surface of the arc tube is prevented and reduced, and the emitter is scattered and adhered. Since the consumption of mercury in the inside is greatly suppressed, the service life is extended.

That is, since the emitter is more effectively used, it is possible to provide a cold-cathode fluorescent lamp which has a good luminous flux rising property and the like and can maintain a required light emission for a long period of time (has a long life). The provision of the cold cathode fluorescent lamp greatly contributes to downsizing and long life of liquid crystal display devices.

[Brief description of the drawings]

FIG. 1 is an enlarged view showing a configuration example of a main part of a cold cathode fluorescent lamp according to an embodiment, in which (a) is a longitudinal sectional view and (b) is a transverse sectional view.

FIG. 2 is a characteristic diagram showing a comparison of mercury consumption during lighting of the cold cathode fluorescent lamps according to the example and the comparative example.

FIG. 3 is a characteristic diagram showing a comparison between the ineffective light emission lengths during the lighting of the cold cathode fluorescent lamps according to the example and the comparative example.

FIG. 4 is an enlarged view showing a configuration of a main part of a conventional cold cathode fluorescent lamp, where (a) is a longitudinal sectional view and (b) is a transverse sectional view.

[Explanation of symbols]

 1,5 glass tube 2,6 phosphor layer 3,3 ', 7,7' cold cathode 4,4 ', 8,8' introduction wire 7a, 7a '... Ni cylinder Cups 7b, 7b ': Emitter layers 7c, 7c': Reduced diameter

Claims (2)

[Claims] 1. A cold cathode fluorescent lamp comprising a glass tube provided with a phosphor layer on an inner wall surface and containing a rare gas, and a pair of cold cathodes respectively sealed at both ends of the glass tube. Wherein the cold cathode is a metal cylindrical cup having an opening on the opposite surface,
An emitter layer provided on the inner wall surface of the cylindrical cup, and wherein the opposed opening diameter of the metal cylindrical cup is 1/2.
A cold cathode fluorescent lamp having a diameter reduced to an inner diameter or less. 2. The cold cathode fluorescent lamp according to claim 1, wherein the cylindrical cup is made of Ni.