JPH11288686A - Discharge tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the length of the light unemitting part, and improve light emitting efficiency by providing a glass tube having the opening parts on both ends and a metallic cap having the opening part on one end and having the blocking-up part on the other end, and using a discharge tube on which the opening part side of the metallic cap is sealed in the respective opening parts of the glass tube. SOLUTION: A discharge tube has a glass tube 5 being composed of borosilicate glass having a prescribed dimension and having the opening parts on both ends and having the phosphor 1-applied inside surface and a metallic cap 6 having the opening part on one end and having the locking-up part on the other end and being composed of covar metal having a thermal expansion coefficient close to a thermal expansion coefficient of the glass tube 5. The metallic cap 6 is sealed in the respective opening parts by inserting the opening part side inside the opening part of the glass tube 5, and operates as a follow type discharge electrode at lighting time. By such constitution, the metallic cap 6 can also serve as a sealing member and an electrode to shorten the length of the light unemitting part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge tube used for a light source for a backlight of a liquid crystal display device, a light source for a strobe of a camera, and the like.

[0002]

2. Description of the Related Art Conventionally, cold cathode fluorescent lamps have been frequently used as discharge tubes for backlights of liquid crystal modules. In this cold cathode fluorescent lamp, as shown in FIG. 9, an introduction wire 3 is sealed at an end of a glass tube 2 having a phosphor 1 coated on the inner surface, and a rod-like or cylindrical shape is attached to the tip of the introduction wire 3. It has a configuration that holds the electrode 4.

In such a cold cathode fluorescent lamp, since the electrode structure is simple, it is easy to make the lamp thin and compact, and therefore, it is useful as a light source suitable for reducing the size and weight of a liquid crystal display device. Those having an outer diameter of 1.8 mm have been put to practical use.

[0004]

However, in the conventional cold cathode fluorescent lamp, the length of the so-called non-light emitting portion including the sealing portion and the electrode portion is hardly reduced. For this reason, in contrast to the recent narrowing of the frame of the liquid crystal module, the conventional cold cathode fluorescent lamp has a problem that the luminance at the edge of the liquid crystal screen is reduced due to the long non-light emitting portion. Similarly, in a xenon flash lamp used as a light source for a strobe of a camera, a long non-light-emitting portion has similarly been an obstacle to downsizing the reflector unit. Furthermore, such a cold cathode discharge tube has a problem that the tube voltage and the tube power are high because the cathode drop voltage is high, and the luminous efficiency is low.

The present invention has been made to solve such a problem, and is suitable for a light source for a backlight of a liquid crystal module having a narrow frame, and a light source for an illumination device requiring other compactness. It is an object of the present invention to provide a discharge tube having a short non-light-emitting portion and high luminous efficiency.

[0006]

In order to solve the above-mentioned problems, a discharge tube according to the present invention comprises a glass tube having openings at both ends, a metal cap having an opening at one end and a closing portion at the other end. Wherein the opening side of the metal cap is sealed to each opening of the glass tube.

[0007] With this configuration, the metal cap can serve as both the sealing member and the discharge electrode, so that the length of the non-light emitting portion can be reduced as compared with a conventional discharge tube.

Further, the discharge tube of the present invention has a glass tube having an opening at both ends and a metal cap having an opening at one end and a closing portion at the other end. A side is sealed to each opening of the glass tube, and an electron emitter is provided on the inner surface of the metal cap.

According to this configuration, the efficiency of electron emission from the discharge electrode can be increased, so that the cathode drop voltage can be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a discharge tube according to a first embodiment of the present invention has an outer diameter of 2.1 mm and an inner diameter of 1.5 mm.
mm, both ends made of borosilicate glass having an outer diameter of 2.0 mm and an inner diameter of 1.4 mm, having openings at both ends, a glass tube 5 coated with the phosphor 1 on the inner surface, and an opening at one end. ,
A metal cap 6 having a closed portion at the other end and made of Kovar metal having a thermal expansion coefficient close to the thermal expansion coefficient of the glass tube 5 is provided. The opening side of the metal cap 6 is inserted into the inside of the opening of the glass tube 5, heated to 900 ° C. using high frequency heating or the like, and sealed to each opening of the glass tube 5. It operates as a hollow discharge electrode. The outer diameter of the metal cap 6 is 1.4.
mm, the inner diameter is 1.2 mm, and the length is 3 mm. The distance between the tips of the metal cap 6, that is, the distance between the electrodes is 80 mm, and the total length of the discharge tube is 86 mm. The inner surface of the closed portion of the metal cap 6 is provided with a disk-shaped mercury alloy member 7 having a diameter of 1.1 mm and a thickness of 0.5 mm and containing a getter material such as titanium. This is for sealing mercury into the glass tube 5 by heating when the metal cap 6 is sealed. The getter material such as titanium is for removing impurity gas in the glass tube 5. Further, a mixed gas of argon and neon together with mercury is sealed in the glass tube 5 so that the total pressure becomes 11 kPa.

According to this configuration, since the metal cap 6 can serve as both the sealing member and the electrode, the length of the non-light emitting portion can be reduced as compared with the conventional discharge tube.

When the discharge tube in the first embodiment of the present invention and the conventional discharge tube are lit at a lighting frequency of 50 kHz and a tube current of 5 mA using a high-frequency lighting circuit, the brightness of the tube surface in the axial direction of the discharge tube is obtained. As a distribution, a result as shown in FIG. 2 was obtained. In FIG. 2, a curve A shows the luminance distribution characteristics in the case of the discharge tube according to the first embodiment of the present invention, and a curve B shows the luminance distribution characteristics in the case of the conventional discharge tube. The coordinates on the horizontal axis represent the distance from one end of the discharge tube along the axial direction. In the conventional discharge tube, as shown in FIG. 9, an introduction wire 3 made of Kovar metal is sealed at the end of a glass tube 2 having a phosphor 1 coated on the inner surface. The rod-shaped electrode 4 made of tungsten having a length of 0.8 mm and a length of 3 mm is held. This conventional discharge tube has the same overall length of 86 mm as the discharge tube of the present invention, and the distance between the electrodes is 76 mm.

From FIG. 2, it has been confirmed that the discharge tube in the first embodiment of the present invention has a longer light emitting portion than the conventional discharge tube. Further, the power consumption of the discharge tube according to the first embodiment of the present invention was not different from the conventional one.
As a result, it was recognized that the discharge tube according to the first embodiment of the present invention had a luminous efficiency improved by about 5% as compared with the conventional discharge tube.

As shown in FIG. 3, a discharge tube according to a second embodiment of the present invention has a mercury alloy member 7 containing a getter material such as titanium and an electron emitter on the inner surface of a closed portion of a metal cap 6. 8 is provided. Other configurations are the same as those shown in FIG. Metal oxide La having a perovskite crystal structure as electron emitter 8
_0.5 Sr _0.5 MnO ₃ , outer diameter 1.1 mm, inner diameter 0.
The sintered body was formed into a cylindrical shape having a length of 7 mm and a length of 2 mm. Then, the outer diameter is 1.4 mm, the inner diameter is 1.2 mm, and the length is 3.
The electrode 9 was accommodated in a metal cap 6 having a thickness of 8 mm.
The glass tube 5 coated with the phosphor 1 on the inner surface has an outer diameter of 2.1 mm at the center, an inner diameter of 1.5 mm, and an outer diameter of 2.0 m at both ends.
m, an inner diameter of 1.4 mm, made of borosilicate glass. The total length of the discharge tube is 86 mm, and the glass tube 5
Is filled with 11 kPa of a mixed gas of argon and neon together with mercury. Also, the metal cap 6
Glass tube 5 heated to 900 ° C. using high-frequency heating or the like
Is sealed at each opening.

According to this configuration, since the work function of the electron emitter 8 is smaller than that of metal, electrons can be easily emitted from the electrodes, and the cathode voltage is reduced, so that the tube voltage is reduced. As a result, the tube power is reduced. Thus, the luminous efficiency of the discharge tube can be improved. In addition, a discharge is induced in the hollow portion of the electron emitter 8 formed in a cylindrical shape, the discharge area of the electrode 9 is increased, electrons are more easily emitted, the tube voltage is reduced, and the luminous efficiency is thereby improved. be able to.
Further, since the electron emitter 8 is a sintered body, scattering due to ion bombardment is small, and amalgam formation between the scattering substance and mercury sealed in the tube is reduced, so that the electron emitter 8 and the mercury alloy member 7 are consumed. As a result, the life of the discharge tube can be prolonged.

With respect to the discharge tube provided with the electron emitter 8, the discharge tube provided only with the metal cap 6, and the conventional discharge tube, when the lamp was lit at 50 kHz using a high frequency lighting circuit, the tube current as shown in FIG. -Tube voltage characteristics were obtained.
In FIG. 4, a curve A represents a discharge tube provided with the electron emitter 8 (hereinafter referred to as a discharge tube A), and a curve B represents a discharge tube provided with only the metal cap 6 (hereinafter referred to as a discharge tube B).
Curve C is the characteristic in the case of a conventional discharge tube (hereinafter referred to as discharge tube C). The discharge tube B is a discharge tube having the glass tube 5 coated with the phosphor 1 and the metal cap 6 made of Kovar metal described in the first embodiment. The distance between the electrodes is 80 mm. The total length of the tube is 86 mm. The discharge tube C has a structure as shown in FIG.
Lead-in wire 3 made of Kovar metal with a sealing part length of 2 mm
And a rod-shaped electrode 4 made of tungsten having an outer diameter of 0.8 mm and a length of 3 mm.
mm, the total length is 86 mm.

As apparent from FIG. 4, the discharge tubes B and C had substantially the same tube voltage. On the other hand, discharge tube A
It has been confirmed that can reduce the tube voltage by about 30 V as compared with the discharge tube B. Here, the luminance of the central portion of the discharge tube was 35,000 cd / m ² irrespective of the form of the electrode, so that the discharge tube A emitted about 10% of the discharge tube B and emitted about 15% of the discharge tube C. It was found that the efficiency was improved.

Although La _0.5 Sr _0.5 MnO ₃ is used as a material constituting the electron emitter 8, other composition ratios and elements may be used as long as they are metal oxides having a perovskite crystal structure. Also, for example, La ₂ O _3-X (where 0 ≦
Other metal oxides having no perovskite-type crystal structure such as x <3) may be used.

As the mercury alloy member 7, a metal, compound or mixture containing mercury may be used.

The discharge tube according to the third embodiment of the present invention has an electron emitter 8 applied to the inner surface of a metal cap 6 as shown in FIG. According to this configuration, the luminous efficiency can be improved as compared with the conventional discharge tube.

In the discharge tube according to the fourth embodiment of the present invention, as shown in FIG. 6, an electron emitter 8 is housed in the form of a sintered body having no hollow portion. According to this configuration, the luminous efficiency can be improved as compared with the conventional discharge tube.

The discharge tube according to the fifth embodiment of the present invention is provided with a sintered body in which an electron emitter 8 is formed in a thin rod shape as shown in FIG. . According to this configuration, the luminous efficiency can be improved as compared with the conventional discharge tube.

The discharge tube according to the sixth embodiment of the present invention has a structure in which a metal cap 6 is circumscribed and sealed to a glass tube 5 as shown in FIG. According to this configuration, the luminous efficiency can be improved as compared with the conventional discharge tube.

The present invention can be applied not only to a fluorescent discharge tube but also to other discharge tubes such as a xenon flash discharge tube.

[0026]

As described above, according to the discharge tube of the present invention, the length of the non-light emitting portion can be shortened as compared with the conventional discharge tube, and the luminous efficiency can be improved.

Further, according to the discharge tube of the present invention, by providing the electron emitter having a low work function in the metal cap, the electron emission efficiency from the electrode can be increased and the cathode drop voltage can be reduced. The tube voltage and the tube power can be reduced as compared with the related art, and the luminous efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a discharge tube according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a luminance distribution in a tube axis direction at the time of lighting of the discharge tube according to the first embodiment of the present invention and a conventional discharge tube.

FIG. 3 is a sectional view of a main part of a discharge tube according to a second embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the tube current and the tube voltage when the discharge tube according to the first embodiment of the present invention, the discharge tube according to the second embodiment, and the conventional discharge tube are turned on.

FIG. 5 is a sectional view of a main part of a discharge tube according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a main part of a discharge tube in the fourth embodiment.

FIG. 7 is a sectional view of a main part of a discharge tube in the fifth embodiment.

FIG. 8 is a sectional view of a main part of a discharge tube in the sixth embodiment.

FIG. 9 is a partial sectional view of a conventional discharge tube.

[Explanation of symbols]

 Reference Signs List 1 phosphor 5 glass tube 6 metal cap 7 mercury alloy member 8 electron emitter

Claims (5)

[Claims] 1. A glass tube having an opening at both ends and a metal cap having an opening at one end and a closing portion at the other end, wherein the opening side of the metal cap is each opening of the glass tube. Discharge tube characterized by being sealed in a part. 2. The discharge tube according to claim 1, wherein an opening of the metal cap is inserted inside each opening of the glass tube and sealed at both ends of the glass tube. 3. An opening of the glass tube is inserted inside an opening of the metal cap, and the opening side of the metal cap is sealed to both ends of the glass tube. The discharge tube according to claim 1. 4. The discharge tube according to claim 2, wherein an electron emitter is provided on an inner surface of the metal cap. 5. The discharge tube according to claim 4, wherein said electron emitter is made of a metal oxide having a perovskite crystal structure.