JPH0613025A - Discharge lamp - Google Patents

Abstract

PURPOSE:To achieve long life of a discharge lamp. CONSTITUTION:An electron emitting material 3 is dry-blended with tungsten powder 2 which is a heat resisting metal powder of high melting point, which is treated by a hot hydrostatic pressure HIP treatment, and is impregnated to form an impregnated cathode material 4. The impregnated cathode material 4 is coated on or attached to a filament 7, and a hot cathode electrode 6 is formed. The electrode 6 is arranged on the end part of a discharge line 5. When the filament 7 is electrified and discharge is made with the impregnated cathode material 4 being heated, the electron emitting material 3 is protected by the tungsten powder 2 in the impregnated cathode material 4 against ion bombardment, and the life of the electrode is extended, and the life of a discharge lamp 1 is thus extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hot cathode type and cold cathode type discharge lamps used for general illumination light sources and backlights of liquid crystal display panels, and more particularly to an electrode structure.

[0002]

2. Description of the Related Art Electrodes for hot cathode discharge lamps used for backlights of fluorescent lamps and office automation equipment are made by depositing an alkaline earth carbonate on a filament such as tungsten by electrodeposition or dipping. Electron emission of oxides is the same as that of electron-emissive materials [emitter] consisting of alkaline earth oxides thermally decomposed in a vacuum or carbonates deposited on metal heated by filaments. It is generally used as a substance. Such a discharge lamp is turned on by heating the electron emitting substance to about 1000 ° C. by energizing the filament and applying a high voltage between the electrodes to emit an emission (electron).

[0003]

The hot-cathode type discharge lamp is superior to the cold-cathode type discharge lamp in starting characteristics, has a large discharge current and high brightness, and is effective as a backlight for OA equipment. It had a short life. That is, the electron emitting material in the electrodes of the hot cathode discharge lamp is reduced by emission of ions and also collapsed and reduced by ion bombardment during lighting, which shortens the life of the electrodes, that is, the life of the discharge lamp. There is.

In fact, the life of a hot cathode discharge lamp is 5000
It is 10000 hours, and it is the current situation that it is extremely difficult to extend the life further. On the other hand, a cold cathode discharge lamp has a long life and is capable of 20,000 hours, but the starting voltage is high, so the cost of the lighting device is high, the power consumption at the electrodes is large, the efficiency is low, and the discharge current is limited. There was a problem that it was difficult to improve the brightness.

Therefore, it is an object of the present invention to improve the electrode structure of a hot cathode discharge lamp to increase the life of the hot cathode discharge lamp. In addition, by improving the electrodes of the cold cathode discharge lamp, the starting voltage is reduced, and the electrode drop voltage is reduced to reduce power consumption and improve efficiency.
At the same time, the discharge current can be easily increased to improve the brightness.

[0006]

The present invention achieves the above object by providing an electrode structure including an impregnated cathode material obtained by impregnating a sintered body of refractory metal powder having a high melting point with an electron emitting material. Is.

The refractory metal powder having a high melting point is a tungsten material, and the electron emitting material is preferably a mixture of an alkaline earth oxide of barium oxide BaO, calcium oxide CaO and strontium oxide SrO.

The impregnated cathode material is formed by dry-mixing a refractory metal powder having a high melting point and an electron emitting material by hot isostatic pressing to form a sintered body. Is desirable for manufacturing.

As a concrete structure of the discharge lamp of the present invention, one having an electrode provided with an impregnated cathode substance at least at both ends of a flat emission type discharge path is suitable as a backlight of an OA equipment.

Further, as a concrete structure of the hot cathode type electrode of the discharge lamp of the present invention, an electrode in which an impregnated cathode substance subjected to hot isostatic pressing is directly applied to a coil-shaped heating filament, , An electrode in which an insulating coating such as an oxide is directly applied to a coil-shaped heating filament, and an impregnated cathode material which has been subjected to hot isostatic pressing is applied to the electrode, or a coil-shaped heating filament The solid impregnated cathode, which has been subjected to hot isostatic pressing, is attached to the electrode, or the metal sleeve heated by the heating filament is added to the solid impregnated cathode that has been subjected to hot isostatic pressing. A material-deposited electrode is functionally and manufacturably desirable.

On the other hand, as a concrete structure of the cold cathode type electrode, it is desirable to use the impregnated cathode substance which is sintered into a plate shape, a column shape or the like by the hot isostatic pressing treatment without a filament.

[0012]

[Function] When an impregnated cathode material obtained by impregnating a sintered body of high melting point refractory metal powder of tungsten with an electron emitting substance of alkaline earth oxide is applied to an electrode of a hot cathode discharge lamp, The sintered body protects the electron emitting material impregnated in it from the ion bombardment during lighting of the discharge lamp, suppresses the consumption of the electron emitting material, and prolongs the life of the electrode itself. Has a long life.

Further, when applied to a cold cathode discharge lamp, the electron emitting material improves the electron emitting ability of the cold cathode, so that the starting voltage is greatly reduced and the cathode drop voltage during emission is also reduced to reduce power consumption. The efficiency is improved and the discharge current can be easily increased to improve the brightness.
Further, the ion impact resistance is also high, and even if the discharge current is increased, the life is not so shortened.

As the impregnated cathode material, a material obtained by dry-mixing an electron emitting material with a refractory metal powder having a high melting point is subjected to hot isostatic pressing (HIP treatment), and the quality is stable, and the electrode has various structures. Is advantageous in manufacturing.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments will be described below with reference to the drawings. It should be noted that the same portions or corresponding portions are denoted by the same reference symbols throughout the entire surface to avoid redundant description.

The hot cathode discharge lamp (1) shown in FIGS. 1 and 2 is a flat emission discharge lamp applied to a back panel of a liquid crystal display panel or the like. Discharge lamp (1)
The two transparent glass plates (11) and (12) are stacked and sealed with frit glass, and the meandering discharge path (5) is formed between the two glass plates (11) and (12). It is formed.

A fluorescent film (not shown) is formed on the inner wall of the discharge path (5), and hot cathode electrodes (6) described later are arranged at both ends of the discharge path (5). Note that the electrode (6) may be arranged at the center of the discharge path (5) or at another location as shown by the chain line in FIG. When an inert gas such as argon and mercury vapor are sealed in the discharge path (5) and a high frequency voltage is applied between the electrodes (6), a discharge is generated in the discharge path (5) and the fluorescent film emits light. Penetrates the glass plate (11) and illuminates the liquid crystal display (13).

The feature of the present invention lies in the electrode (6).
Have an impregnated cathode material. The impregnated cathode material (4) is manufactured by impregnating a sintered body of refractory metal powder of tungsten with an electron emitting material of alkaline earth oxide. Specific structures of the impregnated cathode material (4) and the electrode (6) including the same will be described with reference to FIGS. 3 to 8.

The electrode (6) shown in FIG. 3 has a pair of lead wires (14) to which a filament (7) made of tungsten or the like in the form of a double coil is connected to form a filament (7).
It is a structure in which the impregnated cathode material (4) is directly deposited on the substrate. The tungsten wire (7) is energized by the lead wire (14) to drive the impregnated cathode material (4) to about 100.
When heated to 0 ° C., emissions are emitted from the impregnated cathode material (4) and the discharge lamp (1) is turned on.

The impregnated cathode material (4) is manufactured as follows. The tungsten powder (2) is press-molded and then sintered in a hydrogen atmosphere to obtain a porous sintered body. A predetermined molar ratio of electron-emitting material (3) was added to this sintered body.
The mixture obtained by dry-mixing is heated in a hydrogen atmosphere to obtain a sintered body (10) impregnated with the electron-emitting substance (3). The electron emitting substance (3) is, for example, 4 mol of barium oxide BaO,
1 mol of calcium oxide CaO, strontium oxide S
rO is composed of 1 mol of alkaline earth oxide.

As another effective method for producing the sintered body (10) impregnated with the electron emitting substance, a mixed powder of the above tungsten powder (2) and 4% by weight of the electron emitting substance (3) is used. It is desirable to perform hot isostatic pressing treatment (hereinafter referred to as HIP treatment). For example, a mixture of the tungsten powder (2) and the electron emitting substance (3) having the above-mentioned molar ratio and stirring the mixture is press-molded, the molded body is vacuum-sealed in a capsule, and the capsule is heated to 900 to 1300 ° C. for 100
HIP treatment is performed under a condition of 0 to 2000 atm for about 1.5 hours to manufacture an ingot of the sintered body (10) (the press molding step of the mixed powder may be omitted). Next, this ingot is crushed to a few microns by a ball mill to obtain a fine sintered body (10).

The crushed fine sintered body (10) is directly applied to the filament (7) by the electrodeposition method or the dip method to form the impregnated cathode material (4). When the impregnated cathode substance (4) is heated by the filament (7) and the discharge lamp (1) is turned on, the impregnated cathode substance (4) is consumed by emission emission, but the degree of consumption due to ion bombardment is reduced, and The life of (6) is extended. One of the causes of this long life is that the tungsten powder (2) of the impregnated cathode material (4) protects the electron emitting material (3) impregnated therein from ion bombardment, and the electron emitting material (3). It is thought to suppress the consumption due to the collapse of.
In fact, the life of a discharge lamp (1) with electrodes (6) of impregnated cathode material (4) is about 2 times that of a conventional discharge lamp of the same type.
It was confirmed to be double.

In the electrode (6) shown in FIG. 4, the tungsten powder (2) and the electron emitting material (3) are cylindrically HIP-processed in a state where the filament (7) having an insulating coating is partially buried. To form the impregnated card material (4). In the case of this impregnated cathode material (4), a filament (7) is placed in a Pyrex container (not shown) of a predetermined shape.
At the same time, the tungsten powder (2) and the electron emitting substance (3) may be encapsulated and HIP-treated.

The electrode (6) shown in the partial cross section of FIG.
An insulating coating (8) is formed on the filament (7) in advance, and the impregnated cathode material (4) is deposited on the insulating coating (8) in the same manner as described above. The insulating coating (8) is formed as follows, for example. An electrodeposition liquid containing a carbonate and a binder is attached to the filament (7) and dried. When the filament (7) is heated by energization and the attached electrodeposition material is activated to leave only oxides, a thin insulating coating (8) is formed on the filament (7).

The insulating coating (8) prevents short-circuiting between the single wires of the double coil filament (7) by the tungsten powder (2) of the impregnated cathode material (4), and the resistance value of the filament (7). Prevent the decrease of. This suppresses variations in the characteristics of the hot cathode discharge lamp. The formation of such an insulating film (8) is performed by forming each electrode (6) shown in FIGS.
Can be effectively applied to.

The electrode (6) shown in FIG. 6 has a structure in which a HIP-treated cylindrical impregnated cathode material (4) is arranged around a filament (7). The impregnated cathode material (4) is obtained by press-molding a mixed powder of the tungsten powder (2) and the electron emitting material (3) into a cylindrical shape, encapsulating the same, and subjecting it to HIP treatment. The impregnated cathode material (4) is heated by the filament (7) and the emissions are emitted.

The electrode (6) shown in FIG. 7 is obtained by inserting a HIP-treated rod-shaped impregnated cathode material (4) into a filament (7). This impregnated cathode material (4) is also HIP processed using a mold.

FIG. 8 shows an indirectly heated type hot cathode type electrode (6).
Then, the concave portion (15) is formed on the upper surface of the metal sleeve (9) such as molybdenum containing the filament (7 ') which is a heater.
And the impregnated cathode material (4) is formed in the recess (15).
Is put on. As the impregnated cathode material (4), a HIP-treated sintered body is housed in the recess (15) and fixed.
By heating the metal sleeve (9) with the filament (7), the impregnated cathode material (4) is heated and emits emissions. When the filament (7) is not heated electrically, it can be used as a cold cathode discharge lamp.

Although each of the above embodiments has been described mainly for the flat emission type discharge lamp, the present invention can be effectively applied to a discharge lamp such as a general straight tube fluorescent lamp.

Next, as another embodiment of the present invention, a cold cathode type discharge lamp having an impregnated cathode material will be described with reference to FIGS. 9 to 11. FIG. 9 shows a flat emission cold cathode discharge lamp suitable for a backlight of a liquid crystal display panel. This cold cathode discharge lamp (21) has the same structure as the hot cathode discharge lamp (1) shown in FIGS. 1 and 2 except for the electrode (16), and has a meandering discharge path (5).
have. Electrodes (16) having the structure shown in FIG. 10 are hermetically sealed at both ends and the central bent portion of the discharge path (5). FIG. 10 (a) shows a HIP-treated disk-shaped impregnated cathode material (4) of the present invention with a lead wire (14) attached thereto, (b) a columnar shape, and (c) a hollow type.
Although (d) is an example of a rectangular shape, the shape is not limited thereto, and another shape may be used. As a mounting method, general methods such as welding, caulking and press fitting can be used.

FIG. 11 shows an application example of the present invention. A cold cathode discharge lamp (31) in the form of a thin straight tube (for example, 5 mmφ or less) suitable for a sidelight type backlight has a cylindrical electrode (16) of the present invention. ) Is provided. In the case of a thin tube, the hollow type shown in FIG. 10 (c) may be effective in order to increase the surface area of the electrode (16).

Now, the cold cathode discharge lamps (21) (3
When a high frequency voltage is applied between the electrodes (16) and (16) such as 1), discharge starts and a fluorescent film (not shown) emits light. At that time, the electron emission material of the alkaline earth oxide used for the impregnated cathode has a significantly higher electron emission capacity than the conventional iron alloy-based electrode, so discharge starts at a lower applied voltage than before and the electrode is damaged. Is suppressed and the life is extended. In addition, since the cathode drop voltage during discharge maintenance is significantly lower than in the prior art, the lamp voltage (terminal voltage between the electrodes (16) and (16)) is also significantly reduced, the lamp power is also reduced, and the luminous efficiency is reduced. improves. For example, in the case of a straight tubular cold cathode discharge lamp of 4 mmφ and a lamp current of 5 mA, the conventional iron-nickel-based electrode has a brightness of 16000 cd / m ² and a lamp power of 2.0 W.
cd / m ² , the lamp power is 2.0 W, and the luminous efficiency is improved by 1.4 times. Alternatively, when compared at the same brightness, the lamp power can be reduced to 85% of the conventional level.

In order to improve the brightness by increasing the lamp current of a conventional cold cathode discharge lamp having a tube length of 250 mm and a tube diameter (for example, 3 mmφ) having an iron-nickel system electrode,
For example, if the brightness is 16000 cd / m ² to 30000 cd
When it is set to be / m ² , the electrode is abnormally heated and the electrode is significantly damaged and the life is shortened from 20000 hours to 5000 hours. On the other hand, in the cold cathode discharge lamp (31) of the same size having the electrode of the present invention, the same brightness 30000 is obtained.
Even with cd / m ² , the electrode damage is small and the life is 100
This is 00 hours, which is significantly longer than the conventional 5000 hours. At this time, the lamp power is about 2.8 W as compared with the conventional power of about 3.5 W, which can be reduced as compared with the conventional one, and therefore the efficiency is high. It is considered that the above effect is due to the impregnated cathode of the present invention having a high electron emission ability, and the sintered tungsten suppresses the damage and drop-off of the electron emitting substance from ion bombardment.

[0034]

According to the present invention, the sintered body of the refractory metal powder of the impregnated cathode material obtained by impregnating the sintered body of the refractory metal powder of the high melting point with the electron-emitting substance is impregnated with the electron. It acts to protect the radiant substance from ion bombardment when the discharge lamp is lit, and keeps the life of the electrode itself long. As a result, it becomes possible to easily extend the life of the hot cathode discharge lamp.

Further, the electron emission capability is improved and the power consumption is reduced, and it is easy to achieve high brightness and high efficiency without impairing the life of the cold cathode discharge lamp.

The impregnated cathode material obtained by dry-mixing the refractory metal powder having a high melting point and the electron emitting material by hot isostatic pressing (HIP processing) has improved quality and stability, and has a straight tube shape. It facilitates the fabrication of electrodes for discharge lamps of various structures such as fluorescent lamps and flat-emission fluorescent lamps.

[Brief description of drawings]

FIG. 1 is a plan view including a partial cross section of a hot cathode discharge lamp showing an embodiment of the present invention.

FIG. 2 is a front view of the discharge lamp shown in FIG.

FIG. 3 is an enlarged front view showing a first embodiment of electrodes in the discharge lamp of FIG.

FIG. 4 is an enlarged front view showing a second embodiment of the electrodes in the discharge lamp of FIG.

FIG. 5 is a partially enlarged cross-sectional view showing a third embodiment of the electrodes in the discharge lamp of FIG.

FIG. 6 is an enlarged front view showing a fourth embodiment of the electrodes in the discharge lamp of FIG.

FIG. 7 is an enlarged front view showing a fifth embodiment of the electrodes in the discharge lamp of FIG.

FIG. 8 is a partially enlarged sectional view showing a sixth embodiment of the electrodes in the discharge lamp of FIG.

FIG. 9 is a plan view including a partial cross-sectional view of a flat-emission type cold cathode discharge lamp showing another embodiment of the present invention.

FIG. 10 is a perspective view showing an embodiment of electrodes in the discharge lamp of FIG.

FIG. 11 is a partially cutaway perspective view of a thin straight tubular cold cathode discharge lamp showing an application example of the present invention.

[Explanation of symbols]

 1 Hot Cathode Discharge Lamp 2 High Melting Point Heat Resistant Metal Powder (Tungsten Powder) 3 Electron Emissive Material (Emitter) 4 Impregnated Cathode Material 5 Discharge Path 6, 16 Electrode 7 Filament 8 Insulation Coating 9 Metal Sleeve 14 Lead Wire 21, 31 Cold Cathode Type discharge lamp

Claims (7)

[Claims] 1. A discharge lamp comprising an electrode provided with an impregnated cathode material obtained by impregnating a sintered body of refractory metal powder having a high melting point with an electron emitting material. 2. The discharge lamp according to claim 1, wherein the impregnated cathode material is a material obtained by dry-mixing a refractory metal powder having a high melting point and an electron emitting material, which has been subjected to hot isostatic pressing. . 3. A flat light emitting discharge path at least at both ends thereof,
3. A discharge lamp according to claim 1 or 2 having an electrode with an impregnated cathode material. 4. The discharge lamp according to claim 2, wherein a coil-shaped heating filament is coated with an impregnated cathode material which has been subjected to hot isostatic pressing. 5. The discharge lamp according to claim 4, wherein an insulating coating is formed on the coil-shaped heating filament, and an impregnated cathode material which has been subjected to hot isostatic pressing is deposited on the insulating coating. 6. The discharge lamp according to claim 2, wherein a coil-shaped filament for heating is provided with a solid impregnated cathode material which has been subjected to hot isostatic pressing. 7. The discharge lamp according to claim 2, wherein a metal sleeve heated by the heating filament is coated with a solid impregnated cathode material which has been subjected to hot isostatic pressing.