JPH0574412A - Electrode for discharge lamp - Google Patents

Abstract

PURPOSE:To provide an electrode for discharge lamp, with which an efficient characteristic as a lamp is provided, while a sintered body including an emitter material is hard to be broken, and in which no black fragment will be scattered in a bulb. CONSTITUTION:At least two layers of emitter layers mainly composed of an emitter material and of metal layers mainly composed of a metal of high melting point, are alternately laminated, while a sintered body 20, on which a hole in the direction of the deposition, is formed in the enter, is housed in a pipe comprising metal or sintered metal powder, in such a way that a hole 21 of the sintered body 20 is visible. The emitter layer is thus held by a rigid metal layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a discharge lamp, and more particularly to an electrode for a small fluorescent lamp used as a backlight of a liquid crystal panel.

[0002]

2. Description of the Related Art A fluorescent lamp for a backlight used in a display device using a small liquid crystal panel such as a video-integrated camera is described in detail in, for example, Journal of Lighting Society (Vol. 73, No. 5, pp. 40-46). As explained,
In order to make the display of the liquid crystal panel easy to see, the optical characteristics such as brightness, brightness uniformity, and emission color, and the thinness of the liquid crystal panel,
Mechanical dimensions and electrical characteristics that meet the features of light weight and low power consumption are required. In addition, since the liquid crystal panel is weak against heat, it is required that the light emitting surface does not reach a high temperature and the lighting life is long. That is, unlike a general fluorescent lamp for general illumination, it is particularly required that the size is small and the power consumption is small, and at the same time, it is bright, has good color rendering properties, and has a long service life. For this reason, in the fluorescent lamp for the backlight, the current and voltage, the amount of the rare gas for starting and the amount of mercury enclosed are determined so as to meet the low power consumption, and the electrode design is optimized. Then, it is turned on by a high frequency power source to obtain required brightness and color rendering.

By the way, in order to miniaturize the fluorescent lamp, it is necessary to miniaturize the electrodes. Therefore, a hot cathode type electrode having a filament coil with a small wire diameter is often used in order to reduce the power consumption while being small in size, the temperature rises quickly, and the power consumption is 1 W or less, for example 0.5.
In the case of a fluorescent lamp of W 3, the filament coil has a very small strand diameter, but if it is so thin, it is difficult to support the filament coil and it becomes vulnerable to vibration and shock. For this reason, the inventor, as shown in Japanese Utility Model Laid-Open No. Sho 64-19251, arranges a filament coil having an emitter attached in a metal pipe whose one end is fixed to an inner conductor,
We have proposed a metal pipe that holds a filament coil with a small wire diameter. This metal pipe is
Since it has a substantially bottomed tubular shape, that is, because it is a hollow cathode, it not only holds the filament coil, but also the so-called hollow cathode effect as described in, for example, JP-A-64-33844. The cathode drop voltage that does not contribute to light emission decreases. Therefore, there is an advantage that the power consumption is reduced and the luminous efficiency is improved.

However, in the case of an electrode having such a structure, in the case of a fluorescent lamp in which power consumption is increased to several W and power is increased to reduce the power consumption to 1 W or less, a thin filament coil is obtained. Since the amount of the emitter that can be attached to the battery is small, the emitter is consumed early and disappears, and the electron beam etc. increases during discharge,
Since it collides with a thin filament coil, the lighting life is inevitably shortened. In particular, when a high-frequency power source is used for lighting, a small electrode is burdened and the lighting life is shortened.

Therefore, the electrode shown in FIG. 3 has been studied.
That is, a bottomed pipe made of metal or sintered metal
A sintered body 25 in which holes 26 are provided is contained in the sintered body 25. The sintered body 25 includes, for example, a tungsten metal powder and a barium-strontium-calcium oxide powder as an emitter in a weight ratio. At 50:50 and then pressed and sintered.

[0006]

Since such an electrode has a large amount of emitter material and does not use a thin filament coil, the power consumption can be increased a little to prolong the lighting life. However,
When a fluorescent lamp equipped with this electrode is turned on, the sintered body 25 gradually collapses as the emitter material is consumed, and small fragments thereof scatter in the bulb and appear black. This is because the mixing ratio of the emitter material in the sintered body is high and the strength of the sintered body is weak. Therefore, if the mixing ratio of the emitter material is reduced to about 30%, sufficient strength can be obtained, but sufficient characteristics as a lamp cannot be obtained. Therefore, an object of the present invention is to provide an electrode for a discharge lamp, which has sufficient characteristics as a lamp, and in which a sintered body is hard to collapse and black fragments are not scattered in the bulb.

[0007]

In order to achieve the above object, the present invention has two or more layers each including an emitter layer containing an emitter material as a main component and a metal layer containing a refractory metal as a main component alternately. The sintered body is laminated and has a hole formed in the center of the laminated body so that the hole of the sintered body can be visually recognized in a pipe made of metal or metal powder sintering.

[0008]

In such an electrode, the metal layer containing the refractory metal as a main component is strongly sintered, but the emitter layer containing the emitter material as a main component is sandwiched by this metal layer, so that the emitter layer is illuminated during lighting. Is rarely broken. And since the amount of emitter material in the emitter layer is large, the total amount of emitter material in the sintered body does not decrease, sufficient characteristics as a lamp can be obtained, and even if the power consumption is increased a little and the power is turned on. Longer life.
In addition, since a hole in the stacking direction is opened in the center of the sintered body, the emitter material of each layer diffuses to the inner surface of this hole and contributes to discharge, and it is expected that the cathode drop voltage will decrease due to the hollow cathode effect. it can.

[0009]

FIG. 1 is an explanatory view showing one end side of a fluorescent lamp provided with electrodes according to the present invention, and the other end side has the same structure. This fluorescent lamp has a power consumption of about 3.5 W and is used for a backlight of a liquid crystal panel. A pair of electrodes 1 are arranged to face each other in a bulb 30 made of soft glass and having an inner diameter of 5 mm. . The bulb end 31 is sealed with glass beads 15 provided on the lead rod 14. Then, a predetermined amount of rare gas and mercury are enclosed in the bulb 30, and the phosphor layer 32 is attached to the inner surface.

The electrode 1 has a sintered body 20 housed in a bottomed tubular pipe 10 made of metal or metal powder sintered. The rear end 11 of the pipe 10 is fixed to a lead rod 14 by caulking. Has been done. A hole 21 is provided in the center of the sintered body 20, and the tip 22 of the sintered body 20 is the tip of the pipe 10.
It is at a position retracted by 1 mm from 12. In other words, the hole 21 is visible when viewed from the periphery of the other electrode having the same structure, and if the hole 21 is retracted too much from the tip 12, the hole 21 cannot be viewed, and the back side described next will be used. It becomes difficult for the emitter layer to contribute to discharge, and the hollow cathode effect is reduced.

Here, as shown in FIG. 2, the sintered body 20 is formed by alternately stacking, for example, about 10 layers of the emitter layers E and the metal layers M, respectively. The emitter layer E and the metal layer M are both composed of a mixture of an emitter material and a refractory metal, and the emitter layer E contains the emitter material as a main component. For example, the emitter material is 70% by weight or more, and the metal layer M is On the contrary, the high melting point metal is 70% or more. Of course, the metal layer M may be 100% refractory metal, that is, the refractory metal alone, but the emitter layer M is almost impossible to sinter with the emitter material alone. As the emitter material, an oxide of an alkaline earth metal, for example, BaO or a mixture of BaO and an oxide of another alkaline earth metal, or a complex oxide can be used. As a refractory metal, a common electrode material is used. Tungsten, molybdenum, nickel, etc. used in the above can be used.

The method for producing such an electrode will be briefly described. A mandrel for forming a hole 21 is inserted into a pipe 10 having a tip 12 facing upward, and powder for an emitter layer E and powder for a metal layer M are alternately placed. It is filled in a fixed amount, and each layer is pressed at a pressure of several tens Kg / cm ² . Then, the mandrel may be removed, and the firing may be performed at about 1500 ° C. for 30 minutes. As a result, the metal layer M containing a small amount of emitter material or containing no emitter material is strongly sintered. At this time, it is preferable that the metal layer M has a thickness of 20 to 40 μm and the emitter layer E has a thickness of about 100 to 150 μm. The uppermost layer, that is, the layer forming the tip 22 may be any layer, but it is preferable to use the uppermost layer as the emitter layer E from the viewpoint of lamp characteristics. Further, the lowermost layer, that is, the powder to be initially filled may be any. Alternatively, it can be produced by sequentially coating a solution of each powder and firing without pressing, but at this time, the thickness of each layer becomes smaller than the above value.

When a fluorescent lamp provided with such electrodes is energized, an arc discharge occurs between the two electrodes and they are lit, but the emitter material in each layer diffuses into the inner surface of the hole 21, and the total amount of emitter material is reduced. Since it is large, it is possible to obtain extremely good lamp characteristics. Then, when it is turned on for a long time, the emitter material is consumed and the emitter layer E becomes brittle. However, since the emitter layer E is sandwiched by the strong metal layer M, the emitter layer E hardly collapses during lighting. When the uppermost layer is the emitter layer E, this layer is broken and the fragments are scattered in the bulb. However, since the emitter layer E is thin, the amount is small and the concentration of the emitter material is high, so the fragments are white. And is almost unnoticeable. The electrode of the present invention can be used not only as a fluorescent lamp for a backlight of a liquid crystal panel but also as an electrode of a discharge lamp for a light source such as an image reader, which is required to be downsized.

[0014]

As described above, in the electrode for a discharge lamp of the present invention, the sintered body contained in the pipe is a multilayer body of an emitter layer having a high emitter substance concentration and a metal layer having a high melting point metal concentration. Since the structure is provided and the hole in the stacking direction is provided in the center, the emitter layer can be firmly held without reducing the total amount of the emitter material. Therefore, sufficient characteristics as a lamp can be obtained, moreover, the sintered body is hard to collapse and black fragments do not scatter in the bulb.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a fluorescent lamp including an electrode of the present invention.

FIG. 2 is an explanatory diagram of a sintered body.

FIG. 3 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode 10 Pipe 14 Lead rod 20 Sintered body 21 Hole 30 Bulb 32 Phosphor layer E Emitter layer M Metal layer

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[Procedure amendment]

[Submission date] September 9, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

Claims (1)

[Claims] 1. A sintered body in which two or more layers each including an emitter layer containing an emitter material as a main component and a metal layer containing a refractory metal as a main component are alternately laminated, and a hole in the lamination direction is formed in the center. An electrode for a discharge lamp, characterized in that the hole is housed in a pipe made of metal or metal powder sintered so as to be visible.