JP2801790B2 - Discharge lamp electrode - Google Patents

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 for 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 the Illuminating Engineering Institute of Japan (Vol. 73, No. 5, pp. 40-46). As explained,
In order to obtain easy-to-read LCD panel displays, optical characteristics such as brightness, brightness uniformity, emission color, etc.
Mechanical dimensions and electrical characteristics that meet features such as light weight and low power consumption are required. In addition, since the liquid crystal panel is vulnerable to heat, it is required that the light emitting surface does not reach a high temperature and the lighting life is long. In other words, unlike ordinary fluorescent lamps for general illumination, it is particularly required that the dimensions are small and the power consumption is small, and at the same time, the display 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 starting rare gas or mercury charged are determined so as to be suitable for low power consumption, and furthermore, the optimal electrode design is made. Then, the lamp is lit by a high-frequency power supply to obtain required brightness and color rendering.

Incidentally, in order to reduce the size of the fluorescent lamp, it is necessary to reduce the size of the electrodes. Therefore, a hot cathode type electrode having a filament coil having a small strand diameter is often used in order to reduce the power consumption with a small size and a rapid temperature rise, but the power consumption is 1 W or less, for example, 0.5.
In the case of the fluorescent lamp of W 1, the filament diameter of the filament coil is extremely small. However, if the filament diameter is reduced as described above, it is difficult to support the filament coil, and the filament coil is weak against vibration and impact. For this reason, as shown in Japanese Utility Model Application Laid-Open No. 64-19251, the present inventors arranged a filament coil having an emitter attached to a metal pipe having one end 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 cylindrical shape, that is, a hollow cathode shape, it not only holds a filament coil, but also has a so-called hollow cathode effect as described in, for example, JP-A-64-33844. And the cathode drop voltage that does not contribute to light emission is reduced. Therefore, there is also 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, the power consumption is increased to several watts and the power is increased. In the case of a fluorescent lamp with a high luminance, if the power consumption is reduced to 1 W or less, a thin filament coil is required. Since the amount of emitter that can be attached to the surface is small, the emitter is not worn out early, and the amount of electron beams and the like during discharge increases,
Since it collides with a thin filament coil, the lighting life is inevitably shortened. In particular, lighting with a high-frequency power source places a burden on small electrodes, and also has the problem of shortening the lighting life.

Therefore, an electrode shown in FIG. 3 has been studied.
In other words, a bottomed pipe made of metal or sintered metal
10, a sintered body 25 having a hole 26 is provided.The sintered body 25 is composed of, for example, a tungsten metal powder and a barium strontium calcium oxide powder as an emitter in a weight ratio. The mixture was mixed at a ratio of 50:50 and pressed and sintered.

[0006]

Since such an electrode has a large amount of emitter material and does not use a thin filament coil, it is possible to extend the lighting life even if the power consumption is slightly increased and the power is increased. However,
When the fluorescent lamp provided with this electrode is turned on, the sintered body 25 gradually collapses with the consumption of the emitter material, and small pieces thereof are scattered in the bulb and appear black. This is because the mixing ratio of the emitter substance in the sintered body is high and the strength of the sintered body is weak. Therefore, if the mixing ratio of the emitter substance is reduced to about 30%, sufficient intensity can be obtained, but sufficient characteristics as a lamp cannot be obtained. Accordingly, 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 hardly broken and black fragments are not scattered in a bulb.

[0007]

Means for Solving the Problems To achieve the above object, the present invention provides an emitter layer having an emitter material as a main component and a metal layer having a high melting point metal as a main component alternately at least two layers each. The sintered bodies, which are laminated and have a hole in the lamination direction at the center, are placed in a pipe made of metal or metal powder sintering so that the holes of the sintered body can be visually recognized.

[0008]

In such an electrode, the metal layer mainly composed of the high melting point metal is strongly sintered, but the emitter layer mainly composed of the emitter substance is sandwiched between the metal layers. There is almost no collapse. And since the amount of the emitter material in the emitter layer is large, the total amount of the emitter material in the sintered body does not decrease, and sufficient characteristics as a lamp can be obtained. Long life.
In addition, since holes in the stacking direction are drilled at the center of the sintered body, the emitter substance of each layer diffuses into the inner surface of these holes and contributes to discharge, and a drop in cathode drop voltage due to the hollow cathode effect is expected. it can.

[0009]

FIG. 1 is an explanatory view showing one end of a fluorescent lamp provided with an electrode according to the present invention, and the other end 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 opposite to 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 a lead rod 14. A predetermined amount of rare gas and mercury are sealed in the bulb 30, and a phosphor layer 32 is adhered to the inner surface.

The electrode 1 has a sintered body 20 placed in a bottomed tubular pipe 10 made of sintered metal or metal powder, and a rear end portion 11 of the pipe 10 is caulked to a lead rod 14. Have been. A hole 21 is provided in the center of the sintered body 20, and the tip 22 of the sintered body 20 is
It is located about 1mm back from 12. In other words, the hole 21 is made visible when viewed from the periphery of the other electrode having the same structure. If the hole 21 is retracted too far from the tip 12, the hole 21 becomes invisible, and the back side described below will be described. Is less likely to contribute to the discharge, and the hollow cathode effect is reduced.

Here, as shown in FIG. 2, the sintered body 20 is formed by alternately laminating, for example, about 10 layers of the emitter layers E and the metal layers M, respectively. Each of the emitter layer E and the metal layer M is composed of a mixture of an emitter material and a high melting point metal. The emitter layer E contains an emitter material as a main component. For example, the emitter material has a weight ratio of 70% or more. Conversely, the high melting point metal is 70% or more. Of course, the metal layer M may be 100% of the high melting point metal, that is, the high melting point metal alone, but it is almost impossible to sinter the emitter layer M with the emitter substance alone. As the emitter material, an oxide of an alkaline earth metal, for example, BaO 2 or a mixture of BaO and an oxide of another alkaline earth metal, or a composite oxide can be used. Tungsten, molybdenum, nickel, and the like used in the above can be used.

The method of manufacturing 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. A fixed amount is filled, and each layer is pressed at a pressure of about several tens kg / cm ² . Then, the mandrel may be removed and fired at, for example, about 1500 ° C. for 30 minutes. As a result, the metal layer M containing little or no emitter material is firmly sintered. At this time, the thickness of the metal layer M is preferably about 20 to 40 μm, and the thickness of the emitter layer E is preferably about 100 to 150 μm. The uppermost layer, that is, the layer constituting the tip 22 may be any, but it is preferable that the uppermost layer be the emitter layer E from the standpoint of lamp characteristics. The lowermost layer, that is, the powder to be filled first may be any. Alternatively, it can also be produced by successively coating and firing each powder solution without using a press, but in this case, the thickness of each layer is smaller than the above value.

When a fluorescent lamp provided with such electrodes is energized, an arc discharge occurs between the two electrodes and the lamp is turned on. However, the emitter material of each layer is diffused into the inner surface of the hole 21 and the total amount of the emitter material is reduced. Since there are many, very good lamp characteristics can be obtained. When the lamp is lit for a long time, the emitter material is consumed and the emitter layer E becomes brittle. However, since the emitter layer E is sandwiched between the strong metal layers M, the emitter layer E hardly collapses during lighting. When the uppermost layer is the emitter layer E, this layer is broken and fragments are scattered in the bulb. However, since the emitter layer E is thin, the amount is small and the concentration of the emitter substance is high. And almost inconspicuous. 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 for a discharge lamp for a light source such as an image reader which requires miniaturization.

[0014]

As described above, the discharge lamp electrode of the present invention comprises a sintered body contained in a pipe formed of a multilayer structure of an emitter layer having a high emitter substance concentration and a metal layer having a high melting point metal concentration. With the structure and the hole in the stacking direction provided in the center thereof, the emitter layer can be firmly held without reducing the total amount of the emitter substance. Therefore, sufficient characteristics as a lamp can be obtained, and the sintered body is hardly collapsed, so that black fragments are not scattered in the bulb.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a fluorescent lamp provided with 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]

 REFERENCE SIGNS LIST 1 electrode 10 pipe 14 lead rod 20 sintered body 21 hole 30 bulb 32 phosphor layer E emitter layer M metal layer

Claims (1)

(57) [Claims] 1. A sintered body in which two or more emitter layers each containing an emitter substance as a main component and a metal layer mainly containing a high melting point metal are alternately laminated, and a hole in the laminating direction is formed at the center. An electrode for a discharge lamp, wherein the hole is placed in a pipe made of metal or sintered metal powder so that the hole is visible.