JPH04292846A - Low pressure discharge lamp - Google Patents

Abstract

PURPOSE:To obtain a low pressure discharge lamp allowing the extension of effective luminous length relative to overall bulb length, and ensuring long service life via the prevention of sputtering at a cathode. CONSTITUTION:One of two electrodes is a solid electrode 5 supported on a well 8 passing through one end of a bulb in an airtight condition, and the other is a film electrode 10 comprising a conductive film formed on the inner surface of an insulation blocking body 3 sealing the other end of the bulb. In this case, the aforesaid solid electrode 5 is used as a cathode, while the film electrode 10 is used as an anode.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low pressure discharge lamp with a large effective light emitting length.

0002

[Prior Art] Recently, a small liquid crystal display device has been developed as a color viewfinder for a VTR, and this device has a liquid crystal display panel approximately 23 mm x 18 mm in size that is illuminated from the back by a backlight. ing. As a light source for illuminating a small-area liquid crystal display panel like the one above, there are straight tube fluorescent lamps, U-shaped or W-shaped light sources.
Since the shape of a fluorescent lamp would be too large, a very small flat cold cathode fluorescent lamp is used.

[0003] A flat cold cathode fluorescent lamp can create a flat light emitting surface with an area equivalent to that of the liquid crystal display panel, and the liquid crystal display panel can be made almost uniform without using a diffuser or a reflector. It can be irradiated. Further, since the lamp can be made thin, there is an advantage that the thickness of the entire display device can be made thin. By the way, the conventional structure of this type of flat cold cathode fluorescent lamp will be explained based on FIGS. 4 and 5.

In the figure, reference numeral 1 denotes a flat bulb having a cylindrical shape with an oval cross section, and a phosphor coating 2 is formed on the inner surface of the flat bulb 1. The openings at both ends of the flat valve 1 are hermetically closed by flat stems 3, 3 serving as closing members. The stems 3, 3 are made of flat glass and are so-called button stems, and the stems 3, 3 are made of flat glass, and are so-called button stems.
It is airtightly joined to both end openings of the flat valve 1 via. Cold cathodes 5, 5 are attached to such flat stems 3, 3, respectively. The cold cathodes 5, 5 are made of, for example, a nickel plate, with a getter 6 made of zircon-aluminum coated on one side thereof, and a mercury release structure 7 made of a mercury-titanium alloy adhered to the other side. . Note that cold cathodes 5 facing each other,
5, the surfaces coated with getter 6 face each other.

[0005] Such plate-shaped cold cathodes 5, 5 are as follows:
They are respectively joined to wells 8, 8, and these wells 8 pass through the stem 3 in an airtight manner and are led out. The wells 8, 8 are connected to a high frequency lighting circuit 9, and therefore this cold cathode fluorescent lamp is lit at high frequency.

[0006]

[Problem to be Solved by the Invention] In such a flat cold cathode fluorescent lamp, discharge is generated between the cold cathodes 5, so the effective light emitting area L1 is generated between the cold cathodes 5, The back of the cathodes 5, 5 is not activated for light emission. Therefore, the effective light emission length L for the total length L2 of the bulb 1
The ratio L1 /L2 occupied by is desired.

In order to increase the effective light emitting area L1, the length of the cold cathode 5 protruding from the stem 3 can be shortened. However, in the case of the solid cold cathode 5 made of a nickel plate as described above, Even if consideration is given to lowering the protruding height by directing one side toward the counter electrode, a certain length of introduction length of the wells 8 to support the cold cathode 5 is required, so the protruding height of the cold cathode 5 must be reduced. There is a limit to how short it can be.

On the other hand, the inventors of the present invention have developed a system for the stem 3 without using the solid cold cathode 5 made of a nickel plate as described above.
The inner surface of the plate is made of nickel or other conductive metal.
I came up with the idea of forming a film by applying a paint and using this inner surface film as an electrode.

[0009] In this way, since almost the entire length of the bulb emits light, the entire bulb can be used as an effective light emitting area. Therefore, the ratio of the effective light emitting length to the total length of the bulb increases, and conversely, the effective light emitting length increases. If the length is kept the same as before, the overall length of the bulb can be shortened, which is effective in making the lamp more compact.

However, when an electrode made of a film functions in a cathode mode, sputtering occurs violently due to ion bombardment, and therefore there is a problem in life characteristics.

Therefore, an object of the present invention is to provide a low-pressure discharge lamp which can increase the effective light emission length relative to the entire length of the bulb and which has a long life by preventing sputtering of the cathode due to ion bombardment. be.

0012

[Means for Solving the Problems] The present invention provides a low-pressure discharge lamp in which a pair of electrodes are arranged facing each other within the bulb.
One electrode is a solid electrode supported by a well that airtightly penetrates one end of the bulb, and the other electrode is a coated electrode made of a conductive coating formed on the inner surface of an insulating closure that closes the other end of the bulb. It is characterized in that the solid electrode is used as a cathode and the coated electrode is used as an anode.

[0013]

[Operation] According to the present invention, one electrode is a solid electrode supported by the well, and the other electrode is a coated electrode formed on the inner surface of the closing body that closes the other end of the bulb. can be increased. Furthermore, in this case, since the solid electrode is used as the cathode and the coated electrode is used as the anode, sputtering does not occur at the coated electrode, and the lamp life can be extended.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on a first embodiment shown in FIGS. 1 and 2. In this figure, members that may be the same as those in FIGS. 4 and 5 described above are designated by the same numbers, and the description thereof will be omitted. In this embodiment, a solid electrode 5 similar to the conventional one is used as one electrode, and a coated electrode 10 is used as the other electrode.

That is, the solid electrode 5 provided at one end of the bulb 1 is a cold cathode made of, for example, a nickel plate. The surface area of the cold cathode 5 is determined by the lamp current and the filling pressure of the rare gas, and can be calculated from the converted current density (electrode current density/filling pressure 2) when the lighting mode is in the normal glow range. Assuming that the sealing pressure is 60 Torr and the rated lamp current is 31 mA, the required surface area of the cold cathode 5 may be about 20 mm2.

[0016] Such a solid-state cold cathode 5 is a Wells 8,
These wells 8, 8 are connected to valve 1.
The stem 3, which has its end closed, is hermetically penetrated and led out.

Note that zircon is formed on one side of the solid electrode 5.
A getter 6 made of aluminum is applied, and a mercury release structure 7 made of a mercury-titanium alloy is attached to the other side. Note that the getter 6 is provided on the surface facing the discharge space.

The other coated electrode 10 is formed by coating on the inner surface of the stem 3 that closes the other end of the bulb 1. This coated electrode 10 is made of nickel, etc., and includes, for example, nickel powder, additive powder, glass powder, and vehicle (color vehicle).
A paste is prepared by mixing them in a predetermined ratio, and this paste is applied to the inner surface of the stem 3 in a predetermined size and pattern using a screen printing coating method. After drying this, 60
Heat to about 0°C and bake. Note that the film thickness of the coated electrode 10 is approximately 30 μm. This coated electrode 10 is a valve 1
The stem 3 is joined to the wells 8, which hermetically pass through the stem 3, which is joined to the end of the stem 3. These wells 8, 8 are led out to the outside by passing through the stem 3, which has closed the end of the valve 1, in an airtight manner.

The solid-state cold cathode 5 and the coated electrode 10 are connected to a pulse lighting circuit 11. The pulse lighting circuit 11 is a power supply circuit that emits a positive pulse, and has an on/off duty ratio of about 0.1, for example,
It emits pulses at a frequency of about KHz.

In this case, the solid-state cold cathode 5 is connected to the cathode side of the pulse to serve as a cathode electrode, and the coated electrode 10 is connected to the anode side of the pulse to serve as an anode electrode to the pulse lighting circuit 11. Ru. The bulb 1 is filled with mercury released from a mercury release structure 7 made of a mercury-titanium alloy and a rare gas such as argon. In a cold cathode fluorescent lamp having such a configuration, the solid cold cathode 5 serves as a cathode electrode, and the coated electrode 10 serves as an anode electrode, thereby producing a pulse discharge.

[0021] Therefore, the coated electrode 10 does not become a cathode, and therefore the coated electrode 10, which is inherently prone to scattering, is not subjected to ion bombardment, so that sputtering of the coated electrode 10 can be prevented. Therefore, the life of the electrode is extended, the blackening of the tube wall can be prevented, and the life of the lamp is also extended.

Since the coated electrode 10 is formed by directly coating the inner surface of the stem 3, FIGS.
The inter-electrode distance L1 can be made longer than that of the conventional flat cold cathode fluorescent lamp shown in FIG. Therefore, if the total length L2 of the bulb 1 is the same as the conventional one, the effective light emission length can be increased. On the other hand, if the effective light emitting length is the same as that of the conventional lamp, the total length L2 of the bulb 1 can be shortened, which is effective in making the lamp smaller and more compact.

For example, in the conventional case, the effective light emission length L1
was 16 mm, and the total length L2 of the bulb 1 was 23 mm (therefore, the height of each cold cathode 5 was approximately 3.5 mm). However, in the case of this example, if the effective light emission length L1 is set to 16 mm, which is the same as the conventional one, The total length L2 of valve 1 is 20.5
mm (the height of one cold cathode 5 is approximately 3.5 mm).

In the case of the above embodiment, the lamp is lit by a lighting circuit that emits a positive pulse.
The present invention is not limited to this, and any lighting mode may be used as long as the coating electrode 10 does not function as a cathode, and a normal DC power supply or a commercial power supply rectified into DC may be used.

Further, in the above embodiment, the case where the solid electrode 5 is a cold cathode has been described, but the present invention is similar to another embodiment shown in FIG. It may be a case. In this case, the preheated electrode 20 made of a filament needs to be preheated by constantly applying electricity, but even in such a state, the preheated electrode 20 made of a filament must always be heated so that the polarity does not reverse and the coated electrode 10 becomes a cathode. It is necessary to maintain the solid electrode 5 at a lower pulse level than the coated electrode 10.

Further, in the above embodiment, a case has been described in which the stem 3 is joined to the open end of the bulb 1 having a flat cross section, but the present invention is limited by the cross sectional shape of the bulb.
The cross section may be circular, and the lamp is not limited to a flat lamp, but may be a straight tube, a ring, or a bent lamp. Furthermore, the present invention
It is not limited to the case where a liquid crystal display panel is used, and a normal illumination lamp may be used. Alternatively, a rare gas discharge lamp may be used in which at least one of xenon, neon, argon, and krypton is mixed without sealing mercury in the bulb. In the case of such a rare gas discharge lamp, it is possible to implement the method without forming a phosphor coating on the inner surface of the bulb.

[0027]

As explained above, according to the present invention, one electrode is a solid electrode supported by a well, and the other electrode is a coated electrode formed on the inner surface of a closing body that closes the other end of the valve. Therefore, the effective light emission length can be increased compared to the case where both electrodes are solid electrodes. Furthermore, in this case, since the solid electrode is used as the cathode and the coated electrode is used as the anode, the coated electrode is not subjected to ion bombardment, and therefore, the coated electrode is not sputtered, and the lamp life can be extended.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a flat fluorescent lamp showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the assembled lamp in the same embodiment.

FIG. 3 is a sectional view of a flat fluorescent lamp showing another embodiment of the present invention.

FIG. 4 is an exploded perspective view of a flat cold cathode fluorescent lamp showing the background art of the present invention.

FIG. 5 is a sectional view of the assembled lamp in the same example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Bulb, 3...Stem, 5...Solid cold cathode, 10...Coated electrode, 11...Pulse lighting circuit.

Claims (1)

[Claims] Claims: 1. A low-pressure discharge lamp in which a pair of electrodes are disposed facing each other inside the bulb, one electrode being a solid electrode supported by a well that hermetically passes through one end of the bulb, and the other electrode being a solid electrode supported by a well that passes through one end of the bulb. 1. A low-pressure discharge lamp characterized in that the coated electrode is made of a conductive film formed on the inner surface of an insulating closing body that closes an end, the solid electrode is used as a cathode, and the coated electrode is used as an anode.