JPH0544134B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a display discharge lamp having a double conical electrode structure with a conical cathode operating as a hollow cathode, and in particular to maintaining a predetermined electrode spacing. According to
The present invention relates to a display discharge lamp that has high brightness, long life, and stable quality and can be widely used as a light source for various displays.

[Prior technology] Traffic information display on expressways, destination and time display at airport terminals, time display in urban areas, noise and exhaust gas concentration display, general advertising display outdoors, etc., night lights in corridors of buildings, hotels, etc. Conventionally, small incandescent light bulbs and various discharge lamps have been used as light sources for various displays, and each is used depending on its characteristics for the purpose. Among these conventional light sources, incandescent light bulbs provide high brightness, but they consume a lot of power and have a short lifespan.On the other hand, discharge lamps do not have the short lifespan of incandescent light bulbs, but they have low brightness and electrodes. There were other problems such as blackening of the envelope due to spatter and further deterioration of brightness, and high driving voltage.

Therefore, in order to solve the above-mentioned problems, the present applicant has proposed a display discharge lamp according to the invention of Japanese Patent Application Laid-Open No. 59-20960. The above display discharge lamp has a conical cathode, and operates in a hollow cathode state by appropriately selecting various conditions such as the shape and dimensions of the conical cathode, including the opening angle, the pressure of the filled gas, and the magnitude of the current. It is something that makes you Therefore, due to the hollow cathode effect, the display discharge lamp has low driving voltage and power consumption, is comparable in brightness to conventional incandescent lamps, and has a lifespan several times longer. Excellent properties can be obtained, such as the ability to achieve

In particular, for large display discharge lamps, the third
As shown in the figure, since the double conical electrode structure is adopted in which the conical anode 4 is arranged to surround the conical cathode 3, the cathode current density in the operating state is increased and the negative glow is generated in the conical shape. The above-mentioned hollow cathode 3 is formed so that it overflows not only inside the cathode 3 but also at its outer periphery, and the inner surface of the conical anode 4 placed on the outer periphery of the cathode 3 acts as a reflective surface. In addition to the cathode effect, there are advantages in that the light emission can be further strengthened and the light emitting area can be expanded.

[Problems to be Solved by the Invention] In the display discharge lamp having the above-mentioned double conical electrode structure, in order to ensure that the conical cathode operates as a hollow cathode, the distance between the anode and the cathode must be made as small as possible. It's better. However, there is nothing between the anode and the cathode to prevent contact between the two electrodes, and if the electrode spacing is set too small, there is a risk that the two electrodes will be short-circuited due to manufacturing variations or mechanical vibrations. Therefore, the set value of the electrode spacing cannot be made very small, and the value is approximately 0.4 mm.

This electrode spacing of 0.4 mm is about the same as the thickness of the negative glow, depending on the type of discharge gas, its gas pressure, the material and surface condition of the cathode, and the setting of discharge conditions such as discharge current. Therefore, there is a risk that the trigger discharge generated between the inner surface of the anode and the outer surface of the conical cathode facing it will continue as it is, forming a glow discharge, and not transferring to the inner surface of the conical cathode. be. In this state, the cathode does not operate as a hollow cathode, and the excellent characteristics due to the hollow cathode effect and the like described above cannot be obtained.

The present invention has been devised to solve the above problems, and in a display discharge lamp with a double conical electrode structure, the electrode spacing can be formed small without shorting the anode and cathode, and the distance between the electrodes can be reduced reliably. The present invention provides a display discharge lamp that can exhibit a hollow cathode effect and an anode reflection effect.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the display discharge lamp of the present invention includes: an airtight container filled with a discharge gas;
In a display discharge lamp having a double conical electrode structure in which a conical anode is arranged to surround a conical cathode that operates as a hollow cathode, the electrode spacing between the outer surface of the cathode and the inner surface of the anode is set as follows: The present invention is characterized in that an insulating spacer is disposed between the cathode and the anode, the thickness of which is set to provide a narrow electrode spacing so that discharge between the inner surfaces cannot be sustained.

[Function] Since the present invention has the above-described configuration, the electrode spacing between the cathode outer surface and the anode inner surface can be easily set to a value at which discharge cannot be sustained, and the electrode spacing can be easily set to a value that does not allow the discharge to continue. does not change due to
Even if the electrode spacing is formed sufficiently narrower than the thickness of the negative glow, there is no possibility that the two electrodes will be short-circuited. As a result, the trigger discharge formed between the outer surface of the cathode and the inner surface of the anode, which cannot be sustained due to the narrow electrode gap between them, transfers from the outer surface of the cathode to the inner surface of the cathode, causing the inner surface of the anode and the inner surface of the cathode to A glow discharge is generated in between. This glow discharge produces a negative glow on the inner surface of the conical cathode, and the negative glows produced on mutually opposing surfaces of the inner surface of the cathode overlap, causing the cathode to operate as a hollow cathode.

[Example] Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a side view of a display discharge lamp according to an embodiment of the present invention, and FIGS. 2A and 2B are a perspective view and a cross-sectional view showing the electrode structure, respectively.

In the figure, a display discharge lamp 1 is constructed by filling an airtight container 2 made of a glass bulb with a lens portion 2a on the front surface with a discharge gas consisting mainly of a rare element or a mixture of rare elements such as Ne and Ar. A conical cathode 3 having an opening 3a on the front surface, and the cathode 3
Conical anodes 4 having an opening 4a on the front surface were arranged facing each other so as to surround the electrodes, and an insulating spacer 5 was arranged between the electrodes 3 and 4 so that the opening 3a side of the outer surface of the cathode 3 was exposed. It has a structure. Further, the cathode 3 and anode 4 are connected and fixed to a base 8 via lead wires 6 and 7, and a resistor 9 for current limiting is connected to the cathode 3 via a lead wire 6. .

The insulating spacer 5 is made of a metal oxide such as alumina, silicon oxide, or forsterite, or a ceramic material, and the material is coated on the outer surface of the cathode 3 or the inner surface of the anode 4 at a portion facing the cathode 3, or by means of plasma spraying or the like. It is formed by depositing a thin layer with a uniform thickness. However, the above cathode 3
By pressing the sharp portion 3b of the anode 4 in the direction of the sharp portion 4b of the anode 4 and bringing the insulating spacer 5 into close contact with the cathode 3 and anode 4, there is a space between the cathode 3 and the anode 4 equal to the thickness of the insulating spacer 5. An electrode spacing is formed. Further, the insulating spacer 5 may be formed by molding the above-mentioned material into a thin film-like conical shape, and by inserting it closely between the cathode 3 and the anode 4, the electrode spacing can be similarly adjusted. can be formed. In this case, the accuracy of the thickness dimension of the insulating spacer 5 is improved.

The thickness of the insulating spacer 5 is such that the electrode spacing determined by this thickness is a size that cannot sustain a glow discharge, that is, it will be formed on the outer surface of the cathode 3 when a glow discharge is generated. The upper limit must be sufficiently smaller than the thickness of the negative glow. This upper limit value varies depending on the selection of discharge conditions such as the type and gas pressure of the discharge gas, the material and surface condition of the cathode 3, the discharge current, etc., but is practically set to about 0.35 mm. Further, the lower limit of the thickness of the insulating spacer 5 is preferably as small as possible in terms of discharge characteristics, but taking into account contact between the cathode 3 and anode 4 due to mechanical vibration etc., the lower limit value is about 0.03 mm.

The insulating spacer 5 may be formed to cover the entire outer surface of the cathode 3, and in this case, the trigger discharge will be formed at the inner surface of the anode 4 and the open end of the cathode 3.

The conical cathode 3 is made of a metal such as nickel, and its opening angle, that is, the angle at the apex of the cone, is between 20 degrees and 90 degrees, which is compatible with both the light emitting area and the hollow cathode effect. The angle within this range is such that a long life can be obtained. Furthermore, the inner surface of the cathode 3 is coated with oxides of alkaline earth metal elements such as BaO, BaSrO ₂ , BaO・Al ₂ O ₃ , oxides of rare earth elements such as Y ₂ O ₃ , or oxides of rare earth elements such as LaB ₆ . An emitter material 10 made of a single substance or a composite of hexaboride or the like is deposited to reduce the discharge sustaining voltage due to the hollow cathode effect and to reduce the electric charge during operation.

[Effects of the Invention] As detailed above, according to the display discharge lamp of the present invention, the electrode spacing between the outer surface of the cathode and the inner surface of the anode can be easily set to a value at which discharge cannot be sustained; This electrode spacing does not change due to vibrations or the like, and even if the electrode spacing is formed sufficiently narrower than the thickness of the negative glow, there is no risk of short-circuiting between the two electrodes. As a result, the trigger discharge formed between the outer surface of the cathode and the inner surface of the anode, which cannot be sustained due to the narrow electrode gap between them, transfers from the outer surface of the cathode to the inner surface of the anode, causing the inner surface of the anode and the inner surface of the cathode to A glow discharge is generated in between. This glow discharge produces a negative glow on the inner surface of the conical cathode, and the negative glows produced on the mutually opposing surfaces of the inner surface of the cathode overlap, causing the cathode to operate as a hollow cathode.

Therefore, according to the present invention, the problem of short circuit between the anode and the cathode, which often existed in the past, can be solved.
Moreover, it is possible to solve the problem that negative glow emission cannot be formed on the inner surface of the cathode, and to provide a display discharge lamp that exhibits a hollow cathode effect and an anode reflection effect with stable quality.

[Brief explanation of the drawing]

FIG. 1 is a side view of the display discharge lamp of the present invention;
2 shows the electrode structure of the display discharge lamp of the present invention, FIG. 2A is a schematic perspective view, FIG. 2B is a sectional view, and FIG. 3 is a side view of a conventional display discharge lamp. 1...Display discharge lamp, 2...Easy airtightness, 3...
...Cathode, 3a...Opening, 3b...Sharp part, 4...
...anode, 4a...opening, 4b...pointed part, 5...
...Insulating spacer, 6...Lead wire (cathode side), 7
... Lead wire (anode side), 8 ... Base, 9 ... Resistor, 10 ... Emitter material.

Claims (1)

[Claims] 1. In a display discharge lamp with a double conical electrode structure in which a conical anode is arranged to surround a conical cathode that operates as a hollow cathode in an airtight container filled with discharge gas, the outer surface of the cathode and the inner surface of the anode An insulating spacer is disposed between the cathode and the anode, the thickness of which is set so that the electrode spacing between the electrodes is so narrow that discharge between the cathode outer surface and the anode inner surface cannot be sustained. A display discharge lamp characterized by: