JPH04126331A - Cold cathode discharge lamp - Google Patents

Abstract

PURPOSE:To increase a contact area so as to enhance joint strength by mutually displacing center lines of an electrode shaft and an electrode head. CONSTITUTION:An electrode head 41 and an electrode shaft 42 are mutually off-centered, that is both centers made mutually eccentric to be but welded together. In this case, an electron-emitting substance 43 filled in a hollow portion of the electrode head 41 is composed of lanthanum boride LaB6 and the like, and emits electrons from an opening portion of the electrode head 4 on the side of a discharge space 2 into the discharge space. Since the electrode head 41 and the electrode shaft 42 are butt welded together eccentrically to each other the upper end of the electrode shaft 42 is deviating from the opening portion of the electrode head 41 to increase a contact area between the two and thereby enhancing the joint strength.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a cold cathode discharge lamp using a cold cathode as an electrode;
Especially regarding the structure of the cold cathode.

(Prior Art) Recently, a meter using a cold cathode paper pressure gas discharge lamp has been proposed as a display pointer on a display panel of an automobile meter or an electric appliance.

This display pointer consists of a low-pressure discharge lamp, such as a xenon glow discharge tube, whose bulb is shaped like an extremely thin hollow needle, and one end of this lamp is attached to the rotating pointer shaft of the meter, and this rotating pointer shaft rotates. When the lamp moves, the discharge lamp also rotates as a unit, so that the thin discharge lamp functions as a pointer.Moreover, when the discharge lamp is turned on, it emits light itself and illuminates the display scale. It has the advantage of not requiring special lighting.

A discharge lamp used as a pointer for such a meter has an internal electrode made of a cold cathode inside an elongated hollow rod-shaped bulb, and a band-shaped external electrode along the axial direction on the outer surface of the bulb. , is configured to apply high frequency power between these internal electrodes and external electrodes to generate glow discharge within the bulb.

The reason why a cold cathode is used as an internal electrode is that this type of cold cathode generates less heat than a hot cathode and suffers less thermal damage, so it has a longer lifespan. Since it generates less heat, there is less heating of the surrounding bulbs, and the diameter of the bulb can therefore be reduced; conversely, it is advantageous to use a cold cathode for lamps with small bulb diameters.

Conventional cold cathodes are composed of an electrode head made of nickel, etc., and an electrode shaft (lead wire) made of Jume-Soto wire, etc., joined to this.The electrode head has a circular or prismatic shape, a circle or a square shape. They were shaped like cylinders, umbrellas, and plates.

However, recently, thin discharge lamps with bulb inner diameters of 311n1 or less have been developed, and in order to accommodate the cold cathode in the narrow space of such thin bulbs, it is necessary to reduce the size of the electrode head. .

Moreover, since the cold cathode of this type of lamp generates a discharge between it and the external electrode, it is necessary to apply a voltage of about IKV at startup to cause the discharge, and in order to facilitate this startup discharge, it is necessary to It is necessary to increase the amount of electrons emitted, and for this purpose it is desirable that the surface area of the electrode head be large.

In order to satisfy these conditions, it is desirable for the electrode head to have a hollow shape such as a cylinder, an elliptical cylinder, or a rectangular cylinder. With such a hollow structure, the outer diameter can be made small, and the can increase the surface area, increase the current value and increase the amount of electron emission,
A so-called hollow effect can be expected.

Another advantage is that the hollow portion may be filled with powder of an electron emitting substance (emitter) to enhance the electrode function.

(Problem to be Solved by the Invention) However, when joining an electrode shaft to a hollow cylindrical electrode head, a method is adopted in which the ends are brought together and resistance welded. When joining with the centers of the shafts aligned, most of the tip surface of the electrode shaft faces the opening of the cylindrical electrode head, which reduces the contact area between the electrode head and the electrode shaft, resulting in a decrease in joint strength. be.

Even when the hollow part of the cylindrical electrode head is filled with electron emissive material powder, not only does the actual contact area between the electrode head and the electrode shaft become smaller, but the electron emissive material powder also comes into contact with the bonding surface. It has the disadvantage that it adheres and reduces the bonding strength.

In order to increase the contact area between the electrode head and the electrode shaft, it is conceivable to make the electrode shaft thicker, but in this case, the sealing property with respect to the bulb is reduced, and the adhesion with the bulb is deteriorated, making it easy to leak. It is also conceivable to increase the contact area by crushing the tip end surface of the electrode shaft, but in this case, processing becomes troublesome and expensive.

Therefore, the problem of the present invention is that when a hollow cylindrical electrode head and an electrode shaft are butt-joined, the contact area is small and the joining strength is reduced.

The present invention has been made based on the above-mentioned circumstances, and it is an object of the present invention to provide a cold cathode discharge lamp in which the bonding strength between the hollow cylindrical electrode head and the electrode shaft is increased.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, the center lines of the electrode shaft and the electrode head are offset from each other, and the tip end surface of the electrode shaft is butt-jointed to the end surface of the electrode head. Features.

(Function) According to the present invention, since the center lines of the electrode shaft and the electrode head are offset from each other, the tip end surface of the electrode shaft does not face the opening of the electrode head, but faces the thick part. The contact area increases and the bonding strength increases.

(Example) The present invention will be described below based on an example shown in the drawings.

In the figure, 1 is a bulb of a cold cathode xenon glow discharge lamp used for the indicator needle of a meter.This bulb 1 is made of a glass tube with an outer diameter of 2.5 mm, an inner diameter of 1.5+ am, and a total length of about 60 mm. It has an elongated discharge space 2.

As described above, one end of the valve 1, which has a needle shape as a whole, forms a pinch seal 3 as shown in FIG.

An internal electrode 4 is sealed in a pinch seal portion 3 formed at one end of the bulb 1. This internal electrode 4 is formed of a cold cathode, and is composed of an electrode shaft 41 that also serves as a lead wire, and an electron emitting material (emitter) 43 filled inside the electrode head 41. There is.

is nickel (Ni) or zirconium (
It is formed from a tube of a low melting point metal such as an aluminum (An) alloy, and has an outer diameter D1 of 0. 7m+++, inner diameter D2 is 0
．． It is molded to 3 mm and cut into lengths of about 1.5 mm.

Since the electrode shaft 42 also serves as a lead wire that passes through the pinch seal portion 3 in an airtight manner, it is made of Dumet wire, and has a wire diameter d of about 0.3 mm, and the rear end of the electrode head 41 is made of a Dumet wire. Butt welded on the part.

In this case, the outer diameter D1 of the opening at one end of the electrode head 41 is 0.
．． 7mm, and the inner diameter D2 is O,:2+m, whereas the outer diameter d of the tip of the electrode shaft 42 is 0.3 degrees, so there is a relationship of D+>d7D2, and therefore the electrode shaft 42 has a Although the tip end surface can be brought into contact with one end surface of the electrode head 41, the contact area becomes small because the opening portion is not contacted.

For this reason, in this embodiment, as shown in FIGS. 2 and 3, the electrode head 41 and the electrode shaft 42 are offset from each other, that is, their centers are eccentric to each other, and they are butt welded.

The electron-emitting material 43 filled in the hollow part of the electrode head 41 is made of lanthanum La86 or the like, and induces discharge when a starting voltage is applied. The electron emitting material 43 made of lanthanum boride LaB6 is, for example, nickel Ni powder, 10 to 20% by volume of LaB,
The powders are mixed, the mixed powder is filled into the hollow part of the electrode head 41, and the electrode head 41 is subjected to cold wire drawing or swaging processing as described above. Thereafter, heat treatment is performed to melt the nickel powder and solidly weld LaB6. In this way, the electron emitting material 43 made of LaB6 is held in the electrode head 41. The electron emitting material 43 emits electrons toward the discharge space 2 from the opening of the electrode head 41 on the discharge space 2 side.

A phosphor coating 6 is formed on the inner surface of the bulb 1 facing the discharge space 2, and xenon gas is present in the bulb 1 at a temperature of 5 to 40 Torr, specifically 30 T.
It is enclosed to the extent of orr.

An external electrode 7 is provided on the outer surface of the bulb 1 in the form of a band along the axial direction. The external electrode 7 is constructed by applying a paste such as carbon phenol or silver epoxy in a band shape along the axial direction of the bulb 1, and firing the paste.

One end of the external electrode 7 is located at a portion facing the internal electrode 4, and the other end extends to the tip end surface of the tip-off portion of the bulb l.

Further, the width of the external electrode 7 is formed in a range of ⅓ or more of the circumferential length of the bulb 1, that is, an area forming an angle of 120° or more.

A first power receiving terminal IO is formed on the outer surface of the end portion of the bulb 1 that seals the internal cold cathode 4 . This first
The power receiving terminal IO is formed in the form of a film, and is connected to the lead wire 5. Therefore, this first power receiving terminal lO is connected to the cold cathode 4.

Further, on the outer surface of the bulb l, the first power receiving terminal lO
A second power receiving terminal 11 is formed at a position spaced apart from each other in the axial direction. The second power receiving terminal 11 is also made by applying and firing a conductive paste such as silver epoxy, and has a predetermined width and extends in the circumferential direction. This second power receiving terminal 11 is connected to the external electrode 7. Note that the second power receiving terminal 11 is formed so as to avoid a slit portion 9 of the light shielding film 8, which will be described later.

Furthermore, a light-shielding coating 8 is formed on the outer surface of the bulb 2.

The light-shielding film 8 has the components of carbon, epoxy resin, and adhesive, and is applied to the surface of the bulb 2 on which the external electrode 7 is provided, covering the external electrode 7, and is formed by firing the applied film. has been done.

The light-shielding film 8 has a light-transmitting slit portion 9 located on a surface opposite to the surface on which the external electrode 7 is provided and extending in the axial direction. In other words, the light-transmitting slit portion 9 is formed by the light-shielding coating 8
It is formed of a transparent part that does not form a

To explain further, an external electrode 7 is provided on one side of the outer surface of the bulb 2, as shown in cross section in FIG. A light-shielding coating 8 is provided on the other surface 180 degrees opposite to the electrode 7.
A light transmitting slit portion 9 is formed without forming a slit.

The width of the light transmission slit portion 9 is smaller than the width of the external electrode 7.

The light within the bulb 2 is emitted to the outside only through the light transmitting slit portion 9, so that the discharge lamp 1 has an aperture shape.

Note that the second power receiving terminal 11 is not covered with the light shielding film 8 and is exposed on the outer surface of the lamp l, as shown in FIG.

The operation of an embodiment of such a configuration will be explained.

When high frequency power is supplied between the cold cathode 4 provided inside one end of the discharge lamp and the external electrode 7, glow discharge occurs between the internal cold cathode 4 and the external electrode 7 within the discharge space 2.

This glow discharge excites the xenon gas filled in the discharge space 2 and causes it to emit ultraviolet rays with a spectrum unique to xenon gas. This short wavelength light excites the phosphor coating B, which causes the phosphor coating 6 to generate visible light.

The light emitted from the phosphor coating 6 is emitted to the outside through the slit portion 9. For this reason, in addition to the fact that the bulb 2 is originally thin, the narrow slit portion 9 further restricts the light band, so that this discharge lamp emits a needle-like narrow band of light.

Therefore, since the display scale is displayed using this discharge lamp and is illuminated, no other special light source is required.

In the cold cathode 4 of the above embodiment, the electrode head 41 has a hollow cylindrical shape, and the hollow part of the electrode head 41 is filled with an electron emitting substance 43, so that electron emission can be promoted and the electrode function can be enhanced. .

In the case of this embodiment, the hollow cylindrical electrode head 41
Since the ends of the electrode shafts 42 are eccentrically abutted against the end faces of the electrode shafts 42 and resistance welded, the contact area between the electrode head 41 and the electrode shafts 42 is increased, and the joint strength is improved.

For example, set the eccentricity of both to 0 and 0.1** and 0
．． As for 2**, when the peeling strength was measured by a bending test, it was the weakest when the eccentricity was 0;
．． The case with 2mm was the strongest.

For electrodes with the above dimensions, if the eccentricity is set to 0.2 mm or more, the side surface of the electrode shaft 42 protrudes from the side surface of the electrode head 41, which reduces the contact area and causes the electrode head 41 to align with the central axis of the bulb 2. This is not desirable because it deviates greatly from the

Note that the present invention is not limited to the structure of the above embodiment.

That is, in the above embodiment, the case where the hollow part of the electrode head 41 was filled with the electron emitting material 43 was explained, but the present invention can be practiced even when the hollow part of the electrode head 41 is left hollow without being filled with the electron emitting material 43. Further, instead of the electron emitting material 43, a getter may be filled, or a mixture of an electron emitting material and a getter may be filled.

Further, the discharge lamp of the present invention is not limited to being used as an indicator needle of a meter, and any discharge lamp may be used as long as it has a cold cathode.

Further, the discharge gas sealed in the bulb is not limited to xenon alone, and a mixed gas containing at least one of neon, argon, and krypton in addition to xenon may also be sealed.

Then, mercury may be sealed inside the bulb.

Furthermore, the valve is not limited to a straight shape, but may have a bent shape.

[Effects of the Invention] As explained above, according to the present invention, since the electrode head and the electrode shaft are butted and joined eccentrically to each other, the tip of the electrode shaft is shifted from the opening of the electrode head, increasing the contact area between the two. This increases the bonding strength.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a xenon glow discharge lamp used as a guide showing an embodiment of the present invention, Fig. 2 is a sectional view of its sealed end, and Fig. 3 is taken along the line ■-■ in Fig. 2. 4 is a sectional view taken along line IV-IV in FIG. 1, and FIG. 5 is a sectional view taken along line IV-IV in FIG.
It is a sectional view along the -v line. ■... Valve, 3... Sealing part, 4... Cold cathode, 6
... Phosphor coating, 7... Internal electrode, 8... Light-shielding coating, 9... Slit portion, 41... Electrode head, 4
2... Electrode axis, 43... Electron emitting material. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) In a cold cathode discharge lamp in which a cold cathode is sealed at the end of the bulb, and the cold cathode is constructed by butting and joining the tip end of an electrode shaft to the end face of a cylindrical electrode head with open ends, the above-mentioned A cold cathode discharge lamp characterized in that the electrode axis and the center line of the electrode head are joined to each other so as to be offset from each other. (2) The cold cathode discharge lamp according to claim 1, wherein the hollow portion of the electrode head is filled with a powdered electron emitting material.