JPH02257564A - Low pressure discharge lamp - Google Patents

Abstract

PURPOSE:To prevent shortcircuiting between No.1 current receiving terminal in connection with the internal electrode and an external electrode and also a creeping discharge by furnishing a non-covered part, where no light shielding film is formed, between the external electrode and the No.1 current receiving terminal. CONSTITUTION:A non-covered part 12, where no light shielding film 7 is formed, is provided in a recess 2a of a bulb 2 constructed between an external electrode 6 and No.1 current receiving terminal 10. This provides non-continuous condition between them through the action of the non-covered part 12 even in case the light shielding film 7 containing plastics receives heat from the lamp concerned, which is being lit, and carbonized, so that the external electrode will never be put in electrical continuity to the current receiving terminal 10. Accordingly they will never be shortcircuited with each other. A reason similar thereto should prevent generation of creeping discharge.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention provides an internal electrode at one end of a bulb in the shape of an elongated hollow rod, and a strip-like structure along the axial direction on the outer surface of the bulb. This model has an external electrode and a light-shielding coating is formed on the outer surface of the bulb except for the elongated light-transmitting slit.
Regarding low pressure discharge lamps.

(Prior art) Recently, in display panels for automobiles and electrical equipment,
Attempts have been made to use low pressure discharge lamps as direct display indicators.

That is, for example, a low-pressure discharge lamp such as a xenon glow detonator is shaped into an extremely thin hollow needle with a bulb inner diameter of approximately 2 mm to 3 mm, and one end of this discharge lamp is attached to the rotating pointer shaft of a meter. When the shaft rotates, the discharge lamp is also rotated integrally, so that the discharge lamp functions as a pointer, and when the discharge lamp is turned on, it emits light and illuminates the I display scale. Therefore, it has the advantage of not requiring special lighting.

A discharge lamp used as a pointer for such a meter is equipped with an internal electrode inside a bulb in the shape of a long, slender hollow rod, and a band-shaped external electrode is provided along the axial direction on the outer surface of this bulb. The bulb is configured to apply high frequency power between the bulb and the external electrode to generate glow discharge within the bulb.

In addition, a light-shielding coating made of synthetic resin is formed on the outer surface of the bulb, and this light-shielding coating is formed except for a thin strip-shaped light-transmitting slit extending in the axial direction of the bulb. It is designed to emit light from. Therefore, this type of discharge lamp is an aperture-shaped lamp, and the light-emitting part of the pointer is shaped like an extremely thin needle.

By the way, conventionally, a structure has been adopted in which coated cords are connected to the internal electrodes and external electrodes, respectively, and the internal electrodes and the external electrodes are connected to a high-frequency power source through these coated cords.

In the case of using a covered cord as described above, the covered cord is connected to the lead wire connected to the internal electrode by soldering or caulking, so the connection work is troublesome. The discharge lamp used is attached to a rotating pointer shaft and rotated, so if the covered cord is derived from the discharge lamp,
These coated cords tend to be twisted or bent as the discharge lamp rotates, and such deformation of the coated cord is likely to lead to breakage over time. Also,
Deformation of the coated cord creates resistance to the turning operation of the discharge lamp, and also has the drawback of inhibiting the operation of the meter needle, which requires high precision and quick response.

For this reason, a first power receiving terminal made of conductive paste is provided on the outer surface of the bulb end in which the internal electrode is sealed and is connected to the internal electrode. A second power receiving terminal made of conductive paste is provided and connected to the external electrode at a distance from the second power receiving terminal, and these first and m2 power receiving terminals are brought into contact with a power feeding terminal provided on a bulb holder engaged with the bulb, A structure has been proposed in which the device is connected to a power source through this power supply terminal.

In this way, there is no need for a covered cord, there is no need to worry about wire breakage, and when used as a pointer, there will be no problem of impeding rotation.

(Problems to be Solved by the Invention) Conventionally, the light-shielding film forming the light transmission slit is formed over the entire outer surface of the bulb except for the portion where the first and second power receiving terminals are exposed. was.

In such a case, both the first power receiving terminal and the external electrode were in contact with the light shielding film.

However, the light-shielding film is made of a synthetic resin containing carbon, epoxy resin, and adhesive components, and there is a risk that it will be heated and carbonized if it receives heat from the lamp while the lamp is lit. When the light-shielding film is carbonized, the electrical resistance decreases, and the first power receiving terminal and the external electrode become electrically conductive, resulting in a short circuit between them.

Furthermore, if the light-shielding film between the first main power receiving terminal and the external electrode becomes carbonized, creeping discharge may occur, resulting in damage to the lamp.

The present invention aims to provide a low-pressure discharge lamp that prevents short circuits and creeping discharges between the first power receiving terminal and the external electrode, and has a long life.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, a non-light shielding film is formed between the external electrode and the first power receiving terminal so that a light shielding film is not formed between the external electrode and the first power receiving terminal so that these are not connected by the light shielding film. It is characterized by having a membrane part.

(Function) According to the present invention, since no light shielding film is formed between the external electrode and the first power receiving terminal, even if the light shielding film deteriorates due to heat, there will be no short circuit between the first power receiving terminal and the external electrode. Creeping discharge is prevented from occurring.

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

In the figure, l indicates a low-pressure discharge lamp used as a pointer for automobile speedometers, etc. The discharge lamp in this embodiment is a cold cathode discharge lamp, and this discharge lamp l is equipped with a glass bulb 2 in the shape of an elongated hollow rod. ing.

The glass bulb 2 has, for example, an outer diameter of 2.5 ml, a total length of about 60 cm, and is formed into a substantially needle shape.

A cold cathode 3 is sealed as an internal electrode at one end of the bulb 2, and the cold cathode 3 is connected to a lead wire 4 that passes through the sealed end of the bulb 2 in an airtight manner. A recess 2a is formed at the end of the bulb 2 to seal the lead wire 4 therein.

A phosphor coating 5 is formed on the inner surface of the bulb 2.
Further, a discharge gas made of at least one of xenon and krypton is sealed in the bulb 2 at a pressure of 50 torr or more.

An external electrode 6 is provided on the outer surface of the bulb 2 in the form of a band along the axial direction. The external electrode 6 is constructed by applying a paste such as carbon phenol or silver epoxy in the form of a strip to a predetermined length of the bulb 2, and then firing the paste.

A first power receiving terminal IO is formed on the outer surface of the end portion of the bulb 2 in which the internal electrode 3 is sealed.

The first power receiving terminal 1O is made of a conductive paste such as silver epoxy, and is formed in a film form continuously over the entire outer surface of the bulb 2, covering the end surface of the bulb 2 and the region from this end surface to the recess 2a. There is. The first power receiving terminal 10 is connected to a lead wire 4 that passes through the sealed end of the bulb 2 in an airtight manner, and is connected to the cold cathode 3 inside.

Further, on the outer surface of the bulb 2, the first power receiving terminal 10 is provided.
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 of conductive paste such as silver epoxy, and is similar to the first power receiving terminal lO.
It is formed in the circumferential direction with a predetermined width spaced apart from the center in the axial direction. This second power receiving terminal 11 is formed so as to avoid a slit portion 8 of a light shielding film 7, which will be described later, and is connected to an external electrode 6.

A light-shielding coating 7 is formed on the outer surface of the bulb 2.

The light-shielding film 7 has components of carbon, epoxy resin, and adhesive, and is formed on the surface of the bulb 2 on which the external electrode 6 is provided, covering the external electrode 6, and also on the surface of the bulb 2 on which the external electrode 6 is provided. A light transmitting slit portion 8 that extends in the axial direction and does not form the light shielding film 7 is formed on the surface opposite to the above surface.

That is, as shown in cross section in FIG. 4, the outer surface of the bulb 2 is provided with an external electrode 6 on one side, and a light-shielding coating is provided on the other side 180 degrees opposite to the external electrode 6. A light transmitting slit portion 8 is formed in which the slit 7 is not formed.

Therefore, the light within the bulb 2 is emitted to the outside only through the light transmission slit section 8, and for this reason, this cold cathode fluorescent lamp l has an aperture shape.

In addition, the light shielding wave @7 is formed on the entire surface of the bulb 2, except for the first power receiving terminal IO and the second power receiving terminal 11, and further excluding the four parts 2a, in addition to the light transmitting slit part 8. ing.

That is, the first power receiving terminal lO and the second power receiving terminal it
is exposed on the outer surface of the lamp l.

In addition, in the conventional case, as shown by an imaginary line 30 in FIG.
A light-shielding film was formed on the outer surface of the concave portion 2a of the CC jib part, but in this embodiment, the light-shielding film was not formed on these four parts 2a, and the first power receiving terminal 10 and the external electrode 6 were formed here to be shielded from light. The non-light-shielding coating portion 12 is formed so as to prevent electrical conduction through the coating 7.

Note that the non-light-shielding film portion 12 can be formed by once forming a light-shielding film on the outer surface of the bulb 2, and then peeling off the light-shielding film at the relevant portion.

The cold cathode discharge lamp l configured in this way has a lamp holder 2.
Attached to 0.

The lamp holder 20 is made of an electrically insulating material and has a U-shaped cross section, and has first and second power supply terminal tongues 21 and 22 fixed thereto at a distance from each other in the longitudinal direction. These power supply terminal tongue pieces 21 and 22 are formed by bending conductive leaf springs such as phosphor bronze into a substantially U shape, and the holding pieces 23a are opposed to each other as shown by the imaginary lines in FIG.

The valve 2 is held between the parts 23b.

The lamp holder 20 is fixed to a pointer shaft 25 of the meter, and rotates integrally with the pointer shaft 25 when the pointer shaft 25 rotates.

Note that the pointer shaft 25 of this embodiment is constituted by a hollow shaft (not shown), and two covered cords (not shown) are inserted into this hollow pointer shaft 25, and one end of each of these covered cords is connected to the 1 and 2nd power supply terminal tongue piece 21.22
The other end is connected to a high frequency power source.

The cold cathode discharge lamp 1 is adapted to be attached to the lamp holder 20 at the end thereof where the internal electrode 3 is sealed. That is, the first power receiving terminal lO and the second power receiving terminal film 11 formed on the outer surface of the bulb 2 are opposed to the first power feeding terminal tongue piece 21 and the second power feeding terminal tongue piece 22 on the lamp holder 20 side. and place this lamp in the lamp holder 20.
When the bulb 2 is pushed in from the opening side, the clamping pieces 23a and 23b of the first and second power supply terminal tongues 21 and 22 clamp the first power receiving terminal 10 and the second power receiving terminal 11 and close the valve 2. mechanically supported. Therefore, the cold cathode discharge lamp l is fixed to the lamp holder 20. In this case, the first and second power supply terminal tongues 21.22 are in electrical contact with the first power receiving terminal IO and the second power receiving terminal 11, respectively, and are therefore connected to these power supply terminal tongues 21.22. Inner electrode 3 and outer electrode 6 by covered cord
is connected to a high frequency power source.

According to such a configuration, the cold cathode discharge lamp l is supported by the lamp holder 20 on the end side where the internal electrode 3 is sealed.
In this case, the lamp is held between the first power supply terminal tongue piece 21 and the second power supply terminal tongue piece 22 which are located at two locations apart in the axial direction, so the support strength of the lamp is high even though only the end portion is supported. It is something.

In addition, a first power feeding terminal tongue piece 2 is connected to the internal electrode 3 and the external electrode 6 from the first power receiving terminal lO and the second power receiving terminal 11.
Since high frequency power is supplied through the first and second power supply terminal tongues 22, a glow discharge is generated between the internal electrode 3 and the external electrode 6 within the bulb 2.

This glow discharge excites the phosphor wave film 5 and prompts it to emit light, and this emitted light is emitted from the slit portion 8 to the outside. Therefore, in addition to the fact that the bulb 2 is originally thin, the slit portion 8 exhibits an even narrower band of light, so that this discharge lamp 1 is suitable for indicating a display scale as a pointer. Moreover, since it shines by itself, there is no need for any other special light source.

The lamp holder 20 is fixed to a pointer shaft 25, and when the pointer shaft 25 rotates, the lamp holder 20 is also rotated together, so that the discharge lamp l attached to the lamp holder 20 is also rotated together. Since the vehicle is rotated and moved to a position according to the vehicle speed, the speed scale can be indicated.

Since a non-coated portion 12 on which the light-shielding coating 7 is not formed is provided in the four portions 2a of the bulb 2 formed between the external electrode 8 and the first power receiving terminal IO, the light-shielding coating 7 is not formed on the non-coated portion 12. Even if the light-shielding coating 7 having a resin component is carbonized by being heated by the heat from the lamp, the external electrode 6
Since the external electrode B and the first power receiving terminal 10 are in a discontinuous state due to the non-coated portion 12, that is, they are in an insulated state, the external electrode B and the first power receiving terminal 10 are electrically conductive. There isn't. Therefore, there is no problem of short circuit between these.

Further, since the non-coated portion 12 is formed between the external electrode 6 and the first power receiving terminal IO, creeping discharge does not occur, and there is no fear of damage to the lamp.

Because of this, the lamp life is extended.

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

That is, although the above embodiment describes the case where the discharge lamp of the present invention is used as a pointer of a meter, the present invention is not limited to this, and the discharge lamp may be used as a backlight of a liquid crystal display device. .

Furthermore, the internal electrodes 3 may be provided at both ends of the bulb 2.

Further, the electrode is not limited to a cold cathode type, but may be a hot cathode type, and at least one of xenon, krypton, neon, argon, etc., or mercury may be sealed inside.

[Effects of the Invention] As explained above, according to the present invention, since a non-coated portion in which a light-shielding film is not formed is formed between the external electrode and the first power receiving terminal, thermal deterioration of the light-shielding film can be avoided. Also, since insulation is maintained between the main power receiving terminal and the external electrode, short circuits and creeping discharges are prevented from occurring between them, resulting in a long life.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is an exploded perspective view of a discharge lamp and a lamp holder used as a meter pointer, FIG. 2 is a rear view of the discharge lamp, and FIG. In the figure ■−
FIG. 4 is a cross-sectional view taken along the mV-TV line in FIG. 2. l... Cold cathode discharge lamp, 2... Bulb, 3... Internal electrode, 4... Lead wire, 6... External electrode, 7...
Light-shielding coating, 8... Light transmission slit portion, lO... First power receiving terminal, 11... First power receiving terminal, 12...
Non-coated portion, 20... Lamp holder, 21... First power feeding terminal tongue piece, 22... Second power feeding terminal tongue piece, 25.
...Pointer shaft.

Claims (1)

[Claims] An internal electrode is provided at the end of a bulb in the shape of an elongated hollow rod, an external electrode is provided along the axial direction on the outer surface of the bulb, and the outer surface of the bulb end is sealed with the internal electrode. a first power receiving terminal connected to the internal electrode, and a second power receiving terminal spaced apart from the first power receiving terminal in the axial direction and connected to the external electrode; In a low-pressure discharge lamp in which a light-shielding film is formed that forms a light-transmitting slit along the axial direction, a light-shielding film is formed between the external electrode and the first power receiving terminal. 1. A low-pressure discharge lamp characterized in that a non-coated portion having no light-shielding coating formed thereon is provided so that the lamp is not connected to the low-pressure discharge lamp.