JPH03116648A - Low pressure discharge lamp - Google Patents

Abstract

PURPOSE:To improve luminance distribution along an axial direction of a bulb bu insulating a wide electric power supply connecting part formed in an outer electrode from a bulb outer plane with an electrically insulating layer. CONSTITUTION:A wide second electric power supply connecting part 8 is formed on a light shielding film 10 having an insulating property. Since the insulating film is formed between the second electric power supply connecting part 8 and the outer plane of a bulb 2, the wide second electric power supply connecting part 8 does not work as an outer electrode and since that part makes contact with the outer plane of a bulb 2 with a narrow width W3 of an outer electrode 7, the luminance at the part can be lowered. In this way, the whole luminance distribution is improved. Furthermore, the width of the second electric power supply connecting part 8 can be retained wide so that the surface area of the part can be large, the surface area of the contact with the secondary electric power source terminal 22 is kept large, and thus electric connection is stabilized.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a low-pressure discharge lamp such as a cold cathode discharge lamp, a xenon glow discharge lamp, etc. formed by an elongated hollow bulb. .

(Prior Art) Recently, attempts have been made to use low-pressure discharge lamps as indicator needles in display devices for all-in-one equipment, electrical equipment, and the like.

That is, attempts have been made to use cold cathode low pressure discharge lamps, such as xenon glow discharge tubes, as pointers for meters in audio equipment, for example.

This is a discharge lamp arc tube bulb with an inner diameter of 2 to 3 inches.
The discharge lamp is made into an extremely thin hollow rod shape of approximately II11, and one end of the discharge lamp is attached to the rotating shaft of the meter, so that when the rotating wheel rotates, the discharge lamp also rotates as a unit, so that the discharge lamp is aligned with the indicator needle. Moreover, when the discharge lamp is turned on, it emits light itself and illuminates the display scale, so it has the advantage of eliminating the need for special lighting.

The discharge lamp used as a pointer for such a meter has an internal electrode made of a cold cathode inside one end of the bulb, which is shaped like a long, slender hollow rod, and an internal electrode made of conductive paste on the outside surface of the bulb along the axial direction. A band-shaped external electrode is provided, and high frequency power is applied between the internal electrode and the external electrode to generate glow discharge within the bulb.

In addition, this discharge lamp has a light-shielding coating made of synthetic resin formed on the outer surface of the bulb, which is shaped like an elongated hollow rod. , the light is emitted from this elongated strip-shaped light transmission slit.

Therefore, this type of discharge lamp is an aperture-shaped lamp, and therefore the light-emitting part that serves as a pointer is shaped like an extremely thin needle.

Incidentally, in a lamp in which discharge is caused between an internal electrode and an external electrode, the brightness changes depending on the width of the external electrode formed along the axial direction on the outer surface of the bulb. In other words, the brightness increases when the width of the external electrode formed in a band shape using conductive paste on the outer surface of the bulb is increased.

For this reason, the tip of the discharge lamp functions as the tip of the pointer, so high brightness is required, and it is desirable to increase the brightness and make the pointer and scale easier to see. Therefore, the external electrode at the tip of the bulb should be made wider. A method has been adopted to increase the brightness and make it brighter.

However, in the above-mentioned band-shaped external electrode, the part connected to the power supply is provided near the base end of the bulb, and this power supply connection part has to have a large contact area with the external power supply side terminal. , are widely formed.

(Problem to be Solved by the Invention) However, if a wide power supply connection part as described above is formed directly on the outer surface of the bulb in continuation with an external electrode having a predetermined width, the brightness of this part will be as shown by the broken line in FIG. As shown in the figure, there is a problem in that the brightness distribution becomes high and the brightness distribution along the axial direction of the bulb becomes undesirable.

If the width of the power supply connection part is made smaller in an attempt to lower the brightness at this location, the area becomes smaller, so the contact area with the external power supply side terminal becomes smaller, and the electrical connection becomes unstable.

The present invention aims to provide a low-pressure discharge lamp in which the luminance distribution along the axial direction of the bulb is favorable when forming the power supply connection portion of the external electrode.

[Structure of the Invention] (Means for Solving the Problems) The present invention is characterized in that an electrical insulating layer is provided between the wide power supply connection portion continuous with the external electrode and the outer surface of the bulb.

(Function) According to the present invention, since the electrical insulating layer is provided between the wide power supply connection portion and the outer surface of the bulb, there is no wide portion facing the outer surface of the bulb, and it is possible to prevent the brightness from increasing at this portion. Since a wide power supply connection portion is formed on the outer surface of the electrical insulating layer, a large contact area with the terminal on the power supply side can be maintained.

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

In the figure, numeral 1 indicates a low-pressure discharge lamp used as a pointer for a meter or the like in audio equipment, and the discharge lamp in this embodiment is a cold cathode fluorescent lamp.

This lamp 1 is equipped with a glass bulb 2 in the shape of an elongated hollow rod, and the glass bulb 2 has an outer diameter of, for example, 2.5+n.
m, the total length is about 60n+m, and it is formed into a substantially needle shape.

As shown in FIG. 6, a phosphor coating 3 is formed on the inner surface of the bulb 2, and a discharge gas consisting of at least one of xenon and krypton is present at 5 to 90 torr within the bulb 3. Preferably, the pressure is about 50 torr.

A cold cathode 4 as an internal electrode is sealed at one end of the bulb 2, and the cold cathode 4 is connected to a lead wire 5 that passes through the sealed end of the bulb 2 in an airtight manner. A recess is formed at the end of the bulb 2 by sealing the cold cathode 4 therein. A first power connection part 6 made of a conductive paste such as silver epoxy is formed in the form of a film on the surface of the bulb closer to the end than these four parts. This first power supply connection section 6 is connected to the cold cathode 4 via the lead wire 5 mentioned above.

An external electrode 7 is formed on the outer surface of the bulb 2.

The external electrode 7 is provided in the form of a band in the axial direction along the outer surface of the bulb 2, and extends from the recessed portion of the bulb 2 to the tip of the other end. In this embodiment, the external electrode 7 is constructed by applying a paste such as carbon phenol or silver epoxy to the outer surface of the bulb 2 in a band shape along the axial direction, and firing the paste.

As shown in FIG. 5, this external electrode 7 has a wide part W1 on the distal end side of the bulb 2, and a relatively wide part W2 on the proximal end side near the fourth part. Between the wide end portion WI and the wide base portion W2, there is an elongated portion W having a relatively narrow width.

There are wide parts W on the distal and proximal sides of the valve 2, respectively.
The purpose of forming ISW2 is to increase the brightness at these positions.

A second power connection portion 8 connected to the external electrode 7 is formed in the bulb 2 .

This second power supply connection part 8 corresponds to the present invention, and is spaced apart from the first power supply connection part 6 in the axial direction, as shown by the dashed line in FIG. 7
It is formed at a location closer to the proximal end. This second power supply connection part 8 is also formed of a conductive paste such as silver epoxy, and extends in the circumferential direction with a width W4 wider than the wide proximal part W2 of the external mold m7.

In the second power supply connecting portion 8, a wide portion W4 indicated by a dashed line in FIG. 5 is electrically insulated from the outer surface of the bulb 2.
It is formed by

That is, a light-shielding coating 10 is formed on the outer surface of the bulb 2. The light-shielding film 10 contains carbon as a pigment, an epoxy resin, and an adhesive component, and has electrical insulating properties, and is formed on the surface of the bulb 2 on which the external electrode 7 is provided, covering the external electrode 7. .

The light-shielding coating 10 is provided with a portion extending in the axial direction and not forming the light-shielding coating 10 on the surface opposite to the surface on which the external electrode 7 is provided, so that the bulb 2 has a light-transmitting slit portion 11. It is formed. That is, on the outer surface of the bulb 2, as shown in cross section in FIG. That is, a light-transmitting slit portion 11 on which the light-shielding coating 10 is not formed is formed on the upper side in the figure. Therefore, the light within the bulb 2 is emitted to the outside only through the light transmission slit portion 11, and therefore the cold cathode fluorescent lamp 1 has an aperture shape.

In this case, the light-shielding film 10 having electrical insulation performance is formed to cover the external electrode 7, but there is an opening where the light-shielding film 10 is not provided opposite to the location where the second power connection part 8 is formed. 12 is left, and a part of the external electrode 7 is exposed from this opening 12.

Then, on the outer surface of this light-shielding coating 10, the second power supply connecting portion 8, which is shown by a dashed line in FIG. 5, is formed with a width of W4.

That is, an external electrode 7 made of paste such as carbon phenol or silver epoxy is formed on the outer surface of the bulb 2,
By forming a light-shielding film 10 made of carbon, epoxy resin, etc., on this outer surface, which has a light-shielding and electrically insulating effect, and further forming a second power connection part 8 made of a paste such as carbon phenol or silver epoxy, Second
The power supply connection portion 8 is insulated from the outer surface of the bulb 2 by a light-shielding coating 10, but is electrically connected to the external electrode 7 exposed through the opening 12.

The cold cathode discharge lamp 1 configured in this way has a lamp holder 2.
Attached to 0.

The lamp holder 20 is made of an electrically insulating material and is shaped like a machine with a U-shaped cross section, for example. One end of the bulb 2 is inserted into the lamp holder 20. Inside the lamp holder 20, first and second power supply terminals 21 and 22 as power supply side terminals are attached spaced apart in the axial direction. These power supply terminals 21.
Reference numeral 22 is made of a conductive plate spring made of phosphor bronze or the like and has a U-shaped cross section, and elastically holds the bulb 2. Due to this clamping, these power supply terminals 21 and 22 are connected to the first and second power supply connection portions 68, respectively.

The lamp holder 20 is fixed to a rotating shaft 23 of the meter, and rotates integrally with the rotating shaft 23 when the rotating shaft 23 rotates.

Note that the rotating shaft 23 is constituted by a hollow shaft (not shown), and two coated cords (not shown) are inserted into the hollow rotating shaft 23, and one end of each of these coated cords is connected to the first and second coated cords, respectively. 2, and the other end is connected to a high frequency power source.

When the end of the cold cathode discharge lamp 1 is pushed into the lamp holder 20, the first power connection part 6 and the second power connection part 8 formed on the outer surface of the bulb 2 are connected to the lamp holder 2.
0, the lamp 1 is held between the first power supply terminal 21 and the second power supply terminal 22 of the lamp holder 20, so that the lamp 1 is mechanically supported and electrically connected to the lamp holder 20. For this reason, the internal cold cathode 4 and the external electrode 7 of the lamp 1
is connected to a high frequency power source by a coated cord via power supply terminals 21 and 22.

In such a configuration, when high frequency power is supplied between the internal cold cathode 4 and the external electrode 7, glow discharge occurs within the bulb 2. This glow discharge excites the phosphor coating 3 and prompts it to emit light, and this emitted light is emitted to the outside from the slit portion]1. Therefore, in addition to the bulb 2 being originally thin, the slit portion 11 exhibits an even narrower band of light, making this lamp 1 suitable for pointing out the 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 rotating shaft 23, and when the rotating wheel 23 rotates, the lamp holder 20 is also rotated together, so that the lamp 1 attached to the lamp holder 20 is also rotated together. The scale will be rotated to the position you want to display on the device, so you can point out the scale. In this case, since the cold cathode fluorescent lamp 1 is mechanically held by the lamp holder 20, the rotating shaft 2
3 rotates, there is no need to worry about it coming off from the lamp holder 20 due to centrifugal force.

By the way, when a high frequency glow discharge occurs between the internal cold cathode 4 and the external electrode 7 as described above, the brightness changes depending on the width of the external electrode 7.

That is, FIG. 7 shows the relationship between the width of the external electrode 7 and the brightness, where the characteristic shown by solid line A is for this embodiment, and the broken line B is for the conventional one.

In the conventional case, the second power supply connection part 8 was formed by coating directly on the outer surface of the bulb 2 continuously with the external electrode 7, and this second power supply connection part 8 was exposed from the light-shielding coating 10. The width of the second power supply connection part 8 or the external electrode 7 is substantially widened, and therefore the brightness becomes higher as shown by the broken line B at the part corresponding to the wide second power supply connection part 8. Such a brightness distribution is not preferable as a guideline.

On the other hand, in the case of this embodiment, the wide second power supply connection part 8 is formed on the outer surface of the light-shielding coating 10 having an insulating effect. Since an insulating layer is formed between them, this wide second power supply connection part 8 does not act as an external electrode, and therefore this part is in contact with the outer surface of the bulb 2 with the narrow width W3 of the external electrode 7. , the brightness can be lowered at this location as shown by solid line A.

Therefore, the overall luminance distribution becomes good.

Moreover, since the second power supply connection part 8 can secure a wide width, the area is large, and the contact area with the second power supply terminal 22 is large, as can be understood from the contact state shown in FIG. It can be kept large and the electrical connection is stable.

Note that the present invention is not limited to the above embodiments.

That is, the discharge lamp of the present invention is not limited to being used as a meter pointer, but may be used, for example, as a backlight of a liquid crystal display device.

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.

Further, the external electrode 7 is not limited to one formed by forming a paste such as carbon phenol or silver epoxy into a belt shape along the tube axis direction, but may be formed by winding a conductive wire in a spiral shape around the outer surface of the bulb.

Further, the electrical insulating layer between the power supply connection part 8 and the bulb is not limited to one having a light shielding effect.

[Effects of the Invention] As explained above, according to the present invention, an electrical insulating layer is provided between the wide power supply connection part and the outer surface of the bulb, so there is no wide area facing the outer surface of the bulb, and the brightness is increased at this area. This will be prevented. Therefore, the brightness distribution along the axial direction of the bulb becomes good. Further, since a wide power supply connecting portion is formed on the outer surface of the electrical insulating layer, a large contact area with the terminal on the power supply side can be maintained.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is an exploded perspective view of a lamp used as a meter pointer and a lamp holder, FIG. 2 is a plan view of the lamp, and FIG. 3 is a side view of the lamp. , FIG. 4 is a bottom view of the lamp, FIG. 5 is a developed plan view of the external electrode, and FIG. 6 is a sectional view taken along the line Vl-Vl in FIG. 2.
FIG. 7 is a characteristic diagram showing the luminance distribution. 1...cold cathode fluorescent lamp, 2...bulb, 3...
- Phosphor coating, 4... Internal electrode, 6... First power connection part, 7... External electrode, 8... Second power connection part, 10... Light shielding wave film, DESCRIPTION OF SYMBOLS 11... Light transmission slit part, 20... Lamp holder, 21.22... Power supply terminal, 23... Rotation shaft.

Claims (1)

[Claims] An internal electrode is sealed at one end of the arc tube, and an external electrode extending linearly with a predetermined width is provided on the outer surface of the bulb. In a low-pressure discharge lamp which is provided with a wide power supply connection part, and which connects the above-mentioned external electrode to a power supply via the above-mentioned internal electrode and the above-mentioned power supply connection part, and discharges between these internal electrodes and the external electrode, A low-pressure discharge lamp characterized by having a wide power connection part and the outer surface of the bulb insulated with an electrically insulating layer.