JPH0286047A - Low-pressure mercury vapor discharge lamp - Google Patents

Abstract

PURPOSE:To resolve the difference in brightness by forming a heater with a film printed and coated with an electric resistor on the surface of a bulb end making the printed electric resistor film thicker at the portion with a recess on the surface of the bulb than at other portions. CONSTITUTION:The film of a heater 20 is made thick at the portion with a recess on the outer surface of a bulb 6 and a bent section 7 and thin at linear sections 8a and 8b, the current resistance value of the heater 20 at the recess and the bent section 7 is low, and the heating value is small. On the other hand, the current resistance value at the linear sections 8a and 8b is high, and the heating value is large. As a result, the linear sections 8a and 8b of the bulb 6 are heated by the heater 20 more than the bent section 7, and the mercury vapor pressure at the linear sections 8a and 8b is increased. The mercury excitation level is unified over the whole lamp, the emission quantity of ultraviolet rays is made equal, and the brightness along the axial direction can be unified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a low-pressure mercury vapor discharge lamp with improved start-up characteristics during lamp operation, particularly in a cold atmosphere.

(Prior technology) Liquid crystal meters used in automobile instrument panels display light on the liquid crystal surface by shining light from the back of the liquid crystal. A lighting device is needed that can illuminate the entire liquid crystal surface with uniform brightness.

Conventionally, this type of backlight includes a hot cathode or cold cathode fluorescent lamp housed as a light source in a casing that has a reflective surface on its inner surface, and the light from this lamp is reflected by the reflective surface and then exits from the opening of the casing. A lighting device that emits light is used.

When a hot cathode or cold cathode fluorescent lamp is used as the above light source, these fluorescent lamps have superior luminous efficiency, generate less heat, and have a longer lifespan than incandescent lamps.Moreover, they have a long discharge path, so their light emitting area is small. It has the advantage that it is large and the light distribution can be easily made uniform. In addition, in the case of a fluorescent lamp, it is easy to configure the discharge path into a curved shape, such as a U-shape or a W-shape, and the light-emitting surface becomes wider in plan, so a display surface with a predetermined spread can be illuminated evenly. There is also the advantage of being easy.

However, when a low-pressure mercury vapor discharge lamp, typically a fluorescent lamp, is turned on in a low ambient temperature,
The mercury vapor pressure sealed inside the bulb is low and it is dark, and it takes a long time for the mercury vapor pressure to increase and reach the desired brightness. That is, when the lamp is turned on in an extremely cold atmosphere, it takes a long time for the luminous flux to rise.

Automotive instrument panels are around +40°C to -30°C.
Therefore, when a fluorescent lamp is used as a backlight light source, it is necessary to take measures against the luminous flux rise characteristics.

In order to improve the rise time of the luminous flux, methods of heating the fluorescent lamp with a heater are being considered.

Such a heater is attached to the outer surface of the fluorescent lamp, and when the ambient atmosphere is low, it heats the bulb to increase the mercury vapor pressure, making it possible to obtain a predetermined brightness in a short time.

(Problem to be solved by the invention) However, in fluorescent lamps, the outer surface of the bulb may have dents, and especially if there is a bent part in the middle, it is necessary to prevent wrinkles from forming when bending the part. Therefore, the bending process is performed while applying a tensile load, resulting in a narrowing of the diameter at the bent part.

In this way, in areas where the surface of the bulb is concave or the diameter is narrow, the cross-sectional area of the discharge space becomes smaller, which increases the potential gradient, which increases the density of the discharge current, and therefore the degree of excitation of mercury. Because it is larger, it emits more ultraviolet rays, and as a result it becomes brighter than other parts.

This difference in brightness is not noticeable when the lighting is stable, but
There is a problem in which there is a noticeable difference in brightness and darkness when the lamp starts up.

However, when the heater is attached to the outer surface of the fluorescent lamp, there is a drawback that the above-mentioned problems cannot be solved if the heat generation performance of the heater is - like that along the entire lamp.

The present invention has a recess on the outer surface of the bulb, so the parts that become dark at startup are started up quickly to eliminate the difference in brightness and brightness, and the low-pressure mercury vapor release makes it easy to configure. The aim is to provide electric lamps.

[Structure of the invention]

(Means for Solving the Problems) According to the present invention, a heater is formed by a coating formed by printing and coating an electric resistor on the outer surface of a bulb, and this printed electric resistor coating has dents on the outer surface of the bulb. The film is characterized by being thicker in some parts than in other parts.

(Function) According to the present invention, the thickness of the heater made of the printed electrical resistor film is large in the portion where the outer surface of the bulb has a recess, so that the resistance value is small here and the amount of heat generated is small. Compared to this, the thickness of the heater made of the printed electrical resistor film is smaller in areas other than the recessed areas on the outer surface of the bulb (therefore, the resistance value increases and the amount of heat generated increases here, and the potential gradient outside of the recessed areas Areas with a small amount of light are heated strongly, which promotes a rise in vapor pressure in areas that darken at the time of startup, and the luminous flux rises quickly, eliminating the difference in brightness.Moreover,
When printing and coating an electrical resistor on the outer surface of a bulb, the outer surface of the film is formed into a uniform surface, so the film will be applied thicker in areas where the bulb has dents or narrow diameters. Therefore, it becomes easy to form a difference in film thickness in the heater.

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

In the figure, reference numeral 1 denotes a casing, which is made of synthetic resin such as polycarbonate and has a hammer-shaped cross section with a quadratic curve. A partition protrusion 2 is integrally formed in the center of the bottom surface of the casing 1 along the longitudinal direction. As shown in FIG. 2, this protrusion 2 has a substantially triangular cross section.

The entire bottom surface and protrusion 2 of the casing 1 are made into a reflective surface 3.

A cold cathode fluorescent lamp 5 is accommodated in such a casing l. In this embodiment, a U-shaped cold cathode fluorescent lamp 5
is used.

That is, B is a valve bent into a U shape,
This valve 8 has straight portions 8a and 8b at both ends of a U-shaped bent portion 7, which are substantially parallel to each other.

Cold cathode type electrodes 9a are provided at the ends of these straight portions 8a and 8b.
.

9b is sealed, and caps 10a and lOb are attached.

A phosphor wave film 15 (shown in FIG. 3) is formed on the inner surface of the bulb 8, and a predetermined amount of mercury and a starting rare gas such as argon or xenon are contained inside the bulb B. It is enclosed.

A heater 20 is attached to such a fluorescent lamp 5.

The heater 20 is connected to a valve B facing the bottom surface of the casing l.
A strip of uniform width is provided on the lower surface of the U-shaped valve 6 along the tube axis.

The heater 20 is formed of a coating formed by printing and coating an electric resistor on the outer surface of the bulb 6.

When applying the electrical resistor by printing, the outer surface is finished uniformly.
The film thickness t1 of the cloth film is formed to be thicker than the film thickness t2 of other parts where flatness is maintained.

Therefore, the heater 20 has a large film thickness tl at the bent portion 7 of the bulb B, so the cross-sectional area is large, the current resistance value is low, and the amount of heat generated is small.
In the straight portions 8a and 8b, the film thickness t2 is small, so the cross-sectional area is small, and the current resistance is small.

The value is high and the amount of heat generated is large.

Such a fluorescent lamp 5 is housed in the casing l such that its straight portions 8a and 8b are substantially parallel to the bottom surface of the casing l. In this case, the U-shaped valve B
The substantially parallel straight parts 8a and 8b are arranged along the protrusion 2, and the protrusion 2 is interposed between these straight parts 8a and 8b, that is, the straight straight part 8 where the protrusion 2 is adjacent
It is installed so as to separate the area between a and 8b.

Note that the protrusion 2 is cut away at a portion of the U-shaped bulb 6 that faces the bent portion 7.

The fluorescent lamp 5 has caps 10a at both ends,
The lOb portion is attached to the casing l by being fitted into fixing notches 11a and llb formed in the side wall 4 of the casing l and fixed by appropriate means such as adhesive.

A light diffusing and transmitting plate 12 is attached to the upper opening of the casing l. This light diffusing and transmitting plate 12 is made of acrylic resin or the like and has a milky white color and has a light diffusing effect. A portion 13 is formed.

The thickness of this thick portion 13 gradually becomes thinner as it moves away from the valve 6.

The operation of the lighting device having such a configuration will be explained.

When the surrounding atmospheric temperature is low, the heater 20 is energized to heat the bulb B. Then, the evaporation of the encapsulated mercury is promoted and a predetermined vapor pressure is achieved, so that when the lamp 5 is turned on, the luminous flux quickly rises and stable lighting is achieved.

In this case, the outer surface of the bulb B of the fluorescent lamp 5 does not have uniform flatness; for example, the bent portion 7 is bent while applying a tensile load to prevent wrinkles from forming there. , the outer diameter di becomes thinner than the other portion d2, and therefore the cross-sectional area becomes thinner. In areas where the cross-sectional area of the discharge path becomes narrower, the potential gradient becomes higher, which means that the density of the discharge current becomes higher.As a result, the degree of excitation of mercury increases, resulting in a greater amount of ultraviolet radiation. It will be brighter than other parts with a larger cross-sectional area.

This difference in brightness is not noticeable when the lighting is stable, but
There is a problem in which there is a noticeable difference in brightness and darkness when the lamp starts up.

On the other hand, in this embodiment, the film thickness of the heater 20 is such that the film thickness is less than the thickness at the bent portion 7 of the bulb 6, and
8b is thin, so the heater 2 at the bending part 7
The current resistance value at 0 is low and the amount of heat generated is small, whereas in the straight portions 8a and 8b, the current resistance value is high and the amount of heat generated is large.

As a result, in the bulb 6, the straight portions 8a and 8b are heated at a greater rate by the heater 20 than the bent portion 7, which promotes an increase in the mercury vapor pressure in the straight portions 8a and 8b.

Therefore, in the entire lamp, the degree of excitation of mercury is equalized, the amount of ultraviolet radiation is equalized, and the brightness along the axial direction is equalized.

In particular, the difference in brightness and darkness at the time of lamp startup is eliminated, and problems such as conspicuous differences are eliminated.

In this way, when the fluorescent lamp 5 is turned on, the light emitted from the lamp 5 is directed directly and after being reflected by the reflective surface 3 to the opening of the casing l, and the light emitted from the lamp 5 is directed to the opening of the casing l. The light is diffused by the diffuser-transmitting plate 12 and irradiated to the outside.

In this case, since the reflective surface 3 of the casing l has a quadratic curved surface, the light reflected by the reflective surface 3 has approximately equal brightness at the opening with respect to the opening in the casing 1. Furthermore, since the protrusion 2 is interposed between the substantially parallel straight parts 8a and 8b of the 0-shaped bulb 6, the protrusion 2 reflects the light emitted from the straight parts 8a and 8b, respectively. The light is reflected upward to increase the brightness on the light diffusing and transmitting plate 12.

Further, since the thick part 13 is formed on the inner surface of the light diffusing and transmitting plate 12, the thick part 13 faces directly above the bulb 6, and this thick part reduces the amount of light transmitted. As the distance from the wall increases, the wall thickness decreases, increasing the amount of light transmitted.

Because of this, uneven brightness over the entire surface of the light diffusing and transmitting plate 12 is eliminated.

Note that since the heater 20 is attached to the lower surface of the valve 6,
Even if the heater 20 blocks some light, there is no problem as long as it is in this direction.

Since the heater 20 having such a configuration is formed by printing and coating directly on the outer surface of the valve 6, the number of parts is reduced and special assembly is unnecessary.

In addition, when printing and applying electrical resistors, the outer surface should be evenly coated.
Since the surface is finished on a flat surface, if the outer surface of the valve G has a recess or has a small diameter part such as the bent part 7, the film thickness t1 of the printed coating film may differ from other parts where flatness is maintained. Therefore, even if the heater 20 has a difference in film thickness, it can be formed very easily.

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

That is, in addition to providing a difference in film thickness, the heater 20 may also have a different width, which can be easily implemented using a printing coating method.

Furthermore, the present invention is not limited to cold cathode fluorescent lamps, but may also be applied to hot cathode fluorescent lamps.

Further, the lamp is not limited to the U-shape, but may be W-shape, or may be ring-shaped or linear.

〔Effect of the invention〕

As explained above, according to the present invention, the thickness of the heater made of the printed electrical resistor film is increased in areas where there are recesses on the outer surface of the bulb, and therefore the resistance value is decreased here and the amount of heat generated is increased. Compared to this, the thickness of the heater made of the printed electrical resistor film is smaller in areas other than the recessed areas on the outer surface of the bulb, so the resistance value increases here and the amount of heat generated increases. Areas with a small potential gradient other than the recessed areas are heated strongly (heated), which promotes a rise in vapor pressure in areas that darken at startup, and the luminous flux rises quickly, eliminating the difference in brightness. .

Moreover, when printing and coating the electrical resistor on the outer surface of the bulb, the outer surface of the film is formed into a uniform surface.
The film is coated thickly in areas where the bulb has a recess or a small diameter, so there is an advantage that heaters with different film thicknesses can be easily formed.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is an exploded perspective view of the entire lighting device, FIG. 2 is a cross-sectional view of the assembled state, and FIG.
The figure is a developed cross-sectional view taken along the line ■-■ in FIG. DESCRIPTION OF SYMBOLS 1... Casing, 3... Reflective surface, 5... Cold cathode fluorescent lamp, 6... Bulb, 7... Bent part of bulb, 8a, 8b... Straight part of bulb, 9a , 9b
...Cold cathode, 12...Light diffusing and transmitting plate, 20...Heater.

Claims (1)

[Claims] In a low-pressure mercury vapor discharge lamp in which a heater is attached along the axial direction of the bulb and the heater heats the bulb to promote an increase in mercury vapor pressure, the heater has an electric resistor printed on the surface of the bulb. A low-pressure mercury vapor discharge lamp comprising a coating formed by coating, and the printed electrical resistor coating is thicker in the portion where the bulb surface has a recess than in other portions.