JPH0286046A - Low-pressure mercury vapor discharge lamp - Google Patents

Abstract

PURPOSE:To make the rising of the light flux quick and resolve the difference in brightness by making the resistance value per unit length of a heater at the position with a small potential gradient larger than that at the position with a large potential gradient. CONSTITUTION:The width W1 of a mesh heater 21 is made large at the bent section 22a of a heater 20, and the width W2 at the linear section 22b of the heater 20 is made smaller than W1. The current resistance value at the bent section 22a of the heater 20 is low, the heating value is low, on the other hand the current resistance value at the linear section 22b is high, thus the heating value is large. As a result, linear sections 8a and 8b 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 are also significant advantages.

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, so it is dark.
Moreover, it takes a long time for the mercury vapor pressure to increase and reach a predetermined 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.

(Problems to be Solved by the Invention) However, when a heater is attached to the outer surface of a fluorescent lamp, the following problems occur if the heat generation performance of the heater is uniform along the axial direction of the lamp.

That is, in a fluorescent lamp, the cross-sectional area of the bulb, that is, the cross-sectional area of the discharge path may not be uniform.

In particular, if there is a bent part in the middle, the cross-sectional area of the bent part becomes narrower because the bending process is performed while applying a tensile load to prevent wrinkles from forming.

In areas where the cross-sectional area of the discharge path is narrowed in this way, the potential gradient becomes higher, which means the density of the discharge current becomes higher, and as a result, the degree of excitation of mercury increases, resulting in a greater amount of ultraviolet radiation, and therefore other areas brighter than.

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.

The present invention aims to provide a low-pressure mercury vapor discharge lamp that quickly starts up the dark part at the time of startup, eliminates the difference in brightness, and provides uniform brightness throughout.

[Structure of the invention]

(Means for Solving the Problems) The present invention is characterized in that the resistance value per unit length of the heater is made higher at locations where the potential gradient is small than at locations where the potential gradient is large.

(Function) According to the present invention, areas with a small potential gradient are strongly heated by the heater, which promotes an increase in vapor pressure in areas that become dark at the time of startup, and the rise of the luminous flux becomes rapid, resulting in a difference in brightness and darkness. can be resolved.

(Example) The present invention will be described below based on an example shown in FIGS. 1 and 2.

In the figure, the casing is made of synthetic resin such as polycarbonate, and is shaped like a quadratic curve in cross section. A partition protrusion 2 is integrally formed in the center of the bottom surface of the casing l 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, 6 is a valve bent into a U shape,
This valve B 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 a base 10a and LOb are attached.

A fluorescent coating (not shown) is formed on the inner surface of the bulb 6, and a predetermined amount of mercury and a starting rare gas such as argon or xenon are sealed inside the bulb 6.

A heater 2o is attached to such a fluorescent lamp 5. The heater 20 has a sheet shape and is attached to the lower surface of the valve 6 along the tube axis of the U-shaped valve 6, that is, formed in a U-shape opposite to the valve shape and facing the bottom surface of the casing l.

Although not shown in detail, the heater 20 of this embodiment is formed by a mesh heater 21 formed by chemically etching a thin conductive plate made of stainless steel or the like into an elongated mesh body.

In this case, the width W1 of the mesh heater 21 is increased at the portion facing the U-shaped bent portion 7 of the valve 6, that is, the bent portion 22a of the heater, and the width W1 is increased at the portion facing the straight portions 8a, 8b of the valve G. That is, the width w2 of the straight portions 22b and 22b of the heater is made smaller than the width w1. In a heater, when the thickness is the same, increasing the width increases the cross-sectional area, so the current resistance per unit length decreases, and therefore the current resistance at the bent portion 22a of the heater decreases, reducing the amount of heat generated. On the other hand, the linear portions 22b and 22b of the heater are set so that the current resistance value per unit length is high and the amount of heat generated is large.

Such a mesh heater 21 is laminated and reinforced with resin sheets 23 from both sides.

The heater 20 is mounted in close contact with the bulb 0 of the fluorescent lamp 5. To attach the heater 20 in close contact with the valve G, it may be bonded with adhesive, but a transparent heat-shrinkable tube (not shown) may be attached to the heater 2.
It is also possible to hold the heater 20 in close contact with the outer surface of the bulb 8 by covering the entirety of the tube 0 and the bulb 6 and heating the whole to shrink the heat-shrinkable tube.

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 6
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. 8
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 bases tea at both ends,
The lOb portion is attached to the casing 1 by being fitted into fixing notches 11a and llb formed in the side wall 4 of the casing 1 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 6. 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, a luminous flux is immediately emitted and stable lighting is achieved.

In this case, the cross-sectional area of the bulb 6 of the fluorescent lamp 5, that is, the cross-sectional area of the discharge path, is not uniform, and a tensile load is applied to the bent portion 7 to prevent the occurrence of wrinkles when bending the portion. Due to the bending process, the cross-sectional area becomes thinner. In the part where the cross-sectional area of the discharge path becomes narrower, the potential gradient becomes higher, that is, the density of the discharge current becomes higher, and as a result, the degree of excitation of mercury becomes greater, and the amount of ultraviolet radiation is increased. It will be brighter than other parts that have a larger 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 width w1 of the mesh heater 21 is made larger at the bent portion 22a of the heater 20, and the width w2 is made smaller than the width wl at the straight portions 22b, 22b of the heater 20. bending part 2
2a, the current resistance value is low and the amount of heat generated is small; on the other hand, the linear portion 22b of the heater 20.

22b has a high current resistance value and therefore generates a large amount of heat.

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 portions f, promoting an increase in mercury vapor pressure in the straight portions aa 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 toward the opening of the casing 1, and the light emitted from the lamp 5 is directed toward the opening of the casing 1, The light is diffused by the light diffusing and 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 U-shaped bulb 6, the protrusion 2 reflects the light emitted from the straight parts 8a and Bb, 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 bulb 6, even if the heater 20 blocks some light, there is no problem as long as it is oriented in this direction.

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

That is, the heater 20 is not limited to a laminate heater in which the mesh heater 21 is laminated with a resin sheet 23, but may be a printed resistor heater, a linear heater, or the like.

Therefore, the heater is not restricted in shape or material.

Furthermore, the heater 20 is not limited to being attached directly to the bottom surface of the valve 6, but may be arranged along the shape of the valve 6 by being fixed to the bottom surface of the casing 1, as shown in FIG. It's okay.

In addition, if you want to equalize the brightness distribution on the front side of the light diffusing and transmitting plate 12, since the front surface of the light diffusing and transmitting plate 12 is flat, a mesh film that functions as an electromagnetic shield and a light distribution adjustment function can be placed on this surface. It may be provided.

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 electrical resistance value per unit length of the heater is made higher in the parts of the lamp where the potential gradient is small compared to the parts where the potential gradient is large, so that the heater It begins to heat up strongly,
Therefore, the rise in vapor pressure in the darkened area at the time of startup is promoted, and the rise of the luminous flux becomes rapid, so that the difference in brightness and darkness can be eliminated.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is an exploded perspective view of the entire lighting device, FIG. 2 is a sectional view of the assembled state, and FIG. 3 is another embodiment of the present invention. It is a sectional view showing an example. ■... Casing, 3... Reflective surface, 5... Cold cathode fluorescent lamp, 6... Bulb, 7... Bent portion of bulb, 8a. 8b...Light line part of bulb, 9a, 9b...Cold cathode, 12...Light diffusing and transmitting plate, 20...Heater, 21...Mesh heater, 22a
... Bent part of the heater, 22b... Straight part of the heater. Applicant's Representative Patent Attorney Takehiko Suzue

Claims (1)

[Claims] In a low-pressure mercury vapor discharge lamp, 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. A low-pressure mercury vapor discharge lamp characterized by a heater having a higher resistance value per unit length in areas where the potential gradient is smaller than that of the lamp.