JPH0448501A - Illumination device - Google Patents

Abstract

PURPOSE:To reduce the interrupting ratio of the light advancing toward a light diffusion permeation plate from the upper faces of bulbs by making the width of heaters formed above the bulbs smaller than the width of heaters formed below the heaters. CONSTITUTION:Although the bottom face of a casing 1 and a light diffusion permeation plate 18 are located near bulbs 6, heaters 15a formed below the bulbs 6 are faced to the bottom face of the casing 1, heaters 15b formed above the bulbs 6 are faced to the light diffusion permeation plate 18, thus the temperature reduction on the bottom faces and upper faces of the bulbs 6 is prevented by the heating of the heaters 15a, 15b. The bottom faces and upper faces of the bulbs 6 are heated, heat escapes from the bottom faces and upper faces through the bottom face of the casing 1 and the light diffusion permeation plate 18, thus the temperature distribution in the peripheral direction of the bulbs 6 rises uniformly and quickly. The rise of the mercury steam pressure is accelerated, mercury is excited in the whole lamps, the lamps quickly become bright, and the rising time at the time of a lamp start is shortened.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a lighting device suitable for use as a backlight of a liquid crystal display device, etc. The present invention relates to a lighting device with improved start-up characteristics in an atmosphere.

(Prior technology) Liquid crystal meters used in automobile instrument panels display characters and figures on the liquid crystal surface by shining light from the back of the liquid crystal. ,
A lighting device is required that can illuminate a liquid crystal surface of a predetermined extent with uniform brightness as a whole.

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 lit in a low-temperature atmosphere, it takes a long time to reach the desired brightness due to the low mercury vapor pressure sealed inside the bulb, and the luminous flux decreases. Rise time becomes longer.

In the case of an automobile instrument panel, it is used in an area with a temperature difference of about +40°C to -30°C, so if a fluorescent lamp is used as the backlight source,
It is necessary to take measures against the luminous flux rise characteristics.

In order to improve the rise time of the luminous flux, means have been adopted to heat the fluorescent lamp with a heater.

In the conventional case, a method has been proposed in which a heater film is formed by printing and coating an electrical resistor such as a silver (Ag) base on the outer surface of the bulb, and the bulb is heated with this coated heater (Japanese Patent Application Laid-Open No. 1983-1989). No. 120066).

However, when a heater film is formed on the outer surface of the bulb, heat tends to escape from the outer surface of the heater.

In particular, in lighting devices used for backlights, etc., the lamp is housed in a casing that has a light diffusion and transmission plate on the top surface and a reflective surface on the bottom surface, and the distance between the light diffusion and transmission plate and the reflection surface is narrower and thinner casing (
shallow). Therefore, the upper and lower surfaces of the bulb are close to the light diffusing and transmitting plate and the reflecting surface, respectively, and heat easily escapes through the light diffusing and transmitting plate and the reflecting surface.

In other words, if a heater is formed around the entire circumference of the bulb, the temperature will be difficult to rise in a portion of the bulb in the circumferential direction that is close to the light diffusing and transmitting plate and the reflecting surface, and the entire bulb will not be heated evenly. Therefore, there is a problem that the mercury vapor pressure does not rise smoothly and the luminous flux rise characteristics vary.

For this reason, it is conceivable to provide heaters on the upper and lower surfaces of the valve, where heat can easily escape. In this way, even if the upper and lower surfaces of the bulb are heated intensively, a large amount of heat escapes from these parts, and as a result, the entire circumference of the bulb is heated evenly.

(Problems to be Solved by the Invention) However, when a heater is provided on the top surface of the bulb, there are problems in that the heater blocks the light emitted from the lamp, creating a shadow and reducing the amount of light directed toward the light diffusion and transmission plate.

The present invention has been made based on the above circumstances, and aims to provide a lighting device that uniformly heats the outer surface of the bulb along the circumferential direction and reduces the rate at which the amount of light directed toward the light diffusing and transmitting plate is reduced. It is something.

[Structure of the invention]

(Means for Solving a Problem) The present invention provides an illumination device in which filters are formed on the upper and lower surfaces of the bulb, facing the light diffusing and transmitting plate and the reflecting surface, respectively, and extending in the tube axis direction. The valve is characterized in that the width of the heater formed on the top surface of the bulb is smaller than the width of the heater formed on the bottom surface.

(Function) According to the present invention, since the heater heats the surface of the bulb that faces the light diffusing and transmitting plate and the reflecting surface, even if some heat escapes from the light diffusing and transmitting plate and the reflecting surface, it will not be generated in the circumferential direction of the bulb. The entire area will be heated evenly. Moreover, since the width of the heater formed on the upper surface of the bulb is made smaller than the width of the heater formed on the lower surface, the proportion of light that is blocked from the upper surface of the bulb toward the light diffusing and transmitting plate is reduced.

(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 or metal, and is formed into a shallow dish shape. A protrusion 2 having a substantially triangular cross section is integrally formed in the center of the bottom surface of the casing 1 along the longitudinal direction.

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 1 . 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 6 has straight portions 8a and 8b at both ends of a U-shaped bent portion 7 that are substantially parallel to each other. These straight parts 8
Cold cathode type electrodes 9a and 9b are sealed to the ends of electrodes g and 8b, respectively. The cold cathodes 9a and 9b are constructed by forming a metal plate 10 into a square shape and joining it to a lead wire 11.

A phosphor coating 12 (shown in FIG. 2) 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. has been done.

Such a fluorescent lamp 5 is provided with a heater 15a115b. These heaters 15a.

15b is formed by a coating formed by printing and coating an electric resistor on the outer surface of the bulb 6, and one heater 15
The heater 15a is formed in the shape of a band extending along the tube axis with an equal width on the lower surface of the valve 6 facing the bottom surface of the casing 1, and the other heater 15b is formed on the lower surface of the valve 6 facing the bottom surface of the casing 1. 6 is formed in the form of a band extending along the tube axis with equal width.

In this case, as shown in FIG. 2, the width W of the heater 15b provided on the upper surface of the bulb 6 is smaller than the width W2 of the heater 15a provided on the lower surface. Therefore, the proportion of light directed upward in the bulb 6 that is blocked is reduced.

Such a fluorescent lamp 5 includes a straight portion 8a of the bulb 6,
8b is housed in the casing 1 so as to be substantially parallel to the bottom surface of the casing 1. In this case, the U-shaped valve 6
The linear portions 8a are substantially parallel to each other.

8b is arranged along the protrusion 2, and these straight parts 8a
, 8b, that is, the protrusion 2 is installed so as to separate the adjacent double-sided line parts 8a and 8b.

In the fluorescent lamp 5, the bent portion 7 is supported by the bottom surface of the casing 1 via an elastic pad 13 made of heat-resistant rubber, and both ends are passed through cutouts 14a and 14b formed in the side wall of the casing 1. Figure 3 and M4
It is attached to the casing 1 with the support means shown in the figure.

To explain this support means, 20g and 20b are the valve 6
An elastic cap made of heat-resistant rubber or the like that covers the end of the These elastic caps 20a520b are in the shape of a cylinder with a bottom, and are elastically attached to the end of the valve 6.

Metal rings 21 are attached to these elastic caps 20a and 20b.
a and 21b are attached. These metal rings 21a
121b has a cylindrical shape, and the elastic caps 20a, 2
It fits on the outer surface of 0b.

The casing 1 has the above-mentioned notch 14a.

Support pieces 22a and 12b protrude opposite to 14b, and bent stop pieces 23a and 23b are formed at the tips of these support pieces 22a and 22b.

The elastic caps 20a, 20b and the metal link 21
Both ends of the valve 6, to which the bulbs a and 2-1b are attached, are placed on support pieces 22a and 22b, respectively, and the end faces are positioned by stop pieces 23a and 23b.

These support pieces 22a, 22b and metal ring 21a,
21b is surrounded by and integrally engaged with crumbling rings 24a and 24b. Crumbling 24 a, 24
b is partially separated in the circumferential direction to form knob pieces 25a and 25b.
These knob pieces 25a and 25b can be elastically deformed, that is, the diameter can be expanded or contracted so as to move toward and away from each other. For this purpose, both ends of the bulb 6, to which the elastic caps 20a, 2Qb and metal rings 21a, 21b are attached, are placed on support pieces 22a, 22b, respectively, and the outsides of these are placed on clamp rings 24a, 24, respectively.
b, both ends of the valve 6 are attached to the supporting pieces 22a.
, 22b.

Therefore, variations in molding and thermal expansion/contraction of the valve 6 can be absorbed by the elastic deformation of the elastic caps 20a, 20b, and sliding between the metal rings 21a, 21b and the support pieces 22a, 122b, and even when shocks and vibrations are applied, the elastic caps 2
This can be absorbed by elastic deformation of 0a and 20b.

Furthermore, the ends of the bulb 6 are connected to cold cathode electrodes 9a and 9b.
This is the position where the temperature rise is greatest because the ends of the bulb 6 are sealed, but the heat at the ends of the bulb 6 is absorbed by the elastic caps 20a and 20b.
and support pieces 22a, 22b through metal ring 218121b and crumbling rings 24a, 24b.
The heat is transmitted to the surface of the casing 1 and radiated from the surface of the casing 1.

Moreover, this heat is not only radiated through the surfaces of the clamp rings 24g and 24b, but also is dissipated through the surfaces of the clamp rings 24g and 24b.
becomes a heat dissipation fin and is also emitted from here.

A light diffusing and transmitting plate 18 is attached to the upper opening of the casing 1. The light diffusing and transmitting plate 18 is made of acrylic resin or the like and has a milky white color and has a light diffusing effect. A thick portion 19 is formed. The thickness of this thick portion 19 gradually becomes thinner as the distance from the valve 6 increases.

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

When the ambient temperature is low, the heater 15a.

15b to heat the bulb 6. Then, the evaporation of the encapsulated mercury is promoted and a predetermined vapor pressure is reached, so that when the lamp 5 is energized, the luminous flux quickly rises and stable lighting begins.

In this case, since the bulb 6 of the fluorescent lamp 5 is coated with heaters 15a and 15b distributed on the upper and lower surfaces,
The heating efficiency of the bulb 6 is better than when the bulb 6 is formed only at one location in the circumferential direction.

Even if the bottom surface of the casing 1 and the light diffusion/transmission plate 18 are close to the bulb 6, the heater 15a formed on the bottom surface of the bulb 6 faces the bottom surface of the casing 1, and the heater 15b formed on the top surface diffuses and transmits light. Since the heaters 15a and 15b are opposed to the plate 18, the temperature of the bottom and top surfaces of the bulb 6 is prevented from decreasing due to the heat generated by the heaters 15a and 15b. In other words, although the bottom and top surfaces of the bulb 6 are heated, heat escapes from these bottom and top surfaces through the bottom of the casing 1 and the light diffusion/transmission plate 18, so that the temperature distribution in the circumferential direction of the bulb 6 is uniform and Temperature rises quickly. Therefore, the rise in mercury vapor pressure is promoted, mercury is excited throughout the lamp, the lamp becomes bright quickly, and the rise time when starting the lamp is shortened.

Moreover, since the width W1 of the heater 15b provided on the upper surface of the bulb 6 is smaller than the width W2 of the heater 15b formed on the lower surface, light directly directed from the upper surface of the bulb 6 to the light diffusing and transmitting plate 18 can be blocked. The brightness of the light diffusing and transmitting plate 18 is reduced at a low rate.

When the fluorescent lamp 5 is turned on in this way,
The light emitted from this lamp 5 is emitted directly and from the reflecting surface 3.
After being reflected, the light heads toward the opening of the casing 1, passes through the light diffusing and transmitting plate 18 provided in the opening, and is irradiated to the outside.

The light diffusing and transmitting plate 18 is formed with thick portions 19.19, and these thick portions 19.19 face directly above the bulb 6, so that the amount of light transmitted is reduced in these thick portions and the thickness is reduced. Since the wall thickness becomes thinner as the distance from the thick portion 19 increases, the amount of light transmitted is increased compared to the thick portion.

Therefore, even though the width of the heater 15b formed on the upper surface of the bulb 6 is narrowed to reduce the light attenuation effect, there remains some light blocking effect, and this light blocking effect and the light attenuation effect of the thick portion 19. work together to eliminate uneven brightness over the entire surface of the light diffusing and transmitting plate 19.

Note that the heater 15a has the above configuration.

15b can be formed by printing and coating directly on the outer surface of the valve 6, reducing the number of parts and eliminating the need for special assembly.

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

That is, in the above embodiment, an illumination device using a U-shaped cold cathode fluorescent lamp was described, but the lamp shape is not limited to the U-shape, but may be W-shape, or may be annular or linear. .

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

Furthermore, the present invention is not limited to fluorescent lamps, but may also be applied to rare gas discharge lamps, or lamps with external electrodes.

Furthermore, the lighting device of the present invention is not limited to the backlight of a liquid crystal display device.

〔Effect of the invention〕

As explained above, according to the present invention, the heaters provided on the upper and lower surfaces of the bulb heat the surface of the bulb that faces the light diffusing and transmitting plate and the bottom of the casing, so some heat escapes from the light diffusing and transmitting plate and the bottom. However, the bulb is heated almost uniformly in the circumferential direction, and the temperature of the bulb increases quickly, which promotes a rise in mercury vapor pressure and causes a rapid rise in luminous flux. Moreover, the width of the heater installed on the top side of the bulb is narrower than that of the heater installed on the bottom side, so the proportion of light that is blocked from the top side of the bulb toward the light diffusion/transmission plate is reduced, and the amount of light increases, resulting in brightness. There are advantages such as improved performance.

[Brief explanation of drawings]

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 perspective view of the lamp support portion, and FIG. 4 is a sectional view thereof. DESCRIPTION OF SYMBOLS 1...Casing, 3...Reflection surface, 5...Cold cathode fluorescent lamp, 6...Bulb, 98% 9b...Cold cathode, 15a, 15b...Heater, 18... Light diffusing and transmitting plate, 20a, 20b--elastic cab/b, 218
121b...metal ring, 21a, 22b...support piece, 24a, 24b...crumbling ring. Applicant's Representative Patent Attorney Takehiko Suzue Figure 2 Figure 3 Figure 4 Figure 1

Claims (1)

[Claims] A low-pressure mercury vapor discharge lamp is housed in a casing with a light diffusing and transmitting plate attached to the top surface and a reflective surface on the bottom, and the light emitted from this low pressure mercury vapor discharge lamp is transmitted to the outside through the light diffusing and transmitting plate. In the low-pressure mercury vapor discharge lamp, mercury is sealed in a bulb sealed with electrodes, and heaters extending in the tube axis direction are formed on the upper and lower surfaces of the bulb, respectively, and these heaters heat the bulb to release mercury. 1. A lighting device that promotes an increase in vapor pressure, characterized in that the width of the heater formed on the upper surface of the bulb is smaller than the width of the heater formed on the lower surface.