JPH09171179A - Illumination unit and liquid crystal display device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin illumination unit having high luminance efficiency and good assemblability. SOLUTION: In an illumination unit composed of a light guide plate 1, a fluorescent discharge tube 2 arranged on its side and a reflection body 3 held by the side face part of the light guide plate, a distance T from the fluorescent discharge tube 2 to the reflection body 3 in the direction of the thickness of the light guide plate 1 is smaller than a distance S to the reflection body 3 in the right angle direction and the distance is set to be 0.6-1.2mm. A cap 8 covering electrode parts at both ends of the fluorescent discharge tube is made to be an ellipse of elliptic shape and used as a spacer for holding the distance S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination unit used in a transmissive display device and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used in display devices for information equipment such as notebook personal computers and word processors because of their features such as light weight, thin shape and low power consumption. In addition, in order to realize a bright display screen in these liquid crystal display devices,
In many cases, a built-in illumination unit is used to apply illumination light from behind the display element. This lighting unit is roughly classified into an edge light system in which a light guide plate is placed on the back surface of the display body and a line light source such as a fluorescent tube is arranged on the end surface of the light guide plate, and a direct type system in which the light source is provided on the back surface of the display body. To be done. When comparing the two, the direct type can obtain relatively high brightness but is not suitable for thinning, and the edge light system is excellent in thinness and brightness uniformity on the light emitting surface, but is disadvantageous in high brightness. Can be said. As a method of an illumination unit of a liquid crystal display device used in a notebook personal computer or the like, an edge light type method is often adopted in consideration of thinness.

6 and 7 show a conventional edge light type illumination unit. This illumination unit includes a plate-shaped transparent light guide plate 1 for transmitting light, and a fluorescent discharge tube 2 provided near at least one of the four sides of the light guide plate 1.
And a reflection film 3 that guides the light emitted from the fluorescent discharge tube 2 to the incident side end surface D of the light guide plate 1.

A white film having a high reflectance is often used as the reflection film 3, but recently, a polyester film subjected to silver (Ag) vapor deposition is used as a high reflection film for obtaining higher brightness. It has started to be done.

A reflection sheet 4 is arranged on the back surface of the light guide plate 1, and plays a role of returning the light emitted from the back surface of the light guide plate 1 back into the light guide plate 1 and increasing the illumination light emitted from the emission surface E. Have. A diffusing plate 5 is installed on the exit surface side of the light guide plate 1 in order to improve the uniformity.

Leads 6 for supplying a voltage from the outside are provided at both ends of the fluorescent discharge tube 2, and a power supply unit such as an inverter for generating a high frequency alternating current having an output frequency of 40 kHz to 100 kHz. Lead wire 7 connected to
It is connected by soldering or the like.

Generally, a high voltage is required to drive the fluorescent discharge tube 2, and in order to ensure the safety, the exposed portions of the leads 6 and the lead wires 7 are covered with a cylindrical member made of an insulating material such as rubber. The cap 8 formed on the is attached.

[0008]

As described above, when a film having a highly reflective metal film such as silver (Ag) formed on the reflective film 3 is used, this conductive metal film is used as the fluorescent discharge tube 2.
If the fluorescent discharge tube 2 is driven by a high-frequency alternating current of 40 kHz to 100 kHz, the nearby conductor, that is, the metal film, becomes stray capacitance and impedance increases, and the lighting characteristics of the fluorescent discharge tube 2 become abnormal. Or a fluorescent discharge tube 2
However, there is a problem in that the luminous efficiency of is reduced and the luminance of the illumination unit is reduced.

An object of the present invention is to provide a lighting unit which has a simple structure, has stable lighting characteristics, is thin, and can obtain high brightness, and a liquid crystal display device using the lighting unit.

[0010]

In the lighting unit of the present invention, a fluorescent discharge tube is disposed in the vicinity of the incident side end surface of the light guide plate, has a conductive reflection surface inside, and both ends are incident on the light guide plate. The fluorescent discharge tube is wrapped by a reflector held on a side surface portion having a side end surface, and the thickness of the light guide plate with respect to the distance from the outer shape of the fluorescent discharge tube to the reflective surface in the thickness direction of the light guide plate. It is characterized in that the distance from the outer shape of the fluorescent discharge tube to the reflecting surface in the direction perpendicular to the direction is set to be large, and while keeping the overall thickness of the lighting unit thin, the fluorescent discharge tube to the light guide plate with maximum efficiency. Light can be made incident on the end face, and a lighting unit with higher brightness can be realized.

More preferably, the distance from the outer shape of the fluorescent discharge tube to the reflecting surface in the direction perpendicular to the thickness of the light guide plate is set.
Set to 0.6 mm to 1.2 mm. In addition, a cap that covers the electrode portions on both ends of the fluorescent discharge tube is used as a spacer for keeping the distance between the fluorescent discharge tube and the reflection surface, and the outer shape of the cap is an elliptical shape in which the thickness direction of the light guide plate is a minor axis. Alternatively, it has an oval shape.

[0012]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. As shown in FIGS. 1 and 2,
A transparent light guide plate 1 on a flat plate that transmits light, and this light guide plate 1
The fluorescent discharge tube 2 is provided along the incident side end surface D of the, and the reflection film 3 as a reflector that collects the light emitted from the fluorescent discharge tube 2 to the end surface of the light guide plate 1 and guides it inside. .

The fluorescent discharge tube 2 has an outer diameter of 2.4 mm
The thickness was 2.6 mm and the glass thickness was 0.3 mm to 0.5 mm. The power supply frequency for driving the fluorescent discharge tube 2 was 40 kHz to 100 kHz.

A reflection sheet 4 is disposed on the back surface of the light guide plate 1, and has a role of returning the light emitted from the back surface of the light guide plate 1 back into the light guide plate 1 and increasing the emitted illumination light. . In addition, the light guide plate 1 has a dot pattern (not shown) printed on the back surface thereof and the diffusion plate 5 installed on the front surface side to achieve uniform illumination light emitted from the backlight.

In order to obtain higher brightness as the illuminating unit, the reflective film 3 uses a film having a high reflectance by forming a thin film of silver (Ag) on a polyester film by means such as vapor deposition.

Caps 8 are attached so as to cover the ends of the fluorescent discharge tube 2 and the portions of the leads 6 and lead wires 7 at both ends of the fluorescent discharge tube 2. The cap 8 is formed of an insulator such as rubber and is hollow so that the fluorescent discharge tube 2 and the lead wire 7 can be inserted therein. The cap 8 insulates the electrode exposed portion to ensure the safety of the device.

The reflective film 3 is wrapped around the cap 8 to wrap the fluorescent discharge tube 2 and the reflective film 3
Both ends of are fixed to the side surfaces C1 and C2 of the light guide plate 1 with an adhesive.

The outer shape of the cap 8 is an oval shape having a minor axis A in the thickness direction of the light guide plate 1 and a major axis B in the direction perpendicular to the thickness, and having sides parallel to the major axis. The small-diameter minor diameter A is set so that the distance T between the fluorescent discharge tube 2 and the reflective film 3 maintains a constant distance and does not exceed the thickness of the entire illumination unit. It is generally known that the diameter of the fluorescent discharge tube 2 is slightly smaller than the thickness of the light guide plate 1 so that the light utilization efficiency is the highest as an illumination unit, and the minor axis A of the cap 8 is the same as the thickness of the entire illumination unit. The distance T between the outer shape of the fluorescent discharge tube 2 and the reflective film 3 is maintained at about 0.3 mm to 0.5 mm, and the lighting of the fluorescent discharge tube 2 does not occur due to the influence of the reflective film 3. The thickness of the entire unit was also minimized.

On the other hand, the major axis B of the cap 8 is such that the interval S from the fluorescent discharge tube 2 to the reflective film 3 is 0.6 mm.
It is set to be 1.2 mm. Reflective film 3
When is considered as a reflection plate that optically reflects the light emitted from the fluorescent discharge tube 2 and collects it in a predetermined direction, it can be said that it is more efficient to bring the reflective film 3 closer to the fluorescent discharge tube 2. In the case of a film in which a metal film is formed like the reflection film 3, the metal film serves as a close conductor to the fluorescent discharge tube 2 driven at high frequency, and the reflection film 3 is used as the reflection film 3.
The closer it is to, the greater the factor that reduces the luminous efficiency of the fluorescent discharge tube 2. Therefore, considering the effects of both, the relationship between the distance S from the outer shape of the fluorescent discharge tube 2 to the reflective film 3 and the luminance on the light emitting surface of the light guide plate 1 is examined. As a result, FIG. As shown, S is 0.6 mm
High efficiency between ~ 1.2 mm, especially 0.8 mm ~ 1.0 mm
It was revealed that the highest efficiency was obtained in the region of. If the distance is narrower than this, the luminous efficiency of the fluorescent discharge tube 2 is lowered due to the influence of the metal film, and if it is wide, the optical loss as a reflector becomes large and the luminance is lowered as compared with the conventional case.

That is, in order to realize an illumination unit having a simple structure, a thin structure, and high luminous efficiency,
The caps 8 on both ends of the fluorescent discharge tube 2 keep the distance between the fluorescent discharge tube 2 and the reflective film 3 constant, and the distance between them is set to the light guide plate 1.
It is necessary to set the S dimension to be larger than the T dimension in order to optimally set the thickness in the same direction as the thickness in the same direction as the right angle direction, and the outer shape of the cap 8 is an oval shape.

Further, since the oval shape has a vertically and horizontally symmetrical shape, it is possible to use caps 8 arranged at both ends of the fluorescent discharge tube 2 having exactly the same shape.

FIG. 4 shows a liquid crystal display device using the illumination unit according to the present invention. The above-described lighting unit including at least the fluorescent discharge tube 2, the light guide plate 1, the reflective film 3, and the elliptical cap 8 is disposed under the resin frame 9, and the back cover 10 mechanically drives the lighting unit. The resin frame 9 is protected by a screw and the like. At the top of the resin frame 9,
Liquid crystal display element 11 and TAB (Tape Automated Bondi)
ng) The mounted liquid crystal driving LSI 12 and the bus circuit board 13 are installed in a state of being connected to each other. Further, the liquid crystal display device is completed by disposing the metal frame 14 having the liquid crystal display portion opened above the liquid crystal display element 11.

In the above embodiment, the case where the linear fluorescent discharge tube 2 is used has been described, but the linear fluorescent discharge tube 2 may not necessarily be linear, and for example, an L-shaped fluorescent discharge tube may be used. It is possible.

Although the outer shape of the cap 8 is described as the oval shape shown in FIG. 5 (a), an elliptical shape as shown in FIG. 5 (b) can obtain an effect almost equivalent to the oval shape. It is obvious that F is a through hole.

[0025]

As described above, according to the illuminating device of the present invention, the fluorescent discharge tube is arranged in the vicinity of the incident side end surface of the light guide plate, has the conductive reflecting surface inside, and both ends of the light guide plate. With respect to the distance from the outer shape of the fluorescent discharge tube in the thickness direction of the light guide plate to the reflecting surface in the thickness direction of the light guide plate, the light guide plate of the light guide plate is wrapped by the reflector held on the side surface portion having the incident side end face. Since the distance from the outer shape of the fluorescent discharge tube to the reflecting surface in the direction perpendicular to the thickness direction was set to be large, a simple structure with no special member, stable lighting characteristics, and a conventional thin type It is possible to obtain higher brightness than the above.

In addition, the shape of the cap can be optimized to obtain the above-mentioned effect, and the shape of the cap at both ends of the fluorescent discharge tube can be made the same, so that the parts can be shared and the assemblability is good. effective.

Further, according to the liquid crystal display device using this illumination unit, stable display with high brightness can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lighting unit according to an embodiment.

FIG. 2 is a plan view of the same embodiment.

FIG. 3 is an explanatory diagram of a position of a reflective film and a brightness of a lighting unit in the same embodiment.

FIG. 4 is a sectional view of a liquid crystal display device using the illumination unit according to the embodiment.

FIG. 5 is a front view showing a cap shape used in the illumination unit of the same embodiment and a cap shape of another embodiment.

FIG. 6 is a sectional view of a conventional lighting unit.

FIG. 7 is a plan view of a conventional lighting unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Fluorescent discharge tube 3 Reflective film [Reflector] 8 Cap 11 Liquid crystal display element D Incident side end surface of light guide plate E E Light exit surface of light guide plate 1

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Nagahama 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Yasuhiko Karazaki 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd

Claims (5)

[Claims] 1. A reflection device, wherein a fluorescent discharge tube is disposed in the vicinity of an incident side end surface of a light guide plate, has a conductive reflective surface inside, and both ends are held by a side surface portion having the incident side end surface of the light guide plate. The fluorescent discharge tube is wrapped by a body, and, with respect to the distance from the outer shape of the fluorescent discharge tube in the thickness direction of the light guide plate to the reflection surface, of the fluorescent discharge tube in the direction perpendicular to the thickness direction of the light guide plate. An illumination unit set so that the distance from the outer shape to the reflecting surface is increased. 2. The lighting unit according to claim 1, wherein the distance from the outer shape of the fluorescent discharge tube to the reflecting surface of the reflector in the direction perpendicular to the thickness direction of the light guide plate is 0.6 mm to 1.2 mm. 3. The lighting unit according to claim 1, wherein a cap covering the electrode portions at both ends of the fluorescent discharge tube is used as a spacer for keeping a distance between the fluorescent discharge tube and the reflecting surface of the reflector. 4. The outer shape of the cap is an elliptical shape or an oval shape having a minor axis in the thickness direction of the light guide plate.
Illumination unit described. 5. A liquid crystal display device in which a transmissive liquid crystal display element is disposed on the end face of the light guide of the lighting unit according to claim 1 on the exit side.