JPH07248492A - Back light for liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the back light of a liquid crystal display device constituted so that the bright display of an LCD is realized in the most excellent state even with respect to any environmental light intensity by using the back light and external light at the same time as a light source for displaying of the LCD or selectively properly using them. CONSTITUTION:A prism plate 10 is arranged behind the LCD 2 so that a prism surface 11 is faced to the LCD 2 side. Besides, a back lamp 5 and a lighting window 14 constituted so that the external light 13 consisting of solar light is made incident on from the back upper part are arranged at the back lower part of the plate 10. Then, the light from the lamp 5 and the external light 13 is condensed to the parallel synthesized light by the plate 10 so as to illuminate the LCD 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight of a liquid crystal display device suitable for use in a liquid crystal viewfinder of a liquid crystal TV or a video camera.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display devices (hereinafter, referred to as
When a back lamp such as a fluorescent tube is used as a light source for displaying (LCD), power consumption in the back lamp has been a serious problem in the case of a portable device using a battery as a power source for the light source. Further, in a place exposed to strong direct sunlight, even if the illuminance of the back lamp is increased to the limit, it is difficult to increase the brightness so that the LCD display can be clearly seen only by a light source such as a fluorescent tube.

On the other hand, some liquid crystal TVs are adapted to display the LCD by taking in external light as a backlight in a bright place. However, in the case of using external light, it may be impossible to adopt it depending on the product structure because it is necessary to structurally raise the LCD panel. When using outside light,
For example, there is a problem that the display image cannot be seen at all in a dark place such as a tunnel.

The present invention has been made in order to solve the above-mentioned problems, and the backlight and the external light are used together or selectively as a light source for the display of the LCD to obtain any ambient light intensity. On the other hand, it is an object of the invention to obtain a backlight of a liquid crystal display device capable of brightly displaying an LCD in the best condition.

[0005]

In order to achieve the above object, the backlight of the liquid crystal display device according to the present invention has a light source arranged on the back side of the liquid crystal display device 2, and the liquid crystal display screen is provided by the light from the light source. In a backlight of a liquid crystal display device adapted to illuminate, a prism plate 1 having a large number of parallel prism faces 11 on one side behind a liquid crystal display device 2.
0 is arranged, and a plurality of light irradiation means 4, 5, 13 having different irradiation angles are arranged on the back surface side of the prism plate 10, and the light from the light irradiation means 4, 5, 13 is supplied to the prism plate 10.
The liquid crystal display device 2 is condensed and irradiated on the liquid crystal display device 2.

In the backlight of the liquid crystal display device according to the preferred embodiment of the present invention, the prism plate 10 receives light from a plurality of light irradiating means 4, 5, 13 which are symmetrically different from each other in the irradiation angle. The vertical parallel rays are condensed and applied to the liquid crystal display device 2.

In the backlight of the liquid crystal display device according to the preferred embodiment of the present invention, the plurality of light irradiating means are composed of the back lamps 4 and 5 and the external light 13 of the sun rays.

Further, the backlight of the liquid crystal display device according to the preferred embodiment of the present invention is such that a plurality of light irradiating means 4 (or 5) and 13 are simultaneously made into combined light to irradiate the liquid crystal display device 2. is there.

The backlight of the liquid crystal display device according to the preferred embodiment of the present invention irradiates the liquid crystal display device 2 by selectively switching the plurality of light irradiating means 4 (or 5) and 13 according to the ambient light intensity. It is something that is done.

Further, in the backlight of the liquid crystal display device according to the preferred embodiment of the present invention, the plurality of light irradiating means 4 (or 5) and 13 can be automatically switched by the detecting means for detecting the light quantity of the ambient light intensity. Is.

Further, the backlight of the liquid crystal display device according to the preferred embodiment of the present invention has the light diffusion plates 8 and 9 arranged between the prism plate 10 and the light irradiation means 4 (or 5) and 13. .

[0012]

In the backlight of the liquid crystal display device of the present invention configured as described above, when the prism plate 10 is irradiated with light from the plurality of light irradiation means 4, 5, 13 having different irradiation angles, this prism plate is used. The light that enters 10 is the prism surface 11
Accordingly, the liquid crystal display device 2 can be illuminated without being leaked to the outside and condensed.

Light incident on the prism plate 10 from directions in which the irradiation angles are symmetrically different from each other is condensed by the prism surface 11 into parallel light rays in a direction perpendicular to the prism plate 10 and efficiently illuminates the liquid crystal display device 2. be able to.

Further, since the light irradiating means comprises the back lamps 4 and 5 and the external light 13 of the sun rays, the external light 13 supplements the illuminance of the back lamps 4 and 5 and illuminates the liquid crystal display device 2 with sufficient illuminance. be able to.

Further, since the plurality of light irradiating means illuminate the liquid crystal display device 2 by using the back lamps 4, 5 and the external light 13 as combined light, the external light 13 is used when the ambient light intensity is bright. The liquid crystal display device 2 can be illuminated by using the light sources from the back lamps 4 and 5 when the ambient light intensity is dark.

Further, the plurality of light irradiation means selectively switch the back lamps 4, 5 and the external light 13 according to the ambient light intensity to illuminate the liquid crystal display device 2, so that the ambient light intensity is bright. Occasionally, the outside light 13 is used, and at this time the back lamps 4 and 5 can be turned off to save power.

A plurality of light irradiation means 4 (or 5),
Since 13 is electrically switchable by the detection means for detecting the amount of ambient light intensity, it is possible to instantly and automatically switch to the light irradiation means corresponding to the ambient light intensity.

Since the light diffusing plates 8 and 9 are arranged between the prism plate 10 and the light irradiating means 4 (or 5) and 13, the light from the light irradiating means is diffused by the light diffusing plates 8 and 9. As a result, uniform light can be made incident on the prism plate 10.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the backlight of a liquid crystal display device according to the present invention will be described below with reference to the drawings by taking an example of applying the liquid crystal viewfinder of a video camera.

[First Embodiment] FIG. 1 is a sectional view of a liquid crystal viewfinder of this embodiment. Reference numeral 1 denotes a finder lens barrel, 2 denotes a liquid crystal display device (hereinafter referred to as LCD), and 3 denotes an eyepiece lens arranged in front of the display surface side of the LCD 2 (eyepiece portion 1a side). LCD on the back side of LCD2
2 as a light irradiation means for illuminating 2 from the back side
Two back lamps 4 and 5 are provided at upper and lower positions.
Arc-shaped reflectors 6 and 7 are arranged on the back sides of the back lamps 4 and 5, respectively, and light diffusion plates 8 and 9 are arranged on the front sides of the back lamps 4 and 5, respectively. The back plates 4 and 5 as well as the reflection plates 6 and 7 and the light diffusion plates 8 and 9 are arranged to face the LCD 2 at predetermined angles.

LC in front of the above-mentioned back lamps 4 and 5
A prism plate 10 is arranged behind D2. The prism plate 10 is made of a transparent plastic sheet such as polycarbonate, and is formed on one side of the prism plate 10, that is, the LCD
A large number of prism surfaces 11 serving as sawtooth-shaped light emitting surfaces parallel to the lateral direction are provided on the front surface side opposite to the back surface of 2, and one surface on the opposite side is a smoothed light incident surface 12. Figure 2
A perspective view of the prism plate 10 is shown in FIG. The product name "lens film" announced by Sumitomo 3M Ltd. is used for the prism plate 10 thus configured.

The optical action of the prism plate 10 described above is such that, as shown in FIG. 3, the light A and B incident on the light incident surface 12 from the upper and lower predetermined angle directions enter the prism surface 11.
It has a characteristic that it is refracted by and is converted into parallel rays A'and B'perpendicular to the prism plate 10 to be combined and condensed. That is, the incident angle of the incident light is determined by the prism apex angle θ of the prism surface 11.

Therefore, in the case of the embodiment shown in FIG. 1, the angles of the back lamps 4 and 5 are set so that the light emitted from the prism plate 10 is illuminated with the light from the direction perpendicular to the LCD 2. There is.

The backlight of the present invention thus constructed has two back lamps 4, 5 having different vertical directions.
The light from is refracted by the prism plate 10 and synthesized,
There is an advantage that the two back lamps 4 and 5 appear as if they are right behind the prism plate 10 and the light condensed by the prism plate 10 can efficiently illuminate the LCD 2.

Further, since the light diffusion plates 8 and 9 are arranged in front of the back lamps 4 and 5, the back lamps 4 and 5 are
Light from the prism plate 10 is diffused and becomes uniform light.
It is possible to illuminate the LCD 2 by being condensed by.

Further, the back lamps 4 and 5 do not have to be light sources of the same color, and there is an advantage that the background color of the LCD 2 can be changed, for example, by changing the color of emitted light and emitting them simultaneously or separately. It can also be used to detect that the life of the battery is reduced when different emission colors are emitted.

[Second Embodiment] FIG. 4 is a sectional view of a liquid crystal viewfinder of this embodiment. In the case of this example, the part different from the embodiment shown in FIG. 1 is that, in the two back lamps 4 and 5, instead of the upper back lamp 4 and the reflector 6 on the rear side thereof, the outside light from the sunlight 13 is used as a viewfinder mirror. It is used as a backlight of the LCD 2 through the light diffusing plate 8 from the lighting window 14 formed in the cylinder 1.

That is, the light from the back lamp 5 and the external light from the sunlight 13 are incident on the prism plate 10, and these lights are combined into parallel light by the prism plate 10 and are condensed and emitted. To illuminate. Particularly in the case of this embodiment, outside light becomes a main light source for illuminating the LCD 2 in an environment where direct sunlight is strong, and light from the back lamp 5 becomes a main light source for illuminating the LCD 2 in a dim environment.

Since the backlight constructed in this manner uses the back lamp 5 and external light together, the LCD 2 can be illuminated sufficiently bright even in an environment exposed to direct sunlight, and switching between external light and the back lamp is possible. Since a mechanism and a movable mechanism are not required, the structure is simple and the usability is easy, and it is possible to reduce the size without entering dust.
And also highly reliable.

Further, in the case of this embodiment, LC by external light is used.
During the illumination of D2, it is also possible to turn off the power to the back lamp 5 as necessary to save battery consumption.

[Third Embodiment] FIG. 5 is a sectional view of a liquid crystal viewfinder of this embodiment. This example is a modification of the embodiment shown in FIG. 4, in which the light diffusing plate 9 of the back lamp 5 and the light diffusing plate 8 that allows the passage of external light are parallel to each other, and the angles at which the respective lights enter the prism plate 10. Is a change. Therefore, in the case of this example, the light incident angle on the prism plate 10 is the first
Also, since it is different from the second embodiment, a prism plate having a different prism apex angle which is emitted as parallel light from the prism plate 10 is used.

[Fourth Embodiment] FIG. 6 is a sectional view of a liquid crystal viewfinder of the present embodiment. This example is an improved example of the embodiment shown in FIG. 4, and the light-shielding plate 1 that can be opened and closed in the daylighting window 14 is movable.
5 is provided. That is, in an environment where the direct sunlight is strong, the shading plate 15 is opened from the lighting window 14 to let in the outside light to illuminate the LCD 2. The LCD 2 is illuminated with light. In particular, when the LCD 2 is illuminated by the back lamp 5, the light-shielding plate 15 closes the daylighting window 14. Therefore, the light of the backlight 5 does not leak from the daylighting window 14 to the outside, and the light of the backlight 5 is effectively used. Can be used.

Further, in the opening / closing operation of the light shielding plate 15 in this embodiment, for example, an external light sensor such as a photodiode (not shown) is arranged in the vicinity of the daylighting window 14, and the amount of ambient light is detected by the external light sensor to perform automatic operation. The light shielding plate 15 can be automatically opened and closed.

Further, as another example, it is possible to automatically open and close the light shielding plate 15 based on the information on the opening and closing amount of the iris which is the optical mechanism of the video camera.

[Fifth Embodiment] FIG. 7 is a sectional view of a liquid crystal viewfinder of the present embodiment. This example is a modification of the embodiment shown in FIG. 6, in which a movable reflecting mirror 16 is arranged at the position of the diffusion plate 8 instead of the light shielding plate 15. The inner surface side of the reflective mirror 16 acts as a reflective mirror, and the outer surface side serves as a light shielding surface.

That is, in an environment where direct sunlight is strong, the reflection mirror 16 is opened to allow outside light to enter through the lighting window 14.
The CD 2 is illuminated, and in a dim environment, the reflection mirror 16 is closed and the back lamp 5 emits light to the LCD.
Illuminate 2 Especially L by the back lamp 5
When illuminating the CD 2, the light C leaking to the outside without entering the prism plate 10 can be reflected by the reflecting mirror 16 and enter the prism plate 10, and the light of the back lamp 5 can be effectively used. .

Further, also in this embodiment, the reflecting mirror 1
The opening / closing operation of 6 detects the amount of ambient light based on the information from the external light sensor such as a photodiode or the iris of the optical mechanism in the same manner as in the above-described embodiment, and automatically reflects the mirror 1.
6 can be automatically opened and closed.

The present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without departing from the spirit of the invention.

In the embodiment, the example of using the backlight of the liquid crystal display device according to the present invention is applied to the viewfinder of the video camera. In addition, as shown in FIG. 8, the back of the liquid crystal display device 17 of the liquid crystal TV is shown. The prism plate 18 is arranged on the
By disposing the back lamp 20 having 9 and the daylighting window 22 into which the sunlight is incident on the housing 21, the same operation as that of the above-described embodiment can be obtained.

[0040]

As described above, in the backlight of the liquid crystal display device according to the present invention, a prism plate having a large number of parallel prism faces on one side is arranged behind the liquid crystal display device and the prism plate Since a plurality of light irradiation means having different irradiation angles are arranged on the back side and the light from the light irradiation means is combined by the prism plate to be condensed and irradiated to the liquid crystal display device, the light from the light irradiation means is The liquid crystal display device can be efficiently illuminated and the liquid crystal display device can be illuminated sufficiently brightly.

Further, the prism plate is adapted to collect light from a plurality of light irradiating means having different irradiation angles into parallel rays perpendicular to the prism plate and irradiate the liquid crystal display device.
This is effective as a lighting function of the liquid crystal display device.

Further, since the light irradiating means is composed of the back lamp and the external light of the sun rays, the external light can supplement the illuminance of the back lamp to illuminate the liquid crystal display device with sufficient illuminance, and the power required for the back lamp. Consumption can be kept low.

Further, since the plurality of light irradiating means illuminate the liquid crystal display device by using the combined light of the back lamp and the external light, the liquid crystal display device is illuminated by using the external light when the ambient light intensity is bright. Thus, when the ambient light intensity is low, the liquid crystal display device can be illuminated by the light source from the back lamp.

Further, since the plurality of light irradiating means selectively switch the back lamp and the outside light according to the ambient light intensity to irradiate the liquid crystal display device, the outside light is utilized when the ambient light intensity is bright. However, at this time, the back lamp can be turned off to save power.

Further, since the plurality of light irradiating means can be automatically switched by the detecting means for detecting the light quantity of the ambient light intensity, it is possible to instantly and automatically switch to the light irradiating means corresponding to the ambient light intensity.

By disposing the light diffusing plate between the prism plate and the light irradiating means, the light from the light irradiating means is diffused by the light diffusing plate and can be made incident on the prism plate as uniform light. .

[Brief description of drawings]

FIG. 1 is a sectional view of a backlight of a liquid crystal display device according to a first example of the present embodiment.

FIG. 2 is a perspective view of a prism plate.

FIG. 3 is a diagram of an optical operation of a prism plate.

FIG. 4 is a sectional view of a backlight of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a backlight of a liquid crystal display device according to a third embodiment of this example.

FIG. 6 is a cross-sectional view of a backlight of a liquid crystal display device according to a fourth embodiment of this example.

FIG. 7 is a sectional view of a backlight of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 8 is a cross-sectional view of an example in which the backlight of this example is applied to a liquid crystal TV.

[Explanation of symbols]

 1 Finder barrel 2 LCD 3 Eyepiece 4,5 Back lamp 6,7 Reflector 8, 9 Diffuser 10 Prism plate 11 Prism surface 12 Incident surface 13 External light (sunlight) 14 Light-gathering window 16 Light-shielding plate 16 Reflection mirror 17 Liquid crystal display device 18 Prism plate 19 Reflector plate 20 Back lamp 21 Housing 22 Lighting window

Claims (7)

[Claims] 1. A backlight for a liquid crystal display device, wherein a light source is arranged on the back side of the liquid crystal display device, and light from the light source illuminates a liquid crystal display screen. A prism plate having parallel prism surfaces on one side is arranged, and a plurality of light irradiation means having different irradiation angles are arranged on the back side of the prism plate, and the light from the light irradiation means is condensed by the prism plate. A backlight for a liquid crystal display device, characterized in that the liquid crystal display device is illuminated. 2. The prism plate is adapted to collect light from the plurality of light irradiation means having symmetrically different irradiation angles into parallel rays perpendicular to the prism plate and irradiate the liquid crystal display device. A backlight for a liquid crystal display device according to claim 1. 3. The plurality of light irradiating means are external light composed of a back lamp and a sun ray.
Backlight of the described liquid crystal display device. 4. The backlight of a liquid crystal display device according to claim 1, wherein the plurality of light irradiating means simultaneously synthesize light to irradiate the liquid crystal display device. 5. The back light of a liquid crystal display device according to claim 1, wherein the plurality of light irradiating means are selectively switched according to the ambient light intensity to irradiate the liquid crystal display device. Light. 6. The backlight of a liquid crystal display device according to claim 5, wherein the plurality of light irradiating means are automatically switchable by a detecting means for detecting a light quantity of ambient light intensity. 7. A light diffusing plate is arranged between the prism plate and the light irradiating means.
Backlight of the described liquid crystal display device.