JP3506841B2 - Illumination device of reflective liquid crystal display device and reflective liquid crystal display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a reflective display such as a liquid crystal panel or a printed matter, and a reflective liquid crystal display device using the lighting device .

[0002]

2. Description of the Related Art Liquid crystal display devices are thin and light, and are therefore widely used as displays for portable information terminals. The liquid crystal is a light-receiving element that does not emit light by itself, and includes a reflective type in which a reflector is placed on the back surface to illuminate with external light to see a display, and a transmissive type in which a backlight is placed on the back surface.

Since the liquid crystal can be driven by a low voltage of several volts, the reflective liquid crystal element has extremely low power consumption, but it cannot be used in a dark environment, and the color liquid crystal panel using a color filter has a low light utilization rate. The reflective type has the drawback that bright colors cannot be displayed. As a reflection type liquid crystal panel lighting, in wristwatches, a miniature ball lamp is placed diagonally in front of the panel and used as night lighting.
Since it lacks uniformity, it is limited to small LCD panels.

As a solution to this problem, a method has been proposed in which a flat plate-shaped illumination (front light) is attached to the front of a reflective liquid crystal panel to share the ambient light with the front light (for example, SID '95). Digest, pages 375 to 378, CYTai, H.Zou, PKTai
). FIG. 3 shows a block diagram of the illumination of Tai et al. In FIG. 3, 30 is a transparent plastic (usually having a refractive index of 1.5).
A front and rear) light guide plate, 31 is a fluorescent light source provided on the end surface of the light guide plate 30, and 32 is an optical compensation plate provided on the front surface of the light guide plate 30. FIG. 4 shows an enlarged view of the IV portion of FIG.
A prism portion 33 is formed on the front surface of the light guide plate 30.

As shown in FIG. 5, the light 35 emitted from the fluorescent lamp light source 31 is totally reflected by the surface of the wedge-shaped collimating portion 34 of the light guide plate 30 (the critical angle of the total reflection angle is 42 degrees). The light is incident on the plane of the light guide plate 30 at a shallow angle (10 degrees). Then, as shown in FIG. 6, a part of the incident light 36 is generated by the light guide plate 3.
The light is reflected by the inclined surface of the prism portion 33 of 0, exits the light guide plate 30, and illuminates the display surface (not shown) provided on the back surface of the light guide plate 30. Further, the light 37 reflected by the flat surface portion of the light guide plate 30 further penetrates deep inside the light guide plate 30.

Although transparent flat plate illumination is realized in this way, the image on the display is distorted due to the presence of the prism portion 33. Therefore, in order to correct this, the optical compensation plate 32 is used.
Is carried.

[0007]

In the case of a reflection type liquid crystal panel only for external illumination, it has a drawback that it is difficult to colorize and cannot be used in a dark place, and the transmission type liquid crystal panel has a drawback that it consumes a large amount of power. there were. Also, FIG.
In the case of the front light illumination, the prism portion 33 must be provided on the front surface of the light guide plate 30 or the optical compensation plate 32 must be placed, and the structure is complicated.
There is a problem that it is difficult to completely remove the distortion of the image caused by.

Therefore, an object of the present invention is to provide an illuminating device for a reflection type display which has a simple structure and does not cause image distortion, and a reflection type liquid crystal display device which consumes little power and is easy to colorize and can be used even in a dark place. Is.

[0009]

According to another aspect of the present invention, there is provided a lighting device for a reflection type liquid crystal display device, wherein a flat light guide plate, a light source provided on an end face of the light guide plate and an observer side of the light guide plate are opposite to each other. And a polymer film that is attached to the side surface to scatter and transmit incident light in a specific angle range and transmits the incident light in another angle range in a straight line. a viewer direction 0 ° with a line direction, the direction approaching the light source, viewing including the range of 55 degrees to 42 degrees, approximately normal direction of the corner of the other angle range light guide plate
It is characterized by including a range of degrees .

[0010] According to the illumination device of the reflection type liquid crystal display device of the claim 1, wherein a simple structure simply by sticking a polymer film on one surface of the light guide plate provided with the light source on the end face.
Further, when the light incident on the reflection type liquid crystal display device is scattered and reflected by the reflection type liquid crystal display device and returns to the front viewer,
Since the polymer film and the light guide plate are transparent, the image on the display can be seen without distortion or blurring.

The illumination apparatus of the reflection type liquid crystal display device according to claim 2, wherein the Oite to claim 1, partially adhered to the polymer film to the light guide plate, and the area of the portion to be attached to larger farther from the light source It is characterized by According to the illuminating device of the reflection type liquid crystal display device of the second aspect , in addition to the effect of the first aspect, uniform illumination can be performed even when the area of the light guide plate is large.

A reflective liquid crystal display device according to a third aspect includes the illuminating device of the reflective liquid crystal display device according to the first or second aspect , and the polymer film side of the illuminating device of the reflective liquid crystal display device. In addition, the liquid crystal display surface of the reflective liquid crystal panel is in contact with the surface. According to the reflective liquid crystal display device of claim 3 , since it illuminates with both the environmental lighting and the lighting device,
Bright display can be obtained and power consumption is low.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. Figure 1 is reflective
FIG. 1 is a perspective view of a reflective liquid crystal display device including a lighting device 5 of the liquid crystal display device and a reflective liquid crystal panel 6 provided on one surface thereof. First, the fluorescent light source 2 is placed on the end face of the acrylic light guide plate 1 having a thickness of 6 cm × 8 cm × 3 mm, the fluorescent light source 2 is wound with the sheet material 3 having the silver reflection film formed on the inner surface, and the end is placed on the light guide plate 1. Glue into a wedge shape. The polymer film 4 is attached to the back side of the light guide plate 1 as viewed by the observer of the display. The light guide plate 1, the fluorescent lamp light source 2, the sheet material 3, and the polymer film 4 constitute an illuminating device 5 of the reflective liquid crystal display device .

By the way, as the polymer film 4, for example, Lumisty (registered trademark) manufactured by Sumitomo Chemical Co., Ltd. is used. Lumisty is a polymer film having a diffraction grating-like fine structure, and FIG. 2 is a functional explanatory diagram of Lumisty. Light incident from the front of the Lumisty as shown in FIG. 2 (a) travels straight, and light incident from an angle of 20 to 50 degrees is scattered and transmitted as shown in FIG. 2 (b), and is incident at a shallower angle. The light goes straight as shown in FIG. The angle range of the incident angle of scattering and transmission can be changed depending on the manufacturing method, and several types are on the market, and are intended for use in the fields of construction and decoration such as blinds and lighting covers.

The Lumisty used in this embodiment, as shown in FIG. 1, has a viewing direction (arrow 15) of 0 ° in the normal direction of the light guide plate, and 25 ° to 55 ° in the direction approaching the light source. The incident light of a certain degree is scattered and transmitted, and the incident light of other angle ranges is transmitted straight. The light emitted from the light source 2 is reflected by the sheet material 3, enters the light guide plate 1 at a shallow incident angle, and is totally reflected at the interface between the light guide plate 1 and the air. In the case of acrylic, the critical angle of total internal reflection is about 42 degrees, so from 42 degrees to 5
The light totally reflected at 5 degrees is scattered and transmitted like the light ray 13 when passing through the polymer film 4, so that it is emitted from the light guide plate 1 to the display surface and illuminates the display.

Further, in FIG. 1, on the surface of the illuminating device 5 of the reflection type liquid crystal display device on the side of the polymer film 4, a liquid crystal panel 6 contacts the liquid crystal display surface with the surface of the polymer film 4. It is provided facing. The liquid crystal panel 6 has a glass substrate 7
The liquid crystal 8 is sandwiched between them, the glass substrate 7 is sandwiched between the polarizing plate 9 and the aluminum scattering reflection plate 10, and the image is written by being driven by the drive circuit 12 via the electrode 11 on the inner surface of the glass substrate 7. The light ray 13 incident on the liquid crystal panel 6 is reflected by the scattering reflection plate 10 and passes through the polarizing plate 9 again in the return path to form an image.

Light such as the light ray 14 which is totally reflected at an incident angle larger than 55 degrees goes straight through the polymer film 4, but is incident on the liquid crystal panel 6 at a distance from the light source 2 and is scattered and reflected. The light scattered and reflected in the front direction at 10 reaches the observer. The reflection type liquid crystal display device configured as described above.
According to the lighting device 5 in location, since only was stuck a polymer film 4 on one surface of the light source 2 is provided with the light guide plate 1 on the end face,
Thin lighting for a reflective liquid crystal display device can be realized with a simple structure.

The light 13 incident on the liquid crystal panel 6 is
When returning to the front direction, which is the viewing angle of the observer after being reflected by the scattering reflector 10, the polymer film 4 and the light guide plate 1 are transparent, so that the image on the display can be seen without distortion or blurring. Further, since both the ambient lighting and the lighting device 5 of the reflection type liquid crystal display device illuminate, the reflection type liquid crystal display device in which the reflection type liquid crystal panel 6 and the lighting device 5 are combined has very low power consumption. Bright display can be obtained, colorization is easy, and it can be used in dark places.

In the above embodiment, the polymer film 4 was attached to the entire surface of the light guide plate 1. However, when the light guide plate 1 has a large area and the brightness is distributed, the polymer film 4 is used. It is possible to eliminate unevenness in brightness by partially attaching and adjusting the distribution. For example, in a light guide plate 1 having a size of 15 cm × 20 cm, polymer films 4 cut into stripes having a width of 2 mm are attached at intervals, the attachment pitch is 10 mm near the light source, and 4 at the farthest place.
Gradually changing the pitch to mm, it became possible to achieve fairly uniform illumination.

Further, in the above-described embodiment, since the existing Lumisty is used for the polymer film 4, the incident light of 25 to 55 degrees is scattered, but since the total reflection angle is 42 degrees, at least the angle of total reflection is 42 degrees. Any light control function that scatters and transmits an incident angle of 42 to 55 degrees may be used. Incidentally, the above embodiment has used the liquid crystal panel 6, a reflective display with a scattering reflective surface, for example, even for printed matter, the lighting device 5 of the reflection type liquid crystal display device of the present invention is similar effective.

[0021]

[Effect of the Invention] According to the illumination device of the reflection type liquid crystal display device according to claim 1, since only was stuck a polymer film on one surface of the light guide plate provided with the light source on the end face, a thin reflection type liquid crystal display device Lighting can be realized with a simple structure. Also, when the light incident on the reflection type liquid crystal display device is scattered and reflected by the reflection type liquid crystal display device and returns to the front viewer, the polymer film and the light guide plate are transparent, so that the display image is distorted or blurred. Looks lost.

According to the illuminating device of the reflection type liquid crystal display device of claim 2 , in addition to the effect of claim 1, uniform illumination can be performed even when the area of the light guide plate is large. According to the reflection type liquid crystal display device of the third aspect , since it is illuminated by both the environmental illumination and the illumination device, a bright display can be obtained, and colorization is easy and it can be used even in a dark place. Also, it consumes less power.

[Brief description of drawings]

FIG. 1 is a perspective view of a reflective liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a functional explanatory diagram of a transmission / scattering polymer film.

FIG. 3 is a perspective view of a conventional front light illumination device.

FIG. 4 is an enlarged perspective view of an IV portion of FIG.

FIG. 5 is a diagram showing a path of light in a collimating portion of a conventional light guide plate.

FIG. 6 is a diagram showing a path of light in a plane portion of a light guide plate of a conventional example.

[Explanation of symbols]

1 Light Guide Plate 2 Fluorescent Light Source 3 Sheet Material 4 Polymer Film (Lumisty) 5 Illumination Device for Reflective Liquid Crystal Display Device 6 Liquid Crystal Panel (Reflective Display) 7 Glass Substrate 8 Liquid Crystal 9 Polarizing Plate 10 Scattering Reflector 11 Electrode 12 Driving circuit 13, 14 rays

Continuation of front page (56) Reference JP-A-4-97129 (JP, A) JP-A-2-280102 (JP, A) JP-A-8-122757 (JP, A) JP-A-8-50291 (JP , A) JP-A-8-122755 (JP, A) JP-A-5-303069 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/13357

Claims (3)

(57) [Claims] 1. A flat light guide plate, a light source provided on an end face of the light guide plate, and a light guide plate attached to a surface of the light guide plate opposite to an observer side to scatter and transmit incident light in a specific angle range. , A polymer film that allows the incident light in other angle ranges to go straight through, and the specific angle range has a viewer direction of 0 degrees with respect to the normal direction of the light guide plate and a direction of approaching the light source. look including the range of 55 ° degrees, the other angle range of the light guide plate
An illuminating device for a reflective liquid crystal display device, characterized in that it includes an angular range in a substantially normal direction . 2. The illumination device for a reflective liquid crystal display device according to claim 1, wherein the polymer film is partially attached to the light guide plate, and the area of the attached portion is increased as the distance from the light source increases. 3. A lighting device for a reflective liquid crystal display device according to claim 1 or 2, wherein the liquid crystal display surface of the reflective liquid crystal display device is provided on the polymer film side of the lighting device for the reflective liquid crystal display device. A reflective liquid crystal display device characterized in that the liquid crystal display device is in contact with.