JPH07159777A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device reducing power consumption. CONSTITUTION:A color part 21 and a transparent part 22 are alternately arrayed corresponding to respective picture element electrodes 4 arrayed to be matrix-shaped at the color filter 20 of a liquid crystal cell 1, and a light transmissive reflection plate 23 having a light transmissive part 24 corresponding to the colored part 21 and a reflection part 25 corresponding to the transparent part 22 intervenes between a back light device 11 and a lower polarizing plate 10 opposed to the device 11. Therefore, when the back light device 11 is not turned on, the black and white display of picture is performed by guiding external light from the transparent part 22 and reflecting it by the reflection part 25, and when the back light device 11 is turned on, the color display of the picture is performed by guiding light from the back light device 11 from the light transmissive part 24 and making it reach the color part 21. Thus, the power consumption is reduced by properly using the color display and the black and white display.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device used in a liquid crystal television or a notebook personal computer includes a color liquid crystal display device in which a thin film transistor (TFT) is mounted for each pixel. As an example of this color liquid crystal display device, for example, a structure having a structure as shown in FIG. 4 is known. This color liquid crystal display device includes a liquid crystal cell 1. The liquid crystal cell 1 is composed of a pair of upper and lower transparent glass substrates 2 and 3 which are spaced apart and face each other, and a liquid crystal is sealed between them by a sealing material. In this case, a large number of transparent pixel electrodes 4 are arranged in a matrix on the upper surface of the lower glass substrate 3, and a TFT 5 is provided on each pixel electrode 4.
Is provided. Further, on the lower surface of the upper glass substrate 2, there is provided a filter 7 in which red (R), green (G), and blue (B) color portions 6 are alternately arranged in correspondence with the pixel electrodes 4. A transparent electrode 8 is provided on the lower surface of the filter 7. An upper polarizing plate 9 is arranged on the upper surface of the liquid crystal cell 1, a lower polarizing plate 10 is arranged on the lower surface of the liquid crystal cell 1, and the backlight device 1 is arranged on the lower surface side of the lower polarizing plate 10.
1 is arranged. In such a color liquid crystal display device, when the backlight device 11 is turned on to drive the liquid crystal cell 1, light from the backlight device 11 is emitted from the lower polarizing plate 1.
0 is irradiated to the lower surface of the liquid crystal cell 1, and the irradiated light is transmitted through the color portion 6 of the filter 7 corresponding to the driven pixel electrode 4 and is emitted from the upper polarizing plate 8, thereby displaying a color image. It is supposed to do.

[0003]

However, in such a color liquid crystal display device, a color image cannot be displayed unless the backlight device 11 is turned on. It is necessary to keep the light device turned on, which causes a problem that power consumption becomes very large. In particular, since a portable electronic device uses a battery as a power source, there is a problem that battery life is shortened and usage time is shortened. The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device that can reduce power consumption.

[0004]

In order to achieve the above object, the present invention has a liquid crystal cell having a large number of pixels and color filters arranged in a matrix, and a pair of polarizing plates provided with the liquid crystal cell interposed therebetween. And a liquid crystal display device including a backlight device arranged to face one of the pair of polarizing plates, a color filter is provided with a color portion and a transparent portion alternately corresponding to each pixel, and a backlight is provided. A light-transmitting reflector having a light-transmitting portion corresponding to the color portion and a reflecting portion corresponding to the transparent portion is interposed between the device and one polarizing plate facing the device.

[0005]

According to the present invention, when the backlight device is not turned on, external light is introduced from the transparent portion of the filter and reflected by the reflecting portion of the translucent reflector.
An image can be displayed in black and white according to the operation of the liquid crystal cell, and when the backlight device is turned on, the light from the backlight device is introduced from the transmissive part of the translucent reflection plate to the color part of the filter. Will reach
Images can be displayed in color according to the operation of the liquid crystal cell. Therefore, since the image can be displayed in black and white without turning on the backlight device, the power consumption can be reduced by properly using color display and black and white display.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same parts as those in the conventional example shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted as appropriate. A color filter 20 is provided on the lower surface of the glass substrate 2 on the upper side of the liquid crystal cell 1. Color filter 20
1 has a structure in which R, G, and B color portions 21 and transparent portions 22 are alternately provided corresponding to the pixel electrodes 4 on the lower glass substrate 3, as shown in FIGS. ing. That is, the color portions 21 are arranged in a triangular shape so that R, G, and B are not adjacent to each other in the front, rear, left, and right, and the transparent portions 22 are arranged adjacent to the front, rear, left, and right of each color portion 21. The transparent electrode 8 is provided on the lower surface of the color filter 20. Further, a translucent reflection plate 23 is arranged between the lower polarizing plate 10 and the backlight device 11. The translucent reflection plate 23 includes a flat translucent portion 24 corresponding to the collar portion 21 and a flat reflective portion 25 corresponding to the transparent portion 22.
And are provided alternately.

In such a color liquid crystal display device, when the backlight device 11 is not turned on, external light is introduced from the transparent portion 22 of the color filter 20 through the upper polarizing plate 9, and the external light is transmitted to the lower polarizing plate 10. And is reflected by the reflection part 25 of the translucent reflection plate 23, and this reflected light again passes through the lower polarization plate 10 and the transparent part 22 and is emitted from the upper polarization plate 9. When is driven, an image corresponding to the operation of the liquid crystal cell 1 can be displayed in black and white. At this time, the pixel corresponding to the color portion 21 of the color filter 20 is set to display black.
Further, when the backlight device 11 is turned on, light from the backlight device 11 is introduced from the translucent portion 24 of the translucent reflection plate 23, and the introduced light is the color of the lower polarizing plate 10 and the color filter 20. Since the light is transmitted through the portion 21 and emitted from the upper polarizing plate 9, when the liquid crystal cell 1 is driven, an image according to the operation of the liquid crystal cell 1 can be displayed in color. In this case, color filter 2
If the pixel corresponding to the transparent portion of 0 is displayed in black, the contrast can be increased.

As described above, in this color liquid crystal display device, an image can be displayed in black and white without the backlight device 11 being turned on. Therefore, the power consumption can be reduced by using the color image and the black and white image properly. can do. In particular, when it is used in a portable electronic device such as a liquid crystal television or a notebook personal computer, the battery life as a power source can be extended and it can be used for a long time.

Although the reflecting portion 25 of the translucent plate 23 is formed flat in the above embodiment, the present invention is not limited to this, and the reflecting portion 26 of the reflecting portion 26 may be formed as shown in FIGS. 3 (a) and 3 (b), for example. So that the center is convex toward the backlight device 11 side,
The reflecting portion 26 may be formed in the shape of an inclined or curved recess. With this configuration, when the backlight device 11 is not turned on, the external light can be reflected by the reflector 26 so as to be condensed, and when the backlight device 11 is turned on, the backlight is reflected by the reflector 26. Device 1
The light from 1 can be reflected toward the backlight device 11 side so as to be diffused and sent to the translucent portion 24,
Therefore, it is possible to reduce the reflection loss of external light and reduce the loss of light from the backlight device 11.

Further, in the above-mentioned embodiment, the case where the liquid crystal cell 1 in which the thin film transistor 5 is provided for each pixel electrode 4 is used is described. The present invention can be applied to a simple matrix type liquid crystal display device in which a large number of glass substrates are formed and a pair of glass substrates are opposed to each other so that the strip electrodes facing each other are orthogonal to each other.

[0011]

As described above, according to the present invention, the color filter is provided with the color portion and the transparent portion alternately corresponding to each pixel, and the backlight device and the one polarizing plate facing the backlight device are provided. Since a light-transmitting reflector having a light-transmitting portion corresponding to the color portion and a reflecting portion corresponding to the transparent portion is interposed therebetween, when the backlight device is not turned on, external light is introduced from the transparent portion of the color filter to transmit light. An image can be displayed in black and white by reflecting the light at the reflection part of the light reflection plate, and when the backlight device is turned on, the light from the backlight device is introduced from the light transmission part of the light transmission reflection plate to display the color. The image can be displayed in color by reaching the color portion of the filter. Therefore, since the image can be displayed in black and white without turning on the backlight device, the power consumption can be reduced by selectively using color display and black and white display.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of essential parts of a liquid crystal display device of the present invention.

FIG. 2 is a plan view of a main part of the color filter shown in FIG.

3A and 3B show a modified example of a translucent plate, FIG. 3A is a perspective view of a main part thereof, and FIG.

FIG. 4 is an exploded perspective view of a main part of a conventional color liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal cell 4 Pixel electrode 5 TFT 9, 10 Polarizing plate 11 Backlight device 20 Color filter 21 Color part 22 Transparent part 23 Translucent reflection plate 24 Translucent part 25, 26 Reflection part

Claims (3)

[Claims] 1. A liquid crystal cell having a large number of pixels and color filters arranged in a matrix, a pair of polarizing plates sandwiching the liquid crystal cell, and one of the pair of polarizing plates facing each other. In the liquid crystal display device including a backlight device, the color filter is provided with color portions and transparent portions alternately corresponding to the pixels, and the backlight device and the one polarization opposite to the backlight device. A liquid crystal display device, wherein a light-transmitting reflector having a light-transmitting portion corresponding to the color portion and a reflecting portion corresponding to the transparent portion is interposed between the plate and the plate. 2. The liquid crystal cell includes pixel electrodes provided in a matrix corresponding to each of the pixels, and thin film transistors provided in each of the pixel electrodes. Liquid crystal display device. 3. The liquid crystal display device according to claim 1, wherein the reflection portion is formed so that its center is convex toward the backlight device side.