JP2002351407A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize further reduction of the power consumption in a reflection type liquid crystal display device. SOLUTION: When a use environment is in a dark condition and the display of the display part of the device can not be viewed, the operation of a display circuit part is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device which achieves low power consumption.

[0002]

2. Description of the Related Art Conventionally, a display device of a portable information terminal such as a mobile phone or a pager (registered trademark) has been aimed at displaying simple characters such as numbers and characters, but in recent years, the IT technology has taken a leap forward. With the rapid development, there is a demand for practical use of a small, lightweight, thin, and low power consumption display device capable of displaying a color image with high definition even in a portable information terminal.

[0003] For example, a reflection type liquid crystal display device is considered to be a promising display device that satisfies this demand, and has been partially put into practical use. This reflective liquid crystal display device can display an easy-to-view image when used outdoors during the day, but since it does not have a light source inside it, it can hardly be confirmed even when displayed in the dark, and there are restrictions on the use environment. is there.

As a countermeasure, a front light technology has been proposed. In this technique, a light source for supplementing the illuminance of external light is arranged on the display surface side of the reflective liquid crystal display device.

[0005]

A portable information terminal is often carried with its power turned on, and performs a display operation even when visual recognition is not required. In addition, when the portable information terminal is carried in a pocket or bag of clothes, the irradiation light on the display surface is insufficient, and the display cannot be visually recognized even during the display operation.

[0006] As described above, the display operation is often performed even in a state where it cannot be visually recognized due to a use environment such as darkness.
It was wasting power.

Accordingly, an object of the present invention is to provide a reflection type liquid crystal display device which achieves low power consumption.

[0008]

According to the first aspect of the present invention,
A display unit including a plurality of signal lines and gate lines arranged in a matrix on an insulating substrate, and a liquid crystal display pixel arranged near an intersection of the signal lines and the gate lines; A display circuit unit including a signal line driving circuit for supplying a video signal to be displayed, and a gate line driving circuit for supplying a scanning signal to the gate line; And a illuminance monitoring circuit for stopping at least a part of the operation of the display circuit unit when the illuminance is equal to or less than the predetermined illuminance.

According to the present invention, useless power consumption can be suppressed. Hereinafter, a detailed description will be given based on specific examples.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as one embodiment of the present invention,
A reflective liquid crystal display device using a polycrystalline silicon TFT will be described in detail with reference to the drawings. The reflective liquid crystal display device 1 of this embodiment includes a display cell holding a liquid crystal layer between opposing substrates, an external circuit, and a front light for irradiating the display surface of the display cell. FIG. 1 is a schematic plan view showing an array substrate of the reflection type liquid crystal display device 1.

The reflection type liquid crystal display device limits the driving operation depending on the use environment and reduces unnecessary power consumption.

An array substrate 100 of a display cell includes a signal line 101 disposed substantially in parallel at equal intervals on a transparent insulating substrate such as glass, and a gate line substantially orthogonal to the signal line 101 and electrically insulated from the signal line 101. 102 and a TFT (thin film t) as a switch element 103 near the intersection thereof.
The pixel electrodes 104 are arranged in a matrix through a transistor (transistor). This TFT is constituted by a p-Si TFT using a polycrystalline silicon film for its active layer. The reflection type liquid crystal display device 1 includes a signal line driving circuit 105 for driving the signal line 101, a gate line 1
02, a display circuit section 110 that outputs various power supply voltages and signals to the drive circuits 105 and 106, and an operation of the display circuit section 110 based on the illuminance of the display section. Illuminance monitoring circuit 12
0. The illuminance monitoring circuit 120 is formed of a p-Si TFT formed in the same step as the TFT of the display unit, and is formed on the same substrate as the array substrate 100.

The pixel electrode 104 of this display cell is made of a metal material having light reflectivity, and has a function as a reflector for reflecting light incident from the outside. Then, the pixel electrode 104
A reflective liquid crystal display pixel is provided by providing a liquid crystal layer between the liquid crystal layer and the opposing electrode 107 facing the liquid crystal display, and the display unit is configured by arranging the reflective liquid crystal display pixels in a matrix.

The illuminance monitoring circuit 120 includes an optical sensor 121 for detecting a light / dark state of a use environment of the liquid crystal display device,
A comparison circuit 1 that determines ON / OFF of the display circuit unit 110 based on the amount of light detected by the optical sensor 121 and outputs a control signal for controlling ON / OFF of the control switch 123.
22. The comparison circuit 122 sends a control signal to turn on the display circuit unit 110 when the light amount detected by the optical sensor 121 is equal to or more than the reference illuminance, and a control signal to turn off the display circuit unit 110 when the light amount is equal to or less than the reference illuminance to the control switch 123 Output. The reference illuminance is set to a value equal to or higher than the illuminance at which characters and the like displayed on the display screen can be determined, and is set to 0.5 lux here.

The control switch 123 performs a switching operation based on a control signal from the comparison circuit 122, and controls input / non-input of the power supply voltage VDD to the display circuit unit 110.

Therefore, the operation of the display circuit can be controlled depending on the environment in which the liquid crystal display device is used.

Here, the operation of the liquid crystal display device will be described. When the use environment of the liquid crystal display device 1 is bright enough to visually recognize the display operation of the display unit, the control switch 1
23 is turned on, and the display circuit unit 110 performs a display operation.

More specifically, an optical sensor 121 integrally formed on the array substrate 100 detects the illuminance of the display unit, and a comparison circuit 122 compares the illuminance with a reference illuminance. Here, the illuminance at which the screen in the display state is visible to humans, 0.5
lux is set as a reference illuminance, and when the brightness is higher than the reference illuminance, a bright environment is set, and when the brightness is lower than the reference illuminance, a dark environment is set.

When the display section is in a bright environment due to the input of external light or front light, the comparison circuit 122 outputs an ON signal to the control switch.

The control switch 123 receives the ON signal.
Is turned on, and outputs the power supply voltage VDD from the external circuit to the display circuit unit.

DC / DC conversion circuit 1 of display circuit section 110
At 11, the power supply voltage VDD from the external circuit is applied to the common circuit 112, the signal line driving circuit 105, and the gate line driving circuit 10.
In step 6, the power supply voltage is converted into a necessary power supply voltage, and the signal line drive circuit 105 converts the digital display signal DATA into an analog display signal using the grayscale reference voltage, performs a shift operation, and sequentially writes the display signal to the signal line.

The display signal written to the signal line 102 is written to each pixel in synchronization with the shift pulse from the gate line driving circuit 106, and the display operation of the display unit is performed.

When the use environment becomes a dark environment and the light sensor 121 detects an illuminance of 0.5 lux or less, the comparison circuit 122 outputs the OFF signal to the control switch 12.
3 and the output of the power supply voltage VDD to the display circuit unit 110 is stopped. Therefore, the display circuit unit 110 is in a non-operation state, and stops the display operation of the display unit.

As described above, when the use environment is in a dark environment and the display operation cannot be visually recognized even when the display is performed, the electric connection between the power supply voltage VDD and the display circuit unit 110 is cut off, and the display circuit unit is disconnected. By stopping the operation of 110, useless power consumption can be reduced.

Further, when the front light is turned on or moved to a bright environment, etc., and the illuminance of the display unit becomes 0.5 lux or more in a bright environment, the control switch is turned on, and the external circuit and the display circuit unit 110 are connected. The display circuit portion 110 can be operated by the connection and the power supply voltage VDD.

As described above, the display operation is performed only when the display operation can be visually recognized, and in an environment where the user cannot visually recognize the display operation even when the display operation is performed, the display circuit unit is stopped. It is possible to operate with.

Further, the display screen can be made bright by the front light disposed on the display screen side, and the display screen can be visually recognized without being affected by the use environment.

Further, in the above-described embodiment, an example has been described in which the display circuit section and the illuminance monitoring circuit are all formed integrally with the array substrate. However, these circuits are formed on an external circuit board (PCB; printed circuit board).
d) It may be formed on the external circuit board and partly on the array substrate. As an example, in the example shown in FIG.
Are mounted on an external circuit board by COG.

In the above embodiment, a p-Si TFT using a polycrystalline silicon thin film as a TFT has been described. However, an a-type TFT using an amorphous silicon thin film as an active layer is used.
It may be a SiTFT.

In the above-described embodiment, the case where the input of the power supply voltage VDD is stopped and the display circuit section is completely stopped when the surroundings are in a dark environment has been described. The input of CLK to the substrate may be stopped.

For example, the control switch 12 is connected to an external circuit board.
3 is formed, and controls the input / non-input of the clock signal CLK to the display cell based on the control signal detected by the optical sensor 121 and output from the comparison circuit 122.

When the surroundings are dark and the display operation cannot be visually recognized, the input of the clock signal CLK to the display circuit unit 110 is stopped, so that the signal line driving circuit 105 and the gate line driving circuit 106 The clock operation can be stopped.

Therefore, when the display operation cannot be visually recognized, writing to each pixel in the display section can be stopped.
Unnecessary power consumption can be reduced.

Further, since the operation of a part of the display circuit unit 110 is stopped and the operation of the other part can be resumed at any time, the display operation can be performed as soon as the clock signal CLK is input.

As a modified example, the supply of the synchronization signal to the substrate may be stopped to stop a part of the operation of the display circuit unit 110, or the clock signal CLK and the synchronization signal may be supplied to the substrate. The supply may be stopped.

In the above embodiment, the reflection type liquid crystal display pixel in which the pixel electrode functions as a reflection plate has been described. However, the present invention is not limited to this. A reflective plate may be provided on the back side or the like, and the present invention can be applied to all reflective liquid crystal display devices.

[0037]

According to the present invention, it is possible to provide a reflective liquid crystal panel which achieves low power consumption.

[Brief description of the drawings]

FIG. 1 is a schematic view of an array substrate of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a liquid crystal display device showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 101 ... Signal line 102 ... Gate line 105 ... Signal line drive circuit 106 ... Gate line drive circuit 110 ... Display circuit part 120 ... Illuminance monitoring circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 612 G09G 3/20 612G 612K 642 642F F-term (Reference) 2H091 FA14Z FA41Z GA13 LA30 2H093 NA26 NC34 NC42 NC53 ND39 5C006 AF63 AF68 BB16 BF39 BF49 FA47 5C080 AA10 BB05 DD26 FF11 JJ02 KK07 KK47

Claims (7)

[Claims] A display unit comprising: a plurality of signal lines and gate lines arranged in a matrix on an insulating substrate; and a liquid crystal display pixel arranged near an intersection of the signal lines and the gate lines; A display circuit unit including a signal line driving circuit for supplying a video signal corresponding to the signal line, and a gate line driving circuit for supplying a scanning signal to the gate line; And an illuminance monitoring circuit for stopping at least a part of the operation of the display circuit unit when the illuminance of the display unit is equal to or less than the predetermined illuminance. 2. The liquid crystal display device according to claim 1, wherein said predetermined illuminance is 0.5 lux. 3. The reflection type liquid crystal display device according to claim 1, wherein said illuminance monitoring circuit is formed integrally on said insulating substrate. 4. The illuminance monitoring circuit according to claim 1, wherein said illuminance monitoring circuit is a polycrystalline silicon TF.
2. The reflection type liquid crystal display device according to claim 1, wherein the reflection type liquid crystal display device is constituted by T. 5. The reflection type liquid crystal display device according to claim 1, wherein said illuminance monitoring circuit is mounted on an external circuit board provided separately from said insulating board. 6. The reflection type liquid crystal display according to claim 1, wherein said illuminance monitoring circuit stops supplying a power supply voltage to said display circuit section when the illuminance of said display section is equal to or less than a predetermined illuminance. apparatus. 7. The illuminance monitoring circuit according to claim 1, wherein when the illuminance of the display section is equal to or less than a predetermined illuminance, supply of at least one of a clock signal and a synchronization signal to the display circuit section is stopped. The reflective liquid crystal display device as described in the above.