JPH05323902A - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] In an image display device such as a computer, it is an object to realize a long life in a driving method of a matrix type liquid crystal image display device. A matrix type liquid crystal display panel driven by a plurality of data lines and address lines intersecting each other, a data line driving circuit and an address line driving circuit provided at the end portions of the data lines and the address lines, respectively. , A display data memory for storing display contents in units of the number of bits, a circuit for transferring the display data to a data line drive circuit, and a circuit for converting the display data in the data line drive circuit based on a predetermined law by controlling an external signal And a liquid crystal image display device. According to the present invention, when the screen saver for preventing image sticking of the display screen of the liquid crystal display device is in operation, the liquid crystal display device is driven at a voltage lower than the voltage originally driving the liquid crystal panel and an averaged voltage value. You can
The life deterioration of the liquid crystal display device can be significantly reduced.

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 for displaying an image on a computer or the like, and to a drive system for a matrix type liquid crystal image display device for the purpose of extending the life of the liquid crystal display device. ..

[0002]

2. Description of the Related Art Conventionally, a liquid crystal image display device used in a computer or the like includes a matrix type liquid crystal display panel driven by a plurality of data lines and address lines intersecting each other, and the data lines and address lines. A data line drive circuit and an address line drive circuit respectively provided at the ends of the data memory, a data memory for storing display contents in an arbitrary number of bits, a circuit for reading data from the data memory, and a read data for the data line It is composed of a circuit for transferring to a drive circuit. Further, in the case where the data line drive circuit is an analog drive system, the data read out from the data memory is converted into an analog value by an analog / digital conversion circuit (hereinafter, abbreviated as D / A converter), and then converted to a data line drive circuit. It consists of a sending circuit.

In addition to these basic structures, in an image display device such as a computer, in order to prolong the life of the liquid crystal image display device, reduce power consumption, and prevent image sticking on the display screen of the liquid crystal image display device, a predetermined amount is provided. Only when keyboard input of a computer or the like is not made within the time, a method of operating a screen saver function by software or hardware is used.

Currently used software or hardware screen savers have a long life and low power consumption of the backlight by automatically turning off the lighting of the backlight, and have a geometric pattern. The pattern image is displayed randomly to prevent image sticking on the liquid crystal screen, or to prevent image sticking on the liquid crystal display screen at all to prevent image sticking on the liquid crystal screen and extend the life of the liquid crystal display device. A measuring method is used.

[0005]

However, the conventional screen saver for extending the life and preventing the burn-in of the display screen of the liquid crystal image display device is normally driven as the drive voltage applied to the liquid crystal panel. Since the level is the same as that at the time, it is not possible to extend the life of the liquid crystal display device by the drive voltage applied to the liquid crystal panel.

Further, it is very effective as a screen saver to use a method in which no image is displayed on the display screen at all, as a method of prolonging the life and preventing the burn-in of the display screen of the liquid crystal image display device. There are situations where it is difficult to determine whether the computer etc. being used is currently in use.

[0007]

According to the present invention, when the screen saver for extending the life of the liquid crystal display device and preventing the burn-in of the display screen is in operation, the display content actually displayed on the liquid crystal display device is predetermined. The conversion is performed based on the above law, or the data once stored in the data memory is converted based on the predetermined law. When the converted display content is converted into the drive voltage value applied to the liquid crystal panel,
Compared with the voltage value displayed normally, the voltage value is low and the voltage value is averaged. That is, the liquid crystal display device is driven with an averaged voltage that is lower than the originally driven voltage value.

[0008]

Therefore, when the screen saver for preventing the burn-in of the display screen of the liquid crystal display device is in operation, the liquid crystal panel is driven at a voltage value lower than the original driving voltage and averaged. When not used for display purposes, deterioration of life of the liquid crystal display device due to applied voltage can be significantly reduced.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) (FIG. 1) is a block diagram showing an embodiment of the first invention of the present application. 1 is a display data control circuit for a computer or the like, 2 is a display data memory circuit for display data to be displayed on a liquid crystal display device, 3 is a display data control circuit for controlling display data, 4 is a data line drive circuit for the liquid crystal display device, Reference numeral 5 is an address line driving circuit of the liquid crystal display device, and 6 is a liquid crystal display panel.

In the above data line driving circuit 4,
7 is a latch circuit, 9 is a line latch circuit, 11 is a bit data conversion circuit, 12 is a level shift circuit, and 13 is D.
A / A converter, 15 is an output circuit, and 16 is a data line.

The n-bit display signal output from the display data control circuit 1 is sent to the display data memory circuit 2 and temporarily stored in the display data memory circuit 2.
Next, the display data stored by the display data control circuit 3 is converted into a required data structure and sent to the data line driving circuit 4, and the liquid crystal display panel 6 is formed by the data line driving circuit 4 and the address line driving circuit 5. The image is displayed on.

In the data line drive circuit 4, the display data sent is timing-adjusted by the latch circuit 7 and output as n-bit display data 8, and the line latch circuit 9 corresponds to a plurality of data lines 16 existing. It is divided into the displayed data. The n-bit data line signal 10 corresponding to the data line is the bit data conversion circuit 1
Send to 1. The bit data conversion circuit 11 performs bit conversion of n-bit display data only when the screen saver control signal 18 is input, and the level shift circuit 12
A circuit for sending display data to the level shift circuit 12 without bit conversion of the display data unless the screen saver control signal 18 is input.

The display data sent to the level shift circuit 12 is converted into the signal level required for the next D / A converter 13, and the D / A converter 1
At 3, the digital value is converted into an analog value and output as the data line signal 14. This data line signal 14
Is amplified by the output circuit 15 and sent to the data line 16. Display data is displayed on the liquid crystal display panel 6 by the sent signal and the drive signal of the address line drive circuit 5.

When the above screen saver is operating,
The n-bit odd-numbered bit value is sampled in the bit data conversion circuit 11, the sampled data value is stored in order from the lower bit, and the display data is converted according to the rule that the remaining upper bits are all zero.

That is, the display data a represented by n bits
(0), a (1), a (2), a (3), ..., a (n-1) odd-numbered data a (0), a (2), ... are sampled,
This data is a (0), a (1), a (2), a (3), ...
Stored in the lower bits of a (n / 2), a (n / 2 + 1), a (n / 2 +
2), ..., Conversion is performed so that the data value of the upper bits of a (n-1) is all zero.

When the display data thus converted is displayed on the liquid crystal display device, when the digital value of the display data is converted into the analog value which is the applied voltage value of the liquid crystal panel, the applied voltage value is averaged. In addition, the voltage value is also kept low.

Therefore, when the screen saver for preventing burn-in of the display screen of the liquid crystal display device is in operation,
Since the liquid crystal display device is driven by a voltage which is lower than the voltage that is originally driven and which is averaged, deterioration of the life of the liquid crystal display device due to the applied voltage is significantly reduced.

The bit data conversion circuit 11 shown here
Can be realized with a simple circuit configuration such as a switch as shown in FIG. Assuming that the number of bits of display data is 8 bits, the 8-bit data line signal sent from the line latch circuit 9 is a (0), a (1), a
(2), a (3), ..., A (7), the output signals of the bit data conversion circuit 11 are b (0), b (1), b (2), b (3),
… B (7).

Where a (0), a (1), a (2) and a (3)
, And b (0), b (1), b (2), b (3) are the lower bits of the signal, and a (4), a (5), a (6), a (7), and b
(4), b (5), b (6), b (7) are upper bits, and a switch circuit is provided between the respective 8-bit signal lines. This switch circuit is a switch in which all of them operate simultaneously in an 8-bit signal line.

During normal operation, that is, when the liquid crystal display device is used for display purposes, the switch of the switch circuit of FIG. 2 is on the normal operation side 21 as shown in the figure, and the data line signal is a (0) → b (0), a (1) → b (1), a
(2) → b (2), ..., a (7) → b (7), and the display data is output without conversion.

However, during the screen saver operation,
All the switches of the switch circuit of (Fig. 2) are on the screen saver operation side 22, and the data line signal is a
(0) → b (0), a (2) → b (1), a (4) → b (2), a (6)
→ b (3), 0 → b (4), 0 → b (5), 0 → b (6), 0
→ Converted to b (7) and output from the bit data conversion circuit 11.

Further, the bit data conversion method in the bit data conversion circuit 11 is such that the n-bit even-numbered bit value is sampled, the sampled data value is stored in order from the lower bit, and all the remaining upper bits are stored. A method of converting the display data according to the law of setting to zero may be used, and simply n transmitted to the bit data conversion circuit 11 may be used.
Lower / upper n / of the bit data line signal 10
A method may be used in which a 2-bit bit value is sampled, the sampled data values are stored in order from the lower bit, and the display data is converted according to the rule that the remaining upper bits are all zero.

(Embodiment 2) (FIG. 3) is a block diagram showing an embodiment of the second invention of the present application. Reference numeral 1 is a display data control circuit included in a computer or the like, 2 is a display data memory circuit for display data displayed on a liquid crystal display device, 31 is a bit conversion law control signal for controlling a bit conversion method by software, and 11 is a bit conversion law. A bit data conversion circuit that performs bit conversion according to the control signal 31, 32 is a converted display data memory circuit that stores data obtained by converting display data displayed on the liquid crystal display device, and 33 is the display data memory circuit 2.
Alternatively, a display data selection circuit for selecting either display data of the converted display data memory circuit 32, a display data control circuit for controlling display data, a data line driving circuit for a liquid crystal display device, a reference numeral 5 for a liquid crystal display device, The address line drive circuit 6 is a liquid crystal display panel.

The n-bit display signal output from the display data control circuit 1 is sent to the display data memory circuit 2 and stored in the display data memory circuit 2.

Here, when the liquid crystal display device in the normal operation is used for display purposes, the display data selection circuit 33 is used.
Selects the display data stored in the display data memory circuit 2, the display data control circuit 3 converts the display data structure into a required data structure, and the display data control circuit 3 converts the display data structure into a required data structure. Then, the image is displayed on the liquid crystal display panel 6 by the data line driving circuit 4 and the address line driving circuit 5.

The display data stored in the display data memory circuit 2 is bit-converted by the bit data conversion circuit 11 controlled by the bit conversion law control signal 31 and stored in the converted display data memory circuit 32 at any time. To be done.

However, during the screen saver operation,
In response to the screen saver control signal 18, the display data selection circuit 33 selects the display data stored in the converted display data memory circuit 32, and the display data control circuit 3 converts the display data structure into the required data structure, and the data line It is sent to the drive circuit 4, and the data line drive circuit 4 and the address line drive circuit 5 display an image at the time of screen saver operation on the liquid crystal display panel 6.

In the bit data conversion circuit 11 described above,
By the bit conversion law control signal 31 that can be controlled by software from the computer, the display screen at the time of screen saver operation is created from the display data stored in the display data memory circuit 2 using only the lower bits of the n-bit display data. be able to.

Therefore, the display screen during the screen saver operation can be controlled by software, and the degree of freedom of the display screen during the screen saver operation, which cannot be realized in the first embodiment, is widened and the preference of the computer user is limited. However, the reflected screen saver display screen can be displayed.

When the display data subjected to such a conversion is displayed on the liquid crystal display device, the display data is composed of only the lower bits as in the case of the first embodiment. Therefore, this display data is displayed on the liquid crystal panel. When converted into an applied voltage value, the applied voltage value is averaged and the voltage value is suppressed low.

The bit data conversion method in the bit data conversion circuit 11 is similar to that of the first embodiment, in which n-bit odd-numbered or even-numbered bit values are sampled and the sampled data value is converted into the lower-order bits. Alternatively, the display data may be converted in accordance with the rule that all the upper bits are stored again in order, and the remaining upper bits are all zero. A method may be used in which the upper n / 2 bits are sampled, the sampled data values are stored again in order from the lower bits, and the display data is converted according to the rule that all the remaining upper bits are zero. ..

Furthermore, when the data line drive circuit 4 is an analog input drive circuit, the display data selection circuit 33 is provided.
The display data selected by is converted into a data structure required by the display data control circuit 3, converted into an analog value by the D / A converter, sent to the data line drive circuit 4, and displayed on the liquid crystal display panel 6. It

[0034]

As described above, according to the present invention, when the screen saver for preventing burn-in of the display screen of the liquid crystal display device is in operation, the liquid crystal is driven at a voltage lower than the voltage for driving the liquid crystal panel or an averaged voltage. The display device can be driven. Therefore, when the liquid crystal display device is not used for display purposes, the deterioration of the life of the liquid crystal display device can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a first embodiment of the present invention.

FIG. 2 is a bit data conversion circuit diagram in the first embodiment.

FIG. 3 is a circuit block diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 display data control circuit 2 display data memory circuit 3 display data control circuit 4 data line drive circuit 5 address line drive circuit 6 liquid crystal display panel 7 latch circuit 8 n-bit display data 9 line latch circuit 10 n-bit data line signal 11-bit data Conversion circuit 12 Level shift circuit 13 D / A converter 14 Data line signal 15 Output circuit 16 Data line 21 Normal operation side 22 Screen saver operation side 31 Bit conversion law control signal 32 Conversion data memory circuit 33 Display data selection circuit

Claims (2)

[Claims] 1. A matrix type liquid crystal display panel driven by a plurality of data lines and address lines intersecting each other, a data line driving circuit and an address line driving circuit provided at the ends of the data lines and the address lines, respectively. A circuit, a display data memory that stores the display content in bit units, a circuit that transfers the display data to the data line drive circuit, and the display data is converted in the data line drive circuit based on a predetermined law by controlling an external signal. A liquid crystal display device comprising: 2. A matrix type liquid crystal display panel driven by a plurality of data lines and address lines intersecting each other, a data line drive circuit and an address line drive provided at ends of the data lines and the address lines, respectively. A circuit, a display data memory for storing display contents in bit number units, a circuit for converting display data of the display data memory based on a predetermined law, a display data memory for storing the converted display data, and A control circuit that selects one of the display data memory,
A liquid crystal display device comprising: a circuit that transfers selected display data to a data line driving circuit.