Liquid crystal display apparatus

• US 5,404,150 A
• Filed: 10/21/1993
• Issued: 04/04/1995
• Est. Priority Date: 09/03/1990
• Status: Expired due to Term

• Current Assignee: Sharp Electronics Corporation (Hon Hai Precision Industry Co., Ltd.), Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Murata, Tetsuo
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): GOON, GIN F
• Application Number:
  US08/139,063
• Time in Patent Office: 530 Days
• Field of Search: 345/87, 345/89, 345/94, 345/95, 345/96, 345/98, 345/208, 345/209, 345/210, 345/211, 348/790, 348/791, 348/792, 348/793, 340/784, 340/805, 358/236, 358/241
• US Class Current: 345/95
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3692 suitable for passive matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

In order to improve the contrast of a liquid crystal display device by the voltage equalization method, scanning side electrodes totaling D in number are scanned in line sequential fashion while applying a voltage between each selected scanning side electrode and each signal side electrode, the voltage applied being controlled in such a way that, during a total of D times of scanning of the scanning side electrodes for production of one frame, when a particular scanning side electrode and a particular signal side electrode are simultaneously in a select state, a voltage Vop is applied to the corresponding liquid crystal, and when the scanning side electrodes respectively are in a non-select state, which occurs the remaining (D-1) times for each of the scanning side electrodes, a voltage whose polarity is reversed in response to the select and non-select states of the signal side electrodes and whose absolute value is represented by |Vop/B|, where B is the bias ratio, is applied to the corresponding liquid crystal. The bias ratio B can be varied to adjust the contrast of the liquid crystal display device, and it is possible to improve the contrast by increasing the bias ratio.

Claims

1. A liquid crystal display apparatus in which:

scanning side electrodes totaling D in number are scanned in line sequential fashion while applying a voltage between each selected scanning side electrode and each signal side electrode,

the voltage applied being controlled in such a way that, during a total of D times of scanning of the scanning side electrodes for production of one frame,

when a particular scanning side electrode and a particular signal side electrode are simultaneously in a select state, a voltage Vop is applied to the corresponding liquid crystal, and

when the scanning side electrodes respectively are in a non-select state, which occurs the remaining (D-1) times for each of the scanning side electrodes, a voltage whose polarity is reversed corresponding to the select and non-select states of the signal side electrodes and whose absolute value is represented by |Vop/B|, where B is the bias ratio, is applied to the corresponding liquid crystal,

the bias ratio B being varied to adjust the contrast of the liquid crystal display in response to viewer input, the viewer input adjusting an adjustable resistor Ry of a voltage division circuit;

the voltage division circuit including a resistor chain constructed with an even n number of first resistors R connected in series and having an identical resistance value, the adjustable resistor Ry being symmetrically connected in series with the first resistors R at the center of the resistor chain for dividing an output Vop of the DC power supply.

2. A liquid crystal display apparatus comprising:

a liquid crystal display device in which liquid crystal is sandwiched between a plurality of scanning side electrodes totaling D in number and a plurality of signal side electrodes disposed intersecting the scanning side electrodes at right angles;

a DC power supply;

a voltage dividing circuit, the voltage dividing circuit including a resistor chain constructed with an even number n of first resistors R connected in series and having an identical resistance value, the voltage dividing circuit also including a second resistor Ry symmetrically connected in series with the first resistors R at the center of the resistor chain, for dividing an output Vop of the DC power supply, the second resistor Ry being continuously variable during operation to change a basis ratio B and thereby adjust a contrast of the liquid crystal display;

image data generating means for generating image data to be displayed on the liquid crystal display device; and

driving means responsively connected to the image data generating means for supplying divided voltages from the dividing circuit to the scanning side electrodes and signal side electrodes, the driving of the liquid crystal being controlled in such a way that, out of D times of scanning of the scanning side electrodes for one frame,

(1) a voltage is applied to the liquid crystal once per frame when the associated scanning side electrode is in a select state, the voltage being

(a) +Vop or -Vop when the pattern to be displayed is ON, and

(b) +(1-2/B)Vop or -(1-2/B)Vop when the pattern to be displayed is OFF, and

(2) when the scanning side electrode is in a non-select state, a voltage Vop/B or -Vop/B, the polarity being reversed alternately from one frame to another, is applied to the liquid crystal (D-1) times per frame regardless of the display pattern, where B=(n·

R+Ry)/R.

3. A liquid crystal display apparatus as set forth in claim 2, wherein the second resistor Ry is a variable resistor.

4. A liquid crystal display apparatus as set forth in claim 3, wherein Ry is variable in response to viewer input to adjust the contrast of the liquid crystal display.

5. A liquid crystal display apparatus comprising:

a liquid crystal display device in which liquid crystal is sandwiched between a plurality of scanning side electrodes and a plurality of signal side electrodes disposed intersecting the scanning side electrodes;

a DC power supply;

a voltage division circuit for dividing an output Vop of the DC power supply, the voltage division circuit having a bias ratio B associated therewith, wherein the voltage division circuit includes a resistor chain constructed with an even number n of first resistors R connected in series and having an identical resistance value, the voltage dividing circuit also including a second resistor Ry symmetrically connected in series with the first resistors R at the center of the resistor chain, for dividing an output VOP of the DC power supply, the second resistor Ry being continuously variable during operation to change a basis ratio B and thereby adjust a contrast of the liquid crystal display;

image data generating means for generating image data to be displayed on the liquid crystal display device; and

driving means responsively connected to the image data generating means for supplying divided voltages from the division circuit to the scanning side electrodes and signal side electrodes, the driving of the liquids crystal being controlled whereby;

(1) voltages are applied to the scanning side electrode and the signal side electrode for a first frame as follows;

(a) a voltage VOP is applied to the scanning side electrode and 0 voltage is applied to the signal side electrode when the liquid crystal is in a select state;

(b) a voltage is applied to the scanning side electrode and a voltage 2Vop/B is applied to the signal side electrode when the liquid crystal is in an OFF state; and

(2) voltages are applied to the scanning side electrode and the signal side electrode for a subsequent frame as follows;

(a) 0 voltage is applied to the scanning side electrode and a voltage Vop is applied to the signal side electrode when the liquid crystal is

in a select state;

(b) 0 voltage is applied to the scanning side electrode and a voltage (1-2/B)Vop is applied to the signal side electrode when the liquid crystal is in an OFF state.

6. A liquid crystal display apparatus as set forth in claim 5, wherein for the first frame

a voltage Vop/B is applied to the scanning side electrode and a voltage selected from a set consisting of 0 and 2Vop/B is applied to the signal side electrode when the scanning side electrode is in a non-select state;

and for the subsequent frame a voltage (1-1/B)Vop is applied to the scanning side electrode and a voltage selected from a set consisting of Vop and (1-2/B)Vop is applied to the signal side electrode when the scanning side electrode is in a non-select state.

7. A liquid crystal display apparatus as set forth in claim 5, wherein B=(n·

R+Ry)/R.

8. A liquid crystal display apparatus as set forth in claim 5, wherein the bias ratio B is variable in response to viewer input to adjust the contrast of the liquid crystal display.

9. A liquid crystal display apparatus comprising:

a liquid crystal display device in which liquid crystal is sandwiched between a plurality of scanning side electrodes and a plurality of signal side electrodes disposed intersecting the scanning side electrodes;

a DC power supply;

a voltage division circuit for dividing an output Vop of the DC power supply, the voltage division circuit having a bias ratio B associated therewith, wherein the voltage division circuit includes a resistor chain constructed with an even number n of first resistors R connected in series and having an identical resistance value, the voltage dividing circuit also including a second resistor Ry symmetrically connected in series with the first resistors R at the center of the resistor chain, for dividing an output Vop of the DC power supply, the second resistor Ry being continuously variable during operation to change the basis ratio B and thereby adjust a contrast of the liquid crystal display;

image data generating means for generating image data to be displayed on the liquid crystal display device; and

driving means responsively connected to the image data generating means for supplying divided voltages from the dividing circuit to the scanning side electrodes and signal side electrodes, the driving of the liquid crystal being controlled whereby;

(1) voltages are applied to the scanning side electrode and the signal side electrode for a first frame as follows;

(a) a voltage Vop is applied to the scanning side electrode and 0 voltage is applied to the signal side electrode when the liquid crystal is in a select state;

(b) a voltage Vop is applied to the scanning side electrode and a voltage 2Vop/B is applied to the signal side electrode when the liquid crystal is in an OFF state;

(c) a voltage Vop/B is applied to the scanning side electrode and a voltage selected from a set consisting of 0 and 2Vop/B is applied to the signal side electrode when the scanning side electrode is in a non-select state; and

(2) voltages are applied to the scanning side electrode and the signal side electrode for a subsequent frame as follows;

(a) 0 voltage is applied to the scanning side electrode and a voltage Vop is applied to the signal side electrode when the liquid crystal is in a select state;

(b) 0 voltage is applied to the scanning side electrode and a voltage (1-2/B)Vop is applied to the signal side electrode when the liquid crystal is in an OFF state;

(c) a voltage (1-1/B)Vop is applied to the scanning side electrode and a voltage selected from a set consisting of Vop and (1-2/B)Vop is applied to the signal side electrode when the scanning side electrode is in a non-select state.

10. A liquid crystal display apparatus as set forth in claim 9, wherein the bias ratio B is variable in response to viewer input to adjust the contrast of the liquid crystal display.