Method for driving a display device

• US 4,929,058 A
• Filed: 08/30/1988
• Issued: 05/29/1990
• Est. Priority Date: 08/31/1987
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Numao, Takaji
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/238,257
• Time in Patent Office: 637 Days
• Field of Search: 350/333, 350/33 R, 350/350 S, 350/334, 340/784, 340/805
• US Class Current: 345/89
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

A driving method for a display device is disclosed. The display device includes column electrodes and row electrodes, both laid in a matrix of columns and rows, and a display picture element disposed at each intersection between the column and row electrodes and adapted to be selectively set in one of bright an dark memory states. The driving method includes the steps of dividing the column electrodes into K groups of column electrodes; defining the number Z of column electrode lines constituting each group of the column electrodes rendering one frame period; selecting a predetermined one of the K groups of the column electrodes for a time width ZT₀ of each of the blocks so that each picture element in the selected one of the groups of the column electrodes can be set in one of the bright and dark memory states; and selecting a number of times, not smaller than n, the K groups of the column electrodes, during each one-frame period T_F, will operate according to a predetermined sequence.

Claims

1. A method for driving a liquid crystal display device comprised of a matrix of columns and row electrodes intersecting with each other, and forming a display picture element at each point of intersection between said column and row electrodes, each said display picture element adapted to be selectively set in one of bright and dark memory states so as to achieve a desired multi-gradation display, the driving method comprising the steps of:

(1) dividing, to achieve a multi-gradation display of 2ⁿ levels (n being an integer not smaller than

     3), the row electrodes into K groups of row electrodes wherein K is an integer not smaller than 2 and has the following relationship, ##EQU12## (2) defining the number Z of row electrode lines in each group of the row electrodes, wherein y represents the total number of row electrodes and Z is a positive integer and has the following relationship, ##EQU13## (3) defining one frame period T_F, composed of (2ⁿ -1) time blocks, to have the following relationship, ##EQU14## wherein T₀ represents the selection time during which the picture elements on each of the row electrodes are selectively set in one of the bright and dark memory states;

(4) sequentially selecting each one of said K groups of the row electrodes, during a time width ZT₀ defining each of the time blocks, such that each picture element in the selected one of the groups of the row electrodes can be set in one of the bright and dark memory states according to a predetermined selection signal; and

(5) selecting a number of time blocks, not smaller than n, that the K groups of the row electrodes, during each one-frame period T_F, will reset each picture element according to said predetermined signal wherein each predetermined selection signal for each of said K groups, is determined such that each of said K groups will operate so as to reset picture elements during different of said time blocks, said selected number of time blocks being equal for each of said K groups, thereby allowing for an efficient multi-gradation display device.

2. A method for driving a matrix type liquid crystal display device comprising intersecting column and row electrodes, wherein picture elements are formed at each column and row intersection, so as to achieve a selective multi-level gradation display capability at each of said picture elements, said driving method comprising the steps of:

(a) selecting a desired gradation level;

(b) sequentially applying voltage to each of said column electrodes in response to an input data signal;

(c) dividing said row electrodes into groups, the number of row electrodes in each group and the number of groups being dependent upon said desired gradation level;

(d) defining a frame time period over which voltage will be applied, at selected times, to each row electrode group to achieve said desired gradation levels;

(e) dividing said frame time period into a number of equal time blocks, said number of equal time blocks being dependent upon said desired gradation level;

(f) selecting certain of said time blocks, the number of said time blocks being dependent upon said desired gradation level, during which voltage will be applied to a first group of row electrodes;

(g) selecting different ones of said time blocks, equal in number to said time blocks selected in step (f), during which voltage will be applied to a next group of row electrodes;

(h) repeating step (g) for each of said groups of row electrodes;

(i) sequentially selecting each of said row electrodes in each group, during sequential frame time periods, and applying voltage to said row electrodes during each previously selected time blocks during sequential frame time periods to thereby achieve a selectable multi-level gradation display at each of said pixel elements.

3. A method, as claimed in claim 2, wherein said selected desired gradation level is selectable from a multiple of two.

4. A method for efficiently driving a matrix type liquid crystal display device comprising intersecting column and row electrodes, wherein picture elements set in an initial bright or dark memory state are formed at each column and row intersection and are selectively reset to one of a bright or dark memory state, for a certain time period, to thereby achieve a selectable multi-level gradation display device,

(a) selecting a desired gradation level;

(b) dividing said row electrodes into K groups dependent upon the desired gradation level selected;

(c) defining a number Z of row electrodes in each of said K groups by dividing the total number of electrodes Y by said number of K groups;

(d) defining a frame time period during multiples of which said selectable multi-level gradation display will be achieved;

(e) dividing said frame time period into time blocks, said number of blocks being dependent upon said gradation level;

(f) preselecting a number of different time blocks for each of said K groups, during which voltage will be supplied to each of said K groups, said number of time blocks being equal for each of said K groups;

(g) selectively applying voltage, through each of said K groups to thereby reset the memory state to a different memory state than had previously been set for each picture element corresponding to each of said K groups during said preselected time blocks of multiple frame time periods to thereby achieve an efficient, selectable, multi-gradation display device.

5. A method, as claimed in claim 4, wherein said selectable desired gradation level is selectable from a multiple of two.

6. A method, as claimed in claim 4, wherein said step (g) is repeated to continually maintain said selected desired gradation level, for each ensuing frame time period, the total frame time periods being equal in number to aid Z row electrodes in each K group.