Electro-optical device system and method of driving an electro-optical device

• US 5,534,884 A
• Filed: 03/11/1994
• Issued: 07/09/1996
• Est. Priority Date: 12/27/1990
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Mase, Akira, Yamazaki, Shunpei
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Luu, Matthew
• Application Number:
  US08/208,802
• Time in Patent Office: 851 Days
• Field of Search: 345/87, 345/92, 345/98, 345/205, 345/206, 359/59
• US Class Current: 345/87
• CPC Class Codes: G02F 1/136245 having complementary transistors
• CPC Class Codes: G09G 2300/0823 used to establish symmetry in driving, e.g. with polarity inversion
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes

Abstract

An electro-optical device system and a method of driving a liquid crystal display panel thereof capable of constructing clear visual images with low power consumption are described. In the display panel, a plurality of conductive pads are opposed to a back electrode with a liquid crystal layer inbetween. Control signals are supplied to the conductive pads through complementary transistors comprising a p-channel field effect transistor and an n-channel field effect transistor connected between V_DD and V_SS lines of a control circuit. The information being displayed is simultaneously stored in a first memory. Information desired to be displayed is stored in a second memory and compared with the content of the first memory to produce exclusive ORs thereof. The display panel is driven only when and where the information desired to be displayed is dissimilar to the information being displayed.

Claims

1. An electro-optical device system comprising:

a liquid crystal panel comprising a pair of substrates at least one of which is transparent, a liquid crystal layer disposed between said substrates, a plurality of electrodes formed on an inside of one of said substrates in order to define pixels arranged in a matrix, a plurality of pairs of complementary transistors provided for said pixels and connected with said electrodes respectively and a plurality of control lines formed on said inside of one of said substrates and connected with said complementary transistors in order to supply signals to said transistors;

a first memory having storage elements related to said pixels respectively in a one-to-one correspondence for storing a frame of the same information as said panel is displaying;

a second memory for sequentially receiving information desired to be displayed in said panel, said second memory having storage elements for storing a frame related to said pixels respectively in a one-to-one correspondence;

computer means for providing to said second memory said information desired to be displayed in said panel;

a comparator for comparing the contents of said first memory and said second memory; and

a controller operatively connected with said first and second memories and said liquid crystal panel for driving the said storage elements of said first memory and the said pixels of said liquid crystal panel which are dissimilar to the corresponding storage elements of said second memory in order to display said information desired to be displayed in said panel and to make information stored in said first memory equal to information being displayed in said panel.

2. The system of claim 1 wherein said control lines comprises a plurality of column control lines extending in the column direction of said matrix and a plurality of row control lines extending in the row direction of said matrix.

3. The system of claim 1 wherein said first and second memories comprise static random access memories.

4. The system of claim 2 wherein said controller drives said liquid crystal panel through a column driver for supplying signals to said column control lines and a row driver for supplying signals to said row control lines.

5. The system of claim 1 wherein said first and second memories are provided with readers respectively through which information contained in said memories is transmitted to said comparator.

6. The system of claim 1 wherein said comparator produces exclusive ORs of corresponding storage elements of said first and second memories.

7. The system of claim 1 wherein said liquid crystal layer comprises a ferroelectric liquid crystal.

8. An electro-optical device system comprising:

a liquid crystal panel comprising a pair of substrates at least one of which is transparent, a liquid crystal layer disposed between said substrates, and a plurality of pixels each of which is provided with a p-channel transistor, an n-channel transistor, and an electrode on an inside of one of said substrates with said electrode connected to one of source and drain terminals of said p-channel transistor and one of source and drain terminals of said n-channel transistor;

a plurality of column control lines provided on said inside of one of said substrates;

a plurality of pairs of row control lines provided on said inside of one of said substrates;

a first memory comprising storage elements for storing a current display frame of pixels;

a second memory comprising storage elements for receiving information to be displayed in said panel and for storing a next display frame of pixels;

computer means for providing to said second memory said information to be displayed in said panel;

a comparator for comparing a content stored in each of said storage elements of said second memory with a content stored in corresponding one of said storage elements of said first memory;

a controller, which is connected to the other one of the source and drain terminals of said p-channel transistor and the other one of the source and drain terminals of said n-channel transistor through corresponding pair of said row control lines and is connected to gate terminals of the p-channel transistor and the n-channel transistor of each of said pixels through corresponding one of said column control lines, for driving the pixels corresponding to the storage elements of said first memory which are dissimilar to the corresponding storage elements of said second memory in the comparison by supplying an electric signal to the transistors through said column control lines and said row control lines from said controller in order to display said information in said panel.

9. The system of claim 8 wherein said comparator produces exclusive ORs of corresponding storage elements of said first and second memories.

10. The system of claim 8 wherein said information is given to the transistors through the column control lines and the transistors are selectively made active by supplying control signals through the row control lines.

11. The system of claim 8 wherein said first and second memories comprise static random access memories.

12. The system of claim 8 wherein said liquid crystal layer comprises a ferroelectric liquid crystal.

13. A method of driving an electro-optical device comprising a pair of substrates at least one of which is transparent, a liquid crystal layer disposed between said substrates, a plurality of electrodes formed on an inside of one of said substrates in order to define pixels arranged in a matrix, a plurality of pairs of complementary transistors provided for said pixels and connected with said electrodes respectively and a plurality of control lines formed on said inside of one of said substrates and connected with said complementary transistors in order to supply signals to said transistors for driving, said method comprising:

storing, in a first memory, a frame of first information equal to that being displayed in said electro-optical device;

storing, in a second memory, a frame of second information desired to be displayed;

providing to said second memory from a computing means said second information desired to be displayed;

comparing the information stored in said first memory and the information stored in said second memory;

displaying said second information in said electro-optical device by driving the pixels corresponding to storage elements of said second memory which are dissimilar to corresponding elements of said first memory on the basis of the result of said comparing step; and

rewriting said corresponding elements of said first memory in order to make equal information stored in said first memory and information being displayed in said electro-optical device.

14. The method of claim 13 wherein a content stored in each of storage elements of said first and second memories during said storing steps is expressed by a logical variable and the pixels corresponding to storage elements of said second memory which disagree with corresponding storage elements of said first memory about logical variables thereof are driven in said displaying step.

15. The method of claim 14 wherein the disagreement is determined by said comparing step.

16. The method of claim 13 wherein exclusive ORs of corresponding storage elements of said first and second memories are produced in said comparing step in order to indicate agreement and disagreement of respective corresponding elements of said first and second memories.

17. The method of claim 13 wherein said second information is given to said complementary transistors through first control lines extending in one of column and row directions of said matrix and said complementary transistors are selectively made active by supplying control signals through second control lines extending in the other of the column and row directions of said matrix.

18. The method of claim 17 wherein said one direction is the column direction and said the other direction is the row direction.

19. The method of claim 13 wherein said information stored in said second memory is displayed next to said information stored in said first memory.

20. The method of claim 13 wherein said first and second memories comprise static random access memories.

21. The method of claim 13 wherein said liquid crystal layer comprises a ferroelectric liquid crystal.

22. A method of driving an electro-optical device comprising a pair of substrates at least one of which is transparent, a liquid crystal layer disposed between said substrates, a plurality of electrodes provided on an inside of one of said substrates in order to define pixels arranged in a matrix, a plurality of complementary transistors comprising p-channel transistors and n-channel transistors provided on said inside of one of said substrates with source terminals or drain terminals of said p-channel transistors and said n-channel transistors connected to said electrodes, a plurality of column control lines provided on said inside of one of said substrates and connected to gate terminals of the complementary transistors of corresponding columns, and a plurality of row control lines provided on said inside of one of said substrates and connected to source terminals or drain terminals, which are not connected to said electrodes, of the p-channel transistors and the n-channel transistors of corresponding rows, said method comprising:

storing, in a first memory, a frame of first information equal to that being displayed in said electro-optical device;

storing, in a second memory, a frame of second information desired to be displayed;

providing to said second memory from a computing means said second information desired to be displayed;

comparing the information stored in said first memory and the information stored in said second memory;

displaying said second information in said electro-optical device by driving the pixels corresponding to storage elements of said second memory which are dissimilar to corresponding elements of said first memory on the basis of the result of said comparing step, said second information being supplied to the pixels through the column control lines and the row control lines; and

rewriting said corresponding elements of said first memory in order to make equal information stored in said first memory and information being displayed in said electro-optical device.

23. The method of claim 22 wherein a content stored in each of storage elements of said first and second memories during said storing steps is expressed by a logical variable and the pixels corresponding to storage elements of said second memory which disagree with corresponding storage elements of said first memory about logical variables thereof are driven in said displaying step.

24. The method of claim 23 wherein the disagreement is determined by said comparing step.

25. The method of claim 22 wherein exclusive ORs of corresponding storage elements of said first and second memories are produced in said comparing step in order to indicate agreement and disagreement of respective corresponding elements of said first and second memories.

26. The method of claim 22 wherein said second information is given to said complementary transistors only through the column control lines and said complementary transistors are selectively made active by supplying control signals through the row control lines.

27. The method of claim 22 wherein said information stored in said second memory is displayed next to said information stored in said first memory.

28. The method of claim 22 wherein one of said electrodes is connected to one of source and drain terminals of one of said p-channel transistors and to one of source and drain terminals of one of said n-channel transistors.

29. The method of claim 28 wherein gate terminals of said one of said p-channel transistors and said one of said n-channel transistors are connected to each other and to one of said column lines.

30. The method of claim 29 wherein source terminals of said one of said p-channel transistors and said one of said n-channel transistors are connected to each other and drain terminals of said one of said p-channel transistors and said one of said n-channel transistors are connected to said row control lines.

31. The method of claim 30 wherein one of said row control lines is connected to the other one of the source and drain terminals of said one of said p-channel transistors.

32. The method of claim 29 wherein the other one of the source and drain terminals of said one of said p-channel transistors is connected to one of said row control lines and the other one of the source and drain terminals of said one of said n-channel transistors is connected to another one of said row control lines.

33. The method of claim 22 wherein said first and second memories comprise static random access memories.

34. The method of claim 22 wherein said liquid crystal layer comprises a ferroelectric liquid crystal.

35. An electro-optical device system comprising:

a liquid crystal device having a plurality of pixels;

a first memory for storing a current display frame of pixels;

a second memory for storing a next display frame of pixels;

computer means for providing to said second memory each pixel of said next display frame;

a comparator for comparing said first and second memories; and

a controller for rewriting only those pixels of said liquid crystal device for which contents of said first and second memories differ and for changing only those pixels of the first memory which correspond to the rewritten pixels of the liquid crystal device.

36. The system of claim 35 wherein said liquid crystal device comprises a ferroelectric liquid crystal.

37. The system of claim 35 wherein said liquid crystal device is an active matrix type device.