Electro-optical device and method of driving the same

• US 6,975,296 B1
• Filed: 03/31/2000
• Issued: 12/13/2005
• Est. Priority Date: 06/14/1991
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hiroki, Masaaki, Mase, Akira, Yamazaki, Shunpei
• Primary Examiner(s): CHANG, KENT WU
• Application Number:
  US09/540,896
• Time in Patent Office: 2,083 Days
• Field of Search: 345/87, 345/92, 345/94, 345/99, 345/100, 345/691, 345/692, 345/693, 257/61, 257/59, 257/72, 349/43
• US Class Current: 345/89
• CPC Class Codes: G02F 1/136227 Through-hole connection of the pixel electrode to the active element through an insulation layer
• CPC Class Codes: G09G 2300/0823 used to establish symmetry in driving, e.g. with polarity inversion
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2330/04 Display protection
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3685 Details of drivers for data electrodes
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence

Abstract

The method of fine gradation display by an electro-optical device with little influence by difference in elemental devices, is disclosed, which is an object of the present invention. In case of an active matrix electro-optical device, a visual gradation display can be carried out by digitizing an analog image signal externally supplied by means of binary notation, by temporarily storing the digital signal thus obtained, by outputting the digital signal to a circuit of next step in a proper order, and by controlling the output timing of the signal so as to output the signal to the active matrix electro-optical device, and whereby digitally controlling the time for applying voltage to a picture element.

Claims

1. A method for driving an electro-optical device having a plurality of pixels, each of which includes a signal line and at least one switching element, said method comprising the step of:

applying pulses to said signal line at intervals during one frame, wherein said intervals are T₁ between the i-th pulse and the (i+1)-th pulse, 2^/T₁ between the (i+1)-th pulse and the (i+2)-th pulse, and 2T₁ between the (i+2)-th pulse and the (i+3)-th pulse, where / is a natural number and T₁ is a constant period,

wherein said switching element comprises;

a crystalline semiconductor film comprising silicon over a substrate having an insulating surface, and

at least one gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween.

2. A method according to claim 1, wherein said electro-optical device is a liquid crystal display device.

3. A method according to claim 2, wherein said liquid crystal display device comprises a liquid crystal material selected from the group consisting of twisted nematic liquid crystal, super twisted nematic, ferroelectric liquid crystal, antiferroelectric liquid crystal, dispersion liquid crystal, and polymer liquid crystal.

4. A method according to claim 1, wherein said switching element is a thin film transistor.

5. A method according to claim 4, wherein said thin film transistor is an n-channel type thin film transistor or a p-channel type thin film transistor.

6. A method for driving an electro-optical device having a plurality of pixels, each of which includes a signal line and at least one switching element, said method comprising the step of:

applying pulses to said signal line at intervals during one frame,

wherein the intervals are T₁ between the i-th pulse and the (i+1)-th pulse, 2^/T₁ between the (i+1)-th pulse and the (i+2)-th pulse, and 2T₁ between the (i+2)-th pulse and the (i+3)-th pulse, where i is a natural number and T₁ is a constant period,

wherein said switching element comprises;

a crystalline semiconductor film comprising silicon over a substrate having an insulating surface, and

at least one gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween.

7. A method according to claim 6, wherein said electro-optical device is a liquid crystal display device.

8. A method according to claim 7, wherein said liquid crystal display device comprises a liquid crystal material selected from the group consisting of twisted nematic liquid crystal, super twisted nematic, ferroelectric liquid crystal, antiferroelectric liquid crystal, dispersion liquid crystal, and polymer liquid crystal.

9. A method according to claim 6, wherein said switching element is a thin film transistor.

10. A method according to claim 9, wherein said thin film transistor is an n-channel type thin film transistor or a p-channel type thin film transistor.

11. A method according to claim 6, wherein said T₁ is less than 100 μ

sec.

12. A method for driving an electro-optical device having a plurality of pixels, each of which includes a signal line and at least one switching element, said method comprising the step of:

applying pulses to said signal line at intervals during one frame,

wherein the intervals are T₁ between the i-th pulse and the (i+1)-th pulse, 2^/T₁ between the (i+1)-th pulse and the (i+2)-th pulse, 2T₁ between the (i+2)-th pulse and the (i+3)-th pulse, and 2<sup>i−

1</sup>T₁ between the (i+3)-th pulse and the (i+4)-th pulse where / is a natural number and T₁ is a constant period,

wherein said switching element comprises;

a crystalline semiconductor film comprising silicon over a substrate having an insulating surface, and

at least one gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween.

13. A method according to claim 12, wherein said electro-optical device is a liquid crystal display device.

14. A method according to claim 13, wherein said liquid crystal display device comprises a liquid crystal material selected from the group consisting of twisted nematic liquid crystal, super twisted nematic, ferroelectric liquid crystal, antiferroelectric liquid crystal, dispersion liquid crystal, and polymer liquid crystal.

15. A method according to claim 12, wherein said switching element is a thin film transistor.

16. A method according to claim 15, wherein said thin film transistor is an n-channel type thin film transistor or a p-channel type thin film transistor.

17. A method according to claim 12, wherein said T₁ is less than 100 μ

sec.

18. A method for driving a television having a display unit and a tuner for receiving television radio wave, said method comprising the step of:

applying pulses to said signal line at intervals during one frame, wherein said intervals are T₁ between the i-th pulse and the (i+1)-th pulse, 2^/T₁ between the (i+1)-th pulse and the (i+2)-th pulse, and 2T₁ between the (i+2)-th pulse and the (i+3)-th pulse, where / is a natural number and T₁ is a constant period,

wherein said display unit includes a plurality of pixels, and

wherein each of said pixels includes a signal line and at least one switching element.

19. A method according to claim 18, wherein display unit is a liquid crystal display device.

20. A method according to claim 19, wherein said liquid crystal display device comprises a liquid crystal material selected from the group consisting of twisted nematic liquid crystal, super twisted nematic, ferroelectric liquid crystal, antiferroelectric liquid crystal, dispersion, liquid crystal, and polymer liquid crystal.

21. A method according to claim 18, wherein said switching element is a thin film transistor.

22. A method according to claim 21, wherein said thin film transistor is an n-channel type thin film transistor or a p-channel type thin film transistor.

23. A method for driving a television having a display unit and a tuner for receiving television radio wave, said method comprising the step of:

applying pulses to said signal line at intervals during one frame,

wherein the intervals are T₁ between the i-th pulse and the (i+1)-th pulse, 2^/T₁ between the (i+1)-th pulse and the (i+2)-th pulse, 2T₁ between the (i+2)-th pulse and the (i+3)-th pulse, and 2<sup>/−

1</sup>T₁ between the (i+3)-th pulse and the (i+4)-th pulse where / is a natural number and T₁ is a constant period,

wherein said display unit includes a plurality of pixels, and

wherein each of said pixels includes a signal line and at least one switching element.

24. A method according to claim 23, wherein display unit is a liquid crystal display device.

25. A method according to claim 24, wherein said liquid crystal display device comprises a liquid crystal material selected from the group consisting of twisted nematic liquid crystal, super twisted nematic, ferroelectric liquid crystal, antiferroelectric liquid crystal, dispersion liquid crystal, and polymer liquid crystal.

26. A method according to claim 23, wherein said switching element is a thin film transistor.

27. A method according to claim 26, wherein said thin film transistor is an n-channel type thin film transistor or a p-channel type thin film transistor.