Method of driving an electro-optical device

• US 5,424,752 A
• Filed: 12/03/1993
• Issued: 06/13/1995
• Est. Priority Date: 12/10/1990
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hiroki, Masaaki, Mase, Akira, Takemura, Yasuhiko, Yamazaki, Shunpei
• Primary Examiner(s): Brier, Jeffery A.
• Application Number:
  US08/161,094
• Time in Patent Office: 557 Days
• Field of Search: 340/784, 340/793, 340/805, 340/767, 358/236, 358/240, 358/241, 345/90, 345/93, 345/92
• US Class Current: 345/92
• 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 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• 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
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A method of fine intermediate gradation display by an electro-optical device, with little difference in devices is disclosed. In case of driving each picture element of an active matrix electro-optical device, a visual intermediate gradation display can be carried out by using a modified transfer gate complementary field effect device, in a structure where one of input/output terminal thereof is connected with a picture element electrode, by applying a bipolar pulse to its control electrode in a cycle and by applying voltage to the other input/output terminal, or by cutting voltage at the same time, and whereby digitally controlling duration of voltage applied to the picture element.

Claims

1. A method of driving an electro-optical device constructed with a pixel electrode;

a data signal line;

an n-channel transistor having a source, drain, and gate, and connected to said data line at one of said source and drain thereof and to said pixel electrode at the other one of said source and drain; and

a p,channel transistor having a source, drain, and gate, and connected to said data line at one of said source and drain of said p-channel transistor and to said pixel electrode at the other one of said source and drain of said p-channel transistor, said method comprising the steps of;

applying a signal persisting from time T₀ to time T₁ to said data signal line;

applying a positive signal persisting for a period shorter than (T₁ -T₀) to a first one of the gates of said n-channel transistor and said p-channel transistor during duration of said signal applied to said data signal line;

applying a negative signal persisting for a period shorter than (T₁ -T₀) to a second one of said gates during duration of said signal applied to said data signal line;

applying no signal to said data signal line from time T₂ to time T₃ (T₁ <

T₂ <

T₃); and

applying a positive signal persisting for a period shorter than (T₃ -T₂) to said first gate during a period from said time T₂ to said time T₃ ; and

applying a negative signal persisting for a period shorter than (T₃ -T₂) to said second gate during a period from said time T₂ to said time T₃.

2. The method of claim 1 wherein a voltage persisting at least from said time T₁ to said time T₂ is applied to a pixel electrode.

3. The method of claim 1 wherein said signal applied to said data signal line comprises a rectangular pulse.

14. The method of claim 1 wherein all of said signals applied to said gates are applied to both said p-channel transistor gate and said n-channel transistor gate.

15. The method of claim 14 wherein said signals are applied to said gates through a single control line.

4. A method of driving an electro-optical device comprising the steps of:

applying a unipolar pulse under a pulse period of 30 msec or shorter to a pixel electrode of a pixel with a duration of a time between a rising of said pulse and a falling of said pulse being controlled,

where said pixel electrode is connected;

is series with a thin film transistor of said pixel, and said unipolar pulse is applied through said thin film transistor.

5. The method of claim 4 wherein said duration is varied in said applying step.

6. The method of claim 4 wherein said pulse period is constant.

7. The method of claim 4 wherein said applying step is carried out by the steps of:

applying a signal persisting from time T₀ to time T₁ to a data signal line;

applying a signal persisting for a period shorter than (T₁ -T₀) and comprising two pulses having opposite polarities to an address signal line during duration of said signal applied to said data signal line;

applying no signal to said data signal line from time T₂ to time T₃ (T₁ <

T₂ <

T₃); and

applying a signal persisting for a period shorter than (T₃ -T₂) and comprising two pulses having opposite polarities to said address signal line during a period from said time T₂ to said time T₃.

13. The method of claim 4, wherein said electro-optical device is constructed with a pixel electrode;

a data signal line;

an n-channel transistor having a source, drain, and gate, and connected to said data signal line at one of said source and drain thereof and to said pixel electrode at the other one of said source and drain; and

a p-channel transistor having a source, drain, and gate, and connected to said data line at one of said source and drain of said p-channel transistor, and to said pixel electrode at the other one of said source and drain of said p-channel transistor wherein said rising is caused by the steps of;

applying a signal persisting from time T₀ to T₁ to said data signal line;

applying a positive signal persisting for a period shorter than (T₁ -T₀) to a first one of the gates of said n-channel transistor and said p-channel transistor during duration of said signal applied to said data signal line; and

applying a negative signal persisting for a period shorter than (T₁ -T₀) to a second one of said gates during duration of said signal applied to said data signal line, and

wherein said falling is caused by the steps of;

applying no signal to said data signal line from time T₂ to time T₃ (T₁ <

T₂ <

T₃);

applying a positive signal persisting for a period shorter than (T₃ -T₂) to said first gate during a period from said time T₂ to said time T₃ ; and

applying a negative signal persisting for a period shorter than (T₃ -T₂) to said second gate during a period from said time T₂ to said time T₃.

16. The method of claim 13 wherein all of said signals applied to said gates are applied to both said p-channel transistor gate and said n-channel transistor gate.

17. The method of claim 16 wherein said signals are applied to said gates through a single control line.

8. A method of driving an electro-optical device constructed with a pixel electrode;

a data signal line;

an n-channel transistor having a source, drain, and gate, and connected to said data line at one of said source and drain thereof and to said pixel electrode at the other one of said source and drain; and

a p-channel transistor having a source, drain, and gate, and connected to said data line at one of said source and drain of said p-channel transistor and to said pixel electrode at the other one of said source and drain of said p-channel transistor, said method comprising the step of;

applying pulses to at least one of said gates of said n-channel transistor and said p-channel transistor n-times at intervals, said intervals being 2^i-1 T₁ between the i-th pulse and the (i+1)[-]th pulse (1<

i<

n-1) where i and n are natural numbers and T₁ is a constant time.

9. The method of claim 8 further comprising the step of applying a data signal to a data signal line.

10. The method of claim 9 wherein said data signal comprises a rectangular pulse.

11. The method of claim 8 wherein each of said pulses is a bipolar pulse comprising two pulse portions having opposite polarities.

18. The method of claim 8 wherein pulses are applied to both said p-channel transistor gate and said n-channel transistor gate.

19. The method of claim 18 wherein said pulses are applied to said gates through a single control line.

12. A method of driving an electro-optical device constructed with a pixel electrode;

a data signal line;

a complemented signal line carrying a signal complementary to a signal on the data signal line;

an n-channel transistor having a source, drain, and gate, and connected to said complemented signal line at one of said source and drain thereof and to said pixel electrode at the other one of said source and drain; and

a p-channel transistor having a source, drain, and gate, and connected to said data signal line at one of said source and drain of said p-channel transistor, and to said pixel electrode at the other one of said source and drain of said p-channel transistor, said gates being connected to each other, said method comprising the steps of;

applying no signal to said gates from time T₁ to time T₂ ;

applying a positive signal to said gates from time T₃ to time T₄ (T₁ <

T₂ <

T₃ <

T₄);

applying a first positive pulse to said data signal line during a time between the time T₁ to the time T₂ ;

applying a second positive pulse to said data signal line during a time between the time T₃ and the time T₄ ;

applying no signal to said data signal line from a time of falling of said first positive pulse to a time of rising of said second positive pulse; and

applying to said complemented signal line, at the time of applying said first and second positive pulses, signals complementary to said first and second positive pulses.

20. A method of driving an electro-optical device comprising the steps of:

applying a signal persisting from time T₀ to time T₁ to a data signal line;

applying a signal persisting for a period shorter than (T₁ -T₀) and comprising two pulses having opposite polarities to an address signal line during duration of said signal applied to said data signal line;

applying no signal to said data signal line from time T₂ to T₃ (T₁ <

T₂ <

T₃); and

applying a signal persisting for a period shorter than (T₃ -T₂) and comprising two pulses having opposite polarities to said address signal line during a period from said time T₂ to said time T₃ ;

wherein a pulse is applied to a pixel electrode connected in series with a thin film transistor which is connected with said data signal line and said address signal line.

21. A method of driving a electro-optical device comprising the step of:

applying pulses to a gate of a thin film transistor connected in series with a pixel electrode n-times at intervals, said intervals being 2^i-1 T₁ between the i-th pulse and the (i+1) the pulse (1<

i<

n-1) where i and n are natural numbers and T₁ is a constant time.