Liquid crystal display device and its drive method and the drive circuit and power supply circuit device used therein
| Title: | Liquid crystal display device and its drive method and the drive circuit and power supply circuit device used therein |
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| Patent Number: | 6,252,571 |
| Publication Date: | June 26, 2001 |
| Appl. No: | 08/765,894 |
| Application Filed: | January 07, 1997 |
| Abstract: | Liquid crystal display device and its drive method that applies the voltage of the difference of a scanning signal and a data signal having at least a reset period, a selection period and a non-selection period in one frame on a chiral nematic liquid crystal having at least two stable states. A total of eight voltage levels made up of a plurality of levels (V1, V2, V3, V4) of a first group on the low voltage side and a plurality of levels (V5, V6, V7, V8) of a second group on the high voltage side are provided. The voltage levels of scanning signal Yi and data signal Xj are alternated between the first group and second group every mH (where, m is an integer that is 2 or greater and H.noteq.1 frame period), which is an integral multiple of the unit time (1H) equivalent to the selection period T2 of scanning signal Yi. When the data signal (Xj) is a voltage level of the first group, the voltage level of the reset period (T1) in the scanning signal (Yi) is selected from the second group, and when the data signal (Xj) is a voltage level of the second group, the voltage level of the reset period (T1) in the scanning signal (Yi) is selected from the first group. When the data signal (Xj) is a voltage level of the first group, the voltage levels of the selection period (T3) and non-selection period (T4) in the scanning signal (Yi) are each selected from the same first group, and when the data signal is a voltage level of the second group, the voltage levels of the selection period (T3) and non-selection period (T4) in the scanning signal (Yi) are each selected from the same second group. By this means, the polarity of the voltage applied to the liquid crystal is reversed every mH. |
| Inventors: | Nomura, Hiroaki (Suwa, JPX); Inoue, Akira (Suwa, JPX) |
| Assignees: | Seiko Epson Corporation (Tokyo, JPX) |
| Claim: | What is claimed is |
| Claim: | 1. A drive method for a liquid crystal display device comprising |
| Claim: | applying a voltage difference between a data signal and a scanning signal on a chiral nematic liquid crystal having at least two stable states, said scanning signal having at least a reset period, a selection period and a non-selection period in one frame; |
| Claim: | providing a total of eight or more voltage levels made up of a plurality of levels of a first group on a low voltage side and a plurality of levels of a second group on a high voltage side; |
| Claim: | alternating voltage levels of said scanning signal and said data signal between said first group and second group every mH where, m is an integer that is 2 or greater and mH.noteq.1 frame period, and wherein mH is an integral multiple of a unit time (1H) equivalent to said selection period of said scanning signal; |
| Claim: | selecting a voltage level of said reset period in said scanning signal from said second group when said data signal is a voltage level of said first group, and selecting a voltage level of said reset period in said scanning signal from said first group when said data signal is a voltage level of said second group; |
| Claim: | selecting voltage levels of each of said selection period and non-selection period in said scanning signal from said first group when said data signal is a voltage level of said first group, and selecting voltage levels of each of said selection period and non-selection period in said scanning signal from said second group; when said data signal is a voltage level of said second group and |
| Claim: | reversing the polarity of the voltage applied to said liquid crystal every mH. |
| Claim: | 2. A drive method for a liquid crystal display device as in claim 1 wherein |
| Claim: | the absolute value of the voltage difference of a saturation voltage Vsat and a threshold voltage Vth of the chiral nematic liquid crystal changes with the value of m and further comprising selecting the value of m such that the absolute value of said voltage difference is small. |
| Claim: | 3. A drive method for a liquid crystal display device as in claim 2 further comprising |
| Claim: | setting the absolute value of the ON voltage applied to the chiral nematic liquid crystal in said selection period larger than the absolute value of said saturation voltage Vsat of the chiral nematic liquid crystal by at least an allowable margin and setting the absolute value of the OFF voltage applied to the chiral nematic liquid crystal in said selection period smaller than the absolute value of said threshold voltage Vth of the chiral nematic liquid crystal within an allowable margin. |
| Claim: | 4. A drive method for a liquid crystal display device as in one of claims 1 to 3 further comprising |
| Claim: | providing a delay period in said scanning signal between said reset period and said selection period, and |
| Claim: | setting the voltage level in said delay period of said scanning signal the same as the voltage level of said non-selection period. |
| Claim: | 5. A drive method for a liquid crystal display device as in one of claims 1 to 3 further comprising |
| Claim: | setting said data signal every said selection period to a data voltage level containing the voltage level of either the ON voltage level or the OFF voltage level and setting four voltage levels for application of positive and negative ON selection voltages and positive and negative OFF selection voltages to said liquid crystal as said data voltage levels of said data signal, and |
| Claim: | setting said scanning signal to the reset voltage level in said reset period, to the selection voltage level in said selection period, and to the non-selection voltage level in said non-selection period, setting two types of voltage levels for application of positive and negative reset voltages to said liquid crystal as said reset voltage levels in said reset period, setting two types of voltage levels for application of said positive and negative selection voltages to said liquid crystal as said selection voltage levels in said selection period, and setting two types of voltage levels to provide bias voltage levels as said non-selection voltage levels in said non-selection period, and |
| Claim: | driving said liquid crystal using a total of eight voltage levels by using said two types of reset voltage levels and said two types of selection voltage levels in common. |
| Claim: | 6. A drive method for a liquid crystal display device as in claim 5 wherein |
| Claim: | said eight voltage levels comprise [the] four levels (V1, V2, V3, V4; V1 |
| Claim: | 7. A drive method for a liquid crystal display device as in claim 6 wherein |
| Claim: | said scanning signal takes on a waveform having the voltage level of V1 and V8 in said reset period, takes on the voltage level of V1 or V8 in said selection period, and takes on a waveform having the voltage level of V3 and V6 in said non-selection period, and |
| Claim: | said data signal is a waveform including a pulse whose peak value changes to the voltage level of V2 and V4 and a pulse whose peak value changes to the voltage levels of VS and V7. |
| Claim: | 8. A drive method for a liquid crystal display device as in claim 7 further comprising |
| Claim: | setting the relationship V4-V3=V3-V2=V7-V6=V6-V8. |
| Claim: | 9. A drive method for a liquid crystal display device as in claim 6 wherein |
| Claim: | said scanning signal takes on a waveform having the voltage levels of V4 and V8 in said reset period, takes on the voltage levels of V4 or V5 in said selection period, and takes on a waveform having the voltage levels of V2 and V7 in said non-selection period, and |
| Claim: | said data signal is a waveform including a pulse whose peak value changes to the voltage levels of V1 and V3 and a pulse whose peak value changes to the voltage levels of V6 and V8. |
| Claim: | 10. A drive method for a liquid crystal display device as in claim 9 further comprising |
| Claim: | setting the relationship V3-V2=V2-V1=V8-V7=V7-V6. |
| Claim: | 11. A drive method for a liquid crystal display device as in one of claims 1 to 3 wherein |
| Claim: | the value m which determines the reversal time is set to a value such that the value resulting from dividing the number of display scanning lines by m is an integer. |
| Claim: | 12. A drive method for a liquid crystal display device as in one of claims 1 to 3 wherein |
| Claim: | the value m which determines the reversal time is set to a value such that the value resulting from dividing the number of display scanning lines by m is not an integer. |
| Claim: | 13. A drive method for a liquid crystal display device as in one of claims 1 to 3 further comprising |
| Claim: | setting mH<1 frame period, and |
| Claim: | setting the start of the (n+1)th frame to a voltage level of the second group when the voltage at the start of the nth frame is a voltage level of said first group and wherein n is an integer, setting the start of the (n+1)th frame to a voltage level of the first group when the voltage at the start of the nth frame is a voltage level of said second group, and overlapping and repeating reversal every mH and reversal every frame unit. |
| Claim: | 14. A drive method for a liquid crystal display device as in claim 7 further comprising |
| Claim: | setting mH<1 frame period and, in the nth frame where n is an integer, setting the ON selection voltage level of said data signal to V4 of the first group and setting the OFF selection voltage level to V2 of the first group, and setting said reset voltage level at the start of said scanning signal to V8 and setting said selection voltage level to V1, and |
| Claim: | in the following (n+1)th frame, setting the ON selection voltage level of said data signal to V5 of said second group and setting the OFF selection voltage level to V7 of the second group, and setting said reset voltage level at the start of said scanning signal to V1 and setting said selection voltage level to V8, and |
| Claim: | overlapping and repeating reversal every mH and reversal every frame unit. |
| Claim: | 15. A drive method for a liquid crystal display device as in claim 9 further comprising |
| Claim: | in the nth frame, where n is an integer, setting the ON selection voltage level of said data signal to V1 of said first group and setting the OFF selection voltage level to V3 of the first group, and setting said reset voltage level at the start of said scanning signal to V5 and setting said selection voltage level to V4, and |
| Claim: | in the following (n+1)th frame, setting the ON selection voltage level of said data signal to V8 of the second group and setting the OFF selection voltage level to V6 of the second group, and setting said reset voltage level at the start of said data signal to V4 and setting said selection voltage level to V5, and |
| Claim: | 16. A drive method for a liquid crystal display device as in claim 6 wherein |
| Claim: | the voltage level difference between voltage level V4 of said first group and voltage level V5 of said second group is made large and the absolute value of said reset voltage applied to said liquid crystal in said reset period is set large. |
| Claim: | 17. A liquid crystal display device comprising; |
| Claim: | a liquid crystal panel made up of chiral nematic liquid crystal having at least two stable states and infused between a first substrate whereon are formed a plurality of scanning electrodes and a second substrate whereon are formed a plurality of data electrodes; |
| Claim: | a scanning electrode drive circuit that outputs scanning signals having at least a reset period, a selection period and a non-selection period in one frame to each of said scanning electrodes; |
| Claim: | a data electrode drive circuit that outputs data signals to each of said data electrodes; and |
| Claim: | a power supply circuit that outputs a total of eight or more voltage levels made up of a plurality of levels of a first group on a low-voltage side and a plurality of levels of a second group on a high-voltage side as potentials of said scanning signal and said data signal; and wherein |
| Claim: | said scanning electrode drive circuit and said data electrode drive circuit comprise means for alternately changing the voltage levels of said scanning signal and said data signal between said first group and second group every mH where, m is an integer that is 2 or greater and mH g 1 frame period, and wherein mH is an integral multiple of the unit time (1H) equivalent to said selection period of said scanning signal; and |
| Claim: | said scanning electrode drive circuit further comprises means for |
| Claim: | selecting the voltage level of said reset period in said scanning signal from said second group when said data signal is a voltage level of said first group and selecting the voltage level of said reset period in said scanning signal from said first group when said data signal is a voltage level of said second group |
| Claim: | selecting each of the voltage levels of said selection period and non-selection period in said scanning signal from said first group when said data signal is a voltage level of said first group and selecting each of the voltage levels of said selection period and non-selection period in said scanning signal from said second group when said data signal is a voltage level of said second group, and |
| Claim: | 18. A drive circuit for a liquid crystal display device that drives said liquid crystal and is connected to |
| Claim: | a liquid crystal panel comprising chiral nematic liquid crystal having at least two stable states and infused between a first substrate whereon are formed a plurality of scanning electrodes and a second substrate whereon are formed a plurality of data electrodes, and |
| Claim: | a power supply circuit that outputs a total of eight or more voltage levels made up of a plurality of levels of a first group on a low-voltage side and a plurality of levels of a second group on a high-voltage side as drive potentials for said liquid crystal, said drive circuit comprising |
| Claim: | a scanning electrode drive circuit that outputs scanning signals having at least a reset period, a selection period and a non-selection period in one frame to each of said scanning electrodes; and |
| Claim: | a data electrode drive circuit that outputs data signals to each of said data electrodes; wherein |
| Claim: | said scanning electrode drive circuit and said data electrode drive circuit comprise means for alternately changing the voltage levels of said scanning signal and said data signal between said first group and second group every mH where, m is an integer that is 2 or greater and mH.noteq.1 frame period, and wherein mH is an integral multiple of the unit time (1H) equivalent to said selection period of said scanning signal; and |
| Claim: | 19. A Rower supply circuit device for a liquid crystal display device, which generates an even number of a total of 8 or more voltage levels (V1, V2, . . . , V.sub.k/2, . . . ,V.sub.k-1, V.sub.k ; V1 |
| Claim: | means for generating a maximum voltage level V.sub.k ; |
| Claim: | means for generating a potential difference V.sub.B, which becomes a reference for generating voltage levels V2 to V.sub.k-1, not including the maximum voltage level V.sub.k and ground voltage level V1; |
| Claim: | calculation means for calculating and outputting voltage levels V2 to V.sub.k-1 based on said potential difference V.sub.B ; and |
| Claim: | changing means for changing the value of said potential difference V.sub.B externally to adjust each voltage level (V2, . . . , V.sub.k-1) simultaneously except said ground voltage level V1 and said maximum voltage level V.sub.k. |
| Claim: | 20. A power supply circuit device for a liquid crystal display device as in claim 19 wherein |
| Claim: | said means for generating said potential difference V.sub.B generates said potential difference V.sub.B based on said maximum voltage level V.sub.k. |
| Claim: | 21. A power supply circuit device for a liquid crystal display device as in claim 19 or 20 wherein |
| Claim: | said calculation means comprises |
| Claim: | a plurality of calculation circuits to which said voltage level V.sub.B is input and that calculate and output each of the voltage levels (V2, . . . , V.sub.k/2) from among the plurality of levels (V1, V2, . . . , V.sub.k/2), except said ground voltage level V1, of a first group on a low-voltage side of said eight or more voltage levels, and |
| Claim: | a plurality of subtraction circuits that generate each of the voltage levels (V.sub.k-1, . . . , V.sub.k/2+1) of the voltage levels (V.sub.k/2+1, V.sub.k/2+2, . . . , V.sub.k-1, V.sub.k), except said maximum voltage level V.sub.k, of a second group on a high voltage side by subtracting the respective outputs (V2, . . . , V.sub.k/2) of said calculation means from said maximum voltage level V.sub.k. |
| Claim: | 22. A Rower supply circuit device for a liquid crystal display device, which generates a total of 8 or more voltage levels (V1, V2, . . . , V7, V8; V1 |
| Claim: | means for generating a maximum voltage level V8; |
| Claim: | means for generating a potential difference VB, which becomes a reference for generating voltage levels V2 to V7, not including said maximum voltage level V8 and said ground voltage level V1; |
| Claim: | a calculation means for calculating and outputting voltage levels V2 to V7 based on said potential difference V.sub.B ; and |
| Claim: | changing means for changing the value of said potential difference V.sub.B externally to adjust each voltage level (V2, . . . , V7) simultaneously, except said ground voltage level V1 and maximum voltage level V8. |
| Claim: | 23. A power supply circuit device for a liquid crystal display device as in claim 22 wherein |
| Claim: | said means for generating said potential difference V.sub.B generates said potential difference V.sub.B based on said maximum voltage level V8. |
| Claim: | 24. A power supply circuit device for a liquid crystal display device as in claim 22 or 23 wherein |
| Claim: | a plurality of calculation circuits to which said voltage level V.sub.B is input and that calculate and output each of the voltage levels (V2, V3, V4) from among the plurality of levels (V1, V2, V3, V4), except said ground voltage level V1, of a first group on a low-voltage side of said eight or more voltage levels, and |
| Claim: | a plurality of subtraction circuits that generate each of the voltage levels (V5, V6, V7) of the voltage levels (V5, V6, V7, V8), said except maximum voltage level V8, of a second group on a high voltage side by subtracting the respective outputs (V2, V3, V4) of said calculation means from said maximum voltage level V8. |
| Claim: | 25. A power supply circuit device for a liquid crystal display device of one of claims 19, 20, 22 or 23 including means for setting said potential difference level V.sub.B to V.sub.B =.vertline.Von-Voff.vertline./2 determined from Von and Voff of said data signal. |
| Claim: | 26. A liquid crystal display device comprising. |
| Claim: | a power supply circuit that generates an even number of a total of 8 or more voltage levels (V1, V2, . . . , V.sub.k/2, . . . ,V.sub.k-1, V.sub.k ; V1 |
| Claim: | a drive circuit to which is input said voltage levels from said power supply circuit and which drives said liquid crystal by outputting a scanning signal to said scanning electrodes and outputting a data signal to said data electrodes of said liquid crystal panel; and wherein |
| Claim: | said drive circuit comprises |
| Claim: | means for generating a maximum voltage level V.sub.k |
| Claim: | means for generating a potential difference V.sub.B, which becomes a reference for generating voltage levels V2 to V.sub.k-1, except said maximum voltage level V.sub.k and said ground voltage level V1 |
| Claim: | calculation means for calculating voltage levels V2 to V.sub.k-1 based on said potential difference V.sub.B, and |
| Claim: | changing means for changing the value of said potential difference VB externally to adjust each voltage level (V2, . . . , V.sub.k-1) simultaneously except said ground voltage level V1 and maximum voltage level V.sub.k. |
| Claim: | 27. A power supply circuit device of a liquid crystal display device, which generates a total of 8 or more voltage levels (V1, V2, . . . ,V.sub.k/2, . . . ,V.sub.k-1, V.sub.k ; V1 |
| Claim: | (k-1) resistors (R1, R2, . . . , R.sub.k-1) connected in order from one end and in series to a path whose voltage at one end is said maximum voltage level V.sub.k and whose voltage at the other end is ground voltage level V1; |
| Claim: | (k-2) voltage output terminals each connected between two adjacent resistors and that output said voltage levels V.sub.k-2 to V2 obtained by sequentially dropping the voltage via said resistors (R1, R2, . . . , R.sub.k-1); and |
| Claim: | means for changing the resistance value of one of said (k-1) resistors externally to adjust each voltage level (V2 to V.sub.k-1) simultaneously, except said ground voltage level V1 and maximum voltage level V.sub.k. |
| Claim: | 28. A power supply circuit device of a liquid crystal display device, which generates a total of 8 voltage levels (V1, V2, . . . , V7, V8; V1 |
| Claim: | seven resistors (R1, R2, . . . , R7) connected in order from one end and in series to a path whose voltage at one end is said maximum voltage level V8 and whose voltage at the other end is the ground voltage level V1; |
| Claim: | six voltage output terminals each connected between two adjacent resistors and that output said voltage levels V7 to V2 obtained by sequentially dropping the voltage via said resistors (R1, R2, . . . , R7); and |
| Claim: | means for changing the resistance value of said resistor R4 between said voltage output terminal of V5 and said voltage output terminal of V4 externally to adjust each voltage level (V2 to V7) simultaneously, except said ground voltage level V1 and maximum voltage level V8. |
| Claim: | 29. A liquid crystal display device comprising |
| Claim: | a liquid crystal panel comprising chiral nematic liquid crystal having at least two stable states and infused between a first substrate whereon are formed a plurality of scanning electrodes and a second substrate whereon are formed a plurality of data electrodes; |
| Claim: | a power supply circuit that generates an even number of a total of 8 or more voltage levels (V1, V2, . . . , V.sub.k/2, . . . , V.sub.k-1, V.sub.k ; V1 |
| Claim: | (k-1) resistors (R1, R2, . . . , R.sub.k-1) connected in order from one end and in series to a path whose voltage at one end is said maximum voltage level V.sub.k and whose voltage at the other end is said ground voltage level V.sub.1 |
| Claim: | (k-2) voltage output terminals each connected between two adjacent resistors and that output said voltage levels V.sub.k-2 to V2 obtained by sequentially dropping the voltage via said resistors (R1, R2, . . . , R.sub.k-1), and |
| Claim: | means for changing the resistance value of one of said (k-1) resistors externally to adjust each voltage level (V2 to V.sub.k-1) simultaneously except said ground voltage level V1 and maximum voltage level V.sub.k. |
| Current U.S. Class: | 345/95; 345/208; 345/210 |
| Current International Class: | G09G 336 |
| Patent References Cited: | 3837730 September 1974 Hatfield et al. 4239345 December 1980 Berreman et al. 4333708 June 1982 Boyd et al. 4367924 January 1983 Clark et al. 4411496 October 1983 Nonomura et al. 4505548 March 1985 Berreman et al. 4529271 July 1985 Berreman et al. 4566758 January 1986 Bos 4582396 April 1986 Bos et al. 4601542 July 1986 Meyer 4601543 July 1986 Boyd et al. 4601544 July 1986 Cheng et al. 4634229 January 1987 Amstutz et al. 4664483 May 1987 Van Sprang et al. 4701026 October 1987 Yazaki et al. 4717243 January 1988 Boyd et al. 4770500 September 1988 Kalmanash et al. 4850676 July 1989 Yazaki et al. 5095376 March 1992 Umeda et al. 5189535 February 1993 Mochizuki et al. 5196738 March 1993 Takahara et al. 5251048 October 1993 Doane et al. 5287205 February 1994 Yamazaki et al. 5337070 August 1994 Kitajima et al. 5343217 August 1994 Kim 5404150 April 1995 Murata 5488499 January 1996 Tanaka et al. 5563427 October 1996 Yudasaka et al. 5594464 January 1997 Tanaka et al. 5684503 November 1997 Nomura et al. 5835075 November 1998 Nomura et al. 5900852 May 1999 Tanaka et al. |
| Other References: | M. Schadt and W. Helfrich entitled, "Voltage-Dependent Optical Activity Of A Twisting Nematic Liquid Crystal", Applied Physics Letters, vol. 18(4), pp. 127-128 (1971). T.J. Scheffer and J. Nehring entitled, "A New, Highly Multiplexable Liquid Crystal Display", Applied Physics Letters, vol. 45(10), pp. 1021-1023 (Nov. 15, 1984). Robert B. Meyer and R.N. Thurston entitled, "Discovery Of DC Switching Of A Bistable Boundary Layer Liquid Crystal Display", Applied Physics Letters, vol. 43(4), pp. 342-344, (Aug. 15, 1983). IEEE Transcations on Electron Devices, vol. 36, on.9-I, Sep. 1989 New York, US, pp. 1895-1899, Ferroelectric Liquid-Crystal Video Display, W.J.A.M. Hartmann. D.W. Berreman entitled, "Numerical Modeling Of Twisted Nematic Devices", Bell Laboratories, New Jersey; Phil. Trans. R. Soc. Lond. A, pp. 203-216, 1983. |
| Primary Examiner: | Shankar, Vijay |
| Assistant Examiner: | Frenel, Vanel |
| Attorney, Agent or Firm: | Watson, Mark P. |
| Accession Number: | edspgr.06252571 |
| Database: | USPTO Patent Grants |
| Language: | English |
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