US3891306A - Method for driving liquid cell display panel - Google Patents

Method for driving liquid cell display panel Download PDF

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Publication number
US3891306A
US3891306A US381003A US38100373A US3891306A US 3891306 A US3891306 A US 3891306A US 381003 A US381003 A US 381003A US 38100373 A US38100373 A US 38100373A US 3891306 A US3891306 A US 3891306A
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voltage
selection
period
during
high frequency
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US381003A
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English (en)
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Isamu Mitomo
Tetsunori Kaji
Masakazu Fukushima
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Hitachi Ltd
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Hitachi Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3622—Control of matrices with row and column drivers using a passive matrix

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  • the present invention relates to a method for driving a liquid cell display panel. and more particulary to a method for driving a liquid cell display panel. in which a dynamic scattering mode produced during a period of semi-selection (hereinafter referred to as a semiselection response) is controllable.
  • An object of the present invention is to provide a driving method being capable of avoiding a semiselection response.
  • Another object of the present invention is to provide a driving method being capable of effecting display with good contrast.
  • the present invention provides a driving method in which a high frequency voltage having a level necessary for cancelling the scattering mode is superimposed on a DC voltage applied during the period of the semi-selection. and during a period of non-selection the high frequency voltage is made not to be applied in order to prevent the falling time of the scattering mode from being reduced to an unpreferable extent.
  • FIG. 1 is a schematic view showing a conventional liquid cell display panel.
  • FIG. 2 is a graph showing relative brightness of a liquid cell upon application of a DC voltage.
  • FIGS. 3 and 4 are graphs showing conventional driving waveforms.
  • FIG. 5 is a graph showing relative brightness of a liquid cell upon application of a DC voltage with a high frequency voltage superimposed thereon.
  • FIGS. 6a and 6b are graphs illustrating an effect of the high frequency voltage upon the falling time of the dynamic scattering mode of a liquid cell.
  • FIGS. 7 to 9 are graphs showing embodiments of waveforms according to the present invention.
  • FIG. 10 is a graph showing relative brightness of a liquid cell upon application of a DC pulse voltage.
  • FIG. 1 there is schematically shown a liquid cell display panel ofthe nematic type adapted for use in the present invention, which is a well-known display panel.
  • a group of longitudinal lines (X,, X X,,,) arranged in a lateral direction represents a series of horizontal scanning electrodes while a group of lateral lines (Y Y Y,,) represents a series of vertical scanning electrodes, both series of electrodes facing each other through liquid cells.
  • the liquid cell located at an intersection P of the electrodes X and X effects a dynamic scattering mode upon the application of a predetermined voltage across the electrodes X and Y
  • FIG. 1 a group of longitudinal lines (X,, X X,,,) arranged in a lateral direction represents a series of horizontal scanning electrodes while a group of lateral lines (Y Y Y,,) represents a series of vertical scanning electrodes, both series of electrodes facing each other through liquid cells.
  • FIG. 2 there is shown a graph illustrating the dynamic scattering mode in terms of the voltage applied to the liquid cell in the above-mentioned liquid cell display panel.
  • an abscissa represents the voltage applied to one electrode and measured relative to the other electrode serving as a reference while an ordinate represents relative scattering brightness B.
  • Curves u and b show characteristics upon the application of the voltage having positive and negative polarities. respectively. and marks V and V,,. show "a threshold voltage", that is. a voltage at which the dynamic scattering mode of the liquid cell is initiated.
  • FIG. 3 shows a driving signal waveform applied to the electrode X with a voltage V applied thereto during the period of selection of I to I and V shows a driving signal waveform applied to the electrode Y with a voltage applied thereto during the periods of selection of r. to t and 1;, to 1
  • the distribution of the selection periods in FIG. 3 is arranged as a matter of conve nience for the purpose of simplification of the drawings and the description. This applies to the following similar description and drawings.
  • FIG. 3 there is shown a voltage (V,V between the desired electrodes X and Y at the intersection thereof to which the voltage 2V is applied during the period of selection of t.
  • the voltage V is applied during the periods of selection of 1 to t and 1;, to t that is. during the period of a so-called semi-selection in which one electrode is in the period of selection and the other is in the period of no selection; and the voltage zero is applied during the period of selection 1 to I that is. during the period of no selection relative to both the electrodes (hereinafter referred to as a period of non-selection).
  • the dynamic scattering mode of the liquid cell is adapted to be effected only during a period when the period of selection to both the electrodes coincides. that is. during the period of full selection, and hence no dynamic scattering mode thereofis preferably produced during the periods of semi-selection and non-selection.
  • the driving system of FIG. 4. has the same general driving method and the same waveform of the voltage applied between both the electrodes as that of FIG. 3 with the characteristic exception that a DC bias near to the threshold voltage as shown in FIG. 2 is previously applied between both the electrodes X and Y.
  • the DC bias is applied to the electrode X with the voltage V,,, applied during the period of no selection and with the voltage V applied during the period of selection while the voltage zero is applied to the electrode Y during the period of no selection with the voltage 2V,,, applied during the period of selection.
  • the voltage V between both the electrodes is 3V,,, during the period of full selection and V,,, and V during the periods of semi-selection and non-selection, respectively. and therefore the voltage applied during the period of full selection is increased at maximum three times as great as the threshold voltage. Accordingly. it will be calculated from FIG. 2 that the scattering brightness during the period of full selection reaches about 60 percent of its maximum. In any case, in the actual sanning system there is a requirement that the period of full selection should be as short as possible; however, it is unpreferable to restrict the driving voltage because the scattering brightness relative to the level of the applied voltage is always reduced to the level lower than that shown in FIG.
  • FIG. 5 One of the characteristics is shown in FIG. 5 as a dynamic scattering characteristic of the liquid cell upon the application thereto of the DC voltage superimposed by the high frequency voltage.
  • the abscissa indicates the high frequency voltage (the voltage being represented by a peak value) while the ordinate indicates the relative scattering brightness.
  • Bent curves 0. d and e show the relative scattering brightness relative to the high frequency voltage superimposed on the respective different DC voltages with the DC voltage increased in the order of e, d and c.
  • the same figure shows that the increase in the high frequency voltage relative to each DC voltage causes a reduction of the scattering brightness in more than a certain value thereof, eventually falling to zero at the voltages V V and V for each bent lines 0, d and e.
  • FIG. 6a shows the other characteristic as an influence of the high frequency voltage upon the falling time in the scattering mode as shown in FIG. 6a.
  • a waveform g shows the waveform of the dynamic scattering mode produced by the application of the driving voltage (6() ⁇ ' 20 milliseconds) having a waveform f with 50 percent attenuating time being l5 milliseconds.
  • FIG. 6a further shows that the 50 percent attenuating time of the waveform i of the light scattering mode is shortened to 2 to 2.5 milliseconds when the liquid cell is drived by a waveform 11 further including a high frequency voltage (60V, 4KHz) superimposed on a por' tion ofthe waveformffollowing the period of selection.
  • 60V, 4KHz high frequency voltage
  • a relation of a dynamic scattering amount (i.e.. scattering brightness) to the frequency of the high frequency voltage is as shown in FIG. 6b (in which the abscissa shows the frequency F and the ordinate shows the scattering brightness B) with a limiting frequency/b existing therein. That is the scattering disappears above the limiting frequency fiz
  • the low frequency voltage (including the DC voltage) exists in the frequency region below fc while the high frequency voltage exists in the frequency region above fr'.
  • the high frequency voltage is not preferably to be applied during the period of nonselection because it serves to cancel out a desirable memory effect.
  • the fundamental features of the present invention are, on the one hand, to superimpose on the applied DC voltage the high frequency voltage equal to or greater than the voltage V,. shown in FIG. 5 for cancelling the scattering mode during the period of semi-selection, and, on the other hand. to apply no high frequency voltage during the period of nonselection to prevent the falling time of the scattering mode from being shortened to an undesirable extent.
  • the DC voltage or low frequency voltage is primarily applied during the period of full selection as hithertofore to develop the scattering mode and that it is not hindered to superimpose the high frequency voltage having as low amplitude as the scattering mode is not prevented.
  • FIG. 7 A first embodiment is shown in FIG. 7 wherein numeral I indicates the waveform V, of the driving signal applied to the electrode X (dotted lines hereinafter denoting the DC voltage) with the DC voltage of 1 volt superimposed by the high frequency voltage In of 2 volts during the period of selection of z, to 1 and with the voltage reduced to zero during the period of no selection of 1 to Numeral 2 indicates the waveform V of the driving signal applied to the electrode Y [dotted lines hereinafter denoting the DC voltage) with the DC voltage of 2 volts superimposed by the high frequency voltage of 2 volts during the periods of selection of t, to and I;; to l and with the voltage of zero applied during the periods of no selection of 1 to I and t to 1 In this case.
  • numeral 3 shows the voltage waveform V, between the electrodes X and Y at the intersection thereof to which the waveforms I and 2 are applied. respectively. with the DC voltage of 3 volts applied during the period of full selection of r, to 1 with the DC voltage of 1 volt and the high frequency voltage 312 of 2 volts applied during the period of semi-selection of to 1;, and the DC voltage of 2 volts and the high frequency voltage 3c of 2 volts applied during the period of 1;, to r and with the voltage of zero volt applied during the period of non-selection.
  • the above-mentioned embodiment shows that a ratio of the high frequency voltage to DC voltage becomes 2 at maximum during the period of semi-selection when the DC voltage is applied to the electrode X while the ratio thereof becomes 1 at maximum during the period of semi-selection when the DC voltage is applied to the electrode Y.
  • FIG. 8 A second embodiment will be shown in FIG. 8 in which numeral 4 shows the waveform V, of the driving signal applied to the electrode X with the DC voltage of I volt applied during the period of selection of r, to 1;, and with the high frequency voltage 4b of 2 volts applied during the period of no selection of to Numeral 5 indicates the waveform V, of the driving signal applied to the electrode Y with the DC voltage of 2 volts applied during the periods of selection of t, to 1 and I" to 1 and with the high frequency voltage 5b of 2 volts applied during the periods of no selection to I and I to 1 In this case. the high frequency voltage 4b is assumed to have the same frequency phase and voltage as the high frequency voltage 5h. Further. in FIG. 8 numeral 6 indicates the waveform V of the voltage between both the electrodes, which is the same as the waveform 3 shown in FIG. 7.
  • a third embodiment shows a composite combination of the first typical embodiment with the second typical embodiment with the waveform of the driving signal shown in FIG. 9.
  • numeral 7 indicates the waveform V, of the driving signal applied to the electrode X with the DC voltage of 4/3 volts and the high frequency voltage 7a of 2/3 volts applied during the period of selection oft to 1;, and with the high frequency voltage 711 of2 volts applied during the period of no selection of to 15.
  • the high frequency voltage 70 is herein assumed to have the same frequency as the high frequency voltage 7h an 1 the phase opposite thereto.
  • numeral 9 indicates the waveform V ofthe voltage between both the electrodes with the DC voltage of 3%; volts and the high frequency voltage 9a of 2/3 volts applied during the period of full selection. with the DC voltage of l /is volts and the high frequency voltage 9b of 2% volts applied during the period of semi-selection of to with the DC voltage of 2 volts and the high frequency voltage 9c of 2 volts applied during the period of selection of 1 to 1 and with the voltage of zero volt applied during the period of non-selection.
  • An advantage of the third embodiment is that the DC voltage applied during the period of full selection is increased by I/3 volts although the amplitude of the driving voltage ranges the same as that of the first and second embodiments. No problem arises with respect to the high frequency voltage (9a in FIG. 9) subjected to the simultaneous application because it is low frequency voltage of 2/3 volts.
  • the use of the driving system as mentioned above causes no dynamic scattering mode during the period of semi-selection. thus permitting an improvement of an optical contrast.
  • FIG. I0 there is shown a relation of the applied voltage to the relative brightness for each duty ratio of one-tenth to one-fiftieth when the DC pulse voltage is applied to the liquid cell.
  • a maximum driving voltage is 3 X 8 (volts) 24 (volts) when the threshold voltage is set to be 8 volts.
  • the maximum driving voltage experimentally reaches 36 volts in a scanning state (in the duty ratio of one-tenth) because the threshold voltage increases more than 8 volts.
  • the relative brightness becomes 0.36 from the characteristic curve with the contrast where 0.06 represents background brightness.
  • the level of the driving voltage is experimentally as high as I00 volts taking into account the break-down voltage or life span of the liquid cell. so that the relative brightness is 1.5 with the contrast
  • the present invention permits the contrast to be improved about four times as much as that of the conventional one.
  • a ratio of the high frequency voltage to the DC voltage applied during the period of semi-selection has been selected to be I and 2. but suitably ranges from 1 to 2 depending on the characteristics of FIG. 5. Further. it will be appreciated that the driving waveform is not limited to the above embodiments but only required to be of alternating waveform.
  • a method for driving a liquid cell display panel including a plurality of first electrodes arranged in parallel to each other, a plurality of second electrodes re spectively intersecting with each of said first electrodes and arranged in parallel to each other, and liquid cells of nematic type disposed at the respective intersections of said first electrodes with said second electrodes, said method comprising the step of applying a voltage to a predetermined liquid cell of said liquid cells through said first and second electrodes to drive said predetermined liquid cell, wherein said voltage includes a DC voltage and a high frequency voltage superimposed thereon during periods of two types of semi-selection of said liquid cell and said voltage includes at least a DC voltage during a period of full selection thereof, an amplitude ratio of said high frequency voltage to DC voltage during the period of at least one of said two types of semi-selection being in the range of at least 1 and not more than 2.
  • a driving method as set forth in claim 1 including applying a DC voltage having a high frequency voltage superimposed thereon to a first electrode or a second electrode associated with a respective liquid cell during the period of semi-selection of said liquid cell.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
US381003A 1972-07-21 1973-07-20 Method for driving liquid cell display panel Expired - Lifetime US3891306A (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004848A (en) * 1973-03-13 1977-01-25 Kabushiki Kaisha Suwa Seikosha Liquid crystal display device
US4041481A (en) * 1974-10-05 1977-08-09 Matsushita Electric Industrial Co., Ltd. Scanning apparatus for an electrophoretic matrix display panel
US4040721A (en) * 1975-07-14 1977-08-09 Omron Tateisi Electronics Co. Driver circuit for liquid crystal display
US4076385A (en) * 1974-08-14 1978-02-28 Kabushiki Kaisha Daini Seikosha Liquid crystal display device
US4150361A (en) * 1975-03-11 1979-04-17 Citizen Watch Co., Ltd. Drive control for drive circuit of liquid crystal display
US4241344A (en) * 1977-07-29 1980-12-23 Bbc Brown, Boveri & Company, Limited Electro-optical device for the display of dark symbols composed of separately selectable display segments against a bright background and a means for addressing this device
US4297695A (en) * 1978-12-28 1981-10-27 Xerox Corporation Electrochromic display device
US4462027A (en) * 1980-02-15 1984-07-24 Texas Instruments Incorporated System and method for improving the multiplexing capability of a liquid crystal display and providing temperature compensation therefor

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3575492A (en) * 1969-07-10 1971-04-20 Rca Corp Turnoff method and circuit for liquid crystal display element
US3740717A (en) * 1971-12-16 1973-06-19 Rca Corp Liquid crystal display
US3786486A (en) * 1971-08-11 1974-01-15 Olivetti & Co Spa Multiplex driving circuit

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5128999A (ja) * 1974-09-05 1976-03-11 Fuji Heavy Ind Ltd Shitsusokukeihosochi

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3575492A (en) * 1969-07-10 1971-04-20 Rca Corp Turnoff method and circuit for liquid crystal display element
US3786486A (en) * 1971-08-11 1974-01-15 Olivetti & Co Spa Multiplex driving circuit
US3740717A (en) * 1971-12-16 1973-06-19 Rca Corp Liquid crystal display

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004848A (en) * 1973-03-13 1977-01-25 Kabushiki Kaisha Suwa Seikosha Liquid crystal display device
US4076385A (en) * 1974-08-14 1978-02-28 Kabushiki Kaisha Daini Seikosha Liquid crystal display device
US4041481A (en) * 1974-10-05 1977-08-09 Matsushita Electric Industrial Co., Ltd. Scanning apparatus for an electrophoretic matrix display panel
US4150361A (en) * 1975-03-11 1979-04-17 Citizen Watch Co., Ltd. Drive control for drive circuit of liquid crystal display
US4040721A (en) * 1975-07-14 1977-08-09 Omron Tateisi Electronics Co. Driver circuit for liquid crystal display
US4241344A (en) * 1977-07-29 1980-12-23 Bbc Brown, Boveri & Company, Limited Electro-optical device for the display of dark symbols composed of separately selectable display segments against a bright background and a means for addressing this device
US4297695A (en) * 1978-12-28 1981-10-27 Xerox Corporation Electrochromic display device
US4462027A (en) * 1980-02-15 1984-07-24 Texas Instruments Incorporated System and method for improving the multiplexing capability of a liquid crystal display and providing temperature compensation therefor

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