US3895373A - Method and apparatus for selectively exciting a matrix of voltage responsive devices - Google Patents

Method and apparatus for selectively exciting a matrix of voltage responsive devices Download PDF

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US3895373A
US3895373A US477204A US47720474A US3895373A US 3895373 A US3895373 A US 3895373A US 477204 A US477204 A US 477204A US 47720474 A US47720474 A US 47720474A US 3895373 A US3895373 A US 3895373A
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voltage
amplitude
row
frequency
voltages
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Marvin J Freiser
Dale T Teaney
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International Business Machines Corp
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International Business Machines Corp
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Priority to GB14279/75A priority patent/GB1501268A/en
Priority to FR7514032A priority patent/FR2274098A1/fr
Priority to DE19752521101 priority patent/DE2521101A1/de
Priority to JP50056221A priority patent/JPS51835A/ja
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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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  • a method and apparatus for selectively exciting a matrix of voltage responsive devices in which each of said device is responsive to a voltage difference between a row and column drive line.
  • a plurality of row and column drive lines are fed with an AC voltage. the phases of said voltage on said column drive lines being different from the phases on said row drive lines.
  • a device is selectively excited by adjusting the phase of voltage on the row and column drive lines, associated with said selected device, to be equal to each other. and different from either the phases on other column or other row drive lines.
  • the three different phases of voltage available (one on unselected columns. another on unselected rows. the third on the selected row and column) differ in increments of 21r/3. In this manner the voltage across a selected device can be reduced to zero without affecting the amplitude of voltage applied to any other device.
  • FIG. 10b VH/F W 41 f fL 42 VOLTAGE GENERATOR PHASE /45 45 SHIFT 46 PHASE 44 SHIFT ,3 -21 5 55 53 44 42 j J A a FIG. 10b
  • a further embodiment provides a further driving voltage of higher frequency to the row and column drive lines for decreasing the delay in the opaque to transmissive transition and for increasing the delay in the transmissive to opaque transition.
  • the columns are normally not driven by this further voltage and the rows are all driven by a further voltage of equal amplitude and phase.
  • the column drive line associated therewith has applied to it a further voltage twice the amplitude with the same phase as the row driving voltage and the row driving voltage associated with the selected device is altered by 11' radians. In this manner the further voltage component across the selected device is three times the further voltage component applied to each other device.
  • the use of the two driving voltages of different frequencies allows larger matrices to be effectively driven.
  • inventions include different combinations of transmissive and opaque states to which the devices are driven.
  • the devices need not comprise nematic liquid crystals but may be other voltage responsive devices.
  • the present invention relates to a method and apparatus for selectively exciting a selected voltage responsive device in a matrix of voltage responsive devices where it is necessary to alter the voltage applied to a particular selected device without varying the amplitude of the voltage supplied to other devices in the matrix. More particularly, one embodiment of the present invention relates to a method and apparatus for selectively exciting a matrix of liquid crystals which comprise an optical display.
  • the liquid crystal may be that disclosed in copending application of D. C. Green and W. R. Young entitled Nematic Materials and Method for Their Preparation," Ser. No. 299,991, filed Oct. 24, 1972, now U.S. Pat. No. 3,836,478'and assigned to the assignee of this application. The disclosure thereof is incorporated herein by reference.
  • This latter time can be referred to as a rise time (Y In determining the extent to which multiplexing can be utilized, or the size of a matrix which can be driven, the ratio (Y /Y of the decay time to the rise time is significant. The larger this ratio the larger the matrix that can be driven. A larger ratio means that for any given period of time during which a driving signal must be present, the period of time between driving signals can be enlarged. Of course, the period of time between driving signals for any element in the matrix can be utilized for driving other elements in the matrix.
  • the voltage responsive devices with which this invention is concerned are arranged in a matrix, it is convenient to drive them with row and column drive lines and multiplex the driving signals to drive one row at a time.
  • the voltage applied to any given device in the matrix then is the difference between, the voltage applied on the column drive line with which the device is associated, and the voltage provided on the row drive line with which the device is associated.
  • the contribution to the voltage provided to all devices in a given column, by the column drive line is identical.
  • the contribution to the voltage difference at any device in a given row, by the row drive line is also identical.
  • One of the characteristics of the nematic liquid crystals with which this invention is concerned is a dielectric anisotropy (Ae) which changes sign with frequency. That is, at some low frequency, f,, the dielectric anisotropy is positive (Ae 0) while at some higher frequency, f,,, the dielectric anisotropy is negative (Ae,, 0).
  • Ae dielectric anisotropy
  • the material of the crystal presents the highest dielectric constant possible to an applied electric field, it is possible, by controlling the voltage and frequency of one or more voltages applied across the device to control the orientation of the material.
  • This control over the orientation of the material allows the material to be switched between a light transmissive state and a light extinguishing or opaque state.
  • the transmissive and light extinguishing states of the material are selected so as to increase the decay time (Y and to decrease the rise time (Y In other words, the states are so chosen that the material responds quickly to a driving signal and responds slowly to the absence of the driving signal.
  • a driving signal may be any change in applied voltage which tends to order the material in such a configuration that it is light transmissive.
  • the driving signal may actually be the removal of any voltage applied to the material where the applied voltage results in the material being light extinguishing.
  • a matrix of voltage responsive devices are driven by a voltage difference provided between column and row drive lines, each of the devices being fed by one of a plurality of column drive lines and one of a plurality of row drive lines.
  • the voltage difference normally provided at each of the devices are equal in magnitude and, in order to excite a selected device, the voltage across that device is reduced to zero without affecting the amplitude of the voltage across any of the other devices.
  • Each of the column drive lines is normally provided with an alternating current voltage of identical phase.
  • Each of the row drive lines is provided with an alternating current voltage equal in magnitude to the voltage provided to the column drive lines, but having its phase displaced by 21r/3 radians.
  • the alternating current voltage provided to the column and row drive lines associated with that device is shifted in phase with respect to either of the voltages driving the other column or row drive lines by an amount equal to 21'r/3 radians.
  • the effect of these driving voltages is to provide, at the selected device, a zero voltage difference between the column and row drive lines since these lines have voltages of equal amplitude and phase.
  • the voltage difference at devices in the matrix, not associated with the row or column drive lines whose signal has been shifted in phase remains unchanged.
  • the phase of the voltage difference provided to nonselected devices associated with either the row or column drive lines whose phase has been shifted, changes, but the amplitude of the voltage difference provided to such devices is unchanging. As a result, only the selected device has its voltage difference set to zero without affecting the voltage difference provided to any of the other devices in the matrix.
  • the voltage responsive devices comprise liquid crystals and, in particular, nematic liquid crystals.
  • a suitable material for the nematic liquid crystal is disclosed in the aforementioned copending application of D. C. Green and W. R. Young, Ser. No. 299,991. This material has an index of refraction for any direction which varies and is related to the direction of the optic axis. Furthermore, the direction of the optic axis can be controlled by application of an electric field. The material also exhibits a dielectric anisotropy which changes sign as the frequency of the electric field is varied.
  • a further alternating current voltage of higher frequency is also applied to the matrix.
  • the nematic liquid crystal material exhibits a negative dielectric anisotropy atthe frequency of the further alternating current voltage.
  • the column drive lines are not normally provided with this further driving voltage and all the row drive lines are normally provided with this further driving voltage of the equal amplitude and phase.
  • the column drive line associated with that device is provided with the further alternating current voltage with an amplitude twice that provided to the row drive lines, and at the same phase.
  • the row drive line associated with the selecteddevice is provided with the further alternating current voltage at the same amplitude as that provided to all the other rows, but whose phase is displaced 11' radians.
  • the selected device will have a voltage difference, at the higher frequency, three times that existing at any other selected device.
  • the effect of this further driving voltage, in addition to the first driving voltage, is to further increase the decay time (Y and decrease the rise time (Y, of the'display. In this manner, a still larger matrix can be driven with multiplexed driving signals.
  • FIG. 1a illustrates a plan view of a nematic liquid crystal matrix comprising an optical display
  • FIG. 1b is a cross section of FIG. 1a taken on lines lb-lb;
  • FIG. 2 is a representation of one element of the matrix with associated light polarizers
  • FIG. 3 is a representation of the variation of the dielectric anisotropy of the nematic liquid crystal with frequency
  • FIG. 4 is a diagram in voltage space illustrating the operating points of the nematic liquid crystal
  • FIGS. 5a through 5d illustrate voltages applied to column and row drive lines and resulting voltage differences at each device in a matrix of devices
  • FIGS. 6a, through 6d illustrate the voltages applied to a matrix of voltage responsive devices and the resulting voltage differences
  • FIG. 7 illustrates the pattern resulting from the application of such voltages
  • FIG. 8 shows a suitable column drive generator
  • FIG. 9 shows a suitable row drive generator
  • FIGS. 10a andlOb show suitable column and row drivers.
  • FIG. 1a illustrates a matrix of voltage responsive devices in accordance with one preferred embodiment of the present invention.
  • a plurality of orthogonal transparent electrodes 14 and 16 are provided.
  • Column electrodes 16 overlie and are perpendicular to row electrodes 14.
  • FIG. 1b illustrates a cross section of the matrix illustrated in FIG. 1a taken on lines lblb.
  • polarizers and 12 are also illustrated.
  • the nematic liquid crystal material 18 is illustrated as lying between the orthogonal electrodes 16 and 14.
  • the polarizers l0 and 12 are parallel to one another and one of the polarizers has its polarization axis rotated 90 with respect to the axis of the other polarizer.
  • the surfaces of the electrodes 14 and 16 which are in contact with the nematic liquid crystal 18 are treated such that the molecules of the liquid crystal, and therefore the optic axis of the material, lie parallel to the surface of the electrodes in a preferred direction.
  • the preferred direction at the electrodes 16 is rotated 90 with respect to the preferred direction at the electrodes14.
  • the optic axis of the nematic liquid crystal 18 willbe parallel to the electrodes 14in the region adjacent the electrodes 14, and will be parallel to the electrodes 16 adjacent the region of electrodes 16. Since these preferred directions are rotated 90 one with respect to the other, the optic axis of the nematic liquid crystal 18 rotates 90 from the region at electrodes 14 to the region at electrodes 16. As a result the optic axis twists between the two electrodes.
  • FIG. 2 illustrates one element of the matrix illustrated in FIG. 1a with the electrodes 14 and 16 enclosing the nematic, liquid crystal 18 in a flat-film configuration. Adjacent each of the electrodes 14 and 16 are polarizers 10 and 12. In the absence of an electric field, the optic axis of the nematic liquid crystal 18 rotates 90 from the region adjacent electrode ,16 to the region adjacent electrode 14. Therefore, with crossed polarizers l0 and 12, as illustrated in FIG. 2, the combination of polarizers 10 and 12, transparent electrodes 16 and 14, and nematic liquid crystal 18, will be light transmissive.
  • FIG. 3 illustratesthe relationship of the dielectric anisotropy of the'-liquid crystal material with respect to frequency and also illustrates the variation in e and L As shown in FIG. 3,6" at low frequencies, is
  • phase boundaries define two regions, the first, denoted IIII, in which the molecules of the nematic liquid material are parallel with the electric field, and the second, denoted I, where the molecules remain perpendicular to the applied electric field.
  • crossed polarizers such as that illustrated in FIG. 2, of course, the twisted state (I) will be light transmissive and the parallel state (IIII) will be light extinguishing. It is within the scope of the present invention to employ parallel polarizers such that the parallel state (IIII) is light transmitting and the twisted state (I) is light extinguishing.
  • the first significant factor is the time (Y taken by the elemental portion of the nematic liquid crystal to respond to the application of a signal.
  • the second significant factor is the decay time (Y,,,), the time taken by an elemental portion of the nematic liquid crystal material to return from an abnormal to its normal state.
  • the normal state of an element in a matrix conveys no information whereas the abnormal state conveys the information.
  • the abnormal state conveys the information.
  • state B would be the off or normal state and state A would be the on or abnormal state.
  • the cell could be in statelC (FIG. 4) as the normal state and it could, at times, beswitched to state D (FIG. 4) for purposes of displaying information.
  • state combinations represent preferred embodiments of the present invention taken with the crossed polarizers as illustrated in FIG. 2.
  • the coordinates of state C (V V and D(O, 3V correspond to the off and on states respectively. It can be shown that the characteristic time for the response of the liquid crystal which is initially at C to a voltage pulse driving it to state D is
  • y is a viscosity
  • L is the thickness of the cell
  • V is the critical voltage, which is defined as the low frequency voltage required to overcome surface forces in driving the cell from the twisted state to the parallel state in the absence of a high frequency electric field.
  • the characteristic response time of the liquid is The ratio of these times, that is the ratio of Y /Y, is a measure of the extent to which signals driving the matrix can be multiplexed and In order to maximize this ratio it is desirable to operate as close to the transition region as feasible (for the state C) and with as large a high frequency voltage as possible.
  • state C V V lies close to the transition region and state D (0, 3V has a high frequency voltage three times that of state C and a zero low frequency voltage.
  • the function to be performed by the information writing equipment is to selectively change the state of a selected element from state C in which it is light extinguishing to state D in which it is light transmissive for those portions of the display which are to be illuminated.
  • the high frequency drive will be of the form KV sin (W NH) where N equals zero or I and K l or 2, or O.
  • N equals zero or I and K l or 2, or O.
  • FIG. 7 illustrates a three by three matrix in which one element in each row is illuminated. Of course, those with ordinary skill in the art will understand that more than one element in each row may be illuminated and in some rows no elements need be illuminated.
  • Each of the elements in the matrix, 21 through 29, is associated with one row and one column conductor or drive line.
  • the voltage applied across each element of the matrix is the difference between the voltage applied on the column conductor associated with the element and the voltage applied on the row conductor associated with the element.
  • the high frequency voltage should be V and that the high frequency voltage on illuminated elements 22, 26, and 28 should be at some point in the writing cycle 3V The manner in which this is effected will now be explained with reference to FIGS. 6a through 6d.
  • FIG. 6a illustrates the exemplary matrix in the condition before writing information therein. Since each of the elements in the matrix is to be light extinguishing it will be in state C (FIG. 4) with a high frequency voltage difference of V To effect this, each of the columns is driven with a zero voltage of frequency f (K The first row, that is, the row comprising matrix elements 21 through 23 has applied to it a voltage with amplitude V with a zero relative phase shift (K 1, N
  • each of the elements 21 through 23 will have a voltage of magnitude V with a relative phase angle ofrr radians.
  • each of the other rows in the matrix has the same voltage applied to it and therefore each of the other elements in the matrix has the same resulting potential difference across it.
  • FIG. 6a illustrates that each matrix element has the numerals V /1r therein indicating a voltage magnitude of V at a relative phase angle of 1r radians.
  • FIG. 6b illustrates the state of the matrix upon writing information in the first row.
  • the column drive lines have voltages of zero, 2V and zero at a relative phase angle of zero, zero, and zero, respectively.
  • the first row drive line is driven with a voltage at a magnitude of V with a relative phase angle of 11' radians (N I).
  • matrix element 21 has a potential difference of magnitude V and a relative phase angle of zero.
  • Matrix element 22, however, has a resulting potential difference of 3V at a zero phase angle.
  • Matrix element 23 has the same potential difference as matrix element 21.
  • the other two rows in the matrix are driven at a voltage of magnitude V at a zero relative phase angle.
  • matrix elements 24, 26, 27, and 29 have a potential difference across them of magnitude V at relative phase angle 1r radians.
  • the matrix elements 25 and 28 have the same magnitude potential difference but a zero relative phase angle. It will be seen that the high frequency component across matrix element 22 is three times the high frequency voltage across any other matrix element.
  • FIG. 6c illustrates the condition of the matrix when writing information in the second row.
  • the column drive line voltages applied to the matrix are zero, zero, and 2V at a relative phase angle of zero radians.
  • the row drive lines have applied to them respectively V at a zero phase angle, V H at a phase angle of 11 radians and V at a zero phase angle.
  • matrix elements 21, 22, 27 and 28 have a voltage difference of magnitude of V and a relative phase angle of w radians.
  • Matrix elements 23, 24, 25, and 29 have a voltage difference of V at a zero phase angle.
  • Matrix element 26 has a voltage difference magnitude 3V H at a zero phase angle.
  • FIG. 6d shows writing in the third row of the matrix.
  • the column drive lines have applied thereto, respectively, a zero voltage, a voltage of 2V at a zero relative phase angle, and zero voltage.
  • the row drive lines have applied to them voltages of V H at a zero phase angle, V at a zero phase angle, and V at a relative phase angle of 11' radians.
  • the resulting difference across matrix elements 21, 23, 24 and 26 is V at a relative phase angle of w radians.
  • the voltage difference across matrix elements 22, 25, 27 and 29 is V at a zero phase angle.
  • the voltage difference across matrix element 28 is 3V at a zero phase angle.
  • FIG. a illustrates the condition of the row and column drive lines'and the condition of each of the matrix elements in the state when no information is being written.
  • the voltages applied at each of the column drive lines are of a magnitude V with a relative phase angle of zero, that is, M O. V V VS.
  • the voltages applied to each of the row drive lines is of magnitude V and a relative phase angle of 2 1r/3, that is M 1.
  • the low frequency voltage difference applied to each of the matrix elements has a magnitude V with a relative phase angle of 'rr/6.
  • each of the matrix elements Since the voltage difference applied to each of the matrix elements is the difference between the voltage on the column drive line and the row drive line, constructing a vector addition of V V? at an angle of zero with the vector V,/ V?) at an angle of -2 'rr/3 results in a vector of magnitude V at an angle 1r/6.
  • each of the matrix elements has a-low frequency voltage applied thereto of magnitude V
  • FIG. 5b illustrates the condition of the matrix when writing information in the first row.
  • the voltage magnitudes applied to each of the row and column drive lines are identical and are each equal to V V, VS.
  • the relative phase angle of the voltages applied to the column drive lines are zero, 2 'rr/3 and zero corresponding to M O, -l and 0.
  • the relative phase angles of the voltages applied to the row drive lines are 2 1r/3, 2 77/3 and 2 1r/3, respectively.
  • the voltage across matrix elements 21 and 23 has a magnitude of V and a relative phase angle of 1-r/6 radians.
  • the voltage applied to matrix elements 24, 26, 27, and 29 has a magnitude V at a phase angle of-1r/6.
  • the voltage applied to matrix elements and 28 has a magnitude V and a relative phase angle 'rr/2.
  • matrix element 22 has a zero low frequency voltage applied thereto.
  • matrix element 22 has a zero low frequency voltage applied thereto and a high frequeny voltage of 3V whereas each of the other elements in the matrix has a high frequency voltage applied thereto of V and a low frequency voltage applied thereto of V
  • matrix element 22 has been switched from state C to state D.
  • the voltages applied to the column drives are V at a zero relative phase angle, V at a zero relative phase angle, and V at a phase angle of-2 11/3 radians.
  • the voltages applied to the row drive lines are each V, and have phase angles of +2 17/3, -2 1r/3, and +2 1r/3, respectively.
  • the resulting voltage difference at elements 21, 22, 27, and 28 is a voltage with amplitude V at a relative phase angle of 7r/6.
  • the resulting voltage difference at matrix elements 24 and 25 has an amplitude of V with a relative phase angle of 1r/6.
  • the voltage difference at elements 23 and 29 has an amplitude of V, at a relative phase angle 1r/2.
  • the voltage difference at matrix element 26 is zero. Again, referring to FIG. 6c it will be seen that each of the elements in the matrix other than element 26 has the same high frequency voltage V and the same low frequency volt-' age V related to state C (FIG. 4). However, matrix element 26 has a zero low frequency voltage and a high frequency voltage of 3V corresponding to state D (FIG. 4). Thus, when the voltages of FIGS. 5c and 6c are simultaneously applied, matrix element 26 is switched from state C to state D.
  • FIG. 5d this illustrates writing in the third row.
  • the voltages applied to the matrix are illustrated as well as the resulting low frequency voltage across each of the matrix elements.
  • Matrix element 28 has a zero low frequency voltage across it. All the other matrix elements have a low frequency voltage of magnitude V Referring to FIG. 6d, it will be seen that the high frequency voltage across matrix element 28 is 3V H whereas the high frequency voltage across each of the other matrix elements is V Thus, with the voltages of FIGS. 6d and 5d applied to the matrix, all the elements in the matrix will be in state C except for matrix element 28 which will be in state D.
  • FIGS. 5a through 5d illustrates that the magnitude of the low frequency voltage driving all the columns and all the rows remains unchanging and furthermore that all the columns are normally driven with a voltage of zero relative phase angle. Likewise, all the rows are normally driven with a relative phase angle of +2 7r/3.I-Iowever, when it is desired to select a particular device, the relative phase angle of the voltages on the row and column drive lines associated with that device are shifted to a relative phase angle of 2 1r/3.
  • the absolute phase shift values are a matter of choice; what is significant is the relative phase shift between the unselected columns and unselected rows and between the selected columns and rows.
  • the voltage patterns shown in any of FIGS. 5a-6a; 5b-6b, 5c-6c and 5c-6d must be maintained for a sufficient period of time for the nematic liquid crystal material to respond thereto. This time has been defined as Y above. Furthermore, in order for the pattern to remain apparently stationary to a viewer, the time elapsed between applying the voltage patterns shown in FIGS. 5b-6b for instance, and the time the same pattern is repeated must be less than the decay time (Y,,,) for the nematic liquid crystal material which has also been defined above.
  • the foregoing apparatus has been operated with the material disclosed in the aforementioned Green et al application with a cell /2 mil in thickness.
  • V 3 volts
  • the transition region, shown as shaded in FIG. 4 has a width of approximately 2 volts.
  • the low frequency was chosen as hertz and the high frequency was chosen as 2 kilohertz with V equal to 20 volts and V equal to 27 volts (RMS).
  • the cycle time used was I second with 25 millisecond writing pulses.
  • FIGS. 6a through 6d illustrate that there are three high frequency voltages that are required to operate the matrix, i.e., a voltage of 2V a voltage of V at the same phase as the voltage 2V and a third voltage V shifted by 1r radians with respect to the other two high frequency voltages.
  • FIG. 8 illustrates an apparatus which may be used to generate these voltages.
  • a high frequency voltage generator 31 of frequency f feeds a push-pull amplifier 32.
  • One output of push-pull amplifier 32 is coupled to terminal 33 where the voltage 2V is available.
  • a voltage divider comprising resistors 36 and 37 of equal magnitude, is serially connected between ground and terminal 33.
  • resistors 36 and 37 i.e., terminal 34
  • a voltage V at the same phase angle as the voltage 2V
  • the other output from push-pull amplifier 32 is connected to a resistor 39 which is connected to resistor 38 which, in turn, is grounded.
  • Resistors 39 and 38 are of equal magnitude.
  • a terminal, 35, at the junction of resistors 39 and 38 provides the voltage V which is shifted by 11 radians from the other high frequency voltages available at taps 33 and 34.
  • FIG. a through FIG. 5d illustrates that there are three low frequency voltages required.
  • a voltage generator 41 (FIG. 9) operates at a frequency f
  • the output of generator 41 is coupled to terminal 42 to provide the voltage V.
  • a phase shifter 45 is connected to the output of voltage generator 41.
  • the output of phase shifter 45 is connected to terminal 43 to provide a voltage V shifted in phase with respect to the voltage at terminal 42 by 2 1r/3 radians.
  • the voltage V/2 1r/ 3 is available at terminal 44 from a phase shifter 46.
  • Alternatively a three-phase source may be used.
  • FIGS. 5a through 5d illustrate that the column drive lines utilize only two low frequency voltages, that is, they require V'/0 and V'/2 1r/3.
  • FIG. a illustrates a typical column driver which has two inputs 51 and 52. Input 51 is the low frequency input and it is connected to switching contact 53 which is selectively positionable in two positions. In a first position it connects to contact 42 to provide the voltage V'/0. In its other position it contacts terminal 44 to provide the voltage V'/2 17/3. Input 52 to column driver 50 is the high frequency input and it is likewise connected to a switching contact 54 which is capable of assuming two different positions.
  • FIGS. 6a through 6d illustrate that the column drive lines need noly these two voltages.
  • FIG. 10b illustrates a typical row driver 60.
  • This driver 60 also has two inputs 61 and 62.
  • the low frequency input 61 is connected to a switching contact 63 capable of assuming two positions. In a first position it makes contact with terminal 43 to provide the voltage V/2 1r/3. In its second position, it contacts terminal 44 to provide the voltage V/2 7r/3.
  • the high frequency input to row driver 60 is via input 62 which is connected to a switching contact 64.
  • Contact 64 is capable of assuming two positions. In a first position it contacts terminal 34 to provide the voltage V /O. In its second position, it. contacts terminal 35 to provide the voltage VH/7T-
  • the switching contacts 53, 54, 63, and 64 may be manually operable.
  • these switching contacts represent electronic switching circuits which can respond much more quickly than can the manual switches to make the different connections required.
  • the particular form of electronic switching arrangement forms no part of the present invention as there are many varieties in the prior art which can be employed for this function.
  • the light extinguishing the light transmissive states of the material are taken at state B and A. respectively.
  • V the high frequency voltage
  • the abscissa at state B may be less than V
  • the low frequency voltage must be correspondingly reduced.
  • FIGS. 5a through 5d the ratio of the decay time to the rise time, Y /Y, is a measure of the size of a matrix which can be written with an apparently stationary pattern.
  • the nematic liquid crystal material can be driven between the states EF (FIG. 4).
  • states EF FOG. 4
  • the polarizers 16 and 18 in a parallel configuration such that state F would correspond to a light extinguishing state and state E would correspond to a light transmitting state.
  • state combination A-E could also be used. Since the low frequency voltage of state B and state E may be varied (so long as it is above V this combination is similar to the BA combination with the exception that the off and on states have been changed by making the polarizers parallel instead of orthogonal.
  • Another state combination that could be used with parallel polarizers is F-E. In this case the phase shift arrangement of FIGS. 5a-5d is used to control the matrix.
  • Apparatus for selectively controlling a matrix of voltage responsive devices in which each device is associated with and driven by a different pair of a plurality of row and column drive lines, each said device responding to a difference in voltage between its associated column and row drive line, the improvement comprising drive means for normally providing a voltage to each said device equal in amplitude to a voltage supplied to each other device and for selectively reducing the voltage at a selected device to zero without varying the voltage amplitude supplied to each other device, said drive means including,
  • switching means normally connecting one of said voltages to said column drive lines, and another of said voltages to said row drive lines and for selectively connecting said third voltage only to a row and column drive line associated with said selected device
  • each of said devices comprises a fiat-film nematic liquid crystal cell, with a positive dielectric anistropy at the frequency of said voltage.
  • the apparatus of claim 2 which further includes a first and second light polarizing means, said cell being located between said first and second light polarizing means.
  • said nematic liquid crystal having a negative dielectric anistropy at said second frequency.
  • said means for coupling normally provides no voltage at said second frequency to said column drive lines and normally provides a second voltage of equal magnitude and phase at said second frequency to each of said row drive lines and, at said times, provides to a column drive line associated with said selected device of voltage at said second frequency greater in amplitude than said second voltage at the same phase as said second voltage, and provides to a row drive line associated with said selected device a voltage at said second frequency equal in amplitude to said second voltage but displaced 1r radians relative to said second voltage.
  • each of said devices comprises a flat-film nematic liquid crystal cell with a negative dielectric anistropy at the frequency of said voltage.
  • the apparatus of claim 10 which further includes a first and second light polarizing means, said cell being located between said first and second light polarizing means.
  • the apparatus of claim 12 which further includes means for coupling voltages at a second frequency to said drive lines,
  • said nematic liquid crystal being a positive dielectric anistorpy at said voltages of second frequency.
  • said means for coupling normally provides no voltage at said second frequency to said column drive lines and normally provides a second voltage of equal magnitude and phase at each of said row drive lines and, at times, provides to a column drive line associated with said selected device a voltage at said second frequency greater in amplitude than said second voltage, and at the same phase as said second voltage, and provides to a row drive line associated with said selected device a voltage at said second frequency equal in amplitude to said second voltage but displaced 1r radians relative to said second voltage.
  • each of said voltages has a different value of m selected from the group comprising l, 0, +1

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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)
  • Transforming Electric Information Into Light Information (AREA)
US477204A 1974-06-07 1974-06-07 Method and apparatus for selectively exciting a matrix of voltage responsive devices Expired - Lifetime US3895373A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US477204A US3895373A (en) 1974-06-07 1974-06-07 Method and apparatus for selectively exciting a matrix of voltage responsive devices
GB14279/75A GB1501268A (en) 1974-06-07 1975-04-08 Array of voltage responsive elements
FR7514032A FR2274098A1 (fr) 1974-06-07 1975-04-29 Procede et appareil pour exciter selectivement une matrice de dispositifs sensibles a la tension
DE19752521101 DE2521101A1 (de) 1974-06-07 1975-05-13 Verfahren und schaltung zur wahlweisen erregung einer matrix aus spannungsempfindlichen elementen, insbesondere fluessigkristallen
JP50056221A JPS51835A (de) 1974-06-07 1975-05-14

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US477204A US3895373A (en) 1974-06-07 1974-06-07 Method and apparatus for selectively exciting a matrix of voltage responsive devices

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JP (1) JPS51835A (de)
DE (1) DE2521101A1 (de)
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GB (1) GB1501268A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2294501A1 (fr) * 1974-12-11 1976-07-09 Raynes Edward Procede d'adressage de dispositifs d'affichage a cristaux liquides
US4028692A (en) * 1975-09-15 1977-06-07 Bell Telephone Laboratories, Incorporated Liquid crystal display device
US4109241A (en) * 1974-12-11 1978-08-22 The Secretary Of State For Defence In Her Britannic Majesty's Government Of Great Britain And Northern Ireland Liquid crystal displays
FR2382722A1 (fr) * 1977-03-02 1978-09-29 Seikosha Kk Procede de commande pour un dispositif d'affichage a cristal liquide
EP0014100A2 (de) * 1979-01-26 1980-08-06 National Research Development Corporation Analoge Anzeigevorrichtung

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19549408A1 (de) * 1995-05-24 1997-01-09 Hoechst Ag Mit hochsubstituierter Stärke aminierte Celluloseregeneratfasern

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3043988A (en) * 1955-04-27 1962-07-10 Hurvitz Hyman Two-dimensional displays
US3409876A (en) * 1965-05-28 1968-11-05 Navy Usa Electroluminescent grid control by voltage variable capacitors
US3466501A (en) * 1966-09-08 1969-09-09 Gordon W Young Self-illuminating devices and systems
US3654606A (en) * 1969-11-06 1972-04-04 Rca Corp Alternating voltage excitation of liquid crystal display matrix
US3740717A (en) * 1971-12-16 1973-06-19 Rca Corp Liquid crystal display
US3835463A (en) * 1971-07-29 1974-09-10 Matsushita Electric Ind Co Ltd Liquid crystal x{14 y matrix display device
US3839715A (en) * 1971-12-30 1974-10-01 Fujitsu Ltd Display system for a plasma display device

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3043988A (en) * 1955-04-27 1962-07-10 Hurvitz Hyman Two-dimensional displays
US3409876A (en) * 1965-05-28 1968-11-05 Navy Usa Electroluminescent grid control by voltage variable capacitors
US3466501A (en) * 1966-09-08 1969-09-09 Gordon W Young Self-illuminating devices and systems
US3654606A (en) * 1969-11-06 1972-04-04 Rca Corp Alternating voltage excitation of liquid crystal display matrix
US3835463A (en) * 1971-07-29 1974-09-10 Matsushita Electric Ind Co Ltd Liquid crystal x{14 y matrix display device
US3740717A (en) * 1971-12-16 1973-06-19 Rca Corp Liquid crystal display
US3839715A (en) * 1971-12-30 1974-10-01 Fujitsu Ltd Display system for a plasma display device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2294501A1 (fr) * 1974-12-11 1976-07-09 Raynes Edward Procede d'adressage de dispositifs d'affichage a cristaux liquides
US4109241A (en) * 1974-12-11 1978-08-22 The Secretary Of State For Defence In Her Britannic Majesty's Government Of Great Britain And Northern Ireland Liquid crystal displays
US4028692A (en) * 1975-09-15 1977-06-07 Bell Telephone Laboratories, Incorporated Liquid crystal display device
FR2382722A1 (fr) * 1977-03-02 1978-09-29 Seikosha Kk Procede de commande pour un dispositif d'affichage a cristal liquide
EP0014100A2 (de) * 1979-01-26 1980-08-06 National Research Development Corporation Analoge Anzeigevorrichtung
EP0014100A3 (en) * 1979-01-26 1981-11-04 National Research Development Corporation Analogue displays

Also Published As

Publication number Publication date
FR2274098A1 (fr) 1976-01-02
DE2521101A1 (de) 1976-01-02
JPS51835A (de) 1976-01-07
GB1501268A (en) 1978-02-15

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