Driving method and apparatus for liquid crystal display device

Claim 2

A driving method for a liquid crystal display device having a liquid crystal layer exhibiting a cholesteric phase and switchable between a planar state and a focal conic state according to the magnitude of an applied voltage, said method comprising the steps of: in a first period, simultaneously applying a voltage to a plurality of pixels arranged in a matrix array, thereby resetting the plurality of pixels to the focal conic state; and in a second period after the first period, sequentially applying voltages respectively comprising pulse components having pulse widths which respectively correspond to image data of the pixels, thereby updating the display contents of the pixels.

Claim 3

A driving method for a liquid crystal display device according to claim 1 , wherein said liquid crystal display device has a memory characteristic such that when no voltage is applied, the liquid crystal display is stable in a display state, said method further comprising the step of: in a third period after the second period, retaining the display state by utilizing the memory characteristic of the liquid crystal.

Claim 4

A driving method for a liquid crystal display device according to claim 1 , wherein the matrix of pixels are formed by an array of scanning electrodes driven by a scan driving section and an array of signal electrodes driven by a signal driving section, the method further comprising the steps of: in the second period, applying a scan select signal to a given scanning electrode while, at the same time, applying a scan deselect signal to the other scanning electrodes, whereby selecting the given scanning electrode as a scan select electrode and the other scanning electrodes as scan deselect electrodes, and applying data signals to the signal electrodes in synchronism with the scan select signal.

Claim 5

A driving method for a liquid crystal display device according to claim 3 , further comprising the steps of: forming a select signal from a difference between the scan select signal and each data signal, which is applied to the liquid crystal forming each pixel on the scan select electrode to select its display state; and forming a deselect signal from a difference between the scan deselect signal and each data signal, which is applied to the liquid crystal forming each pixel on each scan deselect electrode.

Claim 6

A driving method for a liquid crystal display device according to claim 1 , wherein in said first period, said method further comprising the step of: applying a first voltage that is equal to or larger than a threshold voltage for setting the liquid crystal exhibiting the cholesteric phase into a homeotropic state before the liquid crystal is reset to the focal conic state.

Claim 7

A driving method for a liquid crystal display device according to claim 5 , further comprising the step of: applying a second voltage after the first voltage to cause the liquid crystal in the homeotropic state to change to the planar state.

Claim 8

A driving method for a liquid crystal display device according to claim 3 , further comprising the step of: varying the pulse width of each data signal, thereby varying the ratio of the application period of a voltage Vp, which is necessary to select the planar state, to the application period of a voltage Vf, which is necessary to select the focal conic state, in a select period during which the scan select signal is applied.

Claim 9

A driving method for a liquid crystal display device according to claim 7 , wherein in the second period, the method further comprising the step of: applying a voltage whose absolute value is (Vp−Vt)/2 to the liquid crystal during a deselect period during which the scan deselect signal is applied.

Claim 10

A driving method for a liquid crystal display device according to claim 3 , wherein in the second period, the method further comprising the step of: providing a quiescent period during which no voltage is applied to the liquid crystal between each of the data signals being applied successively.

Claim 11

A driving method for a liquid crystal display device according to claim 4 , comprising a data converting section or converting image data for each scanning electrode, wherein in the second period, the method further comprising the step of: varying the voltage of the select signal or the ratio of the application period of a voltage Vp, which is necessary to select the planar state, to the application period of a voltage Vf, which is necessary to select the focal conic state, for each scanning electrode by the image data conversion through the data converting section even when selecting the same display state.

Claim 12

A driving method for a liquid crystal display device according to claim 7 , wherein in the second period, the method further comprising the step of: varying the pulse width of the select period for each scanning electrode.

Claim 13

A driving method for a liquid crystal display device according to claim 1 , further comprising the step of: providing an additional period in which no voltage is applied to the liquid crystal between the first period and the second period.

Claim 14

A driving method for a liquid crystal display device according to claim 2 , further comprising the step of: providing an additional period during which voltages are not applied to all the signal electrodes but a voltage of a waveform different for each scanning electrode is applied between the second period and the third period.

Claim 15

A driving method for a liquid crystal display device according to claim 3 , wherein said liquid crystal display device comprises first and second image memories for respectively storing all of current display data and all of new display data, and first and second line memories for sequentially reading data per scanning electrode from the first and second image memories, and for storing the read out data, said method further comprising the steps of: comparing new display data with the corresponding current data on a scanning electrode by scanning electrode basis; storing an address of a scanning electrode where the data compared in the comparing step do not match; and selectively driving the liquid crystal display device at the address stored in the address storing step.

Claim 16

A driving method for a liquid crystal display device having a matrix of pixels formed by an array of scanning electrodes driven by a scan driving section and an array of signal electrodes driven by a signal driving section, with a liquid crystal exhibiting a cholesteric phase being placed in operative association with the scanning electrodes and the signal electrodes, said liquid crystal display device having a memory characteristic such that when no voltage is applied, the liquid crystal display device is stable in one of the display states consisting of a planar state, a focal conic state, and [an] at least one intermediate state therebetween, wherein the liquid crystal display device is driven by applying voltages to the scanning electrodes and the signal electrodes from the scan driving section and the signal driving section, respectively, and by applying resulting difference voltages to the liquid crystal, said method comprising the steps of: in a first period, simultaneously applying a scan reset signal to all the scanning electrodes and a data reset signal to all the signal electrodes, thereby applying a reset signal, formed from a difference between the scan reset signal and the data reset signal, to the liquid crystal in every pixel and thus resetting all the pixels to the focal conic state; in a second period after the first period, applying a scan deselect signal to the other electrodes, and applying data signals, which respectively have pulse widths corresponding to image data, to the signal electrodes in synchronism with the scan select signal, thereby performing an update operation wherein a select signal, formed from a difference between the scan select signal and each data signal, is applied to the liquid crystal forming each pixel on the scan select electrode to select its display state, and a deselect signal, formed from a difference between the scan deselect signal and each data signal, is applied to the liquid crystal forming each pixel on each scan deselect electrode, said update operation being repeated by selecting the scanning electrodes one after another as the scan select electrode, thereby updating the display state of the liquid crystal forming all the pixels; and in a third period after the second period, applying a display retaining signal to all the scanning electrodes and signal electrodes so that the display state is retained by utilizing the memory characteristic of the liquid crystal.

Claim 17

A driving method for a liquid crystal display device having a matrix of pixels formed by an array of scanning electrodes driven by a scan driving section and an array of signal electrodes driven by a signal driving section, with a liquid crystal exhibiting a cholesteric phase being placed in operative association with the scanning electrodes and the signal electrodes, said liquid crystal display device having a memory characteristic such that when no voltage is applied, the liquid crystal display device is stable in one of the display states consisting of a planar state, a focal conic state, and [an] at least one intermediate state therebetween, wherein the liquid crystal display device is driven by applying voltages to the scanning electrodes and the signal electrodes from the scan driving section and the signal driving section, respectively, and by applying resulting difference voltages to the liquid crystal, said method comprising the steps of: in a first period, simultaneously applying a scan reset signal to all the scanning electrodes and a data reset signal to all the signal electrodes, thereby applying a reset signal, formed from a difference between the scan reset signal and the data reset signal, to the liquid crystal in every pixel and thus resetting all the pixels to the focal conic state; in a second period after the first period, applying a scan deselect signal to the other electrodes, and applying data signals, which respectively have pulse widths corresponding to image data, to the signal electrodes in synchronism with the scan select signal, thereby performing an update operation wherein a select signal, formed from a difference between the scan select signal and each data signal, is applied to the liquid crystal forming each pixel on the scan select electrode to select its display state, and a deselect signal, formed from a difference between the scan deselect signal and each data signal, is applied to the liquid crystal forming each pixel on each scan deselect electrode, said update operation being repeated by selecting the scanning electrodes one after another as the scan select electrode, thereby updating the display state of the liquid crystal forming all the pixels; and in a third period after the second period, applying a display retaining signal to all the scanning electrodes and signal electrodes so that the display state is retained by utilizing the memory characteristic of the liquid crystal.

Claim 18

A driving apparatus for a liquid crystal display device having a liquid crystal layer exhibiting a cholesteric phase and switchable between a planar state and a focal conic state according to the magnitude of an applied voltage, a plurality of scanning electrodes, and a plurality of signal electrodes, said driving apparatus comprising: drive circuitry for driving said scanning and signal electrodes, including a scan driving section for driving said scanning electrodes, and a signal driving section for driving said signal electrodes; wherein said drive circuitry is configured to, in a first period, simultaneously apply a voltage to a plurality of pixels arranged in a matrix array, thereby resetting the plurality of pixels to the focal conic state; and in a second period after the first period, sequentially apply voltages respectively comprising pulse components having pulse widths which respectively correspond to image data of the pixels, thereby updating the display contents of the pixels.

Claim 19

A driving apparatus for a liquid crystal display device having a liquid crystal layer exhibiting a cholesteric phase and switchable between a planar state and a focal conic state according to the magnitude of an applied voltage, a plurality of scanning electrodes, and a plurality of signal electrodes, said driving apparatus comprising: drive circuitry for driving said scanning and signal electrodes, including a scan driving section for driving said scanning electrodes, and a signal driving section for driving said signal electrodes; wherein said drive circuitry is configured to, in a first period, simultaneously apply a voltage to a plurality of pixels arranged in a matrix array, thereby resetting the plurality of pixels to the focal conic state; and in a second period after the first period, sequentially apply voltages respectively comprising pulse components having pulse widths which respectively correspond to image data of the pixels, thereby updating the display contents of the pixels.

Claim 20

A driving apparatus for a liquid crystal display device according to claim 16 , wherein said liquid crystal display device has a memory characteristic such that when no voltage is applied, the liquid crystal display is stable in a display state, wherein said display circuitry is configured to, in a third period after the second period, retain the display state by utilizing the memory characteristic of the liquid crystal.

Claim 21

A driving apparatus for a liquid crystal display device according to claim 16 , wherein said display circuitry is configured to: in the second period, select a given scanning electrode as a scan select electrode and the other scanning electrodes as scan deselect electrodes, and apply a scan select signal to the scan select electrode while, at the same time, applying a scan deselect signal to the scan deselect electrodes; and apply data signals to the signal electrodes in synchronism with the scan select signal.

Claim 22

A driving apparatus for a liquid crystal display device according to claim 18 , wherein said drive circuitry is configured to: form a select signal from a difference between the scan select signal and each data signal, which is applied to the liquid crystal forming each pixel on the scan select electrode to select its display state; and form a deselect signal from a difference between the scan deselect signal and each data signal, which is applied to the liquid crystal forming each pixel on each scan deselect electrode.

Claim 23

A driving apparatus for a liquid crystal display device according to claim 16 , wherein in said first period, said drive circuitry is configured to: apply a first voltage that is equal to or larger than a threshold voltage for setting the liquid crystal exhibiting the cholesteric phase into a homeotropic state before the liquid crystal is reset to the focal conic state.

Claim 24

A driving apparatus for a liquid crystal display device according to claim 20 , wherein said drive circuitry is configured to: apply a second voltage after the first voltage to cause the liquid crystal in the homeotropic state to change to the planar state.

Claim 25

A driving apparatus for a liquid crystal display device according to claim 18 , wherein said drive circuitry is configured to vary the pulse width of each data signal, thereby varying the ratio of the application period of a voltage Vp, which is necessary to select the planar state, to the application period of a voltage Vf, which is necessary to select the focal conic state, in a select period during which the scan select signal is applied.

Claim 26

A driving apparatus for a liquid crystal display device according to claim 22 , wherein in the second period, the drive circuitry is configured to: apply a voltage whose absolute value is (Vp−Vf)/2 to the liquid crystal during a deselect period during which the scan deselect signal is applied.

Claim 27

A driving apparatus for a liquid crystal display device according to claim 18 , wherein in the second period, the drive circuitry is configured to: provide a quiescent period during which no voltage is applied to the liquid crystal between each of the data signals being applied successively.

Claim 28

A driving apparatus for a liquid crystal display device according to claim 19 , further comprising a data converter for converting image data for each scanning electrode, wherein in the second period, the drive circuitry is configured to: vary the voltage of the select signal or the ratio of the application period of a voltage Vp, which is necessary to select the planar state, to the application period of a voltage Vf, which is necessary to select the focal conic state, for each scanning electrode by the image data conversion through the data converter even when selecting the same display state.

Claim 29

A driving apparatus for a liquid crystal display device according to claim 22 , wherein in the second period, the drive circuitry is configured to: vary the pulse width of the select period for each scanning electrode.

Claim 30

A driving apparatus for a liquid crystal display device according to claim 16 , wherein said drive circuitry is configured to: provide an additional period in which no voltage is applied to the liquid crystal between the first period and the second period.

Claim 31

A driving apparatus for a liquid crystal display device according to claim 17 , wherein said drive circuitry is configured to: provide an additional period during which voltages are not applied to all the signal electrodes but a voltage of a waveform different for each scanning electrode is applied between the second period and the third period.

Claim 32

A driving apparatus for a liquid crystal display device according to claim 18 , further comprising: first and second image memories for storing all of current display data and all of new display data, respectively; a device for sequentially reading data per scanning electrode from the first and second image memories, and for storing the readout data; a comparing device for comparing new display data with the corresponding current data on a scanning electrode by scanning electrode basis; a storage device for storing an address of a scanning electrode where the data compared in the comparing device do not match; and wherein the driving circuitry selectively drives the liquid crystal display device at the address stored in the address storage device.

Claim 33

A driving method for a liquid crystal display device having plural liquid crystal layers, each exhibiting a cholesteric phase and each switchable between a planar state and a focal conic state according to the magnitude of an applied voltage, said method comprising the steps of: specifying a desired color; selecting voltages to apply to said liquid crystal display layers based on said desired color, wherein the voltages are selected from: (a) a highest voltage corresponding to a planar state; (b) a lowest voltage corresponding to a focal conic state; and (c) at least one intermediate voltage which is selected between the highest voltage and the lowest voltage; and applying said selected voltages to respective layers.

Claim 34

A driving method for a liquid crystal display device having plural liquid crystal layers, each exhibiting a cholesteric phase and each switchable between a planar state and a focal conic state according to the magnitude of an applied voltage, said method comprising the steps of: specifying a desired color; selecting voltages to apply to said liquid crystal display layers based on said desired color, wherein the voltages are selected from: (a) a highest voltage corresponding to a planar state; (b) a lowest voltage corresponding to a focal conic state; and (c) at least one intermediate voltage which is selected between the highest voltage and the lowest voltage; and applying said selected voltages to respective layers.

Claim 37

A driving method for a liquid crystal display device having a liquid crystal layer exhibiting a cholesteric phase and a switchable between a planar state and a focal conic state according to the magnitude of an applied voltage, said method comprising the steps of: in a first period, simultaneously applying a first voltage to a plurality of pixels arranged in a matrix array, thereby causing the plurality of pixels to be in a homeotropic state; in a second period after the first period, simultaneously applying a second voltage to the plurality of pixels; in a third period after the second period, simultaneously applying a third voltage to the plurality of pixels, thereby causing the plurality of pixels to be in the focal conic state; and in a fourth period after the third period, sequentially applying voltages corresponding to image data to the pixels, thereby updating the display contents of the pixels, wherein the second voltage Is smaller than both the first and third voltages.

Claim 38

A driving method for a liquid crystal display device having a liquid crystal layer exhibiting a cholesteric phase and a switchable between a planar state and a focal conic state according to the magnitude of an applied voltage, said method comprising the steps of: in a first period, simultaneously applying a first voltage to a plurality of pixels arranged in a matrix array, thereby causing the plurality of pixels to be in a homeotropic state; in a second period after the first period, simultaneously applying a second voltage to the plurality of pixels; in a third period after the second period, simultaneously applying a third voltage to the plurality of pixels, thereby causing the plurality of pixels to be in the focal conic state; and in a fourth period after the third period, sequentially applying voltages corresponding to image data to the pixels, thereby updating the display contents of the pixels, wherein the second voltage Is smaller than both the first and third voltages.

Claim 39

A driving method for a liquid crystal display device according to claim 32 , wherein, in the second period, the plurality of pixels tends to set to the planar state.

Claim 40

A driving method for a liquid crystal display device according to claim 32 , wherein said liquid crystal display has a memory characteristic such that when no voltage is applied, the liquid crystal display is stable in a display state, said method comprising the step of: in a fifth period after the fourth period, retaining the display state by utilizing the memory characteristic of the liquid crystal.

Claim 41

A driving method for a liquid crystal display device according to claim 1 , wherein the focal conic state is a light-transmitting state for which liquid crystal in the focal conic state is substantially transparent.

Claim 42

A driving method for a liquid crystal display device according to claim 15 , wherein the focal conic state is a light-transmitting state for which liquid crystal in the focal conic state is substantially transparent.

Claim 43

A driving apparatus for a liquid crystal display device according to claim 16 , wherein the focal conic state is a light-transmitting state for which liquid crystal in the focal conic state is substantially transparent.

Claim 44

A driving method for a liquid crystal display device according to claim 30 , wherein the focal conic state is a light-transmitting state for which liquid crystal in the focal conic state is substantially transparent.

Claim 45

An apparatus for driving a liquid crystal display device according to claim 31 , wherein the focal conic state is a light-transmitting state for which liquid crystal in the focal conic state is substantially transparent.

Claim 46

A driving method for a liquid crystal display device according to claim 32 , wherein the focal conic state is a light-transmitting state for which liquid crystal in the focal conic state is substantially transparent.