Liquid crystal display device and its drive method

Abstract

A MVA type liquid crystal panel is slow in a response speed when a black state at a drive voltage about 1V is switched to a low brightness halftone state at the drive voltage about 2 to 3V. According to the present invention, in a liquid crystal display device for driving the MVA type liquid crystal panel, when a liquid crystal pixel at a pixel electrode is changed from a first transmittance to a second transmittance greater than the first transmittance, a drive voltage greater than a fist target drive voltage in correspondence with a second transmittance is applied to the pixel electrode in a first frame period of changing to the second transmittance, and the first target display voltage is applied from a second frame period. According to the present invention, even when either switching is performed from a black state to a low brightness halftone state, from the black state to a high brightness halftone state, for from the black state to a white state, a response time is shortened, and the switching can be performed without generating an overshoot.

1 . A liquid crystal display device, wherein a liquid crystal is provided between a pixel electrode and a counter electrode to which voltage is applied, and an alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, further comprising:
 a drive circuit which applies a drive voltage greater than a threshold voltage of the alignment of the liquid crystal to the pixel electrode when transmittance of a pixel is set to be a predetermined value, or less.   
   
   
       2 . The liquid crystal display device according to  claim 1 , further comprising:
 optical compensation structure for generating an optical characteristic reverse to the optical characteristic of the liquid crystal.   
   
   
       3 . A liquid crystal display device according to  claim 2 , wherein the optical compensation structure has an optical characteristic of canceling the optical characteristic generated in the liquid crystal when the drive voltage is applied to the pixel electrode. 
   
   
       4 . The liquid crystal display device according to  claim 2 , wherein the optical compensation structure is a retardar. 
   
   
       5 . The liquid crystal display device according to  claim 2 , wherein the optical compensation structure is provided by laminating the pixel electrodes. 
   
   
       6 . A method for driving a liquid crystal display device in which a liquid crystal is provided between a pixel electrode and a counter electrode to which voltage is applied, and an alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, wherein when the transmittance of the pixel is set to be a predetermined value or less, a drive voltage greater than a threshold value of the alignment of the liquid crystal is applied to the pixel electrode. 
   
   
       7 . A liquid crystal display device, including domain restriction structure for restricting so that a liquid crystal is provided between a pixel electrode and a counter electrode to which voltage is applied, and an alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, and further a direction that the alignment of the liquid crystal is inclined to set to be a plurality of parts in each pixel when a voltage smaller than the predetermined voltage is applied, further comprising:
 a drive circuit which in case where the pixel is changed from a first transmittance to a second transmittance greater than the first transmittance, when a frame period of the first transmittance is continued, applies to a drive voltage greater than a target drive voltage in correspondence with the second transmittance and greater than a drive voltage when the frame period of the first transmittance is not continued to the pixel electrode in a first period of changing to the second transmittance.   
   
   
       8 . The liquid crystal display device according to  claim 7 , wherein when the pixel is set to the first transmittance, the drive circuit applies a maximum drive voltage to the pixel electrode in the range that the first transmittance does not change. 
   
   
       9 . The liquid crystal display device according to  claim 7 , wherein when temperatures rise, the drive circuit compensates the temperatures so as to reduce the drive voltage to be applied to the pixel electrode in the first period. 
   
   
       10 . A method for driving a liquid crystal display device including domain restriction structure for restricting so that a liquid crystal is provided between a pixel electrode and a counter electrode to which voltage is applied, and an alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, and further a direction that the alignment of the liquid crystal is inclined is set to be a plurality of parts in each pixel when a voltage smaller than the predetermined voltage is applied,
 wherein when the pixel is set to a first transmittance in a continuous predetermined frame periods and is set to a second transmittance greater than the first transmittance in a first period thereafter, a drive voltage greater than a target drive voltage corresponding to the second transmittance and greater than a drive voltage when the frame period of the first transmittance is not continued is applied to the pixel electrode in the first period.   
   
   
       11 . A liquid crystal display device, comprising:
 a liquid crystal provided between a pixel electrode and a counter electrode to which a drive voltage is applied;   a domain restriction structure for restricting an alignment of the liquid crystal so that the alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, and further a direction that the alignment of the liquid crystal is inclined is set to be a plurality of parts in each pixel when a voltage smaller than the predetermined voltage is applied; and   a drive circuit in which, in case where the pixel is changed from a first transmittance to a second transmittance greater than the first transmittance, a maximum drive voltage is applied between the pixel electrode and the counter electrode in the range that the first transmittance does not change, while the pixel is set to the first transmittance.   
   
   
       12 . A method for driving a liquid crystal display device including a liquid crystal provided between a pixel electrode and a counter electrode to which a drive voltage is applied, and a domain restriction structure for restricting an alignment of the liquid crystal so that the alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, and further a direction that the alignment of the liquid crystal is inclined is set to be a plurality of parts in each pixel when a voltage smaller than the predetermined voltage is applied, the method comprising:
 in a case where the pixel is changed from a first transmittance to a second transmittance greater than the first transmittance, applying a maximum drive voltage between the pixel electrode and the counter electrode in the range that the first transmittance does not change, while the pixel is set to the first transmittance.   
   
   
       13 . A liquid crystal display device, comprising:
 a liquid crystal provided between a pixel electrode and a counter electrode to which a drive voltage is applied;   a domain restriction structure for restricting an alignment of the liquid crystal so that the alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, and further a direction that the alignment of the liquid crystal is inclined is set to be a plurality of parts in each pixel when a voltage smaller than the predetermined voltage is applied; and   a drive circuit in which, when the pixel is changed from a first transmittance to a second transmittance greater than the first transmittance, a voltage greater than a first target drive voltage corresponding to the second transmittance is applied between the pixel electrode and the counter electrode in a first period of changing to the second transmittance, and the first target display voltage is applied between the pixel electrode and the counter electrode in a second period after the first period,   wherein when temperatures rise, the drive circuit compensates the temperatures so as to reduce the drive voltage to be applied between the pixel electrode and the counter electrode in the first period.   
   
   
       14 . A method for driving a liquid crystal display device including a liquid crystal provided between a pixel electrode and a counter electrode to which a drive voltage is applied, and a domain restriction structure for restricting an alignment of the liquid crystal so that the alignment of the liquid crystal is substantially vertical when non-voltage is applied, substantially parallel when a predetermined voltage is applied, and inclined when a smaller voltage than the predetermined voltage is applied, and further a direction that the alignment of the liquid crystal is inclined is set to be a plurality of parts in each pixel when a voltage smaller than the predetermined voltage is applied, the method comprising:
 when the pixel is changed from a first transmittance to a second transmittance greater than the first transmittance, applying a voltage greater than a first target drive voltage corresponding to the second transmittance between the pixel electrode and the counter electrode in a first period of changing to the second transmittance, and applying the first target display voltage between the pixel electrode and the counter electrode in a second period after the first period,   wherein when temperatures rise, the drive voltage to be applied between the pixel electrode and the counter electrode in the first period is reduced.