OCB-mode liquid crystal display apparatus with initial transition of OCB liquid crystal
View Patent ↗There is provided an liquid crystal display apparatus configured to invert a pixel voltage and a common voltage on a frame to frame basis while setting a transition voltage Vt in such a manner that the polarity of the pixel voltage to be applied to a pixel electrode of each display pixel and the polarity of the common voltage to be applied to a common electrode of a common substrate are differentiated.
1. A liquid crystal display apparatus comprising:
an array substrate having a plurality of pixel electrodes in a matrix;
a common electrode opposing the pixel electrode;
a display panel having an OCB liquid crystal sandwiched between the pixel electrode and the common electrode; and
a drive circuit configured to apply a pixel voltage in a positive pixel voltage range, which ranges from a first reference voltage through a maximum applicable pixel voltage, and a negative pixel voltage range, which ranges from the first reference voltage through a minimum applicable pixel voltage, to the pixel electrode, and to alternately apply a positive common voltage and a negative common voltage, which are respectively larger and smaller than a second reference voltage by a predetermined amount, to the common electrode,
wherein the drive circuit applies the positive common voltage to the common electrode and applies, throughout each period of applying the positive common voltage at a level larger than the second reference voltage by a predetermined amount, an alternating pixel voltage to the pixel electrode, which alternates between the first reference voltage and a pixel voltage smaller than the first reference voltage, and
the drive circuit applies the negative common voltage to the common electrode and applies, throughout each period of applying the negative common voltage at a level smaller than the second reference voltage by the predetermined amount, an alternating pixel voltage to the pixel electrode, which alternates between the first reference voltage and a pixel voltage larger than the first reference voltage,
wherein the pixel voltage is maintained during a transition of the common voltage from a negative common voltage to a positive common voltage;
thereby achieving initial transition of the OCB liquid crystal from a splay alignment to a bend alignment.
2. The apparatus according to claim 1 , wherein said pixel voltage smaller than the first reference voltage is equal to or smaller than half the negative pixel voltage range, and
said pixel voltage larger than the first reference voltage is equal to or larger than half the positive pixel voltage range.
3. The apparatus according to claim 2 , wherein said pixel voltage smaller than the first reference voltage is the minimum applicable pixel voltage, and
said pixel voltage smaller than the first reference voltage is the maximum applicable pixel voltage.
4. The apparatus according to claim 1 , wherein the drive circuit applies a constant common voltage between the positive common voltage and the negative common voltage to the common electrode after having ended the initial transition.
5. A liquid crystal display apparatus comprising:
an array substrate having a plurality of pixel electrodes in a matrix;
a common electrode opposing the pixel electrodes;
a display panel having an OCB liquid crystal sandwiched between the pixel electrodes and the common electrode; and
a drive circuit configured to apply a pixel voltage a positive pixel voltage range, which ranges from a first reference voltage through a maximum applicable pixel voltage, and a negative pixel voltage range, which ranges from the first reference voltage through a minimum applicable pixel voltage, to the pixel electrode, and to alternately apply positive common voltage and a negative common voltage, which are respectively larger and smaller than a second reference voltage by a predetermined amount, to the common electrode,
wherein the drive circuit applies the positive common voltage to the common electrodes and applies, throughout each period of applying the positive common voltage at a level larger than the second reference voltage by the predetermined amount, an alternating pixel voltage to the pixel electrode, which alternates between the first reference voltage and a pixel voltage smaller than the first reference voltage, and
the drive circuit applies said alternating pixel voltage having a phase opposite to that for said one of the pixel electrodes during the application of the positive common voltage, to another one of the pixel electrodes which is adjacent to the one of the pixel electrodes,
wherein the pixel voltage is maintained during a transition of the common voltage from a negative common voltage to a positive common voltage;
thereby achieving initial transition of the OCB liquid crystal from a splay alignment to a bend alignment.
6. The apparatus according to claim 5 , wherein the drive circuit applies the negative common voltage to the common electrode and applies, throughout said each period of applying the negative common voltage at a level larger than the second reference voltage by the predetermined amount, an alternating pixel voltage to the pixel electrode, which alternates between the first reference voltage and a pixel voltage larger than the first reference voltage to the one of the pixel electrodes, and
the drive circuit applies said alternating pixel voltage having a phase opposite to that for said one of the pixel electrodes, a pixel voltage the negative pixel voltage range to said another one of the pixel electrodes, thereby achieving the initial transition of the OCB liquid crystal from the splay alignment to the bend alignment.
7. The apparatus according to claim 5 , wherein said pixel voltage smaller than the first reference voltage and applied to the one of the pixel electrodes is equal to or smaller than half the negative pixel voltage range; and
said pixel voltage applied to the another one of the pixel electrodes is equal to or smaller than half the positive pixel voltage range.
8. The apparatus according to claim 5 , wherein said pixel voltage smaller than the first reference voltage and applied to the one of the pixel electrodes is the minimum applicable pixel voltage; and
said pixel voltage applied to the another one of the pixel electrodes is the minimum applicable pixel voltage.
9. The apparatus according to claim 8 , wherein the one of the pixel electrodes and the another one of the pixel electrodes are arranged adjacently in the row direction.
10. The apparatus according to claim 8 , wherein the one of the pixel electrodes and the another one of the pixel electrodes are arranged adjacently in the column direction.
11. The apparatus according to claim 5 , wherein the drive circuit applies a constant common voltage between the positive common voltage and the negative common voltage to the common electrode after having ended the initial transition.
12. The apparatus according to claim 5 , including a backlight laminated on the display panel, wherein the drive circuit extinguishes the backlight during the initial transition.