Transflective liquid crystal display with gamma harmonization

• US 20110115996A1
• Filed: 11/16/2010
• Published: 05/19/2011
• Est. Priority Date: 05/10/2006
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Lin, Ching-Huan, Chang, Chih-Ming, Su, Jenn-Jia
• Granted Patent: US 8,427,414 B2
• Time in Patent Office: Days
• US Class Current: 349/34
• CPC Class Codes: G09G 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

In a transflective liquid crystal display having a transmission area and the reflection area, the transmissive electrode is connected to a switching element to control the liquid crystal layer in the transmission area, and the reflective electrode is connected to the switching element via a separate capacitor to control the liquid crystal layer in the reflection area. The separate capacitor is used to shift the reflectance in the reflection area toward a higher voltage end in order to avoid the reflectance inversion problem. In addition, an adjustment capacitor is connected between the reflective electrode and a different common line. The adjustment capacitor is used to reduce or eliminate the discrepancy between the gamma curve associated with the transmittance and the gamma curve associated with the reflectance.

Claims

1. A method comprising:

adjusting in a liquid display a second voltage relative to a first voltage, the liquid crystal display comprising a liquid crystal layer and a common electrode, the liquid crystal having a first side and an opposing second side, the common electrode disposed on the first side of the liquid crystal layer, the common electrode arranged to receive a common voltage, wherein the liquid crystal display comprises a plurality of pixels and at least some of the pixels comprise a first area and a second area, the first area comprising a first electrode disposed on the second side of the liquid crystal layer, the second area comprising a second electrode disposed on the second side of the liquid crystal layer adjacent to the first electrode, wherein the first electrode is arranged to receive the first voltage to achieve a first optical transmissivity through the liquid crystal layer in the first area in response to the first voltage, and the second electrode is arranged to receive the second voltage to achieve a second optical transmissivity through the second area in response to the second voltage, wherein the first optical transmissivity comprises a lower transmissivity section and a higher transmissivity section and the second optical transmissivity comprises a lower transmissivity section and a higher transmissivity section, and wherein the second voltage is adjusted for substantially matching the higher transmissivity section of the second optical transmissivity to the higher transmissivity section of the first optical transmissivity, leaving a discrepancy between the lower transmissivity section of the second optical transmissivity and the lower transmissivity section of the first optical transmissivity; and

providing a voltage different from the common voltage to the second electrode via a charge storage device so as to reduce the discrepancy between the lower transmissivity section of the second optical transmissivity and the lower transmissivity section of the first optical transmissivity.

2. A method according to claim 1, wherein the first electrode comprises a transmissive electrode and the second electrode comprises a reflective electrode.

3. A method according to claim 2, wherein the first optical transmissivity is equal to the transmittance of the liquid crystal layer through the transmissive electrode in the first area and the second optical transmissivity is equal to the reflectance of the liquid crystal layer reflected from the reflective electrode in the second area.

4. A method according to claim 2, wherein the first voltage comprises a data signal.

5. A method according to claim 4, wherein the second area comprises a charge storage capacitor having a first terminal electrically connected to a data line providing the data signal and a second terminal operatively connected to the reflective electrode, and the second voltage is a voltage signal at the second terminal of the charge storage capacitor.