TRANSFLECTIVE TYPE LCD DEVICE HAVING EXCELLENT IMAGE QUALITY

• US 20090009447A1
• Filed: 01/09/2008
• Published: 01/08/2009
• Est. Priority Date: 01/10/2007
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Original Assignee: NEC LCD Technologies Limited (Tianma Microelectronics Company Limited)
• Inventors: SAKAMOTO, Michiaki, NAKA, Kenichirou, MORI, Kenichi, NAGAI, Hiroshi
• Granted Patent: US 8,466,860 B2
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G02F 1/133555 Transflectors
• 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 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• 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 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

An LCD device has a reflective area that reflects light incident from a polarizing film side using a reflection film, and a transmissive area that transmits light of a backlight incident from a TFT substrate side. The drive voltages of the reflective area and transmissive area are Vr and Vt, the black voltage in the reflective area is Vr (K), the black voltage in the transmissive area is Vt (K). The reflectance R, the transmittance T, characteristics of R with respect to drive voltage [Vr(K)-Vr] and characteristics of T with respect to drive voltage [Vt-Vt (K)] substantially match each other.

Claims

1. A transflective liquid crystal display (LCD) device comprising an LCD panel including an array of pixels each having a reflective area and a transmissive area in a liquid crystal (LC) layer, and a drive circuit for driving said reflective area and said transmissive area of said LC layer by using an inverting drive scheme, wherein, characteristics of reflectance of said reflective area with respect to a value of [Vr (K)-Vr] and characteristics of transmittance of said transmissive area with respect to a value of [Vt-Vt (K)] substantially match each other, where Vr and Vt are drive voltages of said LC layer in said reflective area and transmissive area, respectively, Vr (K) is a dark-state setup voltage in said reflective area, and Vt (K) is a dark-state setup voltage in said transmissive area.

2. The transflective LCD device according to claim 1, wherein:

said drive circuit generates a first pixel signal corresponding to an input pixel signal, a second pixel signal obtained by performing a predetermined gradation conversion processing to said input pixel signal, and a common electrode signal common to said pixels;

said drive circuit drives one of said reflective area and said transmissive area based on said first pixel signal and said common electrode signal, and the other of said reflective area and said transmissive area based on said second pixel signal and said common electrode signal.

3. The transflective LCD device according to claim 2, wherein, said gradation conversion is such that:

said drive circuit drives one of said reflective area and said transmissive area by using a drive voltage V1 for display of bright state and a drive voltage V2 for display of dark state; and

said drive circuit drives the of said reflective area and said transmissive area by using a drive voltage V3 for display of bright state OR of dark state, where V3 is within a range between V1 and V2.

4. The transflective LCD device according to claim 1, wherein:

said drive circuit generates a first common electrode signal having a first amplitude and periodically inverted in the polarity thereof, a second common electrode signal having a second amplitude larger than said first amplitude and periodically inverted to have a phase opposite to a phase of said first common electrode signal, and a common pixel signal common to said reflective area and said transmissive area;

said drive circuit drives one of said reflective area and said transmissive area based on said first common electrode signal and said common pixel signal, and the other of said reflective area and said transmissive area based on said second common electrode signal and said common pixel signal.

5. A transflective liquid crystal display (LCD) device comprising:

an LCD panel including an array of pixels each having a reflective area and a transmissive area in a liquid crystal (LC) layer; and

a drive circuit for driving said reflective area and said transmissive area of said LC layer by using an inverting drive scheme, wherein;

said drive circuit drives said reflective area and said transmissive area by using drive voltages Vr and Vt, respectively,

said reflective area has a dark-state setup voltage Vr(K) and a bright-state setup voltage Vr(W), and said transmissive area having a dark-state setup voltage Vt(K) and a bright-state setup voltage Vt(W);

a first characteristic curve for reflectance of said reflective area with respect to a value of [Vr (K)-Vr] and a second characteristic curve for transmittance of said transmissive area with respect to a value of [Vt-Vt (K)] have therebetween a relationship such that;

a slope of said first characteristic curve in a vicinity of said Vr(K), a slope of said first characteristic curve in a vicinity of said Vr(W), a slope of said second characteristic curve in a vicinity of said Vt(K), and a slope in a vicinity of said St(W) substantially match one another.