Transflective liquid-crystal-display device with single retardation film between half-waveplate and liquid crystal layer

• US 8,502,941 B2
• Filed: 08/31/2010
• Issued: 08/06/2013
• Est. Priority Date: 03/07/2006
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Original Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Inventors: Nagai, Hiroshi, Sakamoto, Michiaki, Mori, Kenichi, Naka, Kenichirou, Ikeno, Hidenori
• Primary Examiner(s): Nguyen, Hoan C
• Application Number:
  US12/873,108
• Publication Number:
  US 20100328592A1
• Time in Patent Office: 1,071 Days
• Field of Search: 349/114, 349141-143, 349117-121
• US Class Current: 349/119
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133565 inside the LC elements, i.e. between the cell substrates
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133631 with a spatial distribution of the retardation value
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 2413/03 Number of plates being 3
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127

Abstract

A LCD device has a LC layer sandwiched between a TFT substrate and a counter substrate, first and second polarizing films, a first λ/2 film between the first polarizing film and the counter substrate, and a second λ/2 film between the second polarizing film and the TFT substrate. Angle θ1 between the direction of the optical axis of the LC layer and the polarized direction of the light entering the LC layer satisfies the relationship: 0 degree<θ1<45 degrees. The resultant LCD device has lower leakage light and coloring.

Claims

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

a liquid crystal (LC) layer defining a plurality of pixels each having a transmissive area and a reflective area, at least said transmissive area operating in a lateral-electric-field mode;

first and second polarizing films sandwiching therebetween said LC layer, said first polarizing film being effective common to said transmissive area and said reflective area, said second polarizing film being effective only to said transmissive area;

a ½

wavelength film sandwiched between said first polarizing film and said LC layer;

another ½

wavelength film between said second polarizing film and said LC layer; and

a single retardation film, said retardation film sandwiched between said another ½

wavelength film and said LC layer,

wherein the relationship (nx−

nz)/(nx−

ny)=0.3 or (nx−

nz)/(nx−

ny)=1.0 and (nx−

ny)xd is satisfied as per the retardation film,

wherein, nx, ny, nz denote a refractive index in the direction of the slow axis of the retardation film, a refractive index in the direction of the fast axis of the retardation film, a refractive index in the thickness direction of the retardation film, respectively,

wherein the value defined by (nx−

nz)/(nx−

ny)=0.3 or (nx−

nz)/(nx−

ny)=1.0 and (nx−

ny)xd being set approximately equal to the retardation of the LC layer, where d is a thickness of the retardation film,

wherein the wavelength dispersion of the birefringence of the retardation film is a reverse dispersion, and

wherein each of said pixels includes a pixel electrode driven by a pixel data signal supplied in common to said transmissive area and said reflective area, a first common electrode driven by a first common signal supplied in common to said reflective areas of said plurality of pixels, and a second common electrode driven by a second common signal supplied in common to said transmissive areas of said plurality of pixels.

2. The transflective LCD device according to claim 1, wherein an angle θ

1 between an optical axis of said LC layer in said transmissive area upon display of a dark image and a polarized direction of light incident onto said LC layer is zero degree.

3. A transflective liquid-crystal-display (LCD) device according to claim 1,

wherein said LC layer includes homogeneously-oriented liquid crystal.