Transflective liquid crystal display with partial switching

• US 7,015,997 B2
• Filed: 04/29/2003
• Issued: 03/21/2006
• Est. Priority Date: 04/30/2002
• Status: Expired due to Fees

• Current Assignee: InnoLux Corporation
• Original Assignee: Toppoly Optoelectronics Corporation (InnoLux Corporation), University of Central Florida Research Foundation Inc. (State University System of Florida)
• Inventors: Wu, Shin-Tson, Choi, Wing Kit
• Primary Examiner(s): Schechter, Andrew
• Assistant Examiner(s): Duong, Thoi V.
• Application Number:
  US10/425,582
• Publication Number:
  US 20030202139A1
• Time in Patent Office: 1,057 Days
• Field of Search: 349/113, 349/114, 349/141, 349/143, 349/75
• US Class Current: 349/114
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02F 1/01716 Optically controlled superlattice or quantum well devices
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/1343 Electrodes reflective electrodes G02F1/133553
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 2201/128 field shaping

Abstract

A high reflection and transmission transflective liquid crystal display (TLCD) that requires only a single cell gap. Instead of reducing the cell gap of the R sub-pixel region, the invention reduces the birefringence change Δn of reflective pixels (R) so that the total retardation change Δnd of R is equal to that of the transmissive pixels (T). This is realized by a partial switching of the pixels of approximately 45 degrees which occurs in the reflective pixel (R) region of the single cell gap by applying fringing fields, generated by a discontinuous electrode, to the molecules in the reflective pixel (R) region of the cell gap.

Claims

1. A method of producing high reflection (R) and transmission (T) transflective liquid crystal displays (LCDs) with a single gap, comprising the step of:

providing a single gap liquid crystal display (LCD) having a licquid crystal layer between a discontinuous pixel electrode and a common electrode, the liquid crystal layer having a cell gap thickness d that is approximately identical throughout the single cell gap liquid crystal display;

reducing the birefringence change Δ

n of reflective pixels (R) in the single gap liquid crystal display (LCD) by approximately ½

by partially switching molecules in the reflective pixels (R) approximately 45 degrees so that total retardation Δ

nd of the reflective pixels (R) is approximately equal to total retardation Δ

nd of transmissive pixels in the single gap LCD; and

applying an electric field between the discontinuous pixel electrode and the common electrode to generate a fringing field in the reflective pixels (R) to partially switch the liquid crystal molecules to said approximately 45 degrees to achieve said total retardation Δ

nd in the reflective pixels (R), wherein said total retardation Δ

nd is achieved without the use of compensators, polarizers and alignment films for obtaining the approximately 45 degree reorientation of the liquid crystal molecules.

2. The method of claim 1, wherein the discontinuous pixel electrode includes:

a narrow width of less than approximately 10 μ

m; and

a narrow gap of less than approximately 3 μ

m.

3. The method of claim 1, further comprising the step of:

increasing width and gap spacing limits in the discontinuous electrode as the cell gap size increases.

4. A high reflection (R) and transmission (T) transflective liquid crystal display (TLCD), comprising:

a single gap liquid crystal display (LCD) having transmissive pixels (T) and reflective pixels (R) in a transmissive region and a reflective region that has a mirror-reflector with a thickness, the single gap liquid crystal display having a liquid crystal layer thickness between a discontinuous reflective pixel electrode and a common electrode that remains identical in both the transmissive region and the reflective region when taking into account the thickness of the mirror-reflector in the reflective region; and

,

means for applying an electric field between the discontinuous pixel electrode and the common electrode to generate a fringing field in the reflective pixels (R) to partially switch the liquid crystal molecules to approximately 45 degrees in the reflective region to reduce the birefringence change Δ

n of reflective pixels (R) in a single gap liquid crystal display (LCD) to approximately Δ

n/2 without reducing the cell gap d so that total retardation Δ

nd of the reflective pixels (R) is approximately equal to the total retardation Δ

nd of the transmissive pixels in the single gap LCD, wherein said total retardation Δ

nd is achieved without the use compensators, polarizers and alignment films for obtaining the approximately 45 degree reorientation of the liquid crystal molecules.

5. The LCD of claim 4, wherein the discontinuous pixel electrode includes:

a narrow width of less than approximately 10 μ

m; and

a narrow gap of less than approximately 3 μ

m.