Reflective liquid crystal display (LCD) device having an internal reflection reducer

• US 6,052,165 A
• Filed: 12/22/1997
• Issued: 04/18/2000
• Est. Priority Date: 12/22/1997
• Status: Expired due to Fees

• Current Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Original Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Inventors: Janssen, Peter J.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US08/995,822
• Time in Patent Office: 848 Days
• Field of Search: 349/110, 349/111, 349/84, 349/158
• US Class Current: 349/84
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/136 Liquid crystal cells structurally associated with a semi-conducting layer or substrate, e.g. cells forming part of an integrated circuit G02F1/135 takes precedence
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 2203/02 reflective

Abstract

A reflective liquid crystal display (LCD) device includes an array of reflective pixel electrodes over a surface of a silicon substrate, with light transmissive regions being located between the reflective pixel electrodes. A nematic liquid crystal layer is provided over both the reflective pixel electrodes and the light transmissive regions between the reflective pixel electrodes. A reflection reducer is provided for reducing the percentage of light entering the device through the nematic crystal layer and the light transmissive regions which is reflected back out of the device through the light transmissive regions and the nematic liquid crystal layer. In one form, the reflection reducer is a vee-shaped groove in the substrate which is provided with a vee-shaped layer of low reflectivity. Alternatively, the reflection reducer may be provided by having modules of the nematic liquid crystal layer aligned in a direction at an angle of about 45° to the axis of the reflective pixel electrodes when the LCD device is in a bright state. A third possibility is to combine both of the foregoing features in a single device. In this manner, light reflection from the inter-pixel areas back in the viewing direction is reduced, and contrast is improved, without the need for a light shield.

Claims

1. A reflective liquid crystal display (LCD) device comprising an array of reflective pixel electrodes over a surface of a silicon substrate, with light transmissive regions being located between said reflective pixel electrodes, and a nematic liquid crystal layer over said reflective pixel electrodes and said light transmissive regions, characterized in that said LCD device comprises an internal reflection reducer for reducing the percentage of light entering the device through said nematic liquid crystal layer and said light transmissive regions which is reflected back out of the device through said light transmissive regions and said nematic liquid crystal layer, said internal reflection reducer being located substantially only at said light transmissive regions.

2. An LCD device as in claim 1, wherein said reflection reducer comprises a vee-shaped groove in said substrate and provided with a vee-shaped layer of low reflectivity.

3. An LCD device as in claim 2, wherein said vee-shaped layer of low reflectivity is provided on an insulating layer which insulates said vee-shaped layer from said substrate.

4. An LCD device as in claim 3, wherein said vee-shaped layer of low reflectivity comprises polysilicon.

5. An LCD device as in claim 4, further comprising black polyimide provided between said reflective pixel electrodes and said silicon substrate.

6. An LCD device as in claim 1, wherein said reflection reducer comprises said reflective pixel electrodes being of rectangular shape so that their edges define two mutually-perpendicular axes, and molecules of said nematic liquid crystal layer being aligned in a direction at an angle of about 45°

to said axes when said LCD device is in a bright state.

7. An LCD device as in claim 6, wherein voltages of alternate polarity are applied to alternate pixel electrodes in a dark state of the device.

8. An LCD device as in claim 1, wherein said reflection reducer comprises both a vee-shaped groove in said substrate and provided with a vee-shaped layer of low reflectivity and said reflective pixel electrodes being of rectangular shape so that their edges define two mutually-perpendicular axes, and molecules of said nematic liquid crystal layer being aligned in a direction at an angle of about 45°

to said axes when said LCD device is in a bright state.