Liquid crystal display device and apparatus including such

• US 5,963,282 A
• Filed: 11/13/1995
• Issued: 10/05/1999
• Est. Priority Date: 12/15/1994
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Battersby, Stephen J.
• Primary Examiner(s): Dang, Hung X.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US08/558,055
• Time in Patent Office: 1,422 Days
• Field of Search: 359/67, 359/48, 359/72, 359/51, 359/85, 345/50, 345/52, 345/87, 345/207, 345/211, 349/86, 349/116, 349/61, 349/143, 349/110
• US Class Current: 349/86
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/13324 Circuits comprising solar cells
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/133509 Filters, e.g. light shielding masks

Abstract

A liquid crystal display device (10) capable of displaying dark characters on a light background, for example a paper white type display, having an LC medium (20), such as PDLC material, switchable between a state in which ambient light incident on one side is back scattered towards a viewer and a state in which incident visible light is transmitted through the medium to a light absorber at the other side so that a viewer perceives a dark display, and in which a photovoltaic structure (25) is used as the light absorber for generating an output voltage in response to the visible light transmitted thereto. In equipment such as a portable computer or the like, the generated power can be utilised to supplement a battery power supply (45).

Claims

1. A liquid crystal display device having a display area and comprising:

a. a liquid crystal medium extending across the display area and including first and second sides, said medium having a reflective state in which visible light incident to the first side is backscattered and having a transmissive state in which visible light incident to the first side is transmitted through said medium;

b. first and second arrangements of electrodes arranged adjacent the first and second sides, respectively, said arrangements overlapping at predefined areas of the liquid crystal medium that can be selectively placed in the transmissive state by applying a predetermined voltage to selected ones of the electrodes in at least one of the first and second arrangements, said predetermined areas being substantially uniformly distributed across and covering a major part of the display area and said electrodes being light-transmissive at least at said predefined areas; and

c. light-absorbing means disposed opposite the second side of the liquid crystal medium for substantially preventing light transmitted through the medium from returning to said medium, said light-absorbing means including a photovoltaic structure which is disposed for receiving substantially all of the visible light transmitted through the predefined areas of the liquid crystal medium and is operable for producing an output voltage in response to the received visible light.

2. The display device as in claim 1, wherein the first and second arrangements of electrodes comprise transversely-arranged row and column electrode arrangements, respectively.

3. The display device as in claim 1, wherein the liquid crystal medium comprises a PDLC material.

4. A liquid crystal display device having a display area and comprising:

a. a liquid crystal medium extending across the display area and including first and second sides, said medium having a reflective state in which visible light incident to the first side is backscattered and having a transmissive state in which visible light incident to the first side is transmitted through said medium;

b. first and second arrangements of electrodes arranged adjacent the first and second sides, respectively, said arrangements overlapping at predefined areas of the liquid crystal medium that can be selectively placed in the transmissive state by applying a predetermined voltage to selected ones of the electrodes in at least one of the first and second arrangements, said predetermined areas being substantially uniformly distributed across and covering a major part of the display area and said electrodes being light-transmissive at least at said predefined areas; and

c. light-absorbing means disposed opposite the second side of the liquid crystal medium for substantially preventing light transmitted through the medium from returning to said medium, said light-absorbing means including a photovoltaic structure;

which is disposed for receiving substantially all of the visible light transmitted through the predefined areas of the liquid crystal medium;

which is operable for producing an output voltage in response to the received visible light; and

which comprises a photodiode structure extending continuously across the display area of the liquid crystal medium.

5. A liquid crystal display device having a display area and comprising:

a. a liquid crystal medium extending across the display area and including first and second sides, said medium having a reflective state in which visible light incident to the first side is backscattered and having a transmissive state in which visible light incident to the first side is transmitted through said medium;

b. first and second arrangements of electrodes arranged adjacent the first and second sides, respectively, said arrangements overlapping at predefined areas of the liquid crystal medium that can be selectively placed in the transmissive state by applying a predetermined voltage to selected ones of the electrodes in at least one of the first and second arrangements, said predetermined areas being substantially uniformly distributed across and covering a major part of the display area and said electrodes being light-transmissive at least at said predefined areas;

c. light-absorbing means disposed opposite the second side of the liquid crystal medium for substantially preventing light transmitted through the medium from returning to said medium, said light-absorbing means including a photovoltaic structure which is disposed for receiving substantially all of the visible light transmitted through the predefined areas of the liquid crystal medium and is operable for producing an output voltage in response to the received visible light; and

d. control means for placing ones of the predefined areas covering at least a majority of the display area into the transmissive state.