Optical modulation device with pixels each having series connected electrode structure

• US 6,177,968 B1
• Filed: 08/28/1998
• Issued: 01/23/2001
• Est. Priority Date: 09/01/1997
• Status: Expired due to Fees

• Current Assignee: Regenmacher Ltd.
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Okada, Shinjiro, Enomoto, Takashi, Munakata, Hirohide, Inaba, Yutaka, Hachisu, Takahiro
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US09/143,393
• Time in Patent Office: 879 Days
• Field of Search: 349/144, 349/33, 349/139, 349/100, 349/38, 349/172
• US Class Current: 349/38
• CPC Class Codes: G02F 1/133757 with different alignment orientations
• CPC Class Codes: G02F 1/134336 Matrix
• 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 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 1/1412 Antiferroelectric liquid crystals
• CPC Class Codes: G02F 2201/121 common or background
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals

Abstract

An optical modulation device is constituted by a first substrate provided with a plurality of first electrodes each comprising a plurality of portions electrically independent of each other, a second substrate disposed opposite to the first substrate and provided with a plurality of second electrodes each confronting a corresponding first electrode, and an optical modulation substance disposed between the first and second substrates so as to form a plurality of pixels each having a particular electrode structure. In the electrode structure, the optical modulation substance is sandwiched between each second electrode and said portions of said corresponding first electrode so as to form a series circuit providing a plurality of capacitance, thus reducing the capacitance for each pixel to improve a switching characteristic while minimizing a defective portion due to a short-circuit between the confronting electrodes.

Claims

1. An optical modulation device, comprising:

a first substrate provided with a plurality of first electrodes each comprising a plurality of portions electrically independent of each other,

a second substrate disposed opposite to the first substrate and provided with a plurality of second electrodes each confronting a corresponding first electrode, and

an optical modulation substance disposed between the first and second substrates so as to form a plurality of pixels each having an electrode structure wherein a respective portion of the optical modulation substance is sandwiched between a respective second electrode and said portions of a corresponding first electrode so as to provide a plurality of capacitances connected in series, each of said plurality of capacitances being provided by a combination of each portion of the corresponding first electrode and the respective second electrode sandwiching the respective portion of the optical modulation substance.

2. A device according to claim 1, wherein said first electrodes comprise a plurality of scanning electrodes and a plurality of data electrodes intersecting the scanning electrodes, said second electrodes comprise a plurality of counter electrodes electrically independent of each other, and said portions comprise at least one scanning electrode and at least one data electrode.

3. A device according to claim 2, wherein said counter electrodes are coated with an electroconductive alignment film.

4. A device according to claim 2, wherein said counter electrodes contact the optical modulation substance.

5. A device according to claim 2, wherein said counter electrodes, said scanning electrodes and said data electrodes comprise a layer of an electroconductive resin, respectively.

6. A device according to claim 2, wherein said second substrate comprises a resin substrate.

7. A device according to claim 6, wherein said resin substrate comprises a polarizing plate.

8. A device according to claim 2, wherein said scanning electrodes and said data electrodes are electrically connected with auxiliary electrodes, respectively, via a common insulating layer.

9. A device according to claim 2, wherein said scanning electrodes and said data electrodes are electrically connected with a layer of a low-resistance substance, respectively.

10. A device according to claim 2, wherein each of said counter electrodes is in a floating state.

11. A device according to claim 2, wherein said optical modulation substance comprises a ferroelectric liquid crystal.

12. A device according to claim 2, wherein said optical modulation substance comprises an antiferroelectric liquid crystal.

13. A device according to claim 2, wherein said optical modulation substance comprises a nematic liquid crystal showing bistability.

14. A device according to claim 2, wherein said optical modulation substance comprises a liquid crystal and is placed in a state such that first liquid crystal molecules disposed between each counter electrode and its corresponding scanning electrode and second liquid crystal molecules disposed between the counter electrode and its corresponding data electrode form a prescribed angle providing a first transmittance of a bright state when supplied with a voltage of a first polarity and that said first and second liquid crystal molecules form an angle of zero degrees when supplied with a voltage of a second polarity opposite to the first polarity.

15. A device according to claim 14, wherein said liquid crystal comprises a ferroelectric liquid crystal having bistability and providing a tilt angle which is a half of an angle formed between liquid crystal molecules placed in one stable state and those placed in the other stable state, and said prescribed angle is four times the tilt angle.

16. An optical modulation device, comprising:

a first substrate provided with a plurality of scanning signal lines, a plurality of data signal lines intersecting the scanning signal lines, a plurality of pixel electrodes each comprising a plurality of portions electrically independently of each other, and a plurality of switching elements;

a second substrate provided with a plurality of counter electrodes confronting the pixel electrodes and electrically independent of each other, and

an optical modulation substance disposed between the first and second substrates so as to form a plurality of pixels each provided with one switching element and each having an electrode structure wherein a respective portion of the optical modulation substance is sandwiched between a respective counter electrode and each portion of a corresponding pixel electrode so as to provide a plurality of capacitances connected in series as a load for each switching element, each of the plurality of capacitances being provided by a combination of each portion of the corresponding pixel electrode and the respective counter electrode sandwiching the respective portion of the optical modulation substance.

17. A device according to claim 16, wherein each of said counter electrodes comprises a plurality of portions electrically independent of each other for each pixel, and said series circuit provides at least three capacitances.

18. A device according to claim 16, wherein each of said switching elements comprises a thin film transistor.

19. A device according to claim 16, wherein said optical modulation substance comprises an antiferroelectric liquid crystal.

20. A device according to claim 16, wherein said optical modulation substance comprises a liquid crystal showing first to third alignment states such that said liquid crystal is in said first alignment state providing a first transmittance under no voltage application, and changes its alignment state from said first alignment state to said second alignment state providing a second transmittance under application of a voltage (V₀) of a first polarity and changes its alignment state from said first alignment state to aid third alignment state opposite to said second alignment state and providing said second transmittance under application of a voltage (−

V₀) of a second polarity opposite to the first polarity, and wherein said device shows a voltage-transmittance characteristic such that a transmittance is continuously changed depending on an applied voltage between said first and second transmittances.

21. A device according to claim 16, wherein said portions of each pixel electrode comprises a first pixel electrode electrically connected with a corresponding switching element and a second pixel electrode electrically connected with a reference voltage signal line.

22. A device according to claim 16, wherein said portions of each pixel electrode comprises a first pixel electrode electrically connected with a corresponding switching element and a second pixel electrode electrically connected with an adjacent scanning signal line not electrically connected with said corresponding switching element.

23. A device according to claim 16, wherein said portions of each pixel electrode comprises a first pixel electrode and a second pixel electrode, and said optical modulation substance comprises a liquid crystal and is placed in a state such that first liquid crystal molecules disposed between each counter electrode and said first pixel electrode and second liquid crystal molecules disposed between the counter electrode and said second pixel electrode form a prescribed angle providing a first transmittance of a bright state when supplied with no voltage and when supplied with a voltage of a first polarity and that said first and second liquid crystal molecules form an angle of zero degrees when supplied with a voltage of a second polarity opposite to the first polarity;

and wherein said device shows a voltage-transmittance characteristic such that a transmittance is continuously changed depending on an applied voltage between said first and second transmittances.

24. A device according to claim 23, wherein said liquid crystal comprises a smectic liquid crystal providing a tilt angle which is a half of an angle formed between liquid crystal molecules placed in a stable state and those placed in another stable state, and said prescribed angle is four times the tilt angle.