Display apparatus having a liquid crystal device with separated first and second thin film transistors

• US 6,614,415 B2
• Filed: 03/11/2002
• Issued: 09/02/2003
• Est. Priority Date: 11/06/1998
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Onitsuka, Yoshihiro, Mizutani, Hidemasa
• Primary Examiner(s): NGUYEN, CHANH DUY
• Application Number:
  US10/093,379
• Publication Number:
  US 20020093480A1
• Time in Patent Office: 540 Days
• Field of Search: 345/84, 345/87, 345/94, 345/97, 345/89, 345/92, 345/90, 345/91, 345/96, 349/41, 349/42, 349/46, 349/45, 349/47
• US Class Current: 345/90
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/063 Waveforms for resetting the whole screen at once
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A display apparatus features an optical modulation device including a plurality of pixels and a pair of electrodes to which a voltage is applied, and an illumination device for illuminating the optical modulation device instantaneously and successively with a plurality of monochromatic lights of different colors in a frame period to provide a full-color image in combination with application of the voltage to the electrodes of the optical modulation device thereby effecting a full-color display over a succession of the prescribed period. A controller divides each frame period into two periods including a first period for displaying a full-color image at each pixel and a second period immediately after the first period and for placing the optical modulation device in a non-display state, thus effectively suppressing an after image phenomenon adversely affecting a full-color image display in a subsequent frame period.

Claims

1. A liquid crystal apparatus, comprising:

a liquid crystal device including a liquid crystal, a plurality of pixel electrodes for applying a voltage to said liquid crystal arranged in a matrix form, a plurality of first thin film transistors for simultaneous transfer connected to said pixel electrodes, a plurality of second thin film transistors for successive charge storage, a plurality of sample-and-hold circuits each connected to and disposed between a first thin film transistor and a second thin film transistor, a plurality of gate lines each connected to gates of associated second thin film transistors for successive charge storage along a same gate line, and a whole-writing line, different from said plurality of gate lines, connected to all of the gates of said first thin film transistors for simultaneous transfer;

a buffer disposed between one of said first thin film transistors and a pixel electrode or between one of said second thin film transistors and one of said first thin film transistors;

means for generating picture image signals for defining gradation images for three primary colors to be visually recognized and displayed on said liquid crystal device as a full-color image; and

a light source for illuminating said liquid crystal device with a plurality of color lights corresponding to the gradation images displayed on said liquid crystal device in a three primary color sequential display scheme, wherein

said liquid crystal has a spontaneous polarization.

2. An apparatus according to claim 1, further comprising control means for dividing frames into a first frame period for displaying a full-color image by applying a voltage of one polarity to said liquid crystal, and a second frame period for not displaying the full-color image by applying a voltage of the other polarity.

3. An apparatus according to claim 2, wherein said liquid crystal exhibits a voltage-transmittance characteristic of showing a transmittance increasing monotonously in response to the voltage of one polarity and a transmittance which is non-zero but is little changed in response to the voltage of the other polarity.

4. An apparatus according to claim 3, wherein in each frame, DC components applied to said liquid crystal are counterbalanced with each other.