Displaying device

• US 6,166,714 A
• Filed: 06/06/1997
• Issued: 12/26/2000
• Est. Priority Date: 06/06/1996
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kishimoto, Tomoji
• Primary Examiner(s): Luu, Matthew
• Assistant Examiner(s): Blackman, Anthony J.
• Application Number:
  US08/870,713
• Time in Patent Office: 1,299 Days
• Field of Search: 345/89, 345/94, 345/95, 345/96, 345/97, 345/98, 345/99, 345/100, 345/208, 345/209, 345/210, 345/87, 345/103
• US Class Current: 345/96
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

A displaying device includes an array substrate on which a plurality of pixel electrodes are arrayed, a counter substrate having a common electrode arranged to oppose the pixel electrodes on the array substrate, a liquid crystal cell held between the array substrate and the counter substrate, and a display control circuit for controlling the potential difference between each pixel electrode and a common electrode to periodically invert the direction of an electric field in the liquid crystal cell. Particularly, the display control circuit includes an X-driver for level-inverting a pixel signal voltage (VSIG) of a first amplitude every predetermined period and supplying the pixel signal voltage to each pixel electrode to set a display gray scale level, and a common electrode driver for level-inverting a common voltage (VCOM) of a second amplitude in synchronism with level inversion of the pixel signal voltage (VSIG) and supplying the common voltage to the common electrode. The second amplitude is determined to be smaller than the first amplitude not exceeding the range from the minimum level to the maximum level of the pixel signal voltage (VSIG).

Claims

1. A displaying device comprising:

an array substrate on which a plurality of pixel electrodes are arrayved;

a common electrode arranged in association with the pixel electrodes;

an optical modulation layer set to have an optical modulation ratio corresponding to a potential difference between each pixel electrode and the common electrode; and

a display control circuit for controlling the potential difference between each pixel electrode and the common electrode;

wherein the display control circuit includes;

a pixel electrode driving unit for supplying a pixel signal voltage to each pixel electrode to set a display gray scale level every predetermined period; and

a common electrode driving unit for supplying a common voltage to the common electrode every predetermined period a relationship between the pixel signal voltage and the common voltage being determined such that an electric field in the optical modulation layer depends on the display gray scale level in the predetermined period; and

wherein the relationship between the pixel signal voltage and the common voltage is determined such that the direction of the electric field in the optical modulation layer in a range from a first gray scale level to an (n-2)-th gray scale level is reversed to that in a remaining gray scale range where n is a total number of gray scale levels (n;

positive integer).

2. A displaying device comprising:

an array substrate on which a plurality of pixel electrodes are arrayed;

a common electrode arranged in association with the pixel electrodes;

an optical modulation layer set to have an optical modulation ratio corresponding to a potential difference between each pixel electrode and the common electrode; and

a display control circuit for controlling the potential difference between each pixel electrode and the common electrode;

wherein said display control circuit includes;

a pixel electrode driving unit for supplying a pixel signal voltage to each pixel electrode to set a display gray scale level every predetermined period; and

a common electrode driving unit for supplying a common voltage to the common electrode every predetermined period, a relationship between the pixel signal voltage and the common voltage being determined such that an electric field in the optical modulation layer depends on the display gray scale level in the predetermined period; and

wherein the relationship between the pixel signal voltage and the common voltage is determined such that the direction of the electric field in said optical modulation layer in one of a range from a first gray scale level to an (n/2)-th gray scale level and a range from the (n/2)-th gray scale level to an (n-2)-th gray scale level is reversed to that in a remaining gray scale range where n is a total number of gray scale levels (n;

positive integer).

3. A displaying device comprising:

an array substrate on which a plurality of pixel electrodes are arrayed;

a common electrode arranged in association with the pixel electrodes;

an optical modulation layer set to have an optical modulation ratio corresponding to a potential difference between each pixel electrode and the common electrode; and

a display control circuit for controlling the potential difference between each pixel electrode and the common electrode;

wherein said display control circuit includes;

a pixel electrode driving unit for supplying a pixel signal voltage to each pixel electrode to set a display gray scale level every predetermined period; and

a common electrode driving unit for supplying a common voltage to the common electrode every predetermined period, a relationship between the pixel signal voltage and the common voltage being determined such that an electric field in the optical modulation layer depends on the display gray scale level in the predetermined period; and

wherein the relationship between the pixel signal voltage and the common voltage is determined such that the direction of the electric field in said optical modulation layer in one of a first gray scale level and an n-th gray scale level is reversed to that in a remaining gray scale level where n is a total number of gray scale levels (n;

positive integer).

4. A displaying device comprising:

an array substrate on which a plurality of pixel electrodes are arrayed;

a common electrode arranged in association with the pixel electrodes;

an optical modulation layer set to have an optical modulation ratio corresponding to a potential difference between each pixel electrode and the common electrode; and

a display control circuit for controlling the potential difference between each pixel electrode and the common electrode;

wherein said display control circuit includes;

a pixel electrode driving unit for supplying a pixel signal voltage to each pixel electrode to set a display gray scale level every predetermined period; and

a common electrode driving unit for supplying a common voltage to the common electrode every predetermined period, a relationship between the pixel signal voltage and the common voltage being determined such that an electric field in the optical modulation layer depends on the display gray scale level in the predetermined period;

wherein the relationship between the pixel signal voltage and the common voltage is determined such that the direction of the electric field in said optical modulation layer in one of a first gray scale level and an n-th gray scale level is reversed to that in a remaining gray scale level where n is a total number of gray scale levels (n;

positive integer); and

wherein said optical modulation layer is a liquid crystal layer of a normally white type for displaying a brightest image as the first gray scale level when the potential difference between the pixel electrode and said common electrode is substantially zero, and the relationship between the pixel signal voltage and the common voltage is determined such that the direction of the electric field in said liquid crystal layer only in the first gray scale level is reversed to that in the remaining gray scale level.

5. A displaying device comprising:

an array substrate on which a plurality of pixel electrodes are arrayed;

a common electrode arranged in association with said pixel electrodes;

an optical modulation layer set to have an optical modulation ratio corresponding to a potential difference between each pixel electrode and said common electrode; and

a display control circuit for controlling the potential difference between each pixel electrode and said common electrode to periodically inverting an electric field in said optical modulation layer;

wherein said display control circuit includes;

a pixel electrode driving unit for level-inverting a pixel signal voltage of a first amplitude every predetermined period and supplying the pixel signal voltage to each pixel electrode to set a display gray scale level, and

a common electrode driving unit for level-inverting a common voltage of a second amplitude in synchronism with level inversion of the pixel signal voltage and supplying the common voltage to the common electrode, the first and second amplitudes being determined such that a voltage polarity of the difference between the pixel signal voltage and the common voltage is inverted every predetermined period except when a specific gray scale range including a gray scale level corresponding to a minimum optical modulation ratio is selected for displaying.

6. A displaying device comprising:

an array substrate having a plurality of pixel electrodes arrayed thereon;

a common electrode arranged in association with said pixel electrodes;

an optical modulation layer positioned in the vicinity of said common electrode and adapted to have an optical modulation ratio corresponding to a potential difference between each pixel electrode and said common electrode; and

a display control circuit controlling the potential difference between each pixel electrode and said common electrode and periodically inverting an electric field in said optical modulation layer;

wherein said display control circuit includes;

a pixel electrode driving unit level-inverting a pixel signal voltage having a first amplitude every predetermined period and supplying the pixel signal voltage to each pixel electrode to set a display gray scale level; and

a common electrode driving unit level-inverting a common voltage having a second amplitude in synchronism with the level inversion of the pixel signal voltage and supplying the common voltage to the common electrode, the second amplitude (i) being predetermined to be smaller than the first amplitude and (ii) not exceeding a range from a minimum level to a maximum level of the pixel signal voltage;

wherein a voltage polarity of the difference between the pixel signal voltage and the common voltage is determined based on the display gray scale level.

7. A device according to claim 6, wherein a minimum level of the common voltage is determined to be equal to that of the pixel signal voltage.

8. A device according to claim 6, wherein a minimum level of the common voltage is determined to be higher than that of the pixel signal voltage.

9. A device according to claim 6, wherein said display control circuit further includes a power source circuit for generating a stable power source voltage which is shared by said pixel electrode driving unit and said common electrode driving unit to obtain the pixel signal voltage and the common voltage, respectively.

10. A displaying device comprising:

an array substrate having a plurality of pixel electrodes arrayed thereon;

a common electrode arranged in association with said pixel electrodes;

an optical modulation layer positioned in the vicinity of said common electrode and adapted to have an optical modulation ratio corresponding to a potential difference between each pixel electrode and said common electrode; and

a display control circuit controlling the potential difference between each pixel electrode and said common electrode;

wherein said display control circuit includes;

a pixel electrode driving unit supplying a pixel signal voltage to each pixel electrode to set a display gray scale level; and

a common electrode driving unit supplying a common voltage to the common electrode, the common voltage having an amplitude smaller than an amplitude of the pixel signal voltage;

wherein the pixel signal voltage and the common voltage are each level-inverted in a predetermined manner during a number of predetermined periods; and

wherein a voltage polarity of the difference between the pixel signal voltage and the common voltage is determined based on the display gray scale level.