Display device

• US 6,518,941 B1
• Filed: 04/28/1999
• Issued: 02/11/2003
• Est. Priority Date: 08/28/1997
• Status: Expired due to Term

• Current Assignee: Intellectual Keystone Technology LLC (Samsung Electronics Co. Ltd.)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kimura, Mutsumi
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): Kovalick, Vincent E.
• Application Number:
  US09/297,263
• Time in Patent Office: 1,385 Days
• Field of Search: 315/169.3, 345/7, 345/76, 345/77, 345/80, 345/90, 345/92, 345/214, 345/55
• US Class Current: 345/55
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

In a display device in accordance with the present invention, each pixel includes a plurality of luminescent elements having different luminous intensities to represent gray scales by controlling the turning ON/OFF of the luminescent elements. A digital signal is transmitted to each pixel to carry out control by thin film transistors connected in series with the luminescent elements. The luminous intensities of the luminescent elements are the geometric progressions of a common ratio of 2. The ON resistance of the thin film transistors is set to be lower than the ON resistance of the luminescent elements, while the OFF resistance of the thin film transistors is set to be higher than the OFF resistance of the luminescent elements. These features have reduced the nonuniformity in the luminous intensities of the luminescent elements caused by the nonuniformity in the conductance of the transistors, thus achieving improved image quality.

Claims

1. A display device, comprising:

a shift register;

a plurality of digital signal supply lines;

a plurality of scanning lines;

a plurality of signal-line sets, each of the plurality of signal-line sets comprising a plurality of bit signal lines, the number of the bit signal lines being the same as that of the plurality of digital signal supply lines;

a plurality of transmission-switch sets, each transmission-switch set of the plurality of transmission switch sets comprising a plurality of transmission switches, the plurality of transmission switches being controlled together by one pulse of the shift register, each of the plurality of transmission switches controlling transmission of signals from one digital signal supply line of the plurality of digital signal supply lines to one bit signal line of the plurality of bit signal lines corresponding to the one digital signal supply line; and

a plurality of pixels, each of the plurality of pixels comprising;

a plurality of current transistors;

a plurality of luminescent elements, each of the plurality of luminescent elements being connected with one of the plurality of current transistors in series, the plurality of luminescent elements having different areas so that the luminous intensities of the respective luminescent elements within each of the pixels are different;

a plurality of switching transistors, the plurality of switching transistors being controlled by one of the plurality of scanning lines, and at least one of a source and a drain of each of the plurality of switching transistors being connected to corresponding bit signal lines of the plurality of bit signal lines; and

a plurality of retention capacitors, each of the plurality of retention capacitors receiving signals through a corresponding switching transistor of the plurality of switching transistors and a corresponding bit signal line of the plurality of bit signal lines.

2. The display device according to claim 1, each of the luminescent elements taking any one of an emissive state and a non-emissive state.

3. The display device according to claim 1, luminous intensities of the luminescent elements for each of the pixels being geometric progressions of a common ratio of 2.

4. The display device according to claim 1, an ON resistance of the current transistors being lower than an ON resistance of the luminescent elements, and an OFF resistance of the current transistors being higher than an OFF resistance of the luminescent elements.

5. The display device according to claim 1, the current transistors being polycrystalline silicon thin film transistors produced at a low temperature process at 600 degrees Celsius or below.

6. The display device according to claim 1, the luminescent elements being organic electroluminescent elements produced by an ink-jet process.

7. The display device according to claim 1, each of the pixels corresponding to four of the luminescent elements.

8. The display device according to claim 1, the areas of the luminescent elements for each of the pixels being geometric progressions of a common ratio of 2.

9. A display device, comprising:

a shift register;

a plurality of digital signal supply lines;

a plurality of scanning lines;

a plurality of signal-line sets, each of the plurality of signal-line sets comprising a plurality of bit signal lines, a number of the bit signal lines being same as that of the plurality of digital signal supply lines;

a plurality of transmission-switch sets, each transmission-switch set of the plurality of transmission switch sets comprising a plurality of transmission switches, the plurality of transmission switches being controlled together by one pulse of the shift register, each of the plurality of transmission switches controlling transmission of signals from one digital signal supply line of the plurality of digital signal supply lines to one bit signal line of the plurality of bit signal lines corresponding to the one digital signal supply line; and

a plurality of pixels, each of the plurality of pixels comprising;

a plurality of current transistors;

a plurality of luminescent elements, each of the plurality of luminescent elements being connected with one of the plurality of current transistors;

a plurality of switching transistors, the plurality of switching transistors being controlled by one of the plurality of scanning lines, and at least one of a source and a drain of each of the plurality of switching transistors being connected to a corresponding bit signal line of the plurality of bit signal lines; and

a plurality of retention capacitors, each of the plurality of retention capacitors receiving signals through a corresponding switching transistor of the plurality of switching transistors and a corresponding bit signal line of the plurality of bit signal lines.

10. A display device, comprising:

a shift register;

a plurality of digital signal supply lines;

a plurality of scanning lines;

a plurality of signal-line sets, each of the plurality of signal-line sets comprising a plurality of bit signal lines, a number of the bit signal lines being same as that of the plurality of digital signal supply lines;

a plurality of transmission-switch sets, each transmission-switch set of the plurality of transmission switch sets comprising a plurality of transmission switches, the plurality of transmission switches being controlled together by one pulse of the shift register, each of the plurality of transmission switches controlling transmission of signals from one digital signal supply line of the plurality of digital signal supply lines to one bit signal line of the plurality of bit signal lines corresponding to the one digital signal supply line; and

a plurality of pixels, each of the plurality of pixels comprising;

a plurality of current transistors;

a plurality of luminescent elements, each of the plurality of luminescent elements being connected with one of the plurality of current transistors, and luminous intensities of the luminescent elements being different from each other;

a plurality of switching transistors, the plurality of switching transistors being controlled by one of the plurality of scanning lines, and at least one of a source and a drain of each of the plurality of switching transistors being connected to a corresponding bit signal line of the plurality of bit signal lines; and

a plurality of retention capacitors, each of the plurality of retention capacitors receiving signals through a corresponding switching transistor of the plurality of switching transistors and a corresponding bit signal line of the plurality of bit signal lines.

11. A display device, comprising:

a shift register;

a plurality of digital signal supply lines;

a plurality of scanning lines;

a plurality of signal-line sets, each of the plurality of signal-line sets comprising a plurality of bit signal lines, a number of the bit signal lines being same as that of the plurality of digital signal supply lines;

a plurality of transmission-switch sets, each transmission-switch set of the plurality of transmission switch sets comprising a plurality of transmission switches, the plurality of transmission switches being controlled together by one pulse of the shift register, each of the plurality of transmission switches controlling transmission of signals from one digital signal supply line of the plurality of digital signal supply lines to one bit signal line of the plurality of bit signal lines corresponding to the one digital signal supply line; and

a plurality of pixels, each of the plurality of pixels comprising;

a plurality of current transistors;

a plurality of luminescent elements, each of the plurality of luminescent elements being connected with one of the plurality of current transistors, areas of the plurality of luminescent elements being different from each other;

a plurality of switching transistors, the plurality of switching transistors being controlled by one of the plurality of scanning lines, and at least one of a source and a drain of each of the plurality of switching transistors being connected to a corresponding bit signal line of the plurality of bit signal lines; and

a plurality of retention capacitors, each of the plurality of retention capacitors receiving signals through a corresponding switching transistor of the plurality of switching transistors and a corresponding bit signal line of the plurality of bit signal lines.