Image display apparatus

• US 6,583,775 B1
• Filed: 06/15/2000
• Issued: 06/24/2003
• Est. Priority Date: 06/17/1999
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sekiya, Mitsunobu, Yumoto, Akira
• Primary Examiner(s): Chow, Dennis-Doon
• Application Number:
  US09/594,087
• Time in Patent Office: 1,104 Days
• Field of Search: 345/92, 345/87, 345/76, 345/77, 345/80, 345/82, 345/55, 315/169.4, 315/169.3, 315/169.1, 340/815.45
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 3/2081 with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• CPC Class Codes: G09G 3/30 using electroluminescent panels
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• 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

The invention provides an image display apparatus which increases the degree of freedom in designing of an active element of a pixel to allow good designing and can adjust the display brightness freely and simply. Each pixel includes a light emitting element (OLED) with a brightness value which varies depending upon an amount of current supplied thereto, a first TFT controlled by a scanning line for writing brightness information given thereto from a data line into the pixel, and a second TFT for controlling the amount of current to be supplied to the OLED corresponding to the brightness information written. Writing of the brightness information into each pixel is performed by applying an electric signal corresponding to the brightness information to the data line while the scanning line is selected. The brightness information written in each pixel is held by the pixel also after the scanning line is placed into a non-selected state so that the OLED can continue lighting with a brightness value corresponding to the brightness information held by the pixel. A stopping control line compulsorily extinguishes the OLEDs of the pixels connected to the same scanning line at least in a unit of a scanning line so that the OLEDs are placed into an extinguished state from a lit state within a period of one scanning cycle after the brightness information is written into the pixels until new brightness information is written into the pixels subsequently.

Claims

1. An image display apparatus, comprising:

a plurality of pixels arranged in a matrix;

a plurality of scanning lines for selecting said pixels in a predetermined scanning cycle;

a plurality of data lines extending perpendicularly to said scanning lines for providing brightness information to drive said pixels;

said pixels being disposed at intersecting points of said scanning lines and said data lines;

each of said pixels including a light emitting element for emitting light with a brightness value which varies depending upon an amount of current supplied thereto, a first active element controlled by one of said scanning lines for writing the brightness information given thereto from one of said data lines into the pixel connected to said data line while the scanning line connected to said pixel is selected, a second active element for controlling the amount of current to be supplied to the light emitting element in response to the brightness information written in the pixel;

and means for holding the brightness information written in each of said pixels also after the scanning line connected to the pixel is placed into a non-selected state so that the light emitting element of the pixel can continue lighting with a brightness value corresponding to the brightness information held by the pixel characterized in that it further comprises control means for compulsorily extinguishing the light emitting elements of those of said pixels which are connected to a same one of said scanning lines in at least one scanning line so that the light emitting elements are placed into an extinguished state from a lit state within a period of one scanning cycle corresponding to the period between the writing of the brightness information into said pixels and the writing of new brightness information into said pixels subsequently, thereby controlling temporal average brightness of the light emitting elements.

2. An image display apparatus according to claim 1, wherein said control means is capable of adjusting the time at which each of the light emitting elements is changed over from a lit state to an extinguished state within a period of one scanning cycle.

3. An image display apparatus according to claim 1, wherein said control means includes a third active element connected to a gate of said second active element, which is in the form of a field effect transistor of the insulated gate type, of each of said pixels and is capable of providing a control signal to said third active element to control a gate potential of said second active element thereby to extinguish the light emitting element of the pixel, the control signal being applied to the third active elements included in those of said pixels which are on a same one of said scanning lines over a stopping control line provided for and in parallel to each of said scanning lines.

4. An image display apparatus according to claim 1, wherein said control means includes a third active element connected in series to said light emitting element of each of said pixels and is capable of providing a control signal to said third active element to cut off current to flow to said light emitting element, the control signal being applied to the third active elements included in those of said pixels which are on a same one of said scanning lines over a stopping control line provided for and in parallel to each of said scanning lines.

5. An image display apparatus according to anyone of claims 1 to 4, wherein said light emitting element of each of said pixels includes a two-terminal element having a rectification function and having a first terminal connected to said second active element and a second terminal connected to the second terminals of those of said pixels which are connected to a same one of said scanning lines to which the pixel is connected but electrically isolated from the second terminals of those of said pixels which are connected to any other one of said scanning lines, and said control means controls a potential of the second terminals of the two-terminal elements which are connected commonly to the same scanning line to extinguish the two-terminal elements.

6. An image display apparatus according to anyone of claims 1 to 4, wherein said control means selects, within a period of one scanning cycle, said scanning lines again to write information representative of brightness of zero into said pixels from said data lines to extinguish the light emitting elements of said pixels.

7. An image display apparatus according to anyone of claims 1 to 4, wherein each of said pixels further includes a capacitive element having an end connected to a gate of a field effect transistor of the insulated gate type which forms said second active element for controlling the amount of current to flow to said light emitting element, and said control means controls a potential of the other end of said capacitive element to control a potential of the gate of said field effect transistor of the insulated gate type which forms said second active element to extinguish the light emitting element.

8. An image display apparatus according to anyone of claims 1 to 4, wherein said control means controls the lighting time and the extinguishing time of said light emitting element included in each of said pixels at least in one scanning line within one scanning cycle after the brightness information is written into the pixel.

9. An image display apparatus according to anyone of claims 1 to 4, wherein said control means extinguishes said pixels for each of said scanning lines.

10. An image display apparatus according to anyone of claims 1 to 4, wherein said pixels include pixels for red, green and blue which are connected commonly to each of said scanning lines, and said control means extinguishes the light emitting elements included in the pixels for red, green and blue at different times from one another.

11. An image display apparatus according to anyone of claims 1 to 4, wherein said light emitting element is an organic electroluminescence element.

12. An image display apparatus according to any one of claims 1 to 4, further comprising a scanning line drive circuit to which a first vertical start pulse in synchronism with a vertical clock signal for successively selecting said scanning lines is inputted, and wherein said control means includes a control circuit for receiving a second vertical start pulse in synchronism with the vertical clock signal obtained by delaying the first vertical start pulse by a predetermined period to select the control lines provided in parallel to said scanning lines, said scanning lines are successively selected in synchronism with the vertical clock signal by said scanning line drive circuit to light said pixels, and said pixels which have been lit are extinguished through said control lines within the period of one scanning cycle in synchronism with the vertical clock signal by said control circuit.

13. An image display apparatus according to claim 12, further comprising a data line drive circuit for providing the brightness information to said data lines, and wherein each of outputs of said scanning line drive circuit is connected to an input terminal of a logical OR circuit having an output terminal connected to one of said scanning lines while each of outputs of said control circuits is connected an input terminal of a logical AND circuit connected to the other input terminal of said logical OR circuit, and the vertical clock signal is inputted to the other input terminal of said logical AND circuit.

19. A driving method for an image display apparatus according to anyone of claims 11 to 14, wherein said light emitting element of each of said pixels includes a two-terminal element having a rectification function and having a first terminal connected to said second active element and a second terminal connected to the second terminals of those of said pixels which are connected to a same one of said scanning lines to which the pixel is connected but electrically isolated from the second terminals of those of said pixels which are connected to any other one of said scanning lines, a potential of the second terminals of the two-terminal elements which are connected commonly to the same scanning line being controlled to extinguish the two-terminal elements.

15. A driving method for an image display apparatus which includes a plurality of pixels arranged in a matrix, a plurality of scanning lines for selecting said pixels in a predetermined scanning cycle, and a plurality of data lines extending perpendicularly to said scanning lines for providing brightness information to drive said pixels and wherein said pixels are disposed at intersecting points of said scanning lines and said data lines and each of said pixels including a light emitting element for emitting light with a brightness value which varies depending upon an amount of current supplied thereto, a first active element controlled by one of said scanning lines for writing the brightness information given thereto from one of said data lines into the pixel, and a second active element for controlling the amount of current to be supplied to the light emitting element in response to the brightness information written in the pixel, comprising the steps of

writing brightness information into each of said pixels by applying an electric signal corresponding to the brightness information to the data line connected to the pixel while the scanning line connected to the pixel is selected, the brightness information written in each of said pixels being held by the pixel also after the scanning line connected to the pixel is placed into a non-selected state so that the light emitting element of the pixel can continue lighting with a brightness value corresponding to the brightness information held by the pixel, characterized in that it further comprises the step of compulsorily extinguishing the light emitting elements of those of said pixels which are connected to a same one of said scanning lines in at least one scanning line so that the light emitting elements are placed into an extinguished state from a lit state within a period of one scanning cycle, corresponding to the period between the writing of the brightness information into said pixels and the writing of new brightness information into said pixels subsequently, thereby controlling temporal average brightness of the light emitting elements.

14. A driving method for an image display apparatus according to anyone of claims 15 to 18, wherein, in the control step, said pixels for each of said scanning lines are extinguished.

16. A driving method for an image display apparatus according to claim 15, wherein the time at which each of the light emitting elements is changed over from a lit state to an extinguished state is adjustable within a period of one scanning cycle.

17. A driving method for an image display apparatus according to claim 15, wherein a third active element is connected to a gate of said second active element, which is in the form of a field effect transistor of the insulated gate type, of each of said pixels such that a control signal can be provided to said third active element to control a gate potential of said second active element thereby to extinguish the light emitting element of the pixel, the control signal being applied to the third active elements included in those of said pixels which are on a same one of said scanning lines over a stopping control line provided for and in parallel to each of said scanning lines.

18. A driving method for an image display apparatus according to claim 15, wherein a third active element is connected in series to said light emitting element of each of said pixels such that a control signal can be provided to said third active element to cut off current to flow to said light emitting element, the control signal being applied to the third active elements included in those of said pixels which are on a same one of said scanning lines over a stopping control line provided for and in parallel to each of said scanning lines.

20. A driving method for an image display apparatus according to anyone of claims 15 to 18, wherein, within a period of one scanning cycle, said scanning lines are selected again to write information representative of brightness of zero into said pixels from said data lines to extinguish the light emitting elements of said pixels.

21. A driving method for an image display apparatus according to anyone of claims 15 to 18, wherein each of said pixels further includes a capacitive element having an end connected to a gate of a field effect transistor of the insulated gate type which forms said second active element for controlling the amount of current to flow to said light emitting element, and a potential of the other end of said capacitive element is controlled to control a potential of the gate of said field effect transistor of the insulated gate type which forms said second active element to extinguish the light emitting element.

22. A driving method for an image display apparatus according to anyone of claims 15 to 18, wherein a lighting point of time and an extinguishing point of time of said light emitting element included in each of said pixels are controlled at least in a unit of a scanning line within one scanning cycle after the brightness information is written into the pixel.

23. A driving method for an image display apparatus according to anyone of claims 15 to 18, wherein pixels include pixels for red, green and blue are connected commonly to each of said scanning lines, and the light emitting elements included in the pixels for red, green and blue are extinguished at different points of time from one another.

24. A driving method for an image display apparatus according to anyone of claims 15 to 18, wherein said light emitting element is an organic electroluminescence element.

25. A driving method for an image display apparatus according to anyone of claims 15 to 18, further comprising a scanning line drive step of receiving a first vertical start pulse in synchronism with a vertical clock signal for successively selecting said scanning lines, and wherein the control step includes a step of receiving a second start pulse in synchronism with the vertical clock signal, obtained by delaying the first vertical pulse by a predetermined period to select control lines provided in parallel to said scanning lines, said scanning lines are successively selected in synchronism with the vertical clock signal in the scanning line drive step to light said pixels, and said pixels which have been lit are extinguished through said control lines within the period of one scanning cycle in synchronism with the vertical clock signal in the control step.

26. A driving method for an image display apparatus according to claim 25, further comprising a data line drive step of providing the brightness information to said data lines, and wherein each of outputs of said scanning line drive circuit is connected to an input terminal of a logical OR circuit having an output terminal connected to one of said scanning lines while each of outputs in said control step is connected to an input terminal of a logical AND circuit connected to the other input terminal of said logical OR circuit, and the vertical clock signal is inputted to the other input terminal of said logical AND circuit.