Electro-optical device, method of driving the same, and electronic apparatus

• US 20060092185A1
• Filed: 07/06/2005
• Published: 05/04/2006
• Est. Priority Date: 10/19/2004
• Status: Active Grant

• Current Assignee: Element Capital Commercial Company Pte. Ltd.
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Jo, Hiroaki, Kasai, Toshiyuki, Horiuchi, Hiroshi, Nozawa, Takeshi
• Granted Patent: US 7,932,876 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

An electro-optical device includes a plurality of pixel circuits each including a light-emitting element and a driving transistor for driving the light-emitting element; data lines that are connected to the plurality of pixel circuits and that supply data signals representing light-emitting gray-scale levels to the pixel circuits; and a data line driving circuit that supplies the data signals to the pixel circuits through the data lines. In addition, the data line driving circuit applies to each pixel circuit in a predetermined sequence a forward frame period supplying a data signal having a forward bias voltage for making the light-emitting element emit light and a backward frame period supplying a data signal having a backward bias voltage for making the light-emitting element not emit light, and drives each of the pixel circuits.

Claims

1. An electro-optical device comprising:

a plurality of pixel circuits each including a light-emitting element and a driving transistor for driving the light-emitting element;

data lines that are connected to the plurality of pixel circuits and that supply data signals representing light-emitting gray-scale levels to the pixel circuits; and

a data line driving circuit that supplies the data signals to the pixel circuits through the data lines,

wherein the data line driving circuit applies to each pixel circuit in a predetermined sequence a forward frame period supplying a data signal having a forward bias voltage for making the light-emitting element emit light and a backward frame period supplying a data signal having a backward bias voltage for making the light-emitting element not emit light, and drives each of the pixel circuits.

2. The electro-optical device according to claim 1,

wherein the data line driving circuit carries out switching between the forward frame period and the backward frame period in the predetermined sequence, and simultaneously applies any one of the forward frame period and the backward frame period to all of the plurality of the pixel circuits.

3. The electro-optical device according to claim 1,

wherein the plurality of pixel circuits is divided into pixel blocks each having a predetermined size, and

the data line driving circuit carries out switching between the forward frame period and the backward frame period in the predetermined sequence for each of the pixel blocks.

4. The electro-optical device according to claim 3,

wherein the plurality of pixel circuits is arranged in a matrix, and

each pixel block is composed of a plurality of pixel circuits corresponding to one row.

5. The electro-optical device according to claim 3,

wherein the plurality of pixel circuits is arranged in a matrix, and

each pixel block is composed of a plurality of pixel circuits corresponding to one column.

6. The electro-optical device according to claim 1,

wherein the plurality of pixel circuits are divided into first and second pixel circuit groups, and

the data line driving circuit applies a first combined frame applying period for which the forward frame period is applied to the first pixel circuit group while the backward frame period is applied to the second pixel circuit group, and a second combined frame applying period for which the backward frame period is applied to the first pixel circuit group while the forward frame period is applied to the second pixel circuit group in the predetermined sequence.

7. The electro-optical device according to claim 6,

wherein the first pixel circuit group is discriminated from the second pixel circuit group on a pixel block unit having a predetermined size.

8. The electro-optical device according to claim 7,

wherein the plurality of pixel circuits are arranged in a matrix, and

the pixel block is composed of a plurality of pixel circuits corresponding to one row.

9. The electro-optical device according to claim 7,

wherein the plurality of pixel circuits are arranged in a matrix, and

the pixel block is composed of a plurality of pixel circuits corresponding to one column.

10. The electro-optical device according to claim 1,

wherein the data line driving circuit applies the backward frame period once after applying the forward frame period to each of the pixel circuits M times (M is an integer equal to or greater than 1), and determines a backward bias voltage applied to the data line in the backward frame period in accordance with a sum of N forward bias voltages applied to the data line in the forward frame period for the M times right before the backward frame period.

11. The electro-optical device according to claim 10,

wherein the data line driving circuit sets the backward bias voltage such that a first value obtained by multiplication of a backward bias voltage applied to the data line and its applying period in the backward frame period, and a second value obtained by multiplication of a forward bias voltage applied to the data line and its applying period in the previous M forward frame periods have the same absolute value but have polarities opposite to each other.

12. The electro-optical device according to claim 10,

wherein the data line driving circuit carries out alternative switching between the forward frame period and the backward frame for each pixel circuit, and sets the backward bias voltage such that a backward bias voltage applied to the data line in the backward frame period and a forward bias voltage applied to the data line in the previous forward bias period have the same absolute value but have polarities opposite to each other.

13. The electro-optical device according to claim 1,

wherein the data line driving circuit sets the backward bias voltage to a predetermined constant value.

14. The electro-optical device according to claim 1,

wherein the data line driving circuit includes:

a forward bias generating circuit that generates a plurality of forward bias voltages representing a plurality of light-emitting gray-scale levels;

a backward bias generating circuit that generates a plurality of backward bias voltages each having the same potential difference as and a polarity opposite to each of the plurality of forward bias voltages with respect to a predetermined reference voltage; and

a selection circuit that selects any one among the plurality of forward bias voltages and the plurality of backward bias voltages to apply the selected one to the data line.

15. The electro-optical device according to claim 1,

wherein the data line driving circuit includes:

a power supply circuit that supplies a high forward bias potential and a low forward bias potential used to generate a plurality of forward bias voltages representing a plurality of light-emitting gray-scale levels, and a high backward bias potential and a low backward bias potential used to generate a plurality of backward bias voltages each having the same potential difference as and a polarity opposite to each of the plurality of forward bias voltages with respect to a predetermined reference voltage;

a voltage dividing circuit having a plurality of resistors, and a plurality of voltage supplying lines for extracting voltages divided by the plurality of resistors;

a first switch that selects any one of the high forward bias potential and the low backward bias potential and connects the selected one to a high voltage terminal of the voltage dividing circuit; and

a second switch that selects any one of the low forward bias potential and the high backward bias potential and connects the selected one to a low voltage terminal of the voltage dividing circuit.

16. The electro-optical device according to claim 1,

wherein the light-emitting element is an organic electroluminescent (EL) element.

17. The electro-optical device according to claim 1,

wherein the driving transistor is a transistor formed of amorphous silicon.

18. An electronic apparatus comprising, as a display device, the electro-optical device according to claim 1.

19. A method of driving an electro-optical device including a plurality of pixel circuits each including a light-emitting element and a driving transistor for driving the light-emitting element;

and data lines connected to the plurality of pixel circuits to supply data signals representing light-emitting gray-scale levels to the pixel circuits, the method comprising;

applying to each of the pixel circuits in the predetermined sequence a forward frame period supplying a data signal having a forward bias voltage for making the light-emitting element emit light to the pixel circuit, and a backward frame period supplying a data signal having a backward bias voltage for making the light-emitting element not emit light to the pixel circuit; and

driving each of the pixel circuits.