Pixel circuit with large and small OLED elements connected to a single driving transistor wherein the large OLED element is further controlled by a memory circuit within the pixel

Patent metadata

Field	Value
Publication number	US-9711084-B2
Application number	US-201414552519-A
Country	US
Kind code	B2
Filing date	Nov 25, 2014
Priority date	Nov 26, 2013
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

An organic EL display device includes a first pixel circuit for displaying a first color. The first pixel circuit includes a large light emitting element, a small light emitting element, and a current control circuit that controls whether a current is supplied to the small light emitting element and the large light emitting element or not respectively, and the amount of the current to be supplied to at least one of the small light emitting element and the large light emitting element, according to a tone to be displayed by the first pixel circuit. The current control circuit supplies the current to the small light emitting element if the tone is equal to or smaller than a threshold value, and supplies the current to at least the large light emitting element if the tone is larger than the threshold value.

First claim

What is claimed is:

1. An organic EL display device comprising:
a first pixel having a first pixel circuit for displaying a first color;
a second pixel being adjacent to the first pixel and having a second pixel circuit for displaying a second color different from the first color;
the first pixel circuit including:
a large light emitting element;
a small light emitting element smaller in a light emitting area than the large light emitting element; and
a current control circuit that controls whether a current is supplied to the small light emitting element and the large light emitting element or not respectively, and the amount of the current to be supplied to the small light emitting element or the large light emitting element to which the current is supplied, according to a tone to be displayed by the first pixel circuit,
the second pixel circuit including:
only one light emitting element; and
a current regulator circuit for regulating the amount of current to be supplied to the only one light emitting element,
wherein
the first pixel has a first light emitting area,
the first light emitting area consists of a large light emitting area corresponding to the large light emitting element and a small light emitting area corresponding to the small light emitting element,
the second pixel has a second light emitting area,
the second light emitting area consists of only one light emitting area corresponding to the only one light emitting element, and
wherein the current control circuit included in the first pixel circuit supplies the current to the small light emitting element if the tone to be displayed by the first pixel circuit is equal to or smaller than a threshold value, and supplies the current to at least the large light emitting element if the tone to be displayed by the first pixel circuit is larger than the threshold value,
a drive transistor included in the current control circuit regulates the amount of the current to be supplied to the small light emitting element and the large light emitting element,
the large light emitting element and the small light emitting element are electrically connected to one electrode of a source electrode and a drain electrode of the drive transistor in parallel through a switch, and
the current control circuit includes the switch that is between the one electrode and the large light emitting element, the switch is controlled by a signal from a control line, and a gate of the switch is connected to a memory circuit which stores the signal, wherein the current control circuit includes the memory circuit and the memory circuit supplies the signal by processing using a NOT logic circuit.

2. The organic EL display device according to claim 1 ,
wherein the current control circuit included in the first pixel circuit supplies the current to the large light emitting element so that the amount of current supplied to the large light emitting element simply monotonically increases according to an increase in a tone if the tone to be displayed by the first pixel circuit is larger than the threshold value.

3. The organic EL display device according to claim 1 ,
wherein the drive transistor regulates the amount of the current to be supplied to the small light emitting element and the large light emitting element to which the current is supplied, according to the tone to be displayed by the first pixel circuit.

4. The organic EL display device according to claim 1 , further comprising a pixel including a plurality of sub pixels,
wherein the plurality of sub pixels include the first pixel and the second pixel.

5. The organic EL display device according to claim 1 wherein the current control circuit supplies the current to both the large light emitting element and the small light emitting element if the tone to be displayed by the first pixel circuit is larger than the threshold value.

6. The organic EL display device according to claim 5 , wherein the current control circuit supplies a first current to the small light emitting element if the tone is equal to the threshold value and a second current to the small light emitting element if the tone is a subsequent level of the threshold value, and
the first current is larger than the second current.

7. The organic EL display device according to claim 5 , wherein the current control circuit supplies a first current to the small light emitting element if the tone is equal to the threshold value and a second current to the small light emitting element if the tone is a subsequent level of the threshold value, and
a current density of the first current is larger than a current density of the second current.

Assignees

• Japan Display Inc

Inventors

• Uetake Naoki

Classifications

• G09G3/207

  by domain size control (G09G3/3637 takes precedence) · CPC title

• G09G2300/0842

  forming a memory circuit, e.g. a dynamic memory with one capacitor · CPC title

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title

• G09G2300/0452

  Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components · CPC title

• G09G3/2074

  using sub-pixels · CPC title