KR20090042405A - Organic light emitting display - Google Patents

Abstract

An organic electroluminescent display device of a digital voltaic driving method is provided to improve the display quality by preventing the generation of the brightness difference in the display unit. The sub pixel positioned in the display unit comprises the capacitor(C) in which one end is connected to the first power source wiring(VDD). The first transistor(T1) is driven by the data signal stored in the capacitor. The second transistor(T2) controls the power source supplied through the first transistor. In the organic light-emitting diode(D), the first electrode is connected to the other end of the second transistor and the second electrode is connected to the second power line(GND) and the light emitting period is determined by the actuating time of the second transistor. The display unit is positioned in the sub pixel including the transistor circuit part(MT).

Description

Organic Light Emitting Display

The present invention relates to an organic light emitting display device.

An organic light emitting display device used in an organic light emitting display device is a self-light emitting device in which a light emitting layer is formed between two electrodes positioned on a substrate.

In addition, the organic light emitting display device may include a top-emission method, a bottom-emission method, or a dual-emission method according to a direction in which light is emitted. According to the driving method, it is divided into a passive matrix type and an active matrix type.

In the organic light emitting display device, when a scan signal, a data signal, and a power are supplied to a plurality of subpixels arranged in a matrix form, the selected subpixels emit light to display an image.

On the other hand, in the conventional organic light emitting display device, the voltage supplied to the organic light emitting diode included in each subpixel is changed by the parasitic resistance formed in the panel. Thus, when current flows through the organic light emitting diode, sub-pixels located far from the sub-pixels close to the point where power is supplied are supplied with different voltages.

As such, when the voltage supplied through the power source is changed, the current flowing through the organic light emitting diode is changed to change the luminance. In this case, when all the sub-pixels positioned in the panel emit light, a difference in luminance occurs from the first line to the last line to which power is wired.

Accordingly, in the organic light emitting display device, a method for solving a problem in which luminance difference occurs in all subpixels positioned in a panel should be prepared.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic light emitting display device that can solve the problem of a luminance difference occurring in a display unit.

According to the above-described problem solving means, the present invention provides a capacitor, a first transistor driven by a data signal stored in the capacitor, a second transistor switching driving to control power supplied through the first transistor, and a second transistor. A display unit located in a plurality of subpixels including an organic light emitting diode in which a light emitting period is determined according to a driving time, and a transistor circuit unit including one or more transistors for switching and storing a data signal in a capacitor; And a digital current source unit for storing a data signal in a capacitor through the transistor circuit unit.

The subpixel includes a capacitor having one end connected to the first power line, a first transistor connected at one end to the first power line and a gate connected to the other end of the capacitor, and one end connected to the other end of the first transistor and having a first signal line. A second transistor having a gate connected to the organic light emitting diode, an organic light emitting diode having a first electrode connected to the other end of the second transistor, and a second electrode connected to the second power line; It may include a transistor circuit portion including one or more transistors for switching driving.

The transistor circuit unit may include a third transistor having a gate connected to the second signal line, one end of which is connected to a capacitor, and one end of which is connected to the other end of the second transistor, and one end of which is connected to a gate of the second signal line and the other end of the third transistor And a fourth transistor connected to the other end of the digital current source unit.

The transistor circuit unit includes a third transistor having a gate connected to the second signal wire and one end connected to the capacitor, and one end connected to the other end of the second transistor, a gate connected to the second signal wire, and one end connected to the other end of the capacitor. It may include a fourth transistor connected to the other end of the digital current source.

The first to fourth transistors may be p-type transistors.

The digital current source unit may store a data signal in a capacitor by sinking the power supplied from the first power line when the second and third transistors are driven.

The organic light emitting diode may emit light when the first and second transistors are driven.

The present invention is to provide a digital current drive type organic light emitting display device which can improve the display quality by solving a problem that a luminance difference occurs in the display unit.

Hereinafter, with reference to the accompanying drawings, the specific content for the practice of the present invention will be described.

1 is a schematic plan view of an organic light emitting display device.

As illustrated in FIG. 1, the organic light emitting display device may include a display unit 120 on which a plurality of sub pixels P are positioned on the substrate 110. The plurality of sub pixels P located on the substrate 110 are vulnerable to moisture or oxygen.

Thus, the sealing substrate 130 may be provided, and the adhesive member 140 may be formed on the outer substrate 110 of the display unit 120 to encapsulate the substrate 110 and the sealing substrate 130. Meanwhile, the plurality of sub pixels P may be driven by the driver 150 positioned on the substrate 110 to represent an image.

Here, the subpixel P may be defined as one unit pixel by combining the red, green, and blue subpixels into one. However, four or more subpixels P may be defined as one unit pixel, further including a subpixel emitting white or other colors (for example, orange, yellow, etc.).

The subpixel P may include at least an organic light emitting layer. The organic light emitting layer may further include at least one of a hole injection layer, a hole transport layer, an electron transport layer, or an electron injection layer. In addition, the organic light emitting layer may further include a buffer layer, a blocking layer, and the like to control the flow of holes or electrons between the anode and the cathode. It may be.

Although not shown, the sub-pixel P may include a capacitor, a first transistor driven by a data signal stored in the capacitor, a second transistor switching switching to control power supplied through the first transistor, and a second transistor. The transistor may include an organic light emitting diode having a light emitting time determined according to a driving time of the transistor, and a transistor circuit including one or more transistors for driving switching to store a data signal in a capacitor. More details will be described below with reference to the drawings.

Meanwhile, although one driver 150 is illustrated on the substrate 110, the driver 150 includes a scan driver for supplying a scan signal to a subpixel and a digital current source unit for supplying a data signal to the subpixel. can do.

Hereinafter, the cross-sectional structure of the subpixel will be attached and described in more detail.

FIG. 2A is an exemplary cross-sectional view of the subpixel illustrated in FIG. 1, and FIG. 2B is another exemplary cross-sectional view of the subpixel illustrated in FIG. 1.

As shown in FIG. 2A, the substrate 110 may be located. The substrate 110 may be selected as a material for forming an element having excellent mechanical strength or dimensional stability. As the material of the substrate 110, a glass plate, a metal plate, a ceramic plate or a plastic plate (polycarbonate resin, acrylic resin, vinyl chloride resin, polyethylene terephthalate resin, polyimide resin, polyester resin, epoxy resin, silicone resin, fluorine) Resin, etc.) is mentioned.

The buffer layer 111 may be positioned on the substrate 110. The buffer layer 111 may be formed to protect the thin film transistor formed in a subsequent process from impurities such as alkali ions flowing out of the substrate 110. The buffer layer 111 may use silicon oxide (SiO ₂ ), silicon nitride (SiNx), or the like.

The semiconductor layer 112 may be positioned on the buffer layer 111. The semiconductor layer 112 may include amorphous silicon or polycrystalline silicon obtained by crystallizing the same. Although not shown here, the semiconductor layer 112 may include a channel region, a source region, and a drain region, and the source region and the drain region may be doped with P-type or N-type impurities.

The gate insulating layer 113 may be positioned on the substrate 110 including the semiconductor layer 112. The gate insulating layer 113 may be selectively formed using silicon oxide (SiO ₂ ), silicon nitride (SiNx), or the like.

The gate electrode 114 may be positioned on the gate insulating layer 113 to correspond to the channel region of the semiconductor layer 112. The gate electrode 114 is made of aluminum (Al), aluminum alloy (Al alloy), titanium (Ti), silver (Ag), molybdenum (Mo), molybdenum alloy (Mo alloy), tungsten (W), tungsten silicide (WSi _2). It may include any one of).

An interlayer insulating film 115 may be positioned on the substrate 110 including the gate electrode 114. The interlayer insulating film 115 may be an organic film or an inorganic film, or may be a composite film thereof.

When the interlayer insulating film 115 is an inorganic film, the interlayer insulating film 115 may include silicon oxide (SiO ₂ ), silicon nitride (SiNx), or SOG (silicate on glass). On the other hand, the organic film may include an acrylic resin, a polyimide resin or a benzocyclobutene (BCB) resin. First and second contact holes 115a and 115b may be disposed in the interlayer insulating layer 115 and the gate insulating layer 113 to expose a portion of the semiconductor layer 112.

The first electrode 116a may be positioned on the interlayer insulating film 115. The first electrode 116a may be an anode and may have a single layer structure including a conductive layer such as indium tin oxide (ITO) or indium zinc oxide (IZO).

In addition, the first electrode 116a may have a multilayer structure including a conductive layer such as indium tin oxide (ITO) or indium zinc oxide (IZO). The description thereof will be described in more detail with reference to the accompanying drawings.

Source and drain electrodes 116b and 116c may be positioned on the interlayer insulating film 115. The source electrode and the drain electrode 116b and 116c may be electrically connected to the semiconductor layer 112 through the first and second contact holes 115a and 115b. A portion of the drain electrode 116c may be positioned on the first electrode 116a and electrically connected to the first electrode 116a.

The source and drain electrodes 116b and 116c may include a low resistance material to lower the wiring resistance. Here, the source electrode and the drain electrode 116b and 116c may be formed of aluminum (Al), aluminum (Alnd), molybdenum (Mo), chromium (Cr), titanium nitride (TiN), molybdenum nitride (MoN), or chromium. It may be formed into a multilayer structure including a metal layer such as nitride (CrN). The description thereof will be described in more detail with reference to the accompanying drawings.

The transistor located on the ideal substrate 110 may include a gate electrode 114, a source electrode, and a drain electrode 116b and 116c, and a transistor array having a plurality of transistors and capacitors may be electrically connected to the following organic light emitting diodes. have. (However, the structure of the capacitor is omitted)

An insulating layer 117 exposing a portion of the first electrode 116a may be disposed on the first electrode 116a (eg, an anode). The insulating layer 117 may include an organic material such as benzocyclobutene (BCB) resin, acrylic resin, or polyimide resin.

The organic light emitting layer 118 may be disposed on the exposed first electrode 116a, and the second electrode 119 (eg, a cathode) may be positioned on the organic light emitting layer 118. The second electrode 119 may be a cathode for supplying electrons to the organic light emitting layer 118, and may include magnesium (Mg), silver (Ag), calcium (Ca), aluminum (Al), or an alloy thereof. .

The organic light emitting diode connected to the source or drain electrodes 116b and 116c of the transistor included in the transistor array on the ideal substrate 110 includes the first electrode 116a, the organic light emitting layer 118, and the second electrode 119. It may include.

Unlike FIG. 2A, referring to FIG. 2B, the first electrode 116a positioned on the source or drain electrodes 116b and 116c may be positioned on the planarization layer 117a to planarize the surface of the transistor array. In this case, the insulating layer 117b may be positioned to expose a portion of the first electrode 116a (eg, an anode) on the planarization layer 117a.

In the cross-sectional structure of a subpixel as shown in FIGS. 2A and 2B, the structure of the transistor included in the transistor array may vary depending on whether the gate structure is a top gate or a batam gate. In addition, the structure of the transistor may vary depending on the number of masks used in forming the transistor array and the semiconductor layer material. Therefore, the cross-sectional structure of the sub pixel is not limited to this.

On the other hand, the organic light emitting display device according to the present invention can store the data signal using the digital current source unit. Accordingly, the subpixels positioned in the display unit of the organic light emitting display device may include a transistor circuit unit.

Hereinafter, a circuit configuration of the subpixels positioned in the display unit of the organic light emitting display device will be described in detail with reference to the accompanying drawings.

First Embodiment

3 is an exemplary diagram of a subpixel circuit configuration according to the first embodiment of the present invention.

As illustrated in FIG. 3, the subpixel positioned in the display unit may include a capacitor C having one end connected to the first power line VDD. In addition, a gate may be connected to the other end of the capacitor C and may include a first transistor T1 having one end connected to the first power line VDD. In addition, one end may be connected to the other end of the first transistor T1 and may include a second transistor T2 having a gate connected to the first signal line S1. The organic light emitting diode D may include an organic light emitting diode D connected to the other end of the second transistor T2 and a second electrode connected to the second power line GND. In addition, the transistor circuit unit MT may include one or more transistors connected to the second signal wiring S2 and configured to drive switching to store a data signal in the capacitor C.

The digital current source unit SOURCE may store a data signal in the capacitor C through the transistor circuit MT. The digital current source unit SOURCE may output a current pulse in a form in which a current mirror for copying one current source is uniformly implemented.

Here, the transistor circuit MT includes a third transistor T3 having a gate connected to the second signal wire S2, one end connected to the capacitor C, and the other end connected to one end of the second transistor T2. can do. In addition, the gate may be connected to the second signal line S2, and may include a fourth transistor having one end connected to the other end of the third transistor T3 and the other end connected to the digital current source unit SOURCE.

According to such a configuration, the digital current source unit SOURCE sinks the power supplied from the first power supply line VDD when the second and third transistors T2 and T3 are driven to form a capacitor ( The data signal can be stored in C).

Meanwhile, the first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 described above may be p-type transistors.

The sub pixel having such a structure is driven by the driving method as shown in FIG.

4 is an example of driving waveforms.

First, the scan signal scan2 is supplied to the second signal wiring S2 to turn on the third and fourth transistors T3 and T4 included in the transistor circuit MT. The data signal data is stored in the capacitor C using the digital current source unit SOURCE. The scan signal scan2 supplied to the second signal wire S2 is cut off to turn off the third and fourth transistors T3 and T4. The scan signal scan1 is supplied to the first signal wiring S1. Then, the first transistor T1 is turned on by the data signal data stored in the capacitor C. At this time, the organic light emitting diode D is powered through the turned on first and second transistors T1 and T2. It receives light and emits light.

Here, when the first and second transistors T1 and T2 are driven, the organic light emitting diode D may emit light by receiving the current I _EL from the first power line VDD.

Therefore, the present invention is a method of expressing the gray scale by writing a current in the capacitor (C) and adjusting the light emission period by using a digital current source (SOURCE) for current sourcing to a digital value. More specifically, the present invention is a method of expressing brightness by adjusting the driving time of the second transistor T2 turned on according to the scan signal scan1 supplied to the first signal wiring S1 during one frame.

Second Embodiment

5 is an exemplary diagram of a subpixel circuit configuration according to the second embodiment of the present invention.

As illustrated in FIG. 5, the subpixel positioned in the display unit may include a capacitor C having one end connected to the first power line VDD. In addition, a gate may be connected to the other end of the capacitor C and may include a first transistor T1 having one end connected to the first power line VDD. In addition, one end may be connected to the other end of the first transistor T1 and may include a second transistor T2 having a gate connected to the first signal line S1. The organic light emitting diode D may include an organic light emitting diode D connected to the other end of the second transistor T2 and a second electrode connected to the second power line GND. In addition, the transistor circuit unit MT may be connected to the second signal line S2 and include one or more transistors that switch to drive the data signal in the capacitor C.

The digital current source unit SOURCE may store a data signal in the capacitor C through the transistor circuit MT. The digital current source unit SOURCE may output a current pulse in a form in which a current mirror for copying one current source is uniformly implemented.

Here, the transistor circuit MT includes a third transistor T3 having a gate connected to the second signal wire S2, one end connected to the capacitor C, and the other end connected to one end of the second transistor T2. can do. In addition, the gate may be connected to the second signal line S2, one end of which is connected to the other end of the capacitor C, and the other of which is connected to the other end of the digital current source unit SOURCE.

According to such a configuration, the digital current source unit SOURCE sinks the power supplied from the first power supply line VDD when the second and third transistors T2 and T3 are driven to form a capacitor ( The data signal can be stored in C).

Meanwhile, the first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 described above may be p-type transistors.

The subpixel having the above structure is driven by the driving method as shown in FIG.

4 is an example of driving waveforms.

The description will be made with reference to FIGS. 4 and 5 to assist in understanding the description.

First, the scan signal scan2 is supplied to the second signal wiring S2 to turn on the third and fourth transistors T3 and T4 included in the transistor circuit MT. The data signal data is stored in the capacitor C using the digital current source unit SOURCE. The scan signal scan2 supplied to the second signal wire S2 is cut off to turn off the third and fourth transistors T3 and T4. The scan signal scan1 is supplied to the first signal wiring S1. Then, the first transistor T1 is turned on by the data signal data stored in the capacitor C. At this time, the organic light emitting diode D is powered through the turned on first and second transistors T1 and T2. It receives light and emits light.

Here, when the first and second transistors T1 and T2 are driven, the organic light emitting diode D may emit light by receiving the current I _EL from the first power line VDD.

Therefore, the present invention is a method of expressing the gray scale by writing a current in the capacitor (C) and adjusting the light emission period by using a digital current source (SOURCE) for current sourcing to a digital value. More specifically, the present invention is a method of expressing brightness by adjusting the driving time of the second transistor T2 turned on according to the scan signal scan1 supplied to the first signal wiring S1 during one frame.

As described above, the first and second embodiments of the present invention provide an organic light emitting display device that can solve a problem in which a luminance difference occurs in a display unit, thereby preventing a problem in which a luminance difference occurs as well as a load effect generated during driving. There is an effect that can be solved.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical configuration of the present invention described above may be modified in other specific forms by those skilled in the art to which the present invention pertains without changing its technical spirit or essential features. It will be appreciated that it may be practiced. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. In addition, the scope of the present invention is shown by the claims below, rather than the above detailed description. Also, it is to be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention.

1 is a schematic plan view of an organic light emitting display device.

FIG. 2A is an exemplary cross-sectional view of the subpixel illustrated in FIG. 1. FIG.

FIG. 2B is another exemplary cross sectional view of the sub-pixel illustrated in FIG. 1; FIG.

3 is a diagram illustrating a subpixel circuit configuration according to the first embodiment of the present invention.

4 is an exemplary drive waveform.

Fig. 5 is an exemplary diagram of a sub pixel circuit configuration according to the second embodiment of the present invention.

<Explanation of symbols on main parts of the drawings>

110: substrate 120: display unit

130: sealing substrate 140: adhesive member

150: driver P: subpixel

VDD: first power wiring GND: second power wiring

T1: first transistor T2: second transistor

T3: third transistor T4: fourth transistor

D: organic light emitting diode S1: first signal wiring

S2: second signal wiring SOURCE: digital current source unit

Claims (7)

A light emitting period according to a driving time of the capacitor, a first transistor driven by a data signal stored in the capacitor, a second transistor switching driving to control power supplied through the first transistor, and a driving time of the second transistor A display unit located in a plurality of subpixels including a predetermined organic light emitting diode and a transistor circuit unit including at least one transistor configured to switch driving to store a data signal in the capacitor; And And a digital current source unit for storing the data signal in the capacitor through the transistor circuit unit. The method of claim 1, The sub pixel is, A first signal connected to one end of the capacitor connected to a first power line, a first transistor connected to a gate of the other end of the capacitor, and one end connected to a first end of the first power wire, and a first signal A second transistor having a gate connected to a wiring, the organic light emitting diode having a first electrode connected to the other end of the second transistor, and a second electrode connected to a second power supply wiring, and a second signal wiring connected to the capacitor. And a transistor circuit unit including one or more transistors for switching driving to store the data signal. The method of claim 2, The transistor circuit unit, A third transistor having a gate connected to the second signal line, one end of which is connected to the capacitor, and another end of which is connected to one end of the second transistor, and a gate of which is connected to the second signal line, and one end of the third transistor And a fourth transistor connected to the other end of the digital current source unit. The method of claim 2, The transistor circuit unit, A third transistor having a gate connected to the second signal line, one end of which is connected to the capacitor, and the other end of which is connected to one end of the second transistor; And a fourth transistor having the other end connected to the digital current source unit. The method according to claim 3 or 4, The first to fourth transistors, An organic light emitting display device which is a p-type transistor. The method according to claim 3 or 4, The digital current source unit, And driving the second and third transistors to store the data signal in the capacitor by sinking the power supplied from the first power line. The method of claim 1, The organic light emitting diode, An organic light emitting display device which emits light when the first and second transistors are driven.

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