Organic light emitting display device and method of manufacturing the same

Disclosed is an organic light emitting display device including a substrate having a plurality of sub-pixel areas, a switching thin film transistor formed on each of the sub-pixel areas, a driving thin film transistor connected to the switching thin film transistor, a color filter formed on at least one of sub-pixel areas, an insulating layer formed on the switching thin film transistor, the driving thin film transistor and the color filter, a pixel electrode connected to the driving thin film transistor, an organic light emitting member formed on the pixel electrode, and a common electrode formed on the organic light emitting member. The insulating layer has a groove. The groove is formed along a boundary of the pixel electrode. The groove has a width of about 0.2 to about 4 μm. The groove has a depth of about 0.2 to about 4 μm. The pixel electrode has an edge declined in the groove.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2006-0131045, filed on Dec. 20, 2006, which is hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an organic light emitting display device and a method of manufacturing the display device.

(b) Description of the Related Art

An organic light emitting display device includes an anode, a cathode and an organic layer interposed between the anode and the cathode. Electrons from the cathode and holes from the anode form excitons in the organic layer. The organic layer is illuminated by the energy emitted from the excitons.

Generally, the organic light emitting display device is of two types, a passive matrix type and an active matrix type. The active matrix type organic light emitting display device has a thin film transistor as a switching device.

A conventional organic light emitting display device has a partition that defines a pixel. Usually formation of the partition takes a long time during the manufacturing process. Moreover, moisture, oxygen or solvent permeated in the partition damages the organic layer and reduces the lifetime of the display device.

SUMMARY OF THE INVENTION

A display device according to an embodiment of the present invention includes an organic light emitting display device including a substrate having a plurality of sub-pixel areas, a switching thin film transistor formed on each of the sub-pixel areas, a driving thin film transistor connected to the switching thin film transistor, a color filter formed on at least one of the sub-pixel areas, an insulating layer formed on the switching thin film transistor, the driving thin film transistor and the color filter, a pixel electrode connected to the driving thin film transistor, an organic light emitting member formed on the pixel electrode, and a common electrode formed on the organic light emitting member. The insulating layer has a groove. The groove is formed along a boundary of the pixel electrode. The groove has a width of about 0.2 to about 4 μm. The groove has a depth of about 0.2 to about 4 μm. The pixel electrode has an edge declined in the groove.

A display device according to another embodiment of the present invention includes a substrate having a plurality of sub-pixel areas, a switching thin film transistor formed on each of the sub-pixel areas, a driving thin film transistor connected to the switching thin film transistor, an insulating layer formed on the driving thin film transistor, a pixel electrode connected to the driving thin film transistor, an organic light emitting member contacting an entire surface of the pixel electrode, and a common electrode formed on the organic light emitting member. The insulating layer has a groove. The groove is formed along a boundary of the pixel electrode. The pixel electrode has an edge declined in the groove.

According to a method of forming the display device, a switching thin film transistor and a driving thin film transistor are formed on a substrate in a sub-pixel area. A color filter is formed on at least one of the sub-pixel areas. An insulating layer having a grove is formed on the switching thin film transistor, the driving thin film transistor and the color filter. A pixel electrode having an edge declined in the groove is formed on the insulating layer. A light emitting member is formed on the pixel electrode. A common electrode is formed on the organic light emitting member.

DETAILED DESCRIPTION OF EMBODIMENTS

In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numerals refer to like elements throughout. It will be understood that when an element such as a layer, film, region, substrate, or panel is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

An organic light emitting display device according to an exemplary embodiment of the invention will be described with reference toFIG. 1.

FIG. 1is an equivalent circuit diagram of an organic light emitting display device according to an embodiment of the present invention.

Referring toFIG. 1, the organic light emitting display device includes a plurality of signal lines102,104, and106and a plurality of pixels PX arranged in a matrix shape.

The signal lines include a plurality of gate lines102for transmitting gate signals (or scanning signals), a plurality of data lines104for transmitting data signals, and a plurality of power supply lines106for transmitting a driving voltage. The gate lines102extend substantially in a row direction and substantially parallel to each other. The data lines104and the power supply lines106extend substantially in a column direction and substantially parallel to each other. In another embodiment, the power supply lines106may extend in a direction substantially parallel to the gate lines102. In another embodiment, the power supply lines106may have a net shape and extend in a direction substantially parallel to the gate lines102and a direction substantially parallel to the data lines104.

Each pixel PX includes a switching thin film transistor T1, a driving thin film transistor T2, a storage capacitor C, and an organic light emitting diode LD.

The switching thin film transistor T1has a control terminal connected to one of the gate lines102, an input terminal connected to one of the data lines104, and an output terminal connected to the driving thin film transistor T2. The switching thin film transistor T1transmits the data signals applied to the data line104to the driving thin film transistor T2in response to the gate signal applied to the gate line102.

The driving thin film transistor T2has a control terminal connected to the switching thin film transistor T1, an input terminal connected to the driving signal line106, and an output terminal connected to the organic light emitting diode LD. The driving thin film transistor T2drives an output current ILDhaving a magnitude depending on the voltage between the control terminal and the output terminal thereof.

The storage capacitor C is connected between the control terminal and the output terminal of the driving thin film transistor T2. The storage capacitor C stores the data signal applied to the control terminal of the driving thin film transistor T2and maintains the data signal after the switching thin film transistor T2turns off.

The organic light emitting diode LD has an anode connected to the output terminal of the driving thin film transistor T2and a cathode connected to a common voltage Vss. The anode functions as a pixel electrode and the cathode functions as a common electrode. The organic light emitting diode LD emits light having intensity depending on an output current ILDof the driving thin film transistor T2and an image is displayed.

The switching thin film transistor T1and the driving thin film transistor T2are n-channel field effect transistors. However, the switching thin film transistor T1and/or the driving thin film transistor T2may be a p-channel field effect transistor. In another embodiment, the connection configurations among the switching thin film transistor T1, the driving thin film transistor T2, the storage capacitor C, and the organic light emitting diode LD may be modified.

A detailed structure of the organic light emitting display device ofFIG. 1will be described in detail with reference toFIGS. 2 to 11and14.

A plurality of driving semiconductors122ais formed on a substrate101.

The substrate101includes an insulating material such as transparent glass or plastic.

The driving semiconductor122amay include a crystalline semiconductor material such as microcrystalline silicon or polycrystalline silicon. In one embodiment, the driving semiconductor122ais formed by a solid phase crystallization process using infrared and/or a magnetic field.

A plurality of driving input electrodes124, a plurality of driving output electrodes125and a plurality of power supply lines106are formed on the driving semiconductor122a.

The input electrodes124are extended from the power supply lines106. A driving input electrode124and a driving output electrode125are disposed on opposite sides of each other with respect to the driving semiconductor122a.

In one embodiment, the driving input electrodes124, the driving output electrodes125and the power supply lines106include an Al-containing metal such as Al and an Al alloy, an Ag-containing metal such as Ag and an Ag alloy, a Cu-containing metal such as Cu and a Cu alloy, a Mo-containing metal such as Mo and a Mo alloy, Cr, Ta, Ti, etc. The driving input electrodes124, the driving output electrodes125and the power supply lines106may have a multi-layered structure including two films having different physical characteristics.

The lateral sides of the driving input electrodes124, the driving output electrodes125and the power supply lines106are inclined relative to a surface of the substrate101, and the inclination angle thereof is in a range from about 30 to about 80 degrees.

A plurality of ohmic contacts122bis formed between the driving semiconductor122aand the driving input electrode124, and between the driving semiconductor122aand the driving output electrode125, respectively.

In one embodiment, the ohmic contacts122binclude a crystalline semiconductor material such as microcrystalline silicon or n+hydrogenated a-Si heavily doped with an n-type impurity such as phosphorus.

A gate insulating layer126is formed on the driving input electrodes124, the driving output electrodes125and the power supply lines104. In one embodiment, the gate insulating layer126includes silicon oxide (SiOx) or silicon nitride (SiNx). The gate insulating layer126may have a single-layered structure, or may have a multi-layered structure including a first layer of silicon oxide and a second layer of silicon nitride.

A plurality of driving control electrodes121, a plurality of switching control electrodes111and a plurality of gate lines102are formed on the gate insulating layer126.

Each of the switching control electrodes111is extended from each of the gate lines102and each of the driving control electrodes121is separated from each of the gate lines102.

The driving control electrodes121, the switching control electrodes111and the gate lines102may include the same material as power supply lines106.

The driving control electrodes121, the switching control electrodes111and the gate lines102have inclined edge profiles, and the inclination angles thereof are in a range from about 30 to about 80 degrees.

A portion106aof the power supply line106and a portion of the driving control electrode121overlaps to form a storage capacitor C.

A second gate insulating layer116is formed on the driving control electrodes121, the switching control electrodes111and the gate lines102. In one embodiment, the second gate insulating layer116includes silicon oxide (SiOx) or silicon nitride (SiNx)

A plurality of switching semiconductors112aincluding hydrogenated a-Si is formed on the second gate insulating layer116. The switching semiconductor112aoverlaps the switching control electrodes111.

A plurality of switching input electrodes114, a plurality of switching input electrodes115and a plurality of data lines104are formed on the switching semiconductor112a.

Each of the switching input electrodes114is extended from each of the data lines104.

A plurality of ohmic contacts112bare formed between the switching semiconductors112aand the switching input electrodes114, and between the switching semiconductors112aand the switching output electrodes115, respectively. In one embodiment, the ohmic contacts112bincludes n+hydrogenated a-Si heavily doped with an n-type impurity such as phosphorus.

The switching output electrode115is connected to the driving control electrode121through a first contact hole129formed in the second gate insulating layer116. The switching output electrode115is in direct contact with the driving control electrode121. Because the switching output electrode115is directly connected to the driving control electrode121without an auxiliary electrode, the process becomes simplified. Moreover, the contact resistance between the switching output electrode115and the driving control electrode121is lowered.

A passivation layer127is formed on the switching input electrodes114, the switching input electrodes115and the data lines104.

The passivation layer127includes an inorganic layer such as silicon nitride or silicon oxide.

In one embodiment, a color filter132is formed on the passivation layer127. The color filter132is formed on at least one of the sub-pixel areas. In one embodiment, the sub-pixel areas include a red sub-pixel area, a green sub-pixel area, a blue sub-pixel area and a white sub-pixel area. The red sub-pixel area, the green sub-pixel area, the blue sub-pixel area and the white sub-pixel area form a pixel unit area. Each sub-pixel area includes a sub-pixel. Examples of the sub-pixel include a red sub-pixel, a green sub-pixel, a blue sub-pixel and a white sub-pixel. The red sub-pixel, the green sub-pixel, the blue sub-pixel and the white sub-pixel form a pixel unit. In one embodiment, a red color filter is formed on the red sub-pixel area, a green color filter is formed on the green sub-pixel area, and a blue color filter is formed on the blue sub-pixel area.

An insulating layer133is formed on the color filter132, and a pixel electrode130is formed on the insulating layer133.

The insulating layer133covers uneven surfaces of the color filter132and serves as a leveling layer. In one embodiment, the insulating layer133includes an organic material. The insulating layer has a groove131. The groove has a width of about 0.2 to about 4 μm. The groove has a depth of about 0.2 to about 4 μm. When the width and the depth of the groove is beyond the scope, the pixel electrode130may be formed outside the groove, or the groove131may penetrate the insulating layer133. In one embodiment, the pixel electrode130has a thickness of about 0.1 μm and the groove has a width of about 0.5 μm and a depth of about 0.5 μm to contain the edge130aof the pixel electrode130. In one embodiment, the groove is formed along a boundary of the pixel electrode.

A second contact hole128is formed together with the groove. The second contact hole128exposes at least a portion of the driving output electrode125. The second contact hole128is formed through the insulating layer133, the passivation layer127, the second gate insulating layer116and the first gate insulating layer126.

The pixel electrodes130are connected to the driving output electrodes125through the second contact hole128.

The pixel electrodes130may include a transparent conductor such as indium tin oxide or indium zinc oxide. Alternatively, when the organic light emitting display device according to an exemplary embodiment of the present invention is a top-emission type, the pixel electrodes130may include an opaque conductor such as Al or an Al alloy, Au, Pt, Ni, Cu, or W that have a high work function, or alloys thereof.

The pixel electrode130has an edge130adeclined in the groove131. Usually, pixel electrode130has a steep taper angle. If an organic light emitting member134on the pixel electrode130is not thick enough to cover the edge130aof the pixel electrode130, the pixel electrode130becomes connected with the common electrode136and a short circuit is generated. In this embodiment, because the edge130aof the pixel electrode130is declined in the groove131, the possibility of the short circuit between the pixel electrode130and a common electrode136is lowered. Because the edge130aof the pixel electrode130is stably formed in the groove of the insulating layer133, the process of forming a partition could be omitted.

In this embodiment, a portion of the color filter132that is usually covered by the partition can serve as a display pixel area to improve the aperture ratio of the display device.

Hereinafter, a process of forming the insulating layer133will be explained in detail.

Referring toFIGS. 11A to 11C, a photoresist material PR is formed on an insulating material133a. The photoresist material PR is exposed to light through a mask140having slits. The mask140has at least one light blocking area S1, at least one slit area S2and at least one light penetrating area S3. The second contact hole128is formed in the light penetrating area S3and the groove131is formed in the slit area S2.

The photoresist material PR is exposed and then developed. In a first developing process, the photoresist material PR in the light penetrating area S3is removed and a portion of the photoresist material PR in the slit area S2is removed. The exposed insulating layer133a, the passivation layer127, the second gate insulating layer116and the first gate insulating layer126are then dry etched to form the second contact hole128exposing the driving output electrode125.

In a second developing process, the photoresist material PR in the slit area S2is removed to expose a portion of the insulating layer133. A second etching process is performed to form the groove131. The remaining photoresist material PR is then stripped. In another embodiment, other masks such as a half-tone mask may be used instead of the slit mask.

FIG. 12is a cross-sectional view illustrating a process of insulating the edge130aof the pixel electrode130according to another embodiment of the invention.

Referring toFIG. 12, the insulating layer133is cured after the pixel electrode130is formed. When the insulating layer133is cured, a portion133aof the insulating layer133reflows to cover the edge130aof the pixel electrode130. The insulating layer is thermally cured or cured by light.

In one embodiment, the insulating layer133is primarily cured before the pixel electrode130is formed. While the formation of the pixel electrode130, the insulating layer133is developed using a developer for the pixel electrode130. The developer may dissolve the insulating layer133and the insulating layer133may cover the edge of the pixel electrode133. The insulating layer133is secondarily cured at a temperature higher than the primary curing.

In this embodiment, the edge130aof the pixel electrode130is securely insulated from the common electrode136by the reflowed insulating layer133without using a photolithography process.

The organic light emitting display device may further include a cover member138(seeFIG. 13B) covering the edge130aof the pixel electrode130. The cover member138secures insulation between the pixel electrode130and the common electrode136.

A process of forming the cover member138will be explained in detail. Referring toFIG. 13A, an organic material138ais coated on the entire surface of the substrate having the pixel electrode130formed thereon. Referring toFIG. 13B, the organic material138ais ashed such that a position of an upper surface of the cover member138is substantially the same or is lower than a position of an upper surface of the pixel electrode130.

In this embodiment, the edge130aof the pixel electrode130is securely insulated without using a photolithography process.

Referring toFIG. 14, an organic light emitting member134is formed on the pixel electrodes130.

Because a partition is not formed, the organic light emitting member134contacts the entire surface of the pixel electrode130.

The organic light emitting member134has at least two layers. In one embodiment, the organic light emitting member134includes a hole injection layer, a hole transport layer, an organic light emitting layer, an electron injection layer and an electron transport layer. The lowest layer of the organic light emitting member134is in direct contact with the pixel electrode130, and the lowest layer contacts the entire surface of the pixel electrode130. In one embodiment, the hole injection layer becomes the lowest layer.

In one embodiment, the organic light emitting layers include a low molecular weight material.

Examples of the low molecular weight materials include anthracene such as 9,10-diphenylanthracene, butadiene such as tetraphenylbutadiene, tetracene, a distyrylarylene derivative, a benzazole derivative, a carbazole derivative, etc. Alternatively, the low molecular weight material is used as a host. The host is doped by a dopant such as xanthene, perylene, cumarine, rhodamine, rubrene, a dicyanomethylenepyran compound, a thiopyran compound, a (thia)pyrilium compound, a periflanthene derivative, an indenoperylene derivative, a carbostyryl compound, Nile red, and quinacridone to enhance the efficiency of light emission.

In one embodiment, a red organic light emitting layer, a green organic light emitting layer and a blue organic light emitting layer are vertically formed in each pixel.

The red organic light emitting layer, the green organic light emitting layer and the blue organic light emitting layer are formed not only in each sub-pixel areas but also areas outside the sub-pixel areas. The red organic light emitting layer, the green organic light emitting layer and the blue organic light emitting layer are formed all over a display area. In one embodiment, the vertically stacked red organic light emitting layer, the green organic light emitting layer and the blue organic light emitting layer emit white light all together and each sub-pixel emits red, green, blue or white color after passing through the color filter132if a color filter exists under the pixel electrode of the sub-pixel.

In another embodiment, the organic light emitting layers include a polymer. Examples of the polymers include a polyfluorene derivative, a (poly)paraphenylenevinylene derivative, a polyphenylene derivative, polyvinylcarbazole, a polythiophene derivative, etc.

In one embodiment, the hole transport layer and/or the hole injecting layer including a material having a work function of a magnitude are intermediate between the pixel electrode130and the organic light emitting layer. The electron transport layer and/or the electron injecting layer including a material having a work function are intermediate between the common electrode136and the organic light emitting layer. Examples of the hole transport layer and the hole injecting layer include a diamine compound, [4,4′,4″-tris (3-methylphenyl) phenylamino]triphenylamine (MTDATA), N,N′-diphenyl-N,N′-di(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD), 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane, N,N,N′,N′-tetra(2-naphthyl)-4,4-diamino-p-terphenyl, 4,4′,4-tris[(3-methylphenyl)phenylamino]triphenylamine, polypyrrole, polyaniline, or a mixture of poly-3,4-ethylenedioxythiophene and polystyrenesulfonate (PEDOT:PSS).

Four sub-pixels for red, green, blue, and white may be disposed in a stripe shape or a mosaic shape.

The common electrode136is formed on the light emitting members134. The common electrode136is formed on the entire surface of the organic light emitting members134, and applies a current to the organic light emitting member134along with the pixels electrodes130.

The pixel electrode130, the organic light emitting member134, and the common electrode136form an organic light emitting diode LD.

In embodiments of the present invention, it is described that each of the pixels includes one switching thin film transistor T1and one driving thin film transistor T2, but they may further include at least one transistor and a plurality of wires such that deterioration of the organic light emitting diode LD and the driving thin film transistor T1is compensated and the lifetime of the organic light emitting diode is improved.

As described above, according to one embodiment of the invention, a process of forming a partition can be omitted. Therefore, the overcall processing time is reduced and conventional problem that moisture, oxygen or solvent permeated in the partition deteriorates organic layer can be minimized. Moreover, a portion of the color filter that was covered by the partition can be used as a display pixel area to improve the aperture ratio of the display device. Because the switching output electrode is in direct contact with the driving control electrode, the contact resistance between the switching output electrode and the driving control electrode is lowered.