Display apparatus and manufacturing method thereof

A display apparatus includes; a substrate, a transistor formed on the substrate, a pixel electrode connected to the transistor, a wall surrounding the pixel electrode, the wall including a main wall and a sub wall, the main wall having a first height and the sub wall having a second height less than the first height of the main wall, an organic layer formed on the pixel electrode, a common electrode formed on the organic layer, and an encapsulation substrate coupled to the substrate.

This application claims priority to Korean Patent Application No. 2006-0016202, filed on Feb. 20, 2006, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a display apparatus and a manufacturing method thereof, and more particularly, to a display apparatus and a manufacturing method thereof using an encapsulation substrate.

2. Description of the Related Art

Recently, as one of flat panel displays, an organic light emitting diode (“OLED”) has become popular since OLED's have the advantages of requiring a low driving voltage, being relatively light weight and slim, having a wide viewing angle, having a high pixel response speed and other positive attributes.

The OLED display includes a light emitting layer which is made of an organic material, and which is formed on an insulation substrate. The light emitting layer is supplied with an electron and a hole to generate light. The light emitting layer is apt to be damaged by oxygen and moisture because the light emitting layer is formed of an organic material.

To protect the light emitting layer from oxygen and moisture, the OLED uses an encapsulation substrate formed of a glass or a metal. However, the encapsulation substrate is apt to be deformed since it is relatively thin to reduce the weight thereof. Therefore the deformation thereof becomes larger as the OLED display part increases in size.

As such, the deformed encapsulation substrate pushes against a display element, and accordingly, the display element deteriorates.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide a display apparatus and a manufacturing method thereof which prevents deterioration due to the deformation of an encapsulation substrate.

An exemplary embodiment of the display apparatus includes; a substrate, a transistor formed on the substrate, a pixel electrode connected to the transistor, a wall surrounding the pixel electrode, the wall including a main wall and a sub wall, the main wall having a first height and the sub wall having a second height less than the first height of the main wall, an organic layer formed on the pixel electrode, a common electrode formed on the organic layer and an encapsulation substrate coupled to the substrate.

According to an exemplary embodiment of the present invention, at least one of the first height and the second height of the wall is greater than a height of the pixel electrode.

According to an exemplary embodiment of the present invention, a surface of the substrate is encapsulated when the encapsulation substrate is coupled to the substrate.

According to an exemplary embodiment of the present invention, the pixel electrode is formed at the encapsulated surface of the substrate.

According to an exemplary embodiment of the present invention, the first height is about 50 micrometers (μm) to about 1000 micrometers (μm).

According to an exemplary embodiment of the present invention, the second height is about 0.5 micrometers (μm) to about 30 micrometers (μm).

According to an exemplary embodiment of the present invention, the second height is about 10 percent to about 50 percent of the first height.

According to an exemplary embodiment of the present invention, the encapsulation substrate includes a first part and a second part, wherein the first part is substantially parallel to the substrate, and the second part extends from the first part toward the substrate.

According to an exemplary embodiment of the present invention, the display apparatus further includes a sealant interposed between the substrate and the second part, and which attaches the substrate to the encapsulation substrate.

According to an exemplary embodiment of the present invention, the encapsulation substrate is formed by etching a glass plate.

According to an exemplary embodiment of the present invention, the wall is formed of a photoresist material.

An exemplary embodiment of a method of manufacturing a display apparatus includes; forming a transistor on a substrate, forming a pixel electrode connected to the transistor, forming a wall surrounding the pixel electrode and including a main wall and a sub wall, the main wall having a first height and the sub wall having a second height less than the first height, forming an organic layer on the pixel electrode, forming a common electrode on the organic layer and coupling an encapsulation substrate to the substrate.

According to an exemplary embodiment of the present invention, the forming the wall includes forming the wall with at least one of the first height and the second height greater than a height of the pixel electrode.

According to an exemplary embodiment of the present invention, the coupling includes encapsulating a surface of the substrate.

According to an exemplary embodiment of the present invention, the pixel electrode is formed at the encapsulated surface of the substrate.

According to an exemplary embodiment of the present invention, the forming the wall includes forming the first height to about 50 micrometers (μm) to about 1000 micrometers (μm).

According to an exemplary embodiment of the present invention, the forming the wall includes forming the second height to about 0.5 micrometers (μm) to about 30 micrometers (μm).

According to an exemplary embodiment of the present invention, the forming the wall includes forming the second height to about 10 percent to about 50 percent of the first height.

According to an exemplary embodiment of the present invention, the forming the wall includes forming a photoresist layer, and exposing the photoresist layer.

According to an exemplary embodiment of the present invention, the forming the wall includes one of a slit coating, a spin coating and a screen printing process.

According to an exemplary embodiment of the present invention, the exposing the photoresist layer includes using a slit mask or a semitransmissive mask.

According to an exemplary embodiment of the present invention, the forming the wall includes forming a wall material layer, and imprinting the wall material layer.

According to an exemplary embodiment of the present invention, the encapsulation substrate comprises includes a first part and a second part, wherein the first part is substantially parallel to the substrate, and the second part extends from the first part toward the substrate, and wherein the coupling the substrate and the encapsulation substrate includes applying a sealant to one of the substrate and the second part.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a circuit diagram of a first exemplary embodiment of a display apparatus according to the present invention which includes a pixel provided with a plurality of signal lines. The signal lines include a gate line transmitting an emitting signal, a data line transmitting a data signal and a power supply line transmitting a driving voltage. The data lines are arranged adjacently and substantially in parallel to the power supply line, and the gate lines extend substantially perpendicular to and intersects the data line and the power supply line.

Referring toFIG. 1, each pixel includes an organic light emitting element LD, a switching thin film transistor Tsw, a driving thin film transistor Tdr and a capacitor C.

The driving thin film transistor Tdr includes a control terminal connected to the switching thin film transistor Tsw and one side of the capacitor C, an input terminal connected to the power supply line and an output terminal connected to the organic light emitting element LD.

The organic light emitting element LD includes an anode connected to the output terminal of the driving thin film transistor Tdr, and a cathode connected to a common voltage Vcom. The organic light emitting element LD emits light with varying intensity according to an output current of the driving thin film transistor Tdr. The current outputted by the driving thin film transistor Tdr varies according to the voltage supplied between the control terminal and the output terminal thereof. A plurality of organic light emitting elements LD may work together to display an image.

Still referring toFIG. 1, the switching thin film transistor Tsw includes a control terminal connected to the gate line, an input terminal connected to the data line, and an output terminal connected to the control terminal of the driving thin film transistor Tdr and one side of the capacitor C. The switching thin film transistor Tsw transmits the data signal supplied from the data line to the driving thin film transistor Tdr based on the emitting signal supplied from the gate line.

The capacitor C is connected between the control terminal and the input terminal of the driving thin film transistor Tdr. The capacitor C is charged with the data signal inputted to the control terminal of the driving thin film transistor Tdr.

As shown inFIGS. 2 and 3, the display apparatus according to the first exemplary embodiment of the present invention includes a display substrate100, an encapsulation part200coupled to the display substrate100and a sealant300which attaches the respective circumferences of the display substrate100and the encapsulation part200to each other. The display substrate100includes an insulation substrate110having a substantially planar shape, and a display element formed on the insulation substrate110.

Referring toFIG. 2, the encapsulation part200includes an encapsulation substrate210, and a moisture absorbing layer220provided on an inner side of the encapsulation substrate210. The encapsulation substrate210includes a first plane211which is substantially in parallel to the insulation substrate110, and a second plane212extending in a direction substantially perpendicular to the first plane211from the first plane211toward the insulation substrate110. That is, the encapsulation substrate210is formed to have an accommodating space. Exemplary embodiments of the encapsulation substrate210may be formed of a glass or a metal. The encapsulation substrate210formed of a glass may be manufactured by etching a planar glass.

The interval d1between the insulation substrate110and the encapsulation substrate210may be about 100 micrometers (μm) to about 1100 micrometers (μm).

Referring toFIG. 3, the driving thin film transistor Tdr is illustrated, however the switching thin film transistor Tsw is not shown.

Still referring toFIG. 3, a gate insulation layer131, formed of silicon nitride (“SiNx”), or other similar substances, is formed on the insulation substrate110and on a gate electrode121. A semiconductor layer122formed of amorphous silicon and an ohmic contact layer123formed of a hydrogenated n+ amorphous silicon doped with an n-type impurity of high density are sequentially formed over the gate insulation layer131. The semiconductor layer122and the ohmic contact layer123corresponds to the gate electrode121. The ohmic contact layer123is divided, such that a space is formed over the gate electrode121, as illustrated inFIG. 3.

A source electrode124and a drain electrode125are formed over the ohmic contact layer123and the gate insulation layer131. The source electrode124and the drain electrode125are separated from each other to interpose the gate electrode121therebetween, as illustrated inFIG. 3.

A passivation layer141is formed over the source electrode124, the drain electrode125and the semiconductor layer122. A portion of the semiconductor layer122is exposed between the source electrode124and the drain electrode125, as illustrated inFIG. 3. The passivation layer141may be formed of silicon nitride (“SiNx”).

Still referring toFIG. 3, a flat layer142is formed of an organic material over the passivation layer141. Exemplary embodiments of the flat layer142may be formed of one of benzocyclobutene (“BCB”) series, olefin series, acrylic resin series, polyimide series, polytetrafluoroethylene (e.g., Teflon series), Cytop™, and perfluorocyclobutane (“PFCB”).

A contact hole143is formed in the flat layer142and the passivation layer141to expose the drain electrode125, as illustrated inFIG. 3.

A pixel electrode151is formed over the flat layer142. The pixel electrode151supplies a hole to a light emitting layer172. Exemplary embodiments of the pixel electrode151may be formed of a transparent conductive material such as indium tin oxide (“ITO”), indium zinc oxide (“IZO”), or other similar substances by a sputtering method. The pixel electrode151may be patterned to have a quadrangle shape in a plan view.

A wall160is formed between the respective pixel electrodes151. The wall160divides the respective pixel electrodes151to define a pixel area. The wall160prevents the source electrode124and the drain electrode125from being short-circuited with a common electrode180. Exemplary embodiments of the wall160may be formed of a photoresist material with thermal resistance and solvent resistance, such as an acrylic resin, a polyimide, or other similar substances.

The wall160includes a main wall160aand a sub wall160c. A first side160bconnecting the main wall160awith the sub wall160cincludes a first inclination angle θ1with respect to the insulation substrate110, and a second side160dextending substantially from the sub wall160cto the pixel electrode151, includes a second inclination angle θ2with respect to the insulation substrate110, as illustrated inFIG. 3.

The height h1of the main wall160amay be about 50 micrometers (μm) to about 1000 micrometers (μm), and the height h2of the sub wall160cmay be about 0.5 micrometers (μm) to about 30 micrometers (μm). The height h1(FIG. 3) of the main wall160ais determined according to the interval d1(FIG. 2) between the insulation substrate110and the encapsulation substrate210. The height h1(FIG. 3) of the main wall160ais slightly less than the interval d1(FIG. 2) between the insulation substrate110and the encapsulation substrate210. The driving thin film transistor Tdr can be efficiently protected when the encapsulation substrate210is deformed, if the height h1(FIG. 3) of the main wall160ais less than 50 micrometers (μm). Also, if the height h1(FIG. 3) of the main wall160ais greater than 1000 micrometers (μm), the first inclination angle θ1excessively increases, and accordingly, the common electrode180becomes difficult to form.

However, if the height h2(FIG. 3) of the sub wall160cis less than 0.5 micrometers (μm), the insulation thereof is weakened, and accordingly, the source electrode124and the drain electrode125are apt to be short-circuited with the common electrode180. Also, if the height h2(FIG. 3) of the sub wall160cis greater than 30 micrometers (μm), the second inclination angle θ2excessively increases, and accordingly, the common electrode180becomes difficult to form.

An organic layer170, which includes a hole injection layer171and the light emitting layer172, is formed over the pixel electrode151.

Exemplary embodiments of the hole injection layer171may be formed of a mixture of polythiophen derivatives such as poly (3,4-ethylenedioxythiophene) (“PEDOT”), or other similar substances and polystyrene sulphonate (“PSS”), or other similar substances.

The light emitting layer172includes a red light emitting layer172a, a green light emitting layer172band a blue light emitting layer172c.

A hole transmitted from the pixel electrode151and an electron transmitted from the common electrode180are coupled to form an exciton. When the exciton de-excites, e.g., when the electron falls from a higher energy state to a lower energy state, a photon is emitted.

As illustrated inFIG. 3, the common electrode180is positioned over the wall160and the light emitting layer172. The common electrode180supplies an electron to the light emitting layer172. Exemplary embodiments of the common electrode180may include a lithium fluoride layer and an aluminum fluoride layer. In a bottom emission type display, the common electrode180is formed of an opaque material such as aluminum, silver, or other similar substances, and the light of the light emitting layer172is emitted toward the insulation substrate110, as illustrated inFIG. 3.

As shown inFIG. 4, as the display part of the display apparatus1increases in size, the encapsulation substrate210becomes larger and is apt to be deformed toward the insulation substrate100along the deformation direction, due to its own weight. When the encapsulation substrate210is deformed, the encapsulation substrate210contacts the main wall160aof the wall160first, thereby preventing the driving thin film transistor Tdr from being damaged.

Hereinafter, a first exemplary embodiment of a manufacturing method of the first exemplary embodiment of the display apparatus according to the present invention will now be described in more detail with reference toFIGS. 5 to 13.

Referring toFIG. 5, the pixel electrode151and other layers are formed above the display substrate101.

Referring toFIGS. 6A and 6B, a photoresist layer165is formed over the pixel electrode151. An exemplary embodiment of the photoresist layer165may be formed by a spin coating method, and may be formed by other suitable methods. A photoresist161is jetted onto the display substrate101through a nozzle10while the display substrate101is rotated, in order to uniformly distribute the photoresist161onto the display substrate101when forming the photoresist layer165.

Referring toFIG. 7A, the photoresist layer165is exposed. The photoresist layer165is divided into parts, a part B which is to remain, a part C which is to partially remain and a part D which is to be completely removed. Part B becomes the main wall160a, and part C becomes the sub wall160c.

A mask20used for exposing the photoresist layer165includes a transparent mask substrate21, a blocking pattern22formed to part B and a slit pattern23formed to part C. An exemplary embodiment of the mask substrate21may be formed of a quartz material, and the blocking pattern22and the slit pattern23may be formed of a chrome layer.

FIG. 7Bis a plan view illustrating an exemplary embodiment of the mask20. In the exemplary embodiment ofFIG. 7B, part D may have a quadrangle shape and may be disposed on the mask20to form a matrix shape. Part D is surrounded by part C, and part B is dotted. In addition, the number of part B's forming the main wall160amay vary, and may be similar to the number of part D's.

Referring toFIG. 8, photoresist patterns166aand166bare formed by developing the exposed photoresist layer165. The photoresist pattern166acorresponding to part B includes a relatively large width, and the photoresist pattern166bcorresponding to part C includes a relatively small width.

Referring toFIG. 9, the wall160is formed by heating the photoresist patterns166aand166bin a reflow process. The relatively wide photoresist pattern166amaintains the height thereof to form the main wall160a. The relatively narrower photoresist patterns166bmerges with one another, which decreases the height thereof, to thereby form the sub wall160c.

A hole injection ink175is then dropped onto the pixel electrode151by an ink jet method to form the hole injection layer171, as illustrated inFIG. 10. An exemplary embodiment of the hole injection ink175includes a mixture of polythiophen derivatives such as poly (3,4-ethylenedioxythiophene) (“PEDOT”), or other similar substances and polystyrene sulphonate (“PSS”), or other similar substances, and a solvent dissolving the same.

The hole injection layer171is then formed by drying the hole injection ink175. In an exemplary embodiment, the hole injection ink175may be dried in a nitrogen environment and at an atmospheric pressure of about 1 Torr. If the pressure is excessively low, the hole injection ink175may dangerously and abruptly boil. Also, if the temperature is higher than the standard temperature, the solvent rapidly evaporates, and accordingly, a hole injection layer171with a uniform thickness may be difficult to form.

A heat treatment may be performed at about 200 degrees Celsius for about 10 minutes under an environment supplied with nitrogen after the hole injection ink175is dried. The heat treatment may be performed in a vacuum environment so that a solvent and/or moisture are completely removed from the hole injection layer171.

Then, referring toFIG. 11, light emitting inks176a,176band176care dropped onto the hole injection layer171to form the light emitting layer172. The light emitting inks176a,176band176crespectively include a red light emitting material, a green light emitting material and a blue light emitting material. The respective light emitting inks176a,176band176cmay further include a solvent. The solvent is formed of a nonpolar solvent which is insoluble with respect to the hole injection layer171, such as cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene, tetramethylbenzene, or other similar substances to prevent the hole injection layer171from redissolving.

In an exemplary embodiment, the light emitting layer172is then formed by drying the light emitting inks176a,176band176cby a drying method similar to the drying of the hole injection ink175.

The common electrode180is then formed over the wall160and the light emitting layer172to complete the display substrate100, as shown inFIG. 3.

Referring toFIG. 13, the sealant300is disposed to surround the display element, and the encapsulation substrate210is attached to the display substrate100to complete the display apparatus1.

Hereinafter, other exemplary embodiments of a method of manufacturing the display apparatus according to the first embodiment of the present invention will be now described in more detail with reference toFIGS. 14 to 17.

FIGS. 14 and 15respectively illustrate alternative exemplary embodiments of methods for forming the photoresist layer165, andFIGS. 16 and 17respectively illustrate alternative exemplary embodiments of methods for forming the wall160.

Referring toFIG. 14, the photoresist layer165is formed by a slit coating method. A slit coater30moves in a moving direction over the display substrate101to form the photoresist layer165.

Referring toFIG. 15, the photoresist layer165is formed by a screen printing method, in another exemplary embodiment. A screen mask40is positioned above the display substrate101, and a photoresist material162is positioned over the screen mask40. A squeezer45then moves in a moving direction as illustrated inFIG. 15, and the screen mask40is deformed toward the display substrate101, such that the photoresist material162passes through the screen mask40and the photoresist material162is jetted onto the display substrate101.

Referring now toFIG. 16, the photoresist layer165is exposed by using a semitransmissive mask50in an exemplary embodiment. The semitransmissive mask50includes a light transmissive mask substrate51, a blocking pattern52formed to a part B, and a semitransmissive pattern53formed to a part C. The blocking pattern52and the semitransparent pattern53may be formed of molybdenum silicide (“MoSi”) or chromium nitride (“CrN”), and may have a different transmissivities according to the thickness thereof.

Referring toFIG. 17, the wall160is formed by an imprint method, in an exemplary embodiment. A wall material layer167is formed on the pixel electrode151. In an exemplary embodiment, the wall material layer167may be formed of material other than a photoresist material.

A mold60is provided above the wall material layer167to have intaglio with respect to the wall160. If the wall material layer167is imprinted with the mold60, the intaglio of the mold60is filled with some wall material layer167, and the remaining wall material layer167is removed. In an exemplary embodiment, the mold60may include a throughhole (not shown) through which the remaining wall material layer167is discharged. The mold60is then removed, and the wall160is thereby completed.

Hereinafter, a second exemplary embodiment of a display apparatus according to the present invention will now be described in more detail with reference toFIG. 18.

FIG. 18illustrates an alternative exemplary embodiment of a display apparatus1according to the present invention. The display apparatus1includes an encapsulation part210as well as an insulation substrate110, each having a planar shape. The interval between the insulation substrate110and the encapsulation part210is maintained constant by a sealant300. The sealant300may include a spacer (not shown).

Hereinafter, another alternative exemplary embodiment of a display apparatus according to the present invention will now be described in more detail with reference toFIG. 19.

As shown inFIG. 19, an exemplary embodiment of a wall160of this alternative exemplary embodiment of a display apparatus according to the present invention includes two stairs E and F.

Hereinafter, yet another alternative exemplary embodiment of a display apparatus according to the present invention will now be described in more detail with reference toFIG. 20.

As shown inFIG. 20, an exemplary embodiment of an organic layer170of the present alternative exemplary embodiment of a display apparatus according to the present invention includes a lower organic layer171, a light emitting layer172and an upper organic layer173. The lower organic layer171and the upper organic layer173are formed all over the wall160, as illustrated inFIG. 20. An exemplary embodiment of the organic layer170is formed of a low molecular substance by a vaporization method. The light emitting layer172may be formed all over the wall160, and a color filter may be formed between an insulation substrate110and a pixel electrode151, wherein the light emitting layer172emits a white light.

The lower organic layer171includes a hole injection layer and a hole transporting layer, and is formed of an intensively fluorescent amine derivatives such as triphenyldiamine derivatives, styrylamine derivatives, amine derivatives having aromatic condensation ring, or other similar substances.

The upper organic layer173includes an electron transporting layer, and is formed of quinoline derivatives, especially tris (8-hydroxyquinoline) aluminum (“Alq3”).

As described above, exemplary embodiments of a display apparatus and exemplary embodiments of a manufacturing method thereof according to the present invention can prevent deformation of an encapsulation substrate and deterioration of the display apparatus due to the deformation of the encapsulation substrate.