Patent Application
20110177640
1. Field
Embodiments relate to a method for manufacturing an organic light emitting diode (OLED) display.
2. Description of the Related Art
An organic light emitting diode (OLED) display has a self-light emitting characteristic such that it is advantageous for down-sizing and weight reduction, since a separate light source is not required. Also, the organic light emitting diode (OLED) display has high quality characteristics such as low power consumption, high luminance, and high reaction speed, and has been spotlighted as a next-generation display device for, e.g., portable electronic devices.
The organic light emitting diode (OLED) display may include an organic light emitting element (organic light emitting diode) having an anode, an organic emission layer, and a cathode, and a thin film transistor driving the organic light emitting element. Electrons and holes are injected into the organic emission layer from the anode and the cathode, respectively, and when excitons (formed by coupling of the holes and electrons that are injected into the organic emission layer) drop from an exited state to a ground state, light is emitted by the released energy. The display of the light emitting diode (OLED) display is realized through the light emitted thereby.
The organic emission layer may be formed by a deposition process using a fine metal mask (FMM). To improve the resolution of the display device, a method executing a plurality of deposition processes of red, green, and blue organic emission layers may be used. In this case, defects such as a black point and a spot may be increased by the plurality of deposition processes, and as a result the yield of the organic light emitting diode (OLED) display may be deteriorated. Also, the same organic emission layers are formed through the plurality of deposition processes such that the cost of the light emitting material consisting of the organic emission layer is also increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
It is a feature of an embodiment to provide a method for manufacturing an organic light emitting diode display that reduces a number of deposition processes of red, green, and blue organic emission layers and maintains uniform luminous efficiency.
At least one of the above and other features and advantages may be realized by providing a method for manufacturing an organic light emitting diode (OLED) display, the method including forming a first electrode having different thicknesses corresponding to a first pixel, a second pixel, and a third pixel, forming a first emission layer, a second emission layer, and a third emission layer respectively corresponding to the first pixel, the second pixel, and the third pixel, and forming a second electrode on the first emission layer, the second emission layer, and the third emission layer. Forming the first electrodes may include forming a first electrode material layer on the substrate, forming a photoresist pattern having different thicknesses corresponding to the first pixel, the second pixel, and the third pixel, respectively, and etching the first electrode material layer along with the photoresist pattern.
The first electrode corresponding to the first pixel may be thicker than the first electrode corresponding to the second pixel, and the first electrode corresponding to the second pixel may be thicker than the first electrode corresponding to the third pixel.
The photoresist pattern corresponding to the first pixel may have a first thickness, the photoresist pattern corresponding to the second pixel may have a second thickness that is less than the first thickness, and the photoresist pattern corresponding to the third pixel may have a third thickness that is less than the second thickness.
The photoresist pattern may be formed using a mask that provides respectively different amounts of exposure to each of the first pixel, the second pixel, and the third pixel.
In the mask, the exposure amount of the photoresist pattern corresponding to the first pixel may be less than the exposure amount of the photoresist pattern corresponding to the second pixel, and the exposure amount of the photoresist pattern corresponding to the second pixel may be less than the exposure amount of the photoresist pattern corresponding to the third pixel.
The mask may include light blocking patterns corresponding to the first pixel, the second pixel, and the third pixel, respectively, and the light blocking pattern corresponding to the first pixel may be thicker than the light blocking pattern corresponding to the second pixel, and the light blocking pattern corresponding to the second pixel may be thicker than the light blocking pattern corresponding to the third pixel.
The light blocking pattern may include chromium.
The first electrode material layer may be dry-etched through the photoresist pattern.
The first pixel may be a red pixel, the second pixel may be a green pixel, and the third pixel may be a blue pixel.
At least one of the above and other features and advantages may be realized by providing a method for manufacturing an organic light emitting diode (OLED) display, the method including forming a pixel electrode corresponding to a first pixel and a pixel electrode corresponding to a second pixel, where the first pixel includes an emission material having a first luminous efficiency and the second pixel has a second luminous efficiency that is greater than the first luminous efficiency, and forming a second electrode on the first emission layer and the second emission layer. Forming the pixel electrodes may include forming an electrode material layer on the substrate, and simultaneously forming the pixel electrode corresponding to the first pixel and the pixel electrode corresponding to the second pixel by etching the electrode material layer using a photoresist pattern to control an amount of the electrode material layer that is removed by the etching, the photoresist pattern having a first thickness in a region corresponding to the first pixel and a second thickness in a region corresponding to the second pixel, the first thickness being greater than the second thickness.
The above and other features and advantages will become more apparent to those of skill in the art by describing in detail example embodiments with reference to the attached drawings, in which:
Korean Patent Application No. 10-2010-0004931, filed on Jan. 19, 2010, in the Korean Intellectual Property Office, and entitled: “Method for Manufacturing an Organic Light Emitting Diode Display,” is incorporated by reference herein in its entirety.
Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In order to describe the exemplary embodiments more clearly, parts that are not related to the description may be omitted from the drawings.
In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.
As described herein, a manufacturing method for an organic light emitting diode (OLED) display according to embodiments may simplify the process of forming pixel electrodes having the different thicknesses.
In
Referring to
One pixel may be defined by a boundary of a gate line 151, a data line 171, and a common power line 172.
A buffer layer 120 may be disposed between the substrate main body 111, and the switching thin film transistor 10 and the organic light emitting element 70. The buffer layer 120 may help flatten the surface while preventing the intrusion of undesired components like impurities or moisture. The buffer layer 120 may be omitted depending upon the kind and processing conditions of the substrate main body 111.
The organic light emitting element 70 may include the first electrode (hereinafter, “pixel electrode”) 710, an organic emission layer 720 formed on the pixel electrode 710, and a second electrode (hereinafter, “common electrode”) 730 formed on the organic emission layer 720. A pixel electrode 710 is formed for each pixel, respectively. Thus, the organic light emitting diode display 101 may have a plurality of pixel electrodes 710 spaced apart from each other.
The pixel electrode 710 may be an anode serving as a hole injection electrode, and the common electrode 730 may be a cathode serving as an electron injection electrode. In another implementation, the pixel electrode 710 may be the cathode and the common electrode 730 may be the anode according to the driving method of the organic light emitting diode (OLED) display 101.
Light may be emitted when excitons, created by combination of holes and electrons injected to the organic emission layer 720, drop from an exited state to a ground state.
The capacitor 80 may include a pair of capacitor plates 158 and 178 disposed with an interlayer insulating layer 160 interposed therebetween. The interlayer insulating layer 160 may be a dielectric material. The charges charged to the capacitor 80 and the voltage between the first and the second capacitor electrode plates 158 and 178 determines the capacitance.
The switching thin film transistor 10 may include a switching semiconductor layer 131, a switching gate electrode 152, a switching source electrode 173, and a switching drain electrode 174. The driving thin film transistor 20 may include a driving semiconductor layer 132, a driving gate electrode 155, a driving source electrode 176, and a driving drain electrode 177. The switching and driving semiconductor layers 131 and 132, and the switching and driving gate electrodes 152 and 155, may be disposed with the gate insulating layer 140 interposed therebetween. The switching and driving semiconductor layers 131 and 132, the switching and driving source electrodes 173 and 176, and the switching and driving drain electrodes 174 and 177 may be connected to each other through contact holes formed in the gate insulating layer 140 and the interlayer insulating layer.
The switching thin film transistor 10 may be used as a switch for selecting pixels to emit light. The switching gate electrode 152 may be connected to the gate line 151, and the switching source electrode 173 may be connected to the data line 171. The switching drain electrode 174 may be separated from the switching source electrode 173 and may be connected to one capacitor plate, e.g., capacitor plate 158.
The driving thin film transistor 20 may apply a driving voltage to the pixel electrode 710 to excite the organic emissive layer 720 of the organic light emitting diode 70 in the selected pixel. The driving gate electrode 155 may be connected to the capacitor plate 158 connected to the switching drain electrode 174. The driving source electrode 176 and the other capacitor plate 178 may be respectively connected to the common power line 172. The driving drain electrode 177 may be connected to the pixel electrode 710 of the organic light emitting element 70 through a contact hole of a planarization layer 180. In another implementation, the planarization layer 180 may be omitted, and the driving drain electrode 177 and the pixel electrode 710 may be at the same layer. The pixel electrodes 710 may be insulated from each other by a pixel definition layer 190 formed on the planarization layer 180.
The switching thin film transistor 10 may be operated by the gate voltage applied to the gate line 151, and may transmit the data voltage applied to the data line 171 to the driving thin film transistor 20
A voltage with a value corresponding to a difference between the common voltage applied to the driving thin film transistor 20 from the common power line 172 and the data voltage transmitted from the switching thin film transistor 10 may be stored at the capacitor 80. A current corresponding to the voltage stored at the capacitor 80 may flow to the organic light emitting diode 70 through the driving thin film transistor 20 to thereby excite the organic light emitting diode 70.
In the organic light emitting element 70, the pixel definition layer 190 covering the pixel electrode 710 may have an opening 199 exposing the pixel electrode 710, thereby covering the region except for the opening 199. The organic emission layer 720 may be formed on the pixel electrode 710 in the opening 199 of the pixel definition layer 190, and the common electrode 730 may be formed on the pixel definition layer 190 and the organic emission layer 720.
The organic emission layer 720 may be made of, or may include, a low molecular weight organic material or a high molecular weight organic material. The organic emission layer 720 may be formed in a multi-layer structure. The multi-layer structure may include one or more of a hole injection layer (HIL), a hole transport layer (HTL), an emission layer, an electron transport layer (ETL), and an electron injection layer (EIL). In an example implementation of the organic emission layer 720, the hole injection layer (HIL) is disposed on the pixel electrode 710 (the anode), and is sequentially overlaid with the hole transport layer (HTL), the emission layer, the electron transport layer (ETL), and the electron injection layer (EIL).
Examples of the low molecular weight material may include an aluminum quinolinate complex such as Alq3, anthracene, cyclopentadiene, BeBq2, Almq, ZnPBO, Balq, DPVBi, BSA-2, and 2PSP. Examples of the high molecular weight material may include polyphenylene (PPP) and derivatives thereof, poly(p-phenylenevinylene) (PPV) and derivatives thereof, and polythiophene (PT) and derivatives thereof.
The thicknesses of the respective pixel electrodes 710 may be controlled to compensate for the different luminous efficiencies. For example, the red, green, and blue pixel electrodes 710R, 710G, and 710B (which are respectively formed in the red, green, and blue pixels 30R, 30G, and 3013) may have different thicknesses corresponding to the differences of the luminous efficiencies of the red, green, and blue organic emission layers 720R, 720G, and 720B.
In an embodiment, the electrode thicknesses decrease in the sequence of the red pixel electrode 710R (thickest), the green pixel electrode 710G, and the blue pixel electrode 710B (thinnest) in correspondence with the increasing luminous efficiencies in the sequence of the red organic emission layer 720G (lower than that of the green organic emission layer 720G and lower than that of the blue organic emission layer 720B), the green organic emission layer 720G (higher than that of the red organic emission layer 720G and lower than that of the blue organic emission layer 720B), and the blue organic emission layer 720B (higher than that of the red organic emission layer 720G and higher than that of the green organic emission layer 720G). Thus, in an implementation a thickness t1 of the red pixel electrode 710R may be greater than a thickness t2 of the green pixel electrode 710G, and the thickness t2 of the green pixel electrode 710G may be greater than a thickness t3 of the blue pixel electrode 710B.
As described above, when the pixel electrode corresponding to the organic emission layer made of the material having low luminous efficiency is thickly formed, the low luminous efficiency of the corresponding organic emission layer may be compensated.
In the example illustrated in
A method of manufacturing the organic light emitting diode (OLED) display 101 according to an embodiment will now be described with reference to
Referring to
In operation ST10, the substrate defined with a red pixel (the first pixel) (reference numeral 30R of
In operation ST20, red, green, and blue pixel electrodes (reference numerals 710R, 710G, and 710B of
In operation ST30, the pixel definition layer (reference numeral 190 of
In operation ST40, the red, green, and blue emission layers 720R, 720G, and 720B (respectively corresponding to the red, green, and blue pixels 30R, 30G, and 30B) may be formed in respective openings 199 of the pixel definition layer 190.
In operation ST50, the common electrode 730 may be formed on the pixel definition layer 190 and on the red, green, and blue emission layers 720R, 720G, and 720B.
The providing of the substrate ST10, the forming of the pixel definition layer ST30, the forming of the emission layer ST40, and the forming of the common electrode ST50 may be realized through various generally known methods, details of which are known to those of skill in the art and need not be repeated.
Hereinafter, the method of forming the pixel electrode ST20 through the forming of the red, green, and blue pixel electrodes 710R, 710G, and 710B having different thicknesses will be described.
The forming of the pixel electrode ST20 may include forming a pixel electrode material layer (first electrode material layer) ST21, forming a photoresist material layer ST23, forming a photoresist pattern ST25, and etching the photoresist pattern and the pixel electrode material layer ST27. These operations will now be described with reference to
Referring to
Referring to
Next, referring to
In an implementation, when forming the photoresist pattern 740R, 740G, and 740B, the mask 750 allows different amounts of exposure in the red, green, and blue pixels 30R, 30G, and 30B. For example, the mask 750 may include light blocking patterns 752R, 752G, and 752B having different thicknesses corresponding to the red, green, and blue pixels 30R, 30G, and 30B. In the example illustrated in
Using the mask described above, the exposure amount in the light blocking pattern 752R of the red pixel 30R is less than the exposure amount in the light blocking pattern 752G of the green pixel 30G, and the exposure amount in the light blocking pattern 752G of the green pixel 30G is less than the exposure amount in the light blocking pattern 752B of the blue pixel 30B. Thus, the photoresist material 740a made of the positive photoresist material may be removed (upon developing) in an amount that is increased as the exposure amount is increased. For example, a thinner light blocking pattern, e.g., 740B, may result in a greater exposure amount and more positive photoresist material being removed.
In the example shown in
Next, as shown in
In the example shown in
The red, green, and blue pixel electrodes 710R, 710G, and 710B having different thicknesses may be formed at one time by using the photoresist patterns 740R, 740G, and 740B having the different thicknesses, such that the number of deposition processes, exposures, and etching processes may be reduced.
In contrast, using a conventional approach to form electrodes having different thicknesses would involve forming the red organic emission layer from three films, the green organic emission layer from two films, and the blue organic emission layer from one film. In such a case, when forming three films or two films of the red organic emission layer and the green organic emission layer, the portion deposited on the blue organic emission layer must be removed. However, defects, e.g., wherein a portion of the blue organic emission layer is damaged, may be generated in this process. Also, such a manufacturing process would be complicated by the additional deposition process and patterning process involved therein, such that productivity may be decreased. Moreover, where a light emitting assistance layer is used to compensate for the organic emission layer having low efficiency, the light emitting assistance layer must be deposited by using a very fine metal mask, such that the possibility of defect generation and increased material cost may further occur.
In the embodiments described above, electrodes having different thicknesses corresponding to different luminous efficiencies of the emitting materials may be formed at one time, such that the manufacturing process may be simplified and the material costs may be significantly reduced.
Exemplary embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2010-0004931 | Jan 2010 | KR | national |
