KR101731821B1 - Organic light emitting diode and method of fabricating the same - Google Patents

Abstract

The present invention provides a liquid crystal display comprising: a driving thin film transistor formed in each of first and second pixel regions on a substrate; A protective layer formed on the driving thin film transistor; A color filter pattern formed on the first pixel region on the protection layer; A planarization layer formed on the color filter pattern and having a first opening in the second pixel region; A transparent first electrode formed on the planarization layer and formed in the first opening in the second pixel region and connected to the driving thin film transistor; A bank layer formed on the first electrode and having a second opening exposing the first electrode; An organic light emitting layer formed on the bank layer and the exposed first electrode, the organic light emitting layer emitting white light; And a second electrode formed on the organic light emitting layer, wherein in the second pixel region, the step of the bank layer defining the second opening has a multistage structure.

Description

[0001] The present invention relates to an organic light emitting diode (OLED)

The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device and a method of manufacturing the same.

2. Description of the Related Art [0002] As an information-oriented society develops, demands for a display device for displaying an image have increased in various forms. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various flat display devices such as an organic light emitting diode (OLED) have been utilized.

Among these flat panel display devices, the organic light emitting element is a self-light emitting element and can be lightweight and thin because it does not require a backlight used in a liquid crystal display device which is a non-light emitting element. Further, the liquid crystal display device has a better viewing angle and contrast ratio than the liquid crystal display device, and is also advantageous from the viewpoint of power consumption. In addition, it can be driven by DC low voltage, has a high response speed, and is resistant to external impact because its internal components are solid, has a wide operating temperature range, and is especially advantageous in terms of manufacturing cost.

Generally, pixel regions of red, green, and blue are formed in an organic light emitting element to display a color image. On the other hand, in recent years, an organic light emitting element in which a white pixel region is further formed for improving brightness of an image has been developed.

As described above, in the organic light emitting element in which the white pixel region is further formed, red, green, and blue color filter patterns corresponding to red, green, and blue pixel regions are formed, and a separate color filter pattern is formed in the white pixel region Do not.

A planarization layer is formed over the entire surface of the substrate, and a bank layer having openings corresponding to the pixel regions is formed on the planarization layer. An organic light-emitting layer for generating white light is formed on the bank layer along the opening.

The white light generated in the organic light emitting layer passes through the planarization layer and goes toward the substrate. Here, in the red, green, and blue pixel regions, white light passes through the corresponding color filter pattern, so that light of the corresponding color is emitted to the outside. On the other hand, in the white pixel region, there is no separate color filter pattern, so that white light is emitted to the outside.

As described above, a separate color filter is not used for the white pixel region, and the planarization layer is formed to be relatively thick. As a result, the light transmittance is lowered and the power consumption is increased. In order to solve this problem, it has been proposed to remove the planarization layer corresponding to the opening of the bank layer located in the white pixel region.

However, as the planarization layer is removed, the deterioration of the organic luminescent layer located in the white pixel region proceeds. That is, as the flattening layer is removed in the white pixel region, the step height of the bank layer in the pixel region becomes high. This results in a thin organic emission layer at the stepped portion. As a result, the current density is increased at the stepped portion and the organic light emitting layer deteriorates, and such deterioration proceeds to the center portion of the organic light emitting layer. As a result, in the white pixel region, a defect occurs in which the light emitting region is gradually reduced inside.

As a result, the reliability of the organic light emitting device is deteriorated.

The present invention has a problem in improving the reliability of the organic light emitting element.

According to an aspect of the present invention, there is provided a liquid crystal display comprising: a driving thin film transistor formed in each of first and second pixel regions on a substrate; A protective layer formed on the driving thin film transistor; A color filter pattern formed on the first pixel region on the protection layer; A planarization layer formed on the color filter pattern and having a first opening in the second pixel region; A transparent first electrode formed on the planarization layer and connected to the driving thin film transistor; A bank layer formed on the first electrode and having a second opening exposing the first electrode; An organic light emitting layer formed on the bank layer and the exposed first electrode, the organic light emitting layer emitting white light; And a second electrode formed on the organic light emitting layer, wherein in the second pixel region, the step of the bank layer defining the second opening has a multistage structure.

Here, the multi-level structure of the bank layer may be a dual level structure.

The color filter pattern may be one of a red color filter pattern, a green color filter pattern, and a blue color filter pattern.

The first electrode located at the first opening may contact the lower protective layer.

In another aspect, the present invention provides a method of manufacturing a liquid crystal display, comprising: forming a driving thin film transistor in each of first and second pixel regions on a substrate; Forming a protective layer on the driving thin film transistor; Forming a color filter pattern in a first pixel region on the protective layer; Forming a planarization layer having a first opening in the second pixel region on the color filter pattern; Forming a transparent first electrode connected to the driving thin film transistor on the planarization layer; Forming a bank layer on the first electrode, the bank layer having a second opening exposing the first electrode; Forming an organic light emitting layer emitting white light on the bank layer and the exposed first electrode; And forming a second electrode on the organic light emitting layer, wherein a stepped portion of the bank layer defining the second opening in the second pixel region has a multistage structure.

Here, the multi-level structure of the bank layer may be a dual level structure.

The color filter pattern may be one of a red color filter pattern, a green color filter pattern, and a blue color filter pattern.

The first electrode located at the first opening may contact the lower protective layer.

In the present invention, the step of the bank layer located in the white pixel region is formed to have a double step structure. Therefore, deterioration of the organic light emitting layer at the lower end portion of the step portion, which is an edge portion of the light emitting region, can be prevented and the phenomenon of progressing to the inside can be prevented. Thus, the reliability of the organic light emitting device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are diagrams schematically showing a pixel region arrangement structure of an organic light emitting diode according to an embodiment of the present invention;
3 is an equivalent circuit diagram of a pixel region of an organic light emitting diode according to an embodiment of the present invention.
4 is a cross-sectional view illustrating an organic light emitting device according to an embodiment of the present invention.
FIG. 5 is an enlarged view of some configurations including a bank layer formed in the second pixel region of FIG. 4; FIG.
6A to 6B are cross-sectional views illustrating a method of manufacturing an organic light emitting device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are views schematically showing a pixel region arrangement structure of an organic light emitting diode according to an embodiment of the present invention, and FIG. 3 is an equivalent circuit diagram of a pixel region of an organic light emitting diode according to an embodiment of the present invention.

1 and 2, an organic light emitting diode 100 according to an embodiment of the present invention includes red (R), green (G), blue (B), and white (W) pixel regions P . Accordingly, a color image can be expressed, and further the brightness of the image can be improved by further including the white (W) pixel region (P).

As shown in Fig. 1, the four pixel regions P may be sequentially arranged in one direction, for example, along the row direction. Such a layout scheme is called a stripe scheme.

Meanwhile, as shown in FIG. 2, the four pixels P may be arranged in a quad-like manner at the intersections of two adjacent rows and columns.

It will be apparent to those skilled in the art that the arrangement schemes as described above are examples, and can be arranged in various other ways.

Referring to FIG. 3, gate lines and data lines GL and DL intersecting each other define respective pixel regions P. In FIG. In the pixel region P, a switching transistor STr, a driving transistor DTr, and a light emitting diode E may be formed.

The switching transistor STr is connected to the gate wiring and the data lines GL and DL. The gate electrode of the driving transistor DTr is connected to the drain electrode of the switching transistor STr. The source electrode of the driving transistor DTr is connected to the power supply line PL and the drain electrode of the driving transistor DTr is connected to the first electrode of the light emitting diode E. The second electrode of the light emitting diode E may be grounded.

On the other hand, a storage capacitor StgC connected between the gate electrode and the source electrode of the driving transistor DTr may further be formed in the pixel region P. [

Here, for example, when a gate high voltage is applied to the gate line GL as a turn-on voltage, the switching transistor STr is turned on. In synchronism with this, a data voltage may be output to the data line DL and applied to the gate electrode of the driving transistor DTr. The amount of current flowing through the channel of the driving transistor DTr is determined according to the magnitude of the applied data voltage. Such a current is supplied to the light emitting diode (E), and the light emitting diode (E) emits light. The luminance of the light emitted from the light emitting diode E is determined according to the amount of the supplied current.

On the other hand, in the embodiment of the present invention, an organic light emitting layer for generating white is used as the organic light emitting layer formed in the light emitting diode (E). Therefore, the light emitting diode E emits white light.

Hereinafter, the organic light emitting diode according to the embodiment of the present invention will be described in more detail with reference to FIG.

4 is a cross-sectional view illustrating an organic light emitting device according to an embodiment of the present invention. In FIG. 4, red (R), green (G), and blue (B) pixel regions that emit colored light such as red (R), green (G), and blue And a white (W) pixel region that emits white, which is colorless, is shown as a second pixel region P2.

On the substrate 110, although not shown, a buffer layer may be formed on the entire surface. The buffer layer may be made of an inorganic insulating material. For example, there silicon oxide (SiO ₂₎ or silicon nitride (SiNx) can be used, but is not limited to this.

The buffer layer may be configured to prevent the characteristics of the semiconductor layer 113 from being deteriorated by the alkali ions emitted from the inside of the substrate 110 when the semiconductor layer 113 formed on the upper part is crystallized.

On the buffer layer, a semiconductor layer 113 is formed in each of the pixel regions P1 and P2. The semiconductor layer 113 may be made of crystalline silicon. The semiconductor layer 113 includes a first region 113a positioned at the center and serving as a channel and a second region 113b located at both sides of the first region 113a. The first region 113a may be made of pure silicon and the second region 113b may be made of silicon doped with impurities.

A gate insulating layer 116 is formed on the semiconductor layer 113 along the entire surface of the substrate 110. The gate insulating film 116 may be made of an inorganic insulating material. For example, there silicon oxide (SiO ₂₎ or silicon nitride (SiNx) can be used, but is not limited to this.

A gate electrode 120 is formed on the gate insulating film 116 in correspondence with the first region 113a of the semiconductor layer 113. [ Although not shown, a gate wiring (see GL in Fig. 3) is formed of the same material at the time of forming the gate electrode 120. [

On the gate electrode 120, an interlayer insulating film 123 is formed along the entire surface of the substrate 110. A semiconductor layer contact hole 125 is formed in the interlayer insulating film 123 and the gate insulating film 116 to expose the second region 113b.

On the interlayer insulating film 123, the source electrode and the drain electrode 133, 136 are formed. The source and drain electrodes 133 and 136 are brought into contact with the corresponding second regions 113b through the corresponding semiconductor layer contact holes 125. [

The semiconductor layer 113, the gate electrode 120, the source electrode and the drain electrodes 133 and 136 as described above constitute the driving transistor DTr. On the other hand, a switching transistor (see STr in FIG. 3) can be formed with a structure similar to the driving transistor DTr.

On the other hand, data lines (see DL in FIG. 3) are formed of the same material when the source electrode and the drain electrode 133 and 136 are formed.

A protective layer 140 is formed on the source and drain electrodes 133 and 136 along the entire surface of the substrate 110. The protective layer 140 may be formed of an inorganic insulating material or an organic insulating material, and more preferably an inorganic insulating material.

On the passivation layer 140, a color filter pattern 141 may be formed in the first pixel region P1. For example, a red (R) color filter pattern, a green (G) color filter, and a blue (G) color filter pattern are formed for each of the red (R) pixel region, the green Pattern, and a blue (B) color filter pattern may be formed.

On the other hand, no separate color filter pattern is formed in the second pixel region P2 which is a white region.

A planarization layer 145 may be formed on the color filter pattern 141 along the entire surface of the substrate 110. With such a planarization layer 145, the substrate 110 on which the planarization layer 145 is formed is substantially planarized. The planarization layer 145 may be made of a transparent organic insulating material. For example, polyimide, BCB (benzocyclobutene), or acrylic resin may be used, but is not limited thereto.

On the other hand, the first opening OP1 may be formed in the planarization layer 145 of the second pixel region P2. The first opening OP1 is formed by removing the planarization layer 145 located in the second pixel region P2. This is configured in terms of improvement of transmittance and power consumption.

A drain contact hole 143 is formed in the planarization layer 145 and the protective layer 140 to expose the drain electrode 136 of the driving transistor DTr.

On the planarization layer 145, the first electrodes 147 are formed corresponding to the pixel regions P1 and P2. The first electrode 147 is connected to the drain electrode 136 through the drain contact hole 143.

The first electrode 147 located in the second pixel region P 2 is also formed in the first opening OP 1. The first electrode 147 located in the first opening OP 1 is formed in the lower protective layer (Not shown).

The first electrode 147 may be made of a transparent conductive material. For example, ITO (indium-tin-oxide), IZO (indium-zinc-oxide), or ITZO (indium-tin-zinc-oxide) are used.

Since the first electrode 147 has a transparent characteristic, the light emitted from the organic light emitting layer 155 on the first electrode 147 passes through the first electrode 147 and moves toward the substrate 110. The method of emitting light in the direction of the lower substrate 110 and displaying an image is called a lower light emitting method.

On the first electrode 147, a bank layer 150 may be formed. The bank layer 150 may be formed so as to overlap the edges of the first electrode 147 in the form of surrounding the boundaries of the pixel regions P1 and P2. The bank layer 150 may be made of an organic insulating material. For example, polyimide, BCB (benzocyclobutene), or acrylic resin may be used, but is not limited thereto.

The bank layer 150 has the second openings OP2 corresponding to the pixel regions P1 and P2.

On the other hand, the second opening OP2 formed in the second pixel region P2 can be located in the first opening OP1. Furthermore, the portion of the bank layer 150 surrounding and defining the second opening OP2 has a dual step structure. That is, in the second pixel region P2, the stepped portion of the bank layer 150 formed along the stepped portion of the planarization layer 145 has a double stepped structure.

The organic light emitting layer 155 may be formed on the first electrode 147 exposed through the bank layer 150 and the second opening OP2. The organic light emitting layer 155 generates white light. The organic light emitting layer 155 may be formed along the entire surface of the substrate 110. On the other hand, the organic light emitting layer 155 may be formed for each of the pixel regions P1 and P2.

On the organic light emitting layer 155, a second electrode 158 is formed along the entire surface of the substrate 110. The second electrode 158 may be made of an opaque conductive material having a high reflection characteristic. For example, aluminum (Al), an aluminum alloy, silver (Ag), magnesium (Ag), or gold (Au) may be used.

The first electrode 147, the organic emission layer 155, and the second electrode 158 constitute the light emitting diode E as described above. Here, the first electrode 147 may be made of a material having a relatively high work function and may function as an anode, and the second electrode 158 may be formed of a material having a relatively low work function to function as a cathode can do. The second electrode 158 has a reflection characteristic. As described above, the white light generated from the organic light emitting layer 155 moves toward the first electrode 147.

As described above, the color filter pattern is formed in the first pixel region P1 with respect to white light generated in the organic light emitting layer 155, so that light of a color corresponding to the color filter pattern is emitted to the outside. On the other hand, a separate color filter pattern is not formed in the second pixel area P2, and white light is emitted to the outside.

As described above, in the bank layer 150 located in the second pixel region P2, the step portion defining the second opening portion OP2 has a double step structure, which will be described in more detail with reference to Fig. 5 .

5 is an enlarged view of a part of the structure including the bank layer formed in the second pixel region of FIG.

5, the step ST of the bank layer 150 defining the second opening OP2 has the first step ST1 at the top and the second step ST2 at the bottom, Step structure.

As such, since the step ST is formed of the dual step structure, the step coverage characteristic of the organic light emitting layer 155 formed along the second opening OP2 can be improved.

That is, when the stepped portion of the bank layer has a single step structure in the same shape as the stepped portion of the lower planarization layer 145, the depth of the stepped portion is relatively large. Accordingly, the thickness of the organic light emitting layer formed along the inclined surface of the step portion of the single step structure becomes relatively thin. As a result, the current density increases at the lower end of the step portion of the single step structure, that is, at the edge portion of the light emitting region, and the organic light emitting layer deteriorates at this portion. The deterioration thus generated is diffused inside.

On the other hand, in the embodiment of the present invention, the stepped portion ST of the bank layer has a dual step structure. That is, the lower step ST2 protruding toward the central portion of the second opening OP2, that is, toward the center of the light emitting region, is further structured. Thus, by further configuring the second step ST2 in the lower part, the depth of the inclined surface of the stepped portion ST, that is, the inclined surface of the first step ST1 at the upper portion is smaller than that of the single stepped structure. As a result, the phenomenon that the thickness of the organic light emitting layer 155 becomes thin at the stepped portion ST can be improved.

Moreover, the second step ST2 is substantially flat. The organic light emitting layer 155 formed along the second step ST2 is thicker than the organic light emitting layer 155 formed along the inclined surface and has the organic light emitting layer 155 formed on the second electrode 147, As shown in FIG.

Therefore, it is possible to improve the deterioration of the organic light emitting layer at the lower end portion of the stepped portion ST which is the edge portion of the light emitting region.

Hereinafter, a method of manufacturing an organic light emitting diode according to an embodiment of the present invention will be described with reference to FIGS. 6A to 6B.

Referring to FIG. 6A, a semiconductor layer 113 is formed in each pixel region P1 and P2 on a substrate 110. FIG. The semiconductor layer 113 may be made of crystalline silicon. The semiconductor layer 113 includes a first region 113a located at the center and serving as a channel and a second region 113b located at both sides of the first region 113a. Although not shown, a buffer layer may be formed on the entire surface of the substrate 110 under the semiconductor layer 113.

Next, a gate insulating film 116 is formed on the semiconductor layer 113 along the entire surface of the substrate 110.

Next, the gate electrode 120 is formed on the gate insulating film 116 in correspondence with the first region 113a of the semiconductor layer 113. Next, Although not shown, a gate wiring (see GL in Fig. 3) is formed of the same material at the time of forming the gate electrode 120. [

Next, an interlayer insulating film 123 is formed on the gate electrode 120 along the front surface of the substrate 110. On the other hand, the interlayer insulating film 123 and the gate insulating film 116 are patterned to form a semiconductor layer contact hole 125 exposing the second region 113b.

Next, on the interlayer insulating film 123, the source electrode and the drain electrode 133, 136 are formed. The source and drain electrodes 133 and 136 are brought into contact with the corresponding second regions 113b through the corresponding semiconductor layer contact holes 125. [

The semiconductor layer 113, the gate electrode 120, the source electrode and the drain electrodes 133 and 136 as described above constitute the driving transistor DTr. On the other hand, a switching transistor (see STr in FIG. 3) can be formed with a structure similar to the driving transistor DTr.

On the other hand, data lines (see DL in FIG. 3) are formed of the same material when the source electrode and the drain electrode 133 and 136 are formed.

Next, a protective layer 140 is formed on the source electrode and the drain electrode 133, 136 along the entire surface of the substrate 110.

Next, the color filter pattern 141 is formed in the first pixel region P1 on the protective layer 140. [ For example, the red (R) color filter pattern, the green (G) color filter pattern, the green (G) color filter pattern, , And a blue (B) color filter pattern may be formed.

On the other hand, no separate color filter pattern is formed in the second pixel region P2 which is a white region.

Next, a planarization layer 145 is formed on the color filter pattern 141 along the front surface of the substrate 110. [ On the other hand, the planarization layer 145 of the second pixel region P2 is patterned and removed to form the first opening OP1.

The planarization layer 145 and the passivation layer 140 are patterned to form a drain contact hole 143 for exposing the drain electrode 136 of the driving transistor DTr.

Next, the first electrode 147 is formed in each of the pixel regions P1 and P2 on the planarization layer 145. The first electrode 147 is connected to the drain electrode 136 through the drain contact hole 143.

Next, the bank layer 150 is formed on the first electrode 147. The bank layer 150 is patterned and removed to form the second openings P2 in the pixel regions P1 and P2.

The bank layer 150 may be formed so as to overlap the edge of the first electrode 147 in the form of surrounding the boundaries of the pixel regions P1 and P2 and the first electrode 147 may overlap the edge of the second opening 147 OP2).

On the other hand, the second opening portion OP2 formed in the second pixel region P2 is located in the first opening portion OP1. Furthermore, the stepped portion ST of the bank layer 150 surrounding and defining the second opening OP2 has a dual step structure.

Next, referring to FIG. 6B, an organic light emitting layer 155 is formed on the first electrode 147 exposed through the bank layer 150 and the second opening OP2. The organic light emitting layer 155 generates white light. The organic light emitting layer 155 may be formed along the entire surface of the substrate 110. On the other hand, the organic light emitting layer 155 may be formed for each of the pixel regions P1 and P2.

A second electrode 158 is formed on the organic light emitting layer 155 along the entire surface of the substrate 110.

The first electrode 147, the organic emission layer 155, and the second electrode 158 constitute the light emitting diode E as described above.

Through the above-described process, the organic light emitting device 100 according to the embodiment of the present invention can be manufactured.

As described above, according to the embodiment of the present invention, the stepped portion of the bank layer located in the white pixel region is formed to have a double step structure. Therefore, deterioration of the organic light emitting layer at the lower end portion of the step portion, which is an edge portion of the light emitting region, can be prevented and the phenomenon of progressing to the inside can be prevented. Thus, the reliability of the organic light emitting device can be improved.

In the embodiment of the present invention described above, the case where the stepped portion of the bank layer has the double step structure has been described as an example. On the other hand, in the case of a dual step structure as well as a step structure having a higher order, that is, a multi step structure, the case of the present invention may also be included.

The embodiment of the present invention described above is an example of the present invention, and variations are possible within the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and equivalents thereof.

145: planarization layer 147: first electrode
150: bank layer 155: organic light emitting layer
OP1: first opening OP2: second opening
ST: Step difference ST1: First step
ST2: Second step

Claims (8)

A driving thin film transistor formed in each of the first and second pixel regions on the substrate;
A protective layer formed on the driving thin film transistor;
A color filter pattern formed on the first pixel region on the protection layer;
A planarization layer formed on the color filter pattern and having a first opening in the second pixel region;
A transparent first electrode formed on the planarization layer and formed in the first opening in the second pixel region and connected to the driving thin film transistor;
A bank layer formed on the first electrode and having a second opening exposing the first electrode;
An organic light emitting layer formed on the bank layer and the exposed first electrode, the organic light emitting layer emitting white light;
And a second electrode formed on the organic light emitting layer,
In the second pixel region, the step portion of the bank layer defining the second opening has a multi-step structure
Organic light emitting device.
The method according to claim 1,
The multi-level structure of the bank layer may be a dual step structure
Organic light emitting device.
The method according to claim 1,
Wherein the color filter pattern is one of a red color filter pattern, a green color filter pattern, and a blue color filter pattern
Organic light emitting device.
The method according to claim 1,
The first electrode located at the first opening is in contact with the lower protective layer
Organic light emitting device.
Forming driving thin film transistors in each of the first and second pixel regions on the substrate;
Forming a protective layer on the driving thin film transistor;
Forming a color filter pattern in a first pixel region on the protective layer;
Forming a planarization layer having a first opening in the second pixel region on the color filter pattern;
Forming a transparent first electrode connected to the driving thin film transistor on the planarization layer and in the first opening in the second pixel region;
Forming a bank layer on the first electrode, the bank layer having a second opening exposing the first electrode;
Forming an organic light emitting layer emitting white light on the bank layer and the exposed first electrode;
And forming a second electrode on the organic light emitting layer,
In the second pixel region, the step portion of the bank layer defining the second opening has a multi-step structure
A method of manufacturing an organic light emitting device.
6. The method of claim 5,
The multi-level structure of the bank layer may be a dual step structure
A method of manufacturing an organic light emitting device.
6. The method of claim 5,
Wherein the color filter pattern is one of a red color filter pattern, a green color filter pattern, and a blue color filter pattern
A method of manufacturing an organic light emitting device.
6. The method of claim 5,
The first electrode located at the first opening is in contact with the lower protective layer
A method of manufacturing an organic light emitting device.

Images