KR101796934B1 - Organic Light Emitting Diode Display Device Having A Reflective Electrode And Method For Manufacturing The Same - Google Patents

Abstract

The present invention relates to an organic light emitting display device having a reflective electrode and a method of manufacturing the same. An organic light emitting display device according to the present invention includes: a substrate; A scan line, a data line, and a drive current line defining a pixel region on the substrate; A thin film transistor formed in the pixel region; A pad formed on one end of the scan line, the data line, and the drive current line; And a cathode connected to the thin film transistor and formed in the pixel region, and a pad terminal formed on the pad, wherein the cathode and the pad terminal are laminated with a reflective electrode layer and a transparent conductive layer. The present invention has a structure in which a reflective electrode layer and a transparent conductive layer are sequentially stacked in a cathode and a pad portion so that even if a transparent conductive layer is laminated thinly, defects such as contact resistance decrease or disconnection in the pad portion do not occur, The organic electroluminescent display device of the top emission type improved in reflectivity can be obtained.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display device having a reflective electrode and a method of manufacturing the organic electroluminescent display device,

The present invention relates to an organic light emitting display device having a reflective electrode and a method of manufacturing the same. In particular, the present invention relates to a top emission organic electroluminescence display device, which includes a lower electrode layer including a lower electrode layer, and transmits light emitted from the organic layer to the upper portion without loss, The present invention relates to an organic light emitting display device and a method of manufacturing the same.

2. Description of the Related Art Recently, various flat panel display devices capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), have been developed. Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electroluminescence device (EL) have.

The electroluminescent device is divided into an inorganic electroluminescent device and an organic light emitting diode device depending on the material of the light emitting layer, and is self-luminous device that emits itself, has a high response speed, and has a large luminous efficiency, brightness and viewing angle. 1 is a view showing a structure of an organic light emitting diode. The organic light emitting diode includes an organic electroluminescent compound layer that electroluminesces as shown in FIG. 1, and a cathode and an anode that face each other with an organic electroluminescent compound layer interposed therebetween. The organic electroluminescent compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer layer, EIL).

In the organic light emitting diode, an excitation is formed in the excitation process when the holes and electrons injected into the anode and the cathode recombine in the light emitting layer (EML), and the organic light emitting diode emits light due to energy from the exciton. The organic light emitting diode display device displays an image by electrically controlling the amount of light generated from the emission layer (EML) of the organic light emitting diode as shown in FIG.

2. Description of the Related Art An organic light emitting diode display (OLEDD) using an organic light emitting diode (OLED) as an electroluminescent device includes a passive matrix type organic light emitting diode display (PMOLED) Type organic light emitting diode display device (Active Matrix type Organic Light Emitting Diode Display (AMOLED)). In addition, depending on the direction in which the light is emitted, there are a top-emission type and a bottom-emission type.

An active matrix type flexible organic light emitting diode display device (flexible AMOLED) displays an image by controlling a current flowing in an organic light emitting diode using a thin film transistor (TFT). In order to secure the rigidity and flexibility of the substrate at the same time, a TFT and an organic light emitting diode are formed on a thin foil-shaped metal thin film. Therefore, a top light emitting method that emits light to the upper side of the substrate is used. For the top emission type, an inverted type organic light emitting diode (hereinafter referred to as "IOD") which forms an organic compound layer for electroluminescence on a cathode is most suitable.

In the organic light emitting display, it is preferable to use ITO (Indium Tin Oxide) which is a transparent electrode satisfying a work function condition. However, in the top emission method, since light must be emitted from the cathode toward the anode, it is preferable to use a reflective electrode at the bottom of the cathode. Since functional and structural conditions are in conflict with each other, a solution is needed to solve the problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic electroluminescent display device having a reflective electrode for reflecting light toward an upper portion under a transparent electrode satisfying a work function condition and a method of manufacturing the same, There is. Another object of the present invention is to provide an organic electroluminescent display device having a reflective electrode in which the thickness of a transparent electrode is reduced in a top emission type organic electroluminescent display device to improve reflection efficiency and a method of manufacturing the same . It is still another object of the present invention to provide an organic light emitting display device having a reflective electrode having improved contact resistance even if the thickness of the transparent electrode is reduced by forming the pad electrode to have the same structure as the cathode even when the transparent electrode is formed thin, And a manufacturing method thereof. It is another object of the present invention to provide a method of manufacturing an organic electroluminescent display device having a reflective electrode that has a transparent electrode and a reflective electrode and simplifies a mask process.

An organic light emitting display device according to the present invention includes: a substrate; A scan line, a data line, and a drive current line defining a pixel region on the substrate; A thin film transistor formed in the pixel region; A pad formed on one end of the scan line, the data line, and the drive current line; And a cathode connected to the thin film transistor and formed in the pixel region, and a pad terminal formed on the pad, wherein the cathode and the pad terminal are laminated with a reflective electrode layer and a transparent conductive layer.

The reflective electrode layer has a thickness of 500 ANGSTROM or more; And the transparent conductive layer has a thickness of 300 angstroms or less.

The reflective electrode layer has a thickness of 1000 to 1500 ANGSTROM; And the transparent conductive layer has a thickness of 50 to 100 ANGSTROM.

The reflective electrode layer may include at least one of aluminum (Al), neodymium, nickel, titanium, tantalum, copper, silver, .

The transparent conductive layer may include at least one of indium tin oxide (ITO) and indium zinc oxide (IZO).

The pad includes a gate pad formed at one end of the scan line, and a data pad formed at one end of the data line and the drive current line; The pad terminal includes a gate pad terminal formed on the gate pad and a data pad terminal formed on the data pad.

The thin film transistor includes a switching thin film transistor and a driving thin film transistor.

Wherein the switching thin film transistor includes a switching gate electrode that branches off from the scan wiring, a switching source electrode that branches to the data wiring, and a switching drain electrode that faces the switching source electrode; The driving thin film transistor includes a driving gate electrode contacting with the switching drain, a driving source electrode branched from the driving current wiring, and a driving drain electrode facing the driving source electrode and connected to the cathode.

According to another aspect of the present invention, there is provided a method of manufacturing an organic light emitting display, including: forming a scan line, a data line, a drive current line, and a thin film transistor disposed in the pixel region; A cathode connected to the thin film transistor by continuously depositing and patterning a reflective electrode layer and a transparent electrode layer in a pixel region on the substrate, and a pad terminal connected to one end of the scan line, the data line and the drive current line .

The reflective electrode layer has a thickness of 500 ANGSTROM or more; And the transparent conductive layer has a thickness of 300 angstroms or less.

The reflective electrode layer has a thickness of 1000 to 1500 ANGSTROM; And the transparent conductive layer has a thickness of 50 to 100 ANGSTROM.

The reflective electrode layer may include at least one of aluminum (Al), neodymium, nickel, titanium, tantalum, copper, silver, .

The transparent conductive layer may include at least one of indium tin oxide (ITO) and indium zinc oxide (IZO).

The thin film transistor forming step may include forming a gate electrode on the substrate, forming a gate element including a switching gate electrode, the scan wiring, a gate pad connected to one end of the scan wiring, and a driving gate electrode, fair; A gate insulating layer, a semiconductor material, and an impurity semiconductor material are coated on the gate element to form a switching semiconductor layer and a switching ohmic contact layer overlapping the switching gate electrode, and a driving semiconductor layer and a driving ohmic contact layer overlapping the driving gate electrode A second masking step of exposing a portion of the driving gate electrode; A source electrode, a source electrode, and a drain electrode; and a gate electrode formed on the source electrode, the source electrode, and the gate electrode, A driving drain electrode facing the driving source electrode and contacting the cathode, and a data pad connected to one end of the data wiring and the driving current wiring, thereby completing the switching thin film transistor and the driving thin film transistor. And a third mask process for performing a second mask process.

Wherein the step of forming the cathode and the pad terminal comprises the steps of applying a planarizing film on the substrate on which the switching thin film transistor and the driving thin film transistor are formed and patterning the thin film to form the driving drain electrode, 4 mask process; Then, the reflective electrode layer and the transparent conductive layer are sequentially coated on the planarization layer and patterned to form a cathode pad connected to the driving drain electrode, a gate pad terminal connected to the gate pad, and a data pad terminal connected to the data pad And a fifth mask process of performing a second mask process.

Forming an organic light emitting layer on the cathode; And forming an anode on the organic light emitting layer.

The organic electroluminescent display of the present invention includes a cathode in which a reflective electrode layer and a transparent conductive layer are sequentially stacked, and a top emission organic electroluminescent display device for efficiently reflecting light generated from an organic light emitting layer interposed between a lower cathode and an upper anode Device can be obtained. In addition, the present invention has a structure in which the reflective electrode layer and the transparent conductive layer are sequentially stacked in the pad portion in the same manner as the cathode, so that even if the transparent conductive layer is laminated thinly, I never do that. As a result, the organic electroluminescent display device of the top emission type in which the transparent conductive layer can be formed thin and thus the reflectivity at the cathode is improved can be obtained. A reflective electrode layer and a transparent electrode layer constituting the cathode and pad portions are continuously vapor-deposited and patterned simultaneously, so that a simple manufacturing process of the organic light emitting display device can be achieved without an additional mask process.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a structure of an organic light emitting diode. FIG.
2 is a plan view showing a structure of an organic light emitting diode display device according to the present invention.
FIGS. 3A to 3F are cross-sectional views taken along the cutting line I-I 'of FIG. 1 to show a process of manufacturing the organic light emitting diode display device according to the present invention.

Hereinafter, a detailed embodiment of the present invention will be described with reference to the accompanying drawings. 2 is a plan view showing the structure of an organic light emitting display device according to the present invention. FIGS. 3A to 3F are cross-sectional views taken along the cutting line I-I 'of FIG. 1 to show a process of manufacturing the organic light emitting display device according to the present invention.

Referring to FIG. 2, an active matrix organic light emitting diode display device, which is an example of a top emission type organic light emitting diode, will be described. The organic light emitting diode display device according to the present invention includes a switching TFT (SWT), a driving TFT (DRT) connected to the switching TFT, and an organic light emitting diode (OLED) connected to the driving TFT (DRT).

In the case of a flexible organic light-emitting diode display, a thin metal film such as stainless steel or aluminum is used for the substrate to have rigidity and flexibility at the same time. In addition, since electrical problems may occur when devices are directly formed on a metal substrate, it is preferable that an insulating film or a planarization film is coated on the entire surface with an inorganic insulating material such as SiNx.

The switching TFT (SWT) is formed at a position where the scan line (SL) and the data line (DL) cross each other. The switching TFT (SWT) functions to select a pixel. The switching TFT SWT includes a switching gate electrode WG, a switching semiconductor layer WA, a switching source electrode WS and a switching drain electrode WD which branch off from the scan wiring SL.

The driving TFT DRT serves to drive the organic light emitting diode OLED of the pixel selected by the switching TFT SWT. The driving TFT DRT includes a driving gate electrode RG connected to the switching drain electrode WD, a driving source electrode RS connected to the driving semiconductor layer RA, the driving current wiring VDD, and a driving drain electrode RD ). The driving drain electrode RD is connected to the cathode of the organic light emitting diode OLED.

A scan wiring line SL extending in the horizontal direction and a data line DL extending in the vertical direction cross each other to define a rectangular pixel region. A gate pad GP for receiving a scan signal is formed at one end of the scan line SL. The gate pad GP contacts the gate pad terminal GPT through the gate pad contact hole GPH from which a part of the insulating film covering the gate pad GP is removed.

A data pad DP for receiving the cathode voltage and the data voltage of the image data is formed at one end of the data line DL. The data pad DP contacts the data pad terminal DPT via the data pad contact hole DPH from which a part of the insulating film covering the data pad DP is removed.

In the organic light emitting diode display according to the present invention, the cathode, the gate pad terminal GPT and the data pad terminals DPT constituting the organic light emitting diode OLED have a two-layer structure in which a reflective electrode layer and a transparent conductive layer are stacked. 3A to 3F, the structure of the organic light emitting diode according to the present invention and the process for manufacturing the organic light emitting diode display according to the present invention will be described in more detail.

A gate metal is deposited on the substrate SUB and patterned by a first mask process to form a gate element. The gate element SL includes a switching gate electrode WG branched to the pixel region in the scan line SL, a gate pad GP formed at one end of the scan line SL, And the gate electrodes DG of the formed driving TFT DRT are included (Fig. 3A).

A gate insulating film GI is formed on the entire surface of the substrate SUB on which the gate element is formed. A semiconductor material doped with a semiconductor material and an impurity is continuously deposited on the gate insulating film (GI). A semiconductor material doped with a semiconductor material and an impurity is patterned by a second mask process to form a switching semiconductor channel layer WA and a switching ohmic contact layer Wn overlapping the switching gate electrode WG.

At the same time, a driving semiconductor channel layer (RA) and a driving ohmic contact layer (Rn) overlapping with a part of the driving gate electrode (RG) are formed. A gate contact hole GH exposing a part of the driving gate electrode RG which is not overlapped with the driving semiconductor channel layer RA and the driving ohmic contact layer Rn is formed. In order to simultaneously pattern regions having different degrees of patterning, it is preferable to use a half-tone mask in the second mask process (FIG. 3B).

On the entire surface of the substrate SUB on which the channel layers WA, RA are formed, the source metal material is deposited on the entire surface and patterned by the third mask process to form the source-drain element. The data line DL and the drive current line VDD orthogonal to the scan line SL are connected to the source and drain elements and the switching source electrode D2 branched from the data line DL and in contact with one side of the switching ohmic contact layer Wn A driving source electrode DS branched from the driving current line WS and the driving current line VDD and contacting one side of the driving ohmic contact layer Dn and a switching ohmic contact layer A switching drain electrode WD in contact with the other side of the driving source electrode DS and a driving drain electrode RD in contact with the other side of the driving ohmic contact layer Rn while being spaced apart from the driving source electrode DS by a predetermined distance.

At this time, the switching drain electrode WD contacts the driving gate electrode RG exposed through the gate contact hole GH formed in the gate insulating film GI. A data pad DP is formed at one end of the data line DL and the driving current line VDD. In the switching ohmic contact layer Wn, the exposed portion between the switching source electrode WS and the switching drain electrode WD and the exposed portion between the driving source electrode < RTI ID = 0.0 > Thereby removing exposed portions between the source electrode RS and the driving drain electrode RD. This completes the switching TFT (SWT) and the driving TFT (DRT) (Fig. 3C).

The protective film PAS and the planarizing film PL are continuously applied to the entire surface of the substrate SUB including the switching TFT SWT and the driving TFT DRT. In the fourth mask process, the planarizing film PL, the protective film PAS, and / or the gate insulating film GI are patterned to form contact holes. A drain contact hole DH for exposing a part of the driving drain electrode RD and a data pad contact hole for exposing the data pad DP are formed in the contact holes by removing a part of the planarization film PL and the protective film PAS DPH). And includes a gate pad contact hole GPH for removing the planarizing film PL, the protective film PAS and a part of the gate insulating film GI to expose the gate pad GP (FIG. 3D).

The reflective electrode layer AL and the transparent conductive layer IT are continuously deposited on the entire surface of the substrate SUB on which the contact holes are formed. The reflective electrode layer AL may be formed of any one selected from the group consisting of Aluminum, Neodium, Nickel, Titanium, Tantalum, Copper, and Ag, AlNi, and mixtures of two or more of the above materials. The transparent conductive layer IT includes ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide).

In the fifth mask process, the reflective electrode layer AL and the transparent conductive layer IT are simultaneously patterned to form a cathode CAT, a gate pad terminal GPT, and a data pad terminal DPT. The cathode (CAT) is in contact with the driving drain electrode (RD) exposed through the drain contact hole (DH). The gate pad terminal GPT is in contact with the gate pad GP through the gate pad contact hole GPH and the data pad terminal DPT is in contact with the data pad DP through the data pad contact hole DPH. The cathode (CAT), the gate pad terminal (GPT), and the data pad terminal (DPT) according to the present invention all have a two-layer structure in which a reflective electrode layer AL and a transparent conductive layer IT are laminated (FIG.

A bank BANK is formed on the substrate SUB on which the cathode CAT and the pad terminals GPT and DPT are formed, in the region excluding the effective pixel region and the pad terminals. Then, the organic light emitting material OL is formed on the cathode CAT exposed between the banks BANK. The organic light emitting material OL may be formed of a multilayer organic film having a structure as shown in FIG. Then, a transparent conductive material is deposited on the organic light emitting material OL to form an anode ANO. In this case, the anode ANO may be formed so as to cover the bank BANK so that the anodes ANO of all the pixel regions are connected together (FIG. 3F).

Transparent conductive materials such as ITO and IZO have higher transparency as they are formed thinner. Therefore, in the organic EL display device of the top emission type as in the present invention, the higher the transparency of the transparent conductive material used as the cathode, the higher the luminance is. However, when the reflective electrode layer is formed only on the cathode, or when the transparent conductive layer is used alone, if the transparent conductive layer is formed thin to improve brightness, the gate pad terminal and the data pad terminal are necessarily thin. At this time, the contact resistance may increase at the pad terminal portion, or defects such as disconnection may occur. Therefore, there is a limit to thinning the transparent conductive layer.

However, in the present invention, not only the cathode CAT but also the gate pad terminal GPT and the data pad terminal DPT all include the reflective electrode layer AL and the transparent electrode layer IT. Therefore, even if the transparent electrode layer IT is formed to a minimum thickness, the presence of the reflective electrode layer AL does not cause problems such as increase in contact resistance and disconnection at the pad terminal portion. Accordingly, in the cathode (CAT) portion, the transparent electrode layer IT is thinned, thereby maximizing the reflection efficiency of the reflective electrode layer AL.

For example, when the pad terminal is formed only of a transparent conductive layer, it should have a thickness of 1000 ANGSTROM or more in order to prevent contact resistance problems and disconnection problems. However, in the present invention, when the reflective electrode layer (AL) having a thickness of 500 to 1000 angstroms is deposited first and then the transparent conductive layer (IT) having a thickness of 300 angstroms or less is formed, contact resistance problems and disconnection problems In addition, the reflection efficiency increases at the cathode (CAT).

In order to maximize the reflection efficiency of the reflective electrode layer AL while ensuring the work function of the cathode CAT, the transparent conductive layer IT may be formed to a thickness of about 50 to 100 ANGSTROM. In this case, it is preferable to form the reflective electrode layer AL to have a thickness of 1000 to 1500 ANGSTROM in order to prevent a contact resistance problem and a disconnection problem in the pad terminal portion.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

SUB: substrate SL: scan wiring
DL: Data wiring VDD: Driving current wiring
SWT: switching thin film transistor DRT: driving thin film transistor
WG: switching gate electrode WA: switching channel layer
Wn: switching ohmic contact layer WS: switching source electrode
WD: Switching drain electrode GH: Gate contact hole
GP: Gate pad GPH: Gate pad Contact hole
GPT: gate pad terminal GI: gate insulating film
RG: driving gate electrode RA: driving channel layer
Rn: driving ohmic contact layer RS: driving source electrode
RD: Driving drain electrode DH: Drain contact hole
DP: data pad DPH: data pad contact hole
DPT: Data pad terminal PAS: Shield
PL: planarization film CAT: cathode
OL: organic light emitting film ANO: anode
OLED: Organic Light Emitting Diode BANK: Bank

Claims (16)

Board;
A scan line, a data line, and a drive current line defining a pixel region on the substrate;
A switching thin film transistor formed in the pixel region and a driving thin film transistor connected to the switching thin film transistor;
A pad formed on one end of the scan line, the data line, and the drive current line; And
A cathode connected to the driving thin film transistor and formed in the pixel region, and a pad terminal formed on the pad,
Wherein the pad includes a gate pad formed at one end of the scan line and a data pad formed at one end of the data line and the drive current line,
The pad terminal includes a gate pad terminal formed on the gate pad and a data pad terminal formed on the data pad,
Both the cathode, the gate pad terminal, and the data pad terminal have a structure in which the same reflective electrode layer and the transparent conductive layer are laminated,
The switching thin film transistor includes:
A switching gate electrode that branches off from the scan wiring; A switching semiconductor layer disposed on the switching gate electrode with a gate insulating film interposed therebetween, the switching semiconductor layer overlapping a part of the switching gate electrode; A switching source electrode connected to one side of the switching semiconductor layer; And a switching drain electrode connected to the other side of the switching semiconductor layer,
The driving thin film transistor includes:
A driving gate electrode; A driving semiconductor layer disposed on the driving gate electrode with the gate insulating film interposed therebetween, the driving semiconductor layer overlapping a part of the driving gate electrode; A driving source electrode connected to one side of the driving semiconductor layer and connected to the driving current wiring; And a driving drain electrode connected to the other side of the driving semiconductor layer and connected to the cathode,
The driving gate electrode
Wherein the gate electrode is in direct contact with the switching drain electrode through a contact hole passing through the gate insulating film,
The driving gate electrode
A first portion extending in parallel with the scan line; And a second portion extending from the first portion in parallel with the drive current wiring and partially overlapping the drive current wiring.
The method according to claim 1,
The reflective electrode layer has a thickness of 500 ANGSTROM or more;
Wherein the transparent conductive layer has a thickness of 300 ANGSTROM or less.
3. The method of claim 2,
The reflective electrode layer has a thickness of 1000 to 1500 ANGSTROM;
Wherein the transparent conductive layer has a thickness of 50 to 100 ANGSTROM.
The method according to claim 1,
The reflective electrode layer may include at least one of aluminum (Al), neodymium, nickel, titanium, tantalum, copper, silver, The organic light emitting display device comprising:
The method according to claim 1,
Wherein the transparent conductive layer comprises at least one of ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide).
delete delete delete A method of manufacturing an organic light emitting display device including a scan line, a data line, a drive current line, and a thin film transistor disposed in the pixel region, the pixel defining a pixel region on the substrate,

A first mask process for forming a gate element including a switching gate electrode, the scan line, a gate pad connected to one end of the scan line, and a drive gate electrode by applying a gate metal on the substrate;
A gate insulating layer, a semiconductor material, and an impurity semiconductor material are coated on the gate element to form a switching semiconductor layer and a switching ohmic contact layer overlapping the switching gate electrode, and a driving semiconductor layer and a driving ohmic contact layer overlapping the driving gate electrode A second masking step of exposing a portion of the driving gate electrode;
A switching source electrode which is branched from the data wiring; a switching drain electrode which is opposite to the switching source electrode and is in direct contact with the driving gate electrode; And a data pad connected to one end of the data line and the driving current line to form a switching thin film transistor and a driving thin film transistor, A third masking process;
A fourth masking step of exposing the driving drain electrode, the gate pad, and the data pad by applying and patterning a planarizing film on the substrate on which the switching thin film transistor and the driving thin film transistor are formed; And
A reflective electrode layer and a transparent conductive layer are sequentially formed on the planarizing film and patterned to form a gate pad terminal connected to the cathode, a gate pad terminal connected to the driving drain electrode, and a data pad terminal connected to the data pad, Comprising a mask process,
The driving gate electrode
A first portion extending in parallel with the scan line; And a second portion extending from the first portion in parallel with the drive current wiring and partially overlapping the drive current wiring.
10. The method of claim 9,
The reflective electrode layer has a thickness of 500 ANGSTROM or more;
Wherein the transparent conductive layer has a thickness of 300 ANGSTROM or less.
11. The method of claim 10,
The reflective electrode layer has a thickness of 1000 to 1500 ANGSTROM;
Wherein the transparent conductive layer has a thickness of 50 to 100 ANGSTROM.
10. The method of claim 9,
The reflective electrode layer may include at least one of aluminum (Al), neodymium, nickel, titanium, tantalum, copper, silver, Wherein the organic electroluminescent display device has a plurality of pixels.
10. The method of claim 9,
Wherein the transparent conductive layer comprises at least one of ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide).
delete delete 10. The method of claim 9,
Forming an organic light emitting layer on the cathode; And
And forming an anode on the organic light emitting layer.

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