JP2003131593A - Active matrix driven organic led panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a short circuit between a metallic pixel electrode and a transparent counter electrode. SOLUTION: This active matrix driven organic LED panel is provided with a substrate, a plurality of TFT circuits formed on the substrate, a flattening film formed to cover the whole TFT circuits, through-holes formed on the flattening film and reaching each TFT circuit, metallic pixel electrodes formed at the positions corresponding to respective TFT circuits on the flattening film and connected with the TFT circuits via the through-holes, through-hole insulating films formed inside the through-holes and on metallic pixel electrodes in the periphery of the through-holes, an organic layer formed on each metallic pixel electrode and through-hole insulating film, and a transparent counter electrode formed on the organic layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an active matrix drive type organic LED panel.

[0002]

2. Description of the Related Art In recent years, organic thin-film LED devices have been developed by CW Wang of Eastman Kodak Co., Ltd., research institutes and companies, and drive systems have been studied. The drive system is mainly the duty drive system and the TF that has been developed along with liquid crystal displays.
Various studies have been made on active matrix driving methods using T, and various panel structures corresponding to these driving methods have been proposed.

As a conventional technique related to the present invention, an organic LED display device (for example, Japanese Laid-Open Patent Application No. 7-1113) which uses a thin film transistor and performs active matrix driving.
41, JP-A-7-122360, JP-A-7-
-122361, JP-A-7-153576, JP-A-8-241047, and JP-A-8-227.
276), or for the purpose of improving the aperture ratio of a pixel, an organic LED display device having a structure in which an organic LED element section is arranged on a thin film transistor via an insulating film and light emission is taken out from the opposite side of the substrate (for example, Japanese Patent Laid-Open No. H10-242242) No. 10-189252) and the like are known.

[0004]

The TFT (thin film transistor) technology has been developed mainly with the liquid crystal technology in recent years, and when it is used for driving an organic LED element, not only in a driving circuit but also in a panel structure, It is necessary to have a structure optimized for the LED element. In a low temperature polysilicon TFT drive panel for liquid crystal, a flattening film made of resin or the like is formed on a TFT circuit, and a transparent electrode is formed on the flattening film. The transparent electrode is electrically connected to the TFT circuit under the flattening film through a through hole. For liquid crystal,
Pixels are formed between the electrodes formed on another piece of the laminated glass. The electric field between these two electrodes is ON /
When turned off, the liquid crystal functions as a light valve.

Also in the organic LED panel, after the TFT circuit is formed, a flattening film made of resin or the like is formed, and a metal thin film electrode is formed thereon. The metal electrode is T under the flattening film.
It is electrically connected to the FT circuit through a through hole.
An organic layer is formed on this, and a transparent electrode is further formed on it. The organic layer is sandwiched between the transparent electrode and the metal electrode, and emits light when a voltage is applied and a current flows.
The organic LED panel has the following problems.

When the organic layer is formed on the through hole, a phenomenon occurs in which the organic layer is not formed with a sufficient thickness due to the depression of the through hole of about 3 μm. When the transparent electrode layer is formed on the organic layer, a transparent electrode is formed. The metal electrode is short-circuited and cannot emit light.

Further, at the end of the electrode, 100-300n
Since there is a step of m and the organic layer becomes thin due to this step, the electric field applied to the organic layer becomes a high electric field. This step difference occurs because the thickness of the metal electrode is approximately 100 to 300 nm. If the thickness of the metal electrode is reduced, this step becomes smaller, but the sheet resistance of the electrode increases, so that uniform light emission cannot be obtained in the pixel, so a certain thickness is required. Not only can uniform light emission not be obtained, but the electric field concentration may damage the organic layer, resulting in a short circuit between the metal electrode and the transparent electrode, which may prevent lighting.

Further, there is a problem that the surface of the metal electrode on which the organic layer is formed is oxidized. In order for the organic layer to emit light, it is necessary to form the organic layer on a clean metal electrode film, but since it is oxidized in the steps of etching, peeling, and cleaning the insulating film, the oxide film on the surface of the metal electrode is removed. Need to be removed. The present invention has been made in consideration of such circumstances, and provides an active matrix type organic LED panel in which a metal electrode and a transparent electrode do not cause a short circuit.

[0009]

The present invention is directed to a substrate, a plurality of TFT circuits formed on the substrate, a flattening film formed so as to cover the entire plurality of TFT circuits, and a flattening film formed on the flattening film. Through holes reaching the respective TFT circuits, and metal pixel electrodes formed at positions corresponding to the respective TFT circuits on the flattening film and connected to the TFT circuits through the through holes,
Through hole insulating films formed on the metal pixel electrodes inside the through holes and on the periphery of the through holes, organic layers formed on the metal pixel electrodes and the through hole insulating films, and transparent facing formed on the organic layers An active matrix drive type organic LED panel including electrodes is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The active matrix organic LED panel of the present invention is characterized by a substrate, a plurality of TFT circuits formed on the substrate, and a flattening film formed so as to cover the entire plurality of TFT circuits. , Each TF formed on the planarization film
Each through-hole reaching the T circuit and each TFT on the flattening film
The through hole is formed at the position corresponding to the circuit, and the T
A metal pixel electrode connected to the FT circuit, a through hole insulating film formed on the metal pixel electrode inside the through hole and on the periphery of the through hole, and an organic layer formed on each metal pixel electrode and the through hole insulating film. , Is provided with a transparent counter electrode formed on the organic layer. A peripheral insulating film may be further formed on the peripheral edge of each metal pixel electrode, and the organic layer may be formed on the peripheral insulating film.

Further, according to the present invention, the substrate, the TFT circuits respectively formed on the substrate corresponding to the plurality of pixel regions set at a predetermined interval, and the TFT circuit formed on the substrate are formed so as to cover the entire TFT circuits. And a through hole formed in the flattening film in the interval between two adjacent pixel regions and reaching the TFT circuit, and a TFT circuit through the through hole formed in each pixel region and the region including the through hole. Provided is an active matrix drive type organic LED panel including metal pixel electrodes connected to each other, an organic layer formed on the metal pixel electrodes in each pixel region, and a transparent counter electrode formed on the organic layer. .

A single through hole may be formed in the flattening film in the interval between two adjacent pixel regions so as to reach the TFT circuit corresponding to one pixel region.
Two through holes are formed in the flattening film in the interval between two adjacent pixel regions, one through hole reaches the TFT circuit corresponding to one pixel region, and the other through hole corresponds to the other pixel region. The TFT circuit may be formed so as to reach the TFT circuit.

The substrate used in this invention is glass,
Insulating substrates made of inorganic materials such as quartz, plastics such as polyethylene terephthalate or ceramics such as alumina, and metal substrates such as aluminum and iron can be used for Si.
Examples thereof include a substrate coated with an insulator such as O ₂ and an organic insulating material, and a substrate obtained by subjecting the surface of a metal substrate such as aluminum to an insulating treatment by a method such as anodic oxidation.

The TFT circuit is mainly composed of one or more TFs.
The TFT is composed of a T (thin film transistor) and a capacitor for holding a signal. The TFT has a known material, structure, and
It can be formed using a film forming method.

For example, as the material of the active layer of the thin film transistor, an inorganic semiconductor material such as amorphous silicon, polycrystalline silicon, microcrystalline silicon, cadmium selenide, or thiophene oligomer, poly (p-phenylene vinylene) is used. Organic semiconductor materials such as

As the structure of the TFT, for example, a stagger type, an inverted stagger type, a top gate type and a coplanar type can be used. Further, a single gate structure, a double gate structure, and a multi-gate structure having three or more gate electrodes may be used.

As a film forming method of the active layer of the TFT, for example, a method of laminating amorphous silicon by plasma CVD method and performing ion doping, or a method of forming amorphous silicon by LPCVD method using SiH ₄ gas and performing solid phase growth. Method to crystallize amorphous silicon by method to obtain polysilicon, and then ion doping by ion implantation method, or LP using Si ₂ H ₆ gas
Amorphous silicon is formed by a CVD method or a PECVD method using SiH ₄ gas, annealed by a laser such as an excimer laser, the amorphous silicon is crystallized to obtain polysilicon, and then ion doping is performed by an ion doping method. (Low temperature process)
Is mentioned.

Further, polysilicon is laminated by the low pressure CVD method or the LPCVD method and is thermally oxidized at 1000 ° C. or more to form a gate insulating film 4, on which an n + polysilicon gate electrode is formed, and thereafter, A method of performing ion doping by an ion implantation method (high temperature process) or the like can also be used.

The capacitor used in the TFT circuit is not particularly limited, and for example, SiO ₂ , SiN or the like used as an insulating film can be used as the dielectric layer of the capacitor.

As the flattening film used in the present invention, for example, SiO ₂ , spin-on glass, SiN (Si ₃ N
₄ ), TaO (Ta ₂ O ₅ ), Ni _X Z _NY Fe ₂ O _{4 and} other inorganic materials, acrylic resins, resist materials, and black matrix materials and other organic materials.

The flattening film can be formed of these materials by using a dry process such as CVD or vacuum deposition, or a wet process such as spin coating. Also,
It is also possible to perform patterning by a photolithography method. Organic L constituting each pixel of the panel of the present invention
The ED element is composed of a metal pixel electrode, an organic layer and a transparent counter electrode.

For the organic layer of the present invention, for example, any of the following six kinds of constitutions can be adopted. Organic light emitting layer hole transport layer / organic light emitting layer organic light emitting layer / electron transport layer hole transport layer / organic light emitting layer / electron transport layer hole injection layer / hole transport layer / organic light emitting layer / electron transport layer buffer layer / Hole transport layer / organic light emitting layer / electron transport layer

Here, the organic light emitting layer may be a single layer or a multilayer structure. As the light emitting material that can be used for the organic light emitting layer, known light emitting materials for organic LEDs can be used, but the light emitting material is not particularly limited.

As a light emitting material which can be used for the organic light emitting layer, for example, a low molecular weight light emitting material (for example, 4,4'-bis (2,2'-diphenylvinyl) -biphenyl (DPV) is used.
Aromatic dimethylidene compounds such as Bi), 5-methyl-
Oxadiazole compounds such as 2- [2- [4- (5-methyl-2-benzoxazolyl) phenyl] vinyl] benzoxazole, 3- (4-biphenylyl) -4-
Triazole derivatives such as phenyl-5-t-butylphenyl-1,2,4-triazole (TAZ), 1,4-
Fluorescent organic materials such as styrylbenzene compounds such as bis (2-methylstyryl) benzene, thiopyrazine dioxide derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, diphenoquinone derivatives, fluorenone derivatives, azomethine zinc complexes, (8-hydroxyquinoline) Linato) aluminum complex (Alq3) and other fluorescent organometallic compounds), polymeric light-emitting material (for example, poly (2-decyloxy-1,4-phenylene) DO-PP
P, poly [2,5-bis- [2- (N, N, N-triethylammonium) ethoxy] -1,4-phenyl-alto-1,4-phenylene] dibromide (PPP-
NEt3 +), poly [2- (2'-ethylhexyloxy) -5-methoxy-1,4-phenylenevinylene]
(MEH-PPV), poly [5-methoxy- (2-propanoxysulfonyl) -1,4-phenylenevinylene] (MPS-PPV), poly [2,5-bis- (hexyloxy) -1, 4-phenylene- (1-cyanovinylene)] (CN-PPV), (poly (9,9-dioctylfluorene)) (PDAF), etc., precursor of polymer light-emitting material (for example, PPV precursor, PNV precursor) Or PPP
Precursor etc.) and the like.

The organic light emitting layer may be composed of only the above light emitting material, or may be a hole transport material, an electron transport material, an additive (donor, acceptor, etc.), or
The luminescent dopant may be contained, and these may be dispersed in the polymer material or the inorganic material.

Here, the charge transport layer may be a single layer or a multilayer structure. As the charge transport material that can be used in the charge transport layer, known charge transport materials for organic LEDs and organic photoconductors can be used, but the charge transport material is not particularly limited.

Examples of the charge transport material include hole transport materials (for example, inorganic p-type semiconductor materials, porphyrin compounds, N, N'-bis- (3-methylphenyl) -N, N'-
Bis- (phenyl) -benzidine (TPD), N, N'-
Aromatic tertiary amine compound such as di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (NPD), low molecular weight material such as hydrazone compound, quinacridone compound, styrylamine compound, polyaniline (PANI),
Polymer materials such as 3,4-polyethylenedioxythiophene / polystyrene sulphonate (PEDT / PSS), poly [triphenylamine derivative] (Poly-TPD), polyvinylcarbazole (PVCz), poly (p
-Phenylenevinylene) precursor (Pre-PPV), poly (p-naphthalenevinylene) precursor (Pre-PN
V) and other polymeric material precursors), electron transport materials (for example, inorganic n-type semiconductor materials, oxadiazol derivatives, triazole derivatives, thiopyrazine dioxide derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, diphenoquinone) Derivatives, low molecular weight materials such as fluorenone derivatives, poly [oxadiazole [(Pol
polymeric materials such as y-OXZ)).

The charge transport layer may be composed of only the charge transport material described above, may contain additives, etc., and the charge transport material may be a polymer material or an inorganic material. It may be dispersed therein.

Further, these materials are applied by a coating method such as a spin coating method, a dipping method, a doctor blade method, a wet process such as an ink jet method or a printing method,
Alternatively, it can be formed by a dry process such as a vacuum vapor deposition method or a laser transfer method, but a printing method or a laser transfer method is preferable in view of increasing the area, productivity and production speed.

A conventional electrode material can be used as the metal pixel electrode of the present invention, and it can act as an anode or a cathode in pairs with the transparent counter electrode. When acting as an anode, a metal Au having a high work function,
Pt, Ni, etc. can be used. When it is used as a cathode, it contains at least a metal having a low work function (Ca, Ce, Al, Mg: Ag alloy, Li: Al).
Alloy) or a combination of a thin insulating layer and a metal electrode (LiF / Al or the like) can be used.

The metal pixel electrode can be formed by the EB, the sputtering, the resistance heating vapor deposition method, or the laser transfer method using the above-mentioned material, but it is not particularly limited. It is also possible to perform patterning by a photolithography method. The through-hole insulating film and the peripheral insulating film can be formed in the same step by etching and peeling a film formed by sputtering such as SiO ₂ or SiNx. The transparent counter electrode can be formed by a laser transfer method using a conventional electrode material.

Embodiments The present invention will be described in detail below based on the embodiments shown in the drawings. This does not limit the invention.
FIG. 1 is an electrical equivalent circuit of the organic LED panel of the present invention. As shown in the figure, the plurality of TFT circuits 1 are organic L
Together with the ED elements 2, they are arranged in a matrix in the row direction (arrow X direction) and the column direction (arrow Y direction). TF of each line
A scanning line (select line) 3 is provided for the T circuit 1, and a signal line (data line) 4 is provided for the TFT circuit 1 in each column.

A transparent counter electrode 5 and a current supply line 6 are arranged in parallel with each signal line 4, and a DC voltage is applied to the transparent counter electrode 5 and the current supply line 6 from a power supply 7. In addition,
The transparent counter electrodes 5 are short-circuited to each other by conductors 9.

The TFT circuit 1 includes two TFTs 1a and 1b.
The TFT 1a has a source connected to the signal line 4, a gate connected to the scanning line 3, and a drain connected to the gate of the TFT 2a.

The source of the TFT 1b is a metal pixel electrode (described later) of the organic LED element 2 through a through hole 8 (described below).
And the drain is connected to the current supply line 6. The capacitor 1c is connected between the gate and drain of the TFT 1b.

Then, a set of TFT circuit 1 and organic LED
The element 2 constitutes one pixel. The TFT circuit 1 selected by the scanning line 3 and receiving a signal from the signal line 4 is activated to light the corresponding organic LED element 2.

2 and 3 are cross-sectional views of a main part showing the manufacturing process of the organic LED panel of the present invention, and FIGS. 4 and 5 are plan views showing the manufacturing process. The manufacturing method will be described with reference to these drawings.

As shown in FIG. 2A, the thickness is 2.0 mm.
On the alumina substrate 11, due to decomposition of SiH ₄ LP-
An α-Si film having a film thickness of 50 nm is formed by the CVD method,
After that, α-Si is polycrystallized by the solid layer growth method.
Next, a Poly-S composed of a gate, source / drain
The i film is subjected to etching processing, and p-Si as the insulating film 14 is thermally oxidized at 1000 ° C. or higher to form SiO ₂ having a thickness of 100 nm.
To form. After that, Al is formed as a gate by sputtering, and then the gate is patterned, and at the same time, the signal line 4 (FIG. 1) and the current supply line 6 (FIG. 1) are patterned. Further, the lower electrode of the capacitor 1c (FIG. 1) is processed.

Next, the side surface of the gate is anodized to form an offset portion, and thereafter, the source / drain portion is heavily doped with phosphorus by an ion implantation method. Next, after forming the scan line 3 (FIG. 1), the source and the upper electrode of the capacitor are formed, and the Poly-Si is formed by a high temperature process.
The TFT 12 is formed in the pixel region 100 shown in FIG.

Next, as shown in FIG. 2B, SiO ₂ is formed as the flattening film 16 to a film thickness of 3 μm. next,
A resist is applied on the flattening film 16 and a through pattern for the through hole 8 is formed by a photolithography method, and then etching is performed so that the cross section faces upward from the substrate 11 side as shown in FIG. 2C. A through hole 8 having a shape that spreads out is formed (see FIG. 4B).

Next, as shown in FIG. 2D, silver is deposited as the pixel electrode 17 by a resistance vapor deposition method to a film thickness of 100 nm, and lithium fluoride is deposited thereon by a resistance heating vapor deposition method to a film thickness of 1 nm. Deposition and patterning with laser (Fig. 4
(See (c)). Thereby, the pixel electrode 17 is connected to the TFT circuit 12 through the through hole 8.

Next, as the insulating film 20, Si is formed by sputtering.
O ₂ film Is formed to a film thickness of 200 nm, and is then removed by etching, so that the insulating film 20 is left only inside and the periphery of the through hole 8 and the periphery of the pixel electrode 17 as shown in FIG. (See (d)).

On this, a metal mask having openings only in the pixels is brought into close contact, and an organic light emitting material is vapor-deposited to form an organic layer 19 having a film thickness of 30 nm as shown in FIGS. 3 (e) and 4 (e). To form a film.

On top of that, a transparent electrode material (ITO or
A transfer sheet having IDIXO) formed on the surface is laminated. Next, the organic layer 19 is scanned with a laser beam. When you remove the transfer sheet after scanning,
(F) and the state shown in FIG. 5 (f). That is, the transparent counter electrode 5 is formed, and the active matrix type organic L
The ED panel is completed.

In this way, since the insulating film 20 is formed on the metal pixel electrode 17 inside and on the periphery of the through hole 8, even if the organic layer 19 is thinned at this portion, it is transparently opposed to the pixel electrode 17. The electrode 5 is not electrically short-circuited.
Further, since the peripheral edge of the pixel electrode 17 is also covered with the insulating film 20, even if the organic layer 19 becomes thin at the peripheral edge of the pixel electrode 17,
Since no current flows in the thin portion, the light emission in the pixel is made uniform, and the organic layer is prevented from being damaged by the concentration of the electric field. In the above embodiment, the surface oxide film (insulating film) is removed by plasma ashing the pixel electrode 17 immediately before forming the organic layer 19 so that the organic layer can effectively emit light.

6 to 8 are plan views showing a structure and a manufacturing method of a modified example of the above embodiment. In this modified example, FIG.
TFT circuit 1 formed in the pixel region 100 as shown in FIG.
2a has a protrusion 13 that protrudes to a distance from the adjacent pixel region 100. Then, as shown in FIG.
After forming 6, the through hole 8a is formed in the flattening film 16 by T
It is formed so as to reach the protrusion 13 of the FT circuit 12a.

Next, as shown in FIG. 8, the pixel electrode 17a is formed on the pixel region 100 and the protruding portion 13, and the pixel electrode 17a is connected to the TFT circuit 12a through the through hole 8a. The organic layer 1 is formed in each of the pixel regions 100.
9 is formed, the transparent counter electrode 5 is formed on it, and a panel is completed. Therefore, since the transparent counter electrode 5 is not formed in the through hole 8a, the pixel electrode 17a and the transparent electrode 5 are not electrically short-circuited in the through hole 8a.

FIG. 9 is a plan view showing still another modified example. In this modified example, a part of the TFT circuits of both pixels is made to protrude in the interval between two adjacent pixels, and corresponding to them. Through holes 8a and 8b in the flattening film 16
And the metal pixel electrodes 17a and 17b are connected to the TFT circuit via the through holes 8a and 8b, respectively. With such a configuration, it is possible to increase the pixel density by reducing the interval between the two adjacent pixel regions in which the metal pixel electrodes 17a and 17b do not project.

[0049]

According to the present invention, the metal pixel electrode is connected to the TFT circuit through the through hole formed in the flattening film, and the metal pixel electrode in the through hole and on the periphery of the through hole is covered with the insulating film. Therefore, even if the organic layer formed on the metal pixel electrode becomes thin, the metal pixel electrode and the transparent counter electrode are not short-circuited.

[Brief description of drawings]

FIG. 1 is an electrical equivalent circuit diagram of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of an embodiment of the present invention.

FIG. 4 is a plan view showing a manufacturing process according to an embodiment of the present invention.

FIG. 5 is a plan view showing the manufacturing process of the embodiment of the present invention.

FIG. 6 is a plan view showing a manufacturing process of a modified example of the invention.

FIG. 7 is a plan view showing a manufacturing process of a modified example of the invention.

FIG. 8 is a plan view showing a manufacturing process of a modified example of the invention.

FIG. 9 is a plan view showing a manufacturing process of another modification of the present invention.

[Explanation of symbols]

1 TFT circuit 1a TFT 1b TFT 1c capacitor 2 Organic LED element 3 scan lines 4 signal lines 5 Transparent counter electrode 6 current supply line 7 power supply 8 through holes 11 board 16 Flattening film 17 pixel electrodes 19 Organic layer 20 insulating film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/22 H05B 33/22 B CD

Claims (5)

[Claims] 1. A substrate and a plurality of TFs formed on the substrate
T circuit, a flattening film formed so as to cover the entire plurality of TFT circuits, through holes formed in the flattening film to reach each TFT circuit, and formed on the flattening film at a position corresponding to each TFT circuit. A metal pixel electrode connected to the TFT circuit through the through hole, a through hole insulating film formed on the metal pixel electrode inside the through hole and on the periphery of the through hole, and on each metal pixel electrode and the through hole insulating film. An active matrix drive type organic LED panel comprising an organic layer formed and a transparent counter electrode formed on the organic layer. 2. The active matrix drive type organic LED panel according to claim 1, further comprising a peripheral insulating film formed on a peripheral edge of each metal pixel electrode. 3. A substrate and a TFT formed corresponding to a plurality of pixel regions set on the substrate at a predetermined interval.
Circuit, a flattening film formed so as to cover the entire TFT circuit on the substrate, through holes reaching the TFT circuit formed in the flattening film in the interval between two adjacent pixel regions, and each pixel region and through hole A metal pixel electrode formed in a region including the pixel electrode and connected to the TFT circuit through a through hole, an organic layer formed on the metal pixel electrode in each pixel region, and a transparent counter electrode formed on the organic layer. An active matrix drive type organic LED panel provided. 4. The active matrix drive type organic LED according to claim 3, wherein a single through hole is formed in the flattening film in a space between two adjacent pixel regions and reaches a TFT circuit corresponding to one pixel region. panel. 5. Two through holes are formed in a flattening film in a space between two adjacent pixel regions, one through hole reaches a TFT circuit corresponding to one pixel region, and the other through hole is the other. Corresponding to the pixel area of
The active matrix drive type organic LED panel according to claim 3, which is formed so as to reach the FT circuit.