JP3893386B2 - Method for manufacturing organic electroluminescence display device - Google Patents

Description

  The present invention relates to a method for manufacturing an organic electroluminescence display device.

  In recent years, with the diversification of information processing equipment, there has been an increasing demand for flat display devices that consume less power than conventional cathode ray tubes (CRTs) and can be reduced in thickness. Examples of such a flat display device include a liquid crystal display device and an electroluminescence display device (hereinafter sometimes abbreviated as “EL display device”). Among them, the organic EL display device has features such as low voltage driving, all solid-state type, high-speed response, and self-luminous property, and therefore, research and development are being actively performed.

  The organic EL display device is largely divided into a passive matrix method (hereinafter abbreviated as “PM method”) and an active matrix method (hereinafter abbreviated as “AM method”) depending on the driving method. Separated.

  Since the PM method is line-sequential driving, in order to obtain high panel luminance, it is necessary to apply a large instantaneous power to each pixel as the display capacity increases, that is, the number of scanning electrodes increases. The organic EL display device of PM type has a problem that the product life is short.

  On the other hand, in the AM method, since switching can be performed for each pixel by a TFT provided for each pixel, the number of scanning electrodes is not limited in principle, and display close to static drive with a duty ratio of 100% can be performed. Enables high-quality and large-capacity display with good panel brightness and response.

  Further, in the AM system, it is not necessary to apply large electric power to each pixel in order to obtain a high panel luminance as in the PM system, and a lower voltage drive and a longer life can be achieved.

  For this reason, in recent years, research and development of AM-type organic EL display devices have been particularly active.

  FIG. 4 is a schematic cross-sectional view of a general organic EL display device 200.

  The organic EL display device 200 includes a substrate 201, a first electrode 202, one or more organic layers 203 including a light emitting layer, and a second electrode 204.

  The first electrode 202 is configured to be light transmissive and has a function of injecting holes into the organic layer 203. The second electrode 204 is configured to reflect light and has a function of injecting electrons into the organic layer 203.

  The holes and electrons injected from the first electrode 202 and the second electrode 204 recombine in the organic layer 203, whereby the organic layer 203 emits light.

  The organic layer 203 emits light through the first electrode 202 and the substrate 201 and is extracted from the organic EL display device 200 (bottom emission method).

  However, in such an AM type organic EL display device 200, it is necessary to dispose TFTs and electrodes made of silicon or the like that do not transmit light on the substrate 201. Therefore, the ratio of the emission area to the pixel area (opening) There is a problem that the rate is small.

  In particular, a current-driven organic EL display device that can suppress variation in display performance for each pixel and suppress display performance deterioration due to deterioration of a light emitting material is compared with a voltage-driven organic EL display device. More TFTs are required for each pixel. Therefore, the current driving type organic EL display device has a problem that the aperture ratio is further reduced.

  In view of the problem, the second electrode is configured to be light transmissive, and the first electrode is configured to be light reflective so that the organic layer can be formed from the second electrode side opposite to the substrate on which a circuit such as a TFT is configured. A top-emission method has been devised to extract the emitted light.

  According to the top emission method, light emitted from the organic layer can be taken out without going through a substrate on which a circuit such as a TFT is formed. This is because a bright organic EL display device can be realized.

  In the top emission type organic EL display device, the first electrode has a function of reflecting light emitted from the organic layer to the second electrode side and a function of injecting holes. Therefore, it is preferable that the first electrode has high light reflection performance and a large work function.

  Examples of the material having a large work function include gold and nickel. However, a metal having a large work function such as gold or nickel has a light reflectance lower than that of Al or silver. Therefore, there is a problem that sufficient luminance cannot be obtained in an organic EL display device having a first electrode made of gold, nickel, or the like.

  Therefore, in Patent Document 1, a first conductor layer made of Al having a high light reflectance and a light-transmitting indium-tin oxide (hereinafter referred to as “ITO”) having a large work function. There is disclosed a top emission type organic EL display device having a first electrode having a multilayer structure composed of a second conductor layer configured as described above.

  In this organic EL display device, a second conductive layer made of ITO having a large work function is formed under the organic layer. Therefore, this organic EL display device is described as having high hole injection efficiency into the organic layer.

  In this organic EL display device, the first electrode is composed of a first conductive layer made of Al having high light reflectivity and a second conductive layer made of ITO showing good light transmittance. Yes. Therefore, it is described that the first electrode has higher light reflectance than the first electrode made of a metal thin film having a large work function such as gold or nickel. Therefore, it is described that light emitted from the organic layer toward the substrate can be efficiently reflected to the second electrode side.

Therefore, it is described that an organic EL display device with higher luminance can be realized by this organic EL display device.
JP 2002-246185 A

  However, when the first conductive layer made of Al and the second conductive layer made of ITO are simultaneously wet-etched, a local battery is formed between the first conductive layer and the second conductive layer. Since corrosion and discoloration occur at the interface, the first conductive layer and the second conductive layer cannot be formed satisfactorily. Therefore, in such an organic EL display device, the first conductive layer and the second conductive layer must be patterned by dry etching which requires higher cost than wet etching. Therefore, there is a problem that such an organic EL display device requires high cost for manufacturing.

  This invention is made | formed in view of this point, The place made into the objective is to provide the method of manufacturing a high-intensity organic electroluminescent display apparatus at low cost.

A substrate, a first electrode sequentially stacked on the substrate, one or more organic layers including a light-emitting layer, and a second electrode, the first electrode including a light-reflective first conductive layer, a light A method of manufacturing a top emission type organic electroluminescence display device having a laminated structure with a transmissive second conductive layer and taking out light emission of the organic layer from the second electrode side,
The first conductive layer is mainly composed of Al, and the second conductive layer is composed mainly of IZO.
Forming a layer thickness of the second conductive layer to 5 nm or more;
The first conductive layer and the second conductive layer are patterned simultaneously by a wet etching method using an acid-based etching solution .

  According to this manufacturing method, since the patterning of the first conductive layer and the second conductive layer is simultaneously performed by cheap wet etching, the organic EL display device can be manufactured at low cost.

Further , since the first conductive layer is a layer mainly composed of Al having a high light reflectance in the visible light region, the first electrode has a high reflectance. Therefore, a high-brightness organic EL display device can be manufactured.

Further, since the second conductive layer is a layer mainly composed of IZO having a large work function, the hole injection efficiency into the organic layer is high. Therefore, an organic EL display device with high luminous efficiency can be manufactured .

Also, the present invention is to form a layer thickness of the second conductive layer over 5 nm, a first developing solution such as an acid-based resist used in patterning of the first electrode is caused by seep to the first conductive layer Deterioration of the conductive layer can be effectively suppressed. Therefore, deterioration of the light reflectance of the first conductive layer in the manufacturing process can be suppressed, and a high-brightness organic EL display device can be manufactured.

  According to the present invention, the patterning of the first conductive layer and the second conductive layer can be simultaneously performed by an inexpensive wet etching method. Therefore, the organic EL display device can be manufactured at a low cost.

  According to the invention, the first electrode is formed of the light-reflective first conductive layer and the light-transmissive second conductive layer. Accordingly, the first electrode can efficiently reflect the light emitted from the organic layer toward the first electrode toward the second electrode. Therefore, a high-emission top emission type organic EL display device can be realized.

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

  (Embodiment 1) FIG. 1 is a schematic sectional view of a top emission type organic EL display device 1 manufactured by a manufacturing method according to Embodiment 1 of the present invention.

  The organic EL display device 1 includes a substrate 10 and an organic EL element 2 configured on the substrate 10.

  The organic EL element 2 has a configuration in which a first electrode 20, an organic layer 30, and a second electrode 40 are sequentially stacked.

  The first electrode 20 includes a first conductive layer 21 and a second conductive layer 22.

  The first conductive layer 21 is made of a conductive material having light reflection characteristics, such as Ag.

  The second conductive layer 22 is made of a light transmissive material having a large work function.

  Further, even if the first conductive layer 21 and the second conductive layer 22 are patterned with the same etching solution, a combination in which corrosion and discoloration do not occur at the interface between the first conductive layer 21 and the second conductive layer 22. Consists of materials.

  The first conductive layer 21 may be a layer mainly composed of Al, and the second conductive layer 22 may be a layer mainly composed of IZO.

  Al is excellent in light reflectivity and has a light reflectance of 90% or more in the visible light range. Therefore, the first electrode 20 in which the first conductive layer 21 is a layer mainly composed of Al has a high light reflectance. Therefore, a high-brightness organic EL display device can be manufactured.

  IZO has a large work function of about 5.0 eV. Therefore, the first electrode 20 in which the second conductive layer 22 is a layer mainly composed of IZO has good hole injection efficiency into the organic layer 30.

  By using the first conductive layer 21 as a layer containing Al as a main component and the second conductive layer 22 as a layer containing IZO as a main component, the first conductive layer 21 and the second conductive layer 22 are the same etching solution. Even if the patterning is performed, the corrosion and discoloration do not occur at the interface between the first conductive layer 21 and the second conductive layer 22.

  The first conductive layer 21 may be formed by adding other elements to Al to such an extent that the light reflectance is not lowered. Pure Al is relatively highly corrosive. For example, the corrosivity of the first conductive layer 21 can be improved by adding an element such as Si, Cu, or Nd to Al.

  Further, since Al has a relatively low adhesion to the substrate, a layer for improving the adhesion may be inserted between the substrate and Al. As the layer for improving the adhesion, for example, a metal such as Mo is preferably used.

  The organic layer 30 includes a hole injection layer 31 and a light emitting layer 32. However, the present invention is not limited to this configuration. That is, in the present invention, the organic layer 30 may have a single-layer structure including only the light emitting layer 32. In addition, the organic layer 30 may be configured by one or more of the hole injection layer 31, the hole transport layer, and the electron transport layer, and the light emitting layer 32.

  The hole injection layer 31 is not limited as long as the hole injection efficiency is good. Examples of the material for the hole injection layer 31 include porphyrin compounds, N, N′-bis- (3-methylphenyl) -N, N′-bis-phenyl-benzidine (TPD), N, N′-di (naphthalene-1). -Yl) -N, N′-diphenyl-benzidine (NPD) and other aromatic tertiary amine compounds, hydrazone compounds, quinacridone compounds, styrylamine compounds and other low molecular materials, polyaniline, 3,4-polyethylenedioxythiophene / Polymer materials such as polystyrene sulfonate (PEDOT / PSS), poly (triphenylamine derivative), polyvinylcarbazole (PVCz), poly (P-phenylene vinylene) precursor, poly (P-naphthalene vinylene) precursor, etc. Examples thereof include polymer material precursors.

  Examples of the light emitting material to be contained in the light emitting layer 32 include aromatic dimethylidene compounds such as 4,4′-bis (2,2′-diphenylvinyl) -biphenyl (DPVBi), 5-methyl-2- [2- [ Oxadiazole compounds such as 4- (5-methyl-2-benzoxadyl) phenyl] vinyl] benzoxazole, 3- (4-biphenylyl) -4-phenyl-5-t-butylphenyl-1,2, Triazole compounds such as 4-triazole (TZA), styryl bezene compounds such as 1,4-bis (2-methyryl) benzene, fluorescent organic materials such as thioquinazine derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, azomethine zinc Fluorescent organometallic compounds such as complexes and (8-hydroxynolinato) aluminum complexes Poly (2-decyloxy-1,4-phenylene) (DO-PPP), poly [2,5-bis- [2- (N, N, N-triethylammonium) ethoxy] -1,4-phenyl-alt- 1,4-phenyllene] dibromide (PPP-NEt3 +), poly [2- (2′-ethylhexyloxy) -5-methoxy-1,4-phenylenevinylene] (MEH-PPV) and the like. It is not limited to this.

  The second electrode 40 includes an Al: Ca layer 41, an Al layer 42, and an IZO layer 43.

  The IZO layer 43 has a function as a transparent electrode. The Al: Ca layer 41 has a function of improving the efficiency of electron injection into the organic layer 30. The Al layer 42 has a function of preventing oxidation of the Al: Ca layer 41. However, the second electrode 40 is not limited to this configuration, and is not limited as long as it has a small work function and light transmittance. For example, the second electrode 40 is a laminated film in which a thin film of a metal having a low work function and a transparent electrode are laminated, or a laminated body in which a thin film doped with a metal having a low work function in a stable metal and a transparent electrode are laminated. It does not matter. Examples of the metal having a small work function include Ca, Ce, Cs, Rb, Sr, Ba, Mg, Li, and the like. Examples of the transparent electrode include IZO, SnO2, and ZnO.

  Hereinafter, the manufacturing method of the organic EL display device 1 according to the first embodiment of the present invention will be described with reference to FIG.

  First, the first conductive layer 21 and the second conductive layer 22 are continuously formed on the substrate 10 using a known film formation technique such as a DC sputtering method.

  Here, the first conductive layer 21 is preferably formed with a layer thickness of 10 nm or more. By forming the first conductive layer 21 with a layer thickness of 10 nm or more, it is possible to suppress the occurrence of pinholes in the first conductive layer 21 and to suppress the decrease in the light reflectance of the first conductive layer 21. Because.

  The first conductive layer 21 is preferably formed with a layer thickness of 200 nm or less. A sufficient light reflectance can be obtained with the first conductive layer 21 of 200 nm or less. Conversely, if the thickness of the first conductive layer 21 is increased, it takes a long time to form the first conductive layer. This is because the manufacturing cost of the display device 1 is increased.

  The second conductive layer 22 is preferably formed with a layer thickness of 5 nm or more, and more preferably with a layer thickness of 10 nm or more. This is because deterioration of the first conductive layer 21 due to penetration of the resist developer into the first conductive layer 21 at the time of patterning can be suppressed.

  FIG. 2 is a graph showing the relationship between the layer thickness of the second conductive layer 22 and the light reflectance of the first conductive layer 21. According to this, when the layer thickness of the second conductive layer 22 is 5 nm or more, the reduction ratio of the light reflectance of the second conductive layer 22 can be effectively suppressed, and the layer thickness of the second conductive layer 22 is reduced. It can be seen that if the thickness is 10 nm or more, the reduction ratio of the light reflectance of the second conductive layer 22 can be more effectively suppressed.

  Therefore, by forming the second conductive layer 22 with a layer thickness of 5 nm or more, more preferably 10 mm or more, the light reflection performance of the first conductive layer 21 in the manufacturing process can be prevented from being deteriorated, and the brightness can be increased. An organic EL display device can be manufactured.

  Next, the first electrode 20 is formed by simultaneously patterning the first conductive layer 21 and the second conductive layer 22 in a stripe shape using a photolithographic technique. Patterning is performed using wet etching. Therefore, patterning can be performed at a lower cost than the conventional patterning of the first conductive layer and the second conductive layer by dry etching. Therefore, the organic EL display device 1 can be manufactured at low cost.

  Moreover, you may use Al etching liquid for wet etching. Since the difference between the dissolution rate of Al and the dissolution rate of IZO in the acid-based Al etching solution is small, the patterning of the first conductive layer mainly composed of Al and the second conductive layer mainly composed of IZO By performing wet etching using an acid-based Al etching solution, Al and IZO can be etched uniformly. The Al etching solution is composed of a mixed solution of phosphoric acid, nitric acid and acetic acid.

  Next, the organic layer 30 is formed by sequentially forming the hole injection layer 31 and the light emitting layer 32 on the substrate 10 on which the first electrode 20 is formed by a known film forming technique such as a spin coating method.

  Next, an Al: Ca layer 41, an Al layer 42, and an IZO layer 43 are striped on the organic layer 30 by a known film forming technique such as a vapor deposition method, a sputtering method, or a resistance heating vapor deposition method. The organic EL display device 1 is manufactured by forming the second electrode 40 by forming a film in a stripe shape so as to be orthogonal to the first electrode 20 formed in the above.

  (Embodiment 2) FIG. 3 is a schematic sectional view of a top emission type organic EL display device 100 manufactured by a manufacturing method according to Embodiment 2 of the present invention.

  The organic EL display device 100 includes a substrate 110 and an organic EL element 101.

  The substrate 110 includes an insulating substrate 111, a source wiring 112, a gate wiring 113, a TFT 114, and a planarization film 115.

  The TFTs 114 are connected to each other by the source wiring 112 and the gate wiring 113.

  The TFT 114 covers the gate metal 116, the gate insulating film 117 provided on the gate metal 116, the island-shaped semiconductor 118 insulated from the gate metal 116 by the gate insulating film 117, and the peripheral portion of the island-shaped semiconductor 118. The TFT electrode 119 is formed in a hollow shape as described above (bottom gate structure).

  The planarization film 115 is formed on the insulating substrate 111 so as to cover the source wiring 112, the gate wiring 113, and the TFT 114.

  The organic EL element 101 includes a first electrode 120, an insulating film 124, an organic layer 130, and a second electrode 140.

  The first electrode 120 includes a first conductive layer 121 and a second conductive layer 122.

  The first conductive layer 121 is connected to the TFT electrode 119 through a through hole 123 provided in the planarizing film 115.

  The first conductive layer 121 is made of a conductive material having light reflection characteristics, such as Ag.

  The second conductive layer 122 is made of a light transmissive material having a large work function.

  Further, even if the first conductive layer 121 and the second conductive layer 122 are patterned with the same etchant, the combination of the corrosion and discoloration does not occur at the interface between the first conductive layer 121 and the second conductive layer 122. Consists of materials.

  The first conductive layer 121 may be a layer mainly composed of Al, and the second conductive layer 122 may be a layer mainly composed of IZO.

  Al is excellent in light reflectivity and has a light reflectance of 90% or more in the visible light range. Therefore, the first electrode 120 in which the first conductive layer 121 is a layer containing Al as a main component has high light reflectance. Therefore, a high-brightness organic EL display device can be manufactured.

  IZO has a large work function of about 5.0 eV. Therefore, the first electrode 120 in which the second conductive layer 122 is a layer containing IZO as a main component has good hole injection efficiency into the organic layer 130.

  By using the first conductive layer 121 as a layer containing Al as a main component and the second conductive layer 122 as a layer containing IZO as a main component, the first conductive layer 121 and the second conductive layer 122 are made of the same etching solution. Even if the patterning is performed by this, corrosion and discoloration do not occur at the interface between the first conductive layer 121 and the second conductive layer 122.

  The organic layer 130 includes a hole injection layer 131 and a light emitting layer 132. However, the present invention is not limited to this configuration. That is, in the present invention, the organic layer 130 may have a single layer structure including only the light emitting layer 132. In addition, the organic layer 130 may be configured by one or more of the hole injection layer 131, the hole transport layer, and the electron transport layer, and the light emitting layer 132.

  The second electrode 140 includes an Al: Ca layer 141, an Al layer 142, and an IZO layer 143.

  Note that the materials and the like of each component of the first electrode 120, the organic layer 130, and the second electrode 140 are the same as those in the first embodiment.

  Hereinafter, the manufacturing method of the organic EL display device 100 according to the second embodiment of the present invention will be described with reference to FIG.

  First, the substrate 110 is formed on the insulating substrate 111 by forming the gate electrode 112, the gate wiring 113, the TFT 114, and the planarization film 115 by a known film formation technique.

  Next, the first conductive layer 121 is formed on the planarizing film 115 and in the through hole 123 provided in the planarizing film 115 so as to be connected to the TFT electrode 119. Next, the second conductive layer 122 is formed on the first conductive layer 121. The method for forming the first conductive layer 121 and the second conductive layer 122 is the same as in the first embodiment.

  Next, the 1st electrode 120 is formed by patterning the 1st conductive layer 121 and the 2nd conductive layer 122 to the matrix form isolate | separated for every pixel simultaneously using the photolithographic technique. The patterning is performed using wet etching. Therefore, patterning can be performed at a lower cost than the conventional patterning of the first conductive layer and the second conductive layer by dry etching. Therefore, the organic EL display device 100 can be manufactured at a low cost.

  The wet etching method for the first conductive layer 121 and the second conductive layer 122 is the same as that in the first embodiment.

  Next, an insulating layer 124 is formed so as to cover the upper portion of the through hole 123 and the edge portion of the first electrode 120.

  Next, the organic layer 130 is formed by depositing the hole injection layer 131 and the light emitting layer 132 on the first electrode 120 by a known deposition technique. The materials used for the hole injection layer 131 and the light emitting layer 132 and the film forming method are the same as those in the first embodiment.

  Next, an Al: Ca layer 141, an Al layer 142, and an IZO layer 143 are formed on the organic layer 130 by a known film forming technique such as a vapor deposition method or a sputtering method, so that a light emitting region of the organic EL device 100 is formed. The organic EL display device 100 is manufactured by forming the second electrode 140 by covering the film.

  Example 1 A method for manufacturing an organic EL display device 1 having the same form as that of the first embodiment is referred to as Example 1.

  Example 2 A method for manufacturing the organic EL display device 100 having the same form as that of the second embodiment is referred to as Example 2.

  Moreover, the manufacturing method of the same structure as Example 1 was made into the comparative example except the point which formed the 2nd conductive layer 22 with ITO.

  In Example 1, even when the first conductive layer 21 and the second conductive layer 22 are simultaneously patterned with the same etching solution, corrosion and discoloration are observed at the interface between the first conductive layer 21 and the second conductive layer 22. Was not.

  Similarly, in Example 2, even if the first conductive layer 121 and the second conductive layer 122 are simultaneously patterned with the same etching solution, the interface between the first conductive layer 121 and the second conductive layer 122 is corroded. No discoloration was observed.

  On the other hand, in the comparative example, when the first conductive layer and the second conductive layer were simultaneously patterned with the same etching solution, corrosion and discoloration were observed at the interface between the first conductive layer and the second conductive layer.

  Further, when a DC voltage was applied to the organic EL display device 1 manufactured by the manufacturing method according to Example 1, green light emission from the organic layer 30 was observed under a fluorescent lamp.

  Similarly, in the organic EL display device 100 manufactured by the manufacturing method according to Example 2, when a control signal was applied, green light emission from the organic layer 130 was observed under a fluorescent lamp.

  On the other hand, when a voltage is applied to the organic EL display device manufactured by the manufacturing method according to the comparative example, the organic EL display manufactured by the manufacturing method according to Example 1 and Example 2 emits light from the organic layer. It was very weak compared with the light emission obtained from the device 1 and the organic EL display device 100, and the light emission was only observed in the dark.

  Thus, according to the present invention, it is possible to provide a method for manufacturing a high-luminance top emission type organic EL display device at low cost.

1 is a schematic cross-sectional view of a top emission type organic EL display device 1 manufactured by a manufacturing method according to Embodiment 1 of the present invention. 5 is a graph showing the relationship between the layer thickness of the second conductive layer 22 and the light reflectance of the first conductive layer 21. It is a schematic sectional drawing of the organic EL display device 100 of the top emission system manufactured with the manufacturing method concerning Embodiment 2 of this invention. 1 is a schematic cross-sectional view of a general bottom emission type organic EL display device 200. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100,200 Organic EL display device 2,101 Organic EL element 10,110,201 Substrate 20,120,202 1st electrode 21,121 1st conductive layer 22,122 2nd conductive layer 30,130,203 Organic layer 31, 131 Hole injection layer 32, 132 Light emitting layer 40, 140, 204 Second electrode 41, 141 Al: Ca layer 42, 142 Al layer 43, 143 IZO layer 111 Insulating substrate 112 Source wiring 113 Gate wiring 114 TFT
115 Planarizing film 116 Gate metal 117 Gate insulating film 118 Island-shaped semiconductor 119 TFT electrode 123 Through hole 124 Insulating film

Claims (2)

A substrate, a first electrode sequentially stacked on the substrate, one or more organic layers including a light-emitting layer, and a second electrode, the first electrode including a light-reflective first conductive layer, a light A method of manufacturing a top emission type organic electroluminescence display device having a laminated structure with a transmissive second conductive layer and taking out light emission of the organic layer from the second electrode side,
The first conductive layer is mainly composed of Al, and the second conductive layer is composed mainly of IZO.
Forming a layer thickness of the second conductive layer to 5 nm or more;
A method of manufacturing an organic electroluminescence display device, wherein the patterning of the first conductive layer and the second conductive layer is simultaneously performed by a wet etching method using an acid-based etching solution . In the manufacturing method of the organic electroluminescent display device according to claim 1,
  A method of manufacturing an organic electroluminescence display device, wherein the first conductive layer has a thickness of 10 nm or more.

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