JP4026141B2 - Organic EL display panel and manufacturing method thereof - Google Patents

Description

  The present invention relates to an organic electroluminescence display panel (hereinafter referred to as an organic EL display panel) and a method for manufacturing the same.

  One of organic EL display panels that use electroluminescence of an organic compound material as a light emitting portion is a passive matrix type (simple matrix type) display. Its exemplary structure is shown in FIG.

  The passive matrix display includes a plurality of first electrodes 30 extending in a line pattern on a transparent support substrate 10 and a plurality of second electrodes 50 having a line pattern extending in a direction orthogonal to the line pattern of the first electrode. The organic EL layer 40 is sandwiched between the first and second electrodes. A pixel is formed with an intersection region of one first electrode 30 and one second electrode 50 as one light-emitting portion, and a plurality of pixels are arranged to form a display portion. Then, the first electrode 30 and the second electrode 50 are respectively connected to the external drive circuit via the connection portion 2 formed to extend from the display portion to the periphery of the substrate, thereby forming an image display device (display). .

  As a modification of the passive matrix display, a plurality of island-shaped transparent electrodes made of a high work function material such as ITO, and a plurality of metal anode bus lines connected to the island-shaped transparent electrodes and extending in the first direction And a second external relay terminal connected to the plurality of anode bus lines on a one-to-one basis and extending in a second direction orthogonal to the first direction, thereby forming a first electrode (anode). It has been reported (see Patent Document 1). In this structure, an organic EL medium and a second electrode (cathode) extending in the second direction are stacked on the first electrode, and external connection portions of the first and second electrodes are formed on the same side of the display. Has been.

  In addition, a sealing member is used to isolate the outside air from the display unit. In general, the second electrode 50 used as the cathode is made of Al, Al alloy, Al-Mg alloy, or the like. Since these are easily affected by oxidation by air or the like, they are formed in the sealing member and joined to the connection terminals 20 with the external drive circuit formed on the support substrate 1. In general, the connection terminal 20 includes a conductive oxide layer 23 that is not easily affected by oxidation or the like.

JP 2002-202732 A

  In order to use an organic EL display in a field requiring high reliability such as a vehicle-mounted panel, a display having a small luminance change is required even under adverse conditions such as high temperature and high humidity. However, as one of the causes of the luminance change, there is a problem that the applied voltage to the organic EL layer 40 is lowered due to an increase in the junction resistance between the second electrode 50 serving as the cathode and the connection terminal 20.

  The increase in the junction resistance occurs due to mutual diffusion of component elements of each electrode material at the interface between the second electrode 50 and the connection terminal 20. For example, when an Al—Li alloy is used as the material of the second electrode 50 and ITO (indium-tin oxide) is used as the material of the connection terminal 20, diffusion of oxygen into the second electrode 50 and the connection terminal 20. Al diffusion is observed. This is presumably because the work function difference between these materials is large, so that the reactivity is high and the reaction is promoted by passing an electric current. And since an insulating oxide is formed in both the 2nd electrode 50 and the connecting terminal 20, it is thought that junction resistance rises. In order to prevent this mutual diffusion, it has been practiced to use ITO or the like on which a metal film 24 such as Cr is laminated as the connection terminal 20.

  However, since the connection terminal having such a structure is accompanied by a process of forming a metal film such as Cr on a transparent conductive oxide such as ITO functioning as the first electrode 30, Defects such as etching residue such as Cr on the transparent conductive oxide functioning as the electrode 30 or erosion of the transparent conductive oxide by the etching solution for Cr occur, and a short circuit between the first electrode and the second electrode, Alternatively, the display quality may deteriorate due to the occurrence of pinholes due to energization. Further, in the connection terminal portion, the first electrode (ITO) and the second electrode may be conducted. Patent Document 1 does not teach or suggest the problem of the junction resistance between the second electrode (cathode) and its external connection terminal, nor the problem associated with the process of forming a metal film such as Cr.

An organic EL display panel according to a first embodiment of the present invention includes: a first electrode provided on a transparent support substrate; and disposed to face the first electrode, and comprising aluminum, an aluminum alloy, an alkali metal, and aluminum. A second electrode formed of a material selected from the group consisting of an alloy, an alloy of an alkaline earth metal and aluminum, and an AgMg alloy ; and an organic EL disposed between the first electrode and the second electrode An organic EL display panel having a connection terminal with a layer; an external drive circuit composed of a metal electrode formed on the support substrate and a transparent conductive film formed on the metal electrode, the second electrode, in a region where the not covered with the transparent conductive film of a metal electrode of the connecting terminals, characterized in that it is connected to the metal electrodes of the connection terminal Here, the metal electrode is preferably formed of a material having a difference from a work function of the material of the second electrode of less than 2 eV, and is selected from the group consisting of Al, Cr, Ni, W, and Mo. More preferably, it is made of a material.

The method for manufacturing an organic EL display panel according to the second embodiment of the present invention includes: a first electrode provided on a transparent support substrate; a second electrode disposed opposite to the first electrode; An organic EL layer disposed between an electrode and the second electrode; a metal electrode formed on the support substrate; and an external drive circuit comprising a transparent conductive film formed on the metal electrode; A method of manufacturing an organic EL display panel having a connection terminal of: a step of forming the metal electrode on the support substrate; a step of forming a first electrode on the support substrate; forming a transparent conductive film, a step of laminating the organic EL layer on the first electrode, the aluminum on the organic EL layer, and an aluminum alloy, an alloy of an alkali metal and aluminum, alkaline earth metals Forming a second electrode using a material selected from the group consisting of an alloy with ruminium and an AgMg alloy, wherein the second electrode is covered with the transparent conductive film of the metal electrode of the connection terminal. And a step of connecting to the metal electrode of the connection terminal in a region not connected . Preferably, the first electrode and the transparent conductive film are formed simultaneously. The metal electrode is preferably formed of a material having a difference from the work function of the material of the second electrode of less than 2 eV, and selected from the group consisting of Al, Cr, Ni, W and Mo. It is more desirable to be formed with.

  According to the present invention, it is possible to suppress an increase in junction resistance due to driving between the second electrode functioning as a cathode and the connection terminal of the external driving circuit, and to suppress a decrease in applied voltage to the organic EL layer. It becomes possible. Therefore, according to the present invention, it is possible to provide an excellent organic EL display panel that does not decrease in luminance over a long period of time.

  Hereinafter, the organic EL display panel of the present invention will be described with reference to FIG. The organic EL display panel of FIG. 1 includes a first electrode 30 provided on a transparent support substrate 10, a second electrode 50 disposed opposite to the first electrode 30, and the first electrode 30 and the second electrode 50. It has an organic EL layer 40 disposed therebetween and a connection terminal 20 to an external drive circuit. The connection terminal 20 includes a metal electrode 21 formed on the support substrate 10 and a transparent conductive film 22 formed on the metal electrode 21.

  As the transparent support substrate 10, an insulating substrate made of glass, plastic, or the like, or a flexible film formed from polyolefin, acrylic resin, polyester resin, polyimide resin, or the like can be used.

  A color filter layer or a color conversion layer may be provided as an optional element between the support substrate 10 and the first electrode 30. The color filter layer is a layer that transmits only light in a specific wavelength region among light emitted from the organic EL layer 40. The color conversion filter is a layer that performs so-called wavelength distribution conversion that absorbs a component in a specific wavelength range of light emission from the organic EL layer and emits light in another wavelength range. For example, a red conversion layer that absorbs blue to blue-green components and emits red light may be provided. A color filter layer may be further provided between the color conversion layer and the support substrate 10 to improve the color purity of the emitted light.

  The organic EL display panel of the present invention is formed as a multicolor display panel by forming a plurality of types of color filter layers or color conversion layers corresponding to the light emitting portions where the first electrode 30 and the second electrode 50 intersect. Also good. The color conversion layer and the color filter layer can be formed of any material known in the art.

  The first electrode 30 of the present invention is used as an anode. The first electrode 30 is formed using a material having a large work function in order to efficiently inject holes. Furthermore, in the organic EL display panel of the present invention, since light is emitted to the outside through the first electrode 30 and the support substrate 10, the anode is required to be transparent. As a material for forming the first electrode 30, a transparent conductive metal oxide such as ITO or IZO is used. If necessary, the surface of the transparent conductive metal oxide may be treated with UV, plasma, or the like to improve the hole injection property for the organic EL layer. The first electrode 30 of the present invention is composed of a plurality of parts, and each part preferably has a line pattern extending in one direction on the support substrate.

The organic EL layer 40 is a layer that emits light in the near ultraviolet to visible region, preferably light in the blue to blue-green region, upon injection of holes and electrons. The organic EL layer 40 includes at least an organic light emitting layer, and has a structure in which a hole injection layer, a hole transport layer, an electron transport layer and / or an electron injection layer are interposed as required. Specifically, the following layer structure is adopted.
(1) Organic light emitting layer (2) Hole injection layer / organic light emitting layer (3) Organic light emitting layer / electron injection layer (4) Hole injection layer / organic light emitting layer / electron injection layer (5) Hole injection layer / Hole transport layer / organic light emitting layer / electron injection layer (6) Hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer (in the above, the first electrode 30 is an organic light emitting layer or a positive electrode) The second electrode 50 is connected to the organic light emitting layer or the electron injection layer.

  Known materials are used as the material for each of the above layers. In order to obtain light emission from blue to blue-green, in the organic light emitting layer, for example, a fluorescent whitening agent such as benzothiazole, benzimidazole, and benzoxazole, a metal chelated oxonium compound, a styrylbenzene compound, Aromatic dimethylidin compounds are preferably used. Alternatively, an organic light emitting layer that emits light in various wavelength regions including white light may be formed by adding a dopant to the host compound. As the host compound, a distyrylarylene compound, N, N′-ditolyl-N, N′-diphenylbiphenylamine (TPD), aluminum tris (8-quinolinolato) (Alq), or the like can be used. As dopants, perylene (blue purple), coumarin 6 (blue), quinacridone compounds (blue green to green), rubrene (yellow), 4-dicyanomethylene-2- (p-dimethylaminostyryl) -6-methyl- 4H-pyran (DCM, red), platinum octaethylporphyrin complex (PtOEP, red), or the like can be used.

  The second electrode 50 in the present invention functions as a cathode. The second electrode 50 is desirably formed of a material capable of efficiently injecting electrons into the organic EL layer 40 and reflecting light emitted from the organic EL layer 40 toward the first electrode 30 side. In order to inject electrons efficiently, a material having a small work function such as an electron injecting metal such as alkali metal, alkaline earth metal, aluminum, or an alloy thereof is desirable. Furthermore, in order to achieve high reflectivity and good film formability, it is preferable to use aluminum, an aluminum alloy (particularly, an alloy with an alkali metal or an alkaline earth metal), an AgMg alloy, or the like.

  Similarly to the first electrode 30, the second electrode 50 also includes a plurality of portions. The second electrode 50 includes a plurality of portions having a line pattern extending in a direction intersecting with the line pattern of the first electrode 30. Preferably, the second electrode 50 includes a plurality of portions having a line pattern extending in a direction orthogonal to the line pattern of the first electrode 30. By configuring in this way, by selecting one partial electrode of the first electrode 30 and one partial electrode of the second electrode 50 and applying a predetermined voltage, the organic at the intersection of the partial electrodes is selected. The EL layer 40 can emit light. Various information can be displayed on the organic EL display panel of the present invention by controlling electrode selection and voltage application by an external drive circuit.

  The connection terminal 20 to the external drive circuit of the present invention is used to connect the second electrode 50 and the external drive circuit, and is provided on the metal electrode 21 provided on the support substrate 10 and on the metal electrode 21. The transparent conductive film 22 is formed.

  The metal electrode 21 is a portion that is in direct contact with the second electrode 50. The work function of the material forming the metal electrode 21 is desirably different from the work function of the material forming the second electrode 50 by less than 2 eV. By reducing the difference in work function with the second electrode 50, it is possible to suppress interdiffusion at the interface and prevent an increase in junction resistance. In general, although it depends on the work function of the material forming the second electrode 50, the material forming the metal electrode 21 preferably has a work function of 5 eV or less in a normal case. In addition, since it is necessary to perform patterning when forming the metal electrode 21, it is desirable that patterning is possible by a method such as photolithography. Preferred materials for the metal electrode 21 include Mo, Al, Cr, Ni, and W. In particular, Mo and Cr are preferable materials because they have a relatively low resistance and are less likely to be corroded by a photo process when forming a laminated structure with a transparent conductive film.

  The transparent conductive film 22 is a portion that is in contact with the wiring from the external drive circuit, and is a layer for preventing oxidation and corrosion of the metal electrode 21 due to contact with the atmosphere at the same time. Preferably, the transparent conductive film 22 is formed so as to cover the metal electrode 21 except for a contact portion between the metal electrode 21 and the second electrode 50. The transparent conductive film 22 is formed using a transparent conductive metal oxide such as IZO or ITO. It is preferable to form the transparent conductive film 22 using IZO. This is because IZO can be etched with a weak acid such as oxalic acid, and the metal electrode 21 formed below can be prevented from being corroded during etching.

  Although optional, a connection terminal having a laminated structure of the metal electrode 21 and the transparent conductive film 22 may be provided in a portion where the first electrode 30 is connected to the external drive circuit. By using the low-resistance metal electrode 21, the wiring resistance related to the first electrode 30 can be reduced. However, in order to maintain the light transmission property and the hole injection property, it is necessary that the metal electrode 21 does not exist in the light emitting portion where the first electrode 30 and the second electrode 50 intersect.

  Next, with reference to FIGS. 3-6, the manufacturing method of the organic electroluminescent display panel of this invention is demonstrated. In each of FIGS. 3 to 6, (a) is a top view and (b) is a cross-sectional view.

  First, as shown in FIG. 3, the metal electrode 21 is formed on the transparent support substrate 10. The metal electrode 21 can be formed by sputtering (including DC, high frequency, and magnetron), vapor deposition (including resistance heating type, induction heating type, and electron beam heating type), ion plating method, and the like. . The metal electrode 21 may be formed on the entire surface and then patterned using a photolithographic method to form a desired shape, or may be formed using a mask capable of obtaining a desired shape.

  Next, as shown in FIG. 4, the first electrode 30 and the transparent conductive film 22 are formed. In the present invention, since the first electrode 30 and the transparent conductive film 22 can be formed from the same material, they can be formed in the same process, which is effective in reducing the number of processes. . Preferably, the transparent conductive metal oxide is stacked using a sputtering method, a vapor deposition method, or the like. In this step, a transparent conductive metal oxide may be laminated on the entire surface and then patterned into a desired shape using a photolithographic method or the like, or may be laminated using a mask that gives the desired shape. Also good. In this step, a lift-off method may be used. More preferably, IZO is used as the transparent conductive metal oxide, the IZO film is formed on the entire surface, a resist pattern giving a desired shape is formed, and etching is then performed using an etching solution such as oxalic acid. It is preferable to form one electrode 30 and a transparent conductive film 22. The transparent conductive film 22 is formed so as to cover the metal electrode 21 except for a portion used to connect the metal electrode 21 and the second electrode 50.

  Next, as shown in FIG. 5, the organic EL layer 40 is laminated. The organic EL layer 40 can be laminated by any method known in the art. In the case of using a low molecular organic substance, it is preferable to use a vapor deposition method, and in the case of using a high molecular organic substance, it is preferable to use a coating method (including spin coating, dip coating, roll coating, etc.).

  Next, as shown in FIG. 6, the second electrode 50 is stacked on the organic EL layer 40. In order to prevent deterioration of the characteristics of the organic EL layer 40 due to the etching solution, it is desirable to form the second electrode 50 by a vapor deposition method or a sputtering method using a mask giving a desired shape. Alternatively, an electrode separation partition having a reverse taper cross-sectional shape may be provided before the organic EL layer 40 is stacked, and then the organic EL layer 40 and the second electrode 50 may be stacked. During the lamination, the second electrode 50 is connected to the metal electrode 22 in a region that is not covered with the transparent conductive film 22.

  Finally, sealing is performed except for the transparent conductive film 22 of the connection terminal 20 and the joint portion of the first electrode 30 to the external drive circuit to obtain an organic EL display panel. Sealing can be performed by any suitable method known in the art using sealing glass and an adhesive (UV curing type, thermosetting type, photothermal combination type).

Example 1
Mo was vapor-deposited on the transparent support substrate 10 made of glass, and patterning was performed using a photolithographic method to form a plurality of metal electrodes 21 on one side of the support substrate 10 (FIGS. 3A and 3B). reference). The work function of Mo measured after patterning was about 4.4 eV (measured with an AC-1 atmospheric measurement type photoelectron spectrometer (manufactured by Riken Keiki)).

  Next, ITO was laminated on the entire surface using a sputtering method, followed by patterning using a photolithographic method to form a first electrode 30 composed of a plurality of portions and a transparent conductive film 22 composed of a plurality of portions ( (Refer FIG. 4 (a) and (b)). The transparent conductive film 22 was formed so as to cover the metal electrode 21, leaving a region for connection with the second electrode.

Next, the organic EL layer 40 was formed by using a vapor deposition method (see FIGS. 5A and 5B). The organic EL layer has a two-layer structure of hole transport layer / organic light emitting layer, α-NPD is stacked as the hole transport layer, and Alq ₃ (aluminum tris (8-quinolinolato)) is stacked as the organic light emitting layer.

  Then, without breaking the vacuum, an Ag · Mg alloy (Ag: Mg = 1: 9 in molar ratio) is laminated by a vapor deposition method using a mask and extends in a direction perpendicular to the line pattern of the first electrode 30. A second electrode 50 composed of a plurality of partial electrodes was formed (see FIGS. 6A and 6B). The second electrode 50 was connected to the metal electrode 21 in a region not covered with the transparent conductive film 22. The Ag · Mg alloy forming the second electrode 50 had a work function of 3.46 eV.

  Finally, in a dry nitrogen atmosphere in the glove box (both oxygen concentration and moisture concentration are 10 ppm or less), an external drive circuit for the first electrode 30 and the transparent conductive film 22 is formed using sealing glass and a UV curable adhesive. The organic EL display panel was obtained by sealing except for the part used for connection.

(Comparative Example 1)
An organic EL display panel was obtained by the same method as in Example 1 except that the metal electrode 21 was completely covered with the transparent conductive film 22.

The wiring resistance before and after the organic EL display panel obtained in Example 1 and Comparative Example 1 was driven at a temperature of 80 ° C. for 100 hours with a duty ratio of 1/60 and an average surface luminance of 450 cd / m ² was measured. The amount of change in wiring resistance was evaluated as the amount of change in junction resistance. The results are shown in Table 1.

  The junction resistance of the organic EL display panel of the present invention according to Example 1 hardly changed even after driving for 100 hours, whereas the panel of Comparative Example 1 significantly increased the junction resistance. This is considered due to mutual diffusion between the second electrode 50 and the transparent conductive film 22. In Example 1 according to the present invention, the second electrode 50 is connected to the metal electrode 21 formed of a material having a work function difference of less than 2 eV, thereby generating the above-described mutual diffusion. Therefore, it is considered that a long-life organic EL display panel having a very small change in junction resistance was obtained.

It is a schematic sectional drawing which shows an example of the organic electroluminescent display panel of this invention. It is a schematic sectional drawing which shows an example of the organic EL display panel of a prior art. It is a figure which shows the manufacturing method of the organic electroluminescent display panel of this invention, (a) is a top view, (b) is sectional drawing. It is a figure which shows the manufacturing method of the organic electroluminescent display panel of this invention, (a) is a top view, (b) is sectional drawing. It is a figure which shows the manufacturing method of the organic electroluminescent display panel of this invention, (a) is a top view, (b) is sectional drawing. It is a figure which shows the manufacturing method of the organic electroluminescent display panel of this invention, (a) is a top view, (b) is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Support substrate 20 Connection terminal 21 Metal electrode 22 Transparent conductive film 23 Transparent conductive film 24 Metal film 30 1st electrode 40 Organic EL layer 50 2nd electrode

Claims (7)

A first electrode provided on a transparent support substrate; disposed opposite to the first electrode; from aluminum, an aluminum alloy, an alloy of an alkali metal and aluminum, an alloy of an alkaline earth metal and aluminum, and an AgMg alloy A second electrode formed of a material selected from the group consisting of : an organic EL layer disposed between the first electrode and the second electrode; a metal electrode formed on the support substrate; An organic EL display panel having a connection terminal with an external drive circuit composed of a transparent conductive film formed on a metal electrode, wherein the second electrode is the transparent conductive film of the metal electrode of the connection terminal An organic EL display panel, wherein the organic EL display panel is connected to the metal electrode of the connection terminal in a region not covered with a metal.   2. The organic EL display panel according to claim 1, wherein the metal electrode is formed of a material whose difference from a work function of the material of the second electrode is less than 2 eV.   2. The organic EL display panel according to claim 1, wherein the metal electrode is formed of a material selected from the group consisting of Al, Cr, Ni, W, and Mo. A first electrode provided on a transparent support substrate; a second electrode disposed opposite to the first electrode; an organic EL layer disposed between the first electrode and the second electrode; A method of manufacturing an organic EL display panel having a connection terminal with an external drive circuit composed of a metal electrode formed on a substrate and a transparent conductive film formed on the metal electrode,
Forming the metal electrode on the support substrate;
Forming a first electrode on the support substrate;
Forming the transparent conductive film on the metal electrode;
Laminating the organic EL layer on the first electrode;
A second electrode is formed on the organic EL layer using a material selected from the group consisting of aluminum, an aluminum alloy, an alloy of an alkali metal and aluminum, an alloy of an alkaline earth metal and aluminum, and an AgMg alloy. A step of connecting the metal electrode of the connection terminal to the metal electrode of the connection terminal in a region not covered by the transparent conductive film of the metal electrode of the connection terminal. Manufacturing method of EL display panel.   The method for manufacturing an organic EL display panel according to claim 4, wherein the first electrode and the transparent conductive film are formed simultaneously.   5. The method of manufacturing an organic EL display panel according to claim 4, wherein the metal electrode is formed of a material whose difference from a work function of the material of the second electrode is less than 2 eV. 5. The method of manufacturing an organic EL display panel according to claim 4, wherein the metal electrode is formed of a material selected from the group consisting of Al, Cr, Ni, W and Mo.

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