WO2008032584A1 - Organic el display - Google Patents

Abstract

Provided is an organic EL display which has excellent adhesiveness with other materials and leak repairability, and can be driven with a low voltage. In the organic EL display, an anode (5), an organic EL layer (6) including an organic light emitting layer and a cathode (9) are arranged on a substrate (1) in this order, and a color conversion layer (2) and a gas barrier layer (4) are arranged between the substrate (1) and the anode (5). The cathode (9) is composed of an electron injection metal layer (7), which reflects light and is brought into contact with the organic EL layer, and a metal coat layer (8) which is not directly in contact with the organic EL layer.

Description

 Specification

 OLED display

 Technical field

 The present invention relates to a configuration of an organic electroluminescence (hereinafter referred to as organic EL) display having high definition and excellent visibility and having a wide range of applicability such as display of a portable terminal or an industrial measuring instrument.

 Background art

 An organic EL element is a self-luminous element that emits light from an organic EL layer by injecting holes and electrons from an anode and a cathode. A display incorporating this element has a wider viewing angle and a faster response speed than liquid crystal displays, which are currently the mainstream of flat panel displays. Because of this advantage, development is progressing as a next-generation flat panel display for mobile phones and mobile PCs.

 FIG. 2 shows a layer cross-sectional structure of a conventional bottom emission type organic EL element. First, on the substrate, color conversion layers containing fluorescent materials that emit each color so as to absorb light in the light emitting region of the organic light emitting element and emit each light of RGB are patterned with high definition to form an RGB light emitting region. To do. A planarizing layer 3 and a gas barrier layer 4 are formed so as to cover the light emitting region, and an anode 5 made of a conductive transparent film, an organic EL layer 6 and a cathode 9 made of a metal electrode 21 such as aluminum are formed thereon. Laminate in this order. Here, when a predetermined voltage is applied between the anode 5 and the cathode 9, RGB light is emitted, so that a full color light emitting display can be constructed.

 [0004] In such a light emitting display, regardless of whether it is a bottom emission type or a top emission type, reduction of the driving voltage is a big problem!

[0005] As an attempt to reduce the drive voltage, for example, in the top emission type, a layer composed of an alkali metal or an alkaline earth metal having a small electron injection barrier and Ag having a smaller electric resistivity than the layer are used. An organic EL device having a cathode composed of a coating layer used is disclosed (for example, refer to claim 11 of Patent Document 1). However, with this organic EL device, it is necessary to form a very thin coating layer for the purpose of extracting light from the cathode side, and there is a limit to reducing the wiring resistance (electrical resistance). [0006] In addition, if a defect such as a leak occurs due to a process defect in a subpixel, not only does light emission stop, but a leakage current wraps around the subpixel on the same anode line, resulting in a bright line.

 [0007] In order to repair the leaked portion, generally, a reverse bias voltage is applied between the anode line and the cathode line to cause a reverse current to flow through the leaked portion and to thermally burn out. ing. In order to burn it out thermally, the electrode in the leaked part is pierced by the power to evaporate by heat and by melting and solidifying.

 Patent Document 1: Japanese Patent Application Laid-Open No. 2004-200141, Claim 1, Claim 11, Paragraph 0019, etc. Disclosure of Invention

 Problems to be solved by the invention

 [0008] Based on what has been described above, the functions required of the cathode in contact with the organic EL layer are as follows: (1) low electrical resistance and low power loss; (2) electrons to the organic EL layer; The injection barrier is small, (3) the destruction of the leak can be easily evaporated or melted and solidified easily, and (4) the process is easy, the adhesion to the substrate etc. is good and the dimensions can be secured. The mechanical strength can be ensured.

 [0009] For example, the force of aluminum used as a cathode material in the past. Electric resistivity is smaller than that of aluminum (function (1)). Silver has a smaller work function than aluminum (function (2)), and vapor pressure is also low. Higher than aluminum! /, Making it easy to create fracture holes! /, (Function (3)).

 However, silver has insufficient adhesion to the glass substrate, and lacks mechanical reliability (function (4)). Thus, even if it is going to improve a part of function requested | required of a cathode, another function will deteriorate. Therefore, it is necessary to improve other functions without degrading some of the functions required for the cathode.

 An object of the present invention is to provide an organic EL display that is excellent in leak repairability, has low electrical resistance, is excellent in reliability, and can be driven at a low voltage.

 Means for solving the problem

[0012] The present invention has been made to solve the above problems. That is, the organic EL display according to the present invention includes an anode, an organic EL layer including an organic light emitting layer, and a cathode in this order on a substrate, and a color conversion layer and a gas barrier layer between the substrate and the anode. OLED An organic EL display including an element, wherein the cathode is reflective and has an electron injecting metal layer in contact with the organic EL layer, and is not in direct contact with the organic EL layer! /, A covering metal layer It is composed of power.

 The invention's effect

 [0013] The organic EL display of the present invention has the cathode structure described above, thereby reducing the electrical resistance loss of the cathode, excellent in leak repairability, good adhesion to other materials, and low voltage driving. It becomes possible.

 Brief Description of Drawings

 FIG. 1 is a schematic cross-sectional view of an element included in one embodiment of the organic EL display of the present invention.

 FIG. 2 is a schematic cross-sectional view of elements included in a conventional organic EL display.

 FIG. 3 is an explanatory diagram of a voltage drop of a scan line in the passive matrix method. BEST MODE FOR CARRYING OUT THE INVENTION

[0015] FIG. 1 shows an aspect (bottom emission type) of a cross-sectional structure of an organic EL element included in the organic EL display of the present invention.

The organic EL display of the present invention comprises an anode 5, an organic EL layer 6 including an organic light emitting layer 6, and a cathode 9 in this order on a substrate 1 described later, and a color between the substrate 1 and the anode 5. An organic EL device having a conversion layer 2 and a gas barrier layer 4 is provided.

First, the cathode material and layer structure of the organic EL display of the present invention will be described.

[0018] In the organic EL display of the present invention, the cathode is reflective. In this specification, “reflectivity” means that the reflectance of visible light (400 nm to 700 nm) of a film formed on a glass substrate is 50% or more. A preferable range of light reflectance is 80% or more.

[0019] Several types of cathode materials are considered as candidates. Table 1 shows the results of a comparison of the functions of each cathode candidate material based on aluminum, which has been conventionally used as a cathode material.

[0020] [Table 1] Material Ca Zn in Al Cu Au Vapor pressure PvBpor (Pa) 0 6. 80E + 00 ○ 4. 90E + 03 0 1-20E-03 ○ 6. ΟΟΕ-05 6. 60E-07 X 6. 60E-08 X 7 O0E-10 Work function Φ ( _β ν) 〇 2. 9 〇 3. 63 o 4. 09 〇 4. 26 4. 28 X 4. 65 X 5. 1 Resistivity p (Qcm) X 3. 91 X 5 91 X 8. 37 ○ 1. 59 2. 65 ○ 1. 67 O 2. 35

 Melting point 0C) X 850 ○ 419 0 156 X 961 660 X 1083 X 1063

 Take outside

 Π Threadability X Cannot protrude 〇 o Δ Adhesion 〇 X Adhesion

 No

 Barometric pressure

According to Table 1, silver, copper, and gold are superior to aluminum in terms of electrical resistance (function (1)).

 [0021] From the viewpoint of work function (function (2)), calcium, zinc, indium and silver are excellent.

[0022] As the repair performance (function (3)) of the leak location, calcium, zinc, indium and silver having a low melting point or high vapor pressure are excellent.

[0023] From the viewpoint of processability and stability (function (4)), aluminum, zinc, indium, copper and the like can be employed. Zinc, indium, and copper are relatively stable in the atmosphere and can be taken out as wiring that comes into contact with the atmosphere.

[0024] From the viewpoint of adhesion to a glass substrate or a gas barrier layer and reliability, zinc, indium, aluminum, or copper is preferable.

[0025] In this specification, the resistivity is a value obtained by measurement by the four-terminal method, and the work function

The melting point and vapor pressure should be the values obtained from data books such as the chemical handbook (edited by the Chemical Society of Japan).

 In view of the various properties of the candidate material, the cathode is composed of two or more metal layers. Specifically, the cathode is a laminate including an electron injecting metal layer in contact with the organic EL layer and a covering metal layer not in contact with the organic EL layer.

[0027] The electron injecting metal layer is formed of one kind of simple metal, simple alkali metal, simple alkaline earth metal, or an alloy thereof adjacent to the organic EL layer.

[0028] The coated metal layer may contain two or more kinds of single metals, or may contain an alloy containing ^two or more kinds of metal elements.

[0029] It is preferable that the metal contained in the electron injecting metal layer has a work function smaller than that of at least one metal contained in the covering metal layer not in direct contact with the organic EL layer. [0030] The vapor pressure at 660 ° C and latm of at least one metal contained in the coated metal layer is preferably higher than that of the metal contained in the electron injecting metal layer! /.

 [0031] The melting point of at least one metal contained in the coated metal layer is preferably lower than that of the metal contained in the electron injecting metal layer!

 [0032] The electrical resistivity of at least one metal contained in the coated metal layer is preferably smaller than that of the metal contained in the electron injecting metal layer. In order to improve the electrical resistance, for example, a method of laminating silver on an aluminum electrode can be adopted.

 [0033] The layer structure of the metal layer including the electron injecting metal layer and the coating metal layer is, in order from the layer adjacent to the organic EL layer, Ca / Al, Mg / Two-layered composition of Al, In / Al, Ag / Al, Zn / Al, Al / Ag, etc., Zn / Al / Ag, Ca / Al / Ag, Mg / Al / Ag, In / Al / Ag A combination of three layers such as In the case of a three-layer structure, the leftmost metal is the metal that constitutes the electron injecting metal layer, and the remaining two layers on the right side are the coated metal layer.

 [0034] The thickness of the electron injecting metal layer is preferably 10 nm or more in order to improve the work function. More preferably, it is 30 nm or more and lOOnm or less.

 [0035] When calcium is used as the electron injecting metal layer, calcium is not suitable for extraction to the outside, so that it is formed only on the organic EL layer with a metal mask during vapor deposition. Similarly, when silver is used as the electron injecting metal layer, it is preferable that the metal barrier is formed only on the organic EL layer so that the gas barrier layer and the wiring of the glass substrate portion are in contact with aluminum. All of these materials have a lower melting point or higher vapor pressure than aluminum, so there is no problem in leak repairability (function (3))! /.

 [0036] The thickness of the covering metal layer is preferably 30 nm or more. Moreover, in order to ensure the leak repair function, it is preferably 1 m or less. More preferably, it is lOOnm or more and 500nm or less.

 [0037] Silver is laminated for the purpose of reducing electrical resistance, so the thickness should be 30nm or more! If it is too thick, there will be a problem with the leak repair function. More preferably, it is lOOnm or more and 500nm or less.

[0038] If the thickness of aluminum is lOnm or more, adhesion to the substrate and gas barrier layer can be secured. 厚 Preferably, the thickness is 30 nm or more. Preferably, it is m or less.

 [0039] As a method for forming the electron injecting metal layer and the covering metal layer, a mask method, a cathode partition wall method, a laser ablation method, or the like can be employed.

 [0040] In the organic EL display of the present invention, the anode is a film made of a light-transmitting conductive material. For example, Indium-Tin oxide (ITO), Indium-Zinc oxide (IZO), or the like is used. Power S can be. When depositing ITO, it is necessary to heat the substrate at 200 ° C or higher, and the color conversion layer and color filter described later are likely to be deteriorated by heating. On the other hand, IZO is preferable because IZO does not require heating during film formation.

 [0041] The anode can be formed, for example, by magnetron sputtering.

 [0042] The preferred thickness of the anode is 50-;! OOOnm.

 [0043] The organic EL display of the present invention does not exclude the case where the organic EL element is driven by an active matrix system, but has a particularly preferable configuration when driven by a passive matrix system.

 [0044] In the no / sive matrix method, anodes and cathodes are arranged in a grid pattern, one is assigned to the data line, the other is assigned to the scan line, and a bias voltage is applied from the transistor at the end of each line. This is a method of emitting sub-pixels.

 [0045] Since the current flowing through each subpixel is integrated in the scan line, the amount of current increases as the distance from the extraction electrode increases. For this reason, the lower the electrical resistivity of the scan line, the smaller the voltage drop. Usually the anode is selected as the data line and the cathode as the scan line. In this configuration, particularly in the passive matrix system, as shown in FIG. 3, the closer to the current force extraction electrode flowing in the sub-pixel, the more is added to the scan line composed of the cathode. Therefore, as shown in the following equation (2), the voltage drop V increases in proportion to the square of the number of subpixels n in the scan line direction, and it is necessary to increase the drive voltage as a result.

[0046] [Equation 1] V, = ilr (1)

 nl ■.. (3)

 («+ L) (4)

 2

(Where n is the number of subpixels, r is the resistance, and I is the current flowing through the element)

 Therefore, it is considered that the organic EL display of the present invention in which the electrical resistance loss of the cathode is reduced can realize effective suppression of the voltage drop and reduction of the driving voltage particularly when it is driven by the passive matrix method.

[0047] The organic EL display of the present invention includes an organic EL layer sandwiched between the anode and the cathode.

 [0048] The organic EL layer can be composed of a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, and an electron injection layer. However, the structure is not particularly limited as long as the structure includes at least an organic light emitting layer that emits light by recombination of holes and electrons generated by applying voltage to the anode and the cathode. Specifically, the organic EL layer has a structure as shown below, for example.

 (1) Anode / organic phosphor layer / cathode

 (2) Anode / hole injection layer / organic phosphor layer / cathode

 (3) Anode / organic phosphor layer / electron injection layer / cathode

 (4) Anode / hole injection layer / hole transport layer / organic phosphor layer / cathode

 (5) Anode / hole injection layer / hole transport layer / organic light emitter layer / electron transport layer / cathode

 (6) Anode / hole injection layer / hole transport layer / organic light emitter layer / electron transport layer / electron injection layer / cathode

The material of each layer in the organic EL layer is not particularly limited, and known materials can be used. The material of the organic light emitting layer can be selected according to the desired color tone. For example, in order to obtain light emission from blue to blue-green, benzothiazonole, benzimidazole, benzoxazole, etc. Optical brighteners, metal chelating oxoyuum compounds, styrylbenzene compounds, aromatic dimethylidin compounds, etc. Can be used.

[0049] Materials for the electron injection layer include: alkali metals such as Li, Na, K, or Cs; alkaline earth metals such as Ba and Sr; rare metals; or their fluorides and aluminum chelates (Alq) The force that can be used is not limited to these. Furthermore, the materials that can use Alq3 and benzazul as materials for the electron transport layer are not limited to these.

 [0050] The hole injecting layer is not limited to force capable of using copper phthalocyanine. As the hole transport layer, 4, 4 ′ bis [N— (1 naphthyl) Νphenylamino] biphenyl, triphenyldiamin (TPD), or the like can be used, but is not limited thereto.

 [0051] The film formation method of the organic EL layer depends on whether the material is a high molecular or low molecular material, and for example, a vacuum vapor deposition method, an ionization vapor deposition method, a cocoon method, an ink jet method, etc. can be employed

Yes

 [0052] A preferred thickness of the organic EL layer is 50 to 300 nm.

 The organic EL display of the present invention is obtained by sequentially forming a color filter, a color conversion layer, a planarization layer, and a gas barrier layer that are used as desired on a substrate.

 [0054] The substrate is not particularly limited as long as it is a transparent material with respect to the wavelength of light emitted from each light emitting unit. For example, a substrate such as SiO glass or a film-like transparent substrate can be employed.

[0055] The color filter used as desired is a filter having a function of improving the color purity of emitted light by selectively absorbing or transmitting the wavelength of emitted light. For example, in a full-color display using three primary colors, the color purity is increased by using a color filter that transmits wavelengths of 400 nm to 550 nm for blue, 500 nm to 600 nm for green, and 600 nm or more for red. As a production method, a method is generally used in which a pattern is formed by repeatedly applying, exposing, and developing a colored photosensitive material in which a dye or pigment is dispersed in a photosensitive resin layer. In recent years, color filters in which pigments are dispersed rather than dyes have become increasingly popular as reasons for resistance. Typical pigments used as dispersing agents include azo lake, insoluble azo, condensed azo, phthalocyanine, quinacridone. , Di-xazine, isoindolinone, anthraquinone, verinone, chi-in, berylene, and mixtures thereof.

 The color conversion layer is a layer having a function of emitting different visible light when the fluorescent dye absorbs light in the near ultraviolet region or visible region emitted from the organic light emitting layer. This can emit fluorescence in various wavelength regions depending on the combination of the fluorescent dye and the incident light. Also, for example, a method of absorbing red light and emitting red region fluorescence is a color filter method that selectively transmits white light emitted by a red filter and emits red region light. It is also possible to output light! These are applied to color conversion organic EL devices. As a production method, a method is generally used in which a colored photosensitive material in which a fluorescent dye is dispersed in a photosensitive resin layer is used as a material, and this is repeatedly applied, exposed and developed to form a pattern. Examples of fluorescent dyes that absorb light in the blue or blue-green region and emit fluorescence in the green region include 3— (2 ′ monobenzothiazolyl) 7 Jetylamino-coumarin (coumarin 6), 3— (2, monobenzimidazolyl) 7 Jetylamino Tamarin (Coumarin 7), 3— (2 'N Methylbenzimidazolyl) 7 Jetylamino Coumarin (Coumarin 30), 2, 3, 5, 6-1H, 4H Tetrahydro-8 9, 9a, 1-gh) Coumarin dyes such as coumarin (coumarin 153), or coumarin dye dyes such as basic yellow 51, and naphthalimide dyes such as solvent yellow 11 and solvent yellow 116 It is done. Furthermore, various dyes (direct dyes, acid dyes, basic dyes, disperse dyes, etc.) can be used if they are fluorescent. For example, rhodamine B, rhodamine 6G, rhodamine 3B, rhodamine dish, rhodamine 110, snore holodamine, basic violet 11, and basic red Rhodamine dyes such as 2; cyanine dyes; 1-ethyl-2- (4- (p dimethylaminophenyl) 1,3 butadiene] pyridine dyes such as pyridinium park mouthrate (pyridine 1), or And oxazine dyes. Furthermore, various dyes (direct dyes, acid dyes, basic dyes, disperse dyes, etc.) can be used if they are fluorescent.

[Planarization layer]

As the name suggests, the flattening layer is disposed as desired for the purpose of smoothing the color conversion layer. Therefore, it is necessary to select a material and a process that are light transmissive and can be disposed without deteriorating the color conversion layer. Further, when an inorganic gas barrier film, a transparent conductive film, or the like is formed on the upper surface of the flattening layer, sputtering resistance is also required.

 [0057] As described above, the planarization layer also has a purpose of smoothing, and thus is generally formed by a coating method. At that time, as an applicable material, photocurable or photothermal combination type curable resin was subjected to light and / or heat treatment to generate radical species and ionic species to be polymerized or crosslinked to be insoluble and infusible. Things are common. Further, it is desirable that the photocurable or photothermal combined type curable resin is soluble in an organic solvent or an alkali solution before curing to pattern the fluorescent color conversion film.

 [0058] Specifically, the photocurable or photothermal combination type curable resin is

 (1) Light or heat treatment is performed on a composition film composed of an acrylic polyfunctional monomer and oligomer having a plurality of acryloyl groups and a methacryl group and light or a thermal polymerization initiator to generate a photo radical and generate heat radicals. What

 (2) A composition comprising a polyburcinnamic acid ester and a sensitizer, which is dimerized by light or heat treatment and crosslinked.

 (3) A composition film composed of chain or cyclic olefin and bisazide is generated by nitrene by light or heat treatment, and crosslinked with olefin.

 (4) A composition film composed of an epoxy group-containing monomer and a photoacid generator is generated by polymerization of an acid (cation) generated by light or heat treatment. In particular, the photocurable or photothermal combination type curable resin (1) is highly fine and can be patterned, and is preferable in terms of reliability such as solvent resistance and heat resistance.

[0059] In addition, polycarbonate (PC), polyethylene terephthalate (PET), polyether sulfone, polybutyral, polyphenylene ether, polyamide, polyetherimide, norbornene resin, methacrylic resin, isobutylene maleic anhydride copolymer resin, cyclic Thermoplastic resins such as polyolefin resin, epoxy resin, phenol resin, urethane resin, acrylic resin, butyl ester resin, imide resin, urethane resin, urea resin, melamine resin, or the color of this application Silicone polymer, polystyrene, polyacrylonitrile, polycarbonate, which is also applied to the matrix of the conversion layer A resin-modified silicone polymer containing tetrafunctional alkoxysilane can be used.

[0060] The thickness of the planarization layer may be 0.5 to 10 m.

 [Gasnoria layer]

 When the substrate on which the color conversion layer is laminated is combined with an organic light emitting device, a gas barrier layer may be stacked on the planarizing layer for the purpose of protecting the organic light emitting device from moisture generated from the color conversion layer. The gas layer is required to be a transparent and dense pinhole film. For example, inorganic oxides such as SiOx, SiNx, SiNxOy, A10x, TiOx, TaOx, and ZnOx, inorganic nitrides, and the like can be used. As the method for forming the gas noble layer, it can be formed by a conventional method such as a sputtering method, a CVD method, a vacuum deposition method, a dip method and the like, which are not particularly limited.

[0061] The thickness of the gas barrier layer may be 50 to 1000 nm.

 Example

 [0062] The present invention was applied to an organic thin film light emitting display panel having 320 pixels x 240 pixels. Each pixel is made up of three RGB sub-pixels, and each sub-pixel is a pixel measuring 110 m by 330 μm.

 [0063] After forming R, G, B color filters and color conversion layer 2 (CCM layer) (not shown) on glass substrate 1 as shown in Fig. 1, transparent photosensitive acrylic resin is applied. Thus, the planarizing layer 3 was obtained. Thereafter, a gas barrier layer 4 made of SiNx was formed to a thickness of 300 nm by the CVD method.

[0064] Next, a shadow mask for separating each subpixel was formed of a resist material. The total thickness of the organic EL layer 6 in the following pressure substrate was placed 10- ⁶ Pa in the deposition apparatus is deposited so as to be LOOnm. Then transferred to a chamber one for a different metal deposition while maintaining the pressure, in vacuum of pressure in the vacuum chamber one is 10- ⁶ Pa or less, the following Comparative Examples Contact and examples;! Electrode shown in 1-3 Depending on the type and thickness, cathode materials were deposited.

 [Comparative example]

 On the organic EL layer 6, only aluminum was formed by vapor deposition to a thickness of lOOnm. At this time, R in the above equation (4) was about 160 Ω, and the voltage drop of the subpixel farthest from the extraction electrode was 4.2V.

[Example 1] A cathode 9 was formed by vapor-depositing silver having a thickness of 300 nm on the aluminum electrode of the comparative example. This reduced R to 27 Ω and the voltage drop to 0.7V.

 total

 [Example 2]

On the organic EL layer 6, zinc was formed as an electron injecting metal layer 7 by vapor deposition so as to have a thickness of 30 nm, and then, as a covering metal layer 8, aluminum was formed by vapor deposition so as to have a thickness of lOO nm. did. The wiring resistance is the same as the comparative example. By improving the work function, the driving voltage to obtain a luminance of 150 cd / m ² can be reduced by 0.4V (equivalent to 0.4eV of energy per electron). It was. The difference in work function between zinc and aluminum, which is smaller than 0.665 eV, is considered to be due to the pinning ef feet force S at the zinc / organic EL layer interface. . Also, the leak repairability was good.

[Example 3]

As the electron-injecting metal layer 7, a metal mask is used to deposit calcium on the organic EL layer 6 to a thickness of 30 nm, and then the coated metal layer 8 is made of aluminum with a thickness of 30 nm and then with silver. The cathode 9 was formed by vapor deposition at 300 nm. The voltage applied between the anode and cathode to obtain a luminance of 150 cd / m ² can be reduced by 1.0 V compared to the comparative example by improving the work function, and the voltage at the subpixel farthest from the extraction electrode Since the voltage drop was reduced to 0.7V, the drive voltage was improved by 4.5V as a result. In other words, the drive voltage of the subpixel farthest from the extraction electrode was 17.8V in the comparative example, but was improved to 13.3V, and power consumption was reduced by 25%. The leak repairability was also good.

Claims

The scope of the claims  [1] An organic EL device including an anode, an organic EL layer including an organic light emitting layer, and a cathode on a substrate in that order, and an organic EL element including a color conversion layer and a gas barrier layer between the substrate and the cathode. EL display,  The cathode is composed of an electron injecting metal layer that is reflective and is in contact with the organic EL layer, and a covering metal layer that is not in direct contact with the organic EL layer  Organic EL display.  [2] The organic EL element is driven by a passive matrix method.  1. The organic EL display according to 1. [3] Of the metal layers, the metal contained in the electron injecting metal layer in contact with the organic EL layer is not in direct contact with the organic EL layer! / Compared with at least one metal contained in the coated metal layer. 2. The organic EL display according to claim 1, wherein the work function is small. [4] The vapor pressure at 660 ° C. and latm of at least one metal contained in the covering metal layer is higher than that of the metal contained in the electron injecting metal layer. 1. The organic EL display according to 1. 5. The organic EL display according to claim 1, wherein the melting point of at least one metal contained in the coated metal layer is lower than that of the metal contained in the electron injecting metal layer.  6. The organic EL display according to claim 1, wherein the electrical resistivity of at least one metal contained in the covering metal layer is smaller than that of the metal contained in the electron injecting metal layer. .  7. The organic EL display according to claim 1, wherein the thickness of the covering metal layer is 30 nm or more and 1 μm or less.