JP2007066774A - Organic electroluminescent display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain high luminance efficiency in a top-emission type organic electroluminescent display device of a so-called reverse structure. <P>SOLUTION: The organic electroluminescent display device of a top-emission type taking out emission light of each pixel region from a substrate side and an opposite side. A cathode is formed of a first cathode layer 4a, a second cathode layer 4b and a third cathode layer 6, the first cathode layer 4a being a reflex electrode consisting of a metal membrane, the second cathode layer 4b an electrode consisting of a transparent conductive metal oxide, and the third cathode an electrode consisting of a metal membrane. The third cathode layer 6 is either a discontinuous electrode membrane on a membrane surface direction, or alternatively, a sheet resistance calculated from a membrane thickness of the third cathode layer 6 and an average free path of electrons of an electrode material structuring the third cathode layer 6 is 30Ω/square or more on at least a part of the third cathode layer 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence (organic EL) display device and a method for manufacturing the same, and in particular, relates to a so-called inverted top emission type organic EL display device and a method for manufacturing the same.

  In recent years, an organic EL element has attracted attention as a self-luminous light emitting element, and a display using the organic EL element has been developed. Organic EL elements have features such as fast response speed, low voltage, and low power consumption driving that are suitable for video display, so they can be used as next-generation displays such as next-generation mobile phones and portable terminals (PDAs). Expected.

  The organic EL display includes an organic EL panel having a plurality of pixels for image display. The organic EL element in the organic EL panel has a structure in which an organic EL film is sandwiched between two electrodes on a panel substrate. The organic EL film is mainly composed of an electron transport layer, a light emitting layer, and a hole transport layer, and one of the two electrodes is an anode and the other is a cathode.

  In an organic EL display including such an organic EL panel, positive holes are injected into the organic EL film from the anode by applying a positive voltage to the anode and a negative voltage to the cathode. Then, it reaches the light emitting layer, while the electrons injected from the cathode into the organic EL film reach the light emitting layer through the electron transport layer, and the electron and hole recombine in the light emitting layer to obtain light emission. ing.

  In recent years, in order to realize high brightness and high definition of a display image, the conventional method of extracting light from the panel substrate side is the opposite side, that is, the upper surface of the panel substrate on which the light emitting layer is formed. An organic EL display that employs a top emission method for extracting light from the side has been proposed.

  FIG. 13 is a cross-sectional view of a panel of an organic EL display employing a top emission method formed on an active matrix circuit board. In the structure where light is extracted from the substrate side, there is a problem that the ratio (aperture ratio) where light can actually be extracted is limited by the thin film transistor (TFT) on the substrate. The EL display can solve this problem. Since there is no TFT or the like above the light emitting portion, the aperture ratio can be almost 100%.

FIG. 13 is a cross-sectional view showing one pixel of an active matrix display device having a conventional top emission structure as described above. Referring to FIG. 13, in an active matrix display device having a conventional top emission structure, TFT circuits 2 are formed on a substrate 1 in a matrix. A planarizing film 3 is formed on the substrate 1 and the TFT circuit 2. An anode 8 is formed on the planarizing film 3. A pixel isolation film 5 made of an insulating film having an opening is formed on the planarizing film 3 and the anode 8. The pixel separation film 5 is provided between the pixels between the pixel regions. An organic layer 7 including a light emitting layer is formed in contact with the anode 8 in the opening of the pixel separation film 5. Further, an electron injection layer made of Li, LiF, LiO ₂ or the like and a cathode 4 made of Al, Ag, or the like are formed so as to cover the entire surface of the organic layer 7 and the pixel separation film 5.

  However, in the active matrix type display device having the conventional top emission structure shown in FIG. 13, the structure of the cathode is different from the display device having the bottom emission structure, and the organic EL element structure including the cathode and the anode is optimal for the top emission. It was necessary to make it. Further, since the cathode 4 made of a metal film is formed so as to cover the entire surface of the organic layer 7 including the light emitting layer, it is difficult to increase the light transmittance, and the light emission efficiency is reduced. There was a problem. As a result, in the active matrix display device having the conventional top emission structure shown in FIG. 13, the aperture ratio can be increased, but the above-described element structure must be optimized and the light transmittance is maximum. However, there was a problem of staying at about 70%. Therefore, unlike the conventional top emission structure shown in FIG. 13, the cathode 4 is formed on the substrate 1 side, whereby the cathode 4 having a low transmittance is formed on the substrate 1 side. A display device is conceivable. In this structure, since the same cathode as the bottom emission structure can be used, the element structure of the bottom emission may be turned upside down, and it is not necessary to optimize the element structure for the top emission.

  FIG. 12 is a cross-sectional view showing one pixel of a top emission type active matrix display device having an inverted structure in which the cathode 4 is formed on the substrate side. The reverse top emission type display device shown in FIG. 12 is the same as the conventional top emission structure display device shown in FIG. 13 except that the configuration of the electrode and the organic layer therebetween is reversed upside down. It is the composition. That is, as shown in FIG. 12, the TFT circuit 2, the planarizing film 3, and the cathode 4 are formed on the substrate 1 in this order. A pixel isolation film 5 is formed on the planarization film 3 and the cathode 4. Note that, as described above, the electron injection layer is formed as a part of the cathode 4. An organic layer 7 including a light emitting layer is formed on the cathode 4. An anode (transparent electrode) 8 made of ITO or the like is formed so as to cover the entire surface of the pixel separation film 5 and the organic layer 7.

  In the top emission type display device having the reverse structure shown in FIG. 12, the cathode 4 is formed in a limited manner by patterning only in each pixel region. Such patterning is generally performed by a photolithography method (Patent Document 1, etc.).

  However, when the cathode 4 is patterned by photolithography, there is a problem that the surface of the metal film that is the cathode is oxidized and an oxide film is formed on the surface of the cathode. If an oxide film is formed on the surface of the cathode, electron injection is hindered, the drive voltage of the organic EL element is increased, and the light emission efficiency is lowered.

In addition, a method of providing ribs between pixels instead of patterning the cathode has been proposed (Patent Document 2, etc.). However, when ribs are provided between the pixels, the anode 4 and the anode 8 are also separated, and therefore cannot be used in an active matrix display device.
Japanese Patent Laid-Open No. 11-185971 JP 2001-230073 A

  An object of the present invention is to provide an organic EL display device having high luminous efficiency and a method for manufacturing the same in a so-called inverted top emission organic EL display device.

  The organic EL display device of the present invention is a top emission type organic EL display device that extracts light emitted from each pixel region from the side opposite to the substrate side, and a drive circuit provided on the substrate for supplying a display signal to each pixel; A reflective first cathode layer made of a metal film, connected to the drive circuit and provided separately for each pixel region, and provided on the first cathode layer separately for each pixel region; Provided to separate each pixel region in a second cathode layer made of a transparent conductive metal oxide and a region between pixels between the first cathode layer and the second cathode layer provided for each pixel region. A pixel separation film made of an insulating material, and a third cathode layer made of a metal film and provided on the pixel separation film and the second cathode layer in common to the plurality of pixel regions; and An organic layer including a light emitting layer and an organic layer And the third cathode layer is a discontinuous electrode film in the film surface direction, or the third cathode layer thickness and the third cathode layer are configured. In the electrode material, the sheet resistance calculated from the electron mean free path is 30Ω / □ or more in at least a part of the third cathode layer.

  In the present invention, a second cathode layer made of a transparent conductive metal oxide is provided on a reflective first cathode layer made of a metal film provided separately for each pixel. Therefore, after the first cathode layer is formed and the second cathode layer is formed thereon, the first cathode layer and the second cathode layer are patterned on the first cathode layer by photolithography. Since there are two cathode layers, the surface of the first cathode layer made of a metal film can be patterned by photolithography without being oxidized.

  In the present invention, the third cathode layer is provided in common to the plurality of pixel regions on the pixel separation film and the second cathode layer. Therefore, it is not necessary to pattern the third cathode layer, and after the third cathode layer is formed, an organic layer or the like can be continuously formed thereon. Therefore, after the third cathode layer is formed, the next organic layer or the like can be formed thereon without exposing the third cathode layer to the atmosphere. Since the next layer can be formed without oxidizing the surface of the third cathode layer, there is no obstacle in injecting charges into the organic layer, the driving voltage can be reduced, and the luminous efficiency can be reduced. Can be increased.

  The third cathode layer in the present invention is an electrode film discontinuous in the film surface direction, or the film thickness of the third cathode layer and the mean free path of electrons of the electrode material constituting the third cathode layer. Is an electrode film having a sheet resistance of 30Ω / □ or more in at least a part of the third cathode layer. Accordingly, since electrical conduction in the film surface direction by the third cathode layer does not occur, even if the third cathode layer is provided across a plurality of pixel regions, it is possible to connect to adjacent pixels via the third cathode layer. Electrical conduction does not occur, and it can be prevented that the pixels are lit simultaneously around the lit pixels.

  As a method of forming the third cathode layer as a discontinuous electrode film in the film surface direction, there is a method of forming the film as a discontinuous film having a film thickness of less than 5 nm and separated into islands. Since such an electrode film is a discontinuous film separated into islands, conduction in the film surface direction does not occur.

FIG. 11 is a diagram for explaining the relationship between the mean free path λ of electrons in the third cathode layer 6 and the conductivity of the third cathode layer 6. When the film thickness d is reduced and becomes equal to the average free path λ of free electrons in the film, the free electrons λ are substantially shortened by collision of the free electrons on the film surface. Decreases conductivity. The conductivity σf when the film thickness d is smaller than the mean free path λ of free electrons is expressed by the following equation. In the following formula, σ represents bulk conductivity.
σf = d / λ (3/4 + 1 / 2ln (λ / d) σ

  Accordingly, the sheet resistance of the third cathode layer is calculated from the electron mean free path λ of the electrode material of the third cathode layer, the film thickness d of the third cathode layer, and the bulk conductivity σ of the electrode material of the third cathode layer. Can be calculated.

  In the present invention, an electrode film having a sheet resistance calculated in this manner of at least a part of 30Ω / □ or more may be used as the third cathode layer.

  In the present invention, the thickness of the portion of the third cathode layer on the inclined side surface of the pixel separation film is thinner than the thickness of the other portion of the third cathode layer, and in this portion, the above sheet resistance May be 30 Ω / □ or more.

  FIG. 8 is a cross-sectional view showing a state where the thickness of the third cathode layer is thin on the inclined side surface of the pixel separation film. A pixel isolation film 5 is provided on the planarizing film 3, and the side surface 5 b of the pixel isolation film 5 is an inclined side surface. A third cathode layer 6 is formed on the second cathode layer 4b and the pixel separation film 5, and the film thickness of the third cathode layer 6 is indicated by d. As shown in FIG. 8, the film thickness D of the third cathode layer 6 on the inclined side surface 5b of the pixel separation film 5 is expressed by d × cos θ and is smaller than the film thickness d.

  Therefore, as shown in FIG. 8, the film thickness D is thinner than the film thickness d in the other part on the inclined side surface 5b of the pixel separation film 5, and the sheet resistance is 30 Ω / □ or more in this part. can do.

  Further, in the present invention, the inclination angle formed by the side surface of the pixel separation film with respect to the film surface direction is 90 ° or more, the third cathode layer is divided at the side edge of the pixel separation film, and the discontinuous film It may be. FIG. 9 is a cross-sectional view showing such a state. As shown in FIG. 9, the side surface 5b of the pixel isolation film 5 formed on the planarizing film 3 is formed in a tapered shape, and the inclination angle formed by the side surface 5b with respect to the film surface direction is 90 °. That's it. In such a case, when the third cathode layer 6 is formed on the second cathode layer 4b and the pixel separation film 5, the third cathode layer 6 formed on the upper surface 5a of the pixel separation film 5 and the second cathode The third cathode layer 6 formed on the layer 4b is separated from the side end portion of the pixel separation film 5 and becomes discontinuous. In the state shown in FIG. 9, the organic layer 7 is formed on the divided third cathode layer 6. However, since the organic layer 7 is continuously formed, the organic layer 7 is formed thereon. The anode 8 is also formed as a continuous electrode film.

  FIG. 10 shows a case where the film thickness h of the pixel separation film 5 is thicker than the film thickness d of the organic layer 7 when the inclination angle formed by the side surface of the pixel separation film with respect to the film surface direction is 90 ° or more. ing. In such a case, as shown in FIG. 10, the organic layer 7 is divided at the side end portion of the pixel isolation film 5, so that the anode 8 formed thereon is also the side end portion of the pixel isolation film 5. The continuous anode 8 cannot be formed. For this reason, the structure cannot be applied in the case of active matrix driving by a TFT circuit.

  Therefore, when the inclination angle formed by the side surface of the pixel separation film with respect to the film surface direction is 90 ° or more, the pixel separation film is formed so that the film thickness of the pixel separation film is smaller than the film thickness of the organic layer. It is preferable.

  In the present invention, the second cathode layer made of a transparent conductive metal oxide is provided on the reflective first electrode layer made of a metal film. A third cathode layer is further provided on the second cathode layer. Since the third cathode layer is a thin film, the light emitted from the organic layer is not provided with the reflective first electrode layer. In this case, the light is emitted also to the organic EL element substrate side. In the present invention, by providing the first electrode layer, light emitted from the organic layer can be reflected in one direction and emitted from the sealing substrate side, so that the light emission efficiency can be improved. In the present invention, the microcavity of the organic EL element can be adjusted by adjusting the thickness of the second cathode layer, so that the light emission efficiency can be further improved.

  FIG. 1 is a sectional view showing a region for one pixel of an organic EL display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a plurality of pixel regions of the organic EL display device of the embodiment shown in FIG. As shown in FIG. 1, a TFT circuit 2 is provided on a substrate 1 such as a glass substrate, and a planarizing film 3 is provided on the TFT circuit 2. A first cathode layer 4a is formed on the portion of each pixel region on the planarizing film 3, and a second cathode layer 4b is formed on the first cathode layer 4a. The first cathode layer 4a and the second cathode layer 4b are patterned by a photolithography method or the like, and are provided only on the pixel region. The first cathode layer 4 a is connected to the electrode of the TFT circuit 2 through a through hole formed in the planarizing film 3.

  In a region between the pixels between the first cathode layer 4a and the second cathode layer 4b, a pixel separation film 5 is provided to separate the pixel regions. On the pixel isolation film 5 and the second cathode layer 4b, the third cathode layer 6 is formed on almost the entire surface across the pixel regions.

  An organic layer 7 including a light emitting layer is formed on the third cathode layer 6 so as to straddle a plurality of pixel regions. An anode 8 is formed on the organic layer 7 so as to straddle a plurality of pixel regions. A protective film 9 is formed on the anode 8 so as to straddle a plurality of pixel regions. On the protective film 9, a sealing substrate 11 made of a glass substrate or the like is attached via an adhesive layer 10. When providing a color filter layer, a color filter layer can be provided on the sealing substrate 11.

  In the present invention, the third cathode layer 6 is a discontinuous electrode film in the film surface direction, or the film thickness of the third cathode layer 6 and the electrons of the electrode material constituting the third cathode layer 6 are In the electrode film, the sheet resistance calculated from the mean free path is 30Ω / □ or more in at least a part of the third cathode layer 6.

  In the present invention, the first cathode layer is a reflective electrode made of a metal film, and is made of, for example, aluminum, silver, molybdenum, tungsten, chromium, nickel, copper, gold, or an alloy thereof having high reflectivity. It can be formed from a metal film.

  In the present invention, the second cathode layer is an electrode film made of a transparent conductive metal oxide, and is made of indium tin oxide (ITO), indium zinc oxide (IZO), or the like that is transparent and has a high work function. Can do.

  In the present invention, the third cathode layer can be formed of a metal film, and the electrode material is the same as the electrode material of the first cathode layer, and alkali metals such as lithium, sodium, cesium, calcium, magnesium, etc. And alkaline earth metals thereof, and alloys thereof (for example, MgAg).

  The pixel separation film in the present invention is formed from an insulating material, and can be formed from a polymer material such as PMMA (polymethyl methacrylate).

  The organic layer in this invention is an organic layer containing a light emitting layer, and can form the organic layer conventionally formed in the organic EL element. The organic layer is preferably formed so as to cover a larger area than the pattern of the third cathode layer. As a material of the light emitting layer, for example, in order to obtain light emission from blue to blue green, for example, a fluorescent brightener such as benzothiazole, benzimidazole, benzoxazole, metal chelated oxonium compound, styrylbenzene compound And aromatic dimethylidin compounds.

  The anode in the present invention is an electrode film made of a transparent electrode, and can be formed of ITO, IZO or the like. If necessary, it may be formed from a thin metal film.

  As the protective film 9 shown in FIG. 1, a film that functions as a passivation layer of an organic EL element can be used, has electrical insulation, has barrier properties against moisture and low molecular components, and has transparency in the visible range. Is preferably used (having a transmittance of 50% or more in the wavelength range of 400 to 800 nm). As such a material, inorganic oxides such as SiOx, SiNx, SiNxOy, AlOx, TiOx, TaOx, and ZnOx, inorganic nitrides, and the like can be used. The method for forming the protective film is not particularly limited as long as it does not adversely affect the organic EL element, and can be formed by a sputtering method, a CVD method, a vacuum evaporation method, or the like. Good.

  As the adhesive layer 10, a photocurable resin or a thermosetting resin is used, and the sealing substrate 11 is attached by curing the sealing substrate 11 in a bonded state.

Examples of the structure of the organic EL element portion in the organic EL display device of the present invention include the following structures.
(1) Cathode / organic EL light emitting layer / anode (2) Cathode / organic EL light emitting layer / hole injection layer / anode (3) Cathode / electron injection layer / organic EL light emitting layer / anode (4) Cathode / electron injection layer / Organic EL light emitting layer / hole injection layer / anode (5) cathode / electron injection layer / organic EL light emitting layer / hole transport layer / hole injection layer / anode (6) cathode / electron injection layer / electron transport layer / Organic EL light emitting layer / hole transport layer / hole injection layer / anode

  The method for manufacturing an organic EL display device of the present invention includes a step of forming a second cathode layer on a first cathode layer, and a pixel separation film in a region between pixels between the first cathode layer and the second cathode layer. Patterning, forming a third cathode layer provided in common to the plurality of pixel regions on the pixel isolation film and the second cathode layer, and forming the third cathode layer, The method includes a step of forming an organic layer on the third cathode layer without exposing to the atmosphere and a step of forming a cathode on the organic layer.

  According to the manufacturing method of the present invention, after the third cathode layer is formed, the organic layer is formed on the third cathode layer without exposing the third cathode layer to the atmosphere. Thus, an organic EL display device can be manufactured without making it. Therefore, an organic EL display device with high luminous efficiency can be obtained.

  In the manufacturing method of the present invention, the second cathode layer is formed on the first cathode layer. After the first cathode layer is formed, the first cathode layer is not exposed to the atmosphere. The second cathode layer is preferably formed thereon. In addition, after forming the second cathode layer, the first cathode layer and the second cathode layer are patterned by a photolithography method or the like to form the first cathode layer and the second cathode layer only in the pixel region. It is preferable. After the first cathode layer is formed, the surface of the first cathode layer is not oxidized by forming the second cathode layer on the first cathode layer without exposing the first cathode layer to the atmosphere. Formation of an oxide film on the surface of the layer can be prevented. For this reason, an increase in driving voltage can be suppressed and high luminous efficiency can be obtained.

  According to the present invention, in a top emission type organic EL display device having a so-called reverse structure, an increase in driving voltage can be suppressed and luminous efficiency can be increased.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

(Examples 1 and 2)
An active matrix organic EL display device having the structure shown in FIG. 1 was produced. In this example, the third cathode layer 6 was formed with a film thickness of less than 5 nm.

A manufacturing process of the display device of this example will be described with reference to FIGS. First, a polysilicon TFT circuit 2 including a gate electrode was formed on a substrate 1 in a matrix. A planarizing film 3 made of SiO ₂ was formed on the substrate 1 and the TFT circuit 2. On the planarizing film 3, a first cathode layer 4a made of Al and having a thickness of 100 nm was formed. In the present invention, the thickness of the first cathode layer is preferably in the range of 10 to 1000 nm.

  Next, a second cathode layer 4b having a thickness of 100 nm made of ITO was formed on the first cathode layer 4a. In the present invention, the thickness of the second cathode layer 4b is preferably in the range of 10 to 1000 nm.

  After forming the second cathode layer 4b, patterning was performed using the photolithography method so that the first cathode layer 4a and the second cathode layer 4b were left only on the pixel region. In addition, after forming the 1st cathode layer 4a, the 2nd cathode layer 4b formed the 2nd cathode layer 4b continuously so that the 1st cathode layer 4a might not be exposed to air | atmosphere.

  Next, a pixel separation film 5 (film thickness: 1 μm) made of PMMA (polymethyl methacrylate) was formed on the region between the pixels on the planarizing film 3.

Next, the third cathode layer 6 was formed over the entire surface of the second cathode layer 4b and the pixel separation film 5. In this example, the third cathode layer 6 made of Al was formed at a vacuum degree of 133 × 10 ⁻⁷ Pa or less by using a vacuum deposition method. The film thickness of the third cathode layer 6 was two types of 1 nm and 2.5 nm.

  As described above, by forming the third cathode layer 6 very thinly, the third cathode layer 6 was not a continuous film, but a film separated into islands was formed.

  FIG. 5 is a scanning electron micrograph showing the surface of the third cathode layer (Al film) having a thickness of 1 nm, and FIG. 6 shows the surface of the third cathode layer (Al film) having a thickness of 2.5 nm. It is a scanning electron micrograph. FIG. 7 is a scanning electron micrograph showing the surface of the third cathode layer (Al film) having a thickness of 5 nm. As is apparent from FIGS. 5 to 7, it can be seen that the third cathode layer can be formed as a metal film separated into islands by setting the film thickness to less than 5 nm. Thus, by forming the third cathode layer as a discontinuous film separated into islands, it is possible to prevent conduction between adjacent pixels via the third cathode layer.

Next, in order to avoid oxidation of the third cathode layer 6 after the formation of the third cathode layer 6, a pixel region is used using a metal mask while maintaining a vacuum degree of 133 × 10 ⁻⁷ Pa or less. An electron injection layer and an organic layer 7 were formed thereon. As the electron injection layer, a Li film having a thickness of 1 nm is formed. As the organic layer 7, an electron transport layer (thickness: 30 nm) made of Alq3 (tris- (8-quinolinato) aluminum (III)) and green light emission are formed. A light-emitting layer (thickness 30 nm) made of Alq3 (tris- (8-quinolinolato) aluminum (III)) containing 3% by weight of methylquinacridone as a dopant, and NPB (N, N′-di (naphthasen-1-yl) ) -N, N'-diphenylbenzidine) and a hole injection layer (thickness 10 nm) made of CuPc (copper phthalocyanine).

  Next, an anode (transparent electrode) 8 made of ITO and a protective film 9 made of SiNx were formed so as to cover the entire surface of the organic layer 7. Next, an active matrix type organic EL display device shown in FIG. 1 was manufactured by bonding a sealing substrate 11 made of a glass plate with an adhesive layer 10 made of an epoxy resin.

(Examples 3-12 and Comparative Examples 1-5)
The thickness of the third cathode layer 6 is 5 nm, 10 nm, and 15 nm as shown in Table 2, and the inclination angle θ of the side surface of the pixel separation film is 30 °, 45 °, and 60 ° as shown in Table 2. , 75 °, 90 ° or more (specifically, 120 °), except that the active matrix organic EL display device was fabricated in the same manner as in Example 1 and Example 2 above. In addition, the inclination angle θ of the side surface of the pixel separation film in Examples 1 and 2 is 45 °.

  In this embodiment, since the thickness of the third cathode layer is 5 nm or more, an Al film as the third cathode layer is formed as a continuous film as shown in FIG.

  Table 1 shows the third cathode of the portion on the inclined side surface of the pixel separation film when the inclination angle θ of the side surface of the pixel separation film is 0 °, 15 °, 30 °, 45 °, 60 °, and 75 °. The value of the sheet resistance (Ω / □) of the layer (Al film) is shown, and the value in each case of the film thickness of 10 nm, 25 nm, 50 nm, 100 nm, and 150 nm of the third cathode layer (Al film) is shown. Yes.

  As apparent from Table 1, the sheet resistance of the third cathode layer on the inclined side surface of the pixel separation film can be calculated from the inclination angle θ of the side surface of the pixel separation film and the film thickness of the third cathode layer. For example, when the inclination angle θ of the side surface of the pixel separation film is 45 °, the third cathode layer sheet on the inclined side surface of the pixel separation film is formed by setting the thickness of the third cathode layer made of the Al film to 5 nm or less. It can be seen that the resistance can be increased to 30Ω / □ or more.

(Comparative Examples 6 and 7)
In each of the above embodiments, the second cathode layer made of ITO is provided on the first cathode layer made of Al film, and the third cathode layer made of Al film is formed thereon.

  In Comparative Example 6, an organic EL display device was produced in the same manner as in Example 1 except that an electrode in which an Al film (film thickness 1 nm) was formed on an ITO film (film thickness 100 nm) was used as a cathode.

  In Comparative Example 7, after an Al film (film thickness 100 nm) was formed, patterning was performed while exposed to the atmosphere, and then an Al film (film thickness 1 nm) was formed in the same manner as in Example 1; An organic EL display device was produced in the same manner as in Example 1.

(Examples 13 and 14)
In this embodiment, the lateral resistance of the third cathode layer is increased by increasing the distance between the pixels in the third cathode layer.

  FIG. 3 is a cross-sectional view showing the organic EL device of Example 13. As shown in FIG. 3, in this embodiment, a second pixel isolation film 12 is further formed on the upper surface of the pixel isolation film 5, thereby increasing the distance between the pixels of the third cathode layer 6, The lateral resistance of the cathode layer 6 is increased. In the present embodiment, an organic EL element is fabricated basically under the same conditions as in the third embodiment except that the second pixel separation film 12 is provided. The second pixel separation film 12 is formed in a lattice shape similarly to the pixel separation film 5, and its height (film thickness) is 500 nm. By forming the second pixel separation film 12, the distance between the pixels is increased by 8%.

  FIG. 4 is a cross-sectional view showing the organic EL device of Example 14. In the present embodiment, the distance between the pixels of the third cathode layer 6 is increased by forming the pixel separation film divided into two in the region between the pixels. As in this embodiment, the pixel separation film 5 is divided into two parts, so that the distance between the pixels is 10% longer than in the third embodiment.

[Brightness measurement test]
The light emission luminance of the display devices manufactured in the above examples and comparative examples was measured. As the light emission luminance, the light emission luminance (cd / m ² ) per unit area in each display device was measured. Table 2 shows the measured luminance values.

[Observation of patterning]
When measuring the light emission luminance, the light emission state of adjacent pixels was observed and evaluated according to the following criteria.

◯: The state where the adjacent pixels do not emit light Δ: The state where the adjacent pixels partially emit light X: The state where the adjacent pixels emit light Evaluation results are shown in Table 2.

  Table 2 shows the inclination angle θ of the side surface of the pixel separation film and the sheet resistance value of the third cathode layer on the inclined side surface of the pixel separation film.

  As shown in Table 2, in Comparative Examples 1 to 5, since the sheet resistance of the third cathode layer on the inclined side surface of the pixel separation film is less than 30Ω / □, good results are obtained in patterning. Absent. That is, when a pixel was caused to emit light, light emission was recognized also in an adjacent pixel. Further, in these comparative examples, a high value of light emission luminance was not obtained.

  Further, in Comparative Example 6 in which an Al film is provided on the ITO film and in Comparative Example 7 in which an Al film is formed after exposure to the atmosphere after the Al film is formed, high luminance is not obtained. On the other hand, in Examples 1 to 14 according to the present invention, high emission luminance was obtained, and improvement in emission efficiency was recognized. In Examples 13 and 14, the distance between the pixels of the third cathode layer is longer than that in Example 3. However, the luminance is higher than that in Example 3, and the luminous efficiency is improved. Is recognized.

Sectional drawing which shows the organic electroluminescence display of the Example according to this invention. FIG. 2 is a cross-sectional view showing a plurality of pixel region portions of the organic EL display device shown in FIG. Sectional drawing which shows the organic electroluminescence display of the other Example according to this invention. Sectional drawing which shows the organic electroluminescence display of the further another Example according to this invention. The scanning electron micrograph which shows the surface of Al film | membrane (film thickness of 1 nm) as a 3rd cathode layer. The scanning electron micrograph which shows the surface of Al film | membrane (film thickness of 2.5 nm) as a 3rd cathode layer. The scanning electron micrograph which shows the surface of Al film | membrane (film thickness of 5 nm) as a 3rd cathode layer. Sectional drawing for demonstrating the calculation method of the film thickness of the 3rd cathode layer on the inclination side surface of a pixel separation film. Sectional drawing which shows the state whose film thickness of a pixel separation film is thinner than the film thickness of an organic layer. Sectional drawing which shows the state in which the film thickness of a pixel separation film is thicker than the film thickness of an organic layer. The perspective view for demonstrating the relationship between the film thickness of a thin film, and the mean free path of free electrons. Sectional drawing which shows the top emission type organic electroluminescence display of the conventional reverse structure. Sectional drawing which shows the conventional top emission type organic electroluminescence display.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... TFT circuit 3 ... Flattening film 4a ... 1st cathode layer 4b ... 2nd cathode layer 5 ... Pixel separation film 6 ... 3rd cathode layer 7 ... Organic layer 8 ... Anode 9 ... Protective film 10 ... Adhesive Layer 11 ... Sealing substrate 12 ... Second pixel isolation film

Claims (6)

A top emission type organic electroluminescence display device that extracts light emitted from each pixel region from the side opposite to the substrate side,
A drive circuit provided on the substrate for supplying a display signal to each pixel;
A reflective first cathode layer made of a metal film, connected to the drive circuit and provided separately for each pixel region;
A second cathode layer made of a transparent conductive metal oxide and provided on the first cathode layer separately for each pixel region;
A pixel separation film made of an insulating material provided to separate each pixel region in a region between the first cathode layer and the second cathode layer provided for each pixel region;
A third cathode layer made of a metal film provided in common to a plurality of pixel regions on the pixel isolation film and the second cathode layer;
An organic layer including a light emitting layer provided on the third cathode layer;
An anode comprising a transparent electrode provided on the organic layer;
The third cathode layer is an electrode film discontinuous in the film surface direction, or from the thickness of the third cathode layer and the mean free path of electrons of the electrode material constituting the third cathode layer An organic electroluminescence display device, wherein the calculated sheet resistance is an electrode film having 30Ω / □ or more in at least a part of the third cathode layer.   The film thickness of the third cathode layer portion on the inclined side surface of the pixel separation film is thinner than the film thickness of other portions, and the sheet resistance is 30Ω / □ or more in the portion. The organic electroluminescence display device according to claim 1.   2. The organic electroluminescence display device according to claim 1, wherein the third cathode layer is a discontinuous film having a film thickness of less than 5 nm and formed in an island shape.   The inclination angle formed by the side surface of the pixel separation film with respect to the film surface direction is 90 ° or more, and the third cathode layer is divided and discontinuous at a side end portion of the pixel separation film. The organic electroluminescence display device according to claim 1, wherein   The organic electroluminescence display device according to claim 4, wherein the pixel separation film is formed so that a film thickness of the pixel separation film is smaller than a film thickness of the organic layer. A method for producing the organic electroluminescence display device according to any one of claims 1 to 5,
Forming the second cathode layer on the first cathode layer;
Patterning the pixel isolation layer in a region between the pixels between the first cathode layer and the second cathode layer; and
Forming the third cathode layer provided in common to a plurality of pixel regions on the pixel isolation layer and the second cathode layer;
Forming the organic layer on the third cathode layer without exposing to the air after forming the third cathode layer;
And a step of forming the cathode on the organic layer. A method for manufacturing an organic electroluminescence display device.