JP2010010111A - Organic el display device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an electron hole injection characteristics of laminated organic EL display device. <P>SOLUTION: The organic EL display device has: a base board 10; a first electrode 40 with one principal face to be an anode and the other principal face to be a cathode; a second electrode 20 which is the cathode; a first organic layer 30 pinched by the principal face to be a cathode of the first electrode and the second electrode; a third electrode 60 which is the cathode; and a second organic layer 50 pinched by the principal face to be the anode of the first electrode and the third electrode. A work function of the principal face to be the anode of the first electrode is arranged to be higher than that of the principal face to be the cathode of the first electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL display device and a manufacturing method thereof. In particular, the present invention relates to an organic EL display device in which an organic layer sandwiched between a pair of electrodes is stacked, and relates to a work function of an electrode sandwiching the organic layer.

  In an organic EL display device having an organic layer sandwiched between a pair of electrodes, it is known that different colors can be formed by stacking a plurality of organic layers.

  In the multicolor light emitting element disclosed in Patent Document 1, a structure in which a metal layer having a low work function is disposed on an electron transport layer has been proposed. Note that the work function is the minimum amount of energy required to extract electrons in a solid out of the solid.

  This will be specifically described.

  FIG. 12C of Patent Document 1 (Japanese Patent Laid-Open No. 2001-273939) is cited in FIG. In the figure, a second electrode 152, a first organic layer 156 including blue light emission, a first electrode 160, a second organic layer 164 including green light emission, and a third electrode 170 are sequentially stacked on a substrate 150. .

Here, the first electrode 160 has a two-layer structure of 160M and 160I. In order to increase the electron injection property and decrease the driving voltage, a metal layer 160M (Ag / Mg) having a work function of less than 4.0 [eV] on the electron transport layer 158 and ITO (160I) thereon The structure which laminates | stacks is proposed.
JP 2001-2731979 A

  Here, in Patent Document 1, when green light is emitted, the first electrode injects holes into the second organic layer, but nothing is disclosed about the work function of ITO described above. Therefore, there is no disclosure or suggestion regarding effective injection of holes into the first electrode.

  Therefore, in the first electrode, it is difficult to inject holes into the organic layer, and the drive voltage may be increased.

  Therefore, an object of the present invention is to improve not only the electron injection property of the electrode sandwiched between the organic layer and the organic layer, but also the hole injection property in the stacked organic EL display device. Accordingly, it is an object of the present invention to provide an organic EL display device that can be driven at a low voltage and obtain good display characteristics, and a manufacturing method thereof.

  In order to solve the above problems, the following is provided.

A substrate, a first electrode having one main surface as a cathode and the other main surface as an anode;
A second electrode that is an anode, a main surface that is a cathode of the first electrode and a first organic layer sandwiched between the second electrodes, a third electrode that is a cathode,
In an organic EL display device having a main surface serving as an anode of the first electrode and a second organic layer sandwiched between the third electrodes,
An organic EL display device, wherein a work function of a main surface serving as an anode of the first electrode is higher than a work function of a main surface serving as a cathode of the first electrode.

  According to the present invention, not only the electron injection property from the electrode but also the hole injection property is improved. As a result, the drive voltage can be reduced, so that the power supply voltage can be reduced and the power consumption can be reduced.

  Hereinafter, embodiments of a display device according to the present invention will be described with reference to the drawings.

  In addition, the well-known or well-known technique of the said technical field is applied regarding the part which is not illustrated or described in particular in this specification.

  The embodiment described below is one embodiment of the invention and is not limited thereto. Moreover, combining embodiments described below is also included in the present invention.

Example 1
FIG. 1 is a diagram schematically showing a cross section of an organic EL display device according to the present invention. The manufacturing method of the display device of this embodiment will be described with reference to this drawing.

  In FIG. 1, the organic EL display device of the present embodiment is a top emission type organic EL display device.

  10 is a substrate, 20 is a second electrode (anode), 30 is a first organic layer, 40 is a first electrode, 50 is a second organic layer, 60 is a third electrode (cathode), 90 is a protective layer, and 100 is a power source Means are shown.

  The second electrode 20 is a reflective electrode. The reflective electrode is not limited to the electrode itself made of a reflective material, but also includes a reflective thin film laminated on the lower part of the electrode made of a transparent conductive material such as ITO or IZO. Further, since the emitted light is extracted from the third electrode 60 side, the third electrode functions as a light extraction electrode, and constitutes a top emission type organic EL display device. The same applies to the following embodiments.

  In addition, the organic layer 30 and the organic layer 50 of this embodiment have a three-layer structure, and are stacked on the substrate 10 in the order of a hole transport layer / a light emitting layer / an electron transport layer. The figure schematically shows one pixel.

  In addition, as an organic EL display device, a plurality of pixels including the second electrode 20 to the third electrode 60 may be arranged in parallel.

<Regarding Substrate 10 and Second Electrode 20>
The substrate 10 and the second electrode 20 functioning as an anode will be described.

  A second electrode 20 (anode) is formed on a substrate on which switching elements such as TFTs are formed as necessary. The second electrode 20 is preferably a light-reflective member, and is preferably made of a material such as Cr, Al, Ag, Au, or Pt. This is because the higher the reflectance, the higher the light extraction efficiency.

  In addition, the second electrode is composed of two different materials, that is, a structure in which the first organic layer 30 side of the second electrode 20 is a highly transmissive material and the substrate 10 side of the second electrode 20 is a highly reflective material. It is also good.

<About the first organic layer 30>
Next, the first organic layer 30 will be described.

  The first organic layer 30 is deposited on the substrate 10 and the second electrode 20 as described above by a known means (for example, vapor deposition or ink jet). Here, the 1st organic layer is laminated | stacked on the board | substrate 10 in order of the hole transport material, the organic luminescent material, and the electron transport material. Furthermore, the first organic layer is preferably an amorphous film from the viewpoint of luminous efficiency.

  The following materials are used as the organic light emitting materials for each color (R / G / B). Triarylamine derivatives, stilbene derivatives, polyarylenes, aromatic condensed polycyclic compounds, aromatic heterocyclic compounds, aromatic heterocondensed ring compounds, metal complex compounds, and the like, and single oligo compounds or composite oligo compounds thereof. However, the configuration of the present invention is not limited to the exemplified materials.

  As the hole transport material, phthalocyanine compounds, triarylamine compounds, conductive polymers, perylene compounds, Eu complexes, and the like can be used, but the structure of the present invention is not limited.

  Examples of the electron transport material include Alq3 in which a trimer of 8-hydroxyquinoline is coordinated to aluminum, an azomethine zinc complex, a distyrylbiphenyl derivative system, and the like.

  The film thickness of the first organic layer is preferably about 0.05 μm to 0.3 μm, and preferably about 0.05 to 0.15 μm.

<About the first electrode 40>
Next, the first electrode 40 that is a feature of the present invention will be described.

  Here, the first electrode 40 is formed by forming and patterning a transparent conductive film. At this time, the work function of the main surface serving as the anode on the protective layer 90 side of the first electrode 40 is formed to be higher than the work function of the main surface serving as the cathode on the substrate 10 side of the first electrode 40. ing.

  This is realized, for example, by the following method. During the formation of IZO as a transparent conductive film, the oxygen flow rate is increased stepwise. Thereby, a higher work function can be obtained with an electrode made of IZO having a higher oxygen flow rate than an electrode made of IZO having a lower oxygen flow rate.

  Thus, by arranging the anode having a high work function with respect to the hole transport layer of the first organic layer 30, the hole injection property can be improved, so that the driving voltage can be reduced. As a result, the power supply voltage can be reduced and the power consumption can be reduced.

  Further, the cathode side of the first electrode 40 has a low work function, and therefore has a high electron injection property.

  Here, it has been described that the first electrode described above is required to improve the characteristics of injecting holes into the second organic layer. Generally, the hole injecting property of a transparent conductive film such as ITO or IZO is used. As a method for improving the temperature, there are ultraviolet irradiation, oxygen plasma, and the like. However, in the stacked organic EL display device, the organic layer is disposed on the substrate side of the first electrode. Therefore, the above-described method for improving the hole injection property has a problem that the first organic layer is scraped and desired characteristics cannot be obtained.

  On the other hand, in this example, the hole injection property is improved when the first electrode is formed. Therefore, it is not necessary to perform a surface treatment or the like for improving the hole injecting property after film formation, and the manufacturing process can be shortened. In addition, since there is no surface treatment, damage to the first organic layer can be reduced.

  Moreover, as a material of the 1st electrode 40, in order to ensure light transmittance, the material with a high transmittance | permeability is preferable. For example, it is preferably made of a transparent conductive film such as ITO, IZO or ZnO, or an organic conductive film such as polyacetylene. Furthermore, a semi-transmissive film in which a metal such as Ag or Al is formed in a thickness of about 10 nm to 30 nm may be used.

  The transparent conductive film such as ITO, IZO, and ZnO described above has both a low resistance property for use as an electrode and a high transmittance property for improving light extraction efficiency in order to reduce power consumption. A satisfactory composition is preferred.

  Here, general conditions for depositing IZO, which is a transparent conductive film satisfying both of the above characteristics, by sputtering are shown.

  Conditions vary depending on the capacity, target, pressure, output, etc. of the film forming apparatus, but in the sputtering apparatus currently used, the oxygen flow rate is 0.09-0.2 sccm with respect to the argon flow rate 80-100 sccm. Films are formed at a ratio. By doing so, a composition having a low resistance value and a high transmittance is obtained.

  The first electrode 40 was formed using a ULVAC sputtering apparatus. The film formation was performed using an IZO target under the conditions of a film forming pressure of 1.8 Pa, an argon flow rate of 100 sccm, a cathode output of 850 W, and a cathode voltage of 250 V and an oxygen flow rate of 0.09 sccm. Subsequently, the film thickness was changed to the oxygen flow rate of 5 sccm at the same film thickness as that at the oxygen flow rate of 0.09 sccm.

  The work function was measured using FAC1 manufactured by Riken Keiki. The work function of IZO under an oxygen flow rate of 0.09 sccm was 4.4 eV, and the work function of IZO under an oxygen flow rate of 5 sccm was 5.7 eV.

  As a result, the work function of the main surface serving as the anode of the first electrode 40 is higher than the work function of the main surface serving as the cathode of the first electrode 40.

The work function of the main surface that serves as the anode of the first electrode 40 is preferably 5.5 [eV] or more. This is because hole injection properties can be improved.
Further, the work function of the main surface serving as the anode of the first electrode 40 is more preferably 5.5 [eV] or more and 5.8 [eV] or less. This is because if the work function is high, the hole injecting property is enhanced. On the other hand, if the work function is too high, the resistance as an electrode increases and the drive voltage may increase. (The same applies to the following embodiments.)
Note that the work function of the surface of the electrode and the work function inside the electrode are the same when manufactured under the same material and under the same conditions. Therefore, the work function in this example can be obtained by measuring the surface of the electrode. ing. For example, when forming the IZO film, if the film forming conditions are constant, the same work function can be obtained at each of the start, middle, and end points of the film formation. That is, the work function on one main surface and the inside is the same.

  Next, a method for patterning the first electrode 40 will be described.

  As the patterning, the electrode material may be heated and formed by vapor deposition using a metal mask, or unnecessary electrode portions may be removed by laser processing after the electrode material is formed into a film.

<About the second organic layer 50>
Next, the second organic layer 50 is deposited by the same method as the first organic layer 30. The second organic layer 50 uses an organic light emitting material that exhibits a color development different from that of the first organic layer 30. As a result, two colors can be generated with one pixel.

<About the third electrode 60>
Next, the third electrode 60 functioning as a cathode is formed by sputtering or the like. As the material of the third electrode 60, a material having a high transmittance is preferable like the first electrode 40. Further, silicon nitride oxide was formed as the protective film 90 to obtain an organic EL display device.

<About power supply means 100 and driving method>
The second electrode 20, the first electrode 40, and the third electrode 60 of the organic EL display device thus formed are connected to the power supply means 100.

  Here, when the first organic layer 30 emits light, a voltage is applied to the second electrode 20 and the first electrode 40 by the power supply means 100.

  Here, when the first organic layer 30 is caused to emit light, holes are injected from the main surface serving as the anode of the second electrode 20. At this time, the work function of the main surface serving as the anode of the second electrode 20 is higher than the work function of the main surface of the third electrode 40 serving as the cathode, and the hole injecting property is enhanced, so that a low driving voltage is possible. .

  At the same time, electrons are injected from the main surface serving as the cathode of the first electrode 40. Since the work function of the main surface serving as the cathode of the first electrode 40 is lower than the work function of the main surface of the second electrode 20 serving as the anode and the electron injecting property is high, low voltage driving is possible.

  Next, when the second organic layer 50 is caused to emit light, a voltage is applied to the first electrode 40 and the third electrode 60 by the power supply means 100.

  Here, as in the case of the first organic layer 30, when the second organic layer 50 emits light, holes are injected from the main surface serving as the anode of the first electrode 40. At this time, the work function of the main surface serving as the anode of the first electrode 40 is high, and the hole injection property is high, so that a low driving voltage is possible.

  At the same time, electrons are injected from the main surface serving as the cathode of the third electrode 60. The work function of the main surface serving as the anode of the first electrode 40 is higher than the work function of the main surface serving as the cathode of the first electrode 40, and the hole injection property is high, so that low voltage driving is possible and the power supply voltage is lowered. , Low power consumption can be achieved.

  In the present embodiment, the configuration in which the second electrode 20 is in contact with the substrate 10 is shown, but a top emission type organic EL display device in which the third electrode 60 is in contact with the substrate 10 may be used. In that case, the third electrode 60 is a reflective electrode, and light is extracted from the second electrode 20 side.

(Example 2)
FIG. 2 is a diagram schematically showing a cross section of the organic EL display device according to the present invention.

  The organic EL display device in the figure is a top emission type organic EL display device.

  The differences of the present embodiment from the first embodiment are as follows.

  The third organic layer 80 is formed on the third electrode 60 on the point that one main surface (substrate 10 side) of the third electrode 60 becomes a cathode and the other main surface (protective layer 90 side) becomes an anode. The point is that the fourth electrode 70 is formed on the third organic layer 80, and the point where the fourth electrode 70 is connected to the power supply means 100.

  Here, the third organic layer 80 uses an organic light emitting material that develops a color different from those of the first organic layer 30 and the second organic layer 50.

  The third electrode 60 is formed in the same manner as the first electrode 40.

  The fourth electrode 70 is formed by sputtering or the like. As the material of the fourth electrode 70, a material having a high transmittance is preferable like the first electrode 40.

  In this embodiment, the second electrode 20 is a reflective electrode, and is a top emission type organic EL display device that extracts light from the fourth electrode 70 side.

  Here, when the first organic layer 30 emits light, holes are injected from the main surface serving as the anode of the second electrode 20, and electrons are injected from the main surface (substrate 10 side) serving as the cathode of the first electrode 40. The Since the work function of the main surface serving as the cathode of the first electrode 40 is lower than the work function of the main surface serving as the anode of the second electrode 20, the hole injecting property and the electron injecting property are enhanced. It becomes possible.

  When the second organic layer 50 sandwiched between the first electrode 40 and the third electrode 60 is caused to emit light, holes are injected from the main surface (protective layer 90 side) serving as the anode of the first electrode 40, and the third Electrons are injected from the main surface (substrate 10 side) serving as the cathode of the electrode 60. The work function of the main surface (protective layer 90 side) serving as the anode of the first electrode 40 is higher than the work function of the main surface serving as the cathode (substrate 10 side) of the first electrode 40, and the hole injection property is high. . In addition, since the work function of the main surface (protective layer 90 side) serving as the anode of the first electrode 40 is higher than the work function of the main surface (substrate 10 side) serving as the cathode of the third electrode 60, hole injection is performed. Therefore, low voltage driving is possible.

  Furthermore, when the third organic layer 80 emits light, holes are injected from the main surface (protective layer 90 side) serving as the anode of the third electrode 60, and the main surface (substrate 10 side) serving as the cathode of the fourth electrode 70. From which electrons are injected. The work function of the main surface that serves as the anode of the third electrode 60 is higher than the work function of the main surface that serves as the cathode of the third electrode 60, and the hole injection property is high. Lower power consumption.

  In addition, according to this embodiment, it is possible to develop three colors with one pixel, and display with higher definition than an organic EL display device that emits two colors with one pixel.

  In the present embodiment, the configuration in which the second electrode 20 is in contact with the substrate 10 is shown, but a top emission type organic EL display device in which the fourth electrode 70 is in contact with the substrate 10 may be used. In this case, the fourth electrode 70 becomes a reflective electrode, and light is extracted from the second electrode 20 side.

(Example 3)
FIG. 3 is a diagram schematically showing a cross section of the organic EL display device according to the present invention.

  The organic EL display device in the figure is a top emission type organic EL display device.

  The difference of the present embodiment from the first embodiment is that Pt is used for the second electrode 21 and Ag is used for the third electrode 61.

  The work function of Pt is 5.6 eV, and the work function of Ag is 4.3 eV. Thus, the work function of the main surface serving as the anode of the second electrode 21 is more than the work function of the main surface serving as the cathode of the third electrode 61. Get higher.

  Here, when the first organic layer 30 emits light, holes are injected from the main surface serving as the anode of the second electrode 21, and electrons are injected from the main surface serving as the cathode of the first electrode 40 (substrate 10 side). The The work function of the main surface (protective layer 90 side) serving as the anode of the second electrode 21 is high, the hole injection property to the first organic layer 30 is improved, and low voltage driving is possible.

  Next, when the second organic layer 50 emits light, holes are injected from the main surface (protective layer 90 side) serving as the anode of the first electrode 40, and the main electrode serving as the cathode (substrate 10 side) of the third electrode 61. Electrons are injected from the surface. The work function of the main surface serving as the cathode of the third electrode 61 is low, the electron injection property to the second organic layer 50 is improved, low voltage driving is possible, the power supply voltage is lowered, and the power consumption can be reduced.

Example 4
FIG. 4 is a diagram schematically showing a cross section of the organic EL display device according to the present invention.

  The organic EL display device in the figure is a top emission type organic EL display device.

  The difference of the present embodiment from the first embodiment is that the first electrode 40 has two layers. Here, the two layers constituting the first electrode 40 are referred to as first electrodes 41 and 42.

  Specifically, a method for forming the first electrodes 41 and 42 using a sputtering apparatus made of ULVAC will be described.

  First, the sputtering was performed using an Ag target. The first electrode 41 on the second electrode 20 side was formed by forming a film for 23 seconds under the conditions of a film forming pressure of 0.25 Pa, an argon flow rate of 20 sccm, and a cathode output of 70 W.

  Next, sputtering was performed using an IZO target. The first electrode 42 on the third electrode 60 side was formed at a film forming pressure of 1.8 Pa, an argon flow rate of 100 sccm, a cathode output of 850 W, a cathode voltage of 250 V, and an oxygen flow rate of 5 sccm for 39 seconds.

  Here, the work function of Ag was 4.3 eV, and the work function of IZO under an oxygen flow rate of 5 sccm was 5.7 eV. As a result, the work function serving as the cathode of the first electrode 41 is lower than the work function serving as the anode of the first electrode 42.

  With the above configuration, when the first organic layer 30 emits light, holes are injected from the main surface serving as the anode of the second electrode 20, and electrons are injected from the main surface serving as the cathode of the first electrode 41. Since the work function of the main surface serving as the cathode of the first electrode 41 is low and the electron injecting property is high, low voltage driving is possible.

  Further, when the second organic layer 50 is caused to emit light, holes are injected from the main surface serving as the anode of the first electrode 42, and electrons are injected from the main surface serving as the cathode of the third electrode 60. The work function of the main surface serving as the anode of the first electrode 42 is higher than the work function of the main surface serving as the cathode of the first electrode 41 and the hole injection property is high, so that low voltage driving is possible and the power supply voltage is lowered. , Can reduce power consumption.

  The work function of the main surface that serves as the anode of the first electrode 42 is preferably higher than the work function of the main surface that serves as the cathode of the third electrode 60. As a result, the hole injecting property becomes high, so that low voltage driving is possible, the power supply voltage can be lowered, and the power consumption can be reduced.

(Example 5)
FIG. 5 is a diagram schematically showing a cross section of the organic EL display device according to the present invention. The organic EL display device in the figure is a top emission type organic EL display device.

  The difference between the first embodiment and the first embodiment is that the first electrode 40 has a work function lower than that of the main surface having a high work function and lower than that of the main surface having a low work function in the vicinity of the center in the stacking direction. This is the point that a high intermediate layer is newly provided. That is, the first electrode 40 is composed of three layers, and the first electrodes 41, 43, and 42 are respectively formed from the substrate 10 side.

  Specifically, a method of forming the first electrodes 41, 43, and 42 using a ULVAC sputtering apparatus will be described.

  First, the sputtering is performed using an Ag target. The film was formed for 23 seconds under the conditions of a film forming pressure of 0.25 Pa, an argon flow rate of 20 sccm, and a cathode output of 70 W, thereby forming the first electrode 41.

  Next, sputtering is performed using an IZO target. The film was formed for 56 seconds under the conditions of a film forming pressure of 1.8 Pa, an argon flow rate of 100 sccm, a cathode output of 850 W, a cathode voltage of 250 V, and an oxygen flow rate of 0.09 sccm.

  Next, the sputtering is performed using an IZO target. The first electrode 42 was formed by depositing the film at a pressure of 1.8 Pa, an argon flow rate of 100 sccm, a cathode output of 850 W, a cathode voltage of 250 V, and an oxygen flow rate of 5 sccm for 39 seconds.

  The work functions of the first electrodes 41, 43, and 42 are 4.3 eV, 4.4 eV, and 5.7 eV in this order from the substrate 10 side, and three layers having a work function of low, medium, and high are arranged.

  The resistance of the first electrode 42 having a high work function is higher than that of the first electrode 43 having a low work function. Here, it is considered that the reason why the resistance is increased is that the oxygen content in the film is high and the oxide film is approached.

  Therefore, first, the first electrode 41 having a low work function is formed, thereby improving the electron injection property into the first organic layer 30.

  Next, a first electrode 43 having a medium work function is formed to improve the function of the electrode as a low-resistance conductive film.

  Finally, the first electrode 42 having a high work function is formed, and the hole injection property to the second organic layer 50 is improved.

  Accordingly, the resistance of the electrode is lowered and the injection property of electrons and holes is improved, so that low voltage driving is possible, the power supply voltage is lowered, and the power consumption can be reduced.

  Further, by using Ag as a semi-transmissive film, color purity is improved by the cavity effect, and display with a wide color reproduction range is possible.

(Example 6)
FIG. 6 is a diagram schematically showing a cross section of the organic EL display device according to the present invention.

  The organic EL display device in the figure is a top emission type organic EL display device.

  The difference of the present embodiment from the first embodiment is that the first electrode 44 is continuously changed from a low work function to a high work function.

  The first electrode 44 is formed by a sputtering apparatus using an IZO target. The film formation is started from a pressure of 1.8 Pa, an argon flow rate of 100 sccm, a cathode output of 850 W, a cathode voltage of 250 V, and an oxygen flow rate of 0.09 sccm. The first electrode 44 was used.

  Since the oxygen flow rate is continuously increased, the first electrode 44 is continuously changed from a low work function to a high work function.

  In this embodiment, since the composition inside the electrode changes continuously, there are few barriers to the movement of holes and electrons, and it can be driven at a low voltage, the power supply voltage can be lowered, and the power consumption can be reduced.

(Example 7)
FIG. 7 is a diagram schematically showing a cross section of the organic EL display device according to the present invention.

  The organic EL display device in the figure is a top emission type organic EL display device.

  The difference of the present embodiment from Embodiment 4 is that the thickness of the high work function layer of the first electrode 40 is thinner than the thickness of the low work function layer.

  The first electrode 41 is formed by a sputtering apparatus using an IZO target. First, a film was formed for 56 seconds under the conditions of a film forming pressure of 1.8 Pa, an argon flow rate of 100 sccm, a cathode output of 850 W, a cathode voltage of 250 V, and an oxygen flow rate of 0.09 sccm.

  Next, a film was formed at a pressure of 1.8 Pa during deposition, an argon flow rate of 100 sccm, a cathode output of 850 W, a cathode voltage of 250 V, and an oxygen flow rate of 5 sccm for 20 seconds to form the first electrode.

  The first electrode 41 has a work function of 4.4 eV and a film thickness of 600 mm, and the first electrode 42 has a work function of 5.7 eV and a film thickness of 150 mm. Therefore, the thickness of the high work function layer is smaller than the thickness of the low work function layer.

  The resistance of the first electrode 42 having a high work function is higher than that of the first electrode 41 having a low work function. This is because the oxygen content in the film is high and the composition approaches that of the oxide film.

  In this embodiment, the first electrode 41 having a large film thickness and a low work function reduces the resistance of the electrode and improves the electron injection property. Furthermore, since the hole injection property is improved by the high work function first electrode 42, low voltage driving is possible, the power supply voltage can be lowered, and the power consumption can be reduced.

(Example 8)
FIG. 8 is a diagram schematically showing a cross section of the organic EL display device according to the present invention. The organic EL display device in the figure is a top emission type organic EL display device.

  The difference of the present embodiment from Embodiment 1 is that a hole injection layer 31 is provided in the first organic layer 32 and a hole injection layer 51 is provided in the second organic layer 50. The organic layer is composed of four layers: a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer.

  As the hole injection material, a phthalocyanine compound, a triarylamine compound, a conductive polymer, a perylene compound, an Eu complex, or the like can be used, but the structure of the present invention is not limited.

  In this embodiment, after the second electrode 20 is formed, the hole injection layer 31 is formed, and then the first organic layer 32 is formed. Further, after the first electrode 40 is formed, the hole injection layer 51 is formed, and then the second organic layer 52 is formed. Here, the first organic layer 32 and the second organic layer 52 include a hole transport layer, a light emitting layer, and an electron transport layer.

  The hole injection layer lowers the barrier for hole injection into the first organic layer 32 and the second organic layer 52, so that low voltage driving is possible, power supply voltage can be reduced, and power consumption can be reduced.

Example 9
FIG. 9 is a diagram schematically showing a cross section of the organic EL display device according to the present invention. The organic EL display device in the figure is a top emission type organic EL display device.

  This embodiment differs from the first embodiment in that a hole injection layer 31 and an electron injection layer 33 are provided in the first organic layer 32, and a hole injection layer 51 and an electron injection layer 53 are provided in the second organic layer 50. . That is, the organic layer is composed of five layers: a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

  As an electron injection material, Alq3 in which an 8-hydroxyquinoline trimer is coordinated to aluminum, an azomethine zinc complex, a distyrylbiphenyl derivative system, or the like can be used, but the structure of the present invention is not limited.

  In this embodiment, after the second electrode 20 is formed, the hole injection layer 31, the first organic layer 32, and the electron injection layer 33 are formed. After the first electrode 40 is formed, the hole injection layer 51, the second organic layer 52, and the electron injection layer 53 are formed. Here, the first organic layer 32 and the second organic layer 52 include a hole transport layer, a light emitting layer, and an electron transport layer.

  The electron injection layer lowers the barrier for electron injection into the first organic layer 32 and the second organic layer 52, so that low voltage driving is possible, power supply voltage can be lowered, and power consumption can be reduced.

(Example 10)
FIG. 10 is a diagram schematically showing a cross section of the organic EL display device according to the present invention. The organic EL display device in the figure is a top emission type organic EL display device.
The difference of the present embodiment from the ninth embodiment is that the electron injection layers 34 and 54 contain an alkali metal.

  As the alkali metal contained in the electron injection layers 34 and 54, lithium, cesium, or the like can be used. However, the alkali metal is not limited to the configuration of the present invention.

  As the transparent conductive film, IZO, ITO, or the like can be used.

  By containing an alkali metal in the electron injection layers 34 and 54, the electron injection property is improved, the barrier for electron injection is lowered, and low voltage driving is possible.

  In addition, the transparent conductive film has high light transmissivity, and the structure in which the light emitting layer is laminated has a feature that the light extraction efficiency can be increased. On the other hand, generally, a transparent conductive film has a higher resistance than a metal. Therefore, by disposing the first electrode 45, which is a transparent conductive film, on the alkali metal-containing electron injection layer 34, the drive voltage can be lowered even when a transparent conductive film having a high resistance is used. The light extraction efficiency can be increased.

(Example 11)
FIG. 11 is a diagram schematically showing a cross section of an organic EL display device according to the present invention. The organic EL display device in the figure is a bottom emission type organic EL display device.

  The difference of the present embodiment from the first embodiment is that the first electrode 40 has two layers and the third electrode 60 to the second electrode 20 on the substrate 10 are in reverse order.

  In the present embodiment, the second electrode 20 is a reflective electrode. A bottom emission type organic EL display device that extracts emitted light from the third electrode 60 side is obtained.

  The first electrode was formed using an IZO target under the conditions of a film forming pressure of 1.8 Pa, an argon flow rate of 100 sccm, a cathode output of 850 W, and a cathode voltage of 250 V, and an oxygen flow rate of 5 sccm. Subsequently, the film was formed by changing the oxygen flow rate to 0.09 sccm. The work function of IZO under an oxygen flow rate of 5 sccm was 5.7 eV, and the work function of IZO under an oxygen flow rate of 0.09 sccm was 4.4 eV.

  The first electrode 42 serving as an anode having a high work function is in contact with the second organic layer. In general, surface treatment such as ultraviolet irradiation or oxygen plasma for improving hole injection is performed. However, when the first electrode 42 is disposed on the second organic layer 50, it is difficult to improve the hole injection property of the first electrode 42 because the surface treatment cannot be performed after the interface is formed. is there.

  On the other hand, in this embodiment, since the hole injecting property is already improved when the first electrode 42 is formed, low voltage driving is possible and low power consumption can be achieved.

  In the present embodiment, the configuration in which the third electrode 60 is in contact with the substrate 10 is shown, but a bottom emission type organic EL display device in which the second electrode 20 is in contact with the substrate 10 may be used. In that case, the third electrode 60 is a reflective electrode, and light is extracted from the second electrode 20 side.

The figure which shows the organic light emitting element which concerns on the 1st embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 2nd embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 3rd embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 4th embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 5th embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 6th embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 7th embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 8th embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 9th embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 10th embodiment of this invention. The figure which shows the organic light emitting element which concerns on the 11th embodiment of this invention. The figure which shows the preparation methods of the conventional organic light emitting element.

Explanation of symbols

10 substrate 20, 21 second electrode 30, 32 first organic layer 31 hole injection layer 33, 34 electron injection layer 40, 41, 42, 43, 44, 45 first electrode 50, 52 second organic layer 51 hole Injection layer 53, 54 Electron injection layer 60, 61 Third electrode 70 Fourth electrode 80 Third organic layer 90 Protective layer 100 Power supply means

Claims (18)

A substrate,
A first electrode having one main surface as a cathode and the other main surface as an anode;
A second electrode that is an anode;
A main surface serving as a cathode of the first electrode and a first organic layer sandwiched between the second electrode;
A third electrode which is a cathode;
In an organic EL display device having a main surface serving as an anode of the first electrode and a second organic layer sandwiched between the third electrodes,
An organic EL display device, wherein a work function of a main surface serving as an anode of the first electrode is higher than a work function of a main surface serving as a cathode of the first electrode. Having a fourth electrode which is a cathode;
The third electrode has one main surface as a cathode and the other main surface as an anode,
A third organic layer sandwiched between a main surface serving as an anode of the third electrode and a main surface serving as a cathode of the fourth electrode;
2. The organic EL display device according to claim 1, wherein a work function of a main surface serving as an anode of the first electrode is higher than a work function of a main surface serving as a cathode of the third electrode.   On the substrate, the second electrode, the first organic layer, the first electrode, the second organic layer, and the third electrode are stacked in this order, and the second electrode is a reflective electrode, The organic EL display device according to claim 1, wherein the three electrodes are light extraction electrodes.   On the substrate, the second electrode, the first organic layer, the first electrode, the second organic layer, and the third electrode are laminated in this order, and the second electrode is a light extraction electrode, The organic EL display device according to claim 1, wherein the third electrode is a reflective electrode.   2. The organic EL display device according to claim 1, wherein a work function of a main surface serving as a cathode of the third electrode is lower than a work function of a main surface serving as an anode of the second electrode.   The organic EL display device according to claim 1, wherein the first electrode includes at least two layers having different work functions.   The organic EL display device according to claim 6, wherein the first electrode includes three layers having different work functions, and the work function is configured to be lower as the second electrode is the anode. .   The organic EL display device according to claim 1, wherein the first electrode continuously changes from a low work function to a high work function.   The organic EL display device according to claim 6, wherein the thickness of the high work function of the first electrode is thinner than the thickness of the low work function.   The organic EL display device according to claim 1, wherein the first organic layer and the second organic layer include at least an electron transport layer, a light emitting layer, a hole transport layer, and a hole injection layer.   The organic EL display device according to claim 10, wherein the first organic layer and the second organic layer further include an electron injection layer.   The organic EL display device according to claim 11, wherein the first organic layer and the second organic layer include an electron injection layer containing an alkali metal, and the first electrode is a transparent conductive film.   The third electrode, the second organic layer, the first electrode, the first organic layer, and the second electrode are stacked in this order on the substrate, and the third electrode is a reflective electrode, and the second electrode The organic EL display device according to claim 1, wherein is an optical extraction electrode.   The third electrode, the second organic layer, the first electrode, the first organic layer, and the second electrode are sequentially stacked on the substrate, and the third electrode is a light extraction electrode, and the second electrode The organic EL display device according to claim 1, wherein the electrode is a reflective electrode.   2. The organic EL display device according to claim 1, wherein a work function of a main surface serving as an anode of the first electrode is 5.5 [eV] or more.   The organic EL display device according to claim 15, wherein a work function of a main surface serving as an anode of the first electrode is 5.8 [eV] or less. Forming a second electrode serving as an anode on the substrate;
Forming a first organic layer on the second electrode;
Forming a first electrode on the first organic layer;
Forming a second organic layer on the first electrode;
In the manufacturing method of an organic EL display device having a step of forming a third electrode in the second organic layer,
The oxygen flow rate when forming the first electrode serving as the anode in contact with the second organic layer is greater than the oxygen flow rate when forming the first electrode serving as the cathode in contact with the first organic layer. A method for manufacturing an organic EL display device. Forming a third electrode to be a cathode on a substrate;
Forming a second organic layer on the third electrode;
Forming a first electrode on the second organic layer;
Forming a first organic layer on the first electrode;
In the manufacturing method of an organic EL display device comprising a step of forming a second electrode in the first organic layer,
The oxygen flow rate when forming the first electrode serving as the anode in contact with the second organic layer is greater than the oxygen flow rate when forming the first electrode serving as the cathode in contact with the first organic layer. A method for manufacturing an organic EL display device.

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