JP2011249349A - Display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stack-type display element, in which light emitting units comprising an organic layer are stacked, capable of improving environmental resistance by using a stable material for at least a part of a charge generation layer, capable of improving injection efficiency of a charge from the charge generation layer to the light emitting units, and capable of being manufactured easily.SOLUTION: In a display element 11, a plurality of light emitting units 14-1, 14-2 including at least an organic light emitting layer 14c are stacked between a cathode 16 and an anode 13, and a charge generation layer 15 is held between each of the light emitting units 14-1, 14-2. At least a part of the charge generation layer 15 uses an oxide containing at least one of an alkali metal and an alkaline earth metal or a fluoride containing at least one of an alkali metal and an alkaline earth metal.

Description

  The present invention relates to a display element used for a color display and the like, and more particularly to a self-luminous display element provided with an organic layer.

  FIG. 15 shows a configuration example of a self-luminous display element (organic electroluminescent element) including an organic layer. The display element 1 shown in this figure is provided on a transparent substrate 2 made of, for example, glass. The display element 1 includes an anode 3 made of ITO (Indium Tin Oxide: transparent electrode) provided on a substrate 2, an organic layer 4 provided on the anode 3, and a cathode 5 provided thereon. It is configured. The organic layer 4 has a configuration in which, for example, a hole injection layer 4a, a hole transport layer 4b, and an electron transporting light emitting layer 4c are sequentially stacked from the anode side. In the display element 1 configured as described above, light generated when electrons injected from the cathode and holes injected from the anode are recombined in the light emitting layer 4c is extracted from the substrate 2 side.

  The lifetime of the organic electroluminescent device is generally determined by the injected electric charge, and this can be solved by reducing the initial luminance in driving. However, lowering the initial luminance limits applications in practical use and denies the potential of organic electroluminescence devices, making it impossible to realize next-generation television.

  In order to solve this problem, it is necessary to increase the luminance without changing the driving current, that is, to improve the efficiency, or to realize an element configuration that can obtain the same luminance even if the driving current is decreased.

In view of this, a stack-type multi-photon emission element (MPE element) in which a plurality of organic light-emitting elements are stacked is proposed. In particular, as shown in FIG. 16, a plurality of light emitting units 4-1, 4-2,... Made of an organic layer having at least a light emitting layer 4 c are provided between the anode 3 and the cathode 5. 6, a configuration of an MPE element (display element 1 ′) arranged in an overlapping manner via 6 is proposed. Here, the charge generation layer 6 injects holes into the light emitting unit 4-2 disposed on the cathode 5 side of the charge generation layer 6 when a voltage is applied, while the anode 3 side of the charge generation layer 6 is present. The layer plays a role of injecting electrons into the light emitting unit 4-1, and is made of a metal oxide such as vanadium oxide (V ₂ O ₅ ) or rhenium 7 oxide (Re ₂ O ₇ ). It is configured.

  In order to increase the efficiency of electron injection from the charge generation layer 6 to the light emitting unit 4-1 on the anode 3 side, the electron injection layer 7, which is an “in-situ reaction generation layer”, is formed on the anode 3 of the charge emission layer 6. May be provided on the side. As such an “in-situ reaction generation layer”, for example, a mixed layer of bathocuproine (BCP) and metal cesium (Cs), or a laminated film of (8-quinolinolato) lithium complex and aluminum is used. Used.

  In the stack type organic electroluminescence device in which the light emitting units 4-1, 4-2,... Are stacked through the charge generation layer 6 as described above, when two light emitting units are stacked, ideally, When the luminous efficiency [lm / W] does not change and the luminance [cd / A] is doubled and three light emitting units are stacked, ideally [lm / W] does not change [cd] / A] can be tripled (see the following Patent Documents 1 and 2).

JP 2003-45676 A JP 2003-272860 A

  However, in the display element 1 ′ in which the light emitting units 4-1 and 4-2 are stacked via the charge generation layer 6 as described with reference to FIG. 16, the display element 1 ′ is disposed on the anode 3 side of the charge generation layer 6. The material constituting the electron injection layer 7 as an in-situ reaction product layer is very unstable. For this reason, the stoichiometric ratio of each material constituting the electron injection layer 7 is important. If this balance is lost, it is considered that the layer becomes unstable.

  For example, BCP is rich in complexing ability and has a free metal component, or when there is an organic material having an active site, etc., there is a high possibility of forming a complex with a peripheral material, and the stability of the device It is difficult to use it in consideration of characteristics. In addition, it is considered that the element using BCP has poor reliability in environmental resistance.

In such a stack-type organic electroluminescent device, when the charge generation layer 6 is formed using a metal oxide such as V ₂ O ₅ or Re ₂ O ₇ , a general Alq _{3 type} is used. The efficiency of electrons injected by contacting the electron transport layer directly to the charge generation layer 6 is very low. Therefore, the interface configuration on the anode 3 side of the charge generation layer 6 is a very important point.

  Accordingly, the present invention provides a stack type display element in which light emitting units made of organic layers are stacked, and can improve environmental resistance by using a stable material, and can generate charge sandwiched between the light emitting units. An object of the present invention is to provide a display element that can improve the efficiency of charge injection from a layer to a light-emitting unit, and thus has high luminance, excellent long-term reliability, and is easy to manufacture.

  In order to achieve such an object, in the display element of the present invention, a plurality of light emitting units including at least an organic light emitting layer are stacked between a cathode and an anode, and a charge generation layer is sandwiched between the light emitting units. In the display element, the charge generation layer is in a state in which the intermediate cathode layer including a mixed layer of at least one element of alkali metal or alkaline earth metal and an organic material and the intrinsic charge generation layer are in contact with each other. They are laminated in order from the anode side.

  As described above, according to the display device of the present invention, the charge generation layer is composed of a mixed layer of at least one element of alkali metal and alkaline earth metal and an organic material, and an intrinsic charge generation layer. Since the layers are stacked in order from the anode side in contact with each other, the luminous efficiency of the stack type display element is improved by using a charge generation layer made of a stable material such as an organic compound, alkali metal, or alkaline earth metal. Can be achieved. As a result, in a stack type display element in which light emitting units made of organic layers are stacked, it is possible to improve the life characteristics by improving the luminance and the environmental resistance, that is, improving the long-term reliability. In addition, since a charge generation layer having such excellent charge injection characteristics is formed using a stable material, it is not necessary to perform film formation in consideration of the stoichiometric ratio in the production, and it is easy. Can be produced.

It is sectional drawing which shows one structural example of the display element of 1st Embodiment. It is sectional drawing which shows one structural example of the display element of 2nd Embodiment. It is sectional drawing which shows one structural example of the display element of 3rd Embodiment. It is sectional drawing which shows one structural example of the display element of 4th Embodiment. It is sectional drawing which shows the 1st example which combined the display element and color conversion film of embodiment. It is sectional drawing which shows the 2nd example which combined the display element and color conversion film of embodiment. It is sectional drawing which shows the 3rd example which combined the display element and color conversion film of embodiment. It is sectional drawing which shows the 4th example which combined the display element and color conversion film of embodiment. It is a graph which shows the luminous efficiency of the display element in Example 5, 14 and Comparative Examples 7-11. It is a graph which shows the time-dependent change of the relative luminance of the display element in Example 19 and Comparative Example 12. 14 is a graph showing changes with time in relative luminance of display elements in Example 15 and Comparative Example 7. It is a graph which shows the time-dependent change of the relative luminance of the display element in Example 27 and Comparative Example 13. It is a graph which shows the luminous efficiency of the display element in Example 50 and Comparative Example 15. 22 is a graph showing changes with time in relative luminance of display elements in Example 59 and Comparative Example 16. It is sectional drawing of the conventional display element. It is sectional drawing which shows the other structure of the conventional display element.

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

<First Embodiment>
FIG. 1 is a cross-sectional view illustrating a configuration example of the display element according to the first embodiment. A display element 10 shown in this figure is a stack type display element 10 formed by stacking light emitting units, and includes an anode 13 provided on a substrate 12 and a plurality of light emitting units 14 provided on the anode 13 so as to overlap each other. -1, 14-2,... (Two in this case), the charge generation layer 15-0 provided between the light emitting units 14-1 and 14-2, and the uppermost light emitting unit 14-2. The cathode 16 is provided.

  In the following description, the holes injected from the anode 13 and the light generated when the electrons generated in the charge generation layer 15-0 are combined in the light emitting unit 14-1 and the cathode 16 are simultaneously injected. A structure of a top emission type display element in which light emitted when electrons and holes generated in the charge generation layer 15-0 are combined in the light emitting unit 14-2 is taken out from the cathode 16 side opposite to the substrate 12. Will be explained.

  First, the substrate 12 on which the display element 10 is provided is appropriately selected from a transparent substrate such as glass, a silicon substrate, and a film-like flexible substrate. When the driving method of a display device configured using the display element 10 is an active matrix method, a TFT substrate in which a TFT is provided for each pixel is used as the substrate 12. In this case, the display device has a structure in which the top emission type display element 10 is driven using a TFT.

The anode 13 provided as the lower electrode on the substrate 12 has a high work function from the vacuum level of the electrode material in order to efficiently inject holes, for example, chromium (Cr), gold (Au), An alloy of tin oxide (SnO ₂ ) and antimony (Sb), an alloy of zinc oxide (ZnO) and aluminum (Al), and oxides of these metals and alloys are used alone or in a mixed state. be able to.

  In the case where the display element 10 is a top emission type, it is possible to improve the light extraction efficiency to the outside by the interference effect and the high reflectance effect by configuring the anode 13 with a high reflectance material. As the electrode material, it is preferable to use an electrode mainly composed of Al, Ag, or the like. It is also possible to increase the charge injection efficiency by providing a transparent electrode material layer having a large work function such as ITO on these high reflectivity material layers.

  When the driving method of the display device configured using the display element 10 is an active matrix method, the anode 13 is patterned for each pixel provided with a TFT. An insulating film (not shown) is provided on the upper layer of the anode 13, and the surface of the anode 13 of each pixel is exposed from the opening of the insulating film.

  The light emitting units 14-1 and 14-2 are formed by laminating, for example, a hole injection layer 14a, a hole transport layer 14b, a light emitting layer 14c, and an electron transport layer 14d in this order from the anode 13 side. Each of these layers is composed of an organic layer formed by, for example, a vacuum deposition method or another method such as a spin coating method. There is no limitation on the material constituting each organic layer. For example, if it is the hole transport layer 14b, a hole transport material such as a benzidine derivative, a styrylamine derivative, a triphenylmethane derivative, or a hydrazone derivative can be used.

  Of course, each of the layers 14a to 14d does not interfere with the other requirements. For example, the light emitting layer 14c can be an electron transporting light emitting layer also serving as the electron transporting layer 14d. The light-emitting layer 14c having a hole transport property may be used, and each layer may have a laminated structure. For example, the light emitting layer 14c may be a white light emitting element formed of a blue light emitting part, a green light emitting part, and a red light emitting part.

  The light-emitting layer 14c may be an organic thin film containing a small amount of an organic substance such as a berylene derivative, a coumarin derivative, a pyran-based dye, or a triphenylamine derivative. In this case, the light-emitting layer 14c corresponds to the material constituting the light-emitting layer 14c. It is formed by co-deposition of trace molecules.

  In addition, each of the above organic layers, for example, the hole injection layer 14a and the hole transport layer 14b, may have a laminated structure including a plurality of layers. The hole injection layer 14a is preferably made of, for example, an organic material that is not an arylamine-based material such as an azatriphenylene-based material, thereby increasing the efficiency of hole injection into the light emitting unit 14-2.

  Further, the light emitting units 14-1 and 14-2 described above may have exactly the same structure, but may have other structures. For example, when the light emitting unit 14-1 is formed as an organic layer structure for an orange light emitting element and the light emitting unit 14-2 is formed as an organic layer structure for a blue-green light emitting element, the emission color is white.

  The charge generation layer 15-0 provided between the light emitting unit 14-1 and the light emitting unit 14-2 is configured using an oxide containing at least one of an alkali metal and an alkaline earth metal. Yes. In the following description, Li, Na, K, Rb, Cs, and Fr are exemplified as alkali metals, and Be, Mg, Ca, Sr, Ba, and Ra are exemplified as alkaline earth metals. Here, the charge generation layer 15-0 is configured using an oxide containing at least one of these elements.

Here, as the oxide constituting the charge generation layer 15-0, in addition to general alkali metal oxide and alkaline earth metal oxide, other elements together with at least one of alkali metal and alkaline earth metal are used. The composite oxide containing is used. Specific examples of oxides that constitute the composite oxide together with alkali metal or alkaline earth metal include metaborate, tetraborate, germane oxide, molybdenum oxide, niobium oxide, silicate, and tantalum oxide. , Titanium oxide, vanadium oxide, tungsten oxide, zircon oxide, carbonate, soot oxide, chromium oxide, chromium oxide, heavy chromium oxide, ferrite, selenium oxide, selenium oxide, tin oxide At least one selected from the group consisting of oxides, tellurium oxides, tellurium oxides, bismuth oxides, tetraborates and metaborates. Among these, it is particularly preferable to use Li ₂ CO ₃ , Cs ₂ CO _3, or Li ₂ SiO ₃ as the main component, and include at least one of an alkali metal and an alkaline earth metal. The oxide is represented by Li ₂ CO ₃ .

The charge generation layer 15-0 may have a single layer structure made of, for example, Li ₂ CO ₃ .

The charge generation layer 15-0 is mainly composed of Li ₂ CO ₃ and, as a hole or electron (charge) hopping site, for example, a charge transporting organic material such as a hole transport material or an electron transport material is formed from Li _2. A mixed layer formed by co-evaporation with CO ₃ may be used. Moreover, the layer which has this mixed layer may be sufficient.

Further, the charge generation layer 15-0, and Li ₂ CO _3, may be a stacked structure of the mixed layer of Li ₂ CO ₃ and the charge-transporting organic material. In this case, the mixed layer of Li ₂ CO ₃ and the electron transporting organic material is laminated on the interface on the anode 13 side of the layer made of Li ₂ CO ₃ . In addition, the mixed layer of Li ₂ CO ₃ and the hole transporting organic material is laminated on the interface on the cathode 16 side of the layer made of Li ₂ CO ₃ . In this case, the hole transporting material is preferably composed of an organic material that is not an arylamine-based material such as an azatriphenylene-based material. Such a laminated structure may have a configuration in which a mixed layer is provided on at least one of the anode 13 side and the cathode 16 side of the layer made of Li ₂ CO ₃ .

Furthermore, the charge generation layer 15-0 may have a laminated structure of a layer made of Li ₂ CO ₃ and a layer made of another oxide or composite oxide. In this case, as the oxide or composite oxide, metaboric oxide, tetraboric oxide, germane oxide, molybdenum oxide, niobium oxide, silicic oxide, tantalum oxide, titanium oxide, vanadium oxide, tungsten oxide , Zircon oxide, carbonate, sulfur oxide, chromium oxide, chromium oxide, dichromium oxide, ferrite, selenium oxide, selenium oxide, tin oxide, tellurium oxide, tellurium oxide, bismuth Other common oxides or composite oxides such as oxide, tetraborate, metaborate and the like are exemplified.

  Each charge generation layer 15-0 configured as described above may be configured such that a fluoride is further laminated.

In this case, a fluoride containing at least one of alkali metal and alkaline earth metal (at least one element) as an intermediate cathode layer (intermediate cathode layer) at the interface on the anode 13 side in the charge generation layer 15-0. It is preferable to provide the used layer. Furthermore, a layer using a fluoride containing at least one of an alkali metal and an alkaline earth metal is provided as an intermediate cathode layer at the interface on the anode 13 side in the charge generation layer 15-0 via a conductive material layer. It is preferable to provide it.

Specific examples of the alkali metal fluoride and the alkaline earth metal fluoride include lithium fluoride (LiF), CsF, CaF _{2 and the} like. The conductive material layer includes at least one of magnesium (Mg), silver (Ag), and aluminum (Al). Specifically, a conductive material layer made of MgAg or Al is exemplified.

  Still further, the charge generation layer 15-0 has a layer made of a hole injecting material having a phthalocyanine skeleton such as copper phthalocyanine (CuPc) at the interface on the cathode 16 side as an intermediate anode layer (intermediate anode layer). It may be provided.

  Note that the charge generation layer 15-0 and each layer stacked on the interface are not necessarily limited to a structure that is clearly separated, and each constituent material may be mixed at the interface of each layer. good.

  Next, the cathode 16 has a three-layer structure in which a first layer 16a, a second layer 16b, and in some cases a third layer 16c are stacked in this order from the anode 13 side.

The first layer 16a is formed using a material having a small work function and good light transmittance. Examples of such materials include Li ₂ O which is an oxide of lithium (Li), Li ₂ CO ₃ which is a carbonate, Cs ₂ CO ₃ which is a carbonate of cesium (Cs), Li ₂ SiO ₃ which is a silicate, and Mixtures of these oxides can be used. Further, the first layer 16a is not limited to such a material, and examples thereof include alkaline earth metals such as calcium (Ca) and barium (Ba), and alkali metals such as lithium (Li) and cesium (Cs). Further, metals having a small work function such as indium (In), magnesium (Mg), silver (Ag), and further fluorides and oxides of these metals alone or these metals and fluorides, oxidation You may use it, improving stability as a mixture or alloy of a thing.

  The second layer 16b is composed of an electrode containing MgAg or alkaline earth metal, or an electrode such as Al. An electrode or an electrode such as Al is used. When the cathode 16 is composed of a semi-transmissive electrode like a top light emitting device, light can be extracted by using a thin MgAg electrode or Ca electrode. By configuring the display element 10 with a material having light permeability and good conductivity, the display element 10 emits light from the top, particularly having a cavity structure that resonates and extracts emitted light between the anode 13 and the cathode 16. In the case of an element, the second layer 16b is formed using a semi-transmissive reflective material such as Mg-Ag. Thereby, light emission is reflected at the interface of the second layer 16b and the interface of the anode 13 having light reflectivity to obtain a cavity effect.

  Furthermore, the third layer 16c can also be formed as a sealed electrode that can extract light emission by providing a transparent lanthanoid-based oxide for suppressing deterioration of the electrode.

  The first layer 16a, the second layer 16b, and the third layer 16c are formed by a technique such as vacuum deposition, sputtering, or plasma CVD. Further, when the driving method of the display device configured using this display element is an active matrix method, the cathode 16 includes an insulating film covering the periphery of the anode 13 (not shown here) and the light emitting units 14-1˜. The laminated film of the light emitting unit 14-2 may be formed as a solid film on the substrate 12 while being insulated from the anode 13, and may be used as a common electrode for each pixel.

  The electrode structure of the cathode 16 shown here is a three-layer structure. However, the cathode 16 may be formed of only the second layer 16b or between the first layer 16a and the second layer 16b as long as it is a laminated structure required when the functions of the layers constituting the cathode 16 are separated. In addition, it is possible to form a transparent electrode such as ITO, and it is needless to say that an optimal combination and laminated structure may be taken for the structure of the device to be produced.

In the display element 10 having the above-described configuration, the charge generation layer 15-0 mainly composed of a stable material, Li ₂ CO ₃ , is sandwiched between the light emitting units 14-1 and 14-2. Electron injection efficiency from the layer 15-0 to the light emitting unit 14-1 on the anode 13 side is improved. Therefore, it is possible to stabilize the stack type display element 10 in which the light emitting units 14-1 and 14-2 are stacked via the charge generation layer 15-0.

  In particular, in the case where a layer using a fluoride containing at least one of an alkali metal and an alkaline earth metal is provided as an intermediate cathode layer at the interface on the anode 13 side in the charge generation layer 15-0, such as MgAg By forming an intermediate cathode layer with a conductive material layer and a layer made of a fluoride containing at least one of an alkali metal and an alkaline earth metal disposed on the anode 13 side of the conductive material layer, a charge generation layer The effect of increasing the efficiency of electron injection from the charge generation layer 15-0 to the light emitting unit 14-1 provided on the anode 13 side of 15-0 can be enhanced.

  Further, by providing the charge generation layer 15-0 with an intermediate anode layer (not shown) having a phthalocyanine skeleton, the charge generation layer to the light emitting unit 14-2 provided on the cathode 16 side of the charge generation layer 15-0 is provided. The hole injection efficiency from 15-0 can be increased.

As a result, in the stack type display element, it is possible to improve not only the luminance but also the life characteristics by improving the environmental resistance, that is, the long-term reliability. In addition, since the charge generation layer 15-0 having such excellent charge injection characteristics is configured by using a stable material, it is necessary to perform film formation in consideration of the stoichiometric ratio in the production thereof. And can be easily manufactured. In addition, the driving voltage can be suppressed as compared with the case of using a general charge generation layer made of V ₂ O _5, and it is possible to improve long-term reliability.

Second Embodiment
FIG. 2 is a cross-sectional view illustrating a configuration example of the display element according to the second embodiment. The difference between the display element 11 shown in this figure and the display element 10 described with reference to FIG. 1 is the configuration of the charge generation layer 15, and the other configurations are the same. Hereinafter, the configuration of the display element 11 according to the second embodiment will be described in detail with a focus on the charge generation layer 15.

  That is, in the display element 11 of the second embodiment, the charge generation layer 15 provided between the light emitting unit 14-1 and the light emitting unit 14-2 has at least one of an alkali metal and an alkaline earth metal (at least 1). It is configured using an oxide containing various kinds of elements. The charge generation layer 15 has a structure in which an interface layer 15a and an intrinsic charge generation layer 15b are stacked in this order from the anode 13 side. The interface layer 15a serves as a cathode for the light emitting unit 14-1 provided in contact with the anode 13. Therefore, hereinafter, the interface layer 15a is referred to as an intermediate cathode layer 15a. And this intermediate cathode layer 15a shall be comprised using the oxide containing at least one of an alkali metal and alkaline-earth metal.

The intrinsic charge generation layer 15b provided in contact with the intermediate cathode layer 15a uses V ₂ O ₅ which is a charge generation layer described in Japanese Patent Application Laid-Open Nos. 2003-45676 and 2003-272860. Or an organic compound described below is used.

  Here, as the oxide containing at least one of an alkali metal and an alkaline earth metal constituting the intermediate cathode layer 15a, the same oxide as described in the first embodiment is used.

Among these, the intermediate cathode layer 15a is preferably made of Li ₂ SiO ₃ .

Further, as a material constituting the intrinsic charge generation layer 15b, an organic compound represented by the following general formula (1) is used in addition to V ₂ O _{5 and the} like.

In the general formula (1), R ^{1 to} R ⁶ are each independently hydrogen, halogen, hydroxyl group, amino group, arylamino group, substituted or unsubstituted carbonyl group having 20 or less carbon atoms, carbon number 20 The following substituted or unsubstituted carbonyl ester groups, substituted or unsubstituted alkyl groups having 20 or less carbon atoms, substituted or unsubstituted alkenyl groups having 20 or less carbon atoms, substituted or unsubstituted alkoxyl groups having 20 or less carbon atoms, The substituent is selected from a substituted or unsubstituted aryl group having 30 or less carbon atoms, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a nitrile group, a nitro group, a cyano group, or a silyl group. Further, among R ^{1 to} R ⁶ , adjacent R ^m (m = 1 to 6) may be bonded to each other through a cyclic structure. And X < ¹ > -X < ⁶ > in General formula (1) is a carbon or a nitrogen atom each independently.

Specific examples of the organic compound represented by the general formula (1) include organic compounds represented by the structural formulas (1) -1 to (1) -66 shown in the following Tables 1 to 7. In these structural formulas, [Me] represents methyl (CH ₃ ), and [Et] represents ethyl (C ₂ H ₅ ). In addition, in the structural formulas (1) -63 to (1) -66, among R ^{1 to} R ⁶ in the general formula (1), adjacent R ^m (m = 1 to 6) is through a cyclic structure. The example of the organic compound couple | bonded with each other is shown.

  The intermediate cathode layer 15a and the intrinsic charge generation layer 15b are not necessarily limited to a structure that is clearly separated, and the material constituting the intrinsic charge generation layer 15b is contained in the intermediate cathode layer 15a. Or vice versa.

  The charge generation layer 15 may have a structure in which an intermediate anode layer (not shown) is laminated together with the intermediate cathode layer 15a and the intrinsic charge generation layer 15b in this order from the anode 13 side. This intermediate anode layer is configured using an organic material having a phthalocyanine skeleton, and specifically, an intermediate anode layer made of copper phthalocyanine (CuPc) is exemplified.

  In addition, in the case where the intrinsic charge generation layer 15b of the charge generation layer 15 is configured using the organic compound represented by the general formula (1), the intrinsic charge generation layer 15b also serves as the hole injection layer 14a. Also good. In this case, the hole injection layer 14a is not necessarily provided in the light emitting unit 14-2 provided on the cathode 16 side of the charge generation layer 15.

  In the display element 11 of the second embodiment having the configuration described above, the charge generation layer 15 uses an oxide containing at least one of an alkali metal and an alkaline earth metal as a material constituting the intermediate cathode layer 15a. This improves the efficiency of electron injection from the charge generation layer 15 to the light emitting unit 14-1 on the anode 13 side. In particular, the above oxide constituting the intermediate cathode layer 15a in the charge generation layer 15 is supplied as a stable material from the film formation stage. For this reason, the intermediate cathode layer 15a using this, that is, the charge generation layer 15 is stabilized.

  Further, by providing an intermediate anode layer (not shown) made of an organic material having a phthalocyanine skeleton at the interface of the charge generation layer 15 on the cathode 16 side, the light emitting unit 14-2 disposed on the cathode 16 side of the charge generation layer 15 is provided. The efficiency of injecting holes from the charge generation layer 15 can be increased.

  As a result, in the stack type display element 11, not only the luminance can be improved, but also the life characteristics can be improved by improving the environmental resistance, that is, the long-term reliability can be improved. Further, since the charge generation layer 15 having such excellent charge injection characteristics is configured using a stable material, it is not necessary to perform film formation in consideration of the stoichiometric ratio in the production, It is possible to easily manufacture such a stack type display element 11 having excellent long-term reliability.

Further, even when the organic compound represented by the general formula (1) described above is used as the intrinsic charge generation layer 15b in the charge generation layer 15, the same level of charge injection as in the case of using the conventional V ₂ O ₅ is used. Efficiency can be obtained. In this case, since the intrinsic charge generation layer 15b can also serve as the hole injection layer, the hole injection layer is specially added to the light emitting unit 14-2 disposed on the cathode 16 side of the charge generation layer 15. 14a is not necessarily provided, and the layer structure can be simplified.

<Third Embodiment>
FIG. 3 is a cross-sectional view illustrating a configuration example of the display element according to the third embodiment. The difference between the display element 11 ′ shown in this figure and the display element 10 described with reference to FIG. 1 is the configuration of the charge generation layer 15 ′, and the other configurations are the same. Hereinafter, the configuration of the display element 11 ′ of the third embodiment will be described in detail with a focus on the charge generation layer 15 ′.

  That is, the charge generation layer 15 ′ in the display element 11 ′ of the third embodiment has a configuration in which the interface layer 15a ′ and the intrinsic charge generation layer 15b are sequentially stacked from the anode 13 side. Since this interface layer 15a ′ acts as a cathode for the light emitting unit 14-1 provided in contact with the anode 13, it is the same as in the second embodiment. Is referred to as an intermediate cathode layer 15a ′.

  In the charge generation layer 15 ′ having such a configuration, the intermediate cathode layer 15a ′ is characterized by using a fluoride containing at least one of alkali metal and alkaline earth metal (at least one element). In particular, the intermediate cathode layer 15a ′ includes a fluoride layer 15a-1 made of a fluoride containing at least one of an alkali metal and an alkaline earth metal, and a conductive material layer 15a-2, which are arranged in order from the anode 13 side. Or it is preferable to set it as a laminated structure with an insulating material layer (15a-2 ').

Here, as the fluoride that includes at least one of an alkali metal and an alkaline earth metal constituting the fluoride layer 15a-1, specifically, lithium fluoride (LiF), cesium fluoride (CsF), fluoride An example is calcium (CaF ₂ ).

  The material constituting the conductive material layer 15a-2 includes at least one of magnesium (Mg), silver (Ag), and aluminum (Al). Specifically, the conductive material layer 15a-2 made of MgAg or Al is exemplified.

  Furthermore, as the insulating material layer (15a-2 ′), a layer made of an oxide containing at least one of alkali metal and alkaline earth metal (at least one element) can be suitably used. As the oxide containing at least one of alkali metal and alkaline earth metal, the same oxide as described in the first embodiment is used.

In addition, the intrinsic charge generation layer 15b provided in contact with the intermediate cathode layer 15a ′ is made of V ₂ O ₅ which is a charge generation layer described in Japanese Patent Application Laid-Open Nos. 2003-45676 and 2003-272860. It is comprised using, or is comprised using the organic compound shown by the said General formula (1). When the intrinsic charge generation layer 15b of the charge generation layer 15 ′ is configured using the organic compound represented by the general formula (1), the intrinsic charge generation layer 15b also serves as the hole injection layer 14a. May be. In this case, it is not necessary to provide the hole injection layer 14a in the light emitting unit 14-2 provided on the cathode 16 side with respect to the charge generation layer 15 ′. Further, in the charge generation layer 15 ′, an intermediate anode layer made of an organic material having a phthalocyanine skeleton such as copper phthalocyanine (CuPc) (not shown) is stacked on the cathode 16 side of the intrinsic charge generation layer 15b. It may be a configuration. About the above, it is the same as that of 2nd Embodiment.

  In the display element 11 ′ of the third embodiment having such a configuration, the charge generation layer 15 ′ includes an oxide containing at least one of an alkali metal and an alkaline earth metal as a material constituting the intermediate cathode layer 15a ′. By including, the injection efficiency of electrons from the charge generation layer 15 ′ to the light emitting unit 14-1 on the anode 13 side is improved. In particular, a material such as an oxide containing at least one of an alkali metal and an alkaline earth metal constituting the intermediate cathode layer 15a ′ in the charge generation layer 15 ′ is supplied as a stable material from the film formation stage. For this reason, the intermediate cathode layer 15a ′ using this, that is, the charge generation layer 15 ′ can be stabilized.

  The intermediate cathode layer 15a ′ includes, in order from the anode 13 side, a fluoride layer 15a-1 made of a fluoride containing at least one of an alkali metal and an alkaline earth metal, and a conductive material layer 15a− such as MgAg. 2 is laminated, an effect of further increasing the electron injection efficiency to the light emitting unit 14-1 disposed on the anode 13 side with respect to the intermediate conductive layer 15a ′ can be obtained.

Further, the charge generation layer 15 ′ is provided on the cathode 16 side of the intrinsic charge generation layer 15 b with an intermediate anode layer (not shown) made of an organic material having a phthalocyanine skeleton, whereby the charge generation layer 15 ′ is on the cathode 16 side of the charge generation layer 15. The efficiency of injecting holes from the charge generation layer 15 ′ into the light emitting unit 14-2 disposed in can be increased.

  As a result, according to the display element 11 ′ of the third embodiment, as in the first embodiment, the stack type display element 11 ′ in which the light emitting units 14-1 and 14-2 made of organic layers are stacked. Therefore, it is possible to improve the long-term reliability, and it is possible to easily manufacture such a stack type display element 11 ′ having excellent long-term reliability.

Further, even when the organic compound represented by the general formula (1) is used as the intrinsic charge generation layer 15b in the charge generation layer 15 ′, the charge is about the same as that when the conventional V ₂ O ₅ is used. As in the second embodiment, it is possible to obtain the injection efficiency and thereby to simplify the layer structure.

<Fourth embodiment>
FIG. 4 is a cross-sectional view illustrating a configuration example of the display element according to the fourth embodiment. The difference between the display element 11 ″ shown in this figure and the display element 10 described with reference to FIG. 1 is the configuration of the charge generation layer 15 ″, and the other configurations are the same. Hereinafter, the configuration of the display element 11 ″ according to the fourth embodiment will be described in detail focusing on the charge generation layer 15 ″.

  That is, the charge generation layer 15 ″ in the display element 11 ″ of the fourth embodiment has a structure in which the mixed layer 15a ″ and the intrinsic charge generation layer 15b are stacked in this order from the anode 13 side. Since the layer 15a ″ acts as a cathode for the light emitting unit 14-1 provided in contact with the anode 13, hereinafter, the mixed layer 15a ″ will be referred to as an intermediate cathode layer 15a ″.

  In the charge generation layer 15 ″ having such a configuration, the intermediate cathode layer (mixed layer) 15a ″ is made of a material obtained by mixing at least one element of alkali metal and alkaline earth metal and an organic material. . Specific examples of the alkali metal and alkaline earth metal include lithium (Li), cesium (Cs), sodium (Na), potassium (K), rubidium (Rb), calcium (Ca), strontium (Sr), and barium. (Ba) can be exemplified. Further, as the organic material constituting the intermediate cathode layer (mixed layer) 15a ", it is preferable to use an organic material having electron transport properties such as Alq3 and ADN.

  The intrinsic charge generation layer 15b is provided in contact with the intermediate cathode layer (mixed layer) 15a "and is formed using the organic compound represented by the general formula (1).

  Although illustration is omitted here, the intermediate cathode layer 15a ″ is composed of an oxide containing at least one of alkali metal and alkaline earth metal (at least one element) in order from the anode 13 side. The structure which laminated | stacked the fluoride layer and the mixed layer mentioned above may be sufficient.

  In the fourth embodiment, since the intrinsic charge generation layer 15b is configured using the organic compound represented by the general formula (1), the intrinsic charge generation layer 15b also serves as the hole injection layer 14a. May be. Therefore, it is not necessary to provide the hole injection layer 14a in the light emitting unit 14-2 provided on the cathode 16 side of the charge generation layer 15 ". Further, the charge generation layer 15" is more than the intrinsic charge generation layer 15b. Alternatively, an intermediate anode layer made of an organic material having a phthalocyanine skeleton such as copper phthalocyanine (CuPc) (not shown) may be laminated on the cathode 16 side. About the above, it is the same as that of 2nd Embodiment.

  In the display element 11 ″ of the fourth embodiment having such a configuration, a mixed layer 15a ″ of at least one element of alkali metal and alkaline earth metal and an organic material, and the above-described general formula (1) is used. The charge generation layer 15 ″, in which the intrinsic charge generation layer 15b made of an organic compound is stacked in order from the anode 13 side in contact with each other, is sandwiched between the light emitting units 14a-1 and 14a-2. Thus, it was confirmed that light emission with sufficient luminous efficiency can be obtained in a stack type display element in which light emitting units are stacked. In addition, both the materials constituting the charge generation layer 15 ″ are stable materials. Therefore, the charge generation layer using this can be stabilized.

  As a result, according to the fourth embodiment, similarly to the display elements of the second and third embodiments, a stack type display in which the light emitting units 14-1 and 14-2 made of organic layers are stacked. It is possible to improve the long-term reliability of the element 11 ″, and it is possible to easily manufacture such a stack type display element 11 ″ having excellent long-term reliability. Further, by using the organic compound represented by the general formula (1) described above as the intrinsic charge generation layer 15b, the layer structure can be simplified.

  Note that the display element of the present invention described in each of the above embodiments is not limited to a display element used for an active matrix type display device using a TFT substrate, but as a display element used for a passive type display device. Can be applied, and the same effect (improvement of long-term reliability) can be obtained.

  Further, in each of the above embodiments, the case of the “top emission type” in which light emission is extracted from the cathode 16 side provided on the side opposite to the substrate 12 has been described. However, the present invention is also applied to a “transmission type” display element in which the substrate 12 is made of a transparent material to extract emitted light from the substrate 12 side. In this case, in the laminated structure described with reference to FIGS. 2 to 4, the anode 13 on the substrate 12 made of a transparent material is configured using a transparent electrode material having a large work function such as ITO. Thereby, emitted light is extracted from both the substrate 12 side and the opposite side of the substrate 12. Further, in such a configuration, by forming the cathode 16 with a reflective material, emitted light is extracted only from the substrate 12 side. In this case, a sealing electrode such as AuGe, Au, or Pt may be attached to the uppermost layer of the cathode 16.

Furthermore, even if the laminated structure described with reference to FIGS. 1 to 4 is stacked in reverse from the substrate 12 side made of a transparent material and the anode 13 is the upper electrode, the emitted light is extracted from the substrate 12 side. A “transmission type” display element can be formed. Also in this case, by changing the anode 13 serving as the upper electrode to a transparent electrode, emitted light is extracted from both the substrate 12 side and the opposite side of the substrate 12.
<Other embodiments>
The display elements of the first to fourth embodiments described above can be combined with a color conversion film. Hereinafter, the configuration of the display element using the color conversion film will be described taking the display element of FIG. 1 described in the first embodiment as an example, but the same applies to the display elements of the second to fourth embodiments. It is.

  First, FIG. 5 shows a display element 10 a in the case where the display element (10) described in the first embodiment is a “top emission type” in which emitted light is extracted from the side opposite to the substrate 12. In this case, the display element 10a in which the color conversion layer 18 is provided on the cathode 16 on the side from which the emitted light is extracted is configured. Here, when the light emitting layer 14c in the display element 10a is a blue wavelength excitation light source, the color conversion layer 18 is a color conversion film that converts the blue wavelength excitation light source into a red wavelength corresponding to each pixel portion. 18a and a color conversion film 18b for converting a blue wavelength excitation light source into green are disposed. Further, a material film that allows a blue wavelength excitation light source to pass through without being converted is provided in the color conversion layer 18 other than the color conversion film 18a and the color conversion film 18b. The display element 10a having such a configuration can perform full-color display.

  In addition, the color conversion layer 18 provided with the color conversion films 18a and 18b having such a configuration can be formed by using a photolithography technique which is a known technique.

  FIG. 6 shows another display element 10b in the case where the display element (10) described in the first embodiment is a “top emission type”. As shown in this figure, color conversion layers 18 and 19 may be laminated on the cathode 16 on the side from which emitted light is extracted. In this case, the color conversion films 18a and 19a for converting the blue wavelength excitation light source to the red wavelength are stacked in correspondence with the respective pixel portions, and the color conversion films 18b and 19b for converting the blue wavelength excitation light source to green are laminated. Are stacked. The color conversion films 18a and 19a and the color conversion films 18b and 19b arranged in a stacked manner are combined so that the light passing through both is converted into a desired wavelength. Further, 19c may be provided for converting the blue wavelength excitation light source into blue having better chromaticity. A material film that allows the blue wavelength excitation light source to pass therethrough without wavelength conversion is provided on the color conversion layer 19 other than the color conversion films 19a to 19c. Even the display element 10b having such a configuration can perform full-color display.

  FIG. 7 shows the display element 10c in the case where the display element (10) described in the first embodiment is a “transmitted light type” that extracts emitted light from the substrate 12 side. In this case, the display element 10c in which the color conversion layer 18 is provided between the anode 13 on the side from which emitted light is extracted and the substrate 12 is configured. The configuration of the color conversion layer 18 is the same as described above. Even the display element 10c having such a configuration can perform full-color display.

  FIG. 8 shows another display element 10 d when the display element (10) described in the first embodiment is a “transmission type”. As shown in this figure, color conversion layers 18 and 19 may be laminated between the anode 13 on the side from which emitted light is extracted and the substrate 12. The configurations of the color conversion layers 18 and 19 are the same as described above. Even the display element 10d having such a configuration can perform full-color display.

  In the configuration of the display elements 10a to 10d described with reference to FIGS. 5 to 8, the charge generation layer 15-0 is replaced with the charge generation layers 15, 15 ', and the configurations of the configurations described in the embodiments 2 to 3 described above. By changing to 15 ″, display elements 11a, 11a ′, 11a ″,... Corresponding to the respective embodiments are configured.

  Next, a specific example of the present invention, a manufacturing procedure of a display device of a comparative example for these examples, and an evaluation result thereof will be described. In the following <Examples 1 to 4>, the production of each display element 10 of the first embodiment shown in FIG. 1 will be described with reference to Table 8. In the following <Examples 5 to 20>, with reference to Table 9, the production of each display element 11 of the second embodiment shown in FIG. 2 will be described. In Examples 21 to 24, the production of each display element 11 ′ of the third embodiment shown in FIG. 3 will be described with reference to Table 10. And in <Examples 25-36>, with reference to Table 11, preparation of each display element 11 "of 4th Embodiment shown in FIG. 4 is demonstrated. Furthermore, in <Examples 37-58>, table | surface is demonstrated. The production of the display element 10a having the configuration shown in Fig. 5 will be described with reference to Tables 12 to 14. The production and evaluation results of the comparative example will be described before and after the description of each example.

<Examples 1-4>
In each of Examples 1 to 4, each display element 10 in which the charge generation layer 15-0 was made of each material and laminated structure in the configuration of the display element 10 of the first embodiment described with reference to FIG. Below, the manufacturing procedure of the display element 10 of Examples 1-4 is demonstrated first.

An organic material in which ITO (film thickness of about 120 nm) is formed as an anode 13 on a substrate 12 made of a glass plate of 30 mm × 30 mm, and a light emitting region other than 2 mm × 2 mm is masked with an insulating film (not shown) by SiO ₂ vapor deposition. A cell for an electroluminescent element was produced.

  Next, as the hole injection layer 14a constituting the light emitting unit 14-1 of the first layer, the hole injection material structural formula (1) -10, which is an azatriphenylene organic material, is formed to 15 nm (deposition rate 0. 2 to 0.4 nm / sec).

Next, α-NPD (Bis [N- (1-naphthyl) -N-phenyl] bendizine) represented by the following structural formula (2) is formed to 15 nm (deposition rate: 0.2) by the vacuum evaporation method as the hole transport layer 14b. (-0.4 nm / sec).

Further, as the light-emitting layer 14c, ADN represented by the following structural formula (3) is used as a host, BD-052x (Idemitsu Kosan Co., Ltd .: trade name) is used as a dopant, and the film thickness ratio is 5% by vacuum deposition. In addition, these materials were deposited in a total film thickness of 32 nm.

Finally, as the electron transport layer 14d, Alq3 [Tris (8-hydroxyquinolinato) aluminum (III)] represented by the following structural formula (4) was deposited by a vacuum deposition method with a film thickness of 18 nm.

After forming the light emitting unit 14-1 of the first layer as described above, the materials shown in the following Table 8 were vapor-deposited with respective film thicknesses on the charge generation layer 15-0.

Here, in Example 1, a charge generation layer 15-0 having a single layer structure was formed by forming a Li ₂ SiO ₃ film with a thickness of 15 mm. In Examples 2 and 3, Li ₂ SiO ₃ and hole injection material LGCHIL001 were co-evaporated to form a charge generation layer 15-0 having a single layer structure having a mixed film thickness. The composition ratio was Li ₂ SiO ₃ : LGCHIL001 = 4: 1 (film thickness ratio). Then, in Example 4, on the first layer made of _{Li 2 SiO 3, Li 2 SiO} 3: LGCHIL001 = 4: 1 charge generation layer 15 having a second layer laminated comprising a mixed layer of (film thickness ratio) -0 formed.

  After the above, the second layer light emitting unit 14-2 was formed in the same manner as the first layer light emitting unit 14-1.

  Next, as the first layer 16a of the cathode 16, LiF is formed with a film thickness of about 0.3 nm by a vacuum deposition method (deposition rate of 0.01 nm / sec or less), and then MgAg is vacuum-deposited as the second layer 16b. The film was formed with a thickness of 10 nm by the method, and finally, Al was formed with a film thickness of 300 nm as the third layer 16c.

<Comparative Examples 1-4>
In the configuration of the display element described with reference to FIG. 1, a display element having the configuration of the charge generation layer 15-0 shown in Table 8 was manufactured. The manufacturing procedure is a procedure in which only the formation process of the charge generation layer 15-0 is changed in the manufacturing procedure of the above-described embodiment. In the charge generation layer 15-0 formation process of each of Comparative Examples 1 to 4, first, a first layer having a thickness of 15 mm made of Li ₂ SiO ₃ is formed, and each film made of V ₂ O ₅ is formed thereon. A thick second layer was formed.

<Comparative Example 5>
In the configuration of the display element described with reference to FIG. 1, a light emitting unit 14-1 is provided on the anode 13, and the light emitting unit 14-2 is directly stacked without passing through the charge generation layer 15-0, and a cathode is formed thereon. A display element provided with 16 was produced. The manufacturing procedure is a procedure in which only the formation of the charge generation layer 15-0 is omitted in the manufacturing procedure of the above-described embodiment.

<Comparative Example 6>
In the structure of the display element described with reference to FIG. 1, a mono unit display element in which a light emitting unit 14-1 was provided on the anode 13 and a cathode 16 was directly provided on the light emitting unit 14-1 was manufactured. The production procedure was the same as the production procedure of the above-described embodiment, except that only the anode 13, the light emitting unit 14-1, and the cathode 16a were formed.

≪Evaluation result-1≫
Table 8 also shows the luminous efficiency (Quantum Yield: Q / Y) of the display elements of Examples 1 to 4 and Comparative Examples 1 to 6 manufactured as described above. As shown in this result, the light generation efficiency is improved in any of the display elements of Examples 1 to 4 with respect to the mono unit structure of Comparative Example 6, and the charge generation layer 15-in the present invention forming a stack type is shown in FIG. The effect of 0 was confirmed.

And even if it attaches to Comparative Examples 1-4, the effect almost equivalent to Examples 1-4 is acquired, but a drive voltage becomes high compared with Examples 1-4, and IV characteristic is on the high voltage side. Shifted. This suggests that there is power consumption in the charge generation layer 15-0 in this comparative example using V ₂ O ₅ which is generally used as a conventional charge generation layer. Therefore, it was confirmed that the drive voltage can be lowered by configuring the charge generation layer 15-0 with Li ₂ SiO ₃ as a main component without using V ₂ O ₅ .

  Incidentally, the comparative example 5 in which the light emitting units 14-1 and 14-2 are stacked without the charge generation layer has substantially the same luminous efficiency as the comparative example 6, and the charge generation layer 15-0 has the same luminous efficiency. Necessity was shown.

  Further, in Examples 1 to 4 described above, it is possible to easily form each display element using only a stable material without forming a film whose composition is severe in terms of stoichiometry by using an unstable material. It was possible to make it.

<Examples 5 to 16>
In each of Examples 5 to 16, each display element 11 in which the charge generation layer 15 was made of each material and laminated structure in the configuration of the display element 11 of the second embodiment described with reference to FIG. Below, the manufacturing procedure of the display element 11 of Examples 5-16 is demonstrated first.

An organic material in which ITO (film thickness of about 120 nm) is formed as an anode 13 on a substrate 12 made of a glass plate of 30 mm × 30 mm, and a light emitting region other than 2 mm × 2 mm is masked with an insulating film (not shown) by SiO ₂ vapor deposition. A cell for an electroluminescent element was produced.

  Next, as a hole injection layer 14a constituting the light emitting unit 14-1 of the first layer, a hole injection material HI-406 manufactured by Idemitsu Kosan Co., Ltd. is formed by vacuum deposition to a thickness of 15 nm (deposition rate: 0.2 to 0. 4 nm / sec).

  Next, α-NPD (Bis [N- (1-naphthyl) -N-phenyl] bendizine) represented by the above structural formula (2) is formed as a hole transport layer 14b by vacuum deposition to a thickness of 15 nm (deposition rate: 0. 0). 2 to 0.4 nm / sec).

  Furthermore, as a light emitting layer 14c, ADN shown in the above structural formula (3) is used as a host, BD-052x (Idemitsu Kosan Co., Ltd .: trade name) is used as a dopant, and these materials are formed into a total film of 32 nm by vacuum deposition The film was formed so that the thickness was 5% in terms of the film thickness ratio.

  Finally, as the electron transport layer 14d, Alq3 [Tris (8-hydroxyquinolinato) aluminum (III)] represented by the above structural formula (4) was deposited by a vacuum deposition method to a film thickness of 18 nm.

  After forming the first light emitting unit 14-1 as described above, the materials shown in the following Table 9 were deposited as the charge generation layer 15 in respective film thicknesses.

  Here, in Examples 5 to 16, first, as the intermediate cathode layer 15a of the charge generation layer 15, each material shown in Table 9 was formed to a thickness of 15 mm.

Next, in Examples 5 to 14, V ₂ O ₅ was vapor-deposited with a thickness of 120 mm as the intrinsic charge generation layer 15b. On the other hand, in Examples 15 and 16, as the intrinsic charge generation layer 15b, an organic compound represented by the structural formula (1) -10 in Table 1 was formed to a thickness of 120 mm.

  In Example 14 alone, copper phthalocyanine (CuPc) was further deposited in a thickness of 20 mm as an intermediate anode layer (not shown).

  After the above, the second layer light emitting unit 14-2 was formed in the same manner as the first layer light emitting unit 14-1.

  Next, as the first layer 16a of the cathode 16, LiF is formed with a film thickness of about 0.3 nm by a vacuum deposition method (deposition rate of 0.01 nm / sec or less), and then MgAg is vacuum-deposited as the second layer 16b. The film was formed with a thickness of 10 nm by the method, and finally, Al was formed with a film thickness of 300 nm as the third layer 16c. Thus, a transmissive display element 11 that extracts light from the substrate 12 side was obtained.

<Examples 17 and 18>
In Examples 17 and 18, in the configuration of Example 15, as the hole injection layer 14a in the first light emitting unit 14-1, the structural formula (1) -10 in Table 1 is used instead of HI-406. Was formed with a film thickness of 15 nm. Then, the hole injection layer 14a in the light emitting unit 14-2 of the second layer is not formed, and a display element having a configuration shared with the intrinsic charge generation layer 15b having the structural formula (1) -10 in Table 1 is manufactured. did. However, the structure of the charge generation layer 15 was set to each film thickness shown in Table 9.

<Examples 19 and 20>
In Examples 19 and 20, a top-emission display element that extracts emitted light from the side opposite to the substrate 12 in the configuration of the display element 11 of the first embodiment described with reference to FIG. Here, in the manufacturing procedures of Examples 5 to 16 described above, a silver alloy (film thickness of about 100 nm) is formed as the anode 13 instead of ITO, and the third layer 16c of the cathode 16 is replaced with Al as IZO (indium). Zinc composite oxide) was formed to 200 nm. Each charge generation layer 15 was formed in the same manner as in Example 5 and in Example 20 as in Example 13, as shown in Table 9 above.

<Examples 21 and 22>
In Examples 21 and 22, each display element 11 ′ in which the charge generation layer 15 ′ is made of each material and a laminated structure in the configuration of the display element 11 ′ of the third embodiment described with reference to FIG. In these Examples 21 and 22, the same procedure as in Examples 5 to 16 except that the configuration of the charge generation layer 15 ′ was changed to the configuration shown in Table 10 below in the manufacturing procedure of Examples 5 to 16 described above. A transmissive display element 11 ′ was produced by the procedure. That is, in Examples 21 and 22, the charge generation layer 15 ′ has a three-layer structure, and the conductive material layer 15a− made of an MgAg (composition ratio 10: 1) film on the fluoride layer 15a-1 made of LiF. 2 and an intrinsic charge generation layer 15b made of V ₂ O ₅ was further laminated. The film thickness of each layer is as shown in Table 10.

<Examples 23 and 24>
In Examples 23 and 24, in the configuration of the display element 11 ′ of the third embodiment described with reference to FIG. 3, a top emission type display element that extracts emitted light from the side opposite to the substrate 12 was manufactured. Here, in the manufacturing procedures of Examples 21 and 22 described above, a silver alloy (film thickness of about 100 nm) is formed as the anode 13 instead of ITO, and further, the third layer 16c of the cathode 16 is replaced with Al as IZO (indium). Zinc composite oxide) was formed to 200 nm. Each charge generation layer 15 ′ was formed in the same manner as in Example 21 and in Example 24 as in Example 22 as shown in Table 10 above.

<Comparative Example 7>
In the structure of the display element described with reference to FIG. 3, a mono unit display element in which a light emitting unit 14-1 was provided on the anode 13 and a cathode 16 was directly provided on the light emitting unit 14-1 was manufactured. For the production procedure, only the anode 13, the light emitting unit 14-1, and the cathode 16 were formed in the same procedure as in the production procedures of Examples 5 to 16 described above.

<Comparative Example 8>
In the configuration of the display element described with reference to FIG. 3, the light emitting unit 14-1 is provided on the anode 13, and the light emitting unit 14-2 is directly stacked without using the charge generation layer 15 ′. A display element provided with was manufactured. The manufacturing procedure was a procedure in which only the formation of the charge generation layer 15 was omitted in the manufacturing procedures of Examples 5 to 16 described above.

<Comparative Examples 9-11>
In the configuration of the display element described with reference to FIG. 3, a display element having the configuration of the charge generation layer 15 ′ shown in Table 10 was manufactured. The production procedure was the same as that of Examples 5 to 16 described above. However, in Comparative Example 9, in the formation of the charge generation layer 15 ′, only the intrinsic charge generation layer 15b was deposited with a V ₂ O ₅ thickness of 120 mm. In Comparative Examples 10 and 11, in the formation of the charge generation layer 15 ′, LiF was formed as the intermediate cathode layer 15a ′ in each film thickness, and then V ₂ O ₅ was formed as the intrinsic charge generation layer 15b in a film thickness of 120 mm. Vapor deposited.

<Comparative Example 12>
In the structure of the mono unit type display element manufactured in Comparative Example 7, a top emission type display element that extracts emitted light from the side opposite to the substrate 12 was manufactured. Here, in the manufacturing procedure of the display element described in Comparative Example 7, an Ag alloy (film thickness of about 100 nm) was formed as the anode 13, and IZO (indium zinc composite oxide) was used as the third layer 16c of the cathode 16. A display element was produced in the same procedure as in Comparative Example 7, except that the thickness was 200 nm.

≪Evaluation result-2≫
FIG. 9 shows the luminous efficiencies of the display elements of Examples 5 and 14 and Comparative Examples 7 to 11 manufactured as described above. As shown in this graph, the luminous efficiency of the display elements of Examples 5 and 14 was doubled with respect to the luminous efficiency of the mono-unit type light emitting element of Comparative Example 7. Also, in other Examples 6 to 13 and 15 to 24, some of the transmission type and top emission type, particularly the organic compounds of the structural formula (1) -10 as in Examples 15 and 16 were used. Even in the configuration in which the hole injection layer 14a is omitted, the light emission efficiency is doubled with respect to the light emission efficiency of the mononit type light emitting element of Comparative Example 7. Thereby, the effect of the charge generation layers 15 and 15 'in the present invention forming the stack type was confirmed.

  In particular, in Example 14 in which the charge generation layer 15 has an intermediate anode layer (CuPc) at the cathode 16 side interface, a further increase in luminous efficiency was confirmed as compared with the other examples. Thus, it has been confirmed that the provision of such an intermediate anode layer improves the efficiency of hole injection into the light emitting unit 14-2 disposed on the cathode 16 side with respect to the charge generation layer 15.

Incidentally, the display element having the structure in which the light emitting units of Comparative Example 8 are directly laminated cannot obtain the light emission efficiency as compared with the mono unit type of Comparative Example 7, and the necessity of the charge generation layer 15 (15 ′). It has been shown. In the display element using the V ₂ O ₅ single-layer charge generation layer of Comparative Example 9, electrons and holes are effectively injected from the charge generation layer into the electron transport layer 14d and the hole injection layer 14a, respectively. Thus, only a luminous efficiency substantially equivalent to that of Comparative Example 1 could be obtained.

In Comparative Examples 10 and 11, even when the fluoride layer (LiF) 15a-1 is directly laminated on the intrinsic charge generation layer (V ₂ O ₅ ) 15b, good electron injection cannot be performed. As shown in Examples 21 and 22, it was shown that electrons can be effectively injected through the conductive material layer (MgAg or the like) 15a-2.

Further, from the result of Comparative Example 11, it is considered that when the drive voltage is increased, the interface in the charge generation layer 15 is destroyed and the efficiency is suddenly increased. From this fact, the fluoride layer (LiF) 15a -1 directly stacked on the intrinsic charge generation layer (V ₂ O ₅ ) 15b suggests that efficient charge injection is not performed, and during this time, the conductive material layer (MgAg or the like) 15a- The effect by providing 2 was confirmed.

  In Examples 5 to 24 described above, each display element can be easily formed using only a stable material without forming a film having a composition that is stoichiometrically severe by using an unstable material. It was possible to make it.

≪Evaluation result-3≫
FIG. 10 shows the results of measuring the lifetime of the display elements of Example 19 and Comparative Example 12 manufactured as described above at an initial luminance of 3000 cd / m ² . From this result, even in the top emission type element configuration, the half life in the stack type display element manufactured in Example 19 is greatly improved with respect to the mono unit type display element of Comparative Example 12, and long-term reliability is improved. It was confirmed that it is effective for improvement.

≪Evaluation result-4≫
FIG. 11 shows the results of lifetime measurement of the display elements of Example 15 and Comparative Example 7 manufactured as described above, with the initial luminance set to 1500 cd / m ² , Duty 50, and room temperature maintained. From this result, even for the display element in which the intrinsic charge generation layer 15b is formed using the organic compound represented by the structural formula (1) -10, the present invention was carried out on the mono unit type display element of Comparative Example 7. The half-life of the stack type display device manufactured in Example 15 was improved by more than twice, and it was confirmed that it was effective in improving long-term reliability. The reason is due to the acceleration constant for each element, and the acceleration constant generally indicates 1 or more. If the efficiency is improved by a factor of 2, the lifetime is expected to improve by a factor of 2 or more. Yes, this result is obtained in that way.

<Examples 25 to 36>
In Examples 25 to 36, each display element 11 ′ having the charge generation layer 15 ″ as a material and a laminated structure in the configuration of the display element 11 ″ according to the fourth embodiment described with reference to FIG. 4 was manufactured. In these Examples 25 to 36, the same procedure as in Examples 5 to 16 except that the configuration of the charge generation layer 15 "was changed to the configuration shown in Table 11 below in the production procedure of Examples 5 to 16 described above. A transmissive display element 11 ′ was produced by the procedure.

  That is, in Examples 25 to 36, as the intermediate cathode layer 15a "of the charge generation layer 15", each alkali metal or alkaline earth metal and organic material (ADN or Alq) as shown in Table 11 above is used. An intermediate cathode layer 15 ″ made of a mixed layer was used. However, in Examples 27, 28, 35, and 36, as the intermediate cathode layer 15a ″, a fluoride layer and a mixed layer were sequentially formed from the anode 13 side. A laminated structure having a thickness was used. Furthermore, an intrinsic charge generation layer 15b in contact with the intermediate cathode layer 15a ″ was formed using an organic material represented by the structural formula (1) -10 in Table 1.

<Comparative Example 13>
In Comparative Example 13, as in Comparative Example 7, a mono-unit type display element in which only the anode 13, the light emitting unit 14-1, and the cathode 16 were formed was produced. However, the cathode 16 has the same configuration as the charge generation layer 15 ″ of Example 27. That is, the configuration of the cathode 16 is the first layer 16a / second layer 16b / third layer 16c = LiF (about 0. 3 nm) / Alq3 + Mg (5%) (5 nm) / Al (20 nm), thereby obtaining a transmissive display element 11 ″ for extracting light from the substrate 12 side.

<Comparative example 14>
In Comparative Example 14, the cathode 16 in the configuration of Comparative Example 13 has the same configuration as the charge generation layer 15 ″ of Example 28. That is, the configuration of the cathode 16 includes the first layer 16a / second layer 16b /. The third layer 16c = LiF (about 0.3 nm) / Alq3 + Ca (5%) (5 nm) / Al (20 nm), thereby obtaining a transmissive display element 11 ″ that extracts light from the substrate 12 side.

≪Evaluation result-5≫
FIG. 12 shows the results of performing life characteristics at the time of measuring Duty 50 and room temperature when the current density is 125 mA / cm ² for the display elements of Example 27 and Comparative Example 13 manufactured as described above. . In this case, the initial luminance was about twice that of Comparative Example 13 in Example 27. And since the half life with respect to the initial brightness | luminance of the display element of Example 27 is more than the half life with respect to the initial brightness | luminance of the display element of the comparative example 13 as shown in FIG. Compared to Comparative Example 13, the efficiency improvement effect is twice or more. Therefore, as in Example 27, in order from the anode 13 side, a mixed layer of at least one of an alkali metal and an alkaline earth metal (Mg) and an organic material (Alq3), and a structural formula (1) -10 are represented. It was confirmed that the life and efficiency of the display device having a stack structure provided with the charge generation layer 15 ″ formed by laminating the intrinsic charge generation layer 15b made of the organic compound is improved.

The same applies to the comparison between Example 28 and Comparative Example 14. However, the efficiency of the display element of Example 28 was about 1.3 times that of the display element of Comparative Example 14. However, when the lifetimes are compared under the same conditions as described above (when the current density is 125 mA / cm ² , Duty 50, measurement at room temperature), the half-life is almost the same in Comparative Example 14 and Example 28. The long-life effect due to the structure was confirmed.

  In comparison with Examples 25 and 26 and Examples 27 and 28, the LiF (conductive material layer) is closer to the interface side than the display elements of Examples 25 and 26 in which the intermediate cathode layer 15a ″ has a single layer structure. In the display elements of Examples 27 and 28 having the intermediate cathode layer 15a ″ having a laminated structure in which is inserted, it was possible to confirm the improvement in luminous efficiency and the effect of extending the lifetime. However, the difference was small, and it was confirmed that the efficiency was improved and the life was extended by the stack structure in which the light emitting units were stacked.

  As a comparison of Examples 25, 29, and 30, the indications of Examples 25, 29, and 30 differ in the amount of addition of at least one of an alkali metal and an alkaline earth metal (Mg) added to the intermediate cathode layer 15a ″. In the device, the light emission efficiency was almost the same as that of Example 25. However, as the Mg ratio was increased, the variation in lifetime was increased. Compared with the improvement effect, there was a tendency for the effect to become smaller in the order of Examples 29 and 30. This factor is derived from the change in the film quality of the intermediate cathode layer 15a ″ accompanying the increase in the Mg ratio. Predicted. According to the study by the inventors, the upper limit of the ratio of alkali metal and alkaline earth metal is about 50% (relative film thickness ratio) in Example 30, and increasing the ratio further reduces the transmittance and the intermediate cathode layer. This resulted in an increase in the instability of the film quality of 15a ″, which was considered disadvantageous in forming a stack structure in which light emitting units were stacked.

  As compared with Examples 31 to 34, in these display elements, Li and Cs, which are alkali metals, are used in the intermediate cathode layer (mixed layer) 15a "constituting the charge generation layer 15", respectively, and co-evaporated. Alq3 and ADN are used as organic materials for performing the above. In all the display elements of Examples 31 to 34, the light emission efficiency was about twice that of Comparative Example 13, and the life improvement effect was almost the same as in FIG.

  As a comparison of Examples 35 and 36, these display elements have the same tendency as in the comparison between Examples 27 and 28 and Examples 25 and 26, and LiF (conductive) is applied to the intermediate cathode layer 15a ″. Efficiency improvement and longer life could be confirmed again by the stack structure in which the light emitting units were stacked rather than the laminated structure in which the conductive material layer) was inserted.

<Examples 37 to 58>
In Examples 37 to 58, the transmissive display elements 11c, 11c ′, and 11c ″ described with reference to FIG. 7 were manufactured. In manufacturing these Examples 37 to 58, first, a glass of 30 mm × 30 mm was used. A color conversion layer 18 is formed by patterning a color conversion film 18a for converting a blue wavelength excitation light source into a red wavelength and a color conversion film 18b for converting a blue wavelength excitation light source into green on a substrate 12 made of a plate. The photolithographic technique, which is a known technique, was used.

Thereafter, the anode 13 to the cathode 16 were formed on the upper surface of the color conversion layer 18 in accordance with the manufacturing procedures of Examples 5 to 16 described above. However, 2-TNATA [4,4 ′, 4 ”-tris (2-naphtylphenylamino) triphenylamine] represented by the following structural formula (5) is deposited as a hole injection layer 14a of the light emitting units 14-1 and 14-2 by 15 nm (deposition). The charge generation layers 15, 15 ′, and 15 ″ were changed to the configurations shown in Tables 12 to 14 below.

<Comparative Example 15>
In the configuration of the display element described with reference to FIG. 7, a color conversion layer 18 is provided between the substrate 12 and the anode 13, a light emitting unit 14-1 is provided on the anode 13, and the light emitting unit 14-1 is provided on the light emitting unit 14-1. A mono unit display element provided with a cathode 16 directly was produced. The production procedure was the same as the production procedure of Examples 37 to 58, except that only the color conversion layer 18, the anode 13, the light emitting unit 14-1, and the cathode 16 were formed.

≪Evaluation result-6≫
FIG. 13 shows the luminous efficiencies of the display elements of Example 50 and Comparative Example 15 manufactured as described above. As shown in this graph, the luminous efficiency of the display element of Example 50 was doubled with respect to the luminous efficiency of the mono-unit type light emitting element of Comparative Example 15. Also in other Examples 45 to 58, the light emission efficiency was doubled with respect to the light emission efficiency of the mononit type light emitting device of Comparative Example 15. Thereby, even when the color conversion layer 18 was used, the effect of the charge generation layers 15 to 15 ″ in the present invention forming the stack type was confirmed.

<Example 59>
In Example 59, each top emission type display element 11c ″ described with reference to FIG. 5 was manufactured. Here, in the manufacturing procedure of Example 50 described above, instead of ITO as the anode 13, chromium (Cr: film) was manufactured. In addition, the third layer 16c of the cathode 16 is formed of 200 nm of IZO (indium zinc composite oxide) instead of Al, and light is extracted from the cathode 16 side, and the color conversion layer 18 is formed. Was formed on the cathode 16.

<Comparative Example 16>
A mono-unit type display element corresponding to Example 59 was produced.

≪Evaluation result-7≫
FIG. 14 shows the results of measuring the lifetime of the display elements of Example 59 and Comparative Example 16 manufactured as described above, with an initial luminance of 3000 cd / m ² . From this result, also in the top emission type element configuration, the half life in the stack type display element manufactured in Example 59 is greatly improved with respect to the mono unit type display element of Comparative Example 16, and long-term reliability is improved. It was confirmed that it is effective for improvement.

DESCRIPTION OF SYMBOLS 11 ... Display element, 13 ... Anode, 14-1, 14-2 ... Light emitting unit, 14c ... Light emitting layer (organic light emitting layer), 15, 15 ', 15 "... Charge generation layer, 15a, 15a' ... Intermediate cathode layer (Interface layer), 15a "... intermediate cathode layer (mixed layer), 15b ... intrinsic charge generation layer, 16 ... cathode

Claims (5)

In a display element in which a plurality of light emitting units including at least an organic light emitting layer are stacked between a cathode and an anode, and a charge generation layer is sandwiched between the light emitting units,
The charge generation layer includes an intermediate cathode layer including a mixed layer of at least one element of alkali metal and alkaline earth metal and an organic material, and an intrinsic charge generation layer sequentially stacked from the anode side in a state of being in contact with each other. Display element. The display element according to claim 1,
The display element in which the intrinsic charge generation layer contains an organic compound represented by the following general formula (1).

However, in General formula (1), R < ¹ > -R < ⁶ > is respectively independently hydrogen, a halogen, a hydroxyl group, an amino group, an arylamino group, a C20 or less substituted or unsubstituted carbonyl group, carbon number A substituted or unsubstituted carbonyl ester group having 20 or less carbon atoms, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted alkenyl group having 20 or less carbon atoms, a substituted or unsubstituted alkoxyl group having 20 or less carbon atoms A substituent selected from a substituted or unsubstituted aryl group having 30 or less carbon atoms, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a nitrile group, a nitro group, a cyano group, or a silyl group, which are adjacent to each other. R ^m (m = 1 to 6) may be bonded to each other through a cyclic structure. X ^{1 to} X ⁶ are each independently a carbon or nitrogen atom. The display element according to claim 1,
The display element, wherein a ratio of at least one of the alkali metal and the alkaline earth metal in the mixed layer is 50% or less in terms of a relative film thickness ratio. The display element according to claim 1,
A display element, wherein an interface layer using a fluoride containing at least one of an alkali metal and an alkaline earth metal is provided at an interface on the anode side in the charge generation layer. The display element according to claim 1,
A display element, wherein an intermediate anode layer made of an organic material having a phthalocyanine skeleton is provided at an interface on the cathode side in the charge generation layer.

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