JP2006351398A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure in which brightness is superior and long term reliability is superior in a display element in which a plurality of light-emitting units consisting of an organic layer are laminated via connecting layers. <P>SOLUTION: In the display element 10 in which between a cathode 16 and an anode 13, the light-emitting units 14-1 including at least organic light-emitting layers 14-1, 14-2 are laminated in a plurality of numbers and a connecting layer 15 is pinched between the light-emitting layers 14-1, 14-2, this is equipped with a laminated part in which the connection layer 15 is equipped with an oxide containing layer 15a using an oxide containing at least one of alkaline metal and an alkaline-earth metal (containing beryllium and magnesium), an organic material layer 15b having electric charge transportation nature, and a triphenylene layer 15c using at least one of a triphenylene derivative and an azatriphenylene derivative are laminated in this order from the anode 13 side. <P>COPYRIGHT: (C)2007,JPO&INPIT

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. 11 shows a structural example of a self-luminous display element (organic electroluminescent element) provided with 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 structure 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. FIG. 12 shows an example of such an MPE element. The MPE element shown in this figure includes a plurality of light emitting units 4-1, 4-2,... Made of an organic layer having at least a light emitting layer 4c between an anode 3 and a cathode 5, and an insulating charge generation layer 6. It is the structure arranged so as to overlap with each other. 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 on the anode 3 side of the charge generation layer 6. This is a layer that plays a role of injecting electrons into the arranged light emitting unit 4-1.

Such a charge generation layer 6 is configured using, for example, a metal oxide such as vanadium oxide (V ₂ O ₅ ) or rhenium oxide (Re ₂ O ₇ ). In order to increase the electron injection efficiency 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 generation layer 6. May be provided on the side. Examples of such an “in-situ reaction generation layer” as the electron injection layer 7 include a mixed layer of bathocuproine (BCP) and metal cesium (Cs), and a mixed film of (8-quinolinolato) aluminum complex and magnesium. It is 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 Patent Documents 1 and 2 below).

JP 2003-45676 A JP 2003-272860 A

  In addition to the charge generation layer 6 as described above, an n-type doped organic layer, a p-type doped organic layer, or a combination of these has been proposed as a layer disposed between the light emitting units ( See Patent Document 3 below).

JP 2004-039617 A

  Furthermore, as another layer disposed between the light emitting units, a configuration using at least a hole transport layer and an electron transport layer and a connecting unit disposed between adjacent organic electroluminescent units has been proposed. The connecting unit includes, in order, an n-type doped organic layer, an interface layer, and a p-type doped organic layer, and the interface layer prevents diffusion or reaction between the n-type doped organic layer and the p-type doped organic layer. Comprising what to do. Specific examples of such connecting units include (1) Alq3: Li (30nm) / PbO (2nm) / NPB: F4-TCNQ (60nm), (2) Alq3: Li (30nm) / Sb2O5 (4nm) / NPB: F4-TCNQ (60 nm), (3) Alq3: Li (30 nm) / Ag (0.5 nm) / NPB: F4-TCNQ (60 nm), etc. are shown. That is, the linking unit includes a layer in which Alq3 [8-hydroxyquinoline) showing an electron transport property as an n-type doped organic layer is doped with Li, which is an alkali metal, and an NPB [N , N'-Di (naphthalen-1-yl) -N, N'-diphenyl-benzidine] has strong electron withdrawing F4-TCNQ [2,3,5,6-tetrafluoro-7,7,8,8 It is a structure in which an oxide film or a metal film is sandwiched between layers doped with [-tetracyanoquinodimethane] (see Patent Document 4 below).

JP 2004-281371 A

  In addition to the above, as a layer disposed in the light emitting unit type, a laminated structure of a LiF layer and a mixed layer of Alq and Mg has been proposed (see Patent Document 5 below).

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.

  Further, in the display element in which the light emitting unit is stacked through the doped organic layer or the layer called the connection unit as described above, the initial deterioration is large and the variation in characteristics is also large. This is because the n-type additive exemplified as being doped in the doped organic layer tends to vary in characteristics unless it is controlled stoichiometrically, while the material exemplified as the p-type additive is also essential. This is because it is difficult to obtain a long-life device structure.

  Accordingly, an object of the present invention is to provide a structure having high luminance and excellent long-term reliability in a display element in which a plurality of light emitting units made of an organic layer are stacked via a connection layer.

  In order to achieve such an object, the display element of the present invention is formed by laminating a plurality of light emitting units including at least an organic light emitting layer between a cathode and an anode, and a connection layer is provided between the light emitting units. In the sandwiched display element, the structure of the connection layer is characteristic. That is, the connection layer disposed between the light emitting units includes a layer using an oxide containing at least one of an alkali metal and an alkaline earth metal (including beryllium and magnesium), a layer using a charge transporting organic material, , A layer using at least one of a triphenylene derivative and an azatriphenylene derivative is laminated from the anode side.

  Here, examples of the layer using the charge transporting organic material include a layer using an electron transporting organic material and a layer using a hole transporting organic material.

  On the other hand, as a layer using an oxide, for example, a mixed layer of the oxide and a charge transport material may be provided. Another example of the layer using an oxide may be a stacked structure in which a layer made of the oxide and a mixed layer of the oxide and a charge transport material are stacked from the anode side.

  In the display element having such a configuration, the connection layer sandwiched between the light emitting units is configured to have the above-described laminated structure, so that the initial deterioration of the light emission luminance is small as described in the following examples. It turns out that it can be suppressed.

  As described above, according to the display element of the present invention, the structure of the connection layer disposed between the light emitting units is an oxide containing at least one of alkali metal and alkaline earth metal (including beryllium and magnesium). A connection layer provided with a laminated portion obtained by laminating, from the anode side, a layer using a charge transporting organic material and a layer using at least one of a triphenylene derivative and an azatriphenylene derivative. As a result, it is possible to suppress the initial deterioration of the light emission luminance. As a result, it is possible to improve the light emission lifetime and realize long-term reliability in the display element having excellent light emission luminance by stacking the light emitting units.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In order to distinguish the display element of the present invention from a conventional display element, the stack type is called a tandem type and the charge generation layer is called a connection layer.

<First Embodiment>
FIG. 1 is a cross-sectional view illustrating a configuration example of the display element according to the first embodiment. The display element 10 shown in this figure is a tandem type display element 10 formed by laminating light emitting units, and includes an anode 13 provided on a substrate 12 and a plurality of light emitting units 14 provided so as to be stacked on the anode 13. -1, 14-2,... (Two here), the connection layer 15 provided between the light emitting units 14-1 and 14-2, and the cathode provided on the uppermost light emitting unit 14-2. 16 is provided.

  In the following description, after describing the configuration of the substrate 12, the anode 13, the light emitting units 14-1 and 14-2, and the cathode 16, the configuration of the connection layer 15 that is a feature of the present invention will be described. Further, here, in the connection layer 15, the light emitted when the holes injected from the anode 13 and the electrons generated in the connection layer 15 are combined in the light emitting unit 14-1 and the electrons injected from the cathode 16 at the same time. A structure of a display device of a top emission type that takes out light emitted when the generated holes are combined in the light emitting unit 14-2 from the cathode 16 side opposite to the substrate 12 will be described.

  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), oxidation Use an alloy of tin (SnO ₂ ) and antimony (Sb), an alloy of zinc oxide (ZnO) and aluminum (Al), or an oxide of these metals or alloys alone or in a mixed state. Can do.

  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, for example, an electrode containing Al, Ag, or the like as a component is preferably used. 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 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 hole-transporting light-emitting layer 14c 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 dye, or a triphenylamine derivative. It is formed by co-deposition of trace molecules.

  Further, 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.

  Next, the cathode 16 provided on the uppermost light emitting unit 14-2 has a three-layer structure in which a first layer 16a, a second layer 16b, and in some cases a third layer 16c are laminated in order from the anode 13 side. It is configured.

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), and Li ₂ SiO which is a silicate. ₃ Furthermore, a mixture of these oxides can be used. Further, the first layer 16a is not limited to such a material. For example, alkaline earth metals such as calcium (Ca), barium (Ba), magnesium (Mg), lithium (Li), cesium (Cs ) And the like, and may be stabilized as a film quality by adding a metal such as indium (In) or silver (Ag). Furthermore, oxides of these metals may be used alone or with these metals and You may use it, improving stability as a mixture and alloy of an oxide.

  The second layer 16b is composed of an electrode containing an alkaline earth metal typified by MgAg, 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 long-life 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.

  Next, the structure of the connection layer 15 that is a feature of the present invention will be described.

  The connection layer 15 is sandwiched between the light emitting units 14-1 and 14-2. In the first embodiment, the connection layer 15 has a three-layer structure, for example, and the oxide layer sequentially from the anode 13 side. The inclusion layer 15a, the charge transporting organic material layer 15b, and the triphenylene layer 15c are laminated.

  Among these, the oxide containing layer 15a is configured using an oxide containing at least one of an alkali metal and an alkaline earth metal (including beryllium and magnesium). Here, the alkali metal is Li, Na, K, Rb, Cs, Fr, and the alkaline earth metal includes beryllium (Be) and magnesium (Mg), Be, Mg, Ca, Sr, Ba , Ra.

The oxide constituting the oxide-containing layer 15a includes a composite containing other elements together with at least one of alkali metal and alkaline earth metal in addition to general alkali metal oxide and alkaline earth metal oxide. An oxide 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.

  Examples of the oxide-containing layer 15a using such an oxide include the layer structures shown in FIGS. 2 (1) to 2 (4).

That is, as shown in FIG. 2A, the oxide-containing layer 15a may have a single-layer structure of “mixed layer 15-1” in which the oxide and the charge transport material described above are mixed. In this case, a hole transport material or an electron transport material is used as the charge transport material constituting the mixed layer together with the above-described oxide. As such an oxide-containing layer 15a, for example, Li ₂ CO ₃ among the above-described oxides is used as a main component, and as a hopping site for holes and electrons (charges), for example, charges such as hole transport materials and electron transport materials A mixed layer formed by co-evaporating a transporting organic material together with the above-described oxide (for example, Li ₂ CO ₃ ) may be used.

  As shown in FIG. 2B, the oxide-containing layer 15a includes, in order from the anode 13 side, a mixed layer 15-2 of the above-described oxide and an electron transport material, and a layer 15 made of the above-described oxide. 3 may be a laminated structure of “mixed layer 15-2 / oxide layer 15-3”.

  Further, as shown in FIG. 2 (3), the oxide-containing layer 15a includes, in order from the anode 13 side, a layer 15-3 made of the oxide described above, and a mixed layer 15 of the oxide and hole transport layer described above. 4 may be an “oxide layer 15-3 / mixed layer 15-4” structure. 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. This is because it can be expected that the charge transporting property is higher than that of the arylamine material. This configuration is combined with the configuration of FIG. 2 (2), and “a mixed layer including an electron transporting organic material layer / oxide layer / a mixed layer including a hole transporting organic material layer” in order from the anode 13 side. You may comprise the organic substance content layer 15a.

  Furthermore, as shown in FIG. 2 (4), the oxide-containing layer 15a includes, in order from the anode 13 side, the layer 15-3 made of the above-described oxide and the layer 15 made of another oxide or composite oxide. 5 may be a laminated structure of “oxide layer 15-3 / other oxide layer 15-5”. In this case, as the other oxide layer 15-5, an oxide or a composite oxide is used, such as metaborate, tetraborate, germane oxide, molybdenum oxide, niobium oxide, silicate, 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 Other general oxides or composite oxides such as oxides, tellurium oxides, tellurium oxides, bismuth oxides, tetraborate oxides, metaborate oxides are exemplified.

  The charge transporting organic material layer 15b provided on the oxide-containing layer 15a is made of an electron transporting organic material, a hole transporting organic material, or a both charge transporting organic material. In particular, the charge transporting organic material layer 15b does not include an additive component such as a metal material or a material having a strong electron withdrawing property, and is made of only an electron transporting organic material or a layer made of only a hole transporting organic material. In some cases, it may be preferable to use as a mixed layer with at least one of an alkali metal and an alkaline earth metal.

  Examples of the electron transporting organic material constituting the charge transporting organic material layer 15b are shown in the following Table 1-1 to Table 1-5.

  Further, as the hole transporting organic material constituting the charge transporting organic material layer 15b, organic materials represented by the following general formula (2) and the following general formula (3) are used.

A _{3 to} A ₆ in the general formula (2) each independently represent an aromatic hydrocarbon having 6 to 20 carbon atoms. These aromatic hydrocarbons may be unsubstituted or have a substituent. Examples of the substituent include hydrogen, halogen, hydroxyl group, aldehyde group, carbonyl group, carbonyl ester group, alkyl group, alkenyl group, cyclic alkyl group, alkoxy group, aryl group, amino group, heterocyclic group, cyano group, and nitrile. Selected from a group, a nitro group, or a silyl group. Y in the general formula (2) represents an aromatic hydrocarbon, which is selected from benzene, naphthalene, anthracene, phenanthrene, naphthacene, fluoranthene, and perylene. Moreover, m in General formula (2) shows an integer greater than or equal to 1.

A _{7 to} A ₁₂ in the general formula (3) each independently represent an aromatic hydrocarbon having 6 to 20 carbon atoms. These aromatic hydrocarbons may be unsubstituted or have a substituent. Examples of the substituent include hydrogen, halogen, hydroxyl group, aldehyde group, carbonyl group, carbonyl ester group, alkyl group, alkenyl group, cyclic alkyl group, alkoxy group, aryl group, amino group, heterocyclic group, cyano group, and nitrile. Selected from a group, a nitro group, or a silyl group. In the general formula (3), Z _{1 to} Z ₃ represent aromatic hydrocarbons and are selected from benzene, naphthalene, anthracene, phenanthrene, naphthacene, fluoranthene, and perylene. Moreover, p, q, and r in General formula (3) show an integer greater than or equal to 1.

Typical examples of the hole transporting organic material represented by the general formula (2) as described above are shown in the following compounds (2) -1 to (2) -80 in Table 2-1 to Table 2-2. . However, the skeleton of Y in the general formula (2), the molecular skeleton of A ₃ to A ₆ , symmetry, and types of substituents are not limited to those shown below.

Typical examples of the hole transporting organic material represented by the general formula (3) are shown in the following compounds (2) -81 to (2) -95 in Table 2-3. However, the skeleton of Z in the general formula (3), the molecular skeleton of A _{7 to} A ₁₂ , symmetry, and types of substituents are not limited to those shown below.

  The electron transporting organic material and the hole transporting organic material constituting the charge transporting organic material layer 15b are not limited to the skeletons shown in Tables 1 and 2 above, and have electron transporting properties. The effect is widely recognized if it is a material or a material having hole transportability.

  Next, the triphenylene layer 15c provided on the charge transporting organic material layer 15b described above is configured using at least one of a triphenylene derivative and an azatriphenylene derivative represented by the following general formula (1). . The triphenylene derivative is a compound having a mother skeleton composed of only carbon, and the azatriphenylene derivative is a compound having a mother skeleton composed of azatriphenylene skeleton containing nitrogen in the triphenylene skeleton.

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 triphenylene derivative or azatriphenylene derivative represented by the general formula (1) include compounds (3) -1 to (3) -66 shown in the following Table 3-1 to Table 3-7. In these formulas, [Me] represents methyl (CH ₃ ), and [Et] represents ethyl (C ₂ H ₅ ). Further, among the compounds (3) -63 to (3) -66, among R ^{1 to} R ⁶ in the general formula (1), adjacent R ^m (m = 1 to 6) are bonded to each other through a cyclic structure. An example of an organic compound is shown.

  Here, the triphenylene layer 15c is configured by combining at least one or more of the triphenylene derivatives and azatriphenylene derivatives exemplified above. In addition to the triphenylene derivative and azatriphenylene derivative, the triphenylene layer 15c includes aromatic amines represented by the general formula (2) or the general formula (3), specifically, Tables 2-1 and 2 above. -2 and aromatic amines exemplified in Table 2-3 may be contained.

  Note that the connection layer 15 described above and each layer stacked on the interface thereof are not necessarily limited to a clearly separated configuration, and respective constituent materials may be mixed at the interface of each layer.

  For example, if it is the connection layer 15, each layer 15a, 15b, 15c is not necessarily limited to the structure separated clearly, The material which comprises the charge transportable material layer 15b in the oxide containing layer 15a May be contained or vice versa. Furthermore, on the interface side of the charge transporting organic material layer 15b, a mixed layer with the material constituting the upper and lower layers of the charge transporting organic material layer 15b may be provided.

  Moreover, when the organic compound layer 15c in the connection layer 15 is configured using the organic compound represented by the general formula (1), the organic compound layer 15c may also serve as the hole injection layer 14a. In this case, the hole injection layer 14 a is not necessarily provided in the light emitting unit 14-2 provided on the cathode 16 side with respect to the connection layer 15.

According to the display element 10 including the connection layer 15 having the above-described configuration, an oxidation mainly composed of an alkali metal such as Li ₂ CO ₃ or an alkaline earth metal is provided between the light emitting units 14-1 and 14-2. By sandwiching the connection layer 15 in which the material-containing layer 15a and the charge transporting organic material 15b such as an electron transport material or a hole transport material are stacked, as described in the next embodiment, Electron injection efficiency into the light emitting unit 14-1 on the anode 13 side is improved, or stability against driving is improved by suppressing deterioration due to the interaction between the oxide-containing layer 15a and the triphenylene layer 15c. The Therefore, stabilization of the tandem display element 10 formed by stacking the light emitting units 14-1 and 14-2 via the connection layer 15 is achieved.

  In particular, in the configuration in which the electron transporting charge transporting organic material layer 15b is sandwiched between the oxide-containing layer 15a described above and a system organic material such as the triphenylene layer 15c, the driving stability of the connection layer 15 is achieved. It has been found that the improvement effect of the tandem display element 10 is great and the effect of stabilizing the tandem display element 10 is also great.

  However, by using the electron transport layer made of the electron transport material according to the present invention as the layer structure of the intrinsic connection layer, N-stage N times efficiency can be obtained in the tandem type element, and also in terms of life. Initial deterioration can be suppressed, and an element having a long life can be obtained.

As a result, in the tandem 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 connection layer 15 having such excellent charge injection characteristics is formed by using a stable material, it is not necessary to perform film formation in consideration of the stoichiometric ratio in the production. Can be produced. In addition, the driving voltage can be suppressed as compared with the case of using a general connection layer made of V ₂ O ₅ , thereby improving long-term reliability.

  Further, in the display element 10 of the first embodiment, the charge transporting organic material layer 15b constituting the connection layer 15 does not contain an additive and is composed of only an electron transporting material or a hole transporting material. From this, it is possible to stabilize the connection layer 15 as compared with the case where N-type and P-type doped layers are used, and it is possible to extend the life of the display element.

  In the embodiment described above, the case where the connection layer 15 has a three-layer structure in which the oxide-containing layer 15a, the charge transporting organic material layer 15b, and the triphenylene layer 15c are stacked has been described. However, the connection layer 15 sandwiched between the light emitting units 14-1 and 14-2 is a layer made of a hole injecting material having a phthalocyanine skeleton such as copper phthalocyanine (CuPc) at the cathode 16 side interface. May be provided as an intermediate anode layer (intermediate anode layer). Thereby, the efficiency of hole injection from the connection layer 15 into the light emitting unit 14-2 provided on the cathode 16 side of the connection layer 15 can be increased.

Further, instead of the triphenylene layer 15c, may be configured with V ₂ O ₅ is a connection layer described in JP 2003-272860 and JP 2003-45676 Patent.

<Other embodiments>
The display element of the first embodiment 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 by taking the display element of FIG. 1 described in the first embodiment as an example.

  First, FIG. 3 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. 4 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. 5 shows a 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. 6 shows another display element 10d in the case where the display element (10) described in the first embodiment is “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.

  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 these Examples 1-24, each display element 10 of 1st Embodiment demonstrated using FIG. 1 was produced. At this time, the connection layer 15 is configured as shown in Table 4 below. In Examples 1 to 12, an electron transporting material is used as the charge transporting organic material layer 15b in the connection layer 15, and in Examples 13 to 24. A hole transporting material was used as the charge transporting organic material layer 15 b in the connection layer 15. Hereinafter, first, a procedure for manufacturing display elements of Examples 1 to 24 will be described with reference to Table 4 below.

<Examples 1 to 10>
A silver alloy is formed as an anode 13 on a substrate 12 made of a 30 mm × 30 mm glass plate, ITO (film thickness is about 10 nm) is formed as a protective layer and hole injection electrode, and light emission of 2 mm × 2 mm is performed by SiO ₂ vapor deposition. A top emission evaluation substrate for an organic electroluminescence device in which the region other than the region was masked with an insulating film (not shown) was produced.

  Next, as a hole injection layer 14a constituting the light emitting unit 14-1 of the first layer, a hole injection material made of a triphenylene derivative: Compound (3) -10 (see Table 3-1) is formed to 11 nm by vacuum evaporation. The film was formed with a film thickness of (deposition rate 0.2 to 0.4 nm / sec).

Next, as the hole transport layer 14b, the following α-NPD (Bis [N- (1-naphthyl) -N-phenyl] bendizine) is 11 nm (deposition rate 0.2 to 0.4 nm / sec) by vacuum deposition. It was formed with a film thickness.

Further, as the light-emitting layer 14c, the following ADN is used as a host, BD-052x (Idemitsu Kosan Co., Ltd .: trade name) is used as a dopant, and these materials are 28 nm so that the film thickness ratio is 5% by vacuum deposition. The total film thickness was formed.

Finally, as the electron transport layer 14d, the following Alq3 [Tris (8-hydroxyquinolinato) aluminum (III)] was deposited by vacuum deposition to a thickness of 10 nm.

After forming the first light emitting unit 14-1 as described above, the materials shown in Table 4 below were sequentially deposited as the oxide-containing layer 15a, the charge transporting organic material layer 15b, and the triphenylene layer 15c. Thus, the connection layer 15 was formed.

For example, in Example 1, as the oxide-containing layer 15a, Li ₂ CO ₃ was formed to a thickness of 0.3 nm, and then the electron transporting charge transporting organic material layer 15b was compound (1) -1 Was formed with a film thickness of 5 nm, and finally, the compound (3) -10 was formed with a film thickness of 60 nm as the triphenylene layer 15c. Also in Examples 2 to 10, the materials shown in Table 4 were formed by vapor deposition with the same film thickness as in Example 1.

  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 cathode 16 having a two-layer structure was formed with a thickness of 10 nm by the method. Thereby, the top emission type display element 10 was produced.

<Example 11>
Example 1 except that Li ₂ CO ₃ and compound (1) -1 were co-deposited as the oxide-containing layer 15a in the production procedure of Example 1 to form an oxide-containing layer 15a composed of a mixed layer. As well as. The composition ratio of the oxide-containing layer 15a made of a mixed layer was Li ₂ CO ₃ : compound (1) -1 = 4: 1 (film thickness ratio), and was formed to a thickness of 3 nm. The charge transporting organic material layer 15b made of the compound (1) -1 was formed with a thickness of 2 nm.

<Example 12>
In the manufacturing procedure of Example 1, as the charge transporting organic material layer 15b, the compound (1) -1 was formed with a film thickness of 3 nm, and then the mixed layer of the compound (1) -1 and the compound (3) -10 Was performed in the same manner as in Example 1 except that the charge transporting organic material layer 15b having a two-layer structure was formed. The composition ratio of compound (1) -1 and compound (3) -10 in the mixed layer was 1: 1 (film thickness ratio).

<Examples 13 to 22>
In the formation of the connection layer 15 in the manufacturing procedure of Example 1, the materials shown in Table 4 above were sequentially deposited as the oxide-containing layer 15a, the charge transporting organic material layer 15b, and the triphenylene layer 15c, whereby the connection layer 15 Formed. Except this, the same procedure as in Example 1 was performed.

For example, in Example 13, as the oxide-containing layer 15a, Li ₂ CO ₃ was formed to a thickness of 0.3 nm, and then the hole transporting charge transporting organic material layer 15b was compound (2) -34. Was formed to a thickness of 2.5 nm, and finally the compound (3) -10 was formed to a thickness of 62.5 nm as the triphenylene layer 15c. Also in Examples 14 to 22, the materials shown in Table 4 were vapor-deposited with the same film thickness as in Example 13.

<Example 23>
Example 13 except that Li ₂ CO ₃ and compound (2) -34 were co-deposited as the oxide-containing layer 15a in the production procedure of Example 13 to form the oxide-containing layer 15a composed of a mixed layer. As well as. The composition ratio of the oxide-containing layer 15a made of the mixed layer was Li ₂ CO ₃ : compound (2) -34 = 4: 1 (film thickness ratio), and was formed to a thickness of 3 nm. The charge transporting organic material layer 15b made of the compound (2) -34 was formed to a thickness of 2 nm.

<Example 24>
In the production procedure of Example 13, as the charge transporting organic material layer 15b, the compound (2) -34 was formed to a thickness of 3 nm, and then a mixed layer of the compound (2) -34 and the compound (3) -10 Was performed in the same manner as in Example 13 except that the charge transporting organic material layer 15b having a two-layer structure was formed. The composition ratio of compound (2) -34 and compound (3) -10 in the mixed layer was 1: 1 (film thickness ratio).

<Comparative Example 1>
In the manufacturing procedure of Example 1, the formation of the connection layer 15 was carried out except that the electrotransport organic material layer 15b was not formed and the connection layer 15 having a laminated structure of the oxide-containing layer 15a and the triphenylene layer 15c was used. Performed as in Example 1.

<Comparative Example 2>
In the production procedure of Example 1, in the formation of the connection layer 15, a connection layer having a configuration in which the LiF layer, the mixed layer of Alq3 and Mg, and the layer made of the compound (3) -10 are stacked in this order is formed. did.

<Comparative Example 3>
In Comparative Example 3, in the manufacturing procedure of Example 1, the cathode 16 was directly formed on the light emitting unit 14-1 of the first layer, and a display unit having a one-unit configuration that was not a tandem type was manufactured.

≪Evaluation results≫
Table 4 also shows the luminous efficiency (Quantum Yield: Q / Y) of the display elements manufactured in Examples 1 to 12, 13 to 24, and Comparative Examples 1 to 3. From this result, the light emission efficiency in the display elements of Examples 1 to 24 is approximately twice the efficiency of the display element having a one-unit configuration of Comparative Example 3, and the effect of forming the tandem type by stacking the light emission units in two layers. It was confirmed that In the case of a tandem type element, it is predicted that the luminous efficiency will be doubled by stacking the light emitting units in two stages. In Examples 1 to 24, these ideally close elements are used. It was confirmed that it could be configured. In Comparative Examples 1 and 2, the luminous efficiency is approximately doubled, and the effect of the tandem type is obtained.

  In (a) to (h) in Table 5 below, initial 100 hours at room temperature (30 ° C.) and high temperature (60 ° C.) of Examples 1 and 13 and Comparative Examples 1 to 3 prepared as described above ( 100h), relative luminance and driving voltage after steady 800 hours (800h) driving. The driving condition at room temperature was a constant current driving of 70 mA / cm 2, and the driving condition at a high temperature was a constant current driving of 20 mA / cm 2.

(A) Relative luminance (30 ° C, 100h)
In Examples 1 and 13 including the connection layer 15 having the stacked structure of the present invention, the initial (100 h) luminance reduction is clearly improved as compared with Comparative Example 1 including no connection layer having such a stacked structure. It was confirmed that it was closer to Comparative Example 3 having a one-unit configuration. In particular, in Example 1 in which an electron transporting material is used as the charge transporting organic material layer 15b of the connection layer 15, the initial luminance reduction is improved as compared with Comparative Example 2, and the charge transporting organic material is improved. The effect of using an electron transporting material as the material layer 15b was confirmed.

(B) Relative luminance (30 ° C, 800h)
The results of Example 1 and Example 13 including the connection layer 15 having the laminated structure of the present invention are clearly suppressed from deterioration as compared with Comparative Examples 1 and 2 that do not include the connection layer having such a stacked structure. Thus, the effect of improving the long-term reliability by the configuration of the present invention was confirmed. Moreover, since the comparative example 2 in which the initial deterioration at 100 h was relatively small deteriorated most after 800 h, it was suggested that the structure of the comparative example 2 had a fast steady deterioration rate. On the other hand, it was confirmed that Example 1 and Example 13 have a slow steady deterioration rate and are excellent in long-term reliability.

(C) (d) Drive voltage (30 ° C., 100 h, 800 h)
The change with time of the drive voltage in Example 1 and Example 13 including the connection layer 15 having the laminated structure of the present invention was larger than that in Comparative Example 3 having a one-unit structure. However, as compared with Comparative Example 1, it was confirmed that the drive voltage increase was clearly suppressed.

(E) (f) Relative luminance (60 ° C., 100 h, 800 h)
It was confirmed that the luminance deterioration at high temperatures of Example 1 and Example 13 having the configuration of the present invention was clearly suppressed as compared with Comparative Example 1 and Comparative Example 2.

(G) (h) Driving voltage (60 ° C., 100 h, 800 h)
The voltage increase at high temperature of Example 1 provided with the connection layer 15 having the laminated structure of the present invention is obviously smaller than those of Comparative Example 1, Comparative Example 2 and Comparative Example 3. This suggests that the structure has excellent driving stability at high temperatures. On the other hand, the voltage increase at room temperature and high temperature in Example 13 was larger than that in Comparative Example 1, Comparative Example 2, and Comparative Example 3, but the brightness considered to be the most important is shown in FIG. Deterioration suppression has been achieved.

  In Examples 2 to 12, the relative luminance change at room temperature and high temperature and the drive voltage increase are the same tendency as in Example 1 for both 100 h and 800 h, and the connection layer having the configuration of the present invention is used. The effect was obvious.

  Further, in Examples 14 to 24, the relative luminance change at room temperature and high temperature and the drive voltage increase were the same as in Example 13 for both 100 h and 800 h.

  In FIG. 7, the life curve of Example 1 is shown with the life curve of Comparative Examples 1-3. FIG. 8 shows the life curve of Example 13 together with the life curves of Comparative Examples 1 to 3. Also from these results, it is clear that Comparative Example 1 has a large initial deterioration of the relative luminance, and Example 1 and Example 13 improve this.

  In FIG. 9, the relative voltage change of Example 1 is shown with the relative voltage change of Comparative Examples 1-3. FIG. 10 shows the relative voltage change of Example 13 together with the relative voltage changes of Comparative Examples 1 to 3. From these results, it is clear that the voltage increase is particularly improved in Example 1 using the electron transporting material as the charge transporting organic material layer in the connection layer 15 as compared with Comparative Example 1.

It is a schematic sectional drawing which shows the structure of the display element of 1st Embodiment. It is sectional drawing which shows the structural example of the oxide content layer of the connection layer in the display element of 1st 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 time-dependent change (life curve) of the relative luminance in the display element of Example 1 and Comparative Examples 1-3. It is a graph which shows the time-dependent change (life curve) of the relative luminance in the display element of Example 13 and Comparative Examples 1-3. It is a graph which shows the time change of the relative voltage in the display element of Example 1 and Comparative Examples 1-3. It is a graph which shows the time change of the relative voltage in the display element of Example 13 and Comparative Examples 1-3. It is sectional drawing of the conventional display element. It is sectional drawing which shows the other structure of the conventional display element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Display element, 13 ... Anode, 14c ... Organic light emitting layer, 14-1, 14-2 ... Light emitting unit, 15 ... Connection layer, 15a ... Oxide containing layer, 15b ... Charge transporting organic material layer, 15-1 , 15-2, 15-4 ... mixed layer, 15c ... triphenylene layer, 16 ... cathode

Claims (13)

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 connection layer is sandwiched between the light emitting units,
The connection layer includes a layer using an oxide containing at least one of an alkali metal and an alkaline earth metal (including beryllium and magnesium), a layer using a charge transporting organic material, a triphenylene derivative, and an azatriphenylene derivative. A display element comprising: a laminated portion in which a layer using at least one of them is laminated in this order from the anode side. The display element according to claim 1,
The display element, wherein the charge transporting organic material constituting the connection layer is an electron transporting organic material. The display element according to claim 2, wherein
The layer using the charge transporting organic material is composed of only an electron transporting organic material. The display element according to claim 1,
The charge transporting organic material constituting the connection layer is a hole transporting organic material. The display element according to claim 4, wherein
The layer using the charge transporting organic material is made of only a hole transporting organic material. The display element according to claim 1,
The layer using the oxide includes a mixed layer of the oxide and a charge transport material. The display element according to claim 6.
The layer using the oxide has a stacked structure in which a mixed layer of the oxide and an electron transport material and a layer made of the oxide are stacked from the anode side. . The display element according to claim 6.
The display element characterized in that the layer using the oxide has a stacked structure in which a layer made of the oxide and a mixed layer of the oxide and a hole transport material are stacked from the anode side. . The display element according to claim 6.
The total proportion of the alkali metal and alkaline earth metal constituting the oxide in the mixed layer is 50% or less in relative film thickness ratio. The display element according to claim 1,
The layer using the oxide constitutes the interface layer on the anode side in the connection layer. The display element according to claim 1,
The display element, wherein the oxide is at least one selected from Li ₂ SiO ₃ , Li ₂ CO ₃ , Cs ₂ CO ₃ , Li ₂ WO ₄ , and SrO. The display element according to claim 1,
The connection layer is characterized in that a layer using at least one of a triphenylene derivative and an azatriphenylene derivative represented by the following general formula (1) is provided on the cathode side in the layer using the charge transporting organic material. Display element to be used.

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 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, and adjacent R ^m (m = 1 to 6) may be bonded to each other through a ring structure. X ^{1 to} X ⁶ are each independently a carbon or nitrogen atom. The display element according to claim 12,
A display element, wherein a layer using at least one of the triphenylene derivative and the azatriphenylene derivative constitutes an interface layer on the cathode side in the connection layer.

Images