JP2007299766A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an organic EL element easily adaptable to a complex display pattern, a large-screen display, a high-luminance drive or a drive at a high duty ratio, with wiring resistance lowered of a hole injection electrode. <P>SOLUTION: The organic EL element is provided with a hole injection electrode, an electron injection electrode, and a kind or more of organic layers fitted between these electrodes, of which, the hole injection electrode is to be equipped with a transparent electrode at a light-emitting part, as well as a metal electrode with a sheet resistance of 1 Ω/Square at a part other than the light-emitting part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL device using an organic compound, and more particularly to an improvement of a hole injection electrode for supplying holes (charges) to a light emitting layer.

In recent years, organic EL elements have been actively studied. This is because a hole transport material such as triphenyldiamine (TPD) is deposited on the hole injection electrode as a thin film, a fluorescent material such as an aluminum quinolinol complex (Alq3) is laminated as a light emitting layer, and a work function such as Mg is further formed. It is an element having a basic configuration in which a small metal electrode (electron injection electrode) is formed, and has attracted attention because it can obtain extremely high luminance of several hundreds to several 10,000 cd / m ² at a voltage of about 10V.

  As a material used as a hole injection electrode of such an organic EL element, it is considered effective to inject many holes into a light emitting layer, a hole injection transport layer, or the like. In addition, the light emitting light is usually extracted from the substrate side, and it is necessary to be a transparent conductive material.

As such transparent electrodes, ITO (tin-doped indium oxide), IZO (zinc-doped indium oxide), ZnO, SnO ₂ , In ₂ O _{3 and the} like are known. In particular, ITO electrodes are widely used as transparent electrodes for liquid crystal displays (LCDs), light control glasses, solar cells, etc., as transparent electrodes that have a visible light transmittance of 90% or more and a sheet resistance of 10Ω / □ or less. It is also considered promising as a hole injection electrode for organic EL elements.

By the way, the organic EL element requires a predetermined light emission current, and the light emission luminance increases in proportion to the current density. For this reason, even in the hole injection electrode, if the wiring length is short, the wiring resistance that can be ignored can be realized with a complicated display pattern, a large screen display, or driving with high brightness and high duty ratio. In this case, a voltage drop at the hole injection electrode becomes a problem. That is, for example, the display of the horizontal 256 dots × 64 dots, the case of driving the light emitting luminance of 150 cd / m ^2, so that the light emission 1/64 seconds emission luminance of 150 × 64cd / m ^2. When the sheet resistance of the hole injection electrode is sufficiently small, for example, driving with a voltage value close to the effective applied voltage shown in FIG. 15 is possible. However, when the resistance of the hole injection electrode is about 260Ω, the same applies. As shown by the applied voltage in the figure, the drive voltage must be as high as 2V. Further, even if the sheet resistance is about 7-8Ω / □, such as low resistance ITO, a resistance of 64 × 7 = 448Ω exists only in the pixel portion of 64 dots. The voltage drop is a big problem.

  An object of the present invention is to reduce the wiring resistance of the hole injection electrode, and to realize an organic EL element that can easily cope with a complicated display pattern, a large screen display, or a drive with high luminance or a high duty ratio. That is.

The object is achieved by the following configurations (1) to (3).
(1) having a hole injection electrode, an electron injection electrode, and one or more organic layers provided between these electrodes;
The hole injection electrode has a transparent electrode in a portion including a light emitting portion, and is disposed in a portion other than the light emitting portion, and has a metal electrode having a sheet resistance of 1Ω / □ or less connected to the transparent electrode,
An organic EL element in which an insulating film is formed so as to cover a portion other than the light emitting portion of the transparent electrode and the metal electrode.
(2) The organic EL element according to (1), wherein an element isolation structure is formed on the insulating film.
(3) The organic EL element according to (2), wherein the element isolation structure has a width narrower than that of the insulating film.

  As described above, according to the present invention, the wiring resistance of the hole injection electrode is lowered, and an organic EL that can easily cope with a complicated display pattern, a large-screen display, or a drive with high luminance or a high duty ratio. An element can be realized.

  Hereinafter, a specific configuration of the present invention will be described in detail. The organic EL device of the present invention has a hole injection electrode, an electron injection electrode, and one or more organic layers provided between these electrodes, and the hole injection electrode has a transparent electrode in the light emitting portion. And a metal electrode having a sheet resistance of 1 Ω / □ or less that is disposed in a portion other than the light emitting portion and electrically connected to the transparent electrode. As described above, the transparent electrode is provided in the light emitting portion that needs light extraction, and the metal electrode having a low sheet resistance is provided in the non-light emitting portion that does not require light extraction, so that the resistance value of the entire hole injection electrode is kept low. be able to.

  The transparent electrode is provided at least in the light emitting part (pixel part). Here, the light emitting portion refers to a region where light can be emitted by the light emitting layer, and the emitted light can be taken out and used. The transparent electrode may exist to some extent other than the light emitting part, for example, around the light emitting part. However, if the area of the transparent electrode is increased more than necessary, the resistance of the hole injection electrode is increased, and thus light emission is caused. It is preferable that the area be equal to or close to the area.

Examples of the transparent electrode include ITO (tin-doped indium oxide), IZO (zinc-doped indium oxide), ZnO, SnO ₂ , In ₂ O _{3 and the} like, but preferably ITO (tin-doped indium oxide), IZO (zinc-doped). Indium oxide) is preferred. The mixing ratio of SnO ₂ to In ₂ O ₃ is preferably 1 to 20% in wt%, and more preferably 5 to 12%. The mixing ratio of ZnO to In ₂ O ₃ is preferably 1 to 20% by weight%, more preferably 5 to 12%. In addition, Sn, Ti, Pb and the like may be contained in an oxide form in an amount of 1 wt% or less in terms of oxide.

  The thickness of the transparent electrode is sufficient if it has a certain thickness or more that can sufficiently inject holes, and is usually in the range of 10 to 100 nm, particularly preferably in the range of 30 to 100 nm, more preferably 50 to 900 nm. By setting the film thickness to 100 nm or less, the surface roughness of the transparent electrode is reduced, the surface property of the transparent electrode is improved, and the light emission characteristics and the light emission lifetime are improved. If the thickness is too thin, there are problems in terms of film strength and hole transport capability during production.

  The metal electrode preferably has a sheet resistance of 1Ω / □ or less, particularly 0.5Ω / □ or less, and the lower limit is not particularly restricted, but is usually about 0.1Ω / □. The film thickness is preferably 10 to 2000 nm, particularly 20 to 1000 nm, and more preferably about 100 to 500 nm.

  As the material of the metal electrode, metals such as Al, Cu, Au, and Ag, or Al and Sc, Nb, Zr, Hf, Nd, Ta, Cu, Si, Cr, Mo, Mn, Ni, Pd, Pt, and W Alloys with transition elements such as Al are mentioned, and Al and Al alloys are particularly preferable. In the case of using an Al alloy, an alloy of Al and one or more transition elements is preferable. In this case, Al is 90 at% or more, preferably 95 at% or more.

  In the hole injection electrode of the present invention, it is preferable that a barrier metal layer is further provided between the transparent electrode and the metal electrode. By providing the barrier metal layer, the interface between the transparent electrode and the metal electrode is stabilized, and the contact resistance is stabilized. Examples of the constituent material of the barrier metal layer include metals such as Cr and Ti, and nitrides such as titanium nitride (TiN). Among them, Cr or TiN uses a transparent electrode such as ITO as a reagent when etching them. Since it does not invade, wet etching is possible, which is preferable. The thickness of the barrier metal layer is preferably 10 to 200 nm, particularly 30 to 100 nm.

The transparent electrode, metal electrode, and barrier metal layer can be formed by vapor deposition or the like, but preferably formed by sputtering. When the sputtering method is used for forming the ITO or IZO transparent electrode, a target obtained by doping In ₂ O ₃ with SnO ₂ or ZnO is preferably used. Further, when forming a metal electrode or a barrier electrode, it is preferable to use a sintered body of the above-mentioned metal or alloy, and it is preferable to form it by DC sputtering or RF sputtering. When the ITO transparent electrode is formed by sputtering, the luminance change with time is less than that of the film formed by vapor deposition. The input power is preferably in the range of 0.1 to 4 W / cm ² . In particular, the power of the DC sputtering apparatus is preferably in the range of 0.1 to 10 W / cm ² , particularly 0.2 to 5 W / cm ² . The film forming rate is preferably 2 to 100 nm / min, particularly 5 to 50 nm / min.

  The sputtering gas is not particularly limited, and an inert gas such as Ar, He, Ne, Kr, or Xe, or a mixed gas thereof may be used. The pressure during sputtering of such a sputtering gas is usually about 0.1 to 20 Pa.

  The means for providing the transparent electrode, the metal electrode, and the barrier layer in the light emitting part and the non-light emitting part are not particularly limited, but for example, a patterning method using a resist material that is usually used may be used. . Etching may be dry or wet, and the wet etching solution is preferably an aqua regia in the case of an ITO transparent electrode, and in the case of a metal electrode, a mixed solution system of phosphoric acid, nitric acid and acetic acid is used if Al, etc. It is preferable to use an etchant capable of selectively etching the metal.

  Next, a specific configuration example of the hole injection electrode of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a configuration example of a hole injection electrode according to the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A ′. The hole injection electrode in the illustrated example has an electrode structure for constituting a so-called 7-segment type display, and has a transparent electrode 2 and a metal electrode 3 on a substrate 1. The transparent electrode 2 is formed on the light emitting portion (pixel portion) of each segment, and the metal electrode is formed on the periphery and on the wiring portion to the terminal electrode. Thus, by forming a transparent electrode on the light emitting part and forming a metal electrode on the part outside the light emitting part, most of the resistance of the hole injection electrode is due to the sheet resistance component of the metal electrode, thereby reducing the resistance. Can be achieved.

  In addition, after forming the hole injection electrode, an insulating layer is formed outside the light emitting portion, and an element isolation structure is provided if necessary, and then an organic layer such as a hole injection transport layer, a light emitting layer, or an electron injection transport layer is formed. The layers are stacked, an electron injection electrode (common electrode) is formed, and a protective layer or the like is stacked as necessary to form a segment type organic EL display.

  FIGS. 3 to 12 are diagrams showing another configuration example of the hole injection electrode according to the present invention, and are schematic configuration diagrams sequentially illustrating an electrode structure for configuring a so-called simple matrix type display in a manufacturing process. 3, 5, 7, 9 and 11 are plan views, and FIGS. 4, 6, 8, 10 and 12 are BB ′ or C− corresponding to FIGS. 3, 5, 7, 9 and 11, respectively. FIG.

  First, as shown in FIGS. 3 and 4, a transparent electrode (ITO) 2 is placed on a substrate 1 (not shown on the plan view), and a normal scanning line is placed in a region that becomes a light emitting portion, that is, a pixel portion. It forms into a predetermined pattern so that it may form. Next, as shown in FIGS. 5 and 6, the metal electrode 3 is formed on a portion outside the light emitting portion so that a portion thereof covers the transparent electrode. In addition, it is also possible to reverse the process so far. Thereafter, as shown in FIGS. 7 and 8, an insulating layer 4 is formed in order to insulate other than the light emitting portion, that is, the pixel portion.

  Further, in the examples of FIGS. 9 and 8, an element isolation structure 5 having a predetermined pattern is provided in order to form an organic layer such as a light emitting layer and an electron injection electrode so that a normal data line is formed. This element isolation structure is a three-dimensional structure having an overhang portion as shown in FIG. 10, and this element isolation structure 5 and its shadowed portion when forming an organic layer or an electron injection electrode Vapor deposition or sputtered particles are deposited in a region other than the above, and the structural film for each line is separated. For details, refer to Japanese Patent Application No. 8-0147313. Next, as shown in FIGS. 11 and 12, a mask 6 is bonded together, and an organic layer, an electron injection electrode, and the like are formed into a matrix type organic EL display. The organic EL element of the present invention can have various configurations without being limited to the illustrated examples, and the number of segments, the number of pixels, their pattern, and the like may be determined as appropriate.

  Each of the organic layers may have at least one hole transport layer and a light emitting layer, an electron injection electrode thereon, and a protective electrode as an uppermost layer. The hole transport layer can be omitted. The electron injection electrode is made of a metal, a compound or an alloy having a low work function formed by vapor deposition, sputtering, or the like, preferably by sputtering.

The constituent material of the electron injection electrode to be formed is preferably a low work function substance that effectively performs electron injection. For example, K, Li, Na, Mg, La, Ce, Ca, Sr, Ba, Al, Ag, In, Sn, Zn, Zr, Cs, Er, Eu, Ga, Hf, Nd, Rb, Sc, Sm, Ta, Y, Yb, or other metal element alone, or BaO, BaS, CaO, HfC, LaB _{6, MgO, MoC, NbC,} PbS, SrO, TaC, ThC, ThO 2, ThS, TiC, TiN, UC, UN, UO 2, W 2 C, Y 2 O 3, ZrC, ZrN, compounds such as ZrO ₂ It is good to use. Alternatively, in order to improve stability, it is preferable to use a two-component or three-component alloy system containing a metal element. For example, Al.Ca (Ca: 5 to 20 at%), Al.In (In: 1 to 10 at%), Al.Li (Li: less than 0.1 to 20 at%), Al.R [R Represents a rare earth element including Y and Sc] and the like, and In.Mg (Mg: 50 to 80 at%) are preferable. Among these, Al alone, Al·Li (Li: 0.4 to 6.5 (excluding 6.5) at%) or (Li: 6.5 to 14 at%), Al · R (R : 0.1 to 25, particularly 0.5 to 20 at%), and the like are preferable because compressive stress hardly occurs. Therefore, as the sputtering target, such an electron injection electrode constituent metal or alloy is usually used. These work functions are 4.5 eV or less, and metals and alloys having a work function of 4.0 eV or less are particularly preferable.

  By using the sputtering method to form the electron injection electrode, the deposited electron injection electrode film has a relatively high kinetic energy for the sputtered atoms and atomic groups compared to the case of vapor deposition. The migration effect works and the adhesion at the organic layer interface is improved. Also, by performing pre-sputtering, the surface oxide layer can be removed in vacuum, or moisture and oxygen adsorbed on the organic layer interface can be removed by reverse sputtering, so that a clean electrode-organic layer interface and electrode can be formed. As a result, a high-quality and stable organic EL element can be obtained. As a target, an alloy having the above composition range or a metal alone may be used, and in addition to these, a target of an additive component may be used. Further, even when a mixture of materials having vastly different vapor pressures is used as a target, there is little deviation in the composition of the film to be generated and the target, and there is no restriction on the materials used due to vapor pressure or the like unlike the vapor deposition method. Further, it is not necessary to supply the material for a long time compared with the vapor deposition method, and the film thickness and film quality are excellent in uniformity, which is advantageous in terms of productivity.

  Since the electron injection electrode formed by sputtering is a dense film, the amount of moisture entering the film is very small compared to a rough deposited film, resulting in high chemical stability and a long-life organic EL device. It is done.

  The sputtering gas pressure during sputtering is preferably in the range of 0.1 to 5 Pa. By adjusting the sputtering gas pressure in this range, an AlLi alloy having a Li concentration in the above range can be easily obtained. Further, the electron injection electrode having the Li concentration gradient can be easily obtained by changing the pressure of the sputtering gas within the above range during the film formation. Moreover, it is preferable to set it as the film-forming conditions with which the product of film-forming gas pressure and the distance between substrate targets satisfies 20-65 Pa * cm.

As the sputtering gas, an inert gas used in a normal sputtering apparatus, or a reactive gas such as N ₂ , H ₂ , O ₂ , C ₂ H ₄ , NH ₃ in addition to this can be used in reactive sputtering. is there.

As the sputtering method, a high-frequency sputtering method using an RF power source or the like is possible, but the film formation rate can be easily controlled, and the DC sputtering method can be used to reduce damage to the organic EL element structure. preferable. The power of the DC sputtering apparatus is preferably in the range of 0.1 to 10 W / cm ² , particularly 0.5 to 7 W / cm ² . The film forming rate is preferably 5 to 100 nm / min, particularly preferably 10 to 50 nm / min.

  The thickness of the electron injecting electrode thin film may be a certain thickness that allows sufficient electron injection, and may be 1 nm or more, preferably 3 nm or more. Moreover, although there is no restriction | limiting in particular in the upper limit, Usually, a film thickness should just be about 3-500 nm.

  In the organic EL device of the present invention, a protective electrode may be provided on the electron injection electrode, that is, on the side opposite to the organic layer. By providing the protective electrode, the electron injection electrode is protected from the outside air, moisture, etc., the deterioration of the constituent thin film is prevented, the electron injection efficiency is stabilized, and the element life is dramatically improved. Further, this protective electrode has a very low resistance, and also has a function as a wiring electrode when the resistance of the electron injection electrode is high. This protective electrode contains one or more of Al, Al and transition metals (excluding Ti), Ti or titanium nitride (TiN), and when these are used alone, It is preferable that Al: 90-100 at%, Ti: 90-100 at%, TiN: 90-100 mol% are contained. Further, the mixing ratio when two or more kinds are used is arbitrary, but in the mixture of Al and Ti, the Ti content is preferably 10 at% or less. Moreover, you may laminate | stack the layer containing these independently. In particular, when Al, Al, and a transition metal are used as a wiring electrode described later, a good effect is obtained, and TiN has high corrosion resistance and a great effect as a sealing film. TiN may deviate by about 10% from its stoichiometric composition. Further, the alloy of Al and transition metal may be transition metal, especially Sc, Nb, Zr, Hf, Nd, Ta, Cu, Si, Cr, Mo, Mn, Ni, Pd, Pt and W, preferably these The total amount may be 10 at% or less, particularly 5 at% or less, particularly 2 at% or less. The smaller the transition metal content, the lower the thin film resistance when functioning as a wiring material.

  The thickness of the protective electrode may be a certain thickness or more in order to ensure the electron injection efficiency and prevent the ingress of moisture, oxygen or organic solvent, preferably 50 nm or more, more preferably 100 nm or more, particularly 100 to 1000 nm. A range is preferred. If the protective electrode layer is too thin, the effect of the present invention cannot be obtained, and the step coverage of the protective electrode layer is lowered, and the connection with the terminal electrode is not sufficient. On the other hand, if the protective electrode layer is too thick, the stress of the protective electrode layer increases, and the growth rate of the dark spot increases. In addition, the thickness when functioning as a wiring electrode has a high film resistance because the film thickness of the electron injection electrode is thin. When supplementing this, the thickness is usually about 100 to 500 nm, when it functions as another wiring electrode. Is about 100 to 300 nm.

  The total thickness of the electron injecting electrode and the protective electrode is not particularly limited, but is usually about 100 to 1000 nm.

After forming the electrode, in addition to the protective electrode, a protective film using an inorganic material such as SiO _X, an organic material such as Teflon (registered trademark), a fluorocarbon polymer containing chlorine, or the like may be formed. The protective film may be transparent or opaque, and the thickness of the protective film is about 50 to 1200 nm. The protective film may be formed by a general sputtering method, vapor deposition method, PECVD method or the like in addition to the reactive sputtering method described above.

  Furthermore, it is preferable to form a sealing layer on the element in order to prevent oxidation of the organic layer and electrode of the element. The sealing layer is an adhesive resin layer such as a commercially available low-hygroscopic photocurable adhesive, epoxy adhesive, silicone adhesive, cross-linked ethylene-vinyl acetate copolymer adhesive sheet, etc. in order to prevent moisture from entering. Is used to adhere and seal a sealing plate such as a glass plate. Besides a glass plate, a metal plate, a plastic plate, etc. can also be used.

  Next, the organic material layer provided in the EL element of the present invention will be described.

  The light emitting layer has a hole (hole) and electron injection function, a transport function thereof, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

  The hole injecting and transporting layer has the function of facilitating the injection of holes from the positive electrode, the function of stably transporting holes, and the function of blocking electrons. The electron injecting and transporting layer facilitates the injection of electrons from the negative electrode. , The function of transporting electrons stably and the function of blocking holes, these layers increase and confine holes and electrons injected into the light emitting layer, optimize the recombination region, Improve luminous efficiency.

  The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited and vary depending on the forming method, but are usually about 5 to 500 nm, particularly preferably 10 to 300 nm. .

  The thickness of the hole injecting and transporting layer and the thickness of the electron injecting and transporting layer may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times depending on the design of the recombination / light emitting region. When the injection layer and the transport layer for holes or electrons are separated, the injection layer is preferably 1 nm or more, and the transport layer is preferably 1 nm or more. In this case, the upper limit of the thickness of the injection layer and the transport layer is usually about 500 nm for the injection layer and about 500 nm for the transport layer. Such a film thickness is the same when two injection transport layers are provided.

  The light emitting layer of the organic EL device of the present invention contains a fluorescent material which is a compound having a light emitting function. Examples of such a fluorescent substance include at least one selected from compounds such as those disclosed in JP-A 63-264692, such as quinacridone, rubrene, and styryl dyes. Further, quinoline derivatives such as metal complex dyes having 8-quinolinol or a derivative thereof such as tris (8-quinolinolato) aluminum as a ligand, tetraphenylbutadiene, anthracene, perylene, coronene, 12-phthaloperinone derivatives, and the like can be given. Furthermore, a phenylanthracene derivative of Japanese Patent Application No. 6-110568, a tetraarylethene derivative of Japanese Patent Application No. 6-114456, and the like can be used.

  Further, it is preferably used in combination with a host material capable of emitting light by itself, and is preferably used as a dopant. In such a case, the content of the compound in the light emitting layer is preferably 0.01 to 10 wt%, more preferably 0.1 to 5 wt%. When used in combination with a host material, the emission wavelength characteristic of the host material can be changed, light emission shifted to a longer wavelength can be achieved, and the light emission efficiency and stability of the device can be improved.

  The host material is preferably a quinolinolato complex, and more preferably an aluminum complex having 8-quinolinol or a derivative thereof as a ligand. Examples of such aluminum complexes are those disclosed in JP-A-63-264692, JP-A-3-255190, JP-A-5-70733, JP-A-5-258859, JP-A-6-215874, and the like. Can be mentioned.

  Specifically, first, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis (benzo {f} -8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) aluminum oxide, tris (8-quinolinolato) indium, tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-8-quinolinolato) gallium, bis (5-chloro-8-quinolinolato) calcium, 5,7-dichloro-8-quinolinolato aluminum, tris (5,7-dibromo-8-hydroxyquinolinolato) aluminum, poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane], Etc.

  In addition to 8-quinolinol or a derivative thereof, an aluminum complex having another ligand may be used, and examples thereof include bis (2-methyl-8-quinolinolato) (phenolato) aluminum (III). Bis (2-methyl-8-quinolinolato) (ortho-cresolato) aluminum (III), bis (2-methyl-8-quinolinolato) (meta-cresolato) aluminum (III), bis (2-methyl-8-quinolinolato) ( Para-cresolato) aluminum (III), bis (2-methyl-8-quinolinolato) (ortho-phenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (meta-phenylphenolato) aluminum ( III), bis (2-methyl-8-quinolinolato) (para-phenylphenolato) aluminum (III), bis ( -Methyl-8-quinolinolato) (2,3-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,6-dimethylphenolato) aluminum (III), bis (2-methyl) -8-quinolinolato) (3,4-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2-methyl-8) -Quinolinolato) (3,5-di-tert-butylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,6-diphenylphenolato) aluminum (III), bis (2-methyl) -8-quinolinolato) (2,4,6-triphenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,3,6-trimethylphenola) ) Aluminum (III), bis (2-methyl-8-quinolinolato) (2,3,5,6-tetramethylphenolato) Aluminum (III), bis (2-methyl-8-quinolinolato) (1-naphtholato) Aluminum (III), bis (2-methyl-8-quinolinolato) (2-naphtholato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) (ortho-phenylphenolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) (para-phenylphenolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) (meta-phenylphenolato) aluminum (III), bis (2 , 4-Dimethyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) (3 -Di-tert-butylphenolato) aluminum (III), bis (2-methyl-4-ethyl-8-quinolinolato) (para-cresolato) aluminum (III), bis (2-methyl-4-methoxy-8- Quinolinolato) (para-phenylphenolato) aluminum (III), bis (2-methyl-5-cyano-8-quinolinolato) (ortho-cresolato) aluminum (III), bis (2-methyl-6-trifluoromethyl-) 8-quinolinolato) (2-naphtholato) aluminum (III) and the like.

  In addition, bis (2-methyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (2-methyl-8-quinolinolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (2,4-dimethyl-8-quinolinolato) aluminum (III), bis (4-ethyl-2-methyl-8-quinolinolato) aluminum (III) -μ-oxo-bis ( 4-ethyl-2-methyl-8-quinolinolato) aluminum (III), bis (2-methyl-4-methoxyquinolinolato) aluminum (III) -μ-oxo-bis (2-methyl-4-methoxyquinolino) Lato) aluminum (III), bis (5-cyano-2-methyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (5-cyano-2-methyl-8-quinolinolato) a Luminium (III), bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) Etc.

  As other host substances, a phenylanthracene derivative described in Japanese Patent Application No. 6-110568 and a tetraarylethene derivative described in Japanese Patent Application No. 6-114456 are also preferable.

  The light emitting layer may also serve as an electron injecting and transporting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. What is necessary is just to vapor-deposit these fluorescent substances.

  Further, if necessary, the light emitting layer is preferably a mixed layer of at least one kind of hole injecting and transporting compound and at least one kind of electron injecting and transporting compound, and a dopant is contained in the mixed layer. Is preferred. The content of the compound in such a mixed layer is preferably 0.01 to 20 wt%, more preferably 0.1 to 15 wt%.

  In the mixed layer, a carrier hopping conduction path can be formed, so that each carrier moves in a material that is dominant in polarity, carrier injection of the opposite polarity is less likely to occur, the organic compound is less likely to be damaged, and the device life is shortened. Although there is an advantage of extending, by including the above-mentioned dopant in such a mixed layer, the emission wavelength characteristic of the mixed layer itself can be changed, the emission wavelength can be shifted to a long wavelength, The emission intensity can be increased and the stability of the element can be improved.

  The hole injecting and transporting compound and the electron injecting and transporting compound used for the mixed layer may be selected from a compound for a hole injecting and transporting layer and a compound for an electron injecting and transporting layer, which will be described later. Among them, as the compound for the hole injection / transport layer, an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative which is a hole transport material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring is used. preferable.

  As the electron injecting and transporting compound, it is preferable to use a quinoline derivative, a metal complex having 8-quinolinol or a derivative thereof as a ligand, particularly tris (8-quinolinolato) aluminum (Alq3). Moreover, it is also preferable to use the above phenylanthracene derivatives and tetraarylethene derivatives.

  As the compound for the hole injecting and transporting layer, it is preferable to use an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative which is the above hole transporting material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring. .

  The mixing ratio in this case is determined by considering the carrier mobility and carrier concentration of each, but generally the weight ratio of the compound having a hole injecting and transporting compound / the compound having an electron injecting and transporting function is 1 / 99 to 99/1, more preferably 10/90 to 90/10, and particularly preferably about 20/80 to 80/20.

  Further, the thickness of the mixed layer is preferably less than the thickness of the organic compound layer from the thickness corresponding to one molecular layer, specifically 1 to 85 nm, more preferably 5 to 60 nm, In particular, the thickness is preferably 5 to 50 nm.

  In addition, as a method for forming the mixed layer, co-evaporation is preferably performed by evaporating from different evaporation sources, but when the vapor pressure (evaporation temperature) is the same or very close, the mixture is previously mixed in the same evaporation board, It can also be deposited. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may be present in an island shape. In general, the light emitting layer is formed to have a predetermined thickness by depositing an organic fluorescent material or coating the light emitting layer by dispersing it in a resin binder.

  Examples of the hole injecting and transporting layer include, for example, Japanese Patent Application Laid-Open No. 63-295695, Japanese Patent Application Laid-Open No. 2-191694, Japanese Patent Application Laid-Open No. Hei 3-792, Japanese Patent Application Laid-Open No. Hei 5-23481, and Japanese Patent Application Laid-Open No. 5-239455. Various organic compounds described in JP-A No. 5-299174, JP-A No. 7-126225, JP-A No. 7-126226, JP-A No. 8-100192, EP0650955A1, and the like can be used. For example, tetraarylbenzidine compounds (triaryldiamine or triphenyldiamine: TPD), aromatic tertiary amines, hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having amino groups, polythiophenes, etc. . Two or more of these compounds may be used in combination, and when used in combination, they may be laminated as separate layers or mixed.

  When the hole injecting and transporting layer is divided into the hole injecting layer and the hole transporting layer, a preferred combination can be selected from the compounds for the hole injecting and transporting layer. At this time, it is preferable to laminate in order of a compound layer having a small ionization potential from the hole injection electrode (ITO or the like) side. Further, it is preferable to use a compound having a good thin film property on the surface of the positive electrode. Such a stacking order is the same when two or more hole injecting and transporting layers are provided. By adopting such a stacking order, the drive voltage is lowered, and the occurrence of current leakage and the generation / growth of dark spots can be prevented. In addition, in the case of elementization, since vapor deposition is used, a thin film of about 1 to 10 nm can be made uniform and pinhole-free, so that the ion injection potential is small in the hole injection layer and the visible portion has absorption. Even if such a compound is used, it is possible to prevent a decrease in efficiency due to a change in color tone of light emission and reabsorption. The hole injecting and transporting layer can be formed by evaporating the above compound in the same manner as the light emitting layer and the like.

  In addition, an electron injecting and transporting layer provided as necessary includes a quinoline derivative such as an organometallic complex such as tris (8-quinolinolato) aluminum (Alq3) or a derivative thereof such as 8-quinolinol or a derivative thereof, oxadi An azole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, a quinoxaline derivative, a diphenylquinone derivative, a nitro-substituted fluorene derivative, or the like can be used. The electron injecting and transporting layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The electron injecting and transporting layer may be formed by vapor deposition or the like as in the light emitting layer.

  When the electron injecting and transporting layer is divided into an electron injecting layer and an electron transporting layer, a preferred combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to laminate in the order of compounds having a large electron affinity value from the electron injection electrode side. Such a stacking order is the same when two or more electron injecting and transporting layers are provided.

  As the substrate material, a transparent or translucent material such as glass, quartz, or resin is used. Further, the emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

  The color filter film may be a color filter used in a liquid crystal display or the like, but it is only necessary to adjust the characteristics of the color filter according to the light emitted by the organic EL to optimize the extraction efficiency and color purity. .

  In addition, if a color filter that can cut off short-wavelength external light that is absorbed by the EL element material or the fluorescence conversion layer is used, the light resistance and display contrast of the element can be improved.

  Further, an optical thin film such as a dielectric multilayer film may be used instead of the color filter.

  The fluorescence conversion filter film absorbs EL emission light and emits light from the phosphor in the fluorescence conversion film, thereby converting the color of the emitted light. The composition includes a binder, a fluorescent material, It is formed from three light absorbing materials.

  Basically, a fluorescent material having a high fluorescence quantum yield may be used, and it is desirable that the fluorescent material has strong absorption in the EL emission wavelength region. In fact, laser dyes are suitable, including rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalo) naphthalimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds, A styryl compound or a coumarin compound may be used.

  Basically, a material that does not quench the fluorescence may be selected as the binder, and a material that can be finely patterned by photolithography, printing, or the like is preferable. Further, a material that is not damaged during the film formation of ITO or IZO is preferable.

  The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may not be used when it is not necessary. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

  In forming the hole injecting and transporting layer, the light emitting layer, and the electron injecting and transporting layer, it is preferable to use a vacuum deposition method because a homogeneous thin film can be formed. When the vacuum deposition method is used, a homogeneous thin film having an amorphous state or a crystal grain size of 0.1 μm or less can be obtained. If the crystal grain size exceeds 0.1 μm, non-uniform light emission occurs, the drive voltage of the device must be increased, and the charge injection efficiency is also significantly reduced.

The conditions for vacuum deposition are not particularly limited, but it is preferable that the degree of vacuum is 10 ⁻⁴ Pa or less and the deposition rate is about 0.01 to 1 nm / sec. Moreover, it is preferable to form each layer continuously in a vacuum. If formed continuously in a vacuum, impurities can be prevented from adsorbing to the interface of each layer, so that high characteristics can be obtained. Further, the driving voltage of the element can be lowered, and the growth / generation of dark spots can be suppressed.

  In the case of using a vacuum deposition method for forming each of these layers, when a plurality of compounds are contained in one layer, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

  The organic EL element of the present invention is usually used as a direct current drive type EL element, but may be alternating current drive or pulse drive. The applied voltage is usually about 2 to 20V.

Hereinafter, specific examples of the present invention will be shown to describe the present invention in more detail.
<Example 1>
An ITO transparent electrode (hole injection electrode) having a film thickness of 85 nm was formed on a glass substrate, and pixels having a size of 280 × 280 μm ² were patterned with 64 dots × 7 lines at 20 μm intervals. Next, an Al—W (W: 3.0 at%) alloy electrode (sheet resistance: 0.4Ω / □) having a thickness of about 1.2 μm was patterned around the ITO transparent electrode. In addition, the metal electrode between each pixel and line was made common. When the resistance of the obtained hole injection electrode was measured, an extremely low resistance value of 64Ω per line was obtained, which was 1/50 or less compared to the hole injection electrode made of ITO alone.

<Example 2>
Except for the film thickness of 120 nm, the substrate on which the hole injection electrode composed of the ITO transparent electrode and the metal electrode obtained in the same manner as in Example 1 was ultrasonically cleaned using a neutral detergent, acetone, and ethanol Then, it was pulled up from boiling ethanol and dried. Next, the surface was washed with UV / O ₃ and then fixed to a substrate holder of a vacuum evaporation apparatus, and the inside of the tank was depressurized to 1 × 10 ⁻⁴ Pa or less. 4,4 ′, 4 ″ -tris (—N- (3-methylphenyl) -N-phenylamino) triphenylamine (hereinafter, m-MTDATA) was deposited to a thickness of 40 nm at a deposition rate of 0.2 nm / sec. N, N′-diphenyl-N, N′-m-tolyl-4,4′-diamino-1,1′-biphenyl (hereinafter referred to as “TPD”) is formed by evaporating to form a hole injection layer and then maintaining the reduced pressure state. Was vapor deposited at a deposition rate of 0.2 nm / sec to a thickness of 35 nm to form a hole transport layer, and tris (8-quinolinolato) aluminum (hereinafter referred to as Alq3) was deposited at a deposition rate of 0.2 nm while maintaining a reduced pressure. The electron injection transport / light-emitting layer was deposited at a thickness of 50 nm / sec .. Next, MgAg was co-evaporated (binary deposition) while maintaining the reduced pressure to a deposition rate ratio of Mg: Ag = 10: 1. A film having a thickness of 200 nm was formed as an electron injection electrode.

The obtained organic EL element was driven in a dry air atmosphere so that the luminance was 100 cd / m ² . When the luminance of the current supply side (terminal electrode side) of this organic EL element was compared with the luminance of 7 dots × 7 lines on the opposite side (terminal side), no difference in emission luminance could be confirmed. . From this, it was confirmed that there was no influence by the voltage drop.

<Example 3>
In Example 2, an organic EL device was obtained in the same manner as Example 2 except that the film thickness of the ITO transparent electrode was 50 nm. When this device was driven for 5000 hours, the density of dark spots was reduced to 1/2 or less, and the reliability was greatly improved.

  The obtained organic EL device was driven and evaluated in the same manner as in Example 2. As a result, there was little luminance unevenness, and almost the same result as in Example 2 was obtained.

<Example 4>
In Example 2, the constituent material of the metal electrode was changed from Al to Al—Si—Cu (Si: 0.97 at%, Cu: 0.53 at%), Al—Nd (Nd: 2.1 at%), Al—Ta ( Ta: 2.1 at%), Al-Sc (Sc: 0.13 at%), Al-W (W: 2.0 at%) .

  When the obtained organic EL device was evaluated in the same manner as in Example 2, almost the same result as in Example 2 was obtained.

<Example 5>
In Example 2, after forming the ITO transparent electrode, a Cr barrier layer having a width of 15 μm and a film thickness of 60 nm was formed on the portion of the ITO transparent electrode that becomes the interface with the surrounding metal electrode. An organic EL device was obtained in the same manner as in Example 2 except that a metal electrode was formed on the substrate.

  When the obtained organic EL device was evaluated in the same manner as in Example 2, almost the same result as in Example 2 was obtained.

<Example 6>
In Example 5, an organic EL device was obtained in the same manner as in Example 5 except that the constituent material of the barrier layer was changed from Cr to Ti and TiN (N: 52 at%), and evaluated in the same manner as in Example 5. However, almost the same results were obtained.

<Example 7>
In Example 2, an organic EL device was obtained in the same manner as in Example 2 except that an IZO transparent electrode produced in the same manner as in Example 1 was used.

  When the obtained organic EL device was driven and evaluated in the same manner as in Example 2, almost the same result as in Example 2 was obtained.

<Example 8>
As shown in FIGS. 13 and 14, an ITO transparent electrode (hole injection electrode) 2 having a thickness of 95 nm is formed on a glass substrate, and pixels of 280 × 280 μm ² size are 64 dots × 256 lines at 20 μm intervals. Patterned to line up. Here, FIG. 13 is a partial plan view, and FIG. 14 is a sectional view taken along the line DD ′ of FIG. Next, as a barrier layer 7, a Cr film having a thickness of 100 nm and an Al metal electrode (sheet resistance: 0.1Ω / □) 3 having a film thickness of 300 nm are continuously formed and patterned around the ITO transparent electrode so as to have a total width of 30 μm. did.

Next, the substrate on which the hole injection electrode composed of the ITO transparent electrode and the metal electrode was formed was subjected to ultrasonic cleaning using a neutral detergent, acetone and ethanol, and then pulled up from boiling ethanol and dried. Next, the surface was washed with UV / O ₃ and then fixed to a substrate holder of a vacuum evaporation apparatus, and the inside of the tank was depressurized to 1 × 10 ⁻⁴ Pa or less. 4,4 ′, 4 ″ -tris (—N- (3-methylphenyl) -N-phenylamino) triphenylamine (hereinafter, m-MTDATA) was deposited to a thickness of 40 nm at a deposition rate of 0.2 nm / sec. N, N′-diphenyl-N, N′-m-tolyl-4,4′-diamino-1,1′-biphenyl (hereinafter referred to as “TPD”) is formed by evaporating to form a hole injection layer and then maintaining the reduced pressure state. Was vapor deposited at a deposition rate of 0.2 nm / sec to a thickness of 35 nm to form a hole transport layer, and tris (8-quinolinolato) aluminum (hereinafter referred to as Alq3) was deposited at a deposition rate of 0.2 nm while maintaining a reduced pressure. The electron injection transport / light-emitting layer was deposited at a thickness of 50 nm / sec .. Next, MgAg was co-evaporated (binary deposition) while maintaining the reduced pressure to a deposition rate ratio of Mg: Ag = 10: 1. A film having a thickness of 200 nm was formed as an electron injection electrode.

The obtained organic EL element was driven in a dry air atmosphere so that the luminance was 100 cd / m ² . The range of 7 dots × 7 lines on the current supply side (terminal electrode side) of this organic EL element was taken as one unit of measurement, and the luminance was measured from the current supply side to the opposite side (terminal side). / m with respect to ² times the average light emission luminance, it was confirmed that the emission luminance change within 5% in all regions. From this, it was confirmed that the influence of the voltage drop is small even in a display with a large display area.

<Comparative Example 1>
In Example 2, an organic EL element was obtained in the same manner as in Example 2 except that the hole injection electrode was formed using only the ITO transparent electrode. At this time, the resistance of the hole injection electrode per line was 3.2 kΩ.

When the obtained organic EL device was driven and evaluated in the same manner as in Example 1, a maximum luminance change of −20% was confirmed with respect to the time average light emission luminance of 100 cd / m ² on the current supply side.

It is a schematic block diagram of the 7 segment type hole injection electrode which shows one structural example of the organic EL element of this invention. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1. It is the schematic block diagram which shows the film-forming process of the simple matrix type hole injection electrode which shows the other structural example of the organic EL element of this invention, and is the figure which showed the process of forming an ITO transparent electrode into a film. FIG. 4 is a B-B ′ cross-sectional view of FIG. 3. It is the schematic block diagram which shows the other structural example of the organic EL element of this invention, and is the figure which showed the process of forming a metal electrode into a film. FIG. 6 is a B-B ′ cross-sectional view of FIG. 5. It is the schematic block diagram which shows the other structural example of the organic EL element of this invention, and is the figure which showed the process of forming an insulating film. FIG. 8 is a cross-sectional view taken along the line B-B ′ of FIG. 7. It is the schematic block diagram which shows the other structural example of the organic EL element of this invention, and is the figure which showed the process of forming an element isolation structure into a film. FIG. 10 is a cross-sectional view taken along the line C-C ′ of FIG. 9. It is the schematic block diagram which shows the other structural example of the organic EL element of this invention, and is the figure which showed the process of bonding a mask. It is a C-C 'cross section arrow directional view of FIG. It is the partial top view which showed the pattern of the ITO transparent electrode and metal electrode which are one Example of this invention. It is D-D 'cross section arrow directional view of FIG. It is the graph which showed the relationship between the applied voltage of an organic EL element, and light emission luminance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Transparent electrode 3 Metal electrode 4 Insulating film 5 Element isolation structure 6 Mask 7 Barrier layer

Claims (3)

A hole injection electrode, an electron injection electrode, and one or more organic layers provided between the electrodes,
The hole injection electrode has a transparent electrode in a portion including a light emitting portion, and is disposed in a portion other than the light emitting portion, and has a metal electrode having a sheet resistance of 1Ω / □ or less connected to the transparent electrode,
An organic EL element in which an insulating film is formed so as to cover a portion other than the light emitting portion of the transparent electrode and the metal electrode.   The organic EL element according to claim 1, wherein an element isolation structure is formed on the insulating film.   The organic EL element according to claim 2, wherein the element isolation structure has a width narrower than that of the insulating film.

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