JP2014072322A - Organic light-emitting display device and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress color purity degradation due to the effect from a blue light-emitting layer in a red organic EL element and a green organic EL element.SOLUTION: An organic light-emitting display device has a pixel electrode 3 and a counter electrode 11, and a hole injection layer 5, a hole transport layer 6, a red light-emitting layer 7, a green light-emitting layer 8, a blue light-emitting layer 9, and an electron transport layer 10 are formed between the pixel electrode 3 and counter electrode 11. The blue light-emitting layer 9 contains an electron transporting host material and a hole transporting dopant material. Concentration of the hole transporting dopant material in the blue light-emitting layer 9 decreases gradually from the counter electrode 11 side toward the pixel electrode 3 side.

Description

  The present invention relates to a display device, and more particularly, to an organic light emitting display device and a manufacturing method thereof.

  An organic light emitting display device (organic EL display device) recombines electrons and holes injected in the organic light emitting layer in the organic light emitting medium layer by applying a voltage to the conductive organic light emitting medium layer. The organic light emitting molecules in the organic light emitting layer are once excited by the recombination energy, and then return from the excited state to the ground state. By taking out the energy released at this time as light, the organic light emitting display device emits light. In order to apply a voltage to the organic light emitting medium layer, a pixel electrode and a counter electrode are provided on both sides of the organic light emitting medium layer. In order to extract light from the organic light emitting medium layer to the outside, the pixel electrode and the counter electrode are provided. At least one of them has translucency. As an example of the structure of such an organic light emitting display device, a light transmissive pixel electrode, an organic light emitting medium layer, and a counter electrode are sequentially stacked on a light transmissive substrate. There is an embodiment in which the pixel electrode to be formed is used as an anode and the counter electrode formed on the organic light emitting medium layer is used as a cathode.

  Furthermore, for the purpose of increasing luminous efficiency, in addition to the hole transport layer provided between the pixel electrode and the organic light emitting layer, the hole injection layer, an electron transport layer between the organic light emitting layer and the counter electrode, In many cases, an electron injection layer is appropriately selected and configured as an organic light emitting display device. These hole transport layer, hole injection layer, electron transport layer, and electron injection layer are called carrier transport layers. The carrier transport layer, the organic light emitting layer, and the hole blocking layer, the electron blocking layer, the insulating layer, and the like are collectively referred to as an organic light emitting medium layer.

  When manufacturing an image display device, an image is displayed by a large number of pixels arranged vertically and horizontally. For this purpose, it is necessary to selectively dispose a light emitting material, a hole injection material, or the like on the pixel electrode to form an independent organic EL element for each pixel. At that time, in order to uniformly distribute the material to each pixel and to uniformly emit light, a method of providing partition walls that partition each pixel in advance is generally used.

  Common emission color combinations are red, green, and blue. The lifetime of the organic light emitting display device is determined by the organic EL element having a short lifetime. At present, the lifetime of blue organic EL elements tends to be shorter than that of red organic EL elements and green organic EL elements. Therefore, extending the lifetime of the blue organic EL element has been a problem for achieving long-term reliability as an organic light emitting display device.

Materials used for the organic light emitting layer and the like constituting the organic EL element are roughly classified into low molecular materials and high molecular materials. In general, it is known that a low molecular weight material exhibits higher luminous efficiency and longer life, and blue performance is particularly high.
The low molecular weight material is generally formed using a vacuum deposition method. The vacuum deposition method has an advantage that it is not necessary to dissolve an organic material in a solvent, and a step of removing the solvent after film formation is unnecessary. However, vacuum vapor deposition is difficult to separate with a metal mask, and has the disadvantages that it is difficult to apply to large screen substrates and difficult to mass-produce, especially because of the high equipment manufacturing cost in the production of large panels. It was.

2. Description of the Related Art In recent years, active research has been conducted on dissolving or dispersing a low molecular weight material or a high molecular weight material in a solvent and forming an organic light emitting layer by a wet method such as a coating method or a printing method. Compared with the organic light-emitting display device using the above-described vacuum evaporation method, there is an advantage that film formation under atmospheric pressure is possible and equipment cost is low.
These are generally formed of a material that is easily dissolved in a solvent. Thereby, a wet coating method such as a spin coating method under atmospheric pressure, a letterpress printing method, a letterpress inversion offset printing method (for example, refer to Patent Documents 1 and 2), an ink jet method (for example, refer to Patent Documents 3 and 4), Each layer can be formed by using a printing method such as a nozzle printing method (see, for example, Patent Document 5), thereby reducing the cost of manufacturing equipment and improving productivity.

However, among the luminescent materials used in the wet method, in particular, the blue luminescent material has low luminance and lifetime characteristics and is not practical. Therefore, it has been difficult to pattern the blue luminescent layer by the wet method.
In response to this problem, a display device is disclosed that is formed by a vacuum deposition method using a blue light emitting layer and a subsequent layer, which have insufficient characteristics by a wet method, on a red light emitting layer and a green light emitting layer formed by a wet method. (See Patent Document 6). Such a structure eliminates the need for fine patterning on the blue light-emitting layer, so that the possibility of enlargement is particularly high.

  However, the organic light emitting display device of Patent Document 1 has a problem that the color purity of the red organic EL element and the green organic EL element is lowered. Since the blue light emitting layer is laminated directly on the red light emitting layer and the green light emitting layer, carriers move from the red light emitting layer and the green light emitting layer to the blue light emitting layer, and light emission of the blue light emitting layer is added. The chromaticity in the green organic EL element changes. Therefore, it has been demanded to reduce blue light emission in the red organic EL element and the green organic EL element.

JP 2003-17248 A JP 2004-296226 A Japanese Patent No. 3541625 JP 2009-267299 A JP 2001-189192 A JP 2006-140434 A

  The present invention relates to an organic light emitting display device in which a blue light emitting layer is laminated by a vapor deposition method on a red light emitting layer and a green light emitting layer formed by a wet method, and the blue color in the red organic EL element and the green organic EL element. An object of the present invention is to provide an organic light emitting display device capable of suppressing a decrease in color purity due to an influence from a light emitting layer, and a method for manufacturing the same.

  In order to achieve the above object, the invention of claim 1 is formed on a pixel electrode provided on each of a red organic EL element, a green organic EL element, and a blue organic EL element on a substrate. A hole injection / transport layer having at least one of the characteristics of hole injection or hole transport, a red light emitting layer and a green light emitting layer formed on the hole injection / transport layer, and the red light emitting layer, A green light-emitting layer, a blue light-emitting layer formed on the whole surface of the hole injection / transport layer, and an electron injection / transport layer having at least one of the characteristics of electron injection or electron transport formed in order on the entire surface of the blue light-emitting layer And the blue light emitting layer contains at least an electron transporting host material and a hole transporting dopant material, and the concentration of the hole transporting dopant material in the blue light emitting layer is In which the counter electrode side gradually decreases toward the pixel electrode side.

According to a second aspect of the present invention, in the organic light emitting display device according to the first aspect, the concentration of the hole transporting dopant material in a region in the vicinity of the pixel electrode side interface of the blue light emitting layer may be that of the blue light emitting layer. It is 0 mass% or more and 50 mass% or less with respect to the density | concentration of the said hole transportable dopant material in the area | region of the said counter electrode side interface vicinity.
According to a third aspect of the present invention, in the organic light emitting display device according to the second aspect, the concentration of the hole transporting dopant material in the blue light emitting layer is 3% by mass or less in a region near the interface on the pixel electrode side. It is what is.
According to a fourth aspect of the present invention, in the organic light emitting display device according to the third aspect, the concentration of the hole transporting dopant material in the blue light emitting layer is 5% by mass or more in a region near the counter electrode side interface. It is what is.

A fifth aspect of the present invention is a method of manufacturing the organic light emitting display device according to any one of the first to fourth aspects, wherein each of a red organic EL element, a green organic EL element, and a blue organic EL element is formed on a substrate. Forming a pixel electrode provided for each, a step of forming a hole injection / transport layer having at least one of hole injection and hole transport on the pixel electrode by a wet method, and the positive electrode Forming a red light emitting layer and a green light emitting layer on the hole injecting / transporting layer by a wet method; and depositing a blue light emitting layer on the entire surface of the red light emitting layer, the green light emitting layer, and the hole injecting / transporting layer. And at least a step of forming an electron injection / transport layer having at least one of electron injection or electron transport and a counter electrode over the entire surface of the blue light-emitting layer, At least electronic It contains a transmission host material and the hole transporting dopant material, the concentration of the hole transporting dopant material in the blue light-emitting layer in which is gradually decreased toward the pixel electrode side from opposing electrode side.
The invention according to claim 6 is the method for manufacturing the organic light emitting display device according to claim 5, wherein an ink jet method, a nozzle printing method, letterpress printing, gravure printing, or reverse offset printing is used as the wet method. .

  According to the present invention, the concentration of the hole-transporting dopant material in the blue light-emitting layer is gradually decreased from the counter electrode side to the pixel electrode side, so that the red light-emitting layer and the green light-emitting layer are transferred to the blue light-emitting layer. Since carrier movement is suppressed, and as a result, light emission of the blue light emitting layer is suppressed, it is possible to suppress a decrease in color purity due to the influence from the blue light emitting layer in the red organic EL element and the green organic EL element.

1 is a cross-sectional view schematically showing a configuration of an organic light emitting display device according to an embodiment of the present invention. It is a schematic sectional drawing which shows typically the relief printing apparatus used for manufacture of the organic light emitting display apparatus which concerns on embodiment of this invention.

  Embodiments of the present invention include a pixel electrode provided for each of a red organic EL element, a green organic EL element, and a blue organic EL element on a substrate, and hole injection or hole transport formed on the pixel electrode. A hole injection / transport layer having at least one of the following characteristics: a red light emission layer and a green light emission layer formed on the hole injection / transport layer; a red light emission layer, a green light emission layer, and a hole injection / transport layer; A blue light-emitting layer formed on the entire surface, and an electron injection / transport layer and a counter electrode having at least one of the characteristics of electron injection or electron transport, which are sequentially formed on the entire surface of the blue light-emitting layer, are formed; It contains at least an electron-transporting host material and a hole-transporting dopant material, and the concentration of the hole-transporting dopant material in the blue light-emitting layer gradually decreases from the counter electrode side to the pixel electrode side.

In the present invention, the gradual decrease means that the voltage gradually decreases from the counter electrode side to the pixel electrode side, and this is the gist of the present invention, which changes continuously or stepwise. May be. Alternatively, even if there is a region that is partially reduced, it may be reduced overall.
Further, in this specification, “region near the pixel electrode side interface” and “region near the counter electrode side interface” are defined to refer to a thickness region of 10% of the total thickness of the organic light emitting layer. Further, the density in the region is defined as an average density in the region. Further, the concentration of each material can be measured by a method such as etching X-ray photoelectron spectroscopy (XPS / ESCA).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 schematically shows a configuration of an organic light emitting display device according to the present embodiment. An organic light emitting display device 1 according to this embodiment is an organic light emitting display device having a so-called active matrix structure, and is provided on a translucent substrate 2 on which a TFT (thin film transistor) is formed and on one surface of the translucent substrate 2. A plurality of pixel electrodes 3, a partition wall 4 that linearly partitions each pixel electrode 3, a hole injection layer 5 stacked on the pixel electrode 3, and a hole transport layer stacked on the hole injection layer 5 6, a red light emitting layer 7 and a green light emitting layer 8 laminated on the hole transport layer 6, and a blue light emitting layer 9 laminated on the red light emitting layer 7, the green light emitting layer 8 and the hole transport layer 6, blue An electron transport layer 10 stacked on the light emitting layer 9, a counter electrode 11 stacked on the electron transport layer 10 and disposed opposite to the pixel electrode 3, and a resin layer 12 sealed so as to cover the counter electrode 11 and sealing In the following description, the pixel electrode 3 has an anode, a counter electrode, and the like. 11 is described for the case of the cathode.

The organic light emitting display device 1 according to this embodiment may have a so-called passive matrix structure.
The translucent substrate 2 is a substrate that supports the pixel electrode 3, the organic light emitting layer (the red light emitting layer 7, the green light emitting layer 8, the blue light emitting layer 9), the counter electrode 11, and the like, and is made of metal, glass, plastic, or the like. It is comprised by the film or sheet | seat. As the plastic film, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, or polycarbonate can be used.

In addition, another gas barrier film such as a ceramic vapor-deposited film, polyvinylidene chloride, polyvinyl chloride, ethylene-vinyl acetate copolymer saponified product is laminated on the other surface of the translucent substrate 2 where the pixel electrode 3 is not formed. May be.
The translucent substrate 2 of the present embodiment may be an active drive system substrate on which TFTs are formed. When the printed body of the present embodiment is an active drive type organic EL element, a planarization layer is formed on the TFT, and a lower electrode of the organic EL element is provided on the planarization layer. In addition, the TFT and the lower electrode are preferably electrically connected via a contact hole provided in the planarization layer.

  By comprising in this way, the outstanding electrical insulation can be obtained between TFT and an organic EL element. The TFT and the organic EL element formed above the TFT are supported by a support of the translucent substrate 2. The support is preferably excellent in mechanical strength and dimensional stability. Specifically, the materials described above as the substrate can be used. As the TFT provided on the support, a known TFT can be used.

  Specifically, a TFT composed mainly of an active layer in which a source / drain region and a channel region are formed, a gate insulating film, and a gate electrode can be given. The structure of the TFT is not particularly limited, and examples thereof include known structures such as a staggered type, an inverted staggered type, a top gate type, a bottom gate type, and a coplanar type. In the case of a bottom emission type organic EL element, it is necessary to use a translucent substrate.

  Next, a layer made of the material of the pixel electrode 3 is formed on the translucent substrate 2, and patterning is performed as necessary. The layer made of the material of the pixel electrode 3 is partitioned by the partition walls 4 and becomes the pixel electrode 3 corresponding to each pixel. Examples of the material of the pixel electrode 3 include metal composite oxides such as ITO (indium tin composite oxide), indium zinc composite oxide, and zinc aluminum composite oxide, metal materials such as gold and platinum, these metal oxides, Either a single layer or a laminate of fine particle dispersion films in which fine particles of a metal material are dispersed in an epoxy resin or an acrylic resin can be used.

  When the pixel electrode 3 is used as an anode, it is preferable to select a material having a high work function such as ITO. In the case of a so-called bottom emission structure in which light is extracted from below, it is necessary to select a light-transmitting material. If necessary, a metal material such as copper or aluminum may be provided as an auxiliary electrode in order to reduce the wiring resistance of the pixel electrode. The film thickness of the pixel electrode 3 varies depending on the element configuration of the organic light emitting display device, but is 100 to 10,000 mm, more preferably 100 to 3000 mm, regardless of single layer or stacked layers.

As a method for forming the pixel electrode 3, depending on the material, a dry film forming method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, a gravure printing method, or a screen printing method is used. A wet film forming method such as a method can be used.
The partition walls 4 are formed so as to cover the end portions of the pixel electrodes 3 in order to prevent the organic EL elements formed on the pixel electrodes 3 from mixing with each other. The pattern of the partition walls 4 is the pixel electrode 3. It is desirable that the shape is a linear shape.

  As a method of forming the partition walls 4, as in the conventional method, an inorganic film is uniformly formed on the translucent substrate 2, masked with a resist, and then dry-etched, or photosensitive on the substrate. There is a method of laminating a resin and forming a predetermined pattern by a photolithography method. If necessary, a water repellent can be added, or plasma or UV can be irradiated to impart liquid repellency to the ink after formation.

The material of the partition 4 needs to have insulating properties, and a photosensitive material or the like can be used. The photosensitive material may be a positive type or a negative type, a photo-curing resin of a photo radical polymerization system, a photo cationic polymerization system, or a copolymer containing an acrylonitrile component, polyvinyl phenol, polyvinyl alcohol. , Novolac resin, polyimide resin, cyanoethyl pullulan, and the like can be used. In addition, as a material for forming the partition walls 4, SiO ₂ , TiO ₂ or the like can be used.
The preferable height of the partition wall 4 is 0.1 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 2 μm or less. If the height of the partition wall 4 exceeds 10 μm, the formation and sealing of the counter electrode 11 is hindered. If it is less than 0.1 μm, the end of the pixel electrode 3 cannot be covered, or it is adjacent when the organic light emitting medium layer is formed. This is because the pixel is short-circuited or mixed in color.

  Next, an organic light emitting medium layer is formed as an organic functional thin film of the present embodiment on the translucent substrate 2 on which the pixel electrode 3 and the partition wall 4 are formed. The organic light emitting medium layer in the present embodiment includes at least a hole injection layer 5 formed on the upper surface of the pixel electrode 3, a hole transport layer 6 stacked on the hole injection layer 5, and a hole transport layer 6. A red light-emitting layer 7 and a green light-emitting layer 8 stacked on each other, a blue light-emitting layer 9 stacked on the red light-emitting layer 7, the green light-emitting layer 8 and the hole transport layer 6, and a layer stacked on the blue light-emitting layer 9. The electron transport layer 10 is laminated.

  The hole injection layer 5 and the hole transport layer 6 advance the holes injected from the pixel electrode 3 serving as the anode toward the counter electrode 11 serving as the cathode, and electrons pass through the holes while passing the holes. It has a function to prevent progress. A positive hole injection layer having a function of stabilizing the injection of holes from the pixel electrode 3 when an electric field is applied, and a positive function having a function of transporting holes injected from the pixel electrode 3 into the light emitting layer by the force of the electric field. It may be a case having either one of the hole transport layers, and may have both functions of a hole injection layer and a hole transport layer. The hole injection layer 5 and the hole transport layer 6 may be composed of one layer or a plurality of layers. The hole injection layer 5 and the hole transport layer 6 are formed between the organic light emitting layer (red light emitting layer 7, green light emitting layer 8, blue light emitting layer 9) and the pixel electrode 3.

Examples of hole transport materials used for the hole injection layer 5 and the hole transport layer 6 include metal phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine, and metal-free phthalocyanines, quinacridone compounds, 1-bis (4-di-p-tolylaminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, Aromatic amine low molecular hole injection and transport materials such as N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine, polyaniline, polythiophene , Polyvinyl carbazole, polymeric hole transport materials such as poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid, polythiophene oligomer materials _{, Cu 2 O, Cr 2 O} 3, Mn 2 O 3, FeOx (x~0.1), NiO, CoO, Pr 2 O 3, Ag 2 O, MoO 2, Bi 2 O 3, ZnO, TiO 2, It can be selected from inorganic materials such as SnO ₂ , ThO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO ₂ , and other existing hole injection / transport materials.

As a solvent for dissolving or dispersing the hole injection transport material, toluene, xylene, anisole, dimethoxybenzene, tetralin, cyclohexanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, Among butyl acetate, water, etc., any one or a mixture thereof can be mentioned.
A surfactant, an antioxidant, a viscosity modifier, an ultraviolet absorber, or the like may be added to the solution or dispersion of the hole injecting and transporting material as necessary. Examples of the viscosity modifier include: Polystyrene, polyvinyl carbazole, or the like can be used.

  As a method for forming the hole injection layer 5 and the hole transport layer 6, depending on the materials used for the hole injection layer 5 and the hole transport layer 6, spin coating, bar coating, wire coating, slit coating, spray coating, Wet methods such as curtain coating, flow coating, letterpress printing, letterpress reverse printing, ink jet method, nozzle printing method, resistance heating evaporation method, electron beam evaporation method, reactive evaporation method, ion plating method, sputtering method, etc. An evaporation method can be used.

  An interlayer layer may be formed on the hole injection layer 5 and the hole transport layer 6. Examples of materials used for the interlayer layer include polymers containing aromatic amines such as polyvinyl carbazole or derivatives thereof, polyarylene derivatives having aromatic amines in the side chain or main chain, arylamine derivatives, and triphenyldiamine derivatives. . These materials are dissolved or dispersed in a solvent, such as spin coating, bar coating, wire coating, slit coating, spray coating, curtain coating, flow coating, letterpress printing, gravure printing, reverse offset printing, inkjet printing, nozzle printing printing, etc. It can be formed using a wet method.

  The materials of the red light emitting layer 7, the green light emitting layer 8, and the blue light emitting layer 9 are functional materials of an organic light emitting layer that emits red, green, and blue light when a voltage is applied. The red light emitting layer 7 and the green light emitting layer 8 are prepared by spin-coating, bar coating, wire coating, slit coating, spray coating, curtain coating, flow coating, organic light emitting ink (ink) dissolved or dispersed on the hole transport layer 6, It is formed by attaching using a wet method such as letterpress printing, gravure printing, reverse offset printing, ink jet method, nozzle printing method, and then drying. As a method for forming the blue light emitting layer 9, a vacuum vapor deposition method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, or the like can be used. In addition, the film thickness of an organic light emitting layer should just be the range of 0.01 micrometer or more and 0.1 micrometer or less. When the thickness is out of the range, the luminous efficiency tends to decrease.

  Organic light emitting materials for forming the organic light emitting layer are, for example, coumarin, perylene, pyran, anthrone, porphyrene, quinacridone, N, N′-dialkyl substituted quinacridone, naphthalimide, N, N′-diaryl. Light-emitting pigments such as substituted pyrrolopyrrole and iridium complex systems dispersed in polymers such as polystyrene, polymethylmethacrylate, and polyvinylcarbazole, and polyarylene, polyarylene vinylene, and polyfluorene polymer materials However, the present invention is not limited to these.

  These organic light emitting materials are dissolved or stably dispersed in a solvent to form an organic light emitting ink. Examples of the solvent for dissolving or dispersing the organic light emitting material include toluene, xylene, acetone, anisole, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or a mixed solvent thereof. Among them, aromatic organic solvents such as toluene, xylene, and anisole are preferable from the viewpoint of the solubility of the organic light emitting material. Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. may be added to organic luminescent ink as needed.

  In addition to the above-described polymer materials, organic light-emitting materials for forming the organic light-emitting layer are 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8 -Quinolate) aluminum complex, tris (4-methyl-8-quinolate) aluminum complex, bis (8-quinolate) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolate) aluminum complex, tris (4 -Methyl-5-cyano-8-quinolato) aluminum complex, bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl- 5-cyano-8-quinolinolato) [4- (4-cyanophenyl) phenolate Aluminum complex, tris (8-quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, poly-2,5-di Low molecular weight light emitting materials such as heptyloxy-para-phenylene vinylene can also be used.

Examples of the electron transport material used for the electron transport layer 10 include 2- (4-bifinylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1- Naphthyl) -1,3,4-oxadiazole, oxadiazole derivatives, bis (10-hydroxybenzo [h] quinolinolato) beryllium complexes, triazole compounds, and the like can be used. Alternatively, these electron transport materials may be used as an electron injection layer by doping a small amount of alkali metal or alkaline earth metal having a low work function such as sodium, barium, or lithium.
As a method for forming the electron transport layer 10, a vacuum evaporation method such as a resistance heating evaporation method, an electron beam evaporation method, a reactive evaporation method, an ion plating method, or a sputtering method can be used depending on the material to be used.

Next, the counter electrode 11 is formed. When the counter electrode 11 is a cathode, a substance having a high electron injection efficiency into the organic light emitting medium layer and a low work function is used. Specifically, simple metals such as Mg, Al, and Yb may be used, and a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface contacting the light emitting medium, and Al or Cu may be laminated and used. Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function and stable Ag, An alloy system with a metal element such as Al or Cu may be used.
As a method for forming the counter electrode 11, a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method can be used depending on the material. Although there is no restriction | limiting in particular in the thickness of the counter electrode 11, 10 nm or more and 1000 nm or less are desirable.

  Next, for example, a passivation layer may be formed on the counter electrode 11 between the counter electrode 11 and the sealing material. Examples of the material for the passivation layer include metal oxides such as silicon oxide and aluminum oxide, metal fluorides such as aluminum fluoride and magnesium fluoride, metal nitrides such as silicon nitride, aluminum nitride and carbon nitride, and silicon oxynitride. A laminated film of a metal carbide such as metal oxynitride or silicon carbide, and a polymer resin film such as an acrylic resin, an epoxy resin, a silicone resin, or a polyester resin may be used as necessary. In particular, from the viewpoint of barrier properties and transparency, it is preferable to use silicon oxide (SiOx), silicon nitride (SiNx), or silicon oxynitride (SiOxNy). Furthermore, a laminated film in which the film density is variable depending on the film forming conditions. Alternatively, a gradient membrane may be used.

  As a method for forming the passivation layer, a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, or a CVD method can be used depending on the material. It is preferable to use a CVD method in terms of translucency. As the CVD method, a thermal CVD method, a plasma CVD method, a catalytic CVD method, a VUV-CVD method, or the like can be used.

In addition, as a reaction gas in the CVD method, a gas such as N ₂ , O ₂ , NH ₃ , H ₂ , or N ₂ O is added to an organic silicone compound such as monosilane, hexamethyldisilazane (HMDS), or tetraethoxysilane. It may be added as necessary. For example, the density of the film may be changed by changing the flow rate of silane, and hydrogen or carbon may be contained in the film by the reactive gas used. The thickness of the passivation layer varies depending on the electrode step of the organic EL element, the height of the partition wall of the substrate, the required barrier characteristics, and the like, but generally about 0.01 μm to 10 μm is generally used.

Since the organic light emitting material is easily deteriorated by moisture and oxygen in the atmosphere, a sealing material for blocking the organic light emitting medium layer from the outside is provided. For example, the sealing material can be formed by providing the sealing substrate 13 and the resin layer 12. The sealing substrate 13 needs to be a base material having low moisture and oxygen permeability. Examples of the material include ceramics such as alumina, silicon nitride, and boron nitride, glass such as alkali-free glass and alkali glass, metal foil such as quartz, aluminum, and stainless steel, and moisture-resistant film. Examples of moisture-resistant films include films formed by CVD of SiO _x on both sides of a plastic substrate, films with low permeability and water-absorbing films, or polymer films coated with a water-absorbing agent. The water vapor permeability of the film is preferably 10 ⁻⁶ g / m ² / day or less.

  Examples of the material of the resin layer 12 include a photo-curing adhesive resin, a thermosetting adhesive resin, a two-component curable adhesive resin, and an ethylene ethyl acrylate (EEA) made of an epoxy resin, an acrylic resin, a silicone resin, or the like. ) Acrylic resins such as polymers, vinyl resins such as ethylene vinyl acetate (EVA), thermoplastic resins such as polyamide and synthetic rubber, and thermoplastic adhesive resins such as acid-modified products of polyethylene and polypropylene. .

  Examples of the method for forming the resin layer 12 include a solvent solution method, an extrusion lamination method, a melting / hot melt method, a calendar method, a nozzle coating method, a screen printing method, a vacuum laminating method, and a hot roll laminating method. A material having a hygroscopic property or an oxygen absorbing property may be contained as necessary. The thickness of the resin layer 12 formed on the sealing material is arbitrarily determined depending on the size and shape of the organic light emitting medium layer to be sealed, but is preferably 5 μm or more and 500 μm or less.

  The organic light emitting medium layer and the sealing substrate 13 are bonded together in a sealing chamber. When the sealing material has a two-layer structure of the sealing substrate 13 and the resin layer 12 and a thermoplastic resin is used for the resin layer 12, it is preferable to perform only the pressure bonding with a heated roll. When a thermosetting adhesive resin or a photocurable adhesive resin is used for the resin layer 12, it is preferable to perform light or heat curing in a state of roll pressing or flat plate pressing.

Next, an outline of a method for manufacturing the organic light emitting display device 1 having the above-described configuration by a relief printing method and a vacuum deposition method will be described. The present invention is not limited to this, and as described above, a nozzle printing method or the like can be used instead of the relief printing method.
First, the pixel electrode 3 is formed on the translucent substrate 2 on which the TFT is formed so as to be connected to the TFT. This is because an ITO film is formed on the entire surface of the translucent substrate 2 using a sputtering method, and further, exposure and development are performed by a photolithography technique, and a main part remaining as the pixel electrode 3 is covered with a photoresist. Then, unnecessary portions are etched with an acid solution to remove the ITO film. In this way, a plurality of pixel electrodes 3 arranged at predetermined intervals are formed.

Next, the partition walls 4 are formed between the pixel electrodes 3. In this method, a photoresist is applied on the translucent substrate 2 and the pixel electrode 3, and exposure and development are performed by a photolithography technique so that the photoresist remains between the pixel electrodes 3. Thereafter, the photoresist is cured by baking.
Then, using a relief printing apparatus 30 as shown in FIG. 2, ink of a hole injection material is applied onto the pixel electrode 3 by a relief printing method to form the hole injection layer 5. The relief printing apparatus 30 includes an ink tank 33, an ink chamber 34, an anilox roll 35, a doctor 30, and a plate cylinder 38 on which a relief plate 37 provided with projections is mounted. The ink tank 33 contains organic material ink, and the organic material ink is fed into the ink chamber 34 from the ink tank 33. The anilox roll 35 is rotatably supported in contact with the ink supply part of the ink chamber 34.

  As the anilox roll 35 rotates, the ink layer 39 of the organic material ink supplied to the surface of the anilox roll 35 is formed with a uniform film thickness. The ink in the ink layer 39 is transferred to the convex portion of the relief plate 37 mounted on the plate cylinder 38 that is driven to rotate in the vicinity of the anilox roll 35. A printing substrate 32 is installed on the stage 31, and the ink on the projections of the relief plate 37 is printed on the printing substrate 32, and an organic layer is formed on the printing substrate 32 through a drying process as necessary. Is done.

Next, after the hole transport layer 6 is formed, organic light emitting layers (red light emitting layer 7 and green light emitting layer 8) are similarly formed on the hole transport layer 6 by letterpress printing.
Next, the organic light emitting layer is formed by letterpress printing, and then the blue light emitting layer 9 is formed on the red light emitting layer 7 serving as the light emitting region, the green light emitting layer 8, the hole transporting layer 6, and the partition wall 4 serving as the non-light emitting region. It is formed on the entire surface by vacuum deposition such as resistance heating deposition.

When the blue light emitting layer 9 is formed by vacuum deposition, the blue light emitting layer 9 contains an electron transporting host material and a hole transporting dopant material, and the concentration of the hole transporting dopant material in the blue light emitting layer 9 is opposite. The deposition rate is adjusted as the deposition progresses so that the co-deposition ratio of the electron transporting host material and the hole transporting dopant is gradually decreased from the electrode 11 side toward the pixel electrode side 3.
Subsequently, the electron transport layer 10 and the counter electrode 11 are formed by vapor deposition on the blue light emitting layer 9 by vapor deposition such as resistance heating vapor deposition. Finally, the pixel electrode 3, the organic light emitting medium layer, and the counter electrode 11 are filled with a resin layer 12 in order to protect them from oxygen and moisture in the air, covered with a sealing substrate 13, and sealed for organic light emitting display. The apparatus 1 is manufactured.

  According to the organic light emitting display device 1 and the manufacturing method thereof configured as described above, the concentration of the hole transporting dopant material in the blue light emitting layer 9 gradually decreases from the counter electrode 11 side toward the pixel electrode 3 side. Therefore, carrier movement from the red light emitting layer 7 and the green light emitting layer 8 to the blue light emitting layer 9 is suppressed, and as a result, light emission of the blue light emitting layer 9 is suppressed, and blue light emission in the red organic EL element and the green organic EL element is achieved. A decrease in color purity due to the influence from the layer 9 can be suppressed.

  In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention. For example, a hole blocking layer, an electron injection layer, or an electron blocking layer may be formed. Here, in the same manner as the hole transport layer 6, the electron blocking layer advances holes from the pixel electrode 3 serving as the anode toward the counter electrode 11 serving as the cathode and passes the holes, but electrons are passed through the pixel electrode 3. It has the function to prevent progressing in the direction. In addition, the hole blocking layer, the electron transport layer, and the electron injecting layer allow electrons to pass from the counter electrode 11 that is the cathode toward the pixel electrode 3 that is the anode and pass the electrons. It has a function to prevent progress.

  Further, a thin film such as lithium fluoride or sodium fluoride may be provided between the counter electrode 11 and the organic light emitting medium layer. To pattern the counter electrode 11, a metal film, a ceramic film deposition mask, or the like can be used. Furthermore, although the partition 4 is formed between the pixel electrodes 3, the partition 4 may not be provided.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description.
[Element creation]
As shown in FIG. 1, a strip-like pixel electrode 3 having a width of 80 μm and a thickness of 0.15 μm is formed on a light-transmitting substrate 2 (white plate glass: length 100 mm × width 100 mm × thickness 0.7 mm) by a sputtering method to 80 μm. Formed at intervals. Here, the surface roughness Ra of the pixel electrode 3 was 20 nm in an arbitrary plane having an area of 200 μm ² . The partition 4 has a lower end width of 90 μm, an upper end width of 45 μm, and a height of 2 μm in contact with the translucent substrate 2, and has a substantially trapezoidal cross section.

Here, the partition 4 was spin-coated with positive photosensitive polyimide, and as a condition for spin coating, the light-transmitting substrate 2 was rotated at 110 rpm for 5 seconds and then rotated at 400 rpm for 20 seconds. A photomask hidden only on the partition wall 4 was prepared, and a portion other than the partition wall 4 of the photosensitive material applied to the entire surface of the substrate by photolithography was exposed to 180 mJ / cm ² by an i-line stepper. After the exposure, development was performed, and baking was performed at 200 ° C. for 60 minutes using an oven to form partition walls 4. Further, the hole injection layer 5 is applied to the partition wall 4 by a relief printing method using a mixture of poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid as a hole injection material. It was formed by drying at 30 ° C. for 30 minutes. In addition, the hole transport layer 6 uses a polyarylene derivative as a hole transport material, dissolves this in xylene, and applies an ink having a concentration of 3.0 wt% to the partition wall 4 by a relief printing method. It was formed by drying at 200 ° C. for 10 minutes.

  2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl-1H-benzimidazole) (TPBi) is used as the host material of the red light emitting layer 7, and 2,3 ′ is used as the doped material. , 7,8,12,13,17,18-octaethyl-21H, 23H-Polyphyrin Platinum 2 (PtOEP) so that the weight ratio is 1% at TPBi / PtOEP = 0.90 / 0.10. The organic light emitting ink dissolved in toluene was applied to the partition walls by letterpress printing and formed by drying for 10 minutes at 100 ° C. The thickness of the red light emitting layer 7 after drying was 50 nm at the center of the pixel. It became.

  The host material of the green light emitting layer 8 is TPBi, and the doping material is tris (2- (p-tolyl) pyridine) iridium III (Ir (mppy) 3), and the weight ratio is TPBi / Ir (mppy) 3 = 0. The organic light-emitting ink dissolved in toluene so as to have a concentration of 1% at 0.94 / 0.06 was applied to the partition walls 4 by a relief printing method. This was formed by drying at 100 ° C. for 10 minutes. The film thickness of the green light emitting layer 8 after drying was 50 nm at the center of the pixel.

As the blue light-emitting layer 9, 9,10-di- (2-naphthyl) anthracene (hereinafter referred to as "DNA") is formed on the red light-emitting layer 7, the green light-emitting layer 8, and the hole transport layer 6 by a vacuum deposition method. A film co-deposited with 2,5,8,11-tetra-t-butylperylene (hereinafter referred to as “TBP”) was formed. The co-deposition ratio of DNA and TBP was changed as the deposition progressed. The deposition rate was adjusted so that the mixing ratio of TBP was 1% by mass on the pixel electrode 3 side in the initial stage of vapor deposition, and the mixing ratio of TBP was 20% by mass on the counter electrode 11 side in the stage of vapor deposition. The mixing ratio was continuously changed between these regions to form a thickness of 30 nm.
Further, a thickness of 20 nm was formed on the blue light emitting layer 9 by a vacuum deposition method using Alq ₃ as the electron transport layer 10 at a film formation rate of 0.01 nm / sec. Thereafter, LiF / Al = 0.5 nm / 150 nm was formed as the counter electrode 11 by vapor deposition. Thereafter, the sealing substrate 13 was bonded to obtain the organic light emitting display device 1.

In the peripheral portion of the display unit of the organic light emitting display device 1 thus obtained, an anode-side extraction electrode connected to each pixel electrode and a cathode-side extraction electrode connected to the cathode layer are provided. It has been. These extraction electrodes were connected to a power source, the organic light emitting display device 1 was turned on and displayed, and the lighting state and the display state were confirmed.
When the obtained organic light emitting display device 1 was driven and the display was confirmed, the light emission state was good. Moreover, the color purity fall by the influence from the blue light emitting layer 9 in a red organic EL element and a green organic EL element was suppressed, and the display characteristic was favorable.

[Comparative example]
First, a red light emitting layer and a green light emitting layer are formed by the same method as in the above example, and the mixing ratio of TBP is constant at 20% by mass without changing the co-evaporation ratio of DNA and TBP in the blue light emitting layer. The organic light emitting display device was obtained from the electron transport layer by the same method as in the above example.
When the organic light emitting display device thus obtained was driven, a decrease in color purity due to the influence from the blue light emitting layer was observed in the red organic EL element and the green organic EL element. Therefore, the display characteristics as an organic light emitting display device have been degraded.

  From the evaluation result of the comparative example, the co-evaporation ratio of DNA and TBP in the blue light emitting layer was not reduced gradually from the counter electrode side to the pixel electrode side. The light emission of the blue light emitting layer in the EL element was not suppressed, and the color purity was lowered. On the other hand, in the embodiment, since the TBP concentration gradually decreased from the counter electrode 11 side toward the pixel electrode 3 side, the red organic EL element and the green organic EL element have good color purity and display characteristics. A good organic light emitting display device 1 was obtained.

  The present invention relates to an organic light emitting display device in which a blue light emitting layer is laminated by a vapor deposition method on a red light emitting layer and a green light emitting layer formed by a wet method, and a blue light emitting layer in a red organic EL element and a green organic EL element. This is useful in suppressing a decrease in color purity due to the influence of the above.

DESCRIPTION OF SYMBOLS 1 ... Organic light-emitting display device 2 ... Translucent substrate 3 ... Pixel electrode 4 ... Partition wall 5 ... Hole injection layer 6 ... Hole transport layer 7 ... Red light emitting layer 8 ... Green light emitting layer 9 ... Blue light emitting layer 10 ... Electron transport Layer 11 ... Counter electrode 12 ... Resin layer 13 ... Sealing substrate 30 ... Letterpress printing device 31 ... Stage 32 ... Printed substrate 33 ... Ink tank 34 ... Ink chamber 35 ... Anilox roll 36 ... Doctor 37 ... Letterpress 38 ... Plate cylinder 39 ... Ink layer

Claims (6)

On the board
A pixel electrode provided for each of the red organic EL element, the green organic EL element, and the blue organic EL element;
A hole injection / transport layer having at least one of the characteristics of hole injection or hole transport formed on the pixel electrode;
A red light emitting layer and a green light emitting layer formed on the hole injection / transport layer;
A blue light emitting layer formed on the entire surface of the red light emitting layer, the green light emitting layer, and the hole injection / transport layer;
At least an electron injection / transport layer having at least one characteristic of electron injection or electron transport and a counter electrode, which are sequentially formed on the entire surface of the blue light emitting layer, are formed,
The blue light-emitting layer contains at least an electron-transporting host material and a hole-transporting dopant material, and the concentration of the hole-transporting dopant material in the blue light-emitting layer is from the counter electrode side toward the pixel electrode side. An organic light-emitting display device that is gradually reduced.   The concentration of the hole transporting dopant material in the region near the pixel electrode side interface of the blue light emitting layer is greater than the concentration of the hole transporting dopant material in the region near the counter electrode side interface of the blue light emitting layer. The organic light emitting display device according to claim 1, wherein the organic light emitting display device is 0% by mass or more and 50% by mass or less.   3. The organic light emitting display device according to claim 2, wherein a concentration of the hole transporting dopant material in the blue light emitting layer is 3 mass% or less in a region near the interface on the pixel electrode side.   4. The organic light emitting display device according to claim 3, wherein a concentration of the hole transporting dopant material in the blue light emitting layer is 5% by mass or more in a region near the counter electrode side interface. A method for manufacturing the organic light emitting display device according to claim 1,
Forming a pixel electrode provided for each of the red organic EL element, the green organic EL element, and the blue organic EL element on the substrate;
Forming a hole injection / transport layer having at least one of hole injection and hole transport on the pixel electrode by a wet method;
Forming a red light emitting layer and a green light emitting layer on the hole injection / transport layer by a wet method;
Forming a blue light emitting layer on the entire surface of the red light emitting layer, the green light emitting layer and the hole injection / transport layer by vapor deposition;
And at least a step of forming an electron injection / transport layer having at least one of electron injection or electron transport and a counter electrode over the entire surface of the blue light emitting layer,
The blue light emitting layer contains at least an electron transporting host material and a hole transporting dopant material, and the concentration of the hole transporting dopant material in the blue light emitting layer is gradually decreased from the counter electrode side to the pixel electrode side. A method for manufacturing an organic light emitting display device.   6. The method of manufacturing an organic light emitting display device according to claim 5, wherein an ink jet method, a nozzle printing method, letterpress printing, gravure printing, or reverse offset printing is used as the wet method.

Images