JP2014063699A - Organic el display panel and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL display panel which exhibits high efficiency, has long life, and can be manufactured simply.SOLUTION: The organic EL display panel includes: a first electrode formed on a substrate corresponding to each of red, green and blue sub-pixels; a red organic luminescent layer containing a low molecular hole transport material and a red luminescent material and a green organic luminescent layer containing a low molecular hole transport material and a green luminescent material, both being formed corresponding to the red and green sub-pixels on the first electrode; a hole transport layer containing a low molecular hole transport material and formed corresponding to the blue sub-pixel on the first electrode; a blue organic luminescent layer containing a blue luminescent material and formed on the red and the green organic luminescent layers corresponding to the red and the green sub-pixels and on the hole transport layer corresponding to the blue sub-pixel; and a second electrode on the blue organic luminescent layer. The low molecular hole transport materials included in the red and the green organic luminescent layers are each formed so that their concentration is higher on the first electrode side than on the other side in the red and the green organic luminescent layers.

Description

  The present invention relates to an organic EL display panel using electroluminescence (hereinafter also referred to as EL) and a manufacturing method thereof.

  An organic electroluminescence element (hereinafter referred to as an organic EL element) is one in which an organic light emitting layer made of an organic light emitting material is formed between two opposing electrodes, and light is emitted by passing a current through the organic light emitting layer.

  FIG. 1 shows a schematic diagram of a general organic electroluminescence display panel. One pixel (pixel) 101 includes sub-pixels 102 of R (red), G (green), and B (blue) of the three primary colors. Each sub-pixel 102 is formed with an organic EL element of each emission color, and in the case of active driving, a thin film transistor (hereinafter also referred to as TFT) is formed.

  In general, a display substrate is used in which an insulating material such as patterned photosensitive polyimide is formed in a partition shape so as to partition subpixels. At this time, the barrier rib pattern is formed so as to cover the edge portion of the transparent electrode formed as an anode, and the barrier rib pattern defines the subpixel region.

  Then, a hole injection layer is formed on the transparent electrode and the barrier rib pattern. There are two methods for forming a hole injection layer for injecting hole carriers, dry film formation and wet film formation. In the case of using a wet film formation method, a polythiophene derivative dispersed in water is generally used. A hole transport layer may be formed on the hole injection layer.

  Similarly, there are two methods for forming the organic light emitting layer: dry film formation and wet film formation. However, when using the vacuum evaporation method, which is dry film formation that facilitates uniform film formation, a fine pattern mask is used. Therefore, it is necessary to perform patterning, and large substrates and fine patterning are very difficult.

JP 2001-93668 A JP 2001-155858 A Japanese Patent Laid-Open No. 10-12377 Japanese Patent No. 38995666 Japanese Patent No. 40623352 JP 2006-140434 A JP 2011-108462 A JP 2011-181915 A

  On the other hand, it is possible to use a method in which a polymer material or a low molecular material is dissolved in a solvent to form a coating solution, and this is formed into a thin film by a wet film forming method. When a light emitting medium layer including an organic light emitting layer is formed by a wet film formation method using a coating material of a polymer material or a low molecular material, the layer structure is laminated with a hole transport layer and an organic light emitting layer from the anode side. A layer structure is common. At this time, the organic light emitting layer is formed by dissolving or stably dispersing organic light emitting materials having respective emission colors of red (R), green (G), and blue (B) in a solvent in order to form a color panel. It can be applied separately using organic luminescent ink (see Patent Documents 1 and 2).

  When the organic layer is formed by vacuum deposition, the large area, high definition is difficult as described above, and the equipment cost is high, whereas the wet film formation method does not use vacuum equipment, so the equipment cost is relatively low, Since no mask is used, there is an advantage in increasing the area.

  For the patterning film formation by the wet film formation method, pattern formation by an ink jet method, a printing method, or a nozzle printing method has been proposed. For example, the ink jet method disclosed in Patent Document 3 is a method for obtaining a desired pattern by ejecting a light emitting layer material dissolved in a solvent from an ink jet nozzle onto a substrate and drying the material on the substrate.

  Although the wet film formation method has the above-described advantages, there is a problem in that the light emission characteristics are low as compared with an element formed using a vacuum deposition method in a blue element. This means that when a hole transport layer used in an organic EL device prepared by vacuum deposition is applied to a wet film formation method, the hole transport layer is dissolved in the step of applying an organic light emitting layer thereon. This is because it cannot be applied due to a problem. Therefore, in order to wet-deposit the organic light emitting layer, it has been common to use an insolubilizing material such as a crosslinkable material for the hole transport layer. However, in the blue element, the hole transport layer adjacent to the light emitting layer is required to have high electron blocking properties and exciton blocking properties, whereas insoluble materials such as crosslinkable materials satisfy these requirements. Was not obtained.

  In Patent Documents 4 and 5, red and green organic light-emitting layers are formed on the red and green organic EL elements by an inkjet method, respectively, and a blue organic light-emitting layer is formed on the entire surface of the red, green, and blue organic EL elements from above. A method of forming the film by a vapor deposition method is disclosed. The process is simplified by forming a blue organic light-emitting layer with insufficient characteristics by vapor deposition and forming it on the entire surface without further patterning, but the characteristics of the organic EL element are still insufficient.

  Patent Document 6 discloses a method of simplifying the process by forming a blue organic light emitting layer on the entire surface and not performing fine patterning. However, this method has a problem that the characteristics of the red and green organic EL elements are deteriorated.

  In Patent Documents 7 and 8, a blue organic light-emitting layer is formed on the entire surface by vapor deposition, and different materials are used for the hole injection / transport layer for red and green organic EL elements and blue organic EL elements. A method of forming is disclosed. The characteristics are improved by using a low-molecular material for the hole injection / transport layer of the blue organic EL element. However, even in these methods, the characteristics of the organic EL element are still insufficient, and there is a problem that the number of steps increases by separately coating the hole injection / transport layer.

  The present invention has been made in view of the above problems, and provides an organic EL display panel that can be easily manufactured with high efficiency and a long lifetime, and a manufacturing method thereof.

  According to a first aspect of the present invention, there is provided a first electrode formed on a substrate, a light emitting medium layer including at least an organic light emitting layer, and the first electrode facing the first electrode so as to sandwich the light emitting medium layer. An organic EL display panel having at least a red subpixel, a green subpixel, and a blue subpixel, the red subpixel, the green subpixel, and the blue subpixel on the substrate. The organic light emitting layer, comprising: the first electrode corresponding to each of the pixels; and at least a low molecular hole transport material and a red light emitting material formed in a portion corresponding to the red subpixel on the first electrode. A red organic light emitting layer, and at least the low molecular hole transport material and the green light emitting material formed in a portion corresponding to the green subpixel on the first electrode. A green organic light emitting layer as the organic light emitting layer, a hole transport layer including at least the low molecular hole transport material formed in a portion corresponding to the blue subpixel on the first electrode, and a red sub Formed on the red organic light emitting layer in a portion corresponding to a pixel, on the green organic light emitting layer in a portion corresponding to a green subpixel, and on the hole transport layer in a portion corresponding to a blue subpixel. In addition, at least a blue light emitting material, the blue organic light emitting layer as the organic light emitting layer, and the second electrode formed on the blue organic light emitting layer, the low organic light emitting layer The molecular hole transport material is formed with a concentration gradient so that the concentration on the first electrode side in the red organic light emitting layer is higher, and the low molecular hole contained in the green organic light emitting layer. The transport material is Towards the first electrode side in the color organic light-emitting layer is formed a concentration gradient such that the concentration is high.

  According to a second invention, in the first invention, between the first electrode and the red organic light emitting layer in the red subpixel, between the first electrode and the green organic light emitting layer in the green subpixel, and An insoluble second hole transport layer is included between the first electrode and the hole transport layer in the blue subpixel.

  According to a third invention, in the first or second invention, an electron transport layer is included between the blue organic light emitting layer and the second electrode.

  According to a fourth aspect of the present invention, there is provided a first electrode formed on a substrate, a light emitting medium layer including at least an organic light emitting layer, and a second electrode formed opposite to the first electrode so as to sandwich the light emitting medium layer. A method for manufacturing an organic EL display panel having a red subpixel, a green subpixel, and a blue subpixel, wherein the first electrode corresponds to each of the red subpixel, the green subpixel, and the blue subpixel. Forming a hole transport layer including a low-molecular hole transport material on the first electrode, and red organic light emission in a portion corresponding to the red subpixel on the hole transport layer. Forming a green organic light emitting layer on a portion corresponding to the green subpixel on the hole transport layer by a coating method, and before the portion corresponding to the red subpixel. A blue organic light emitting layer is vacuum-deposited on the red organic light emitting layer, on the green organic light emitting layer corresponding to the green subpixel, and on the hole transporting layer corresponding to the blue subpixel. And a step of forming the second electrode on the blue organic light emitting layer.

  The fifth invention includes a step of forming an insoluble second hole transport layer between the step of forming the first electrode and the step of forming the hole transport layer in the fourth invention. It is characterized by.

  According to a sixth invention, in the fourth or fifth invention, the method includes a step of forming an electron transport layer between the step of forming the blue organic light emitting layer and the step of forming the second electrode. It is said.

  According to a seventh invention, in any one of the fourth to sixth inventions, the red organic light emitting layer and the green organic light emitting layer are formed by relief printing.

  An eighth invention is characterized in that, in any of the fourth to seventh inventions, the hole transport layer is formed by a vacuum deposition method.

  According to a ninth invention, in any one of the fourth to eighth inventions, the second hole transport layer is formed by a coating method.

  According to the present invention, an organic EL display panel that can be easily manufactured with high efficiency and long life can be obtained.

Schematic diagram showing the configuration of a general organic EL display panel in plan view Sectional drawing which shows the structural example of the organic EL element with which the organic EL display panel which concerns on one Embodiment of this invention is provided. Sectional drawing which shows the structural example of the TFT substrate with a partition which can be used for the organic electroluminescent display panel which concerns on one Embodiment of this invention.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a cross-sectional configuration example of the organic EL element included in the organic EL display panel according to the present embodiment. FIG. 2 shows an organic EL element for one pixel for convenience.
The organic EL element has regions corresponding to the red subpixel 211, the green subpixel 212, and the blue subpixel 213 on the substrate 200. In the region of the red subpixel 211, the first electrode 201, the hole injection layer 203, the second hole transport layer 204, the red organic light emitting layer 206, the blue organic light emitting layer 208, the electron transport layer 209, and the second electrode 210 are stacked in this order. In the region of the green subpixel 212, the first electrode 201, the hole injection layer 203, the second hole transport layer 204, the green organic light emitting layer 207, the blue organic light emitting layer 208, the electron transport layer 209, and the second electrode 210 are stacked in this order. In the region of the blue subpixel 213, the first electrode 201, the hole injection layer 203, the second hole transport layer 204, the hole transport layer 205, the blue organic light emitting layer 208, the electron transport layer 209, and the second electrode 210 are stacked in this order. The first electrodes 201 are electrically separated between the sub-pixels by a partition wall 202 provided on the substrate 200.

  Next, an outline of a method for producing the organic EL element having the above-described configuration will be described.

  First, the first electrode 201 is formed on the substrate 200 at positions corresponding to the red subpixel 211, the green subpixel 212, and the blue subpixel 213. Next, the partition wall 202 is formed so as to partition the light emitting region. Next, the hole injection layer 203 is formed on the first electrode 201.

  Next, an insoluble second hole transport layer 204 is formed on the hole injection layer 203. Insoluble means that it is insoluble in the solvent of the ink used when an organic film is formed on the second hole transport layer 204 by a coating method. By forming the insoluble second hole transport layer 204, when the red organic light emitting layer 206 and the green organic light emitting layer 207 are formed thereon by the coating method, the second hole transport layer 204 is not dissolved. Since it is formed, it has an electron block property and an exciton block property, and improves device characteristics of the red subpixel 211 and the green subpixel 212. The second hole transport layer 204 is preferably formed by a coating method. In the case where the second hole transport layer 204 is formed by a coating method, it is preferable to apply an insolubilizing treatment such as a heat treatment after coating using an ink mixed with a soluble material.

  Next, a hole transport layer 205 containing a low molecular hole transport material is formed on the second hole transport layer 204. The hole transport layer 205 is preferably formed by a vacuum evaporation method. This is because the state of the interface with the blue organic light emitting layer 208 formed thereon is good. In this case, it is not necessary to use a fine metal mask by depositing the hole transport layer 205 on the entire surface. It can also be formed by a coating method.

  Next, a red organic light emitting layer 206 and a green organic light emitting layer 207 are formed on the hole transport layer 205 at portions corresponding to the red and green subpixels 211 and 212, respectively, by a coating method. At this time, the red organic light emitting layer 206 is mixed with the low molecular hole transport material formed thereunder, and the green organic light emitting layer 207 is formed with the low molecular hole transport material formed thereunder. Mix. In general, the recombination region of holes and electrons is biased toward the hole transport layer side in the organic light emitting layer, and this is one factor of element deterioration during driving. By including the low molecular hole transport material, the recombination region bias can be reduced by a simple method.

  Here, the low molecular hole transport material contained in the red organic light emitting layer 206 is formed with a concentration gradient such that the concentration on the first electrode 201 side in the red organic light emitting layer 206 is higher. The low molecular hole transport material contained in the organic light emitting layer 207 has a concentration gradient such that the concentration on the first electrode 201 side in the green organic light emitting layer 207 is higher. By forming such a concentration gradient, it becomes possible to promote the injection of holes into the organic light emitting layer and to suppress the leakage of holes to the second electrode 210 side. In order to further utilize such effects, it is preferable that the concentration of the low molecular hole transport material is 100% at the interface of the organic light emitting layer on the first electrode 201 side. In addition, the concentration of the low molecular hole transport material is preferably 0% at the interface of the organic light emitting layer on the second electrode 210 side. In order to form such a structure, the red organic light emitting layer 206 and the green organic light emitting layer 207 are preferably formed by a relief printing method. In letterpress printing, it is common to use ink with a relatively high viscosity, and such a structure is easily controlled.

  Next, on the red organic light emitting layer 206 corresponding to the red subpixel 211, on the green organic light emitting layer 207 corresponding to the green subpixel 212, and in the hole corresponding to the blue subpixel 213. A blue organic light emitting layer 208 is formed on the transport layer 205 by a vacuum deposition method. The blue organic light emitting layer 208 is deposited on the entire surface, so that it is not necessary to use a fine metal mask. In addition, by using the vacuum deposition method, an interface can be formed without dissolving the hole transport layer 205 including the low molecular hole transport material thereunder, thereby achieving electron blocking properties and exciton blocking properties. The

Next, the electron transport layer 209 is formed on the blue organic light emitting layer 208 by a vacuum deposition method. Next, the second electrode 210 is formed on the electron transport layer 209.
An organic EL element is formed through the above steps.

  The organic EL display panel in the present invention can be applied to both passive driving and active driving.

  Below, the detailed structure of an organic electroluminescent display panel provided with the said organic electroluminescent element is demonstrated.

<Board>
The substrate used in the embodiment of the present invention may be any substrate that can support an organic EL element, but in the case of an active matrix system, a TFT substrate (active matrix substrate) on which a thin film transistor is formed is used. FIG. 3 shows an example of a TFT substrate with a partition which can be used in the present invention. A pixel electrode as a first electrode of the TFT and the organic EL display panel is provided, and the TFT and the pixel electrode are electrically connected. For example, an active layer 301, a gate insulating film 302, a gate electrode 305, a scanning line 309, an insulating film 306, a source electrode 303, a drain electrode 304, a pixel electrode 307, a partition wall 308, and the like are formed over the substrate 300. The active layer 301 is formed on the substrate 300, and the gate insulating film 302 covers the active layer 301. The gate electrode 305 is formed to be connected to each other in the same layer as the scanning line 309 and is provided on the gate insulating film 302. The insulating film 306 is formed on the gate insulating film 302 so as to cover the pattern of the gate electrode 305 and the scanning line 306. The source electrode 303 and the drain electrode 304 are in contact with the active layer 301 from above the insulating film 306 through a contact hole. The pixel electrode 307 is formed on the insulating film 306 so as to be connected to the drain electrode 304. The partition 308 is formed so as to cover the upper part of the TFT configured as described above.

  The TFT and the portion of the active matrix driving type organic EL display panel formed above the TFT are supported by a support. Any material can be used as the support as long as it has mechanical strength and insulation and is excellent in dimensional stability. For example, plastic films and sheets such as glass, quartz, polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, etc., or oxidation to these plastic films and sheets Metal oxides such as silicon and aluminum oxide, metal fluorides such as aluminum fluoride and magnesium fluoride, metal nitrides such as silicon nitride and aluminum nitride, metal oxynitrides such as silicon oxynitride, acrylic resins and epoxy resins A transparent resin substrate made of a polymer resin film such as a silicone resin or a polyester resin, or a combination of a plurality of layers and laminated, a metal foil such as aluminum or stainless steel, a sheet, a plate, or the plastic It can be used click film or aluminum sheet, copper, nickel, stainless steel and metal film non-translucent substrate as a laminate of such. What is necessary is just to select the translucency of a support body according to which surface light extraction is performed from. The support made of these materials has been subjected to moisture-proofing treatment or hydrophobic treatment by forming an inorganic film or applying a fluororesin in order to avoid intrusion of moisture into the organic EL display panel. It is preferable. In particular, it is preferable to reduce the moisture content and gas permeability coefficient of the support in order to avoid the intrusion of moisture into the luminescent medium layer.

  As the thin film transistor (TFT) provided on the support, a known thin film transistor can be used. Specifically, a thin film transistor composed mainly of an active layer where a source / drain region and a channel region are formed, a gate insulating film, and a gate electrode as described above can be given. The structure of the thin film transistor is not particularly limited, and examples thereof include a staggered type, an inverted staggered type, a top gate type, and a coplanar type.

The active layer 301 is not particularly limited, and examples thereof include inorganic semiconductor materials such as amorphous silicon, polycrystalline silicon, microcrystalline silicon, and cadmium selenide, metal oxide semiconductor materials such as ZnO and IGZO, or thiol. It can be formed of organic semiconductor materials such as a fuen oligomer and poly (p-ferylene vinylene). As a method for forming these active layers 301, for example, amorphous silicon is deposited by plasma CVD and ion doping is performed; amorphous silicon is formed by LPCVD using SiH ₄ gas, and amorphous silicon is formed by solid phase growth. After obtaining polysilicon by crystallization of silicon, ion doping is performed by ion implantation; amorphous silicon is formed by LPCVD using Si ₂ H ₆ gas and PECVD using SiH ₄ gas. A method of annealing with a laser such as laser to crystallize amorphous silicon to obtain polysilicon, and then ion doping by ion doping method (low temperature process); depositing polysilicon by low pressure CVD method or LPCVD method, and 1000 ° C. Is thermally oxidized to form a gate insulating film 302 above the gate electrode 305 of the n + polysilicon is formed thereon, then, a method of ion doping (high temperature process), and the like by an ion implantation method.

As the gate insulating film 302, a film normally used as a gate insulating film can be used. For example, the gate insulating film 302 is obtained by thermally oxidizing SiO ₂ formed by PECVD, LPCVD, or the like, or a polysilicon film. SiO ₂ or the like can be used.

  As the gate electrode 305, those normally used as the gate electrode can be used, for example, metals such as aluminum and copper; refractory metals such as titanium, tantalum and tungsten; polysilicon; silicide of refractory metals Polycide; and the like.

  The thin film transistor may have a single gate structure, a double gate structure, or a multi-gate structure having three or more gate electrodes. Moreover, you may have a LDD structure and an offset structure. Further, two or more thin film transistors may be arranged in one pixel.

  In the organic EL display panel of this embodiment, the thin film transistor is connected so as to function as a switching element for selecting a pixel, and the drain electrode 304 and the pixel electrode 307 of the thin film transistor are electrically connected to each other.

<Pixel electrode>
The pixel electrode (first electrode) 307 is formed on the TFT substrate, and is patterned as necessary. Examples of the material of the pixel electrode 307 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, A fine particle dispersion film in which fine particles of a metal material are dispersed in an epoxy resin, an acrylic resin, or the like can be used in any form formed as a single layer or laminated in combination with a plurality of layers. When the pixel electrode 307 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. As a formation method of the pixel electrode 307, depending on the material, dry film forming methods such as resistance heating vapor deposition method, electron beam vapor deposition method, reactive vapor deposition method, ion plating method, sputtering method, gravure printing method, screen printing, etc. A wet film forming method such as a method can be used. As a patterning method for the pixel electrode 307, an existing patterning method such as a mask vapor deposition method, a photolithography method, a wet etching method, or a dry etching method can be used depending on a material or a film forming method. In the present invention, the photolithography method is preferable.

<Partition wall>
The partition 308 is formed so as to partition the light emitting region corresponding to the pixel. A partition wall 308 is formed to form an opening for containing a solution in which an organic material is dissolved when the organic layer is formed by a coating method.

  As a method for forming the partition wall 308, an inorganic film is uniformly formed on a substrate, masked with a resist, and then dry etching is performed, or a photosensitive resin is laminated on the substrate, and a predetermined pattern is formed by photolithography. The method to do is mentioned. A preferable height of the partition wall 308 is 0.1 μm to 10 μm, and more preferably about 0.5 μm to 4 μm. This is because if it is too high, formation and sealing of the counter electrode are hindered, and if it is too low, colors are mixed with adjacent pixels when the light emitting medium layer is formed. As the partition wall 308, a photosensitive resin can be preferably used. As the photosensitive resin, either a positive resist or a negative resist may be used, and specific examples include polyimide, acrylic resin, and novolak resin photosensitive resins. If necessary, a water repellent can be added, or plasma or UV can be irradiated to impart liquid repellency to the ink after formation.

<Organic EL device>
As an example of the organic EL element, on the first electrode 201, a hole injection layer 203, a hole transport layer 205, an organic light emitting layer (a red organic light emitting layer 206, a green organic light emitting layer 207, a blue organic light emitting layer) as a light emitting medium layer. 208), an electron transport layer 209 is sequentially provided, and a second electrode 210 is further formed. A part of these layers sandwiched between the electrodes can be omitted, and a layer such as a hole blocking layer can be further added, and is appropriately selected from known ones.

<Hole injection layer>
The hole injection layer 203 has a function of injecting holes from the first electrode 210. The physical property value of the hole injection layer 203 preferably has a work function equal to or higher than that of the pixel electrode 307. This is because holes are efficiently injected from the pixel electrode 307. Although it varies depending on the material of the pixel electrode 307, 4.5 eV or more and 6.5 eV or less can be used. When the pixel electrode 307 is ITO or IZO, 5.0 eV or more and 6.0 eV or less can be suitably used. The specific resistance of the hole injection layer 203 is preferably 1 × 10 ³ to 2 × 10 ⁶ Ω · m, more preferably 5 × 10 ³ to 1 × 10 ⁶ Ω, in a thickness of 30 nm or more. -M. Further, in the bottom emission structure, emitted light is extracted from the pixel electrode 307 side. Therefore, if the light transmittance is low, the extraction efficiency is lowered. It can be preferably used.

As a material constituting the hole injection layer 203, for example, a polymer material such as polyaniline, polythiophene, polyvinyl carbazole, a mixture of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid can be used. In addition, a conductive polymer having a conductivity of 10 ⁻² S / cm or more and 10 ⁻⁶ S / cm or less can be preferably used. The polymer material can be used in a film forming process by a wet method. Therefore, it is preferable to use a polymer material when forming the hole injection layer 203. Such a polymer material is dispersed or dissolved in water or a solvent and used as a dispersion or solution.

In the case of using an inorganic material as a hole transport _{material, Cu 2 O, Cr 2 O} 3, Mn 2 O 3, FeO x (x~0.1), NiO, CoO, Bi 2 O 3, SnO 2, ThO ₂ , Nb ₂ O ₅ , Pr ₂ O ₃ , Ag ₂ O, MoO ₂ , ZnO, TiO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO _2, etc. are used. be able to.

  As a method for forming the hole injection layer 203, the entire surface of the display region on the pixel electrode 307 is formed by a simple method such as a slit coating method, a spin coating method, a die coating method, a dipping method, a blade coating method, or a spray method. However, existing film forming methods such as a relief printing method, a gravure printing method, and a wet film forming method such as a screen printing method can also be used. In forming the hole injection layer 203, ink (liquid material) in which the hole transport material is dissolved in water, an organic solvent, or a mixed solvent thereof is used. As the organic solvent, toluene, xylene, anisole, mesitylene, tetralin, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate and the like can be used. In addition, surfactants, antioxidants, viscosity modifiers, ultraviolet absorbers and the like may be added to the ink. When the hole injection layer 203 is an inorganic material, it can be formed using a dry process such as 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.

<Hole transport layer>
The hole transport layer 205 is laminated between the organic light emitting layer and the hole injection layer 203 so as to transport holes to the organic light emitting layer and have electron blocking properties and exciton blocking properties to emit light from the device. Has the function of improving efficiency and life.

  The hole transport layer 205 includes a low molecular hole transport material. Examples of the low molecular hole transport material include aromatic amine, (triphenylamine) dimer derivative (TPD), (α-naphthyldiphenylamine) dimer (α-NPD), [(triphenylamine) dimer] spirodimer ( Spiro-TAD), TPTE, triarylamines such as TPT1, 4,4 ′, 4 ″ -tris [3-methylphenyl (phenyl) amino] triphenylamine (m-MTDATA), 4,4 ′, 4 ″ -Starburst amines such as tris [1-naphthyl (phenyl) amino] triphenylamine (1-TNATA) and 5,5′-α-bis- {4- [bis (4-methylphenyl) amino] phenyl} -2,2 ': oligothiophenes such as 5', 2'-α terthiophene (BMA-3T), etc. However, it is not limited to these.

  The hole transport layer 205 can include a matrix polymer. As the matrix polymer, for example, polycarbonate, polystyrene, polymethyl methacrylate, polypropylene, polyethersulfone, cycloolefin polymer, polyarylate, polyamide, polyethylene terephthalate, polyethylene naphthalate and the like can be preferably used.

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

  As these hole transport layer materials, it is preferable to select a material having a work function equal to or higher than that of the hole injection layer 203, and it is more preferable that the work function is equal to or lower than that of the organic light emitting layer. This is because an unnecessary injection barrier is not formed when carriers are injected from the hole injection layer 203 into the organic light emitting layer. Further, in order to obtain the effect of confining charges that could not contribute to light emission from the organic light emitting layer, the band gap is preferably 3.0 eV or more, more preferably 3.5 eV or more.

  As a method for forming the hole transport layer 203, a dry process such as a vacuum deposition method or a wet process can be used, but a vacuum deposition method is preferable. This is because the state of the interface with the blue organic light emitting layer 208 formed thereon is good. As the wet process, it is preferable to form all over the display area on the pixel electrode 307 by a simple method such as a slit coating method, a spin coating method, a die coating method, a dipping method, a blade coating method, or a spray method.

  In addition, an insoluble second hole transport layer 204 is preferably provided between the hole injection layer 203 and the hole transport layer 205. The material applied to the second hole transport layer 204 can be appropriately selected from known materials. For example, polyvinylcarbazole or a derivative thereof, a polyarylene derivative having an aromatic amine in a side chain or a main chain, And polyfluorene derivatives.

  The second hole transport layer 204 is preferably formed by a coating method. In the case where the second hole transport layer 204 is formed by a coating method, it is preferable to apply an insolubilizing treatment such as a heat treatment after coating using an ink mixed with a soluble material.

<Organic light emitting layer>
After the formation of the hole transport layer 205, an organic light emitting layer is formed. The organic light emitting layer is a layer that emits light by passing an electric current.

  Examples of the organic light emitting material forming the organic light emitting layer include 9,10-diarylanthracene derivatives, pyrene, coronene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolato) aluminum complex, tris ( 4-methyl-8-quinolato) aluminum complex, bis (8-quinolato) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolato) aluminum complex, tris (4-methyl-5-cyano-8) -Quinolate) 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 ( -Quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, coumarin, perylene, pyran, anthrone, porphyrene Low molecular weight light emitting materials such as quinacridone, N, N′-dialkyl-substituted quinacridone, naphthalimide, N, N′-diaryl-substituted pyrrolopyrrole, and iridium complex can be used. It is not limited.

  Further, polyarylene-based, polyarylene vinylene-based, and polyfluorene-based polymer materials can be given.

  The organic light emitting layer can include a matrix polymer. As the matrix polymer, for example, polycarbonate, polystyrene, polymethyl methacrylate, polypropylene, polyethersulfone, cycloolefin polymer, polyarylate, polyamide, polyethylene terephthalate, polyethylene naphthalate and the like can be preferably used.

  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.

  The blue organic light emitting layer 208 can be appropriately selected from known blue light emitting materials, but is preferably a low molecular weight material that can be vacuum deposited. Examples include anthracene derivatives, naphthalene derivatives, pyrene derivatives, styrylamine derivatives, metal complex systems, and the like.

  As a method for forming the red organic light emitting layer 206 and the green organic light emitting layer 207, a wet film forming method is preferable. For patterning film forming, wet methods such as an ink jet method, a nozzle printing method, a relief printing method, a gravure printing method, and a screen printing method are used. An existing film formation method such as a film formation method can be used. In particular, the relief printing method is preferable. As a method for forming the blue organic light emitting layer 208, a dry film forming method is preferable, and a vacuum deposition method is particularly preferable.

<Electron injection layer>
After forming the organic light emitting layer, a hole blocking layer, an electron injection layer, and the like can be formed. The material used for the hole blocking layer and the electron injection layer may be any material that is generally used as an electron transport material, such as triazole, oxazole, oxadiazole, silole, and boron. A film can be formed by a vacuum deposition method using a material, an alkali metal such as lithium fluoride or lithium oxide, or a salt or oxide of an alkaline earth metal. In addition, these electron transport materials or those obtained by mixing these electron transport materials in polymers such as polystyrene, polymethyl methacrylate, and polyvinyl carbazole are toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl A film can be formed by a printing method by dissolving or dispersing in alcohol, ethyl acetate, butyl acetate, water or the like alone or in a mixed solvent to form an electron injection coating solution.

<Counter electrode>
Next, a counter electrode (second electrode) is formed. When the counter electrode is a cathode, a material having a high electron injection efficiency into the organic light emitting layer and a low work function is used. Specifically, a single metal such as Mg, Al, or Yb is used, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface contacting the light emitting medium layer, and Al or Cu having high stability and conductivity is placed. You may use it, laminating | stacking. 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, Al An alloy system with a metal element such as Cu or Cu may be used. Specifically, alloys such as MgAg, AlLi, and CuLi can be used.

  As a method for forming the counter electrode, 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.

<Sealing>
As an organic EL display panel, it is possible to emit light by sandwiching a light emitting material between electrodes and passing an electric current. However, since an organic light emitting material is easily degraded by moisture and oxygen in the atmosphere, Seal for blocking.

<Can sealing>
For sealing, for example, a sealing can may be bonded onto the substrate. The sealing can needs to be low in gas permeability and can be made of glass or metal such as stainless steel. As the adhesive, a UV curable adhesive is preferable.

<Passivation layer>
In order to protect the organic EL element from oxygen and moisture from the outside, a passivation layer may be formed on the counter electrode. The passivation layer includes 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 metal acids such as silicon oxynitride. A laminated film of a metal carbide such as nitride 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 required. In view of the above, it is preferable to use silicon oxide, silicon oxynitride, or silicon nitride. Furthermore, by using a laminated film or a gradient film having a variable film density, a film having both step coverage and barrier properties can be obtained. .

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. The CVD method is preferably used because the film density and film composition can be easily varied depending on the step coverage surface and the film formation conditions. 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 , N ₂ O is added to an organic silicon compound such as monosilane, hexamethyldisilazane (HMDS), or tetraethoxysilane. The film density may be changed by changing the gas flow rate of silane or the like, or the plasma power, if necessary. Hydrogen or carbon may be added to the film by the reactive gas used. It can also be contained.

  The thickness of the passivation layer is preferably 5 μm or less, more preferably 1 μm or less.

<Sealing body>
For sealing, a resin layer may be provided on the sealing material and bonded together.

The sealing material 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, quartz, and moisture resistant film. Examples of moisture-resistant films include films formed by CVD of SiOx on both sides of plastic substrates, films with low permeability and water-absorbing films, or polymer films coated with a water-absorbing agent. The water vapor transmission rate is preferably 10 ⁻⁶ g / m ² / day or less.

  Examples of the material for the resin layer include a photo-curing adhesive resin, a thermosetting adhesive resin, a two-component curable adhesive resin, and an ethylene ethyl acrylate (EEA) made of epoxy resin, acrylic resin, silicone resin, etc. Examples thereof include 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 methods for forming a resin layer on a sealing material include solvent solution method, extrusion lamination method, melting / hot melt method, calendar method, nozzle coating method, screen printing method, vacuum laminating method, hot roll laminating method, etc. Can be mentioned. A material having a hygroscopic property or an oxygen absorbing property may be contained as necessary. Although the thickness of the resin layer formed on a sealing material is arbitrarily determined by the magnitude | size and shape of the organic electroluminescent display panel to seal, about 5-500 micrometers is desirable. In addition, although formed as a resin layer on the sealing material here, it can also be formed directly on the organic EL display device side.

  Finally, the organic EL display device and the sealing body are bonded together in a sealing chamber. When the sealing body has a two-layer structure of a sealing material and a resin layer, and a thermoplastic resin is used for the resin layer, it is preferable to perform only pressure bonding with a heated roll. When a thermosetting adhesive resin is used, it is preferable to perform heat curing at a curing temperature after pressure bonding with a heated roll. In the case where a photocurable adhesive resin is used, curing can be performed by further irradiating light after pressure bonding with a roll.

[Example 1]
Examples of the present invention will be described below.
As the substrate, an active matrix substrate including a thin film transistor (TFT) functioning as a switching element provided on a support and a pixel electrode 307 formed thereabove was used. The size of the substrate is 200 mm × 200 mm, in which a display with a diagonal of 5 inches and a pixel number of 320 × 240 is arranged in the center.

  ITO was used as the pixel electrode 307. An ITO film was formed on the substrate by sputtering and patterned. The film thickness was 40 nm. Next, the partition 308 (202) was formed in a shape that covers the end of the pixel electrode 307 and partitions the pixel. The partition wall 308 was formed using a positive resist over the entire surface of the substrate by a spin coater method with a thickness of 2 μm, and then patterned using a photolithography method.

  Next, as the hole injection layer 203, a mixture of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid was formed on the entire red, green, and blue subpixels with a film thickness of 50 nm by a die coating method.

  Next, as the second hole transport layer 204, a polyfluorene derivative was formed on the entire red, green, and blue subpixels by a die coating method and insolubilized by heat treatment. The film thickness of the second hole transport layer 204 after the heat treatment was 20 nm.

  Next, as the hole transport layer 203, a low molecular hole transport material TPT1 was formed to a thickness of 20 nm on the entire red, green, and blue subpixels by vacuum deposition. A fine metal mask is not used because it is formed over the entire subpixel.

  Next, an organic light-emitting ink in which a polyfluorene derivative, which is a red organic light-emitting material, is dissolved in toluene so as to have a concentration of 2% is used, this substrate is set in a printing machine, and the red organic light-emitting layer 206 is placed on the red subpixel 211. Was printed by letterpress printing. At the time of printing, TPT1 formed on the lower side was mixed with the red organic light emitting layer 206. The film thickness of the red organic light emitting layer 206 after printing and drying was 50 nm.

  Next, an organic light emitting ink in which a polyfluorene derivative, which is a green organic light emitting material, is dissolved in toluene so as to have a concentration of 2% is used, this substrate is set in a printing machine, and the green organic light emitting layer 207 is placed in the green subpixel 212. Was printed by letterpress printing. At the time of printing, TPT1 formed on the lower side was mixed with the green organic light emitting layer 207. The thickness of the green organic light emitting layer 207 after printing and drying was 50 nm.

  Next, as the blue organic light-emitting layer 208, an anthracene derivative and a styrylamine derivative were co-deposited at a ratio of 94: 6 on the entire red, green, and blue sub-pixels by a vacuum deposition method to have a thickness of 30 nm. A fine metal mask is not used because it is formed over the entire subpixel.

  Next, as the electron transport layer 209, 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl-1H— is formed on the entire red, green, and blue subpixels by vacuum deposition. Benzimidazole) (TPBi) was formed with a film thickness of 15 nm, and since it was formed on the entire subpixel, a fine metal mask was not used.

  Next, as the second electrode (cathode) 210, LiF was deposited to a thickness of 0.5 nm by a vacuum deposition method, and then an aluminum film was deposited to a thickness of 150 nm.

  Thereafter, these organic EL constituents were hermetically sealed using a glass cap and an adhesive in order to protect them from external oxygen and moisture.

  When the thus obtained active matrix driving type organic EL display panel was driven, it was possible to drive it satisfactorily. The hole transport layer 205 having a high electron blocking property and a high exciton blocking property could be formed under the blue organic light emitting layer 208 of the blue subpixel 213 without performing fine metal mask patterning. From the panel luminance measurement when this panel is caused to emit light, the characteristic of the red subpixel 211 is efficiency 12 cd / A, the characteristic of the green subpixel 212 is efficiency 15 cd / A, and the characteristic of the blue subpixel 213 is efficiency 6.2 cd / A. Met.

[Comparative Example 1]
An active matrix driving type organic EL display panel was produced in the same manner as in Example 1 except that the step of forming the hole transport layer 205 was not performed. The red organic light emitting layer 206 and the green organic light emitting layer 207 are not mixed with a low molecular hole transport material.

  When the obtained active matrix drive type organic EL display panel was driven, it was able to drive well. From the panel luminance measurement when this panel is made to emit light, the characteristic of the red subpixel 211 is efficiency 9.3 cd / A, the characteristic of the green subpixel 212 is efficiency 12 cd / A, and the characteristic of the blue subpixel 213 is efficiency 4.5 cd. / A.

The efficiency was improved in Example 1 compared to Comparative Example 1. Also, the luminance half-life during continuous driving is improved by 20% in the red subpixel 211, 30% in the green subpixel 212 and 50 in the blue subpixel 213 in the first embodiment compared to the comparative example 1. % Improved.
Thus, it has been clarified that the characteristics of the organic EL display panel are improved in the present invention.

  The present invention can be applied to a display of a television, a personal computer, a portable terminal, or the like.

100: organic EL display panel 101: pixel 102: subpixel 200: substrate 201: first electrode 202: partition 203: hole injection layer 204: second hole transport layer 205: hole transport layer 206: red organic light emitting layer 207: Green organic light emitting layer 208: Blue organic light emitting layer 209: Electron transport layer 210: Second electrode 211: Red subpixel 212: Green subpixel 213: Blue subpixel 300: Substrate 301: Active layer 302: Gate insulating film 303 : Source electrode 304: Drain electrode 305: Gate electrode 306: Insulating film 307: Pixel electrode (first electrode)
308: Partition 309: Scan line

Claims (9)

A red color comprising at least a first electrode formed on a substrate, a light emitting medium layer including at least an organic light emitting layer, and a second electrode formed to face the first electrode so as to sandwich the light emitting medium layer An organic EL display panel having subpixels, green subpixels, and blue subpixels,
On the substrate,
The first electrode corresponding to each of a red sub-pixel, a green sub-pixel, and a blue sub-pixel;
A red organic light-emitting layer as the organic light-emitting layer, comprising at least a low molecular hole transport material and a red light-emitting material, formed in a portion corresponding to the red sub-pixel on the first electrode;
A green organic light-emitting layer as the organic light-emitting layer, comprising at least the low-molecular hole transport material and the green light-emitting material formed in a portion corresponding to the green sub-pixel on the first electrode;
A hole transport layer including at least the low-molecular hole transport material formed in a portion corresponding to the blue subpixel on the first electrode;
On the red organic light emitting layer in a portion corresponding to a red subpixel, on the green organic light emitting layer in a portion corresponding to a green subpixel, and on the hole transport layer in a portion corresponding to a blue subpixel A formed blue organic light-emitting layer as the organic light-emitting layer, comprising at least a blue light-emitting material;
The second electrode formed on the blue organic light emitting layer,
The low molecular hole transport material contained in the red organic light emitting layer has a concentration gradient formed so that the concentration on the first electrode side is higher in the red organic light emitting layer,
The organic EL display in which the low molecular hole transport material contained in the green organic light emitting layer has a concentration gradient so that the concentration is higher on the first electrode side in the green organic light emitting layer panel.   Between the first electrode and the red organic light emitting layer in the red subpixel, between the first electrode and the green organic light emitting layer in the green subpixel, and the first electrode and the hole in the blue subpixel. The organic EL display panel according to claim 1, further comprising an insoluble second hole transport layer between the transport layer.   The organic EL display panel according to claim 1, further comprising an electron transport layer between the blue organic light emitting layer and the second electrode. A red sub, comprising at least a first electrode formed on a substrate, a light emitting medium layer including at least an organic light emitting layer, and a second electrode formed opposite to the first electrode so as to sandwich the light emitting medium layer A method of manufacturing an organic EL display panel having a pixel, a green subpixel, and a blue subpixel,
Forming the first electrode corresponding to each of a red subpixel, a green subpixel, and a blue subpixel;
Forming a hole transport layer containing a low molecular hole transport material on the first electrode;
A red organic light emitting layer is formed on a portion corresponding to the red subpixel on the hole transport layer, and a green organic light emitting layer is formed on the portion corresponding to the green subpixel on the hole transport layer by a coating method. Process,
On the red organic light emitting layer in a portion corresponding to a red subpixel, on the green organic light emitting layer in a portion corresponding to a green subpixel, and on the hole transport layer in a portion corresponding to a blue subpixel A step of forming a blue organic light emitting layer by a vacuum deposition method;
And a step of forming the second electrode on the blue organic light emitting layer.   The organic material according to claim 4, further comprising a step of forming an insoluble second hole transport layer between the step of forming the first electrode and the step of forming the hole transport layer. Manufacturing method of EL display panel.   6. The organic EL display panel according to claim 4, further comprising a step of forming an electron transport layer between the step of forming the blue organic light emitting layer and the step of forming the second electrode. Manufacturing method.   The method for producing an organic EL display panel according to claim 4, wherein the red organic light emitting layer and the green organic light emitting layer are formed by letterpress printing.   The method for producing an organic EL display panel according to any one of claims 4 to 7, wherein the hole transport layer is formed by a vacuum deposition method.   The method for producing an organic EL display panel according to any one of claims 4 to 8, wherein the second hole transport layer is formed by a coating method.