WO2002065817A1

WO2002065817A1 - Organic field light emitting element

Info

Publication number: WO2002065817A1
Application number: PCT/JP2002/000967
Authority: WO
Inventors: Yasuo Imanishi; Sukekazu Aratani
Original assignee: Hitachi, Ltd.
Priority date: 2001-02-09
Filing date: 2002-02-06
Publication date: 2002-08-22
Also published as: TW550964B; JPWO2002065817A1

Abstract

An organic field light emitting element in which the light take out efficiency, electrical characteristics, lifetime, and the like, of the element are enhanced. An organic field light emitting element which can inject and transport both positive and negative charges and can emit light through recombination of holes and electrons generated by both positive and negative charges and having a light emitting layer containing a recombined light emitting substance contained in the organic field light emitting element or a fluorescent substance which can emit secondary light upon receiving light from the light emitting substance, characterized in that, a first class intermediate layer is provided between an interface for taking out light to the outside of the organic field light emitting element and the outside of the light emitting layer and the intensity orientation distribution of light taken out from the light emitting layer is enlarged after passing through the first class intermediate layer.

Description

Description Organic electroluminescent device Technical field

The present invention relates to a novel organic electroluminescent device, and more particularly to an organic electroluminescent device that injects both positive and negative charges and generates light by recombination of holes and electrons generated by the two charges. . Background art

In recent years, with the spread of various mobile phones, mobile terminals, mobile computers, and power navigation, the demand for lightweight, high-definition, high-brightness, and inexpensive small-sized flat displays is increasing. You. In homes and offices, flat displays such as space-saving desktop displays and wall-mounted TVs are replacing conventional CRT tube displays.

In particular, with the spread of high-speed Internet and the progress of digital broadcasting, digital signal transmission of several hundreds to several gigabits / second has been put to practical use in both wired and wireless, and general users have been extremely large. We are moving to an era where real-time information is exchanged. For this reason, demands for these flat displays require not only lighter weight than before, but also high definition, high brightness, and low price, as well as high-speed display performance capable of digital signal processing.

Examples of such a flat display include a liquid crystal display (LCD), a plasma display (PD), and a field emission display. (Field Emission Display: FED) is being studied. In addition to these various flat displays, in recent years, a new type of flat display called an organic electroluminescent device (0 ELD) or an organic light emitting diode (0LED) has attracted attention. It is getting.

An organic electroluminescent device is a device that displays by emitting a fluorescent or phosphorescent organic molecule contained therein by passing a current through an organic compound sandwiched between a cathode and an anode.

Organic Electronics Materials Research Group, “Key Issues Remaining in Organic LED Devices and Strategies for Practical Use”, Bunshin Publishing, 1999, pp. 1-11, pp. 1-111, Yoshiharu Sato, “Introduction : Materials and Devices: Current Status and Issues ”, research on organic electroluminescent devices has long been focused on organic semiconductor single crystals such as anthracene and perylene. In 1987, Tang et al. Proposed a two-layer organic electroluminescent device in which an organic compound thin film emitting light and a thin film of an organic compound capable of transporting holes were laminated (C. W. Tangand S.A.Van Slyke, Ap 1. Phys.Lett. 5 1.913, 1989), and the luminescence characteristics can be greatly improved (luminous efficiency l.'5 ' The starting point of the research is that the driving voltage is 10 V and the brightness is 100 cd / m ² ).

After that, elemental technologies such as dye doping technology, polymer 0 LED, low work function electrode, and mask evaporation method were researched and developed.In 1997, organic electric field by the charge injection method called simple matrix method was developed. Some light-emitting elements have been put into practical use. Furthermore, the development of organic electroluminescent devices using a new charge injection method called the active matrix method has also been developed. It is being considered.

Such an organic electroluminescent device is driven by the following principle.

A thin film of a fluorescent or photoluminescent organic light emitting material is formed between a pair of electrodes, and electrons and holes are injected from positive and negative electrodes. In the organic light-emitting material, the injected electrons become one-electronized organic molecules (simply referred to as electrons) in the lowest unoccupied molecular orbital (LUM 0) of the luminescent molecule.

Also, the injected holes become one-hole organic molecules (simply called holes) in the highest occupied molecular orbital (HOMO) of the luminescent molecule, and they face each other in the organic material. Move toward the electrode. When electrons and holes meet on the way, a singlet or triplet excited state of a luminescent molecule is formed, which is deactivated while radiating light, thereby emitting light.

In general, many organic light emitting materials having high quantum efficiency for photoexcitation such as various laser dyes are known. When attempting to emit light by charge injection, many organic compounds have low charge transport properties of electrons and holes because they are insulators. Was necessary.

However, taking advantage of the high charge transport performance of the organic electrophotographic photoreceptor used as a photoreceptor in copiers, the thin film that transports charges (holes) and the thin film that emits light are functionally separated to emit light. The two-layer type organic electroluminescent device of Tang described above is an improvement.

Today, a three-layer organic electroluminescent device has been reported in which another organic thin film has the property of transporting another charge of electrons. In addition, a thin film with various functions, such as a charge injection layer to improve the injection characteristics of holes and electrons into the organic material, and a hole stop layer to increase the recombination probability of both, should be added. Thus, a function-separated or multilayer organic electroluminescent device has been proposed.

However, the source of the light emission is still the light radiation in the process of deactivating the excited state from the organic light emitting molecules contained in the organic light emitting layer.

Organic Electronics Materials Research Group, “Key Issues Remaining in Organic LED Devices and Strategies for Practical Use”, Bunshin Publishing, 1999, pp. 25-38, Yuji Hamada, Section 2: Current Status and Issues of Light-Emitting Materials], many organic light-emitting materials that emit fluorescence or phosphorescence have been developed for various uses such as inks, dyes, and scintillators.

These organic light emitting materials are used for organic electroluminescent elements. When classified by molecular weight, the types are classified into low-molecular type and high-molecular type. The low-molecular type is formed by a dry process such as vacuum evaporation, and the high-molecular type is formed by a cast method.

It is said that one of the reasons why high-efficiency organic electroluminescent devices in the early stage (before Tang) could not be obtained was that a high-quality organic thin film could not be formed. As a necessary condition for a low molecular system,

(1) Thin film (100 nm level) can be manufactured by vacuum evaporation method.

(2) Uniform thin film structure can be maintained after film formation (no crystal precipitation),

(3) High fluorescence quantum yield in the solid state,

(4) Moderate carrier transportability,

(5) heat resistance, (6) Easy purification,

(7) electrochemically stable,

And the like.

In addition, depending on the classification of the light-emitting process, the light-emitting material may be divided into a light-emitting material that emits light by direct recombination of electrons and holes, and a fluorescent material (or dopant material) that emits light by light excitation generated from the light-emitting material. . ·

Also, due to differences in chemical structure, metal complex-type luminescent materials (eg, 8-quinolinol, benzoxazole, azomethine, flavones, etc. as ligands. A 1, Be, Zn, Ga, Eu, Pt, etc.) and fluorescent dye-based light emitting materials (oxaziazol, villazolin, dis. Chili reale lane, cyclopentene, tetraphenyl butadiene, bisstyrylanthracene, perylene) , Phenanthrene, oligothiophene, pyrazolipid quinoline, thiadiazolipid pyridine, layered beta-askite, p-sexiphenyl, spiro compounds, etc.) are known. '

As described above, a wide variety of materials and methods have been studied for the light-emitting materials of the organic electroluminescent device and the process of forming the device. It is still unclear how much efficiency can be obtained from such organic electroluminescent devices at the maximum.

Organic Electronics Materials, Study Group, “The Remaining Important Issues of Organic LED Devices and Strategies for Practical Use”, Bunshin Publishing, 1999, pp. 105-118, Tetsuo Tsutsui According to Section 1, Interpretation and Limitations of Luminous Efficiency, the photoenergy extracted outside the organic electroluminescent device is given by the number of emitted photons per electron or hole flowing through the device. Table external quantum efficiency 77 ₀ (ext) of this electroluminescent In other words, the following relationships are known.

(Equation 1)

_Ext X 7? _Ii unt) = 7? _Ext x (7 X 7? _R x? 7 f)? 7 _{? 1} (ext) = ??

... (1) Here, 77 ₀ (int) is the internal quantum efficiency which represents the number of emitted photons per electron or Hall flowing element inside the element,? ? _ext indicates the light extraction efficiency to the outside of the device after the light generated inside the device is reduced by reflection and absorption at the device interface.

In addition, a is a charge balance corresponding to the ratio of the number of electrons and holes injected into the device, and 77r is a singlet exciton that indicates a ratio of generation of a singlet exciton that contributes to light emission from the injected charge. The production efficiency, Vt, represents the luminescence quantum efficiency, which indicates the rate at which light is generated and deactivated in singlet excitons.

External quantum efficiency 77, which corresponds to a light emission amount in these devices external (ext) is, 7? _R and on the nature of the luminescent material itself? ? _f , depends on the injection ratio of electrons and holes into the device, and depends on the device structure? ? It can be broadly divided into _ext and _ext .

7? _P and 77 _f are effectively related to the physical properties of the luminescent material itself is uniquely determined by the luminescent materials used. Further, the amount is determined by the electric potential difference between the electrode and the organic layer in contact with the electrode, the interfacial potential, the mobility of electrons and holes in the organic layer, and the like. This efficiency is uniquely determined by the physical properties of the electrode material and the organic material inside the device.

One of these factors is charge balancer 1. Singlet excitation Gene generation efficiency? 7 p is said to be 7? _P ≤ 0.25 from the relation of charge spin. Emission quantum efficiency? ? _f is 77 _f <1 except for the superradiative process. Therefore, it can be said that the part of the factor (the part of (x ?? _rx ?? _f ) in equation (1)) determined by the organic material and the electrode material inside the device is 0.25 or less.

On the other hand, according to N.C.Greenh am, R.H.Friend, D.D.C.Bradley, Ad v. Mater. Determined by the law of reflection and refraction, where n is the refractive index of the light-emitting layer,

(Equation 2)

_{7? Ext = 1 / (2} n 2) is given by (2). _

The refractive index of the light-emitting layer of many organic electroluminescent elements or the glass substrate that holds them is about 1.6, and it is set to 77 _ext = 0.2 from this. '

From these facts, the external quantum efficiency of electroluminescence as a whole is 7 7 ø (ext) ≤ 0.2 X 0.25 = 0.05, and it is said that the external quantum efficiency is at most 5%.

For practical use of the organic electroluminescent device, it is essential to improve the external quantum efficiency. However, since the external quantum efficiency of the above-mentioned conventional organic electroluminescent device has an upper limit, a different function is required. The development of organic electroluminescent devices having the following features is underway.

One of the methods is the luminescence quantum efficiency of the luminescent material itself. Singlet exciton generation efficiency? ? _{The goal is} to improve _r . In the conventional charge injection and recombination processes, singlet excitons are generated at a rate of 0.25 and triplet excitons at a rate of 0.75.

On the other hand, the spin-orbit of organic light-emitting materials containing heavy metals Spinning of triplet excitons into singlet excitons by intersystem crossing due to angular momentum interaction, conversion to singlet excitons by collision of triplet excitons confined in the nanoscale region, etc. Thus, it is intended to increase the ratio of excitons that contribute to light emission by converting the generated triplet excitons into singlet excitons. As a material having such a new exciton generation mechanism: An organic electroluminescent device capable of emitting light with high efficiency using fac ris (2-phenylpyridine) iridium [Ir ^ ppy) 3] has been developed by MA Bald, S. Laman sky, P. E. Burr. ow s, M.E.T.li, mp son, S.R.Forrest, Ap 1. Phys.Lett. 75, 4-16, 1999.

Another method is to improve the external quantum efficiency outside the device by improving the extraction efficiency 7 _ext . In other words, a uniform thin film structure in which no crystal is precipitated has been regarded as a necessary condition for manufacturing an organic electroluminescent device. However, in this case, the organic light-emitting material constituting the light-emitting layer is in a spatially random orientation state, so that light is emitted isotropically in all directions inside the device. '' On the other hand, as a means to control light emission in the direction parallel to the light emitting surface of the device and to increase light emission in the vertical direction, for example, from a molecule uniaxially oriented by the rubbing method An organic electroluminescent device having a light-emitting layer is described in Japanese Patent Application Laid-Open No. H4-144013.

The light-emitting layer is formed in a vacuum by a dry process, and the organic molecules constituting the light-emitting layer are oriented parallel to the light-emitting surface by a photoisomerization reaction. Japanese Patent Application Laid-Open No. 11-107283 describes that an anisotropic light-emitting characteristic inside a light-emitting layer can be similarly obtained in an organic electroluminescent element formed by the above method.

However, these publications do not specifically describe the improvement of the extraction efficiency due to the orientation. Only Japanese Patent Application Laid-Open No. 11-10783 discloses that the luminous efficiency outside the device is 0.5 lm. It is merely stated that the improvement was about 1.6 times from / W to 0.8 l mZW.

Previously, M. Hamaguchianid K. Yoshhino, Jpn. J. App1: Phys. Volume 34, Volume L7

On page 12, 1995, a more detailed measurement of the emission anisotropy and the extraction efficiency of an oriented organic electroluminescent device was required.

According to Fig. 1, there is a remarkable difference in the amount of light taken out between the direction parallel to the orientation direction and the direction perpendicular to the orientation direction. No significant difference in the amount of light taken out was found.

Another proposed method is to convert the component of light randomly generated inside the light-emitting layer, which propagates in the plane of the film, to the direction perpendicular to the film plane by devising the structure of the device. Have been. For example, according to Japanese Patent Application Laid-Open No. 10-172726, the lateral end face of the light emitting layer is processed and formed by dry etching, and the end face of the film functions as a translucent reflecting mirror. A method is proposed that reduces the loss by returning a certain percentage of light to the inside of the film, increases the total amount of effective light emitted to the front surface of the film, and improves the output light emission per input energy of the light emitting element. Have been.

However, this method is not suitable for organic thin films that are originally poor in mechanical strength. Therefore, it is extremely difficult to form an optically superior end face that can act as a reflector or damage the film itself due to dry etching.

Similarly, according to Japanese Patent Application Laid-Open No. 10-229432, an organic light-emitting device having a resonator structure in the direction perpendicular to the film surface and having a fine periodic structure utilizing near-field light in the direction parallel to the film. A method has been proposed in which a fine periodic structure is formed and performs a reflection function in a direction parallel to the film surface, and the emitted light is modulated by the fine periodic structure.

However, this method also has a problem with the processability of the film, and in particular, the processing accuracy for forming the resonator structure in the film surface has become even more severe. The thickness of the organic light emitting layer itself is about 100 nm at most, and it is extremely difficult to process this end face at an optical level.

According to Japanese Patent Application Laid-Open No. 10-39811, a thin film electroluminescent element is formed on the inner surface of a concave portion of a curved transparent substrate to improve the efficiency of light emission from the transparent substrate to the outside. A method has been proposed. However, it is extremely difficult to form a functional thin film such as a pixel electrode, a light emitting layer, a hole transport layer, etc., capable of displaying a complex image on a flexible substrate. In addition, when viewed as a display element, there is a problem in that the entire display portion is largely curved, which significantly limits the viewing characteristics of the user.

As described above, methods for improving the luminous efficiency of organic electroluminescent devices more than ever have been studied.However, since these many factors are included, no clear guidelines have been issued. This is the situation.

The present invention is based on this external quantum Improving efficiency is essential. However, there is an upper limit to the external quantum efficiency of the above-mentioned conventional organic electroluminescent device, and one of the methods is to improve the luminescence quantum efficiency of the luminescent material itself and the efficiency of generating singlet excitons 7 to _r , and It is intended to improve the external quantum efficiency outside the device by improving the extraction efficiency 7? _Ext . Among them, it improves the extraction efficiency of the latter, 77 _ext , and provides a wider range of efficiency improvement means.

In other words, by adopting an element structure that can be formed more easily, the extraction efficiency has been improved by 77 _ext . It proposes a method to extract more light out of the device.

The purpose of such efficiency is to reduce the required power, optimize the pixel size, increase the definition, and extend the life of the device.

In particular, when driving as a large-screen display element of 10 inches or more, or a high-definition image display element even with a small area, it has been considered to be an essential matter in using an organic material. The use as an image display device was limited, and only an image display device of up to 8 inches was proposed. It proposes the basic configuration required for these next-generation organic electroluminescent devices. Disclosure of the invention

The gist of the present invention that achieves the above object to improve the light extraction efficiency of the organic electroluminescent device is as follows.

[1] Both positive and negative charges can be injected and transported, and light can be generated by recombination of holes and electrons generated by the positive and negative charges. An organic electroluminescent element having a light-emitting layer containing a light-emitting substance contained in the organic electroluminescent element by recombination or a fluorescent substance capable of receiving light from the light-emitting substance and generating light secondarily. In organic electroluminescent devices,

A light-emitting layer outside the light-emitting layer, a first-type intermediate layer between the light-emitting layer outside the organic electroluminescent element, and an intensity azimuth distribution of light extracted from the light-emitting layer. An organic electroluminescent device characterized in that it expands after passing through one kind of intermediate layer.

[2] The organic electroluminescent device according to the above, wherein the first type intermediate layer is capable of scattering light or diffusing an optical path.

[3] The organic electroluminescent device, wherein the first type intermediate layer is separated for each pixel having a specific shape, or is separated for each pixel by a partition made of a material having a property different from that of the intermediate layer. It is in.

[4] The shape of the first type intermediate layer or the shape of the partition wall divided for each pixel facing the takeout interface is a polygon, and at least two of the shape surfaces forming the polygon are parallel The above-mentioned organic electroluminescent device is provided.

[5] In the organic electroluminescent device described above, which is at least 0.25 to 2 wavelengths of the wavelength of the light generated by at least one of the pairs of parallel shaped surfaces forming a polygon. is there.

[6] The organic electroluminescent device according to the above, wherein the shape of the first type intermediate layer or the shape of the partition wall divided for each pixel facing the takeout interface is circular.

[7] The organic electroluminescent device as described above, wherein the diameter of the circular first type intermediate layer or the partition wall is 0.25 to 2 wavelengths of the wavelength of the generated light. You.

[8] The organic layer described above, wherein the cross-sectional shape of the first-type intermediate layer or the cross-sectional shape of the partition wall divided for each pixel facing the light extraction interface has a plane structure or a curved surface structure that is not parallel to the light extraction interface. In electroluminescent devices.

[9] The organic light-emitting device, wherein the light extraction interface and the interface not in contact with the light-emitting layer of the first-type intermediate layer or the partition wall separated for each pixel facing the extraction interface can reflect or refract light. In electroluminescent devices.

[10] The organic electroluminescent device according to the above, wherein the reflection at the interface is not regular reflection.

[1 1] The cross-sectional shape of the first type intermediate layer is a shape in which the opening is enlarged from the light emitting surface side to the light extraction surface side, and light can be reflected on the side surface of the first type intermediate layer. The organic electroluminescent device according to the above, wherein the taper angle 7? On the side surface of the intermediate layer is below the total reflection angle? C on the light extraction surface side of the first type intermediate layer.

[1 2] The cross-sectional shape of the first type intermediate layer is a shape in which the opening is enlarged from the light emitting surface side to the light extraction surface side, and light can be reflected on the side surface of the first type intermediate layer. The taper angle on the side of the intermediate layer with respect to the total reflection angle Φ _c on the light extraction surface side of the type 1 intermediate layer? 7 is 4 5 ° — Φ. / 2 to φ. Wherein the thickness d of the first type intermediate layer is not more than a a2 tan 77 on the same cross section with respect to the width a of the light emitting surface side opening.

[13] The organic electroluminescent device described above, further comprising an optical waveguide layer having a cross-sectional area equal to or less than the area of the light-emitting layer between the first-type intermediate layer and the light-transmitting electrode layer related to the light-emitting layer. It is in. [14] An optical waveguide layer having a sectional area equal to or less than the area of the light emitting layer without contacting the light transmitting electrode layer is provided between the first type intermediate layer and the light transmitting electrode layer related to the light emitting layer. In the organic electroluminescent device.

[15] The organic electroluminescent device as described above, wherein the first type intermediate layer contains a substance capable of absorbing light generated in the light emitting layer and generating light of another color.

[16] The organic electroluminescent device according to the above, wherein the first type intermediate layer is formed inside the substrate supporting the light emitting layer.

[17] The organic electroluminescent device according to the above, wherein the first type intermediate layer is formed outside the light-transmitting substrate that carries the light-emitting layer.

[18] The organic field emission device, wherein the light emitting layer is formed on a substrate on which an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor is formed, or formed on a substrate on which an organic thin film transistor is formed. It is in. '--[19] The light emitting layer is formed separately from the substrate on which the amorphous silicon thin film transistor or the polycrystalline silicon thin film transistor is formed or the substrate on which the organic thin film transistor is formed and then integrated. In organic electroluminescent devices.

The organic electroluminescent device mentioned here is capable of injecting holes from an anode electrode and electrons from a cathode electrode into a light emitting layer containing organic light emitting molecules, and by recombination of holes and electrons inside the light emitting layer. An organic electroluminescent device capable of emitting light, and the light-emitting layer may be a single layer or a multilayer.

In addition, the light emitting layer can absorb light generated from the organic light emitting molecule and generate another light in addition to the organic light emitting molecule that emits light by recombination of holes and electrons. Contains fluorescent (or phosphorescent) materials You may go out.

Further, the light emitting layer may include a hole transporting substance or an electron transporting substance capable of increasing the mobility of holes or electrons inside the light emitting layer.

Further, the light emitting layer may contain a hole-trapping substance or an electron-trapping substance for trapping holes or electrons at a specific spatial position or reducing transportability. Further, these organic light-emitting molecules, fluorescent substances (or phosphorescent substances), hole transport substances, electron transport substances, hole trap substances, and electron trap substances may be contained in the same layer, or may be separated. It may be separated into layers. Even when a layer containing these constituent materials is formed by being separated into a plurality of layers, it is collectively referred to as a light emitting layer in the present invention.

Further, a hole injection layer or an electron injection for improving hole or electron injection efficiency is provided between the light emitting layer of the present invention and an anode or a cathode for injecting holes or electrons into the light emitting layer. A layer may be provided.

Further, a substrate for holding the light emitting layer, the anode, the cathode, the hole injection layer, and the electron injection layer may be provided, and an intermediate layer other than these may be provided as appropriate. Such intermediate layers include reflectors and partial transmission mirrors for modulating the reflection characteristics of light, filters for transmitting specific light, light switches for adjusting light emission timing, and light phase. Examples include a wavelength plate for adjusting the characteristics, a diffusion plate for diffusing the light emission direction, and a protective film for preventing a substance constituting the element from being deteriorated by external light, heat, oxygen, moisture, or the like.

These intermediate layers can be suitably provided between the light emitting layer, the anode, the cathode, the hole injection layer, the electron injection layer, and the substrate, or outside thereof, with specifications that do not significantly degrade the device characteristics. In particular, the organic electroluminescence The layer that is the outermost surface from which light is extracted from the device to the outside is referred to as the extraction outermost layer.

Examples of the electroluminescent material that can be used in the present invention include various metal complex type luminescent materials (8-quinolinol, benzoxazole, azomethine, flavone, etc. as ligands). For example, A 1, Be, Zn, Ga, Eu, Ru, Pt, etc. can be used. In addition, fluorescent dye-based light-emitting materials (oxazidazole, pyrazoline, distyrylarylene, cyclopentene, tetraphenylbutadiene, bisstyrylanthracene, perylene, phenanthrene, oligothiophene, pyrazoguchi quinoline, thiadiazolopirene) Resin, layered perovskite, p-sexiphenyl, spiro compounds, etc.) can be used.

Alternatively, various polymer materials (polyvinylenevinylene, polyvinylcarbazole, poly'fluorene, etc.) are used as the light-emitting material, or non-light-emitting polymer materials (polyethylene, polystyrene, polyoxyethylene, polyvinylalcohol, polymer) are used. Mixing or copolymerizing various luminescent or fluorescent materials using methyl acrylate, polymethyl acrylate, polyisoprene, polyimide, polycarbonate, etc. as a matrix. Both are possible.

In addition, various organic hole or electron transport materials (such as triphenylamine) can be interposed. Furthermore, various hole or electron injection layers (for example, Li, Ca, Mg, Cs, CuPc, etc.) can be interposed, and materials can be appropriately selected according to the element configuration. You can choose.

Means for producing the organic electroluminescent device of the present invention include various thin film forming techniques, for example, a spin coating method, a coating method, a casting method, and a spa method. Method, vacuum evaporation method, molecular beam evaporation method, liquid phase epitaxy method, atomic layer epitaxy method, roll method, screen printing method, ink jet method, electropolymerization method, rubbing method, spraying method , Water surface spreading method, Langmuir project film method, etc. can be used.

In order to promote orientation during or after film formation, a crystalline substrate having an alignment regulating force on the substrate itself, an alignment film-coated substrate, or a physical or chemical surface treatment is performed. A substrate or the like can be used.

Further, as a molecular skeleton in a compound suitable for such an alignment treatment, one having liquid crystallinity during the alignment treatment is desirable. After the alignment treatment, the sample is cooled to a temperature below the glass transition temperature, and a new chemical bond is formed between the molecules by the reaction of light, heat, etc., thereby fixing the alignment state. This is also effective. ·

Substrates made of inorganic substances such as glass, silicon, gallium arsenide, etc., and substrates made of organic substances such as polycarbonate, polyethylene, polystyrene, polypropylene, and polymethyl methacrylate. Alternatively, a substrate in which both are combined can be used.

These substrates can be formed by methods such as cutting and polishing from the base material, injection molding, sand, stamping, and dicing.

It is also possible to use a substrate on which a thin film transistor is formed in order to control the light emitting state. An organic electroluminescent layer is formed on the substrate on which such a thin film transistor is formed. Alternatively, the substrate on which the thin-film transistor is formed and the substrate on which the organic electroluminescent layer is formed are separately formed, and then the two are joined to form a single unit. It is also possible to let them.

Further, in the organic electroluminescent device of the present invention, various precision processing techniques can be used in order to produce a required optical device structure in the process of forming the device. Examples include precision diamond cutting, laser processing, etching, photolithography, reactive ion etching, and focused ion beam etching.

In addition, a plurality of organic electroluminescent elements that have been processed in advance can be arranged, multi-layered, coupled between them by an optical waveguide, or sealed in that state.

Also, the element can be stored in a container filled with an inert gas or an inert liquid. Further, a cooling or heating mechanism for adjusting the operating environment can coexist. Materials that can be used for these containers include various metals such as copper, silver, stainless steel, aluminum, brass, iron, and chromium, and alloys thereof, and polymer materials such as polyethylene and polypropylene. In addition, composite materials and ceramic materials in which the above metals are dispersed can be used.

In addition, styrene foam, porous ceramics, glass fiber sheets, paper, etc. can be used for the heat insulating layer. In particular, it is possible to apply a coating to prevent condensation.

In addition, as the inert liquid to be filled therein, liquids such as low-melting wax and mercury, and mixtures thereof can be used. Helium, argon, nitrogen and the like can be cited as the inert gas to be filled inside. It is also possible to add a desiccant to reduce the humidity inside the container.

The organic electroluminescent device of the present invention may be subjected to a process for improving the appearance and characteristics and prolonging the life after forming the product. This post-processing and Examples include thermal annealing, radiation irradiation, electron beam irradiation, light irradiation, radio wave irradiation, magnetic field line irradiation, and ultrasonic irradiation.

Further, the organic electroluminescent device may be formed into various types of composites, for example, by means such as adhesion, fusion, electrodeposition, vapor deposition, pressure bonding, dyeing, melt molding, kneading, press molding, coating, etc., depending on the purpose or purpose. Can be combined.

Further, the organic electroluminescent device of the present invention can be mounted in high density in the vicinity of an electronic circuit for driving, and can be integrated with an external interface for transmitting and receiving signals to the outside, an antenna, and the like. It can also be converted. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a basic element configuration of an organic electroluminescent element for extracting light from the substrate side of the present invention. · FIG. 2 shows the basic structure of an organic electroluminescent device that extracts light from the cathode side of the present invention.

FIG. 3 is an example of the geometric shape of the first type intermediate layer of the present invention. FIG. 4 is a structural diagram of a reflecting mirror inside the first kind intermediate layer of the present invention.

FIG. 5 is an example of a manufacturing procedure of an organic electroluminescent device having a first type intermediate layer of the present invention.

FIG. 6 is an example of a procedure for producing an organic electroluminescent device having a first type intermediate layer of the present invention.

FIG. 7 is a configuration diagram of a device manufacturing apparatus in an embodiment of the organic electroluminescent device of the present invention.

FIG. 8 shows a test for confirming the effect of the first class intermediate layer of the present invention. FIG.

FIG. 9 is a system for measuring the characteristics of a test element for confirming the effect of the first type intermediate layer of the present invention.

FIG. 10 is a drawing for explaining the type 1 intermediate layer pixel arrangement of the present invention.

FIG. 11 is a drawing for explaining the optimum pixel size of the type 1 intermediate layer of the present invention. ·

FIG. 12 is an example of a first type intermediate layer for display pixels of the present invention. FIG. 13 is an example of a first type intermediate layer for display pixels of the present invention. FIG. 2 is an explanatory diagram of a case where a first-type intermediate layer is used for an image display element in a thin film transistor of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION "

(Example 1)

FIG. 1 is a basic structural diagram of the organic electroluminescent device of the present invention. Organic electroluminescent devices are organic electroluminescent devices that can inject and transport both positive and negative charges and can generate light by recombination of holes and electrons generated by the two charges. . '' In an organic electroluminescent element including a luminescent substance due to recombination contained in the organic electroluminescent element or a fluorescent substance capable of receiving light from the luminescent substance and generating light secondarily, A first type intermediate layer is provided between the light emitting layer that emits light and the light extraction surface to the outside of the organic electroluminescent element, and the intensity orientation distribution of light extracted from the light emitting layer is: Expanding after passing through the Type 1 intermediate layer It is characterized by.

Ordinarily, an organic electroluminescent element has an organic electroluminescent material sandwiched between a pair of electrodes, and injects electrons from a cathode and holes from an anode to recombine in the luminescent material, thereby emitting light. It has occurred.

5 For example, in FIG. 1 (a), the light emitting layer 2 is sandwiched between the cathode 1 and the transparent anode 3, and in FIG. 1 (b), it is sandwiched between the cathode 1 ′ and the transparent anode 3 ′. Light is generated from the light emitting layer 2 ′.

Various known organic electroluminescent materials can be used for the light emitting layers 2 and 2 '. Although not specifically illustrated here, functionalized layers such as a hole transport layer and an electron transport layer, and a hole injection layer and an electron injection layer can be multilayered as necessary. '

Since these electroluminescent portions are thin films having a thickness of at most 100 nm, they are formed on substrates 4 and 4 ′ such as glass and transparent plastics. Emitting layer 2, 2 'light generated in the transparent anode 3, 3' through the further transmitted through the substrate 4, 4 ^f, taken out to the outside of the device. The device interface from which light is finally extracted to the outside of the device is referred to as the light extraction interface 6, 6 'here.

• The basic structure which is a feature of the present invention is that the first type intermediate layers 5 and 5 ′ are provided outside the light emitting layers 2 and 2 ′ and between the light extraction interfaces 6 and 6 ′. That is, an area is formed.

In the process in which light passes through this region and is guided to the outside, the characteristic is that the intensity distribution of light expands after passing through the first type intermediate layer 5. FIG. 1 (a) shows the case where such a type 1 intermediate layer is formed inside 5 of the substrate 4, and FIG. 1 (b) shows the case where the intermediate layer is formed inside the holding medium 7 outside the substrate 4 '. 1st intermediate layer 5 'formed FIG. 2 shows a structure in which the bonded parts are joined.

FIG. 2 shows a structure of an element from which light is extracted from the upper surface side opposite to the substrate 11. The order of stacking the anode 8, the light emitting layer 9, and the transparent anode 10 on the substrate 11 is reversed, and the light generated inside the light emitting layer 9 is guided to the upper part of the element. In such a case, the first type intermediate layer 12 formed inside the holding medium 14 is joined to the upper part of the transparent anode 10, and the light inside passes through this intermediate layer 12 to collect light. It reaches the outgoing interface 13 and reaches the outside of the device.

For example, FIG. 1 (a) shows the first type intermediate layer in the in-plane direction inside the substrate, and FIG. 1 (b) and FIG. 2 show the first type in the in-plane direction inside the holding medium. At the interface of the seed intermediate layer, light can be reflected or diffused, and the inside of the first intermediate layer is a uniform optical medium.

Light generated inside the light emitting layer generally generates light isotropically, and is reflected at the interface of each thin film up to the light extraction interface, and a large amount of light is lost without being extracted outside the device. The loss due to the reflection increases as the difference in the refractive index between the thin films increases, and the loss at the interface between the substrate and air is particularly large. Such reflection generally increases as the angle of the interface with respect to the normal direction increases, and light emitted at an azimuth angle equal to or greater than the so-called total reflection angle cannot be taken out of the device forever.

For example, assuming that the refractive index of the substrate is 1.50 and the refractive index of air is 1, the total reflection angle ec sin- ¹ (1 / 1.50) = 41.8 °, which is emitted at a wider angle. The light propagates only in the in-plane direction of the substrate, resulting in complete loss.

Therefore, as in the case of the type 1 intermediate layer, specific layers are included in the film surface of one layer. By forming the first type intermediate layer having a geometric structure, the optical path of the light propagating in the in-plane direction can be changed, and the light can be guided in the out-of-plane direction.

Further, in order to effectively perform such light scattering or light path diffusion by the first type intermediate layer, it is necessary to minimize reflection at the interface between the transparent anode of the light emitting layer and the first type intermediate layer. is necessary. That is, it is desirable to reduce the refractive index difference, or to increase the refractive index on the side of the type 1 intermediate layer. However, in the latter case, separate anti-reflection means may be required because the difference in refractive index from air at the final light extraction interface becomes larger.

It is preferable that the first type intermediate layer is formed for each pixel which is a light emitting unit of the electroluminescent device. That is, the first type intermediate layer is separated for each pixel having a specific shape, or is separated for each pixel by a partition made of a material having a property different from that of the intermediate layer. And features.

FIG. 3 shows an example of such a geometric shape of the type 1 intermediate layer. 3 (a) to 3 (d) show the cross-sectional structure on the left and the three-dimensional structure on the right. In each case, the upper side was the light emitting layer side, and the lower side was the light extraction interface side. -Fig. 3 (a) shows a trapezoidal shape with four sides, and the light entering from the upper light emitting layer is reflected by the four sides and changes its traveling direction, and the lower light extraction Reach the interface. Therefore, light can be reflected and diffused in four directions.

Fig. 3 (b) shows that the cross section is trapezoidal, but the whole is conical and the shape of the reflecting surface is circular as viewed from the light extraction interface, so that the reflection and diffusion of light in the in-plane direction is uniform. Become. Fig. 3 (c) shows a rectangular parallelepiped structure in which the light is simply reflected on the side surface, and the light incident and exit angles on the light emitting layer side and the light extraction interface side are the same. The structure needs to be improved in the light extraction area. However, if the side surface is light scattering, it is possible to increase the light extraction amount.

Fig. 3 (d) shows a hemispherical shape. By providing a parabolic reflection structure in the first type intermediate layer, more light propagating in the plane can be changed to the extraction direction outside the element. It becomes possible.

In addition to the above, the shape of the first type intermediate layer or the shape of the partition walls divided for each pixel approaching the extraction interface by a special optical design is a plane or curved surface that is not parallel to the light extraction interface. By doing so, it is possible to design to change the light in the in-plane direction out of the plane. In particular, in the structure shown in FIG. 3 (b), the shape of the first type intermediate layer or the shape of the partition wall divided for each pixel facing the extraction interface is a polygon, and the polygon forms a polygon. It is sufficient that at least two of the shaped surfaces are parallel.

For this parallel surface, at least one set of pairs of parallel-shaped surfaces forming a polygon should have a length of 0.25 to 2 wavelengths of the wavelength of the generated light. Set to. This makes it possible to impart light amplifying property due to the micro-cavity effect to light reflected between the surfaces.

Such an effect is particularly realized by dispersing a dye capable of laser oscillation in a light-guiding medium. Similarly, although not shown in the drawings, even when the type 1 intermediate medium has a cylindrical shape and the circular diameter is 0.25 to 2 wavelengths of the wavelength of the generated light, Similarly, it becomes possible to have a micro-resonator effect inside. Fig. 4 shows how light of the first type intermediate layer or partition, which is separated for each pixel facing the light extraction interface, is reflected or refracted at the light extraction interface and the interface not in contact with the light emitting layer. The specific structure of the first class intermediate layer having functions is shown.

FIG. 4 (a) shows an example in which a reflecting mirror is formed on the side surface of the type 1 intermediate medium, and the side surface of the trapezoidal type 1 type intermediate layer 18 formed in the holding medium 15 is reflected. Mirror 16 is formed. The central portion is filled with a light guiding medium 17 whose refractive index has been adjusted.

Fig. 4 (b) shows a type 1 intermediate medium 18 'formed in the holding medium 15', in which a scattering mirror 19 is formed instead of the reflecting mirror 16 in Fig. (A). The central part is filled with a light guiding medium 17 whose refractive index has been adjusted.

Such a reflection or scattering function is possible even when the difference in the refractive index between the first type intermediate layer and its holding medium is large. For example, a type 1 intermediate medium 18 ′ ″ having the same shape as that of FIG. 4 (a) formed in the holding medium 15 of FIG. 4 ′ (c), and the refractive index is also adjusted at the center. A similar function can be obtained even with a structure filled with the light guiding medium 173 ³ . However, in this case, a part of the light reaching the side surface may escape to the holding medium 1 '5'. ''

The light guiding medium in the center is a part that guides light from the light emitting layer to the outside. By dispersing various functional dyes in the medium, it is possible to enhance the function of the organic electroluminescent device. is there. .

In particular, by containing a substance that can absorb light generated in the light-emitting layer and generate light of another color, color conversion of light emission can be performed. Each pixel is assigned a responsible color so that light of the three primary colors of red, green, and blue can be generated, and some of the light is converted to light in the light-emitting layer. With this, simple and efficient color display can be achieved.

Such a first type intermediate layer is desirably a layer sufficiently thicker than the wavelength of light from the viewpoint of preventing a change in emission color outside the element due to interference due to multiple reflections inside.

In addition, as described above, in order to guide all the light generated from the light emitting layer to the first type intermediate layer, it is preferable that there is no difference in refractive index between the two. It is desirable that the light emitting layer side of the surface of the contact portion is covered with the first type intermediate layer side. This is because, if the light emitting layer side is large, a light emitting portion is generated outside the first type intermediate layer, and it is difficult to sufficiently guide the generated light. .

Further, the pixel size is desirably about the area of the light extraction interface side of the first type intermediate layer. For this reason, it is desirable that the area on the light emitting layer side be smaller.

Normally, when considering the loss due to total reflection at the interface, at most 20% of the light generated in the light emitting layer is extracted to the outside, but the light propagating in the in-plane direction is not If all of them are guided outside the element, the extraction efficiency is 100%. Therefore, the area of the light emitting layer portion per pixel may be 1/5. As shown in FIG. 1 (b), when the transparent substrate 4 ′ is interposed between the transparent anode 3 ′ and the first kind intermediate layer 5 ′, the light generated from the light emitting layer 2 ′ is Since they diffuse before reaching the seed intermediate layer, the shorter the distance between them, the better. Practically, it needs to be larger than the wavelength of light and about 1 mm or less.

By providing the first type intermediate layer satisfying the conditions of the shape, dimensions, and refractive index as described above between the light emitting layer and the light extraction interface, the number of layers can be increased. More light can be guided to the outside of the device.

(Example 2)

Next, among the structures of the first type intermediate layer shown in Example 1, an example of a procedure for manufacturing a first type intermediate layer having a conical structure is shown in FIG.

(1) Borosilicate glass (size 40 X 40 X 0.8 mm, double-side polished) was used for the glass substrate 20 on which the organic electroluminescent element was formed.

(2) The sandblast method (a method of high-speed injection of fine sand-like particles) is applied to the glass substrate. The injection area is 100 x 60 mm, and the upper hole is 295.5 jum. Drill a conical hole with a drilling hole of 86.5 m and a taper angle of 70 °.

(3) On this, 100 nm of aluminum was deposited from the prepared hole side using a molecular beam deposition apparatus to form a reflector 22.

(4) Fill the processed hole with the refractive index adjusting resin 23 as a light guiding medium. As the refractive index adjusting resin, a resin close to the refractive index of the organic electroluminescent layer to be used is selected. In this example, a material selected from polymethyl methacrylate, polystyrene, polyvinyl alcohol, and polyamide was used.

(5) After sufficient curing, the excess resin that had protruded on the upper and lower surfaces was polished with an abrasive to flatten the surface. ''

(6) Next, a thin film of IZ0 ('Indium Zinc Oxide: InZnO) was formed on the upper surface side at a substrate temperature of room temperature by a sputtering device to obtain a transparent anode 25. The film thickness of IZ 0 was 100 nm, and the sheet resistance was 60 Ω / port. This was washed in running pure water for 1 hour, and then ultrasonically washed twice in pure water for 15 minutes, and then ultrasonically washed in acetone (special grade reagent manufactured by Wako Pure Chemical Industries) for 15 minutes. Then, it was dried by blowing dry nitrogen. After irradiating this with an ultraviolet lamp for 5 minutes in the atmosphere, it was mounted on a molybdenum substrate holder (manufactured by Nippon Bax Metal) and quickly mounted together with the substrate holder in the exchange room of the molecular beam deposition system.

(7) An organic electroluminescent layer 26 was formed in the molecular beam deposition apparatus, and a cathode 27 was formed via a patterning mask. In order to confirm the effects of the present invention, here, a two-layer structure including a hole transport layer and an organic light emitting material layer was adopted as the light emitting layer. One NPD (4,4-bis-CN- (l-naphthyl) -N-phenylamino) biphenyl) was used for the hole transport layer, and Alq3 (aluminiium tris) was used for the organic luminescent material. (8-hydroquinoline)) was used.

Each film thickness was 60 nm, and a hole transport layer and an organic luminescent material were vacuum-deposited on IZO in this order. On top of that, 0.5 nm of LiF was deposited as an electron injection layer. The region from the hole transport layer to the electron injection layer corresponds to the organic electroluminescent layer 26. Further, A1 was deposited as a cathode.

FIG. 7 shows an apparatus configuration of a molecular beam evaporation apparatus used for preparing a sample of this example. The hole transport layer, light emitting layer and cathode were formed by vapor deposition in a molecular beam deposition apparatus (models OMB E, IMBE-620, manufactured by Nidec ANELVA).

The molecular beam deposition apparatus includes an exchange chamber for exchanging and mounting a substrate holder, a pretreatment chamber capable of transporting a substrate in the exchange chamber and heating the substrate up to a maximum of 130 ° C., a hole transport layer, and an organic luminescent material layer. It consists of a first growth chamber for forming an inorganic barrier layer, a second growth chamber for forming metal electrodes, and an analysis chamber for analyzing the surface condition of the formed thin film by ESCA and AES.

The base pressure of each chamber is 10 to ^{1 Q} Torr units except for the exchange room, and 10 to ⁹ Torr units for the exchange room. A gate valve is used between each room. The structure is such that the substrate can be moved together with the substrate holder under ultra-high vacuum if necessary.

In addition, the mounting of the substrate in the exchange chamber and the removal of the film-formed sample are performed at atmospheric pressure through a glove box (manufactured by Miwa Seisakusho), which is separated by a gate valve, but with dry nitrogen from which oxygen and moisture have been removed. It is possible to perform under the environment.

At the time of vapor deposition, the substrate was moved to the first and second growth chambers as necessary. At the time of vapor deposition, while the corresponding growth chamber chamber was cooled with liquid nitrogen, the raw material previously mounted in each growth chamber was heated and sublimated or evaporated to form a thin film on the substrate. Raw materials are stored in a crucible made of quartz (made by Nidec ANELVA) for organic substances and in a crucible made of boron nitride (made by Shin-Etsu Chemical) for inorganic substances. The raw material is vaporized.

At the exit of the crucible? A mechanical shut down is provided, and when the shut down is opened for a predetermined time, the vaporized raw material is deposited on the substrate, and the film thickness of the deposited raw material is placed near the substrate. A thin film having a predetermined thickness was formed by measurement using a quartz crystal film thickness gauge. The temperature of the substrate can be maintained at a predetermined temperature within a range of −90 ° C. to 150 ° C. ·

The deposition rate was set so that the crucible temperature was about 0.1 nm Zs for the organic and inorganic barrier layers and about 30 nm / s for the cathode material. In the deposition procedure, first, a hole transport layer was formed to have a predetermined thickness in the first growth chamber, and then a light emitting layer including an organic light emitting material layer and an inorganic barrier layer was formed to have a predetermined thickness in the same chamber. This is once transported to the exchange room. The sample was placed on a substrate holder with a stainless steel metal mask. After the replacement, the sample was transported to the second growth chamber to form a cathode. The mixing ratio of the alloy cathode was determined from the abundance ratio of each element by XPS in the analysis room. The substrate temperature during the formation of the cathode was set to a predetermined temperature in the range of 190 to 30 ° C.

The sample formed up to the cathode was moved to an exchange room, taken out of the glove box, covered with a glass plate inside the glove box, and the end was sealed with an ultraviolet curable resin. In the final sample, the light emitting layer area is sealed, and the anode and cathode are drawn out of the area. A voltage can be applied to these electrodes from outside using a prober.

FIG. 6 shows a part of a procedure for fabricating an organic electroluminescent device having a transparent anode which is difficult to form a film at a low temperature. '

(1) Preparation of substrate,

(2) Taper hole processing and '(3) The process up to reflector mirror deposition is exactly the same as in the case of FIG. 5 and will not be described here. '

In FIG. 5, the transparent resin encapsulated in FIG. 5 (4) was used as a substrate, and then a transparent anode such as IZO was formed. On the other hand, in order to form an electrode with a low sheet resistance using a transparent anode such as IT0 (Indium Tin Oide: InSn), the substrate temperature must be 100 ° C or higher. Therefore, it is not possible to use a substrate in which a refractive index adjusting resin is sealed in advance as a substrate.

Therefore, in this case, sputter deposition was performed using IT◦ as a transparent anode 30 separately on a glass substrate 31 having a thickness of 50 m, and the hole transport layer and the organic luminescence were similarly formed using a molecular beam deposition apparatus. The light-emitting layer 29 was obtained by sequentially depositing the material and the electron injection layer. A1 cathode 2 8 After the attachment, a glass-sealed one was used as a basic organic electroluminescent element part 32.

As shown in FIG. 6 (4 '), the basic organic electroluminescent element 32 was bonded to the bonding surface 33 of the substrate. At this time, it was effective to preliminarily join the adhesive surface 33 by thinly penetrating a dilute solution of the refractive index adjusting resin.

Next, as shown in FIG. 6 (5 '), a refractive index adjusting resin 33 was sealed in the processed hole, and the protruding resin was polished and removed to complete the element. These operations were performed while aligning the two outside the glove box.

In any case, when forming an image display element, electrode patterning as a display pixel is necessary for the transparent anode and the cathode, but they are not shown here.

In order to drive as an image display element, a plurality of processing holes were formed in one substrate to produce a first intermediate medium. However, due to the current accuracy, it was difficult to make a finer hole than a hole of this size, so the anode and cathode sandwiching the light-emitting layer had a width of 300 zm. It has a trix structure. Such electrodes were formed at intervals of 100 m, each vertically and horizontally, and each intersection was defined as one 'pixel' portion.

External wires were bonded to the anode and cathode using a silver paste, an arbitrary anode and cathode were selected one by one, and a voltage of 8 V was applied. Light emission was confirmed at all pixel positions. Was.

(Example 3)

Next, a test organic electroluminescent device having a single pixel was formed, and its light diffusion characteristics were evaluated by the following method. FIG. 8 shows a device configuration of the test organic electroluminescent device. FIG. 8 (a) shows a device having the first kind intermediate layer, and FIG. 8 (b) shows a device without the first kind intermediate layer.

The portions causing organic electroluminescence were the same in all cases, and were manufactured by the method shown in FIG. 6 of Example 2. That is, in FIG. 8 (a), a cathode 35, an electron injection layer 36, an organic luminescent material 37, a hole transport layer 38, and a transparent anode 39 are formed on a glass substrate 40 from the top. The organic electroluminescent device section was designated as 41.

On the other hand, according to the method shown in FIG. 6, a hole for forming a first-class intermediate layer was formed, and a holding medium 43 on which a reflecting mirror was deposited was joined. However, here, a light shielding mask 42 for preventing light from leaking was formed in a portion other than the processing hole on the upper surface.

Specifically, a thin resin was applied on the upper surface, and a bonbon powder was sprayed on the resin. The thus-prepared holding medium 43 was joined to the basic organic electroluminescent element section 41, and in this state, a refractive index adjusting resin 44 was sealed to form an element. Here, the glass of the holding medium part 43 and the glass substrate 40 on which the basic element part 41 is formed are made of the same kind of glass material, and the refractive index adjustment resin has the same refractive index as the glass. Selected. '

On the other hand, the organic electroluminescent device for comparison also has the same portion that causes organic electroluminescence, and was manufactured by the method shown in FIG. 6 of Example 2. That is, in FIG. 8 (b), the cathode 35 5 ′, the electron injection layer 36 ′, the organic luminescent material 37 ′, the hole transport layer 38 ′, and the transparent anode 39 ′ are placed on the glass substrate 40 ′ from the top. The element formed above was used as a basic organic electroluminescent element section 41 '. On the other hand, as the holding medium 4 3 ′ having no type 1 intermediate layer to be bonded, The previous glass plate itself was used. However, a light-shielding mask 42 ′ was formed on a part of the light-shielding mask so that light was transmitted only in an area having the same size as the upper surface hole of the first type intermediate layer in FIG. 8A. The thus-obtained holding medium 43 'was similarly joined to obtain a comparative element.

Fig. 9 shows an evaluation system diagram of the device that evaluated differences in light diffusion characteristics. A voltage is supplied to the fabricated organic electroluminescent device 45, and at the same time a current is measured. A current measuring device 48 (Hewlett-Packard, p AMeter / DCVoltageSource 4) A voltage was applied from 140 B), and a current was caused to flow from the anode to the cathode inside the device, thereby causing the device to emit light.

The amount of generated light is measured by a brightness meter camera 46 installed in front of the center of the element and a brightness meter controller 47 controlling the brightness meter (Spectra Pritchard P hotometer, Model 1998, manufactured by P hotoresearch). 0 A— by PL)

The luminance was measured. The azimuth of the element with respect to the normal direction of the light extraction interface of the element with respect to the luminance meter camera was set at 0 using a rotary stage 5 (manufactured by Chuo Seiki) driven by a pulse motor.

The control and measurement of the luminance meter controller 47, the voltage supply and current measuring device 48 and the rotary stage 50 were controlled by a control personal computer 49. All measurements were performed at room temperature, and no temperature control was performed.

A comparison of the light emission characteristics observed from outside of the device of Fig. 8 (a) and the same device (b) showed that the front brightness (0 = 0 °) of the device of Fig. 8 (b) was the maximum value. It shows a so-called Lambertian light emission characteristic in which the light emission intensity is attenuated almost at COS ²⁰ and the light intensity is 10 Front view at V 1 200 cd / m ² , 0 = 20. It was l OOO cd Zm ² .

On the other hand, in the element of Fig. 8 (a), 0 observed almost the same brightness in the range of 0 ° to 30 °, and the light intensity was 6300 cd Zm ² at 10 V. Was. This indicates that almost all of the light that could not be extracted in the out-of-plane direction and propagated in the in-plane direction of the holding medium 43 'in the element of FIG. 8 (b) could be extracted to the outside.

From the taper angle of the machined hole, it is expected that light will be observed at ± 20 ° in the case of this element, but light was observed at a slightly wider angle in the experiment. This is considered to be due to the effect of irregular reflection caused by roughening of the machined surface by the sandblast method.

(Example 4)

Next, an example of the structural dimensions and design of the present invention when used in an organic electroluminescent device for image display will be described.

When used as an image display element, the light emitting portion of each organic electroluminescent element is divided into regions called pixels, and the light emission amount and the light emission time of each pixel are controlled by a control circuit of the image display element. The pixels in the image display device are two-dimensionally arranged, and the number of pixels is standardized according to the resolution of the image display device.

For example, V GA = 6 4 0 X 4 8 0, SV GA = 8 0 0 X 6 0 0, X GA = 10 2 4 X 7 6 8, SX GA = 1 2 8 0 X 1 0 2 4, UX GA = 16 0 0 X 12 00, HDTV = 19 20 0 X 10 08 0, QX GA = 20 48 X 15 36.

Therefore, the size of each pixel in the image display element is determined according to the screen size and the resolution. For example, the screen size is 123 × 31 mm, and the resolution XGA (the number of pixels is 10 24 × 7 In the case of 6 8), one pixel The size must be in the area of less than 120 x 40 m.

FIG. 10 shows the arrangement between pixels of an image display element using a general organic electroluminescent element (a), and the arrangement between pixels of an image display element incorporating the structure of the organic electroluminescent element of the present invention. The relationship with (b) was shown. However, in FIG. 10, for the sake of simplicity, the portion above the substrate of the organic electroluminescent device is collectively displayed as pixels.

For pixels 1, 2, and 3 formed on a substrate with a substrate thickness d, if the pixel size is L i and the pixel pitch indicating the distance between pixels is L ₂ , the size occupied by one pixel is light. pixel unit for generating the pixel pitch portion and. it, its length is L i + L _2.

Although not specifically described herein, there are various pixel regions in the direction perpendicular to the paper surface, and the length thereof is also the sum of the pixel size and the pixel pitch. When the light emitted from each pixel is emitted from the substrate side to the outside, the light emitted from the interface between the pixel and the substrate diffuses while reaching the light extraction interface at the bottom of the substrate, and partially diffuses at the interface between the substrate and air. The light arriving at an angle wider than the critical angle is totally reflected and propagates in the lateral direction of the substrate. For this reason, if the pixel is too close to the adjacent pixel, the adjacent light will be mixed, and in the case of full color image display, color mixture will occur.

In addition, incorporating an optical resonator structure in the pixel itself or providing a tapered surface in the lateral direction of each pixel enhances the directivity of light traveling in the substrate, and suppresses propagation in the lateral direction of the substrate. However, even when the light exits the device, the light directivity remains, and the viewing angle as an image display device is narrowed, and the light interference color due to the resonator effect is mixed, resulting in display color unevenness.

On the other hand, in the case of the image display device comprising the organic electroluminescent device of the present invention, as the first type intermediate layer, for example, a method in which the tapered surface is formed on the substrate surface. The angle between the line and the line? ? When light is provided at the midpoint between pixels at the light extraction interface, light generated from each pixel is emitted without mixing inside the substrate and without directivity outside the substrate. You. FIG. 11 is an explanatory diagram for determining the optimum size of the first type intermediate layer of the organic electroluminescent device of the present invention used as such an image display device.

Light entering the substrate from the pixel is emitted at various azimuthal angles because the pixel itself is a two-dimensional light emitter, and is reflected at the interface of the type 1 intermediate layer that restricts the lateral direction of the substrate. Finally, it reaches the light extraction interface at various angles. For this reason, part of the light is reflected at the light extraction interface. In particular, when light having a wider angle than the total reflection angle exists, the light returns to the pixel again and cannot be extracted. Therefore, it is necessary to estimate the optimal taper angle of the first type intermediate layer, and its thickness and refractive index. '

If the angle between the taper surface of the type 1 intermediate layer and the normal to the substrate surface is V, the taper angle is 7Γ Ζ 2—? ? And the light emitting point on the bottom of the substrate

W is the position where the light emitted from P in the direction 方位 reaches the tapered surface, V is the position where the light is reflected by W and reaches the top surface of the substrate, and G is the point corresponding to the height of point W on the z-axis. Let F be the intersection of the z-axis with the normal to the taper plane at point W, and E be the intersection of the tapered surface and the X-axis.

The incident angle of the emitted light to the taper surface is ZPWF, and the direction of the reflected light is the point W and the inverse vector of the azimuthal vector of the incident light is rotated in the negative direction by ZPWV = 2 ZPWF. Keep in mind that at this time, note that 0> 7.

(Equation 3) GWP = --0, LGWE =-~ n

twenty two

LPWE = LGWE-LGWP = φ-η

lx \ sin0,

Azimuth vector of radiation at point p

cos

Normal ^{vector of the taper} surface fx ' ^cos (-) ^Sln (-^ ") cos? 7,

, ζ '., 7Γ, π cos? sin?

^-sm (-) ^cos (-The angle between the inverse vector of the azimuthal vector of synchrotron radiation and the normal vector of the taper surface is

(Equation 4)

(− Cosi) (— sm ^) + smi-one cos ^>) = sm (^ —) = cos (Φ + η) ■ '■ The angle is (2) — 0 + 7 ?.

The direction of the reflected light is the one rotated in the positive direction by twice this angle, and the azimuth vector of the reflected light is

(Equation 5)

cosi π-1 2 {ψ1 η)] smπ-1 2 (φ -η)] \ ί-sin φ

\ ^ζノ I− sin [jv 一 2 (φ− η)] cos? r— 2 (φ ™)] 1— cos φ

I-1 sin 7r -φ + 2η) \ ί1 sin (-1 2τ7) \

I -COS (JT -φ + 2η) J I cos (^ »― 2η) I

Becomes The azimuth angle is

(Equation 6)

Becomes

When n = 1.6, it is 25.66 ° and 7? <38.68 °, but when n = 2.2, it is ø. 2 27.0 4 °, (7Γ / 4)-(ø.2) = 3 1.

The angle is 48 °, making it difficult to determine the optimal taper angle.

Therefore, all the light can be guided to the outside by embedding a resin having a refractive index of about 1.6 in the center of the taper.

Since the transmittance of light arriving at an angle close to the critical angle is not high, it is practically (25.66 + 38.6.68) no2 = 32.1.17

. With this level, both direct radiation and reflected light can be kept at a slightly smaller angle than the sea angle.

Next, a substrate thickness at which a gain is generated by the amount of light taken out is obtained. Below pixel Assuming that the diameter of the side surface is a and the substrate thickness is d, the radius of the upper extraction surface is a / 2 + dtan? =. Assuming that 100% of the light on the lower surface is extracted, the light amount from a simple pixel of the same size as the upper surface (the extraction efficiency is T) is the same as the light amount on the lower surface.

(Equation 8)

T = 0.2, a = 120 m,? ? = 3 2.17 °, d =

Therefore, when the thickness d is smaller than this, a gain is generated in the extracted light amount. On the other hand, if the dog on the upper side is 120 / m, a = 107 and d = 105 zm.

This means that when the pixel size a is determined, the angle? ? This indicates that the effective substrate thickness d is determined by the above equation (5). If the substrate thickness is larger than this, it is not possible to extract all the light generated in the pixel to the outside, and the gain is not necessarily great.

FIG. 12 shows an example of a device structure incorporating a type 1 intermediate layer having such an optimum thickness.

FIG. 12 (a) shows a case where the first type intermediate layer, which is sufficiently thinner than the thickness of the entire substrate, directly contacts the lower part of the pixel. Such an arrangement is less effective because there is room for light to diffuse before reaching the final light extraction interface.

FIG. 12 (b) shows a case where the thickness of the entire substrate is the same as the thickness of the first type intermediate layer. In this case, the light extraction gain is obtained as described above, but the substrate thickness is small. For this reason, in order to maintain the mechanical strength of the substrate, the pixels as shown in Fig. Substrates with a certain distance dw between them and the intermediate layer are also possible. In this case, the value of dw should not be too large in order to avoid mixing of light with adjacent pixels during the time when the light reaches the first type intermediate layer from the pixel.

FIG. 13 shows an element structure in which a type 1 intermediate layer and a pixel are separated from each other and a waveguide layer is formed in a substrate under the condition that they are connected to each other. In this case, the pixel unit and the first type intermediate layer are directly connected by the waveguide layer as shown in Fig. 13 (a), and the first type is connected through the distance dw as shown in Fig. 13 (b). In some cases, the intermediate layers are coupled by a waveguide layer. In particular, in the latter case, in order to avoid mixing of light with adjacent pixels while the light reaches the first type intermediate layer from the pixel, the value of d w should not be too large.

As described above, in the organic electroluminescent device, the cross-sectional shape of the first type intermediate layer is a shape in which the opening portion expands from the light-emitting surface side to the light extraction surface side, and Light can be reflected on the side surface of the intermediate layer, and the total reflection angle on the light extraction surface side of the type 1 intermediate layer

The taper angle 7? Of the side surface of the intermediate layer is 0 C or less with respect to ΦC. In particular, 7? — / 2 or more,. In the following, when the element structure is designed so that the thickness d of the first type intermediate layer is equal to or less than / 2 tan ?? with respect to the width a of the light emitting surface side opening a on the same cross section, the light generated in the pixel portion is Most can be taken out of the device while maintaining the limitation on the pixel size as a display device.

(Example 5)

In this embodiment, an image is formed on a substrate on which an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor is formed, or is formed on a substrate on which an organic thin film transistor is formed. The element structure and drive circuit of the image display element will be described with reference to FIG.

When an organic electroluminescent device is used as an image display device, it is necessary to control the light emitting state of each pixel. As the screen size increases, it is effective to form a thin film transistor for each pixel inside the device that can drive each pixel independently.

FIG. 14 (a) shows the structure of one pixel section incorporating such a thin film transistor. A thin film transistor layer is formed on the upper surface of the substrate opposite to the light extraction surface. Here, two transistors per pixel (T sw: switching transistor, T dr: drain transistor) The transparent anode, light-emitting layer, and cathode of the organic electroluminescent device were formed on the thin-film transistor layer.

Part of the transparent anode and part of the cathode are connected to the transistor via A1 wiring. An intermediate layer of the first type is formed under the light emitting layer, and the structure can take various structures as shown in Example 4.

Fig. 14 (b.) Shows a circuit diagram of a transistor for driving each pixel ', gate wiring (G1 to G4) for driving switching transistors, and a drain. Drain wires (D1 to D4) for driving the transistors are formed between the pixels.

In order to display a specific pixel, these two types of wiring are selected, a transistor at a specific pixel position is driven, and light is generated by the light emitting unit. The generated light is guided to the first type intermediate layer formed below the layer containing the thin film transistor, where light is extracted while the optical path is diffused. Reach the interface.

As described above, in an image display device including an organic electroluminescent layer with a built-in thin-film transistor, a transistor portion and a wiring portion coexist in addition to a light-emitting pixel portion, so that a non-light-emitting region is necessarily included. However, by arranging those drive circuit portions on the tapered portion of the type 1 intermediate layer, it becomes possible to make the device more dense and to maximize the light extraction efficiency.

The organic electroluminescent device of the present invention can improve the extraction efficiency 7 _ext by a simpler method without changing the basic structure of the light-emitting portion of the organic electroluminescent device, which has been reported in many cases, and achieves more Light can be extracted outside the device.

In particular, when driving as a large-screen display element of 10 inches or more or a high-definition image display element even with a small area, it has been conventionally considered to be an essential matter in using organic materials, so high density Its use as a simple image display device was limited, and only an image display device of up to 8 inches was proposed. The organic electroluminescent device can be applied to such a high definition device and a large screen device.

By improving the electrical characteristics of these devices, it is possible to lower the driving voltage, increase the brightness, and extend the life of the devices. Industrial applicability

According to the present invention, a thin-film, light-weight, high-definition and high-efficiency organic electroluminescent device, and a thin-film flat display using the same, a small portable projection display, a mobile phone display device, a three-dimensional display, electronic paper, Portable personal computer evening display, real evening Provide various new opto-electronic devices such as electronic bulletin boards, light-emitting diodes, lasers, two-dimensional light pattern generators, optical computers, optical cross connectors, optical routers, etc., and systems and services using them. Becomes possible.

Claims

The scope of the claims

1. An organic electroluminescent device capable of injecting and transporting both positive and negative charges and generating light by recombination of holes and electrons generated by the positive and negative charges. An organic electroluminescent device having a light-emitting layer containing a light-emitting substance by recombination contained in or a fluorescent substance capable of receiving light from the light-emitting substance and generating light secondarily,

2. The organic electroluminescent device according to claim 1, wherein the first type intermediate layer is capable of scattering light or diffusing an optical path.

3. A claim in which the first type intermediate layer is separated for each pixel having a specific shape, or is separated for each pixel by a partition made of a material having a property different from that of the intermediate layer. 2. The organic electroluminescent device according to item 1, wherein

4. The first type intermediate layer is separated for each pixel having a specific shape, or is separated for each pixel by a partition made of a material having a property different from that of the intermediate layer. The shape of the first type intermediate layer or the shape of the partition, which is divided for each pixel facing from, is a polygon, and at least two of the shape surfaces forming the polygon are parallel. Item 10. The organic electroluminescent device according to item 8.

5. A force in which the first type intermediate layer is separated for each pixel having a specific shape, or a partition made of a material having a property different from that of the intermediate layer. The shape of the first type intermediate layer or the shape of the partition wall divided for each pixel facing the take-out interface is a polygon, and at least one of the shape surfaces forming the polygon 2. The method according to claim 1, wherein at least one pair of the pairs of parallel shaped surfaces forming two polygons that are parallel to each other has a length of 0.25 to 2 wavelengths of light generated. Organic electroluminescent device.

6. The first-type intermediate layer is separated for each pixel having a specific shape, or is separated for each pixel by a partition made of a material having a property different from that of the intermediate layer. 2. The organic electroluminescent device according to claim 1, wherein the shape of the first-type intermediate layer or the shape of the partition wall divided for each pixel facing from is circular.

7. The organic electroluminescent device according to claim 1, wherein the diameter of the circular first type intermediate layer or the partition wall is 0.25 to 2 wavelengths of the wavelength of the generated light.

8. The cross-sectional shape of the first type intermediate layer or the cross-sectional shape of the partition, which is divided for each pixel facing the light extraction interface, has a plane structure or a curved surface structure that is not parallel to the light extraction interface. Item 2. The organic electroluminescent device according to item 1.

9. The light-extraction interface of the first-type intermediate layer or the partition, which is separated for each pixel facing the extraction interface, and the interface that is not in contact with the light-emitting layer can reflect or refract light. Item 2. The organic electroluminescent device according to item 1.

10. The light-extraction interface of the first-type intermediate layer or the partition and the interface not in contact with the light-emitting layer, which are separated for each pixel facing the extraction interface, can reflect or refract light. 2. The organic electroluminescent device according to claim 1, wherein reflection at the device is not specular reflection.

1 1. The cross-sectional shape of the first type intermediate layer is a shape in which the opening is enlarged from the light emitting surface side to the light extraction surface side, and light can be reflected on the side surface of the first type intermediate layer. It is possible that the taper angle 7? On the side surface of the intermediate layer is Φ with respect to the total reflection angle (i) c on the light extraction surface side of the first type intermediate layer. 2. The organic electroluminescent device according to claim 1, which is as follows.

1 2. The cross section of the first type intermediate layer has a shape in which the opening is enlarged from the light emitting surface side to the light extraction surface side, and light can be reflected on the side surface of the first type intermediate layer. It is possible, and the taper angle? 7 on the side surface of the intermediate layer is 45 °-Φ with respect to the total reflection angle φc on the light extraction surface side of the first type intermediate layer. The thickness of the first-type intermediate layer is not more than aZ 2 t an? 7 with respect to the width a of the opening on the light-emitting surface side on the same cross section from Ζ 2 (i> _c) . Item 10. The organic electroluminescent device according to item 8.

13. An optical waveguide layer having a cross-sectional area equal to or less than the area of the light-emitting layer between the first-type intermediate layer and the light-transmitting electrode layer of the light-emitting layer. Organic electroluminescent device.

14. An optical waveguide layer having a cross-sectional area equal to or less than the area of the light-emitting layer without being in contact with the light-transmitting electrode layer is provided between the first-type intermediate layer and the light-transmitting electrode layer related to the light-emitting layer. The organic electroluminescent device according to claim 1, wherein

15. The organic electroluminescent device according to claim 1, wherein the first type intermediate layer includes a substance capable of absorbing light generated in the light emitting layer and generating light of another color.

16. The organic electroluminescent device according to claim 1, wherein the first type intermediate layer is formed inside a substrate supporting the light emitting layer.

17. The organic electroluminescent device according to claim 1, wherein the first type intermediate layer is formed outside a light-transmitting substrate that carries the light-emitting layer.

18. The organic electroluminescent device according to claim 1, wherein the light emitting layer is formed on a substrate on which an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor is formed, or on a substrate on which an organic thin film transistor is formed. element.

19. The organic electric field according to claim 1, wherein the light emitting layer is formed separately from the substrate on which the amorphous silicon thin film transistor or the polycrystalline silicon thin film transistor is formed or the substrate on which the organic thin film transistor is formed, and then integrated. Light emitting element.