JP2006127780A - Electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroluminescent element emitting light with high efficiency and a long life in a desired phosphor. <P>SOLUTION: A light-emitting layer, a dielectric layer and a charge-supplying layer are intercalated between a back electrode and a transparent electrode, the charge-supplying layer includes a needle-like substance, and is in contact with both surfaces of the light-emitting layer. Since the charge-supplying layer having the needle-like substance is provided on both surfaces of the light-emitting layer, high-energy electrons can effectively be collided with the desired phosphor, so that the electroluminescent element is capable of having a long life, high efficiency and multicolor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electroluminescence (EL) element used for an information display device and illumination.

  Electroluminescent (EL) elements include an electroluminescent type that emits light by exciting a phosphor by applying an alternating high electric field, and a charge injection type such as a light emitting diode. Among these, the electroluminescent type is broadly classified into a dispersion type EL element in which phosphor particles are dispersed in a binder and a thin film type EL element in which a phosphor or a dielectric is thinned by vapor deposition or the like to form an element.

  The distributed EL element can be driven at a low voltage, can easily be increased in area, and can be easily flexible. Therefore, the display unit and the operation unit of a small portable terminal such as a mobile phone or a PDA, as well as a poster or a signboard can be used. It is often used as a backlight. On the other hand, thin-film EL elements require vacuum deposition and are difficult to increase in area. However, since high-luminance light-emitting elements are obtained, application to color displays is being studied.

  FIG. 9 shows a cross-sectional view of an example of a conventional dispersion type EL element.

  Back electrode 101 such as silver or aluminum plate, transparent substrate 102 such as glass or PET (Poly Ethylene Terephthalate) film, transparent electrode 103 such as indium tin oxide (ITO) formed on the surface of transparent substrate 102, and back electrode A light emitting layer 105 and a dielectric layer 106 interposed between the transparent electrode 103 and the transparent electrode 103, a conductive wire 108, and a moisture-proof layer 109 are included. The light emitting layer 105 is a mixture in which a phosphor powder 104 doped with Cu, Mn, or the like in a host material such as ZnS is dispersed in an organic binder such as cyanoethyl cellulose. This is a mixture in which a dielectric powder 106 having a high dielectric constant such as barium titanate is dispersed in a similar organic binder.

  The light emission principle of the conventional dispersion-type EL element is considered as follows from the report of Fisher et al.

By adding Cu to ZnS, which is a phosphor, Cu _x S needle crystals are deposited along the ZnS line defects. This Cu _x S exhibits a very high conductivity. When an electric field is applied to the phosphor, electric lines of force are concentrated near both ends of the line defect, and a high electric field (10 ⁵ to 10 ⁶ V / cm ) Occurs. When an alternating electric field is applied, electrons and holes are emitted from both ends of the conductive defect line. The emitted holes are trapped in the emission center and emit light, and after a further half cycle, the electric field is reversed, and when electrons are released this time, they recombine with the trapped holes and emit light. Therefore, the light emission of the dispersive EL starts from two spots at both ends of the defect line, and as the voltage is increased, they gradually grow and are observed as a comitated light emission facing each other.

  On the other hand, FIG. 10 shows a cross-sectional view of an example of a conventional thin film EL element.

A back electrode 111 such as silver or aluminum plate, a transparent substrate 112 such as glass or PET (Poly Ethylene Terephthalate) film, a transparent electrode 113 such as ITO formed on the transparent substrate, a back electrode 111 and a transparent electrode 113 The light-emitting layer 114 and the dielectric layer 115 are interposed between the conductive layer 116 and the moisture-proof layer 117. The light emitting layer 114 is made of a phosphor obtained by doping a host material such as ZnS with Mn or TbF ₃ , and is formed into a thin film by a sputtering method, a vacuum deposition method, a CVD method, or the like. The dielectric layer 115 is made of a dielectric material such as SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , and is formed in a thin film shape by sputtering, vacuum deposition, CVD, or the like.

  The light emission principle of the thin film EL element is that light (hot electrons) accelerated by a high electric field excites the phosphor directly to emit light.

  Patent Document 1 describes that by providing a carbon nanotube layer on the cathode side, an electric field concentration point is generated, the device can be driven at a low voltage, and high efficiency and long life are achieved.

  Patent Document 2 describes that a transparent conductive oxide such as ITO needle-like powder is used for the needle-like substance 11 on the transparent electrode side.

J. et al. Electrochem. Soc. 109, p1043 (1962), J. et al. Electrochem. Soc. , 110, p733 (1963) JP 2002-305087 A Japanese Patent Laid-Open No. 06-293515

  However, in the conventional dispersion type EL element, when an electric field is applied, the number of line defects and CuxS needle crystals is slowly decreased, so that there is a problem that the light emission lifetime is short. In addition, when a dispersion type EL device is manufactured using a phosphor other than ZnS / CuxS, high-energy electrons are not efficiently injected into the phosphor, and it is impossible to emit light with high brightness and long life. It has become. Furthermore, for the reasons described above, there is a problem that the types of phosphors that can be used for the dispersion type EL are limited, and the emission color is limited.

  Also, conventional thin-film EL elements can emit EL more efficiently than dispersion-type EL elements, but it is required to generate hot electrons with high efficiency in order to aim for more efficient light emission. It has been.

  Further, unlike a dispersion type EL element or a thin film type EL element, a current injection type organic EL element that emits light by injecting holes and electrons into a light emitting layer is disclosed in Patent Document 1, as disclosed in Patent Document 1. By providing a carbon nanotube layer on the side, an electric field concentration point is generated, enabling the device to be driven at a low voltage, and achieving high efficiency and long life.

  However, with such a configuration, for an EL element that emits light by applying an alternating electric field with a high electric field, such as a dispersion type EL element or a thin film type EL element, the carbon nanotube layer is formed only from one side of the light emitting layer. Thus, the structure cannot be used to increase the efficiency and life of the EL element.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an electroluminescent device capable of emitting a desired phosphor with high efficiency and long life light emission. .

  In the electroluminescent device according to the present invention, a light emitting layer, a dielectric layer, and a charge supply layer are interposed between a back electrode and a transparent electrode, and the charge supply layer has a needle-like substance. It is provided on both surfaces of the light emitting layer.

  In the present invention, since a charge supply layer having a needle-like substance is provided on both sides of the light emitting layer, when an alternating electric field is applied, a high electric field can be efficiently applied to the phosphor from both sides of the light emitting layer, High efficiency and longevity of the EL element can be achieved. When the present invention is used for a dispersion type EL device, high energy electrons can be efficiently collided with a desired phosphor powder, so that the long life, high efficiency, and multiple colors of the dispersion type EL device can be achieved.

  Further, when the present invention is used for a thin film type EL element, as in the case of a dispersion type EL element, hot electrons can be supplied to the phosphor thin film more efficiently than a conventional thin film type EL element. Long life, high efficiency, and multiple colors are possible.

  For the acicular substance, it is preferable to use a nanotube or a nanowire so that a high electric field is easily generated and a large number can be added to the charge supply layer. Specifically, a carbon nanotube, a metal nanotube, or a metal is used. Examples thereof include nanowires. Among them, carbon nanotubes, in particular, have a structure that easily concentrates the electric field, have a high melting point, and have a stable structure, so that they can function stably as a charge supply source for a long time and can be mass-produced. Therefore, it is a suitable material for use as the acicular material of the present invention.

  The present invention may be a mixture of the nanotube and the nanowire. The carbon nanotubes preferably have a large proportion of the major axis oriented in the direction perpendicular to the layer surface. By using such a structure, the electric field concentration point can be formed more efficiently. It becomes like this. Here, the nanotubes are those having an inner diameter of several hundreds of nanometers to several hundreds of nanometers, an outer diameter of several hundreds of nanometers to several hundreds of nanometers, and a length of several nanometers to several millimeters. Nanowires have a diameter of several nanometers. It refers to those of nm to several hundred nm and length: several tens of nm to several mm.

  According to the present invention, an EL element capable of long-life and high-efficiency light emission can be provided by contacting a charge supply layer having a needle-like substance on both sides of a light-emitting layer. In addition, since long-life and high-efficiency light emission is possible with a desired phosphor, according to the present invention, the dispersion-type EL element can select various phosphor materials and emit various colors.

  In the EL element according to the present invention, by providing a charge supply layer containing an acicular substance, an electric field concentration point is generated, and high-energy electrons or holes can be generated with high efficiency. The needle-like substance is preferably a highly conductive nanotube or nanowire in order to efficiently provide an electric field concentration point. Among them, the carbon nanotube has a structure in which an electric field is easily concentrated, and has a melting point. Since it is high and stable, it is also a substance that has been studied as an electron source for field emission display (FED), and is suitable for use as the needle-like substance of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. As shown in FIG. 1, an example of the EL element of the present invention is a back electrode 1, a dielectric layer 2, a light emitting layer 3, a charge supply layer 4, 5, a transparent electrode 6, a transparent substrate 7, a conductor 8, and an element. A moisture-proof layer 9 is provided to protect the film from moisture.

The back electrode 1 may be any conductive material, and specifically includes aluminum, vanadium, cobalt, nickel, tungsten, silver, gold and the like. A transparent EL element can be manufactured by using a transparent and highly conductive material such as ITO, tin oxide (SnO ₂ ), or zinc oxide (ZnO).
Examples of the dielectric layer 2 include a dispersion type in which dielectric particles are dispersed in an organic binder, and a thin film type in which a dielectric thin film is directly formed by sputtering or the like. Dielectric used in the dielectric layer 2, for _{example, SiO 2, SiN x, SiO} x N y, TiO 2, Al 2 O 3, Si 3 N 4, SiAlON, Ta 2 O 5, Y 2 O 3, HfO ₂ , BaTiO ₃ , S ₃ O ₃ , Ta _x Sn _y O _z , ZrO ₂ , BaTa ₂ O ₆ , PbNb ₂ O ₆ , SrTiO ₃ , PbTiO ₃ or a dielectric solution such as a solid solution in which an element other than the above constituent elements is dissolved. The body is illustrated.

  In the dispersion type, dielectric particles made of the above dielectric are dispersed in an organic solvent such as dimethylformamide or isopropyl alcohol in an organic binder having a high dielectric constant such as cyanoethyl cellulose or cyanoethyl saccharose. A blade method, a screen printing method, a spin coating method, or the like is used to coat and form on the back electrode 1, the light emitting layer 3, the transparent electrode 6, or the charge supply layer 4 or 5.

  On the other hand, the thin film type is formed on the back electrode 1, the light emitting layer 3, the transparent electrode 6, the charge supply layer 4 or 5 by sputtering, CVD (Chemical Vapor Deposition), vapor deposition or the like. A thin film may be formed, or the dielectric particles having a particle size of several μm or less may be formed on the back electrode 1, the light emitting layer 3, the transparent electrode 6, or the charge supply layer 4 or 5 using the aerosol deposition method. Alternatively, the dielectric thin film may be formed by spraying directly on the substrate. The film thickness of the dielectric layer 2 is preferably 1 nm to 100 μm.

  Examples of the light emitting layer 3 include a dispersion type (dispersion type EL element) in which dielectric particles are dispersed in an organic binder and a thin film type (thin film type EL element) in which a dielectric thin film is directly formed by sputtering or the like. Can do.

  In the dispersion type, phosphor particles are mixed in an organic binder having a high dielectric constant such as cyanoethyl cellulose or cyanoethyl saccharose. The forming method is such that a liquid obtained by dispersing the organic binder and the phosphor particles in an organic solvent such as dimethylformamide is used on the back electrode 1 or a dielectric using a doctor blade method, a screen printing method, a spin coating method, or the like. Coating is performed on the layer 2, the transparent electrode 6, or the charge supply layer 4 or 5.

  On the other hand, the thin film type is formed on the back electrode 1, the dielectric layer 2, the transparent electrode 6, or the charge supply layer 4 or 5 by the sputtering method, the CVD (Chemical Vapor Deposition) method, the vapor deposition method, or the like. Alternatively, phosphor particles having a particle size of several μm or less may be formed on the back electrode 1, the light emitting layer 3, the transparent electrode 6, or the charge supply layer 4 or 5 using the aerosol deposition method. The light emitting layer thin film may be formed by spraying directly.

  The film thickness of the light emitting layer 3 is preferably 1 nm to 100 μm.

The phosphor used in the present invention may be any phosphor that emits EL when an electric field is applied. Examples of inorganic substances include II-VI group compound semiconductors, III-V group compound semiconductors, and IV groups. Group compound semiconductor, Group I-VI compound semiconductor, Group I-VII compound semiconductor, Group II-V compound semiconductor, Group II-VII compound semiconductor, Group III-VI compound semiconductor, Group IV-IV compound semiconductor, etc., Or VI group semiconductors, and specific examples of these phosphors include Ca ₂ (PO ₄ ) ₂ .Ca (F, Cl) ₂ , BaMgAl ₁₀ O ₁₇ , ZnSiO ₄ , LaPO ₄ , YBO ₃ , Y ₂ O ₃ , Y ₂ O ₂ S, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, CaS, SrS, GaAs, GaN, GaAlA _{s, GaP, InP, InN,} AlN, SiO 2, BaAl 2 S 4, Y 3 A 15 O 12, ZnO, Si, SiGe, InAs, Zn 2 SiO 4, (Y, Gd) BO 3, Zn 3 (PO _{4) 2,} ZnWO _4, and the like.

Also, a so-called doped phosphor in which at least one selected from manganese, rare earth elements and other elements is added to the above compound may be used. In this case, dope ions contained in the matrix emit light with the above compound as the matrix. The type of doped ions in this case is not particularly limited, but cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, manganese, lead, titanium , Chlorine, potassium, tin, bismuth, Tl, silver, chromium, gallium, gold, indium, iron, VO ₄ ³⁻ , Yb, nickel, copper, aluminum, titanium, LnF ₃ , TbF ₃ , F, etc. The Also, two or more of these ions may be doped at the same time.

  Further, the type of the luminescent dye is not particularly limited, and examples thereof include phthalocyanine dyes, azo dyes, and perylene dyes.

  Furthermore, the type of the conductive polymer having light emission is not particularly limited, but polyparaphenylene polymer, polyparaphenylene vinylene polymer, polythiophene polymer, polyaniline polymer, polypyrrole. Examples thereof include polymer-based polymers, polyvinylcarbazole-based polymers, and copolymers containing them.

  When the present invention is used for a dispersion type EL device, the surface of the phosphor particles coordinates, adsorbs or binds an organic compound / inorganic compound to suppress surface defects that cause light emission killer and improve carrier confinement. It may be coated. Examples of types of organic compounds for the coating layer include thiol compounds, amine compounds, phosphoric acid compounds, etc. Trialkyl phosphine oxides such as tributyl phosphine oxide and trialkyl phosphines such as trioctyl phosphine. And alkylamines such as dodecylamine and hexadecylamine, alkylthiols such as hexanethiol, and thiocresol. In addition, other conductive ligands such as thiophenes, phenylenes, phenylene vinylenes, pyrroles, and carbazoles may be used.

On the other hand, as long as the coating layer is an inorganic compound as long as it is a substance that can coat the phosphor surface, it may be coated with a semiconductor wider than the phosphor band gap in order to efficiently confine carriers in the phosphor. The doped phosphor is preferably covered with a material that is a base material. _{Further, SiO 2, SiN x, SiO} X N y, TiO 2, Al 2 O 3, Si 3 N 4, SiAlON, Ta 2 O 5, Y 2 O 3, HfO 2, BaTiO 3, S 2 O 3, Ta _x Sn _y O _z , ZrO ₂ , BaTa ₂ O ₆ , PbNb ₂ O ₆ , SrTiO ₃ , PbTiO ₃ , or a dielectric in which an element other than the above constituent elements is dissolved may be coated.

  The particle size of the phosphor is not particularly limited, but the phosphor that exhibits a quantum confinement effect by forming nanoparticles in the phosphor and improves the emission luminance is of a nanoparticle size. Is preferred. In addition, since the band gap is changed by using nanoparticles, the emission color can be controlled by controlling the particle size. The quantum confinement effect varies depending on the substance, but is manifested in a size of about several tens of nm or less. In addition, since the nanoparticles are transparent to visible light, by making the light emitting layer transparent, the light can be efficiently extracted outside without being scattered by the light emitting layer. Thus, a transparent light emitting element can be provided.

  In the charge supply layer 5 on the transparent electrode 6 side, the density of the needle-like substance 10 is set to the density of the needle-like substance 11 included in the charge supply layer 4 on the back electrode 1 side so that light can be efficiently extracted outside the device. It is preferable to reduce the thickness of the charge supply layer 5 or to make the thickness of the charge supply layer 5 thinner than that of the charge supply layer 4. Also, in order to efficiently extract light to the outside, a transparent conductive oxide such as ITO needle-like powder produced by the method disclosed in Patent Document 2 is used for the needle-like substance 11 on the transparent electrode side. Is also possible. Further, when the light emitting layer 3 is transparent, a black material such as carbon nanotube is used for the needle-like material 10 of the charge supply layer 4 on the back electrode 1 side, and this occurs when the back electrode 1 uses a metal such as aluminum. Specular reflection can be prevented, and in particular, when the present invention is used for a display, it is possible to increase the contrast.

  The charge supply layers 4 and 5 are preferably oriented such that the long axes of the acicular substances 10 and 11 are perpendicular to the layer surface of the EL element, as shown in FIG. 1, because the electric field concentrates more efficiently. However, other than that, a charge supply layer in which the acicular substance is non-oriented may be used as shown in FIG.

  The needle-like substances 10 and 11 may be anything as long as they are conductive needle-like substances. Specifically, carbon nanotubes, boron nitride nanotubes, silicon nanotubes, metal nanotubes, metal nanowires, and needle-like shapes. Examples thereof include transparent conductive oxides such as ITO having a mixture of the above substances, and further, a mixture of the above substances, among which carbon nanotubes have a structure that is easy to concentrate an electric field, have a high melting point, and a stable structure. Therefore, since it is a substance that can work stably as a charge supply source for a long time and can be mass-produced, it is a suitable substance for use as the acicular substance of the present invention.

  Carbon nanotubes include single-walled carbon nanotubes with a single wall, multi-walled carbon nanotubes with multiple walls, and graphite nanofibers with a graphene sheet stacked to form a cylindrical structure. Depending on the vector, there are metallic and semiconducting materials, but in the present invention, it is preferable to use carbon nanotubes having higher conductivity.

  As for the above-mentioned carbon nanotube production method, CVD method for producing carbon nanotubes from hydrocarbon gas using a metal catalyst, arc discharge method for producing carbon nanotubes by arc discharge of a carbon electrode, high-pressure carbon vapor by striking a graphite rod with a laser And a carbon ablation method in which carbon nanotubes are grown with a collecting device. However, the present invention may use carbon nanotubes produced by any method described above.

  Further, if the CVD method is used in the manufacturing method, the long axis of the carbon nanotube can be oriented in the direction perpendicular to the layer surface of the EL element of the present invention as shown in FIG. High energy electrons and holes can be generated. Specifically, for example, a catalyst of metal fine particles such as cobalt is cast on the back electrode 1, the dielectric layer 2, the light emitting layer 3, and the transparent electrode 6, and for example, a diluent gas of acetylene is supplied and reacted. Thus, a charge supply layer having the desired orientation can be formed. If screen printing or ink jet technology is used for casting of the metal catalyst fine particles, it is possible to cope with an increase in area of the element, patterning, and formation on a curved surface.

  As described above, the charge supply layers 4 and 5 of the present invention are formed by aligning the carbon nanotubes by using the CVD method, and the acicular materials 10 and 11 in a resin such as an acrylic resin and its solvent. You may form using the paste which was disperse | distributed using screen printing or an inkjet technique. With the charge supply layer having such a configuration, a desired acicular substance can be dispersed regardless of the type of acicular substance.

The transparent electrode 6 is preferably made of a light-transmitting material for extracting light. Specifically, the indium and tin composite oxide ITO, tin oxide (SnO ₂ ), zinc oxide (ZnO) ) And the like. The transparent electrode 6 is made of PET or polycarbonate (PC: Poly
Carbonate), polyolefin (PO: Poly Olefin) and polyethersulfone (PES: Poly)
Eter Sulphone) or the like or a transparent substrate 7 such as glass is formed using a vacuum deposition method, a sputtering method, or the like.

  The moisture-proof layer 9 is a substance that is difficult for moisture to permeate, and preferably has an insulating property. Specifically, glass or a film having moisture-proof properties such as ethylene trifluoride chloride and PET is exemplified. it can.

  Further, as an example of the form of the EL element of the present invention other than those shown in FIGS. 1 and 2, as shown in FIG. 3, the charge supply layer 4 on the back electrode 1 side is oriented with the long axis of the acicular substance in the vertical direction. The structure in which the charge supply layer 5 on the transparent electrode 6 side is non-oriented, the structure in which the light emitting layer 3 is sandwiched between the dielectric layers 2 as shown in FIG. Examples include a configuration in which a back substrate 12 made of plastic, ceramics, metal, or the like is provided and the back electrode 1 is formed thereon, or a configuration in which the charge supply layer 4 or 5 also serves as an electrode as shown in FIG. it can.

  Furthermore, by using the EL element of the present invention as a display, a display that emits light with high efficiency and a long lifetime can be provided. An example of the configuration is shown in FIG.

  A dielectric layer 23, a light emitting layer 25, and charge supply layers 24 and 26 are provided between a back electrode 22 formed on the back substrate 21 and an electrode in which transparent electrodes 27 are wired in the X direction and the Y direction perpendicular to each other. It is a structure, and the place where the back electrode 22 and the transparent electrode 27 intersect is one pixel. In the case of producing a full-color display, it is possible to separately coat the phosphor on one electrode at each of the RGB locations. Regarding the types of phosphors used for full color, since the present invention can emit light with a desired phosphor, R (red), G (green), and B (blue) are emitted from each of the phosphors described above. What is necessary is just to select a thing, and when using the nanoparticle from which a luminescent color changes by a quantum confinement effect, particle size control should just be performed and a luminescent color should be controlled. As a display driving method, as shown in FIG. 6, in addition to simple matrix driving, active matrix driving using TFTs may be performed.

  In the present invention, if a flexible substrate such as an aluminum foil is present on the back substrate 21 and a transparent substrate 28 is present on the transparent electrode 27, if a flexible polymer polymer material such as PET is used for the transparent substrate, A flexible display can be provided. Since the dispersion type EL element of the present invention can produce a display without using a large-scale apparatus such as a vacuum apparatus, the screen can be easily enlarged and the display can be inexpensive.

  In addition to the above-described display, by using the present invention for illumination, it is possible to provide illumination that emits light with high efficiency and long life. According to the present invention, selection of a phosphor material is widened as compared with a conventional EL element, and various colors can be emitted. Therefore, it is possible to provide illumination that emits more kinds of colors. For example, when used as white illumination, for example, phosphor particles emitting RGB colors are mixed, or a phosphor emitting blue light and a color that emits yellow light that is complementary to blue by being excited by blue light. What is necessary is just to mix the fluorescent substance to convert.

  Since the EL element of the present invention can be manufactured without using a large apparatus such as a vacuum apparatus in the manufacturing process, the screen can be easily enlarged and inexpensive illumination can be provided. For this reason, it is possible to easily provide large-area lighting for the above reasons. For example, if the EL element of the present invention is attached to a ceiling or a wall, it can be used as room lighting, and the back of a large-screen liquid crystal display. It can also be used as a light.

  Hereinafter, although an Example demonstrates concretely, this invention is not limited to what is shown below.

  In this example, the EL element of the present invention is used as a lighting device, and is a dispersion type EL element in which phosphor powder is dispersed in an organic binder as a light emitting layer.

  In this embodiment, in FIG. 1, an aluminum foil is used for the back electrode 1, and the dielectric layer 2 is formed by forming a thin film of alumina having a thickness of about 100 nm on the back electrode by sputtering. Then, cobalt fine particles (particle size: about 4 nm) are cast on the dielectric layer 2 by a screen printing method, and reacted with a dilute gas of acetylene at 700 to 900 ° C. under normal pressure, whereby the long axis of the carbon nanotube is obtained. A charge supply layer 4 (thickness: about 3 μm) oriented perpendicular to the layer surface of the EL element is produced.

  On the other hand, PET is used for the transparent substrate 7, and the transparent electrode 6 is formed on the transparent substrate 7 using ITO by sputtering. Then, a needle-like ITO transparent conductive paste (manufactured by Sumitomo Metal Mining: SC-100 series) is formed as a charge supply layer 5 to a film thickness of about 10 μm by screen printing. The light emitting layer 3 is obtained by dispersing phosphor powder ZnS: Mn in cyanoethyl cellulose as a binder, and the weight ratio thereof is binder: phosphor powder = 3.0: 1.0. The light-emitting layer 3 is formed by dispersing the binder and the phosphor powder in dimethylformamide, which is an organic solvent, so that the mixing ratio is the same, and then forming a film thickness on the charge supply layer 5 using a screen printing method. The coating is performed so that the thickness becomes 50 μm.

  As shown in FIG. 7, the EL element of this example includes a transparent electrode 6, a charge supply layer 5, and a light emitting layer 3 formed on the back electrode 1 side on which the dielectric layer 2 and the charge supply layer 4 are formed. The substrate 7 side is integrally bonded using a roller to form a conductive wire 8, and then sandwiched from above and below by a trifluorinated ethylene chloride film used as a moisture-proof layer 9.

  By forming an AC electric field as described above, a flexible lighting device that emits light with a long lifetime and high efficiency can be provided.

  In this example, the EL element of the present invention is used as a display.

  This example is a display driven by a simple matrix, and is a thin film type EL element using a phosphor thin film as a light emitting layer.

  The method of forming the display of this example is as follows.

  In FIG. 7, an aluminum thin film is formed by vapor deposition on a glass substrate used as the back substrate 21, and then patterned by ordinary etching using a photoresist to form the back electrode 22 having the pattern shown in FIG. . Then, an alumina thin film having a thickness of about 100 nm is formed thereon as the dielectric layer 23 by sputtering. Further, a charge supply layer 24 is formed thereon so as to have a film thickness of about 3 μm by the same method as that of the charge supply layer 3 of Example 1, and then the light-emitting layer 25 is formed using a sputtering method to a film thickness of about A 1 μm ZnS: Mn thin film is formed on the charge supply layer 24. The charge supply layer 26 is formed by the same method as the charge supply layer 24, but is formed to have a thickness of about 0.5 μm, which is thinner than the charge supply layer 24, in order to make it easy to extract light outside the device. . Thereafter, an ITO film is formed on the charge supply layer 26, and patterning is performed by ordinary etching using a photoresist, so that the transparent electrode 25 is formed so as to have the pattern shown in FIG. Thereafter, a conductive wire for connection to the driving IC is formed, sandwiched from above and below by a moisture-proof film, and this is heated and pressed to perform thermocompression bonding.

  A display that emits light with a long lifetime and high efficiency can be provided by applying the AC electric field formed as described above.

It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows an example of embodiment of this invention. It is a figure at the time of using the EL element of this invention as a display. 3 is a cross-sectional view showing a method for forming an EL element according to Example 1. FIG. It is sectional drawing of the conventional dispersion-type EL element. It is sectional drawing of the conventional thin film type EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back electrode 2 Dielectric layer 3 Light emitting layer 4 Charge supply layer (back electrode side)
5 Charge supply layer (transparent electrode side)
6 Transparent electrode 7 Transparent substrate 8 Conductor 9 Moisture-proof layer 10 Needle-like substance (transparent electrode side)
11 Needle-like material (back electrode side)
12 Back substrate 21 Back substrate 22 Back electrode 23 Dielectric layer 24 Charge supply layer (back electrode side)
25 Light emitting layer 26 Charge supply layer (transparent electrode side)
27 Transparent Electrode 28 Transparent Substrate 31 Phosphor Particle 101 Back Electrode 102 Transparent Substrate 103 Transparent Electrode 104 Phosphor Particle 105 Light-Emitting Layer 106 Dielectric Particle 107 Dielectric Layer 108 Conductive Wire 109 Moisture Proof Layer 111 Back Electrode 112 Transparent Substrate 113 Transparent Electrode 114 Light Emitting layer
115 Dielectric layer 116 Conductor 117 Moisture-proof layer

Claims (5)

  A light emitting layer, a dielectric layer, and a charge supply layer are interposed between the back electrode and the transparent electrode, the charge supply layer has a needle-like substance, and the charge supply layer is in contact with both surfaces of the light emitting layer. An electroluminescent element characterized by the above.   2. The electroluminescent element according to claim 1, wherein the electroluminescent element is the dispersion type EL element.   2. The electroluminescent device according to claim 1, which is a thin film EL device.   The electroluminescent element according to claim 1, wherein the acicular substance is a carbon nanotube.   5. The electroluminescent device according to claim 4, wherein the carbon nanotube has a large proportion of the major axis oriented in a direction perpendicular to the layer surface.

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