JP7496194B2 - Inorganic EL element, display element, image display device, and system - Google Patents

Description

The present invention relates to a DC-driven inorganic EL element, a display element, an image display device, and a system.

In recent years, organic electroluminescence (OLED) elements and compound semiconductor LEDs have been developed for use as illumination light sources and displays. These are current-injection type light-emitting elements that emit light when driven by direct current, and are characterized by the ability to emit light with high brightness even at low voltages. However, since OLEDs are made of organic materials, they have the disadvantage of low durability. In addition, LEDs have the disadvantage that RGB elements cannot be formed on active matrix thin-film transistors (AM-TFTs), which are widely used in displays, because LEDs are made by epitaxially growing compound semiconductors on a single crystal substrate. On the other hand, inorganic EL elements made of oxide or oxysulfide luminescent materials are highly durable and may be able to form RGB elements on AM-TFTs, making them promising light-emitting elements for next-generation displays.

Inorganic EL elements are broadly divided into AC-driven and DC-driven types, depending on the driving method. AC-driven inorganic EL elements emit light by sandwiching a thin inorganic light-emitting layer between dielectric layers, or by applying an AC voltage of several hundred volts to a layer in which fluorescent particles are dispersed in a dielectric binder. This method has been extensively researched and developed, and is now in practical use.

On the other hand, DC-driven inorganic EL elements, which are a type of EL (Electroluminescence), are well known in the past as DC-driven inorganic EL elements that use inorganic phosphors as the light-emitting layer. In DC-driven inorganic EL elements, for example, a light-emitting layer is provided between a pair of electrodes, and when a voltage is applied between the pair of electrodes, the light-emitting layer emits light, thereby illuminating the surroundings. DC-driven inorganic EL has the advantages of being inexpensive and not generating heat when emitting light, and is expected to become more widespread in the future. As an inorganic EL element phosphor, a technology in which rare earth elements are added to zinc oxide and used as a DC-driven inorganic EL light-emitting layer is well known (see Non-Patent Document 1, etc.).

In addition, an inorganic EL element has been proposed in which a rare earth diffusion prevention film is provided between the light-emitting layer and the substrate (see Patent Document 1, etc.).

However, with conventional technology, it has not been possible to realize an inorganic EL element that can be driven with a direct current at a low voltage and emits light with high efficiency.
An object of the present invention is to provide a direct-current-driven inorganic EL element which emits light at a sufficiently low voltage and with high efficiency.

The means for solving the above problems are as follows.
The inorganic EL element of the present invention is an inorganic EL element including an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode laminated thereon,
the hole transport layer is an oxide film,
the light-emitting layer is an oxide film,
The electron transport layer is an oxide film.

The inorganic EL element of the present invention makes it possible to provide a durable light-emitting element that emits light at a low voltage and with high efficiency.

FIG. 1 is a schematic diagram showing an example of the DC-driven inorganic EL element of the present invention. FIG. 2 is a diagram for explaining the image display device. FIG. 3 is a diagram for explaining an example of a display element of the present invention. FIG. 4 is a schematic diagram showing an example of the positional relationship between an inorganic EL element and a field effect transistor in a display element. FIG. 5 is a schematic diagram showing another example of the positional relationship between an inorganic EL element and a field effect transistor in a display element. FIG. 6 is a diagram for explaining the display control device. FIG. 7 is a diagram showing the IV characteristics of the inorganic EL element prepared in Example 1. FIG. 8 is a diagram showing the EL spectrum of the inorganic EL element prepared in Example 1. FIG. 9 is a schematic diagram showing an energy diagram of the inorganic EL elements prepared in Examples 1 and 4. FIG. 10 is a schematic diagram showing an energy diagram of the inorganic EL element prepared in Example 2. FIG. 11 is a schematic diagram showing an energy diagram of the inorganic EL element prepared in Example 3. FIG. 12 is a schematic diagram showing an energy diagram of the inorganic EL element prepared in Example 5. FIG. 13 is a schematic diagram showing an energy diagram of the inorganic EL element prepared in Example 6.

(Inorganic EL element)
The inorganic EL device of the present invention has at least a light-emitting layer, and further has other members such as an anode, a cathode, a hole transport layer, and an electron transport layer, if necessary.
The inorganic EL element is of a direct current driving type.

The light-emitting layer is an oxide film, and is preferably an amorphous oxide film.
The hole transport layer is an oxide film, and is preferably an amorphous oxide film.
The electron transport layer is an oxide film, and is preferably an amorphous oxide film.

The oxide film may contain microcrystals.

The oxide film serving as the light-emitting layer is preferably made of an oxide doped with a light-emitting center.
The luminescent center is preferably a transition metal ion or a rare earth ion.
The luminescent center preferably contains at least one of titanium (Ti), chromium (Cr), manganese (Mn), tungsten (W), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb).

In the oxide film that is the light-emitting layer, it is preferable that an oxide having a band gap energy equal to or greater than the excitation energy of the light-emitting center serves as a host for the light-emitting center.
In the oxide film that is the light-emitting layer, it is preferable that an oxide having a band gap energy equal to or greater than the light-emitting energy of the light-emitting center serves as a host for the light-emitting center.

The oxide film that is the hole transport layer is preferably a p-type oxide semiconductor.

The oxide film that is the electron transport layer is preferably an n-type oxide semiconductor.

It is preferable that the oxide film serving as the hole transport layer is a p-type oxide semiconductor doped with a light emitting center, and also serves as the light emitting layer.
It is preferable that the oxide film serving as the electron transport layer is an n-type oxide semiconductor doped with a light-emitting center, and also serves as the light-emitting layer.
The luminescent center is preferably a transition metal ion or a rare earth ion.
The luminescent center preferably contains at least one of titanium (Ti), chromium (Cr), manganese (Mn), tungsten (W), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb).

FIG. 1 is a schematic diagram showing an example of the DC-driven inorganic EL element of the present invention.
The inorganic EL element 350 in FIG. 1 includes a cathode 312 , an anode 314 , and an inorganic EL thin film layer 340 .

<Cathode>
The material of the cathode 312 is not particularly limited and can be appropriately selected according to the purpose. For example, aluminum (Al), magnesium (Mg)-silver (Ag) alloy, aluminum (Al)-lithium (Li) alloy, gold (Au)-germanium alloy, ITO (indium tin oxide) and the like can be mentioned. Note that magnesium (Mg)-silver (Ag) alloy becomes a highly reflective electrode if it is sufficiently thick, and becomes a semi-transparent electrode if it is an extremely thin film (less than about 20 nm). In the figure, light is extracted from the anode side, but light can be extracted from the cathode side by making the cathode a transparent or semi-transparent electrode.

<Anode>
The material of the anode 314 is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include ITO (indium tin oxide), IZO (indium zinc oxide), silver (Ag)-neodymium (Nd) alloy, aluminum (Al)-silicon (Si)-copper (Cu) alloy, etc. When a silver alloy is used, it becomes a high reflectivity electrode, which is suitable for extracting light from the cathode side.

<Inorganic EL Thin Film Layer>
The inorganic EL thin film layer 340 has, for example, an electron transport layer 342, a light emitting layer 344, and a hole transport layer 346. The electron transport layer 342 is connected to the cathode 312, and the hole transport layer 346 is connected to the anode 314. When a predetermined voltage is applied between the anode 314 and the cathode 312, the light emitting layer 344 emits light.

Here, the electron transport layer 342 and the light emitting layer 344 may form one layer, or the hole transport layer 346 and the light emitting layer 344 may form one layer. In addition, an electron injection layer may be provided between the electron transport layer 342 and the cathode 312, and further, a hole injection layer may be provided between the hole transport layer 346 and the anode 314.
In addition, the so-called "bottom emission" in which light is extracted from the substrate side (the lower side in FIG. 1) has been described, but "top emission" in which light is extracted from the side opposite the substrate (the lower side in FIG. 1) may also be used.

<<Light-emitting layer>>
The oxide film, which is the light-emitting layer in the inorganic EL element of the present invention, is preferably composed of an oxide doped with a light-emitting center. The light-emitting center is not particularly limited, and transition metal ions or rare earth ions can be appropriately selected depending on the purpose, and examples thereof include Ti, Cr, Mn, Cu, W, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb.
The host oxide can be appropriately selected depending on the purpose, but it is preferable that the band gap energy is equal to or greater than the excitation energy of the luminescence center, and it is also preferable that the band gap energy is equal to or greater than the luminescence energy of the luminescence center. Examples of such host oxides include _Al2O3 , _{Ga2O3 , La2O3 , ZrO2} , _YAO (yttrium aluminum oxide), YGO (yttrium gadolinium oxide), and LAO (lanthanum aluminum oxide).
The concentration of the luminescence center can be appropriately selected depending on the purpose, but for example, it is preferably 10 atom % or less of the host cation, and particularly preferably about 1 to 5 atom %.

The oxide film, which is the light-emitting layer, is preferably an oxide containing at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), lutetium (Lu), boron (B), aluminum (Al), gallium (Ga), silicon (Si), germanium (Ge), antimony (Sb), bismuth (Bi), and tellurium (Te).

The thickness of the light-emitting layer can be appropriately selected depending on the purpose, but for example, a thickness of 100 nm or less is preferable, and a thickness of about 5 to 30 nm is particularly preferable.

<<Electron Transport Layer>>
The oxide film, which is the electron transport layer in the inorganic EL element of the present invention, is preferably composed of an n-type oxide semiconductor. The material of the n-type oxide semiconductor is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include InGaZnO (indium gallium zinc oxide), IMO (indium magnesium oxide), ZTO (zinc tin oxide), IAO (indium aluminum oxide), and ILO (indium lanthanum oxide). In order to control the electron carrier of the n-type oxide semiconductor, carrier doping is also preferable.

The oxide film that is the electron transport layer is preferably an n-type oxide semiconductor that contains at least one of zinc (Zn), cadmium (Cd), gallium (Ga), indium (In), thallium (Tl), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), titanium (Ti), and tungsten (W).

The oxide film, which is the electron transport layer, is preferably an n-type oxide semiconductor further containing at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanoids (Ln), boron (B), aluminum (Al), silicon (Si), antimony (Sb), and tellurium (Te).

The thickness of the electron transport layer can be appropriately selected depending on the purpose, but is preferably 100 nm or less, and more preferably about 5 to 30 nm.

<<Hole transport layer>>
The oxide film serving as the hole transport layer in the inorganic EL element of the present invention is preferably composed of a p-type oxide semiconductor. The material of the p-type oxide semiconductor is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include _Cu2O , _CuInO2 (copper indium oxide), _CuAlO2 (copper aluminum oxide), MCO (magnesium copper oxide), CCO (calcium copper oxide), SCO (strontium copper oxide), ACO (antimony copper oxide), CTO (copper tin oxide), NiO, _ZnIr2O4 (zinc iridium oxide), etc. Carrier doping is also suitable for controlling hole carriers in the _p -type oxide semiconductor.

The oxide film that is the hole transport layer is preferably a p-type oxide semiconductor that contains at least one of nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), thallium (Tl), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), and tellurium (Te).

The thickness of the hole transport layer can be appropriately selected depending on the purpose, but for example, a thickness of 100 nm or less is preferable, and a thickness of about 5 to 30 nm is particularly preferable.

When the light-emitting layer and the electron-transporting layer are formed in one layer, it is preferable to dope the electron-transporting layer with the light-emitting center of the light-emitting layer.
When the light emitting layer and the hole transporting layer are formed in one layer, it is preferable to dope the hole transporting layer with the light emitting center of the light emitting layer.
The combination of the type and concentration of the luminescent center, the material and film thickness of the electron transport layer and the hole transport layer, etc. can be appropriately selected.

<<Electron injection layer>>
The electron injection layer in the inorganic EL element of the present invention is present between the cathode and the electron transport layer, and serves to facilitate the injection of electrons from the cathode. As described above, it is particularly useful when the light emitting layer and the electron transport layer are configured as one layer. The oxide film as the electron injection layer in the inorganic EL element of the present invention is preferably configured from an n-type oxide semiconductor. There is no particular limitation on the material of the n-type oxide semiconductor, and it can be appropriately selected according to the purpose, and examples thereof include InGaZnO (indium gallium zinc oxide), IMO (indium magnesium oxide), ZTO (zinc tin oxide), IAO (indium aluminum oxide), and ILO (indium lanthanum oxide).

The oxide film that is the electron injection layer is preferably an n-type oxide semiconductor that contains at least one of zinc (Zn), cadmium (Cd), gallium (Ga), indium (In), thallium (Tl), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), titanium (Ti), and tungsten (W).

The n-type oxide semiconductor, which is the electron injection layer, is preferably carrier-doped to lower the barrier for electron injection from the cathode. As the carrier dopant, it is preferable to add an element having a higher valence than the constituent elements of the n-type oxide semiconductor. For example, tin (Sn), titanium (Ti), niobium (Nb), and tungsten (W) are preferable for IMO (Indium Magnesium Oxide). For ZTO (Zinc Tin Oxide), niobium (Nb), molybdenum (Mo), and tungsten (W) are preferable.

The thickness of the electron injection layer can be appropriately selected depending on the purpose, but for example, a thickness of 100 nm or less is preferable, and a thickness of about 5 to 30 nm is particularly preferable.

<<Hole injection layer>>
The hole injection layer in the inorganic EL element of the present invention is present between the anode and the hole transport layer, and serves to facilitate the injection of holes from the anode. As described above, this is particularly useful when the light emitting layer and the hole transport layer are configured as one layer. The oxide film that is the hole injection layer in the inorganic EL element of the present invention is preferably configured from a p-type oxide semiconductor. The material of the p-type oxide semiconductor is not particularly limited and can be appropriately selected depending on the purpose. Examples of the material include _Cu2O , _CuInO2 (copper indium oxide), _CuAlO2 (copper aluminum oxide), MCO (magnesium copper oxide), CCO (calcium copper oxide), SCO (strontium copper oxide), ACO (antimony copper oxide), CTO (copper tin oxide), NiO, _{and ZnIr2O4 (} zinc iridium oxide).

The oxide film that is the hole injection layer is preferably a p-type oxide semiconductor that contains at least one of nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), thallium (Tl), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), and tellurium (Te).

The p-type oxide semiconductor serving as the hole injection layer is preferably carrier-doped to lower the barrier for hole injection from the anode. As the carrier dopant, an element having a lower atomic valence than the constituent elements of the p-type oxide semiconductor is preferably added. For example, magnesium (Mg), calcium (Ca), and strontium (Sr) are preferable for CuInO ₂ (copper indium oxide).

The thickness of the hole transport layer can be appropriately selected depending on the purpose, but for example, a thickness of 100 nm or less is preferable, and a thickness of about 5 to 30 nm is particularly preferable.

There are no particular limitations on the method for forming the inorganic EL thin film layer, and it can be appropriately selected depending on the purpose. Examples include vacuum film formation methods such as CVD and ALD, and printing methods such as spin coating and slit die coating.

The sealing film and other components can be selected appropriately depending on the purpose.

There are no particular limitations on the substrate, and it can be selected appropriately depending on the purpose. Examples include glass substrates and plastic substrates.

There are no particular limitations on the method for forming the electrode layers (anode and cathode), and the method can be appropriately selected depending on the purpose. Examples include vacuum film formation methods such as sputtering, CVD, and vacuum deposition, and printing methods such as spin coating and slit die coating.

<Method of Manufacturing Inorganic EL Element>
The method for producing the inorganic EL element is not particularly limited and can be appropriately selected depending on the purpose. For example, the method includes a step of forming the inorganic EL thin film layer using a coating liquid for forming an inorganic EL thin film, and further includes other steps as necessary.
The inorganic EL thin film-forming coating liquid is a coating liquid for forming at least one of the hole transport layer, the light emitting layer, and the electron transport layer that constitute the inorganic EL thin film layer.

- Coating solution for forming inorganic EL thin film -
The inorganic EL thin film forming coating liquid is preferably one in which the metal elements constituting the light emitting layer, p-type, and n-type oxide semiconductors are dissolved in a solvent as at least one of oxides, inorganic salts, carboxylates, organic compounds, and organic metals. The oxides, inorganic salts, carboxylates, organic compounds, and organic metals may be dissolved uniformly in the solvent, and may be dissociated into ions. When the oxides, inorganic salts, carboxylates, organic compounds, and organic metals are dissolved in the inorganic EL thin film forming coating liquid, segregation of the concentration in the inorganic EL thin film forming coating liquid is unlikely to occur, so the inorganic EL thin film forming coating liquid can be used for a long period of time. In addition, the thin film prepared using this coating liquid also has a uniform composition, so the uniformity of characteristics is also good when used in an inorganic EL thin film layer.

Preferred luminescence center raw materials constituting the coating liquid for forming the luminescent layer, which is an example of the coating liquid for forming the inorganic EL thin film, include transition metal compounds including titanium (Ti), chromium (Cr), manganese (Mn), tungsten (W), etc., and rare earth metal compounds including cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb), etc.

The following describes examples of the above compounds that are the luminescence center raw materials that make up the coating liquid for forming the luminescent layer.

<<Manganese (Mn)-containing compounds>>
The manganese (Mn)-containing compound is not particularly limited and can be appropriately selected depending on the purpose. Examples of the manganese (Mn)-containing compound include organic manganese compounds and inorganic manganese compounds.

-Organic manganese compounds-
The organic manganese compound is not particularly limited and may be appropriately selected depending on the purpose as long as it is a compound having manganese and an organic group. The manganese and the organic group are bonded, for example, by an ionic bond, a covalent bond, or a coordinate bond.

The organic group is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include an alkoxy group which may have a substituent, an acyloxy group which may have a substituent, an acetylacetonate group which may have a substituent, etc. Examples of the alkoxy group include an alkoxy group having 1 to 6 carbon atoms, etc. Examples of the acyloxy group include an acyloxy group having 1 to 10 carbon atoms, etc.
Examples of the substituent include halogen and a tetrahydrofuryl group.
Examples of the organic manganese compound include manganese(II) acetate tetrahydrate, manganese(II) benzoate tetrahydrate, manganese(III) acetylacetonate, and manganese(II) 2-ethylhexanoate.

- Inorganic manganese compounds -
The inorganic manganese compound is not particularly limited and can be appropriately selected depending on the purpose. Examples of the inorganic manganese compound include manganese oxoacids, manganese halides, and manganese oxides.
Examples of the manganese oxoacid include manganese nitrate, manganese sulfate, and manganese carbonate.
Examples of the manganese halides include manganese fluoride, manganese chloride, manganese bromide, and manganese iodide.
Among these, manganese(II) nitrate tetrahydrate and manganese(II) chloride tetrahydrate are more preferred because of their high solubility in various solvents.

These manganese-containing compounds may be synthetic or commercially available.

<<Europium (Eu)-containing compounds>>
The europium (Eu)-containing compound is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include organic europium compounds and inorganic europium compounds.

-Organic europium compounds-
The organic europium compound is not particularly limited and may be appropriately selected depending on the purpose as long as it is a compound having europium and an organic group. The europium and the organic group are bonded, for example, by an ionic bond, a covalent bond, or a coordinate bond.

The organic group is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include an alkoxy group which may have a substituent, an acyloxy group which may have a substituent, an acetylacetonate group which may have a substituent, etc. Examples of the alkoxy group include an alkoxy group having 1 to 6 carbon atoms, etc. Examples of the acyloxy group include an acyloxy group having 1 to 10 carbon atoms, etc.
Examples of the substituent include halogen and a tetrahydrofuryl group.
Examples of the organic europium compounds include europium(III) acetate hydrate, europium(III) acetylacetonate hydrate, and europium(III) 2-ethylhexanoate.

- Inorganic europium compounds -
The inorganic europium compound is not particularly limited and can be appropriately selected depending on the purpose. Examples of the inorganic europium compound include europium oxoacid, europium halide, and europium oxide.
Examples of the europium oxoacid include europium nitrate, europium sulfate, and europium carbonate.
Examples of the europium halide include europium fluoride, europium chloride, europium bromide, and europium iodide.
Among these, europium (III) nitrate hexahydrate, europium (III) chloride hexahydrate, and europium (III) sulfate octahydrate are more preferred because of their high solubility in various solvents.

These europium-containing compounds may be synthetic or commercially available.

In the above, manganese (Mn) and europium (Eu) have been described in detail, as well as compounds containing them.
A similar explanation applies to, for example, titanium (Ti), chromium (Cr), copper (Cu), tungsten (W), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and the like.
The same explanation also applies to beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), lutetium (Lu), boron (B), aluminum (Al), gallium (Ga), silicon (Si), germanium (Ge), antimony (Sb), bismuth (Bi), tellurium (Te), etc., which constitute an example of the light-emitting layer.
The same explanation also applies to nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), thallium (Tl), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), tellurium (Te), and the like, which constitute an example of the hole transport layer.
The same explanation also applies to zinc (Zn), cadmium (Cd), gallium (Ga), indium (In), thallium (Tl), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), titanium (Ti), tungsten (W), and the like, which constitute an example of the electron transport layer.

(Display element)
The display element of the present invention comprises at least a light control element and a drive circuit for driving the light control element, and further comprises other members as necessary.

<Light Control Element>
The light control element is an element that controls light output in response to a drive signal, and may include other types of light control elements as long as it includes the inorganic EL element of the present invention. The other types of light control elements are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include organic electroluminescence (EL) elements, electrochromic (EC) elements, liquid crystal elements, electrophoretic elements, and electrowetting elements.

<Drive circuit>
The driving circuit is not particularly limited and can be appropriately selected depending on the purpose, but it preferably includes a field effect transistor such as a thin film transistor (TFT) having an active layer made of a-Si, LTPS, or oxide semiconductor.

<Other materials>
The other members are not particularly limited and can be appropriately selected depending on the purpose.

The display element of the present invention has the inorganic EL element of the present invention, so it emits light efficiently at a low voltage and changes little over time, resulting in a display element with a long life.

(Image display device)
The image display device of the present invention includes at least a plurality of display elements, a plurality of wirings, and a display control device, and further includes other members as necessary.

<Display element>
The display elements are not particularly limited as long as they are the display elements of the present invention arranged in a matrix, and can be appropriately selected depending on the purpose.

<Wiring>
The wiring is not particularly limited as long as it is possible to apply a gate voltage and an image data signal individually to each field effect transistor in the display element, and can be appropriately selected depending on the purpose.

<Display Control Device>
The display control device is not particularly limited as long as it is capable of individually controlling the gate voltage and the signal voltage of each field effect transistor via a plurality of wirings in accordance with image data, and can be appropriately selected according to the purpose.

<Other materials>
The other members are not particularly limited and can be appropriately selected depending on the purpose.

The image display device of the present invention has a long life and operates stably because it has the display element of the present invention.

The image display device of the present invention can be used as a display means in portable information devices such as mobile phones, portable music players, portable video players, electronic books, and PDAs (Personal Digital Assistants), as well as imaging devices such as still cameras and video cameras. It can also be used as a display means for various types of information in mobile systems such as cars, airplanes, trains, and ships. Furthermore, it can be used as a display means for various types of information in measuring devices, analytical devices, medical devices, and advertising media.

(system)
The system of the present invention comprises at least the image display device of the present invention and an image data creation device.
The image data creation device creates image data based on image information to be displayed, and outputs the image data to the image display device.

The system of the present invention is equipped with the image display device of the present invention, making it possible to display image information with high definition.

Next, the image display device of the present invention will be described.
The image display device of the present invention may have the configuration described in, for example, paragraphs [0059] to [0060], FIG. 2, and FIG. 3 of JP-A-2010-074148.

An embodiment of the present invention will now be described with reference to the accompanying drawings.
Fig. 2 is a diagram showing a display in which display elements are arranged in a matrix. As shown in Fig. 2, the display has n scanning lines (X0, X1, X2, X3, ..., Xn-2, Xn-1) arranged at equal intervals along the X-axis direction, m data lines (Y0, Y1, Y2, Y3, ..., Ym-1) arranged at equal intervals along the Y-axis direction, and m current supply lines (Y0i, Y1i, Y2i, Y3i, ..., Ym-1i) arranged at equal intervals along the Y-axis direction. Note that in Figs. 3 and 6, the same symbols (e.g., X1, Y1) have the same meaning.
Therefore, the display element 302 can be specified by the scanning line and the data line.

FIG. 3 is a schematic diagram showing an example of the display element of the present invention.
As shown in Fig. 3 as an example, the display element has an inorganic EL (electroluminescence) element 350 and a drive circuit 320 for causing the inorganic EL element 350 to emit light. That is, the display 310 is a so-called active matrix type inorganic EL display. The display 310 is a 55-inch color display. However, the size is not limited to this.

The drive circuit 320 in FIG. 3 will be described with reference to FIG.
The drive circuit 320 includes two field effect transistors 10 and 20 and a capacitor 30 .

The field effect transistor 10 operates as a switching element. A gate electrode G of the field effect transistor 10 is connected to a predetermined scanning line, a source electrode S of the field effect transistor 10 is connected to a predetermined data line, and a drain electrode D of the field effect transistor 10 is connected to one terminal of the capacitor 30.
The field effect transistor 20 supplies a current to the inorganic EL element 350. A gate electrode G of the field effect transistor 20 is connected to a drain electrode D of the field effect transistor 10. The drain electrode D of the field effect transistor 20 is connected to an anode of the inorganic EL element 350, and a source electrode S of the field effect transistor 20 is connected to a predetermined current supply line.

The capacitor 30 stores the state of the field effect transistor 10, i.e., data. The other terminal of the capacitor 30 is connected to a specified current supply line.

When the field effect transistor 10 is turned on, image data is stored in the capacitor 30 via the signal line Y2, and even after the field effect transistor 10 is turned off, the inorganic EL element 350 is driven by maintaining the field effect transistor 20 in the on state corresponding to the image data.

Figure 4 shows an example of the positional relationship between an inorganic EL element 350 in a display element and a field effect transistor 20 as a drive circuit. Here, the inorganic EL element 350 is arranged next to the field effect transistor 20. The field effect transistor and capacitor (not shown) are also formed on the same substrate.

4, it is also preferable to provide a protective film on the active layer 22. As the material for the protective film, SiO ₂ , SiNx, Al ₂ O ₃ , fluorine-based polymer, etc. can be appropriately used.
5, an inorganic EL element 350 may be disposed on the field effect transistor 20. In this case, the gate electrode 26 _is required to be transparent, and therefore a conductive transparent oxide such as ITO, _In2O3 , _SnO2 , ZnO, ZnO doped with Ga, ZnO doped with Al, or _SnO2 doped with Sb is used for the gate electrode 26. Reference numeral 360 denotes an interlayer insulating film (planarizing film). This insulating film may be made of polyimide, acrylic resin, or the like.

4 and 5, the field effect transistor 20 has a substrate 21, an active layer 22, a source electrode 23, a drain electrode 24, a gate insulating layer 25, and a gate electrode 26. The inorganic EL element 350 has a cathode 312, an anode 314, and an inorganic EL thin film layer 340.

FIG. 6 is a schematic diagram showing another example of the image display device of the present invention.
In FIG. 6, the image display device includes a display element 302 , wiring (scanning lines, data lines, and current supply lines), and a display control device 400 .
The display control device 400 includes an image data processing circuit 402 , a scanning line driving circuit 404 , and a data line driving circuit 406 .
The image data processing circuit 402 determines the brightness of the multiple display elements 302 in the display based on the output signal of the video output circuit.
The scanning line driving circuit 404 applies voltages to the n scanning lines individually in response to instructions from the image data processing circuit 402 .
The data line driving circuit 406 applies voltages to the m data lines individually in response to instructions from the image data processing circuit 402 .

Although the above describes a case where the system of the present invention is a television device, the present invention is not limited to this and may be any device that includes an image display device for displaying images and information. For example, the system may be a computer system in which a computer (including a personal computer) is connected to an image display device.

The system of the present invention has a long life and operates stably because it includes the image display device of the present invention.

Examples of the present invention will be described below, but the present invention is not limited to the following examples in any way.

(Production Example 1-1)
<Preparation of Coating Solution for Forming Light-Emitting Layer>
50 mmol of lanthanum 2-ethylhexanoate and 2 mmol of europium 2-ethylhexanoate were weighed out, and dissolved in 1000 mL of 2-ethylhexanoic acid (octylic acid) by mixing at room temperature to prepare a coating liquid for forming a light-emitting layer (coating liquid 1-1).

(Production Example 2-1)
<Preparation of Coating Solution for Forming Electron Transport Layer>
10 mmol each of zinc acetate dihydrate, gallium nitrate octahydrate, and indium nitrate trihydrate were weighed out, and dissolved in 300 mL each of ethylene glycol monomethyl ether, propylene glycol, and ethanol at room temperature to prepare a coating liquid for forming an electron transport layer (coating liquid 2-1).

(Production Example 3-1)
<Preparation of Coating Solution for Forming Hole Transport Layer>
25 mmol of copper nitrate trihydrate and 25 mmol of magnesium nitrate hexahydrate were weighed out, and dissolved in 400 mL each of ethylene glycol monomethyl ether, propylene glycol, and ethanol at room temperature to prepare a coating liquid for forming a hole transport layer (coating liquid 3-1).

Example 1
<Preparation of Inorganic EL Element>
On a non-alkali glass substrate (with a patterned ITO electrode film of 100 nm) that had been cleaned with UV and ozone, the coating solution 3-1 was printed using a spin coater. After drying on a hot plate at 120° C. for 3 minutes, the substrate was baked in an air atmosphere at 400° C. for 1 hour to obtain a hole transport layer with a thickness of 40 nm.

The substrate was then cleaned with UV ozone, and coating solution 1-1 was printed on it using a spin coater. It was then dried on a hot plate at 120°C for 3 minutes, and then baked in air at 400°C for 1 hour to form a 20 nm-thick light-emitting layer.

The substrate was then cleaned with UV ozone and coated with coating solution 2-1 using a spin coater. It was then dried on a hot plate at 120°C for 3 minutes and then baked in air at 400°C for 1 hour to form an electron transport layer with a thickness of 40 nm.

Finally, aluminum was deposited using a metal mask by vacuum deposition to form a 100 nm thick Al cathode.

<Evaluation>
The luminescence characteristics of the inorganic EL element prepared in Example 1 were measured.
When a DC voltage was applied between the electrodes, the voltage-current characteristics were as shown in Figure 7. Moreover, at 4 V, good red light emission specific to europium was observed.
7, "e" represents a power of 10. That is, "e-6" represents "10 ^-6 ".
The EL spectrum of the inorganic EL element prepared in Example 1 was also measured, and the results are shown in FIG.

(Production Examples 1-2 to 1-6)
<Preparation of Coating Solution for Forming Light-Emitting Layer>
Coating solutions for forming a light-emitting layer (Coating Solutions 1-2 to 1-6) were prepared in the same manner as in Production Example 1-1, except that the raw materials in Production Example 1-1 were changed to the raw materials shown in Table 1.

(Production Examples 2-2 to 2-4)
<Preparation of Coating Solution for Forming Electron Transport Layer>
Coating solutions for forming an electron transport layer (Coating Solutions 2-2 to 2-4) were prepared in the same manner as in Production Example 2-1, except that the raw materials in Production Example 2-1 were changed to the raw materials shown in Table 2.

(Production Examples 3-2 to 3-4)
<Preparation of Coating Solution for Forming Hole Transport Layer>
Except for changing the raw materials in Production Example 3-1 to the raw materials shown in Table 3, coating solutions for forming a hole transport layer (Coating Solutions 3-2 to 3-4) were prepared in the same manner as in Production Example 3-1.

(Production Example 4-1 to Production Example 4-2)
<Preparation of Coating Liquid for Forming Hole Injection Layer and Coating Liquid for Forming Electron Injection Layer>
A coating liquid for forming a hole injection layer (Coating Liquid 4-1) and a coating liquid for forming an electron injection layer (Coating Liquid 4-2) were prepared in the same manner as in Production Example 1-1, except that the raw materials in Production Example 1-1 were changed to the raw materials shown in Table 4.

The raw materials in Tables 1 to 4 are as follows.
<Table 1: Raw Material A>
La(C ₈ H ₁₅ O ₂ ) ₃ : Lanthanum 2-ethylhexanoate Y(NO ₃ ) _{3.6H 2} O : Yttrium nitrate hexahydrate Al(NO ₃ ) 3.9H ₂ O : Aluminum nitrate nonahydrate LaCl _{3.7H 2} O : Lanthanum chloride heptahydrate AlCl _{3.6H 2} O : Aluminum chloride hexahydrate La(NO ₃ ) _{3.6H 2 O} : Lanthanum nitrate hexahydrate <Table 1, Raw material B>
Mg( _NO3 ) _2.6H2O : Magnesium nitrate hexahydrate _CaCl2.2H2O : Calcium chloride dihydrate _SrCl2.6H2O : _Strontium chloride hexahydrate <Table _{1 :} Raw material C>
Eu(C ₈ H ₁₅ O ₂ ) ₃ : Europium 2-ethylhexanoate Tb(NO ₃ ) _{3.6H 2} O : Terbium nitrate hexahydrate EuCl _{3.6H 2} O : Europium chloride hexahydrate W(CO) ₆ : Tungsten carbonyl CrCl _{3.6H 2} O : Chromium chloride hexahydrate Tm(NO ₃ ) _{3.6H 2} O : Thulium nitrate hexahydrate

<Table 2: Raw Material A>
Zn( _{CH3COO ) 2.2H2O} : Zinc acetate _dihydrate Zn( _NO3 ) _2.6H2O : Zinc nitrate hexahydrate _Mg ( _NO3 ) _2.6H2O : Magnesium nitrate hexahydrate La( _NO3 ) _2.6H2O : _Lanthanum nitrate hexahydrate <Table 2: Raw material B>
Ga(NO ₃ ) _{3.8H 2} O: Gallium nitrate octahydrate In(NO ₃ ) _{3.3H 2} O: Indium nitrate trihydrate SnCl _{4.5H 2} O: Tin chloride pentahydrate <Table 2: Raw material C>
Tb( _NO3 ) _3.6H2O : Terbium nitrate _{hexahydrate TmCl3.7H2O :} Thulium chloride heptahydrate

<Table 3: Raw Material A>
Cu(NO ₃ ) ₂ ·3H ₂ O: Copper nitrate trihydrate Cu(C ₁₀ H ₁₉ O ₂ ) ₂ : Copper neodecanoate Tl(C ₈ H ₁₅ O ₂ ): Thallium 2-ethylhexanoate CuCl ₂ ·2H ₂ O: Copper chloride dihydrate <Table 3: Raw material B>
Mg(NO ₃ ) _{2.6H 2} O: Magnesium nitrate hexahydrate Sn(C ₈ H ₁₅ O ₂ ) ₂ : Tin 2-ethylhexanoate Bi(C ₈ H ₁₅ O ₂ ) ₃ : Bismuth tris( ₂ -ethylhexanoate) BaCl 2.2H ₂ O: Barium chloride dihydrate <Table 3: Raw material C>
Cr(C ₈ H ₁₅ O ₂ ) ₃ : Chromium tris( ₂ -ethylhexanoate) TbCl 3.6H ₂ O : Terbium chloride hexahydrate <Table 4: Raw material A>
Cu( _{C10H19O2 ) 2} : Copper _neodecanoate Cd( _NO3 ) _2.2H2O : Cadmium nitrate dihydrate <Table ₄ : Raw material B>
Ca(C ₈ H ₁₅ O ₂ ) ₂ : Calcium 2-ethylhexanoate InCl _{3.4H 2} O : Indium chloride tetrahydrate <Table 4: Raw material C>
_SnCl4.5H2O : _tin chloride pentahydrate

<Tables 1 to 4: Solvent D>
Octylic acid EGME: Ethylene glycol monomethyl ether PGME: Propylene glycol 1-monomethyl ether DMF: N,N-dimethylformamide EGIPE: Ethylene glycol monoisopropyl ether Toluene: Toluene Xylene: Xylene <Tables 1 to 4: Solvent E>
EG: Ethylene glycol PG: Propylene glycol CHB: Cyclohexylbenzene <Tables 1 to 4, Solvent F>
MeOH: Methanol EtOH: Ethanol IPA: Isopropanol _H2O : Water

Example 2
<Preparation of Inorganic EL Element>
An inorganic EL device was produced in the same manner as in Example 1, except that the hole transport layer (HTL), the light emitting layer (EML), and the electron transport layer (ETL) were produced using the coating solutions shown in Table 5.
The inorganic EL device thus produced was evaluated in the same manner as in Example 1.
In the inorganic EL element of Example 2, the oxide film serving as the hole transport layer is a p-type oxide semiconductor doped with a light emitting center, and also serves as the light emitting layer.

(Examples 3 and 4)
<Preparation of Inorganic EL Element>
An inorganic EL element was produced in the same manner as in Example 1, except that the anode and cathode in Example 1 were as shown in Table 5, and further, the hole transport layer (HTL), the light emitting layer (EML), and the electron transport layer (ETL) were produced using the coating liquids shown in Table 5.
The inorganic EL device thus produced was evaluated in the same manner as in Example 1.
In the inorganic EL element of Example 3, the oxide film serving as the electron transport layer is an n-type oxide semiconductor doped with a light-emitting center, and serves also as the light-emitting layer.

In Table 5, "ITO" stands for "tin-doped indium oxide" and "ASC" stands for "aluminum (Al)-silicon (Si)-copper (Cu) alloy."

FIG. 9 shows a schematic diagram of an energy diagram of the inorganic EL elements prepared in Examples 1 and 4.
FIG. 10 shows a schematic diagram of an energy diagram of the inorganic EL element prepared in Example 2.
FIG. 11 shows a schematic diagram of an energy diagram of the inorganic EL element prepared in Example 3.

Example 5
<Preparation of Inorganic EL Element>
On a non-alkali glass substrate (with a patterned ITO electrode film of 100 nm) that had been subjected to UV ozone cleaning, the coating solution 4-1 was printed using a spin coater. After drying on a hot plate at 120° C. for 3 minutes, the substrate was baked in an air atmosphere at 400° C. for 1 hour to obtain a hole injection layer (HIL) with a thickness of 30 nm.

The substrate was then cleaned with UV ozone, and coating solution 3-3 was printed on it using a spin coater. It was then dried on a hot plate at 120°C for 3 minutes, and then baked in air at 400°C for 1 hour to form a 30 nm-thick light-emitting layer that also functions as a hole transport layer (hole transport layer that also functions as a light-emitting layer).

The substrate was then cleaned with UV ozone and coated with coating solution 2-2 using a spin coater. It was then dried on a hot plate at 120°C for 3 minutes and then baked in air at 400°C for 1 hour to form an electron transport layer with a thickness of 60 nm.

Finally, aluminum was deposited using a metal mask by vacuum deposition to form a 100 nm thick Al cathode.

Example 6
<Preparation of Inorganic EL Element>
On a non-alkali glass substrate (with a patterned ITO electrode film of 100 nm) that had been subjected to UV ozone cleaning, the coating solution 3-2 was printed using a spin coater. After drying on a hot plate at 120° C. for 3 minutes, the substrate was baked in an air atmosphere at 400° C. for 1 hour to obtain a hole transport layer with a thickness of 60 nm.

The substrate was then cleaned with UV ozone, and coating solution 2-3 was printed on it using a spin coater. It was then dried on a hot plate at 120°C for 3 minutes, and then baked in air at 400°C for 1 hour to form a 30-nm-thick light-emitting layer that also functions as an electron transport layer (electron transport layer that also functions as a light-emitting layer).

The substrate was then cleaned with UV ozone and coated with coating solution 4-2 using a spin coater. It was then dried on a hot plate at 120°C for 3 minutes, and then baked in air at 400°C for 1 hour to form an electron injection layer (EIL) with a thickness of 30 nm.

Finally, aluminum was deposited using a metal mask by vacuum deposition to form a 100 nm thick Al cathode.

The layer structures of the inorganic EL elements of Examples 5 and 6 are shown in Table 6.

FIG. 12 is a schematic diagram showing an energy diagram of the inorganic EL element prepared in Example 5.
FIG. 13 is a schematic diagram showing an energy diagram of the inorganic EL element prepared in Example 6.

The inorganic EL elements of Examples 2 to 6 also exhibited good voltage-current characteristics and emission spectra, similar to the inorganic EL element of Example 1. In other words, they were direct-current-driven inorganic EL elements that emitted light at a sufficiently low voltage and with high efficiency.

As described above, the inorganic EL element of the present invention can provide a stable light-emitting element with high efficiency at a low voltage. Furthermore, the image display device of the present invention is suitable for displaying high-quality images on a large screen. Furthermore, the system of the present invention can display image information with high definition, and can be suitably used in television devices, computer systems, smartphones, etc.

For example, aspects of the present invention are as follows.
<1> An inorganic EL element including an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode laminated together,
the hole transport layer is an oxide film,
the light-emitting layer is an oxide film,
The inorganic EL element is characterized in that the electron transport layer is an oxide film.
<2> The inorganic EL element according to <1>, wherein the oxide film serving as the hole transport layer is a p-type oxide semiconductor.
<3> The inorganic EL element according to any one of <1> to <2>, wherein the oxide film serving as the electron transport layer is an n-type oxide semiconductor.
<4> The inorganic EL element according to any one of <1> to <3>, wherein the oxide film serving as the light-emitting layer is made of an oxide doped with a light-emitting center.
<5> The inorganic EL element according to any one of <1> to <4>, wherein the oxide film serving as the hole transport layer is a p-type oxide semiconductor doped with a light-emitting center and serves as the light-emitting layer.
<6> The inorganic EL element according to any one of <1> to <5>, wherein the oxide film serving as the electron transport layer is an n-type oxide semiconductor doped with a light-emitting center and serves as the light-emitting layer.
<7> The inorganic EL element according to any one of <4> to <6>, wherein the luminescent center is a transition metal ion or a rare earth ion.
<8> The inorganic EL element according to any one of <4> to <7>, wherein the luminescent center contains at least one of titanium (Ti), chromium (Cr), manganese (Mn), copper (Cu), tungsten (W), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb).
<9> The inorganic EL element according to any one of <4> to <6>, wherein in the oxide film serving as the light-emitting layer, an oxide having a band gap energy equal to or greater than an excitation energy of the light-emitting center serves as a host for the light-emitting center.
<10> The inorganic EL element according to any one of <4> to <6>, wherein in the oxide film serving as the light-emitting layer, an oxide having a band gap energy equal to or higher than the light-emitting energy of the light-emitting center serves as a host for the light-emitting center.
<11> The inorganic EL element according to any one of <1> to <10>, wherein the oxide film serving as the light-emitting layer is an oxide containing at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), lutetium (Lu), boron (B), aluminum (Al), gallium (Ga), silicon (Si), germanium (Ge), antimony (Sb), bismuth (Bi), and tellurium (Te).
<12> The inorganic EL element according to any one of <1> to <11>, wherein the oxide film serving as the hole transport layer is a p-type oxide semiconductor containing at least one of nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), thallium (Tl), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), and tellurium (Te).
<13> The inorganic EL element according to any one of <1> to <12>, wherein the oxide film serving as the electron transport layer is an n-type oxide semiconductor containing at least one of zinc (Zn), cadmium (Cd), gallium (Ga), indium (In), thallium (Tl), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), titanium (Ti), and tungsten (W).
<14> The inorganic EL element according to <13>, wherein the oxide film serving as the electron transport layer is an n-type oxide semiconductor further containing at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanoid (Ln), boron (B), aluminum (Al), silicon (Si), antimony (Sb), and tellurium (Te).
<15> The oxide film serving as the light-emitting layer is an amorphous oxide film,
the oxide film serving as the hole transport layer is an amorphous oxide film,
The inorganic EL element according to <1>, wherein the oxide film serving as the electron transport layer is an amorphous oxide film.
<16> The inorganic EL element according to <1>, which is a DC drive type.
<17> A light control element having the inorganic EL element according to any one of <1> to <16>, wherein the light output is controlled in response to a drive signal;
and a drive circuit for driving the light control element.
<18> An image display device that displays an image according to image data,
A plurality of display elements according to the above item <17>, which are arranged in a matrix, and the drive circuit has a field effect transistor;
a plurality of wirings for individually applying a gate voltage and a signal voltage to each of the field effect transistors in the plurality of display elements;
The image display device further comprises a display control device that controls the gate voltage and the signal voltage of each of the field effect transistors individually via the plurality of wirings in accordance with the image data.
<19> The image display device according to <18>,
and an image data creation device which creates image data based on image information to be displayed and outputs the image data to the image display device.

REFERENCE SIGNS LIST 10, 20 Field effect transistor 21 Substrate 22 Active layer 23 Source electrode 24 Drain electrode 25 Gate insulating layer 26 Gate electrode 302 Display element 310 Display 320 Pixel circuit 340 Inorganic EL thin film layer 342 Electron transport layer 344 Light emitting layer 346 Hole transport layer 350 Inorganic EL element 400 Display control device

JP 2014-35827 A

J. C. Ronford-Haret, J. Kossanyi, "Electro- and photoluminescence of the Tm3+ ion in Tm3+- and Li+-doped ZnO ceramics. Influence of the sintering temperature", Chem. Phys. 241 (1999) 339-349

Claims (18)

An inorganic EL element comprising an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode,
the hole transport layer is an oxide film that is a p-type oxide semiconductor,
the light-emitting layer is an oxide film doped with a light-emitting center,
2. An inorganic EL element, wherein the electron transport layer is an oxide film that is an n-type oxide semiconductor. The inorganic EL element according to claim 1, wherein the oxide film serving as the hole transport layer is a p-type oxide semiconductor doped with a light-emitting center and also serves as the light-emitting layer. 2. The inorganic EL element according to claim 1 , wherein the oxide film serving as the electron transport layer is an n-type oxide semiconductor doped with a light-emitting center, and also serves as the light-emitting layer. The inorganic EL element according to any one of claims 1 to 3, wherein the luminescent center is a transition metal ion or a rare earth ion. The inorganic EL element according to claim 4, wherein the transition metal ions include at least one of titanium (Ti), chromium (Cr), manganese (Mn), copper (Cu), and tungsten (W), or the rare earth ions include at least one of cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb). The inorganic EL element according to any one of claims 1 to 3, wherein the luminescent center is a transition metal ion. The inorganic EL element according to claim 6, wherein the transition metal ions include at least one of titanium (Ti), chromium (Cr), manganese (Mn), copper (Cu), and tungsten (W). The inorganic EL element according to any one of claims 1 to 7, wherein in the oxide film that is the light-emitting layer, an oxide having a band gap energy equal to or greater than the excitation energy of the light-emitting center serves as a host for the light-emitting center. The inorganic EL element according to any one of claims 1 to 8, wherein in the oxide film that is the light-emitting layer, an oxide having a band gap energy equal to or greater than the light-emitting energy of the light-emitting center serves as a host for the light-emitting center. The inorganic EL element according to any one of claims 1 to 9, wherein the oxide film, which is the light-emitting layer, is an oxide containing at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), lutetium (Lu), boron (B), aluminum (Al), gallium (Ga), silicon (Si), germanium (Ge), antimony (Sb), bismuth (Bi), and tellurium (Te). An inorganic EL element according to any one of claims 1 to 10, wherein the oxide film that is the hole transport layer is a p-type oxide semiconductor containing at least one of nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), thallium (Tl), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), and tellurium (Te). The inorganic EL element according to any one of claims 1 to 11, wherein the oxide film that is the electron transport layer is an n-type oxide semiconductor containing at least one of zinc (Zn), cadmium (Cd), gallium (Ga), indium (In), thallium (Tl), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), titanium (Ti), and tungsten (W). The inorganic EL element according to claim 12, wherein the oxide film, which is the electron transport layer, is an n-type oxide semiconductor further containing at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanoids (Ln), boron (B), aluminum (Al), silicon (Si), antimony (Sb), and tellurium (Te). the oxide film serving as the light-emitting layer is an amorphous oxide film,
the oxide film serving as the hole transport layer is an amorphous oxide film,
2. The inorganic EL device according to claim 1, wherein the oxide film serving as the electron transport layer is an amorphous oxide film. The inorganic EL element according to claim 1, which is a direct current driven type. A light control element having the inorganic EL element according to any one of claims 1 to 15, the light output of which is controlled in response to a drive signal;
A display element comprising: a drive circuit for driving the light control element. An image display device that displays an image according to image data,
17. A display element according to claim 16, wherein the driving circuit includes a field effect transistor, and the display element is arranged in a matrix.
a plurality of wirings for individually applying a gate voltage and a signal voltage to each of the field effect transistors in the plurality of display elements;
and a display control device that controls the gate voltage and the signal voltage of each of the field effect transistors individually via the plurality of wirings in accordance with the image data. The image display device according to claim 17 ;
and an image data creation device which creates image data based on image information to be displayed and outputs the image data to the image display device.

Images