JP2009298902A - Inorganic phosphor - Google Patents

Abstract

The present invention is applicable to a light emitting device having a new light emission center and can be driven by either direct current or alternating current, has sufficient luminous efficiency, has sufficient luminance for lighting use, etc., and particularly has high luminance in blue. Provided are an inorganic phosphor that emits light, a light emitting element using the inorganic phosphor, and a direct current thin film inorganic EL element.
An inorganic phosphor according to the present invention is an inorganic phosphor having at least one selected from a group 2-16 compound and a group 12-16 compound, or a mixed crystal thereof as a base material. And Mn, and at least one of the metal elements belonging to the second transition series of Groups 6 to 11 of the periodic table and the metal elements belonging to the third transition series, and an element constituting the base material It contains at least 1 sort (s) among group 16 elements other than these, and is used suitably for a light emitting element, especially a direct current thin film type inorganic EL element.
[Selection figure] None

Description

  The present invention relates to an inorganic phosphor (hereinafter also referred to as an inorganic phosphor material) useful for an AC dispersion type inorganic EL element, an AC thin film type inorganic EL element, a DC thin film type inorganic EL element, and the like.

  A phosphor is a material that emits light when given energy such as light, electricity, pressure, heat, and electron beam from the outside, and has been known for a long time. Among them, phosphors made of inorganic materials have been used for cathode ray tubes, fluorescent lamps, electroluminescence (EL) elements, and the like because of their light emission characteristics and stability. In recent years, as a color conversion material for LEDs, active research has been made for low-energy electron beam excitation such as PDP.

  Electroluminescence (EL) elements using inorganic phosphors are roughly classified into an AC driving type and a DC driving type depending on the driving method. There are two types of AC drive type: an AC dispersion type EL element in which phosphor particles are dispersed in a high dielectric binder, and an AC thin film type EL element in which a phosphor thin film is sandwiched between dielectric layers. Among the molds, there is a direct current thin film type EL element that is driven by a low voltage direct current with a phosphor thin film sandwiched between a transparent electrode and a metal electrode.

Next, a direct-current drive type inorganic EL element will be taken up and described.
Research on the direct-current drive type inorganic EL element was actively made in the 1970s and 1980s (Non-patent Document 1). This is an element formed by depositing ZnSe: Mn on a GaAs substrate by MBE and sandwiching it with an Au electrode. By applying about 4 V, electrons are injected from the electrode by the tunnel effect, and Mn which is the emission center is excited to emit light. However, since this device has low luminous efficiency (˜0.05 lm / W) and low reproducibility, it has not been put into practical use or studied academically since then.

  In recent years, a new direct-current drive type inorganic EL element has been reported (Patent Document 1). The light-emitting material is a ZnS-based material containing a conventionally known light emission center such as Cu or Mn, and has a configuration in which this is sandwiched between an ITO electrode as a transparent electrode and an Ag electrode as a back electrode. Although the light emission mechanism is not described, it is considered that a DA pair pair is formed with Cl contained together with Cu, and recombination of electrons and holes injected therein, that is, light emission.

  Compared with an organic EL element that emits light by a similar driving method, the light-emitting elements are all made of an inorganic material, so that they have high durability and can be used in various fields such as lighting and displays. Furthermore, LEDs that are driven in a similar manner are similar in that they are all composed of an inorganic material. However, since LEDs have a very small emission area, that is, point emission, the luminance per unit area is high, but the absolute light quantity Since there are few (light beams), a use is limited. On the other hand, an inorganic EL element is naturally surface emitting, which is advantageous in that a large amount of light can be obtained.

Patent Document 2 includes copper as an activator, at least one selected from chlorine and bromine as a coactivator, and a second transition series or a third group from Group 6 to Group 10. An inorganic phosphor made of zinc sulfide particles containing at least one metal element belonging to the transition series, Patent Document 3 uses zinc sulfide as a base, copper as an activator, chlorine as a first coactivator, Each of the phosphor materials containing at least one bromine and gold as the second coactivator is disclosed.
Patent Document 4 uses rare earth sulfide as a base material, generates a mixture of the base material and an activator containing Pr, Mn, Au and activates the base material, and heats the generated mixture. Thus, a method for manufacturing a light emitter that activates the base material is disclosed.

International Publication No. 07/043676 Pamphlet JP 2006-233147 A JP-A-4-270780 JP 2006-199794 A Journal of Applied Physics, 52 (9), 5797, 1981.

However, the direct current drive inorganic EL element of Patent Document 1 has low luminous efficiency and is not practical. Further, since the phosphors described in Patent Document 2 and Patent Document 3 contain copper as an activator, they are of the DA (donor acceptor) pair emission type, but are in a particle dispersion type and an AC thin film type. However, there is a problem that the application is limited. Further, the phosphor described in Patent Document 4 is considered to be a local emission type of Mn and / or Pr using a rare earth sulfide as a base material. Although it can be applied to a light emitting element that can be driven by any alternating current, there is a problem that sufficient light emission efficiency cannot be obtained.
In addition, none of the phosphors of Patent Documents 1 to 4 have sufficient luminance for lighting applications, and in particular, none of blue phosphors emit light with high luminance.

From the above, it can be applied to a light emitting device that has a new light emission center and can be driven by either direct current or alternating current, has sufficient light emission efficiency, has sufficient luminance for lighting use, etc. Development of a phosphor that emits light with high brightness has been desired.
Therefore, the present invention can be applied to a light emitting element having a new light emission center and can be driven by either direct current or alternating current, has sufficient light emission efficiency, has sufficient luminance for lighting use, etc. An object of the present invention is to provide an inorganic phosphor that emits light with high brightness, a light emitting element using the inorganic phosphor, and a direct current thin film type inorganic EL element.

  As a result of intensive studies, the inventors belong to the second transition series from Group 6 to Group 11 of the periodic table without adding conventionally known luminescent center metals such as Cu, Mn, and rare earths. By adding a metal element or a metal element belonging to the third transition series and an element other than the element constituting the base material belonging to the group 16 of the periodic table to the group 2-16 compound, by ultraviolet excitation. The present inventors have found a novel phosphor exhibiting photoluminescence and electroluminescence by direct current drive.

That is, the present invention is achieved by the following requirements.
(1) An inorganic phosphor having as a base material at least one selected from Group 2-16 compounds and Group 12-16 compounds, or a mixed crystal thereof, which does not contain Cu and Mn, and has a periodic rule At least one of the metal elements belonging to the second transition series of Group 6 to Group 11 of the table and the metal elements belonging to the third transition series, and at least of the Group 16 elements other than the elements constituting the base material 1 type of inorganic fluorescent substance characterized by the above-mentioned.
(2) The element belonging to the second transition series of Group 6 to Group 11 or the element belonging to the third transition series is at least one of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au. (1) The inorganic phosphor as described above.
(3) The inorganic phosphor according to (1), wherein the base material is composed of zinc sulfide, zinc selenide or a mixed crystal thereof.
(4) The inorganic phosphor according to (3) above, wherein the group 16 element other than the elements constituting the host material is oxygen.
(5) The inorganic phosphor according to (1) above, which contains at least one element selected from elements belonging to Groups 13 and 15 of the periodic table.
(6) A light emitting device having the inorganic phosphor according to any one of (1) to (5).
(7) A direct-current thin film inorganic EL element having the inorganic phosphor according to any one of (1) to (5).
(8) The direct current thin film inorganic EL element according to (7), which has a p-type semiconductor layer.

  The inorganic phosphor of the present invention not only exhibits high-intensity blue light emission due to a new emission center that has never been seen before, but is also useful as a phosphor for inorganic electroluminescent elements, and has excellent emission luminance and long life. It is.

The present invention will be described in detail below.
The inorganic phosphor of the present invention has at least one selected from Group 2-16 compounds or Group 12-16 compounds, or a mixed crystal thereof as a base material, and further includes Groups 6 to 11 of the periodic table. And at least one of a metal element belonging to the second transition series and a metal element belonging to the third transition series, and at least one of group 16 elements other than the elements constituting the base material, To do.

The Group 2-16 compound used as the base material of the inorganic phosphor of the present invention is at least one element belonging to Group 2 of the periodic table and at least 1 belonging to Group 16 of the periodic table. A compound composed of a seed element, a group 12-16 compound means a compound composed of at least one element belonging to group 12 of the periodic table and at least one element belonging to group 16 of the periodic table. This is a notation / expression commonly used by those having ordinary knowledge in the technical field to which the present invention belongs (one skilled in the art).
Examples of the base material include at least one selected from Group 2-16 compounds such as ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, CaS, SrS, BaS, and the like, or a mixture thereof. Crystals are used. ZnS, ZnSe, ZnSSe, SrS, CaS, SrSe, SrSSe are preferable, and ZnS, ZnSe, ZnSSe are more preferable.
The base material refers to all materials constituting 1 mol% or more of the compounds constituting the phosphor material. For example, when the ratio of ZnS to ZnSe is 99 mol% and 1 mol%, the ZnSSe mixed crystal is regarded as a base material, and when 99.1 mol% and 0.9 mol%, ZnS simple substance is considered as the base material.

  Examples of metal elements belonging to the second transition series of Groups 6 to 11 of the periodic table and metal elements belonging to the third transition series used in the inorganic phosphor of the present invention include Mo, Tc, Ru, There are Rh, Pd, Ag, W, Re, Os, Ir, Pt, and Au. Among them, Ru, Pd, Ag, Os, Ir, Pt, and Au are preferable, and Os, Ir, Pt, and Au are more preferable. . These metals may be contained alone or in plural.

Any method may be used for adding a metal element belonging to the second transition series of Group 6 to Group 11 of the above periodic table and a metal element belonging to the third transition series to the base material, that is, a doping method. Although it is not limited, for example, it may be mixed in the form of a metal salt at the time of particle formation by firing, or may be mixed in the form of a compound crystal if it can be melted, sublimated or reacted under firing conditions. good. These metals are preferably removed by etching, washing or the like on the crystal surface other than the portion taken into the crystal of the base material and on the crystal surface. The metal salt may be any compound such as oxide, sulfide, sulfate, oxide, halide, nitrate, nitride, etc. Among them, oxide, sulfide, and halide are preferably used. Each may be used alone, but a plurality of types of metal salts may be used. The dope amount is preferably 1 × 10 ⁻⁷ mol or more and less than 1 × 10 ⁻² mol, more preferably 1 × 10 ⁻⁵ mol or more and less than 5 × 10 ⁻³ mol, relative to 1 mol of the base material.

  Examples of Group 16 elements other than those constituting the host material used in the inorganic phosphor of the present invention include O, Se, and Te when the host material is a sulfur compound, and in the case of selenide In the case of a mixed crystal compound of sulfur and selenium, they are O and Te. These elements may be contained singly or plurally. In particular, when the base compound is a sulfur compound, sulfur defects in the crystal structure are likely to be generated. Therefore, by adding a homovalent -2 element, the generation of crystal defects that cause a reduction in efficiency with respect to light emission is suppressed. , Luminous efficiency can be increased. In ZnS containing a metal element belonging to the second transition series of Group 6 to Group 11, such as Ir, the distortion of the local crystal structure around Ir cannot be filled with S alone, and Se having a large ionic radius can be obtained. Since the lattice position can be occupied by O having a small ion radius, crystal defects can be reduced, and as a result, a remarkable increase in luminous efficiency can be obtained.

The method of incorporating the group 16 element other than the elements constituting the matrix material into the matrix material, that is, the doping method, is a metal belonging to the second transition series of groups 6 to 11 of the periodic table. The method is not limited to any method, as is the case with the inclusion of the element and the metal element belonging to the third transition series into the base material. For example, the above-mentioned second transition series of Group 6 to Group 11 are not limited. As the metal salt used for inclusion in the base material of the metal element belonging to the group 3 and the metal element belonging to the third transition series, an oxide, sulfide, selenide, telluride is used, or the base material oxide, sulfide, selenium By using a compound or telluride, a group 16 element other than the elements constituting the base material can be doped. Further, if it can be melted, sublimated or reacted under firing conditions, it may be mixed in the form of compound crystals. Further, oxygen, sulfur, and selenium may be doped by controlling the partial pressure as a firing atmosphere. These elements are preferably removed by etching, washing, or the like, on the crystal surface other than the portion taken into the crystal of the host material and on the crystal surface. The doping amount is preferably 1 × 10 ⁻⁷ mol or more and less than 1 × 10 ⁻² mol, more preferably 1 × 10 ⁻⁵ mol or more and less than 5 × 10 ⁻³ mol, relative to 1 mol of the base material.

Further, in order to improve the performance as a phosphor, it is effective to contain at least one element selected from elements belonging to Group 13 and elements belonging to Group 15 of the periodic table.
Preferably, it contains at least one element selected from elements belonging to Group 13, and at least one element selected from elements belonging to Group 15, and more preferably Al as an element belonging to Group 13 And at least one selected from Ga, In and Tl, and at least one selected from N, P, Sb, As and Bi as an element belonging to Group 15, and particularly preferably in Group 13 Ga is contained as an element belonging, and at least one selected from N, P and Sb is contained as an element belonging to Group 15.
In addition, when these elements are contained in the phosphor, it is preferable to add a compound composed of an element belonging to Group 13 and an element belonging to Group 15 (Group 13-15 compound).
The content of at least one element selected from the elements belonging to Group 13 and the elements belonging to Group 15 of these periodic tables is not particularly limited, but is 1 × 10 ⁻⁷ mol with respect to 1 mol of the base material. Above, less than 1 × 10 ⁻² is preferable.

In general, an AC driven inorganic EL element is driven at a voltage of 50 to 300 V and a frequency of 50 to 5000 Hz, but a DC driven inorganic EL element can be driven at a low voltage of 0.1 to 20 V. The inorganic phosphor of the present invention is useful for an AC drive type element such as a dispersion type inorganic EL element and a thin film type inorganic EL element, and also for a DC drive type inorganic EL element. is there.
Next, the direct current drive type inorganic EL element will be described in detail.
The direct current drive type inorganic EL element includes at least a transparent electrode (also referred to as a transparent conductive film), a phosphor layer (also referred to as a light emitting layer), and a back electrode. If the thickness of the light emitting layer becomes too thick, the voltage between both electrodes rises in order to obtain the electric field strength necessary for light emission. Therefore, in order to realize low voltage driving, it is preferably 50 μm or less, more preferably 30 μm or less. . If the thickness is too thin, the electrodes on both sides of the phosphor layer are easily short-circuited. Therefore, the thickness is preferably 50 nm or more, more preferably 100 nm or more in order to avoid a short circuit.
Further, the emission intensity can be increased by providing a p-type semiconductor layer between the transparent electrode and the phosphor layer or between the phosphor layer and the back electrode. The material constituting the p-type semiconductor layer is a sulfide material using holes as carriers. For example, copper sulfide (Cu ₂ S) or a mixture of zinc sulfide (ZnS) and copper sulfide can be used. Also, ZnS doped with acceptor elements such as lithium (Li), potassium (K), rubidium (Rb), cesium (Cs), aluminum (Al), gallium (Ga), or indium (In) Can also be used. Further, ZnS excessively doped with Cu or Ag can also be used.

  As a film forming method, a physical heating method such as resistance heating evaporation, electron beam evaporation, sputtering, ion plating, CVD (Chemical Vapor Deposition), or the like is generally used. Since the phosphor used in the present invention is stable and has a high melting point even at a high temperature, an electron beam vapor deposition method suitable for depositing a high melting point material or a sputtering method is suitably used when the deposition source can be targeted. . Furthermore, in the case of electron beam evaporation, if the vapor pressure of the metal contained in the phosphor is significantly different from the vapor pressure of the host material, an evaporation method using multiple evaporation sources as individual evaporation sources is also useful. is there. In order to enhance crystallinity, an MBE (Molecular Beam Epitaxy) method considering lattice matching with the substrate is also suitable.

The surface resistivity of the transparent conductive film preferably used in the present invention is preferably 10Ω / □ or less, more preferably 0.01Ω / □ to 10Ω / □. In particular, 0.01Ω / □ to 1Ω / □ is preferable.
The surface low efficiency of the transparent conductive film can be measured according to the method described in JIS K6911.
The transparent conductive film is preferably formed on a glass or plastic substrate and contains tin oxide.

That is, as glass, general glass such as alkali-free glass or soda lime glass is used, but it is preferable to use glass having high heat resistance and high flatness. As the plastic substrate, a transparent film such as polyethylene terephthalate, polyethylene naphthalate, or triacetyl cellulose base is preferably used. Using these as a substrate, a transparent conductive material such as indium tin oxide (ITO), tin oxide, or zinc oxide can be deposited and formed by a method such as vapor deposition, coating, or printing.
In this case, it is preferable that the surface of the transparent conductive film is mainly composed of tin oxide for the purpose of increasing durability.

The preferable adhesion amount of the transparent conductive material constituting the transparent conductive film is 100% by mass to 1% by mass, more preferably 70% by mass to 5% by mass, and still more preferably 40% by mass with respect to the transparent conductive film. -10 mass%.
The method for preparing the transparent conductive film may be a gas phase method such as sputtering or vacuum deposition. Paste-like ITO or tin oxide may be formed by coating or screen printing, or the whole film may be heated or heated with a laser to form a film.
In the EL device of the present invention, any transparent electrode material that is generally used is used for the transparent conductive film. For example, tin-doped tin oxide, antimony-doped tin oxide, zinc-doped tin oxide, fluorine-doped tin oxide, zinc oxide and other oxides, a multilayer structure in which a silver thin film is sandwiched between high refractive index layers, polyaniline, polypyrrole and other conjugated systems Examples include molecules.

  In order to further reduce the resistance, it is preferable to improve the conductivity by arranging, for example, a comb-shaped or grid-shaped mesh or stripe-shaped fine metal wire. Copper, silver, aluminum, nickel, or the like is preferably used as the metal or alloy thin wire. The thickness of the fine metal wire is arbitrary, but is preferably between about 0.5 μm and 20 μm. The fine metal wires are preferably arranged at a pitch of 50 μm to 400 μm, and a pitch of 100 μm to 300 μm is particularly preferable. Although the light transmittance is reduced by arranging the fine metal wires, it is important that this reduction is as small as possible, and it is preferable to secure a transmittance of 80% or more and less than 100%.

For the fine metal wires, the mesh may be bonded to the transparent conductive film, or a metal oxide or the like may be applied and vapor-deposited on the fine metal wires previously formed on the film by mask vapor deposition or etching. Moreover, you may form said metal fine wire on the metal oxide thin film formed previously.
Although this is a different method, a transparent conductive film suitable for the present invention can be obtained by laminating a metal thin film having an average thickness of 100 nm or less with a metal oxide instead of a thin metal wire. The metal used for the metal thin film is preferably a metal having high corrosion resistance such as Au, In, Sn, Cu, and Ni and excellent in spreadability, but is not particularly limited thereto.
These multilayer films preferably realize high light transmittance, specifically, preferably have a light transmittance of 70% or more, and particularly preferably have a light transmittance of 80% or more. The wavelength that defines the light transmittance is 550 nm.
Regarding the light transmittance, monochromatic light of 550 nm can be taken out using an interference filter, and can be measured using an integral light quantity measurement or a spectrum measuring apparatus using a commonly used white light source.

(Back electrode)
For the back electrode on the side from which light is not extracted, any conductive material can be used. It is selected from gold, silver, platinum, copper, iron, aluminum and other metals, graphite, etc., depending on the form of the device to be produced, the temperature of the production process, etc., among which it is important that the thermal conductivity is high. 2.0 W / cm · deg or more is preferable.
It is also preferable to use a metal sheet or a metal mesh in order to ensure high heat dissipation and electrical conductivity in the periphery of the EL element.

The inorganic phosphor usable in the present invention can be formed by a firing method (solid phase method) widely used in the industry. For example, in the case of zinc sulfide, a fine particle powder (called raw powder) of 10 nm to 50 nm is prepared by a liquid phase method, this is used as a primary particle, an impurity called an activator is mixed therein, and a crucible together with a flux. First baking is performed at a high temperature of 900 ° C. to 1300 ° C. for 30 minutes to 10 hours to obtain particles.
The intermediate phosphor powder obtained by the first firing is repeatedly washed with ion exchange water to remove alkali metal or alkaline earth metal, excess activator and coactivator.
Next, second baking is applied to the obtained intermediate phosphor powder. In the second baking, heating (annealing) is performed at a temperature lower than that of the first baking at 500 to 800 ° C. and for a short time of 30 minutes to 3 hours.
Inorganic phosphors can be obtained by the above-described manufacturing method, but when used for a direct current drive type inorganic EL element, the phosphor obtained by the above-described manufacturing method is pressure-molded and an EL element is obtained by physical vapor deposition such as electron beam vapor deposition. be able to.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.
[Example 1]
With respect to 1 mol of ZnS, IrO ₂ (Ir source, O source), ZnO (O source), IrCl ₃ (Ir source), Ir ₂ S ₃ (Ir source), ZnSe (Se source) are in the ratios shown in Table 1 below. Weigh. They are put in a mortar and mixed for 20 minutes or more, and then baked in vacuum at 1100 ° C. for 3 hours. The fired powder was pulverized in a mortar, washed with water, and dried to obtain phosphors A to G.
Table 2 below summarizes the relative emission intensity when the photoluminescence emission wavelength and the emission intensity of the phosphor D are set to 100 when the obtained phosphor is irradiated with light having a wavelength of 330 nm as excitation light.

The phosphors A to G all showed blue light emission with an emission peak around 450 nm. Phosphor D is simply IrCl ₃ added as an Ir source, and Ir is just Ir ₂ S ₃ added as Ir source, and does not contain any Group 16 elements other than the base material. On the other hand, the phosphor A is added with IrO ₂ as an O source which is a Group 16 element other than the Ir source and the base material. The emission intensity was the highest. Phosphor B is the same as phosphor A, but only the amount of IrO ₂ added is halved. Still, it showed relatively high emission intensity. In the phosphor C, IrCl ₃ was added as an Ir source and ZnO was added as an O source. However, the phosphor C showed slightly higher emission intensity as compared with the phosphor B in which the addition amounts of Ir and O were the same. Furthermore, phosphor F added IrCl ₃ as an Ir source and ZnSe as a Se source which is a group 16 element other than the base material, and showed strong emission intensity similar to phosphors B and C. In the phosphor G, IrCl ₃ was added as an Ir source, and ZnO and ZnSe were added as an O source and a Se source which are Group 16 elements other than the base material, respectively, but strong emission similar to the phosphors B, C, and F was made. Intensity was shown. By adding Group 16 elements other than the base material such as O and Se, it is considered that they filled in the sulfur defects in ZnS as the base material, and highly efficient light emission was obtained.

[Example 2]
Further, phosphor H is synthesized in the same manner as phosphor A except that GaAs powder is synthesized by adding 2 × 10 ⁻⁴ mol to 1 mol of Zn. The phosphor H was evaluated in the same manner as in Example 1. As a result, the emission wavelength was 443 nm, the emission intensity was 280, and the highest emission intensity was obtained for the other phosphor samples.

Example 3
Using the inorganic phosphors of the phosphors A to H of Examples 1 and 2, a direct current drive type inorganic EL element was produced. An outline of the structure of the direct current drive type inorganic EL element is shown in FIG.
The phosphors A to H obtained in Example 1 are deposited on the ITO layer by the electron beam evaporation method on the glass substrate 1 on which the ITO layer having a thickness of 200 nm is formed as the first electrode 2. Thus, the light emitting layer 3 was formed. The film thickness of the light emitting layer 3 was 2 μm, the degree of vacuum in the vapor deposition chamber at that time was set to 1 × 10 ⁻⁶ Torr, and the substrate 1 temperature was set to 200 ° C. Further, in order to improve the crystallinity, the deposited light emitting layer 3 is heat-treated at 600 ° C. for 1 hour in the same chamber, and then the second electrode 4 is formed on the light emitting layer 3 by resistance heating vapor deposition. Al was vapor-deposited to obtain a light emitting device.
When a direct current was passed through the obtained light emitting device using Al as a positive electrode and ITO as a negative electrode, light emission was confirmed.

Example 4
Using the inorganic phosphors of the phosphors A to H of Examples 1 and 2, a direct current drive type inorganic EL element was produced. An outline of the structure of the direct current drive type inorganic EL element is shown in FIG.
With respect to the glass substrate 1 on which the ITO layer having a thickness of 200 nm is formed as the first electrode 2, a Cu ₂ S layer as the p-type semiconductor layer 5 is further formed on the ITO layer, and the Cu ₂ S layer is further formed thereon as in Examples 1 and 2. The obtained phosphors A to H were all deposited continuously in the same chamber by the electron beam evaporation method to form the p-type semiconductor layer 5 and the light emitting layer 3. The film thickness of the Cu ₂ S layer was 100 nm, the film thickness of the light emitting layer 3 was 2 μm, the degree of vacuum in the vapor deposition chamber at that time was set to 1 × 10 ⁻⁶ Torr, and the substrate 1 temperature was set to 200 ° C. Further, in order to improve the crystallinity, the deposited light emitting layer 3 is heat-treated at 600 ° C. for 1 hour in the same chamber, and then the second electrode 4 is formed on the light emitting layer 3 by resistance heating vapor deposition. Al was vapor-deposited to obtain a light emitting device.
When a direct current was passed through the obtained light emitting device using Al as a positive electrode and ITO as a negative electrode, light emission of 2 to 10 times the intensity of Example 3 was confirmed.

FIG. 4 is a diagram showing an outline of the structure of a direct current drive type inorganic EL element of Example 3. FIG. 5 is a diagram showing an outline of the structure of a direct current drive type inorganic EL element of Example 4.

Explanation of symbols

1 Glass substrate 2 First electrode (ITO electrode)
3 Light emitting layer 4 Second electrode (Al electrode)
5 p-type semiconductor layer

Claims (8)

  An inorganic phosphor having, as a base material, at least one selected from Group 2-16 compounds and Group 12-16 compounds, or a mixed crystal thereof, and containing no Cu and Mn. At least one of a metal element belonging to the second transition series of Group 6 to Group 11 and a metal element belonging to the third transition series, and at least one of Group 16 elements other than the elements constituting the base material; An inorganic phosphor characterized in that it contains   The element belonging to the second transition series of Group 6 to Group 11 or the element belonging to the third transition series is at least one of Ru, Rh, Pd, Ag, Os, Ir, Pt and Au. The inorganic phosphor according to claim 1.   2. The inorganic phosphor according to claim 1, wherein the base material is made of zinc sulfide, zinc selenide or a mixed crystal thereof.   The inorganic phosphor according to claim 3, wherein the Group 16 element other than the element constituting the base material is oxygen.   The inorganic phosphor according to claim 1, comprising at least one element selected from elements belonging to Group 13 and Group 15 of the Periodic Table.   The light emitting element which has the inorganic fluorescent substance in any one of Claims 1-5.   A direct-current thin-film inorganic EL element comprising the inorganic phosphor according to any one of claims 1 to 5.   The direct current thin film type inorganic EL element according to claim 7, which has a p-type semiconductor layer.

Images