Patent Application
20060181197
1. Technical Field
The present invention relates to electroluminescent elements used for a planar light source and a flat display device.
2. Description of the Related Art
Conventional light emitting devices, used for planar light sources and flat display devices, use light emitting diodes or electroluminescent elements (referred to as EL elements).
Light emitting diodes are advantageous in high brightness and high luminous efficiency. However, they must be formed on a compound semiconductor substrate, and it is difficult to increase the size of one semiconductor substrate. Further, in order to increase the size of a flat display device, a large number of light emitting diodes must be arranged in two dimensions.
The structure of an EL element will be explained by using
However, in order to increase the size of a planar light emitting device using the light emitting diodes described above, a number of light emitting diodes are required. This causes a problem of an increase in the manufacturing cost in proportion to the number of elements.
Further, a planar light emitting device using the EL elements described above has no problem in increasing the size, and is more advantageous than other displays in such points as thin shape, high-speed response, large viewing angle, and high contrast. However, the luminous efficiency and brightness are low, and the lifetime is as short as about ten thousands hours, so there are shortcomings practically. Further, it is required to apply an AC voltage of several hundreds V in a high frequency of several kHz generally. Therefore, it is difficult to perform a drive of active matrix type using general purpose thin film transistors, causing a problem that the cost of driving circuit increases.
Further, in an inorganic phosphor such as CaS:Eu or Y2O3:Mn typically used for an EL element, a luminescence center of a transition metal such as Mn or a rear earth metal such as Eu is added in an inorganic compound crystal such as sulfide including CaS and oxide including Y2O3. Therefore, luminescence due to ultraviolet light excitation is realized. On the other hand, an electron is less likely to transmit an inorganic phosphor although an electric field is applied, and an electrification repulsion is strong. Therefore, it is required to excite the luminescence center in the inorganic phosphor by causing a high-speed electron accelerated in the high electric field to collide. Therefore, it is required to apply an AC voltage of several hundreds V in a high frequency of several kHz generally, causing a problem that the cost of the driving circuit increases.
The present invention has been developed in view of such problems. It is therefore an object of the present invention to provide luminescent elements capable of realizing a drive with a low voltage of several V to several tens V (low power consumption), a high luminous efficiency, and an increase in size at low cost.
An electroluminescent element according to the present invention is characterized as to include a pair of electrodes facing each other, and one or a plurality of phosphor layers formed between the pair of electrodes. At least one of the phosphor layers includes a phosphor semiconductor with wide band-gap.
The phosphor layer may have a laminated structure of a phosphor layer and a semiconductor layer with wide band-gap.
Further, the electroluminescent element may further include at least one transparent conductive layer interposed between the pair of electrodes. The transparent conductive layer may be a partially discontinuous layer.
Further, at least one of the phosphor layer and the semiconductor layer constituting the phosphor layer may be a partially discontinuous layer. In such a case, any of the following cases is acceptable: both of the semiconductor layer and the phosphor layer are discontinuous layers, the semiconductor layer is a continuous layer and the phosphor layer is a discontinuous layer, the semiconductor layer is a discontinuous layer and the phosphor layer is a continuous layer, and both of the semiconductor layer and the phosphor layer are continuous layers.
Further, the phosphor layer may include phosphor particles, in each of which at least a part of the surface thereof is covered with a semiconductor having a wide band-gap.
Further, the phosphor layer may include phosphor particles in each of which substantially all surface thereof is covered with a semiconductor having a wide band-gap.
Further, the phosphor layer may be so configured that the phosphor particles, in each of which at least a part of the surface thereof is covered with a semiconductor having a wide band-gap, are dispersed in a matrix material.
Further, the phosphor layer may be so configured that the phosphor particles, in each of which substantially all surface thereof is covered with a semiconductor having a wide band-gap, are dispersed in a matrix material.
The matrix material may be a transparent conductor.
Further, it is preferable that the semiconductor included in the phosphor layer have a band-gap causing to emit light of a shorter wavelength region than blue light by applying an electric field. As the semiconductor, a compound semiconductor having a band-gap of 2.0 eV may be used. More preferably, a compound semiconductor having a band-gap of 2.5 eV may be used. For example, any one of the following is more preferable: a 13th-15th group compound semiconductor, a mixed crystal thereof, or a mixtures thereof in which a partial segregation is allowed; a 12th-16th group compound semiconductor, a mixed crystal thereof, or a mixture thereof in which a partial segregation is allowed; a 2nd-16th group compound semiconductor, a mixed crystal thereof, or a mixture thereof in which a partial segregation is allowed; a 12th-13th-16th group compound semiconductor, a mixed crystal thereof, or a mixture thereof in which a partial segregation is allowed; a 11th-13th-16th group compound semiconductor, a mixed crystal thereof, or a mixture thereof in which a partial segregation is allowed; and a 12th-14th-15th group compound semiconductor, a mixed crystal thereof, or a mixture thereof in which a partial segregation is allowed.
Further, in order to improve the flow of electrons within the phosphor layer, it is preferable that an electron transport layer of a metallic complex of 8-hydroxyquinoline such as Alq3, an amorphous material such as BMB-2T of a thiophene compound, or the like be provided between the phosphor layer and at least one of the electrodes.
In order to make a typical EL element emit light, it is necessary to cause a high-acceleration electron to collide with a phosphor so as to cause an electron beam excitation, whereby it is required to apply a high voltage of several hundreds V. On the other hand, in the electroluminescent element of the present invention, a wide band-gap semiconductor layer or a semiconductor cover layer first emits light in an ultraviolet region of the wavelength of 300 nm to 350 nm to a blue green light region of 500 nm band, with a low voltage. More preferably, it emits light in an ultraviolet region of the wavelength of 300 nm to 350 nm to a blue light region of 400 nm band. The phosphor layer or phosphor particles are excited with the light, whereby the phosphor layer emits light as a whole, so high brightness and high luminous efficiency can be obtained. Then, electrons flow into an adjacent transparent conductive layer, to thereby induce the next light emission. Since this light emitting mechanism is repeated, the flow of electrons continues, whereby a low voltage drive (low power consumption) and a long lifetime are realized.
Further, the pair of electrodes may be positive electrode and negative electrode. In such a case, a DC voltage is applied between the pair of positive electrode and negative electrode. Further, at least one semiconductor layer constituting the phosphor layer may be located nearer the negative electrode side than the phosphor layer.
Further, the electroluminescent element according to the present invention may further include a thin film transistor connected with one of the pair of electrodes. In the electroluminescent element of the present invention, it is possible to use a thin film transistor since the driving voltage is as low as several V.
A display device according to the present invention is characterized as to include: an electroluminescent array in which electroluminescent elements are arranged in two dimensions; a plurality of x electrodes, in parallel with each other, extending in a first direction in parallel with a face of the electroluminescent array; and a plurality of y electrodes extending in parallel with a second direction, orthogonal to the first direction, in parallel with the face of the electroluminescent array. The thin film transistor of the electroluminescent array is connected with the x electrode and the y electrode, respectively.
As described above, according to the electroluminescent element of the present invention, a wide band-gap semiconductor performs ultraviolet region luminescence or blue light luminescence with a low voltage, and the phosphor is excited by the short wavelength light thereof, so the phosphor layer emits light as a whole. Therefore, high brightness and high luminous efficiency can be obtained. Further, since the matrix consists of a transparent conductor, the flow of electrons continues, whereby a low voltage drive (low power consumption) and a long lifetime are realized. Further, an increase in size is easily realized, whereby a cost reduction can be achieved.
The present invention will become readily understood from the following description of preferred embodiments thereof made with reference to the accompanying drawings, in which like parts are designated by like reference numeral and in which:
Electroluminescent elements according to the present invention will be explained by using accompanying drawings. Note that substantially same members in the drawings are denoted by the same reference numerals.
An electroluminescent element according to an embodiment 1 of the present invention will be explained by using
Next, each member constituting the electroluminescent element will be described.
First, the substrate 11 is preferably quartz, glass or ceramic with fine transparency. Further, the positive electrode 12 is formed on the substrate 11. The positive electrode 12 preferably consists of ITO (SnO2 is doped in In2O3) which is a transparent conductor, InZnO, tin oxide, zinc oxide or the like. Further, the negative electrode 13 is provided opposite the positive electrode 12. The negative electrode 13 may be Pt or Ir. Further, a material with low work function such as Al, In, Mg, Ti, MgAg, and AlLi may be used.
In between the positive electrode 12 and the negative electrode 13, the phosphor layer 14 consisting of the semiconductor layer 15 and the phosphor layer 16 is laminated repeatedly via the transparent conductive layer 17. The semiconductor layer 15 and the phosphor layer 16 constituting the phosphor layer 14 are discontinuous layers, in which discontinuous parts between respective phosphor layers 14 are filled with the transparent conductive layer 17.
The transparent conductive layer 17 may be ITO, InZnO or tin oxide. Thereby, it is possible to prevent charging, and to prevent repulsion of subsequent electrons. Further, it is also possible to extract light outside without interrupting the light emitted from the phosphor layer 14. Other preferable examples include metallic oxide such as ZnO, In2O3 and Ga2O3, and compound oxide including these materials. Further, a transparent conductive resin material may be used as the transparent conductive layer 17. Preferable examples of the transparent conductive resin materials include: polyacetylene series, polyphenylene series such as polyparaphenylene, polyphenylene vinylene, polyphenylene sulfide, and polyphenylene oxide, heterocyclic polimer series such as polypyrrole, polythiophene, polyfuran, polyselenophene and polytellurophene, ionicity polimer series such as polyaniline, polyacene series, polyoxadiazole series, metal phthalocyanine series, polyvinyl series, and their conductive materials, copolymers, and compounds. Further, more preferably, poly-N-vinylcarbazole (PVK), polyethylene dioxythiophene (PEDOT), polystyrene sulfonic acid (PSS), polymethyl phenylsilane (PMPS), poly-[2-methoxy-5-(2-ethyl hexyl oxy)-1,4-(1-cyano vinylene)phenylene] (CN-PPV), poly-quinoxaline may be used. Doping with H2SO4 or the like may be performed in order to adjust the conductivity. Further, a form in which a low molecular electron transporting material described later is molecular-dispersed in the conductive resin or nonconductive resin, or a form in which the structure is incorporated in a molecular chain may be acceptable. Moreover, a form in which conductivity is applied by dispersing the conductive or semiconductive inorganic material of the above-mentioned metal oxide or compound metal oxide or the like in the conductive resin or nonconductive resin may be acceptable.
It is preferable that the semiconductor layer 15 of a wide band-gap have a band-gap causing to emit light of a shorter wavelength area than blue light by applying an electric field. Specifically, a compound semiconductor of 2.0 eV or more band-gap can be used, and more preferably, a compound semiconductor of 2.5 eV or more band-gap can be used. It is preferable that such a semiconductor be one of the following: a 13th-15th group compound semiconductor such as AlN (band-gap: 5.7 eV), AlP (2.4 eV), AlAs (2.2 eV), GaN (3.4 eV), GaP (2.3 eV), and a mixed crystal thererof (e.g., AlGaN, AlGaP, AlGaAs, GalnN, Galn P, InGaAlN, InGaAlP), and a mixture thereof in which a partial segregation is allowed; a 12th-16th group compound semiconductor such as ZnO (3.2 eV), ZnS (3.7 eV), ZnSe (2.6 eV), ZnTe (2.3 eV), CdO (2.1 eV), CdS (2.5 eV), HgS (2.0 eV), and a mixed crystal thereof (e.g., ZnCdS, ZnCdSe, ZnCdTe, ZnSSe, ZnCdSSe, ZnCdSeTe), and a mixture thereof in which a partial segregation is allowed; a 2nd-16th group compound semiconductor such as BeSe (3.8 eV), BeTe (3.4 eV), MgS (4.5 eV), MgSe (3.6 eV), MgTe (3.2 eV), and a mixed crystal thereof (e.g., ZnMgSSe, ZnMgBeSe), and a mixture thereof in which partial segregation is allowed; Al2th-13th-16th group compound semiconductor such as (Zn, Cd)-(Al, Ga, In)-(O, S, Se) including ZnGa2O4(4.4 eV) as another example of a ternary compound, and a mixed crystal thereof, and a mixture thereof in which a partial segregation is allowed; an 11th-13th-16th group compound semiconductor such as CuAlS2 (3.5 eV), CuAlSe2 (2.7 eV), CuAlTe2 (2.1 eV), CuGaS2 (2.4 eV), AgAlS2 (3.1 eV), AgAlSe2 (2.6 eV), AgAlTe2 (2.3 eV) and AgGaS2 (2.7 eV), and a mixed crystal thereof, and a mixture thereof in which a partial segregation is allowed; and a 12th-14th-15th group compound semiconductor such as ZnSiP2 (3.0 eV), ZnSiAs2 (2.1 eV), ZnGeP2 (2.3 eV), and CdSiP2 (2.5 eV), and a mixed crystal thereof, and a mixture thereof in which a partial segregation is allowed. Note that the above-described compounds are exemplary given, and the present invention is not limited to these. Further, the band-gap may be adjusted by doping one or plural kinds of impurity elements serving as donors or accepters in these compound semiconductors. For example, they are selected from: metallic or non-metallic elements such as Li, Na, Cu, Ag, Au, Be, Mg, Zn, Cd, B, Al, Ga, In, C, Si, Ge, Sn, Pb, N, P, As, O, S, Se, Te, F, Cl, Br, I, Ti, Cr, Mn, Fe, Co and Ni; rear earth elements such as Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm; fluoride such as TbF3 and PrF3; oxide such as ZnO and CdO.
Further, the phosphor layer 16 may be: a 2nd-16th group compound phosphor material such as CaS, SrS, CaSe or SrSe including the above described CaS:Eu, a 12th-16th group compound phosphor material such as ZnS, CdS, ZnSe, CdSe, or ZnTe, a mixed crystal of the above-mentioned compounds such as ZnMgS, CaSSe or CaSrS, or a mixture thereof in which a partial segregation is allowed, a thiogallate phosphor material such as CaGa2S4, SrGa2S4 or BaGa2S4, a thioaluminate phosphor material such as CaAl2S4, SrAl2S4 or BaAl2S4, a metallic oxide phosphor material such as Ga2O3, Y2O3, CaO, GeO2, SnO2 or ZnO, and a polyoxide phosphor material such as Zn2SiO4, Zn2GeO4, ZnGa2O4, CaGa2O4, CaGeO3, MgGeO3, Y4GeO8, Y2GeO5, Y2Ge2O7, Y2SiO5, BeGa2O4, Sr3Ga2O6, (Zn2SiO4—Zn2GeO4), (Ga2O3—Al2O3), (CaO—Ga2O3) and (Y2O3—GeO2). In these phosphor materials, at least one kind of element selected from the group including Mn, Cu, Ti, Cr, Fe, Ni, Ag, Au, Al, Ga, Sn, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb may be activated as an activator agent. The activator agent may be a nonmetallic element such as Cl or I, or fluoride such as TbF3 or PrF3, or more than two kinds thereof may be activated together. There is no limitation provided that a phosphor is one used for EL element.
As described above, according to the electroluminescent element of the present embodiment, a wide band-gap semiconductor performs a ultraviolet range emission or blue light emission with a low voltage, and the phosphor particles are excited by the short wavelength light thereof, whereby the phosphor layer emits light as a whole, so high brightness and high luminous efficiency can be obtained. Further, since the matrix material is a transparent conductor, the flow of electrons is continued, whereby a low voltage drive (low power consumption) and a long lifetime are realized. Further, since an increase in size is easily realized, an effect of low cost is also achieved.
An electroluminescent element 20 according to an embodiment 2 of the present invention will be described by using
An electroluminescent element 30 according to an embodiment 3 will be described by using
An electroluminescent element 40 according to an embodiment 4 will be described by using
The electron transport layers 18, 19, may consist of, in particular, a metal complex of 8-hydroxyquinoline such as tris(8-quinolinolato)aluminum (Alq3), or an amorphous material such as 5,5′-bis(dimesitylboryl)-2,2′bithiophene (BMB-2T) of a thiophene compound. Further, other preferred examples of low-molecular materials includes oxadiazole derivative, triazole derivative, 1,10-phenanthroline derivative, fluorene derivative, quinone derivative, styrylbenzene derivative, silole derivative, and their dimmer and trimer. Among others, the following materials are included: 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 2,5-bis(1-naphthyl)-1,3,4-oxadiazole (BND), 2,5-bis[1-(3-methoxy)-phenyl]-1,3,4-oxadiazole (BMD), 1,3,5-tris[5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-il]benzene (TPOB), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ), 3-(4-biphenyl)-4-(4-ethylphenyl)-5-(4-tert-butylphenyl)-1,2,4-triazole(p-EtTAZ), 4,7-diphenyl-1,10-phenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 3,5-dimethyl-3′,5′-di-tert-butyl-4,4′-diphenoquinone (MBDQ), 2,5-bis[2-(5-tert-butylbenzoxazolyl)]-thiophene (BBOT), trinitrofluorenone (TNF). Further, high-molecular materials include the above-mentioned CN-PPV, polyquinoxaline, and polymer in which a molecular structure showing the electron transportation ability with low molecular system is incorporated in a molecular chain. A single type or a mixture of plural types thereof may be acceptable, but the present invention is not limited to these. Further, a single crystal or a polycrystal of inorganic material such as an n-type compound semiconductor or an n-type oxide semiconductor, and resin dispersed layer of their particle powder may be used. Note that the electron transport layer 18 provided on the positive electrode 12 side also serves as a hole block layer.
Although the case of applying a DC voltage between the electrodes 12 and 13 has been explained in the embodiments 1 to 4 described above, the present invention is not limited to this configuration. An AC voltage or a pulse voltage may be applied.
Further, in the embodiments 1 to 4, a luminescent light extracted from the luminescent element is determined by the semiconductor layer 15 and the phosphor layer 16 constituting the phosphor layer 14. For a multiple display, a white display and an adjustment of color purity of each RGB color, a color conversion layer may be provided in front of the phosphor layer 14 in a light extracting direction, or a color conversion material may be mixed in the transparent conductive layer 17. As the color conversion layer and the color conversion material, those emitting light by using light as the excitation source may be used, including well-known phosphors, pigments, dyes and the like, whether organic materials or inorganic materials. In the case of inorganic materials, materials used as phosphor layer 16 described above can be used. As organic materials, a polycyclic aromatic hydrocarbon compound such as naphthalene, perylene, rubrene, anthracene, pyrene, naphthacene and a derivative thereof, and hetero aromatic compounds such as coumarin, quinoline, oxadiazole, lophine, nile red, 4H-pyranilidenepropanedinitrile and phenoxazone, and a derivative thereof are used. Further, as other luminescent materials, there are used: a polymethine compound such as cyanine, oxole, azulenium or pyrylium, a styrylbenzene compound such as bis-(diphenylvynil)biphenyl, a porphyrin compound such as chlorophyll, a chelate metal complex such as an aluminum quinolinol complex, a zinc hydroxyphenyloxazole complex, a zinc hydroxyphenylthiazole complex, or an azomethine metal complex, chelate lanthanoid complex, a xanthene compound such as phenolphthalein, Malachite green, fluorescein, Rhodamine B or Rhodamine 6G, quinacridone, diketopyrrolopyrrole, magnesium phthalocyanine, or a derivative thereof, but the present invention is not limited to these materials.
Further, the electroluminescent element according to the embodiments 1 to 4 may be manufactured by means of a ceramic forming method such as doctor blade method, hot pressing, HIP and sol-gel process, a thin film forming method such as vapor deposition, sputtering, ion plating and molecular beam epitaxial (MBE) method, a thin film processing method such as wet etching and ion etching, or spin coating, an ink jet method, or the like.
An electroluminescent element 60 according to an embodiment 5 of the present invention will be explained by using
A display device according to an embodiment 6 of the present invention will be described by using
An electroluminescent electrode 80 according to an embodiment 7 of the present invention will be explained by using
Further, the phosphor layer 83 is formed on the positive electrode 82. The phosphor layer 83 is so configured that phosphor particles 86 are dispersed in the matrix material consisting of transparent conductor 84. It is preferable that at least a part of the surface of the phosphor particle be covered with a semiconductor 85 of a wide band-gap, or chemisorption be performed. Further, as shown in
As described above, according to the electroluminescent element of the present embodiment, a semiconductor of a wide band-gap performs ultraviolet range emission and blue light emission with a low voltage, and the phosphor particles are excited by the short wavelength light thereof, whereby the phosphor layer emits light as a whole. Therefore, high brightness and high luminous efficiency can be obtained. Further, since the matrix material is a transparent conductor, the flow of electrons continues, and a low voltage drive (low power consumption) and a long lifetime are realized. Further, since an increase in size is easily realized, an effect of low cost is also achieved.
An electroluminescent element 100 according to an embodiment 8 of the present invention will be explained by using
Although explanation has been given for the case of applying a DC voltage between the electrodes 82 and 87 in the embodiments 7 and 8, the present invention is not limited to this configuration. An AC voltage or a pulse voltage may be applied.
Further, an electroluminescent elements according to the embodiments 7 and 8 may be manufactured by means of a ceramic forming method such as doctor blade method, hot pressing, HIP or sol-gel process, a thin film forming method such as vapor deposition, sputtering, ion plating or molecular beam epitaxial (MBE) method, spin coating, an ink jet method, or the like.
An electroluminescent element 110 according to an embodiment 9 of the present invention will be explained by using
A display device 120 according to an embodiment 10 of the present invention will be explained by using
An electroluminescent element 130 according to an embodiment 11 of the present invention will be explained by using
Further, the phosphor layer 133 is one in which phosphor particles 136 are dispersed in the matrix material formed of a transparent conductor 134. It is preferable that at least a part of the surface of the phosphor particle 136 be covered with a semiconductor 135 with a wide band-gap, or chemisorption be performed. Further, it is more preferable that substantially all surface of the phosphor particle 136 be covered with the semiconductor 135. By covering substantially all surface in this way, a large effect in moisture proof of the phosphor particle 136 is achieved.
Further, as the transparent conductor 134 constituting the electroluminescent element 130, transparent conductive resin can be used. The transparent conductive resin has less conductivity comparing with ITO, InZnO, tin oxide which are examples of the transparent conductive layer body layer 17 and the transparent conductor 84 described above, but defectives such as pinholes are less caused, so it is preferable in pressure resistance. A stable element characteristic can be obtained even applying several tens V to hundred and several tens V. Preferable examples as the transparent conductive resin materials are substantially same as materials used for the transparent conductive layer 17 of the electroluminescent element 10 according to the embodiment 1, so the detailed explanation thereof is omitted. Further, other constitutional members of the electroluminescent element 130 are substantially same as those of the electroluminescent element 80 according to the embodiment 7, respectively, so the detailed explanation is omitted. In the configuration of the electroluminescent element 130, the first electrode 132 is a transparent electrode and light is extracted from the side of the first electrode 132.
As described above, according to the electroluminescent element of the present embodiment, a semiconductor of a wide band-gap performs ultraviolet range emission or blue light emission, and the phosphor particles are excited by the short wavelength light thereof, so the phosphor layer emits light as a whole. Therefore, a high brightness and high luminous efficiency can be obtained. Further, an increase in size is easily realized, so an effect of low cost can be achieved.
An electroluminescent element 140 according to an embodiment 12 of the present invention will be explained by using
Although the case of applying an AC voltage between the electrodes 132 and 137 has been described in the embodiments 11 and 12 described above, the present invention is not limited to this. A DC voltage or a pulse voltage may be applied.
Further, the electroluminescent elements according to the embodiments 11 and 12 described above may be manufactured by means of a ceramic forming method such as doctor blade method, hot pressing, HIP or sol-gel process, a thin film forming method such as vapor deposition, sputtering, ion plating or molecular beam epitaxial (MBE) method, spin coating, an ink jet method, or the like.
An electroluminescent element 150 according to an embodiment 13 of the present invention will be explained by using
Further, the phosphor layer 153 is formed of a phosphor material and a semiconductor material of a wide band-gap, and is deposited by co-vapor-deposition. Therefore, it is possible to provide an electroluminescent element of high brightness and high luminescent efficacy, similar to the embodiments described above. Further, since an increase in size is easily realized, an effect of low cost is also achieved. Respective constitutional members of the electroluminescent element 150 are substantially same as those of the electroluminescent element 10 according to the embodiment 1, so detailed explanation is omitted.
Although explanation has been given for the case of applying a DC voltage between the electrodes 152 and 154 in the embodiment 13, the present invention is not limited to this configuration. An AC voltage or a pulse voltage may be applied.
Further, in the embodiments 7, 8 and 11 to 13, the luminescent light extracted from the luminescent element is determined by the phosphor materials and semiconductor materials in the phosphor layers 83, 133 and 153. However, for a multiple display, a white display and an adjustment of color purity of each RGB color, a color conversion layer may be provided in front of the phosphor layer in a light extracting direction, or a color conversion material may be mixed in the phosphor layer.
As described above, the present invention is explained in detail by way of the preferred embodiments. However, the present invention is not limited to these embodiments, and it is obvious for those skilled in the art that various preferable deformations and modifications are possible within the technical range of the present invention described in the scope of claims below.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/09673 | 7/1/2004 | WO | 12/29/2005 |
