JP2000208257A - Light emitting device and image display unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance luminescent brightness. SOLUTION: A dielectric film 3 for reflecting an ultraviolet light and transmitting a visible light, an ultraviolet light emitting electroluminescent element 10 for radiating the ultraviolet light and a wavelength conversion film 9 for wavelength-converting the ultraviolet light and radiating the visible light in the incident direction of the ultraviolet light are stacked in this order and formed on a transparent substrate 2. Thereby, the ultraviolet light radiated from the ultraviolet light emitting electroluminescent element 10 to the dielectric film 3 side is reflected from the dielectric film 3 and enters the wavelength conversion film 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device which emits visible light by converting the wavelength of ultraviolet light. The present invention also relates to a thin image display device using an ultraviolet light emitting element as an excitation energy source for a wavelength conversion film that emits visible light.

[0002]

2. Description of the Related Art An image display device is a device that is used in combination with, for example, an information processing device and various broadcast receivers, and displays image information and character information. In recent years, it has been desired that the image display device be made thinner and have a larger screen, and various display methods have been studied and developed.

As the image display device, there has been proposed a thin image display device which can easily realize a reduction in thickness and a large screen by using a thin film type light emitting element. As a thin-film light-emitting element used for such a thin image display device, for example, there is a thin-film electroluminescence element (hereinafter, referred to as a thin-film EL element).

[0004] The thin-film EL element has a structure in which a first conductive film, a first insulating film, a light emitting film, a second insulating film, and a second conductive film are sequentially stacked on a substrate. Is done. Thin-film EL
In the element, a light-emitting film is formed by adding an element serving as a light-emission center to a base material, and the light-emitting film is formed by applying an electric field between the first conductive film and the second conductive film. Is configured to emit light.

As an image display device using a thin film type EL element, a thin film type E in which a light emitting film is formed of ZnS: Mn is used.
A pixel is formed by providing red and green color filters for the L element and obtaining blue light emission by a thin film EL element in which a light emitting film is formed of SrS: Ce or SrGa ₂ S ₄ : Ce. A proposal has been made (El
ectroluminescent Displays, Y.Ono, World Scientifi
c).

A similar image display device is Sr.
There is also a proposal that a pixel is configured by arranging red, green, and blue color filters with respect to a thin-film EL element that emits white light and includes a light-emitting film in which S: Ce and ZnS: Mn are stacked. It has been done.

On the other hand, in an image display device, a pixel is constituted by a light emitting element having an ultraviolet light emitting element that emits ultraviolet light and a wavelength conversion film that emits visible light by converting the wavelength of the ultraviolet light. Has been made. That is, in this image display device, the ultraviolet light emitted by the ultraviolet light emitting element is used as the excitation energy of the wavelength conversion element. More specifically, for example,
No. 16495, JP-A-63-18319,
`` Japanese Journal of Applied Physics, Vol. 30, NO.1
0A, 1991, L1815 ”, etc., an ultraviolet light-emitting electroluminescent element (hereinafter, referred to as an ultraviolet light-emitting EL device).
It is called an element. ) And a phosphor are proposed to form an image display device in which pixels are configured.

In an image display device, Japanese Patent Laid-Open No.
As described in Japanese Patent Application No. 299175, "EL light emitting device", a configuration has been proposed in which a wavelength conversion layer is formed of a thin film phosphor and formed between a transparent electrode and an ultraviolet light emitting film. Thereby, the image display device can prevent the ultraviolet light from being absorbed by the transparent electrode, and can improve the luminance.

In the image display device, the wavelength of ultraviolet light emitted from the ultraviolet light emitting element is converted into visible light by the wavelength conversion film, so that the selection of a light emitting material is facilitated.
Image information or character information can be displayed with high quality.

[0010]

However, in the image display device, when the wavelength of the ultraviolet light is converted into visible light as described above, the ultraviolet light emitted from the ultraviolet light emitting element emits the ultraviolet light. Emitted equally from both sides of the device. For this reason, in the conventional image display device, there was a problem that the ultraviolet light emitted from the surface opposite to the wavelength conversion film was not effectively used as the excitation energy of the wavelength conversion film. That is, the conventional image display device has a problem that sufficient light emission luminance cannot be obtained efficiently.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light emitting device having an improved utilization efficiency of ultraviolet light by providing a dielectric film that reflects ultraviolet light and transmits visible light. Further, the present invention improves the utilization efficiency of ultraviolet light by arranging a dielectric film that reflects ultraviolet light and transmits visible light to a plurality of ultraviolet light emitting elements arranged in a matrix. It is intended to provide an image display device which displays an image with high brightness by using the same.

[0012]

In order to achieve the above object, a light emitting device according to the present invention comprises at least an ultraviolet light emitting device having an ultraviolet light emitting film between a pair of conductive films and emitting ultraviolet light. A dielectric film that reflects ultraviolet light and transmits visible light, and a wavelength conversion film that converts the wavelength of ultraviolet light and emits visible light, and is formed by laminating them, and the dielectric film is The ultraviolet light-emitting film is formed on the opposite side of the wavelength conversion film from the ultraviolet light-emitting film, and reflects ultraviolet light incident from the ultraviolet light-emitting film to be incident on the wavelength conversion film.

In the light emitting device configured as described above, the ultraviolet light emitted from the ultraviolet light emitting film to the side where the dielectric film is located can be reflected by the dielectric film toward the wavelength conversion film. Thus, the light emitting element can efficiently use the ultraviolet light emitted from the ultraviolet light emitting film as excitation energy of the wavelength conversion film.

Further, the image display device according to the present invention comprises a plurality of ultraviolet light emitting elements which are arranged in a matrix, each of which has an ultraviolet light emitting film between a pair of electrodes and emits ultraviolet light, and a device which reflects ultraviolet light. A dielectric film that transmits visible light, and a wavelength conversion film that converts the wavelength of ultraviolet light to emit visible light, and is formed by laminating them, and the dielectric film is formed on the ultraviolet light-emitting film. On the other hand, it is formed on the side opposite to the wavelength conversion film, and reflects ultraviolet light incident from each of the ultraviolet light-emitting films to be incident on the wavelength conversion film.

The image display device configured as described above is
Ultraviolet light emitted from the ultraviolet light emitting film to the side where the dielectric film is located can be reflected toward the wavelength conversion film by the dielectric film. Thus, the image display device can efficiently use the ultraviolet light emitted from the ultraviolet light emitting film as excitation energy of the wavelength conversion film.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, first, the light emitting element 1 as shown in FIG. 1 will be described. In the following description, specific examples are given for each member and its material, size, film thickness, film forming method, and the like, but the present invention is not limited to the following examples.

The light emitting element 1 has one main surface 2 of a transparent substrate 2.
a, a dielectric film 3, a first conductive film 4, a first insulating film 5, an ultraviolet light emitting film 6, a second insulating film 7, a second conductive film 8, The film 9 is formed in this order,
It has a laminated structure as a whole. In the light emitting element 1, the first conductive film 4, the first insulating film 5, the ultraviolet light emitting film 6, the second insulating film 7, and the second conductive film 8 form the ultraviolet light emitting electroluminescence. An element 10 (hereinafter, referred to as an ultraviolet light emitting EL element 10) is configured.

The light emitting element 1 has a configuration in which an ultraviolet light emitting film 6 emits ultraviolet light by applying an electric field between the first conductive film 4 and the second conductive film 8. Light emitting element 1
In the above, the ultraviolet light emitted from the ultraviolet light emitting film 6 is incident on the wavelength conversion film 9 so that the wavelength conversion film 9
Are configured to emit visible light in the direction of incidence of ultraviolet light. The light emitting element 1 is configured so that visible light emitted by the wavelength conversion film 9 passes through the transparent substrate 2 and exits from the other main surface 2b of the transparent substrate 2. That is, in the light emitting element 1, the main surface 2b of the transparent substrate 2 is a visible light emitting surface.

In the following description, ultraviolet light means
This refers to electromagnetic waves having a wavelength of 450 nm or less.

The transparent substrate 2 is made of a translucent hard material such as synthetic quartz glass, for example, and is formed in a substantially flat plate shape. The size, thickness, shape, and the like of the transparent substrate 2 are not limited, and may be any thickness as long as the transparent substrate 2 has a predetermined mechanical strength according to the purpose.

The dielectric film 3 is formed as a thin film on the main surface 2a of the transparent substrate 2. The dielectric film 3 has a multilayer structure in which a high refractive index layer and a low refractive index layer are laminated for one or more periods. The high refractive index layer is made of, for example, HfO ₂ (refractive index 2.30), ZnS (refractive index 2.30), ZrO ₂ (refractive index 2.20), Y ₂ O ₃ (refractive index 2.10), MgO.
(Refractive index: 1.80) It is formed in a thin film of a material having a high dielectric constant, a high refractive index, and a light-transmitting property. The low refractive index layer is made of, for example, SiO 2
₂ (refractive index 1.46), MgF ₂ (refractive index 1.38), L
The thin film is formed of a material having a high dielectric constant, such as iF (refractive index: 1.36), and having a low refractive index and a light-transmitting property.

In the dielectric film 3, the combination of the materials constituting the high refractive index layer and the low refractive index layer and the thickness of each layer are appropriately selected so as to reflect ultraviolet light and transmit visible light. It should just be formed. Specifically, the wavelength of the light to be reflected is λ, and the refractive index of the material forming the high refractive index layer is n.
(H), the refractive index of the material forming the low refractive index layer is n (L)
When the thickness of the high refractive index layer is n (H) · λ / 4,
The low refractive index layer is formed so that the layer thickness becomes n (L) · λ / 4.

Regarding the design and fabrication of a dielectric film having a multilayer structure as described above, for example, “Lens optics,
"Toru Kusakawa, Tokai University Press", "Applied Optics I / II, Masao Tsuruta, Baifukan", "Optical Thin Film, Shiro Fujiwara, Kyoritsu Publishing", etc.

The dielectric film 3 is formed by electron beam evaporation,
By using various film forming methods such as an ion plating method, a sputtering method, an ion beam sputtering method, and the like, the layer thicknesses of the high refractive index layer and the low refractive index layer are precisely controlled and formed.

As described above, the dielectric film 3 has a laminated structure of a high refractive index layer and a low refractive index layer, and is configured to reflect ultraviolet light and transmit visible light. Therefore, the dielectric film 3 can reflect the ultraviolet light emitted from the ultraviolet light emitting film 6 toward the wavelength conversion film 9. Further, the dielectric film 3 can transmit visible light emitted from the wavelength conversion film 9 toward the main surface 2b of the transparent substrate 2 which is a light emitting surface.

The first conductive film 4 is made of, for example, In ₂ O ₃ , S
It is formed in a thin film shape using a conductive and translucent material such as nO ₂ , ZnO, indium tin oxide (ITO), and indium zinc oxide (In ₂ O ₃ : Zn). The first conductive film 4 has a light-transmitting property,
The visible light emitted from the wavelength conversion film 9 can be transmitted toward the light emitting surface.

The second conductive film 4 is formed, for example, by a vacuum evaporation method,
It can be formed by various PVD methods represented by a sputtering method, a reactive sputtering method, an ion plating method, an electron beam evaporation method and the like.

The first insulating film 5 is formed in a thin film of a material having electrical insulation. First insulating film 5
Are the first conductive film 4, the ultraviolet light emitting film 6, and the second conductive film 8
And a function of preventing an electrical short circuit with the In addition, the first insulating film 5 prevents an electrical short circuit (breakdown mode) due to the formation of a minute defect when an excessive voltage is applied to the ultraviolet light emitting film 6, and also prevents moisture, oxygen,
It has a function of protecting the ultraviolet light emitting film 6 from an external environment such as carbon dioxide.

The first insulating film 5 is made of, for example, SiO 2
_{2, SiN, Si 3 N 4} , SiON, Al 2 O 3, SiAl
ON, BaTiO ₃ , SrTiO ₃ , Ta ₂ O ₅ , Sm
It is desirable to be formed of a material having electrical insulation and a large dielectric constant, such as ₂ O ₃ , BaTa ₂ O ₆ , TiO ₂ , Y ₂ O _{3 and} the like. Thereby, the first insulating film 5 increases the amount of charge accumulated at the interface with the ultraviolet light emitting film 6 and increases the amount of charge transfer in the ultraviolet light emitting film 6,
Light emission luminance can be improved.

The ultraviolet light emitting film 6 is formed in a thin film shape, and is formed by adding a light emitting center to a base material.
In the ultraviolet light emitting film 6, as a base material, for example, 3B
A nitride represented by a group III element or a compound represented by Zn ₂ SiO ₄ is selected, and a rare earth element such as Gd and / or a compound of a rare earth element is selected as a luminescence center. Further, the ultraviolet light emitting film 6
It is formed between the first conductive film 4 and the second conductive film 8, and is formed by applying an electric field between the first conductive film 4 and the second conductive film 8. Emit ultraviolet light.

In the ultraviolet light emitting film 6, the rare earth element added as the luminescent center may be a single rare earth element, or may be a fluoride, chloride, bromide, iodide, oxide or nitride. . Further, a mixture thereof may be used.

Further, in the ultraviolet light emitting film 6, when the amount of the light emitting center exceeds 10 atomic%, the concentration disappears due to a non-radiation process such as resonance energy transfer. Therefore, in the ultraviolet light emitting film 6, it is desirable to add the luminescent center at a ratio of 0.1 atomic% to 10 atomic% with respect to the base material.

Specifically, the ultraviolet light emitting film 6 is made of a base material such as BN, AlN, GaN, InN, and InGaAs.
formed by a nitride of a Group 3B element such as 1N,
The base material is formed by adding a rare earth element such as Gd and / or a compound of a rare earth element as a luminescent center. Thereby, the ultraviolet light emitting film 6 can emit ultraviolet light when an electric field is applied, and since the nitride of the group 3B element is a chemically stable compound, the ultraviolet light emitting film 6 is exposed to a strong electric field or ultraviolet light. Even under the condition, the luminance can be maintained for a long time without being deteriorated by moisture, oxygen, carbon dioxide and the like in the atmosphere.

The ultraviolet light emitting film 6 is formed of a base material, for example, a compound represented by Zn ₂ SiO _{4. In the} base material, as a luminescence center, a rare earth element such as Gd and / or a rare earth element is used. It may be formed by adding a compound. Thereby, the ultraviolet light emitting film 6
Can emit ultraviolet light when an electric field is applied, and since the base material is formed of an oxide, deterioration of characteristics due to moisture in the air and the like is less likely to occur.

At this time, the ultraviolet light emitting film 6 may be formed so that some of Si in the base material is replaced by Ge, and the film has some oxygen vacancies. That is, the base material of the ultraviolet light emitting film 6 is the general formula Zn ₂ Si _1-x Ge _x O
It may be formed by a compound represented by _4-y (0 ≦ x ≦ 1, 0 ≦ y <1). Thereby, the band gap energy of the base material is improved to 5 eV or more. G
The d atom has an energy level difference of 4 eV when the core transitions from the ⁶ P _7/2 state to the ⁸ S state. Therefore, when the luminescent center of the ultraviolet light emitting film 6 emits ultraviolet light due to the inner shell transition of the Gd atom, the ultraviolet light is not absorbed by the base material.

The second insulating film 7, like the first insulating film 5, is formed as a thin film of a material having electrical insulation. The second insulating film 5 has a function as a protective film for the ultraviolet light emitting film 6 while preventing an electrical short circuit between the second conductive film 9 and the ultraviolet light emitting film 6 and the first conductive film 4. I have.

The second insulating film 7 is made of the first insulating film 5
Similarly to the above, it is desirable to be formed of a material having electrical insulation and a large dielectric constant.

The second insulating film 7 is formed on the first insulating film 5 on which the ultraviolet light emitting film 6 is formed.
It is formed so that it may cover. In other words, in the ultraviolet light emitting EL element 10, the ultraviolet light emitting film 6 has the first insulating film 5 and the second
And a so-called double insulating structure completely surrounded by the insulating film 7.

The second conductive film 8 is made of In ₂ O ₃ , SnO ₂ :
F, ZnO: Al, indium tin oxide (ITO), indium zinc oxide (In ₂ O ₃ : Zn), and the like, are formed in a thin film from a material having conductivity and translucency. . Since the second conductive film 8 has translucency, the second conductive film 8 can transmit the ultraviolet light emitted from the ultraviolet light emitting film 6 and make it incident on the wavelength conversion film 9.

The wavelength conversion film 9 is made of a material that absorbs ultraviolet light and emits visible light, and is formed in a thin film shape on the second insulating film 7 on which the second conductive film 8 is formed. As a material for forming the wavelength conversion film 9, for example, Y ₂ O ₂ S: E
u, ZnCdS: Ag, etc., an inorganic phosphor powder that emits red light, ZnS: Cu, Al, Y ₂ SiO ₅ : Tb, C
e, inorganic phosphor powder that emits green light such as ZnS:
An inorganic phosphor powder that emits blue light such as Ag, Al, BaMgAl ₁₄ O ₂₃ : Eu can be used. Also,
The wavelength conversion film 9 is formed by adding these inorganic phosphor powders to, for example,
It may be formed of a fluorescent sheet dispersed in an organic binder such as polyvinyl alcohol, polycarbonate and polymethyl methacrylate.

The wavelength conversion film 9 may be formed of a general organic dye material such as rhodamine or coumarin as a dye laser medium in addition to the above-described phosphor material.

Further, the wavelength conversion film 9 is made of, for example, europium trifluoroacetonate (EuTTA), N,
N-bis (2,5-ditert-butylphenyl)-
3,4,9,10-Perylenedicarboximide (P
D), 4-dicyanomethylene-2-methyl-6- (p-
Dimethylaminostyryl) -4H-pyran (DCM),
Triphenylamine derivative (NSD), 8-hydroxyquinoline aluminum (Alq3), 3- (2'-benzothiazolyl) -7-diethylaminocoumarin (coumarin 6), 2,5-bis (5-tert-butyl-2-benzoxazol) ) An organic dye such as thiophene (BBOT) or anthracene may be formed, for example, by a polymer sheet in which a polymer such as polymethyl methacrylate is dispersed.

The wavelength conversion film 9 is formed as described in “J. Appl. Phys. 82 (8), 19”.
97, p. 4126 ", when the dye concentration is high, the disappearance process due to the resonance energy transfer between the dyes becomes remarkable, so that the dye is formed at a low dye concentration. Therefore, when the thickness of the wavelength conversion film 9 is less than 0.3 μm, it becomes difficult to completely absorb the ultraviolet light emitted from the ultraviolet light emitting EL element 11. Further, when the thickness of the wavelength conversion film 9 exceeds 100 μm, the portion excited by the ultraviolet light is located only near the surface of the incident surface of the ultraviolet light, and the wavelength-converted visible light can be efficiently emitted. It will be difficult. Therefore, the wavelength conversion film 9 has a thickness of 0.3 μm to 100 μm.
It is desirable to be formed with a thickness of μm.

In the light emitting device 1 configured as described above, when an electric field is applied between the first conductive film 4 and the second conductive film 8, the ultraviolet light emitting film 6 emits ultraviolet light. . The light emitting element 1 converts the wavelength of the ultraviolet light emitted from the ultraviolet light emitting film 6 into visible light by the wavelength conversion film 9 and emits the light outward from the light emitting surface. The light emitting element 1 emits visible light by operating as described above.

In the light emitting element 1, the ultraviolet light radiated from the ultraviolet light emitting film 6 is reflected by the wavelength conversion film 9 of the ultraviolet light emitting film 6 as shown by arrows A and B in FIG.
The light is emitted equally from the main surface 6a on the light emitting side and the main surface 6b on the light emitting surface side.

The light emitting element 1 converts the wavelength of the ultraviolet light radiated from the main surface 6a of the ultraviolet light emitting film 6 as shown by an arrow A in FIG. C
Emitted from the light emitting surface as shown by. Light emitting element 1
2 reflects ultraviolet light emitted from the main surface 6b of the ultraviolet light emitting film 6 as shown by the arrow B in FIG. 2 by the dielectric film 3, and is reflected by the wavelength conversion film 9 as shown by the arrow D in FIG. Make it incident. Then, the light emitting element 1 converts the wavelength of the ultraviolet light reflected by the dielectric film 3 into visible light by the wavelength conversion film 9 and emits the light from the light emitting surface as indicated by an arrow E in FIG.

That is, in the light emitting element 1, the dielectric film 3 formed on the side opposite to the wavelength conversion film 9 with respect to the ultraviolet light emitting film 6 reflects the ultraviolet light and transmits the visible light, thereby forming the ultraviolet light emitting film. The ultraviolet light emitted from the main surface 6b opposite to the wavelength conversion film 9 can be reflected and made incident on the wavelength conversion film 9. Thereby, the light emitting element 1 can effectively use the ultraviolet light radiated from the main surface 6a and the main surface 6b of the ultraviolet light emitting film 6 as the excitation energy of the wavelength conversion film 9. Therefore, the light emitting element 1 can improve the luminance of visible light emitted from the wavelength conversion film 9. In other words, since the light emitting element 1 includes the dielectric film 3, the light emission luminance on the light emitting surface can be improved.

In the light emitting element 1, the wavelength conversion film 9 converts the wavelength of the incident ultraviolet light into visible light, and reflects the visible light in the incident direction of the ultraviolet light to radiate the visible light. Therefore, it is a so-called reflection type light emitting element.

Therefore, the light emitting element 1 has high luminous efficiency, and particularly has high visible light extraction efficiency. Further, in the light emitting element 1, the light from the wavelength conversion film 9 is transmitted and attenuated like a so-called transmission type light emitting element in which the wavelength conversion element emits visible light in a direction opposite to the direction of incidence of the excitation energy. Nothing. Therefore, in the light emitting device 1, the luminous efficiency of the wavelength conversion film 9 is restricted only to the ultraviolet light absorption efficiency and the ultraviolet / visible light conversion efficiency depending on the physical properties of the wavelength conversion film 9, and the visible light from the wavelength conversion film 9 is restricted. The light extraction efficiency can be regarded as approximately 1.0.

In the light emitting device 1, the ultraviolet light emitting film 6
Is desirably formed so that its cross-sectional shape is trapezoidal and the main surface 6b side where the dielectric film 3 is located is widened. Specifically, for example, as shown in FIG. 3, both end portions 6c of the ultraviolet light emitting film 6 have a taper angle Θ (45 ° <Θ <9).
0 °).

Since the ultraviolet light emitting film 6 is formed of a material having a higher refractive index than the first insulating film 5 and the second insulating film 7 formed therearound, the first insulating film The critical angle of total reflection of light at the interface with the fifth and second insulating films 7 is small.

Therefore, in the light emitting device 1, an optical waveguide having the ultraviolet light emitting film 6 as a core layer and the first insulating film 5 and the second insulating film 7 as cladding layers is formed. 6 is not efficiently emitted from the main surface. Specifically, the refractive index of the ultraviolet light emitting film 6 is 2.
When the refractive index of the first insulating film 5 and the second insulating film 7 is about 1.5 to 2.0, and light scattering inside the ultraviolet light emitting film 6 is not considered, The ultraviolet light emitted from the main surface of the ultraviolet light emitting film 6 is about 20%, and the remaining about 80% of the ultraviolet light is emitted from the side end.

Therefore, when the end portion is formed vertically, the ultraviolet light emitting film 6 cannot allow the ultraviolet light radiated from the side end portion to enter the wavelength conversion film 9, and It is wasted without being used as excitation energy.

However, the light emitting element 1 is formed so that both end portions 6c of the ultraviolet light emitting film 6 have a taper angle Θ, so that the light emitting element 1 is directed toward the both end portions 6c as shown by an arrow F in FIG. The ultraviolet light radiated by the light can be reflected toward the dielectric film 3 as shown by an arrow G in FIG. Then, the light emitting element 1 converts the ultraviolet light reflected by the both end portions 6c into the dielectric film 3 as shown by an arrow H in FIG.
Is reflected and made incident on the wavelength conversion film 9, and the wavelength-converted visible light can be emitted from the light emitting surface as shown by an arrow I in FIG. That is, the light emitting element 1 has the ultraviolet light emitting film 6
Are formed so as to have a taper angle Θ, the ultraviolet light radiated from the both ends 6c can be used as excitation energy of the wavelength conversion film.

The ultraviolet light emitting film 6 has a taper angle 両 側 (45 ° <Θ <90) not only at both end portions 6c but also over the entire side end portion as shown in FIG.゜) may be formed.

In the light emitting device 1, when the wavelength conversion film 9 is formed of a phosphor powder, the phosphor powder generally has a particle size of about 2 μm. Therefore, in the light emitting element 1, it is desirable that ultraviolet light be incident on the wavelength conversion film 9 at a large incident angle. Therefore, the ultraviolet light emitting film 6 has a taper angle で
It is desirable to be formed in the range of ゜ <Θ <80 ゜. Thereby, the ultraviolet light emitting film 6 can make the ultraviolet light radiated from the side end portion enter the wavelength conversion film 9 at a large incident angle.

In the above description, the dielectric film 3, the first conductive film 4, the first insulating film 5, and the ultraviolet light emitting film 6 are formed on one main surface 2 a of the transparent substrate 2. , The second insulating film 7, the second conductive film 8, and the wavelength conversion film 9 are formed in this order, but the present invention is not limited to such a configuration. The light-emitting element according to the present invention includes at least an ultraviolet light-emitting element that emits ultraviolet light by providing an ultraviolet light-emitting film between a pair of conductive films, a dielectric film that reflects ultraviolet light and transmits visible light, and an ultraviolet light. A wavelength conversion film that converts the wavelength of light and emits visible light may be provided, and may be formed by laminating them.

Specifically, the light emitting element 2 as shown in FIG.
0, the wavelength conversion film 9 may be formed on the main surface 2 b side of the transparent substrate 2, and the dielectric film 3 may be formed on the second conductive film 8. The light emitting element 20 has the same configuration as the light emitting element 1 described above except that the formation positions of the wavelength conversion film 9 and the dielectric film 3 are different. Therefore, in the following, the light emitting element 20
The description of the components constituting is omitted, and the same reference numerals as in the light emitting element 1 are used in FIG.

In the light emitting element 20, an ultraviolet light emitting EL element 10 and a dielectric film 3 are formed in this order on the main surface 2a of the transparent substrate 2, and a wavelength conversion film 9 is formed on the main surface 2b of the transparent substrate 2. Be formed. Further, the light emitting element 20 includes a main surface 7 a facing the outside of the second insulating film 7 and a main surface 3 facing the outside of the dielectric film 3.
a is a light emitting surface. That is, in the light emitting element 20, the ultraviolet light radiated from the ultraviolet light emitting film 6 toward the wavelength conversion film 9 is transmitted through the transparent substrate 2 and is incident on the wavelength conversion film 9, and at the same time, Ultraviolet light emitted toward the dielectric film 3 is reflected by the dielectric film 3 and enters the wavelength conversion film 9. Then, the wavelength of the ultraviolet light is converted into visible light by the wavelength conversion film 9 and emitted from the light emitting surface.

In the light emitting device 20, the dielectric film 3
And the second conductive film 8 are made of Al, Mo,
It may be formed of various metal materials such as W, Ti, Cr, and Ni.

Further, as in a light emitting device 30 as shown in FIG. 7, the dielectric film 3 may be formed on the main surface 2b side of the transparent substrate 2. The light emitting element 30 has the same configuration as the light emitting element 1 described above except that the formation position of the dielectric film 3 is different. Therefore, in the following, the description of each part constituting the light emitting element 30 will be omitted, and the same reference numerals as those of the light emitting element 1 will be used in FIG.

In the light emitting element 30, an ultraviolet light emitting EL element 10 and a wavelength conversion film 9 are formed in this order on the main surface 2a of the transparent substrate 2, and the dielectric film 3 is formed on the main surface 2b of the transparent substrate 2. Be formed. In the light emitting element 30, the main surface 3a facing the outside of the dielectric film 3 is a light emitting surface. That is, in the light emitting element 30, the ultraviolet light emitted from the ultraviolet light emitting film 6 toward the wavelength conversion film 9 is incident on the wavelength conversion film 9 and the ultraviolet light is emitted from the ultraviolet light emission film 6 to the dielectric film 3 side. The ultraviolet light emitted toward the wavelength conversion film 9 is transmitted through the transparent substrate 2, is reflected by the dielectric film 3 toward the wavelength conversion film 9, and is incident on the wavelength conversion film 9. Then, the wavelength of the ultraviolet light is converted into visible light by the wavelength conversion film 9 and emitted from the light emitting surface.

Further, as in a light emitting element 40 as shown in FIG. 8, a first phosphor thin film 41 and a second phosphor thin film 42 are formed instead of the first insulating film 5 and the second insulating film 7. May be provided. The light emitting element 40 includes a first insulating film 5 and a second insulating film 7, a first phosphor film 41 and a second phosphor film 42.
Unlike the light emitting device 1, the light emitting device 1 has the same configuration except that the wavelength conversion film 9 is not provided. Therefore, the description of the same or equivalent parts as the light emitting element 1 will be omitted below, and the same reference numerals as those of the light emitting element 1 will be used in FIG.

In the light emitting element 40, the dielectric film 3 and the ultraviolet light emitting EL element 10 are formed in this order on the main surface 2a of the transparent substrate 2. The ultraviolet light emitting EL element 10 includes a first conductive film 4, a first phosphor thin film 41, an ultraviolet light emitting film 6, and a second
Of the phosphor thin film 42 and the second conductive film 8 are laminated in this order. The light emitting element 40 has a main surface 2b facing the outside of the transparent substrate 2 as a light emitting surface.

The first phosphor thin film 41 and the second phosphor thin film 42 correspond to the first insulating film 5 in the light emitting element 1 described above.
And has a function as a wavelength conversion film 9. That is, in the light emitting element 40, the first phosphor thin film 41 that converts the wavelength of ultraviolet light to emit visible light is provided between the pair of conductive films 4 and 8 of the ultraviolet light emitting EL element 10 and the ultraviolet light emitting film 6. And the second phosphor thin film 42 are formed.

As a material for forming the first phosphor thin film 41 and the second phosphor thin film 42, for example, Y ₂ O ₂ S: Eu, YVO ₄ : Eu or the like for emitting red light may be used. it can. In addition, Ba emits green light.
MgAl ₁₄ O ₂₃ : Eu, Z ₂ SiO ₄ : MnY ₂ SiO ₅ :
Tb, Ce, etc., or those emitting blue light
aMgAl ₁₄ O ₂₃ : Eu, Sr ₂ P ₂ O ₇ : Eu, ZnG
a ₂ O ₄ or the like can be used.

In the light emitting element 40, the second conductive film 8 does not need to have a light transmitting property.
It may be formed of various metal materials such as 1, Mo, W, Ti, Cr, and Ni. Since the second conductive film 8 is formed of such a metal material, the second conductive film 8 reflects the ultraviolet light radiated from the ultraviolet light emitting film 6 and transmitted through the second phosphor thin film 42, and again reflects the first conductive film 8. Phosphor thin film 41 and second
To the phosphor thin film 42. Further, the second conductive film is formed of a metal material, so that the second conductive film reflects visible light emitted from the first phosphor thin film 41 and the second phosphor thin film 42, and is directed toward the light emitting surface. Radiation in any direction.

The light emitting element 40 causes the ultraviolet light emitted from the ultraviolet light emitting film 6 to be incident on a first phosphor thin film 41 and a second phosphor thin film 42 formed around the ultraviolet light emitting film 6. The ultraviolet light is wavelength-converted into visible light by the first phosphor thin film 41 and the second phosphor thin film 42 and emitted from the light emitting surface. In addition, the light emitting element 40 reflects the ultraviolet light transmitted to the dielectric film 3 side without being absorbed by the first phosphor thin film 41 by the dielectric film 3, and the first phosphor thin film again. 41 and second phosphor thin film 4
2 can be incident.

The light emitting element 40 comprises a first phosphor thin film 41 and a second phosphor thin film 42 for converting the wavelength of ultraviolet light into visible light.
Is formed between the pair of conductive films 4 and 8,
Before the ultraviolet light passes through the first conductive film 4 or the second conductive film 8 and is attenuated, the ultraviolet light is converted into the first phosphor thin film 4.
It can be used as excitation energy for the first and second phosphor thin films 42. Therefore, since the light emitting element 4 can improve the utilization efficiency of ultraviolet light, the light emission luminance can be improved.

In the above description, the ultraviolet light-emitting EL element 10 is provided in the light-emitting element 1, the light-emitting element 20, the light-emitting element 30, and the light-emitting element 40 as the ultraviolet light-emitting elements that emit ultraviolet light. The invention is not limited to such a configuration. In the light emitting element described above, instead of the ultraviolet light emitting EL element 10 as the ultraviolet light emitting element,
For example, Japanese Patent Application Laid-Open Nos. 63-18319 and
No. 207786, etc.
S: an ultraviolet light emitting element using Gd as an ultraviolet light emitting film,
`` Japanese Journal of Applied Physics, Vol. 30, No.
10A, 1991, L1815 "as described in a ZnF _2:
An ultraviolet light emitting element using Gd as an ultraviolet light emitting film may be used.

Further, as an ultraviolet light emitting device, Japanese Unexamined Patent Publication No.
No. 53645, “Japanese Journal of Applied Ph
ysics, Vol. 37, 1998, L129 "and" Appl. Phys. Let
t., 67 (13), 1995, p1868 "and the like, or a group III nitride-based light emitting diode such as InAlGaN may be used.

In the present invention, the structure of the ultraviolet light emitting device is not limited, and any other conventionally used devices that emit ultraviolet light can be used as the ultraviolet light emitting device. .

Next, an image display device 50 as shown in FIGS. 9 and 10 will be described. The image display device 50 includes a dielectric film 52 on a transparent substrate 51 and first dielectric films 52 substantially parallel to each other.
Electrode 53, first insulating film 54, and ultraviolet light emitting film 55
And the second insulating film 56 is substantially orthogonal to the first electrode 54,
A plurality of second electrodes 57 substantially parallel to each other and a wavelength conversion film 59 are stacked in this order.

In the image display device 50, the first electrode 53, the first insulating film 54, the ultraviolet light emitting film 55,
The insulating film 56 and the second electrode 57 constitute an ultraviolet light emitting EL element 59. Further, the image display device 50 is configured as shown in FIG.
As shown in (1), an ultraviolet light emitting EL element 59 is formed at each intersection of the first electrode 53 and the second electrode 57, and a plurality of ultraviolet light emitting EL elements 59 are arranged in a matrix. .

Further, the image display device 50 includes a control unit 60
The control unit 60 is electrically connected to the first electrode 53 and the second electrode 57 by the first wiring 61 and the second wiring 62, respectively. Control unit 60
Controls the electric field applied between the first electrode 53 and the second electrode 57. Then, in the image display device 50, by applying an electric field between the first electrode 53 and the second electrode 57, each ultraviolet light emitting EL element 59 emits ultraviolet light, and the ultraviolet light is wavelength-converted. The film 58 converts the wavelength into visible light and emits the light outward from the transparent substrate 51. That is, in the image display device 50, the main surface 51a facing the outside of the transparent substrate 51 is used as the image display surface.

The image display device 50 comprises an ultraviolet light emitting EL element 5
By providing a plurality of 9 and arranging them in a matrix, one image can be displayed as a whole.

In FIG. 9, the dielectric film 52, the first insulating film 54, the second insulating film 56, and the wavelength conversion film 58
Are not shown, and a part of the second electrode 57 and the second wiring 62 is omitted.

The basic structure of the image display device 50 is substantially the same as that of the light emitting device 1 described above. That is, in the image display device 50, the transparent substrate 51, the dielectric film 52, the first electrode 53, the first insulating film 54,
The ultraviolet light emitting film 55, the second insulating film 56, and the second electrode 5
7, and the wavelength conversion film 58, respectively, the transparent substrate 2, the dielectric film 3, the first conductive film 4,
A first insulating film 5, an ultraviolet light emitting film 6, and a second insulating film 7
And the second conductive film 8 and the wavelength conversion film 9. Therefore, in the following description, description of the same or equivalent members as the light emitting element 1 will be omitted.

The first electrode 53 is formed in a strip shape by using the same material as the first conductive film 4 in the light emitting element 1.
A plurality of dielectric films are provided on the dielectric film 52 so as to be substantially parallel to each other. The first electrode 53 can be formed on the dielectric film 52 by various PVD methods typified by, for example, a vacuum evaporation method, a sputtering method, a reactive sputtering method, an ion plating method, and an electron beam evaporation method. it can.

The second electrode 57 is formed in a strip shape using the same material as the second conductive film 8 in the light emitting element 1.
The plurality of second insulating films 56 are provided so as to be substantially parallel to each other. The second electrode 57 can be formed by a method similar to that of the first electrode 53 described above.

As described above, the image display device 50 includes a plurality of first electrodes 53 substantially parallel to each other, and a plurality of second electrodes 57 substantially orthogonal to the first electrodes 53 and substantially parallel to each other. And Thereby, the image display device 50
Means a plurality of ultraviolet light emitting EL elements 5 arranged in a matrix
9 can be controlled independently.

The wavelength conversion film 58 is formed on the second electrode 57 in the form of a thin film using the same material as the wavelength conversion film 9 in the light emitting element 1. Further, in the image display device 50, the wavelength conversion film 58 sequentially arranges a material that emits red light, a material that emits green light, and a material that emits blue light for each column of the ultraviolet light-emitting EL elements 59 arranged in a matrix. It is a structure formed by the material to be used.

That is, in the image display device 50,
A basic unit of an image (hereinafter referred to as a pixel) is a set of three ultraviolet light emitting EL elements 59 each having a wavelength conversion film 58 formed of a material that emits red light, a material that emits green light, and a material that emits blue light. ).
In the image display device 50, each pixel can display multiple colors by adjusting the emission luminance of each color in each pixel.

The control section 60 is connected to the first electrode 53 and the second electrode 57 via the first wiring 61 and the second wiring 62, and emits light of each ultraviolet light emitting EL element 59. Have the function of individually controlling The image display device 50
By providing the control unit 60, a plurality of ultraviolet light emitting EL
By controlling the light emission of the elements 59, one image can be displayed as a whole.

Hereinafter, an example of a specific configuration of the control unit 60 will be described. Note that the control unit 60 is not limited to the example described below, and it is needless to say that the control unit 60 may have the above-described functions as appropriate.

The control section 60 includes, for example, a drive power supply and a control circuit. As shown in FIG. 11, the control circuit includes a control instruction unit, switching elements T1 to T4 that operate according to signals S1 to S4 from the control instruction unit, and a diode connected in parallel with switching elements T1 and T2. D
3 and D4, and diodes D3 and D4 connected in series with the switching elements T3 and T4.

In such a control circuit, the switching elements T1 and T3 and the diode D1 have one terminal connected to the driving power source, respectively.
2, T4 and diode D2 have one terminal grounded. The control circuit includes the other terminal of the switching element T1 and the diode D1 and the switching element T2
And the other terminal of the diode D2, and to the first electrode 53 of the ultraviolet light emitting EL element 59. The control circuit is connected to the terminals of the diodes D3 and D4 opposite to the terminals connected to the switching elements T3 and T4, respectively.
It is connected to the second electrode 57 of the element 59. The diodes D1 to D4 have a function of preventing backflow of charges from the ultraviolet light emitting EL element 59.

The switching element T1 connects the drive power supply to the first electrode 53 and applies a voltage to the first electrode 53 in accordance with the signal S1 from the control instruction section. The switching element T2 responds to a signal S2 from the control instruction unit.
The first electrode 53 is grounded. The switching element T3 is
In response to a signal S3 from the control instruction unit, the drive power supply is connected to the second electrode 57, and a voltage is applied to the second electrode 57. The switching element T4 grounds the second electrode 57 in response to the signal S4 from the control instruction unit.

The control unit 60 is configured, for example, as described above, and is provided between a predetermined first electrode 53 and a second electrode 57 among a plurality of first electrodes 53 and second electrodes 57. On the other hand, by applying a voltage or grounding, the light emission of the ultraviolet light emitting EL element 59 located at the intersection of the first electrode 53 and the second electrode 57 is controlled. The control unit 60 can individually control the light emission of each ultraviolet light emitting EL element 59 by selecting the first electrode 53 and the second electrode 57 and applying a voltage or grounding.

The image display device 50 constructed as described above
The control unit 60 controls the electric field applied to each of the plurality of ultraviolet light emitting EL elements 59 arranged in a matrix, so that each ultraviolet light emitting EL element 59 controls the emission of ultraviolet light. It becomes. Then, in the image display device 50, the ultraviolet light radiated from each ultraviolet light emitting EL element 59 is absorbed by the wavelength conversion film 58 and converted into visible light, and this visible light is converted to the main surface 51 a side of the transparent substrate 51. To Penetrate. Thereby, the image display device 50 displays one image as a whole.

In the image display device 50, similarly to the light emitting element 1, the dielectric film 52 is formed on the side opposite to the wavelength conversion film 58 with respect to the ultraviolet light emitting film 55, and reflects visible light by reflecting ultraviolet light. , The ultraviolet light emitted from the ultraviolet light-emitting film 55 can be effectively used as the excitation energy of the wavelength conversion film 58. Therefore, the image display device 50 can improve the luminance of the visible light emitted from the wavelength conversion film 58. In other words, the image display device 50 includes the dielectric film 52,
The brightness on the image display surface can be improved.

In the image display device 50, similarly to the light emitting element 1, the wavelength conversion film 58 converts the wavelength of the incident ultraviolet light into visible light, and reflects the visible light in the incident direction of the ultraviolet light. Since it is configured to emit light, it is a so-called reflection type image display device. Therefore, the image display device 50 has high luminous efficiency similarly to the light emitting element 1, and particularly has high visible light extraction efficiency.

In the image display device 50, the ultraviolet light emitting film 55 has a trapezoidal cross section,
It is desirable that the side on which 2 is located be formed wide. As a result, the image display device 50
Similarly to the above, the ultraviolet light emitted from the end of the ultraviolet light emitting film 55 can be made incident on the wavelength conversion film 58, and the utilization efficiency of the ultraviolet light can be improved. Therefore, in the image display device 50, the luminance on the image display surface is further improved.

In the above description, the image display device 50 includes the ultraviolet light emitting EL element 59 as the ultraviolet light emitting element that emits ultraviolet light. However, the present invention is not limited to such a configuration, and As in the case of the light emitting element 1,
Various ultraviolet light emitting elements may be used.

The image display device 50 includes a transparent substrate 51.
The dielectric film 52, the first electrode 53, the first insulating film 54, the ultraviolet light emitting film 55, the second insulating film 56, the second electrode 57, and the wavelength conversion film 59 Are formed in this order, but the present invention is not limited to such a configuration. The image display device according to the present invention is arranged in a matrix, a plurality of ultraviolet light emitting elements that emit ultraviolet light with an ultraviolet light emitting film between each pair of electrodes, and reflects visible light to emit visible light. What is necessary is to provide a transparent dielectric film and a wavelength conversion film that emits visible light by converting the wavelength of ultraviolet light, and these may be formed by laminating them. Specifically, for example, the light emitting element 20, the light emitting element 30, the light emitting element 40, and the like may have a stacked structure similar to that described above, and the ultraviolet light emitting elements 10 may be arranged in a matrix.

The image display device 50 may be configured without the control unit 60. In this case, the image display device 50
The operation of the ultraviolet light emitting EL element 59 may be controlled by a control unit provided in other various devices.

Further, the image display device 50 includes the first electrode 5
The 3 and the second electrode 57 need not have a so-called simple matrix structure. In the image display device 50, for example, the first electrode 53 and the second electrode 57 of each ultraviolet light emitting EL element 59 may be formed in an arbitrary electrode pattern.

[0098]

Embodiment 1 First Embodiment Hereinafter, an embodiment in which a first light emitting element is manufactured based on the light emitting element 1 described above will be described.

First, a quartz glass transparent substrate was prepared,
The transparent substrate was subjected to ultrasonic cleaning with a neutral detergent and an organic solvent. Next, a dielectric film was formed on the transparent substrate by an RF magnetron sputtering method. In this film forming step, the design center wavelength λ of the ultraviolet light reflection is set to 31.
4 nm, the high refractive index layer is made of MgO (refractive index n (H) =
1.80), the low-refractive-index layer is made of SiO ₂ (refractive index n (L) =
1.46). The high-refractive-index layer and the low-refractive-index layer each have a thickness of n (H) · λ / 4, n
(L) A film was formed to have a thickness of λ / 4, and six layers were laminated.

Therefore, the dielectric film has a high refractive index layer and a low refractive index layer alternately laminated, and has a laminated structure of 12 layers in total. When the reflectance of the dielectric film was measured, it was confirmed that the dielectric film exhibited optical characteristics as shown in FIG. As can be seen from FIG. 12, it was confirmed that the dielectric film reflects at least 90% of ultraviolet light having a wavelength of 314 nm and transmits at least 95% of visible light over almost the entire region.

Next, a first conductive film having a thickness of 100 nm was formed on the dielectric film using indium tin oxide (ITO) by RF magnetron sputtering. Next, on the first conductive film, a first insulating film having a thickness of 30 was formed using SiO ₂ as a material by RF magnetron sputtering.
A film was formed at 0 nm.

Next, an ultraviolet light emitting film having a thickness of 500 nm was formed on the first insulating film by RF magnetron sputtering. In the step of forming the ultraviolet light emitting film, Gd
Sputtering was performed using a Zn ₂ SiO ₄ target on which a metal chip was mounted, and an ultraviolet light-emitting film in which Gd ³⁺ was added as a light-emitting center was formed in a base material formed of Zn ₂ SiO ₄ .

In this film forming step, Ar is used as the discharge gas, but a mixed gas of Ar and O ₂ may be used. In this film forming step, by using a mixed gas of Ar and O ₂ , the ultraviolet light emitting film can be easily formed based on the stoichiometric composition. In order to achieve this, it is important to increase the amount of charge transfer by forming a film containing some oxygen vacancies. In this embodiment, oxygen deficiency is intentionally introduced into the ultraviolet light emitting film by using only Ar as a discharge gas, and the composition of the base material is Zn ₂ SiO _4-y (0 <y
<1).

Further, in this film forming step, an ultraviolet light emitting film is formed while the substrate is heated to 400 ° C., and after the film is formed, an infrared lamp light at 650 ° C. is irradiated in vacuum for 5 minutes to perform an annealing treatment. Was given. It has been confirmed by X-ray diffraction that the annealing of the ultraviolet light emitting film improves the crystallinity of the ultraviolet light emitting film. Further, by performing an annealing process on the ultraviolet light emitting film, the band gap energy of the base material is reduced at both ends of the energy distribution, and the ultraviolet transmittance is improved.

Next, the ultraviolet light emitting film was shaped into a substantially trapezoidal trapezoid. In this shaping step, first, a mask pattern having a square opening on the ultraviolet light emitting film is used, and Si ₃ N ₄
Was used as a material to form a 500-nm-thick square etching mask. Next, isotropic etching was performed by a reactive ion etching method (RIE method), and the end of the ultraviolet light emitting film was shaped so as to have a taper angle around the etching mask. Thereafter, by removing the etching mask, the cross-sectional shape of the ultraviolet light emitting film was finally shaped into a trapezoidal shape.

Next, on the ultraviolet light emitting film, a second insulating film was formed in a thickness of 300 nm from SiO _{2 in} the same manner as the above-mentioned first insulating film. Next, a second conductive film having a thickness of 100 nm is formed on the second insulating film using indium tin oxide (ITO) as a material in the same manner as the first conductive film.
Was formed. This second conductive film was formed in the same size as the ultraviolet light-emitting film and directly above the ultraviolet light-emitting film using a mask pattern having a square opening, as in the case of shaping the ultraviolet light-emitting film. .

Next, a first conductive film, a first insulating film,
For an ultraviolet light emitting EL element composed of an ultraviolet light emitting film, a second insulating film, and a second conductive film, an AC voltage having a driving waveform of a sine wave of 1 kHz is applied to the first conductive film and the second conductive film. And the EL emission spectrum thereof was measured.
As a result, under an applied voltage of 300 V, a strong emission peak was observed at a wavelength of 314 nm as shown in FIG.

Next, a wavelength conversion film was formed on the second insulating film. The wavelength conversion film was formed by dissolving polyvinyl alcohol as a binder in water and dispersing a surfactant and a fluorescent material to a thickness of 100 μm by a coating method, and dried at about 110 ° C. As the surfactant, for example, sodium polysterenesulfonate such as Polyty PS-1900 manufactured by Lion Corporation was used. As the fluorescent material, ZnS: Cu, Al, which is a phosphor powder that emits green light, was used. The fluorescent material used had an average particle size of 2 μm.

In the step of forming the wavelength conversion film, in addition to the above-described combination, for example, polycarbonate as a binder is dissolved in methyl ethyl ketone, and sodium sulfosuccinate di-2-ethylhexyl ester sodium salt is used as a surfactant. Is also good. In this case, about 9
Dry at 0 ° C.

An AC voltage showing a 1 kHz sine wave was applied between the first conductive film and the second conductive film of the ultraviolet light emitting EL device to the first light emitting device manufactured as described above.
As a result, it was confirmed that the first light-emitting element emitted green light having a center wavelength of 530 nm.

The light emission luminance of each of the first light emitting element and a light emitting element manufactured without forming a dielectric film was measured under an applied voltage of 250 V. As a result, the first light-emitting element showed about four times the emission luminance as compared to a light-emitting element manufactured without forming a dielectric film. This is because the first light emitting element has a dielectric film,
It is considered that ultraviolet light emitted from the ultraviolet light emitting film to the dielectric film side was reflected by the dielectric film toward the wavelength conversion film. Therefore, it can be seen that in the first light emitting element, the visible light emitted from the ultraviolet light emitting film is efficiently incident on the wavelength conversion film.

Further, the light emission luminance of each of the first light emitting element and the light emitting element manufactured without shaping the cross-sectional shape of the ultraviolet light emitting film into a trapezoid was measured under an applied voltage of 250 V. . As a result, the first light-emitting element exhibited about twice the luminance of the light-emitting element manufactured without shaping the cross-sectional shape of the ultraviolet light-emitting film into a trapezoidal shape. This is because the ultraviolet light emitting film of the first light emitting element is shaped so that its cross-sectional shape becomes trapezoidal, so that ultraviolet light radiated from the end of the ultraviolet light emitting film is directed toward the dielectric film. It is considered that the light was reflected and, as a result, was efficiently incident on the wavelength conversion film.

<Second Embodiment> Next, an embodiment in which a second light emitting element is manufactured based on the above-described light emitting element 40 will be described. The second light emitting element includes a first phosphor thin film and a second phosphor film instead of the first insulation film and the second insulation film.
Is different from the above-described first light-emitting element in that the phosphor thin film is formed without the wavelength conversion film.

First, a transparent substrate made of quartz glass was prepared.
The transparent substrate was subjected to ultrasonic cleaning with a neutral detergent and an organic solvent. Next, a dielectric film and a first conductive film were formed on the transparent substrate in the same manner as in the first example.

Next, a first phosphor thin film was formed on the first conductive film. In this film forming step, Y ₂ O ₂ S: E
A first phosphor thin film was formed to a thickness of 300 nm by RF magnetron sputtering using a sintered target of u. Y ₂ O ₂ S: Eu is generally used as a red light emitting phosphor of a CRT display. In this film forming step, a film can be formed using other various sintered body targets, and, for example, EB can be used instead of the RF magnetron sputtering method.
It can be formed by various thin film forming techniques such as a vapor deposition method.

Next, an ultraviolet light emitting film was formed on the first phosphor thin film in the same manner as in the first embodiment. Next, a second phosphor thin film was formed on the ultraviolet light-emitting film in the same manner as the first phosphor thin film so as to have a thickness of 300 nm. Next, a second conductive film was formed on the second phosphor thin film using Al as a material to a thickness of 100 nm. Second
In the same manner as in the first embodiment, the conductive film having the same size as the ultraviolet light emitting film using a square mask pattern,
Further, it was formed immediately above the ultraviolet light emitting film.

The second light emitting device manufactured as described above,
The light emission luminance of each of the light emitting devices having the conventional structure manufactured without forming the dielectric film was measured under an applied voltage of 250 V. As a result, the second light-emitting element exhibited approximately four times the luminance of the light-emitting element manufactured without forming a dielectric film. This is because, since the second light emitting element includes the dielectric film, the ultraviolet light emitted from the ultraviolet light emitting film and transmitted without being absorbed by the first phosphor thin film is reflected by the dielectric film. It is considered that this is because the light was again incident on the first phosphor thin film and the second phosphor thin film. Therefore, it is understood that the second light emitting element can efficiently use the ultraviolet light emitted from the ultraviolet light emitting EL element as the excitation energy of the wavelength conversion film.

<Third Embodiment> Next, an embodiment in which an image display device is manufactured based on the above-described image display device 50 will be described. First, a transparent substrate made of synthetic quartz glass was prepared, and this substrate was subjected to ultrasonic cleaning with a neutral detergent, an organic solvent, and the like. Next, as in the first embodiment, a dielectric film was formed on the entire surface of the transparent substrate.

Next, a striped resist pattern was formed on the dielectric film by using a positive photoresist for i-line exposure. Thereafter, an indium tin oxide (ITO) thin film was formed into a thin film by an RF magnetron sputtering method. Then, the resist pattern was removed by ultrasonic cleaning using an organic solvent such as acetone to form a striped electrode pattern. Indium tin oxide (I
The TO) thin film is formed into this striped electrode pattern, and finally becomes the first electrode.

Next, in the same manner as in the first embodiment, a first insulating film, an ultraviolet light emitting film, and a second insulating film were formed on the first electrode. At this time, the first insulating film and the second insulating film are formed over the entire surface on which the first insulating film and the second insulating film are formed, and the ultraviolet light emitting film is formed at an intersection between the first electrode and a second electrode described later. , And a plurality of independent ultraviolet light-emitting films were formed in a matrix. Next, similarly to the first electrode, a second electrode was formed of indium tin oxide (ITO) in a striped electrode pattern so as to be orthogonal to the first electrode. Thereby, the first electrode and the second electrode
UV light emitting EL elements are formed at the intersections with the electrodes.

Next, on the second insulating film on which the second electrode was formed, a wavelength conversion film was formed at a position corresponding to the intersection between the first electrode and the second electrode. The wavelength conversion film was formed by dissolving polyvinyl alcohol in water as a binder and dispersing a surfactant and a fluorescent material using a pattern mask.

As a fluorescent material, ZnS: Ag,
Al, ZnS: Cu, Al, Y ₂ O ₂ S: Eu were used.
The fluorescent material used had an average particle size of 2 μm. As the surfactant, for example, sodium polystyrene sulfonate was used in the same manner as in the first example.

A control unit similar to the control unit 60 described above was connected to the image display device manufactured as described above. In this image display device, by applying a voltage to a desired first electrode and a desired second electrode, the first
Ultraviolet light emitting EL located at the intersection of the first electrode and the second electrode
It was confirmed that the device emitted ultraviolet light, whereby the wavelength conversion film emitted visible light.

It has been confirmed that the image display device can display one color image as a whole by controlling the drive voltage and timing for emitting light from each pixel by the control unit.

[0125]

As described above, the light emitting device according to the present invention includes the dielectric film that reflects ultraviolet light and transmits visible light, and this dielectric film has a wavelength conversion function with respect to the ultraviolet light emitting film. It is formed on the opposite side of the film. Therefore, the light emitting element
Ultraviolet light emitted from the ultraviolet light emitting film can be reflected by the dielectric film and incident on the wavelength conversion film. Thereby, the light emitting element can improve the utilization efficiency of ultraviolet light, and can improve the emission luminance of visible light emitted from the wavelength conversion film. That is, the light emitting element is
The emission luminance can be improved without increasing the power consumption.

Further, the image display device according to the present invention includes a dielectric film that reflects ultraviolet light and transmits visible light, and the dielectric film is formed on the side opposite to the wavelength conversion film with respect to the ultraviolet light emitting film. At the same time, the ultraviolet light emitting elements are arranged in a matrix. Therefore, the image display device can reflect the ultraviolet light emitted from the ultraviolet light emitting film by the dielectric film and make the ultraviolet light incident on the wavelength conversion film. Thereby, the image display device can improve the utilization efficiency of ultraviolet light, and can improve the emission luminance of visible light emitted from the wavelength conversion film. That is, the image display device can display a high-luminance image without increasing power consumption.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a light emitting device according to the present invention.

FIG. 2 is a cross-sectional view illustrating an optical path of ultraviolet light and visible light in the light emitting device.

FIG. 3 is a three-side view showing an ultraviolet light emitting film of the light emitting device.

FIG. 4 is a cross-sectional view illustrating an optical path of ultraviolet light in the light emitting device.

FIG. 5 is a three-view drawing showing another ultraviolet light emitting film of the light emitting device.

FIG. 6 is a cross-sectional view showing another light emitting device according to the present invention.

FIG. 7 is a cross-sectional view showing another light emitting device according to the present invention.

FIG. 8 is a cross-sectional view showing another light emitting device according to the present invention.

FIG. 9 is a plan view showing an image display device according to the present invention.

FIG. 10 is a sectional view showing the image display device.

FIG. 11 is a circuit diagram showing a control unit in the image display device.

FIG. 12 is a diagram showing the reflectance of a dielectric film in a light emitting device according to an example of the present invention.

FIG. 13 is a view showing EL emission intensity of an ultraviolet light emitting film in the light emitting device.

[Explanation of symbols]

Reference Signs List 1 light emitting element, 2 transparent substrate, 3 dielectric film, 4 first
5, a first insulating film, 6 an ultraviolet light emitting film, 7 a second insulating film, 8 a second conductive film, 9 a wavelength conversion film, 10
UV light emitting EL device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H05B 33/14 H05B 33/14 Z 33/24 33/24 F term (reference) 2H048 FA05 FA09 FA18 FA22 GA07 GA12 GA24 GA33 GA61 3K007 AB02 AB03 AB04 BA06 BB00 BB06 CA01 CA02 CB01 DA02 DA05 DB01 DB02 DC02 DC04 EA04 EC01 EC02 EC03 EC04 FA01 FA03 5C094 AA10 BA29 DA13 ED20 FB16 HA08

Claims (10)

[Claims] 1. An ultraviolet light-emitting element that emits ultraviolet light by providing an ultraviolet light-emitting film between a pair of conductive films, a dielectric film that reflects ultraviolet light and transmits visible light, A wavelength conversion film that converts and emits visible light, and is formed by laminating them, and the dielectric film is formed on the side opposite to the wavelength conversion film with respect to the ultraviolet light emitting film, A light emitting device, wherein the ultraviolet light incident from the ultraviolet light emitting film is reflected and made incident on the wavelength conversion film. 2. The light emitting device according to claim 1, wherein the dielectric film has a multilayer structure in which a high refractive index layer and a low refractive index layer are stacked for one or more periods. 3. The light emitting device according to claim 1, wherein the ultraviolet light emitting film has a trapezoidal cross-sectional shape, and has a wider side on which the dielectric film is located. 4. The light emitting device according to claim 1, wherein the wavelength conversion film is provided between the pair of conductive films. 5. The light-emitting element according to claim 1, wherein at least one of the pair of conductive films has a light-transmitting property. 6. A plurality of ultraviolet light emitting elements which are arranged in a matrix and each have an ultraviolet light emitting film between a pair of electrodes and emit ultraviolet light, and a dielectric film which reflects ultraviolet light and transmits visible light. And a wavelength conversion film that converts the wavelength of ultraviolet light to emit visible light, and is formed by laminating them. The dielectric film is on the opposite side of the ultraviolet light emitting film from the wavelength conversion film. An image display device, wherein the ultraviolet light incident from each of the ultraviolet light emitting films is reflected and made incident on the wavelength conversion film. 7. A pair of electrodes, comprising: a plurality of first electrodes substantially parallel to each other; and a plurality of second electrodes substantially orthogonal to the first electrodes and substantially parallel to each other. The image display device according to claim 6. 8. The image display device according to claim 6, wherein the dielectric film has a multilayer structure in which a high refractive index layer and a low refractive index layer are stacked for one or more periods. 9. The image display device according to claim 6, wherein the ultraviolet light emitting film has a trapezoidal cross-sectional shape, and has a wide side on which the dielectric film is located. 10. The image display device according to claim 6, wherein at least one of the pair of conductive films has a light transmitting property.