JP2004179157A - Light emitting element, light emitting element manufacturing method, and plasma display panel manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element restricted in the occurrence of deterioration of light emitting luminance with the lapse of time. <P>SOLUTION: This light emitting element obtains the visible light from the ultraviolet rays generated by discharge in the discharging medium containing the rare gas. A phosphor layer 115b exists inside a container sealed with the discharging medium, and the light emitting element exists in an area, to which the ultraviolet rays and the light emitted from the phosphor arrive, inside the container, and has an optical catalyst 200 to be exposed with the discharging medium. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a light emitting device, and more particularly to a technique for suppressing a temporal decrease in luminance of a light emitting device such as a plasma display panel (hereinafter, referred to as “PDP”) or an electrodeless discharge lamp.

2. Description of the Related Art In recent years, among display devices used for computers, televisions, and the like, PDPs have been attracting attention as display devices that are large, thin, and lightweight.
This PDP is a display device that realizes a color display by irradiating a phosphor (red, green, blue) with ultraviolet rays generated by plasma discharge in a gas.

FIG. 8 is a schematic diagram of a general AC type (AC type) PDP 100.
The PDP 100 is composed of a front plate 90 and a back plate 91 disposed with their main surfaces facing each other, and in an overlapped state, its outer peripheral edge is fused and sealed by a sealing glass 190, A discharge space 116 is formed inside.
The front plate 90 includes a front glass substrate 101, a display electrode 102, a dielectric layer 106, and a protective layer 107.

The front glass substrate 101 is a material serving as a base of the front plate 90, and the display electrodes 102 are formed on the front glass substrate 101.
The display electrode 102 and the front glass substrate 101 are further covered with a dielectric layer 106 and a protective layer 107 made of magnesium oxide (MgO).
The rear plate 91 is formed on a wall surface of a rear glass substrate 111, an address electrode 112, a dielectric layer 113, a partition 114, and a gap between adjacent partitions 114 (hereinafter, referred to as "partition groove"). It is composed of phosphor layers 115r, g, and b corresponding to each color of red, green, and blue.

The discharge space 116 is filled with a discharge gas composed of a rare gas component such as He, Xe, and Ne.
A region where a pair of adjacent display electrodes 102 and one address electrode 112 intersect with a discharge space 116 interposed therebetween is a cell that contributes to image display.
In the discharge space 116, vacuum ultraviolet rays are generated with the discharge, and the phosphor layers 115r, g, and b corresponding to each color of red, green, and blue emit and emit light, thereby performing color display.

At the time of manufacturing the PDP 100, in order to remove the impurity gas, a process for bonding the front plate 90 and the back plate 91 with a glass frit and a sealing process for sealing the inside of the PDP 100 are usually performed as shown in FIG. As shown in FIG. 9, an impurity gas removing step of removing the impurity gas by exhausting the internal gas while heating the entire PDP 100 is performed.
JP-A-2001-35372

However, there is a limit to completely removing the impurity gas in this step.
Most of the members provided inside the PDP 100 are formed by applying a mixture of a base material and a paste-like organic substance (hereinafter, referred to as “organic paste”) and then baking the mixture. This removes most of the impurity gas, but it is difficult to completely remove the impurity gas.

Therefore, even if the impurity gas is sufficiently removed over time in the above-described impurity gas removing step, a new impurity gas may be released from the member over time.
Therefore, an impurity gas inside the PDP 100, for example, an impurity gas such as a hydrocarbon or carbon monoxide, undergoes a chemical reaction that changes into a solid carbide or the like due to discharge generated inside the cell, and the carbide scatters inside the PDP 100. Then, it adheres to the inner wall surface, for example, the surface of the phosphor layer or the inside of the front plate 90.

When the carbide adheres to the surface of the phosphor layer, the inside of the front plate 90, or the like, the transmittance of light on the surface of the phosphor layer decreases, and the transmittance of the front plate 90 also decreases. There is a problem that light emission luminance is reduced.
Also, in an electrodeless discharge lamp that excites a metal atom in a rare gas by electromagnetic induction to generate ultraviolet light, and irradiates the ultraviolet light to the fluorescent material to cause the fluorescent material to emit light and obtain visible light, the above-described PDP also has Similarly, there is a problem that carbide is precipitated from the impurity gas in the rare gas with time and adheres to the inner wall, thereby lowering the emission luminance.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a light-emitting element in which a light-emitting luminance does not easily decrease over time.
Another object of the present invention is to provide a method for manufacturing the light emitting device, particularly, a PDP.

To achieve the above object, the present invention has the following features.
(1). A light-emitting element that obtains visible light from ultraviolet light caused by discharge in a discharge medium containing a rare gas, wherein a phosphor is present in a container that seals the discharge medium, and the ultraviolet light in the container. Alternatively, there is a photocatalyst exposed to the discharge medium in a first region where the emission light of the phosphor reaches.

The photocatalyst exerts a self-cleaning action mainly by ultraviolet rays accompanying the discharge, thereby suppressing the adhesion of solids such as carbides in the discharge vessel, particularly around the phosphor.
That is, the photocatalyst oxidatively decomposes impurity gases such as hydrocarbons and oxidatively decomposes precipitated carbides.
That is, since the amount of precipitates such as carbides that block ultraviolet rays applied to the phosphor and visible light emitted from the phosphor is reduced, a decrease in emission luminance is suppressed.
(2). The light emitting device according to the above (1) is a plasma display panel, wherein the container is formed by sealing outer edges of a first substrate and a second substrate facing each other, and the first substrate is formed. On the top, a plurality of partitions are formed, and the phosphor forms a phosphor layer disposed on a wall surface of a second region sandwiched between adjacent partitions, and the photocatalyst includes the It exists in two regions.

Since the photocatalyst and the phosphor are present in the same region, when carbide is attached to the phosphor surface, the carbide is more easily decomposed, and the effect of lowering the emission luminance is improved.
(3). The photocatalyst according to the above (2) is dispersed in the phosphor layer.
Since the photocatalyst and the phosphor are present in a mixed state, when carbide is attached to the phosphor surface, the carbide is easily decomposed.
(4). The phosphor layer according to the above (2) has a porous structure through which the discharge medium can flow, and the photocatalyst is laminated on the surface of the phosphor layer on the first substrate side.
(5). The phosphor layer according to (2) has a porous structure through which the discharge medium can flow, and the photocatalyst is stacked on the partition wall side of the phosphor layer.

Normally, the phosphor layer is present in the second region sandwiched by the partition walls, but the above structure allows the carbide to be decomposed without inhibiting light emission from the phosphor layer.
(6). The photocatalyst according to the above (2) exists at the top of the partition wall or in the vicinity thereof.
In general, a phosphor layer is not provided on the top of the partition wall. Therefore, by providing a photocatalyst in such a location, the decomposition of the carbide can be substantially prevented without substantially inhibiting light emission from the phosphor layer. Is carried out.
(7). The phosphor layer according to the above (3), (4), (5) or (6) is divided into three types of emitting red, green and blue light by absorbing ultraviolet light, and the photocatalyst is The blue wavelength band in the visible light region has an absorption edge, and is unevenly distributed in the vicinity where the phosphor layer that emits blue light exists.

Since blue has low visibility, the decrease in emission intensity is particularly noticeable, and there is a demand to suppress the decrease in emission intensity in the blue phosphor layer as much as possible.
By setting the absorption end of the photocatalyst in the blue wavelength band and shortening the distance between the blue light source and the photocatalyst, the self-cleaning action of the photocatalyst is further promoted, and the above requirement can be satisfied.
(8). The phosphor layer formed between the partition walls according to (3), (4), (5) or (6) emits red, green, and blue light, respectively, by absorbing ultraviolet light. The photocatalyst is divided into at least two types having absorption wavelengths in different wavelength bands, and the type is determined according to the type of the phosphor present in the vicinity of the place where the photocatalyst is disposed. .

Thereby, by setting the absorption end of the photocatalyst to the wavelength band of the emission light of the phosphor existing near the disposition position, the light emitted from the phosphor of each color can be efficiently used. The self-cleaning action is further promoted.
(9). The photocatalyst described in the above (3), (4), (5) or (6) exists in all of the second regions sandwiched between adjacent partitions.

With the above configuration, the amount of the existing photocatalyst can be increased, and the self-cleaning action of the photocatalyst is further promoted.
(10). The photocatalyst according to the above (3), (4), (5) or (6) contains TiO ₂ of anatase type as a main component.
Anatase-type TiO ₂ is suitable as a photocatalyst used in the present invention.

In addition, since anatase-type TiO ₂ is inexpensive and easily available, it is possible to suppress the decrease in the luminescence intensity over time at low cost.
(11). The photocatalyst according to the above (10) has an absorption edge in a visible light region.
The distance between the phosphor layer, which is a light source of light having a visible light wavelength band corresponding to the absorption edge of the photocatalyst, and the photocatalyst can be shortened. Normally, TiO ₂ exhibits a self-cleaning action by ultraviolet rays. According to the method, since the visible light from the phosphor layer is also used, the self-cleaning action of the photocatalyst is further promoted.
(12). The light emitting device according to the above (1) is a plasma display panel, wherein the container has a first substrate and a second substrate facing each other, and their outer edges are sealed in a state where the first substrate and the second substrate are opposed to each other. The phosphor exists outside the image display area where the phosphor exists.

Due to the convection of the discharge gas in the container, the gas self-purified by the photocatalyst existing outside the image display region spreads also in the image display region, so that the effect of suppressing a decrease in light emission luminance is exhibited.
(13). The photocatalyst according to the above (12) is disposed near the outer edge.
In the vicinity of the outer edge, a flat portion is usually provided for sealing, and a photocatalyst is easily provided by printing or coating.

In order to achieve the second object, the present invention has the following features.
(14). What is claimed is: 1. A method for producing a light-emitting element for obtaining visible light from ultraviolet light caused by discharge in a discharge medium containing a rare gas, wherein a phosphor layer is formed by mixing phosphor particles and a photocatalyst to form a precursor of the phosphor layer. A precursor forming step, a precursor arranging step of arranging the precursor in a region where the ultraviolet rays reach, and in contact with the discharge medium, and baking the precursor to form the phosphor layer Phosphor layer forming step.

Thereby, after mixing the phosphor particles and the photocatalyst, the photocatalyst included in the phosphor precursor is also disposed along with the disposition of the phosphor precursor, so that the exclusive photocatalyst is disposed. A photocatalyst that exhibits a self-cleaning action is provided in the region without providing a step.
(15). A method for manufacturing a light-emitting element that obtains visible light from ultraviolet light caused by discharge in a discharge medium containing a rare gas, wherein a phosphor is provided in a region where the ultraviolet light reaches, and A photocatalyst arranging step of arranging a photocatalyst in a region where the light emitted from the phosphor reaches and comes into contact with the discharge medium.

Thus, a photocatalyst that exerts a self-cleaning action is provided in the region.
(16). The photocatalyst according to the above (14) or (15) is subjected to a nitriding treatment to adjust an absorption edge.
By performing the nitriding treatment and adjusting the absorption edge to a predetermined wavelength, the light irradiated on the photocatalyst can be efficiently used and the catalytic action can be exhibited, so that the self-cleaning action is efficiently exhibited.
(17). A method for manufacturing a plasma display panel in which a first substrate provided with a plurality of partition walls and a second substrate are sealed with their outer edges sealed in opposition to each other, wherein a phosphor particle and a photocatalyst are mixed. A phosphor mixing step of forming a mixture by forming the mixture on a wall surface of a region sandwiched between adjacent partitions on the first substrate to form a precursor of a phosphor layer And a phosphor layer forming step of firing the precursor to form the phosphor layer.

Thereby, after mixing the phosphor particles and the photocatalyst, the photocatalyst included in the phosphor precursor is also disposed along with the disposition of the phosphor precursor, so that the exclusive photocatalyst is disposed. A photocatalyst that exhibits a self-cleaning action is provided in the region without providing a step.
(18). A method for manufacturing a plasma display panel in which a first substrate provided with a plurality of partition walls and a second substrate are sealed with their outer edges sealed in a state where the first substrate and the second substrate face each other, wherein a phosphor is provided in a region where ultraviolet rays reach. Arranging a phosphor, and a photocatalyst arranging in the first substrate or the second substrate in a region where the ultraviolet light or the emission light of the phosphor reaches and comes into contact with the discharge medium. Setting step.

Thus, a photocatalyst that exerts a self-cleaning action is provided in the region.
(19). The photocatalyst according to the above (17) or (18) has been subjected to a nitriding treatment.
By performing a nitriding treatment and adjusting the absorption edge to a predetermined wavelength according to the wavelength of the light irradiated to the photocatalyst, the self-cleaning action can be efficiently exhibited.

  In the PDP according to the present invention, the photocatalyst is present in the phosphor layer or in the vicinity where the phosphor layer is provided, thereby decomposing carbides by the oxygen activating action of the photocatalyst while maintaining the same light emission intensity as before. Thus, it is possible to suppress the deposition of carbide on the wall surface inside the PDP including the phosphor surface.

<Embodiment>
<Structure>
Hereinafter, the PDP 195 according to the present embodiment will be described.
The PDP 195 is an AC-type plasma display panel in which the luminance does not easily decrease with time.

This PDP 195 differs from the conventional PDP 100 in the structure of the back substrate.
More specifically, in the PDP 195, the photocatalyst 200 is interposed between the dielectric layer 113 on which the phosphor layers 115r, g, and b are stacked, and the phosphor layers 115r, g, and b.
FIG. 1 is a schematic diagram of the PDP 195 in the present embodiment.
In PDP 195, the outer periphery of front plate 90 and back plate 92 arranged with their main surfaces facing each other is fused and sealed by sealing glass 190 to form an envelope. A discharge space 116 is formed inside the container.

The front plate 90 has a display electrode 102 and a dielectric layer 106 laminated on a front glass substrate 101 similarly to the conventional PDP 100, and is further covered with a protective layer 107 made of magnesium oxide (MgO).
The display electrode 102 includes a transparent electrode 103, a black electrode film 104, and a bus electrode 105.

The black electrode film 104 plays a role of preventing reflection of external light when viewed from the glass surface side because the main component ruthenium oxide is black.
Further, since the bus electrode 105 contains silver having high conductivity as a main component, it plays a role of lowering the overall resistance value.
Here, for convenience, the combination of the black electrode film 104 and the bus electrode 105 is referred to as a multilayer electrode 309.

The multilayer electrode 309 has, at one end in the longitudinal direction, a rectangular terminal portion 108 whose electrode width is locally enlarged as an interface for connecting to a drive circuit.
As shown in FIG. 2, the back plate 92 is formed on the back glass substrate 111, the address electrode 112, the dielectric layer 113, the partition 114, and the wall surface of the partition groove formed between the partition 114. The phosphor layers 115r, g, and b corresponding to the red, green, and blue colors, respectively, and the photocatalyst 200.

Like the PDP 100, the discharge space 116 is filled with a discharge gas (filled gas) composed of a rare gas component such as He, Xe, or Ne at a pressure of about 500 to 600 Torr (66.5 to 79.8 kPa). A region where a pair of adjacent display electrodes 102 and one address electrode 112 intersect with a discharge space 116 interposed therebetween is a cell that contributes to image display.
In the discharge space 116, vacuum ultraviolet rays (mainly at a wavelength of 147 nm) are generated with the discharge, and the phosphor layers 115r, g, and b corresponding to the red, green, and blue colors emit and emit light, thereby providing color display. Is done.

In the photocatalyst 200, the photocatalyst is formed in a layer shape (with a film thickness of 0.1 μm to 20 μm) on the wall surface between the adjacent partition walls 114, that is, on the side surfaces of the dielectric layer 113 and the partition walls 114.
The photocatalyst is a material exhibiting a so-called self-cleaning action that acts as an oxidation catalyst when irradiated with light to oxidize and decompose impurities. In the present embodiment, for example, anatase-type TiO ₂ (dielectric constant: 15 to 15) 70).

This anatase-type TiO ₂ has a strong oxygen activating power (hereinafter referred to as “active power”), and has a property of generating active oxygen with an absorption edge in a wavelength band of an ultraviolet region or a blue wavelength band. .
In addition, TiO ₂ is known to have rutile type, brookite type, and the like. However, from the results of the evaluation test described below, TiO ₂ has a low activity and hardly achieves the intended effect. Cannot use rutile-type or brookite-type TiO ₂ as a photocatalyst.

The photocatalyst, by its oxidizing action, prevents impurities such as hydrocarbons contained in the discharge medium from being precipitated as solid carbides, and oxidizes the precipitated carbides to chemically change them into gaseous COx, Oxidative decomposition of carbides deposited on the surface of the phosphor layer.
That is, the solid carbide that blocks light becomes a component of the transparent gas, and a decrease in the emission luminance of the PDP is suppressed.

In order to generate active oxygen in this way, it is necessary that the conduction band position on the band model is above the hydrogen generation potential and the upper end of the valence band is below the oxygen generation potential.
The material used for the photocatalyst satisfies at least the above conditions. More specifically, in addition to anatase-type TiO ₂ , SrTiO ₃ , ZnO, SiC, GaP, CdS, CdSe, MoS _3, etc. An example is given below.

In addition, when the particles are formed into fine particles, the position of the conduction band moves upward. Therefore, if the particles are about 1 to 10 nm, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Bi ₂ O _{3, and the} like can also generate active oxygen. Such a material is also included in the category of the photocatalyst.
In addition, the photocatalyst 200 has a higher reflectance value than the phosphor layers 115r, g, and b, and reflects light emitted from the phosphor layer stacked thereover to the front plate 90 side to increase the light emission efficiency. I have.

The respective phosphor layers 115r, g, and b corresponding to red, green, and blue are stacked on the photocatalyst 200.
As shown in FIG. 2, each of these phosphor layers is a porous body in which a large number of phosphor particles are bonded and gaps (pores) are formed between the particles. It can pass through the inside of the phosphor layer.
<Method of forming photocatalyst 200>
The photocatalyst 200 is formed by printing or applying an organic paste containing the photocatalyst to the inner wall of the partition groove and then firing the same, like many members constituting the PDP.
<Method of forming phosphor layers 115r, g, and b>
The phosphor layers 115r, 115g, and 115b are formed by printing or coating an organic paste containing a phosphor on the photocatalyst 200 and firing the paste.
<Emission luminance degradation test>
The inventors conducted a test on PDP195 to confirm the degree of decrease in emission luminance over time.
<PDP specifications>
(Example product 1)
Arrangement position of photocatalyst: lower layer of phosphor layer Thickness of photocatalyst: 5 μm
Photocatalyst material: TiO ₂ (anatase type)
Absorption edge: 380 nm to 420 nm (ultraviolet region)
Others: Same as the following conventional products (conventional products)
With / without photocatalyst: None (same structure as PDP100)
(Comparative product 1)
Arrangement position of photocatalyst: lower layer of phosphor layer Thickness of photocatalyst: 5 μm
Photocatalyst material: TiO ₂ (rutile type)
Absorption edge: 380 nm to 420 nm (ultraviolet region)
Others: Same as conventional products <Test conditions>
Room temperature: 25 ° C
External UV: 0
Above sea level: 10m
<Test method>
With respect to the above-described example product 1, the conventional product, and the comparative product 1, the emission luminance of a predetermined plurality of cells at the start of driving was measured to determine the average value A of the emission luminance. Of the cells, the average value B of the emission luminance was obtained, and the value obtained by dividing the average value B by the average value A was multiplied by 100 to calculate the emission intensity maintenance ratio (%).
<Test results>
As shown in FIG. 3, the emission intensity maintenance rate after 1000 hours from the start of driving is about 79% for the conventional product, whereas it is about 89% for the product 1 of the embodiment, and is 10%. Therefore, in the example product 1, a decrease in the light emission luminance over time is suppressed.

Further, the comparative product 1 has a light emission intensity maintenance ratio of about 81% after 1000 hours from the start of driving, and a difference of about 3% from the conventional product, and suppresses a decrease in light emission luminance over time. No effect is seen.
That is, rutile-type TiO ₂ cannot expect the effect as the photocatalyst used in the present embodiment, that is, the self-cleaning effect.
<Setting absorption edge of photocatalyst>
In recent years, it has been reported that by subjecting TiO ₂ , CdS and InTaO ₄ to a nitriding treatment, a chromium ion doping treatment or a dye sensitizer adsorption treatment, these photocatalysts are activated not only by ultraviolet rays but also by visible light. ing.

In view of the above fact, the inventors have found a method for activating oxygen by actively utilizing visible light from a phosphor.
In other words, the inventors can efficiently activate oxygen by laminating photocatalysts having absorption wavelengths of emission wavelength bands of phosphors corresponding to red, green and blue, respectively, under each phosphor layer. I thought I could do it.

In order to verify the validity of the above idea, the present inventors conducted a test on a blue phosphor in which the emission luminance was significantly reduced when carbides were attached.
More specifically, Example Product 2 in which TiO ₂ having an absorption edge in the blue wavelength band is laminated below the europium-activated barium magnesium aluminate phosphor that emits blue light, and the above-described light emission is produced. The same test as the luminance deterioration test was performed.
<PDP specifications>
(Example product 2)
Arrangement position of photocatalyst: lower layer of phosphor layer Thickness of photocatalyst: 5 μm
Photocatalyst material: TiO ₂ (anatase type)
Absorption edge: 380 nm to 550 nm (visible light region)
Others: Same as the conventional product As shown in FIG. 3, the product 2 of the embodiment has a light emission intensity maintenance ratio of about 91% after a lapse of 1000 hours from the start of driving, and a difference from the conventional product of about 12%. A decrease in emission luminance over time is suppressed.

Further, since the emission intensity maintenance ratio of the product of Example 2 is about 2% larger than that of the product of Example 1, the effect of suppressing the degradation of the emission luminance is equivalent to that of the product of Example 1. There is.
As described above, according to the present embodiment, in the PDP, by laminating the photocatalyst layer below the phosphor layer, the carbide is decomposed by the oxygen activating action of the photocatalyst while maintaining the same emission intensity as before. As a result, it is possible to suppress the deposition of carbide on the wall surface inside the PDP including the phosphor surface.

In the present embodiment, the photocatalyst 200 is assumed to have anatase-type TiO ₂ formed in a layer. However, the photocatalyst 200 is impregnated in a base made of glass beads, glass wool, activated carbon powder, copper powder, alumina particles, or the like. It may be arranged in a state.
In that case, several nm to several mm can be applied as the average particle diameter of these glass beads and alumina particles.

Further, in the present embodiment, the photocatalyst is laminated below the phosphor layer. However, the place where the photocatalyst is disposed is not limited to this, and inside the PDP, the ultraviolet light or the light emitted from the phosphor reaches and the discharge occurs. It may be placed anywhere as long as it can contact the gas.
For example, as shown in FIG. 4, a phosphor layer 215 b in which phosphor particles 216 and photocatalyst particles 217 are mixed (hereinafter, referred to as “photocatalyst-containing phosphor layer”) is disposed on the wall surface of the partition groove. You may.

In this case, since the photocatalyst particles 217 are in contact with the respective phosphor particles 216, the action of decomposing the carbide adhered to the surface of the phosphor particles 216 by the photocatalyst particles 217 is large.
In such a case, usually, the photocatalyst-containing phosphor layer is formed by the following method.
(Method of forming photocatalyst-containing phosphor layer)
(1. Phosphor precursor preparation step)
A fine powder of a photocatalyst is put into an organic paste as a phosphor precursor used in forming a phosphor layer, and the mixture is stirred to make the components uniform.
(2. Phosphor precursor disposing step)
The homogenized phosphor precursor is provided by coating or printing at the place where the phosphor layer is to be formed.
(3. Phosphor forming step)
The provided phosphor precursor is fired to remove the organic components, thereby forming a phosphor layer.
<Emission luminance degradation test>
In order to confirm the effect of suppressing the decrease in luminance of the photocatalyst-containing phosphor layer, an example product 3 and a comparative product 2 having the following specifications were prepared, and a test having the same content as the above-described emission luminance deterioration test was performed.
<PDP specifications>
(Example product 3)
Arrangement position of photocatalyst: dispersedly arranged in phosphor. Film thickness of phosphor containing photocatalyst: 20 μm
Weight ratio of photocatalyst to phosphor: 3%
Photocatalyst material: TiO ₂ (anatase type)
Absorption edge: 380 nm to 420 (ultraviolet region)
Others: Same as conventional product (Comparative product 2)
Arrangement position of photocatalyst: dispersed in phosphors Thickness of photocatalyst-containing phosphor: 20 μm
Weight ratio of photocatalyst to phosphor: 3%
Photocatalyst material: TiO ₂ (rutile type)
Absorption edge: 380 nm to 420 (ultraviolet region)
Others: Same as conventional products <Test results>
As shown in FIG. 3, the emission intensity maintenance rate after 1000 hours from the start of driving is about 79% for the conventional product, whereas it is about 89% for the example product 3 and 10%. A difference is caused, and in the example product 3, a decrease in emission luminance over time is suppressed.

Further, the comparative product 2 has a light emission intensity maintenance ratio of about 81% after 1000 hours from the start of driving, and a difference of about 3% from the conventional product, and suppresses a decrease in light emission luminance over time. No effect is seen.
That is, even if rutile-type TiO ₂ is present in the phosphor layer, the effect as the photocatalyst used in the present embodiment, that is, the self-cleaning effect, cannot be expected, as in Comparative Example 1.
<Example of disposing photocatalyst in other places>
As shown in FIG. 5, the photocatalyst 201 may be provided near the end of the partition 114 in the phosphor layer 115b formed on the wall surface of the partition groove.

Since the surface facing the front glass substrate 101, that is, the phosphor layer laminated on the dielectric layer 113 contributes greatly to the emission luminance, no photocatalyst exists near the surface of the phosphor layer. However, as described above, in the vicinity of the upper end of the side wall of the partition wall, even if the photocatalyst 201 is present, the decrease in the emission intensity is slight.
In addition, since the discharge is generated in the vicinity of the display electrode 102, the intensity of the ultraviolet light increases as it approaches the end of the partition, and the effect of the self-cleaning action is further promoted.

It is also effective to dispose the photocatalyst 202 on the top of the partition 114 as shown in FIG.
The top of the partition is a place where the phosphor does not exist, and even if the phosphor exists, it hardly affects the light emission characteristics.
Therefore, if a photocatalyst is arranged on the top, the light emitted by the phosphor is not obstructed. Further, since the photocatalyst is in contact with the front plate 90, the ultraviolet light for activating the photocatalyst is strong, and the action of the photocatalyst is further promoted.

Further, as shown in FIG. 7, the photocatalyst 201 may be provided on the front plate 90 along the inner periphery of the sealing glass 190 outside the image display region, that is, outside the region where the cell exists.
The inner peripheral portion serves as a flow path for the discharge gas, and is flat, so that the photocatalyst can be easily applied or printed.
The sealing glass 190 is formed by baking a material obtained by mixing an organic paste and glass. Therefore, since the periphery of the sealing glass 190 contains more impurities generated from organic substances than the central part of the panel, the emission luminance is increased. Is likely to deteriorate.

Therefore, it is effective to make the photocatalyst exist around the sealing glass 190 outside the display area.
When the photocatalyst is disposed outside the display area in this manner, the photocatalyst moves away from the display electrode 102, which is a discharge site, but self-cleaning occurs because ultraviolet rays generated by the discharge of cells near the outer periphery reach the photocatalyst. The action is exerted.
In addition, the photocatalyst disposed in the peripheral portion also exerts a self-cleaning action when natural light enters from the front side of the front plate 90.

  Further, in FIG. 7, the photocatalyst 201 is disposed around the sealing glass 190 on the front plate 90 side, but may be disposed around the sealing glass 190 on the rear plate 91 side.

  The light emitting device according to the present invention is applicable to a device that obtains visible light by irradiating a phosphor with ultraviolet light.

FIG. 2 is a schematic diagram of a PDP in the present embodiment. It is an expanded sectional view of a partition peripheral part of PDP in this embodiment. It is a figure showing a result of a light emission luminance degradation test. It is a first modification of the arrangement position of the photocatalyst. It is a second modification of the arrangement position of the photocatalyst. It is a modification 3 regarding the arrangement position of the photocatalyst. It is a fourth modification of the arrangement position of the photocatalyst. It is the schematic of the conventional general alternating current type (AC type) PDP100. It is a figure explaining the outline of an impurity gas removal process.

Explanation of reference numerals

Reference Signs List 90 front plate 91 back plate 92 back plate 101 front glass substrate 102 display electrode 103 transparent electrode 104 black electrode film 105 bus electrode 106 dielectric layer 107 protective layer 108 terminal portion 111 rear glass substrate 112 address electrode 113 dielectric layer 114 partition 115b Phosphor layer 115r Phosphor layer 116 Discharge space 190 Sealing glass 195 PDP
Reference Signs List 200 photocatalyst 201 photocatalyst 202 photocatalyst 216 phosphor particle 217 photocatalyst particle 309 multilayer electrode

Claims (19)

  A light-emitting element that obtains visible light from ultraviolet light caused by discharge in a discharge medium containing a rare gas, wherein a phosphor is present in a container that seals the discharge medium, and the ultraviolet light in the container. Alternatively, a light-emitting element, wherein a photocatalyst exposed to the discharge medium is present in a first region where light emitted by the phosphor reaches.   The light emitting element is a plasma display panel, and the container is formed by sealing outer edges of a first substrate and a second substrate facing each other, and a plurality of partitions are provided on the first substrate. Is formed, the phosphor forms a phosphor layer disposed on a wall surface of a second region sandwiched between adjacent partitions, and the photocatalyst is present in the second region. The light emitting device according to claim 1, wherein   The light emitting device according to claim 2, wherein the precatalyst is dispersed in the phosphor layer.   The phosphor layer has a porous structure through which the discharge medium can flow, and the photocatalyst is stacked on a surface of the phosphor layer on the first substrate side. Light emitting element.   The light emitting device according to claim 2, wherein the phosphor layer has a porous structure through which the discharge medium can flow, and the photocatalyst is stacked on the partition wall side of the phosphor layer. .   The light emitting device according to claim 2, wherein the photocatalyst is present at a top of the partition or in the vicinity thereof.   The phosphor layer is divided into three types of emitting red, green and blue light by absorbing ultraviolet light, and the photocatalyst emits blue light by using the blue wavelength band in a visible light region as an absorption end. 7. The light emitting device according to claim 3, wherein the light emitting element is unevenly distributed in the vicinity of the presence of the phosphor layer.   The phosphor layer formed between the partition walls is divided into three types of emitting red, green, and blue light by absorbing ultraviolet light, and the photocatalyst has at least different wavelength bands as absorption ends. 7. The light-emitting device according to claim 3, wherein the light-emitting element is divided into two types, and the type is determined according to the type of a phosphor present near a place where the phosphor is provided. .   7. The light emitting device according to claim 3, wherein the photocatalyst is present in all of the second regions sandwiched between adjacent partitions. The photocatalyst light emitting device according to claim 3, 4, 5 or 6, characterized in that the TiO ₂ in anatase form with its main component.   The light emitting device according to claim 10, wherein the photocatalyst has an absorption edge in a visible light region.   The light emitting element is a plasma display panel, wherein the container has a first substrate and a second substrate facing each other, and their outer edges are sealed, and the photocatalyst includes the phosphor. The light emitting device according to claim 1, wherein the light emitting device exists outside an image display area. The light emitting device according to claim 12, wherein the photocatalyst is provided near the outer edge.   What is claimed is: 1. A method for producing a light-emitting element for obtaining visible light from ultraviolet light caused by discharge in a discharge medium containing a rare gas, wherein a phosphor layer is formed by mixing phosphor particles and a photocatalyst to form a precursor of the phosphor layer. A precursor forming step, a precursor arranging step of arranging the precursor in a region where the ultraviolet rays reach, and in contact with the discharge medium, and baking the precursor to form the phosphor layer And a phosphor layer forming step.   A method for manufacturing a light-emitting element that obtains visible light from ultraviolet light caused by discharge in a discharge medium containing a rare gas, wherein a phosphor is provided in a region where the ultraviolet light reaches, and A photocatalyst arranging step of arranging a photocatalyst in a region where the light emitted from the phosphor reaches and comes into contact with the discharge medium.   16. The method according to claim 14, wherein the photocatalyst has been subjected to a nitriding treatment to adjust an absorption edge.   A method for manufacturing a plasma display panel in which a first substrate provided with a plurality of partition walls and a second substrate are sealed with their outer edges sealed in opposition to each other, wherein a phosphor particle and a photocatalyst are mixed. A phosphor mixing step of forming a mixture by disposing the mixture on a wall surface of a region sandwiched between adjacent partitions on the first substrate to form a precursor of a phosphor layer And a step of forming the phosphor layer by firing the precursor to form the phosphor layer.   A method for manufacturing a plasma display panel in which a first substrate provided with a plurality of partition walls and a second substrate are sealed with their outer edges sealed in a state where the first substrate and the second substrate face each other, wherein a phosphor is provided in a region where ultraviolet rays reach. Arranging a phosphor, and a photocatalyst arranging in the first substrate or the second substrate in a region where the ultraviolet light or the emission light of the phosphor reaches and comes into contact with the discharge medium. And a method for manufacturing a plasma display panel. 19. The method according to claim 17, wherein the photocatalyst has been subjected to a nitriding treatment.

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