JP2006312695A - Blue light-emitting phosphor for display device, and field emission type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heighten emission intensity and to improve a usable life by reducing deterioration of luminance in a blue light-emitting fluorescent substance usable for an FED or the like. <P>SOLUTION: The blue light-emitting phosphor for a display device consists essentially of a zinc sulfide phosphor of a cubic system, having silver and aluminum as activators, and regulated so that the concentration of the silver as the activator may be 300-1,200 ppm based on the zinc sulfide. The characteristics concerning luminance deterioration can be improved by forming a layer containing magnesium and phosphorus on the surface of the particle of the zinc sulfide phosphor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a blue light emitting phosphor for a display device and a field emission display device.

  With the advent of the multimedia era, display devices, which are core devices of digital networks, are required to have large screens, high definition, and compatibility with various sources such as computers.

  Among display devices, field emission display devices (field emission display; FED) using electron emission elements such as field emission cold cathode elements are large screens capable of displaying various information in a precise and high definition. As a thin and thin digital device, research and development have been actively conducted in recent years.

  The FED has the same basic display principle as a cathode ray tube (CRT) and excites a phosphor with an electron beam to emit light. However, the acceleration voltage (excitation voltage) of the electron beam is lower than that of a CRT. In addition, the current density by the electron beam is low, and the irradiation time of the electron beam is as long as several μs. For this reason, when the predetermined luminance life is converted into the input charge amount per unit area, it increases from the CRT. Accordingly, the current situation is that sufficient light emission luminance and lifetime cannot be obtained when a phosphor for CRT is used. (For example, see Patent Document 1)

  That is, there is a demand for a strong long-life phosphor that can sufficiently maintain the initial light emission characteristics even when the input charge amount is higher than that of a conventional CRT.

However, there is currently no phosphor that exceeds the emission characteristics of the conventional CRT phosphor, and it can be said that it is an important issue to improve the CRT phosphor for FED.
JP 2002-226847 A

  The present invention has been made to solve such problems. In a blue light-emitting phosphor used in a field emission display (FED), the emission luminance is increased and the luminance is suppressed to improve the service life. The purpose is that. It is another object of the present invention to provide an FED having such a blue light emitting phosphor that has high luminance, excellent display characteristics such as color reproducibility, and improved life.

  The blue light-emitting phosphor for a display device of the present invention is an electron beam mainly composed of a cubic zinc sulfide phosphor containing silver and aluminum as an activator, with an acceleration voltage of 15 kV or less and an irradiation time of 0.1 to 20 μs. The cubic silver and aluminum activated zinc sulfide phosphors are excited by the above and have a concentration of silver as an activator of 300 to 300 zinc relative to zinc sulfide as a phosphor matrix. It is characterized by being 1200 ppm.

  The field emission display device according to the present invention includes a phosphor layer including a blue light-emitting phosphor layer, a green light-emitting phosphor layer, and a red light-emitting phosphor layer, and irradiating the phosphor layer with an electron beam having an acceleration voltage of 15 kV or less. A field emission display device comprising: an electron source that emits light; and an envelope that vacuum seals the electron source and the phosphor layer, wherein the blue light-emitting phosphor layer is the display of the present invention described above. A blue light-emitting phosphor for a device is included.

  Since the blue light-emitting phosphor of the present invention is composed of silver and aluminum-activated zinc sulfide phosphors having a concentration of silver as an activator of 300 to 1200 ppm, which is significantly increased from the conventional one, the acceleration voltage is high. The light emission luminance when excited by an electron beam with an irradiation time of 0.1 to 20 μs at 15 kV or less is improved as compared with a conventional blue light emitting phosphor. In addition, luminance degradation due to impact of a high-density electron beam is small, and the lifetime is long. Therefore, by using such a blue light-emitting phosphor, it is possible to realize a thin flat display device such as an FED having high luminance, excellent display characteristics such as color reproducibility, and improved life.

  Hereinafter, modes for carrying out the present invention will be described.

  The blue light-emitting phosphor of the first embodiment of the present invention is composed of cubic silver and aluminum-activated zinc sulfide phosphor substantially represented by the general formula: ZnS: Ag, Al, and is an activator. The concentration of silver (Ag) is 300 to 1200 ppm.

  In the silver and aluminum activated zinc sulfide phosphor (ZnS: Ag, Al) of the first embodiment, Ag is a first activator (main activator) that forms an emission center, It contains in the range of 300-1200 ppm with respect to a certain zinc sulfide. A more preferable Ag concentration is in the range of 500 to 800 ppm. When the content concentration of Ag is out of the range of 300 to 1200 ppm, the effect of improving the luminance deterioration is not sufficient, which is not preferable.

  Al is called a coactivator and compensates for charge of Ag activated to zinc sulfide. That is, the tetravalence of the total valence of Al ions and the monovalence of Ag ions is electrically compensated by the tetravalence of the two divalent zinc ions in zinc sulfide. Therefore, the Al concentration is preferably the same as Ag as the number of ions, that is, the number of atoms.

  The blue light-emitting phosphor that is the first embodiment of the present invention is manufactured as follows. First, a predetermined amount of activator raw material is added to the zinc sulfide raw material which is a phosphor matrix, and a flux such as potassium chloride or magnesium chloride is added as necessary, and these are mixed in a wet manner. Specifically, the phosphor raw material is dispersed in ion-exchanged water to form a slurry, and a predetermined amount of activator raw material and flux are added thereto and mixed with a stirrer. The mixing time is set so that the activator is sufficiently dispersed. Next, the slurry containing the phosphor material and the activator is transferred to a drying container and dried by a dryer to obtain a phosphor material.

  Next, such a phosphor material is filled in a heat-resistant container such as a quartz crucible together with appropriate amounts of sulfur and activated carbon. At this time, it is preferable to add and mix sulfur with a phosphor raw material for about 30 to 180 minutes using a blender or the like, and after filling the mixed material in a heat-resistant container, the surface is covered with sulfur. . This is fired in a sulfide atmosphere such as a hydrogen sulfide atmosphere, a sulfur vapor atmosphere, or a reducing atmosphere (for example, an atmosphere of 3 to 5% hydrogen-remaining nitrogen).

  Firing conditions are important in controlling the crystal structure of the phosphor matrix (ZnS). In order to obtain the target cubic crystal structure, the firing temperature is preferably in the range of 900 to 990 ° C. If the firing temperature is less than 900 ° C., the crystal grains of zinc sulfide cannot be grown sufficiently. On the other hand, if the firing temperature exceeds 990 ° C., the crystal structure of zinc sulfide becomes hexagonal. Although the firing time depends on the set firing temperature, it is preferably 15 to 90 minutes, and after firing, it is preferably quenched in the same atmosphere as firing. Thereafter, the fired product obtained is washed with ion-exchanged water and dried, and then subjected to sieving to remove coarse particles, if necessary, to obtain a cubic zinc sulfide phosphor. It is done.

  The blue light emitting phosphor of the first embodiment thus obtained has high emission luminance when excited with a high current density electron beam having an acceleration voltage of 15 kV or less and an irradiation time of 0.1 to 20 μs, and is good. Color purity. In addition, it has excellent resistance to high-current density electron beams and suppresses deterioration in luminance over time, thus improving the service life.

  The blue light-emitting phosphor of the second embodiment of the present invention includes magnesium and phosphorus on the surface of the silver and aluminum-activated zinc sulfide phosphor (ZnS: Ag, Al) particles of the first embodiment described above. Has a layer.

  In the blue phosphor according to the second embodiment, Ag as an activator is contained in a range of 300 to 1200 ppm with respect to zinc sulfide as the phosphor matrix, and is uniformly dispersed in the zinc sulfide particles. Yes. Here, the state where the activator is uniformly dispersed means that the concentration distribution of the activator in the phosphor base particles (concentration distribution in the depth direction from the surface) is approximately constant. It is shown. As shown in the manufacturing method of the first embodiment, such a phosphor is fired by uniformly mixing a material for forming zinc sulfide as a phosphor matrix and a material for forming an activator. It can be obtained by a method or the like.

  A layer containing both magnesium and phosphorus (hereinafter referred to as Mg and P-containing layer) is formed on the surface of such zinc sulfide phosphor particles. The Mg and P-containing layer can improve the effect of preventing luminance deterioration by covering at least a part of the surface of the zinc sulfide phosphor particles, but it is more preferable to form the Mg and P-containing layer so as to cover the entire surface without any gap.

  The thickness of the Mg- and P-containing layer is not particularly limited, but it is desirable that the P content be 0.01 to 1 mol% with respect to zinc sulfide as the phosphor matrix. When the content of P is out of the above range, the effect of improving the luminance deterioration of the phosphor is small. In addition, in the formation of the Mg and P-containing layer described later, the content of P is changed by changing the compounding amount of the compound containing Mg and P to be added and changing the thickness of the formed Mg and P-containing layer. Can be adjusted. The P content can be measured, for example, by ICP (inductively coupled plasma) emission analysis or XPS analysis (X-ray photoelectron analysis).

  In the phosphor for display device according to the second embodiment described above, the Mg and P-containing layers can be formed, for example, as follows.

  A powder of silver and aluminum activated zinc sulfide phosphor (ZnS: Ag, Al) obtained by the method shown in the first embodiment is added to an aqueous solution of magnesium sulfate and disodium hydrogen phosphate, and the mixture thereof Add sodium bicarbonate or sodium tetraborate. And after the said liquid mixture is fully mixed, alkaline liquids, such as ammonia, are dripped gradually, and magnesium phosphate is deposited by making pH of a liquid mixture alkaline. Thus, a layer covering the phosphor surface is formed.

  Next, after filtering and drying the phosphor, the dried product is heat-treated (baked). The heating is performed in the same atmosphere as the phosphor firing, but the temperature needs to be lower than the firing temperature. For example, heating is performed at a temperature of 300 to 600 ° C. Heating below 300 ° C. cannot remove magnesium phosphate crystal water. In addition, the phosphor is decomposed by heating above 600 ° C. Thus, a phosphor in which the surface of the zinc sulfide phosphor particles is coated with the Mg and P-containing layer can be obtained with good reproducibility.

  In the blue light emitting phosphor of the second embodiment thus obtained, a layer containing both magnesium and phosphorus (containing Mg and P) on the surface of silver and aluminum activated zinc sulfide phosphor (ZnS: Ag, Al) particles Layer), the light emission brightness is high when excited by an electron beam with an acceleration voltage of 15 kV or less and an irradiation time of 0.1 to 20 μs and a high current density, and has good color purity. Yes. In addition, the resistance to a high current density electron beam is superior to that of the blue light emitting phosphor of the first embodiment, and luminance deterioration with time is suppressed, so that the service life is further improved.

  In the blue light-emitting phosphor of the second embodiment, the reason why the luminance deterioration is improved by coating the surface of the zinc sulfide phosphor particles with the Mg and P-containing layer is not necessarily clear, but the Mg and P-containing layer Is considered to be due to the effect of suppressing the disturbance of atoms on the surface of the zinc sulfide phosphor due to the electron beam (change in crystal structure).

  Using the blue light emitting phosphors of the first and second embodiments, a blue light emitting phosphor layer can be formed by a known slurry method or printing method. In the slurry method, a phosphor slurry is prepared by mixing powder of a blue light emitting phosphor with a photosensitive material such as pure water, polyvinyl alcohol and ammonium dichromate, and a surfactant, and this slurry is prepared by a spin coater or the like. After coating and drying on the substrate, a predetermined pattern is exposed and developed by irradiating ultraviolet rays or the like, and the obtained phosphor pattern is dried. Thus, a blue light emitting phosphor layer having a predetermined pattern can be formed.

  Next, a field emission display device (FED) in which a blue light-emitting phosphor layer is configured using the blue light-emitting phosphors of the first and second embodiments of the present invention will be described.

  FIG. 1 is a cross-sectional view showing a main configuration of an embodiment of an FED. In FIG. 1, reference numeral 1 denotes a face plate, which has a phosphor layer 3 formed on a transparent substrate such as a glass substrate 2. The phosphor layer 3 has a blue light-emitting phosphor layer, a green light-emitting phosphor layer, and a red light-emitting phosphor layer formed corresponding to the pixels, and the light-emitting layer 4 made of a black conductive material is separated between these layers. It has a structure. Of the phosphor layers of each color constituting the phosphor layer 3, the blue light-emitting phosphor layer is composed of the blue light-emitting phosphor of the above-described embodiment.

  The thickness of the blue light emitting phosphor layer is desirably 1 to 10 μm, more preferably 6 to 10 μm. The reason why the thickness of the blue light emitting phosphor layer is limited to 1 μm or more is that it is difficult to form a phosphor layer having a thickness of less than 1 μm and phosphor particles uniformly arranged. On the other hand, if the thickness of the blue light-emitting phosphor layer exceeds 10 μm, the light emission luminance is lowered and cannot be put to practical use.

  Each of the green light emitting phosphor layer and the red light emitting phosphor layer can be composed of various known phosphors. It is desirable that the green light emitting phosphor layer and the red light emitting phosphor layer have the same thickness as the blue light emitting phosphor layer so that no step is generated between the phosphor layers of the respective colors.

  The blue light-emitting phosphor layer, the green light-emitting phosphor layer, the red light-emitting phosphor layer, and the light absorption layer 4 that separates them are sequentially and repeatedly formed in the horizontal direction, and these phosphor layers 3 And the part in which the light absorption layer 4 exists becomes an image display area. Various patterns such as a dot shape or a stripe shape can be applied to the arrangement pattern of the phosphor layer 3 and the light absorption layer 4.

  A metal back layer 5 is formed on the phosphor layer 3. The metal back layer 5 is made of a metal film such as an Al film, and improves the luminance by reflecting light traveling in the rear plate direction, which will be described later, from light generated in the phosphor layer 3.

  The metal back layer 5 has a function of imparting conductivity to the image display area of the face plate 1 to prevent electric charges from accumulating, and serves as an anode electrode for the electron source of the rear plate. Further, the metal back layer 5 has a function of preventing the phosphor layer 3 from being damaged by ions generated by ionizing the gas remaining in the face plate 1 or the vacuum vessel (envelope) with an electron beam, Furthermore, the gas generated from the phosphor layer 3 during use is prevented from being released into the vacuum container (envelope), and the vacuum degree is prevented from being lowered.

  On the metal back layer 5, a getter film 6 made of an evaporable getter material made of Ba or the like is formed. The getter film 6 efficiently adsorbs the gas generated during use.

  The face plate 1 and the rear plate 7 are arranged to face each other, and the space between them is hermetically sealed via the support frame 8. The support frame 8 is bonded to the face plate 1 and the rear plate 7 by a frit glass or a bonding material 9 made of In or an alloy thereof, and is surrounded by the face plate 1, the rear plate 7, and the support frame 8. A vacuum vessel as a container is configured.

  The rear plate 7 includes a substrate 10 made of an insulating substrate such as a glass substrate or a ceramic substrate, or a Si substrate, and a large number of electron-emitting devices 11 formed on the substrate 10. These electron-emitting devices 11 include, for example, a field-emission cold cathode, a surface conduction electron-emitting device, and the like, and the surface of the rear plate 7 on which the electron-emitting devices 11 are formed is provided with wiring (not shown). That is, a large number of electron-emitting devices 11 are formed in a matrix according to the phosphors of each pixel, and wirings (XY wirings) crossing each other that drive the matrix-shaped electron-emitting devices 11 row by row. have. The support frame 8 is provided with a signal input terminal and a row selection terminal (not shown). These terminals correspond to the cross wiring (XY wiring) of the rear plate 7 described above. Further, when a flat plate-type FED is enlarged, there is a possibility that bending or the like may occur due to the thin flat plate shape. In order to prevent such deflection and to provide strength against atmospheric pressure, a reinforcing member (atmospheric pressure support member, spacer) 12 may be appropriately disposed between the face plate 1 and the rear plate 7. Good.

  In this FED, the blue light-emitting phosphor layer according to the first or second embodiment described above is used as the blue light-emitting phosphor layer that emits light by electron beam irradiation. Therefore, display characteristics such as luminance and color reproducibility are obtained. In addition to being good, luminance deterioration with time is suppressed, and the service life is greatly improved.

  Next, specific examples of the present invention will be described.

Examples 1-5
To zinc sulfide (ZnS), silver nitrate (AgNO ₃ ) and aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) are added together with an appropriate amount of water, and potassium chloride, magnesium chloride, etc. are added as necessary. After adding flux and mixing well, it was dried with a dryer. Appropriate amounts of sulfur and activated carbon were added to the obtained phosphor material, filled in a quartz crucible, and fired in a reducing atmosphere. Thereafter, the fired product was washed with water, dried and sieved to obtain cubic silver and aluminum-activated zinc sulfide phosphor (ZnS: Ag, Al) powder. Table 1 shows the content ratio of Ag as an activator to zinc sulfide in the obtained silver and aluminum-activated zinc sulfide phosphor.

  Next, using the obtained cubic zinc sulfide phosphor (ZnS: Ag, Al), a phosphor layer having a thickness of 8 μm is formed by screen printing, and an aluminum metal back layer is further formed thereon by a lacquer method. Formed.

Next, the phosphor layer thus obtained was examined for luminance deterioration characteristics as follows. That is, each phosphor layer was continuously irradiated with an electron beam having an acceleration voltage of 10 kV and a current density of 36 μA / cm ² , and the relationship between the total amount of charges injected by the electron beam irradiation and the light emission luminance was examined. Then, the amount of charge input until the emission luminance reached 70% of the initial value was obtained. Further, the relative input charge amount was determined as a relative value when the input charge amount of the phosphor layer according to Comparative Example 1 was set to 1.00. These results are shown in Table 1.

  As is clear from Table 1, the phosphor layers obtained in Examples 1 to 5 have a better luminance life than that of Comparative Example 1. In particular, the phosphor layers obtained in Examples 2 to 4 have a luminance life significantly improved by 1.5 to 2 times that of Comparative Example 1.

Example 6
Using the blue light-emitting phosphor, the green light-emitting phosphor (cubic ZnS: Cu, Al phosphor), and the red light-emitting phosphor (Y ₂ O ₂ S: Eu phosphor) obtained in Example 1, respectively. A phosphor layer was formed on a glass substrate to obtain a face plate. The face plate and the rear plate having a large number of electron-emitting devices were assembled through a support frame, and the gap between them was hermetically sealed while evacuating. It was confirmed that the FED produced in this way was excellent in color reproducibility including light emission luminance, and showed good luminance characteristics even after being driven at room temperature and rated operation for 1000 hours.

Examples 7-12
In the same manner as in Example 1, cubic zinc sulfide phosphor (ZnS: Ag, Al) powder having a content ratio of Ag as an activator to zinc sulfide of 600 ppm was prepared.

  Next, this phosphor was added to an aqueous solution containing magnesium sulfate and disodium hydrogen phosphate, and then sodium hydrogen carbonate was added. Furthermore, in order to make the pH of the mixed solution alkaline, an alkaline solution such as ammonia was gradually dropped to form a phosphoric acid compound on the phosphor surface. Thereafter, the phosphor was dried and baked in a hydrogen sulfide atmosphere at 500 ° C. for 1 hour to remove crystal water of the phosphoric acid compound. Such treatment was not performed on the phosphor of Example 7. Thus, a phosphorus-containing layer having a phosphorus-containing concentration (analyzed value by XPS) shown in Table 2 was formed on the zinc sulfide phosphor.

Then, using the zinc sulfide phosphor of Example 7 and the zinc sulfide phosphor having the surface treatment layer containing phosphorus obtained in Examples 8 to 12, a phosphor layer having a thickness of 8 μm was formed by screen printing. Further, an aluminum metal back layer was formed thereon by a lacquer method. And the luminance deterioration characteristic was investigated as follows about the obtained fluorescent substance layer. That is, each phosphor layer was continuously irradiated with an electron beam having an acceleration voltage of 10 kV and a current density of 36 μA / cm ² , and the relationship between the total amount of charges injected by the electron beam irradiation and the light emission luminance was examined. Then, the input charge amount until the luminance reached 70% of the initial value was examined. Further, the relative input charge amount was obtained as a relative value when the 70% input charge amount of the phosphor layer according to Example 7 was set to 1.00. The results are shown in Table 2.

  As is apparent from Table 2, the phosphor layers obtained in Examples 8 to 10 have improved luminance deterioration characteristics as compared with those of Example 7, and have a good luminance life.

Example 13
The blue light-emitting phosphor, the green light-emitting phosphor (cubic ZnS: Cu, Al phosphor), and the red light-emitting phosphor (Y ₂ O ₂ S: Eu phosphor) obtained in Example 9 were used. A phosphor layer was formed on a glass substrate to obtain a face plate. The face plate and the rear plate having a large number of electron-emitting devices were assembled through a support frame, and the gap between them was hermetically sealed while evacuating. It was confirmed that the FED produced in this way was excellent in color reproducibility including light emission luminance, and showed good luminance characteristics even after being driven at room temperature and rated operation for 1000 hours.

  According to the blue light-emitting phosphor of the present invention, it is possible to realize blue light emission with high brightness, good color purity, and long life when irradiated with an electron beam having a low voltage and a high current density. Therefore, by using such a blue light-emitting phosphor, it is possible to realize a thin flat display device such as an FED having high luminance, excellent display characteristics such as color reproducibility, and improved life.

It is sectional drawing which shows schematically FED which is embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Face plate, 2 ... Glass substrate, 3 ... Phosphor layer, 4 ... Light absorption layer, 5 ... Metal back layer, 6 ... Getter film, 7 ... Rear plate, 8 ... Support frame, 11 ... Electron emission element.

Claims (6)

It has a cubic crystal structure using silver and aluminum as an activator (hereinafter referred to as “cubic”), and is mainly composed of a zinc sulfide phosphor, with an acceleration voltage of 15 kV or less and an irradiation time of 0.1. A phosphor that emits blue light when excited by an electron beam of ˜20 μs,
The cubic silver and aluminum activated zinc sulfide phosphor is characterized in that the concentration of silver as an activator is 300 to 1200 ppm with respect to zinc sulfide as a phosphor matrix, blue light emission for a display device Phosphor.   2. The blue light emission for a display device according to claim 1, wherein a concentration of silver in the cubic silver and aluminum-activated zinc sulfide phosphor is 500 to 800 ppm with respect to zinc sulfide as a phosphor matrix. Phosphor.   3. The blue light emitting phosphor for a display device according to claim 1, wherein the cubic silver and aluminum activated zinc sulfide phosphor has a surface treatment layer containing magnesium and phosphorus.   4. The blue light emitting phosphor for a display device according to claim 3, wherein a content ratio of phosphorus to the cubic silver and aluminum activated zinc sulfide phosphor is 0.01 to 1 mol%. A phosphor layer including a blue-emitting phosphor layer, a green-emitting phosphor layer, and a red-emitting phosphor layer; an electron source that emits light by irradiating the phosphor layer with an electron beam having an acceleration voltage of 15 kV or less; A field emission display device comprising a source and an envelope for vacuum-sealing the phosphor layer;
5. The field emission display device according to claim 1, wherein the blue light emitting phosphor layer includes the blue light emitting phosphor for display device according to any one of claims 1 to 4.   6. The field emission light emitting display device according to claim 5, wherein the blue light emitting phosphor layer has a thickness of 1 to 10 [mu] m.

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