JP2007177156A - Phosphor and its manufacturing method, and light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor that is not deteriorated by low-accelerated electron beams and gives high intensity luminance, its manufacturing method and a light-emitting element containing the phosphor. <P>SOLUTION: The phosphor comprises a matrix comprised of at least one selected between Y<SB>2</SB>O<SB>3</SB>and Gd<SB>2</SB>O<SB>3</SB>and, added thereto as activating metals, 0.5-5 mol% of Eu and 5-25 mol% of Zn, each based on the total molar number of the metal constituting the matrix and the activating metals. The manufacturing method of the phosphor comprises dissolving or dispersing at least one inorganic salt selected from among inorganic salts of Y and Gd, inorganic salts of Eu and Zn, and an organic acid in a solvent followed by baking. The light-emitting element comprises the nanoparticle phosphor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phosphor, a manufacturing method thereof, and a light emitting device, and more particularly, to a red nanoparticle phosphor, a manufacturing method thereof, and a light emitting device including the phosphor.

  Today, in the display field, a cathode ray tube (CRT) is shifting to a thin flat panel display (FPD), such as a liquid crystal display, a plasma display panel (PDP), an organic EL display, a field emission display (FED), Various FPDs have been developed. Among them, the FED emits light by causing an electron beam generated from the cathode to collide with the phosphor of the anode on the same light emission principle as that of the CRT. It is desirable that the phosphor serving as the light source has excellent characteristics such as light emission luminance, color purity, and lifetime. Phosphors mainly used in conventional CRTs and current FEDs still have problems such as high cost, deleterious substances, and reduction in luminous efficiency due to phosphor surface deterioration. There are problems to be solved, and alternative materials are being actively developed. However, there are still no satisfactory ones.

  In the phosphors used in such CRTs and PDPs, it is mainstream to use particles having a particle size of about several microns (for example, 3 to 10 μm). However, when these phosphors are used for FED, there are the following problems. In the FED, due to its structure, the emitted electrons have a low acceleration voltage. Therefore, when a conventional phosphor is used, the penetration depth of electrons is shallow, and electrons cannot sufficiently reach the light-emitting portion, so that satisfactory light emission luminance cannot be obtained. Further, electrons that cannot pass through the phosphor are charged up on the phosphor surface and do not contribute to light emission. Therefore, it is conceivable to solve the problems of electron penetration depth and charge-up by making the phosphor nano-sized or imparting conductivity.

Further, ZnS-based phosphors used in CRT phosphors and Y ₂ O ₂ S: Eu (see, for example, Patent Document 1) are often used as FED phosphors. These phosphors are sulfides. Therefore, it is a deleterious substance, and there is a problem that irradiation with a low acceleration electron beam causes a decrease in luminous efficiency due to deterioration of the phosphor surface.

Furthermore, it has been proposed to solve the above-mentioned problem of electron penetration depth using a nanometer-sized ZnS-based or CdS-based phosphor (see, for example, Patent Document 2). However, since this phosphor is a sulfide, there are problems as described above.
JP-A-10-250214 (Claims etc.) JP-A-11-293241 (Claims etc.)

  An object of the present invention is to solve the above-mentioned problems of the prior art, and includes a phosphor capable of emitting red light with high luminance without being deteriorated by an electron beam, a method for manufacturing the phosphor, and the phosphor. The object is to provide a light emitting element.

The phosphor of the present invention comprises at least one oxide selected from Y ₂ O ₃ and Gd ₂ O ₃ as a base material, and an activator metal composed of Eu and Zn is added to the base material. And By including such an activator metal, it becomes a phosphor capable of emitting high-luminance red light without being deteriorated by an electron beam, and also contains a conductive metal, thereby solving the problem of charge-up. Can be done.

  The addition amount of the Eu is 0.5 to 5 mol% based on the total number of moles of the constituent metal of the base and the activator metal. If it is less than 0.5 mol%, light emission cannot be confirmed with a low-acceleration electron beam, and if it exceeds 5 mol%, the amount of addition is too large and the crystal structure of the phosphor is destroyed, resulting in weak emission. .

  The added amount of Zn is 5 to 25 mol% based on the total number of moles of the base metal and the activator metal. If the amount is less than 5 mol%, there is no effect of imparting conductivity due to the addition of Zn. If the amount exceeds 25 mol%, the amount added is too large, and the phosphor crystal structure collapses, resulting in weak emission, and ZnO: Zn The derived green emission peak appears.

  The phosphor of the present invention is prepared by dissolving at least one inorganic salt selected from an inorganic salt of Y and an inorganic salt of Gd, an inorganic salt of Eu and an inorganic salt of Zn, and an organic acid in a solvent, or After the dispersion, the solution or dispersion obtained as desired is gelled and then fired to produce a phosphor.

  The Eu inorganic salt is added in such an amount that it is contained in the phosphor in an amount of 0.5 to 5 mol% in terms of Eu, based on the total number of moles of constituent metals of all the inorganic salts. Features.

  The inorganic salt of Zn is added in such an amount that it is contained in the phosphor in an amount of 5 to 25 mol% in terms of the total number of moles of constituent metals of all the inorganic salts in terms of Zn. To do.

The firing is performed at a temperature of 900 to 1500 ° C. Particles obtained when the temperature is lower than 900 ° C., and inorganic salts such as nitrates and organic acids are left unburned, and the phosphors obtained have poor crystallinity, resulting in poor emission luminance. The particle size of the film becomes too large and exceeds 300 nm.

  The organic acid is at least one amino acid, preferably at least one amino acid selected from glycine, aspartic acid and glutamic acid.

  The number of moles of the organic acid is 1 to 50 times, preferably 1 to 10 times, more preferably 1 to 2 times the total number of moles of all the inorganic salts. If it is less than 1 time, the dispersion in the gel state is poor when gelling before firing, so the particle size becomes large (for example, about 500 nm), and if it exceeds 50 times, unburned organic acid remains. A large amount of light emission occurs, resulting in a decrease in light emission luminance.

  The light-emitting element of the present invention includes the phosphor or the phosphor manufactured by the manufacturing method. The light emission luminance of this light emitting element is extremely high because the phosphor is not deteriorated by the low acceleration electron beam.

  According to the phosphor of the present invention, it is possible to emit red light with high luminance without being deteriorated by an electron beam and to prevent charge-up. Therefore, the red light emission of the light emitting element obtained using this phosphor has an effect of showing extremely high luminance.

  In addition, the phosphor of the present invention has an effect that it can be produced by an easy process by ordinary firing.

  Furthermore, since the phosphor of the present invention exhibits excellent light emission luminance as described above, and charge-up is prevented, the light-emitting element including this phosphor can be used for a display such as an FED. .

  Embodiments of the present invention will be described below.

  According to one embodiment of the present invention, the phosphor of the present invention is a phosphor that emits red light composed of nanoparticles. The nanoparticle in the present invention refers to a particle having a particle size of preferably 300 nm or less, more preferably 100 nm or less. When the particle size exceeds 300 nm, the penetration depth is shallow at a low acceleration voltage, so that the charge is increased and the emission luminance is lowered.

As described above, such a red nanoparticle phosphor is based on at least one oxide selected from Y ₂ O ₃ and Gd ₂ O ₃ , and this activator metal is composed of Eu and Zn. In which at least one inorganic salt selected from an inorganic salt of Y and an inorganic salt of Gd, an inorganic salt of Eu, an inorganic salt of Zn, and an organic acid are dissolved or dispersed in a solvent. After the caking, the obtained solution or dispersion is heated to a predetermined temperature (80 to 120 ° C.) to be gelled, and then fired at a predetermined temperature, for example, in the atmosphere.

  The inorganic salt of Y and Gd may be a compound that can be decomposed into an oxide upon firing, such as nitrate, carbonate, oxalate, sulfate, acetate, hydroxide, halide ( For example, chloride, bromide and the like).

  Examples of inorganic salts of Eu and Zn include nitrates, carbonates, oxalates, sulfates, acetates, hydroxides, halides (eg, chlorides and bromides), and the like.

  Hereinafter, an embodiment of a method for producing a phosphor of the present invention will be described.

  The method for producing the nanoparticle phosphor of the present invention is not particularly limited. For example, as described above, at least one inorganic salt selected from an inorganic salt of Y and an inorganic salt of Gd, an inorganic salt of Eu, an inorganic salt of Zn, and an organic acid were dissolved or dispersed in a solvent. Thereafter, it is produced by firing. That is, a red nanoparticle phosphor is produced by a self-propagating combustion method in order to increase the crystallinity of the product obtained by the high temperature treatment.

  According to the present invention, for example, an inorganic salt containing a metal constituting the matrix and an inorganic salt containing an activator metal are weighed together with the composition of the target phosphor, and a known ball mill, jet mill, Mix and pulverize using a V-type mixer, a stirrer, etc., add the organic acid and a solvent such as water or isopropanol to the resulting mixture to prepare a solution or dispersion, and then a predetermined temperature (preferably The gel is heated to about 100 ° C. to be gelled, and then the gel is subjected to 900 to 1500 ° C. (preferably 900 to 1100 ° C.) in an oxidizing gas atmosphere (air, oxygen, oxygen atom-containing gas, etc.). The target phosphor can be obtained by firing for a predetermined time. The particle size of the phosphor thus obtained is about 50 to 300 nm (preferably about 50 to 100 nm) from the analysis results based on the transmission electron microscope and the broadening of the X-ray diffraction peak. Thus, since it is nano size, the problem of electron penetration depth can be solved.

  Since the red nanoparticle phosphor of the present invention obtained as described above is not subject to surface deterioration due to a low acceleration electron beam, it has an extremely high red emission luminance as compared with conventional phosphors.

  Using this phosphor, a light emitting device can be manufactured by a known manufacturing method. An example of a light emitting element for FED using this phosphor will be briefly described below.

  For example, the nanoparticle phosphor obtained as described above is dispersed in an organic solvent solution of a binder made of a polymer compound (for example, a cellulose compound, polyvinyl alcohol, etc.) to prepare a phosphor paste. This phosphor paste is applied to the surface of the front substrate on which a conductive film (for example, an ITO film) is formed (this conductive film is used as an anode electrode) by a known application method such as screen printing. The front substrate provided with this phosphor layer and the back substrate provided with an electron source (for example, carbon nanotube, graphite nanofiber, etc.) and a cathode electrode are laminated and bonded together with a spacer for securing a vacuum region. . Next, the target FED model can be manufactured by evacuating the inside and vacuum-sealing to form an electron flight space.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited at all by these examples.

Gd: Eu: Zn = (95-x): 5: x (x = 0, 5, 10,) by converting gadolinium nitrate, europium nitrate and zinc nitrate into the number of moles of each constituent metal, in molar ratio 15, 20, 25, 30, 35 and 40), 0.0809 g of glutamic acid (equal moles with the total number of moles of the above three nitrates) is added thereto, and H ₂ O is further added. The total amount was 5.0 g. The nine kinds of mixed solutions thus obtained were each heated at 100 ° C. for 1 hour to gel, and then fired in the atmosphere at 1000 ° C. for 1 hour to obtain [Gd ₂ O ₃ : Eu, Zn _x ]. A nanoparticle phosphor sample of composition was prepared. The particle diameters of the prepared phosphor samples were all about 50 nm. Each sample paste (dispersion medium: ethyl cellulose) was applied onto the ITO film (coating amount: 0.42 mg / cm ² ), dried at 70 ° C., and then fired at 400 ° C. in the atmosphere. This phosphor-attached ITO film is put into a vacuum chamber, and the inside of the chamber is evacuated to 1 × 10 ⁻⁴ Pa. Then, the phosphor is irradiated with an electron beam with an acceleration voltage of 3.0 kV and a current density of 70 μA / cm ² , and red The emission luminance (cd / m ² ) was measured. In FIG. 1, the value of the light emission luminance with respect to each Zn amount (mol%) is plotted.

  As apparent from FIG. 1, when 5 mol% of Zn is added, the luminance is improved, and when the Zn addition amount is further increased, the luminance remains high up to 25 mol%, but exceeds 25 mol% and exceeds 30 mol. When it became mol%, the luminance was lowered and became almost the same as when Zn was not added. From this, it was confirmed that when 5 to 25 mol% of Zn was added, the light emission luminance was improved.

  The nanoparticle phosphor preparation method described in Example 1 was repeated. However, in order to examine the addition amount of Eu, each inorganic salt was added at a molar ratio of Gd: Eu: Zn = (85−x): x: 15 (x = 0, 0.5, 1.5, 2). .5, 3.5, 4.5, and 5.5). The particle diameters of the seven types of nanoparticle phosphors thus obtained were the same as in Example 1. Further, the effect of the Eu amount (mol%) on the red emission luminance was examined in the same manner as in Example 1. As a result, it was confirmed that when 0.5 to 5 mol% of Eu was added, the red emission luminance was improved.

  The nanoparticle phosphor preparation method described in Example 1 was repeated. However, yttrium nitrate was used instead of gadolinium nitrate. The influence of the Zn amount (mol%) on the red emission luminance of the nanoparticle phosphor thus obtained was the same as in Example 1. The particle size of each phosphor was also the same.

  The nanoparticle phosphor preparation method described in Example 2 was repeated. However, yttrium nitrate was used instead of gadolinium nitrate. The effects of the Eu amount (mol%) on the particle size and the red emission luminance of each phosphor for the seven types of nanoparticle phosphors thus obtained were the same as in Example 2.

Yttrium nitrate, europium nitrate, and zinc nitrate are mixed so that the molar ratio of each constituent metal is Y: Eu: Zn = 85: 5: 10, and 0.0809 g of glutamic acid is added thereto. (Equal moles with the total number of moles of the three kinds of nitrates) was added, and H ₂ O was further added so that the total amount became 5.0 g. The mixed solution thus obtained is heated at 100 ° C. for 1 hour to gel, and then fired in the air for 1 hour to produce a nanoparticle phosphor sample having a composition of [Y ₂ O ₃ : Eu, Zn]. did. Firing in this case was performed by changing the temperature to 500, 700, 900, 1000, 1100, 1200, and 1400 ° C.

The particle diameters of the seven phosphor samples prepared as described above were all about 300 nm or less. Each sample paste (dispersion medium: ethyl cellulose) was applied onto the ITO film (coating amount: 0.42 mg / cm ² ), dried at 70 ° C., and then fired at 400 ° C. in the atmosphere. This phosphor-attached ITO film is put into a vacuum chamber, and the inside of the chamber is evacuated to 1 × 10 ⁻⁴ Pa. Then, the phosphor is irradiated with an electron beam with an acceleration voltage of 3.0 kV and a current density of 70 μA / cm ² , and red The emission luminance (cd / m ² ) was measured. In FIG. 2, the value of the light emission luminance with respect to each baking temperature is plotted.

  The phosphor sample obtained at a firing temperature of 500 ° C. could not confirm light emission, and the phosphor sample obtained at a firing temperature of 700 ° C. emitted light, but its emission luminance was extremely low. As can be seen from FIG. 2, a phosphor sample with good emission luminance is obtained at a firing temperature of 900-1500 ° C., and preferably a phosphor sample with further improved emission luminance is obtained at 1000-1400 ° C. . However, the particle size of the obtained phosphor sample was about 50 to 300 nm from the analysis results based on the transmission electron microscope and the spread of the X-ray diffraction peak, but the firing temperature was 900 to 1100 ° C. The range was about 50 to 100 nm, and increased from 100 nm to 300 nm as the temperature increased from 1100 ° C. to 1400 ° C. Accordingly, when the ratio of the number of moles of organic acid to the total number of moles of inorganic salt is 1.0 and the firing temperature is 900 to 1100 ° C., a phosphor with high material efficiency and low brightness can be obtained. At the same time, since the particle size is small, it can be seen that high brightness can be obtained even at an acceleration voltage lower than the above-described measurement conditions of light emission brightness.

  An SEM photograph of the phosphor sample obtained at a firing temperature of 1000 ° C. in the above is shown in FIG. As is apparent from FIG. 3, the phosphor has a small particle size (100 nm or less), and this phosphor sample showed high luminance. A phosphor sample having a small bulk density and a large particle size (exceeding 300 nm) was obtained at a firing temperature exceeding 1500 ° C.

(Comparative Example 1)
The method described in Example 5 was repeated. However, the molar ratio of glutamic acid and nitrate was 0.5 and 0.7, and the firing temperature was 900-1100 ° C. As a result, sufficient luminance could not be obtained due to the influence of impurities, and the particle size was as large as about 500 nm.

The nanoparticle phosphor (Gd ₂ O ₃ : 5% Eu, 15% Zn) obtained in Example 1 and the conventional red phosphor for CRT (Y ₂ O ₂ SiEu) are the same as in Example 1. The sample was irradiated with an electron beam with an acceleration voltage of 3.0 kV and a current density of 70 μA / cm ² , and the red light emission luminance (cd / m ² ) was measured to find 2130 / m ² (invention) and 1240 cd / m ^2. No. ² (conventional invention), and the phosphor of the present invention emitted red light with higher luminance. This is presumably because the nanoparticle phosphor of the present invention is produced by the self-propagating combustion method, so that a phosphor with high crystallinity and higher brightness can be provided.

  According to the present invention, it is possible to provide a red nanoparticle phosphor that is not deteriorated by irradiation with a low-acceleration electron beam, has high emission luminance, prevents charge-up, and has a deep electron penetration depth. Is suitable for a light emitting device. Therefore, the present invention is very useful industrially in the field of display such as FED.

The graph which shows the influence of Zn addition amount (mol%) with respect to light-emitting luminance (cd / m < ² >) about the nanoparticle fluorescent substance obtained in Example 1. FIG. The graph which shows the influence of the calcination temperature with respect to light-emitting luminance (cd / m < ² >) about the nanoparticle fluorescent material obtained in Example 5. FIG. The SEM photograph of the nanoparticle fluorescent substance obtained by baking at 1000 degreeC.

Claims (12)

A phosphor obtained by using at least one oxide selected from Y ₂ O ₃ and Gd ₂ O ₃ as a base material and adding an activator metal composed of Eu and Zn to the base material. 2. The phosphor according to claim 1, wherein the addition amount of Eu is 0.5 to 5 mol% based on the total number of moles of the constituent metal of the base and the activator metal. 3. The phosphor according to claim 1, wherein the added amount of Zn is 5 to 25 mol% based on the total number of moles of the constituent metal of the base and the activator metal. At least one kind of inorganic salt selected from inorganic salt of Y and inorganic salt of Gd, inorganic salt of Eu, inorganic salt of Zn, and organic acid are dissolved or dispersed in a solvent, and then fired to phosphor. A method for manufacturing a phosphor, which is characterized by comprising: The method for producing a phosphor according to claim 4, wherein after the dissolution or dispersion, the obtained solution or dispersion is gelled before firing. The Eu inorganic salt is added in an amount such that it is contained in the phosphor in an amount of 0.5 to 5 mol% in terms of Eu, based on the total number of moles of constituent metals of all the inorganic salts. The method for producing a phosphor according to claim 4 or 5. The inorganic salt of Zn is added in such an amount that it is contained in the phosphor in an amount of 5 to 25 mol% in terms of Zn, based on the total number of moles of constituent metals of all the inorganic salts. The method for producing a phosphor according to any one of claims 4 to 6. The method for producing a phosphor according to claim 4, wherein the firing is performed at a temperature of 900 to 1500 ° C. The method for producing a phosphor according to claim 4, wherein the organic acid is at least one amino acid. The method for producing a phosphor according to claim 9, wherein the amino acid is at least one selected from glycine, aspartic acid and glutamic acid. The method for producing a phosphor according to any one of claims 4 to 10, wherein the number of moles of the organic acid is 1 to 50 times the total number of moles of all the inorganic salts. A light emitting device comprising the phosphor according to any one of claims 1 to 3 or the phosphor produced by the production method according to any one of claims 4 to 11.