JP2008088397A - Phosphor and process for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor that is inhibited in discoloration, has good reflectance characteristics and can achieve sufficient light emission luminance. <P>SOLUTION: The phosphor is represented by formula (1): (Y<SB>1-x</SB>Ln<SB>x</SB>)<SB>2</SB>O<SB>3</SB>wherein Ln denotes at least one kind of element selected from the group consisting of Tb, Eu, Tm, Ce and Bi; and x denotes a numerical value satisfying the numerical condition of 0.01≤x≤0.2. The phosphor has a crystallite size of 60 nm or more and a value calculated by subtracting the reflectance with respect to a light of a wavelength of 400 nm from the reflectance with respect to a light of a wavelength of 800 nm of 10% or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a phosphor and a method for producing the same.

  As a large-screen television, a CRT projection display (PRT), which is superior in price, is widely used. This is a display of a system that uses three red, green and blue monochrome CRTs (cathode ray tubes) to enlarge and project an image on a screen. The phosphor screen of the cathode ray tube used in this display contains a phosphor. The phosphor is excited by applying a high voltage electron beam of 25 to 30 kV to emit light.

  By the way, field emission display (FED) attracts attention with the recent thinning of the display. The driving principle of the FED is the same as that of the above cathode ray tube (CRT), and the phosphor is excited and emits light by applying an electron beam of 10 kV or less to the phosphor screen.

  Here, in order to obtain sufficient light emission brightness in the PRT and FED, it is necessary to increase the current density of the electron beam. In particular, the FED has a lower electron beam voltage than the PRT. For this reason, in order to obtain sufficient light emission brightness in the FED, a current density higher than the current density of the electron beam in the PRT is required. As a result, in the PRT and FED, the temperature of the phosphor particles rises during driving and may reach a high temperature of 300 ° C. or higher.

Therefore, in order to obtain sufficient emission luminance in the PRT and FED, the thermal stability of the phosphor particles is important. Among phosphor materials used for PRT, FED, etc., rare earth oxides such as Y ₂ O _{3 and} Gd ₂ O ₃ are known as materials having high thermal stability. A phosphor made of a rare earth oxide is described in Non-Patent Document 1, for example.

  In addition, the phosphor made of the rare earth oxide is generally manufactured by using the following solid phase method (see, for example, Non-Patent Document 2). First, after a mixture obtained by mixing a plurality of metal oxide powders as a raw material of the phosphor is put in a container such as a crucible, the mixture is heated at a high temperature for a long time to advance a solid phase reaction. Next, the solid obtained after the reaction is finely pulverized with a ball mill or the like and then classified to obtain a phosphor. This manufacturing method by a solid phase method is a general method for manufacturing a phosphor.

Recently, a phosphor manufacturing method using a sol-gel method (for example, see Patent Document 1) and a phosphor manufacturing method using a high-temperature plasma (for example, see Patent Document 2) have been studied. .
JP-A-2005-75863 Japanese Patent No. 3585967 D. K. Williams et al. , J .; Phys. Chem. B, 1998, 102, 916 Fluorescent Material Society, “Fluorescent Handbook”, published by Ohmsha, 166 pages

However, in a general solid phase method as described in Non-Patent Document 2, even if heating is performed at a high temperature for a long time, a Y ₂ O ₃ raw material powder having a very high melting point of 2410 ° C. and Tb ₄ The raw material powder that becomes the emission center, such as O ₇ (melting point: 2300 ° C.) powder and Eu ₂ O ₃ (melting point: 2290 ° C.) powder, does not sufficiently react. As a result, the crystallinity of the phosphor, that is, the crystallite size and the reflectance characteristics are insufficient, so that sufficient light emission luminance cannot be obtained.

  Further, in the sol-gel method disclosed in Patent Document 1, a sufficiently high emission luminance cannot be obtained because the crystallite size of the phosphor is insufficient. Furthermore, the average particle diameter of the phosphor produced by the sol-gel method is usually as small as 300 nm or less. When this phosphor is used for an FED, sufficient light emission luminance cannot be obtained.

  Further, in the method using high-temperature plasma disclosed in Patent Document 2, since the heating temperature of the phosphor is as high as 2500 ° C. to 6500 ° C., the ratio of defects such as oxygen defects in the crystal structure of the phosphor increases. As a result, the phosphor particles are colored and the reflectance characteristics are insufficient, so that sufficient light emission luminance cannot be obtained.

  The present invention has been made in view of the above circumstances, and provides a phosphor capable of suppressing phosphor coloring, having good reflectance characteristics, and obtaining sufficient light emission luminance, and a method for producing the same. The purpose is to do.

In order to solve the above-mentioned problem, the phosphor of the present invention has the following general formula (1);
(Y _1-x Ln _x ) ₂ O ₃ (1)
[In the general formula (1), Ln represents at least one element selected from the group consisting of Tb, Eu, Tm, Ce and Bi. X represents a numerical value satisfying the condition of 0.01 ≦ x ≦ 0.2. ]
The crystallite size is 60 nm or more, and the value obtained by subtracting the reflectance for light having a wavelength of 400 nm from the reflectance for light having a wavelength of 800 nm is 10% or less.

  According to the phosphor of the present invention, coloring of the phosphor is suppressed, the reflectance characteristics are good, and sufficient light emission luminance can be obtained. This reason is considered as follows, for example, but is not limited to the following reason.

  When the crystallite size is less than 60 nm, the crystallinity of the phosphor is deteriorated, so that the emission luminance is lowered. Further, if the value obtained by subtracting the reflectance for light having a wavelength of 400 nm from the reflectance for light having a wavelength of 800 nm exceeds 10%, the phosphor is colored and a problem occurs in the reflectance characteristics of the phosphor. That is, the ratio of the phosphor itself reabsorbing visible light emission generated by exciting the phosphor with ultraviolet rays or an electron beam increases, resulting in a decrease in emission luminance.

  Moreover, it is preferable that an average particle diameter is 2 micrometers or more.

  If the average particle size is less than 2 μm, the emission luminance per phosphor particle tends to decrease. That is, the number of emission centers contained in one phosphor particle, that is, the number of Ln in the general formula (1) decreases, and the emission luminance tends to decrease.

  The method for producing a phosphor of the present invention comprises a step of producing a phosphor precursor using a solution containing a metal element as a raw material, and the precursor at a temperature of 1500 to 2000 ° C. in the air or in an inert gas atmosphere. The first firing step for obtaining a fired body by firing for 30 minutes or more and 12 hours or less, and the fired body in an inert gas atmosphere or a reducing gas atmosphere at a temperature lower than the temperature of the first firing step and 1000 to 1000 And a second baking step of baking at a temperature of 1500 ° C. for 30 minutes to 8 hours.

  According to the method for producing a phosphor of the present invention, it is possible to produce a phosphor capable of suppressing the coloring of the phosphor, having good reflectance characteristics, and obtaining sufficient emission luminance. The phosphor of the present invention can also be produced by using the phosphor production method of the present invention.

  In the first firing step, when the precursor is fired at less than 1500 ° C., the crystallite size becomes less than 60 nm, thereby reducing the light emission luminance. On the other hand, when the precursor is fired at a temperature higher than 2000 ° C., the ratio of defects such as oxygen defects in the crystal structure of the phosphor is increased, so that the phosphor coloring cannot be sufficiently removed in the second firing step.

  In the first firing step, if the firing time is less than 30 minutes, the crystallite size is less than 60 nm, and the emission luminance is reduced. On the other hand, if the firing time exceeds 12 hours, the ratio of defects such as oxygen defects in the crystal structure of the phosphor becomes high, so that the coloring of the phosphor cannot be sufficiently removed in the second firing step.

  If the fired body is fired at less than 1000 ° C. in the second firing step, the coloring of the phosphor cannot be sufficiently removed. On the other hand, when the fired body is fired at a temperature higher than 1500 ° C., the ratio of defects such as oxygen defects in the crystal structure of the phosphor is increased, so that coloring of the phosphor cannot be sufficiently removed.

  Further, if the firing time is less than 30 minutes in the second firing step, the coloring of the phosphor cannot be sufficiently removed. On the other hand, if the firing time is longer than 8 hours, the ratio of defects such as oxygen defects in the crystal structure of the phosphor becomes high, so that coloring of the phosphor cannot be sufficiently removed.

  ADVANTAGE OF THE INVENTION According to this invention, coloring of a fluorescent substance is suppressed, the reflectance characteristic is favorable, and the fluorescent substance which can obtain sufficient light-emission brightness, and its manufacturing method are provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate descriptions are omitted.

<Phosphor>
The phosphor according to the present embodiment is represented by the following general formula (1).
(Y _1-x Ln _x ) ₂ O ₃ (1)

  In the general formula (1), Ln represents at least one element selected from the group consisting of Tb, Eu, Tm, Ce and Bi. X represents a numerical value satisfying the condition of 0.01 ≦ x ≦ 0.2.

  In the phosphor according to the present embodiment, the crystallite size is 60 nm or more. The crystallite size is preferably 70 nm or less, and particularly preferably 65 nm or less.

  When the crystallite size is less than 60 nm, the crystallinity of the phosphor is deteriorated, and thus the emission luminance is lowered particularly when the phosphor is excited by an electron beam or ultraviolet rays. When the crystallite size exceeds 70 nm, the ratio of oxygen defects or the like in the crystal structure of the phosphor increases, and therefore the color of the phosphor tends not to be sufficiently removed. For this reason, the emission luminance tends to decrease particularly when the phosphor is excited by an electron beam or ultraviolet rays.

Further, a value obtained by subtracting the reflectance R ₄₀₀ for light having a wavelength of 400 nm from the reflectance R ₈₀₀ for light having a wavelength of ₈₀₀ nm (hereinafter referred to as “specific reflectance difference”, R ₈₀₀ −R ₄₀₀ ) is 10% or less. The specific reflectance difference is preferably 4% or more, and particularly preferably 5% or more.

When the specific reflectance difference exceeds 10%, the phosphor is colored. In this case, in particular, the ratio of the phosphor itself absorbing light emitted when the phosphor is excited by an electron beam or ultraviolet light is increased. As a result, the light emission luminance decreases. Furthermore, a problem arises in the reflectance characteristics of the phosphor. Incidentally, the reflectivity _{R 400} for light having a wavelength 400nm is smaller than the reflectivity _{R 800} with respect to light having a wavelength of 800 nm. When the specific reflectance difference is less than 4%, the number of emission centers contained in the phosphor, that is, the number of Ln in the general formula (1) tends to decrease. As a result, the luminance of the emitted light tends to decrease particularly when the phosphor is excited by an electron beam or ultraviolet rays.

  The crystallite size is measured as follows, for example. First, the X-ray diffraction pattern of the phosphor is measured using an X-ray diffraction measurement device such as Rigaku and Geigerflex RAD-IIA. At this time, in order to obtain an accurate diffraction pattern, the diffraction angle 2θ to be measured is preferably 20 to 80 °. Similarly, the diffraction angle interval to be measured is preferably 0.05 ° or less. The measurement time is preferably set so that the diffraction intensity of the maximum peak of the obtained X-ray diffraction pattern is 3000 or more.

Of the X-ray diffraction patterns obtained by the above measurement, the half-width of the maximum peak found near 2θ = 29.15 ° is obtained. The crystallite size d (unit: nm) can be obtained by substituting the half width β (unit: radian) into the following formula (2). λ (unit: nm) is the wavelength of the X-ray used. θ _m (unit: °) is a half of the diffraction angle 2θ _m of the maximum peak.
d = (0.9λ / βcos θ _m ) (2)

Moreover, the reflectance (y is 400 or 800, for example) with respect to the light of wavelength y [nm] is measured as follows, for example. First, the reflectance of the phosphor with respect to light having a wavelength of 300 nm to 800 nm is measured using, for example, an ultraviolet-visible-near infrared region spectrophotometer such as V-570 manufactured by JASCO Corporation. At this time, in order to accurately measure the reflectance, baseline correction before measurement is performed using a white sample having a reflectance of 97% or more at a wavelength of 300 nm to 800 nm, such as magnesium carbonate, barium sulfate, and Spectralone. Preferably it is done. Next, a reflectance R ₈₀₀ having a wavelength of ₈₀₀ nm and a reflectance R ₄₀₀ having a wavelength of 400 nm are selected from the measured data, and the difference (R ₈₀₀ −R ₄₀₀ ) is calculated. In this way, a specific reflectance difference is calculated.

  The phosphor of the present embodiment is a phosphor particle group, and the average particle diameter is preferably 2 μm or more. The average particle size is preferably 10 μm or less.

  If the average particle size is less than 2 μm, the emission luminance per phosphor particle tends to decrease. If the average particle diameter exceeds 10 μm, the surface area of the phosphor particles when the phosphor particles are formed into a film in practical use such as PRT is reduced. As a result, when the phosphor is excited by electron beams or ultraviolet rays in particular, The emission brightness tends to decrease.

  The average particle diameter of the phosphor is calculated as follows, for example. First, a 1500 times fluorescent particle image is observed with a scanning electron microscope, and a plurality of fluorescent particles are selected at random. At this time, it is preferable to select 200 or more phosphor particles for accuracy. Next, the maximum diameter (major axis) and the minimum diameter (minor axis) are measured for each phosphor particle. Further, the square root of the product of the major axis and the minor axis is calculated and used as the particle diameter of the phosphor particles. The average particle size of the phosphor (phosphor particle group) is defined by dividing the obtained particle size of each phosphor particle by the number of the measured phosphor particles.

  In the phosphor of the present embodiment having the above-described configuration, coloring of the phosphor is suppressed, the reflectance characteristics are good, and sufficient light emission luminance can be obtained. The phosphor of this embodiment is used for, for example, a cathode ray tube (CRT), a fluorescent lamp, a plasma display panel (PDP), a field emission display (FED), and the like.

<Method for producing phosphor>
In the phosphor manufacturing method of the present embodiment, first, a phosphor precursor is prepared using a solution containing a metal element as a raw material (precursor preparation step). Subsequently, the obtained precursor is fired at a temperature of 1500 to 2000 ° C. for 30 minutes to 12 hours in the air or in an inert gas atmosphere to obtain a fired body (first firing step). Furthermore, the fired body is fired in an inert gas atmosphere or a reducing gas atmosphere at a temperature lower than the temperature of the first firing step and 1000 to 1500 ° C. for 30 minutes to 8 hours (second firing step). The firing temperature in the first firing step is preferably 1600 to 1700 ° C. The firing temperature in the second firing step is preferably 1200 to 1400 ° C.

  Examples of the solution containing a metal element include a solution containing Y and at least one element selected from the group consisting of Tb, Eu, Tm, Ce, and Bi. Examples of the inert gas include nitrogen, helium, argon, carbon dioxide and the like. Examples of the reducing gas include a mixed gas of nitrogen and hydrogen, carbon monoxide, and the like. Hereinafter, the manufacturing method of the phosphor of this embodiment will be described in more detail.

(Precursor production process)
Examples of a method for producing phosphor precursor particles using a solution containing a metal element as a raw material include a sol-gel method and a spray pyrolysis method. Here, when preparing the particles of the precursor, it is preferable to adjust the average particle diameter so as to be in a desired range. In addition, since the metal oxide powder is used as a raw material in the solid phase method, in order to obtain the phosphor particles of the present embodiment, the precursor produced by the sol-gel method, the spray pyrolysis method, or the like is calcined. Requires high temperature and long reaction time. Therefore, when the phosphor is manufactured using the solid phase method, oxidation of Ln and generation of defects in the crystal structure proceed in the general formula (1). As a result, the light emission luminance is lower than that in the case of producing a phosphor using a sol-gel method, a spray pyrolysis method, or the like. Hereinafter, the sol-gel method and the spray pyrolysis method will be described.

<Sol-gel method>
In the sol-gel method, an aqueous solution containing the metal element in the general formula (1), that is, an aqueous solution containing the elements Y and Ln, respectively, has a desired chemical composition (the desired general formula (1) The chemical composition of the phosphor to be expressed).

  In addition, as the aqueous solution containing the metal elements represented by Y and Ln in the general formula (1), those in which nitrates, acetates, sulfates, chlorides, etc. of these metal elements are used as an aqueous solution are preferably used. It is done. Moreover, in order to obtain more sufficient light emission luminance, the purity of Y and Ln in all the metal elements in these aqueous solutions is preferably 99.9 atomic% or more.

  Next, the solution containing each metal element described above is stirred and mixed to prepare a raw material solution. The obtained raw material solution is dropped into an alkaline aqueous solution having the same volume as that to prepare a phosphor precursor represented by the general formula (1). Examples of the alkaline aqueous solution used at this time include an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and an aqueous ammonia solution, but an aqueous ammonia solution that does not contain a metal element is preferably used. At this time, in order to obtain phosphor particles having an average particle diameter of 2 μm or more, it is preferable to adjust the phosphor precursor so that the average particle diameter of the phosphor precursor is 2 μm or more.

<Spray pyrolysis method>
Next, in the spray pyrolysis method, an aqueous solution containing the metal element constituting the phosphor to be obtained, that is, an aqueous solution containing the elements Y and Ln, respectively, has a desired chemical composition (the above general formula of interest). (The chemical composition of the phosphor represented by (1)) is mixed. In addition, as the aqueous solution containing the metal elements represented by Y and Ln in the general formula (1), those in which nitrates, acetates, sulfates, chlorides, and the like of these metal elements are used as an aqueous solution are preferably used. It is done.

  Moreover, in order to obtain more sufficient light emission luminance, the purity of Y and Ln in all the metal elements in these aqueous solutions is preferably 99.9 atomic% or more. Next, the solution containing each metal element described above is stirred and mixed to prepare a raw material solution. Next, droplets of the obtained raw material solution are formed and expressed by the above general formula (1) using a spray pyrolysis method in which the droplets are introduced into a pyrolysis furnace by spraying using a carrier gas. A phosphor precursor is prepared.

  Here, examples of the method of forming droplets of the raw material solution include a method using a two-fluid nozzle, a method using ultrasonic waves, and the like, from the viewpoint of optimizing the diameter and yield of the generated droplets. Therefore, a method using a two-fluid nozzle is preferable.

  A well-known thing can be used for a 2 fluid nozzle, For example, the 2 fluid nozzle 10 typically shown in FIG. 1 can be used. FIG. 1 is a diagram schematically showing the configuration of a two-fluid nozzle. The two-fluid nozzle 10 includes a cylindrical main body 15, a frustoconical droplet ejecting section 14 provided on the end face of the main body 15, and a cylindrical gas introduction provided protruding from the side surface of the main body 15. Part 13.

  The main body portion 15 has a cylindrical hollow portion 16 in the axial direction. The droplet ejecting portion 14 includes a cylindrical hollow portion 146 connected to the hollow portion 16 of the main body portion 15 from the bottom surface toward the tip. The end of the hollow portion 16 opposite to the droplet ejection portion 14 is a solution introduction port 12. A raw material solution containing a metal element flows into the two-fluid nozzle 10 from the solution inlet 12.

  The gas introduction part 13 has a cylindrical hollow part 136 in the axial direction thereof. An end portion of the hollow portion 136 opposite to the main body portion 15 is a gas introduction port 132. The carrier gas flows into the two-fluid nozzle 10 from the gas inlet 132. The hollow portion 16 and the hollow portion 136 are electrically connected within the main body portion 15. In the connection portion 18 between the hollow portion 16 and the hollow portion 136, the raw material solution and the carrier gas are in contact with each other.

  The raw material solution and the carrier gas that are in contact with each other at the connection portion 18 flow through the hollow portion 16 toward the droplet ejection portion 14 while forming droplets by mixing. The mixture of the raw material solution and the carrier gas that has reached the hollow portion 146 of the droplet ejection portion 14 (partially or mostly forms droplets) is ejected from the droplet ejection port 142 of the droplet ejection portion 14. Then, droplets are sprayed.

  The flow rate of the raw material solution passed through the two-fluid nozzle and the flow rate of the carrier gas can be adjusted according to the concentration of the raw material solution. In order to obtain the phosphor of this embodiment more efficiently, it is preferable to set the residence time of the formed droplets in the pyrolysis furnace to be 1 second or more and 10 minutes or less. The residence time is more preferably 30 seconds or more and 8 minutes or less, and further preferably 1 minute or more and 3 minutes or less.

  In order to obtain a phosphor having an average particle size of 2 μm or more, the average particle size of droplets generated from the two-fluid nozzle is preferably 5 μm or more, more preferably 7 to 20 μm, and more preferably 10 to 15 μm. It is particularly preferred that The average particle diameter of the droplets can be measured by a method of calculating the diameter of the droplets from the laser diffraction angle when the falling droplets are irradiated with a laser beam.

  In addition, examples of the type of carrier gas that is circulated through the two-fluid nozzle when introducing the droplets into the pyrolysis furnace include air and nitrogen, but are not particularly limited. The temperature in the pyrolysis furnace can be adjusted in accordance with the flow rate and flow rate of the raw material solution passed through the two-fluid nozzle, the flow rate and flow rate of the carrier gas, and the residence time of the droplets in the pyrolysis furnace. . In order to obtain the phosphor of this embodiment more efficiently, it is preferable to set the temperature in the pyrolysis furnace to 460 ° C. or more and 950 ° C. or less.

(First and second firing steps)
Subsequently, the obtained precursor is fired by using an electric furnace such as an ultrafast heating furnace HLF-2030 manufactured by Hiroki Co., Ltd. or an NLA-2025D model manufactured by Motoyama Co., Ltd. The phosphor according to the embodiment is manufactured.

  Here, the precursor is fired after primary firing at 1500 ° C. to 2000 ° C. in air or in an inert gas atmosphere, and then secondary at 1000 ° C. to 1500 ° C. in an inert gas atmosphere or a reducing gas atmosphere. It is defined by a two-stage process for performing firing (first and second firing processes). In only one step, the crystallite size and specific reflectance difference of the obtained phosphor do not satisfy the predetermined conditions, so that the emission luminance when excited with an electron beam or ultraviolet light is lowered.

  According to the manufacturing method of the present embodiment described above, it is possible to manufacture a phosphor in which coloring of the phosphor is suppressed, reflectance characteristics are good, and sufficient emission luminance can be obtained.

  In the first firing step, when the precursor is fired at less than 1500 ° C., the crystallite size becomes less than 60 nm, so that the emission luminance when the phosphor is excited with an electron beam or ultraviolet light is lowered. On the other hand, when the precursor is fired at a temperature higher than 2000 ° C., the ratio of defects such as oxygen defects in the crystal structure of the phosphor is increased, so that the phosphor coloring cannot be sufficiently removed in the second firing step. Moreover, since the specific reflectance difference exceeds 10%, the light emission luminance when excited with an electron beam or ultraviolet light is lowered.

  Further, in the first firing step, if the firing time is less than 30 minutes, the crystallite size is less than 60 nm, so that the emission luminance when the phosphor is excited with an electron beam or ultraviolet light is lowered. On the other hand, if the firing time exceeds 12 hours, the ratio of defects such as oxygen defects in the crystal structure of the phosphor becomes high, so that the coloring of the phosphor cannot be sufficiently removed in the second firing step. Moreover, since the specific reflectance difference exceeds 10%, the light emission luminance when excited with an electron beam or ultraviolet light is lowered.

  If the fired body is fired at less than 1000 ° C. in the second firing step, the coloring of the phosphor cannot be sufficiently removed. Moreover, since the specific reflectance difference exceeds 10%, the light emission luminance when excited with an electron beam or ultraviolet light is lowered. On the other hand, when the fired body is fired at a temperature higher than 1500 ° C., the ratio of defects such as oxygen defects in the crystal structure of the phosphor is increased, so that coloring of the phosphor cannot be sufficiently removed. Moreover, since the specific reflectance difference exceeds 10%, the light emission luminance when excited with an electron beam or ultraviolet light is lowered.

  Further, if the firing time is less than 30 minutes in the second firing step, the coloring of the phosphor cannot be sufficiently removed. Moreover, since the specific reflectance difference exceeds 10%, the light emission luminance when excited with an electron beam or ultraviolet light is lowered. On the other hand, if the firing time is longer than 8 hours, the ratio of defects such as oxygen defects in the crystal structure of the phosphor becomes high, so that coloring of the phosphor cannot be sufficiently removed. Moreover, since the specific reflectance difference exceeds 10%, the light emission luminance when excited with an electron beam or ultraviolet light is lowered.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Example 1)
First, the spray pyrolysis _method to produce a precursor of a phosphor consisting of _{(Y 0.95 Tb 0.05) 2 O} 3.

  Specifically, first, a 0.5 mol / l yttrium nitrate aqueous solution (manufactured by Shin-Etsu Chemical Co., Ltd., an aqueous solution having a purity of 99.99%) and a 0.1 mol / l terbium nitrate aqueous solution (manufactured by Shin-Etsu Chemical Co., Ltd., purity) 99.9% aqueous solution) was mixed at a ratio according to the chemical composition of the phosphor to be produced to obtain a mixed solution. By stirring 1000 ml of the mixed solution at 1200 to 1300 rpm for 5 minutes, a raw material solution to be introduced as droplets into the pyrolysis furnace was prepared.

Next, droplets (average particle size: 14 μm) were formed from the raw material solution using a two-fluid nozzle similar to that shown in FIG. 1, and the droplets were introduced into a 620 ° C. pyrolysis furnace by spraying. . At this time, the flow rate (flow rate) of the raw material solution was 1000 ml / hr, and the flow rate (flow rate) of the air that is the carrier gas was 15000 ml / min. It was 2 minutes when the residence time of the droplet in the furnace was calculated from the carrier gas flow rate and the furnace internal volume (31400 cm ³ ). In this way, a phosphor precursor was produced. The obtained precursor was creamy powder.

  Next, the phosphor precursor is placed in an alumina container, and an ultrafast heating furnace (HLF-2030) manufactured by Hiroki Co., Ltd. is used for 5 hours at 1600 ° C. in a nitrogen stream of 5000 ml / min. Firing was performed to obtain a fired body (first firing step). Thereafter, the fired body was subjected to 1300 ° C. in a 0.5% nitrogen balance hydrogen, that is, a mixed gas stream of nitrogen and hydrogen at 5000 ml / min using an atmosphere type high-speed heating furnace (NLA-2025D) manufactured by Motoyama Co., Ltd. Was fired for 5 hours to obtain the phosphor of Example 1 (second firing step). The firing temperature was confirmed with a JIS-B double type thermocouple and controlled with a digital program controller (KP1130B005) manufactured by Chino Corporation.

(Example 2)
The phosphor of Example 2 was obtained in the same manner as Example 1 except that the firing temperature in the first firing step was 1650 ° C.

(Example 3)
A phosphor of Example 3 was obtained in the same manner as Example 1 except that the firing temperature in the first firing step was 1700 ° C.

(Comparative Example 1)
The phosphor of Comparative Example 1 was obtained in the same manner as in Example 1 except that a phosphor composed of (Y _0.95 Tb _0.05 ) ₂ O ₃ was produced by the solid phase reaction method as follows.

  First, a ratio of yttrium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%) and terbium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%) according to the chemical composition of the phosphor to be produced. Were mixed to prepare 500 g of a mixed powder. For mixing, an agate mortar was used and mixed for 30 minutes.

  Next, the mixed powder is put in an alumina container, and the mixed powder is used at 1600 ° C. in a nitrogen stream 5000 ml / min using an ultrafast heating furnace (HLF-2030) manufactured by Hiroki Co., Ltd. Baking was performed for 12 hours to obtain a fired body. Thereafter, the fired body was fired at 1300 ° C. for 5 hours in a 0.5% nitrogen balance hydrogen stream 5000 ml / min using an atmosphere-type high-speed heating furnace (NLA-2025D) manufactured by Motoyama Co., Ltd. The firing temperature was confirmed with a JIS-B double type thermocouple and controlled with a digital program controller (KP1130B005) manufactured by Chino Corporation.

  Furthermore, the sintered body of the phosphor obtained by firing was finely pulverized using a ball mill (P-5) manufactured by Fritsch Japan. The finely pulverized powder was dispersed in water and allowed to stand, and the phosphor of Comparative Example 1 was obtained by sedimentation classification to remove the supernatant.

(Physical property measurement results)
The physical properties of the phosphors obtained in Examples 1 to 3 and Comparative Example 1 were measured. First, X-ray diffraction measurement was performed using Geigerflex RAD-IIA manufactured by Rigaku. The crystallite size (nm) was calculated by the above formula (2) using the obtained X-ray diffraction pattern. Moreover, product of JASCO Corporation, by measuring the reflectance of the phosphor to light of a wavelength 300nm~800nm using V-570, the reflectance for light having a wavelength 800 nm _{(R 800)} and the reflectance to light of wavelength 400nm The difference (R ₈₀₀ −R ₈₀₀ ) from (R ₄₀₀ ) was calculated. Further, a 1500-fold fluorescent particle image was observed with a scanning electron microscope, and the average particle size (μm) was calculated. The measurement results are shown in Table 1.

As shown in Table 1, in the phosphors of Examples 1 to 3, the crystallite size is 60 nm or more, and the reflectance (R ₈₀₀ ) with respect to light with a wavelength of ₈₀₀ nm and the reflectance (R ₄₀₀ ) with respect to light with a wavelength of 400 nm. ) (R ₈₀₀ −R ₈₀₀ ) is 10% or less. On the other hand, in the phosphor of Comparative Example 1, the crystallite size is less than 60 nm, and (R ₈₀₀ -R ₈₀₀ ) exceeds 10%.

(Emission characteristic evaluation)
Next, the light emission characteristics of the phosphors of Examples 1 to 3 and Comparative Example 1 were compared. The emission characteristics were evaluated by the emission intensity when the phosphor was excited using (a) a 1.4 kV low voltage electron beam, (b) a 25 kV high voltage electron beam, and (c) 304 nm ultraviolet rays, respectively. . The light emission luminance was evaluated as a relative luminance with the light emission luminance when the phosphor of Comparative Example 1 was used as 100 (reference).

(A) 1.4 kV low-voltage electron beam First, a phosphor was deposited on a 3 cm × 2 cm ITO (indium-tin oxide) substrate by the following procedure to form a phosphor film. First, 0.1 g of phosphor was added to a 200 ml beaker containing 120 ml of ion-exchanged water and ultrasonically dispersed for 15 minutes to prepare a phosphor-dispersed aqueous solution. Next, the phosphor-dispersed aqueous solution was added to a 300 ml beaker containing an ITO substrate and 150 ml of ion-exchanged water, and left to stand for 1 day to deposit the phosphor on the ITO substrate.

The ITO substrate on which the phosphor was deposited was taken out of water, allowed to stand at room temperature for 1 day, and then dried in vacuum at 240 ° C. for 2 hours to form a fluorescent film on the surface of the ITO substrate. The amount of phosphor applied was 3.2 mg per 1 cm ^{2 of} the ITO substrate surface.

  The fluorescent film thus obtained was irradiated with an electron beam of 1.4 kV and 300 μA using an electron beam irradiation apparatus manufactured by SETEK Corporation. At this time, the light emission luminance of the phosphor was measured using a luminance meter (LS-110) manufactured by Konica Minolta Holdings, Inc. The results are shown in Table 2.

(B) High-voltage electron beam of 25 kV First, a phosphor was deposited on a 3 cm × 2 cm nickel-plated copper substrate by the following procedure to form a phosphor film. First, 0.075 g of the phosphor was added to a 50 ml beaker containing 20 ml of a 12.5 mass% aqueous water glass solution and ultrasonically dispersed for 10 minutes to prepare a phosphor dispersed aqueous solution. Next, the phosphor-dispersed aqueous solution was added to a 100 ml beaker containing a nickel-plated copper substrate and a 0.05 mass% barium acetate aqueous solution (25 ml), and allowed to stand for one day to deposit the phosphor on the nickel-plated copper substrate. I let you.

After the phosphor was deposited, the nickel-plated copper substrate was taken out of the water, allowed to stand at room temperature for 1 day, and then dried in vacuum at 100 ° C. for 2 hours to form a phosphor film on the copper substrate surface. The amount of phosphor applied was 2.4 mg per 1 cm ^{2 of} the copper substrate surface.

  The phosphor film thus obtained was irradiated with an electron beam of 25 kV and 100 μA using an electron beam irradiation apparatus manufactured by T & TS. At this time, the light emission luminance of the phosphor was measured using a silicon photocell (S1133) manufactured by Hamamatsu Photonics Co., Ltd. and a digital voltmeter (7555) manufactured by Yokogawa Electric Corporation. The results are shown in Table 2.

(C) 304 nm ultraviolet ray First, a phosphor is laid on a glass plate for X-ray diffraction measurement of 1 cm × 2 cm, and then fixed in a cell made of quartz glass of 2 cm × 1 cm × 4.5 cm, and a measurement cell It was.

  The measurement cell obtained by the above procedure was set in a spectrofluorophotometer (F-4500) manufactured by Hitachi, Ltd., and then the measurement cell was irradiated with ultraviolet light at 304 nm. Thereby, the light emission luminance of the phosphor was measured. The results are shown in Table 2.

As shown in Table 2, when the phosphors of Examples 1 to 3 and the phosphor of Comparative Example 1 are compared, in any of the phosphors of Examples 1 to 3, any of the evaluation methods (a) to (c) Even in the case of using, a luminance improvement effect of 13 to 30% was obtained. This is because the phosphor of Comparative Example 1 has a crystallite size of less than 60 nm, and the difference (R ₈₀₀ ) between the reflectance (R ₈₀₀ ) for light with a wavelength of ₈₀₀ nm and the reflectance (R ₄₀₀ ) for light with a wavelength of 400 nm. -R ₈₀₀₎ is inferred to be due to more than 10%.

Example 4
First, a phosphor precursor made of (Y _0.95 Tb _0.05 ) ₂ O ₃ was produced by a sol-gel method.

  Specifically, first, a 0.5 mol / l yttrium nitrate aqueous solution (manufactured by Shin-Etsu Chemical Co., Ltd., an aqueous solution having a purity of 99.99%) and a 0.1 mol / l terbium nitrate aqueous solution (manufactured by Shin-Etsu Chemical Co., Ltd., purity) 99.9% aqueous solution) was mixed at a ratio according to the chemical composition of the phosphor to be produced to obtain a mixed solution. A raw material solution was prepared by stirring 100 ml of the mixed solution at 200 to 300 rpm for 3 minutes.

  100 ml of this raw material solution was dropped into 100 ml of an aqueous ammonia solution (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) diluted to 4% by mass over 10 minutes to produce a phosphor precursor. The obtained precursor was in the form of a white powder.

  Next, the phosphor precursor is placed in an alumina container, and an ultrafast heating furnace (HLF-2030) manufactured by Hiroki Co., Ltd. is used for 5 hours at 1600 ° C. in a nitrogen stream of 5000 ml / min. Firing was performed to obtain a fired body (first firing step). Then, the fired body was fired at 1300 ° C. for 5 hours in a nitrogen balance hydrogen stream 5000 ml / min of 0.5% using an atmosphere type high-speed heating furnace (NLA-2025D) manufactured by Motoyama Co., Ltd. The phosphor of Example 4 was obtained (second firing step). The firing temperature was confirmed with a JIS-B double type thermocouple and controlled with a digital program controller (KP1130B005) manufactured by Chino Corporation.

(Example 5)
A phosphor of Example 5 was obtained in the same manner as Example 4 except that the firing time of the first firing step was 8 hours.

(Example 6)
The phosphor of Example 6 was obtained in the same manner as Example 4 except that the firing time of the first firing step was 10 hours.

(Comparative Example 2)
A phosphor precursor made of (Y _0.95 Tb _0.05 ) ₂ O ₃ was produced by a sol-gel method using glycine as a gelling agent.

  Specifically, first, 0.1792 g of yttrium nitrate hydrate (manufactured by Kanto Chemical Co., Inc., purity 99.99%), 0.0123 g of terbium nitrate hydrate (manufactured by Kanto Chemical Co., Ltd., purity 99.99%). 95%) and 0.0413 g of glycine (manufactured by Kanto Chemical Co., Inc., purity 99.0%) were added to ultrapure water to obtain 5.0 g of a mixture.

  Next, the above mixture was dissolved by heating at 80 ° C. for 30 minutes, and then at 1000 ° C. in a nitrogen stream of 5000 ml / min using an ultrafast heating furnace (HLF-2030) manufactured by Hiroki Co., Ltd. The phosphor of Comparative Example 2 was obtained by firing for 1 hour. The firing temperature was confirmed with a JIS-B double type thermocouple and controlled with a digital program controller (KP1130B005) manufactured by Chino Corporation.

(Physical property measurement results)
For the phosphors obtained in Examples 4 to 6 and Comparative Example 2, physical properties were measured in the same manner as the phosphors obtained in Examples 1 to 3 and Comparative Example 1. Table 3 shows the measurement results.

As shown in Table 3, in the phosphors of Examples 4 to 6, the crystallite size is 60 nm or more, and the reflectance (R ₈₀₀ ) with respect to light having a wavelength of ₈₀₀ nm and the reflectance (R ₄₀₀ ) with respect to light having a wavelength of 400 nm. ) (R ₈₀₀ −R ₈₀₀ ) is 10% or less. On the other hand, in the phosphor of Comparative Example 1, the crystallite size is less than 60 nm, and the difference (R ₈₀₀ −) between the reflectance (R ₈₀₀ ) for light with a wavelength of ₈₀₀ nm and the reflectance (R ₄₀₀ ) for light with a wavelength of 400 nm. R ₈₀₀ ) exceeds 10%.

(Emission characteristic evaluation)
Next, as in Examples 1 to 3 and Comparative Example 1, the emission characteristics of the phosphors of Examples 4 to 6 and Comparative Example 2 were compared. The light emission luminance was measured using (a) a low-voltage electron beam of 1.4 kV, (b) a high-voltage electron beam of 25 kV, and (c) 304 nm ultraviolet rays. The results are shown in Table 4. The light emission luminance was evaluated as a relative luminance with the light emission luminance when the phosphor of Comparative Example 2 was used as 100 (reference).

As shown in Table 4, when the phosphors of Examples 4 to 6 and the phosphor of Comparative Example 2 are compared, any of the evaluation methods (a) to (c) is used for the phosphors of Examples 4 to 6. Even when used, a brightness improvement effect of 24 to 32% was obtained. This is because, in the phosphor of Comparative Example 2, the crystallite size is less than 60 nm, and the difference (R ₈₀₀ ) between the reflectance (R ₈₀₀ ) for light having a wavelength of ₈₀₀ nm and the reflectance (R ₄₀₀ ) for light having a wavelength of 400 nm. -R ₈₀₀₎ is inferred to be due to more than 10%.

(Comparative Example 3)
In the same manner as in Example 4, a phosphor precursor was produced by the sol-gel method. The precursor of the phosphor obtained by the method of processing in a high-temperature _plasma, to produce a phosphor consisting of _{(Y 0.95 Tb 0.05) 2 O} 3.

  Specifically, the precursor of the phosphor is 15 g / min in high temperature plasma (average temperature 3800 ° C.) having an outer diameter of 40 mm generated using a mixed gas of argon 52 l / min and oxygen 27 l / min. The phosphor of Comparative Example 3 was obtained.

(Physical property measurement results)
About the fluorescent substance obtained by the comparative example 3, the physical-property measurement was performed similarly to the fluorescent substance obtained by Examples 1-3 and the comparative example 1. FIG. Table 5 shows the measurement results.

As shown in Table 5, in the phosphor of Comparative Example 3, the crystallite size is 60 nm or more, but the reflectance (R ₈₀₀ ) for light with a wavelength of ₈₀₀ nm and the reflectance (R ₄₀₀ ) for light with a wavelength of 400 nm Difference (R ₈₀₀ −R ₈₀₀ ) exceeds 10%.

(Emission characteristic evaluation)
Next, as in Examples 1 to 3 and Comparative Example 1, the light emission characteristics of the phosphors of Comparative Example 3 were compared. The light emission luminance was measured using (a) a low-voltage electron beam of 1.4 kV, (b) a high-voltage electron beam of 25 kV, and (c) 304 nm ultraviolet rays. The results are shown in Table 6. The light emission luminance was evaluated as a relative luminance with the light emission luminance when the phosphor of Comparative Example 1 was used as 100 (reference).

As shown in Table 6, when the phosphors of Comparative Example 3 and Comparative Example 1 were compared, the luminance improvement effect obtained in the phosphors of Examples 1 to 6 was not obtained with the phosphor of Comparative Example 3. . This is because the phosphor of Comparative Example 3 has a crystallite size of 60 nm or more, but the difference (R ₈₀₀ ) between the reflectance (R ₈₀₀ ) for light with a wavelength of ₈₀₀ nm and the reflectance (R ₄₀₀ ) for light with a wavelength of 400 nm. -R ₈₀₀₎ is inferred to be due to more than 10%.

  From the results shown above, the phosphors of Examples 1 to 6 can obtain sufficiently high emission luminance when irradiated with an electron beam or ultraviolet rays as compared with the phosphors of Comparative Examples 1 to 3. confirmed.

It is a figure which shows the structure of a 2 fluid nozzle typically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... 2 fluid nozzle, 12 ... Solution introduction port, 13 ... Gas introduction part, 14 ... Droplet ejection part, 15 ... Main-body part, 16, 136,146 ... Hollow part, 18 ... Connection part, 132 ... Gas introduction port, 142: Droplet outlet.

Claims (4)

The following general formula (1);
_{(Y 1-x Ln x)} 2 O 3 ··· (1)
[In the general formula (1), Ln represents at least one element selected from the group consisting of Tb, Eu, Tm, Ce and Bi. X represents a numerical value satisfying the condition of 0.01 ≦ x ≦ 0.2. ]
Represented by
A phosphor having a crystallite size of 60 nm or more and a value obtained by subtracting the reflectance for light having a wavelength of 400 nm from the reflectance for light having a wavelength of 800 nm is 10% or less.   The phosphor according to claim 1, wherein the average particle diameter is 2 μm or more. Producing a phosphor precursor using a solution containing a metal element as a raw material;
A first firing step of obtaining a fired body by firing the precursor at a temperature of 1500 to 2000 ° C. for 30 minutes to 12 hours in air or an inert gas atmosphere;
A second firing step of firing the fired body in an inert gas atmosphere or a reducing gas atmosphere at a temperature lower than the temperature of the first firing step and 1000 to 1500 ° C. for 30 minutes to 8 hours;
A method for producing a phosphor, comprising:   The phosphor according to claim 1 or 2 obtained by the method for producing a phosphor according to claim 3.

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