JP2008266482A - Phosphor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride-based particulate phosphor excellent in emission efficiency. <P>SOLUTION: A compound, as a fluorescent substance, represented by the formula M<SP>1</SP><SB>a</SB>M<SP>2</SP><SB>b</SB>N<SB>c</SB>(wherein M<SP>1</SP>is one or more elements selected from the group consisting of Mg, Ca, Sr, Ba and Zn; M<SP>2</SP>is one or more elements selected from the group consisting of Al, Ga and In; c=(2a/3)+b; and 0≤a and 0<b) is heteroepitaxially grown on a platy base material particles, to form a particulate phosphor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  For example, the phosphor constitutes a visible light excitation light emitting element such as a white LED in combination with an LED emitting blue light, or constitutes a near ultraviolet light to blue violet light excitation light emitting element in combination with an LED emitting near ultraviolet to blue violet light. It is used for In addition, UV-excited light-emitting elements such as liquid crystal backlights and fluorescent lamps, vacuum ultraviolet-excited light-emitting elements such as plasma display panels and rare gas lamps, electron-beam-excited light-emitting elements such as cathode ray tubes and FEDs (Field Emission Display), and X-rays It is widely used in combination with various light emitting elements such as an X-ray excited light emitting element such as an imaging device and an electric field excited light emitting element such as an inorganic EL display.

  As described above, when a phosphor is used in combination with another element, the phosphor requires various characteristics depending on the element to be combined, for example, a light emitting element. For example, when combined with a white LED, it is used at a temperature close to 100 ° C. or higher, so that thermal stability and chemical stability are also required. In the case of a combination with FED, it is required to have conductivity in order to prevent charging. An example of a phosphor that can satisfy such various requirements is a nitride phosphor.

Since nitride phosphors are excellent in thermal stability and are conductive, they have been expected to be applied to light emitting devices for which it has been difficult to use oxide phosphors or sulfide phosphors. However, in general, synthesis of a nitride phosphor requires high temperature and pressure and requires a special apparatus, which increases costs. In particular, since GaN-based phosphors have a high nitrogen partial pressure at high temperatures and are easily decomposed, it has been difficult to obtain good-quality phosphors. Patent Document 1 proposes a method in which a GaN thin film is grown on fine particles by chemical vapor deposition and used as a powder phosphor.
JP-A-11-279550

  The technique proposed in Patent Document 1 is intended to form a fluorescent material on the surface of AlN particles using a CVD method. Therefore, even if the particle diameters of the AlN particles are made uniform, it is difficult to improve the luminous efficiency of the obtained phosphor, and there is a problem that the luminance is inevitably insufficient. Yes.

  An object of the present invention is to provide a nitride-based particulate phosphor excellent in luminous efficiency and a method for producing the same.

In order to solve the above-mentioned problems, the present inventors have studied the characteristics and the like of a large number of nitride-based compounds having fluorescence, and the formula M ¹ _a M ² _b N _c (where M ¹ is Mg, One or more elements selected from the group consisting of Ca, Sr, Ba and Zn, and M ² is one or more elements selected from the group consisting of Al, Ga and In, and c = (2a / 3 It is found that a nitride phosphor having high luminous efficiency can be obtained in a granular form by heteroepitaxially growing a compound represented by (2) + b and 0 ≦ a and 0 <b) on a plate-like particle. It was. As a result of intensive studies based on this finding, the present inventors have made the present invention.

According to the invention of claim 1, wherein ^{_{M 1 a M 2 b N c}} ( however, M ¹ is, Mg, Ca, Sr, at least one element selected from the group consisting of Ba and Zn, M ² Is one or more elements selected from the group consisting of Al, Ga and In, c = (2a / 3) + b, and 0 ≦ a and 0 <b). There is proposed a phosphor characterized by heteroepitaxial growth on the particles.

According to the invention of claim 2, in the invention of claim 1, a phosphor in which M ¹ is Zn is proposed.

According to the invention of claim 3, in the invention of claim 1 or 2, a phosphor in which M ² is Ga is proposed.

  According to a fourth aspect of the present invention, there is proposed a phosphor according to the first, second or third aspect, wherein the compound is doped with impurities.

  According to invention of Claim 5, in the invention of Claim 1, 2, 3 or 4, the fluorescent substance whose said dopant is Si is proposed.

According to the invention of claim 6, in the invention of claim 1, 2, 3, 4 or 5, a phosphor is proposed in which the particles are Al ₂ O ₃ .

According to the invention of claim 7, in the invention of claim 1, 2, 3, 4, 5 or 6, a phosphor in which the particles are α-Al ₂ O ₃ is proposed.

  According to the invention of claim 8, in the invention of claim 1, 2, 3, 4, 5, 6 or 7, the particles have a hexagonal crystal structure, and the compound is on the C-plane of the particles. Growing phosphors are proposed.

  According to the invention of claim 9, in the invention of claim 1, 2, 3, 4, 5, 6, 7 or 8, the particle size in the height direction of the particles is H, and the longest bottom particle size is D. A phosphor having a D / H ratio of 1 to 30 is proposed.

  According to the invention of claim 10, there is provided a method for producing the phosphor according to any one of claims 1 to 9, wherein particles having crystal faces are arranged on a substrate, and the particles are arranged on the substrate. A phosphor manufacturing method is proposed, in which after the compound is heteroepitaxially grown, the phosphor is manufactured by peeling off the particles on which the compound has grown from the substrate.

According to an eleventh aspect of the present invention, there is proposed a method for manufacturing a phosphor according to the tenth aspect, wherein the substrate is a SiO ₂ substrate or a substrate on which a SiO ₂ thin film is formed.

  According to the invention of claim 12, in the invention of claim 10 or 11, a method for producing a phosphor is proposed in which the heteroepitaxial growth is a metal organic vapor phase epitaxy method.

  Since the granular phosphor according to the present invention is excellent in thermal stability, it is useful for white LEDs. Further, since the phosphor according to the present invention is conductive, it can be used effectively for FED. Furthermore, according to the present invention, since the phosphor has good crystallinity, it emits light with high luminance, and a large amount of phosphor can be produced at one time, which is extremely useful industrially.

  Hereinafter, an example of an embodiment of the present invention will be described in detail.

The phosphor of the present invention has the formula (1)
M ¹ _a M ² _b N _c (1)
A fluorescent substance, which is a compound represented by the formula (1), is grown on a particle serving as a growth substrate (substrate particle) using an appropriate growth method.

In the above formula (1), M ¹ is a Group 2 metal element. M ¹ is one or more selected from the group consisting of Mg, Ca, Sr, Ba and Zn, preferably one or more selected from the group consisting of Ca, Mg and Zn, and more preferably Zn. .

M ² is a Group 3 metal element. M ² includes at least one selected from the group consisting of Al, Ga and In, preferably at least one selected from the group consisting of Ga and In, and more preferably Ga.

Between a, b, and c in Formula (1), it is necessary to satisfy the relationship of c = (2a / 3) + b, and 0 ≦ a and 0 <b. When the above conditions are satisfied, this phosphor is excited by light in the wavelength range of near ultraviolet to blue-violet light, and further from near ultraviolet to blue light, and becomes a phosphor exhibiting high luminance. Further, this phosphor becomes a phosphor exhibiting high luminance by electron beam irradiation. Here, the molar ratio a / b between M ¹ and M ² is preferably 0.00001 or more and 0.001 or less, more preferably 0.00004 or more and 0.0005 or less, and particularly preferably 0.0001 or more and 0.0003 or less.

  The phosphor is preferably doped with impurities. As the impurities, Si, O, Ge, Sn, and Pb are preferable, Si, O, and Ge are more preferable, and Si is most preferable.

The phosphor can be obtained by heteroepitaxially growing the above-described phosphor on the surface of a base particle such as fine particles. For this reason, the substrate particles must be able to withstand the growth process. That is, the condition for forming the nitride phosphor requires a high temperature close to 1000 ° C. and a reducing atmosphere such as NH ₃ . In addition, the fluorescent material needs to be selectively formed on the substrate particles. Examples of the material for the base material particles that satisfy these conditions include Al ₂ O ₃ , Si, SiC, AlN, MgAl ₂ O ₄ , LiTaO _3, etc., preferably Al ₂ O ₃ , Si, and SiC, and more preferably Al ₂ O ₃ and α-alumina is particularly preferred.

  The substrate particles (fine particles) necessary for forming the phosphor of the present invention have a specific crystal structure from the viewpoint of easy formation of the fluorescent material, and it is important to appropriately select the growth direction. is there. The crystal structure is preferably a hexagonal system, and the growth direction is preferably the C-axis direction.

  When the fluorescent material is grown on the base material particles, a method of crystal growth of the fluorescent material in a state where a large number of base material particles are arranged on a substrate having an appropriate size can be used. When such a method is adopted, the fine particles used for forming the phosphor of the present invention must be uniformly distributed without overlapping on the substrate. The substrate particles (fine particles) are plate-like crystals, and the D / H ratio is 1 to 30 when the crystal grain size in the height direction is H and the longest bottom grain size is D. A uniform distribution without any problem is realized.

When base particles are arranged on a substrate and a fluorescent substance is crystal-grown on the base particles by heteroepitaxial growth, the phosphor grows on the surface of the base particles as well as on the substrate surface. there is a possibility. In order to separate the phosphor particles obtained by crystal growth of the fluorescent material on the base material particles from the substrate, it is desirable that the fluorescent material does not form crystals on the substrate. As the substrate on which the fluorescent material represented by the formula (1) is not formed, a SiO ₂ substrate or a substrate in which a SiO ₂ thin film is formed on a substrate other than the SiO ₂ substrate is preferable. However, it is particularly preferable that the SiO ₂ thin film is formed on a substrate other than the SiO ₂ substrate.

  As a method for forming a fluorescent substance on the substrate particles, metal organic vapor phase epitaxy (MOVPE), molecular beam epitaxy (MBE), hydride vapor deposition (HVPE), pulsed laser deposition (PLD), etc. Although it can be used, MOCVD method and MBE method are preferable.

Next, an example of a method for producing the phosphor according to the present invention will be described.
First, a SiO ₂ thin film is formed on a substrate such as sapphire by vapor deposition. Plate-like fine particles serving as base particles are made into a slurry form with ultrapure water or the like, and applied onto a substrate (hereinafter sometimes simply referred to as a substrate) on which a SiO ₂ thin film is formed by a spin coater or the like. By using such a method, the fine particles can be arranged on the required substrate without overlapping. The fine particles can be arranged on the substrate by, for example, a method of immersing the substrate in a slurry containing fine particles and a medium, or a method of applying or spraying the slurry to the substrate. When plate-like fine particles are used, the slurry is applied to the substrate and then sandwiched between different substrates, and then the latter substrate is removed, so that the plate-like fine particles can be placed on the substrate on a relatively flat surface. Is possible. The medium that can be used is water, methanol, ethanol, isopropanol, n-butanol, ethylene glycol, dimethylacetamide, methyl ethyl ketone, methyl isobutyl ketone, etc., preferably water. After drying, the fine particles are fixed to the substrate by intermolecular force.

  For example, a MOVPE apparatus can be used for epitaxial growth for crystal growth of a fluorescent substance on fine particles on a substrate. In this case, as the group 2 source gas, an organic metal compound of one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, and Zn is used in combination. Examples of the organometallic group include a dimethyl group, a diethyl group, a biscyclopentadienyl group, a bismethylcyclopentadienyl group, and a bisethylcyclopentadienyl group.

As the gallium source gas, aluminum source gas, and indium source gas, trialkylates or trihydrides in which an alkyl group having 1 to 3 carbon atoms or hydrogen is bonded to each metal atom are usually used. For example, trimethylgallium ((CH ₃ ) ₃ Ga), triethylgallium ((C ₂ H ₅ ) ₃ Ga), or the like can be used as a raw material for Ga.

  As the nitrogen raw material, ammonia is usually used, and examples thereof include hydrazine, methyl hydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine, and ethylenediamine. These can be used alone or in any combination. Among these raw materials, ammonia and hydrazine are preferable because they do not contain carbon atoms in their molecules and thus cause less carbon contamination in the semiconductor.

  As the growth atmosphere gas and the carrier gas for the organometallic raw material, gases such as nitrogen, hydrogen, argon, and helium can be used alone or in combination. Since the pre-decomposition of the raw material is suppressed in a hydrogen gas or helium gas atmosphere, hydrogen gas or helium gas is more preferable as the carrier gas.

FIG. 1 shows an outline of an example of a vapor growth semiconductor manufacturing apparatus used for manufacturing the phosphor according to the present invention by the MOVPE method. The vapor phase growth semiconductor manufacturing apparatus includes a reaction furnace 2 in which a source gas is supplied through a source supply line 1 from a source supply apparatus (not shown). A susceptor 4 for heating the substrate 3 is provided in the reaction furnace 2. The susceptor 4 is a polygonal column, and a plurality of substrates 3 are attached to the surface thereof. Here, on the SiO ₂ layer (not shown) on each surface of the substrate 3, plate-like fine particles (not shown), which are base material particles, are uniformly applied as described above. .

  The susceptor 4 has a structure that can be rotated by a rotating device 5. An infrared lamp 6 for heating the susceptor 4 is provided inside the susceptor 4. The substrate 3 can be heated to a desired growth temperature by supplying a heating current from the heating power source 7 to the infrared lamp 6. By this heating, the raw material gas supplied to the reaction furnace 2 through the raw material supply line 1 is thermally decomposed on the substrate 3, and a desired compound is vapor-grown on the surface of fine particles (not shown) coated on the substrate 3. Can be done. Of the raw material gas supplied to the reaction furnace 2, unreacted raw material gas is discharged from the exhaust port 8 to the outside of the reactor and sent to an exhaust gas treatment device (not shown).

  Since the granular phosphor obtained by growing the crystal of the fluorescent substance on the fine particles on the substrate in this way is connected to the substrate only by the intermolecular force, it can be scraped off from the substrate with a very weak force. The granular phosphor separated from the substrate by scraping can also be used as a phosphor for various light emitting devices. It can also be used separately from the substrate portion by pulverization by etching, dividing ball, or the like. Further, the phosphor of the present invention may be laminated on the light emitting element by a technique such as laser ablation, magnetron sputtering, plasma CVD or the like without scraping off the substrate.

  As the phosphor of the present invention, a specific type of phosphor can be used alone. However, the phosphor of the present invention can be used in combination with a plurality of emission colors, and can be installed on the light emitting surface of the light emitting element to form a light emitting device. The fluorescent color can be adjusted by changing the emission color of the phosphor to, for example, a combination of blue and yellow, a combination of red and green, a combination of red, green and blue. In particular, by adjusting the amount of the phosphors to be combined so that the mixed fluorescent color light is visually white, the combined phosphors are placed on the light emitting surface of the light emitting element, so that a white light emitting device with high brightness can be obtained. Can be manufactured.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to the following examples.

Example 1
As the substrate, a sapphire whose C surface was mirror-polished and having a SiO _{2 layer} of 100 nm formed by vapor deposition was used. A spin coater obtained by slurrying plate-like α-alumina particles (average major axis 40 μm, average thickness 2 μm) (trade name Sumiko Random: manufactured by Sumitomo Chemical Co., Ltd.) with ultrapure water on the substrate thus formed. Was applied. The substrate to which the water slurry was applied was sandwiched between different sapphire substrates, and the latter sapphire substrate was slid and removed. After drying, it was confirmed by an X-ray diffractometer that the alumina particles arranged on the substrate were C-plane oriented, and the substrate was introduced into a vapor phase growth apparatus.

The atmospheric pressure MOVPE method was used for the vapor phase growth. As a growth method, a two-stage growth method using GaN as a low temperature growth buffer layer was used. At 1 atmosphere, susceptor temperature is 485 ° C., carrier gas is hydrogen, carrier gas, ammonia as nitrogen source, and trimethylgallium (hereinafter sometimes abbreviated as TMG) as Ga source are supplied at 60 slm, 40 slm, and 9.6 sccm, respectively. Then, a GaN buffer layer having a thickness of about 500 mm was grown in a growth time of 5 minutes. Next, after the temperature of the susceptor was set to 960 ° C., carrier gas, ammonia and TMG were supplied at 60 slm, 40 slm, and 40 sccm, respectively, and dimethyl zinc (hereinafter sometimes abbreviated as DMZn) at 400 sccm, and the growth time was 60 minutes. Then, Zn _a1 Ga _b1 N _c1 having a thickness of about 3 μm was grown. The molar ratio (a / b) at that time was 0.000091. Thereafter, the temperature of the reactor was cooled to room temperature while the carrier gas was kept as hydrogen, and the carrier gas was taken out from the reactor. However, slm and sccm are units of gas flow rate. 1 slm indicates that a gas having a weight occupying a volume of 1 liter in a standard state flows per minute, and 1000 sccm corresponds to 1 slm.

  The emission characteristics of the phosphor 1 thus obtained (Example 1) were evaluated from the obtained excitation spectrum and emission spectrum using a fluorescence spectrophotometer (manufactured by JASCO Corporation). The evaluation was performed without removing the phosphor 1 from the substrate. In the emission spectrum, the excitation wavelength was measured in the range of near ultraviolet light, blue light, and green light. It was found that the phosphor 1 was excited by light having a wavelength of 370 nm or less and emitted blue light having a maximum emission intensity in the vicinity of a wavelength of 430 nm. The measurement result is shown in FIG. 2 and the excitation spectrum and the emission spectrum obtained by excitation with near ultraviolet light (365 nm) are shown in FIG. The emission intensity was converted to a value in which the granular phosphor 1 covered the entire surface of the substrate. The molar ratio (Zn atomic weight / Ga atomic weight) of Zn contained in the phosphor 1 was measured by secondary ion mass spectrometry SIMS.

(Example 2)
A phosphor 2 (Example 2) was produced in the same manner as in Example 1 except that the supply of DMZn was 200 sccm and the molar ratio (a / b) was 0.000046. The light emission characteristics of the phosphor 2 were evaluated using a fluorescence spectrophotometer (manufactured by JASCO Corporation) in the same manner as in Example 1. The obtained results are shown in FIG.

(Example 3)
A phosphor 3 (Example 3) was produced in the same manner as in Example 1 except that the supply amount of DMZn was 800 sccm and the molar ratio (a / b) was 0.000182. The light emission characteristics of the phosphor 3 were evaluated using a fluorescence spectrophotometer (manufactured by JASCO Corporation) in the same manner as in Example 1. The obtained results are shown in FIG.

(Comparative Examples 1, 2, 3)
Comparative Examples 1, 2, and 3 (phosphor) corresponding to Examples 1, 2, and 3 in the same manner as Examples 1, 2, and 3 except that a sapphire substrate without SiO ₂ deposition and α-alumina coating was used. 4, 5, 6) were obtained (see FIG. 2). These phosphors 4, 5, and 6 were evaluated by the excitation spectrum and the emission spectrum in the same manner as in Example 1. The measurement results are shown in FIG. FIG. 4 shows the excitation spectrum of phosphor 4 (Comparative Example 1), the emission spectrum obtained by excitation with near ultraviolet light (365 nm), and the measurement results. FIG. 5 shows the emission spectrum of phosphor 4 obtained by excitation with near ultraviolet light and that of phosphor 1.

(Comparative Example 4)
Comparative Example 4 (phosphor 7) was produced in the same manner as in Example 1 except that α-alumina that was not plate-shaped was used as the base particle. Α-alumina that is not plate-like was applied onto the substrate in the same manner as in Example 1, and after drying, it was confirmed that the particles were randomly oriented by an X-ray diffractometer. The subsequent implementation conditions were the same as in Example 1, and a phosphor 7 was obtained. FIG. 2 shows the results of evaluating this phosphor 7 based on the excitation spectrum and the emission spectrum.

The figure which shows schematic structure of the metal-organic vapor phase growth semiconductor manufacturing apparatus used for manufacture of the fluorescent substance of this invention. The figure which shows the measurement result of the light emission characteristic of Examples 1-3 of this invention and Comparative Examples 1-4 as a table | surface. 3 is a graph showing the light emission characteristics of Example 1. 6 is a graph showing the light emission characteristics of Comparative Example 1. 5 is a graph showing a comparison of light emission characteristics between Example 1 and Comparative Example 1.

Explanation of symbols

1 Raw material supply line 2 Reactor 3 Growth substrate 4 Susceptor 5 Rotating device 6 Infrared lamp 7 Power supply for heating 8 Exhaust port

Claims (12)

Formula M ¹ _a M ² _b N _c (where M ¹ is one or more elements selected from the group consisting of Mg, Ca, Sr, Ba and Zn, and M ² consists of Al, Ga and In) A compound represented by one or more elements selected from the group, c = (2a / 3) + b, and 0 ≦ a and 0 <b) is heteroepitaxially grown on a plate-like particle. A phosphor characterized by that. The phosphor according to claim 1, wherein M ¹ is Zn. The phosphor according to claim 1, wherein M ² is Ga.   The phosphor according to claim 1, 2 or 3, wherein the compound is doped with an impurity.   The phosphor according to claim 1, wherein the dopant is Si. The phosphor according to claim 1, 2, 3, 4 or 5 wherein the particles is Al ₂ O _3. The phosphor according to claim 1, 2, ₃ , 4, 5 or 6, wherein the particles are α-Al ₂ O ₃ .   The phosphor according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the particles have a hexagonal crystal structure and the compound is grown on a C-plane of the particles.   The D / H ratio when the particle size in the height direction of the particles is H and the longest bottom particle size is D is 1 to 30. Claims 1, 2, 3, 4, 5, 6, 7 or 8 The phosphor described.   A method for producing the phosphor according to any one of claims 1 to 9, wherein particles having a crystal plane are arranged on a substrate, and the compound is heteroepitaxially grown on the substrate on which the particles are arranged. A method for producing a phosphor, comprising producing a phosphor by peeling off particles on which a compound has grown from a substrate. It said substrate a phosphor manufacturing method according to claim 10 SiO ₂ substrate or SiO ₂ thin film is a substrate which is formed on the surface.   The method for producing a phosphor according to claim 10 or 11, wherein the heteroepitaxial growth is a metal organic chemical vapor deposition method.

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