JP5777242B2 - Phosphor material and light emitting device - Google Patents

Description

  The present invention relates to a phosphor material having a coating layer on the surface of phosphor particles and a light emitting device using the same.

  At present, LED lamps are attracting attention as backlights or next-generation lighting for liquid crystal televisions. In order to make the LED lamp emit white light, the light emitted from the LED element itself is passed through a phosphor, such as red, blue, or green, or a kneaded lens, and the white light is obtained by superimposing the light emitted from the phosphor. There is a need. However, phosphors have a weak point in that their light emission characteristics deteriorate when exposed to moisture, heat, or ultraviolet rays. Therefore, in order to protect against these external causes, the phosphor particles may be coated with a metal oxide film.

Japanese Patent Application No. 2009-137727 JP 2008-291251 A

  There are various coating methods, and one of them is the sol-gel method (see Patent Document 1). However, in the case of the sol-gel method, a precursor film is formed on the surface of the phosphor particles, and then a heat treatment is performed in an oxidizing atmosphere to form a metal oxide film. In some cases, such effects may occur.

  In addition, as another coating method, there is a method of coating the surface of a phosphor using metal oxide fine particles (see Patent Document 2). According to this method, since metal oxide fine particles are used, there is no need for heat treatment in an oxidizing atmosphere, and there is no problem of deterioration in characteristics due to heat treatment. However, in general, when this method is used, it is difficult to coat the entire surface of the phosphor particles, and an exposed portion of the phosphor is confirmed when observed at the electron microscope level. In addition, even if the coating is seemingly uniform, there is a problem that moisture or ultraviolet rays are transmitted from the interface of the metal oxide fine particles and the life is shortened.

  The present invention has been made based on such a problem, and can improve characteristics such as water resistance and ultraviolet light resistance, and can suppress deterioration of characteristics due to coating, and a light emitting device. The purpose is to provide.

  The phosphor material of the present invention has phosphor particles and a coating layer that covers the surface of the phosphor particles, and the coating layer has a structure in which fine particles having an average particle diameter of 10 nm to 40 nm are laminated. Is.

  The light emitting device of the present invention includes the phosphor material of the present invention.

  According to the phosphor material of the present invention, since the coating layer having a structure in which fine particles having an average particle diameter of 10 nm or more and 40 nm or less are laminated, the entire surface of the phosphor particles can be substantially covered. Further, it is possible to prevent moisture or ultraviolet light from being transmitted from the interface of the fine particles. Therefore, characteristics such as water resistance and ultraviolet light resistance can be improved, and the luminance maintenance rate with the passage of time can be improved. In addition, since the structure is formed by laminating fine particles, the phosphor particles can be manufactured without being subjected to heat treatment at a temperature at which the phosphor particles are deteriorated, and deterioration of characteristics due to the heat treatment can be prevented. Therefore, a decrease in initial luminance can be suppressed and high characteristics can be obtained. Therefore, according to the light emitting device using the phosphor material of the present invention, excellent characteristics can be obtained and the life can be extended.

  In particular, if the maximum particle size of the fine particles is 50 nm or less, the phosphor particles can be coated more stably, and characteristics such as water resistance and ultraviolet light resistance can be further improved.

  Moreover, if the coating layer has a structure in which three or more particle layers are laminated in the thickness direction, transmission of moisture or ultraviolet light can be more effectively suppressed, and water resistance, ultraviolet light resistance, etc. Characteristics can be improved.

  Furthermore, if the thickness of the coating layer is 10 nm or more and 1 μm or less, excellent water resistance can be obtained and high permeability can be obtained.

  In addition, the coating layer is at least one member selected from the group consisting of rare earth oxides, zirconium oxides, titanium oxides, zinc oxides, aluminum oxides, composite oxides of yttrium and aluminum, magnesium oxide, and composite oxides of aluminum and magnesium. If the metal oxide is included, characteristics such as water resistance and ultraviolet light resistance can be further improved.

  Furthermore, if the coating layer contains a rare earth oxide containing at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), cerium (Ce) and lanthanum (La), High characteristics can be obtained, and cost can be reduced.

It is a schematic diagram showing the structure of the phosphor material which concerns on one embodiment of this invention. It is a figure showing the structure of the light-emitting device using the fluorescent substance material of FIG. 2 is a SEM photograph of the phosphor material of Example 1. 2 is an SEM photograph of phosphor particles used in Example 1. 2 is a TEM photograph of the phosphor material of Example 1. 6 is an enlarged photograph of the phosphor material of FIG. It is a TEM photograph of the phosphor material of Comparative Example 1-2. It is a characteristic view which shows the brightness | luminance maintenance factor of Example 1 and Comparative Examples 1-1 and 1-2. 4 is a TEM photograph of the phosphor material of Example 3. FIG. 10 is a characteristic diagram illustrating a luminance maintenance rate of Example 3. 6 is a SEM photograph of the phosphor material of Example 4. 4 is a SEM photograph of the phosphor material of Comparative Example 4.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows a phosphor material 10 according to an embodiment of the present invention. The phosphor material 10 includes phosphor particles 11 and a coating layer 12 that covers the surfaces of the phosphor particles 11.

Examples of the phosphor particles 11 include blue phosphors such as BaMgAl ₁₀ O ₁₇ : Eu, ZnS: Ag, Cl, BaAl ₂ S 4: Eu or CaMgSi ₂ O ₆ : Eu, Zn ₂ SiO ₄ : Mn, (Y, Gd ) BO ₃ : Tb, ZnS: Cu, Al or (Ba, Sr, Mg) O.aAl ₂ O ₃ : Green phosphor such as Mn, (Y, Gd) BO ₃ : Eu, Y ₂ O ₂ S: Examples thereof include red phosphors such as Eu or YPVO ₄ : Eu. The particle diameter of the phosphor particles 11 is basically not limited, but it is preferable that the average particle diameter is about 5 μm to 20 μm and the particle diameters are as uniform as possible. This is because the characteristics can be stabilized.

  The coating layer 12 has a structure in which fine particles 12A having an average particle diameter of 40 nm or less are laminated on the surface of the phosphor particles 11. Thereby, the entire surface of the phosphor particles 11 can be substantially covered, and moisture or ultraviolet light can be prevented from being transmitted from the interface of the fine particles 12A. Further, since the phosphor particles 11 can be manufactured without heat treatment at a temperature at which the phosphor particles 11 deteriorate, the characteristics are not deteriorated by the heat treatment, and high characteristics can be obtained. In the present invention, the fact that the coating layer 12 covers the entire surface of the phosphor particles 11 does not exclude even the presence of defects such as vacancies, and is substantially close to 100%. It means that it is coverage. The average particle diameter of the fine particles 12A is the average particle diameter of primary particles.

  For example, the average particle diameter of the fine particles 12A is more preferably 30 nm or less, and further preferably 25 nm or less. The average particle size of the fine particles 12A is preferably 10 nm or more, and more preferably 15 nm or more. This is because if the average particle diameter of the fine particles 12A is too small, coarse secondary aggregated particles are generated and it is difficult to uniformly coat the phosphor particles 11. The average particle diameter of the fine particles 12A is preferably about 1/100 or less to 1/500 or less of the average particle diameter of the phosphor particles 11. This is because the coating layer 12 can be formed more stably.

  The maximum particle diameter of the fine particles 12A is preferably 50 nm or less, for example. This is because if particles larger than 50 nm are present, defects that expose the phosphor particles 11 are likely to occur. For example, the maximum particle size of the fine particles 12A is preferably 40 nm or less, and more preferably 30 nm or less.

  The covering layer 12 preferably has a structure in which the fine particles 12A are laminated in a thickness direction by three or more particle layers. This is because moisture or ultraviolet light can be more effectively suppressed from passing through the interface of the fine particles 12A. The thickness of the covering layer 12 is preferably 10 nm or more and 1 μm or less. This is because if the thickness is thin, the effects of water resistance and ultraviolet resistance are reduced, the phosphor particles 11 are deteriorated, and if the thickness is thick, the light transmittance is lowered and the light emission efficiency is lowered.

The coating layer 12 is made of rare earth oxide, zirconium oxide, titanium oxide, zinc oxide, aluminum oxide, yttrium / aluminum composite oxide such as yttrium / aluminum / garnet, magnesium oxide, and aluminum / magnesium such as MgAl ₂ O ₄ . It is preferable that at least one metal oxide selected from the group consisting of complex oxides is contained as a main component. Specifically, it is preferable that oxide particles containing the metal oxide are included in at least a part of the fine particles 12. This is because characteristics such as water resistance and ultraviolet light resistance can be improved. Among these, rare earth oxides are preferable, rare earth oxides containing at least one element selected from the group consisting of yttrium, gadolinium, cerium and lanthanum are more preferable, and Y ₂ O ₃ is particularly preferable. This is because higher effects can be obtained and costs can be suppressed.

  The coating layer 12 may contain one of these alone, or may contain a mixture of two or more. For example, a plurality of types of oxide particles may be mixed and may be included by laminating different oxide particles in layers, or a plurality of types of oxides may be included in one oxide particle. May be. Moreover, the coating layer 12 may contain other components, but the proportion of the other components is preferably 0.1% by mass or less. This is because when the proportion of other components is increased, the light transmittance and ultraviolet resistance are lowered.

Although the green phosphor is greatly deteriorated by ultraviolet light, it is preferable to form the coating layer 12 with Y ₂ O ₃ because the deterioration can be remarkably suppressed.

  The phosphor material 10 can be manufactured, for example, as follows. First, a slurry in which fine particles 12A having an average particle diameter of 40 nm or less are dispersed in a solvent is prepared. Next, the phosphor particles 11 are mixed with the slurry, or the slurry in the fluidized bed of the phosphor particles 11 The slurry is applied to the surface of the phosphor particles 11 by spraying. Subsequently, the coating layer is dried to remove the solvent, and the coating layer 12 is formed. At that time, heat treatment is not necessary, but heat treatment is preferably performed at a temperature of 450 ° C. or lower. This is because the adhesion of the coating layer 12 can be enhanced while preventing the deterioration of the characteristics of the phosphor particles 11. The atmosphere during the heat treatment may be an air atmosphere, but it is more preferable to use an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere in order to prevent characteristic deterioration due to oxygen during the heat treatment. Moreover, it is preferable to repeat the application | coating process and drying process of the slurry with respect to the fluorescent substance particle 11 twice or more, and it is more preferable if it repeats 3 times or more. This is because it is possible to reliably stack three or more particle layers 12A by repeating. However, there is no need to increase the number of coatings to a plurality of times as long as three or more particle layers can be stacked.

  FIG. 2 shows a configuration example of the light emitting device 20 using the phosphor material 10. In the light emitting device 20, a light emitting element 22 is mounted on a substrate 21, and the light emitting element 22 is electrically connected to a wiring 23 formed on the substrate 21 by a wire 24. For example, a reflector frame 25 is formed around the light emitting element 22, and a sealing layer 26 is formed on the light emitting element 22 so as to cover the light emitting element 22. The sealing layer 26 is made of, for example, a resin in which the phosphor material 10 is dispersed.

  As the light emitting element 22, for example, an element that emits ultraviolet light, blue light, or green light as excitation light is used. As the phosphor material 10, for example, one that emits red light by excitation light emitted from the light emitting element 22, one that emits blue light, one that emits green light, one that emits yellow light, or the like is necessary. Depending on the mixture, they are used.

  As described above, according to the present embodiment, since the coating layer 12 having a structure in which the fine particles 12A having an average particle diameter of 10 nm to 40 nm are stacked is provided, the entire surface of the phosphor particles 11 is substantially covered. In addition, it is possible to prevent moisture or ultraviolet light from being transmitted from the interface of the fine particles 12A. Therefore, characteristics such as water resistance and ultraviolet light resistance can be improved, and the luminance maintenance rate with the passage of time can be improved. Further, since the structure is formed by laminating the fine particles 12A, the phosphor particles 11 can be manufactured without being subjected to heat treatment at a temperature at which the phosphor particles 11 are deteriorated, and deterioration of characteristics due to the heat treatment can be prevented. Therefore, a decrease in initial luminance can be suppressed and high characteristics can be obtained. Therefore, according to the light emitting device 20 using the phosphor material 10, it is possible to obtain excellent characteristics and to extend the life.

  In particular, if the maximum particle diameter of the fine particles 12A is set to 50 nm or less, the phosphor particles 11 can be coated more stably, and characteristics such as water resistance and ultraviolet light resistance can be further improved.

  Further, if the coating layer 12 has a structure in which fine particles are laminated in the thickness direction, three or more particle layers are laminated, so that the transmission of moisture or ultraviolet light can be more effectively suppressed. The characteristics can be improved.

  Furthermore, if the thickness of the coating layer 12 is 10 nm or more and 1 μm or less, excellent water resistance can be obtained and high permeability can be obtained.

  In addition, the coating layer 12 is at least one member selected from the group consisting of rare earth oxides, zirconium oxides, titanium oxides, zinc oxides, aluminum oxides, yttrium and aluminum composite oxides, magnesium oxide, and aluminum and magnesium composite oxides. If a metal oxide of a kind is included, characteristics such as water resistance and ultraviolet light resistance can be further improved.

  Furthermore, if the coating layer 12 includes a rare earth oxide containing at least one element selected from the group consisting of yttrium, gadolinium, cerium and lanthanum, higher properties can be obtained, and the cost can be reduced. Can be suppressed.

Example 1
A slurry in which fine particles 12A of yttrium oxide (Y ₂ O ₃ ) having an average particle diameter of 20 nm and a maximum particle diameter of 50 nm are dispersed in a solvent is prepared, and green phosphor particles 11 having an average particle diameter of about 10 μm are prepared in this slurry. After mixing, the slurry was applied to the surface of the phosphor particles 11. Next, the phosphor particles 11 coated with the slurry were heat-treated and dried. The heat treatment was performed at 300 ° C. for 2 hours in the air or at 400 ° C. for 2 hours in a nitrogen atmosphere. Subsequently, with respect to the dried phosphor particles 11, the slurry application step and the drying step were repeated once more to obtain the phosphor material 10.

  FIG. 3 shows an example of an SEM (Scanning Electron Microscope) photograph of the obtained phosphor material 10, and FIG. 4 shows the phosphor particles 11 before the coating layer 12 is formed. It shows an example of an SEM photograph. FIG. 5 shows an example of a TEM (Transmission Electron Microscope) photograph in the vicinity of the surface of the obtained phosphor material 10, and FIG. 6 shows a part of the TEM photograph of FIG. Is an enlarged version. As shown in FIGS. 3 and 5, it can be seen that the phosphor material 10 has the coating layer 12 formed on the entire surface of the phosphor particles 11. Further, as shown in FIG. 6, it can be seen that the coating layer 12 has a structure in which three or more particle layers are averagely laminated on the surface of the phosphor particles 11.

  Subsequently, a light emitting device 20 as shown in FIG. 2 was produced using the obtained phosphor material 10. The light emitting element 22 used emits ultraviolet light.

(Comparative Example 1-1)
A light emitting device was fabricated in the same manner as in Example 1 except that the phosphor particles were used as they were without forming a coating layer on the phosphor particles.

(Comparative Example 1-2)
Phosphor particles 11 were mixed in a solution in which a yttrium salt was dissolved in a solvent, the solution was adhered to the surface of the phosphor particles 11, dried and gelled, and then baked at 500 ° C. for 2 hours in an air atmosphere. The same phosphor particles 11 as in Example 1 were used. FIG. 7 shows an example of a TEM photograph near the surface of the obtained phosphor material. In FIG. 7, the portion indicated by 111 is a phosphor particle, and the portion indicated by 112 is a coating layer. In addition, the white part on the fluorescent substance particle 11 and the coating layer 112 is a carbon film used at the time of analysis. As shown in FIG. 7, in this phosphor material as well, the coating layer 112 was formed on the entire surface of the phosphor particles 111, but a laminated structure of fine particles was not seen. With respect to this phosphor material, a light emitting device was produced in the same manner as in Example 1.

(Deterioration test)
With respect to each light emitting device 20 of Example 1 and Comparative Examples 1-1 and 1-2, a light emission test was performed to examine a change in luminance with time. FIG. 8 shows a comparison of the results of Example 1 and Comparative Examples 1-1 and 1-2. In FIG. 8, the vertical axis represents the relative luminance maintenance rate when the initial luminance of Comparative Example 1 in which no coating layer is formed is 100%. In Example 1, the same results were obtained when the heat treatment was performed at 300 ° C. for 2 hours in the air and when the heat treatment was performed at 400 ° C. for 2 hours in the nitrogen atmosphere.

  As shown in FIG. 8, according to Example 1 in which the coating layer 12 has a laminated structure of the fine particles 12A, a decrease in luminance over time is significantly suppressed as compared with Comparative Example 1-1 in which the coating layer is not formed. We were able to. Further, in Comparative Example 1-2, although the luminance maintenance ratio with time is high, a decrease in the initial luminance is observed, whereas according to Example 1, the decrease in the initial luminance can be significantly suppressed. . That is, if the surface of the phosphor particles 11 is covered with the coating layer 12 having the laminated structure of the fine particles 12A, the luminance maintenance rate with the passage of time can be improved and the decrease in the initial luminance can be suppressed. It was found that high characteristics can be obtained.

(Examples 2-1 to 2-4, Comparative Example 2-1)
A phosphor material 10 and a light emitting device 20 were produced in the same manner as in Example 1 except that the average particle size and the maximum particle size of the fine particles 12A were changed. In Example 2-1, the average particle size is 40 nm and the maximum particle size is 50 nm. In Example 2-2, the average particle size is 30 nm and the maximum particle size is 50 nm. In Example 2-3, the average particle size is 25 nm and the maximum particle size. In Example 2-4, the average particle size was 20 nm and the maximum particle size was 40 nm. In Comparative Example 2-1, fine particles 12A having an average particle size of 50 nm and a maximum particle size of 80 nm were used. The obtained light-emitting device 20 was subjected to a light emission test in the same manner as in Example 1, and the change in luminance with time was examined. The obtained results are shown in Table 1 together with the results of Example 1 and Comparative Examples 1-1 and 1-2. In Table 1, the luminance maintenance rate after 2000 hours is a relative value when the initial luminance of Comparative Example 1-1 in which no coating layer is formed is 100%.

  As shown in Table 1, good results were obtained when the average particle size of the fine particles 12A was 40 nm or less. That is, it was found that high characteristics can be obtained if the average particle size of the fine particles 12A is 40 nm or less. Further, good results were obtained when the maximum particle size of the fine particles 12A was 50 nm or less. That is, it was found that higher characteristics can be obtained if the maximum particle size of the fine particles 12A is 50 nm or less.

(Example 3)
A phosphor material 10 and a light emitting device 20 were manufactured in the same manner as in Example 1 except that the slurry application step and the drying step were performed only once. When the obtained phosphor material 10 was observed by TEM, it was confirmed that the coating layer 12 was formed on the entire surface of the phosphor particles 11. Moreover, the coating layer 12 had a structure in which the fine particles 12 were laminated between one particle layer and three particle layers on average. FIG. 9 shows a TEM photograph near the surface of the obtained phosphor material 10. Further, the obtained light emitting device 20 was subjected to a light emission test in the same manner as in Example 1, and the change with time of luminance was examined. The obtained results are shown in Table 2 and FIG. 10 together with the results of Example 1 and Comparative Example 1-1. In Table 2 and FIG. 10, the luminance maintenance rate is a relative value when the initial luminance of Comparative Example 1-1 in which no coating layer is formed is 100%.

  As shown in Table 2 and FIG. 10, in Example 3, although the luminance maintenance rate could be significantly improved as compared with Comparative Example 1-1 in which the coating layer 12 was not formed, compared with Example 1. The luminance maintenance rate was low. This is presumably because moisture or ultraviolet light may be transmitted from the interface of the fine particles 12A because the number of the fine particles 12A is small. That is, it has been found that higher characteristics can be obtained by laminating the fine particles 12A in the thickness direction by three or more particle layers.

(Example 4, Comparative Example 4)
The phosphor material 10 and the light emitting device 20 were manufactured in the same manner as in Example 1 except that the average particle size of the fine particles 12A was changed to the small particle size side and the maximum particle size was changed accordingly. In Example 4, fine particles 12A having an average particle size of 15 nm and a maximum particle size of 40 nm, and Comparative Example 4 having an average particle size of 8 nm and a maximum particle size of 30 nm were used. The obtained light-emitting device 20 was subjected to a light emission test in the same manner as in Example 1, and the change in luminance with time was examined. The obtained results are shown in Table 3 together with the results of Example 1 and Comparative Example 1-1. In Table 3, the luminance maintenance rate after 2000 hours is a relative value when the initial luminance of Comparative Example 1-1 in which no coating layer is formed is 100%.

  As shown in Table 3, in Example 4 in which the average particle size of the fine particles 12A was 15 nm, the same good results as in Example 1 were obtained. On the other hand, in Comparative Example 4 in which the average particle diameter of the fine particles 12A was 8 nm, the luminance maintenance rate over time was significantly reduced. That is, it was found that high characteristics can be obtained when the average particle size of the fine particles 12A is 10 nm or more, preferably 15 nm or more.

  In order to verify these causes, the phosphor material 10 obtained in Example 4 and Comparative Example 4 was observed using an SEM. FIG. 11 is an example of an SEM photograph of the phosphor material 10 of Example 4, and FIG. 12 is an example of an SEM photograph of the phosphor material of Comparative Example 4. As shown in FIGS. 11 and 12, in Example 4, the fine particles 12A are uniformly coated, whereas in Comparative Example 4, the fine particles 12A are not uniformly coated, and are regarded as aggregates of the fine particles 12A. It was found that the particles were attached as coarse secondary aggregated particles. That is, if the average particle size of the fine particles 12A is too small, abnormal secondary aggregation of the fine particles 12A occurs before the phosphor particles 11 are coated, and it becomes difficult to uniformly coat the phosphor particles 11. Conceivable.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the case where the coating layer 12 having the structure in which the fine particles 12A are laminated on the surface of the phosphor particles 11 has been described, but the layer containing other substances that do not adversely affect the phosphor particles 11 May be further formed.

  It can be used for light emitting devices such as LEDs.

  DESCRIPTION OF SYMBOLS 10 ... Phosphor material, 11 ... Phosphor particle, 12 ... Coating layer, 12A ... Fine particle, 20 ... Light emitting device, 21 ... Substrate, 22 ... Light emitting element, 23 ... Wiring, 24 ... Wire, 25 ... Reflector frame, 26 ... Sealing layer

Claims (6)

Having phosphor particles and a coating layer covering the surface of the phosphor particles;
The coating layer may have a mean particle diameter are stacked 15 nm or more 40nm less fine structure,
A phosphor material having a maximum particle size of 50 nm or less . The phosphor material according to claim 1, wherein the coating layer has a structure in which three or more particle layers are stacked in the thickness direction. The thickness of the coating layer, the phosphor material of claim 1 or claim 2, characterized in that at 10nm or more 1μm or less. The coating layer includes at least one metal selected from the group consisting of rare earth oxides, zirconium oxide, titanium oxide, zinc oxide, aluminum oxide, yttrium / aluminum composite oxide, magnesium oxide, and aluminum / magnesium composite oxide. phosphor material according to any one of claims 1 to 3, characterized in that it comprises an oxide. The fluorescence according to claim 4 , wherein the rare earth oxide includes at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), cerium (Ce), and lanthanum (La). Body material. Emitting device comprising a phosphor material according to any one of claims 1 to 5.