Fluorescent material and light-emitting device

Abstract

To provide a fluorescent member and a light-emitting device that have good light-emitting properties.SOLUTION: A fluorescent member consists of a single crystal whose crystal structure is a garnet structure and whose general formula is represented by BaxY3-x-yAl5-x-zSix-2zPzO12:Cey, where x and y are values included in the range bounded by the straight line represented by y=0.18x+0.0582, the straight line represented by y=0.18x+0.0182, the straight line represented by x=0.01 and the straight line represented by x=0.12, z satisfies 0<z, and x and z satisfy x>2z.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fluorescent member and a light-emitting device.

Background Art

[0002] Conventionally, a white light source combining a YAG phosphor and a blue LED has been widely known, and research on YAG phosphors has been advanced. For example, Non-Patent Document 1 discloses BaY2Al4SiO :Ce in which Ba and Si are solid-dissolved in a YAG phosphor.

Prior Art Documents

Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] According to this aspect, a fluorescent member with good light emission characteristics can be realized.

[0008] The above fluorescent member may have a plate-like shape. This makes it easier to mount on a light source and the like.

[0009] The thickness t of the above fluorescent member may be in the range of 0.02 mm < t < 0.6 mm. This makes it possible to further improve the light emission characteristics of the fluorescent member.

[0010] The above fluorescent member may be excited by blue light with a peak wavelength in the range of 430 nm to 480 nm and emit yellow light with a dominant wavelength in the range of 567 nm to 571 nm. This makes it possible to realize, for example, white light in combination with a blue light source.

[0011] Another aspect of the present invention is a light-emitting device that emits white light. The light-emitting device includes a light source that emits blue light with a peak wavelength in the range of 430 nm to 480 nm, and the above fluorescent member joined to the above light source. According to this aspect, a light-emitting device with good light emission characteristics can be realized.

[0012] In addition, any combination of the above components, and those obtained by converting the expression of the present invention among manufacturing methods, devices such as lamps and lighting, light-emitting modules, light sources, etc. are also effective as aspects of the present invention.

Advantages of the Invention

[0013] According to the present invention, a fluorescent member and a light-emitting device having good light-emitting characteristics can be provided.

Brief Description of the Drawings

[0014] [Figure 1] It is a diagram for explaining the amounts of Ba and Ce in the fluorescent member according to an embodiment of the present invention. [Figure 2] It is a schematic diagram of the light-emitting device according to the same embodiment. [Figure 3] FIG. 3(a) is a diagram showing an example of diffraction spots of a single crystal, and FIG. 3(b) is a diagram showing an example of diffraction spots of a polycrystal. [Figure 4] It is a diagram showing the charging ratios of Ba and Ce in the examples.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. Note that the configurations described below are examples and do not limit the scope of the present invention in any way.

[0016] [Fluorescent Member] The fluorescent member according to the present embodiment is a member composed of a single crystal phosphor. Specifically, the crystal structure is a garnet structure, and the general formula is Ba x Y 3-x-y Al 5-x-z Si x-2z P z O 12 :Ce y (However, x, y, and z satisfy 0 < x, 0 < y, 0 < z, x + y < 3, x + z < 5, and x > 2z.) It is composed of a single crystal represented by. Here, the garnet structure is a crystal structure in which the crystal system is cubic and the space group is Ia3d.

[0017] The fluorescent member according to this embodiment can be excited by blue light and emit yellow light. For example, the fluorescent member may be excited by blue light having a peak wavelength in the range of 430 to 480 nm and emit yellow light having a dominant wavelength in the range of 567 to 572 nm. Note that the yellow light emission can be realized by Ce 3+ ions or the like doped in the fluorescent member. Thus, by combining the fluorescent member with, for example, a blue LED or the like, a light-emitting device that emits white light can be easily manufactured.

[0018] FIG. 1 is a diagram for explaining the amounts of Ba and Ce in the fluorescent member according to this embodiment. In FIG. 1, the amount of B (x) in the above general formula is taken on the horizontal axis, and the amount of Ce (y) is taken on the vertical axis. The inventors have obtained the knowledge that a fluorescent member showing good light-emitting characteristics can be obtained in a specific composition range in the above general formula by conducting experiments and the like shown in the examples described later.

[0019] More specifically, the inventors have obtained the knowledge that a fluorescent member showing good light-emitting characteristics can be obtained when the amounts of Ba (x) and Ce (y) are included in the region S shown by the hatching in FIG. 1. That is, when (x, y) is included in the range surrounded by the straight line L1 represented by y = 0.18x + 0.0582, the straight line L1' represented by y = 0.18x + 0.0182, the straight line L2 represented by x = 0.01, and the straight line L3 represented by x = 0.12, a fluorescent member showing good light-emitting characteristics can be obtained. Also, z may be in the range of 0 < z < 0.06, and more specifically, may be in the range of 0.01 ≦ z ≦ 0.04.

[0020] The fluorescent member according to this embodiment is composed of a single crystal, realizing better light-emitting characteristics. This is presumably because, in the fluorescent member according to this embodiment, the thermal conductivity is improved compared to the case where it is composed of polycrystals, the heat generated during light emission is easily diffused, and the temperature rise in the fluorescent member is suppressed.

[0021] Polycrystalline materials are solids composed of fine single-crystal particles, and grain boundaries or spaces (voids) exist between adjacent particles that make up the polycrystalline material. These grain boundaries and voids act as resistance to thermal conduction. On the other hand, single crystals are solids in which the constituent elements are arranged regularly, and the crystal axis direction is the same throughout the material. Therefore, single crystals do not have (or have few) grain boundaries and voids between particles, unlike polycrystalline materials. Thus, in the fluorescent material according to this embodiment, which is composed of single crystals, there are (or few) grain boundaries and voids that act as resistance to thermal conduction, improving thermal conductivity and, as a result, enabling the realization of good luminescence characteristics.

[0022] [Manufacturing method] An example of a method for manufacturing a fluorescent material according to one embodiment of the present invention will be described. In the method for manufacturing a fluorescent material according to this embodiment, a single crystal of phosphor is prepared using various methods, and the single crystal of phosphor is processed to produce a fluorescent material.

[0023] The phosphor material has elements included in the general formula described above, and may be, for example, Y2O3, CeO2, α-Al2O3, BaCO3, SiO2, and AlPO4. The shape of the material is not particularly limited, but in this embodiment, an example in powder form will be described.

[0024] These powder raw materials are mixed to obtain a desired composition ratio, and a flux such as BaF2 is added as needed to obtain the mixture. The resulting mixture can be heated in a predetermined atmosphere (e.g., a reducing atmosphere of hydrogen and nitrogen) to synthesize the phosphor powder.

[0025] A single crystal of the phosphor is prepared using the synthesized phosphor powder. For example, the single crystal of the phosphor may be prepared using the FZ (Floating Zone) method. In this case, the phosphor powder is mixed and pulverized in a wet ball mill, and then the phosphor powder is heated and dried to form a predetermined shape to produce a sintering material. This sintering material is heated in an FZ furnace at a predetermined heating temperature to grow a single crystal, thereby producing an ingot of the phosphor single crystal. By processing the single crystal ingot obtained in this way using various known processing methods, a fluorescent component of the desired shape can be obtained.

[0026] Although this document describes a method for obtaining phosphor single crystals using the FZ method, this is not the only method available. Other methods, such as the Bridgman method or the CZ (Czochralski) method, may also be used. For example, a phosphor single crystal produced by the FZ method can be used as a seed crystal to produce a fluorescent component using the Bridgman method or the CZ method.

[0027] [Light-emitting device] An example of a light-emitting device using the fluorescent material described above will be explained with reference to Figure 2. Figure 2 is a schematic side view of the light-emitting device 10 according to this embodiment. As shown in Figure 2, the light-emitting device 10 according to this embodiment comprises a substrate 12, a light source 14 provided on the substrate 12, and a fluorescent material 16 provided on the light source 14.

[0028] The light source 14 emits various types of light and may include, for example, an LED (Light Emitting Diode). The light source 14 can emit, for example, blue light with a peak wavelength in the range of 430 nm to 480 nm. The light source 14 emits light from its upper surface toward the fluorescent member 16, and the emitted light is incident on the fluorescent member 16.

[0029] The fluorescent member 16 converts the wavelength of the light emitted from the light source 14 and emits the converted light. Specifically, the fluorescent member 16 can convert the wavelength of at least a part of the incident light and emit yellow light or the like. The blue light emitted by the light source 14 and the yellow light emitted by the fluorescent member 16 may form, for example, white light. The formed white light is emitted above the fluorescent member 16.

[0030] The shape of the fluorescent member 16 is not particularly limited, but may be a plate shape as shown in FIG. 2. In this case, the thickness t of the fluorescent member 16 is preferably in the range of 0.02 mm < t < 0.6 mm, and more preferably in the range of 0.05 mm < t < 0.6 mm. By making the thickness of the fluorescent member 16 greater than 0.2 mm, the mechanical strength of the fluorescent member 16 can be increased, and for example, the yield during mounting can be improved. Also, by making the thickness of the fluorescent member 16 greater than 0.2 mm, the light emitted from the light source 14 can be sufficiently converted, making it easier to realize the desired light (for example, white light). Further, by making the thickness of the fluorescent member 16 less than 0.6 mm, the amount of light leaking from the side surface of the fluorescent member 16 can be reduced, making it easier to improve the effective luminous flux of the light-emitting device 10.

[0031] The shape of the fluorescent member 16 when viewed from above may be any shape, but may be, for example, rectangular. For example, the shape of the fluorescent member 16 when viewed from above may be square, and its dimensions may be, for example, 1 mm to 3 mm square.

[0032] Also, the fluorescent member 16 may be joined to the light source 14 by any method. For example, the fluorescent member 16 may be joined to the light source 14 by room-temperature joining or the like.

[0033] [Example] Hereinafter, it will be described more specifically using examples. However, descriptions of the raw materials, manufacturing methods, chemical compositions of the fluorescent member, etc. below do not limit the embodiments of the fluorescent member of the present invention in any way.

[0034] (Measurement) In each example, the emission characteristics of a sample excited with light of 460 nm were measured using a spectrophotometer (FP-8500, manufactured by JASCO Corporation). Specifically, the dominant wavelength λ of the sample at 25°C was measured. D We measured the dominant wavelength shift (hereinafter simply referred to as "shift amount"), which is the value obtained by subtracting the dominant wavelength at 25°C from the dominant wavelength at 200°C, and the luminescence intensity maintenance rate when the temperature was raised from 25°C to 200°C.

[0035] The target range for the dominant wavelength was set at 567.6 nm to 570.4 nm. The target value for the shift amount was set at 1.5 nm. Furthermore, the target value for the emission intensity maintenance rate was set at 90%. In each example, the dominant wavelength, shift amount, and emission intensity maintenance rate were evaluated by comparing them with the target values.

[0036] Furthermore, in each example, the crystallinity of the prepared sample was determined using X-ray diffraction (XRD). Specifically, the diffraction spots of the sample were observed using an X-ray diffractometer (single-crystal XRD, manufactured by Rigaku Corporation), and the crystallinity of the sample was determined based on the observed diffraction spots.

[0037] Figure 3(a) shows an example of diffraction spots in a single crystal, and Figure 3(b) shows an example of diffraction spots in a polycrystalline material. As shown in Figure 3(a), in a single crystal, diffracted atoms corresponding to the crystal orientation and interplanar spacing form diffraction spots, exhibiting a geometric pattern. On the other hand, as shown in Figure 3(b), in a polycrystalline material, numerous diffraction spots obtained from multiple crystals exhibit concentric rings (Debye-Scherrer rings). In Examples 1 to 5, the crystallinity of the sample was determined based on the observed diffraction spots.

[0038] (Example 1) The compositional formula of the fluorescent material in Example 1 is Ba 0.05 Y 2.89 Al 4.94 Si 0.03 P 0.01 O 12 :Ce 0.06It is represented as follows. The fluorescent material according to Example 1 was manufactured as follows. First, powder raw materials of Y2O3 (99.99%, manufactured by Kojun Chemical Laboratory Co., Ltd.), CeO2 (99.99%, manufactured by Kojun Chemical Laboratory Co., Ltd.), α-Al2O3 (99.99%, manufactured by Kojun Chemical Laboratory Co., Ltd.), BaCO3 (99.9%, manufactured by Kanto Chemical Co., Ltd.), SiO2 (99.9%, manufactured by Tokuyama Corporation), and AlPO4 (manufactured by Kojun Chemical Laboratory Co., Ltd.) were prepared. In Example 1, these powder raw materials were weighed to have molar ratios of Ba=0.05, Y=2.89, Al=4.94, Si=0.03, Ce=0.06, and P=0.01. The elemental charging ratios for Example 1, along with those for Examples 2 to 5, are shown in Table 1.

[0039] [Table 1]

[0040] BaF2 (99%, manufactured by Kojun Chemical Laboratory Co., Ltd.) was weighed as flux at a concentration of 5 wt% of the total weight of the powder raw materials. This was combined with the powder raw materials and uniformly mixed in a mortar to obtain a mixture. The mixture was then placed in an alumina vessel (SSA-S B1, manufactured by Nikkatoh Co., Ltd.) and heated at 1550°C for 4 hours in a reducing atmosphere (H2:N2 = 5:95 (vol ratio)) to synthesize the phosphor powder. The synthesized phosphor powder was cooled to room temperature, and then the cooled phosphor powder was pulverized in a mortar. The luminescence characteristics of the pulverized phosphor powder, excited by light with a wavelength of 460 nm, were measured using a spectrophotometer. As a result, the dominant wavelength λd of the phosphor according to Example 1 was 569.0 nm, which fell within the center of the target range.

[0041] 25g of phosphor powder was weighed and placed in a 500ml poly pot along with 250g of φ1mm alumina balls and 200ml of pure water. This poly pot was then rotated at 60rpm for 24 hours. Next, the phosphor powder was transferred to an aluminum tray coated with Teflon® and heated to dry the material. The dried material was then passed through a nylon mesh with a mesh size of 50μm. 5g of the dried material was weighed and molded into a shape with dimensions of φ5 × L50mm to obtain a molded body. This molded body was sintered in air at 1500°C for 12 hours to obtain a rod-shaped sintering raw material (also called "sintering raw material rod").

[0042] Subsequently, in an FZ furnace, the sintering raw material rod was heated to 1700°C using concentrated heat from a halogen lamp, and crystal growth was carried out at a growth rate of 1.0 mm / hr in an Ar-hydrogen atmosphere (Ar:H2 = 96:4 (vol ratio)) to obtain an ingot.

[0043] A sample of the fluorescent component was cut from the obtained ingot, and the emission characteristics of the sample excited with light of a wavelength of 460 nm were measured using a spectrophotometer. As a result, the dominant wavelength λd of the sample according to Example 1 was 569.1 nm, which fell within the center of the target range. The shift amount was 0.5 nm, and the emission intensity maintenance rate was 92%, both of which met the targets. Furthermore, when the crystallinity of the sample was determined using an X-ray diffractometer, it was found to be a single crystal.

[0044] The measurement results of the luminescence characteristics and the determination of crystallinity of the sample in Example 1 are shown in Table 1, along with the results of Examples 2 to 4. In Table 1, ○ indicates that the dominant wavelength λd satisfies 567.4 nm ≤ λd ≤ 570.6 nm, and × indicates that it does not. Also, ○ indicates that the luminescence intensity maintenance rate is 90% or higher, and × indicates that it is less than 90%. Furthermore, ○ indicates that the shift amount is less than 1.5 nm, and × indicates that it is 1.5 nm or higher. Regarding crystallinity, ○ indicates that the sample is a single crystal, and × indicates that it is not a single crystal.

[0045] (Example 2) The compositional formula of the fluorescent material according to Example 2 is Ba 0.01 Y 2.97 Al 4.989 Si 0.008 P 0.001 O 12 :Ce 0.02 This is represented by [formula]. In Example 2, the sintering material was obtained in the same manner as in Example 1, except that the powder raw materials were weighed to have a molar ratio of Ba=0.01, Y=2.97, Al=4.989, Si=0.008, Ce=0.02, and P=0.001.

[0046] Subsequently, the sintering material was placed in a platinum crucible, and the single crystal prepared in Example 1 was used as a seed crystal. A single crystal was grown using the Bridgman method to obtain an ingot. The growth conditions were a heating temperature of 1700°C and a growth rate of 1.0 mm / hr. A sample of the fluorescent component was cut from the obtained ingot, and the luminescence characteristics and crystallinity of the sample were measured. As a result, in the sample according to Example 2, the dominant wavelength was 567.6 nm, which is the lower limit of the target range, and the crystallinity was that of a single crystal. In addition, the shift amount was 0.5 nm, and the luminescence intensity maintenance rate was 90%, so the targets were achieved in both respects.

[0047] (Example 3) The compositional formula of the fluorescent material according to Example 3 is Ba 0.01 Y 2.93 Al 4.989 Si 0.008 P 0.001 O 12 :Ce 0.06 This is expressed as follows. In Example 3, the sintering material was obtained in the same manner as in Example 1, except that the powder raw materials were weighed to have a molar ratio of Ba=0.01, Y=2.93, Al=4.989, Si=0.008, Ce=0.06, and P=0.001.

[0048] In Example 3, an ingot was obtained using the CZ method. First, the single crystal sample prepared in Example 1 was attached to the tip of a rotating shaft as a seed crystal, and the sintering material was placed in a crucible and melted at 1700°C in the crucible. The seed crystal was then brought into contact with the melted material, and while rotating the shaft at 1 rpm, the seed crystal was pulled up at 1.0 mm / hr to obtain an ingot. A sample of the fluorescent material was cut from the ingot, and the emission characteristics and crystallinity of the sample were measured. As a result, in the sample according to Example 3, the dominant wavelength was 570.4 nm, which was the upper limit of the target range, and the crystallinity was single crystal. In addition, the shift amount was 0.5 nm, and the emission intensity maintenance rate was 90%, so the targets were achieved in all respects.

[0049] (Example 4) The compositional formula of the fluorescent material according to Example 4 is Ba 0.12 Y 2.84 Al 4.87 Si 0.10 P 0.01 O 12 :Ce 0.04 This is expressed as follows. In Example 4, a fluorescent material sample was prepared in the same manner as in Example 3, except that the powder raw materials were weighed to have a molar ratio of Ba=0.12, Y=2.84, Al=4.87, Si=0.10, Ce=0.04, and P=0.01. When the luminescence characteristics and crystallinity of the sample according to Example 4 were measured, the dominant wavelength was 567.7 nm, which is the lower limit of the target range, and the crystallinity was single crystal. In addition, the shift amount was 0.5 nm and the luminescence intensity maintenance rate was 91%, both of which met the targets.

[0050] (Example 5) The compositional formula of the fluorescent material according to Example 5 is Ba 0.12 Y 2.80 Al 4.84 Si 0.04 P 0.04 O 12 :Ce 0.08This is expressed as follows. In Example 5, a fluorescent material sample was prepared in the same manner as in Example 3, except that the powder raw materials were weighed to have the molar ratios of Ba=0.12, Y=2.80, Al=4.84, Si=0.04, Ce=0.08, and P=0.04. When the luminescence characteristics and crystallinity of the sample according to Example 5 were measured, the dominant wavelength was 570.4 nm, which was the upper limit of the target range, and the crystallinity was single crystal. In addition, the shift amount was 0.5 nm and the luminescence intensity maintenance rate was 92%, and the targets were achieved in both respects.

[0051] Figure 4 shows the charging ratios of Ba and Ce in Examples 1 to 5. In Figure 4, the horizontal axis represents the charging ratio (mol ratio) of Ba, and the vertical axis represents the charging ratio (mol ratio) of Ce.

[0052] From Examples 1 to 5, it was found that when the charging ratio of Ba and Ce falls within the hatched region S shown in Figure 4, the dominant wavelength is within the target range (567.6 nm to 570.4 nm) and the crystallinity is single crystal. That is, the general formula Ba x Y 3-x-y Al 5-x Si x O 12 :Ce y In this case, it was found that when (x,y) is within the range enclosed by the lines L1 represented by y=0.18x+0.0582, L1' represented by y=0.18x+0.0182, L2 represented by x=0.01, and L3 represented by x=0.12, a fluorescent material can be obtained in which the luminescence characteristics are within the target range and the crystallinity is single crystal. Furthermore, in the above embodiment, z is 0 <z<0.06であった。

[0053] The above describes the examples. By using single-crystal fluorescent material synthesized within the composition range of the above-described examples, it is possible to create a light-emitting device that satisfies the chromaticity required for a white LED, for example, by combining it with a blue LED.

[0054] [supplement] The present invention has been described above based on embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of these components and processing processes, and that such modifications also fall within the scope of the present invention. [Explanation of symbols]

[0055] 10 Light-emitting device, 12 Substrate, 14 Light source, 16 Fluorescent component.

Claims

1. The crystal structure is garnet, and the general formula is Ba ｘ Y ３－ｘ－ｙ Al ５－ｘ－ｚ Si ｘ－２ｚ P ｚ O １２ : Ce ｙ A fluorescent material composed of a single crystal represented by (where x and y are values ​​within the range enclosed by the lines y = 0.18x + 0.0582, y = 0.18x + 0.0182, x = 0.01, and x = 0.12, z satisfies 0 < z < 0.06, and x and z satisfy x > 2z).

2. The fluorescent member has a plate-like shape. The fluorescent member according to claim 1.

3. The thickness t of the fluorescent element is in the range of 0.02 mm < t < 0.6 mm. The fluorescent member according to claim 1 or 2.

4. It is excited by blue light with a peak wavelength in the range of 430 nm to 480 nm and emits yellow light with a dominant wavelength in the range of 567 nm to 571 nm. The fluorescent member according to any one of claims 1 to 3.

5. A light-emitting device that emits white light, A light source that emits blue light with a peak wavelength in the range of 430 nm to 480 nm, The light source is joined to the fluorescent member according to any one of claims 1 to 4, Light-emitting device.

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