Red phosphor powder, light-emitting element, and light-emitting device

Abstract

A red phosphor powder having high luminescence efficiency despite having a small particle size, and a light-emitting element and a light-emitting device equipped with the red phosphor powder are provided. The red phosphor powder has a main component comprising strontium (Sr), sulfur (S), and europium (Eu), and has an average primary particle diameter of 2.7 μm or less as observed by SEM, and also has a crystallite diameter of 155 nm or less.

Description

Technology Field

[0001] The present invention relates to a red phosphor powder, a light-emitting element, and a light-emitting device. Background Technology

[0002] Light-emitting devices that use a light-emitting diode (LED) emitting near-ultraviolet or blue light as a light source (excitation source) and combine it with a phosphor are widely used in various light-emitting devices such as lighting, backlights for mobile terminals, and display devices.

[0003] In this light-emitting device, a phosphor absorbs light (synchrotron) emitted by an LED and emits light of a different wavelength from the absorbed light. Therefore, it is possible to obtain light emission with a hue different from the LED synchrotron. For example, green light and / or red light can be obtained by combining a blue LED with a green phosphor and / or a red phosphor, and light-emitting devices equipped with such a configuration are used for applications such as displays. Furthermore, a phosphor refers to a material that emits light (primarily visible light) during the process of returning to the ground state (relaxation process) from an excited state, which is irradiated by excitation light, electron beams, or various other methods.

[0004] In recent years, with the advancement of display technology, attention has been focused on mini LED displays and micro (μ) LED displays. Among these, μLED displays are composed of independent μLEDs for each of the subpixels: R (red), G (green), and B (blue). Each package (cell) corresponding to a subpixel is partitioned by a barrier (package rib), thereby preventing color mixing caused by light from adjacent packages. Reflecting the size of the subpixel, the package is minute, with a side length of, for example, 1000 μm or less. An excitation source, such as an LED, is provided on the bottom surface of the package, and a phosphor layer is provided on top of it. The phosphor layer is manufactured by filling the package with phosphor powder.

[0005] However, the synchrotron radiation of a phosphor varies depending on its composition. (Ca, Sr)S:Eu-based compounds have been proposed as red phosphors. Furthermore, phosphors are often used in powder form, and powdered phosphors (phosphor powders) are, in most cases, synthesized by solid-state methods.

[0006] As a document disclosing such technology, Patent Document 1 contains: general formula: (Ca 1-x Sr x )S: Eu(formula 0 <x≤1)로 표시되는 적색 형광체에 대해서, CaCO3와 SrCO3와 BaCO3를 습식 혼합 및 건조 처리한 후, 황화수소 가스 분위기 중 850℃에서 소성하고, 다음으로 Eu2O를 첨가하여 아르곤 가스 분위기 중 1000℃에서 소성하여, 일반식 (Ca 1-x Sr x )S: It is disclosed to obtain a red phosphor powder represented by Eu, Ba (Claim 2 of Patent Document 1,

[0011] and

[0060] , etc.).

[0007] On the other hand, it has also been proposed to synthesize phosphor powder using a liquid phase method. As a document disclosing such technology, Patent Document 2 discloses a method for manufacturing a phosphor having a precursor formation process for forming a phosphor precursor by a liquid phase method and a calcination process for forming a phosphor by calcining the precursor (Claim 1 of Patent Document 2). It is also described that in the liquid phase method, it is easy to obtain a phosphor of stoichiometrically high purity and that particles of fine particle size can be obtained without performing a grinding process (

[0028] of Patent Document 2). Prior art literature

[0008] International Publication No. 2013 / 021990 and Japanese Patent Publication No. 2007-106831 The problem to be solved

[0009] As such, it has been conventionally known that phosphor powders, such as red phosphor powder, are synthesized by a solid-state or liquid-state method, and that the synthesized phosphor powders are applied to applications such as μLED displays.

[0010] However, as investigated by the inventors, there was room for improvement in conventional phosphor powders. Specifically, in displays such as μLED displays, different phosphors, namely red phosphors or green phosphors, are used for each subpixel. Therefore, a phosphor layer is fabricated by filling each package corresponding to each subpixel with a different phosphor powder.

[0011] On the other hand, there is a demand for high precision in displays, leading to the miniaturization of package sizes. Consequently, the miniaturization of phosphor powder is becoming necessary. This is because it is difficult to uniformly fill coarse phosphor powder into micro-packages. By using fine phosphor powder, it becomes possible to achieve uniform filling into micro-packages and manufacture high-precision displays. Furthermore, using fine phosphor powder offers the advantage of enabling the adoption of cost-effective inkjet processes for phosphor powder filling.

[0012] However, conventional phosphor powders had a problem in that their luminous efficiency decreased as the particle size decreased. For this reason, it was conventionally difficult to obtain phosphor powders with small particle sizes and high luminous efficiency. If the luminous efficiency of the phosphor powder is low, high-intensity light emission cannot be obtained in light-emitting devices such as displays.

[0013] The inventors of the present invention have conducted a thorough examination in consideration of these problems. As a result, they discovered that for a red phosphor powder of a predetermined composition, there is a specific relationship between the crystallite diameter and the luminescence efficiency in the region where the particle size is small. Furthermore, they found that even with a small particle size, the luminescence efficiency can be increased by reducing the crystallite diameter.

[0014] The present invention is completed based on these findings and aims to provide a red phosphor powder having high luminescence efficiency despite having a small particle size, and a light-emitting element and a light-emitting device equipped with said red phosphor powder. means of solving the problem

[0015] The present invention includes the following embodiments (1) to (6). Furthermore, in this specification, the expression “to” includes numerical values ​​at both ends. That is, “X to Y” has the same meaning as “X or greater and Y or less.” Additionally, in this specification, any combination of suitable embodiments may be adopted as long as technical compatibility is achieved. For example, one side of a suitable numerical range and the other side may be arbitrarily combined.

[0016] (1) A red phosphor powder having a main component containing strontium (Sr), sulfur (S), and europium (Eu), an average primary particle diameter of 2.7 μm or less as observed by SEM, and a crystallite diameter of 155 nm or less.

[0017] (2) The above main component is, general formula: (Ca 1-x-y Sr x )S: Eu y (However, 0 <x≤1-y, 0<y≤0.01)로 표시되는 조성을 갖는, 상기 (1)의 적색 형광체 분말.

[0018] (3) The above main component is, general formula: (Ca 1-x-y Sr x )S: Eu y(However, 0 <x<1-y, 0<y≤0.01)로 표시되는 조성을 갖는, 상기 (1) 또는 (2)의 적색 형광체 분말.

[0019] (4) A red phosphor powder of any one of (1) to (3) having an internal quantum efficiency (IQE) of 40% or more.

[0020] (5) A light-emitting device having a light source that generates excitation light and a red phosphor powder of any one of (1) to (4).

[0021] (6) A light-emitting device having the light-emitting element of (5) above. Effects of the invention

[0022] According to the present invention, a red phosphor powder having high luminescence efficiency despite having a small particle size, and a light-emitting element and a light-emitting device having said red phosphor powder are provided. Brief explanation of the drawing

[0023] Figure 1 shows an SEM image of phosphor powder (Comparative Example 1). Figure 2 shows an SEM image of the phosphor powder (Example 5). Specific details for implementing the invention

[0024] Specific embodiments of the present invention (hereinafter referred to as "the present embodiments") are described below. However, the present invention is not limited to the following embodiments, and various modifications are possible within the scope of not altering the gist of the present invention.

[0025] <<1. Red Phosphor Powder>>

[0026] The red phosphor powder of the present embodiment (which may simply be referred to as "phosphor powder") has a main component comprising strontium (Sr), sulfur (S), and europium (Eu). The main component is preferably of the general formula: (Ca 1-x-y Sr x )S: Eu y(However, 0 <x≤1-y, 0<y≤0.01)로 표시되는 조성을 갖고, 특히 바람직하게는 일반식: (Ca 1-x-y Sr x )S: Eu y (However, 0 <x<1-y, 0<y≤0.01)로 표시되는 조성을 갖는다. 즉, 적색 형광체 분말은, 한정되는 것은 아니지만, 상술한 일반식으로 표시되는 화합물(주성분 화합물)을 주성분으로서 포함하는 것이 바람직하다. 이 주성분 화합물은 암염형의 결정 구조를 가진다. 또한, 본 명세서에 있어서, 「주성분」이란, 형광체 분말 중에서의 함유 비율이 50질량% 이상의 성분(화합물)을 가리킨다. 주성분의 함유 비율은 60질% 이상이면 되고, 70질량% 이상이어도 되고, 80질량% 이상이어도 되고, 혹은 90질량% 이상이어도 된다. 또한, 형광체 분말은, Ca, Sr, S 및 Eu 이외의 성분을 포함해도 된다. 그러한 성분으로서, 한정되는 것은 아니지만, 나트륨(Na) 및 칼륨(K)으로 이루어지는 군에서 선택되는 적어도 1종의 알칼리 금속을 들 수 있다.

[0027] The main component compound of the phosphor powder comprises a SrS-based compound or a (Ca, Sr)S-based compound as a matrix crystal and europium (Eu) as a luminescence center. This compound is excited by irradiation light having a wavelength of 420 nm or more and 500 nm or less, and emits red light.

[0028] The parent crystal contains strontium (Sr) as an essential component. The parent crystal may contain both calcium (Ca) and strontium (Sr) as essential components. However, the ratio of Ca to Sr is not limited. By adjusting the ratio of Ca to Sr in the parent crystal, the maximum emission wavelength (emission peak wavelength) of the synchrotron can be controlled. Specifically, when the parent crystal is a CaS-based compound (x=0), the maximum emission wavelength is 655 nm. When the parent crystal is a SrS-based compound (x=1-y), the maximum emission wavelength is 620 nm. Therefore, by adjusting x within the range greater than 0 and less than or equal to 1-y, the maximum emission wavelength can be controlled within the range of 620 nm or more and less than 655 nm.

[0029] Europium (Eu) acts as a luminescence center. By appropriately including Eu, high luminescence efficiency can be obtained while preventing a decrease in luminescence intensity caused by concentration quenching. In this regard, the amount of Eu y is greater than 0 and less than or equal to 0.01 (0 <y≤0.01)가 바람직하다.

[0030] The red phosphor powder of the present embodiment has an average primary particle diameter of 2.7 μm or less as observed by SEM. By reducing the particle diameter, it becomes possible to miniaturize the package and thereby achieve high precision in the display. Furthermore, when filling the phosphor powder into the package, it becomes possible to adopt an inkjet process, which has the effect of reducing manufacturing costs. In contrast, if the particle diameter of the phosphor powder is large, it becomes difficult to fill it into a micro-package of the display and to adopt an inkjet process. The average primary particle diameter is more preferably 2.2 μm or less, and more preferably 1.8 μm or less. On the other hand, by appropriately increasing the particle diameter of the phosphor powder, particle aggregation is suppressed, thereby improving the handling properties of the phosphor powder. The average primary particle diameter is preferably 0.05 μm or more, and more preferably 0.1 μm or more. The average primary particle diameter is preferably 0.05 μm or more and 2.2 μm or less, and more preferably 0.1 μm or more and 1.8 μm or less.

[0031] The red phosphor powder of the present embodiment has a crystallite diameter of 155 nm or less. According to the findings of the inventors, the luminescence efficiency of the red phosphor powder increases when the crystallite diameter is small in the region where the average primary particle diameter is 2.7 μm or less. As for the reason, although this should not be interpreted as a limitation, it is speculated that phosphor powders with small crystallite diameters contain fewer impurities. Furthermore, it is also thought that phosphor powders with small crystallite diameters and large lattice deformations are less susceptible to the influence of temperature quenching. The crystallite diameter is preferably 150 nm or less, and more preferably 130 nm or less. On the other hand, powders with excessively small crystallite diameters have the problem of actually having lower luminescence efficiency. The crystallite diameter is preferably 90 nm or more, and more preferably 100 nm or more. From the perspective of improving luminescence efficiency, the crystallite diameter is preferably 90 nm or more and 150 nm or less, and more preferably 100 nm or more and 130 nm or less. In addition, the crystallite diameter is determined by analyzing the phosphor powder using X-ray diffraction.

[0032] Suitablely, the internal quantum efficiency (IQE) of the phosphor powder is 40% or higher. Internal quantum efficiency is the efficiency of converting light absorbed by the phosphor into other light, and serves as a standard for luminous efficiency. By applying phosphor powder with a high IQE, the luminous intensity of a light-emitting device, such as a display, can be increased. An IQE of 45% or higher is more preferable, and 50% or higher is even more preferable. The upper limit of the IQE is not limited.

[0033] Although not limited to specific values, the circularity of the phosphor powder is preferably 0.60 or higher and 0.75 or lower, and more preferably 0.63 or higher and 0.72 or lower. Circularity is an indicator of the circularity (sphericity) of the particles (phosphor particles) constituting the phosphor powder. If the particles constituting the phosphor powder have a shape close to a perfect sphere, the circularity approaches 1, and if they have a shape that deviates from a perfect sphere, it approaches 0. By appropriately increasing the circularity, the fluidity of the powder is improved. Consequently, it enables the realization of miniaturization of packages and high precision of displays at a higher level. On the other hand, phosphor powder with excessively high circularity may lead to an increase in manufacturing costs. By appropriately decreasing the circularity, a reduction in manufacturing costs is achieved.

[0034] In addition, the circularity is obtained by observing the phosphor powder with an SEM and analyzing the obtained SEM image. Specifically, for a plurality of particles constituting the powder, the area S and perimeter L of each particle in a two-dimensional projection are measured. Then, the circularity of each particle is calculated according to the following equation (1), and the arithmetic mean value is defined as the circularity of the phosphor powder.

[0035]

[0036] <<2. Method for Manufacturing Red Phosphor Powder>>

[0037] The manufacturing method of the red phosphor powder of the present embodiment is not particularly limited, provided that it satisfies the requirements described above. It may be synthesized by a solid-phase method or by a liquid-phase method. However, the phosphor powder synthesized by the liquid-phase method has the characteristic of having high crystallinity despite being fine. It also has the characteristics of high sphericity and excellent fluidity. Therefore, the phosphor powder synthesized by the liquid-phase method is particularly suitable for use in μLED displays.

[0038] An example of a method for manufacturing red phosphor powder by a liquid phase method is shown below. This manufacturing method comprises the following steps: a step of preparing a starting material solution by dissolving starting materials containing a strontium (Sr) source, a europium (Eu) source, a sulfur (S) source, and an alkali metal source in a solvent (raw material mixing step); a step of obtaining a phosphor precursor powder by performing heat treatment and solid-liquid separation treatment on the obtained starting material solution (reaction step); and a step of calcining the obtained phosphor precursor powder (calcination step). Details of each step are described below.

[0039] <Raw Material Mixing Process>

[0040] In the raw material mixing process, a starting material solution is prepared by dissolving starting materials containing a strontium (Sr) source, a europium (Eu) source, a sulfur (S) source, and an alkali metal source in a solvent. The starting materials may include a calcium (Ca) source. Here, the alkali metal is at least one selected from the group consisting of sodium (Na) and potassium (K). Among the alkali metal elements, Na and K have ionic radii close to those of Ca and Sr. Therefore, in the phosphor powder, Eu 3+ Ions are generated, Ca 2+ Even if the phenomenon of ion loss (Schottky defect) occurs, Na + Ions or K + The ion is Ca 2+ It occupies sites and compensates for Schottky defects. As a result, it has the effect of shortening the afterglow time of the phosphor powder. In addition, the alkali metal acts as a flux in the calcination process described later.

[0041] Chlorides, sulfates, nitrates, etc., may be used as the Sr, Ca, Eu, and alkali metal sources. Sulfur, sodium sulfide, potassium sulfide, and / or sulfamic acid, etc., may be used as the sulfur (S) source. Sodium sulfide or potassium sulfide also acts as an alkali metal source. As a solvent, heptane (C7H 16Hydrocarbon-based solvents such as ) may be used. In addition, additives may be added to the solvent. As an additive, oleylamine (C 18 H 37 Examples of reducing agents include N). The dissolution of the starting materials can be carried out using known methods. For example, the solvent to which the starting materials have been added can be stirred using a stirrer.

[0042] <Reaction Process>

[0043] In the reaction process, a phosphor precursor powder is obtained by performing heat treatment and solid-liquid separation treatment on the obtained starting material solution. During the heat treatment, the reaction of the starting material in the solution proceeds, and a precipitate is formed. It is preferable to perform the heat treatment at a temperature of 200°C or higher and 300°C or lower under an inert gas atmosphere such as nitrogen (N2). Subsequently, the precipitate is recovered from the solution by solid-liquid separation treatment to obtain the phosphor precursor powder. Solid-liquid separation can be performed using known methods such as filtration or centrifugation. Additionally, the precipitate recovered by solid-liquid separation may be subjected to washing treatment.

[0044] Firing Process

[0045] In the calcination process, the phosphor precursor powder is calcined. By calcination, a phosphor powder with improved crystallinity can be obtained. The calcination conditions are not particularly limited. However, it is preferable to perform the calcination at a temperature of 500°C or higher and 1200°C or lower. By doing so, a phosphor powder with high crystallinity and fineness can be obtained. In addition, it is also preferable to perform the calcination under a sulfur atmosphere. Sulfur can be supplemented even if the amount of sulfur in the phosphor precursor powder is insufficient.

[0046] <<3. Light-emitting element>>

[0047] The light-emitting element of the present embodiment comprises a light source (excitation source) that generates excitation light and the red phosphor powder described above. The light source has the function of radiating light toward the phosphor powder to excite the phosphor. As a light source, a blue light-emitting LED with a wavelength of 420 nm or more and 500 nm or less is suitable. As long as light from the light source is incident on the phosphor powder, the arrangement of the phosphor powder and the light source is not limited. For example, when the light-emitting element is applied to a μLED display, it is preferable to place the light-emitting LED at the bottom of each package and fill and arrange the phosphor powder on top thereof.

[0048] The light-emitting element may include red phosphor powder in a powder-only state. Alternatively, it may include red phosphor powder and other known phosphor powders. For example, it may include red phosphor powder and green phosphor powder. In addition, it may include a mixture of phosphor powder, such as red phosphor powder, and resin. As the resin, one or more selected from, for example, thermoplastic resin, thermosetting resin, ionizing radiation curable resin, and two-component mixed curable resin may be used.

[0049] <<4. Light-emitting device>>

[0050] The light-emitting device of the present embodiment comprises the light-emitting element described above. The light-emitting element is not limited to any specific applications, but may be used for known applications such as lighting, backlights for mobile terminals, and displays (display devices). Among these, μLED displays, Mini LED displays, and particularly μLED displays are suitable.

[0051] Examples

[0052] The present invention will be explained in more detail using the following examples and comparative examples. However, the present invention is not limited to the following examples.

[0053] (1) Synthesis of fluorescent powder

[0054] [Comparative Example 1]

[0055] In Comparative Example 1, phosphor powder was synthesized by the solid-state method. Specifically, calcium carbonate (CaCO3) was calcined at 850°C for 4 hours in a hydrogen sulfide (H2S) atmosphere to obtain calcium sulfide (CaS). Subsequently, the obtained calcium sulfide (CaS), europium oxide (Eu2O3), and europium fluoride (EuF3) were dry-mixed, and the resulting mixture was calcined at 1000°C for 4 hours in an argon (Ar) atmosphere to obtain a calcined product. The argon (Ar) flow rate during calcination was set to 1.0 L / min. The obtained calcined product was ground and classified using a jet mill (manufactured by Dec) under conditions of a fluid pressure of 12 MPa to obtain phosphor powder with a CaS:Eu composition.

[0056] [Comparative Example 2]

[0057] The phosphor powder of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that the fluid pressure of the jet mill was changed to 0.3 MPa.

[0058] [Comparative Example 3]

[0059] In Comparative Example 3, phosphor powder was synthesized using a liquid-phase method. Specifically, strontium chloride (SrCl2), calcium chloride (CaCl2), sulfur (S), europium chloride (EuCl3), and sodium chloride (NaCl) were prepared as starting materials. In addition, heptane (C7H 16 ) and oleylamine (C 18 H 37 N) was prepared as a solvent, and a starting material solution was prepared by dissolving the starting material in the solvent. In addition, the amount of the starting material was adjusted so that a phosphor powder having the composition shown in Table 2 below was obtained. In addition, the ratio of the starting material (SrCl2~NaCl) to the solvent (heptane, oleylamine) was adjusted so that the solvent was 1,000 parts by mass for every 100 parts by mass of the total starting material. In addition, the mixing ratio of heptane and oleylamine was adjusted so that oleylamine was 150 parts by mass for every 100 parts by mass of heptane.

[0060] Next, the obtained starting material solution was heated at 250°C for 0.5 hours under a nitrogen (N2) flow. A reaction occurred due to the heating, and a precipitate was formed in the solution. After heating, the starting material solution was subjected to solid-liquid separation treatment using a centrifuge, and the obtained precipitate was subjected to washing treatment using ethanol to obtain a fluorescent precursor powder.

[0061] The obtained phosphor precursor powder was placed in a calcination furnace together with sulfur (S) and calcined at 900°C for 2 hours under a nitrogen atmosphere. The nitrogen (N2) flow rate during calcination was set to 0.2 L / min. In this way, phosphor powder was synthesized. In addition, the manufacturing conditions of the phosphor powder are shown in Table 1 below, and the characteristics of the phosphor powder are shown in Table 2 below.

[0062] [Examples 1 to 8 and Comparative Example 4]

[0063] The manufacturing conditions of the phosphor powder were changed as shown in Tables 1 and 2 below. Except for that, the synthesis of the phosphor powder was carried out in the same manner as Comparative Example 3. In addition, in Example 7, Sr source (SrCl2) was used, but Ca source (CaCl2) was not used.

[0064]

[0065] (2) Evaluation of fluorescent powder

[0066] The phosphor powders obtained in Examples 1 to 8 and Comparative Examples 1 to 4 were used as samples, and various characteristics were evaluated as follows.

[0067] <ICP 발광 분석>

[0068] The sample was completely dissolved by acid digestion, measured using the calibration curve method with an ICP emission spectroscopic analyzer (Hitachi High-Tech Science, PS3520UVDDII), and the content of each element was confirmed.

[0069] <SEM 관찰(평균 1차 입자 직경)>

[0070] The average primary particle diameter (SEM diameter) of the phosphor powder was measured. First, the phosphor powder was observed using a scanning electron microscope (SEM) to obtain an SEM image. At this time, observation was performed under conditions of magnification ranging from 1,000 to 3,000 times. Subsequently, the SEM image was analyzed using image analysis particle size distribution measurement software (Mountech, Mac-View, Version 4, File Version: v 1.0.0.14), and the particle diameter (Heywood diameter) of the particles constituting the powder was measured. At this time, more than 300 particles were selected and analyzed from locations where the particles did not overlap. Subsequently, a volume-based particle size distribution was obtained from the obtained particle diameters. Then, the median particle diameter of the particle size distribution was defined as the average primary particle diameter (D50).

[0071] <SEM 관찰(원형도)>

[0072] The circularity of the phosphor powder was determined from the SEM image obtained during the first particle diameter measurement. Specifically, the SEM image was analyzed using image analysis particle size distribution measurement software, and the area S and perimeter L of the two-dimensional projected image of the particles constituting the powder were measured. At this time, more than 300 particles were selected and measured at locations where the particles did not overlap each other. Then, the circularity of each particle was calculated according to the above equation (1), and the arithmetic mean value was defined as the circularity of the phosphor powder.

[0073] <XRD 분석(결정자 직경, 격자 변형)>

[0074] The phosphor powder was analyzed by X-ray diffraction (XRD) to obtain an XRD pattern. The XRD analysis was performed under the following conditions.

[0075] - X-ray diffraction apparatus: Multi-purpose sample horizontal high-power X-ray diffraction apparatus (Rigaku Co., Ltd., RINT-TTRIII)

[0076] - Source: CuKα (X-ray wavelength: 0.154056 nm)

[0077] - Detector: D / teX Ultra 2

[0078] - Scanning axis: 2θ / θ

[0079] - Injection range: 5 to 120 degrees

[0080] -Step width: 0.01deg

[0081] - Injection rate: 1 deg / min

[0082] -Incident slit: 2 / 3°

[0083] - Tube voltage: 50kV

[0084] - Tube current: 300mA

[0085] In addition, measurements were performed on SRM660a (compound name: LaB6) from NIST (National Institute of Standards and Technology) under the same conditions. The obtained XRD patterns were analyzed using integrated powder X-ray analysis software (PDXL, Rigaku Co., Ltd.) in the following order. First, the sample was identified as LaB6 using the software's automatic search function, and the "segmented PearsoVII function" was used as the peak shape model function. Next, "Intensity Resolution" was selected from "Precision Parameter Settings" - "Method" under the "Basic" tab. Then, refinement was performed. During refinement, various parameters were set until convergence was achieved. This was saved as a width standard data file.

[0086] Next, the XRD patterns obtained from each phosphor powder were analyzed to calculate the crystallite diameter and lattice strain. The analysis was performed using integrated powder X-ray analysis software (PDXL, Rigaku Co., Ltd.) in the following procedure. First, the crystal phase was identified using the software's automatic search function. Subsequently, intensity resolution was performed using WPPF. As a line correction, a standard width data file was selected, and the peak angles and widths were corrected. The "Segmented Pearso VII function" was used as the model function for the peak shape. Next, "Intensity Resolution" was selected from "Precision Parameter Settings" - "Method" on the "Basic" tab. Then, refinement was performed. During refinement, various parameters were set until convergence was achieved.

[0087] <Luminescence Characteristics (Absorption Rate, Quantum Efficiency)>

[0088] The absorption rate (Abs) and internal quantum efficiency (IQE) of the phosphor powder were determined using a fluorescence spectrophotometer (JASCO FP-8700DS) according to a quantum efficiency calculation program. The formulas for calculating the absorption rate and internal quantum efficiency are shown below.

[0089] P1(λ) was set as the LED light spectrum of 450 nm, and P2(λ) was set as the sample spectrum. The area L1 enclosed by the excitation wavelength range of 430 nm to 500 nm of spectrum P1(λ) was calculated according to the following equation (i), and the obtained value was set as the excitation intensity. The area L2 enclosed by the excitation wavelength range of 430 nm to 500 nm of spectrum P2(λ) was calculated according to the following equation (ii), and the obtained value was set as the sample scattering intensity. The area E2 enclosed by the excitation wavelength range of 500 nm to 850 nm of spectrum P2(λ) was calculated according to the following equation (iii), and the obtained value was set as the sample fluorescence intensity.

[0090]

[0091] Absorption rate (Abs) is the ratio of the incident light to the reduction of the excitation light by the sample, and was calculated according to Equation (iv) below. In addition, internal quantum efficiency (IQE) is the value obtained by dividing the number of lattice points Nem of the fluorescence emitted from the sample by the number of photons Nabs of the excitation light absorbed by the sample, and was calculated according to Equation (v) below.

[0092]

[0093] (3) Evaluation results

[0094] The evaluation results obtained for the phosphor powders of Examples 1 to 8 and Comparative Examples 1 to 4 are combined and shown in Table 2 below.

[0095] The phosphor powders of Examples 1 to 8 are composed of the composition specified in this embodiment (0 <x≤1-y, 0<y≤0.01), 평균 1차 입자 직경(2.7㎛ 이하) 및 결정자 직경(155㎚ 이하)을 만족시키고 있었다. 이들의 형광체 분말은 발광 피크 파장이 627.0 내지 650.6㎚의 적색광을 방사하였다. 또한, 내부 양자 효율(IQE)이 40% 이상으로 높았다. 특히 결정자 직경이 150㎚ 이하의 실시예 1, 2, 4, 5, 7 및 8은 IQE가 48% 이상이고, 결정자 직경이 130㎚ 이하의 실시예 2, 4, 5 및 8은, IQE가 50% 이상이었다.

[0096] In contrast, Comparative Example 1 does not contain Sr and does not satisfy the composition specified in the present embodiment. Comparative Examples 2 and 3 have either the average primary particle diameter or the crystallite diameter larger and do not satisfy the range specified in the present embodiment. For this reason, Comparative Examples 2 and 3 had a low IQE of 36 to 37%.

[0097] On the other hand, Comparative Example 4, which had large average primary particle diameter and crystallite diameter, had a relatively high IQE of 47%. However, because the average primary particle diameter is large, there is a concern that it may be difficult to achieve uniform filling into a micro package. Therefore, it is not desirable for achieving high precision in displays.

[0098]

[0099] SEM images of the phosphor powders of Comparative Example 1 and Example 5, respectively, are shown in Figures 1 and 2. Both the phosphor powder of Comparative Example 1, synthesized by the solid-phase method, and the phosphor powder of Example 5, synthesized by the liquid-phase method, had a primary particle diameter of approximately 1 μm. However, while the phosphor powder of Comparative Example 1 had a relatively irregular particle shape, the phosphor powder of Example 5 had a particle shape that was relatively close to a spherical shape.

[0100] From the above results, it is understood that according to the present embodiment, a red phosphor powder having high luminescence efficiency despite having a small particle size, and a light-emitting element and a light-emitting device equipped with the red phosphor powder are provided.

Claims

Claim 1 A red phosphor powder having main components including strontium (Sr), sulfur (S), and europium (Eu), an average primary particle diameter of 2.7 μm or less as observed by SEM, and a crystallite diameter of 155 nm or less. Claim 2 In claim 1, the above main component is, general formula: (Ca 1-x-y Sr x )S: Eu y (However, 0 <x≤1-y, 0<y≤0.01)로 표시되는 조성을 갖는, 적색 형광체 분말. Claim 3 In claim 1 or 2, the above main component is, general formula: (Ca 1-x-y Sr x )S: Eu y (However, 0 <x<1-y, 0<y≤0.01)로 표시되는 조성을 갖는, 적색 형광체 분말. Claim 4 A red phosphor powder having an internal quantum efficiency (IQE) of 40% or more, according to claim 1 or 2. Claim 5 A light-emitting element comprising a light source that generates excitation light and a red phosphor powder described in claim 1 or 2. Claim 6 A light-emitting device having a light-emitting element as described in paragraph 5.

Images