Red phosphor and method for producing the same

Abstract

To provide a red phosphor excellent in terms of optical property and durability in high-temperature, high-humidity environments and to provide a production method therefor.SOLUTION: This red phosphor comprises a Mn-activated composite fluoride represented by general formula (1) and a perovskite compound represented by general formula (2). Formula (1): L2MF6:Mn4+ (wherein L represents at least one alkali metal element selected from lithium, sodium, potassium, rubidium and cesium, and M represents at least one tetravalent element selected from silicon, germanium, tin, titanium, zirconium and hafnium.) Formula (2): ABX3 (wherein A represents at least one selected from lithium, sodium, potassium, rubidium, cesium, silver, indium, gold, thallium, ammonium, and primary to quaternary ammonium ions. B represents a specific metal element. X represents at least one element selected from fluorine, chlorine, bromine, iodine and sulfur.)SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a red phosphor that emits red light when excited by excitation light such as ultraviolet light and blue light, and a method for producing the same. More specifically, the present invention relates to a red phosphor containing a Mn (manganese) activated double fluoride and a perovskite compound, wherein the perovskite compound is present on or inside the Mn activated double fluoride, thereby providing a red phosphor with excellent optical properties and durability under high temperature and high humidity environments, and a method for producing the same. [Background technology]

[0002] White LEDs (Light Emitting Diodes) have a longer lifespan and lower power consumption compared to fluorescent lamps. As a result, their use in lighting fixtures and display backlights has rapidly increased. Commercially available white LEDs in lighting fixtures are composed of a blue LED that emits light from near-ultraviolet to blue light and a yellow phosphor that is excited by that light. This allows the white LED to emit pseudo-white light by mixing the light emitted by the blue LED and the light emitted by the yellow phosphor. However, because the pseudo-white light emitted by white LEDs has little or no light-emitting component in the red light region, pseudo-white light has the problem of having inferior color rendering (color rendering refers to the characteristics of how colors appear under that lighting when an object is viewed under that lighting compared to natural light. For example, if an object appears similar in color when illuminated by lighting as it would when illuminated by natural light, it is considered to have high color rendering) compared to natural light (or sunlight, blackbody radiation).

[0003] Therefore, there is a need for red phosphors that emit red light when excited by ultraviolet light emitted from near-ultraviolet LEDs or blue light emitted from blue LEDs. In recent years, the transition metal Mn has been used as such a red phosphor. 4+ Mn-activated polyfluoride (K2SiF6:Mn) that emits red light with ions as the light-emitting centers. 4+A phosphor composition composed of (KSF:Mn) has been developed (see, for example, Patent Documents 1, 2 and Non-Patent Document 1), and its adoption has been progressing rapidly. KSF:Mn has an excitation band in the wavelength range of blue light, and has a red light emission peak with a narrow half-width in a narrow band of 600 to 650 nm.

[0004] In KSF:Mn, K2SiF6 crystals form the framework of the phosphor, and SiF6 2- at the six-coordinate octahedral site formed by ions, the Si 4+ is replaced by Mn 4+ ions via solid solution to form MnF6 2- octahedral sites, which act as luminescence centers.

[0005] However, practical problems have been pointed out for this red phosphor composed of KSF:Mn, such as darkening of the particle surface when it comes into contact with water, water vapor or the like under high-temperature and high-humidity environments. Specifically, on the particle surface of the red phosphor, tetravalent manganese ions constituting the red phosphor react with water to generate manganese dioxide. This manganese dioxide causes absorption of excitation light and suppression of fluorescence, leading to deterioration of optical properties and degradation of optical properties over time (reduction of durability).

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

NON-PATENT DOCUMENTS

[0007]

Non-Patent Document 1

[0008] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a red phosphor with excellent optical properties and durability under high temperature and high humidity environments, and a method for producing the same. [Means for solving the problem]

[0009] The red phosphor according to the present invention is characterized by comprising a Mn-activated complex fluoride represented by the following general formula (1) and a perovskite compound represented by the following general formula (2), in order to solve the above-mentioned problems.

[0010] L2MF6:Mn 4+ (1) (In the formula, L represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and M represents at least one tetravalent element selected from the group consisting of silicon, germanium, tin, titanium, zirconium, and hafnium.) ABX3(2) (In the formula, A represents at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, silver, indium, gold, thallium, ammonium, primary ammonium, secondary ammonium, tertiary ammonium, and quaternary ammonium. The primary ammonium, secondary ammonium, tertiary ammonium, and quaternary ammonium have an alkyl group having 1 to 10 carbon atoms, or an alkyl group having a heteroatom in the range of 1 to 10 carbon atoms. B represents magnesium, calcium, barium, zinc, zirconium, strontium, manganese, iron, cobalt, nickel, copper, titanium, vanadium, chromium, mercury, cadmium, tin, and lead.) 、 X represents at least one element selected from the group consisting of europium, yttrium, beryllium, indium, aluminum, ruthenium, osmium, and antimony. (X represents at least one element selected from the group consisting of fluorine, chlorine, bromine, iodine, and sulfur.)

[0011] In the above configuration, the perovskite compound represented by general formula (2) may be attached to and / or present inside at least a portion of the surface of the Mn-activating complex fluoride represented by general formula (1).

[0012] Furthermore, in the above configuration, the Mn-activating complex fluoride represented by general formula (1) may be attached to and / or present inside the surface of the perovskite compound represented by general formula (2).

[0013] Furthermore, in the above configuration, it is preferable that the average particle size D50 of the perovskite compound represented by the general formula (2) is 0.002 μm to 20 μm in laser diffraction scattering.

[0014] Furthermore, in the above configuration, it is preferable that the content ratio of the Mn-activating complex fluoride represented by general formula (1) to the perovskite compound represented by general formula (2) is in the range of 10:90 to 99.999:0.001 by mass.

[0015] In the above configuration, it is preferable to include a step of contacting a Mn-activated complex fluoride represented by the following general formula (1) with a perovskite compound represented by the following general formula (2) in the presence of a solvent.

[0016] The present invention provides a method for producing a red phosphor, characterized in that, in order to solve the above-mentioned problems, it includes a step of contacting a Mn-activated complex fluoride represented by the following general formula (1) with a perovskite compound represented by the following general formula (2) in the presence of a solvent.

[0017] L2MF6:Mn 4+ (1) (In the formula, L represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and M represents at least one tetravalent element selected from the group consisting of silicon, germanium, tin, titanium, zirconium, and hafnium.) ABX3(2) (In the formula, A represents at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, silver, indium, gold, thallium, ammonium, primary ammonium, secondary ammonium, tertiary ammonium, and quaternary ammonium. The primary ammonium, secondary ammonium, tertiary ammonium, and quaternary ammonium have an alkyl group having 1 to 10 carbon atoms, or an alkyl group having a heteroatom in the range of 1 to 10 carbon atoms. B represents magnesium, calcium, barium, zinc, zirconium, strontium, manganese, iron, cobalt, nickel, copper, titanium, vanadium, chromium, mercury, cadmium) Mi Um, tin, lead 、 X represents at least one element selected from the group consisting of europium, yttrium, beryllium, indium, aluminum, ruthenium, osmium, and antimony. (X represents at least one element selected from the group consisting of fluorine, chlorine, bromine, iodine, and sulfur.)

[0018] In the above configuration, it is preferable that the average particle diameter D50 of the perovskite compound represented by the general formula (2) is 0.002 μm to 20 μm as measured by laser diffraction scattering method.

[0019] In the above configuration, it is preferable that the content ratio of the Mn-activated double fluoride to the perovskite compound in the red phosphor obtained by contacting the Mn-activated double fluoride represented by the general formula (1) with the perovskite compound represented by the general formula (2) is in the range of 10:90 to 99.999:0.001 on a mass basis.

[0020] In the above configuration, it is preferable that the solvent is water, an organic solvent, a mixed solvent thereof, or an acidic solvent thereof.

[0021] In the above configuration, it is preferable that the mixing ratio of the solvent to the Mn-activated double fluoride represented by the general formula (1) and the perovskite compound represented by the general formula (2) is in the range of 2:1 to 100:1 on a mass basis.

[0022] In addition, in the above configuration, it is preferable that the acidic solvent is an acidic solvent containing hydrogen fluoride, and the concentration of the hydrogen fluoride in the acidic solvent containing hydrogen fluoride is in the range of 1% by mass to 70% by mass relative to the total mass of the acidic solvent. Effects of the Invention

[0023] The present invention achieves the following effects by the means described above. That is, according to the red phosphor of the present invention, due to the coexistence of the Mn-activated double fluoride and the perovskite compound, Mn 4+ reacts with water to reduce or prevent the formation of colored manganese dioxide. As a result, it is possible to prevent the absorption of excitation light and fluorescence by manganese dioxide and the decrease in fluorescence emission caused by the absorption of excitation light, thereby providing a red phosphor with good optical properties, reduced degradation of optical properties due to temporal changes in high-temperature and high-humidity environments, and excellent durability.

[0024] Furthermore, according to the method for producing red phosphors of the present invention, a red phosphor composed of a Mn-activated complex fluoride and a perovskite compound can be produced by contacting the Mn-activated complex fluoride with a treatment solution containing a perovskite compound. As a result, it is possible to produce a red phosphor with good optical properties, reduced deterioration of optical properties due to changes over time in high temperature and high humidity environments, and excellent durability. [Brief explanation of the drawing]

[0025] [Figure 1] This graph shows the X-ray diffraction pattern of KMgF3 according to Example 1 of the present invention. [Figure 2] This is an SEM image of KMgF3 according to Example 1 of the present invention. [Figure 3] This graph shows the X-ray diffraction pattern of the red phosphor according to Example 1 of the present invention. [Figure 4] This is an SEM image of the red phosphor according to Example 1 of the present invention. [Modes for carrying out the invention]

[0026] (Red phosphor) The red phosphor according to this embodiment will be described below. The red phosphor according to this embodiment includes a Mn-activated complex fluoride represented by the following general formula (1) (hereinafter sometimes referred to as "Mn-activated complex fluoride") and a perovskite compound represented by the following general formula (2) (hereinafter sometimes referred to as "perovskite compound").

[0027] L2MF6:Mn 4+ (1) (In the formula, L represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and M represents at least one tetravalent element selected from the group consisting of silicon, germanium, tin, titanium, zirconium, and hafnium.) ABX3(2) (In the formula, A represents at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, silver, indium, gold, thallium, ammonium, primary ammonium, secondary ammonium, tertiary ammonium, and quaternary ammonium. The primary ammonium, secondary ammonium, tertiary ammonium, and quaternary ammonium have an alkyl group having 1 to 10 carbon atoms, or an alkyl group having a heteroatom in the range of 1 to 10 carbon atoms. B represents magnesium, calcium, barium, zinc, zirconium, strontium, manganese, iron, cobalt, nickel, copper, titanium, vanadium, chromium, mercury, cadmium) Mi Um, tin, lead 、 X represents at least one element selected from the group consisting of europium, yttrium, beryllium, indium, aluminum, ruthenium, osmium, and antimony. (X represents at least one element selected from the group consisting of fluorine, chlorine, bromine, iodine, and sulfur.)

[0028] The red phosphor in this embodiment may be a single red phosphor or a mixture of two or more red phosphors.

[0029] The general formula L2MF6:Mn represents the aforementioned Mn-activated complex fluoride. 4+ In this context, "L2MF6" represents the composition of the matrix crystal of the red phosphor. Also, "Mn 4+ " represents the activating ion that acts as the luminescence center.

[0030] Herein, in this specification, "activation" refers to the process of activating the L2MF6 matrix crystal with the activator Mn 4+ This means adding Mn. In its activated form, 4+ One example is a form in which Mn is partially substituted for any atom constituting L2MF6. In this embodiment, Mn 4+ Preferably, it is substituted for M in the matrix crystal.

[0031] General formula L2MF6:Mn 4+Examples of Mn-activated complex fluorides represented by this formula include, for example, Li2SiF6:Mn 4+ Na2SiF6:Mn 4+ K2SiF6:Mn 4+ ,Rb2SiF6:Mn 4+ ,Cs2SiF6:Mn 4+ Li2GeF6:Mn 4+ Na2GeF6:Mn 4+ K2GeF6:Mn 4+ ,Rb2GeF6:Mn 4+ ,Cs2GeF6:Mn 4+ Li2SnF6:Mn 4+ Na2SnF6:Mn 4+ K2SnF6:Mn 4+ ,Rb2SnF6:Mn 4+ ,Cs2SnF6:Mn 4+ Li2TiF6:Mn 4+ Na2TiF6:Mn 4+ K2TiF6:Mn 4+ Rb2TiF6:Mn 4+ ,Cs2TiF6:Mn 4+ Li2ZrF6:Mn 4+ Na2ZrF6:Mn 4+ K2ZrF6:Mn 4+ ,Rb2ZrF6:Mn 4+ ,Cs2ZrF6:Mn 4+ Li2HfF6:Mn 4+ Na2HfF6:Mn 4+ K2HfF6:Mn 4+ ,Rb2HfF6:Mn 4+ ,Cs2HfF6:Mn 4+ These are some examples. Of these Mn-activated complex fluorides, K2SiF6:Mn is considered to be the most readily available and easiest to synthesize. 4+ K2TiF6:Mn 4+ ,K2GeF6:Mn 4+ Na2SiF6:Mn 4+ Na2TiF6:Mn 4+ Na2GeF6:Mn 4+ Preferably, K2SiF6:Mn 4+ K2TiF6:Mn 4+This is more preferable. Furthermore, the Mn-activated complex fluoride can be selected according to the optical properties required for various applications. Therefore, it is not particularly limited to the Mn-activated complex fluoride exemplified above.

[0032] Herein, in this specification, "optical properties" refers to the absorption rate and internal quantum efficiency of a red phosphor, etc. "Absorptivity" refers to the efficiency with which a red phosphor absorbs excitation light. For example, if the peak value of the spectral radiance of excitation light (wavelength 449 nm) irradiated from a blue LED is Ex1, and the peak value of the excitation light unabsorbed by the red phosphor is Ex2, then the absorption rate α is expressed by the following formula (1). Absorption rate α(%)=(Ex1-Ex2) / Ex1×100 (1)

[0033] Furthermore, "internal quantum efficiency" refers to the efficiency with which the excitation light absorbed by the red phosphor is converted into fluorescence. For example, when the peak spectral radiance of the red phosphor is Ex2 under irradiation with excitation light from a blue LED (wavelength 449 nm), the internal quantum efficiency η is expressed by the following equation (2). Internal quantum efficiency η(%)=Em / (Ex1-Ex2)×100 (2)

[0034] The Mn-activated complex fluoride is preferably a solid, and more preferably in particulate form. When the Mn-activated complex fluoride is in particulate form, its average particle size is not particularly limited, as long as the proportion of scattering relative to the excitation light does not become too large compared to absorption and conversion, and no problems arise when mixing it with resin for mounting in an LED device.

[0035] The molar ratio of Mn is preferably in the range of 0.005 to 0.15, more preferably in the range of 0.01 to 0.12, and particularly preferably in the range of 0.02 to 0.1, relative to the total number of moles of M and Mn in the red phosphor (or Mn-activated complex fluoride). By setting the molar ratio to 0.005 or higher, good luminescence intensity of the red phosphor can be maintained. On the other hand, by setting the molar ratio to 0.15 or lower, it is possible to suppress the excessive decrease in the durability of the red phosphor under high temperature and high humidity environments.

[0036] In this specification, "durability" refers to the degree to which the initial optical properties of a red phosphor are maintained when stored in a high-temperature, high-humidity environment for a certain period of time. The meaning of optical properties is as described above.

[0037] Examples of perovskite compounds represented by the general formula ABX3 include, for example, LiBaF3, LiMgF3, LiMnF3, LiFeF3, LiCoF3, LiNiF3, LiCuF3, NaCaF3, NaMgF3, NaZnF3, NaZrF3, NaMnF3, NaFeF3, NaCoF3, NaNiF3, NaCuF3, NaTiF3, NaSnF3, NaBeF3, KCaF3, KBaF3, KMgF3, KZnF3, KZrF3, KMnF3, KFeF3, KCoF3, KNiF3, KCuF3, KTiF3, KHgF3, K CdF3, KSnF3, KPbF3, KSrF3, RbCaF3, RbBaF3, RbMgF3, RbZnF3, RbZrF3, RbFeF3, RbNiF3, RbTiF3, RbHgF3, RbCdF3, RbSnF3, RbPbF3, RbSrF3, CsCaF3, C sBaF3, CsZnF3, CsZrF3, CsFeF3, CsCuF3, CsTiF3, CsVF3, CsCrF3, CsHgF3, CsCdF3, CsSrF3, InCaF3, InMgF3, InZnF3, InCdF3, InOsF3, AuBaF3, AuMgF 3, AuZnF3, TlCaF3, TlMgF3, TlZnF3, TlZrF3, TlNiF3, TlTiF3, TlVF3, TlHg F3, TlCdF3, TlSnF3, TlPbF3, TlOsF3, AgMgF3, AgZnF3, AgZrF3, AgFeF3, Ag TiF3, AgVF3, AgCrF3, AgCdF3, XeScF3, HgScF3, HgYF3, HgInF3, GaMgF3, GaZnF3, GaRuF3, ZnScF3, ZnYF3, ZnInF3, ZnAlF3, CdScF3, CdYF3, CdSbF3, Ba Examples include CuF3, AlMgF3, AlZnF3, AlFeF3, BeScF3, BeYF3, BeAlF3, PdScF3, PdYF3, NH4MgF3, NaMgCl3, KMgCl3, RbMgCl3, CsMgCl3, InMgCl3, NaZnCl3, KZnCl3, RbZnCl3, InZnCl3, RbHgCl3, RbTiCl3, TlCaCl3, TlHgCl3, RbCaBr3, CsCaBr3, TlCaBr3, RbHgBr3, CsEuBr3, CsCaI3, CsHgI3, CaZrS3, BaZrS3, etc.Of these perovskite compounds, NaCaF3, KCaF3, NaFeF3, KFeF3, NaNiF3, KNiF3, NaZnF3, NaZrF3, KZnF3, KZrF3, NaMgF3, and KMgF3 are preferred from the viewpoint of ease of availability and ease of synthesis, with NaMgF3 and KMgF3 being more preferred.

[0038] Furthermore, when A in general formula (2) is a primary ammonium, secondary ammonium, tertiary ammonium, or quaternary ammonium, A has an alkyl group having 1 to 10 carbon atoms, preferably 1 to 6, and more preferably 1 to 5 carbon atoms. Alternatively, A has an alkyl group having a heteroatom, and having 1 to 10 carbon atoms, preferably 1 to 6, and more preferably 1 to 5 carbon atoms. In this specification, "heteroatom" means an atom such as oxygen, nitrogen, and sulfur. Also, when a range of carbon atoms is expressed in this specification, that range means that all integer carbon atoms included in that range are included. Therefore, for example, an alkyl group with 1 to 3 carbon atoms means all alkyl groups with 1, 2, and 3 carbon atoms.

[0039] Here, when M in the Mn-activated complex fluoride is one of silicon, germanium, tin, titanium, and zirconium, it is preferable that B in the perovskite compound is one of magnesium, calcium, zinc, iron, nickel, and titanium. Furthermore, when M in the Mn-activated complex fluoride is silicon, it is even more preferable that B in the perovskite compound is magnesium.

[0040] Furthermore, perovskite compounds can be selected according to the durability required for various applications. Therefore, the examples of perovskite compounds are not particularly limited.

[0041] The content ratio of Mn-activated complex fluoride to perovskite compound is preferably in the range of 10:90 to 99.999:0.001 by mass, more preferably in the range of 10:90 to 99.99:0.01, and particularly preferably in the range of 15:85 to 99.97:0.03. By setting the content ratio of Mn-activated complex fluoride to perovskite compound to 10:90 or higher, the optical properties of the red phosphor can be maintained well. On the other hand, by setting the content ratio of Mn-activated complex fluoride to perovskite compound to 99.999:0.001 or lower, the optical properties and durability of the red phosphor in high-temperature and high-humidity environments can be further improved.

[0042] The (initial) absorption rate of the red phosphor is preferably in the range of 30% to 100%, more preferably in the range of 40% to 100%, and even more preferably in the range of 50% to 100%. By setting the absorption rate to 30% or higher, the optical properties of the red phosphor can be maintained well. In particular, in the present invention, even after being stored for a certain period of time in a high-temperature, high-humidity environment, the decrease in the absorption of excitation light by the red phosphor is suppressed, thereby maintaining good optical properties. The above numerical range of absorption rate applies not only to the initial absorption rate of the red phosphor, but also to the absorption rate after the red phosphor has been stored for a certain period of time in a high-temperature, high-humidity environment. The definition of absorption rate is as described above.

[0043] The (initial) internal quantum efficiency of the red phosphor is preferably in the range of 60% to 100%, more preferably in the range of 75% to 100%, and even more preferably in the range of 80% to 100%. By setting the internal quantum efficiency to 70% or higher, the luminescence efficiency of the red phosphor can be maintained well. The above numerical range for internal quantum efficiency applies not only to the initial internal quantum efficiency of the red phosphor, but also to the internal quantum efficiency after storing the red phosphor for a certain period in a high-temperature, high-humidity environment. The definition of internal quantum efficiency is as described above.

[0044] In the red phosphor of this embodiment, the Mn-activated complex fluoride and the perovskite compound can be present in various forms.

[0045] For example, perovskite compounds can be present on at least a portion of the surface of Mn-activated double fluoride. It is believed that the tetravalent manganese ions that constitute Mn-activated double fluoride react with water to produce colored manganese dioxide, causing the Mn-activated double fluoride to darken. Under high temperature and high humidity conditions, this darkening is accelerated, which is presumed to lead to deterioration of the optical properties of the red phosphor and a decrease in durability. However, by presenting a perovskite compound on at least a portion of the surface of the Mn-activated double fluoride, the reaction of tetravalent manganese ions with water can be reduced or prevented. In particular, if the entire surface of the Mn-activated double fluoride is covered with a perovskite compound as a coating layer, it suppresses the penetration of moisture and water vapor into the red phosphor, thereby improving durability and optical properties under high temperature and high humidity environments.

[0046] From the viewpoint of preventing the formation of manganese dioxide, it is preferable that the entire surface of the Mn-activated double fluoride is covered with a perovskite compound as a coating layer. However, covering the entire surface of the Mn-activated double fluoride with a perovskite compound may not be industrially suitable from the viewpoint of manufacturing cost and ease of manufacture. As a result of diligent research by the present inventors, it has been found that even if the perovskite compound is present on only a part of the surface of the Mn-activated double fluoride, improvements in durability under high temperature and high humidity environments and improvements in optical properties can be achieved, so it is not necessarily required that the entire surface of the Mn-activated double fluoride be covered with the compound. The reason for this is not yet clear, but it is thought to be related to the fact that in the manufacturing process of the red phosphor of the present invention, the material passes through a three-phase interface consisting of the perovskite compound formed on the surface of the red phosphor, the Mn-activated double fluoride, and the reaction solution / processing solution. In other words, when the reaction / processing solution is removed by distillation, the perovskite compounds present in small amounts may deposit extremely thinly on the very surface of the Mn-activated double fluoride, for example, at the molecular level. Furthermore, in harsh environments such as high temperature and high humidity, the water molecule adsorption layer on the surface of the Mn-activated double fluoride can be considered as the reaction / processing solution, and the perovskite compounds present on a part of the surface of the Mn-activated double fluoride may act as a reservoir. Thus, it is thought that improved durability in high temperature and high humidity environments can be achieved without covering the entire surface of the Mn-activated double fluoride.

[0047] Furthermore, the perovskite compound may be located inside the Mn-activating complex fluoride. This allows the internally located perovskite compound to induce scattering of excitation light, and Mn 4+ This increases the opportunity for contact with ions, contributing to improved optical properties, particularly absorption.

[0048] Furthermore, Mn-activated complex fluoride may be present on at least a portion of the surface of the perovskite compound. In this form, the perovskite compound is present without causing optical problems, and therefore Mn, which is the light-emitting ion of the red phosphor, is present. 4+This can reduce the amount of Mn-activated complex fluoride containing the substance, which can contribute to cost reduction of phosphor raw materials used in light-emitting devices such as LEDs, lighting fixtures, and image display devices.

[0049] Furthermore, the Mn-activated complex fluoride may be present inside the perovskite compound. This prevents tetravalent manganese ions from coming into contact with water or water vapor, further preventing the formation of manganese dioxide. As a result, the durability of the red phosphor in high-temperature and high-humidity environments can be further improved.

[0050] The red phosphor in this embodiment is preferably a solid, and more preferably in particulate form. When the red phosphor is in particulate form, its average particle size is not particularly limited, as long as the proportion of scattering relative to the excitation light does not become too large compared to absorption and conversion, and no problems arise when mixing it with resin for mounting in an LED device.

[0051] The red phosphor of this embodiment is suitable, for example, as a red phosphor for white LEDs that use blue light as a light source. The red phosphor of this embodiment can be suitably used in light-emitting devices such as lighting fixtures and image display devices.

[0052] (Method for manufacturing red phosphor) Next, the method for producing the red phosphor according to this embodiment will be described below. One embodiment of the method for producing the red phosphor according to this embodiment is a method that includes at least a step of contacting a Mn-activated double fluoride with a perovskite compound in the presence of a solvent. This method makes it possible to produce a red phosphor in which the perovskite compound is present on at least a portion of the surface of the Mn-activated double fluoride, or a red phosphor in which the Mn-activated double fluoride is present on at least a portion of the surface of the perovskite compound.

[0053] Suitable solvents include water, organic solvents, mixtures thereof, or acidic solvents thereof. Of these solvents, those that completely dissolve the Mn-activated complex fluoride may drastically reduce the yield of the red phosphor. Therefore, from the viewpoint of improving productivity, it is preferable to select a solvent that does not completely dissolve the Mn-activated complex fluoride.

[0054] Examples of such solvents include methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, acetone, methyl acetate, ethyl acetate, tetrahydrofuran, and 1,2-dimethoxyethane. Of these organic solvents, methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, and acetone are preferred from the viewpoint of ease of acquisition and simplicity of the working environment, and ethyl alcohol, isopropyl alcohol, and acetone are particularly preferred.

[0055] Examples of such solvents that are acidic (i.e., solvents containing proton-containing acids) include hydrogen fluoride, nitric acid, sulfuric acid, hydrochloric acid, and hydrofluorosilicic acid. From the viewpoint of the manufacturing process and the properties of the red phosphor, hydrogen fluoride, nitric acid, and hydrofluorosilicic acid are preferred, and hydrogen fluoride is particularly preferred.

[0056] The amount of perovskite compound added is preferably set appropriately so that the content ratio of Mn-activated complex fluoride to perovskite compound in the red phosphor obtained by the production method of this embodiment is within the following range. That is, the content ratio of Mn-activated complex fluoride to perovskite compound is preferably in the range of 10:90 to 99.999:0.001 by mass, more preferably in the range of 10:90 to 99.99:0.01, and particularly preferably in the range of 15:85 to 99.97:0.03. By setting the content ratio of Mn-activated complex fluoride to perovskite compound to 99.999:0.001 or less, the optical properties of the red phosphor can be maintained well. On the other hand, by setting the content ratio of Mn-activated complex fluoride to perovskite compound to 10:90 or more, the optical properties and durability of the red phosphor in high temperature and high humidity environments can be further improved.

[0057] The mixing ratio of the solvent to the Mn-activated complex fluoride and perovskite compound can be adjusted as appropriate within a range that does not affect subsequent stirring or filtration (details of stirring and filtration will be described later). Specifically, the mixing ratio of the two is preferably in the range of 2:1 to 100:1 by mass, more preferably in the range of 3:1 to 50:1, and particularly preferably in the range of 3:1 to 10:1. By setting the mixing ratio to 100:1 or less, the amount of solvent discharged as waste liquid can be reduced, thereby reducing the environmental burden. On the other hand, by setting the mixing ratio to 2:1 or more, the dispersibility of the Mn-activated complex fluoride and perovskite compound in the solvent can be improved, preventing the Mn-activated complex fluoride and perovskite compound from existing in a non-uniform manner.

[0058] Furthermore, when using an acidic solvent containing hydrogen fluoride, i.e., hydrofluoric acid or a mixed solvent of hydrofluoric acid and an organic solvent, the concentration of hydrogen fluoride is preferably in the range of 1% to 70% by mass, more preferably in the range of 5% to 60% by mass, and particularly preferably in the range of 10% to 50% by mass, relative to the total mass of the acidic solvent. By setting the concentration of hydrogen fluoride to 70% by mass or less, the solubility of Mn-activated complex fluoride in the acidic solvent containing hydrogen fluoride can be reduced, thereby suppressing a decrease in the yield of red phosphor. On the other hand, by setting the concentration of hydrogen fluoride to 1% by mass or more, the increase in the amount of acidic solvent used can be suppressed, thereby improving productivity.

[0059] The method for contacting the Mn-activated complex fluoride and the perovskite compound in the presence of a solvent is not particularly limited and can be, for example, by immersion (addition) or by spraying. In the former case, for example, the Mn-activated complex fluoride and the perovskite compound are added (immersed) in the solvent in any order or simultaneously. This yields a suspension in which the Mn-activated complex fluoride and the perovskite compound are dispersed in the solvent. The number of additions is not particularly limited and can be done by adding the Mn-activated complex fluoride and the perovskite compound to the solvent all at once or in multiple steps. In the latter case, for example, the solvent to which the perovskite compound has been added is sprayed onto the Mn-activated complex fluoride. The amount of solvent containing the perovskite compound sprayed is not particularly limited and can be set as appropriate. Furthermore, after spraying the solvent containing the perovskite compound onto the Mn-activated complex fluoride, it is preferable to remove any remaining solvent from the surface of the Mn-activated complex fluoride by distillation. The method of removal is not particularly limited, and for example, the drying process described later can be performed. From the viewpoint of industrially producing red phosphors, a method of adding (immersing) the Mn-activated complex fluoride and the perovskite compound in a solvent is preferred.

[0060] When the contact step between the Mn-activated complex fluoride and the perovskite compound is carried out by the immersion method, it is preferable to sequentially perform the following steps after the contact step: a stirring step to stir the obtained suspension, a solid-liquid separation step of the suspension, a washing step of the solid-liquid separated solid, and a drying step of the washed solid.

[0061] The stirring method in the stirring step is not particularly limited and can be carried out using known stirring devices, etc. The stirring time of the suspension is not particularly limited and can be adjusted as appropriate, taking into account the efficiency of the manufacturing equipment. The stirring speed is also not particularly limited and can be set as appropriate and as needed.

[0062] The solid-liquid separation step is a step of separating dispersed solid particles from the suspension after the stirring step. The method of solid-liquid separation is not particularly limited and includes methods such as filtering the suspension, or allowing the suspension to stand or centrifuging to settle the dispersed solid particles, followed by decantation. The standing time of the suspension, the rotation speed of the centrifuge, and the duration are not particularly limited and should be sufficient to allow the solid particles to settle sufficiently.

[0063] The aforementioned washing step is performed to wash the cake obtained by solid-liquid separation. In this washing step, water, organic solvents, mixed solvents thereof, or acidic solvents thereof can be used as cleaning agents. The washing time and number of washes are not particularly limited and can be set as appropriate and necessary.

[0064] The organic solvent used in the washing process is not particularly limited, and examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, acetone, methyl acetate, ethyl acetate, tetrahydrofuran, and 1,2-dimethoxyethane. From the viewpoint of ease of availability and simplicity of the working environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, and acetone are preferred, and ethyl alcohol, isopropyl alcohol, and acetone are particularly preferred.

[0065] Furthermore, the acidic solvent used in the washing process refers to a solution containing a proton-containing acid. The proton-containing acid is not particularly limited and examples include hydrogen fluoride, nitric acid, sulfuric acid, hydrochloric acid, and hydrosilicon fluoride. The content of the proton-containing acid is preferably in the range of 0.1% to 70% by mass, more preferably in the range of 1% to 55% by mass, and particularly preferably in the range of 5% to 50% by mass, relative to the total mass of the acidic solvent.

[0066] The drying process described above is performed on the cake after the washing process. This allows for the removal of any remaining solvent or detergent used in the washing process. The drying method is not particularly limited and examples include heat drying and hot air drying. In the case of heat drying, it is preferable to perform the drying under a nitrogen gas atmosphere. The drying temperature is preferably in the range of 60°C to 200°C, more preferably in the range of 70°C to 150°C, and particularly preferably in the range of 80°C to 110°C. By setting the drying temperature to 60°C or higher, good drying efficiency can be maintained. Furthermore, it is possible to prevent the retention of impurities and suppress the deterioration of the optical properties of the red phosphor caused by the retention of such impurities. On the other hand, by setting the drying temperature to 200°C or lower, it is possible to prevent the obtained red phosphor from degrading due to heat. In the case of heat drying, the drying time is preferably in the range of 0.5 hours to 20 hours, and more preferably in the range of 2 hours to 15 hours. By setting the drying time to 0.5 hours or more, it is possible to prevent the retention of impurities and suppress the deterioration of the optical properties of the red phosphor caused by the retention of such impurities. On the other hand, by limiting the drying time to 20 hours or less, it is possible to prevent a decrease in the production efficiency of the red phosphor.

[0067] As described above, a red phosphor in which a perovskite compound is present on at least a portion of the surface of a Mn-activated double fluoride, or a red phosphor in which a Mn-activated double fluoride is present on at least a portion of the surface of a perovskite compound, can be produced.

[0068] Furthermore, another embodiment of the method for producing the red phosphor according to this embodiment is, for example, a method of adding a perovskite compound during the manufacturing process of the Mn-activated double fluoride. With this method, it is possible to produce a red phosphor in which the perovskite compound is present inside the Mn-activated double fluoride, or a red phosphor in which the Mn-activated double fluoride is present inside the perovskite compound.

[0069] For example, first, a perovskite compound is dissolved or dispersed in a hydrogen fluoride solution containing a Mn-activated double fluoride. Next, a solid substance that does not contain element Mn is added to the hydrogen fluoride solution containing the Mn-activated double fluoride and the perovskite compound. As a result, the solubility of the Mn-activated double fluoride decreases as the solid substance dissolves, causing the Mn-activated double fluoride to precipitate. During the precipitation process of the Mn-activated double fluoride, the perovskite compound is incorporated, resulting in the production of a red phosphor in which the perovskite compound is located inside the Mn-activated double fluoride. Alternatively, raw materials containing elements L, M, and Mn are dissolved or dispersed in a hydrogen fluoride solution. Next, a solution containing a dissolved perovskite compound is added to the hydrogen fluoride solution containing these raw materials. This allows for the production of a red phosphor in which the Mn-activated double fluoride is located inside the perovskite compound. The ratio of Mn-activated complex fluoride to perovskite compound is not particularly limited and can be set appropriately according to the amount of raw materials used, the application of the red phosphor, and the required performance corresponding to that application.

[0070] (Other matters) The method for producing Mn-activated double fluoride, which is a raw material for red phosphors, is not particularly limited, and known methods can be employed. For example, a method in which compounds containing the constituent elements of Mn-activated double fluoride are dissolved in a hydrofluoric acid solution, mixed, and reacted to crystallize (see HDNguyen, CCLin, RSLiu, Angew. Chem. Vol. 54 No. 37 p. 10866 (2015)), a method in which compounds containing the constituent elements of Mn-activated double fluoride are completely dissolved or dispersed in a hydrofluoric acid solution, and then evaporated and concentrated to precipitate (see Japanese Patent Publication No. 2009-528429), or a method in which compounds containing the constituent elements of Mn-activated double fluoride are sequentially dissolved in a hydrofluoric acid solution, and one of the manganese-free constituent elements of solid Mn-activated double fluoride is added to it, resulting in K2SiF6:Mn 4+ Methods include precipitating the crystals and then filtering and drying them (see WO2015 / 093430). [Examples]

[0071] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0072] (Formation of Mn-activated complex fluoride) Mn-activated complex fluorides were synthesized according to the method described in HDNguyen, CCLin, RSLiu, Angew. Chem. Vol. 54, No. 37, p. 10866 (2015) using the following method.

[0073] First, 35 ml of 48% by mass hydrofluoric acid solution was added to a PFA container with an internal volume of 0.1 L. Next, 1.2 g of SiO2 was added to the hydrofluoric acid solution while stirring and dissolved. Furthermore, 0.3 g of K2MnF6 was added to this solution and dissolved.

[0074] Next, 3.5 g of KF was slowly added to the solution over 15 minutes to obtain crystals. These crystals were washed with a 20% by mass hydrofluoric acid solution and acetone, and then dried at 70°C for 6 hours. This yielded K2SiF6:Mn as a Mn-activated complex fluoride.4+ I obtained it.

[0075] (Example 1) Magnesium potassium fluoride was synthesized by the following method, in accordance with the method described in RAJAMANI NAGARAJAN, Bull. Mater. Sci., Vol. 32, No.6, December 2009, pp. 583-587.

[0076] First, 10 g of magnesium chloride was added to 100 mL of anhydrous methanol (dehydrating solvent) and dissolved. 18.3 g of potassium fluoride was then added to the solution. The molar ratio of potassium fluoride to magnesium chloride was adjusted to 3:1. The resulting solution was then stirred for 120 minutes, filtered, and the filtrate was washed with ethanol. After washing, the filtrate was further washed with acetone. The resulting solid was dried under a nitrogen atmosphere at a drying temperature of 105°C. This yielded 11.5 g of a white solid (perovskite compound).

[0077] X-ray diffraction (XRD) analysis of the obtained white solid revealed a peak consistent with the reference sample for magnesium potassium fluoride (KMgF3) (ICSD-56096), as shown in Figure 1. Figure 1 is a graph showing the X-ray diffraction pattern of KMgF3 from Example 1. Furthermore, the white solid was observed using a scanning electron microscope (SEM). As a result, as shown in Figure 2, the observed image confirmed the presence of a 1 μm cubic crystal structure. Figure 2 is an SEM image of the white solid.

[0078] Next, 2 g of potassium magnesium fluoride (KMgF3) was added to 73 g of isopropyl alcohol as a solvent, and the mixture was stirred for 5 minutes to prepare a suspension. Furthermore, while stirring this suspension, the aforementioned K2SiF6:Mn 4+ 20g was added and stirred for another 10 minutes.

[0079] After stirring, the suspension was allowed to stand for 10 minutes to allow the dispersed solids to settle. The filtrate was then collected by suction filtration. Isopropyl alcohol was then added to the filtrate, and the supernatant was removed by suction filtration again. This process was repeated to wash the filtrate. The washed filtrate was collected and dried under a nitrogen atmosphere at a drying temperature of 105°C to evaporate the isopropyl alcohol.

[0080] Based on the above, the red phosphor according to Example 1 was prepared. When the obtained red phosphor was analyzed by X-ray diffraction (XRD), peaks matching those of the reference (ICSD-29407) for K2SiF6, the host crystal of the Mn-activated complex fluoride, and the reference (ICSD-56096) for magnesium potassium fluoride were observed, as shown in Figure 3. Figure 3 is a graph showing the X-ray diffraction pattern of the red phosphor of Example 1. Furthermore, the red phosphor was observed using a scanning electron microscope (SEM). As a result, as shown in Figure 4, it was confirmed that KMgF3, which has a cubic crystal structure of 1 μm, was attached to the surface of the Mn-activated complex fluoride. Figure 4 is an SEM image of the red phosphor.

[0081] (Example 2) In this example, the isopropyl alcohol used in Example 1 was replaced with pure water. Otherwise, the red phosphor according to Example 2 was prepared in the same manner as in Example 1.

[0082] (Example 3) In this example, the isopropyl alcohol used in Example 1 was replaced with hydrofluoric acid at a concentration of 1% by mass. Otherwise, the red phosphor according to Example 3 was prepared in the same manner as in Example 1.

[0083] (Example 4) In this example, the isopropyl alcohol used in Example 1 was replaced with hydrofluoric acid at a concentration of 43% by mass. Also, the amount of potassium magnesium fluoride added was changed from 2 g to 0.12 g. Aside from these changes, the red phosphor according to Example 4 was prepared in the same manner as in Example 1.

[0084] (Example 5) In this example, the isopropyl alcohol used in Example 1 was replaced with hydrofluoric acid at a concentration of 43% by mass. Also, the amount of magnesium potassium fluoride added was changed from 2 g to 0.02 g. Aside from these changes, the red phosphor according to Example 5 was prepared in the same manner as in Example 1.

[0085] (Example 6) In this example, the perovskite compound was changed from potassium magnesium fluoride to sodium magnesium fluoride (NaMgF3). Aside from these changes, the red phosphor according to Example 6 was prepared in the same manner as in Example 4.

[0086] (Comparative Example 1) In this comparative example, the aforementioned K2SiF6:Mn 4+ This was used as a red phosphor.

[0087] (Evaluation of red phosphors) The red phosphors in Examples 1-6 and Comparative Example 1 were evaluated using the methods described below.

[0088] <Evaluation of the optical properties of red phosphors> To evaluate the optical properties of each red phosphor in Examples 1-6 and Comparative Example 1, their respective absorption rates and internal quantum efficiencies were determined.

[0089] Absorption rates and internal quantum efficiency were measured using a quantum efficiency measurement system (product name: QE-2000, manufactured by Otsuka Electronics Co., Ltd.). Specifically, samples of the red phosphors from Examples 1-6 and Comparative Example 1 were packed into powder measurement cells and measured. As a result, the absorption rates of the red phosphors in Examples 1-6 were 62%, 68%, 67%, 72%, 73%, and 72%, respectively, and the internal quantum efficiency was 90% for all of them. On the other hand, the absorption rate of the red phosphor in Comparative Example 1 was 72%, and the internal quantum efficiency was 90%.

[0090] <Evaluation of the durability of red phosphors> Durability tests were conducted as follows: First, 0.3 g of the red phosphor from Examples 1-6 or Comparative Example 1 was placed in a PFA tray and set in a constant temperature and humidity chamber controlled to 85°C and 85% relative humidity. The trays were then stored for 64 hours and 232 hours, respectively. Subsequently, the absorption rate and internal quantum efficiency were determined using the method described above.

[0091] Furthermore, based on the following formula (3), an index of the durability of each red phosphor under high temperature and high humidity conditions was calculated from the measured internal quantum efficiency before and after the durability test. The results are shown in Table 1. (Durability index) = (Internal quantum efficiency after durability test) / (Internal quantum efficiency before durability test) × 100 (3) In formula (3), "after durability test" refers to the case after storage for 64 hours and the case after storage for 232 hours in an environment with a temperature of 85°C and a relative humidity of 85%.

[0092] (result) As shown in Table 1, the red phosphors of Examples 1 to 6, in which the perovskite compound is present on the surface of the Mn-activated complex fluoride, showed a lower rate of change under high temperature and high humidity conditions and improved durability compared to the red phosphor of Comparative Example 1, which does not contain the perovskite compound.

[0093] [Table 1]

Claims

1. It comprises a Mn-activated complex fluoride represented by the following general formula (1) and a perovskite compound represented by the following general formula (2), The perovskite compound is particulate and is a red phosphor attached to the surface of the Mn-activated double fluoride such that a portion of the surface of the Mn-activated double fluoride is exposed. L ２ MF ６ :Mn ４＋ (1) (In the formula, L represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and M represents at least one tetravalent element selected from the group consisting of silicon, germanium, tin, titanium, zirconium, and hafnium.) ABX ３ (2) (In the formula, A represents at least one element selected from the group consisting of sodium and potassium. B represents at least one element selected from the group consisting of magnesium, calcium, zinc, iron, nickel, and copper. X represents fluorine.)

2. The red phosphor according to claim 1, wherein the content ratio of the Mn-activating complex fluoride represented by the general formula (1) to the perovskite compound represented by the general formula (2) is in the range of 10:90 to 99.999:0.001 by mass.

3. A Mn-activated complex fluoride represented by the following general formula (1) and a particulate perovskite compound represented by the following general formula (2) are brought into contact in the presence of a solvent. This method for producing a red phosphor includes the step of producing a red phosphor in which the particulate perovskite compound adheres to the surface of the Mn-activated double fluoride such that a portion of the surface of the Mn-activated double fluoride is exposed. L ２ MF ６ :Mn ４＋ (1) (In the formula, L represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and M represents at least one tetravalent element selected from the group consisting of silicon, germanium, tin, titanium, zirconium, and hafnium.) ABX ３ (2) (In the formula, A represents at least one element selected from the group consisting of sodium and potassium. B represents at least one element selected from the group consisting of magnesium, calcium, zinc, iron, nickel, and copper. X represents fluorine.)

4. A method for producing a red phosphor according to claim 3, wherein the content ratio of the Mn-activating complex fluoride to the perovskite compound in the red phosphor obtained by contacting the Mn-activating complex fluoride represented by the general formula (1) with the perovskite compound represented by the general formula (2) is in the range of 10:90 to 99.999:0.001 by mass.

5. The method for producing a red phosphor according to claim 3 or 4, wherein the solvent is water, an organic solvent, a mixture thereof, or an acidic solvent thereof.

6. A method for producing a red phosphor according to any one of claims 3 to 5, wherein the mixing ratio of the solvent with the Mn-activated complex fluoride represented by general formula (1) and the perovskite compound represented by general formula (2) is in the range of 2:1 to 100:1 by mass.

7. The aforementioned acidic solvent is an acidic solvent containing hydrogen fluoride. The method for producing a red phosphor according to claim 5, wherein the concentration of the hydrogen fluoride in the acidic solvent containing the hydrogen fluoride is in the range of 1% to 70% by mass relative to the total mass of the acidic solvent.

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