JP2017036418A - Fluophor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide boron nitride (h-BN) fluophor having largely improved light emission intensity and a graphite structure.SOLUTION: There is provided a h-BN fluophor consisting of h-BN aggregate particles where h-BN primary particles are aggregated and having characteristics [1] to [4] or [3] to [6]. [1] light emission peak wavelength exists at 300 to 400 nm. [2] oxygen concentration is 0.1 to 10 wt.%. [3] the h-BN aggregate particles are spherical aggregate particles. [4] the h-BN aggregate particles are aggregate particles having a card house structure. [5] light emission peak exists at 200 to 280 nm. [6] oxygen concentration is 0.3 wt.% or less, A fluophor having [1] to [4] characteristics is used as luminaire as a light emitting device together with an excitation light source. A fluophor having [3] to [6] characteristics is as a luminaire for resin curing and for antibacterial and sterilization and further an air purifier used together with a light catalyst as a light emitting device together with an excitation light source.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a phosphor made of hexagonal boron nitride.

Boron nitride (hereinafter referred to as “BN”) is an insulating ceramic, and includes various materials such as c-BN having a diamond structure, h-BN having a graphite structure, α-BN having a turbulent layer structure, and β-BN. Crystal forms are known.
Among these, h-BN has the same layered structure as graphite, and is characterized by being relatively easy to synthesize and excellent in thermal conductivity, solid lubricity, chemical stability, and heat resistance. Therefore, it is widely used in the field of electrical and electronic materials.

  Since h-BN also has a very large band gap energy, it is expected as a light emitting material in the deep ultraviolet wavelength region. After firing a commercially available h-BN powder, h-BN is obtained by cathodoluminescence (CL). It has been disclosed that the light emission of BN was evaluated (Non-patent Document 1).

  Further, it is disclosed that when firing the h-BN powder, the firing temperature was changed, and the CL emission intensity, the oxygen content, and the nitrogen content at each firing temperature were measured (Non-patent Document 2).

  Furthermore, it is disclosed that an h-BN thin film was formed on a c-plane sapphire substrate by high temperature chemical vapor deposition (CVD), and the light emission characteristics of the h-BN film according to temperature conditions were evaluated by CL (non-) Patent Document 3).

Yoichi Ishikawa et al., Time-space-resolved cathodoluminescence evaluation of hexagonal BN microcrystals, Proceedings of the 73rd JSAP Academic Lecture Meeting (Autumn 2012), 15-167 Kazuhiko Hara, etc. Effects of annealing on 320 nm cathode luminescence from hexagonal boron nitride powder, Physica Status Solidi C8, 2011, No. 7-8, 2509-2511 Naomi Umehara et al., Luminescent properties of hexagonal BN thin films grown by high-temperature CVD, Proc. Of the 61st JSAP Spring Meeting (2014 Spring), 15-127

The h-BN powders and h-BN films studied above have low emission intensity and could not be put to practical use.
It is an object of the present invention to provide an h-BN phosphor with greatly improved emission intensity.

As a result of intensive studies, the present inventors have found that when BN aggregated particles obtained by aggregating h-BN primary particles are used as the phosphor, the emission intensity is remarkably increased as compared with the h-BN primary particles, and fluorescence is increased. The present invention was completed by conceiving that it is suitable for use as a body.
The reason why the BN aggregated particles have a large light emission intensity is not clear, but the present inventors consider as follows.

  As described in Non-Patent Documents 1 to 3, oxygen-added h-BN heat-treated in an oxygen atmosphere has an emission peak at 300 nm to 400 nm. As a result of investigations by the present inventors, it has been found that these light emissions are light emissions contributed by impurities such as oxygen rather than h-BN itself. And it turned out that many of these impurities exist in the end surface (edge surface) of h-BN which exhibits a plate-like shape. Therefore, the BN aggregated particles in which the h-BN primary particles are aggregated have a large edge surface of the h-BN primary particles in the aggregated particles, that is, a large amount of impurities contributing to light emission. It is considered to have luminescence intensity.

On the other hand, it was conceived that a specific one of the aggregated h-BN has an emission peak at a shorter wavelength than 300 nm to 400 nm, unlike the case of oxygen-added h-BN. Specifically, it was found that it has an emission peak in the deep ultraviolet region of 200 nm to 280 nm.
The present inventors have estimated that the emission of light of 300 nm to 400 nm is greatly contributed by impurities such as oxygen. However, aggregated h-BN having a very low concentration of impurities such as oxygen does not have an emission peak at 300 nm to 400 nm. This is because it has an emission peak at 200 nm to 280 nm. A feature of aggregated h-BN having an emission peak on the short wave side is that the oxygen concentration is low. Therefore, as another more specific embodiment, the aggregated h-BN is an aggregated h-BN having an emission peak at 200 nm to 280 nm when the oxygen concentration is 0.3 wt% or less.

That is, the present invention is as follows.
[1] A phosphor composed of boron nitride aggregated particles in which primary boron nitride particles are aggregated.
[2] The phosphor according to [1], which has an emission peak wavelength of 300 nm to 400 nm.
[3] The phosphor according to [1] or [2], wherein the oxygen concentration is 0.1 wt% or more and 10 wt% or less.
[4] The phosphor according to any one of [1] to [3], wherein the boron nitride aggregated particles are spherical aggregated particles.
[5] The phosphor according to any one of [1] to [4], wherein the boron nitride aggregated particles are aggregated particles having a card house structure.
[6] A light emitting device having at least an excitation light source and the phosphor according to any one of [2] to [5].
[7] A lighting device having the light emitting device according to [6].
[8] The phosphor according to [1], which has an emission peak wavelength of 200 nm or more and 280 nm or less.
[9] The phosphor according to [1] or [8], wherein the oxygen concentration is 0.3 wt% or less.
[10] The phosphor according to [8] or [9], wherein the boron nitride aggregated particles are spherical aggregated particles.
[11] The phosphor according to any one of [8] to [10], wherein the boron nitride aggregated particles are aggregated particles having a card house structure.
[12] A resin curing light-emitting device having at least an excitation light source and the phosphor according to any one of [8] to [11].
[13] An antibacterial / sterilizing lighting device having at least an excitation light source and the phosphor according to any one of [8] to [11].
[14] A light emitting device having at least an excitation light source and the phosphor according to any one of [8] to [11], and a photocatalyst, and irradiating the photocatalyst with light emitted from the light emitting device And an air purifier that demonstrates the antibacterial and bactericidal action of the photocatalyst.

  ADVANTAGE OF THE INVENTION According to this invention, h-BN fluorescent substance with the luminescent intensity improved significantly can be provided. In particular, the present invention can provide a phosphor composed of h-BN aggregated particles, which has a phosphor having an emission peak at 300 nm to 400 nm, and a phosphor having an emission peak at 200 nm to 280 nm. Depending on the emission peak wavelength, it can be applied to preferred applications.

It is a graph which shows the emission spectrum of BN aggregated particle fluorescent substance. It is a graph which shows the integrated intensity ratio of an emission spectrum. It is a table | surface which shows the elemental-analysis result of the fluorescent substance used in Example 2, 4.

  Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

<Phosphor>
A phosphor composed of h-BN aggregated particles according to an embodiment of the present invention (hereinafter also referred to as BN phosphor) emits fluorescence having a peak at 300 nm to 400 nm when excited by excitation light. Its emission is near-ultraviolet to purple, and is a phosphor that emits fluorescence with a relatively short wavelength.
The BN phosphor emits light when excited by ultraviolet rays or electron beams having a wavelength of usually 190 nm or less.

  The BN phosphor may be an aggregated particle in which h-BN primary particles are aggregated, and may contain other impurities. The impurities are not particularly limited as long as the BN aggregated particles can usually be contained. For example, O, C, Si, Na, Mg, Al, Cl, Ca, Fe, Ni, Sr, Y, S, Cr, Co, Examples thereof include Cu and Mn.

Among these, the amount of oxygen (O) contained in the BN aggregated particles particularly has a great influence on the emission spectrum. It is preferable that the oxygen concentration is usually 0.1 wt% or more and 10 wt% or less because fluorescence having a peak at 300 nm to 400 nm is easily emitted. More preferably, it is 0.3 wt% or more, More preferably, it is 0.5 wt% or more, Most preferably, it is 1.0 wt% or more.
On the other hand, when the oxygen concentration is low, the emission peak wavelength becomes a short wavelength. Therefore, when the oxygen concentration is 0.3 wt% or less, it is easy to emit fluorescence having a peak in the deep ultraviolet region of 200 nm to 280 nm, which is preferable.
Thus, by adjusting the amount of oxygen contained, the peak wavelength can be largely controlled. If the phosphor has a peak wavelength in the range of 300 nm to 400 nm, it emits near ultraviolet to purple light. As a body, it can be used for a light-emitting device. On the other hand, if it is a phosphor having a peak wavelength in the deep ultraviolet region of 200 nm to 280 nm, since it emits in the ultraviolet region and is not in the visible light region, the light emitting device for curing the resin composition or for detecting paper sheets It can be used for a light emitting device or the like. In addition, the photocatalyst can be irradiated with light in the near ultraviolet region to exert antibacterial and bactericidal action.

Further, the amount of carbon (C) contained in the BN aggregated particles is usually 10 ppm or more, preferably 100 ppm or more, and usually 10,000 ppm or less, preferably 2000 ppm or less, more preferably, from the viewpoint of emission intensity. Is 600 ppm or less.
Further, the amount of magnesium (Mg) contained in the BN aggregated particles is usually 0.01 ppm or more, preferably 1 ppm or more, and usually 150 ppm or less, preferably 90 ppm or less, from the viewpoint of light emission intensity. is there.
In addition, the amount of aluminum (Al) contained in the BN aggregated particles is, from the viewpoint of emission intensity,
Usually, it is 1 ppm or more, preferably 20 ppm or more, and usually 10,000 ppm or less, preferably 5000 ppm or less.
Further, the amount of silicon (Si) contained in the BN aggregated particles is usually 1 ppm or more, preferably 5 ppm or more, and usually 100 ppm or less, preferably 15 ppm or less, from the viewpoint of light emission intensity.
Further, the amount of sulfur (S) contained in the BN aggregated particles is usually 0.1 ppm or more, preferably 3 ppm or more, and usually 100 ppm or less, preferably 50 ppm or less, from the viewpoint of emission intensity. is there.
Further, the amount of chlorine (Cl) contained in the BN aggregated particles is usually 0.1 ppm or more, preferably 1 ppm or more, and usually 20 ppm or less, preferably 10 ppm or less, from the viewpoint of emission intensity. is there.
Further, the amount of calcium (Ca) contained in the BN aggregated particles is usually 1 ppm or more, preferably 50 ppm or more, and usually 20000 ppm or less, preferably 10,000 ppm or less from the viewpoint of emission intensity.
The amount of iron (Fe) contained in the BN aggregated particles is usually 5 ppm or more, preferably 25 ppm or more, and usually 1000 ppm or less, preferably 500 ppm or less, from the viewpoint of light emission intensity.
Further, the amount of chromium (Cr) contained in the BN aggregated particles is usually 0.01 ppm or more, preferably 1 ppm or more, and usually 500 ppm or less, preferably 100 ppm or less, from the viewpoint of light emission intensity. is there.
Further, the amount of nickel (Ni) contained in the BN aggregated particles is usually 0.1 ppm or more, preferably 15 ppm or more, and usually 1000 ppm or less, preferably 500 ppm or less, from the viewpoint of light emission intensity. is there.
The amount of strontium (Sr) contained in the BN aggregated particles is usually 0.01 ppm or more, preferably 1 ppm or more, and usually 100 ppm or less, preferably 10 ppm or less from the viewpoint of emission intensity. is there.

The content of impurities is not particularly limited, but the total amount of impurities is usually 2.0 wt% or less, preferably 1.0 wt% or less.
The impurity content can be adjusted as appropriate in the BN aggregated particle manufacturing process and the h-BN primary particle manufacturing process, and the oxygen concentration is adjusted to a desired value depending on the oxygen atmosphere during firing. can do.

In the case of a phosphor having a peak wavelength at 300 nm to 400 nm, the full width at half maximum of the emission spectrum is usually 20 nm or more, preferably 30 nm or more, and usually 100 nm or less, preferably 50 nm or less.
In the case of a phosphor having a peak wavelength at 200 nm to 280 nm, the full width at half maximum of the emission spectrum is usually 5 nm or more, preferably 10 nm or more, and usually 50 nm or less, preferably 30 nm or less.

<Physical properties of phosphor>
The phosphor according to the present embodiment has an average particle diameter (D ₅₀ ) of usually 2 μm or more, preferably 5 μm or more, more preferably 10 μm or more, more preferably 25 μm or more, and further preferably 26 μm or more. Preferably it is 30 μm or more, most preferably 40 μm or more, even 45 μm or more is preferable, and even 50 μm or more is preferable.
Moreover, it is 200 micrometers or less normally, Preferably it is 150 micrometers or less, More preferably, it is 100 micrometers or less.
By setting it as the said range, it becomes easy to form the card house structure that the edge surface of BN primary particle goes to the outer side of an aggregated particle, and becomes aggregated BN with large emitted light intensity, and is preferable.

On the other hand, in the case of a phosphor produced by the production method shown in JP2013-241321A, which will be described later, the average particle diameter (D ₅₀ ) is usually 0.1 μm or more, preferably 0.8. It is 3 μm or more, more preferably 0.5 μm or more, usually 10 μm or less, preferably 7 μm or less, more preferably 5 μm or more, and further preferably 4 μm or more.
By setting it as the said range, it becomes easy to form the card house structure that the edge surface of BN primary particle goes to the outer side of an aggregated particle, and becomes aggregated BN with large emitted light intensity, and is preferable.

<Form of BN aggregated particles constituting phosphor>
The BN aggregated particles only need to be formed by aggregation of BN primary particles, and may contain components other than the BN primary particles as long as the effects of the present invention are not impaired. Examples of components other than the BN primary particles include components derived from a binder, a surfactant, and a solvent that may be added to the slurry, which will be described later in <Method for producing phosphor>.

The form of the BN aggregated particles is not particularly limited, but may be flat, rugby, disc-shaped, spherical, or elliptical, and is preferably a spherical form. The form of the BN aggregated particles is confirmed by SEM. be able to.
Here, “spherical” means that the aspect ratio (ratio of major axis to minor axis) is 1 or more and 2 or less, preferably 1 or more and 1.5 or less. The aspect ratio of the BN aggregated particles is determined by arbitrarily selecting 200 or more particles from an image taken with an SEM, obtaining the ratio of the major axis to the minor axis, and calculating the average value.

  Further, among these aggregated particles, the BN aggregated particles have a form in which BN primary particle crystals grow radially from the center side to the surface side of the BN aggregated particles, and the BN primary particles are platelets. It is preferable that they have a spherical form in which they are sintered and agglomerated, and more specifically, it is more preferable to have a card house structure. The card house structure is, for example, ceramic 43 No. 2 (issued by the Ceramic Society of Japan in 2008), and has a structure in which plate-like particles are complicatedly laminated without being oriented. More specifically, the BN aggregated particle having a card house structure is an aggregate of BN primary particles, and is a BN aggregated particle having a structure in which the planar portion and the end surface portion of the primary particle are in contact with each other. Is spherical. Moreover, it is preferable that the card house structure is the same structure also inside the particle. The aggregation form and internal structure of these BN aggregated particles can be confirmed by a scanning electron microscope (SEM).

  The BN aggregated particles in the BN aggregated particle composition may be at least two types of BN aggregated particles having different primary particle diameters, and the BN aggregated particles are not particularly limited as long as they are aggregated. In addition to the card house structure as described above, the agglomeration may be a structure in which primary particles overlap (also referred to as a cabbage structure). For example, when the BN raw material is fired, BN aggregated particles produced by pressure forming, firing, and then pulverizing may be used. Among them, even if the composition is contained in two or more types, it is a composition containing BN aggregated particles having a card house structure. It is preferable in terms of easy release. It is more preferable that the main component of the BN aggregated particle composition is BN aggregated particles having a card house structure. The term “main” as used herein refers to 70% by volume or more, more preferably 100% by volume, based on the total composition.

D ₅₀ means the particle diameter when the cumulative volume is 50% when the cumulative curve is drawn with the volume of the powder subjected to measurement as 100%, and the measurement method is a wet measurement method. Can be measured using a laser diffraction / scattering particle size distribution measuring device or the like on a sample in which aggregated particles are dispersed in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer. Can be measured using “Morphology” manufactured by Malvern.

The phosphor according to the present embodiment is an aggregated particle, and the major axis of the primary particles constituting the aggregated particle is usually 0.5 μm or more, preferably 0.6 μm or more, more preferably 0.8 μm or more, and still more preferably 1. 0.0 μm or more, particularly preferably 1.1 μm or more. Moreover, it is 10 micrometers or less normally, Preferably it is 5 micrometers or less, More preferably, it is 3 micrometers or less.
The major axis is a value obtained by magnifying one aggregated particle obtained by SEM measurement and averaging the maximum length of primary particles that can be observed on an image for primary particles constituting one aggregated particle. is there.

  In the case of the aggregated particles, the crystal structure of the primary particles includes hexagonal boron nitride (h-BN) as a main component, and may contain impurities as described above. The crystal structure of the boron nitride primary particles can be confirmed by powder X-ray diffraction measurement.

The phosphor according to the present embodiment is an aggregated particle, and has a three-dimensional structure formed by combining the card so-called card house structure described above as a feature on the aggregate structure for increasing the emission intensity. It is preferable. The card house structure is an agglomerated structure in which many end faces of the card are exposed on the surface, and this agglomerated structure can be easily determined by observation with a scanning electron microscope, but is not limited thereto.
Moreover, in order to confirm that the card house structure is formed, the crushing strength of the particles may be measured. When the card house structure is formed, the crushing strength of one particle is usually 1 MPa or more regardless of the size of the particle. Since such particles have a card house structure or a structure similar to the card house structure, the BN primary particle end surface and the plate surface of the BN are in contact with each other, so that the crushing strength is high. Although it tends to be large and forms an agglomerated structure including many edge surfaces, it is not limited to this.

<Method for producing phosphor>
The method for producing the phosphor according to this embodiment is not particularly limited, and can be produced according to a conventional method for producing BN aggregated particles. Examples of the production method include the method described in JP-A-9-202663, the method described in JP-A-2013-241321, and the like.

  As another method, particles are granulated using a slurry containing raw material boron nitride powder having a viscosity of 200 to 5000 mPa · s (hereinafter sometimes referred to as “BN slurry”), and the granulated particles are heated. By the treatment, it is possible to grow and produce crystallites of primary particles constituting the aggregated particles while maintaining the size of the granulated particles. In this case, the viscosity of the BN slurry is preferably 300 mPa · s or more, more preferably 500 mPa · s or more, still more preferably 700 mPa · s or more, particularly preferably 1000 mPa · s or more, preferably 4000 mPa · s or less, more Preferably it is 3000 mPa * s or less.

The viscosity of the BN slurry greatly affects the volume-based average particle diameter D ₅₀ of the aggregated particles to be generated and the average crystallite diameter of the primary particles constituting the aggregated particles, and the viscosity is set to 200 mPa · s or more. , it is possible to increase the average particle diameter D ₅₀ of the volume-based average crystallite diameter and BN agglomerated particles of primary particles.
On the other hand, granulation can be facilitated by setting the viscosity of the BN slurry to 5000 mPa · s or less. A method for adjusting the viscosity of the BN slurry will be described later.

  The viscosity of the BN slurry is a viscosity measured at a blade rotation speed of 100 rpm using a rotational viscometer “VISCO BASIC Plus R” manufactured by FUNGILAB.

  In the preparation of the slurry, the raw material powder is synthesized from commercially available h-BN, commercially available α and β-BN, boron nitride prepared by a reduction nitriding method of boron compound and ammonia, boron compound and nitrogen-containing compounds such as melamine. Any of boron nitride and the like that can be used can be used without limitation, but h-BN is particularly preferably used from the standpoint of more exerting the effects of the present invention.

  As a form of the raw material powder used for the preparation of the slurry, powder particles having a wide half-value width of a peak obtained by powder X-ray diffraction measurement and low crystallinity are preferable. As a measure of crystallinity, the peak half-value width of the (002) plane obtained from powder X-ray diffraction measurement is an angle of 2θ, usually 0.4 ° or more, preferably 0.45 ° or more, more preferably 0.5. More than °. Moreover, it is 2.0 degrees or less normally, Preferably it is 1.5 degrees or less, More preferably, it is 1 degree or less. If it is larger than the above upper limit, the crystallite is not sufficiently large, and it takes a long time to increase the crystallite, so that the productivity tends to deteriorate. If it is less than the above lower limit, the crystallinity is too high and sufficient crystal growth cannot be expected, and the dispersion stability at the time of slurry preparation tends to deteriorate. In addition, the powder X-ray-diffraction measuring method is described in the item of the below-mentioned Example.

  From the viewpoint of BN crystal growth, it is preferable that some oxygen atoms are present in the raw material BN powder, and the total oxygen concentration in the raw material BN powder is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3%. It is at least 4% by mass, more preferably at least 4% by mass. Moreover, it is 10 mass% or less normally, More preferably, it is 9 mass% or less. If it is larger than the above upper limit, oxygen tends to remain even after heat treatment, so that the effect of improving thermal conductivity tends to be small. If it is less than the above lower limit, the crystallinity is too high, crystal growth cannot be expected, and the peak intensity ratio that can be confirmed by powder X-ray diffraction measurement tends to be out of the desired range.

By using a raw material having an oxygen concentration of 1.0% by weight or more present in the raw material BN powder, the average crystallite diameter of the BN primary particles constituting the BN aggregated particles can be controlled within a desired range.
In addition, as a method for adjusting the total oxygen concentration of the raw material BN powder to the above range, for example, a method in which the synthesis temperature at the time of BN synthesis is a low temperature of 1500 ° C. or less, a raw material BN in a low temperature oxidizing atmosphere of 500 ° C. to 900 ° C. The method of heat-processing powder is mentioned.
The total oxygen concentration of the raw material BN powder can be measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba, Ltd.

The total pore volume of the raw material BN powder is usually 1.0 cm ³ / g or less, preferably 0.3 c
m ³ / g or more and 1.0 cm ³ / g or less, more preferably 0.5 cm ³ / g or more and 1.0 cm ³ / g or less. When the total pore volume is 1.0 cm ³ / g or less, since the raw material BN powder is dense, granulation with high sphericity becomes possible.

The specific surface area of the raw material BN powder is usually 50 m ² / g or more, preferably 60 m ² / g or more, more preferably 70 m ² / g or more. Usually, but it is 1000m ² / g or less, 500m ² /
g or less is preferable, and 300 m ² / g or less is more preferable. The specific surface area of the raw material BN powder is 50
It is preferable for it to be m ² / g or more because the dispersed particle size in the BN slurry used for spheronization by granulation can be reduced. Moreover, since it can suppress the increase in a slurry viscosity by setting it as 1000 m < ² > / g or less, it is preferable.
The total pore volume of the raw material BN powder can be measured by a nitrogen adsorption method and a mercury intrusion method, and the specific surface area can be measured by a BET one-point method (adsorption gas: nitrogen). Specific measurement methods for the total pore volume and specific surface area of the raw material BN powder are described in the Examples section below.

  The medium used for the preparation of the slurry is not particularly limited, and water and / or various organic solvents can be used, but from the viewpoint of ease of spray drying, simplification of the apparatus, etc., it is preferable to use water, Pure water is more preferable.

The amount of the medium used for the preparation of the slurry is preferably added in such an amount that the viscosity of the slurry is 200 to 5000 mPa · s.
Specifically, the amount of the medium used for preparing the slurry is usually 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and usually 70% by mass or less, preferably 65% by mass. Hereinafter, it is 60 mass% or less more preferably. If the amount of the medium used is larger than the above upper limit, the slurry viscosity becomes too low, so that the uniformity of the slurry due to sedimentation is impaired, and the crystallite size of the primary particles constituting the obtained aggregated particles tends to be out of the desired range. There is. If it is less than the lower limit, the slurry viscosity is too high, so that granulation tends to be difficult. That is, when the amount of the medium used is out of the above range, it becomes difficult to simultaneously satisfy the size of the aggregated particles, the crystallinity of the primary particles constituting the aggregated particles, and the reduction of the crystal grain boundaries in the primary particles.

In preparing the slurry, it is preferable to add various surfactants from the viewpoint of adjusting the viscosity of the slurry and dispersion stability (inhibition of aggregation) of the raw material powder in the slurry.
As the surfactant, an anionic surfactant, a cationic surfactant, a nonionic surfactant or the like can be used. These may be used alone or in combination of two or more. May be used.

  In general, surfactants can change the viscosity of the slurry. Therefore, when adding a surfactant to the slurry, the amount is adjusted so that the viscosity of the slurry is 200 to 5000 mPa · s. For example, as the raw material BN, boron nitride having a (002) plane peak half-value width 2θ of 0.67 ° and an oxygen concentration of 7.5% by mass obtained by powder X-ray diffraction measurement is used, and the solid content is 50% by mass. When adjusting the slurry, the active ingredient of the anionic surfactant is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on the total amount of the slurry. Usually, it is 10 mass% or less, Preferably it is 7 mass% or less, More preferably, it is 5 mass% or less, More preferably, 3 mass% or less is added. If it is larger than the above upper limit, the slurry viscosity tends to decrease too much and the surfactant-derived carbon component tends to remain in the generated aggregated particles. If it is less than the above lower limit, the slurry viscosity becomes too high and granulation itself tends to be difficult.

In preparing the slurry, a binder may be included in order to effectively granulate the raw material powder into particles. The binder acts to firmly bind the primary particles and stabilize the granulated particles.
As the binder used in the slurry, any material can be used as long as it can enhance the adhesion between the boron nitride particles. However, since the granulated particles are heat-treated after being granulated, the heat resistance against high temperature conditions in this heat treatment step is improved. What has is preferable.

  As such a binder, metal oxides such as aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide, and titanium oxide are preferably used. Among these, aluminum oxide and yttrium oxide are preferable from the viewpoints of thermal conductivity and heat resistance as an oxide, bonding strength for bonding boron nitride particles, and the like. The binder may be a liquid binder such as alumina sol, or may be one that reacts during heat treatment and is converted into another inorganic component. These binders may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The amount of the binder used (in the case of a liquid binder, the amount used as a solid content) is usually 0% by mass to 30% by mass, preferably 0% by mass to 20% by mass, with respect to the raw material powder in the BN slurry. % Or less, more preferably 0 mass% or more and 15 mass% or less. When the above upper limit is exceeded, the content of the raw material powder in the granulated particles decreases, which not only affects crystal growth but also reduces the effect of improving thermal conductivity when used as a thermally conductive filler.

  The slurry preparation method is not particularly limited as long as the raw material powder and medium, and if necessary, the binder and the surfactant are uniformly dispersed and prepared in a desired viscosity range, but the raw material powder and medium, and further, if necessary, the binder When a surfactant is used, it is preferably prepared as follows.

A predetermined amount of raw material powder is weighed into a resin bottle, and then a predetermined amount of binder is added. Further, after adding a predetermined amount of the surfactant, zirconia ceramic balls are added, and the mixture is stirred for about 0.5 to 5 hours with a pot mill rotary table until a desired viscosity is obtained.
The order of addition is not particularly limited, but when slurrying a large amount of raw material powder, it becomes easy to form agglomerates such as lumps, so after preparing an aqueous solution in which a surfactant and a binder are added to water, a predetermined amount of The raw material powder may be added little by little, and zirconia ceramic balls may be added thereto, and dispersed and slurried with a pot mill rotary table.

  For dispersion, a dispersion device such as a bead mill or a planetary mixer may be used in addition to the pot mill. At the time of slurrying, the temperature of the slurry is 10 ° C. or higher and 60 ° C. or lower. When it is lower than the lower limit, the slurry viscosity increases and tends to deviate from the desired viscosity range. When it is higher than the upper limit, the raw material powder is easily decomposed into ammonia in the aqueous solution. Usually, it is 10 ° C. or more and 60 ° C. or less, preferably 15 ° C. or more and 50 ° C. or less, more preferably 15 ° C. or more and 40 ° C. or less, and further preferably 15 ° C. or more and 35 ° C. or less.

In order to obtain granulated particles from the prepared BN slurry, general granulation methods such as a spray drying method, a rolling method, a fluidized bed method, and a stirring method can be used, and among these, the spray drying method is preferable.
In the spray drying method, granulated particles of a desired size are produced based on the concentration of the slurry used as a raw material, the amount of liquid fed per unit time introduced into the apparatus, and the pressure and pressure when the liquid is sprayed. It is possible to obtain spherical granulated particles. Although there is no restriction | limiting in the spray drying apparatus to be used, in order to make a larger spherical granulated particle, the thing by a rotary disk is optimal. Examples of such an apparatus include a spray dryer F series manufactured by Okawara Chemical Co., Ltd., and a spray dryer “MDL-050M” manufactured by Fujisaki Electric Co., Ltd.

The average particle diameter of the granulated particles obtained by granulation is usually the volume-based average particle diameter D ₅₀ when the volume-based average particle diameter range of the BN aggregated particles is preferably 5 μm or more and 200 μm or less. 3 μm or more, preferably 5 μm or more, more preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, particularly preferably 25 μm or more, more particularly preferably 25 μm or more, preferably 26 μm or more, preferably 30 μm or more. Even if it is 35 micrometers or more, it is preferable. Moreover, it is preferable that it is 150 micrometers or less, and it is more preferable that it is 100 micrometers or less. Here, the volume-based average particle diameter D ₅₀ of the granulated particles can be measured by, for example, “LA920” manufactured by Horiba, Ltd. for wet, “Morphology” manufactured by Malvern, for dry.

The above granulated particles can be further subjected to heat treatment in a non-oxidizing gas atmosphere to produce aggregated particles.
Here, the non-oxidizing gas atmosphere is an atmosphere of nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, carbon monoxide gas, or the like. The crystallization speed of the agglomerated particles varies depending on the type of the atmospheric gas used here, and in order to perform crystallization in a short time, nitrogen gas or a mixed gas using a combination of nitrogen gas and other gas is preferably used. .
The heat treatment temperature is usually 1800 ° C. or higher and 2300 ° C. or lower, preferably 1900 ° C.
It is above, Preferably it is 2200 degrees C or less. If the heat treatment temperature is too low, the average crystallite growth of boron nitride becomes insufficient, and the thermal conductivity of the aggregated particles and the compact may be small. If the heat treatment temperature is too high, boron nitride may be decomposed.

By setting the heat treatment temperature to 1800 ° C. or higher and 2300 ° C. or lower, the peak intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the BN primary particles is set to a desired value. it can.
The heat treatment time is usually 3 hours or longer, preferably 4 hours or longer, more preferably 5 hours or longer, and usually 20 hours or shorter, preferably 15 hours or shorter. When the heat treatment time is less than the above lower limit, crystal growth becomes insufficient, and when it exceeds the upper limit, BN may be partially decomposed.

  Since the heat treatment is performed in a non-oxidizing gas atmosphere, it is usually preferable that the firing furnace is evacuated using a vacuum pump and then heated to a desired temperature while introducing a non-oxidizing gas. However, when the inside of the firing furnace can be sufficiently replaced with a non-oxidizing gas, the temperature may be increased by heating while introducing the non-oxidizing gas under normal pressure. Examples of firing furnaces include batch furnaces such as muffle furnaces, tubular furnaces, and atmospheric furnaces, and rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, vertical furnaces, and other continuous furnaces. Can be used properly.

  Usually, the granulated particles to be heat-treated are heated and fired in a circular graphite crucible-covered crucible in order to reduce the non-uniformity of the composition at the time of firing. At this time, in addition to reducing the non-uniformity of the composition, a graphite partition may be inserted for the purpose of suppressing sintering of the agglomerated particles due to firing. The number of divisions by the partition is not particularly limited as long as sintering can be suppressed, but is usually 2 or more and 16 or less. If the division number is larger than the upper limit, sintering can be suppressed, but the primary particle crystals tend not to grow sufficiently. If the division number is smaller than the lower limit, sintering may proceed.

  The aggregated particles after the heat treatment are preferably classified in order to reduce the particle size distribution and suppress an increase in viscosity when blended in the resin composition. This classification is usually performed after the heat treatment of the granulated particles, but may be performed on the granulated particles before the heat treatment and then subjected to the heat treatment.

Although classification may be either wet or dry, dry classification is preferable from the viewpoint of suppressing decomposition of boron nitride. In particular, when the binder has water solubility, dry classification is particularly preferably used.
In addition to classification using a sieve, dry classification includes wind classification that uses a difference between centrifugal force and fluid drag, etc., but swirling air classifiers, forced vortex centrifugal classifiers, semi-free vortex centrifugal classifiers, etc. It can also be performed using a classifier. Among these, particles to be classified such as a swirling air classifier to classify small particles in the submicron to single micron range, and a semi-free vortex centrifugal classifier to classify relatively larger particles. What is necessary is just to use properly according to the particle diameter of this.

[Light emitting device]
The phosphor according to the embodiment of the present invention can be used as a light emitting member in a light emitting device.
In the case of a phosphor that emits near-ultraviolet to violet fluorescence having a peak wavelength of 300 nm to 400 nm, for example, an LED chip that emits ultraviolet light is used as excitation light, and the purple phosphor according to the present embodiment, in addition to this, a green phosphor, By irradiating the phosphor layer mixed with the red phosphor with excitation light, a light emitting device exhibiting white can be obtained.

  On the other hand, if the phosphor emits fluorescence in the deep ultraviolet region having a peak wavelength of 200 nm to 280 nm, for example, an LED chip that emits ultraviolet light or an electron beam is used as excitation light, and the phosphor according to this embodiment is sealed together. Thus, a light-emitting device can be obtained, and the light-emitting device can be used as a light-emitting device for curing a resin composition, or as a light-emitting device for detecting paper sheets, particularly for detecting fake bills. In addition, the photocatalyst can be irradiated with light from the light emitting device to exert antibacterial and bactericidal action. Furthermore, in addition to being used for water quality inspection devices, it can be used for water purification by utilizing the sterilizing action, or can be used as a light source for replacing a conventional mercury lamp as a light source for hospital sterilization.

<Example 1>
<Preparation of BN aggregated particles from BN slurry>
[Preparation of BN slurry (slurry A)]
(material)
Raw material h-BN powder (Half width of (002) plane peak obtained by powder X-ray diffraction measurement (X-ray: CuKα ₁ ) is 2θ = 0.67 °, oxygen concentration is 7.5 mass%): 10000 g
Binder (Takiseram M160L, manufactured by Taki Chemical Co., Ltd., solid content concentration: 21% by mass): 11496 g
Surfactant (surfactant “Ammonium Lauryl Sulfate” manufactured by Kao Corporation: solid concentration 14% by mass): 250 g

(Preparation of slurry)
A predetermined amount of raw material h-BN powder was weighed into a resin bottle, and then a predetermined amount of binder was added. Further, after adding a predetermined amount of a surfactant, zirconia ceramic balls were added and stirred for 1 hour on a pot mill rotary table.
The viscosity of the slurry was 810 mPa · s.

[Granulation]
Granulation from the BN slurry was performed using a FOC-20 manufactured by Okawara Chemical Co., Ltd., at a disk rotational speed of 20000 to 23000 rpm and a drying temperature of 80 ° C.

[Preparation of BN Aggregated Particles (BN-A Aggregated Particles)]
The above BN granulated particles are evacuated at room temperature, then nitrogen gas is introduced and the pressure is restored, the temperature is raised to 1500 ° C. in 7 hours while introducing nitrogen gas as it is, and after reaching 1500 ° C., nitrogen gas is introduced as it is. For 24 hours. Then, it cooled to room temperature and obtained the BN-A aggregated particle.

[Classification]
Furthermore, the BN-A aggregated particles after the heat treatment were lightly pulverized using a mortar and pestle, and then classified using a sieve having an opening of 90 μm. As a result of measuring D ₅₀ of the BN-A aggregated particles after classification, the average particle diameter was 47 μm.

[Oxygen concentration]
The total oxygen concentration of the BN-A aggregated particles was measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba, Ltd. As a result, it was 6.3 wt%.

<Example 2>
In Example 1, except that the slurry A was changed to the following BN slurry (slurry B), and the heat treatment conditions were 1600 ° C. and 24 h, BN-B aggregated particles Was made.

[BN slurry (slurry B)]
(material)
Raw material h-BN powder: 10000 g
Pure water: 7500g
Binder: 5750g
Surfactant: 250g

The viscosity of the slurry during preparation of the BN-B aggregated particles was 2200 mPa · s, and the D ₅₀ of the obtained BN-B aggregated particles had an average particle size of 46.6 μm. The total oxygen concentration of the BN-B aggregated particles was 6.7 wt%. Moreover, the elemental analysis of BN-B was conducted and the results are shown in FIG.

<Example 3>
<Preparation of BN aggregated particles from BN slurry>
[Preparation of BN slurry (slurry C)]
(material)
Raw material h-BN powder (total oxygen concentration 4% by weight): 500 g
Pure water: 4250g
Binder (“Alumina sol 520” manufactured by Nissan Chemical Co., Ltd., solid content concentration 20% by weight): 250 g
Surfactant (Anionic surfactant “Demol NL” manufactured by Kao Corporation): 50 g

(Preparation of slurry C)
A predetermined amount of raw material h-BN powder was weighed into a resin bottle, and then a predetermined amount of binder was added. Further, after adding a predetermined amount of a surfactant, the obtained slurry is mixed well and put into an “OB mill” manufactured by Freund Turbo, with a rotor speed of 2000 rpm and a circulating liquid feed rate of 0.5 L / min. Circulating pulverization was performed for 160 minutes. For pulverization, 0.5 mmφ zirconia beads were used.
The total oxygen concentration of the raw material h-BN powder used for the preparation of the slurry C was 4.0% by weight.
The viscosity of the slurry C was 250 mPa · s.

<Spheroidization>
The slurry C was spheroidized by using a spray dryer “MDL-050M” manufactured by Fujisaki Electric Co., Ltd., setting granulation conditions with a target granulation particle diameter D ₅₀ of 10 μm, and spray drying each. The slurry feed rate was 30 ml / min (15 ml / min × 2), sprayed at a pneumatic pressure of 0.7 MPa and an air flow rate of 92 L / min (46 L / min × 2), and the drying temperature after nozzle injection was 200 ° C. Set to.
D ₅₀ of the obtained granulated particles was 8.9 μm.

<Heat treatment>
The spheroidized BN granulated particles were heat-treated using an atmosphere furnace at 2000 ° C. for 5 hours under a nitrogen gas flow.
The temperature increase and temperature decrease during the heat treatment were performed as follows.
It was raised in 20 minutes while evacuating from room temperature to 400 ° C., and kept at 400 ° C. for 30 minutes while evacuated. The degree of vacuum was 10 ⁻¹ to 10 ⁻² Pa. Subsequently, 2.0 L / min of nitrogen gas was introduced and the pressure was restored. While nitrogen gas was introduced as it was, the temperature was raised to 1500 ° C. at 100 ° C./hour and held at 1500 ° C. for 5 hours, and further from 1500 ° C. to 2000 ° C. The temperature was raised at 50 ° C./hour and held for 5 hours after reaching 2000 ° C. Then, it cooled to room temperature at 7 degree-C / min.

<Classification>
The BN granulated particles after the heat treatment were classified using a swirling airflow classifier “Aero Fine Classifier (AC-20)” manufactured by Nisshin Engineering Co., Ltd.
D ₅₀ of the obtained spherical BN (BN-C) was 4.1 μm.

[Oxygen concentration]
The total oxygen concentration of the obtained BN—C aggregated particles was measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba, Ltd. As a result, it was 0.12 wt%.

<Example 4>
PTX25 (BN-D aggregated particles, average particle size 25 μm, oxygen concentration 0.2 wt%) manufactured by Momentive was used as it was as aggregated BN particles of the type in which the orientation of BN primary particles stuck in the circumferential direction. Moreover, the elemental analysis of BN-D was conducted and the results are shown in FIG.

<Comparative Example 1>
[Production of non-aggregated BN-E]
As a raw material h-BN powder, a commercially available h-BN raw material powder A (in the XRD analysis (X-ray source: CuKα), the peak half-value width of 002 plane is 0.67 °, the oxygen concentration is 8% by mass), Commercially available Li ₂ CO ₃ powder (purity 99.0%) was used. The amounts of raw material h-BN powder and Li ₂ CO ₃ having a melting point of 723 ° C. were 50 mol%, respectively. The h-BN raw material powder A and Li ₂ CO ₃ were put in a crucible and heat-treated at 1000 ° C. for 5 hours under a nitrogen flow. The flux was dissolved and removed from the heat-treated sample (impurities were dissolved with 1M hydrochloric acid) to obtain non-aggregated BN-E particles.

<Comparative Example 2>
As a particle in which the BN primary particles are not aggregated, BN (BN-F particle, average particle diameter: 10 μm) manufactured by Koyo Chemical Co., Ltd. was used as it was.

<Luminescence test>
In the emission spectrum measurement, an electron gun (RHG-303G manufactured by Beamtron) was used as an excitation source. The excitation conditions were an acceleration voltage of −3.5 kV and an emission current of 70 μA. The fluorescence was condensed on a spectroscope (C5094 manufactured by Hamamatsu Photonics) with a condenser lens, dispersed by a diffraction grating (300 grooves / mm), and received by a CCD camera (PMA50 manufactured by Hamamatsu Photonics). The entrance slit of the spectrometer was fixed at 20 μm. The excitation conditions were an acceleration voltage of −3.5 kV and an emission current of 70 μA. The exposure time was adjusted so that the dynamic range of the spectrum was 4 digits or more. The emission intensity was corrected by the exposure time. The integrated intensity was calculated in the region from 200 nm to 500 nm.
The results are shown in FIG. 1 and FIG.

  From FIG. 1, the phosphors of Examples 1 to 3 which are aggregated BN particles are remarkably made to have an emission intensity compared to Comparative Example 2 of non-aggregated BN particles (BN-F). You can see that it has improved. Moreover, it can be understood that the phosphors of Examples 1 and 2 having a high oxygen concentration have particularly improved emission intensity. Further, among the aggregated BN phosphors, the BN phosphor of Example 4 having a low oxygen concentration has an emission peak in the same wavelength region as compared with Comparative Example 1 of non-aggregated BN particles (BN-E). In addition, it can be understood that the emission intensity is remarkably improved and is shifted to the short wavelength side.

Claims (14)

  A phosphor composed of boron nitride aggregated particles in which primary boron nitride particles are aggregated.   The phosphor according to claim 1, wherein an emission peak wavelength is present in a range of 300 nm to 400 nm.   The phosphor according to claim 1 or 2, wherein the oxygen concentration is 0.1 wt% or more and 10 wt% or less.   The phosphor according to any one of claims 1 to 3, wherein the boron nitride aggregated particles are spherical aggregated particles.   The phosphor according to any one of claims 1 to 4, wherein the boron nitride aggregated particles are aggregated particles having a card house structure.   A light emitting device having at least an excitation light source and the phosphor according to any one of claims 2 to 5.   A lighting device comprising the light emitting device according to claim 6.   The phosphor according to claim 1, wherein the emission peak wavelength is in the range of 200 nm to 280 nm.   The phosphor according to claim 1 or 8, wherein the oxygen concentration is 0.3 wt% or less.   The phosphor according to claim 8 or 9, wherein the boron nitride aggregated particles are spherical aggregated particles.   The phosphor according to any one of claims 8 to 10, wherein the boron nitride aggregated particles are aggregated particles having a card house structure.   A light-emitting device for resin curing having at least an excitation light source and the phosphor according to any one of claims 8 to 11.   An antibacterial / sterilizing lighting device having at least an excitation light source and the phosphor according to any one of claims 8 to 11.   A light-emitting device having at least an excitation light source and the phosphor according to any one of claims 8 to 11, and a photocatalyst, and irradiating the photocatalyst with light emitted from the light-emitting device, whereby the photocatalyst Air purifier that demonstrates the antibacterial and bactericidal action of