JP2017155097A - Phosphor and manufacturing method thereof, wave length converting member with phosphor, wave converting film, solar module, light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphor capable of obtaining high brightness, which converts a specific wavelength and transmits light of other wavelengths without diffusing, has a small particle size and excellent crystallinity, and has a uniform distribution of particle sizes (particle size distribution).SOLUTION: A phosphor of AGaS:Eu((A is Sr or Ca) having a particle size d of 1000 nm or smaller, a multi-dispersion index showing broadness of the particle size distribution of 0.3 or smaller, and an amorphous layer of a particle surface layer of 5 nm or thinner, and a manufacturing method thereof. The particle size d is preferably smaller than 250 nm or 250≤d≤500, more preferably 50≤d<250nm.SELECTED DRAWING: None

Description

  The present invention relates to a particulate phosphor that absorbs light in a region from ultraviolet to blue and emits light of a specific wavelength, and a method for producing the same, and further, a wavelength conversion member using the phosphor, wavelength The present invention relates to a conversion film, a solar cell module, and a light emitting device.

Conventionally, a raw material solution is sprayed in a high-temperature furnace to produce precursor fine particles that are SrGa ₂ O ₄ : Eu. After the precursor fine particles are classified, heat treatment in hydrogen sulfide is performed to obtain fine particles of SrGa. A method for producing a ₂ S ₄ : Eu phosphor is known (see Patent Document 1).

In addition, SrGa ₂ O ₄ : Eu, which is a raw material particle, is nanocrystallized by thermal plasma, and after forming the precursor fine particles, heat treatment in hydrogen sulfide is performed to produce fine SrGa ₂ S ₄ : Eu phosphors. The method of doing is also known (refer patent document 2).

US Pat. No. 6,875,372 JP 2012-36372 A

  By the way, like a solar cell wavelength conversion film, if you want to convert a specific wavelength and allow light of other wavelengths to pass through without being scattered, you need a phosphor with a small particle size and excellent crystallinity and high brightness. It becomes. Furthermore, the particle size distribution (particle size distribution) must be as uniform as possible in the desired designed size. If many particles larger than the designed value are mixed, the light component to be transmitted is scattered. The performance of the solar cell is not fully demonstrated. Specifically, a high-luminance phosphor having a particle size of 1000 nm or less and a uniform particle size is required.

  In general, as a method for reducing phosphor particles, a method using pulverization such as a bead mill is known. However, it is known that the light emission characteristics are lowered because crystallinity is lowered by physical impact.

On the other hand, several synthesis methods that do not require physical pulverization have been proposed. However, the conventional SrGa ₂ S ₄ : Eu phosphor cannot obtain sufficient performance particularly at a particle size of 1000 nm or less. There is. The phosphor disclosed in Patent Document 1 is common to the phosphor according to the present invention in that it is a phosphor using thiogallate sulfide as a base material. However, as is clear from the comparative example described later, the size of the crystal phase with respect to the particle size is small under the firing conditions using the simple temperature rising profile described, and this is the reason why sufficient luminance cannot be obtained. it is conceivable that. In addition, as is apparent from the comparative example described later, the phosphor shown in Patent Document 2 is a mixture of phosphor particles having a relatively large size and phosphor particles having a relatively large particle size, resulting in a solar cell or white LED. Further improvement was required for the wavelength conversion application used in the above.

  The present invention provides a phosphor with high particle size uniformity and high brightness even when the particle size is 1000 nm or less, and also provides a solar cell and a high-efficiency white LED with improved conversion efficiency. The purpose is to do.

The first of the present invention is
A particulate phosphor containing a base material of a thiogallate sulfide represented by the following general formula (1) and an activator,
The particle size is 1000 nm or less, the polydispersity index indicating the breadth of the particle size distribution is 0.3 or less, and the volume ratio of the crystal phase in the particles is represented by the following general formula (2) A phosphor.

AGa ₂ S ₄ (A is Ca, Sr) (1)
Vc / Vt ≧ (R−10) ³ / R ³ (2)
(In the above formula, Vc is the volume of the crystal phase in the particle, Vt is the volume of the particle, and R is the particle size)

  Further, the present invention is a wavelength conversion film characterized by dispersing the phosphor of the present invention, and a solar cell module and a light emitting device characterized by using the phosphor of the present invention.

  A fourth aspect of the present invention provides a wavelength conversion film and a sheet in which the phosphor of the first aspect is dispersed in a transparent resin in order to improve the conversion efficiency of the solar cell, and a solar cell using the same Is to provide.

  A fifth aspect of the present invention provides an LED in which the phosphor of the first aspect is dispersed in order to form a white LED.

  According to the present invention, phosphor particles having a particle size as small as 1000 nm or less and high crystallinity can be obtained.

  In addition, the production method of the present invention can prevent abnormally growing particles and particle size uniformity from decreasing, and a phosphor having a low PDI can be produced. As a result, since the phosphor according to the present invention has a large crystal phase size while having a particle size of 1000 nm or less, high luminance can be obtained. Furthermore, the particle | grains which grew more than the expectation disappeared, the wavelength conversion fluorescent substance with which scattering of light was reduced, and the wavelength conversion film and sheet | seat using the fluorescent substance are made. Therefore, high efficiency of the solar cell according to the present invention using this and the white LED according to the present invention can be realized.

It is sectional drawing of the thickness direction which shows typically the structure of embodiment of the solar cell module using the fluorescent substance of this invention. It is sectional drawing of the thickness direction which shows typically the structure of white LED using the fluorescent substance of this invention. It is a figure which shows the cross-sectional TEM image of the fluorescent substance of this invention (Example 1).

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below. Further, in the present invention, the scope of the present invention also includes those in which the embodiments described below are appropriately modified and improved based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. include.

(Phosphor)
The particulate phosphor according to the present invention is a thiogallate sulfide whose particle size is 1000 nm or less and whose base material is represented by the general formula AGa ₂ S ₄ (where A is Ca and Sr).

  The volume ratio of the crystal phase in the particles is represented by the following general formula (2). In the following formula, Vc is the volume of the crystal phase in the particle, Vt is the volume of the particle, and R is the particle size.

Vc / Vt ≧ (R−10) ³ / R ³ (2)

  The particle size in the present invention refers to D50 (median diameter) obtained by measuring the particle size distribution by dynamic light scattering (DLS). D50 can be measured, for example, using “ZETASIZER (Nano-ZS)” manufactured by Malvern Instruments from a dispersion in which a phosphor is dispersed in ethanol.

  In addition, the phosphor of the present invention has an amorphous layer and a crystal phase covered with the amorphous layer. In a transmission electron microscope (TEM) observation, the amorphous layer is The average thickness is 5 nm or less. Therefore, the volume ratio of the crystal phase of the phosphor of the present invention is represented by the general formula (2). When the amorphous layer becomes thicker than 5 nm in the whole particle, the luminance of the phosphor having a small particle size is particularly lowered. For example, when the particle size is 50 nm and the average thickness of the amorphous layer is 6 nm, more than half of the particles become an amorphous layer and the luminance is significantly reduced. In the present invention, as long as the average thickness of the amorphous layer is 5 nm or less, it may partially exceed 5 nm.

  When the phosphor particles as in the present invention are used as a wavelength conversion material, it is important to have a characteristic of absorbing and emitting specific light and a characteristic of transmitting non-absorbed light with as little scattering as possible.

  If it is a wavelength conversion application of a solar cell, it is necessary to convert a wavelength with low power generation efficiency into a wavelength with high power generation efficiency and to transmit a wavelength with high power generation efficiency without being scattered by the phosphor. In addition, for white LED applications, a part of the light emitted from the LED chip is absorbed and converted to other wavelengths, but if the scattering of the light can be reduced, higher light emission efficiency than before can be obtained. It is done.

  In general, it is known that the degree of scattering is maximized at a particle size approximately half the wavelength of the irradiation light. Here, considering solar cell applications, the spectrum of sunlight on the ground surface has a maximum intensity in the vicinity of 500 nm. In this case, scattering is maximum at 250 nm, which is half of the spectrum (Me scattering). It is known that when the particle diameter of the phosphor is smaller than half of this wavelength, the scattering component is dominated by Rayleigh scattering, and the smaller the particle size, the smaller the scattering. On the other hand, even in the range where the particle size of the phosphor is larger than 250 nm, the degree of scattering is reduced although the degree is smaller than that of the small particle size. When using a phosphor for wavelength conversion, a wavelength conversion film is mainly formed by molding a resin composition in which the phosphor is dispersed in a transparent resin. If the particle size of the phosphor is too large, the wavelength conversion film is used. Therefore, the manufacturing method is difficult. In addition, when the particle size of the phosphor is large, there is a problem that the phosphor component in the wavelength conversion film increases and the function as the original resin is impaired. Therefore, a particle size of about 500 nm or less is preferable. Therefore, in the phosphor of the present invention, the particle size is preferably greater than 250 nm and less than or equal to 500 nm or less than 250 nm in view of light transmission characteristics. Further, when the particle size of the phosphor is reduced, the ratio of the crystal phase in the phosphor particles is reduced. When the particle size is less than 50 nm, it is difficult to make the volume ratio of the crystal phase in the particle 50% or more, and the luminance is lowered. Therefore, the particle size is preferably 50 nm or more. Therefore, a more preferable particle size of the phosphor of the present invention is 50 nm or more and less than 250 nm at which scattering is reduced in a wide wavelength range.

  Furthermore, in order to design the balance between the luminance of the phosphor and the suppression of scattering within an optimum range, it is necessary to narrow the particle size distribution. Even if the average particle size is the design value, if the particle size distribution becomes wide, scattering increases if there are many components larger than the average particle size, and if there are many components smaller than the average particle size, The brightness will decrease.

  As a result of particle size measurement by DLS, there is PDI (polydispersity index), which is known as an index indicating uniformity of particle size. This is expressed in the range of 0 to 1, where 0 means an ideal single size particle with no particle size distribution. Monodisperse particles when PDI is 0.1 or less, and dispersions having a value between 0.1 and 0.3 are considered to have a narrow particle size distribution. When PDI is more than 0.3 and 0.5 or less, it is considered that the particle size distribution is relatively wide, and when PDI is larger than 0.5, the dispersion is considered to be polydispersed.

  The phosphor for wavelength conversion of the present invention realizes both emission luminance and suppression of light scattering, and the particle size distribution of the phosphor particles is PDI of 0.3 or less, preferably 0.25 or less. Distribution is preferred. In the case of a phosphor having a PDI distribution larger than 0.3, scattering larger than that assumed from the average particle diameter occurs, and the efficiency of the solar cell or white LED is reduced.

  Next, the crystallinity of the phosphor particles will be described. Whether it is a crystalline substance having a desired composition can typically be determined from an X-ray diffraction measurement. Whether the SrGa2S4 or CaGa2S4 crystal has been synthesized can be confirmed from the profile of the diffraction line. The size of the crystal phase can be confirmed by TEM (transmission electron microscope) observation, electron diffraction analysis, or the like.

The phosphor base material according to the present invention is represented by the general formula AGa ₂ S ₄ (where A is Ca or Sr), but can be selected according to the application. As the wavelength conversion material for the solar cell, SrGa ₂ S ₄ or CaGa ₂ S ₄ is selected according to the wavelength to be converted. When used for a white LED, CaGa ₂ S ₄ that emits yellow light in combination with a blue LED chip is selected. For example, Eu, Ce, or the like can be used as the activator, but Eu and SrGa ₂ S ₄ or Eu and CaGa ₂ S ₄ are used in combination as the green phosphor and the yellow phosphor. Ce and Eu are added by substituting a part of the atoms of A. The concentration can be selected from a range of, for example, 0.1 mol to 15 mol% with respect to A. However, since it is easy to obtain a high luminance, it can be selected in a range of 0.5 mol% to 7 mol%. preferable.

(Phosphor production method)
The phosphor according to the present invention can be manufactured through the following steps (a) to (c). The step (a) is a step of producing raw material particles containing the constituent components of the base material excluding the sulfur component and the constituent components of the activator at a predetermined composition ratio (composition ratio in the phosphor). The step (b) is a step of producing amorphous precursor particles by heating and cooling the raw material particles with thermal plasma. The step (c) is a step of firing the precursor particles in a sulfurizing atmosphere to produce sulfide crystal particles.

  First, in the step (a), each component alone or a compound containing each component is used as a raw material so that the A component, the Ga component, and the activator component constituting the phosphor have a composition ratio in the phosphor to be produced. , Weigh and mix each raw material (gram), and fire.

For example, when SrGa ₂ S ₄ : Eu is manufactured, strontium carbonate (SrCO ₃ ), gallium oxide (Ga ₂ O ₃ ), and europium oxide (Eu ₂ O ₃ ) can be used as raw materials. When the compounding amount of Eu is 2 mol% with respect to the total molar concentration of Sr and Eu (the sum of Sr and Eu is 1 mol, Eu is compounded with 0.02 mol), these raw material powders are converted into , Ga, and Eu are weighed and prepared so that the molar composition ratio of 0.98: 2: 0.02 is obtained and fired.

  Firing is only required to produce particles in which Sr, Ga, and Eu are uniformly diffused, and is performed in an air atmosphere at a temperature of 900 to 1200 ° C. for about 0.5 to 5 hours. The particle size of the raw material particles synthesized at this time is preferably 1 to 30 μm.

  Next, in the step (b), the raw material particles are subjected to thermal plasma treatment with a high-frequency thermal plasma apparatus to produce precursor particles. The precursor particles can be obtained as nano-level particles by putting raw material particles into thermal plasma generated in a plasma torch to form droplets, and then rapidly cooling the droplets from the droplets in a chamber. Plasma is generated by applying a high frequency to the plasma torch. The frequency of the high frequency used is about 0.1 to 5 MHz. What is necessary is just to hold | maintain the pressure in a torch in the state below atmospheric pressure, for example, can be 660 Pa-100,000 Pa. Examples of the gas for generating plasma include argon, nitrogen, hydrogen, oxygen, or a mixed gas thereof. By supplying the raw material particles together with a sufficient amount of carrier gas, it is possible to rapidly cool the droplets from a droplet state. The supply amount of the carrier gas is preferably set so that the average flow velocity in the chamber is about 0.1 to 20 m / sec. As the carrier gas, argon, nitrogen, hydrogen, oxygen, or a mixed gas thereof can be used. The precursor particles are collected by a collection filter connected to the chamber and a vacuum pump. By adjusting the flow rate and power of the gas supplied to the high-frequency thermal plasma apparatus, precursor particles having a particle size of 8 to 50 nm can be obtained. The precursor particles preferably have a particle size of 50 nm or less, more preferably 30 nm or less.

  In the step (c), the precursor particles can be sulfidized and crystallized by firing in a sulfurizing atmosphere. Thereby, a phosphor having a particle size of 1000 nm or less and high crystallinity can be obtained. Specifically, the precursor particles are filled in a quartz crucible or quartz tray, and heated to a temperature equal to or higher than the crystallization temperature of the precursor particles while flowing hydrogen sulfide gas, thereby producing a phosphor. Can do. When the precursor is crystallized in an oxide state, it is difficult to replace it with sulfide at a low temperature. Therefore, the firing process includes a process for sulfiding the precursor in the amorphous chamber of the oxide and a sulfurized amorphous material. It is produced in two steps of a crystallization step for crystallizing the particles. That is, in a sulfur atmosphere, the precursor particles are fired at a first temperature not lower than the crystallization temperature and lower than the crystallization temperature, and then fired at a second temperature not lower than the crystallization temperature. Each temperature varies depending on the type of the precursor, but generally the first temperature in the sulfiding step is 450 ° C. or higher and 530 ° C. or lower, and preferably 470 ° C. or higher and 520 ° C. or lower. The second temperature in the crystallization step is 550 ° C. or higher and 1000 ° C. or lower, and preferably 590 ° C. or higher and 900 ° C. or lower. The particle size of the phosphor can be controlled by the crystallization temperature and the holding time. In the present invention, the particle size of the phosphor can be made less than 250 nm by setting the second temperature to 550 ° C. or more and 700 ° C. or less.

  The temperature profile in the step (c) is preferably a two-stage temperature profile in the temperature range of about 450 to 1000 ° C. as described above. The temperature at the first stage in the two-stage temperature profile is a temperature for changing the oxide precursor particles to sulfide, and is a temperature lower than the temperature at which the oxide crystallizes at a temperature equal to or higher than the sulfurization temperature of the precursor particles. The sulfiding temperature is a temperature at which sulfiding of precursor particles starts in a sulfiding atmosphere, and differs depending on the type of the precursor. Further, the holding time varies depending on the amount of the precursor and the apparatus configuration, but is held for a fixed time from several minutes to several hours. The temperature at the second stage is a temperature for crystallizing the precursor particles and is a temperature equal to or higher than the crystallization temperature. The treatment temperature and the holding time vary depending on the type of necessary phosphor and the required particle size, and may be held for several minutes or may be held for several hours. The reason why the processing temperature in the sulfurized atmosphere is raised in two stages will be described in more detail.

  In order to form a sulfide phosphor having a desired size of 1000 nm or less, it is necessary to complete the sulfiding and crystallization processes at a low temperature. As a result of examining the sulfurization reaction of the precursor particles in detail, it was found that when the amorphous and crystalline precursor particles were compared, the amorphous precursor particles proceeded to sulfidation at a lower temperature. Under the processing conditions in which the temperature is continuously increased, oxide particles are formed before the precursor particles to be processed are completely converted to sulfides, and are not easily sulfided within a predetermined temperature range. As a result, the amount of oxide crystallized particles increases. If it is crystallized in the oxide state, it becomes difficult to sulfidate the precursor particles at a low temperature, and if treated at a high temperature for sulfidation, the particle size increases. That is, by setting a two-stage temperature profile that completely sulfidates the precursor particles before reaching the crystallization temperature, even if a large amount of precursor particles is processed at a time in the step (c), A homogeneous and highly crystalline sulfide phosphor controlled to a desired particle size can be easily formed.

  In the step (c), when the temperature of the phosphor itself during firing was monitored, it was confirmed that the phosphor might have a temperature higher than the set temperature due to the influence of reaction heat generated during sulfidation and crystallization. When the dissociation between the set temperature and the actual temperature increases, it may be difficult to control the particle size and its uniformity. Therefore, in step (c), it is preferable to perform firing so as not to exceed the set value while monitoring the actual temperature of the phosphor. For example, a phosphor having a uniform particle size distribution can be obtained by directly setting a thermocouple such as a tungsten rhenium alloy in a precursor powder set in a firing furnace and firing it while measuring the temperature. Also, without setting a thermocouple in the phosphor powder, the temperature rising rate is set to be slower over time in the temperature rising process to the first temperature and the temperature rising process to the second temperature. Thus, firing may be performed with moderate self-heating.

  In this way, phosphor particles having a narrow particle size distribution can be synthesized by optimizing the firing conditions in step (c). As a result of particle size measurement by DLS, there is PDI (polydispersity index), which is known as an index indicating uniformity of particle size. This is expressed in the range of 0 to 1, where 0 means an ideal single size particle with no particle size distribution. Monodisperse particles with a PDI of 0.1 or less, and dispersions having a value between more than 0.1 and 0.3 or less are known to have a narrow particle size distribution. When PDI is more than 0.3 and 0.5 or less, it is considered that the particle size distribution is relatively wide, and when PDI is larger than 0.5, the dispersion is considered to be polydispersed. As a fluorescent substance used for a solar cell or LED, PDI is preferably 0.5 or less, more preferably 0.3 or less. In the present invention, the temperature increase rate in the temperature increase process of the step (c) is specifically increased at a constant temperature increase rate so as to slow down with time, and the first temperature, When the temperature approaches the temperature, the PDI can be controlled to 0.3 or less by decreasing the rate of temperature rise.

  In addition, in order to obtain high-luminance phosphor particles, it is extremely important to manage impurities other than the constituent elements in the phosphor. In particular, the influence of impurities is large in a phosphor having a small particle diameter. In a small particle size phosphor having a particle size of 1000 nm or less, when the amount of impurities other than the constituent elements exceeds 200 ppm, it becomes clear that the luminance of the small particle phosphor is remarkably lowered, and is preferably set to 200 ppm or less. . More preferably, 100 ppm or less is preferable. There are several factors of impurity contamination. For example, a bead element may be mixed when a phosphor having a large particle size is physically pulverized by a bead mill method. In addition, there may be mentioned a case where a chloride or fluoride raw material is used when the raw material particles are synthesized, a case where a flux composed of a halide is added, and firing is performed. These halogen elements finally remain in the phosphor particles and lower the luminance.

  In the present invention, since a physical pulverization process is not performed, contamination of impurities due to the process can be avoided. Moreover, in this invention, by using an oxide as an activator component, the impurity in a fluorescent substance can be 200 ppm or less, and the luminance fall resulting from an impurity can be suppressed.

For example, SrGa ₂ S ₄ : Eu is prepared from precursor particles obtained by weighing and preparing Sr, Ga, and Eu so that the molar composition ratio of 0.98: 2: 0.02 is obtained, and firing the raw material particles. A case where a phosphor is manufactured will be described as an example. In this case, the temperature of the first stage is set to 450 to 530 ° C., and the sulfidation proceeds. At this time, the temperature rise rate is lowered before the sulfidation temperature is reached, and the rapid temperature rise due to self-heating is alleviated. For example, when the sulfiding temperature, which is the first temperature, is set to 500 ° C., it is preferable to set the temperature so that the temperature is increased up to 450 ° C. at a rate of 10 ° C./min and then increased at 3 ° C. The holding time varies depending on the amount of the precursor to be processed, and an optimal time can be set as appropriate. Thereby, the particle | grains which grew abnormally and the particle | grains with poor sulfidation can be reduced.

  In addition, as the second stage temperature, for example, in the case of 590 ° C. and a holding time of 10 minutes, the temperature is increased at a rate of 10 ° C./min up to 540 ° C. and then increased at 3 ° C. A changed temperature setting is preferred.

(Solar cell)
Next, a solar cell using the phosphor of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view in the thickness direction showing a configuration example of a solar cell module using the phosphor of the present invention. In the solar cell module, a front glass 5, a sealing material 6, solar cells 7, and a back sheet 8 are arranged on the side on which sunlight enters (upward in the drawing). Reference numeral 1 denotes a wavelength conversion member in which the phosphor particles 3 of the present invention are dispersed in a transparent resin, and is formed as a film as a wavelength conversion film. As the transparent resin, EVA (ethylene-vinyl acetic acid copolymer), PVB (polyvinyl butyral resin), or the like is used. However, the transparent resin is not limited to this as long as it has both sunlight permeability and durability. Since the phosphor particles 3 of the present invention are dispersed, the wavelength conversion film 1 absorbs light in a region corresponding to the wavelength conversion characteristics of the phosphor and emits light in a higher wavelength region.

  The sealing material 6 is made of a transparent resin, has a function as a protective film for preventing moisture such as rain and snow, and is disposed so as to cover the solar battery cell 7. As the solar battery cell 7, various solar battery cells such as a single crystal silicon solar battery, a polycrystalline silicon solar battery, an amorphous silicon solar battery, and other compound semiconductor solar batteries can be used. One or a plurality of these solar cells are sealed in the sealing material 3 in a state where they are electrically connected.

  The wavelength conversion film 1 may be attached to the front surface of the solar battery cell 7 as shown in FIG. 1A because the wavelength may be converted before the sunlight reaches the solar battery cell 7. Moreover, you may arrange | position on the front surface or the back surface of the front glass 5 in the state which sealed the photovoltaic cell 7 with the sealing materials 6 and 6 like FIG.1 (b) and FIG.1 (c). Furthermore, as shown in FIG. 1 (d), the wavelength conversion film 1 may be attached to each solar battery cell 7 and sealed with the sealing materials 6 and 6. In the solar cell module, an antireflection film (not shown) may be provided on the front surface of the front glass 5 irradiated with sunlight. In this case, the wavelength conversion film 1 may be disposed on either the front surface or the back surface of the antireflection film. Further, the phosphor 3 may be dispersed in the wavelength prevention film, and the wavelength conversion film and the antireflection film may be used together.

  The phosphor of the present invention is superior in crystallinity and has high wavelength conversion characteristics as compared with conventional phosphors of the same size. Furthermore, the particle size distribution is narrow, and there are few particles having a size greatly deviating from the design value. For this reason, in the solar cell module using the phosphor of the present invention, the scattering of light of wavelengths other than the wavelength to be converted is small, and the power conversion efficiency of the solar cell can be improved.

(Light emitting device)
The phosphor of the present invention is also preferably applied to a light emitting device, and specifically, is suitably used for a white LED. FIG. 2 is a schematic cross-sectional view in the thickness direction showing a configuration example of a white LED using the phosphor of the present invention.

  The white LED in FIG. 2 includes an LED chip 10 as a light source. As the white lamp, a semiconductor light emitting element such as a light emitting diode or a laser diode having a peak emission wavelength in the range of 370 nm to 470 nm is used. As the LED chip 10, various light emitting diodes such as InGaN, GaN, and AlGaN are used. The emission wavelength of this light source preferably has a peak wavelength in the range of 370 nm to 490 nm. A white LED is formed by combining such an LED chip 10 and a phosphor that absorbs part of the light emitted from the LED chip 10 and converts it to another wavelength (blue, green, red, or yellow) to emit light. can do. In the phosphor of the present invention, an appropriate composition ratio of Sr and Ca can be selected according to the required color tone.

  The LED chip 10 is mounted on the substrate 11 via various wirings 12. A cylindrical frame 13 is installed on the substrate 11, and a reflective layer is provided inside the frame 13. The electrodes of the LED chip 10 are electrically connected to the wiring 12 on the substrate 11 by bonding wires 14. The frame 13 is filled with a transparent resin layer 15, and the LED chip 10 is embedded in the transparent resin layer 15. In the example of FIG. 2A, the phosphor particles 3 of the present invention are dispersed in the transparent resin layer 15 in order to obtain white light. The dispersed phosphor particles 3 absorb a part of the light emitted from the LED chip 10 and are excited to emit light, and these lights are combined to obtain white light.

  The phosphor particles 3 do not necessarily have to be dispersed in the transparent resin layer 15. For example, as shown in FIG. 2B, the wavelength conversion layer 16 in which the phosphor particles 3 are dispersed on the transparent resin layer 15 is provided. It may be provided. In the wavelength conversion layer 16, the phosphor particles 3 may be dispersed in a transparent resin, or may be dispersed in an inorganic transparent material such as glass. As shown in FIG. 2C, the phosphor particles 3 may be coated on a transparent layer 17 made of a transparent resin or an inorganic transparent material. The transparent resin used for the transparent resin layer 15, the wavelength conversion layer 16, or the transparent layer 17 is the same EVA (ethylene-vinyl acetate copolymer), PVB (polyvinyl butyral resin), silicone resin, and the like as the solar cell module. Is preferably used.

  Since the phosphor of the present invention is a phosphor that absorbs ultraviolet rays and emits green to yellow-green, white light emission can be obtained by using it in combination with other phosphors emitting blue or red.

  The phosphor of the present invention is superior in crystallinity and has high emission characteristics as compared with a conventional phosphor of the same size. Furthermore, the particle size distribution is narrow, and there are few particles having a size greatly deviating from the design value. Therefore, there is little scattering of light from the light source or light emitted from the phosphor, and white light can be obtained with high efficiency.

[Example 1]
(Synthesis of phosphor particles)
The SrGa ₂ S ₄ : Eu phosphor according to the present invention was produced by the production method of the present invention. As raw materials, strontium carbonate powder (SrCO ₃ ), gallium oxide powder (Ga ₂ O ₃ ) and europium oxide powder (Eu ₂ O ₃ ) were used, and these powders were mixed using a mortar. At this time, each powder is weighed so as to have the following ratio by weight (grams) so that the constituent components of the base material excluding the sulfur component and the constituent components of the activator have a composition ratio in the phosphor to be produced. Used. In other words, the base material before sulfiding was weighed and used so as to be SrGa ₂ O ₄ . The molar concentration of Eu in the obtained phosphor was 2% with respect to the total molar concentration of Sr and Eu.
SrCO ₃ : Ga ₂ O ₃ : Eu ₂ O ₃ ≈4.27: 5.54: 0.10

  Next, the mixed powder was put in an alumina crucible, set in an air atmosphere, and fired in an atmosphere of 1050 ° C. for 2 hours to produce raw material particles. When the particle size distribution of the raw material particles was measured, the result D50 of the particle size measurement by DLS was 7.3 μm.

  Next, the produced raw material particles were processed into a nanosize by a high-frequency thermal plasma method to produce a precursor. Argon gas was introduced into the high-frequency thermal plasma apparatus at a flow rate of 80 L / min (L is liter). In order to generate plasma, power of about 4 MHz and 80 kVA was applied to the high frequency oscillation coil to generate thermal plasma. The raw material particles described above were introduced into the thermal plasma apparatus thus adjusted together with argon as the carrier gas, and the precursor fine particles produced by melting and cooling were collected. As a result of observing the obtained particles with SEM, it was found that the particles had a particle size of about 20 nm. As a result of analyzing the crystal structure by XRD, it was found to be amorphous.

  Next, the produced precursor particles were fired. The firing atmosphere was a 3% hydrogen sulfide gas atmosphere diluted with argon, and 25 g of precursor particles were fired with a two-stage temperature profile to produce a phosphor. In the two-stage temperature profile, the sulfidation temperature as the first temperature was 500 ° C., and the crystallization temperature as the second temperature was 620 ° C. The rate of temperature increase to the first temperature was 10 ° C./min from 450 ° C., 3 ° C./min from 450 ° C. to 500 ° C., and the holding time at 500 ° C. was 2 hours. Subsequently, the rate of temperature increase to the second temperature was 10 ° C./min from 570 ° C. to 3 ° C./min from 570 ° C. to 620 ° C., and the holding time at 620 ° C. was 10 minutes.

The particle size of the phosphor thus prepared was D50 of 97 nm and a polydispersity index PDI of 0.23 as measured by particle size distribution using DLS. Moreover, as a result of analyzing the crystal structure in a Rigaku XRD diffractometer, it was confirmed that it was a single phase of SrGa ₂ S ₄ crystal. Further, when the cross section of the particle was observed with a TEM, it was confirmed that the surface layer of the particle of about 4 nm had an amorphous structure, but other than that was a crystalline phase.

  The light emission characteristics of the phosphors were evaluated. 0.5 g of powder was filled in a measurement cell, set in a spectrofluorometer (manufactured by Hitachi High-Tech, F-4500), and an excitation spectrum and an emission spectrum were measured. As a result, green fluorescence having light absorption in a wide wavelength range from the ultraviolet region to blue color and having a peak wavelength at 532 nm was confirmed.

[Example 2]
(Synthesis of phosphor particles)
The CaGa ₂ S ₄ : Eu phosphor according to the present invention was produced by the production method of the present invention. Calcium carbonate powder (CaCO ₃ ), gallium oxide powder (Ga ₂ O ₃ ), and europium oxide powder (Eu ₂ O ₃ ) were used as raw materials, and these powders were mixed using a mortar. At this time, each powder is weighed so as to have the following ratio by weight (grams) so that the constituent components of the base material excluding the sulfur component and the constituent components of the activator have a composition ratio in the phosphor to be produced. Used. That is, the base material before sulfiding was weighed and used so as to be CaGa ₂ O ₄ . The molar concentration of Eu in the obtained phosphor was 2% with respect to the molar concentration of Ca.
CaCO ₃ : Ga ₂ O ₃ : Eu ₂ O ₃ ≈2.90: 5.54: 0.10

  Next, the mixed powder was put in an alumina crucible, set in an air atmosphere, and fired in an atmosphere of 1050 ° C. for 2 hours to produce raw material particles. When the particle size distribution of the raw material particles was measured, the result D50 of the particle size measurement by DLS was 7.5 μm.

  Next, the produced raw material particles were processed into a nanosize by a high-frequency thermal plasma method to produce a precursor. Argon gas was introduced into the high-frequency thermal plasma apparatus at a flow rate of 80 L / min (L is liter). In order to generate plasma, power of about 4 MHz and 80 kVA was applied to the high frequency oscillation coil to generate thermal plasma. The raw material particles described above were introduced into the thermal plasma apparatus thus adjusted together with argon as the carrier gas, and the precursor fine particles produced by melting and cooling were collected. As a result of observing the obtained particles with SEM, it was found that the particles had a particle size of about 20 nm. As a result of analyzing the crystal structure by XRD, it was found to be amorphous.

  Next, the produced precursor particles were fired. The firing atmosphere was a 3% hydrogen sulfide gas atmosphere diluted with argon, and 25 g of precursor particles were fired with a two-stage temperature profile to produce a phosphor. In the two-stage temperature profile, the sulfidation temperature as the first temperature was 500 ° C., and the crystallization temperature as the second temperature was 620 ° C. The rate of temperature increase to the first temperature was 10 ° C./min from 450 ° C., 3 ° C./min from 450 ° C. to 500 ° C., and the holding time at 500 ° C. was 2 hours. Subsequently, the rate of temperature increase to the second temperature was 10 ° C./min from 570 ° C. to 3 ° C./min from 570 ° C. to 620 ° C., and the holding time at 620 ° C. was 10 minutes.

The particle size of the phosphor thus prepared was D50 of 95 nm and a polydispersity index PDI of 0.24 as measured by particle size distribution using DLS. Moreover, as a result of analyzing the crystal structure in a Rigaku XRD diffractometer, it was confirmed that it was a single phase of CaGa ₂ S ₄ crystal. Further, when the cross section of the particle was observed with a TEM, it was confirmed that the surface layer of the particle of about 4 nm had an amorphous structure, but other than that was a crystalline phase.

  The light emission characteristics of the phosphors were evaluated. 0.5 g of powder was filled in a measurement cell, set in a spectrofluorometer (manufactured by Hitachi High-Tech, F-4500), and an excitation spectrum and an emission spectrum were measured. As a result, yellow fluorescence having a broad light absorption from the ultraviolet region to green and having a peak wavelength at 555 nm was confirmed. The luminance is shown as a relative value with the phosphor of Example 1 as 100.

[Comparative Example 1]
(Synthesis of phosphor particles)
Precursor particles were produced under the same conditions as in Example 1. Next, 25 g of the precursor particles were fired in a 3% hydrogen sulfide gas atmosphere in which the prepared precursor particles were diluted with argon. The temperature profile was raised to 620 ° C. at a constant rate of 10 ° C./min and held for 10 minutes.

As a result of analyzing the crystal structure of the phosphor produced in this way using a Rigaku XRD explanation device, SrGa ₂ S ₄ crystals are slightly formed, but the main component is SrGa ₂ O ₄ crystals, It turns out that it is not a structure. In the particle size distribution measurement by DLS, D50 was 247 nm and PDI was as wide as 0.53.

  The fluorescence properties of this powder were evaluated, but a slight green fluorescence was detected but very weak.

  From this, it was confirmed that it is important to perform the temperature profile in hydrogen sulfide in two stages.

[Comparative Example 2]
(Synthesis of phosphor particles)
Precursor particles were produced under the same conditions as in Example 1. Next, 25 g of the precursor particles were fired in a 3% hydrogen sulfide gas atmosphere in which the prepared precursor particles were diluted with argon. The temperature profile was raised to 500 ° C. at a constant rate of 10 ° C./min and held for 2 hours, then raised to 620 ° C. at a rate of 10 ° C./min and held for 10 minutes.

As a result of analyzing the crystal structure of the phosphor prepared in this manner using a Rigaku XRD diffractometer, SrGa ₂ S ₄ crystals were formed in a substantially single phase, and green emission was confirmed in a fluorescence spectrophotometer. However, in measuring the particle size distribution by DLS, D50 was 112 nm and the polydispersity index PDI was 0.39, indicating that the phosphor had a wide particle size distribution.

  From this, it was confirmed that it is important for the temperature profile in hydrogen sulfide to set the profile in consideration of the heat of reaction during firing in order to improve the uniformity of size.

[Comparative Example 3]
(Synthesis of phosphor particles)
Precursor particles were produced under the same conditions as in Example 2. Next, 25 g of the precursor particles were fired in a 3% hydrogen sulfide gas atmosphere in which the prepared precursor particles were diluted with argon. The temperature profile was raised to 500 ° C. at a constant rate of 10 ° C./min and held for 2 hours, then raised to 620 ° C. at a rate of 10 ° C./min and held for 10 minutes.

As a result of analyzing the crystal structure of the phosphor produced in this manner using a Rigaku XRD diffractometer, CaGa ₂ S ₄ crystals were formed in a substantially single phase, and green emission was confirmed in a fluorescence spectrophotometer. However, in measuring the particle size distribution by DLS, D50 was 115 nm and the polydispersity index PDI was 0.40, indicating that the phosphor had a wide particle size distribution.

[Examples 3 to 8]
Phosphor particles were produced in the same manner as in Example 1. However, the second temperature and the heating rate were synthesized as shown in Table 1, and phosphors having particle sizes corresponding to the respective temperatures could be synthesized.

[Comparative Examples 4 to 8]
Phosphor particles were produced in the same manner as in Comparative Example 2. However, the second temperature and the heating rate were synthesized as shown in Table 1, and phosphors having particle sizes corresponding to the respective temperatures were synthesized.

[Examples 9 to 12]
Phosphor particles were produced in the same manner as in Example 2. However, the second temperature and the heating rate were synthesized as shown in Table 1, and phosphors having particle sizes corresponding to the respective temperatures could be synthesized.

[Comparative Examples 9 to 13]
Phosphor particles were produced in the same manner as in Comparative Example 3. However, the second temperature and the heating rate were synthesized as shown in Table 1, and phosphors having particle sizes corresponding to the respective temperatures were synthesized.

Example 13
(Preparation of wavelength conversion film for solar cells)
100 g of ethylene-vinyl acetate resin as transparent resin material, 1.3 g of peroxide thermal radical initiator, 2.00 g of crosslinking agent, 0.5 g of silane coupling agent, and 3.00 g of the phosphor of Example 1 The resulting mixture was kneaded with a roll mixer to prepare a transparent resin composition containing a phosphor.

  Next, about 30 g of the phosphor-containing transparent resin composition obtained above was sandwiched between release sheets, and 0.6 mm thick stainless steel spacers were used, and a hot plate was adjusted to 90 ° C. to form a sheet. .

  Next, a solar cell panel was created using this wavelength conversion film. A PET sheet was used as a back sheet, and a sealing sheet, a solar battery cell, the wavelength conversion film in which a phosphor was dispersed, and a protective glass were placed in this order and sealed with a vacuum laminator to prepare a solar battery module.

  The output of the solar cell module thus produced was evaluated. Under simulated sunlight, the current-voltage characteristic was 38.4 mA / cm <2> which evaluated the short circuit current density Jsc based on JIS-C8914.

[Comparative Example 14]
A solar cell module was produced in the same manner as in Example 5. However, it produced only with the sealing sheet which does not use the wavelength conversion film. When the output of this module was evaluated, the short-circuit current density Jsc was 35.9 mA / cm 2 under simulated sunlight.

Example 14
Using the phosphor of Example 2, a solar cell module using a wavelength conversion film was produced in the same manner as Example 5. Under simulated sunlight, the short circuit current density Jsc was 38.9 mA / cm 2.

[Comparative Example 15]
Using the phosphor of Comparative Example 2, a solar cell module using a wavelength conversion film was produced in the same manner as in Example 5. Under simulated sunlight, the short circuit current density Jsc was 36.6 mA / cm 2.

[Comparative Example 16]
Using the phosphor of Comparative Example 3, a solar cell module using a wavelength conversion film was produced in the same manner as in Example 5. Under simulated sunlight, the short circuit current density Jsc was 36.9 mA / cm 2.

Example 15
A white LED was produced using the phosphor of Example 2.

  An LED chip having a peak wavelength of 455 nm was mounted on a substrate on which electrical wiring was formed, and a frame material was formed around the periphery. Subsequently, the phosphor of Example 2 was mixed in the silicone resin and sufficiently stirred until it was uniformly dispersed. The mixing amount was adjusted so that the chromaticity coordinates were (x = 0.27 to 0.35, y = 0.27 to 0.35). Subsequently, this phosphor-dispersed resin was poured into a frame material and heated at 140 ° C. to cure the resin, thereby producing a white LED of this example. When a current of 20 mA was passed through the LED, white light could be obtained. When the luminous efficiency was evaluated with MCPD manufactured by Otsuka Electronics, it was 65 lm / W.

[Comparative Example 17]
In the same manner as in Example 7, a white LED was produced using the phosphor of Comparative Example 3. Although white current was able to be obtained by passing a current of 20 mA, the luminous efficiency was 59 lm / W.

1 wavelength conversion film 3 phosphor particles

Claims (13)

A particulate phosphor containing a base material of a thiogallate sulfide represented by the following general formula (1) and an activator,
The particle size is 1000 nm or less, the polydispersity index indicating the breadth of the particle size distribution is 0.3 or less, and the volume ratio of the crystal phase in the particles is represented by the following general formula (2) A phosphor.
AGa ₂ S ₄ (A is Ca, Sr) (1)
Vc / Vt ≧ (R−10) ³ / R ³ (2)
(In the above formula, Vc is the volume of the crystal phase in the particle, Vt is the volume of the particle, and R is the particle size)   The phosphor according to claim 1, wherein the particle size is less than 250 nm or greater than 250 nm and 500 nm or less.   2. The phosphor according to claim 1, wherein the particle size is 50 nm or more and less than 250 nm.   The phosphor according to any one of claims 1 to 3, wherein the activator is Eu.   The phosphor according to any one of claims 1 to 4, wherein a polydispersity index indicating a breadth of a particle size distribution is 0.3 or less. A method for producing a phosphor according to any one of claims 1 to 5,
(A) producing raw material particles containing a constituent component of a base material excluding a sulfur component and a constituent component of an activator at a composition ratio in the phosphor;
(B) A step of producing amorphous precursor particles by heating and cooling the raw material particles with thermal plasma;
(C) In the step of firing the precursor particles at a first temperature not lower than the crystallization temperature and lower than the crystallization temperature in a sulfur atmosphere, and firing at a second temperature not lower than the crystallization temperature, A process of controlling and firing while monitoring the actual temperature,
A method for producing a phosphor, comprising:   The phosphor according to claim 6, wherein in the step (c), the first temperature is 450 ° C or higher and 530 ° C or lower, and the second temperature is 550 ° C or higher and 1000 ° C or lower. Production method.   In the said process (c), said 2nd temperature is 550 degreeC or more and 700 degrees C or less, The manufacturing method of the fluorescent substance of Claim 7 characterized by the above-mentioned.   In the step (c) of firing the precursor particles in a sulfur atmosphere, there are at least a plurality of set values of the heating rate to reach the first temperature and the second temperature. The manufacturing method of fluorescent substance of description.   6. A wavelength conversion member in which the phosphor according to any one of claims 1 to 5 is dispersed.   A wavelength conversion film, wherein the phosphor according to any one of claims 1 to 5 is dispersed in the film.   A solar cell module using the phosphor according to any one of claims 1 to 5.   A light emitting device using the phosphor according to claim 1.