JP6934316B2 - Wavelength conversion member - Google Patents

Description

The present invention relates to a wavelength conversion member containing phosphor particles.

As a phosphor used for a wavelength conversion member for a light emitting device, a YAG phosphor having high brightness is generally used. However, the YAG phosphor has a small amount of red component as its wavelength component, and the white light obtained by mixing the blue visible light of the LED (Light Emitting Diode) and the yellow visible light of the YAG phosphor is due to the lack of the red component. It had the drawback of being inferior in color playability.

On the other hand, visible light is mixed by mixing a YAG phosphor and a red phosphor, and the white light obtained by this is to realize an LED having good color rendering properties that can compensate for the lack of the red component. (Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-152993

Since the red phosphor also absorbs the yellow color emitted by the YAG phosphor and emits red color, it is necessary to use a smaller amount of the red phosphor than the YAG phosphor when it is generally used for lighting. Further, when the amount of the red phosphor compounded is smaller than that of the YAG phosphor, if the particle size of the red phosphor is equal to or larger than that of the yellow YAG phosphor, the yellow and red color unevenness occurs when the light is emitted. Since it is projected as it is, uniform light cannot be obtained.

In Patent Document 1, a solid body composed of a YAG phosphor, a red phosphor, and a glass material is set to a predetermined particle size by using ball mill pulverization. Therefore, the YAG phosphor and the red phosphor have the same particle size. At this time, if the particle size is large, there is a difference in the existence probability of the particles per unit area and unit volume, and there is a possibility that local color unevenness may occur. Further, when the particle size is reduced, the possibility of suppressing local color unevenness increases, but the emission intensity decreases.

The present invention has been made in view of such circumstances. By mixing a YAG phosphor having a large particle size and a red phosphor having a small particle size, the emission intensity of red is maintained and the emission of red is not biased. It is an object of the present invention to provide a wavelength conversion member capable of preventing color unevenness.

(1) In order to achieve the above object, the wavelength conversion member of the present invention includes a base material and a phosphor layer provided on the base material, and the phosphor layer is a translucent inorganic particle. The phosphor particles are formed of a material and phosphor particles dispersed in the inorganic material, and the phosphor particles are yellow phosphor particles having an average particle diameter of 5 μm or more and 30 μm or less, and 1 / of the average particle diameter of the yellow phosphor particles. The weight ratio of the yellow phosphor particles having an average particle diameter of 2 or less, containing the red phosphor particles mixed with the yellow phosphor particles, and existing in the phosphor layer is the weight ratio of the yellow phosphor particles to the red phosphor particles. It is characterized by being 1.2 or more and 50 or less.

In this way, by using the red phosphor particles smaller than the yellow phosphor particles, the red phosphor particles are spread over the entire phosphor layer even if the weight of the red phosphor particles is smaller than that of the yellow phosphor particles. Disperse evenly. As a result, it is possible to prevent color unevenness without biasing the light emission of red. This is particularly effective when a laser with a small beam diameter is applied to the wavelength conversion member. Moreover, since the average particle size of the yellow phosphor particles does not become too small, the emission intensity can be maintained.

(2) Further, in the wavelength conversion member of the present invention, when the color temperature and chromaticity by laser excitation are measured, the fluctuation coefficient with respect to the measured average value of the color temperature is 1% or less, and the average value of the chromaticity. It is characterized in that the fluctuation coefficient with respect to is 0.5% or less. As a result, the wavelength conversion member can irradiate light of a uniform color without biasing the emission of red.

(3) Further, the wavelength conversion member of the present invention is characterized in that the average particle size of the red phosphor particles is 2.5 μm or more and 11 μm or less. As a result, it is possible to prevent the bias of both particles from occurring even in a local range, so that uniform light can be irradiated.

According to the present invention, it is possible to prevent color unevenness without biasing red emission while maintaining the emission intensity of the wavelength conversion member.

It is a schematic diagram which shows the wavelength conversion member of this invention. It is a flowchart which shows the manufacturing method of the wavelength conversion member of this invention. It is a table showing the conditions of Examples and Comparative Examples, the average value and the coefficient of variation of the color temperature, the average value and the coefficient of variation of the chromaticity, and the result of the illuminance test. (A1) to (c2) are a surface photograph of the phosphor layer of the wavelength conversion member of the example by an optical microscope and a photograph after image processing, respectively. (D1) to (f2) are a surface photograph of the phosphor layer of the wavelength conversion member of the comparative example by an optical microscope and a photograph after image processing, respectively.

Next, an embodiment of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference number is assigned to the same component in each drawing, and duplicate description is omitted. In the configuration diagram, the size of each component is conceptually represented, and does not necessarily represent the actual dimensional ratio.

[Structure of wavelength conversion member]
FIG. 1 is a schematic view showing a wavelength conversion member 10. The wavelength conversion member 10 has a phosphor layer 14 formed on the substrate 12. The wavelength conversion member 10 transmits or reflects the absorbed light emitted from the light source, and is excited by the absorbed light to generate light having a different wavelength. For example, while transmitting or reflecting the absorbed light of blue light, the converted light of green and red or yellow converted by the phosphor layer 14 is emitted, and the converted light and the absorbed light are combined, or only the converted light is emitted. It can be used and converted into various colors of light. In particular, the wavelength conversion member 10 can emit white light having good color rendering properties by combining the blue light of the light source and the yellow light and red light converted by the phosphor layer 14.

As the material of the substrate 12, sapphire, aluminum, glass or the like can be used. The transmissive substrate is manufactured of a translucent material. The reflective substrate may be made entirely of a light-reflecting material, but a light-reflecting material may be provided on one surface of the translucent material by plating or the like. From the viewpoint of light emission intensity, at least the portion through which light is transmitted is made of a material that does not easily absorb absorbed light. In addition, since high-energy light is irradiated and the temperature rises, it is better to have high thermal conductivity.

The phosphor layer 14 is provided on the substrate 12 as a film, and is formed of the yellow phosphor particles 16, the red phosphor particles 18, and the binder 20. The binder 20 binds the yellow phosphor particles 16, the red phosphor particles 18, and the substrate 12. As a result, it is possible to efficiently dissipate heat to the irradiation of light having a high energy density because it is bonded to the substrate 12 that functions as a heat radiating material, and it is possible to suppress the temperature quenching of the phosphor. The thickness of the phosphor layer 14 may be 5 μm or more and 400 μm or less, and preferably 10 μm or more and 200 μm or less.

As the yellow phosphor particles 16, for example, yttrium aluminum garnet phosphor (YAG phosphor) and lutetium aluminum garnet phosphor (LAG phosphor) can be used. As the red phosphor particles 18, for example, a nitride phosphor ((Sr, Ca) AlSiN ₃ : Eu) called S-CASN can be used. In addition, the yellow fluorescent particle 16 or the red fluorescent particle 18 can be selected from the following materials. For example, BaMgAl ₁₀ O ₁₇ : Eu, ZnS: Ag, Cl, BaAl ₂ S ₄ : Eu or CaMgSi ₂ O ₆ : Eu, Zn ₂ SiO ₄ : Mn, (Y, Gd) BO ₃ : Tb, ZnS: Cu, Al, (M1) ₂ SiO ₄ : Eu, (M1) (M2) ₂ S: Eu, (M3) ₃ Al ₅ O ₁₂ : Ce, SiAlON: Eu, CaSiAlON: Eu, (M1) Si ₂ O ₂ N: Eu or (Ba, Sr, Mg) ₂ SiO ₄ : Eu, Mn, (M1) ₃ SiO ₅ : Eu or (M1) S: Eu, (Y, Gd) BO ₃ : Eu, Y ₂ O ₂ S: Eu , (M1) ₂ Si ₅ N ₈ : Eu, or YPVO ₄ : Eu. In the above chemical formula, M1 contains at least one of the group consisting of Ba, Ca, Sr and Mg, M2 contains at least one of Ga and Al, and M3 contains Y, Gd, At least one of the group consisting of Lu and Te is included. The above-mentioned phosphor particles are an example, and the phosphor particles used in the wavelength conversion member 10 are not necessarily limited to the above.

The yellow phosphor particles 16 absorb the absorbed light (excitation light) of the light source and emit the yellow conversion light. Further, the red phosphor particles 18 absorb the absorbed light (excitation light) of the light source and emit the red conversion light, and also absorb a part of the yellow conversion light emitted by the yellow phosphor particles 16. , Emits red conversion light. The weight ratio of the yellow phosphor particles 16 and the red phosphor particles 18 contained in the phosphor layer 14 is 1.2 or more and 50 or less. Since the red phosphor particles 18 have a smaller weight ratio than the yellow phosphor particles 16, the converted light is not biased toward red emission. Further, since the red phosphor particles 18 are not too small as the yellow phosphor particles 16, the color rendering property can be maintained.

The average particle size of the yellow phosphor particles 16 is 5 μm or more and 30 μm or less, and preferably 10 μm or more and 20 μm or less. This is because if it is smaller than 5 μm, the emission intensity of yellow light becomes small, and eventually the emission intensity of the wavelength conversion member 10 becomes small. On the other hand, if it is larger than 30 μm, the two particles are likely to be biased in the local range of the phosphor layer 14, and color unevenness occurs. In the present specification, the average particle size is the median diameter (D50). The average particle size can be measured by using a dry measurement or a wet measurement of a laser diffraction / scattering type particle size distribution measuring device. The criteria for determining color unevenness will be described later.

The average particle size of the red phosphor particles 18 is ½ or less of the average particle size of the yellow phosphor particles 16. When the red phosphor particles 18 are smaller in weight ratio than the yellow phosphor particles 16, and the average particle size of the red phosphor particles 18 is larger than 1/2 of the average particle size of the yellow phosphor particles 16, the red phosphor particles This is because a portion where 18 is locally biased is formed and color unevenness occurs.

The average particle size of the red phosphor particles 18 is preferably 2.5 μm or more and 11 μm or less. This is because if it is too small, the emission intensity of red light becomes small, and if it is too large, the two particles tend to be biased in a local range, resulting in color unevenness. Further, by using the red phosphor particles 18 having such an average particle size, even when the red phosphor particles 18 are smaller in weight ratio than the yellow phosphor particles 16, the red phosphor is covered over the entire phosphor layer 14. The particles 18 are uniformly dispersed, and color unevenness can be prevented. Further, since the bias of both particles is less likely to occur even in a local range, it is particularly effective when a laser having a small beam diameter is applied to the wavelength conversion member 10.

The binder 20 is formed by hydrolyzing or oxidizing an inorganic binder, and is made of a translucent inorganic material. The binder 20 is composed of, for example, silica (SiO ₂ ) and aluminum phosphate. Since the binder 20 is made of an inorganic material, it does not deteriorate even when irradiated with high-energy light such as a laser diode. Further, since the binder 20 has a translucent property, it can transmit absorbed light and converted light. As the inorganic binder, ethyl silicate, an aqueous solution of aluminum phosphate, or the like can be used.

The translucent substance is the radiation of light emitted from the opposite side when light is vertically incident on a target substance of 0.5 mm in the wavelength region of visible light (λ = 380 to 780 nm). A substance whose bundle has a property of exceeding 80% of the incident light.

The wavelength conversion member 10 can form a light emitting device by combining with a light source. In particular, the wavelength conversion member 10 of the present invention can be combined with a blue light source to form a light emitting device that emits white light having good color rendering properties and no color unevenness while maintaining light emission intensity. Further, since the phosphor layer 14 of the wavelength conversion member 10 is made of an inorganic material, a high-power laser diode can be used as a light source, and a high-power light emitting device can be configured.

[Manufacturing method of wavelength conversion member]
An example of a method for manufacturing a wavelength conversion member will be described. FIG. 2 is a flowchart showing a method for manufacturing the wavelength conversion member of the present invention. First, a printing paste is prepared. First, yellow phosphor particles and red phosphor particles having a predetermined average particle size are prepared (step S1). For the yellow phosphor particles, for example, particles such as YAG can be used, and for the red phosphor particles, particles such as a nitride phosphor called S-CASN can be used. The average particle size of the yellow phosphor particles is 5 μm or more and 30 μm, and the average particle size of the red phosphor particles is 1/2 or less of the average particle size of the yellow phosphor particles.

Next, the prepared yellow phosphor particles and red phosphor particles are weighed so as to have a specific weight ratio (step S2). The specific weight ratio is 1.2 or more and 50 or less. Then, the weighed yellow phosphor particles and red phosphor particles are dispersed in a solvent and mixed with an inorganic binder to prepare a printing paste (step S3). A ball mill or the like can be used for mixing. As the solvent, a high boiling point solvent such as α-terpineol, butanol, isophorone, and glycerin can be used.

Further, the inorganic binder is preferably an organic silicate such as ethyl silicate. By using the organic silicate, the yellow phosphor particles and the red phosphor particles are dispersed in the entire printing paste, and a printing paste having an appropriate viscosity can be prepared. For example, when ethyl silicate is used as the inorganic binder, the mass of ethyl silicate is 70 wt% or more and 100 wt% or less, preferably 80 wt% or more and 90 wt% or less, based on the mass of water and the catalyst. In addition, the inorganic binder is prepared by reacting a raw material containing at least one of a group consisting of a silicon oxide precursor, a silicic acid compound, silica, and amorphous silica, which becomes silicon oxide by hydrolysis or oxidation, at room temperature. , It may be obtained by heat treatment at a temperature of 500 ° C. or lower. Examples of the silicon oxide precursor include those containing perhydropolysilazane, ethyl silicate, and methyl silicate as main components.

After producing the printing paste, the printing paste is applied onto the substrate to form a paste layer (step S4). The printing paste can be applied by a screen printing method, a spray method, a drawing method using a dispenser, or an inkjet method. The screen printing method is preferable because a thin paste layer can be stably formed. The thickness of the paste layer is preferably 10 μm or more and 200 μm or less.

Then, the substrate formed with the paste layer was fired by using the N ₂ atmosphere furnace to produce a phosphor layer (step S5). The firing temperature is preferably 150 ° C. or higher and 500 ° C. or lower, and the firing time is preferably 0.5 hours or longer and 2.0 hours or lower. The rate of temperature rise is preferably 50 ° C./h or more and 200 ° C./h or less. Further, a drying step may be provided before firing.

By such a manufacturing step, a wavelength conversion member in which the yellow phosphor particles and the red phosphor particles are uniformly dispersed in the entire phosphor layer can be easily manufactured. The obtained wavelength conversion member can prevent color unevenness without biasing red emission while maintaining emission intensity. Further, since the phosphor layer of the wavelength conversion member is made of an inorganic material, it can be suitably used for a light emitting device using a high-power laser diode as an excitation source. Further, since the bias of both particles is less likely to occur even in a local range, a light emitting device using a laser having a particularly small beam diameter can be configured.

[Examples and Comparative Examples]
(Sample preparation method)
Yellow phosphor particles (YAG particles) having an average particle size of 3 μm to 35 μm and red phosphor particles (S-CASN particles) having an average particle size of 1.5 μm to 11 μm were prepared. These phosphor particles were weighed so as to have a predetermined mass ratio, α-terpineol (solvent) was mixed to prepare a dispersant, and ethyl silicate (inorganic binder) was mixed to prepare a printing paste.

Next, a printing paste was applied to the sapphire substrate using a screen printing method to a thickness of 30 μm. After coating, it was dried at 100 ° C. for 20 minutes and then sealed with an inorganic binder. Finally the temperature was raised to 350 ° C. at 0.99 ° C. / h in a reducing atmosphere with N ₂ atmosphere furnace, the sample was completed by baking 30 minutes.

(Sample evaluation method)
FIG. 3 is a table showing various conditions of Examples and Comparative Examples and test results of color temperature, chromaticity and illuminance. For the color temperature, chromaticity and illuminance, the optical characteristics of the sample when laser-excited at 1000 mW were measured using a color illuminometer. The color temperature variation (coefficient of variation) was measured at 5 points in the same sample and calculated by dividing the standard deviation of the 5 points by the average value of the 5 points. The variation in chromaticity (coefficient of variation) is measured at 5 points in the same sample, and the standard deviation of 5 points for each numerical value is averaged by 5 points with respect to the set of numerical values in the chromaticity diagram (described later). Calculated by dividing by the value.

The color temperature is defined as follows. That is, a blackbody is assumed as an ideal object. When this blackbody is heated, it emits light, and the wavelength / spectrum (color of light) of the emitted light is determined for each temperature of the blackbody, and when the temperature changes, the color of the light also changes. By associating the temperature of the blackbody with the color of the emitted light, the "temperature of the blackbody" is determined for a certain "color of light". Generally, this is called color temperature. The unit is Kelvin (K). White light emitted by receiving light from a light source is not always distributed on the radiation trajectory of a blackbody. Therefore, it is practically performed to display at the color temperature of blackbody radiation that appears to be the closest color to the light source. This is called the correlated color temperature. The color temperature in the present invention refers to this "correlated color temperature".

Further, the chromaticity is a numerical value representing the hue, saturation, and lightness of the color properties excluding the lightness. In this specification, it is expressed using a set of numerical values (x, y) corresponding to the xy chromaticity diagram of the CIE-XYZ color system formulated by the International Commission on Illumination (CIE). In the xy chromaticity diagram, the proportion of "redness" increases as the numerical value increases on the x-axis, and the proportion of "blueness" increases as the numerical value decreases. On the y-axis, the larger the value, the higher the ratio of "greenness", and the smaller the value, the higher the ratio of "blueness". Further, a point of x = y = 1/3 (= about 0.33) is called a white point.

In the evaluation of Examples and Comparative Examples, the above-mentioned variation in color temperature and variation in chromaticity were used as criteria for determining color unevenness. The standard of color temperature was that the variation of color temperature was 1% or less. The standard of chromaticity was that the variation in chromaticity was 0.5% or less for both x and y. Then, it was judged that the sample having the color temperature and the chromaticity satisfying the standard had no color unevenness, and the sample not satisfying any one of the standards was judged to have the color unevenness. Further, the standard of emission intensity was that the illuminance was 1000 lpx or more. Since the sample having an illuminance of less than 1000 lx does not satisfy the standard of emission intensity, it was judged that the performance as a wavelength conversion member was low.

Comparative Examples 1 to 3 are samples in which the average particle size of the red phosphor particles is larger than 1/2 of the average particle size of the yellow phosphor particles. At this time, neither the color temperature nor the chromaticity met the criteria. Comparing Comparative Example 1 and Example 5, Comparative Example 2 and Example 6, and Comparative Example 3 and Example 1, the red phosphor particles have the same weight ratio and the average particle size of the yellow phosphor particles as in each comparative example. All the examples in which the average particle size was 1/2 or less of the average particle size of the yellow phosphor particles satisfied the criteria of color temperature and chromaticity. Therefore, it can be seen that the average particle size of the red phosphor particles needs to be 1/2 or less of the average particle size of the yellow phosphor particles.

In Comparative Example 4, Examples 2 to 4, and Comparative Example 5, the weight ratio of the yellow phosphor particles to the red phosphor particles was made constant, and the average particle size of the red phosphor particles was set to the average particle size of the yellow phosphor particles. It is a sample prepared by changing the average particle size of the yellow phosphor particles to 1/2 or less. It can be seen that the color temperature, chromaticity, and illuminance of Examples 2 to 4 all satisfy the criteria. In Comparative Example 4, since the average particle size of the yellow phosphor particles was less than 5 μm, the illuminance was lowered and the performance as a wavelength conversion member was significantly deteriorated. In Comparative Example 5, since the average particle size of the yellow phosphor particles exceeded 30 μm, the skeleton particles became coarse and did not meet the criteria of color temperature and chromaticity.

In Comparative Example 7, Examples 7, 4, 5, 8 and Comparative Example 6, the average particle diameters of the yellow phosphor particles and the red phosphor particles were kept constant, and the weight ratio of the yellow phosphor particles to the red phosphor particles was fixed. It is a sample prepared by changing. It can be seen that the color temperature, chromaticity, and illuminance of Examples 7, 4, 5, and 8 all satisfy the criteria. In Comparative Example 7, since the weight ratio of the yellow phosphor particles to the red phosphor particles was less than 1 (the amount of the red phosphor particles added was large), the red phosphor absorbed the yellow emitted by the yellow phosphor. , The illuminance has decreased. In Comparative Example 6, since the weight ratio of the yellow phosphor particles to the red phosphor particles exceeded 50 (the amount of the red phosphor particles added was small), the red phosphor particles were poorly dispersed, and the color temperature and chromaticity were increased. Did not meet the criteria.

4 (a1) to 4 (c2) are a surface photograph of the phosphor layer of the wavelength conversion member of the example by an optical microscope and a photograph after image processing, respectively. Further, FIGS. 5 (d1) to 5 (f2) are a surface photograph of the phosphor layer of the wavelength conversion member of the comparative example by an optical microscope and a photograph after image processing, respectively.

(D1) and (d2) are a surface photograph of Comparative Example 1 and a photograph after image processing. According to this, since the size of the red phosphor is not so different from that of the YAG phosphor, the dispersibility of the red phosphor is poor and color unevenness occurs. (E1) and (e2) are a surface photograph of Comparative Example 2 and a photograph after image processing. According to this, since the red phosphor is larger than the YAG phosphor, the bias of the red phosphor is also large, and color unevenness occurs. (F1) and (f2) are a surface photograph of Comparative Example 3 and a photograph after image processing. According to this, not only the red phosphor is larger than the YAG phosphor, but also the amount of the red phosphor added is larger than that of Comparative Example 2, so that the red phosphor is further aggregated as compared with Comparative Example 2 and the color unevenness is observed. Is occurring.

From the above results, it was found that the wavelength conversion member of the example was able to prevent color unevenness without biasing the red emission while maintaining the emission intensity.

10 Wavelength conversion member 12 Substrate 14 Fluorescent layer 16 Yellow fluorescent particles 18 Red fluorescent particles 20 Binding material

Claims (2)

With the base material
A phosphor layer provided on the base material is provided.
The phosphor layer is formed of a translucent inorganic material and phosphor particles dispersed in the inorganic material.
The phosphor particles have an average particle size of 5 μm or more and 30 μm or less, and an average particle size of 1/2 or less of the average particle size of the yellow phosphor particles, and are mixed with the yellow phosphor particles. Contains red phosphor particles
The average particle size of the red phosphor particles is 2.5 μm or more and 9 μm or less.
The weight ratio of the yellow phosphor particles present in the phosphor layer to the red phosphor particles is 1.2 or more and 50 or less.
A wavelength conversion member characterized in that the translucent inorganic material is a binder composed of silica or aluminum phosphate. When the color temperature and chromaticity by laser excitation are measured, the coefficient of variation with respect to the average value of the measured color temperature is 1% or less, and the coefficient of variation with respect to the average value of chromaticity is 0.5% or less. The wavelength conversion member according to claim 1, which is characterized.

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