DE112019006473T5 - WAVELENGTH CONVERSION ELEMENT AND LIGHT EMITTING DEVICE - Google Patents

Abstract

The object of the present invention is to provide a wavelength conversion element and a light-emitting device which have a high luminescence intensity. A wavelength converting element 10 contains phosphor particles 2 in a matrix 1 and has a haze value of 0.7 to 0.999 in a visible wavelength range in which an excitation spectrum of the phosphor particles shows a spectral intensity of 5% or less of the maximum peak intensity.

Description

Technical area

The present invention relates to wavelength converting elements for converting the wavelength of light emitted from light emitting diodes (LEDs), laser diodes (LDs) or the like to a different wavelength and light emitting devices.

State of the art

Recently, attention has been paid increasingly to light emitting devices using LEDs or LDs as next generation light emitting devices to replace fluorescent lamps and incandescent lamps in view of their low power consumption, small size, light weight and their easy adjustment to the light intensity. As examples of such next-generation light-emitting devices, there are disclosed light-emitting devices in which a wavelength conversion element is disposed on an LED which can emit blue light and absorbs part of the blue light to convert it into yellow light (Patent Documents 1 and 2).

These light emitting devices emit white light that is synthetic light of blue light (excitation light) emitted from the LED and yellow light (fluorescence) emitted from the wavelength converting element.

Citation list

Patent literature

• PTL 1 JP-A-2000-208815
• PTL 2 JP-A-2003-258308

Summary of the invention

Technical problem

In recent years, with the increasing performance of light emitting devices, there is a need for a wavelength converting element that enables the extraction of white light of higher intensity. However, when conventional wavelength conversion elements are used, there arises a problem that synthetic light composed of excitation light and fluorescence extracted to the outside has insufficient luminous flux and therefore the luminescence intensity cannot be increased sufficiently.

In view of the above, it is an object of the present invention to provide a wavelength converting element and a light emitting device which have a high intensity of luminescence.

the solution of the problem

The inventors made intensive studies and, as a result, found that the luminous flux of synthetic light of excitation light and fluorescence extracted from a wavelength converting element can be improved by adjusting the haze value of the wavelength converting element in a specific wavelength range.

In particular, a wavelength conversion element according to the invention is a wavelength conversion element which contains phosphor particles in a matrix, the wavelength conversion element having a haze value of 0.7 to 0.999 in a visible wavelength range in which an excitation spectrum of the phosphor particles has a spectral intensity of 5% or less of the maximum peak intensity.

In the wavelength conversion element according to the invention, the matrix is preferably glass.

In the wavelength conversion element according to the invention, the phosphor particles can be those phosphor particles which absorb part of the fluorescence. With the use of such phosphor particles, the effects of the present invention can be easily obtained.

In the wavelength conversion element according to the invention, the phosphor particles are preferably particles of a garnet-based ceramic phosphor.

The wavelength conversion element according to the invention preferably contains a light-scattering material.

The wavelength converting element of the present invention preferably has a thickness of 1000 µm or less.

A light emitting device according to the present invention comprises the above wavelength converting element and a light source adapted to irradiate the wavelength converting element with excitation light.

In the light-emitting device according to the invention, the light source is preferably a light-emitting diode or a laser diode.

Advantages of the invention

The present invention makes it possible to provide a wavelength converting element and a light-emitting device which have a high intensity of luminescence.

Figure list

• 1 Fig. 13 is a schematic cross-sectional view showing a wavelength converting element according to an embodiment of the present invention.
• 2 Fig. 13 is a view illustrating a decrease in the luminous flux of synthetic light for a wavelength converting element having a high haze value.
• 3 Fig. 13 is a view illustrating a decrease in the luminous flux of synthetic light with a wavelength converting element having a low haze value.
• 4th Fig. 13 is a schematic diagram representing an excitation spectrum and a fluorescence spectrum of YAG phosphor particles.
• 5 Fig. 13 is a schematic cross-sectional view showing a light emitting device according to an embodiment of the present invention.
• 6th Fig. 13 is a graph showing the relationship between relative luminous flux and haze in Examples of the present invention.

Description of exemplary embodiments

In the following, exemplary embodiments of the present invention are described in detail with reference to the drawings. However, the present invention is by no means limited to the following embodiments.

(Wavelength conversion element 10 )

1 is a schematic cross-sectional view showing a wavelength converting element according to an embodiment of the present invention. As in 1 shown includes the wavelength converting element 10 Fluorescent particles 2 in a matrix 1 . In addition, the wavelength converting element 10 a first main surface 11 and a second major surface 12th on.

As in 1 shown emerges from a light source 6th emitted excitation light A. through the second main surface 12th into the wavelength converting element 10 a. Thus, the phosphor particles become 2 with the excitation light A. irradiated so that from the phosphor particles 2 Fluorescence is emitted. Then through the first main surface 11 a synthetic light B. from the excitation light A. and the fluorescence from the wavelength converting element 10 emitted.

The wavelength conversion element 10 exhibits in a visible wavelength range in which an excitation spectrum of the phosphor particles 2 shows a spectral intensity of 5% or less of the maximum peak intensity, a haze value of 0.7 to 0.999. In the present invention, the visible wavelength range refers to a range from 380 nm to 780 nm. The haze value is calculated from the values of total light transmittance and diffuse transmittance in the above visible wavelength range based on the following formula. $$\text{Tr}\ddot{\text{u}}\text{exercise value}=\left(\text{diffuse transmission}\ddot{\text{a}}\text{sweetness}\right)/\left(\text{Total light transmission}\right)$$

The inventors made intensive studies and, as a result, found that in the wavelength converting element 10 , the phosphor particles 2 in a matrix 1 contains, the luminous flux of synthetic light B. that from the first main surface 11 is extracted by adjusting the turbidity in a visible wavelength range in which the excitation spectrum of the phosphor particles 2 exhibits a spectral intensity of 5% or less of the maximum peak intensity can be improved. The mechanism can be explained as follows.

2 Fig. 13 is a view illustrating a decrease in the luminous flux of synthetic light for a wavelength converting element having a high haze value. An in 2 shown wavelength conversion element 20th contains fluorescent particles 2 and a light diffusing material 3 in a matrix 1 . As the wavelength conversion element 20th a large content of the light diffusing material 3 it has a high haze value. In such a wavelength converting element 20th become excitation light A. and fluorescence C. through the light-scattering material 3 excessively scattered and are therefore more likely to return light D. . Hence, it is less likely to use the synthetic light B. from the first main surface 11 is emitted so that the luminous flux of synthetic light B. rather decreases.

In view of the above problem, the present invention defines the upper limit of the haze value. In particular, the upper limit of the haze value of the wavelength converting element is 10 preferably 0.999 or less, more preferably 0.995 or less, and particularly preferably 0.99 or less. Thus, excessive scattering of the excitation light can occur A. and fluorescence C. can be decreased, so that the decrease in the luminous flux of the from the first main surface 11 emitted synthetic light B. can be reduced.

3 Fig. 13 is a view illustrating a decrease in the luminous flux of synthetic light with a wavelength converting element having a low haze value. An in 3 shown wavelength conversion element 30th contains fluorescent particles 2 in a matrix 1 but does not contain any light-scattering material 3 and therefore has a low haze value. As with a wavelength converting element 30th without any light scattering material 3 the excitation light A. less likely in the matrix 1 is scattered is the amount of excitation light A. that hit the phosphor particles 2 is applied per unit area, generally relatively small, so that the intensity of the emitted fluorescence tends to decrease. Therefore, in the wavelength converting element 30th the content of the phosphor particles 2 increased to obtain a desired chromaticity. However, if the content of the phosphor particles 2 increases, some of the fluorescence is more likely to be absorbed by the phosphor particles 2 itself, ie a so-called fluorescence reabsorption. In particular, as in 3 shown by a phosphor particle 2a emitted fluorescence C. from another phosphor particle 2 B absorbed in the vicinity of the phosphor particle 2a located, and is called new fluorescence E. from the other phosphor particle 2 B emitted. Thus, since energy loss occurs due to the wavelength conversion, the intensity of the fluorescence is E. lower than that of fluorescence C. . Therefore, when fluorescence reabsorption occurs, the intensity of that from the first major surface decreases 11 emitted fluorescence, so that also the luminous flux of the synthetic light B. decreases.

In view of the above problem, the present invention defines the lower limit of the haze value. In particular, the lower limit of the haze value of the wavelength converting element is 10 preferably 0.7, more preferably 0.75 or more, and particularly preferably 0.80 or more. Thus, the fluorescence reabsorption can be reduced, so that the decrease in the luminous flux of the first main surface 11 emitted synthetic light B. can be reduced.

In addition, the haze value used in the present invention is a value measured in a visible wavelength range in which the excitation spectrum of the phosphor particles 2 exhibits a spectral intensity of 5% or less of the maximum peak intensity. The visible one The wavelength range is defined as 380 nm to 780 nm. The excitation spectrum is a spectrum that shows how the fluorescence intensity of the phosphor changes at a certain wavelength (control wavelength) with changes in the wavelength of the excitation light. Although any wavelength can be selected as the control wavelength, a wavelength is generally selected as the control wavelength which has a maximum fluorescence intensity of the phosphor particles 2 results.

For example, if the phosphor particles 2 are irradiated with light of a wavelength which results in a maximum spectral intensity of the excitation spectrum, is the probability of an excitation of the phosphor particles 2 high, so the intensity of the from the phosphor particles 2 fluorescence emitted at the control wavelength reaches a maximum value. On the other hand, if the phosphor particles 2 are irradiated with light of a wavelength that gives a low spectral intensity, the probability of an excitation of the phosphor particles 2 low, so the fluorescence intensity of the phosphor particles 2 is low. When the phosphor particles 2 are irradiated with light of a wavelength that gives a lower spectral intensity, the phosphor particles 2 not excited so that no fluorescence is emitted.

4th Fig. 13 is a schematic diagram representing an excitation spectrum and a fluorescence spectrum of YAG phosphor particles. The dashed line shows the excitation spectrum (control wavelength: 555 nm) and the solid line shows the fluorescence spectrum.

The luminescence intensities of the excitation spectrum and the fluorescence spectrum are expressed as values relative to the maximum spectral intensity of each spectrum, which is taken as 1. As in 4th As shown, the YAG phosphor particles have their excitation spectrum in a wavelength range from 380 nm to 540 nm. Therefore, light absorption, including fluorescence reabsorption, occurs in this wavelength range. In the wavelength region in which light absorption occurs, there arises a problem that the spectral shapes of the total light transmittance and the diffuse transmittance tend to vary due to the effects of scattering factors, which will be described below, and therefore a correlation between the turbidity value and the luminescence intensity is difficult to be determined.

On the other hand, as described above, if the phosphor particles 2 are irradiated with light with a wavelength range in which the excitation spectrum shows a sufficiently low spectral intensity, it is less likely that the phosphor particles 2 can be excited so that fluorescence is less likely to be emitted. In the present invention, as such a wavelength range, a visible wavelength range (540 nm to 780 nm in the example of FIG 4th ), in which the maximum peak intensity in the excitation spectrum is 5% or less. The inventors have found from the above that the wavelength converting element in the defined wavelength range is free from light absorption effects and the like and the correlation between haze value and luminous flux can be established, and completed the present invention.

The haze value is sufficient if it is between 0.7 and 0.999 in a part of the visible wavelength range in which the maximum peak intensity in the excitation spectrum is 5% or less, but it is particularly preferred that the haze value over the entire above visible wavelength range between 0.7 and 0.999.

Regarding the shape of the wavelength converting element 10 there is no particular limitation, but the shape is generally a sheet-like shape (such as a rectangular sheet-like shape or a disk-like shape). The thickness of the wavelength conversion element 10 can be appropriately selected to obtain a desired chromaticity, but it is particularly preferably 1000 µm or less, more preferably 800 µm or less, and particularly preferably 500 µm or less. If the thickness is too large, the luminous flux of synthetic light can B. decrease. The lower limit of the thickness of the wavelength converting element 10 is preferably about 50 µm. If the thickness is too small, the mechanical strength tends to decrease.

Regarding the chromaticity of the wavelength converting element 10 there is no particular restriction. When using YAG phosphor particles as the phosphor particles 2 which can emit yellow light, and when using blue light (with a central wavelength of about 450 nm) as excitation light A. , instructs the synthetic light B. obtained from the wavelength conversion element 10 is emitted, preferably has the following chromaticity. Especially when collecting the synthetic light B. by irradiating the wavelength conversion element arranged in the opening of an integrating sphere 10 with the excitation light A. and measuring the collected synthetic light B. is obtained with a spectrometer, the chromaticity (Cx) is preferably 0.22 to 0.44, more preferably 0, 23 to 0.37 and particularly preferably 0.24 to 0.33. When the chromaticity of synthetic light B. is too low, the proportion of blue light becomes excessively high, so that a desired color tone is difficult to obtain. In addition, in such cases, the amount of phosphor particles added is 2 often low, so that the specified turbidity value is also difficult to achieve. On the other hand, when the chromaticity of synthetic light B. is too high, the proportion of yellow light becomes excessively high, so that it is difficult to obtain a desired color tone. In addition, in such cases, the amount of phosphor particles added is 2 often large so that the luminous flux is likely to be decreased by the effect of fluorescence reabsorption.

In the visible wavelength range, in which the maximum intensity in the excitation spectrum of the phosphor particles 2 to 5% or less, the total light transmittance of the wavelength converting element is 10 preferably 20% or more, more preferably 30% or more, and particularly preferably 40% or more. If the total light transmission is too low, the luminous flux of the first major surface decreases 11 emitted synthetic light B. excessively, so that the luminescence intensity of the wavelength converting element 10 decreases.

In the present invention, the haze value can be set to an arbitrary value by adding scattering factors that the wavelength converting element 10 form, be changed. In particular, the haze value can be adjusted by changing the index of refraction of the matrix 1 and the respective contents, particle diameters, refractive indices, etc. of the phosphor particles 2 and the light diffusing material 3 can be set. Each spreading factor is described in detail below.

(Matrix 1 )

Regarding the type of matrix 1 There is no particular limitation in the present invention as long as it is a transparent material, the phosphor particles 2 can contain inside it and the excitation light A. and the synthetic light B. lets through. For example, resin or glass can be used. With a view to obtaining a wavelength converting element 10 with high heat resistance and high weather resistance, glass is preferably used. On the other hand, with a view to obtaining a light wavelength converting element 10 resin is preferably used.

Examples of the glass include SiO ₂ -B ₂ O ₃ -based glasses, SiO ₂ -B ₂ O ₃ -RO-based glasses (where RO is an alkali metal oxide), SnO-P ₂ O ₅ -based glasses, TeO ₂ -based glasses and Bi ₂ O ₃ based glasses.

Preferred glasses based on SiO ₂ -B ₂ O ₃ are, for example, those with a composition in which, in mol%, 30 to 80% SiO ₂ , 1 to 40% B ₂ O ₃ , 0 to 10% MgO, 0 to 30% Contains CaO, 0 to 20% SrO, 0 to 40% BaO, 5 to 45% MgO + CaO + SrO + BaO, 0 to 20% Al ₂ O ₃ and 0 to 20% ZnO.

Preferred glasses based on SiO ₂ -B ₂ O ₃ -RO are, for example, those with a composition that contains 70 to 90% SiO ₂ , 9 to 25% B ₂ O ₃ , 0 to 5% Li ₂ O, 0 to 5% Na ₂ O, 0 to 5% K ₂ O, 0.1 to 5% Li ₂ O + Na ₂ O + K ₂ O, 0 to 5% Al ₂ O ₃ , 0 to 5% MgO and 0 contains up to 5% CaO + SrO + BaO.

Preferred glasses based on SnO-P ₂ O ₅ are those with a glass composition which contains 35 to 80% SnO, 5 to 40% P ₂ O ₅ and 0 to 30% B ₂ O ₃ in mol%.

Examples of the resin that can be used include translucent thermoplastic resins and thermosetting resins and ultraviolet-curable resins. Specific examples that can be used include polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, polyvinyl alcohol, polystyrene, polycarbonate, acrylic resin, melamine resin and epoxy resin. In particular, polycarbonate or acrylic resin is preferably used because they are excellent in light transmittance.

The index of refraction (nd) of the matrix 1 is preferably 1.3 to 2.2, more preferably 1.4 to 2.1, even more preferably 1.45 to 2.05, even more preferably 1.5 to 2, and particularly preferably 1.55 to 1.95. Thus, excessive scattering can occur at the interface between the phosphor particles 2 and the matrix 1 occurs, can be reduced slightly, so that the haze value of the wavelength converting element 10 can be adjusted easily.

As will be described below, the shape of the matrix is 1 not particularly limited as long as they are the phosphor particles 2 contains inside. For example, if the wavelength Transformation element 10 from a sintered body made of glass powder and phosphor particles 2 is formed, becomes the matrix 1 formed from a sintered body from the glass powder.

The mean particle _{diameter (D 50} ) of the glass powder is preferably 0.1 µm to 50 µm, more preferably 0.5 µm to 40 µm, and particularly preferably 1 µm to 30 µm. If the mean particle diameter (D ₅₀ ) is too small, the effect of the grain boundaries, which are one of the scattering factors, tends to be significant, so that the turbidity value can be excessively high. On the other hand, if the mean particle diameter (D ₅₀ ) is too large, it becomes difficult to get the phosphor particles 2 evenly in the matrix 1 to distribute so that the chromaticity of synthetic light B. is rather uneven.

(Fluorescent particles 2 )

The phosphor particles 2 may be phosphor particles which absorb part of the fluorescence, in which case the effects of the present invention can be easily obtained. The term “absorb a part of the fluorescence” as used herein means that the excitation wavelength range and the luminescence wavelength range overlap each other. In particular, as shown in FIG. 4, the excitation spectrum has an overlap with the fluorescence spectrum in a wavelength range in which the maximum peak intensity in the excitation spectrum is 5% or more.

The phosphor particles 2 preferably have a peak wavelength of the excitation spectrum in a wavelength range from 300 to 500 nm and a luminescence peak in a wavelength range from 380 to 780 nm and are particularly preferably particles of a ceramic phosphor based on garnet, such as YAG phosphor particles (yttrium aluminum garnet phosphor particles) . The type of phosphor particles 2 however, it is not limited to the above, and other examples that can be used include oxides, nitrides, oxynitrides, sulfides, oxysulfides, rare earth sulfides, aluminate chlorides, and halophosphate.

The content of the phosphor particles 2 in the wavelength converting element 10 in terms of volume percent, is preferably 0.01 to 30%, more preferably 0.1 to 20%, and particularly preferably 1 to 15%. If its content is too large, the above-described fluorescence reabsorption is more likely to occur, so that the luminescence intensity of the wavelength converting element 10 rather decreases. If their content is too low, the hue of synthetic light will be B. rather inhomogeneous and a desired chromaticity is difficult to obtain.

The mean particle diameter (D ₅₀ ) of the phosphor particles 2 is preferably from 0.001 to 50 µm, more preferably from 0.1 to 30 µm, and particularly preferably from 1 to 30 µm. When the mean particle diameter of the phosphor particles 2 is too small, it is likely that the phosphor particles 2 agglomerate together so that the chromaticity of synthetic light B. can be uneven. In addition, the scatter tends to be excessively large, so that the haze value can be excessively high. Even if the mean particle diameter is too large, it becomes difficult to get the phosphor particles 2 evenly in the matrix 1 to distribute so that the chromaticity of synthetic light B. can be uneven.

In the present invention, the mean particle _{diameter (D 50} ) of powder particles means a value measured by laser diffractometry and indicates the particle diameter when, in a volume-based cumulative particle size distribution curve as determined by laser diffractometry, the integrated value of the cumulative volume of the smaller particle diameter is 50%. On the other hand, the particle diameter of the particles in the wavelength converting element can be 10 (for example the mean particle diameter in the matrix 1 dispersed phosphor particles 2 ) can be measured, for example, with an X-ray CT scan. In this case, the mean particle diameter is the particle diameter when, in a volume-based cumulative particle size distribution curve measured by the CT scan, the integrated value of the cumulative volume of the smaller particle diameter is 50%.

With regard to the refractive index (nd) of the phosphor particles 2 There is no particular limitation, but in general, the powder has the phosphor particles 2 often a higher index of refraction than that of the matrix 1 forming resin or glass. For example, the index of refraction of borosilicate glass is about 1.5 to about 1.6, while the index of refraction of YAG phosphor particles is about 1.83. When the refractive index difference between the phosphor particles 2 and the matrix 1 is too large, the excitation light becomes A. most likely at the interface between the phosphor particles 2 and the matrix 1 reflected, so that the haze value is rather excessively high. Therefore, the refractive index difference between the matrix is 1 and the phosphor particles 2 preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.3 or less, and particularly preferably 0.25 or less. Consequently can cause excessive scattering at the interface between the phosphor particles 2 and the matrix 1 occurs, can be reduced slightly, so that the haze value of the wavelength converting element 10 can be adjusted easily. However, the refractive index difference is not necessarily limited to the above.

1. (1) Wenn der Brechungsindexunterschied zwischen der Matrix 1 und den Leuchtstoffpartikeln 2 0,5 bis 0,35 beträgt, beträgt der Trübungswert vorzugsweise 0,7 bis 0,99, stärker bevorzugt 0,72 bis 0,9 und besonders bevorzugt 0,7 bis 0,85.
2. (2) Wenn der Brechungsindexunterschied zwischen der Matrix 1 und den Leuchtstoffpartikeln 2 unter 0,35 bis 0,25 liegt, beträgt der Trübungswert vorzugsweise 0,7 bis 0,99, stärker bevorzugt 0,75 bis 0,95 und besonders bevorzugt 0,8 bis 0,9.
3. (3) Wenn der Brechungsindexunterschied zwischen der Matrix 1 und den Leuchtstoffpartikeln 2 unter 0,25 liegt, beträgt der Trübungswert vorzugsweise 0,7 bis 0,999, stärker bevorzugt 0,8 bis 0,995 und besonders bevorzugt 0,9 bis 0,99.

A preferred range of haze values to maximize luminous flux correlates with the refractive index difference between the matrix 1 and the phosphor particles 2 . In particular, the refractive index difference between the matrix 1 and the phosphor particles 2 and the haze value is preferably controlled as follows.

1. (1) When the refractive index difference between the matrix 1 and the phosphor particles 2 Is 0.5 to 0.35, the haze value is preferably 0.7 to 0.99, more preferably 0.72 to 0.9, and particularly preferably 0.7 to 0.85.
2. (2) When the refractive index difference between the matrix 1 and the phosphor particles 2 is below 0.35 to 0.25, the haze value is preferably 0.7 to 0.99, more preferably 0.75 to 0.95, and particularly preferably 0.8 to 0.9.
3. (3) When the refractive index difference between the matrix 1 and the phosphor particles 2 is below 0.25, the haze value is preferably 0.7 to 0.999, more preferably 0.8 to 0.995, and particularly preferably 0.9 to 0.99.

(Light diffusing material 3 )

The wavelength conversion element according to the invention 10 preferably contains a light-scattering material 3 . There is no particular limitation on the type of light diffusing material 3 and inorganic particles such as ceramic powder or glass powder can be used. In particular, ceramic powder is preferably used. Ceramic powder generally has a higher thermal conductivity than the transparent material such as resin or glass that makes up the matrix 1 forms, and can therefore be caused by the phosphor particles 2 efficiently dissipate generated heat when fluorescing to the outside of the wavelength conversion element 10 is emitted, and can reduce the thermal degradation of the phosphor particles 2 to reduce. On the other hand, glass powder enables the refractive index to be fine-tuned with ease and is therefore used in view of the ease of precise adjustment of the haze value of the wavelength converting element 10 preferred.

Examples of the ceramic powder that can be used include silicon dioxide, boron nitride, aluminum nitride, aluminum oxide, magnesium oxide, titanium oxide, niobium oxide and zinc oxide.

Examples of the glass powder that can be used include multi-component glasses and single-component glasses such as quartz glass. When heating a mixture from the matrix 1 and the light diffusing material 3 in a method for manufacturing the wavelength converting element described below 10 changes when the glass powder is used as the light-diffusing material 3 softens and flows, its particle diameter, so it can be difficult to obtain a desired haze value. Therefore, the softening point of the glass powder is compared to the softening point of the matrix 1 preferably 30 ° C or more than 30 ° C higher, more preferably 50 ° C or more than 50 ° C higher, and particularly preferably 100 ° C or more than 100 ° C higher.

The content of the light scattering material 3 in the wavelength converting element 10 in terms of volume percent, is preferably 0 to 50%, more preferably 0.01 to 40%, even more preferably 0.1 to 10%, and particularly preferably 1 to 5%. When the content of the light diffusing material 3 is too large, the haze value of the wavelength converting element becomes 10 excessively high, so that the luminescence intensity tends to decrease. In addition, the total light transmittance of the wavelength converting element 10 lose weight excessively. The mean particle diameter (D ₅₀ ) of the light-scattering material 3 is preferably 0.1 µm to 100 µm, more preferably 0.3 µm to 50 µm, and particularly preferably 1 µm to 30 µm. If the mean particle diameter (D ₅₀ ) of the light scattering material 3 is too small, the haze value is likely to become excessively high. In addition, the scatter is likely to become excessively large, so that the haze value may be excessively large. On the other hand, if the mean particle diameter (D ₅₀ ) of the light diffusing material 3 is too large, it becomes difficult to get the light diffusing material 3 evenly in the matrix 1 to disperse, so that the chromaticity of synthetic light B. can be uneven.

Regarding the shape of the light diffusing material 3 there is no particular limitation, and examples include a spherical shape, a fragment shape, a hollow shape, a rod shape, and a fiber shape.

The refractive index difference between the light scattering material 3 and the matrix 1 is preferably 0.5 or less, more preferably 0.4 or less, and particularly preferably 0.3 or less. Thus, excessive scattering can occur at the interface between the light scattering material 3 and the matrix 1 occurs, can be reduced slightly, so that the haze value of the wavelength converting element 10 can be adjusted easily. However, the refractive index difference is not necessarily limited to the above.

The difference in density between the phosphor particles 2 and the matrix 1 is preferably 4 or less, more preferably 3.5 or less, and particularly preferably 3 or less. If the density difference is too great, it will be difficult to pick up the phosphor particles 2 evenly in the matrix 1 to distribute so that the chromaticity of synthetic light B. becomes rather uneven. On the other hand, the density difference between the light diffusing material is 3 and the matrix 1 preferably 4 or less, more preferably 3.5 or less, and particularly preferably 3 or less. If the difference in density is too great, it becomes difficult to pick up the light diffusing material 3 evenly in the matrix 1 to distribute so that the chromaticity of synthetic light B. becomes rather uneven.

Apart from the above-described scattering factors, voids, grain boundaries, striae and the like can occur in the wavelength conversion element 10 act as scatter factors on the turbidity value. If for the matrix 1 Glass is used can also be used in the below-described method of manufacturing the wavelength converting element 10 Crystals precipitate, in which case the crystals can be a scatter factor. The turbidity value can also be set to any value, taking these scatter factors into account.

The void fraction of the wavelength conversion element 10 in terms of volume percent, is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. If the void fraction is too high, light will appear at the boundaries between the voids and the matrix 1 scattered so that the scatter tends to be excessive.

When the matrix 1 Made of glass, the amount is inside the matrix 1 precipitated crystals, expressed as a volume percentage based on the matrix 1 , preferably 30% or less, more preferably 25% or less, and particularly preferably 20% or less. If the amount of crystals is too large, excessive light scattering occurs, so that the luminescence intensity of the wavelength converting element 10 rather decreases. In addition, the total light transmittance of the wavelength converting element 10 lose weight excessively.

The above void fraction and the volume fraction of the crystals can be measured with a CT scan.

Regarding the manufacturing method of the wavelength converting element 10 there is no particular limitation as long as the wavelength converting element 10 has a structure that contains phosphor particles 2 within a matrix 1 contains. For example, the wavelength conversion element 10 by mixing glass powder and phosphor particles 2 (and, if required, a light-diffusing material 3 ) and burning the same can be obtained. In particular, it is preferable to use the wavelength converting element 10 by pressing the mixture of glass powder and phosphor particles 2 to make a preform and then to fire the preform. The sintered body made of glass powder and phosphor particles 2 however, it is extremely susceptible to the effect of the grain boundaries, which are one of the scattering factors. Therefore, it is with a view to manufacturing a wavelength converting element 10 , which is less susceptible to the effect of grain boundaries, preferably the wavelength converting element 10 Manufacture by adding phosphor particles 2 absorbed in liquid or semi-solid resin and then the resin is cured.

(Light emitting device)

5 Fig. 13 is a schematic cross-sectional view showing a light emitting device according to an embodiment of the present invention. As in 5 shown includes a light emitting device 50 the wavelength converting element 10 and a light source 6th . In this embodiment, the light source is 6th arranged so that excitation light A. into the second main surface 12th entry. That from the light source 6th emitted excitation light A. is made by the wavelength converting element 10 in wavelength into a fluorescence with a longer wavelength than the excitation light A. converted. In addition, part of the excitation light runs A. by the wavelength converting element 10 through. Therefore, the wavelength converting element emits 10 a synthetic light B. resulting from the excitation light A. and the fluorescence. For example, when the excitation light A. is a blue light and the fluorescence is a yellow light, can be a white synthetic light B. to be provided.

Examples of the light source 6th include an LED and an LD. With a view to increasing the luminescence intensity of the light emitting device 10 however, it is preferable to use an LD capable of emitting high-intensity light as the light source 6th used. Although the light source 6th in this embodiment from the wavelength conversion element 10 is located remotely, is the arrangement of the light source 6th not limited to that. For example, the light source 6th and the wavelength converting element 10 be connected to one another in direct contact or by an adhesive layer.

[Examples]

In the following, the wavelength converting element of the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

Tables 1 to 3 show working examples (Nos. 1 to 6 and 9 to 23) of the present invention and comparative examples (Nos. 7 and 8). Table 1 number 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 matrix Type Glass A Glass A Glass A Glass A Glass A Glass A Glass A Glass C Refractive index 1.58 1.58 1.58 1.58 1.58 1.58 1.58 1.58 Fluorescent Type YAG YAG YAG YAG YAG YAG YAG YAG Refractive index 1.82 1.82 1.82 1.82 1.82 1.82 1.82 1.82 Volume concentration (%) 10.6 10.3 9.2 8.3 6.5 5.7 2.0 10.8 Light diffusing material 3 Type - Al ₂ O ₃ Al ₂ O ₃ Al ₂ O ₃ Al ₂ O ₃ Al ₂ O ₃ Al ₂ O ₃ - Volume concentration (%) - 0.1 0.4 0.8 1.5 2.0 8.0 - Difference in refractive index between matrix and phosphor 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 Thickness (µm) 200 200 200 200 200 200 200 200 Turbidity value 0.854 0.876 0.906 0.939 0.972 0.982 1,000 0.691 Luminous flux (au) 0.95 0.96 0.96 0.98 0.99 1.00 0.88 0.92 Chromaticity Cx 0.291 0.290 0.287 0.288 0.291 0.290 0.292 0.289 Table 2 No. 9 No. 10 No. 11 No. 12 No. 13 No. 14 No. 15 No. 16 matrix Type Glass B Glass B Glass B Glass B Glass B Glass B Glass B Glass B Refractive index 1.46 1.46 1.46 1.46 1.46 1.46 1.46 1.46 Fluorescent Type YAG YAG YAG YAG YAG YAG YAG YAG Refractive index 1.82 1.82 1.82 1.82 1.82 1.82 1.82 1.82 Volume concentration (%) 9.2 8.3 7.6 6.5 4.9 8.0 7.3 6.8 Light diffusing material 3 Type - Al ₂ O ₃ Al ₂ O ₃ Al ₂ O ₃ Al ₂ O ₃ - Al ₂ O ₃ Al ₂ O ₃ Volume concentration (%) - 0.2 0.4 0.8 2.0 - 0.1 0.2 Difference in refractive index between matrix and phosphor 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 Thickness (µm) 200 200 200 200 200 180 180 180 Turbidity value 0.830 0.890 0.926 0.963 0.997 0.794 0.815 0.865 Luminous flux (au) 1.00 0.99 0.99 0.98 0.95 1.00 1.00 0.99 Chromaticity Cx 0.291 0.290 0.291 0.288 0.287 0.244 0.238 0.241 Table 3 No. 17 No. 18 No. 19 No. 20 No. 21 No. 22 No. 23 matrix Type Glass B Glass B Resin D Resin E Resin E Resin E Resin E Refractive index 1.46 1.46 1.46 1.51 1.51 1.51 1.51 Fluorescent Type YAG YAG YAG YAG YAG YAG YAG Refractive index 1.82 1.82 1.82 1.82 1.82 1.82 1.82 Volume concentration (%) 6.0 5.0 10.2 12.7 9.9 8.8 6.7 Light diffusing material 3 Type Al ₂ O ₃ Al ₂ O ₃ - - Al ₂ O ₃ Al ₂ O ₃ Al ₂ O ₃ Volume concentration (%) 0.4 0.8 - - 0.5 1.0 1.5 Difference in refractive index between matrix and phosphor 0.36 0.36 0.36 0.31 0.31 0.31 0.31 Thickness (µm) 180 180 180 200 200 200 200 Turbidity value 0.914 0.961 0.740 0.708 0.810 0.871 0.922 Luminous flux (au) 0.98 0.98 0.98 0.96 0.99 1.00 0.97 Chromaticity Cx 0.241 0.241 0.239 0.287 0.289 0.293 0.290

1. (a) Matrix Glas A Pulver - Borosilikatglas (SiO₂-B₂O_3'-basiertes Glas), Brechungsindex (nd): 1,58, Dichte: 3,1 g/cm³, mittlerer Partikeldurchmesser D₅₀: 2,5 µm, Erweichungspunkt: 850 °C Glas B Pulver - Alkaliborosilikatglas (SiO₂-B₂O₃-RO-basiertes Glas), Brechungsindex (nd): 1,46, Dichte: 2,1 g/cm³, mittlerer Partikeldurchmesser D₅₀: 2,5 µm, Erweichungspunkt: 825 °C Harz C - photohärtbares Harz, Brechungsindex (nd): 1,58, Dichte: 2,4 g/cm³ Harz D - Silikonharz, Brechungsindex (nd): 1,46, Dichte: 2,0 g/cm³ Harz E - photohärtbares Harz, Brechungsindex (nd): 1,51, Dichte: 2,4 g/cm³
2. (b) Leuchtstoffpartikel, YAG - Y₃Al₅O₁₂, Brechungsindex (nd): 1,82, mittlerer Partikeldurchmesser D₅₀: 25 µm, Dichte: 4,8 g/cm³
3. (c) Lichtstreuendes Material, Aluminiumoxid - Al₂O₃, mittlerer Partikeldurchmesser: 1 µm, Dichte: 4,0 g/cm³

Each of the working examples (Nos. 1 to 6 and 9 to 23) and comparative examples (Nos. 7 and 8) were produced in the following manner. First, a matrix, phosphor particles and, if necessary, a light diffusing material were mixed to give the contents shown in Tables 1 to 3, whereby a mixture was obtained. The following materials were used in the examples. In Table 1, “Volume Concentration (%)” indicates a volume concentration in the total volume of the matrix, the phosphor particles and the light-scattering material.

1. (a) Matrix glass A powder - borosilicate glass (SiO ₂ -B ₂ O _{3 '} -based glass), refractive index (nd): 1.58, density: 3.1 g / cm ³ , mean particle _{diameter D 50} : 2.5 µm, softening point: 850 ° C glass B powder - alkali borosilicate glass (SiO ₂ -B ₂ O ₃ -RO-based glass), refractive index (nd): 1.46, density: 2.1 g / cm ³ , mean particle _{diameter D 50} : 2.5 µm, softening point: 825 ° C Resin C - photocurable resin, refractive index (nd): 1.58, density: 2.4 g / cm ³ Resin D - silicone resin, refractive index (nd): 1.46, density : 2.0 g / cm ³ Resin E - photocurable resin, refractive index (nd): 1.51, density: 2.4 g / cm ³
2. (b) Phosphor _{particles, YAG - Y 3} Al ₅ O ₁₂ , refractive index (nd): 1.82, mean particle _{diameter D 50} : 25 μm, density: 4.8 g / cm ³
3. (c) Light-scattering material, aluminum oxide - Al ₂ O ₃ , mean particle diameter: 1 µm, density: 4.0 g / cm ³

In Nos. 1 to 7 and 9 to 18, the mixture was put in a mold and pressed at a pressure of 0.20 MPa, thereby obtaining a preform. Then, the preform was fired near the softening point of the glass, thereby producing a sintered glass body.

In Nos. 8 and 20 to 23, the mixture was put in a mold and cured by irradiating with ultraviolet light (having a central wavelength of 405 nm), thereby producing a resin cured body.

At No. 19, the mixture was placed in a mold and cured by heating at 40 ° C, thereby producing a resin cured body.

The above glass sintered bodies and resin hardened bodies were subjected to grinding and polishing processing, whereby rectangular plate-shaped wavelength converting members having a thickness of 200 µm for Nos. 1 to 13 and 20 to 23 or 180 µm for Nos. 14 to 19 were obtained .

The obtained wavelength converting elements were evaluated for haze value, luminous flux and chromaticity in the following manner.

The haze value was obtained by measuring the total light transmittance and the diffuse transmittance with a spectrophotometer V-670 manufactured by JASCO Corporation, and calculating the haze value at a wavelength of 600 nm based on the following formula. The spectral intensity at a wavelength of 600 nm in the excitation spectrum of the phosphor used in these examples was 5% or less of the maximum peak intensity. $$\text{Tr}\ddot{\text{u}}\text{exercise value}=\left(\text{Diffuse passage}\ddot{\text{a}}\text{sweetness}\right)/\left(\text{Total light transmission}\ddot{\text{a}}\text{sweetness}\right)$$

The luminous flux and the chromaticity were measured by irradiating the wavelength converting element with excitation light from the light source and collecting emitted light from the wavelength converting element with an integrating sphere. A blue LED (maximum peak of the excitation spectrum: 450 nm) was used as the light source and its output was kept constant. As a measuring device, a spectrometer PMA-12 manufactured by Hamamatsu Photonics K.K. used. As for the luminous flux, the value in Example No. 6, which was the maximum value in all of the working examples (Nos. 1 to 6 and 9 to 23) and comparative examples (Nos. 7 and 8), was assumed to be 1 and the values in others Examples were expressed as relative values.

6th shows a diagram in which the turbidity value was plotted against the value of the relative luminous flux for each sample.

As in Tables 1 to 3 and 6th shown, in Working Examples (Nos. 1 to 6 and 9 to 23), wavelength conversion elements exhibiting high luminous flux and high luminescence intensity were obtained. In particular, their relative luminous fluxes were 0.95 or more.

List of reference symbols

1

matrix

2

Fluorescent particles

2a

Fluorescent particles

2 B

Fluorescent particles

3rd

light diffusing material

6th

Light sources

10

Wavelength conversion element

11

first major surface

12th

second main surface

20th

Wavelength conversion element

30th

Wavelength conversion element

50

Light emitting device

A.

Excitation light

B.

synthetic light

C.

fluorescence

D.

returning light

E.

fluorescence

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• JP 2000208815 A [0003]
• JP 2003258308 A [0003]

Claims (8)

A wavelength conversion element containing phosphor particles in a matrix, the wavelength conversion element having a haze value of 0.7 to 0.999 in a visible wavelength range in which an excitation spectrum of the phosphor particles shows a spectral intensity of 5% or less of the maximum peak intensity. Wavelength conversion element according to Claim 1 , where the matrix is glass. Wavelength conversion element according to Claim 1 or 2 , wherein the phosphor particles absorb part of the fluorescence. Wavelength conversion element according to one of the Claims 1 until 3 wherein the phosphor particles are particles of a garnet-based ceramic phosphor. Wavelength conversion element according to one of the Claims 1 until 4th containing a light diffusing material. Wavelength conversion element according to one of the Claims 1 until 5 which has a thickness of 1000 µm or less. A light emitting device comprising the wavelength converting element according to any one of Claims 1 until 6th and a light source adapted to irradiate the wavelength conversion element with excitation light. Light emitting device according to Claim 7 , wherein the light source is a light emitting diode or a laser diode.

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