WO2014010211A1

WO2014010211A1 - Light emitting module

Info

Publication number: WO2014010211A1
Application number: PCT/JP2013/004178
Authority: WO
Inventors: 雄壮前野; 岩崎　剛; 大長　久芳
Original assignee: 株式会社小糸製作所
Priority date: 2012-07-10
Filing date: 2013-07-04
Publication date: 2014-01-16
Also published as: JPWO2014010211A1

Abstract

A light emitting module (10) is provided with: a semiconductor light emitting element (14), which emits ultraviolet light or short-wavelength visible light; a first wavelength conversion layer (16) having a first fluorescent body, which is excited by means of the ultraviolet light or the short-wavelength visible light, and which emits blue light; and a second wavelength conversion layer (18) having a second fluorescent body, which is excited by means of the ultraviolet light or the short-wavelength visible light, and which emits yellow light. The first wavelength conversion layer (16) and the second wavelength conversion layer (18) are laminated on the light emitting surface of the semiconductor light emitting element (14), and the first wavelength conversion layer and/or the second wavelength conversion layer is a ceramic layer.

Description

Light emitting module

The present invention relates to a light emitting module.

Conventionally, many fluorescent lamps and light bulbs have been used as lighting fixtures. In recent years, various light-emitting devices using semiconductor light-emitting elements such as light-emitting diodes (hereinafter appropriately referred to as “LEDs”) have been developed as alternatives to such lamps from the viewpoint of power consumption and lifetime.

In such a light-emitting device, there is a technique for obtaining a light-emitting module that emits light of a color different from the color of light emitted from the light-emitting element by converting the wavelength of light emitted from the light-emitting element such as an LED using a phosphor or the like. Are known. On the other hand, in order to increase the conversion efficiency when converting the wavelength of light, a technique has been proposed in which, for example, a ceramic layer including a wavelength conversion material is disposed in the path of light emitted by the light emitting layer (for example, , See Patent Document 1).

JP 2006-5367 A

By the way, in recent years, a technology has been developed that employs a light emitting module using LEDs as an automotive headlamp or lighting fixture. Moreover, in these lamps, it is calculated | required to reduce the number of LED from a cost reduction, and development of a more efficient light emitting module is promoted.

The present invention has been made in view of such a situation, and an object thereof is to provide a technology capable of realizing a highly efficient light emitting module.

In order to solve the above problems, a light emitting module according to an aspect of the present invention includes a light emitting element that emits ultraviolet light or short wavelength visible light, and a first phosphor that emits blue light when excited by ultraviolet light or short wavelength visible light. And a second wavelength conversion layer having a second phosphor that is excited by ultraviolet light or short-wavelength visible light and emits yellow light. The first wavelength conversion layer and the second wavelength conversion layer are laminated on the light emitting surface of the light emitting element, and at least one of the first wavelength conversion layer and the second wavelength conversion layer is a ceramic layer. The second phosphor has a maximum excitation spectrum intensity of Imax in a wavelength region of 300 nm or more, Ia, and the excitation spectrum intensity at the peak wavelength of ultraviolet light or short-wavelength visible light emitted from the light emitting element is Ia. Imax <Ia is satisfied.

According to this aspect, since the second phosphor has high excitation spectrum intensity at the peak wavelength of ultraviolet light or short-wavelength visible light emitted from the light-emitting element, the light from the light-emitting element can be efficiently converted into yellow light.

The first wavelength conversion layer may be disposed between the light emitting element and the second wavelength conversion layer, and the second wavelength conversion layer may be a ceramic layer.

When the maximum intensity of the excitation spectrum in the wavelength region of 300 nm or more is Imax and the intensity of the excitation spectrum at the peak wavelength of visible light emitted from the first phosphor is Ib, the second phosphor has Ib <0.8 × Imax. Meet. Thereby, in the 2nd fluorescent substance, absorption of the light which a 1st fluorescent substance emits can be suppressed.

The first wavelength conversion layer is configured by dispersing the first phosphor in a transparent sealing material, and may have a thickness of 15 to 1000 μm.

The first wavelength conversion layer may contain 0.5 to 35% by volume of the first phosphor. Thereby, the light of the light emitting element which passes through the first wavelength conversion layer and reaches the second wavelength conversion layer can be increased.

The thickness of the second wavelength conversion layer may be 30 to 1000 μm.

It should be noted that an arbitrary combination of the above-described components and a conversion of the expression of the present invention between a method, an apparatus, a system, and the like are also effective as an aspect of the present invention.

According to the present invention, a highly efficient light emitting module can be realized.

1 is a cross-sectional view illustrating a schematic structure of a light emitting module according to Example 1. FIG. It is sectional drawing which shows schematic structure of the light emitting module which concerns on a comparative example. It is a figure which shows the measurement result of the transmittance | permeability of the 1st wavelength conversion layer which concerns on Example 1, and a 2nd wavelength conversion layer. It is a figure which shows the measurement result of the transmittance | permeability of the 1st wavelength conversion layer which concerns on the comparative example 1, and a 2nd wavelength conversion layer. It is a figure which shows the emission spectrum of the light emitting module which concerns on Example 1 and Comparative Example 1. FIG. It is a figure which shows the temperature dependence of the light beam in the light emitting module which concerns on Example 1 and Comparative Example 1. FIG. 6 is a cross-sectional view illustrating a schematic structure of a light emitting module according to Example 2. FIG. It is a figure which shows the emission spectrum of the light emitting module which concerns on Example 2 and Comparative Example 1. FIG. 6 is a cross-sectional view illustrating a schematic structure of a light emitting module according to Example 3. FIG. It is sectional drawing which shows schematic structure of the light emitting module which concerns on the comparative example 2. FIG. It is a figure which shows the measurement result of the transmittance | permeability of the 1st wavelength conversion layer which concerns on Example 3, and a 2nd wavelength conversion layer. It is a figure which shows the measurement result of the transmittance | permeability of the 1st wavelength conversion layer which concerns on the comparative example 1, and a 2nd wavelength conversion layer. It is a figure which shows the emission spectrum of the light emitting module which concerns on Example 3 and Comparative Example 2. FIG. 6 is a cross-sectional view illustrating a schematic structure of a light emitting module according to Example 4. FIG. It is sectional drawing which shows schematic structure of the light emitting module which concerns on the comparative example 3. FIG. It is a figure which shows the emission spectrum of the light emitting module which concerns on Example 4 and Comparative Example 3. FIG. 2 is a diagram showing an emission spectrum of the semiconductor light emitting device according to Example 1. FIG. It is a figure which shows the emission spectrum of the fluorescent substance 2 which concerns on Example 1, and the conventional YAG fluorescent substance. It is a figure which shows the emission spectrum of the fluorescent substance 2 concerning Example 1, and the conventional YAG fluorescent substance, and the emission spectrum of the fluorescent substance 1 concerning Example 1, and the conventional blue LED. It is a figure for demonstrating the method to measure the chromaticity of a light emitting module. It is a figure which shows the change of the chromaticity of the light emitting module by a measurement position.

First, the background that the inventors have conceived of the present invention will be described. Conventionally, a white LED module combines a semiconductor light emitting element that emits light having a wavelength from near ultraviolet to blue with a phosphor that converts light emitted from the semiconductor light emitting element into visible light having a longer wavelength than that light. Is realized.

Examples of white LED modules include a blue LED chip and a YAG (Yttrium Aluminum Garnet) phosphor that emits yellow light, a blue LED chip and two types of fluorescent light that emit red and green, respectively. There are a combination of bodies, an LED chip that emits light having a wavelength corresponding to ultraviolet rays from near ultraviolet rays, and a combination of three types of phosphors that emit red, green, and blue. The most common of these is a combination of a blue LED chip and a YAG phosphor.

As a phosphor layer in an LED module, when a powdered phosphor is dispersed in a transparent sealing material (organic resin material, inorganic amorphous material, inorganic sol-gel material), the powdered phosphor acts as a filler. To do. Therefore, light loss occurs before the light emitted from the LED chip is extracted to the outside, which may be a cause of reducing the light emission efficiency of the light emitting module. This is due to the difference in refractive index between the phosphor and the sealing material, and this difference in refractive index causes scattering and reflection, resulting in light loss.

Therefore, there is a technique for sintering powdered phosphors to make translucent ceramics. According to this method, since the phosphor layer is formed of a phosphor single component, there is no interface between the phosphor and other components in the layer, there is no difference in refractive index, and the above-mentioned light loss is greatly increased. To be reduced. As a result, the luminous efficiency of the LED module can be increased as compared with a case where a powdered phosphor is dispersed in a transparent resin to form a phosphor layer. At present, YAG is the only phosphor that has been successfully made into translucent ceramics while maintaining high quantum efficiency.

However, in the white module composed of the translucent ceramic YAG and the blue LED, the blue LED has higher directivity of light emission than the translucent ceramic YAG, so that the colors are separated. In order to suppress color separation, a technique of adding a scatterer component to the translucent ceramics YAG is effective, but on the other hand, the transmittance of the ceramics YAG is lowered and a sufficient luminous flux cannot be obtained. Also, such a white LED module is suitable for realizing white light having a high color temperature of about daylight white, but it is difficult to form light of low color temperature such as warm white and light bulb color. And in order to form light of these low color temperatures, it is common to mix phosphors that absorb blue light and emit red light, but a red ring is easily formed on the outer periphery of the light emitting surface, It tends to lead to color separation.

As a result of intensive studies by the present inventors based on such knowledge, the following configurations were focused on in order to realize a highly efficient light emitting module with little light loss.

(1) The light emitting module absorbs ultraviolet light and short wavelength visible light, and a semiconductor light emitting element such as an LED chip that emits ultraviolet light and short wavelength visible light (for example, visible light having a wavelength from purple to near ultraviolet). A phosphor layer having a phosphor that emits light, and the phosphor layer may be a ceramic layer densely sintered with a phosphor single component. Moreover, it is preferable that a ceramic layer has translucency.

(2) The phosphor may be of one type or a plurality of types as long as a desired emission color can be obtained as a light emitting module.

(3) At least one kind of phosphor layer may be a ceramic layer. Depending on the combination and amount of the phosphor, a phosphor layer having a shape in which the powder phosphor is sealed with a transparent sealing material (organic resin material, inorganic amorphous material, inorganic sol-gel material) may be included. In this case, the manufacturing cost can be reduced.

(4) Stacking order of translucent ceramic phosphor layers emitting each color, and translucent ceramic phosphor layers and phosphor layers encapsulating powder phosphors, depending on the desired emission color as the light emitting module Is not limited, and can be appropriately selected depending on desired characteristics such as high efficiency and suppression of color unevenness. Preferably, the phosphor layer that emits light with the highest visibility is arranged on the uppermost layer (light extraction surface side).

(Translucent ceramic phosphor)
Next, the translucent ceramic phosphor will be described. The translucent ceramic phosphor is characterized by its high spectral transmittance, and has a transmittance (when measured in air) of 70 to 85%, preferably 80% in the wavelength range of 350 to 900 nm including the visible light region. That's it. However, this is not the case in the absorption band of the phosphor itself (wavelength range of the excitation band). The theoretical maximum transmittance (measured in air) is uniquely determined by the refractive index of the phosphor itself. The transmittance only in the phosphor medium is 80 to 100%, preferably 90% or more. However, this is not the case in the absorption band of the phosphor itself (wavelength range of the excitation band).

Further, when the translucent ceramic phosphor is mounted on the light emitting module, the phosphor layer is processed to have a thickness of 40 to 2000 μm, and preferably 80 to 2000 μm considering workability. In order to improve the light extraction efficiency, the surface of the translucent ceramic phosphor is roughened and patterned by various processes such as Fresnel lens processing, V-groove processing, laser processing, nanoprinting processing, ion milling, and sandblasting. Alternatively, a white transparent material such as resin or glass having an arbitrary refractive index may be applied and formed into a film.

Furthermore, since the translucent ceramic phosphor is excellent in workability, the light extraction direction and orientation can be controlled by, for example, prism shape processing, lens shape processing, various step processing, and vapor deposition of reflectors. Moreover, these shape control can also give a desired shape without said process by shape | molding in a desired shape previously in the formation process of the preparation process of a translucent ceramic fluorescent substance. Further, by using mirror polishing and the total reflection effect that accompanies it, it is possible to dimm only a predetermined part, guide the light, control the light extraction part, and the like.

In addition, the transmittance of the phosphor layer having a shape in which the powdered phosphor is sealed with a transparent sealing material (organic resin material, inorganic amorphous material, inorganic sol-gel material) or the like is the transmittance of the translucent ceramic phosphor. In the case of the same, a sealed phosphor layer may be used, and the manufacturing cost can be reduced. In this case, the spectral transmittance of the sealed phosphor layer is in the range of 60 to 85% (measured in air) in the wavelength range of 350 to 900 nm including the visible light range, preferably 65% or more. is there.

Next, an outline of a method for producing a translucent ceramic phosphor will be described. A fine particle raw material of the phosphor is prepared, and an appropriate sintering aid is added as necessary. Thereafter, the phosphor fine particle material is molded by uniaxial pressure molding, CIP molding (cold one pressure molding) or the like. Or it mixes with resin, such as PVA (polyvinyl alcohol) and PVB (polyvinyl butyral), is made into a slurry, and shape | molds by tape molding, extrusion molding, casting molding, gel casting molding, etc. Thereafter, degreasing, calcination, and hot press firing as needed, and HIP firing (hot one-pressure press firing) are performed under appropriate conditions to obtain a translucent ceramic phosphor. Then, the translucent ceramic fluorescent substance is produced by carrying out surface treatment processing by cutting and polishing to a predetermined size.

In consideration of the above-described knowledge, a light emitting module according to an embodiment of the present invention includes a light emitting element that emits ultraviolet light or short wavelength visible light, and a first phosphor that emits blue light when excited by ultraviolet light or short wavelength visible light. And a second wavelength conversion layer having a second phosphor that is excited by ultraviolet light or short-wavelength visible light and emits yellow light. The first wavelength conversion layer and the second wavelength conversion layer are laminated on the light emitting surface of the light emitting element, and at least one of the first wavelength conversion layer and the second wavelength conversion layer is a ceramic layer. is there. In the following description, an LED is described as an example of a light emitting element, but a laser diode (LD) element, an electroluminescence (EL) element, or the like can also be used.

The light emitting element preferably emits ultraviolet light or short wavelength visible light having a peak wavelength in the wavelength range of 350 to 420 nm. Thereby, white light is realizable using several types of fluorescent substance from which an emission spectrum differs, for example, the blue fluorescent substance and yellow fluorescent substance which concern on each Example. Also, white light can be realized by mixing blue light and yellow light without directly using light from the light emitting element.

Thus, by using a layer containing at least one kind of phosphor as a ceramic layer, the transmittance of the phosphor layer is improved and the scattering loss is greatly reduced, so that the efficiency of the light emitting module can be improved.

Specifically, a white LED module as a light emitting module includes an LED chip that emits near ultraviolet light, a first phosphor (phosphor 1) that absorbs near ultraviolet light and emits blue light, and absorbs near ultraviolet light. And a second phosphor that emits yellow light (phosphor 2). A novel white LED module can be obtained by forming at least one of the first phosphor and the second phosphor into a ceramic plate. The blue light emitted from the first phosphor is, for example, light having a peak wavelength λp of about 400 to 500 nm. The yellow light emitted from the second phosphor is, for example, light having a peak wavelength λp of about 500 to 620 nm, and more preferably light having a peak wavelength λ in the vicinity of 555 nm at which the visibility reaches a peak.

As described above, a white LED module that combines a LED chip that emits near-ultraviolet light and a plurality of types of phosphors forms a white color substantially only by the fluorescence of the phosphors that emit light in all directions, so that color separation occurs. It ’s hard. At this time, it is important that a phosphor that emits light at a relatively long wavelength among a plurality of types of phosphors absorbs the fluorescence of the phosphor that emits light at a relatively short wavelength and does not emit light. Therefore, as a preferred example of the present embodiment, the following phosphor 1 that emits light at a relatively short wavelength and phosphor 2 that emits light at a relatively long wavelength will be described.

(Phosphor 1)
The phosphor 1 according to the present embodiment is a blue phosphor that is excited by ultraviolet light or short-wavelength visible light and emits blue light. For example,
(I) the general formula ^{_{^{_{_{M 1 a (M 2 O 4}}}}} ) b X c: phosphor represented by Re _d ^{(M 1} is, Ca, Sr, and essential one or more kinds of Ba, some Mg , Zn, Cd, K, Ag, Tl can be replaced with elements of M ² that require P and some of them are V, Si, As, Mn, Co, Cr, Mo, W, B X represents at least one halogen element, Re represents Eu ²⁺ and at least one rare earth element or Mn, and a represents 4.2 ≦ a ≦ 5.8. B is 2.5 ≦ b ≦ 3.5, c is 0.8 <c <1.4, and d is 0.01 <d <0.1.)

(Ii) _a phosphor having _a general formula represented by M ¹ _1-a MgAl ₁₀ O ₁₇ : Eu ²⁺ _a (M ¹ is at least one element selected from the group consisting of Ca, Sr, Ba, Zn, a is in the range of 0.001 ≦ a ≦ 0.5.)

(Iii) A phosphor having _a general formula represented by M ¹ _1-a MgSi ₂ O ₈ : Eu ²⁺ _a (M ¹ is at least one element selected from the group consisting of Ca, Sr, Ba, Zn, a is in the range of 0.001 ≦ a ≦ 0.8.)

(Iv) A phosphor represented by the general formula M ¹ _2-a (B ₅ O ₉ ) X: Re _a (M ¹ is at least one selected from the group consisting of Ca, Sr, Ba, Zn) Element, X is at least one halogen element, and a is in the range of 0.001 ≦ a ≦ 0.5.)

(Phosphor 2)
The phosphor 2 according to the present embodiment is a phosphor that emits green to yellow light when excited by ultraviolet light or short-wavelength visible light. For example,
(I) A phosphor (M ^II ) whose general formula is represented by (Ca _{1-xyz w} , Sr _x , M ^II _y , Eu _z , M ^R _w ) ₇ (SiO ₃ ) ₆ X ₂ is Mg, Ba or Zn, ^{M R} is a rare earth element or Mn, X is more halogen element essentially including Cl or Cl, x is 0.1 <x <0.7, y is 0 ≦ y <0 .3, z is 0 <z <0.4, and w is in the range of 0 ≦ w <0.1.)

(Ii) Phosphor having _a general formula represented by CsM ¹ _1-a P ₂ O ₇ : Eu ²⁺ _a (M ¹ is Ca, Sr, a is 0.001 ≦ a ≦ 0.5. )
(Iii) A phosphor whose general formula is represented by Ba _2-a MgSi ₂ O ₇ : Eu ²⁺ _a (a is in the range of 0.001 ≦ a ≦ 0.5)

Such a phosphor 2 is effective in suppressing color separation and hardly deviates in chromaticity because it hardly absorbs blue light emitted from the phosphor 1 even when mixed with the phosphor 1 described above. Further, by combining with a phosphor that emits blue light, it is possible to form a wide range of white colors from light bulb colors to daylight colors.

Hereinafter, some effects of the light emitting module having the translucent ceramic phosphor layer according to the present embodiment will be described.
(1) Color stability in the light emitting module The LED chip that emits near-ultraviolet light and the white LED module that combines the phosphor 1 and the phosphor 2 described above are different in intensity from the near-ultraviolet LED chip derived from the manufacturing method, White chromaticity is less likely to shift with respect to wavelength shift.

(2) High efficiency (power saving)
Near-ultraviolet LED chips typified by InGaN-based LEDs are 1.2 times more efficient in principle than similar blue LED chips, and are effective LED chips particularly in power-based light-emitting modules. And by making at least one kind of phosphor into translucent ceramics, scattering in the phosphor layer is reduced, and high efficiency (power saving) can be achieved.

(3) Improvement of temperature characteristics When assumed to be used as a power-type light emitting module, the amount of heat generated by the Stokes loss of the phosphor increases, and this heat dissipation becomes important. The thermal conductivity of the phosphor itself is more than twice that of a general sealing material (for example, silicone resin, epoxy resin, etc.). As a result, the temperature characteristics of the light emitting module are improved.

(4) Improvement of reliability In general, organic substances are vulnerable to ultraviolet rays. Therefore, when a plurality of phosphor layers are all made of a translucent ceramic plate, and when a sol-gel adhesive or the like is used for adhesion between the phosphor layers and between the phosphor layers and the LED chip, an organic matter-free light emitting module can be realized, The reliability as a power system light emitting module is greatly improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate.
(Example 1)
FIG. 1 is a cross-sectional view illustrating a schematic structure of the light emitting module according to the first embodiment. The light emitting module 10 includes an element mounting substrate 12, a semiconductor light emitting element 14 flip-chip mounted on the element mounting substrate 12, and a first wavelength conversion provided on the light emitting surface of the semiconductor light emitting element 14. The layer 16 and the second wavelength conversion layer 18 provided on the first wavelength conversion layer 16 are provided. Here, “provided on the layer” is not only directly provided on the layer but also indirectly provided on the layer via another member (such as an adhesive or a filter). It is also included.

The semiconductor light emitting element 14 is an LED chip having a peak wavelength λp = 405 nm. The first wavelength conversion layer 16 is a general formula ^{_{^{_{_{M 1 a (M 2 O 4}}}}} ) b X c: has a phosphor 1, represented by Re _d. The second wavelength conversion layer 18 is represented by a general formula (Ca _1-xyzw , Sr _x , M ^II _y , Eu _z , M ^R _w ) ₇ (SiO ₃ ) ₆ X ₂ . The fluorescent substance 2 is provided. The side surfaces of the stacked semiconductor light emitting element 14, first wavelength conversion layer 16, and second wavelength conversion layer 18 are covered with a light reflecting material 20.

Each of the first wavelength conversion layer 16 and the second wavelength conversion layer 18 is prepared by mixing pre-manufactured phosphor particles of sub-micron or less with an appropriate sintering aid and molding, and then adding uniaxially. Processing such as pressure molding, CIP molding, atmospheric pressure firing, HIP firing, etc. is performed, and thereafter, it is thinned and polished so as to have a thickness of 100 μm, thereby forming a translucent ceramic. In this case, _Re

d phosphors

1,2 so that the light emission color temperature of the white light emitting module is 5500K _vicinity, Sr x, the concentration of Eu _z are adjusted. Thereafter, the first wavelength conversion layer 16 and the second wavelength conversion layer 18 which are translucent ceramic phosphors were processed into thicknesses of 100 μm and 1.2 mm square, respectively. The semiconductor light emitting element 14 and the first wavelength conversion layer 16 and the first wavelength conversion layer 16 and the second wavelength conversion layer 18 are bonded with a sol-gel adhesive.

(Comparative Example 1)
FIG. 2 is a cross-sectional view illustrating a schematic structure of a light emitting module according to a comparative example. The light emitting module 22 is different from the light emitting module 10 according to the first embodiment in the configuration of the first wavelength conversion layer 24 and the second wavelength conversion layer 26. The first wavelength conversion layer 24 is obtained by dispersing the same phosphor 1 powder as in Example 1 in a silicone resin. The second wavelength conversion layer 26 is obtained by dispersing the same phosphor 2 powder as in Example 1 in a silicone resin. In this case, _Re

d phosphors

1,2 so that the light emission color temperature of the white light emitting module is 5500K _vicinity, Sr x, the concentration of Eu _z are adjusted. Thereafter, the first wavelength conversion layer 24 and the second wavelength conversion layer 26 were processed into thicknesses of 100 μm and 1.2 mm square, respectively. Silicone resin is adhered between the semiconductor light emitting element 14 and the first wavelength conversion layer 24 and between the first wavelength conversion layer 24 and the second wavelength conversion layer 26.

FIG. 3 is a diagram showing the measurement results of the transmittances of the first wavelength conversion layer 16 and the second wavelength conversion layer 18 according to the first embodiment. FIG. 4 is a diagram showing the measurement results of the transmittances of the first wavelength conversion layer 24 and the second wavelength conversion layer 26 according to Comparative Example 1. As shown in FIGS. 3 and 4, the first wavelength conversion layer 16 and the second wavelength conversion layer 18 according to Example 1 are the first wavelength conversion layer 24 and the second wavelength conversion layer according to Comparative Example 1. 26 has a higher transmittance. That is, it can be seen that the layer obtained by converting the phosphor into ceramic has higher transmittance than the layer in which the phosphor is dispersed in the resin.

FIG. 5 is a diagram showing emission spectra of the light emitting modules according to Example 1 and Comparative Example 1. As described above, each wavelength conversion layer used in Example 1 has a higher transmittance than each wavelength conversion layer used in Comparative Example 1. For this reason, in the light emitting module 10 according to Example 1, light loss due to scattering is reduced in each wavelength conversion layer. Therefore, the light emitting module 10 according to Example 1 has high emission intensity over almost the entire wavelength range.

Table 1 shows the luminous flux ratio, luminous efficiency ratio, and color temperature [K] of the light emitting modules according to the examples and comparative examples. Note that the current applied to the light emitting element is 0.7 A.

As shown in Table 1, the light emitting module 10 according to Example 1 is a highly efficient light emitting module with a luminous flux approximately 1.35 times that of the light emitting module 22 according to Comparative Example 1. Therefore, the light emitting module 10 can save power.

FIG. 6 is a diagram showing the temperature dependence of the luminous flux in the light emitting modules according to Example 1 and Comparative Example 1. In FIG. 6, the horizontal axis represents the junction temperature (Tj) of the light emitting module, and the vertical axis represents the luminous flux as a relative value.

As shown in FIG. 6, the light emitting module 10 according to Example 1 has less decrease in luminous flux as the junction temperature (Tj) increases compared to the light emitting module 22 according to Comparative Example 1. Specifically, the light emitting module 10 according to Example 1 has a luminous flux of 2.3% at Tj = 50 ° C., 6.8% at Tj = 100 ° C., compared with the light emitting module 22 according to Comparative Example 1. It is improved by 11.3% at Tj = 150 ° C. Thus, since the light emitting module 10 using the phosphor layer obtained by converting the phosphor into a ceramic as the wavelength conversion layer has high heat dissipation, it is possible to suppress a decrease in light flux accompanying a temperature rise. In other words, in the light emitting module 10, the temperature dependence of the light flux is reduced.

(Example 2)
As shown in FIGS. 3 and 4, when the first wavelength conversion layer 16 according to Example 1 and the first wavelength conversion layer 24 according to Comparative Example 1 using the phosphor 1 are compared, the ceramic layer and the sealing layer are compared. Although there is a difference in the form of a stop resin layer, there is no significant difference in transmittance. In the case of such a phosphor, even if a wavelength conversion layer in which the phosphor powder is sealed with a resin is used, the performance is hardly lowered, and the manufacturing cost can be reduced.

FIG. 7 is a cross-sectional view illustrating a schematic structure of the light emitting module according to the second embodiment. The light emitting module 28 includes the shape, size, and emission color temperature, including the first wavelength conversion layer 24 (see Comparative Example 1) in which a phosphor is dispersed in a resin. 10 is the same configuration. For the wavelength conversion layer, the first wavelength conversion layer may be prepared and cut in advance, and then the first wavelength conversion layer and the second wavelength conversion layer made of ceramics may be laminated. The wavelength conversion layer is formed by applying the uncured resin of the first wavelength conversion layer onto the semiconductor light emitting element 14 flip-chip bonded to the element mounting substrate 12 by potting or the like, and then forming a second ceramic layer. You may produce by mounting and hardening a wavelength conversion layer. Note that the manufacturing method is not limited to these.

FIG. 8 is a diagram showing emission spectra of the light emitting modules according to Example 2 and Comparative Example 1. As described above, the second wavelength conversion layer 18 used in Example 2 has a higher transmittance than the second wavelength conversion layer 26 used in Comparative Example 1. For this reason, in the light emitting module 28 according to Example 2, the light loss due to scattering is reduced particularly in the second wavelength conversion layer 26. Therefore, the light emitting module 28 according to Example 2 has high emission intensity over the entire wavelength range.

In addition, as shown in Table 1, the light emitting module 28 according to Example 2 has a luminous flux approximately 1.28 times that of the light emitting module 22 according to Comparative Example 1, which reduces the manufacturing cost and increases the manufacturing cost. It is a light emitting module that achieves both efficiency and efficiency. Further, the light emitting module 28 having high efficiency can save power.

(Example 3)
The light emitting module according to Example 3 is characterized in that the order of stacking the first wavelength conversion layer and the second wavelength conversion layer according to Example 1 is changed. FIG. 9 is a cross-sectional view illustrating a schematic structure of the light emitting module according to the third embodiment. The light emitting module 30 is implemented including the shape, size, and emission color temperature, except that the stacking order of the first wavelength conversion layer 16 and the second wavelength conversion layer 18 is opposite to that of the light emitting module 10 according to the first embodiment. The configuration is the same as that of the light emitting module 10 according to Example 1.

(Comparative Example 2)
One feature of the light emitting module according to Comparative Example 2 is that the stacking order of the first wavelength conversion layer and the second wavelength conversion layer according to Comparative Example 1 is changed. FIG. 10 is a cross-sectional view illustrating a schematic structure of a light emitting module according to Comparative Example 2. The light emitting module 32 is a comparison including the shape, size, and emission color temperature, except that the stacking order of the first wavelength conversion layer 24 and the second wavelength conversion layer 26 is opposite to that of the light emitting module 22 according to Comparative Example 1. The configuration is the same as that of the light emitting module 22 according to Example 1.

FIG. 11 is a graph showing the measurement results of the transmittance of the first wavelength conversion layer 16 and the second wavelength conversion layer 18 according to Example 3. FIG. 12 is a diagram illustrating the measurement results of the transmittances of the first wavelength conversion layer 24 and the second wavelength conversion layer 26 according to Comparative Example 1. As shown in FIGS. 11 and 12, the first wavelength conversion layer 16 and the second wavelength conversion layer 18 according to Example 3 are the same as the first wavelength conversion layer 24 and the second wavelength conversion layer according to Comparative Example 2, respectively. 26 has a higher transmittance. That is, it can be seen that the first wavelength conversion layer and the second wavelength conversion layer obtained by converting the phosphor into ceramic have higher transmittance than the layer in which the phosphor is dispersed in the resin, regardless of the stacking order.

FIG. 13 is a diagram showing emission spectra of the light emitting modules according to Example 3 and Comparative Example 2. As described above, each wavelength conversion layer used in Example 3 has a higher transmittance than each wavelength conversion layer used in Comparative Example 2. For this reason, in the light emitting module 30 according to Example 3, light loss due to scattering is reduced in each wavelength conversion layer. Therefore, the light emitting module 30 according to Example 3 has high emission intensity over almost the entire wavelength range.

Further, as shown in Table 1, the light emitting module 30 according to Example 3 has a luminous flux approximately 1.37 times that of the light emitting module 32 according to Comparative Example 2, and is a highly efficient light emitting module. is there. In addition, the light emitting module 32 with high efficiency can save power.

Example 4
FIG. 14 is a cross-sectional view illustrating a schematic structure of the light emitting module according to Example 4. One feature of the light emitting module 34 is that the light emitting module 34 further includes a third wavelength conversion layer 36 including the phosphor 2 that emits green light on the second wavelength conversion layer 18. The configuration is substantially the same as that of the light emitting module 10 according to the first embodiment. The third wavelength conversion layer 36 is formed by sealing the phosphor 2 whose general formula is represented by Ba _2-a MgSi ₂ O ₇ : Eu ²⁺ _a with _a resin.

The light emitting module 34, so that the emission color temperature of the white light emitting module is 5500K vicinity, the concentration of Re _d of the phosphor 1 in the first wavelength conversion layer 16 is adjusted, the second wavelength conversion layer 18 The concentrations of Eu _z and Sr _x of the phosphor 2 in FIG. 3 are adjusted, and the concentration of Eu ²⁺ _a of the phosphor 2 in the third wavelength conversion layer 36 is adjusted. In Example 4, the thickness of each of the first wavelength conversion layer 16 and the second wavelength conversion layer 18 is 90 μm, and the thickness of the third wavelength conversion layer 36 is 50 μm.

(Comparative Example 3)
FIG. 15 is a cross-sectional view illustrating a schematic structure of a light emitting module according to Comparative Example 3. One feature of the light emitting module 38 is that the light emitting module 38 further includes a third wavelength conversion layer 36 including the phosphor 2 that emits green light on the second wavelength conversion layer 26. The configuration is substantially the same as that of the light emitting module 22 according to Comparative Example 1. The third wavelength conversion layer 36 is formed by sealing the phosphor 2 whose general formula is represented by Ba _2-a MgSi ₂ O ₇ : Eu ²⁺ _a with _a resin.

The light emitting module 38, like the light-emitting module 34 described above, so that the light emission color temperature of the white light emitting module is 5500K vicinity, the concentration of Re _d of the phosphor 1 in the first wavelength conversion layer 24 is adjusted Then, the concentrations of Eu _z and Sr _x of the phosphor 2 in the second wavelength conversion layer 26 are adjusted, and the concentration of Eu ²⁺ _a of the phosphor 2 in the third wavelength conversion layer 36 is adjusted. In Comparative Example 3, the thickness of each of the first wavelength conversion layer 24 and the second wavelength conversion layer 26 is 90 μm, and the thickness of the third wavelength conversion layer 36 is 50 μm.

FIG. 16 is a diagram showing emission spectra of the light emitting modules according to Example 4 and Comparative Example 3. The light emitting module 34 according to Example 4 has small light loss due to scattering in each wavelength conversion layer, and has higher light emission intensity over almost the entire wavelength region than the light emitting module 38 according to Comparative Example 3.

Further, as shown in Table 1, the light emitting module 34 according to Example 4 has a luminous flux approximately 1.40 times that of the light emitting module 38 according to Comparative Example 1, and is a highly efficient light emitting module. is there. Therefore, the light emitting module 34 can save power.

Next, a more preferable configuration of the light emitting module will be described. First, the emission spectrum of the semiconductor light emitting device, the emission spectrum of each phosphor, and the excitation spectrum will be described. FIG. 17 is a diagram showing an emission spectrum of the semiconductor light emitting device according to Example 1. FIG. FIG. 18 is a diagram showing emission spectra of the phosphor 2 according to Example 1 and the conventional YAG phosphor. FIG. 19 is a diagram showing excitation spectra of the phosphor 2 according to Example 1 and a conventional YAG phosphor, and emission spectra of the phosphor 1 according to Example 1 and a conventional blue LED.

As shown in FIG. 17, the semiconductor light emitting device according to the example is an LED that emits near-ultraviolet light having a peak wavelength λp = 405 nm. Further, as shown in FIG. 18, the emission spectrum (line L1) of the phosphor 2 according to Example 1 has a blue wavelength (about 450 to 500 nm) compared to the emission spectrum (line L2) of the YAG phosphor. Range).

A line L1 shown in FIG. 19 represents an excitation spectrum of the phosphor 2 emitting yellow light used in Example 1. A line L2 indicates the excitation spectrum of the YAG phosphor. When both are compared, it can be seen that the wavelength range of the excitation light is greatly different. It can be seen that the YAG phosphor has a small excitation spectrum intensity Iy at the peak wavelength (λp = 405 nm) of ultraviolet light or short-wavelength visible light emitted from the light-emitting element, and does not emit light in the near-ultraviolet light. Therefore, in order to realize white color in combination with the YAG phosphor, a blue light emitting LED chip having an emission spectrum (line L3) characteristic as shown in FIG. 19 is required.

On the other hand, the phosphor 2 has the maximum intensity of the excitation spectrum (L1) in the wavelength region of 300 nm or more as Imax, and the intensity of the excitation spectrum in the peak wavelength (λp = 405 nm) of ultraviolet light or short wavelength visible light emitted from the light emitting element as Ia. Then, 0.2 × Imax <Ia is satisfied. Preferably, the phosphor 2 may satisfy 0.5 × Imax <Ia, and may further satisfy 0.8 × Imax <Ia as the phosphor 2 illustrated in FIG.

Thereby, since the phosphor 2 according to the example has high excitation spectrum intensity at the peak wavelength of ultraviolet light or short wavelength visible light emitted from the light emitting element, the light of the light emitting element can be efficiently converted into yellow light.

Moreover, the light emitting module which concerns on each Example emits a light emitting element by obtaining white by combining the different color (blue, yellow) each converted by multiple types of fluorescent substance (phosphor 1, phosphor 2). Compared with the case where white is obtained by combining light and light emitted from the phosphor (combination of YAG phosphor and blue LED chip), chromaticity deviation due to the light emission direction of the module is suppressed.

A line L4 shown in FIG. 19 shows an emission spectrum of the blue-emitting phosphor 1 used in Example 1. As shown in Example 1, a light emitting module in which a first wavelength conversion layer 16 including phosphor 1 is stacked on a semiconductor light emitting element 14 and a second wavelength conversion layer 18 including phosphor 2 is stacked thereon. In this case, when the blue light from the phosphor 1 of the first wavelength conversion layer 16 is wavelength-converted by the phosphor 2 of the second wavelength conversion layer 18, heat generation due to so-called Stokes loss occurs, and the light emission efficiency decreases. End up.

However, the phosphor 2 according to Example 1 has the maximum excitation spectrum intensity Imax in the wavelength region of 300 nm or more, and the excitation spectrum intensity at the peak wavelength (about 450 nm) of visible light emitted from the phosphor 1 according to Example 1. Is Ib, Ib <0.8 × Imax is satisfied. Preferably, the phosphor 2 may satisfy Ib <0.5 × Imax, and may further satisfy Ib <0.2 × Imax as the phosphor 2 illustrated in FIG. Thereby, in the phosphor 2, the absorption of light emitted from the phosphor 1 is reduced, and the Stokes loss is suppressed, so that a highly efficient light emitting module can be realized.

Here, in the white light emitting module that combines a semiconductor light emitting element that emits near-ultraviolet light and a plurality of types of phosphors, the phosphor concentration increases compared to a white LED module that combines a blue LED chip and a YAG phosphor. Tend to. This is because the light of the element is not directly used to realize the white color but is realized by the light emitted from the phosphor. For this reason, when the amount of the phosphor is large, the scattering effect by the phosphor is increased as described above, which may be a cause of a decrease in luminous efficiency.

Therefore, in the following, the configuration of a light emitting module that realizes high light emission efficiency while suppressing the phosphor concentration will be described in more detail based on the knowledge obtained in the above-described embodiment and examples.

Compared with blue and yellow, yellow has higher visibility, so the second wavelength conversion layer that emits yellow than the first wavelength conversion layer that emits blue emits light flux by arranging it on the emission surface side of the light emitting module. (See Example 1 and Example 3 in Table 1). In addition, the phosphor 2 included in the second wavelength conversion layer includes a relatively large amount of blue wavelength (in the range of about 450 to 500 nm) as described above. Therefore, the amount of blue-emitting phosphor 1 included in the first wavelength conversion layer can be reduced. In this case, it is also possible to select the first wavelength conversion layer in which the phosphor is dispersed in the resin.

Therefore, in the following, a preferred example of the thickness of each wavelength conversion layer will be described based on the configuration of the light emitting module 28 shown in Example 2. As shown in FIG. 7, in the light emitting module 28, a first wavelength conversion layer 24 in which a blue light emitting phosphor 1 is dispersed in a resin that is a transparent sealing material is laminated on a semiconductor light emitting element 14. The second wavelength conversion layer 18 in which the yellow-emitting phosphor 2 is ceramicized is laminated thereon.

When the light emitting module is used as a light source for an automobile headlamp, the color temperature of the headlamp is in the range of about 4000 to 6000K. Therefore, if the second wavelength conversion layer is a layer obtained by converting the phosphor 2 into a ceramic, and the first wavelength conversion layer is a layer in which the phosphor 1 is dispersed in a resin, in order to satisfy the light of the color temperature described above, The upper limit amount of the concentration of the phosphor 1 contained in the first wavelength conversion layer 16 is 35 vol. %. As shown in Table 2, if the amount of the phosphor necessary for satisfying a desired color temperature is constant, the concentration of the phosphor 1 contained therein decreases as the thickness of the first wavelength conversion layer increases.

The thickness of the first wavelength conversion layer is preferably in the range of 15 to 1000 μm. More preferably, the thickness is in the range of 15 to 1000 μm. If thickness is 15 micrometers or more, the quantity of fluorescent substance 1 which can implement | achieve desired color temperature can be included. On the other hand, if the thickness is 1000 μm or less, preferably 300 μm or less, light absorption and scattering inside the first wavelength conversion layer can be suppressed. The first wavelength conversion layer may contain 0.5 to 35% by volume of the phosphor 1. Thereby, the light of the light emitting element which passes through the first wavelength conversion layer and reaches the second wavelength conversion layer can be increased.

Moreover, since the light emitted from the phosphor 2 included in the second wavelength conversion layer combined with the first wavelength conversion layer contains a large amount of blue wavelength components as described above, it is included in the first wavelength conversion layer. White light can be realized even if the amount of the phosphor 1 emitting blue light is reduced. That is, since the first wavelength conversion layer can be made very thin, the first wavelength conversion layer in which the phosphor 1 is dispersed in an adhesive resin such as a silicone resin is applied on the semiconductor light emitting element, and the second wavelength conversion layer is applied. By laminating the wavelength conversion layer, the second wavelength conversion layer can be fixed to the semiconductor light emitting device. That is, the semiconductor light emitting element, the first wavelength conversion layer, and the second wavelength conversion layer 18 can be stacked in one step.

The thickness of the second wavelength conversion layer may be appropriately selected according to the configuration of the first wavelength conversion layer, and is, for example, in the range of 30 to 1000 μm, preferably 50 to 300 μm. If the thickness is 30 μm or more, it is possible to prevent cracks and the like when it is made into ceramics. On the other hand, if thickness is 1000 micrometers or less, the fall of the brightness | luminance of a light emitting module can be suppressed.

FIG. 20 is a diagram for explaining a method of measuring the chromaticity of the light emitting module. FIG. 21 is a diagram illustrating a change in chromaticity of the light emitting module depending on a measurement position.

In the light emitting module 40 shown in FIG. 20, an LED chip 46 that emits blue light or ultraviolet light is mounted on a substrate 42 via a submount 44. A fluorescent member 48 is mounted on the light emitting surface of the LED chip 46.

As shown in FIG. 21, in the light emitting module employing a blue LED chip as the LED chip 46 and a YAG phosphor as the fluorescent member 48, the change in chromaticity Cx is large depending on the measurement position. On the other hand, the UV-LED chip as the LED chip 46, the first wavelength conversion layer 24 having the phosphor 1 as the fluorescent member 48, and the second wavelength conversion layer 18 having the phosphor 2 (see Example 2). In the light emitting module adopting, the change in chromaticity Cx depending on the measurement position is very small.

The present invention has been described based on the embodiments and examples. Those skilled in the art will understand that the embodiments and examples are exemplifications, and that various modifications can be made to combinations of the respective components and processing processes, and such modifications are also within the scope of the present invention. It is where it is done.

For example, the configuration of the first and second wavelength conversion layers may be a configuration in which the phosphor is dispersed in an inorganic amorphous material or an inorganic sol-gel material, in addition to being ceramicized or dispersing the phosphor in a resin. . Examples of the inorganic amorphous material include a low melting point glass material. Examples of the inorganic amorphous material include those having a processing temperature of 900 ° C. or lower, preferably 800 ° C. or lower. In addition, an inorganic amorphous material having a transmittance of 70% or more, preferably 80% or more is preferable for light having a wavelength of 350 to 900 nm. Further, an inorganic amorphous material having a refractive index of 1.4 or more and 2.0 or less, preferably 1.6 or more and 2.0 or less is preferable.

In each of the above-described embodiments, the light emitting module is described by combining the blue phosphor and the yellow phosphor, but the color combination is not limited to these.

For example, an aspect of the light emitting module is as follows:
A light emitting element emitting ultraviolet light or short wavelength visible light;
A first wavelength conversion layer having a first phosphor excited by the ultraviolet light or short wavelength visible light and emitting visible light;
A second wavelength having a second phosphor that emits visible light having a peak wavelength longer than a peak wavelength of visible light that is excited by the ultraviolet light or short-wavelength visible light and emitted from the first phosphor. A conversion layer,
The first wavelength conversion layer and the second wavelength conversion layer are stacked on a light emitting surface of the light emitting element,
At least one of the first wavelength conversion layer and the second wavelength conversion layer is a ceramic layer.

The light emitting module of the present invention can be used for various lamps such as lighting lamps, display backlights, vehicle lamps and the like.

10 light emitting module, 14 semiconductor light emitting element, 16 first wavelength conversion layer, 18 second wavelength conversion layer, 22 light emitting module, 24 first wavelength conversion layer, 26 second wavelength conversion layer, 28, 30, 32 , 34 light emitting module, 36 third wavelength conversion layer, 38, 40 light emitting module.

Claims

A light emitting element emitting ultraviolet light or short wavelength visible light;
A first wavelength conversion layer having a first phosphor that is excited by the ultraviolet light or short-wavelength visible light and emits blue light;
A second wavelength conversion layer having a second phosphor that is excited by the ultraviolet rays or short-wavelength visible light and emits yellow light,
The first wavelength conversion layer and the second wavelength conversion layer are stacked on a light emitting surface of the light emitting element,
At least one of the first wavelength conversion layer and the second wavelength conversion layer is a ceramic layer,
The second phosphor is
Imax, the maximum intensity of the excitation spectrum in the wavelength region of 300 nm or more
When the intensity of the excitation spectrum at the peak wavelength of the ultraviolet light or short wavelength visible light emitted from the light emitting element is Ia,
A light emitting module satisfying 0.2 × Imax <Ia.
The first wavelength conversion layer is disposed between the light emitting element and the second wavelength conversion layer,
The light emitting module according to claim 1, wherein the second wavelength conversion layer is a ceramic layer.
The second phosphor is
Imax, the maximum intensity of the excitation spectrum in the wavelength region of 300 nm or more
3. The light emitting module according to claim 2, wherein Ib <0.8 × Imax is satisfied, where Ib is an intensity of an excitation spectrum at a peak wavelength of visible light emitted from the first phosphor.
4. The first wavelength conversion layer according to claim 1, wherein the first phosphor is formed by dispersing the first phosphor in a transparent sealing material and has a thickness of 15 to 1000 μm. The light emitting module according to claim 1.
The light emitting module according to claim 4, wherein the first wavelength conversion layer contains 0.5 to 35% by volume of the first phosphor.
6. The light emitting module according to claim 1, wherein the second wavelength conversion layer has a thickness of 30 to 1000 μm.