Semiconductor light emitting device and vehicle lamp including the same

Abstract

To provide a light emitting device with improved chromaticity uniformity by suppressing changes in chromaticity due to changes in the emission angle of a light emitting element that combines an LED element and a wavelength conversion member.SOLUTION: An optical multilayer film placed on the light emitting element has a transmission spectrum that monotonically increases from 0 degrees to at least 60 degrees in the peak wavelength of an LED element and from 0 degrees to at least 60 degrees in the long wavelength region (650 nm to 700 nm), with a transmittance of at least 90% at 550 nm, when the angle in the direction perpendicular to the light emitting surface is 0 degrees and the angle parallel to the light emitting surface is 90 degrees.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a semiconductor light-emitting device using a light-emitting diode (LED), and more particularly to a semiconductor light-emitting device that combines an LED with a wavelength conversion material and emits white light. [Background technology]

[0002] Semiconductor light-emitting devices that combine an LED and a wavelength conversion material to emit white light typically have a structure in which a plate made of wavelength conversion material or a layer containing wavelength conversion material is layered on the flat light-emitting surface of the LED. In light-emitting devices with this structure, the chromaticity of the light changes as the output angle becomes wider due to the difference in the optical path length from the LED output surface to the light-emitting surface of the device, i.e., the difference in the optical path length when passing through the wavelength conversion material. The change in chromaticity is strong blue near the output angle of 0 degrees, and as the angle becomes wider, the light changes to a yellowish tinge, and the chromaticity difference becomes larger.

[0003] To counter this change in chromaticity, an optical multilayer film is formed on the wavelength conversion section, and wavelength-selective light reflection by the optical multilayer film can be utilized to suppress the yellowish tint. For example, Patent Document 1 proposes that a filter layer made of an optical multilayer film is provided to partially reflect light (blue light) in the wavelength range of approximately 400 to 500 nm emitted from an LED within an emission angle (radiation angle) range of 0 to 30 degrees, thereby controlling the transmittance of blue light and making the ratio of blue light to yellow light uniform over a wide radiation angle range, thereby suppressing the yellow ring that occurs on the wide-angle side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5558483 specification Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional technologies such as Patent Document 1, as shown in Figure 21, only the transmittance of blue wavelengths near an output angle of 0 degrees is controlled, so as the angle becomes wider, a phenomenon occurs in which the wavelength shifts to the short wavelength side (blue shift), causing the transmittance of the blue wavelength band to increase significantly, making it impossible to control blue light.In addition, since the transmittance of yellow light, which becomes stronger as the angle becomes wider, cannot be controlled, the amount of chromaticity change cannot be sufficiently suppressed.

[0006] An object of the present invention is to provide a light emitting device in which a change in chromaticity due to a change in the emission angle is suppressed and chromaticity uniformity is improved. [Means for solving the problem]

[0007] The present invention solves the problems of increased yellowness and blue shift by controlling the transmittance not only in the blue wavelength region of the transmission spectrum of the multilayer film but also on the long wavelength side in a structure in which an optical multilayer film is arranged.

[0008] That is, the semiconductor light-emitting device of the present invention comprises an LED element, a light-emitting element having a wavelength converting portion that receives light emitted by the LED element and emits light of a different wavelength from the light emitted by the LED element, and emitting light that is a mixture of the light emitted by the LED element and the light emitted by the wavelength converting portion, and an optical multilayer film disposed on the light-emitting surface of the light-emitting element. The optical multilayer film has a transmission spectrum that, when the angle to the direction perpendicular to the light-emitting surface is 0° and the angle to the direction parallel to the light-emitting surface is 90°, increases monotonically over an angle range of 0° to at least 60° at the emission peak wavelength of the LED element, and also increases monotonically over an angle range of 0° to at least 60° in the long-wavelength region (650 nm to 700 nm), and has a transmittance at 550 nm of 90% or more.

[0009] The present invention also provides a vehicle lamp including the above-described semiconductor light emitting device. [Effects of the Invention]

[0010] According to the present invention, by controlling the transmittance in the blue wavelength region and the long wavelength region of the optical multilayer film placed on the light-emitting element, it is possible to suppress changes in chromaticity due to the emission angle, and to obtain highly uniform white light over a wide range of emission angles. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing the configuration of a semiconductor light-emitting device to which the present invention is applied; [Figure 2] FIG. 10 is a diagram showing the emission spectrum of a light-emitting element when an optical multilayer film is not provided. [Figure 3] Transmission spectrum of optical multilayer film [Figure 4] (A) and (B) are diagrams illustrating the angle dependence of chromaticity change. [Figure 5] A diagram explaining the effect of multilayer film in suppressing changes in chromaticity [Figure 6] (A) and (B) are diagrams explaining the blue shift. [Figure 7] Graph (A) shows the relationship between the optical thickness of the high refractive index layer and the chromaticity value at angles of 0 degrees and 60 degrees, and graph (B) shows the relationship between the optical thickness of the high refractive index layer and the amount of change in chromaticity. [Figure 8] Graph (A) shows the relationship between the optical thickness of the low refractive index layer and the chromaticity value at angles of 0 degrees and 60 degrees, and graph (B) shows the relationship between the optical thickness of the low refractive index layer and the amount of change in chromaticity. [Figure 9] 1A and 1B are diagrams showing an embodiment of a semiconductor light-emitting device according to the present invention. [Figure 10] 1 is a diagram showing the transmission spectrum of the optical multilayer film of Example 1. [Figure 11] 1A and 1B are diagrams showing the amount of change in chromaticity in the present invention and the prior art. [Figure 12] FIG. 1 is a diagram illustrating chromaticity changes in Example 1. [Figure 13] FIG. 10 is a diagram showing the transmission spectrum of the optical multilayer film of Example 2. [Figure 14] Graph showing angle dependence of chromaticity change amount in Example 2 [Figure 15] Graph showing chromaticity change in Example 2 [Figure 16] 1 is a diagram showing the transmission spectrum of the optical multilayer film of Comparative Example 1. [Figure 17] Graph showing chromaticity change in Comparative Example 1 [Figure 18] 1 is a diagram showing the transmission spectrum of the optical multilayer film of Comparative Example 2. [Figure 19] Graph showing chromaticity change in Comparative Example 2 [Figure 20] FIG. 1 is a diagram showing an example of a vehicle lamp; [Figure 21] FIG. 10 shows an example of the transmission spectrum of a conventional optical multilayer film. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the semiconductor light emitting device of the present invention will be described. 1, the semiconductor light-emitting device of the present invention has a structure in which an LED (light-emitting diode) element 10, a wavelength conversion section 20, and an optical multilayer film (hereinafter simply referred to as the multilayer film) 30 are stacked in this order. Light emitted from the LED element 10 passes through the wavelength conversion section 20, and a portion of the light emitted from the LED element 10 is wavelength-converted by the wavelength conversion section 20. The wavelength-converted light and the remaining light from the LED element 10 are mixed and enter the multilayer film 30, where it is repeatedly reflected and transmitted before being emitted from the top layer.

[0013] The multilayer film has transmittance characteristics that satisfy the following conditions for incident light, thereby improving the angle dependency of light emitted from the top layer.

[0014] Condition 1: The transmittance of the LED element at its emission peak wavelength increases gradually (monotonically) from an incident angle of 0 degrees to at least 60 degrees. Preferably, in the same wavelength range, the transmittance at 0 degrees is 50 to 70%, and the transmittance at 60 degrees is 85% or less. Condition 2: Conversely, the transmittance in the wavelength region of 650 nm to 700 nm decreases as the angle changes from 0 degrees to 60 degrees. Condition 3: The transmittance at a wavelength of 550 nm is 90% or more within the angle range of 0 to 60 degrees.

[0015] By satisfying these conditions 1 to 3, it is possible to suppress the phenomenon of a decrease in blue components at wide angles, the accompanying change in chromaticity to yellow, and the change in chromaticity from white, while maintaining high transmittance in a wavelength range with high luminosity over a wide angle range. That is, the chromaticities Cx and Cy of the CIE 1931 chromaticity system of the light emitted from the light emitting device are both in the range of 0.30 to 0.40, and the amount of change in chromaticity of the CIE 1931 chromaticity system of the emitted light is ΔCx and ΔCy However, both can be suppressed to 0.03 or less.

[0016] The above conditions 1 to 3 and the effects thereof will be described in detail below with reference to Figures 2 and 3. Figure 2 shows the emission spectrum of a light-emitting element (LED + wavelength conversion layer) without a multilayer film, and Figure 3 shows an example of the transmission spectrum of a multilayer film of the present invention. In Figures 2 and 3, differences in incident angles are represented by different line types, and Figure 3 also shows the emission spectrum for an angle of 0 degrees. In Figure 2, the emission spectra for each incident angle are normalized with the peak of the blue emission spectrum component set to 1.

[0017] As shown in Figure 2, the emission spectrum of the light-emitting element (LED + wavelength conversion layer) has a blue emission spectrum component with a peak wavelength of approximately 445 nm and a yellow emission spectrum component with a broad peak wavelength of 540 nm to 570 nm and a broad peak wavelength of 500 nm to 700 nm. Furthermore, the emission spectrum without the multilayer film exhibits a decrease in the blue component as the angle increases (due to changes in the optical path length). On the other hand, as shown in Figure 3, the transmission spectrum of the multilayer film exhibits a monotonically decreasing maximum transmittance at 60 degrees to 0 degrees at the LED's peak emission wavelength of approximately 445 nm when the angle is changed from 0 degrees to 60 degrees. The change in the transmission spectrum is also gradual, with the transmittance at 0 degrees being 50 to 70% and the transmittance at 60 degrees being 85% or less within this wavelength range (Condition 1).

[0018] Increasing the transmittance in the blue region as the angle widens in this way makes it possible to suppress the reduction in the blue component. Furthermore, because the change in transmittance from 0 to 60 degrees is monotonous and gradual, blue shift (color change) due to the angle of emission is also suppressed. The suppression of blue shift will be described in detail later.

[0019] As shown in Figure 2, the 500-700 nm wavelength component of the emission spectrum increases as the angle increases, and this increase in wavelength component generally manifests as a shift in chromaticity toward yellow. Furthermore, the 650-700 nm red wavelength component in the 500-700 nm wavelength component does not show significant change relative to the blue wavelength component, even as the angle increases. In contrast, the transmission spectrum of the optical multilayer film shows a maximum transmittance at 0 degrees in the 650-700 nm wavelength range, decreasing monotonically as the angle increases (Condition 2). Condition 2 reduces the 650-700 nm red wavelength component with increasing output angle, thereby suppressing the increase in the 500-700 nm wavelength component. This works synergistically with the control of the blue wavelength region (Condition 1) described above, suppressing changes in chromaticity and maintaining whiteness.

[0020] The change in chromaticity will be explained with reference to Figs. 4 and 5. Fig. 4 shows the change in chromaticity ( Cx The left figure (A) shows the state where a multilayer film is not provided, and the right figure (B) shows the state where a multilayer film is provided. As shown in the left figure (A), when there is no multilayer film, both the chromaticity Cx and Cy change as the output angle widens from 0 degrees, and the change in the Cy value is particularly large. In contrast, the present invention can significantly suppress the change in chromaticity, as shown in the right figure (B). Specifically, the change in chromaticity in the CIE 1931 chromaticity coordinate system ΔCx and ΔCy Both of these can be set to 0.03 or less.

[0021] In the chromaticity diagram (CIE 1931 chromaticity coordinate system) shown in Figure 5, where blue, green, and red are represented by P1, P2, and P3, respectively, without the multilayer film, as the angle becomes wider, Cx and Cy increase, causing the chromaticity to shift from white toward yellow. However, condition 1 increases the P1 component, shifting the chromaticity toward the lower left in the diagram, and condition 2 decreases the P3 component, shifting the chromaticity toward the left in the diagram, thereby suppressing the increase in Cx and Cy. Suppressing the increase in Cy suppresses the chromaticity shift toward yellow, and also keeps the chromaticity within the white color temperature range enclosed by the dotted line in the diagram (near 0.33, e.g., Cx and Cy in the range of 0.30 to 0.40).

[0022] Furthermore, the multilayer film of the present invention has a transmittance of 90% or more at a wavelength of 550 nm, regardless of the output angle (condition 3). By making the transmittance in the wavelength region with high luminosity high over a wide output angle range, it is possible to maintain high transmittance while maintaining whiteness.

[0023] In other words, while conventional technology only controlled the blue wavelength region, the optical multilayer film of the present invention controls the transmittance on both sides of the wavelength range of 650 nm to 700 nm, gradually increasing and gradually decreasing as the angle becomes wider, while maintaining a high transmittance in the central wavelength region, thereby maintaining high output efficiency for the light-emitting device as a whole and effectively suppressing the blue shift that occurs as the angle becomes wider, thereby preventing the light from becoming yellowish.

[0024] Next, satisfy the above conditions 1 to 3. optical multilayer film The configuration will be explained. An optical multilayer film has a structure in which multiple optical layers with different refractive indices are stacked. The low refractive index layers are made of transparent dielectrics with a refractive index of 1.6 or less, such as SiO2 or MgF2, while the high refractive index layers are made of materials with a refractive index of 1.6 or more, such as TiO2, Al2O3, ZrO2, HfO2, Nb2O5, BaTi2O5, or Ta2O5.

[0025] The multilayer film has an alternating laminate structure of low-refractive index materials and high-refractive index materials, with a refractive index difference of preferably 0.6 to 1.0 (550 nm). A typical example of a combination that achieves such a refractive index difference is SiO2 / Nb2O5. When a low-refractive index layer is disposed as the uppermost layer on the light-emitting side, a structure in which a low-refractive index layer is disposed as the lowermost layer and high-refractive index layers and low-refractive index layers are disposed alternately is preferred.

[0026] The number of layers in the optical multilayer film is 9 or less, preferably 7 or less, and most preferably 5. Generally, multilayer films combined with LEDs have a large number of layers (for example, about 10 to 30) to suppress "waviness" that occurs in the transmission spectrum, but in the present invention, by reducing the number of layers compared to general multilayer films, specifically by setting it to 9 or less, it is possible to suppress the shift of the transmission spectrum to the short wavelength side for each angle (so-called blue shift), and it becomes easier to adjust the chromaticity.

[0027] The blue shift is a phenomenon that occurs when the apparent film thickness changes as the angle of light becomes wider, and the degree of blue shift increases as the number of layers increases and the film thickness increases. With reference to Figure 6, we will explain how the present invention suppresses the blue shift.

[0028] 6(A) and (B) are graphs (partially enlarged) showing examples of transmission spectra of multilayer films with different numbers of layers, with (A) being the transmission spectrum of a five-layer multilayer film and (B) being the transmission spectrum of a nine-layer multilayer film made of the same layer-constituting materials as (A). These graphs show the blue shift at the 70% position in the wavelength at which transmittance begins. The wavelength serving as the reference for the blue shift is the blue peak position in the pseudo-white spectrum (the spectrum of white light obtained by combining an LED and a wavelength conversion section), which is 420 nm to 460 nm, preferably 440 nm to 455 nm.

[0029] 6(B), in the transmission spectrum of a multilayer film with a relatively large number of layers, undulations occur after the rise of the transmission spectrum, and the amount of shift with changes in the output angle is large, but in the transmission spectrum of (A), the rise of the transmission spectrum is gentler, and the blue shift at the 70% transmittance position is significantly smaller than that of the transmission spectrum of (B). In other words, in conventional multilayer films with a large number of layers, the blue shift is large, making it impossible to adjust the chromaticity in the blue wavelength region at wide angles, but the blue shift can be reduced by the present invention, and in combination with condition 1 above, it becomes easier to adjust the chromaticity.

[0030] The thickness (optical film thickness) of the thin films that make up the optical multilayer film can be determined from the correlation between the chromaticity value and the optical film thickness. The optical film thickness (FWOT) is calculated by dividing the physical film thickness by d and Membrane materials The film thickness is defined as nd / λ, where n is the refractive index of the optical multilayer film. λ is the central wavelength of the reflection wavelength band of the optical multilayer film. λ is selected from the range of 400 nm or more and the blue light emission peak wavelength range (in this embodiment, approximately 475 nm or less, which is the long wavelength end of the blue light emission peak), preferably the blue light emission peak wavelength or less (in this embodiment, approximately 445 nm or less, which is the blue light emission peak wavelength).

[0031] Fig. 7 shows the relationship (A) between each optical thickness of the high refractive index layer and the chromaticity value (Cx, Cy) and the relationship (B) between each optical thickness and the amount of chromaticity change (ΔCx, ΔCy), and Fig. 8 shows the relationship (A) between each optical thickness of the low refractive index layer and the chromaticity value (Cx, Cy) and the relationship (B) between each optical thickness and the amount of chromaticity change (ΔCx, ΔCy). In Fig. 7(A) and Fig. 8(A), the four graphs show the Cx and Cy values ​​at angles of 0 degrees and 60 degrees, respectively, and the two graphs in Fig. 7(B) and Fig. 8(B) show the Cx and Cy values ​​at angles of 0 degrees and 60 degrees, respectively. ΔCx , ΔCy. The illustrated example shows a five-layer structure using Nb2O5 as the high refractive index material and SiO2 as the low refractive index material.

[0032] When the optical thickness of the high-refractive index layer and the low-refractive index layer is changed from 0.25 to 1.0, the chromaticity value changes as shown in Figures 7(A) and 8(A), respectively, and the amount of chromaticity change changes as shown in Figures 7(B) and 8(B), respectively. As described above, the chromaticity value of the light-emitting device of this embodiment is around 0.33 (in the range of 0.30 to 0.40), where the chromaticity of Cx and Cy is white, and the amount of chromaticity change (ΔCxCy) is preferably 0.03 or less. Therefore, based on the graphs shown in Figures 7 and 8, the optical thickness of the high-refractive index layer and the low-refractive index layer can be determined within a range that satisfies the chromaticity value and the amount of chromaticity change.

[0033] Specifically, it was found that in order to satisfy the chromaticity conditions, it is preferable that the optical thickness of the high refractive index layer is 0.70 to 0.85 FWOT and the optical thickness of the low refractive index layer is 0.7 to 0.9 FWOT. However, the optical thickness is determined based on the correlation with the chromaticity value and is not limited to the above range. When the material or layer structure is different, the suitable optical thickness can be determined based on the above-mentioned conditions of chromaticity and chromaticity change amount.

[0034] The transmission spectrum and structural characteristics of the optical multilayer film have been described above. Next, the configuration of a semiconductor light emitting device including the above-described optical multilayer film and each element constituting the semiconductor light emitting device will be described.

[0035] 1, the semiconductor light emitting device has a basic structure in which an LED element 10, a wavelength conversion section 20, and an optical multilayer film 30 are laminated in this order. The LED element 10 and the wavelength conversion section 20 are collectively referred to as a light emitting element 50.

[0036] The LED element 10 is an element that emits light mainly in the blue wavelength region, and can be made of known materials such as nitride-based semiconductors such as (Al, Ga, In)N, and the emission wavelength varies depending on the ratio of Al, Ga, and In in the materials that make up the active layer. In this embodiment, an LED with a peak in the blue region of the emission spectrum (for example, a range of 420 nm to 460 nm) is used, although this is not limited thereto.

[0037] The wavelength conversion section 20 is made of a material that absorbs the light emitted by the LED element 10 and emits light of a different wavelength from the light emitted by the LED element 10. Specifically, a wavelength conversion material that contains phosphor particles that convert part of the blue light into yellow light and has light scattering properties can be used. As the wavelength conversion material, for example, YAG (yttrium aluminum garnet, Y3Al5O 12 ):YAG phosphors, such as (Ba,Sr)2SiO4:Eu 2+ Known phosphors such as BOS-based phosphors, typified by the following, can be used. The wavelength conversion section 20 can be in the form of a resin layer containing these phosphor particles, a transparent body containing light-converting nanoparticles, or the like. In this embodiment, although not limited thereto, the wavelength conversion material is excited by the light emitted by the LED element 10 and emits light having a peak wavelength of 540 nm to 570 nm.

[0038] The wavelength converting material converts the wavelength of part of the light incident on the wavelength converting section 20 from the LED element 10, and transmits the remainder. As a result, the light from the LED element 10 and the wavelength-converted light are mixed and emitted from the wavelength converting material. White light can be obtained by appropriately combining the emission wavelength of the LED element 10 with the wavelength of the wavelength-converted light. In this embodiment, a blue LED element having a peak in the range of 420 nm to 460 nm is combined with a wavelength converting material having a peak in the range of 540 nm to 570 nm, but other wavelength converting materials can also be added.

[0039] The multilayer film 30 described above is disposed on the upper surface of the light emitting element 50, which is a combination of the LED element 10 and the wavelength conversion section 20. Part of the blue light emitted from the light emitting element 50 is reflected by the multilayer film 30, and the transmittance increases as the incident angle to the multilayer film increases within the emission angle range of 0 to 60 degrees. The light reflected by the multilayer film is scattered after entering the wavelength conversion member and converted into blue light and yellow light, and part of it re-enters the multilayer film, but the blue light is emitted with a higher transmittance as the incident angle increases.

[0040] Due to the characteristics of the transmission spectrum of the optical multilayer film, the light emitting device of the present invention can emit white light with reduced change in chromaticity depending on the emission angle.

[0041] Next, specific embodiments of the semiconductor light emitting device will be described with reference to Figures 9(A) and 9(B). The semiconductor light emitting device of embodiment 1 shown in Figure 9(A) comprises a blue-emitting LED element 10, a wavelength conversion section 20 disposed thereon, and an optical multilayer film 30 formed on the wavelength conversion section 20, with the uppermost surface of the optical multilayer film 30 being the light emitting surface.

[0042] The wavelength conversion unit 20 of this embodiment is, for example, a ceramic plate made by firing alumina and YAG phosphor at high temperature, and has a refractive index of 1.8. The multilayer film-forming surface of the wavelength conversion member made of a ceramic plate is preferably subjected to a planarization process such as polishing. On the other hand, the surface of the wavelength conversion member made of a ceramic plate opposite the multilayer film-forming surface is preferably a sintered surface without planarization. The wavelength conversion unit 20 is mounted on the LED element 10 via an adhesive layer such as resin. Note that a single crystal phosphor can also be used as the wavelength conversion unit 20 instead of the ceramic plate.

[0043] The optical multilayer film 30 is formed by alternately laminating low-refractive index layers and high-refractive index layers directly on the wavelength conversion unit (ceramic plate) 20 using a known film-forming method such as electron beam sputtering. The multilayer film has an odd number of layers, as shown on the right side of FIG. 9(A), with the first layer in contact with the ceramic plate 20 and the top layer being low-refractive index layers, and high-refractive index layers being disposed between the low-refractive index layers. In the first embodiment shown in FIG. 9(A), the low-refractive index layers are made of SiO2 (n=1.46), and the high-refractive index layers are made of Nb2O5 (n=2.33), resulting in a five-layer multilayer film.

[0044] The top layer functions as an adjustment layer for extracting light, and is referred to here as the adjustment layer to distinguish it from the other low-refractive-index layers. The thickness (physical thickness) d of each layer excluding the adjustment layer is 100 nm to 150 nm for the low-refractive-index layers and 200 nm to 300 nm for the high-refractive-index layers. The optical thickness (FWOT = d * n / λ), taking into account the refractive index n and the wavelength of light λ, is 0.7 to 0.9 at λ = 410. The physical thickness of the top layer is 100 nm or less, and the optical thickness is 0.4 or less.

[0045] As mentioned above, by setting both the low refractive index material and the high refractive index material to around 0.75FWOT, it is possible to obtain characteristics that suppress the amount of chromaticity change due to angle.

[0046] The semiconductor light-emitting device of embodiment 2 shown in Figure 9(B) includes a blue-emitting LED element 10, a wavelength conversion material-containing resin layer (= wavelength conversion section 20, hereinafter referred to as wavelength conversion layer 25) stacked thereon, a plate (hereinafter referred to as glass plate) 40 made of a transparent material such as glass, and an optical multilayer film 30, the top surface of which is the light-emitting surface.

[0047] The wavelength conversion layer 25 is made by dispersing glass beads and YAG phosphor particles in a transparent resin such as a silicone resin, and is formed by coating the surface of the LED 10. For example, the refractive index of the wavelength conversion layer used in this embodiment is 1.82.

[0048] The glass beads define the film thickness of the wavelength conversion layer 25. The film thickness is adjusted based on the conversion efficiency of the wavelength conversion layer 25, which absorbs light from the LED 10 and converts its wavelength, and is not particularly limited, but is about 7 μm to 40 μm. The particle diameter of the phosphor particles is preferably 40 μm or less. 30 μm More preferably, it is:

[0049] The glass plate 40 defines the shape of the surface (light emitting side) of the wavelength conversion layer 25, and also functions as a substrate for the optical multilayer film 30. The thickness of the glass plate 40 is not limited, but is about 0.1 mm to 0.5 mm.

[0050] The optical multilayer film 30 is similar to the optical multilayer film of the first embodiment, except that it is formed on a glass plate 40 .

[0051] The elements constituting the semiconductor light-emitting device of the present invention have been described above. However, for the purpose of mounting, the semiconductor light-emitting device may also include means such as lead wires for supplying power to the LED, members for supporting or holding the LED / wavelength conversion section / optical multilayer film, and known accessories, and light-emitting devices including such members are also encompassed by the present invention.

[0052] The semiconductor light-emitting device of the present invention can be used in all applications where it is desired to eliminate the yellowish color unevenness that occurs in the light emitted from LEDs as it moves from the center to the outside, such as in headlamps and other vehicle lighting fixtures and lighting equipment.

[0053] FIG. 20 shows a schematic side view of a headlamp 60 as an example of a vehicle lamp. The headlamp 60 includes a semiconductor light-emitting device 61, a concentrating reflector 62, a projection lens 63, and a shade 64. The semiconductor light-emitting device 61 is the semiconductor light-emitting device of the present invention described above, and includes an LED, a wavelength conversion unit, and an optical multilayer film. The semiconductor light-emitting device 61 emits light DL within a predetermined angular range. The concentrating reflector 62 is, for example, an elliptical reflecting surface. The concentrating reflector 62 concentrates the light DL emitted from the semiconductor light-emitting device 61, which is disposed at a first focal point F1, to generate concentrating light FL that is concentrated at a second focal point F2. The projection lens 63 projects the concentrating light FL from the concentrating reflector 62 to generate projection light PL. The shade 64 includes a mirror surface and is disposed near the second focal point F2. The shade 64 blocks a portion of the concentrating light FL at its front edge on the projection lens 63 side.

[0054] The headlamp 60 having such a configuration forms a light distribution pattern for passing vehicles (so-called low beam) having a cut-off line at the upper end by inverting and projecting the light source image of the semiconductor light emitting device 61, which is defined by the end of the shade 64 arranged at the second focal point F2, using the projection lens 63. According to the vehicle lamp (headlamp 60 in this case), by employing the semiconductor light emitting device 61 of the present invention as the light emitting element, the light source image and Light distribution Color unevenness in the pattern can be suppressed. [Example]

[0055] Example 1 In the LED package having the configuration shown in FIG. 9(A), a multilayer film having the following configuration was formed on the wavelength conversion member to manufacture the light emitting device of Example 1. [Table 1]

[0056] Figure 10 shows the transmission spectrum of this multilayer film when the incident angle of light is changed in 15-degree increments. This transmission spectrum was calculated by subtracting the emission spectrum without the multilayer film from the emission spectrum after the multilayer film was formed. Figure 10 shows that the multilayer film of this example has a transmittance of 60% or more at an angle of 0 degrees in the blue emission wavelength range (400 nm to 470 nm), and the transmittance gradually increases as the angle increases, allowing the blue component that decreases as the angle becomes wider to be adjusted by the increase in transmittance. Furthermore, in the wavelength range above 600 nm, the transmittance gradually decreases as the angle changes from 0 degrees to 60 degrees, thereby adjusting the chromaticity.

[0057] Fig. 11(A) shows the change in chromaticity (Cx, Cy) with angle (ΔCx, ΔCy) measured for the light-emitting device after laminating the multilayer film of Example 1, and (B) shows the change in chromaticity for a conventional light-emitting device. In Fig. 11, the values ​​of ΔCx and ΔCy are the numerical values ​​of the change in chromaticity for light within ±80 degrees.

[0058] As shown in Figure 11(B), in the conventional light-emitting device, the change in Cx (dotted line) is relatively small, but the change in Cy value (solid line) with the radiation angle is large, and chromaticity is not sufficiently controlled. In contrast, in graph (A) of Example 1, the change in chromaticity with angle for both Cx and Cy is suppressed, and it can be seen that uniform chromaticity is achieved regardless of angle.

[0059] FIG. 12 also shows the chromaticity change with angle of the light-emitting device of Example 1. FIG. 12 is a graph of the chromaticity change at 5-degree intervals when the output angle is changed from 0 degrees to 80 degrees. The lower left of the broken line represents an output angle of 0 degrees, and the upper right represents an incident angle of 80 degrees, with plots at 5-degree intervals connected by lines. From an incident angle of 0 degrees to 40 degrees, Cx and Cy increase, from 40 degrees to 65 degrees, at least one of Cx and Cy decreases, and from 65 degrees to 80 degrees, Cx and Cy increase again. The difference between the Cx and Cy values ​​was greatest at an output angle of 0 degrees and an output angle of 80 degrees. The difference in Cx value between an output angle of 0 degrees and an output angle of 80 degrees was 0.004, and the difference in Cy value was 0.008. That is, the difference in both the Cx and Cy values ​​was suppressed to 0.01 or less over a wide range from an output angle of 0 degrees to an output angle of 80 degrees. In the graph, a large chromaticity coordinate distance between an output angle of 0 degrees and an output angle of 80 degrees indicates a large change, but the broken line in the graph having a chromaticity turning point, or more preferably, a curved line in the graph having a rotating portion, indicates that the change in chromaticity value due to the output angle is effectively suppressed. The graph shown in Figure 12 has a curved line with a rotating portion, and it can be seen that Example 1 has a small change in chromaticity.

[0060] Furthermore, the transmission spectrum of Example 1 (FIG. 10) maintains a transmittance spectrum of 90% or more at 550 nm, which indicates that the luminosity is high and brightness is maintained.

[0061] <Example 2> In the LED package having the configuration shown in FIG. 9(B), a multilayer film having the following configuration was formed on the glass plate 40 above the wavelength conversion layer 25, thereby producing a light emitting device of Example 2. [Table 2]

[0062] The transmission spectrum of this multilayer film when the angle of incidence of light is changed in 15-degree increments is shown in Fig. 13. Like the multilayer film of Example 1, the multilayer film of Example 2 also satisfies conditions 1 to 3 of the present invention, and it was confirmed that as the angle becomes wider, the transmittance of the blue component in the blue wavelength region increases and the transmittance in the long wavelength region decreases, thereby adjusting the change in chromaticity, and that high transmittance is ensured at 550 nm.

[0063] For the light emitting device of Example 2, the change (ΔCx, ΔCy) in chromaticity (Cx, Cy) with angle was measured by changing the emission angle from 0 degrees to 80 degrees, and the change in chromaticity with angle is shown in Fig. 14 and Fig. 15. As shown in Fig. 14, the difference in Cx value between an emission angle of 0 degrees and an incident angle of 80 degrees is 0.002, and the difference in Cy value is 0.002. As shown in Figure 15, the chromaticity (Cx, Cy) values ​​measured at 5-degree intervals for the output angle were (0.330, 0.342) at 0 degrees, (0.329, 0.343) at 20 degrees, (0.329, 0.342) at 40 degrees, (0.329, 0.342) at 45 degrees, (0.330, 0.341) at 55 degrees, (0.331, 0.341) at 60 degrees, (0.329, 0.340) at 75 degrees, and (0.336, 0.354) at 80 degrees. The difference in Cx and Cy values ​​was greatest at output angles of 75 degrees and 80 degrees. The difference in Cx and Cy values ​​at output angles of 75 degrees and 80 degrees was 0.007, and the difference in Cy values ​​was 0.014.

[0064] It can be seen that in this example, the chromaticity change was suppressed to 0.02 or less for both Cx and Cy over a wide angular range. Furthermore, within the emission angle range of 0 to 60 degrees, the difference in Cx value was 0.002 (emission angles of 35 and 60 degrees), and the difference in Cy value was 0.002 (emission angles of 20 and 60 degrees), demonstrating extremely suppressed chromaticity differences. Furthermore, as shown in the chromaticity diagram in Figure 15, the locus showing the chromaticity change also has folding and rotating sections, indicating minimal chromaticity change, and that the chromaticity remains within the white range (0.30 to 0.40) over a wide angular range.

[0065] <Comparative Example 1> A light emitting device of Comparative Example 1 was manufactured using the same LED package structure as in Example 1, but with the multilayer film having the following different configuration. [Table 3]

[0066] The transmission spectrum of this multilayer film is shown in FIG. 16, and the chromaticity change is shown in FIG. 17. As can be seen from the transmission spectrum in FIG. 16, the transmittance of the multilayer film of Comparative Example 1 in the blue emission peak wavelength region increases monotonically from 0 to 45 degrees, but decreases at 60 degrees. This indicates that the multilayer film does not gradually (monotonically) increase from an incident angle of 0 degrees to at least 60 degrees. Furthermore, as can be seen from the transmission spectrum in FIG. 16, the multilayer film of Comparative Example 1 has a transmittance of over 90% in the blue wavelength region (450 nm) at an angle of 0 degrees, making it difficult to adjust the amount of chromaticity change with angle for blue light. The chromaticity change trace in FIG. 17 also shows a nearly linear change, indicating a large chromaticity change with angle. The difference in Cx value between an output angle of 0 degrees and an output angle of 80 degrees was 0.022, and the difference in Cy value was 0.036. The difference in Cx value was greatest between an output angle of 15 degrees and an output angle of 75 degrees. The difference in Cx value between the 15 degree and 75 degree output angles was 0.023. The difference in Cy value was greatest between the 20 degree and 80 degree output angles. The difference in Cx value between the 20 degree and 80 degree output angles was 0.045.

[0067] It has been found that when the optical thickness of the multilayer film is thin, the transmission spectrum at each angle tends to shift toward the short wavelength side, making it difficult to adjust the chromaticity in the blue region.

[0068] <Comparative Example 2> A multilayer film was designed with the same film-forming materials as in Example 1, with nine layers, and transmission spectra (calculated values) were obtained when the incident angle was changed from 0 degrees to 60 degrees in 15-degree increments. [Table 4]

[0069] As shown in Figure 18, the transmission spectrum of the multilayer film of Comparative Example 2 shows a steep change in transmittance in the blue wavelength region, with a large change in transmittance depending on the angle (blue shift). The spectrum also shows a large undulation in the wavelength region of 450 nm or more. Therefore, with the multilayer film of Comparative Example 2, it is not possible to eliminate the blue shift that occurs as the angle becomes wider, and it is difficult to adjust the chromaticity change depending on the angle. The results of Example 1 and Comparative Example 2 show that as the number of layers increases, it becomes difficult to realize the light-emitting device of the present invention (a light-emitting device that satisfies conditions 1 to 3), and that five layers is the optimal number of layers.

[0070] Figure 19 shows the chromaticity change of the light-emitting device using the multilayer film of Comparative Example 2. In Comparative Example 2, although the chromaticity change graph has a turning point, the change turns back significantly from the starting point (output angle of 0 degrees) to the region where the Cy value is small, indicating insufficient chromaticity adjustment. The difference in Cx value between the output angle of 0 degrees and the output angle of 80 degrees was 0.007, and the difference in Cy value was 0.014. The difference in Cx value and Cy value was greatest between the output angle of 45 degrees and the output angle of 75 degrees. The difference in Cx value between the output angle of 45 degrees and the output angle of 75 degrees was 0.011, and the difference in Cy value was 0.022.

[0071] From the results of the above examples, it was confirmed that by controlling the transmittance of the blue region to increase as the angle becomes wider while maintaining it within an appropriate range, controlling the transmittance of the long wavelength region to decrease as the angle becomes wider, and maintaining the transmittance of wavelengths with high luminosity at 90% or more, it is possible to suppress changes in chromaticity due to the emission angle, suppress blue shift, and maintain the amount of light emitted in the region with high luminosity. [Explanation of symbols]

[0072] 10: LED element, 20: wavelength conversion portion, 25: wavelength conversion layer (wavelength conversion portion), 30: optical multilayer film, 40: glass plate, 50: light emitting element (not including multilayer film), 60: headlamp (vehicle lamp), 61: semiconductor light emitting device, 62: light collecting reflector, 63: projection lens, 64: shade

Claims

1. A semiconductor light emitting device comprising: an LED element; a light emitting element having a wavelength converting section that receives light emitted by the LED element and emits light having a wavelength different from that of the light emitted by the LED element, and that emits light that is a mixture of the light emitted by the LED element and the light emitted by the wavelength converting section; and an optical multilayer film disposed on a light emitting surface of the light emitting element, the emission spectrum of light emitted by the light-emitting element comprises a blue emission spectrum component having an emission peak wavelength in the range of 420 nm to 460 nm, and a yellow emission spectrum component having a peak wavelength in the range of 540 nm to 570 nm and consisting of a broad peak over the range of 500 nm to 700 nm; The optical multilayer film has a transmission spectrum in which, when the emission angle in the direction perpendicular to the light emission surface is 0 degrees and the emission angle in the direction parallel to the light emission surface is 90 degrees, the transmittance at the blue emission peak wavelength of the LED element monotonically increases in a range of 0 degrees to at least 60 degrees, and the transmittance at 550 nm monotonically decreases in a range of 650 nm to 700 nm in a range of 0 degrees to at least 60 degrees, and the transmittance at 550 nm is 90% or more.

2. 2. The semiconductor light emitting device according to claim 1, A semiconductor light-emitting device characterized in that the transmission spectrum of the optical multilayer film has a transmittance of 50% or more and 70% or less at an angle of 0 degrees at the blue emission peak wavelength of the LED element, and a transmittance of 85% or less at an angle of 60 degrees.

3. 3. The semiconductor light emitting device according to claim 1, A semiconductor light emitting device characterized in that the chromaticity Cx and Cy of the emitted light in the CIE 1931 chromaticity system are both in the range of 0.30 to 0.

40.

4. 4. The semiconductor light emitting device according to claim 1, A semiconductor light emitting device, characterized in that the chromaticity changes ΔCx and ΔCy of emitted light in the CIE 1931 chromaticity system are both 0.03 or less.

5. 5. The semiconductor light emitting device according to claim 1, The optical multilayer film is a film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately stacked, and the number of layers is 9 or less.

6. 6. The semiconductor light emitting device according to claim 5, The semiconductor light emitting device has a refractive index difference between the high refractive index layer and the low refractive index layer of 0.6 to 1.

0.

7. 7. The semiconductor light emitting device according to claim 5, The optical multilayer film has a high refractive index layer with an optical thickness of 0.7 to 0.85 at the center wavelength λ.

8. 8. The semiconductor light emitting device according to claim 5, The semiconductor light emitting device has an optical film thickness of 0.7 to 0.9 at the center wavelength λ of the optical multilayer film, the low refractive index layer (excluding the uppermost layer of the optical multilayer film).

9. A vehicle lamp comprising the semiconductor light emitting device according to claim 1 as a light source.

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