Semiconductor light emitting device and vehicle light having 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 particularly to a semiconductor light-emitting device that combines an LED and a wavelength conversion material to emit white light.

Background Art

[0002] A semiconductor light-emitting device configured to emit white light by combining an LED and a wavelength conversion material usually has a structure in which a plate made of a wavelength conversion material or a layer containing a wavelength conversion material is stacked on a flat light-emitting surface of the LED. In a light-emitting device having this structure, due to the difference in the optical path length from the LED emission surface to the light-emitting surface of the light-emitting device, that is, the difference in the optical path length when passing through the wavelength conversion material, a phenomenon occurs in which the chromaticity of light changes as the emission angle becomes wide. Regarding this change in chromaticity, an optical multilayer film is formed on the wavelength conversion portion, and by utilizing wavelength-selective light reflection by the optical multilayer film, it becomes possible to suppress yellowing. For example, in Patent Document 1, a filter layer made of an optical multilayer film is provided so as to partially reflect light (blue light) in the wavelength range of about 400 to 500 nm emitted from the LED in the range of an emission angle (radiation angle) of 0 degrees to 30 degrees, and the transmittance of blue light is controlled, and the ratio of blue light and yellow light is made uniform in a wide radiation angle range to suppress the yellow ring generated on the wide-angle side.

[0003] Regarding this change in chromaticity, an optical multilayer film is formed on the wavelength conversion portion, and by utilizing wavelength-selective light reflection by the optical multilayer film, it becomes possible to suppress yellowing. For example, in Patent Document 1, a filter layer made of an optical multilayer film is provided so as to partially reflect light (blue light) in the wavelength range of about 400 to 500 nm emitted from the LED in the range of an emission angle (radiation angle) of 0 degrees to 30 degrees, and the transmittance of blue light is controlled, and the ratio of blue light and yellow light is made uniform in a wide radiation angle range to suppress the yellow ring generated on the wide-angle side.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in conventional technologies such as those described in Patent Document 1, as shown in Figure 21, only the transmittance of blue wavelengths near an emission angle of 0 degrees is controlled. As the angle widens, a phenomenon called blue shift occurs where the wavelength shifts to shorter wavelengths, causing a significant increase in the transmittance of the blue wavelength band, making it impossible to control blue light. Furthermore, since the transmittance of yellow light, which becomes stronger as the angle widens, cannot be controlled, the amount of chromaticity change cannot be sufficiently suppressed.

[0006] The present invention aims to provide a light-emitting device that suppresses changes in chromaticity due to changes in emission angle and improves the uniformity of chromaticity. [Means for solving the problem]

[0007] This invention solves the problems of increased yellowness and blue shift in a structure in which optical multilayer films are arranged, by controlling the transmittance not only in the blue wavelength region but also on the longer wavelength side of the transmission spectrum of the multilayer film.

[0008] In other words, the semiconductor light-emitting device of the present invention comprises an LED element and a wavelength conversion unit that receives light emitted from the LED element and emits light with a different wavelength from that light, and an optical multilayer film disposed on the light-emitting surface of the light-emitting element. The optical multilayer film has a transmission spectrum in which, when the angle perpendicular to the light-emitting surface is 0 degrees and the angle parallel to the light-emitting surface is 90 degrees, the emission peak wavelength of the LED element increases monotonically from 0 degrees to at least 60 degrees, the long wavelength region (650 nm to 700 nm) increases monotonically from 0 degrees to at least 60 degrees, and the transmittance at 550 nm is 90% or more.

[0009] Furthermore, the present invention provides a vehicle light fixture equipped with the semiconductor light-emitting device described above. [Effects of the Invention]

[0010] According to the present invention, by controlling the transmittance of the blue wavelength region and the long wavelength region of the optical multilayer film placed on the light-emitting element, changes in chromaticity due to the emission angle are suppressed, and highly uniform white light can be obtained over a wide emission angle range. [Brief explanation of the drawing]

[0011] [Figure 1] Diagram showing the configuration of a semiconductor light-emitting device to which the present invention is applied. [Figure 2] This figure shows the emission spectrum of a light-emitting element when no optical multilayer film is arranged. [Figure 3] A diagram showing the transmission spectrum of an optical multilayer film. [Figure 4] (A) and (B) are diagrams illustrating the angular dependence of chromaticity change. [Figure 5] A diagram illustrating the effect of multilayer coatings on suppressing changes in chromaticity. [Figure 6] (A) and (B) are diagrams illustrating the blue shift. [Figure 7] (A) is a graph showing the relationship between the optical film thickness of the high refractive index layer and the chromaticity value at angles of 0 and 60 degrees, and (B) is a graph showing the relationship between the optical film thickness of the high refractive index layer and the amount of chromaticity change. [Figure 8] (A) is a graph showing the relationship between the optical film thickness of the low refractive index layer and the chromaticity value at angles of 0 and 60 degrees, and (B) is a graph showing the relationship between the optical film thickness of the low refractive index layer and the amount of chromaticity change. [Figure 9] (A) and (B) are diagrams showing embodiments of the semiconductor light-emitting device of the present invention. [Figure 10] Figure showing the transmission spectrum of the optical multilayer film of Example 1. [Figure 11] (A) and (B) are diagrams showing the chromaticity change amounts of the present invention and the prior art. [Figure 12] Diagram illustrating the chromaticity change in Example 1 [Figure 13] Figure showing the transmission spectrum of the optical multilayer film of Example 2. [Figure 14] Graph showing the angular dependence of chromaticity change in Example 2 [Figure 15] Graph showing the chromaticity change in Example 2 [Figure 16] Figure showing the transmittance spectrum of the optical multilayer film of Comparative Example 1 [Figure 17] Graph showing the chromaticity change of Comparative Example 1 [Figure 18] Figure showing the transmittance spectrum of the optical multilayer film of Comparative Example 2 [Figure 19] Graph showing the chromaticity change of Comparative Example 2 [Figure 20] Figure showing an example of a vehicle lamp [Figure 21] Figure showing an example of the transmittance spectrum of a conventional optical multilayer film

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the semiconductor light-emitting device of the present invention will be described. As shown in FIG. 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 unit 20, and an optical multilayer film (hereinafter simply abbreviated as a multilayer film) 30 are stacked in this order. The light emitted from the LED element 10 passes through the wavelength conversion unit 20, and a part of the light emitted from the LED element 10 is wavelength-converted by the wavelength conversion unit 20. The light obtained by mixing the wavelength-converted light and the remaining light from the LED element 10 is incident on the multilayer film 30 and is emitted from the uppermost layer while repeating reflection and transmission within the multilayer film 30.

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

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

[0015] By satisfying these conditions 1 to 3, it is possible to maintain high transmittance in the wavelength range with high visual sensitivity over a wide angular range, while suppressing the phenomenon of a decrease in the blue component at wide angles, the resulting change in chromaticity towards yellow, and the change in chromaticity from white. Specifically, the chromaticity Cx and Cy of the CIE1931 chromaticity system of the light emitted from the light-emitting device are both in the range of 0.30 to 0.40, and the change in chromaticity ΔCy and Δy of the CIE1931 chromaticity system of the emitted light can both be suppressed to 0.03 or less.

[0016] The conditions 1 to 3 and their effects will be explained 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 the multilayer film of the present invention. In Figures 2 and 3, the difference in incident angle is represented by the difference in line type, 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 shown normalized with the peak of the blue emission spectral 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 spectral component consisting of a peak with a peak wavelength of approximately 445 nm, and a yellow emission spectral component consisting of a broad peak with a peak wavelength of 540 nm to 570 nm, extending from 500 nm to 700 nm. Furthermore, in the emission spectrum without the multilayer film, the blue component decreases as the angle widens (due to the change in optical path length). On the other hand, as shown in Figure 3, when the angle is changed from 0 degrees to 60 degrees, the transmittance at approximately 445 nm, which is the peak emission wavelength of the LED, decreases monotonically from 60 degrees to a maximum of 0 degrees, and the change in the transmission spectrum is gradual. The transmittance at 0 degrees in this wavelength range is 50-70%, and the transmittance at 60 degrees is 85% or less (Condition 1).

[0018] By increasing the transmittance in the blue region as the angle of view widens, the decrease in the blue component can be suppressed. Furthermore, because the change in transmittance from 0 to 60 degrees is monotonous and gradual, the blue shift (color change) due to the emission angle is also suppressed. The suppression of the blue shift will be explained in detail later.

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

[0020] The change in chromaticity will be explained with reference to Figures 4 and 5. Figure 4 shows the amount of chromaticity change (change in Cy and Cy) with respect to the angle. Figure (A) on the left shows the state without a multilayer film, and Figure (B) on the right shows the state with a multilayer film. As shown in Figure (A) on the left, in the absence of a multilayer film, both Cx and Cy change in chromaticity as the emission angle widens from 0 degrees, and the change in Cy value is particularly large. In contrast, the present invention can significantly suppress the change in chromaticity, as shown in Figure (A) on the right. Specifically, the change in chromaticity ΔCy and Δy in the CIE1931 chromaticity coordinate system can both be reduced to 0.03 or less.

[0021] Furthermore, in the chromaticity diagram (CIE1931 chromaticity coordinate system) shown in Figure 5, if blue, green, and red are represented by P1, P2, and P3 respectively, in the absence of a multilayer film, as the angle of view widens, Cx and Cy increase from white, causing a change in chromaticity towards yellow. Under condition 1, the P1 component is increased, shifting it to the lower left side of the diagram, and under condition 2, the P3 component is decreased, shifting it to the left side of the diagram, thereby suppressing the increase in Cx and Cy. By suppressing the increase in Cy, the change in chromaticity towards yellow can be suppressed, and it can also be kept within the white color temperature region enclosed by the dotted line in the diagram (around 0.33, for example, in the range of Cx and Cy from 0.30 to 0.40).

[0022] Furthermore, the multilayer film of the present invention exhibits a transmittance of 90% or more at a wavelength of 550 nm, regardless of the emission angle (Condition 3). By achieving high transmittance in the wavelength range with high visual sensitivity over a wide range of emission angles, it is possible to maintain high transmittance while preserving whiteness.

[0023] In other words, while conventional technology only controlled the blue wavelength region, the optical multilayer film of the present invention controls both sides of the 650nm to 700nm wavelength range in opposite ways, with transmittance gradually increasing and gradually decreasing as the angle widens, while maintaining high transmittance in the central wavelength region. This allows for high emission efficiency as a whole light-emitting device, while effectively suppressing the blue shift that occurs as the angle widens and preventing the yellowish tint.

[0024] Next, we will explain the configuration of a multilayer optical film that satisfies the above-mentioned conditions 1 to 3. Optical multilayer films have a structure in which multiple optical layers with different refractive indices are stacked. For the low refractive index layer, transparent dielectrics with refractive indices in the range of 1.6 or less, such as SiO2 and MgF2, are used, while for the high refractive index layer, materials with refractive indices of 1.6 or higher, such as TiO2, Al2O3, ZrO2, HfO2, Nb2O5, BaTi2O5, and Ta2O5, are used.

[0025] The multilayer film structure is an alternating stacking of low-refractive-index and high-refractive-index materials, with a preferred refractive index difference of 0.6 to 1.0 (550 nm). A typical example of a combination that achieves such a refractive index difference is SiO2 / Nb2O5. Furthermore, when the low-refractive-index layer is placed as the uppermost layer on the light-emitting side, a structure in which the low-refractive-index layer is the bottom layer and high-refractive-index and low-refractive-index layers are arranged 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 used in combination with LEDs have a large number of layers (for example, 10 to 30) to suppress the "undulation" that occurs in the transmission spectrum. However, in this invention, by reducing the number of layers compared to a typical multilayer film, specifically to 9 or less, it is possible to suppress the shift of the transmission spectrum toward shorter wavelengths for each angle (so-called blue shift) and to make it easier to adjust the chromaticity.

[0027] Blue shift is a phenomenon that occurs when the apparent film thickness changes as the angle of light widens, and the degree of blue shift increases with the number of layers and the film thickness. Referring to Figure 6, the suppression of blue shift by the present invention will be explained.

[0028] Figures 6(A) and (B) show examples of transmission spectra of multilayer films with different numbers of layers (the lower part is a magnified view). (A) is the transmission spectrum of a multilayer film with 5 layers, and (B) is the transmission spectrum of a multilayer film with 9 layers, using the same layer composition materials as (A). These figures show the blue shift at the 70% position at the rise wavelength of transmittance. The reference wavelength for the blue shift is the blue peak position in the pseudo-white spectrum (the spectrum of white light obtained by combining the LED and the wavelength conversion unit), which is 420nm to 460nm, preferably 440nm to 455nm.

[0029] As shown in Figure 6(B), in the transmission spectrum of a multilayer film with a relatively large number of layers, a ripple occurs after the rise of the transmission spectrum, and the amount of shift with change in the emission angle is large. However, in the transmission spectrum of (A), the rise of the transmission spectrum is gently sloped, 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 becomes large, making it impossible to adjust the chromaticity in the blue wavelength region at wide angles. However, the present invention can reduce the blue shift, and in combination with the above-mentioned condition 1, it becomes easier to adjust the chromaticity.

[0030] The thickness of the thin film constituting the optical multilayer film (optical film thickness) can be determined from the correlation between the chromaticity value and the optical film thickness. The optical film thickness (FWOT) is defined as nd / λ, where d is the physical film thickness and n is the refractive index of the film material. 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 up to the blue emission peak wavelength range (in this embodiment, up to approximately 475 nm, which is the long-wavelength end of the blue emission peak), preferably up to the blue emission peak wavelength (in this embodiment, up to approximately 445 nm, which is the blue emission peak wavelength).

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

[0032] When the optical film 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 film thickness of the high-refractive-index layer and the low-refractive-index layer can be determined within the range that satisfies the chromaticity value and the amount of chromaticity change.

[0033] Specifically, it was determined that, in order to satisfy the chromaticity requirements, the optical film thickness of the high refractive index layer should preferably be 0.70 to 0.85 FWOT, and the optical film thickness of the low refractive index layer should preferably be 0.7 to 0.9 FWOT. However, the optical film thickness is determined by its correlation with the chromaticity value and is not limited to the above range. If the materials or layer configuration are different, a suitable optical film thickness can be determined based on the above-mentioned chromaticity and chromaticity change conditions.

[0034] The transmission spectrum and structural characteristics of the optical multilayer film have been described above. Next, we will describe the configuration of a semiconductor light-emitting device equipped with the optical multilayer film described above, and the individual elements that constitute the semiconductor light-emitting device.

[0035] As a basic configuration, the semiconductor light-emitting device has a structure in which an LED element 10, a wavelength conversion unit 20, and an optical multilayer film 30 are stacked in order, as shown in Figure 1. The LED element 10 and the wavelength conversion unit 20 together are called the light-emitting element 50.

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

[0037] The wavelength conversion unit 20 consists of a component that absorbs the light emitted by the LED element 10 and emits light of a different wavelength than that emitted by the LED element 10. Specifically, a wavelength conversion material containing phosphor particles that convert a portion of the blue light into yellow light and having light scattering properties can be used. Examples of wavelength conversion materials include YAG (yttrium aluminum garnet, Y3Al5O 12 ):YAG-based phosphors represented by Ce and (Ba,Sr)2SiO4:Eu 2+ Known phosphors such as BOS-based phosphors can be used. The wavelength conversion section 20 can take the form of a resin layer containing these phosphor particles, a transparent body containing photoconversion nanoparticles, etc. In this embodiment, although not limited thereto, the wavelength conversion material is excited by the light emission of the LED element 10 and emits light having a peak wavelength of 540 nm to 570 nm.

[0038] The wavelength conversion material converts a portion of the light incident from the LED element 10 to the wavelength conversion unit 20, while transmitting the remainder. As a result, the light from the LED element 10 and the wavelength-converted light are mixed and emitted from the wavelength conversion material. White light emission is obtained by an appropriate combination of the emission wavelength of the LED element 10 and the wavelength of the wavelength-converted light. In this embodiment, a blue LED element with a peak in the range of 420 nm to 460 nm is used, and a wavelength conversion material with a peak in the range of 540 nm to 570 nm is used, but other wavelength conversion materials can also be added.

[0039] The aforementioned multilayer film 30 is placed on the upper surface of the light-emitting element 50, which is a combination of the LED element 10 and the wavelength conversion unit 20. A portion of the blue light emitted from the light-emitting element 50 is reflected by the multilayer film 30, and the transmittance is higher as the incident angle of light entering the multilayer film increases, at an emission angle of 0 to 60 degrees. Furthermore, the light reflected by the multilayer film is scattered after being incident on the wavelength conversion member and converted into blue light and new yellow light, and a portion of it is incident on the multilayer film again, but the blue light is emitted with higher transmittance as the incident angle increases.

[0040] Due to the transmission spectrum characteristics of such optical multilayer films, the light-emitting device of the present invention can produce white light emission with suppressed changes in chromaticity depending on the emission angle.

[0041] Next, a specific embodiment 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 light-emitting LED element 10, a wavelength conversion unit 20 placed on the LED element, and an optical multilayer film 30 formed on the wavelength conversion unit 20, with the uppermost surface of the optical multilayer film 30 being the light-emitting surface.

[0042] The wavelength conversion unit 20 in this embodiment is, for example, a ceramic plate made by high-temperature firing of alumina and YAG phosphor, and has a refractive index of 1.8. It is preferable that the multilayer film-forming surface of the wavelength conversion member made of the ceramic plate be planarized by polishing or the like. On the other hand, it is preferable that the surface of the wavelength conversion member made of the ceramic plate facing the multilayer film-forming surface be a sintered surface without planarization treatment. The wavelength conversion unit 20 is mounted on the LED element 10 via an adhesive layer such as resin. It is also possible to use a single-crystal phosphor instead of a ceramic plate as the wavelength conversion unit 20.

[0043] The optical multilayer film 30 is formed by alternately stacking low-refractive-index layers and high-refractive-index layers directly on the wavelength conversion section (ceramic plate) 20 using a known film deposition method such as electron beam sputtering. The structure of the multilayer film is as shown on the right side of Figure 9(A), for example, the first layer in contact with the ceramic plate 20 and the top layer are low-refractive-index layers, and high-refractive-index layers are placed between the low-refractive-index layers, resulting in an odd number of layers. In Embodiment 1 shown in Figure 9(A), SiO2 (n=1.46) is used as the material for the low-refractive-index layers and Nb2O5 (n=2.33) is used as the material for the high-refractive-index layers, resulting in a multilayer film with 5 layers.

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

[0045] As described above, by setting both low-refractive-index and high-refractive-index materials to around 0.75FWOT, it is possible to obtain properties that suppress the amount of chromaticity change with angle.

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

[0047] The wavelength conversion layer 25 is formed by dispersing glass beads and YAG phosphor particles in a transparent resin such as a silicone resin, and is coated onto 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 approximately 7 μm to 40 μm. The particle size of the phosphor particles is preferably 40 μm or less, and more preferably 30 μm nm or less.

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

[0050] The optical multilayer film 30 is the same as the optical multilayer film of Embodiment 1, 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, the semiconductor light-emitting device may also include means such as lead wires for supplying power to the LEDs, members for supporting or holding the LEDs / wavelength conversion unit / optical multilayer film, and known accessory parts for mounting purposes. Light-emitting devices including such members are also included in the present invention.

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

[0053] Figure 20 shows a schematic side view of a headlamp 60 as an example of a vehicle lighting device. This headlamp 60 comprises a semiconductor light-emitting device 61, a focusing 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 comprises an LED, a wavelength conversion unit, and an optical multilayer film, and is mounted on a substrate 65. The semiconductor light-emitting device 61 emits light DL within a predetermined angular range. The focusing reflector 62 is, for example, an elliptical reflective surface, and focuses the light DL emitted from the semiconductor light-emitting device 61 positioned at a first focal point F1 to generate focused light FL that is focused at a second focal point F2. The projection lens 63 projects the focused light FL from the focusing reflector 62 to generate projected light PL. The shade 64 includes a mirror surface and is positioned near the second focal point F2, and its front edge on the projection lens 63 side blocks a portion of the focused light FL.

[0054] In this configuration, the headlamp 60 forms a passing light distribution pattern (so-called low beam) with a cutoff line at the upper end by projecting the light source image of the semiconductor light-emitting device 61, which is defined by the end of the shade 64 positioned at the second focal point F2, inverted by the projection lens 63. According to the vehicle lighting device of the present invention (in this case, the headlamp 60), by employing the semiconductor light-emitting device 61 of the present invention as the light-emitting element, color unevenness in the light source image and orientation pattern can be suppressed. [Examples]

[0055] <Example 1> In the LED package with the configuration shown in Figure 9(A), a multilayer film with 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 spectra of this multilayer film when the angle of incidence of light is changed in 15-degree increments. These transmission spectra were obtained using the difference between the emission spectrum when the multilayer film is not formed and the emission spectrum after the multilayer film is formed. From Figure 10, it can be seen that in the blue emission wavelength region (400 nm to 470 nm), the transmittance of the multilayer film in this embodiment is 60% or more at an angle of 0 degrees, and the transmittance gradually increases as the angle increases, indicating that the blue component, which decreases as the angle widens, can be adjusted by the increase in transmittance. Furthermore, in the wavelength region beyond 600 nm, the transmittance gradually decreases from 0 degrees to 60 degrees, indicating that the chromaticity is adjusted accordingly.

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

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

[0059] Figure 12 shows the change in chromaticity with respect to the angle of the light-emitting device of Example 1. Figure 12 is a graph of the change in chromaticity at 5-degree intervals when the emission angle is changed from 0 degrees to 80 degrees. The lower left of the line represents an emission angle of 0 degrees, and the upper right represents an incidence angle of 80 degrees, with plots at 5-degree intervals connected by lines. From an incidence angle of 0 degrees to 40 degrees, Cx and Cy increase; from 40 degrees to 65 degrees, at least one of Cx or 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 emission angle of 0 degrees and an emission angle of 80 degrees. The difference in Cx value between an emission angle of 0 degrees and an emission angle of 80 degrees was 0.004, and the difference in Cy value was 0.008. In other words, the difference between the Cx and Cy values ​​was suppressed to 0.01 or less over a wide range from an exit angle of 0 degrees to an exit angle of 80 degrees. In the graph, a large chromaticity coordinate distance between an exit angle of 0 degrees and an exit angle of 80 degrees indicates a large change, but the fact that the line graph has a chromatic turning point, and more preferably the line graph has a rotational section, means that the change in chromaticity value due to the exit angle is effectively suppressed. The graph shown in Figure 12 is a graph in which the line graph has a rotational section, and it can be seen that the chromaticity change is small in Example 1.

[0060] Furthermore, the transmission spectrum of Example 1 (Figure 10) shows that the transmittance spectrum at 550 nm retains 90% or more, indicating that the luminous sensitivity is high and brightness is maintained.

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

[0062] Figure 13 shows the transmission spectra of this multilayer film when the angle of incidence of light is changed in 15-degree increments. The multilayer film of Example 2, like the multilayer film of Example 1, satisfies conditions 1 to 3 of the present invention, and it was confirmed that the change in chromaticity can be adjusted by increasing the transmittance of the blue component in the blue wavelength region and decreasing the transmittance in the long wavelength region as the angle of incidence widens, and that high transmittance is ensured at 550 nm.

[0063] Figure 14 and Figure 15 show the changes in chromaticity (ΔCx, ΔCy) with respect to the angle, measured for the light-emitting device of Example 2 when the emission angle was changed from 0 degrees to 80 degrees. As shown in Figure 14, the difference in Cx value between the emission angle of 0 degrees and the incident angle of 80 degrees is 0.002, and the difference in Cy value is also 0.002. As shown in Figure 15, the chromaticity (Cx, Cy) values ​​measured at 5-degree intervals of emission 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 between the Cx and Cy values ​​was greatest at emission angles of 75 degrees and 80 degrees. The difference in Cx values ​​between emission angles of 75 degrees and 80 degrees was 0.007, and the difference in Cy values ​​was 0.014.

[0064] In this embodiment as well, it can be seen that the change in chromaticity of both Cx and Cy can be suppressed to 0.02 or less over a wide angular range. Furthermore, in the range of emission angles from 0 to 60 degrees, the difference in Cx values ​​was 0.002 (emission angles of 35 and 60 degrees), and the difference in Cy values ​​was 0.002 (emission angles of 20 and 60 degrees), demonstrating extremely suppressed chromaticity differences. Moreover, as shown in the chromaticity diagram of Figure 15, the trajectory showing the change in chromaticity also has folding and rotating parts, indicating that the change in chromaticity is small, and that it remains within the white range (0.30 to 0.40) over a wide angular range.

[0065] <Comparative Example 1> Comparative Example 1 was manufactured using the same LED package structure as Example 1, but with the multilayer film configured as described below. [Table 3]

[0066] The transmission spectrum of this multilayer film is shown in Figure 16, and the chromaticity change is shown in Figure 17. As can be seen from the transmission spectrum in Figure 16, the multilayer film of Comparative Example 1 shows a monotonically increasing transmittance in the blue emission peak wavelength region from 0 to 45 degrees, but the transmittance decreases at 60 degrees, indicating that it does not have a configuration that gradually (monotonically) increases from an incident angle of 0 degrees to at least 60 degrees. Also, as can be seen from the transmission spectrum in Figure 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 using blue light. The trajectory of chromaticity change in Figure 17 also shows an almost linear change, indicating a large chromaticity change with angle. The difference in Cx value between an exit angle of 0 degrees and an exit angle of 80 degrees was 0.022, and the difference in Cy value was 0.036. The difference in Cx value was largest at an exit angle of 15 degrees and an exit angle of 75 degrees. The difference in Cx values ​​between an exit angle of 15 degrees and an exit angle of 75 degrees was 0.023. The difference in Cy values ​​was greatest at an exit angle of 20 degrees and an exit angle of 80 degrees. The difference in Cx values ​​between an exit angle of 20 degrees and an exit angle of 80 degrees was 0.045.

[0067] As shown above, when the optical film thickness of a multilayer film is thin, the transmission spectrum at each angle tends to shift towards shorter wavelengths, making it difficult to adjust the chromaticity in the blue region.

[0068] <Comparative Example 2> Using the same film constituent materials as in Example 1, a multilayer film was designed with 9 layers, and the 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 exhibits a steep change in transmittance in the blue wavelength region and a large change in transmittance with respect to angle (blue shift). The spectral fluctuations are also large in the wavelength region above 450 nm. Therefore, the multilayer film of Comparative Example 2 cannot eliminate the blue shift that occurs as the angle widens, and it becomes difficult to adjust the chromaticity change with respect to angle. From the results of Example 1 and Comparative Example 2, it can be seen 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 5 layers are preferable.

[0070] Figure 19 shows the chromaticity change of the light-emitting device when using the multilayer film of Comparative Example 2. In Comparative Example 2, although the graph of chromaticity change has a turning point, the change is such that it turns back significantly to a region where the Cy value is small compared to the starting point (emission angle 0 degrees), indicating that the chromaticity adjustment is insufficient. The difference in Cx value between the emission angle 0 degrees and the emission angle 80 degrees was 0.007, and the difference in Cy value was 0.014. The difference in Cx and Cy values ​​was largest at the emission angle 45 degrees and the emission angle 75 degrees. The difference in Cx value between the emission angle 45 degrees and the emission angle 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 in the blue region to increase as the angle widens while maintaining it within an appropriate range, controlling the transmittance in the long wavelength region to decrease as the angle widens, and maintaining the transmittance of wavelengths with high visual sensitivity at 90% or more, changes in chromaticity due to emission angle are suppressed, blue shift is suppressed, and the amount of light emitted in the region with high visual sensitivity is maintained. [Explanation of symbols]

[0072] 10: LED element, 20: Wavelength conversion unit, 25: Wavelength conversion layer (wavelength conversion unit), 30: Optical multilayer film, 40: Glass plate, 50: Light-emitting element (excluding multilayer film), 60: Headlamp (vehicle lighting device), 61: Semiconductor light-emitting device, 62: Focusing reflector, 63: Projection lens, 64: Shade.

Claims

1. A semiconductor light emitting device comprising: a light emitting element having an LED element; and a wavelength converting section which receives light emitted by the LED element and emits light having a wavelength different from that of the light emitted by the LED element, the light emitting element emitting light which 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 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 increases monotonically in the range of 0 degrees to at least 60 degrees at the emission peak wavelength of the LED element, the transmittance decreases monotonically in the range of 0 degrees to at least 60 degrees in the range of 650 nm to 700 nm, and the transmittance at 550 nm is 90% or more in the range of 0 degrees to at least 60 degrees.

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 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 emitted light in the CIE 1931 chromaticity system are both within 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 laminated, 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, wherein the difference in refractive index between the high refractive index layer and the low refractive index layer is 0.6 to 1.

0.

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

8. 8. The semiconductor light emitting device according to claim 5, A semiconductor light emitting device, wherein the optical thickness of the low refractive index layer (excluding the uppermost layer of the optical multilayer) at the center wavelength λ of the optical multilayer is 0.7 to 0.

9.

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

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