Lighting device and color conversion element

Abstract

A lighting device (100) comprises: a white light source (110) that includes a blue light-emitting element and a yellow phosphor and emits first white light; and a color conversion element (130) that converts the first white light into second white light. Where the average transmittance in the range of 435-480 nm of the color conversion element (130) is defined as TB, the average transmittance in the range of 540-590 nm of the color conversion element (130) is defined as TG, the color temperature (unit: K) of the first white light is defined as T1, and the color temperature (unit: K) of the second white light is defined as T2, 2500 ≤ (TG / TB) * T2 ≤ 5000 and T1 - T2 ≥ 300 are satisfied.

Description

Technical Field

[0001] The present invention relates to a lighting device and a color conversion element.

Background Art

[0002] Patent Document 1 discloses an optical filter including an optical multilayer film in which the average reflectance of light is selectively improved for light in the wavelength range of green light to yellow light and the wavelength range of blue light. It is described that according to the optical filter disclosed in Patent Document 1, it is possible to improve color rendering properties while suppressing a decrease in luminous efficiency and a change in color temperature.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a lighting device and a color conversion element that can achieve both improvement of color rendering properties and reduction of color temperature.

Means for Solving the Problems

[0005] A lighting device according to one aspect of the present invention includes a white light source that includes a blue light emitting element and a yellow phosphor and emits first white light, and a color conversion element that converts the first white light into second white light. When TB is defined as the average transmittance of the color conversion element in the range of 435 nm to 480 nm, TG is defined as the average transmittance of the color conversion element in the range of 540 nm to 590 nm, T1 is defined as the color temperature (unit: K) of the first white light, and T2 is defined as the color temperature (unit: K) of the second white light, the relationships 2500≦(TG÷TB)×T2≦5000 and T1-T2≧300 are satisfied.

[0006] A color conversion element according to one aspect of the present invention is a color conversion element that converts first white light into second white light, wherein the average transmittance of the color conversion element in the range of 435 nm to 480 nm is TB, the average transmittance of the color conversion element in the range of 540 nm to 590 nm is TG, the color temperature (unit: K) of the first white light is T1, and the color temperature (unit: K) of the second white light is T2, and the following conditions are met: 2500 ≤ (TG ÷ TB) × T2 ≤ 5000 and T1 - T2 ≥ 300. [Effects of the Invention]

[0007] According to the present invention, it is possible to achieve both improved color rendering and a lower color temperature. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic perspective view of a lighting device according to an embodiment. [Figure 2] Figure 2 shows the configuration of a lighting device according to an embodiment. [Figure 3] Figure 3 is a schematic plan view of the white light source of the lighting device according to the embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view of the white light-emitting element of the lighting device according to the embodiment. [Figure 5] Figure 5 shows the transmittance of a color conversion element in a comparative example and the intensity of light before and after passing through the color conversion element. [Figure 6] Figure 6 shows the transmittance of the color conversion element according to Example 1 and the intensity of light before and after passing through the color conversion element. [Figure 7] Figure 7 shows the transmittance of the color conversion element according to Example 2 and the intensity of light before and after passing through the color conversion element. [Figure 8] Figure 8 shows the transmittance of the color conversion element according to Example 3 and the intensity of light before and after passing through the color conversion element. [Figure 9] Figure 9 shows the transmittance of the color conversion element according to Example 4 and the intensity of light before and after passing through the color conversion element. [Figure 10]Figure 10 shows the transmittance of the color conversion element according to Example 5 and the intensity of light before and after passing through the color conversion element. [Figure 11] Figure 11 shows the transmittance of the color conversion element according to Example 6 and the intensity of light before and after passing through the color conversion element. [Figure 12] Figure 12 shows the transmittance of the prototype color conversion element shown in Figure 7, and the intensity of light before and after passing through the prototype. [Figure 13] Figure 13 shows the transmittance of the prototype color conversion element shown in Figure 10, and the intensity of light before and after passing through the prototype. [Figure 14] Figure 14 shows the transmittance of the prototype color conversion element shown in Figure 11, and the intensity of light before and after passing through the prototype. [Figure 15] Figure 15 shows the relationship between the color temperature of the transmitted light from the color conversion element and the evaluation index. [Modes for carrying out the invention]

[0009] In the following, an illumination device and a color conversion element according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are all specific examples of the present invention. Therefore, the numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit the present invention. Accordingly, components in the following embodiments that are not described in an independent claim will be described as optional components.

[0010] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, for example, the scale may not necessarily match in each figure. Also, in each figure, substantially identical components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0011] Furthermore, in the present specification, terms indicating the relationship between elements such as parallel, terms indicating the shape of elements, and numerical ranges are not expressions representing only strict meanings, but are expressions meaning that they also include a substantially equivalent range, for example, a difference of about several percent.

[0012] For example, in the present specification, "parallel light" does not mean only perfectly parallel light, but also refers to so-called substantially parallel light, that is, light that can be regarded as substantially parallel light, and that can spread or converge at a rate within several percent.

[0013] Furthermore, in the present specification, ordinal numbers such as "first" and "second" do not mean the number or order of constituent elements unless otherwise specified, and are used for the purpose of avoiding confusion and distinguishing constituent elements of the same type.

[0014] (Embodiment) [Configuration] First, the configuration of the illumination device according to the embodiment will be described with reference to FIG. 1 to FIG. 4.

[0015] FIG. 1 is a schematic perspective view of an illumination device 100 according to the present embodiment. FIG. 2 is a diagram showing the configuration of the illumination device 100 according to the present embodiment. FIG. 3 is a schematic plan view of a white light source 110 of the illumination device 100 according to the present embodiment. FIG. 4 is a schematic cross-sectional view of a white light emitting element 111 of the illumination device 100 according to the present embodiment. Note that in FIG. 4, hatching indicating a cross section is omitted in the illustration.

[0016] As shown in FIG. 1, the illumination device 100 is, for example, a spotlight, and is attached to a wiring fixture (for example, a wiring duct, a ceiling hook rosette) provided on a ceiling or a wall. The illumination device 100 may be a downlight or a ceiling light.

[0017] As shown in FIG. 2, the illumination device 100 includes a white light source 110, a first optical system 120, a color conversion element 130, and a second optical system 140. Moreover, as shown in FIG. 1, the illumination device 100 includes a housing 150.

[0018] The white light source 110 is a light source that emits white light L11. White light L11 is an example of first white light. As shown in Figure 3, the white light source 110 comprises a plurality of white light-emitting elements 111 arranged in a two-dimensional matrix. The plurality of white light-emitting elements 111 are arranged regularly in an M x N matrix. Here, M and N are natural numbers greater than or equal to 2. M may be equal to N, or M may not be equal to N. The spacing between the rows and columns of the white light-emitting elements 111 may be the same or different. The outline of the area in which the plurality of white light-emitting elements 111 are arranged is rectangular, but may also be circular.

[0019] Multiple white light-emitting elements 111 have the same configuration as each other. Specifically, as shown in Figure 4, each white light-emitting element 111 includes a blue light-emitting element 112 and a yellow phosphor 114. The yellow phosphor 114 is positioned on the light-emitting side of the blue light-emitting element 112.

[0020] The blue light-emitting element 112 emits blue light Lb. The blue light-emitting element 112 is, for example, an LED (Light Emitting Diode). The blue light-emitting element 112 is, for example, a fine LED with a size of 100 μm × 100 μm or less, but is not limited to this. The blue light-emitting element 112 may also be a blue semiconductor laser element.

[0021] The yellow phosphor 114 is a phosphor that emits yellow light Ly when excited by blue light Lb. The mixed light of yellow light Ly and blue light Lb that has passed through the yellow phosphor 114 is the white light L11 emitted from the white light-emitting element 111. The yellow phosphor 114 is, for example, a YAG (yttrium aluminum garnet) type phosphor, but is not limited to this. The yellow phosphor 114 is provided in contact with the light-emitting surface of the blue light-emitting element 112.

[0022] The blue light-emitting element 112 and the yellow phosphor 114 may be arranged separately from each other. Furthermore, the blue light-emitting element 112 and the yellow phosphor 114 do not necessarily have to be provided in a one-to-one ratio. Also, the yellow phosphor 114 may be provided so as to cover multiple blue light-emitting elements 112. For example, for multiple blue light-emitting elements 112 arranged in a two-dimensional matrix, a yellow phosphor plate that completely covers the multiple blue light-emitting elements 112 may be provided as the yellow phosphor 114.

[0023] Although not shown in the diagram, the lighting device 100 includes a control unit that controls the emission of light from multiple white light-emitting elements 111 (blue light-emitting elements 112). The control unit independently controls each of the multiple blue light-emitting elements 112. That is, the control unit can individually control the on / off state, light intensity, light emission time, etc., of each of the multiple blue light-emitting elements 112. For example, by individually controlling the on / off state of the multiple blue light-emitting elements 112, it is possible to emit illumination light with varying brightness levels in different areas.

[0024] The control unit is implemented, for example, by an integrated circuit (IC), specifically a Large Scale Integration (LSI). However, the integrated circuit is not limited to an LSI; it may also be a dedicated circuit or a general-purpose processor. For example, the control unit may be a microcontroller. A microcontroller includes, for example, non-volatile memory where the program is stored, volatile memory which is a temporary storage area for executing the program, input / output ports, and a processor for executing the program. Alternatively, the control unit may be a programmable Field Programmable Gate Array (FPGA), or a reconfigurable processor in which the connections and settings of circuit cells within the LSI can be reconfigured. The functions performed by the control unit may be implemented in software or in hardware.

[0025] The first optical system 120 converts the white light L11 emitted from the white light source 110 into parallel light. As shown in Figure 2, the first optical system 120 converts the white light L11 into parallel white light L12 and emits it toward the color conversion element 130. The first optical system 120 is, for example, a single collimator lens, but is not limited thereto. The first optical system 120 may be realized with multiple collimator lenses and may include other optical elements such as mirrors and / or focusing lenses.

[0026] In this embodiment, the first optical system 120 is positioned between the white light source 110 and the color conversion element 130, as shown in Figure 2. The first optical system 120 is provided so as to cover the entire light-emitting surface of the white light source 110 and converts the white light L11 from each of the multiple white light-emitting elements 111 into parallel white light L12. The first optical system 120 only needs to be optically positioned between the white light source 110 and the color conversion element 130. That is, the first optical system 120 only needs to be positioned on the optical path of the first white light from the white light source 110 to the color conversion element 130. At least a part of the first optical system 120 does not need to be physically (mechanically) positioned between the white light source 110 and the color conversion element 130.

[0027] The color conversion element 130 is an element that converts first white light into second white light. The second white light is light with a different color temperature from the first white light. Specifically, the color conversion element 130 emits second white light, which has a different color temperature and spectral distribution from the first white light, by suppressing the transmission of specific wavelength components of the first white light.

[0028] In this embodiment, as shown in Figure 2, the color conversion element 130 converts white light L12 into white light L21. White light L12 is an example of first white light emitted from the white light source 110 and has a spectrum substantially equivalent to that of white light L11. That is, white light L12 and white light L11 have substantially the same color temperature. White light L21 is an example of second white light and has a different spectrum and color temperature from white light L12. The specific transmission spectrum of the color conversion element 130 will be described later.

[0029] In this embodiment, the color conversion element 130 is an optical element that adjusts spectral transmittance by utilizing light reflection. For example, the color conversion element 130 is a dichroic filter. A dichroic filter has a multilayer structure in which a dielectric film with a high refractive index and a dielectric film with a low refractive index are alternately stacked. As the dielectric film, metal oxide films such as SiO2, TiO2, Nb2O5, and HfO2 can be used. By adjusting the materials of the two types of dielectric films, the thickness of each film, the number of layers, etc., a desired transmission spectrum can be achieved.

[0030] The second optical system 140 projects the white light L21 emitted from the color conversion element 130. As shown in Figure 2, the second optical system 140 converts the white light L21 into projected white light L22 and radiates it to the outside. The second optical system 140 is, for example, one or more projection lenses, but is not limited thereto. The second optical system 140 may also include other optical elements such as mirrors and / or focusing lenses.

[0031] The housing 150 houses the white light source 110, the first optical system 120, the color conversion element 130, and the second optical system 140. The housing 150 includes, for example, an outer shell housing that forms the outer casing of the lighting device 100, and several components such as a heat sink, but is not particularly limited. The components constituting the housing 150 are formed using resin or metal.

[0032] The housing 150 has an opening on the light-emitting side of the white light source 110 (normal to the main surface of the substrate), and the second optical system 140 is positioned to cover this opening. For example, if multiple blue light-emitting elements 112 can be individually controlled, there is no need to provide a liquid crystal display or DMD (Digital Mirror Device) inside the housing 150, as is the case with typical projectors, thus enabling miniaturization of the lighting device 100.

[0033] [Color conversion element] Next, we will describe the specific transmission spectrum of the color conversion element 130.

[0034] The color conversion element 130 has high transmittance for visible light, except for two wavelength bands. That is, in the transmission spectrum of the color conversion element 130, there are two dips in transmittance, i.e., wavelength bands where the transmittance is lower than a predetermined value. The predetermined value is, for example, 60%. In this specification, the visible light band is considered to be in the range of 400 nm to 750 nm.

[0035] Specifically, the color conversion element 130 is designed to have low transmittance for the blue component with a wavelength of 450 nm or less and for the green component with a wavelength near 550 nm. For example, the minimum transmittance of the color conversion element 130 in the range of 400 nm to 450 nm is smaller than the minimum transmittance of the color conversion element 130 in the range of 525 nm to 575 nm. The minimum transmittance of the color conversion element 130 in the range of 400 nm to 450 nm is between 10% and 60%, but is not limited to this. The minimum transmittance of the color conversion element 130 in the range of 400 nm to 450 nm may be 50% or less, 40% or less, 30% or less, or 20% or less. Also, the minimum transmittance of the color conversion element 130 in the range of 525 nm to 575 nm is between 20% and 70%, but is not limited to this. The minimum transmittance of the color conversion element 130 in the range of 525 nm to 575 nm may be 60% or less, 50% or less, or 40% or less. Furthermore, the minimum transmittance of the color conversion element 130 in the range of 525 nm to 575 nm may be 30% or more.

[0036] Furthermore, for example, the maximum transmittance of the color conversion element 130 in the range of 450 nm to 500 nm, and the maximum transmittance of the color conversion element 130 in the range of 600 nm to 750 nm, are 90% or more, but may be 95% or more, or 97% or more.

[0037] Let TB be the average transmittance of the color conversion element 130 in the range of 435 nm to 480 nm, and let TG be the average transmittance of the color conversion element 130 in the range of 540 nm to 590 nm. In this case, the following equation (1) is satisfied.

[0038] (1) 2500 ≤ (TG ÷ TB) × T² ≤ 5000

[0039] The average transmittance is the average value of the spectral transmittance (transmittance for each wavelength) within the corresponding range. By satisfying the above equation (1), the color rendering of the white light L21 emitted from the color conversion element 130 can be improved.

[0040] The average color rendering index Ra of the white light L12 before it enters the color conversion element 130 is approximately 70. Since the white light L12 is a mixture of blue light Lb from the blue light-emitting element 112 and yellow light Ly from the yellow phosphor 114, the blue and yellow components are strong, resulting in low color rendering.

[0041] In contrast, the color conversion element 130 has low transmittance for the blue and yellow components of the white light L12, thus suppressing the transmission of blue and yellow light. As a result, the fluctuations in the intensity spectrum of the white light L21 after passing through the color conversion element 130 are suppressed, making it closer to natural white light (sunlight). Therefore, the average color rendering index Ra of the white light L21 after passing through the color conversion element 130 can be made 90 or higher.

[0042] Furthermore, the transmittance of blue light in the color conversion element 130 is set lower than that of yellow light. In other words, since the transmission of blue light is suppressed in the color conversion element 130, the color temperature of the transmitted white light can be lowered.

[0043] Specifically, the color temperature of white light L21 is lower than the color temperature of white light L12. Let T1 be the color temperature (in K) of white light L11 and L12, and T2 be the color temperature (in K) of white light L21. In this case, the following equation (2) is satisfied.

[0044] (2) T1-T2≧300

[0045] For example, the color temperature T1 of white light L12 is 5000K or higher, may be 5200K or higher, 5500K or higher, 5700K or higher, or 6000K or higher. The color temperature T2 of white light L21 will be 300K or more lower than the color temperature T1 of such white light L12.

[0046] [Examples] Next, several specific embodiments of the color conversion element 130 will be described using Figures 5 to 14.

[0047] Figure 5 shows the transmittance of a color conversion element in a comparative example and the intensity of light before and after passing through the color conversion element. Figures 6 to 11 show the transmittance of a color conversion element in Examples 1 to 6 and the intensity of light before and after passing through the color conversion element.

[0048] Figures 5 to 11 show the simulation results of the transmission spectrum of a color conversion element, where a target color temperature of white light after passing through the element was set, and the spectral transmittance of the element was designed to achieve the target value. In contrast, Figures 12 to 14 show the transmittance of the prototype (sample) color conversion element shown in Figures 7, 10, and 11, and the intensity of light before and after passing through the prototype, respectively.

[0049] In each figure, the horizontal axis represents the wavelength of light. The vertical axis represents transmittance or light intensity. Transmittance is expressed as the ratio of the intensity of the emitted light to the intensity of the incident light. Light intensity is expressed in arbitrary units.

[0050] The spectrum of the first white light incident on the color conversion element is common to the comparative example and Examples 1-6. The color temperature T1 of the first white light is 5500K. For example, as shown in Figure 5, the first white light has a first intensity peak of the blue component and a second intensity peak of the yellow component. The peak wavelength of the first intensity peak is approximately 447 nm. The peak wavelength is the wavelength at which the light intensity is maximum. The peak wavelength of the second intensity peak is approximately 555 nm. The maximum intensity of the first intensity peak is greater than the maximum intensity of the second intensity peak. Also, the full width at half maximum of the first intensity peak is narrower than the full width at half maximum of the second intensity peak.

[0051] The target color temperature for the comparative example shown in Figure 5 is 5500K. In other words, the color conversion element in the comparative example is designed to improve color rendering without changing the color temperature. The target color temperatures for each of Examples 1 to 6 shown in Figures 6 to 11 are 5000K, 4500K, 4000K, 3500K, 3000K, and 3000K, respectively.

[0052] Table 1 summarizes the color temperature T2 of the transmitted light (second white light), the average transmittance TG in the range of 540 nm to 590 nm, the average transmittance TB in the range of 435 nm to 480 nm, the index A (=TG÷TB×T2) in formula (1) and the index B (=T1-T2) in formula (2) for comparative examples and examples 1 to 6.

[0053] [Table 1]

[0054] <Example 1> The target color temperature of the color conversion element in Example 1 shown in Figure 6 is 5000K. Therefore, index B in Table 1 is 500K, satisfying the condition of equation (2).

[0055] Furthermore, in the transmission spectrum of the color conversion element according to Example 1, the transmittance is set to be constant at 38% in the wavelength range of 400 nm to 440 nm. It is also set to be constant at 52% in the wavelength range of 540 nm to 585 nm. In addition, the transmittance is set to be constant at 95% in both the wavelength range of 460 nm to 525 nm and the wavelength range of 610 nm to 750 nm. In the transmittance transition region (the range in which transmittance increases or decreases with change in wavelength), the change in transmittance is set to be constant. As a result, in Example 1, the average transmittance TG is 52% and the average transmittance TB is 76%, and index A in Table 1 is 3421 K, satisfying the conditions of equation (1).

[0056] <Example 2> The target color temperature of the color conversion element in Example 2 shown in Figure 7 is 4500K. Therefore, index B in Table 1 becomes 1000K, satisfying the condition of equation (2).

[0057] Furthermore, in the transmission spectrum of the color conversion element according to Example 2, the transmittance is set to be constant at 23% in the wavelength range of 400 nm to 440 nm. It is also set to be constant at 53.5% in the wavelength range of 535 nm to 585 nm. In addition, the transmittance is set to be constant at 95% in both the wavelength range of 460 nm to 515 nm and the wavelength range of 606 nm to 750 nm. In the transmittance transition region, the change in transmittance is set to be constant. As a result, in Example 2, the average transmittance TG is 54%, and the average transmittance TB is 71%, resulting in index A in Table 1 being 3422 K, satisfying the conditions of equation (1).

[0058] <Example 3> The target color temperature of the color conversion element in Example 3 shown in Figure 8 is 4000K. Therefore, index B in Table 1 is 1500K, satisfying the condition of equation (2).

[0059] Furthermore, in the transmission spectrum of the color conversion element according to Example 3, the transmittance is set to be constant at 21.5% in the wavelength range of 400 nm to 444 nm. It is also set to be constant at 48.1% in the wavelength range of 535 nm to 575 nm. In addition, the transmittance is set to be constant at 95% in both the wavelength range of 464 nm to 515 nm and the wavelength range of 596 nm to 750 nm. In the transmittance transition region, the change in transmittance is set to be constant. As a result, in Example 3, the average transmittance TG is 53% and the average transmittance TB is 64%, and index A in Table 1 is 3312 K, satisfying the conditions of equation (1).

[0060] <Example 4> The target color temperature of the color conversion element in Example 4 shown in Figure 9 is 3500K. Therefore, index B in Table 1 becomes 2000K, satisfying the condition of equation (2).

[0061] Furthermore, in the transmission spectrum of the color conversion element according to Example 4, the transmittance is set to be constant at 19.5% in the wavelength range of 400 nm to 451 nm. It is also set to be constant at 41.2% in the wavelength range of 531 nm to 574 nm. In addition, the transmittance is set to be constant at 95% in both the wavelength range of 471 nm to 511 nm and the wavelength range of 595 nm to 750 nm. In the transmittance transition region, the change in transmittance is set to be constant. As a result, in Example 4, the average transmittance TG is 48% and the average transmittance TB is 52%, and index A in Table 1 is 3230 K, satisfying the conditions of equation (1).

[0062] <Example 5> The target color temperature of the color conversion element in Example 5 shown in Figure 10 is 3000K. Therefore, index B in Table 1 becomes 2500K, satisfying the condition of equation (2).

[0063] Furthermore, in the transmission spectrum of the color conversion element according to Example 5, the transmittance is set to be constant at 11.3% in the wavelength range of 400 nm to 455 nm. It is also set to be constant at 29.9% in the wavelength range of 520 nm to 550 nm. It is also set to be constant at 54.5% in the wavelength range of 590 nm to 595 nm. In addition, the transmittance is set to be constant at 95% in both the wavelength range of 485 nm to 490 nm and the wavelength range of 625 nm to 750 nm. In the transmittance transition region, the change in transmittance is set to be constant. As a result, in Example 5, the average transmittance TG is 40% and the average transmittance TB is 31%, and index A in Table 1 is 3871 K, satisfying the conditions of equation (1).

[0064] <Example 6> The target color temperature of the color conversion element in Example 6 shown in Figure 11 is 3000K. Therefore, index B in Table 1 is 2500K, satisfying the condition of equation (2).

[0065] Furthermore, in the transmission spectrum of the color conversion element according to Example 6, the transmittance is set to be constant at 14.8% in the wavelength range of 400 nm to 455 nm. It is also set to be constant at 28% in the wavelength range of 536 nm to 552 nm. In addition, the transmittance is set to be constant at 95% in both the wavelength range of 485 nm to 496 nm and the wavelength range of 608 nm to 750 nm. In the transmittance transition region, the change in transmittance is set to be constant. As a result, in Example 6, the average transmittance TG is 45% and the average transmittance TB is 34%, and index A in Table 1 is 3970 K, satisfying the conditions of equation (1).

[0066] <Prototype> The inventors of this application created prototypes for Examples 2, 5, and 6 of the six embodiments described above. The prototypes were dichroic filters, and the transmission characteristics shown in each embodiment were adjusted by modifying the materials of the two types of dielectric films, the thickness of each film, the number of layers, etc.

[0067] As shown in Figures 12 to 14, the transmission spectra of each prototype have a smoother shape compared to the design values, but generally follow the transmission spectra of the corresponding embodiments. The parameters of the prototypes, such as color temperature T2, are shown in Table 2 below. The color temperature T1 of the incident light, the first white light, is set to 5534K.

[0068] [Table 2]

[0069] Figure 15 shows the relationship between the color temperature of the transmitted light from a color conversion element and the evaluation index. In Figure 15, the horizontal axis represents the color temperature of the transmitted light, and the vertical axis represents index A.

[0070] Figure 15 plots index A for a total of 19 examples, including 16 examples (including Examples 1-6 described above) and 3 prototypes. Note that the color temperature T2 of the transmitted light (second white light) also depends on the color temperature and spectrum of the incident light (first white light), so index A is calculated for each of the three different types of incident light. The three different types of incident light have color temperatures T1 of 5534K, 5263K, and 5684K, respectively, and have spectra equivalent to the light intensity spectra before transmission shown in Figures 5-14.

[0071] As shown in Figure 15, although there is some variation depending on the color temperature and spectral difference of the incident light, it can be seen that index A remains within the range of 2500K to 5000K regardless of the color temperature of the transmitted light. In other words, it can be seen that by satisfying the relationship between equations (1) and (2) above, it is possible to achieve both improved color rendering and a lower color temperature.

[0072] [summary] As described above, the lighting device according to the first aspect of the present invention is, for example, the lighting device 100 described above, and comprises a white light source 110 that emits first white light and includes a blue light-emitting element 112 and a yellow phosphor 114, and a color conversion element 130 that converts the first white light into second white light. When the average transmittance of the color conversion element 130 in the range of 435 nm to 480 nm is denoted as TB, the average transmittance of the color conversion element 130 in the range of 540 nm to 590 nm is denoted as TG, the color temperature (unit: K) of the first white light is denoted as T1, and the color temperature (unit: K) of the second white light is denoted as T2, then 2500 ≤ (TG ÷ TB) × T2 ≤ 5000 and T1 - T2 ≥ 300 are satisfied.

[0073] This makes it possible to achieve both improved color rendering and lower color temperature. White light L11 from a white light source 110 containing a blue light-emitting element 112 and a yellow phosphor 114 tends to have a high color temperature because the intensity of the blue component is strong, making it difficult to realize a lighting device with a low color temperature. In contrast, by using a color conversion element 130, it is possible to lower the color temperature of high-color-temperature white light while improving color rendering.

[0074] Furthermore, a lighting device according to a second aspect of the present invention is a lighting device according to a first aspect, comprising a first optical system 120 arranged between a white light source 110 and a color conversion element 130, which converts the first white light emitted from the white light source 110 into parallel light.

[0075] This allows white light L12 to be incident on the color conversion element 130 from the front. Since the influence of the angle dependence of the transmittance of the color conversion element 130 can be suppressed, the desired high color rendering and low color temperature can be achieved.

[0076] Furthermore, a lighting device according to a third aspect of the present invention is a lighting device according to the first or second aspect, comprising a second optical system 140 that projects second white light emitted from a color conversion element 130.

[0077] This allows for the efficient emission of white light with high color rendering and low color temperature to the desired area.

[0078] Furthermore, the lighting device according to the fourth aspect of the present invention is a lighting device according to any one of the first to third aspects, wherein the white light source 110 includes a plurality of blue light-emitting elements 112 arranged in a two-dimensional matrix. The yellow phosphor 114 is arranged on the light-emitting side of the plurality of blue light-emitting elements 112.

[0079] This allows for the miniaturization of the white light source 110 while increasing its intensity by arranging multiple blue light-emitting elements 112 together in a narrow area. The miniaturization of the white light source 110 also contributes to the miniaturization of the lighting device according to this embodiment.

[0080] Furthermore, the fifth aspect of the present invention is a lighting device according to any one of the first to fourth aspects, wherein the blue light-emitting element 112 is a blue semiconductor laser element.

[0081] This can improve energy efficiency.

[0082] Furthermore, the sixth aspect of the present invention is a lighting device according to any one of the first to fifth aspects, wherein the color conversion element 130 is a dichroic filter.

[0083] This makes it possible to easily realize a color conversion element 130 having a desired transmission spectrum by adjusting the material, thickness, number of layers, etc., of the dielectric film constituting the dichroic filter.

[0084] Furthermore, the seventh aspect of the present invention is a lighting device according to any one of the first to sixth aspects, wherein the minimum transmittance of the color conversion element 130 in the range of 400 nm to 450 nm is smaller than the minimum transmittance of the color conversion element 130 in the range of 525 nm to 575 nm.

[0085] This makes it possible to suppress the transmission of yellow and blue components, achieving both improved color rendering and a lower color temperature.

[0086] Furthermore, the lighting device according to the eighth aspect of the present invention is a lighting device according to any one of the first to seventh aspects, wherein the maximum transmittance of the color conversion element 130 in the range of 450 nm to 500 nm, and the maximum transmittance of the color conversion element 130 in the range of 600 nm to 750 nm, are 90% or more.

[0087] This allows for increased light extraction efficiency.

[0088] Furthermore, a color conversion element according to the ninth aspect of the present invention is, for example, the color conversion element 130 described above, which is a color conversion element that converts first white light into second white light. When the average transmittance of the color conversion element in the range of 435 nm to 480 nm is denoted as TB, the average transmittance of the color conversion element in the range of 540 nm to 590 nm is denoted as TG, the color temperature of the first white light (unit: K) is denoted as T1, and the color temperature of the second white light (unit: K) is denoted as T2, then 2500 ≤ (TG ÷ TB) × T2 ≤ 5000 and T1 - T2 ≥ 300 are satisfied.

[0089] This makes it possible to achieve both improved color rendering and lower color temperature. White light L11 from a white light source 110 containing a blue light-emitting element 112 and a yellow phosphor 114 tends to have a high color temperature because the intensity of the blue component is strong, making it difficult to realize a lighting device with a low color temperature. In contrast, by using a color conversion element 130, it is possible to lower the color temperature of high-color-temperature white light while improving color rendering.

[0090] (others) Although the lighting device according to the present invention has been described above based on the above embodiments, the present invention is not limited to the above embodiments.

[0091] For example, in the above embodiment, the white light source 110 comprises a plurality of white light-emitting elements 111 arranged in a two-dimensional matrix, but is not limited to this. The white light source 110 may be a single white light-emitting element.

[0092] The color conversion element 130 may be an optical element whose spectral transmittance is adjusted by utilizing light absorption. For example, the color conversion element 130 may include a light-transmitting substrate such as resin or glass, and an absorbing dye provided inside or on the surface of the light-transmitting substrate.

[0093] The color conversion element 130 may be used in devices other than the lighting device 100. For example, the color conversion element 130 may be used in a display or projector.

[0094] Furthermore, the present invention also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art could conceive, as well as forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of the present invention. [Explanation of Symbols]

[0095] 100 Lighting devices 110 White light source 112 Blue light-emitting element 114 Yellow phosphor 120 1st optical system 130 color conversion elements 140 Second optical system

Claims

1. A white light source comprising a blue light-emitting element and a yellow phosphor, which emits first white light, The system comprises a color conversion element that converts the first white light into a second white light, When the average transmittance of the color conversion element in the range of 435 nm to 480 nm is denoted as TB, the average transmittance of the color conversion element in the range of 540 nm to 590 nm is denoted as TG, the color temperature (unit: K) of the first white light is denoted as T1, and the color temperature (unit: K) of the second white light is denoted as T2, 2500 ≤ (TG ÷ TB) × T² ≤ 5000 and, T1 - T2 ≥ 300 Satisfying the conditions, The minimum transmittance of the color conversion element in the range of 400 nm to 450 nm is smaller than the minimum transmittance of the color conversion element in the range of 525 nm to 575 nm. Lighting device.

2. The system includes a first optical system positioned between the white light source and the color conversion element, which converts the first white light emitted from the white light source into parallel light. The lighting device according to claim 1.

3. The system includes a second optical system that projects the second white light emitted from the color conversion element, The lighting device according to claim 1.

4. The white light source includes a plurality of blue light-emitting elements arranged in a two-dimensional matrix, The yellow phosphor is arranged on the light-emitting side of the plurality of blue light-emitting elements. A lighting device according to any one of claims 1 to 3.

5. The aforementioned blue light-emitting element is a blue semiconductor laser element. A lighting device according to any one of claims 1 to 3.

6. The aforementioned color conversion element is a dichroic filter. A lighting device according to any one of claims 1 to 3.

7. The maximum transmittance of the color conversion element in the range of 450 nm to 500 nm, and the maximum transmittance of the color conversion element in the range of 600 nm to 750 nm, are 90% or more. A lighting device according to any one of claims 1 to 3.

8. A color conversion element that converts first white light into second white light, When the average transmittance of the color conversion element in the range of 435 nm to 480 nm is denoted as TB, the average transmittance of the color conversion element in the range of 540 nm to 590 nm is denoted as TG, the color temperature (unit: K) of the first white light is denoted as T1, and the color temperature (unit: K) of the second white light is denoted as T2, 2500 ≤ (TG ÷ TB) × T² ≤ 5000 and, T1 - T2 ≥ 300 Satisfying the conditions, The minimum transmittance of the color conversion element in the range of 400 nm to 450 nm is smaller than the minimum transmittance of the color conversion element in the range of 525 nm to 575 nm. Color conversion element.

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