Wavelength conversion element, and light-emitting device using same

Abstract

A wavelength conversion element of the present invention comprises: a first reflective layer; a second reflective layer; and a phosphor layer located between these reflective layers. The first reflective layer reflects light in a first wavelength region. The second reflective layer reflects light in a second wavelength region that overlaps at least a portion of the first wavelength region. The phosphor layer has an excitation wavelength dependence on light-emission wavelength and converts projected excitation light into light having a longer wavelength than the excitation light. / The first reflective layer and the second reflective layer resonate, therebetween, light of a wavelength in a region of overlap between the first wavelength region and the second wavelength region, the light being of the light obtained by wavelength-converting the excitation light by the phosphor layer. The resonated light is converted by the phosphor layer into light of a wavelength longer than the longest wavelength in the second wavelength region. At the second reflective layer, of the light obtained by the excitation light being wavelength-converted by the phosphor layer, light of a wavelength outside the second wavelength region and light of a wavelength longer than the longest wavelength in the second wavelength region and obtained by the resonated light being wavelength-converted by the phosphor layer are each transmitted by, and exit from, the second reflective layer.

Description

Wavelength conversion element and light-emitting device using same

[0001] The present invention relates to a wavelength conversion element and a light emitting device using the same. More particularly, the present invention relates to a wavelength conversion element that emits white light and a light emitting device using the same.

[0002] In recent years, carbon nanoparticle phosphors have been developed using carbon, which is abundant on Earth, as a raw material (see, for example, Patent Document 1). Patent Document 1 reports that a composition in which a carbon nanoparticle phosphor is dispersed in an aqueous solvent, the carbon nanoparticle phosphor containing carbon atoms, oxygen atoms, nitrogen atoms, and optionally hydrogen atoms, in which the intensity of a peak (285.98 eV) derived from a C—N bond and / or a C—O bond in an X-ray photoelectron spectroscopy spectrum is greater than that (284.95 eV) derived from a C—C bond and / or a C—H bond, and the Raman spectrum has peaks derived from the G band and the D band, becomes a phosphor that emits blue light when excited by ultraviolet light.

[0003] Furthermore, Patent Document 1 discloses that a white light-emitting device can be provided by combining such a carbon nanoparticle phosphor with a red phosphor or a green phosphor and using it together with an excitation source that emits ultraviolet light. However, it is difficult to adjust the chromaticity of such a white light-emitting device once it is combined with the phosphor. Furthermore, in order to obtain light emitted from such a white light-emitting device with a color temperature close to the blackbody locus, highly accurate adjustment of the phosphor combination is required. Therefore, it would be advantageous if the chromaticity and color temperature could be adjusted more easily.

[0004] International Publication No. 2018 / 163955

[0005] An object of the present invention is to provide a wavelength conversion element and a light emitting device capable of adjusting chromaticity using only one type of phosphor.A further object of the present invention is to provide a wavelength conversion element and a light emitting device capable of emitting white light along the blackbody locus using only one type of phosphor.

[0006] The wavelength conversion element according to the present invention comprises a first reflective layer, a second reflective layer, and a phosphor layer located between the first reflective layer and the second reflective layer, wherein the phosphor layer has an emission wavelength dependent on an excitation wavelength and converts irradiated excitation light into light having a wavelength longer than the excitation light, the first reflective layer reflects light in a first wavelength region located on the longer wavelength side than the wavelength of the excitation light, the second reflective layer reflects light in a second wavelength region overlapping with at least a part of the first wavelength region, and The present invention solves the above-mentioned problem by providing a light source having a wavelength in a region where the first wavelength region and the second wavelength region overlap, the light being wavelength-converted from the excitation light by the phosphor layer, and the second reflective layer transmitting and emitting light having a wavelength outside the second wavelength region from the excitation light being wavelength-converted from the excitation light by the phosphor layer and light having a wavelength longer than the longest wavelength of the second wavelength region from which the resonated light was wavelength-converted by the phosphor layer. The light being wavelength-converted from the excitation light by the phosphor layer and the light having a wavelength longer than the longest wavelength of the second wavelength region from which the resonated light was wavelength-converted by the phosphor layer may be mixed to emit white light. The first wavelength region may be in the range of 480 nm to 590 nm, and the second wavelength region may be in the range of 450 nm to 520 nm. The emission spectrum of the emitted light may have peaks in a wavelength range of 450 nm to 500 nm and a wavelength range of 580 nm to 650 nm, respectively, and the intensities of the peaks may be dependent on the output power of the excitation light. The first wavelength range may be 480 nm to 590 nm, and the second wavelength range may be 395 nm to 425 nm and 500 nm to 560 nm.The emission spectrum of the emitted light may have peaks in a wavelength range of 450 nm to 500 nm and a wavelength range of 580 nm to 650 nm, respectively, and the peak intensity in the wavelength range of 450 nm to 500 nm may not depend on the output of the excitation light, while the peak intensity in the wavelength range of 580 nm to 650 nm may depend on the output of the excitation light. The phosphor layer may be excited by light with a wavelength of 330 nm to 420 nm to emit blue light having a peak in a wavelength range of 450 nm to 500 nm. The phosphor layer may contain a phosphor selected from the group consisting of carbon nanoparticle phosphors, organic nanoparticle phosphors, organometallic complex phosphors, inorganic phosphors, and semiconductor quantum dot phosphors. The phosphor layer may contain a carbon nanoparticle phosphor and emit blue light when irradiated with ultraviolet light. The carbon nanoparticle phosphor contains carbon, oxygen, nitrogen, and hydrogen elements, and the carbon element exists as amorphous carbon and graphite-like carbon, and the amorphous carbon and graphite-like carbon account for 60% by volume or more and less than 99% by volume of the total, respectively, and the graphite-like carbon accounts for 1% by volume or more and less than 40% by volume of the total, and the nitrogen element exists as at least pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen, and the content of the pyridine-type nitrogen may be greater than that of the graphite-type nitrogen. The carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) may respectively satisfy the following: 0.58≦p / (p+q+r)≦0.65, 0.15≦q / (p+q+r)≦0.30, and 0.12≦r / (p+q+r)<0.25. The phosphor layer may be a resin molded body in which the carbon nanoparticle phosphor is dispersed. The excitation light may have a wavelength in the range of 330 nm to 420 nm. The first reflective layer may have a superlattice structure of an aluminum nitride layer and a silicon dioxide layer. The second reflective layer may have a superlattice structure of a tantalum oxide layer and a silicon dioxide layer.The light-emitting device according to the present invention includes an excitation source and a wavelength conversion element, and the wavelength conversion element is the wavelength conversion element described above, thereby solving the above-mentioned problem. The excitation source may emit excitation light having a wavelength in the range of 330 nm to 420 nm. The excitation source may be selected from the group consisting of a light-emitting diode (LED), a laser diode (LD), a semiconductor laser, and an organic electroluminescent (EL) emitter (OLED). The excitation source may have a variable output. The light-emitting device may be a white light-emitting diode, a lighting fixture including a plurality of white light-emitting diodes, or a backlight for a liquid crystal panel.

[0007] The wavelength conversion element of the present invention comprises a first reflective layer, a second reflective layer, and a phosphor layer positioned therebetween, the phosphor layer having an emission wavelength dependent on the excitation wavelength. The first reflective layer reflects light in a first wavelength region, and the second reflective layer reflects light in a second wavelength region that overlaps at least a portion of the first wavelength region. This allows light with a wavelength in the region where the first and second wavelength regions overlap to resonate in the wavelength conversion element. Because the phosphor layer has an emission wavelength dependent on the excitation wavelength, it can convert the wavelength of the irradiated excitation light as well as the wavelength of the resonated light trapped within the wavelength conversion element. As a result, the wavelength conversion element of the present invention enables emission of light with adjusted chromaticity, combining light wavelength-converted from the excitation light and light wavelength-converted from the resonated light. Furthermore, by appropriately setting the first and second wavelength regions, white light emission along the blackbody locus is possible. By using such a wavelength conversion element together with an excitation source, a light-emitting device such as a white lighting device or a display backlight can be provided.

[0008] 1 is a schematic diagram showing a wavelength conversion element of the present invention; FIG. 2 is a schematic diagram showing a light-emitting device of the present invention; FIG. 3 is a diagram showing a synthesis process of carbon nanoparticle phosphor (CD1); FIG. 4 is a diagram showing an XRD pattern of carbon nanoparticle phosphor (CD1) powder; FIG. 5 is a diagram showing TEM images of a carbon nanoparticle phosphor (CD1) solution at various magnifications; FIG. 6 is a diagram showing an XPS spectrum of a carbon nanoparticle phosphor (CD1) solution; FIG. 7 is a diagram showing a deconvoluted HRXPS spectrum of a carbon nanoparticle phosphor (CD1) solution; FIG. 8 is a diagram showing an emission spectrum of a carbon nanoparticle phosphor (CD1) solution; FIG. 9 is a diagram showing two-dimensional emission mapping of a carbon nanoparticle phosphor (CD1) solution; FIG. 10 is a diagram showing the emission state of a carbon nanoparticle phosphor (CD1)-containing resin molded body; FIG. 11 is a diagram showing an emission spectrum of a carbon nanoparticle phosphor (CD2) solution; FIG. 11 is a diagram showing a transmission spectrum of a reflective layer M1 in the wavelength conversion element of Example 1; FIG. 12 is a diagram showing a transmission spectrum of a reflective layer M1 in the wavelength conversion element of Example 1; FIG. 13 is a diagram showing an emission spectrum of a light-emitting device using the wavelength conversion element of Example 1, and an emission spectrum of a phosphor layer used in the wavelength conversion element. 1 is a diagram showing chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 1. FIG. 2 is a diagram showing the transmission spectrum of the reflective layer M1 in the wavelength conversion element of Example 2. FIG. 3 is a diagram showing the transmission spectrum of the reflective layer M2 in the wavelength conversion element of Example 2. FIG. 4 is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 2, and the emission spectrum of a phosphor layer used in the wavelength conversion element. FIG. 5 is a diagram showing chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 2. FIG. 6 is a diagram showing the transmission spectrum of the reflective layer M1 in the wavelength conversion element of Example 3. FIG. 7 is a diagram showing the transmission spectrum of the reflective layer M3 in the wavelength conversion element of Example 3. FIG. 8 is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 3, and the emission spectrum of a phosphor layer used in the wavelength conversion element. FIG. 9 is a diagram showing the chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 3. FIG. 10 is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 4, and the emission spectrum of a phosphor layer used in the wavelength conversion element. FIG. 11 is a diagram showing the chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 4.16A is a diagram showing the emission spectra of a light emitting device using the wavelength conversion element of Example 2 when irradiated with excitation light of different outputs. FIG. 16B is a diagram showing chromaticity calculated from the emission spectrum of FIG. 16A. FIG. 16C is a diagram showing the emission spectra of a light emitting device using the wavelength conversion element of Example 3 when irradiated with excitation light of different outputs. FIG. 17A is a diagram showing the chromaticity calculated from the emission spectrum of FIG. 17A. FIG. 17D is a diagram showing the XRD pattern of a yellow powder obtained by the synthesis procedure of graphite-like carbon nitride phosphor (g-C3N4). FIG. 17E is a diagram showing the XRD pattern of a yellow powder obtained by the synthesis procedure of graphite-like carbon nitride phosphor (g-C3N4). １３ 1 is a diagram showing a C-CP-MAS-NMR spectrum; 2 is a diagram showing an emission spectrum of a graphite-like carbon nitride phosphor (g-C3N4) dispersion; 3 is a diagram showing an emission spectrum of a light-emitting device using the wavelength conversion element of Example 5, and an emission spectrum of a phosphor layer used in the wavelength conversion element; 4 is a diagram showing chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 5;

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that like elements are given like numbers and their description will be omitted. (Embodiment 1) As embodiment 1, a wavelength conversion element of the present invention will be described. Figure 1 is a schematic diagram showing a wavelength conversion element of the present invention.

[0010] The wavelength conversion element 100 of the present invention includes a first reflective layer 110, a second reflective layer 120, and a phosphor layer 130 located therebetween. The phosphor layer 130 is not particularly limited as long as it converts irradiated excitation light into light having a wavelength longer than the excitation light and has excitation wavelength dependency of the emission wavelength. The excitation wavelength dependency of the emission wavelength refers to the property that when the wavelength of the excitation light is shifted to a longer wavelength, the emission wavelength also shifts to a longer wavelength, and when the wavelength of the excitation light is shifted to a shorter wavelength, the emission wavelength also shifts to a shorter wavelength.

[0011] The first reflective layer 110 reflects light in a first wavelength range (also referred to as a first stop band) that is longer than the wavelength of the excitation light, and transmits light of other wavelengths. The second reflective layer 120 reflects light in a second wavelength range (also referred to as a second stop band) that overlaps with at least a portion of the first wavelength range, and transmits light of other wavelengths. Note that the second wavelength range may include the entire first wavelength range.

[0012] FIG. 1 shows a wavelength conversion element 100 in which a laminate 140 consisting of a first reflective layer 110, a second reflective layer 120, and a phosphor layer 130 located therebetween is disposed on a substrate 150. The substrate 150 is not essential, but its use is preferred because it simplifies handling of the wavelength conversion element 100. The substrate 150 may be made of a material having a transmittance of at least 50% for the wavelength of the excitation light. The substrate 150 is preferably made of a material having a transmittance of at least 70% for light having a wavelength in the range of not less than the wavelength of the excitation light and not more than 1 μm. In this case, the light converted by the wavelength conversion element 100 can be extracted through the substrate 150.

[0013] The substrate 150 may be, for example, glass such as quartz glass, borosilicate glass, or soda-lime glass, fluoride single crystal such as calcium fluoride or barium fluoride, or resin such as cycloolefin polymer, cycloolefin copolymer, polyimide resin, polycarbonate resin, polyethylene terephthalate, acrylic resin, or epoxy resin. These are preferable because they have a transmittance of more than 80% for the wavelength range from ultraviolet light of about 350 nm to 1 μm.

[0014] 1, light having a specific wavelength is confined and resonates within the laminate 140. The light having a specific wavelength that is enhanced by resonance is further wavelength-converted in the phosphor layer 130 within the laminate 140. As a result, the wavelength conversion element of the present invention emits light that is a combination of wavelength-converted excitation light from an excitation source and wavelength-converted light from the resonated and enhanced light having a specific wavelength, thereby enabling emission of light with adjusted chromaticity using only one type of phosphor. This will be explained in detail.

[0015] In the wavelength conversion element 100, excitation light 160 from an excitation source (not shown) is incident via the substrate 150. It is assumed that the peak position of the wavelength of the excitation light 160 incident on the wavelength conversion element 100 is on the shorter wavelength side than the lower limit of the first wavelength range of the first reflective layer 110.

[0016] The excitation light 160 passes through the first reflective layer 110 and reaches the phosphor layer 130. The phosphor layer 130 is excited by the excitation light 160 and emits light 170 having a longer wavelength than the excitation light 160 (by wavelength conversion).

[0017] The wavelength-converted light 170 is incident on the second reflective layer 120. The second reflective layer 120 reflects light 180 having a second wavelength region of the light 170 and transmits the remaining light 170'. Of the light 180 reflected by the second reflective layer 120, light with a wavelength in the region where the first wavelength region and the second wavelength region overlap is repeatedly reflected and resonates within the stack 140. Since the phosphor layer 130 has an emission wavelength dependent on the excitation wavelength, it is excited by the light 180 reflected and resonated within the stack 140 and emits light 190 having a wavelength longer than the wavelength of the light 180 (wavelength conversion). Of the wavelength-converted light 190, light 190' having a wavelength longer than the longest wavelength in the second wavelength region of the second reflective layer 120 passes through the second reflective layer 120 and is emitted from the wavelength conversion element 100.

[0018] As a result, the wavelength conversion element 100 can emit at least light 170' that is part of the wavelength-converted light 170 and that is transmitted through the second reflective layer 120, and light 190' that is part of the wavelength-converted light 190 and that is transmitted through the second reflective layer 120, and can exhibit an emission color that is a mixture of these. For example, the light 170' and the light 190' may be mixed to emit white light.

[0019] When the wavelength-converted light 170 is completely contained in the second wavelength region (second stop band), most of the wavelength-converted light 170 is reflected by the second reflective layer 120, and very little light 170′ is transmitted through the second reflective layer 120, although this depends on the transmittance of the stop band. The present invention also includes such a case.

[0020] Therefore, in the wavelength conversion element 100 of the present invention, by adjusting the wavelength ranges of the first stop band of the first reflective layer 110 and the second stop band of the second reflective layer 120, and further the transmittance of these stop bands and other wavelength regions, it is possible to control the wavelength and intensity of the light 170′ and the wavelength and intensity of the light 190′, and therefore it is possible to adjust the chromaticity and color temperature of the emitted color from the wavelength conversion element 100.

[0021] Next, we will explain how to adjust the chromaticity and color temperature of the emitted color of the wavelength conversion element 100 when using a phosphor whose emission wavelength depends on the excitation wavelength, which emits blue light having an emission peak wavelength in the range of 450 nm to 500 nm when excited by ultraviolet light having a wavelength of 330 nm to 420 nm.

[0022] <Yellow to Red Light Emission> The first reflective layer 110 reflects light in a first wavelength region of 480 nm to 590 nm and transmits other wavelengths. The second reflective layer 120 reflects light in a second wavelength region of 450 nm to 520 nm and transmits other wavelengths. In this case, yellow to red light is emitted by irradiation with ultraviolet light.

[0023] Specifically, excitation light 160, which is ultraviolet light, passes through the first reflective layer 110 and is wavelength-converted to blue light 170 in the phosphor layer 130. Of the light 170, light with a wavelength within the second stop band is reflected by the second reflective layer 120 to become light 180, and this light 180 resonates within the stack 140. The amplified light 180 then resonates within the stack 140, exciting the phosphor in the phosphor layer 130 and is wavelength-converted to yellow to red light 190 having a wavelength of, for example, 580 nm or more and 650 nm or less. Of the light 190, light with a wavelength longer than the longest wavelength of the second stop band passes through the second reflective layer 120 and is emitted as light 190'. In this way, when a single phosphor that emits blue light upon ultraviolet excitation is used, a wavelength conversion element that emits yellow to red light can be provided.

[0024] In this case, the chromaticity can be adjusted by selecting the transmittance (or reflectance) of the first reflective layer 110 or the second reflective layer 120. For example, if the transmittance of the second stop band in the second reflective layer 120 is 50%, part of the blue light 170 passes through the second reflective layer 120 and is emitted as light 170′, thereby enabling emission of a mixture of a small amount of blue and yellow to red.

[0025] More preferably, the first reflective layer 110 has a transmittance of substantially 0% in the first stop band and a transmittance of 60% or more outside the first stop band, and the second reflective layer 120 has a transmittance of 3% to 5% in the second stop band and a transmittance of 60% or more outside the second stop band, thereby providing a wavelength conversion element that emits yellow to orange light.

[0026] The wavelength conversion element 100 may also have an emission spectrum of emitted light having peaks in the wavelength range of 450 nm to 500 nm and in the wavelength range of 580 nm to 650 nm, respectively, and these peak intensities may be dependent on the output power of the ultraviolet light (excitation light) irradiated. That is, the higher the output power of the excitation light, the higher the emission intensity. In this case, the chromaticity does not change even when the output power of the excitation light changes, so a stable wavelength conversion element can be provided.

[0027] <White Light Emission> The first reflective layer 110 reflects light in a first wavelength range of 480 nm to 590 nm and transmits light of other wavelengths. The second reflective layer 120 reflects light in a second wavelength range of 395 nm to 425 nm and 500 nm to 560 nm and transmits light of other wavelengths. In this case, white light is emitted by irradiating ultraviolet light.

[0028] Specifically, excitation light 160, which is ultraviolet light, passes through the first reflective layer 110 and is wavelength-converted to blue light 170 in the phosphor layer 130. Light 170' having a wavelength greater than 425 nm and less than 500 nm of light 170 passes through the second reflective layer 120 and is emitted. On the other hand, light 180 reflected without passing through the second reflective layer 120, having a wavelength of 500 nm or more, resonates within the stack 140. The light 180 then resonates and is amplified within the stack 140, excites the phosphor layer 130, and is wavelength-converted to yellow to red light 190 having a wavelength of, for example, 580 nm or more and 650 nm or less. Light 190 passes through the second reflective layer 120 and is emitted as light 190'. In this way, when a single phosphor that emits blue light upon ultraviolet excitation is used, a wavelength conversion element that emits white light that is a mixture of blue light and yellow to red light can be provided.

[0029] Preferably, by adjusting the transmittance of light having a wavelength longer than 425 nm and shorter than 500 nm in the second reflective layer 120, the intensity of light 180 reflected and resonated by the second reflective layer 120 out of the blue light 170 is controlled, and the intensity of yellow to red light 190 generated by wavelength conversion of this light 180 is controlled. As a result, white light emission at various color temperatures, such as incandescent white, warm white, neutral white, and daylight white, is possible. More preferably, the first reflective layer 110 has a transmittance of substantially 0% in the first stop band and a transmittance of 60% or more outside the first stop band, and the second reflective layer 120 has a transmittance of 7% to 15% in the second stop band and a transmittance of 60% or more outside the second stop band. This makes it possible to provide a wavelength conversion element that emits white light along the blackbody locus.

[0030] Furthermore, the wavelength conversion element 100 may have an emission spectrum with peaks in the range of 450 nm to 500 nm and in the range of 580 nm to 650 nm, respectively. The peak intensity in the wavelength range of 450 nm to 500 nm may not depend on the output of the irradiated ultraviolet light (excitation light), while the peak intensity in the wavelength range of 580 nm to 650 nm may depend on the output of the irradiated excitation light. In this case, the chromaticity and color temperature can be controlled by changing the output of the excitation light, so that when combined with an excitation source, a light-emitting device can be provided whose chromaticity can be adjusted by controlling the output of the excitation source. Therefore, for example, white light can be emitted whose color temperature changes along the blackbody locus in the chromaticity coordinate system, such that increasing the output of the excitation light produces a white light closer to incandescent light, and decreasing the output of the excitation light produces a white light closer to bluish-white light.

[0031] In particular, by appropriately selecting the first reflective layer 110 and the second reflective layer 120, specifically, by appropriately selecting the wavelength ranges of the first stop band and the second stop band, and further, the transmittances of the first reflective layer 110 and the second reflective layer 120, the wavelength conversion element 100 of the present invention can emit white light whose color temperature changes along the blackbody locus in the chromaticity coordinate, and the deviation can be suppressed within a range of ±0.01. Such selection can be made by a person skilled in the art who understands the emission characteristics of phosphors from the contents of this specification.

[0032] As described above, the second wavelength region of the second reflective layer 120 overlaps with at least a portion of the first wavelength region of the first reflective layer 110, but the second wavelength region may include all of the first wavelengths.

[0033] Subtle chromaticity adjustment is possible when the second reflective layer 120 is the same as the first reflective layer 110. The following describes a case where the first wavelength region and the second wavelength region of the reflective layer are both in the range of 480 nm to 590 nm, and a phosphor that emits blue light when excited by ultraviolet light is used.

[0034] Excitation light 160, which is ultraviolet light, passes through the first reflective layer 110 and is wavelength-converted to blue light 170 in the phosphor layer 130. Most of the light 170 passes through the second reflective layer 120 and becomes light 170'. On the other hand, light 180 that is slightly reflected by the second reflective layer 120 is resonated within the stack 140. At this time, the enhancement of light 180 due to resonance is limited, so light 180 is used as excitation light, and only a small amount of yellow to red light 190 is generated by wavelength conversion in the phosphor layer 130. This small amount of light passes through the second reflective layer 120 and becomes light 190'. Therefore, the light emitted from the wavelength conversion element is a mixture of blue light and a small amount of yellow to red light, making it possible to provide a wavelength conversion element that emits blue light with a delicately adjusted chromaticity.

[0035] Next, each component of the wavelength conversion element 100 of the present invention will be described. There are no particular limitations on the first reflective layer 110 and the second reflective layer 120 as long as they can reflect light having a specific wavelength and transmit other wavelengths as described above. Typically, a distributed Bragg reflector (DBR) can be used. Such a DBR has a superlattice structure in which two or more dielectrics with different refractive indices are stacked. Examples of dielectrics include nitrides such as gallium nitride (GaN) and aluminum nitride (AlN), and niobium oxide (Nb ２ O ５ ), titanium oxide (TiO ２ ), zirconium oxide (ZrO ２ ), tantalum oxide (Ta ２ O ５ ), silicon dioxide (SiO ２ Two or more dielectric materials having relatively different refractive indices may be selected from these, and the film thickness and the number of pairs may be appropriately changed.

[0036] For example, the first reflective layer 110 may have a superlattice structure of aluminum nitride layers and silicon dioxide layers, and the second reflective layer 120 may have a superlattice structure of tantalum oxide layers and silicon dioxide layers. By changing the film thickness and the number of pairs, the first stop band and the second stop band described above can be adjusted.

[0037] There are no particular limitations on the phosphor layer 130, as long as it contains a phosphor that, upon irradiation with excitation light, converts the irradiated excitation light into light having a longer wavelength and has an emission wavelength that is excitation wavelength dependent. Whether or not the emission wavelength is excitation wavelength dependent can be easily determined by measuring the excitation spectrum and emission spectrum of the phosphor.

[0038] The phosphor contained in the phosphor layer 130 can be one that is excited by ultraviolet light with a wavelength of 330 nm or more and 420 nm or less, and emits blue light with a peak in the wavelength range of 450 nm or more and 500 nm or less. By using such a phosphor, it is possible to provide a wavelength conversion element that emits yellow to red light, or even white light, using ultraviolet light as excitation light. Alternatively, it is possible to use a phosphor that is excited by blue light with a wavelength of 420 nm or more and 480 nm or less, and emits green light with a wavelength of 490 nm or more and 550 nm or yellow to red light with a wavelength of 550 nm or more and 770 nm or less. By using such a phosphor, it is possible to provide a wavelength conversion element that emits white light using blue light as excitation light.

[0039] The phosphor layer 130 preferably contains at least one phosphor selected from the group consisting of carbon nanoparticle phosphors, organic nanoparticle phosphors, organometallic complex phosphors, inorganic phosphors, and semiconductor quantum dot phosphors.

[0040] Examples of organic nanoparticle fluorescent materials include 4,4'-(2,7-bis[4-{1,2,2-triphenylvinyl}phenyl]-9H-fluorene-9,9-diyl)bis(N,N,N-trimethylbutan-1-amino) bromide (TPEFN), 10 bis(monoacylglycerol)bisphenol-A, and Ttrz-DI. Examples include nano-dot (TNAP (N,N,6,10-tetra(naphthalen-2-yl)-6,10-dihydro-6,10-diaza-16b-boraanthr a[3,2,1-de]tetracen-8-amine)). These organic nanoparticle fluorescent materials are well known and can be easily obtained and manufactured. Alternatively, amorphous ionic polymers, 2,4,6-triamino-1,3,5-triazine, [Pt(tpp)(ed)] ＋ [Pt(ftpp)(CN) ２ ] － (where ttp = 2-(4-(trifluoromethyl)phenyl)pyridine, ed = ethane-1,2-diamine, and ftpp = 2-(4-fluoro-3-(trifluoromethyl)phenyl)pyridine), non-aromatic organic aggregation-induced luminescence (AIE) substances such as 1,2-dinaphthyl-ortho-carborane, pyromellitic diimide (PMDI), and bis(3,4,5-tris(16-alkyloxy)monobenzoylglyceride)bisphenol A10 (16-EDFONP).

[0041] Examples of organometallic complex fluorescent materials include Ca-MOF, LIFM-41, [Ca ３ (HL) ２ (DMF) ５ ] ｎ , (DMF=N,N-dimethylformamide, H4L=2'-amino-[1,1':4',1"-terphenyl]-3,3",5,5"-tetracarboxylic acid), [Pt(tpp)(ed)]+[Pt(ftpp)(CN) ２]-(ttp=2-(4-(trifluoromethyl)phenyl)pyridine, ed=ethane-1,2-diamine, ftpp=2-(4-fluoro-3-(trifluoromethyl)phenyl)pyridine)), 2D Ge-TCNQ microplate crystals (TCNQ, 7,7,8,8-tetracyanoquinodimethane), or La-containing organic complexes ([Eu ２－ｘ La ｘ (phen) ２ (k2-TC) ２ (μ2-TC) ２ (η3-TC) ２ ]・2(H ２ O)(Eu ２－ｘ La ｘ－３ ; x = 0.47-1.51) (see, for example, R. Lee Ayscue III et al., Norg. Hem. 2020, 59, 11, 7539-7552), [Tb ２－ｙ La ｙ (phen) ２ (k2-TC) ２ (μ2-TC) ４ ]・2(H ２ O)(Tb ２－ｙ La ｙ－４ ;y=0.42, 0.67) (see the above-mentioned literature), lanthanide organic hybrids such as (Ln-POM)[N(CH ３ ) ４ ] ３ K ２ Sm (C ７ H ５ O ２ ) (H ２ O) ２ (α-PW １１ O ３９ ) 11H ２ O, [Ln(3,4'-oba)(phen)(ox) ０．５ ] ｎ (Ln=1 for Sm, 2 for Eu, 3 for Gd, 4 for Tb, 5 for Dy) and other lanthanide polyacids. These organometallic complex phosphors are well known and can be easily obtained and produced. ４ N ２ H １４ PbC １４The metal halide may be an organic or inorganic metal halide such as:

[0042] The inorganic phosphor is, for example, (NH ４ ) SnCl ６ : Sb ３＋ , Cs ２ ScCl ５ ・H ２ O perovskite, BaZrO ３ : M (where M is Eu ３＋ , Pb ２＋ , Mn ２＋ , and Y ３＋ , Tb ３＋ , Yb ３＋ Eu etc. ３＋ at least one lanthanide cation selected from the group consisting of lanthanide cations other than ２ O ３ : Bi, Ba ９ Lu ２ Si ６ O ２４ :Bi ３＋ , Eu ３＋ These inorganic phosphors are well known and can be easily obtained and produced.

[0043] The semiconductor quantum dot phosphor is, for example, CsPbBr ３ , CdSe / CdS, Zn ０．４５ Cd ０．５５ , Si nanoparticles, In ２ S ３ :Mn, Cu, MoS ２ , W.S. ２ , ZnS, rhenium oxide, etc. These semiconductor quantum dot phosphors are well known and can be easily obtained and produced.

[0044] Carbon nanoparticle phosphors are phosphors made of nanoparticles whose main component is carbon, such as amorphous carbon or graphite carbon. Carbon nanoparticle phosphors are preferably excited by irradiation with ultraviolet light having a wavelength of 330 nm or more and 420 nm or less, and emit blue light having a peak in the wavelength range of 450 nm or more and 500 nm or less. Such carbon nanoparticle phosphors are described in detail below.

[0045] The carbon nanoparticle phosphor preferably contains carbon, oxygen, nitrogen, and hydrogen, the carbon being present as amorphous carbon and graphite-like carbon, the amorphous carbon accounting for 60% by volume or more and less than 99% by volume, and the graphite-like carbon accounting for 1% by volume or more and less than 40% by volume, respectively, the nitrogen being present as at least pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen, the content of the pyridine-type nitrogen being greater than that of the graphite-type nitrogen.When the volume ratio of amorphous carbon to graphite-like carbon and the existence form and ratio of the nitrogen element satisfy a predetermined relationship, the carbon nanoparticle phosphor emits blue light upon irradiation with ultraviolet light, and the emission wavelength is excitation wavelength dependent. The contents of amorphous carbon and graphite carbon are calculated using the intensities of the peaks at 2θ=20.5° and 27° in powder X-ray diffraction using Cu—Kα radiation.

[0046] More preferably, the carbon nanoparticle phosphor has a ratio of the amorphous carbon to the total volume of 60% to 65% by volume, and the graphite carbon to the total volume of 35% to 40% by volume, respectively, which can result in a phosphor with good color purity.

[0047] The carbon nanoparticle phosphor preferably has a carbon element content p (atomic %), a nitrogen element content q (atomic %), and an oxygen element content r (atomic %) that satisfy the following: 0.58≦p / (p+q+r)≦0.65, 0.15≦q / (p+q+r)≦0.30, and 0.12≦r / (p+q+r)<0.25. This allows the deviation from the blackbody locus in the chromaticity coordinates to be limited to within ±0.03. More preferably, the p and q satisfy 0.25≦q / p≦0.3.

[0048] Such carbon nanoparticle fluorescent materials are produced by heating a raw material solution in which a carbon source is dissolved in a nitrogen-containing organic solvent. A nitrogen source may also be dissolved in the raw material solution.

[0049] The carbon source is an organic substance that decomposes to carbon upon heating. Examples of such organic substances include at least one selected from the group consisting of citric acid, citric acid monohydrate, ammonium citrate, benzoic acid, ascorbic acid, glucose, fructose, and sucrose. Examples of nitrogen-containing organic solvents include formamide and N-methylformamide.

[0050] The concentration of the carbon source in the organic solvent is preferably 0.05 mol / L or more and 0.2 mol / L or less. This range allows for the production of a phosphor in which the volume percentages of amorphous carbon and graphite carbon relative to the total amount are both within the aforementioned preferred ranges. More preferably, the concentration of the carbon source in the organic solvent is 0.1 mol / L or more and 0.15 mol / L or less. This allows the color emitted by the carbon nanoparticle phosphor when irradiated with ultraviolet light to satisfy the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.2≦x<0.3 and 0.25≦y≦0.4.

[0051] Examples of nitrogen sources include ethylenediamine, ammonia, formamide, and arginine.

[0052] The heating conditions are not particularly limited as long as the carbon source is decomposed and the carbon reacts with the nitrogen in the organic solvent or the nitrogen in the nitrogen source. Preferably, the raw material solution is heated at a temperature of 150°C or higher and 230°C or lower for 5 hours or longer and 15 hours or shorter. Under these conditions, the reaction proceeds efficiently and a carbon nanoparticle fluorescent material is obtained. More preferably, the heating is performed at a temperature of 170°C or higher and 210°C or lower for 7 hours or longer and 10 hours or shorter.

[0053] In this way, the carbon nanoparticle phosphor is obtained in a dispersed state in the solvent. When the carbon nanoparticle phosphor is obtained in a powder form, the solid content may be recovered from the obtained product by centrifugation or the like, and then heated and dried in a vacuum.

[0054] The phosphor layer 130 may be a single crystal of the above-mentioned phosphor, or may be a resin molded body in which a powder of the above-mentioned phosphor is dispersed. The resin used for the resin molded body may be a water-soluble polymer that transmits light with wavelengths from the ultraviolet to the visible range, and may be selected from polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyethyleneimine, polyethylene oxide, polyvinylpyrrolidone, carboxyl vinyl polymer, etc. Such resins can be used to form a thin-film phosphor layer 130 by spin coating, dripping, etc., or to form a bulk phosphor layer 130 by drying. Alternatively, a fiber-shaped resin molded body can be provided by electrospinning, etc. Such resin molded bodies are easy to handle.

[0055] For example, when a carbon nanoparticle phosphor is used as the phosphor, the content of the phosphor in the resin molded body is preferably in the range of 0.01% by mass to 5% by mass. Within this range, concentration quenching can be suppressed, and high luminescence intensity and high quantum efficiency can be expected. More preferably, the content of the carbon nanoparticle phosphor is in the range of 0.01% by mass to 1% by mass. The content can be appropriately designed depending on the selected phosphor.

[0056] The manufacturing method of the wavelength conversion element 100 of the present invention is not particularly limited as long as the laminate 140 shown in Figure 1 can be obtained. For example, when the phosphor is a powder, a first reflective layer 110 is formed on a substrate 150 by physical vapor deposition, chemical vapor deposition, or the like, and then a solution containing the phosphor is applied to the first reflective layer 110 by drop casting, spray coating, immersion, spin coating, or the like to form a phosphor layer 130. Then, a second reflective layer 120 is formed on the phosphor layer 130 by physical vapor deposition, chemical vapor deposition, or the like. On the other hand, when the phosphor is a single crystal, for example, a first reflective layer 110 is formed on one side of the single crystal phosphor layer 130 by physical vapor deposition, chemical vapor deposition, or the like, and a second reflective layer 120 is similarly formed on the other side of the phosphor layer 130.

[0057] (Embodiment 2) As embodiment 2, a light emitting device using the wavelength conversion element of the present invention, that is, the wavelength conversion element according to embodiment 1, will be described. Fig. 2 is a schematic diagram showing the light emitting device of the present invention.

[0058] The light emitting device 200 in Fig. 2 is a substrate-mounted white light emitting diode lamp. The light emitting device 200 of the present invention includes at least an excitation source 240 and a wavelength conversion element 100, and the wavelength conversion element 100 is the wavelength conversion element described in embodiment 1. With this configuration, a light emitting device having a desired emission color can be provided.

[0059] A source that emits light having a peak in the wavelength range of 200 nm to 600 nm is used as the excitation source 240. Examples of such excitation sources include light-emitting diodes (LEDs), laser diodes (LDs), organic electroluminescent devices (OLEDs), semiconductor lasers, and fluorescent lamps.

[0060] The wavelength of the excitation light from excitation source 240 is set appropriately depending on the selected phosphor. For example, if the phosphor in phosphor layer 130 emits blue light when excited by ultraviolet light, a purple light-emitting diode having a peak in the range of 330 nm to 420 nm may be used as excitation source 240. For example, if the phosphor in phosphor layer 130 emits green or red light when excited by blue light, a blue light-emitting diode having a peak in the range of 430 nm to 480 nm may be used as excitation source 240.

[0061] The excitation source 240 may have a variable output, which allows the wavelength conversion element 100 to be designed so that the chromaticity and color temperature can be adjusted by controlling the output of the excitation light.

[0062] Light-emitting device 200 has lead wires 210 and 220, which are fixed to a white alumina substrate 230 with high visible light reflectance. One end of one lead wire 210 is mounted with, for example, a purple light-emitting diode element with an emission peak wavelength of 380 nm as excitation source 240, and is electrically connected to it via a conductive paste or the like. One end of the other lead wire 220 is electrically connected to excitation source 240 via a thin gold wire 250. The other ends of lead wires 210 and 220 extend outside and function as electrodes.

[0063] The wavelength conversion element 100 according to the first embodiment is placed on the excitation source 240. The wavelength conversion element 100 here includes, for example, a first reflective layer 110 that reflects light in a first wavelength region of 480 nm or more and 590 nm or less and transmits other wavelengths, a second reflective layer 120 that reflects light in a second wavelength region of 395 nm or more and 425 nm or less and 500 nm or more and 560 nm or less and transmits other wavelengths, and a phosphor layer 130 that is a resin molded body in which a carbon nanoparticle phosphor is dispersed, the phosphor layer being excited by ultraviolet irradiation and emitting blue light having a peak in the range of 450 nm or more and 500 nm or less and having an emission wavelength dependent on the excitation wavelength, and the laminate 140 is disposed on a quartz substrate.

[0064] Here, the transmittance of the first reflective layer 110 in the first wavelength region is set to substantially 0%, and the average transmittance of the other wavelength regions is set to 70%. The transmittance of the second reflective layer 120 in the second wavelength region is set to 10%, the average transmittance in the wavelength range of more than 425 nm and less than 500 nm is set to 60%, and the average transmittance in the wavelength range of less than 395 nm and more than 560 nm is set to 80%.

[0065] A wall member 280 made of white silicone resin or the like is provided on the periphery of the alumina substrate 230, and the excitation source 240 on which the wavelength conversion element 100 is mounted is located in the center of the alumina substrate 230. The excitation source 240 and the wavelength conversion element 100 are sealed with a transparent resin 270 such as epoxy resin that is filled in a recess surrounded by the wall member 280.

[0066] When the lead wires 210, 220 of the light emitting device 200 are energized, the excitation source 240 emits light with a peak wavelength of 380 nm. This light enters the wavelength conversion element 100 of the present invention, passes through the quartz substrate and the first reflective layer 110, and is wavelength-converted into blue light (light 170 in FIG. 1 ) by the phosphor layer 130. Of the light 170, light 170′ having a wavelength longer than 425 nm and shorter than 500 nm passes through the second reflective layer 120 and is emitted from the wavelength conversion element 100.

[0067] Of the light 170, light having a wavelength of 425 nm or less and light having a wavelength of 500 nm or more is reflected by the second reflective layer 120. Of the reflected light, light 180 having a wavelength of 500 nm or more is also reflected by the first reflective layer 110, and is therefore repeatedly reflected between the first reflective layer 110 and the second reflective layer 120, causing resonance. The resonated light 180 excites the phosphor layer 130, and is wavelength-converted to yellow to red light (light 190 in FIG. 1 ). Of the light 190, light 190′ having a wavelength exceeding 560 nm is transmitted through the second reflective layer 120 and is emitted from the wavelength conversion element 100.

[0068] During the energization, ultraviolet light is constantly emitted from the excitation source 240, so that the above-described wavelength conversion and resonance occur repeatedly, and light 170' and light 190' are continuously emitted from the wavelength conversion element 100.

[0069] The light 170' and light 190' emitted from the wavelength conversion element 100 are reflected by the wall member 280, transmitted through the resin 270, and emitted from the light emitting device 200. The light emitted from the light emitting device 200 is a mixture of light 170', such as blue, and light 190', such as yellow to red, and is therefore white light. In this way, even when using a single phosphor that emits blue light upon ultraviolet excitation, by adjusting the stop bands of the first reflective layer 110 and the second reflective layer 120, it is possible to provide a light emitting device 200 that emits white light that is a mixture of blue light (light 170') and yellow to red light (light 190'). In addition, by adjusting the design of the wavelength conversion element and the output of the excitation source, it is also possible to provide a light emitting device 200 that can emit white light along the blackbody locus.

[0070] In the second embodiment, the phosphors used in the first reflective layer 110, the second reflective layer 120, and the phosphor layer 130 in the wavelength conversion element 100 are not limited to the above-described configurations and can be appropriately adjusted to obtain a desired emission color. By adopting the wavelength conversion element 100 according to the first embodiment, even when one type of phosphor is used, a light emitting device capable of emitting any emission color can be provided, and a light emitting device capable of tunable emission from blue to red, white, and even infrared can be provided. Such modifications are also within the scope of the present invention.

[0071] Although the substrate-mounted white light-emitting diode lamp has been described with reference to Fig. 2, the wavelength conversion element according to the first embodiment may also be employed in a bullet-type white light-emitting diode lamp. Such modifications can be easily made by those skilled in the art.

[0072] The light emitting device according to the second embodiment may be a white light emitting diode including the wavelength conversion element according to the first embodiment, or may be a lighting fixture including a plurality of such diodes, a backlight for a liquid crystal panel, or the like.

[0073] The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

[0074] [Carbon nanoparticle phosphor (CD1)] Carbon nanoparticle phosphor (CD1), which emits blue (cyan) when irradiated with ultraviolet light and whose emission wavelength is variable depending on the excitation wavelength, was synthesized using a solvothermal method. Figure 3 shows the synthesis process of carbon nanoparticle phosphor (CD1).

[0075] Specifically, a raw material solution was prepared by dissolving 0.12 M citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a carbon source in 20 mL of formamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an organic solvent, and then heating the raw material solution at 200°C for 8 hours.

[0076] The resulting product was centrifuged (rotation speed: 800 rpm), and the separated solid was washed several times with ethanol and then with ultrapure water (manufactured by Merck using Milli-Q (registered trademark)). After washing, the solid was dried in a vacuum (vacuum degree: 1 to 1000 Pa) at 60°C for 4 hours to obtain a carbon nanoparticle phosphor (CD1) powder.

[0077] The carbon nanoparticle phosphor (CD1) powder thus obtained was subjected to X-ray diffraction measurement using an X-ray diffractometer (Rigaku Corporation, Rint Ultima III) with Cu-Kα radiation. The results are shown in FIG.

[0078] FIG. 4 shows the XRD pattern of the carbon nanoparticle phosphor (CD1) powder.

[0079] 4, the XRD pattern of the carbon nanoparticle phosphor (CD1) powder showed a broad peak near 2θ = 20.5° and a sharp peak near 2θ = 27°. This result indicated that the carbon nanoparticle phosphor (CD1) powder was primarily composed of amorphous carbon and graphite-like carbon. The volume percentages of amorphous carbon and graphite-like carbon were calculated based on the intensities of these peaks, resulting in 62% amorphous carbon and 38% graphite-like carbon.

[0080] The carbon nanoparticle phosphor (CD1) powder was dispersed in dimethyl sulfoxide (DMSO, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and passed through a 20 nm syringe filter. At this time, the concentration of the carbon nanoparticle phosphor (CD1) in DMSO was 0.0025 mass% (0.025 mg / mL). When the carbon nanoparticle phosphor (CD1) dispersion liquid obtained in this way was irradiated with light of 365 nm wavelength emitted by a lamp, blue light emission was confirmed.

[0081] A dispersion of carbon nanoparticle phosphor (CD1) was prepared by a dispersion method and observed with a high-resolution transmission electron microscope (HR-TEM) (JEOL, JEM 2100F). The results are shown in FIG.

[0082] FIG. 5 shows TEM images of the carbon nanoparticle phosphor (CD1) dispersion at various magnifications.

[0083] In Figure 5, as shown by the dotted line, a layer structure derived from amorphous carbon was confirmed. Furthermore, when the circled area was enlarged, lattice fringes were confirmed, indicating the presence of crystalline graphitic carbon. The average particle size of the carbon nanoparticle phosphor (CD1) was found to be in the range of 1 nm to 20 nm. The average particle size was calculated by measuring the particle sizes of at least 100 nanoparticles observed in any 500 nm square area in a transmission electron microscope (TEM) image obtained at a magnification of 1000 times or more. Since the nanoparticles are not perfectly spherical, the longest diameter was used as the particle size of the nanoparticles. From the above, it was confirmed that carbon nanoparticle phosphors were dispersed in the liquid sample.

[0084] The chemical state analysis and composition analysis of the liquid sample were performed using an X-ray photoelectron spectroscopy (XPS) analyzer (Quautera SXM, manufactured by ULVAC-PHI, Inc.) The results are shown in FIGS.

[0085] FIG. 6 is a diagram showing the XPS spectrum of the carbon nanoparticle phosphor (CD1) dispersion.

[0086] 6, it was found that carbon, oxygen, and nitrogen elements were present in the carbon nanoparticle phosphor in the liquid sample. Note that peaks due to elements in the solvent (DMSO) were removed from the XPS spectrum. Furthermore, composition analysis revealed that the sample contained 62.31 atomic % carbon, 17.32 atomic % nitrogen, and 20.37 atomic % oxygen, with an N / C atomic ratio of 0.28. It was also confirmed that the ratios of the carbon content p (atomic %), nitrogen content q (atomic %), and oxygen content r (atomic %) to their sum satisfied the following: 0.58≦p / (p+q+r)≦0.65, 0.15≦q / (p+q+r)≦0.30, and 0.12≦r / (p+q+r)<0.25, respectively.

[0087] FIG. 7 shows the deconvoluted HRXPS spectrum of a carbon nanoparticle phosphor (CD1) dispersion.

[0088] Figure 7 shows the results of deconvolution of the N-1s peak in the XPS spectrum shown in Figure 6. Figure 7 shows that the N-1s peak is composed of four main peaks corresponding to binding energies of 398.7 eV, 399.6 eV, 400.3 eV, and 401.3 eV. These peaks were determined to correspond to the types of nitrogen doping centers in the carbon framework, namely, pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen, respectively.

[0089] The FTIR spectrum of the carbon nanoparticle phosphor (CD1) dispersion was measured by attenuated total reflection infrared spectroscopy (ATR-FTIR) using a spectrophotometer (Nicolet iS50 FTIR, manufactured by Thermo Scientific). It was found that the C═O bond (1697 cm ) contained in the amide bond －１ C=C bonds contained in aromatic compounds (around 1530 cm －１ around 1310-1380 cm), and the OH and CH bonds contained in phenol (1310-1380 cm －１ This indicates that the carbon nanoparticle phosphor has functional groups and bonds such as -OH, C=O, C=C, and C-H.

[0090] The absorption spectrum of the carbon nanoparticle phosphor (CD1) dispersion was measured using an ultraviolet-visible-near-infrared spectrophotometer (V-570, manufactured by JASCO Corporation), and it was found that it absorbed light well in the wavelength range of 200 nm to 600 nm. The emission spectrum of the carbon nanoparticle phosphor (CD1) dispersion was measured using a spectrofluorophotometer (FP-8500, manufactured by JASCO Corporation). The results are shown in Figures 8 and 9.

[0091] FIG. 8 is a diagram showing the emission spectrum of the carbon nanoparticle phosphor (CD1) dispersion liquid.

[0092] 8 shows the emission spectrum when the carbon nanoparticle phosphor (CD1) dispersion liquid is irradiated with excitation light having a wavelength of 370 nm. The emission spectrum shows that the carbon nanoparticle phosphor (CD1) dispersion liquid emits blue light having a peak at 450 nm when exposed to excitation light having a wavelength of 370 nm.

[0093] FIG. 9 shows two-dimensional emission mapping of a carbon nanoparticle phosphor (CD1) solution.

[0094] In Figure 9, the graph is shown in grayscale, with brighter areas indicating light emission. Figure 9 also shows the state when irradiated with excitation light of various wavelengths. Figure 9 shows that the carbon nanoparticle phosphor (CD1) dispersion changes its emission wavelength as the wavelength of the excitation light changes, and that the emission wavelength is excitation wavelength dependent. Specifically, when the wavelength of the excitation light was 400 nm to 450 nm, it emitted blue-green light; when the wavelength of the excitation light was 500 nm, it emitted green light (peak wavelength near 525 nm); when the wavelength of the excitation light was 550 nm to 575 nm, it emitted orange light; and when the wavelength of the excitation light was 600 nm, it emitted red light (peak wavelength 660 nm).

[0095] Next, a resin molded body with carbon nanoparticle phosphor (CD1) powder dispersed therein was formed. Polyvinylpyrrolidone (PVP) powder (2 g) was added to deionized water (60 mL) and held at 90°C for 3 hours to prepare a PVP aqueous solution (PVP concentration: 3.3% by mass). Carbon nanoparticle phosphor (CD1) powder was added to PVP aqueous solution (4 mL) and stirred. This was drop-cast onto quartz glass and dried at 90°C for 1 hour to obtain a quartz glass / thin film resin molded body laminate. The laminate was irradiated with excitation light of various wavelengths and observed. The results are shown in Figure 10.

[0096] FIG. 10 is a diagram showing the light emission state of a resin molded body containing a carbon nanoparticle phosphor (CD1).

[0097] In Fig. 10, the areas shown in gray scale are bright areas that emit light. As shown in Fig. 10, the emission wavelength of the obtained resin molded body changed as the wavelength of the excitation light changed, similar to the liquid sample shown in Fig. 9.

[0098] [Carbon Nanoparticle Phosphor (CD2)] Carbon nanoparticle phosphor (CD2), which emits blue (cyan) light when irradiated with ultraviolet light and whose emission wavelength does not depend on the excitation wavelength, was synthesized by a hydrothermal synthesis method using an acid.

[0099] The synthesis conditions for carbon nanoparticle phosphor (CD2) were the same as those in Example 1 described in Patent Document 1, and it was confirmed that, as in Patent Document 1, blue light was emitted when irradiated with ultraviolet light. As with CD1, the carbon nanoparticle phosphor (CD2) powder was dispersed in DMSO to produce a carbon nanoparticle phosphor (CD2) dispersion, and the emission spectrum of the resulting dispersion was measured using a spectrofluorometer. The results are shown in Figure 11.

[0100] FIG. 11 is a diagram showing the emission spectrum of the carbon nanoparticle phosphor (CD2) dispersion liquid.

[0101] According to FIG. 11, even when the excitation wavelength was changed, the emission peak wavelength (445 nm) did not change, and it was found that the carbon nanoparticle phosphor (CD2) did not have excitation wavelength dependency of the emission wavelength.

[0102] [Examples 1 to 4: Wavelength conversion element] In Examples 1 to 4, the wavelength conversion element shown in Table 2 was manufactured by combining the above-mentioned carbon nanoparticle phosphor CD1 or CD2 that emits blue light when excited by ultraviolet light with a reflective layer shown in Table 1.

[0103]

[0104]

[0105] First, aluminum nitride (AlN) and silicon oxide (SiO ２ ) and tantalum oxide (Ta ２ O ５ The reflective layers M1 to M3 were formed on the quartz glass substrates in an RF (radio frequency) sputtering apparatus (Shibaura Mechatronics Corporation, CFS-4EP-LL). The sputtering conditions were a substrate distance of 110 mm, an RF output of 300 W, and no substrate heating.

[0106] The reflective layer M1 is made of AlN and SiO ２ The high refractive index layer was made of AlN with a total thickness of 65 nm, and the low refractive index layer was made of SiO ２ The reflective layer M2 was made of Ta and had a total thickness of 98 nm. ２ O ５ and SiO ２ Five pairs of Ta and Ta-based high refractive index layers were stacked. ２ O５ The total thickness is 178 nm, and the low refractive index layer is SiO ２ The reflective layer M3 was made of Ta and had a total thickness of 240 nm. ２ O ５ and SiO ２ Five pairs of Ta and Ta-based high refractive index layers were stacked. ２ O ５ The total thickness is 170 nm, and the low refractive index layer is SiO ２ The total thickness of the reflective layers M1 to M3 was 290 nm. The transmission spectrum of each of the reflective layers M1 to M3 was measured using an ultraviolet-visible-near-infrared spectrophotometer (V-570, manufactured by JASCO Corporation). The results are shown in Figures 12A, 12B, 13A, 13B, 14A, and 14B, respectively.

[0107] Next, a phosphor layer, a resin molded body with CD1 or CD2 dispersed therein, was formed on the reflective layer M1. Polyvinylpyrrolidone (PVP) powder (2 g) was added to deionized water (60 mL) and held at 90°C for 3 hours to prepare a PVP aqueous solution (PVP concentration: 3.3 wt%). CD1 or CD2 was added to 4 mL of PVP aqueous solution and stirred. This was drop-cast onto the reflective layers M1 to M3 and dried at 90°C for 1 hour to obtain a quartz glass / reflective layer / phosphor layer laminate. The carbon nanoparticle phosphor content in the resulting phosphor layer was 0.07 wt%.

[0108] Next, the laminate of quartz glass / reflecting layer / resin molded body was placed in an RF sputtering device, and reflective layers M1 to M3 were formed on the resin molded body. The film formation conditions for each reflective layer were as described above. In this way, wavelength conversion elements of Examples 1 to 4 were obtained.

[0109] The wavelength conversion elements of Examples 1 to 4 were combined with an ultraviolet light-emitting diode element having an emission peak at a wavelength of 355 nm as an excitation source to form light-emitting devices. Ultraviolet light (output: 0.03 mW) from the ultraviolet light-emitting diode element was incident on the quartz glass side of the wavelength conversion elements of Examples 1 to 4, and the emission spectra of the light emitted from the wavelength conversion elements were measured. The results are shown in Figures 12C, 13C, 14C, and 15A, respectively. The CIE 1931 chromaticity (x, y) was also calculated from the emission spectra. The results are shown in Figures 12D, 13D, 14D, and 15B, as well as Table 3, respectively.

[0110]

[0111] 12A and 12B are diagrams showing the transmission spectrum of the reflective layer M1 in the wavelength conversion element of Example 1. FIG. 12C is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 1, and the emission spectrum of the phosphor layer used in the wavelength conversion element. FIG. 12D is a diagram showing the chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 1. FIG. 13A and 13B are diagrams showing the transmission spectra of the reflective layer M1 and the reflective layer M2 in the wavelength conversion element of Example 2. FIG. 13C is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 2, and the emission spectrum of the phosphor layer used in the wavelength conversion element. FIG. 13D is a diagram showing the chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 2. FIG. 14A and 14B are diagrams showing the transmission spectra of the reflective layer M1 and the reflective layer M3 in the wavelength conversion element of Example 3. 14C is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 3, and the emission spectrum of the phosphor layer used in the wavelength conversion element. Fig. 14D is a diagram showing the chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 3. Fig. 15A is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 4, and the emission spectrum of the phosphor layer used in the wavelength conversion element. Fig. 15B is a diagram showing the chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 4.

[0112] 12A, 12B, 13A, and 14A show the transmission spectrum of the reflective layer M1, respectively. FIG. 13B shows the transmission spectrum of the reflective layer M2. FIG. 14B shows the transmission spectrum of the reflective layer M3. These transmission spectra confirmed that each of the reflective layers was as designed in Table 1. The transmittance of the stop band of the reflective layer M1 was essentially 0%, and the average transmittance of the other regions was 70%. The transmittance of the stop band of the reflective layer M2 was 5%, and the average transmittance of the other regions was 75%. The transmittance of the stop band of the reflective layer M3 was 18% on the short wavelength side and 8% on the long wavelength side, and the average transmittance of the other regions was 80%.

[0113] In the emission spectra of Figures 12C, 13C, 14C, and 15A, the emission spectra indicated by dotted lines are all emission spectra obtained when the phosphor layer used in each example is excited with light having a wavelength of 355 nm.

[0114] 12C, 12D and Table 3, it was found that the wavelength conversion element of Example 1, which uses a phosphor that emits blue light when excited by ultraviolet light and has an emission wavelength that depends on the excitation wavelength, and which employs reflective layers M1 for both the first and second reflective layers, can be combined with an ultraviolet light-emitting diode element as an excitation source to form a light-emitting device in which the subtle chromaticity of blue is adjusted.

[0115] Specifically, ultraviolet excitation light passes through the reflective layer M1 and is wavelength-converted to blue light in the phosphor layer. Most of the blue light passes through the opposing reflective layer M1 and is emitted, with only a small amount of reflected light resonating between the reflective layers. At this time, the resonated light is not sufficiently enhanced, so the yellow to red light emitted by the phosphor layer after wavelength conversion of the resonated light also has low intensity. This yellow to red light passes through the opposing reflective layer M1 and is emitted together with the aforementioned blue light. In this way, even when a single phosphor that emits blue light upon ultraviolet excitation is used, the blue light from the phosphor and a small amount of yellow to red light are mixed, making it possible to provide a wavelength conversion element in which the chromaticity of blue is delicately adjusted.

[0116] 13C, 13D and Table 3, it was found that by combining the wavelength conversion element of Example 2, which employs reflective layer M1 as the first reflective layer and reflective layer M2 as the second reflective layer, with a phosphor that emits blue light upon excitation by ultraviolet light and has an emission wavelength that depends on the excitation wavelength, with an excitation source, the emission of blue light is suppressed and the emission of yellow to red light is increased, resulting in a light emitting device that emits yellow to red light.

[0117] Specifically, ultraviolet excitation light passes through the reflective layer M1 and is wavelength-converted to blue light in the phosphor layer. A portion of the blue light passes through the reflective layer M2 and is emitted, while another portion of the blue light is reflected by the reflective layer M2 and resonates between the reflective layers M1 and M2. The resonated and enhanced blue light excites the phosphor layer and is wavelength-converted to yellow to red light. This yellow to red light passes through the reflective layer M2 and is emitted. In this way, when a single phosphor that emits blue light upon excitation with ultraviolet light is used, a light emitting device can be provided in which blue light emission is suppressed and yellow to red light emission is increased.

[0118] 14C, 14D and Table 3, it was found that by combining the wavelength conversion element of Example 3, which employs reflective layer M1 as the first reflective layer and reflective layer M3 as the second reflective layer, with a phosphor that emits blue light upon excitation by ultraviolet light and has an emission wavelength that depends on the excitation wavelength, with an excitation source, the emission of blue light and yellow to red light is increased, resulting in a light emitting device that emits white light.

[0119] Specifically, ultraviolet excitation light passes through the reflective layer M1 and is wavelength-converted to blue light in the phosphor layer. Components of the blue light with wavelengths greater than 422 nm and less than 507 nm pass through the reflective layer M3 and are emitted. On the other hand, components of the blue light with wavelengths equal to or less than 422 nm and components with wavelengths equal to or greater than 507 nm are reflected by the reflective layer M3 and resonate between the reflective layers M1 and M3. The resonated and enhanced blue light components excite the phosphor layer and are wavelength-converted to yellow to red light. This yellow to red light passes through the reflective layer M3 and is emitted. In this way, when a single phosphor that emits blue light upon ultraviolet excitation is used, a wavelength conversion element that emits white light that is a mixture of blue light and yellow to red light can be provided.

[0120] 15A, 15B and Table 3, in the case of the wavelength conversion element of Example 4, which employs the reflective layer M1 as the first reflective layer and the reflective layer M3 as the second reflective layer together with a phosphor that emits blue light upon ultraviolet excitation and whose emission wavelength does not have excitation wavelength dependency, white light was not emitted, unlike the case of using the wavelength conversion element of Example 3. This shows that it is essential for the phosphor to have an emission wavelength that depends on the excitation wavelength.

[0121] From the above, it has been shown that in a wavelength conversion element comprising a first reflective layer, a second reflective layer, and a phosphor layer located between them, having an emission wavelength dependent on the excitation wavelength, and converting irradiated excitation light into light having a wavelength longer than the excitation light, by making the first reflective layer reflect light in a first wavelength region located on the longer wavelength side than the peak wavelength of the excitation light, and making the second reflective layer reflect light having a second wavelength region overlapping with at least a part of the first wavelength region, it is possible to provide a wavelength conversion element capable of emitting light with adjusted chromaticity. This type of light emission occurs because light emitted from the phosphor layer and having a wavelength in the region where the first wavelength region and the second wavelength region overlap resonates between the first reflective layer and the second reflective layer, the resonated light is converted by the phosphor layer into light with a wavelength longer than the longest wavelength in the second wavelength region, and the light with a wavelength outside the second wavelength region from the light obtained by wavelength conversion of the excitation light by the phosphor layer, and the light with a wavelength longer than the longest wavelength in the second wavelength region from the resonated light by wavelength conversion by the phosphor layer each pass through the second reflective layer and are emitted, and these lights are mixed.

[0122] Furthermore, it was shown that by adjusting the first wavelength region of the first reflective layer and the second wavelength region of the second reflective layer in accordance with the phosphor employed, it is possible to provide a wavelength conversion element that emits blue light, yellow to red light, or even white light.

[0123] Next, using the wavelength conversion elements of Example 2 and Example 3, the output of the ultraviolet light-emitting diode element having an emission peak at 355 nm was changed from 0.03 mW to 0.65 mW, and the emission spectrum of the light emitted from the wavelength conversion element was measured. Also, the CIE1931 chromaticity (x, y) was calculated from the emission spectrum. These results are shown in Figure 16A, Figure 16B, Figure 17A, Figure 17B and Table 4.

[0124] Fig. 16A is a diagram showing the emission spectrum of a light emitting device using the wavelength conversion element of Example 2 when irradiated with excitation light of different outputs, and Fig. 16B is a diagram showing the chromaticity calculated from the emission spectrum of Fig. 16A. Fig. 17A is a diagram showing the emission spectrum of a light emitting device using the wavelength conversion element of Example 3 when irradiated with excitation light of different outputs, and Fig. 17B is a diagram showing the chromaticity calculated from the emission spectrum of Fig. 17A.

[0125]

[0126] According to Fig. 16A, when the wavelength conversion element of Example 2 is irradiated with ultraviolet light, the emission spectrum has peaks in the range of 450 nm to 500 nm and in the range of 580 nm to 650 nm, and these peak intensities have ultraviolet light, i.e., excitation light output power dependence. In this case, as shown in Fig. 16B, the chromaticity does not change even with the change in the excitation light output, so it has been shown that a stable wavelength conversion element can be provided.

[0127] On the other hand, according to FIG. 17A , the emission spectrum when ultraviolet light was irradiated onto the wavelength conversion element of Example 3 had peaks in the range of 450 nm or more and 500 nm or less and in the range of 580 nm or more and 650 nm or less, respectively, and the peak intensity in the range of 450 nm or more and 500 nm or less did not have any dependency on the output of ultraviolet light, i.e., the excitation light, while the peak intensity in the range of 580 nm or more and 650 nm or less had a dependency on the output of the excitation light.

[0128] In this case, as shown in Figure 17B, the chromaticity and color temperature can be controlled by changing the output of the excitation light, demonstrating that the light-emitting device can adjust the color temperature by the output of the excitation source. As shown in Figure 17B, increasing the output of the excitation light resulted in a light closer to incandescent white, while decreasing the output of the excitation light resulted in a light closer to bluish-white. Furthermore, surprisingly, all of this control of chromaticity and color temperature was along the blackbody locus, with a deviation within ±0.01.

[0129] [Graphite-like carbon nitride phosphor (g-C3N4)] As a phosphor different from the carbon nanoparticle phosphor, graphite-like carbon nitride phosphor (g-C3N4) was synthesized by the following procedure.

[0130] Melamine was placed in an alumina crucible in a nitrogen atmosphere and heated at 550°C for 2 hours at a temperature increase rate of 3°C / min. 2.5g of yellow powder was obtained from 5g of melamine.

[0131] The yellow powder thus obtained was subjected to X-ray diffraction measurement using an X-ray diffractometer (Rigaku Corporation, Rint Ultima III) with Cu-Kα radiation. The results are shown in FIG.

[0132] FIG. 18 shows the XRD pattern of the yellow powder obtained in the synthesis procedure of graphitic carbon nitride phosphor (g-C 3 N 4 ).

[0133] 18, a sharp peak attributable to the 002 reflection of graphitic carbon nitride was observed near 2θ=27.6°, and a relatively small broad peak attributable to the 001 reflection of graphitic carbon nitride was observed near 2θ=12.9°. The sharp peak observed near 2θ=27.6° is characteristic of a graphite structure, and its position indicates the spacing between graphite layers. The broad peak observed near 2θ=12.9° indicates the positional relationship between heptazine ring structures within the graphitic layers.

[0134] The yellow powder was analyzed using a nuclear magnetic resonance spectrometer. １３ The C-CP-MAS-NMR spectrum was measured, and the results are shown in FIG.

[0135] Figure 19 shows the yellow powder obtained by the synthesis procedure of graphitic carbon nitride phosphor (g-C3N4). １３ FIG. 1 shows a C-CP-MAS-NMR spectrum.

[0136] According to Figure 19, resonances were confirmed at 164.5 ppm and 156.5 ppm. The resonance at 164.5 ppm is due to the amino group (-NH ２ The resonance at 156.5 ppm is due to the sp2 carbon attached to the three nitrogen atoms in the triazine or heptazine ring.

[0137] The powder XRD pattern and solid-state NMR spectrum confirmed that the obtained yellow powder was graphitic carbon nitride (g-C3N4).

[0138] Graphite-like carbon nitride phosphor (g-CN) powder was dispersed in dimethyl sulfoxide (DMSO, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and passed through a 20 nm syringe filter to obtain a graphite-like carbon nitride phosphor (g-CN) dispersion. The concentration of graphite-like carbon nitride phosphor (g-CN) in DMSO was 0.0025 mass% (0.025 mg / mL). The emission spectrum of the graphite-like carbon nitride phosphor (g-CN) dispersion was measured using a spectrofluorometer (FP-8500, manufactured by JASCO Corporation). The results are shown in Figure 20.

[0139] FIG. 20 is a diagram showing the emission spectrum of a graphite-like carbon nitride phosphor (g-C 3 N 4 ) dispersion liquid.

[0140] Figure 20 shows the emission spectra of graphite-like carbon nitride phosphor (g-CN) dispersion when it is irradiated with excitation light of various wavelengths. The emission spectrum shows that the graphite-like carbon nitride phosphor (g-CN) dispersion emits blue light with a peak near 460 nm when exposed to excitation light with a wavelength of 300 to 400 nm. The emission spectrum also shows that the graphite-like carbon nitride phosphor (g-CN) dispersion has an emission wavelength that is dependent on the excitation wavelength.

[0141] [Example 5: Wavelength conversion element] In Example 5, the graphite-like carbon nitride phosphor (g-C3N4) that emits blue light when excited by ultraviolet light described above was combined with a reflective layer shown in Table 5 to produce a wavelength conversion element shown in Table 6.

[0142]

[0143]

[0144] First, aluminum nitride (AlN) and silicon oxide (SiO ２ ) and tantalum oxide (Ta ２ O ５ The Ta film was placed on the quartz glass substrate in an RF (radio frequency) sputtering device (Shibaura Mechatronics Corporation, CFS-4EP-LL). ２ O ５ and SiO ２ The reflective layer M4 was formed by laminating nine pairs of Ta and Ta-based high refractive index layers. ２ O ５ The total thickness is 200 nm, and the low refractive index layer is SiO ２ The sputtering conditions were a substrate distance of 110 mm, an RF output of 300 W, and no substrate heating.

[0145] The transmission spectrum of the resulting reflective layer M4 was measured using an ultraviolet-visible-near-infrared spectrophotometer (V-570, manufactured by JASCO Corporation), and it was confirmed that the reflective layer M4 had a stop band in the wavelength range of 450 nm to 550 nm.

[0146] Next, a phosphor layer, a resin molded product with g-CN4 dispersed therein, was formed on the reflective layer M4. Polyvinylpyrrolidone (PVP) powder (2 g) was added to deionized water (60 mL) and held at 90°C for 3 hours to prepare a PVP aqueous solution (PVP concentration: 3.3 wt%). g-CN4 was added to 4 mL of PVP aqueous solution and stirred. This was drop-cast onto the reflective layer M4 and dried at 90°C for 1 hour to obtain a quartz glass / reflective layer / phosphor layer laminate. The content of graphite-like carbon nitride phosphor in the resulting phosphor layer was 0.07 wt%.

[0147] Next, the laminate of quartz glass / reflecting layer / resin molded body is placed in an RF sputtering device, and reflective layer M4 is formed on the resin molded body.The film forming conditions of reflective layer are as described above.In this way, the wavelength conversion element of Example 5 is obtained.

[0148] The wavelength conversion element of Example 5 was combined with an ultraviolet light-emitting diode element having an emission peak at a wavelength of 355 nm as an excitation source to form a light-emitting device. Ultraviolet light (output 0.03 mW) from the ultraviolet light-emitting diode element was incident on the quartz glass side of the wavelength conversion element of Example 5, and the emission spectrum of the light emitted from the wavelength conversion element was measured. The results are shown in Figure 21A. The CIE 1931 chromaticity (x, y) was also calculated from the emission spectrum. The results are shown in Figure 21B and Table 7, respectively.

[0149]

[0150] 21A is a diagram showing the emission spectrum of a light-emitting device using the wavelength conversion element of Example 5, and the emission spectrum of a phosphor layer used in the wavelength conversion element. Fig. 21B is a diagram showing the chromaticity calculated from the emission spectrum of a light-emitting device using the wavelength conversion element of Example 5.

[0151] In the emission spectrum of FIG. 21A, the emission spectrum indicated by the dotted line is the emission spectrum when the phosphor layer used is excited with light having a wavelength of 355 nm.

[0152] 21A, 21B and Table 7, it was found that the wavelength conversion element of Example 5, which uses a phosphor that emits blue light when excited by ultraviolet light and has an emission wavelength that depends on the excitation wavelength, and which employs reflective layers M4 for both the first and second reflective layers, becomes a light-emitting device that emits white light by combining it with an ultraviolet light-emitting diode element as an excitation source, as the emission intensity of blue light decreases and the emission intensity of yellow to red light increases.

[0153] Specifically, ultraviolet excitation light passes through the reflective layer M4 and is wavelength-converted to blue light in the phosphor layer. Of the blue light, components with wavelengths less than 450 nm and components with wavelengths greater than 550 nm pass through the reflective layer M4 and are emitted. On the other hand, of the blue light, components with wavelengths between 450 nm and 550 nm pass through the reflective layer M4 and are emitted, while the other components are reflected by the reflective layer M4 and resonate between the opposing reflective layers M4. The resonated and enhanced blue light components excite the phosphor layer and are wavelength-converted to yellow to red light. This yellow to red light is emitted through the reflective layer M4. In this way, when using a single phosphor that emits blue light upon ultraviolet excitation, a wavelength conversion element that emits white light that is a mixture of blue light and yellow to red light can be provided.

[0154] According to the present invention, a wavelength conversion element with chromaticity and color temperature adjusted by simply selecting the width of the stop band of a pair of reflective layers using a phosphor whose emission wavelength is dependent on the excitation wavelength can be provided, which is advantageous for element design. In particular, since the long-wavelength component of the phosphor can be enhanced, a wavelength conversion element that emits white light can be provided. Such wavelength conversion elements are used in light-emitting devices such as lighting devices and display backlights.

[0155] REFERENCE SIGNS LIST 100 Wavelength conversion element 110 First reflective layer 120 Second reflective layer 130 Phosphor layer 140 Laminated body 150 Substrate 160 Excitation light 170, 170', 180, 190, 190' Light 200 Light emitting device 210, 220 Lead wire 230 Alumina substrate 240 Excitation source 250 Gold thin wire 270 Resin 280 Wall member

Claims

1. A first reflective layer; a second reflective layer; and a phosphor layer located between the first and second reflective layers; Equipped with the phosphor layer has an emission wavelength dependent on an excitation wavelength, converts irradiated excitation light into light having a longer wavelength than the excitation light, the first reflective layer reflects light in a first wavelength region that is longer than the wavelength of the excitation light, the second reflective layer reflects light in a second wavelength region that overlaps with at least a portion of the first wavelength region; between the first reflective layer and the second reflective layer, light having a wavelength in a region where the first wavelength region and the second wavelength region overlap, among light obtained by wavelength-converting the excitation light in the phosphor layer, resonates; the phosphor layer converts the resonated light into light having a wavelength longer than the longest wavelength of the second wavelength range; the second reflective layer transmits and emits light having a wavelength outside the second wavelength range obtained by wavelength conversion of the excitation light in the phosphor layer, and light having a wavelength longer than the longest wavelength in the second wavelength range obtained by wavelength conversion of the resonated light in the phosphor layer.

2. 2. The wavelength conversion element according to claim 1, wherein white light is emitted by mixing light outside the second wavelength region obtained by wavelength conversion of the excitation light in the phosphor layer and light having a wavelength longer than the longest wavelength of the second wavelength region obtained by wavelength conversion of the resonated light in the phosphor layer.

3. The first wavelength region is in the range of 480 nm to 590 nm, The wavelength conversion element according to claim 1 , wherein the second wavelength region is in the range of 450 nm to 520 nm.

4. the emission spectrum of the emitted light has peaks in a wavelength range of 450 nm or more and 500 nm or less and a wavelength range of 580 nm or more and 650 nm or less, 4. The wavelength conversion element according to claim 3, wherein the intensity of each of the peaks has a dependency on the output power of the excitation light.

5. The first wavelength region is in the range of 480 nm to 590 nm, 2. The wavelength conversion element according to claim 1, wherein the second wavelength region is in the range of 395 nm to 425 nm and in the range of 500 nm to 560 nm.

6. the emission spectrum of the emitted light has peaks in a wavelength range of 450 nm or more and 500 nm or less and a wavelength range of 580 nm or more and 650 nm or less, the peak intensity in the wavelength range of 450 nm or more and 500 nm or less does not have output dependency of the excitation light, The wavelength conversion element according to claim 5 , wherein the peak intensity in the wavelength range of 580 nm to 650 nm has a dependency on the output of the excitation light.

7. 2. The wavelength conversion element according to claim 1, wherein the phosphor layer is excited by light having a wavelength of 330 nm or more and 420 nm or less, and emits blue light having a peak in the range of 450 nm or more and 500 nm or less.

8. The wavelength conversion element according to claim 1 , wherein the phosphor layer contains a phosphor selected from the group consisting of carbon nanoparticle phosphors, organic nanoparticle phosphors, organometallic complex phosphors, inorganic phosphors, and semiconductor quantum dot phosphors.

9. The wavelength conversion element according to claim 8 , wherein the phosphor layer contains a carbon nanoparticle phosphor and emits blue light when irradiated with ultraviolet light.

10. The carbon nanoparticle phosphor contains carbon, oxygen, nitrogen, and hydrogen elements; The carbon element is present as amorphous carbon and graphitic carbon; The amorphous carbon and the graphite-like carbon account for 60% by volume or more and less than 99% by volume of the total amount of the amorphous carbon and 1% by volume or more and less than 40% by volume of the graphite-like carbon, The nitrogen element is present as at least pyridine type nitrogen, amide type nitrogen, pyrrole type nitrogen, and graphite type nitrogen; The wavelength conversion element according to claim 9 , wherein the content of the pyridine-type nitrogen is greater than that of the graphite-type nitrogen.

11. The carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) are, respectively, 0.58≦p / (p+q+r)≦0.65 0.15≦q / (p+q+r)≦0.30 0.12≦r / (p+q+r)<0.25 The wavelength conversion element according to claim 10 ,

12. The wavelength conversion element according to claim 9 , wherein the phosphor layer is a resin molded body in which the carbon nanoparticle phosphor is dispersed.

13. The wavelength conversion element according to claim 1 , wherein the excitation light has a wavelength in the range of 330 nm to 420 nm.

14. The wavelength conversion element according to claim 1 , wherein the first reflective layer has a superlattice structure of an aluminum nitride layer and a silicon dioxide layer.

15. The wavelength conversion element according to claim 1 , wherein the second reflective layer has a superlattice structure of a tantalum oxide layer and a silicon dioxide layer.

16. A light emitting device comprising an excitation source and a wavelength conversion element, A light emitting device, wherein the wavelength conversion element is a wavelength conversion element according to claim 1 .

17. The light emitting device according to claim 16 , wherein the excitation source emits excitation light having a wavelength in the range of 330 nm to 420 nm.

18. 17. The light emitting device of claim 16, wherein the excitation source is selected from the group consisting of a light emitting diode (LED), a laser diode (LD), a semiconductor laser, and an organic electroluminescent light emitter (OLED).

19. 17. The light emitting device of claim 16, wherein the excitation source is variable in output.

20. The light emitting device according to claim 16 , wherein the light emitting device is a white light emitting diode, a lighting fixture including a plurality of white light emitting diodes, or a backlight for a liquid crystal panel.