Phosphor wheel with inorganic binder

Abstract

To provide a phosphor wheel with an inorganic binder. [Solution] An optical conversion device is disclosed. The optical conversion device comprises a substrate and a wavelength conversion element (111). The wavelength conversion element (111) comprises an inorganic binder such as sodium silicate. Also disclosed are a phosphor wheel and an optical engine comprising such a phosphor wheel. Further disclosed is a high-power laser projection display system comprising a laser having a power of about 60 W to about 300 W and an optical conversion device. The use of an inorganic binder enables high thermal stability at a reasonable cost.

Description

Technical Field

[0001] The present disclosure relates to projection display systems and optical light conversion devices, such as phosphor wheels, used in such systems. The present disclosure also generally relates to solid state devices and the illumination provided thereby. The device includes a wavelength conversion element using an inorganic binder. These are used in optical devices for producing light of different colors or different wavelengths.

Background Art

[0002] Phosphor wheels are used in various optical devices, such as projection-based or other image generation systems, that use digital light processing (DLP) technology. The phosphor wheel includes a hub portion that is a cylinder that acts as a rotor when coupled to a motor. Typically, an optically active radial portion, which is a metal plate or substrate, is attached to or integrated with the hub portion. A wavelength conversion material (phosphor) on the optically active radial portion generates emitted light of a wavelength different from the incident excitation light. Blue laser illumination sources are commonly used in many laser projectors.

[0003] Solid state illumination generally refers to light emitted by solid state electroluminescence, in contrast to thermal radiation (e.g., white light) or fluorescence emission. Solid state light generally produces blue light. However, other colors may also be useful / desired.

[0004] Wavelength conversion materials such as phosphors are typically provided in one of two ways. Firstly, in phosphor-containing silicone products, phosphor powder is mixed into a silicone binder or adhesive and then dispensed or printed in the desired pattern. Silicone binders are popular due to their high transparency, high bonding strength, lower refractive index, and suitable viscosity. For example, a popular binder option is Dow Corning® OE-6336, a silicone adhesive manufactured by Dow Corning®, which has a mixed viscosity of 1,425 centipoise (cP), 99.6% transparency at 450 nm, a thickness of 1 mm, a refractive index of 1.4, and a heat-curing time of 60 minutes at 150°C.

[0005] However, silicone binders / adhesives have poor thermal stability. At temperatures above 200°C, silicone adhesives will decompose, typically beginning to yellow and gradually burning. This undesirably leads to a short operational life for phosphor wheels, and it has been observed that the photoconversion efficiency drops sharply (>10% at 200°C) due to thermal loss. It has also been found that the phosphor-containing silicone layer in phosphor wheels at temperatures above 195°C cracks after approximately 1,000 hours. At a lower temperature of approximately 185°C, phosphor performance was found to show only a 10% decrease after 20,000 hours without any cracking. In applications involving high brightness (e.g., laser power up to 300W), the temperature of the phosphor wheel is generally expected to exceed 200°C, thus making the use of silicone adhesives undesirable. In other words, phosphor-containing silicone products cannot achieve a long operational life in high-power laser projectors. Life testing for such products has established that the safe operating temperature should be controlled to be below 150°C. Therefore, the use of organic binders (e.g., silicones) on or as reflective layers for optical light conversion devices such as phosphor wheels is undesirable due to the temperature limits of such organic binders.

[0006] Secondly, in phosphor-containing ceramic products, the phosphor is mixed with a ceramic binder and sintered to produce a solid phosphor-containing ceramic product. Phosphor-containing ceramic products have a good operating temperature of up to 300°C. However, the sintering temperature far exceeds 1,000°C, and as a result, such products are also very expensive.

[0007] Therefore, it would be desirable to provide an optical conversion device suitable for use in high-power, high-temperature sources (e.g., high-power laser projection systems) without significant reductions in efficiency and operating life, and without any other significant changes in parameters or performance. [Overview of the project] [Means for solving the problem]

[0008] This disclosure relates to an optical-to-optical conversion device suitable for use in high-power, high-temperature sources. Briefly, an inorganic binder is used in combination with a phosphor to fabricate a wavelength conversion element. In certain embodiments, the inorganic binder is sodium silicate, which can withstand the high operating temperatures of high-power lighting systems (e.g., exceeding 200°C).

[0009] In certain embodiments, the wavelength conversion element comprises an inorganic binder and a phosphor (usually in powder form). The substrate may be an annular disk. The annular disk may be made from a reflective material such as a metallic material, or from a non-metallic material or composite material having a reflective coating. For example, the reflective material / reflective coating may be made from a metallic material, a dielectric material, or a combination thereof.

[0010] The inorganic binder can be sodium silicate. The SiO2:Na2O ratio in the sodium silicate may be about 2:1 to about 3.75:1. The weight ratio of phosphor to inorganic binder in the wavelength conversion element may be about 1:1 to about 5:1.

[0011] The inorganic binder may be substantially optically transparent (for example, the inorganic binder may have a light transmittance of at least 80%, with a maximum of 90% to 98%). The inorganic binder may be able to withstand temperatures above 200°C. The inorganic binder may have an initial bond strength of at least 100 psi (or higher) before aging. The bond strength will gradually decrease during high-temperature aging. Even after aging, the bond strength should be greater than 20 psi. The inorganic binder may have a curing temperature of about 100°C to about 500°C. The inorganic binder may have a viscosity of about 0 centipoise (cP) to about 2,000 cP. The wavelength conversion element may have a thickness of about 0.05 mm to about 0.3 mm.

[0012] Optical conversion devices may be used in phosphor wheels, optical engines, automotive headlights, or other lighting devices. The phosphor wheel may be rotatable about an axis normal to the plane of the substrate. In this case, the assembly may further include a motor that rotates the substrate about this axis. The optical engine may also include a light source (e.g., a laser-based illuminator) arranged to apply light of an excitation wavelength to the wavelength conversion element.

[0013] Furthermore, disclosed in various embodiments of this specification are methods for producing phosphor wheels, the methods comprising the step of applying a wavelength conversion element, comprising an inorganic binder and a phosphor, to a substrate.

[0014] In some embodiments, the inorganic binder can be applied to the substrate by dispensing, spraying, brush coating, or silk screen printing. The inorganic binder can be cured by thermosetting or hybrid curing (heat and UV curing). The inorganic binder can be cured at temperatures of about 100°C to about 500°C and may be able to withstand temperatures above 200°C. .

[0015] Further disclosed in various embodiments herein are laser projection display systems comprising a laser having a power of about 60 W to about 300 W, and a phosphor wheel, the phosphor wheel comprising an optional substrate and a wavelength conversion element, the wavelength conversion element being configured to absorb light of an excitation wavelength and generate light of an emission wavelength, and the phosphor wheel comprising an inorganic binder and a phosphor. The inorganic binder may be able to withstand temperatures above 200°C.

[0016] These and other non-limiting characteristics of this disclosure are specifically disclosed below. [Brief explanation of the drawing]

[0017] The following is a brief description of the drawings, which are presented for illustrative purposes only and not intended to limit the exemplary embodiments disclosed herein.

[0018] [Figure 1] Figure 1A is a plan view of a conventional reflective phosphor wheel. Figure 1B is a side view showing the optical path through it.

[0019] [Figure 2] Figure 2A is a plan view of a conventional transmissive phosphor wheel. Figure 2B is a side view showing the optical path through it. [Modes for carrying out the invention]

[0020] A more complete understanding of the components, processes, and apparatus disclosed herein can be obtained by reference to the accompanying drawings. These drawings are merely schematic diagrams based on convenience and ease of demonstrating the disclosure and are therefore not intended to show the relative sizes and dimensions of the device or its components, and / or to define or limit the scope of the exemplary embodiments.

[0021] Specific terms are used in the following description for clarity, but these terms are intended to refer only to the specific structures of the embodiments selected for illustration in the drawings and are not intended to define or limit the scope of the present disclosure. In the drawings and the following description below, it should be understood that like numerals denote like components in terms of function.

[0022] Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include plural referents.

[0023] As used herein and in the claims, the terms “comprise,” “include,” “having,” “has,” “can,” “contain,” and variations thereof are intended to be open transitional phrases, terms, or words that, as used herein, require the presence of the recited ingredient / steps and allow the presence of other ingredients / steps. However, such descriptions should also be construed as describing compositions or processes as “consisting of” and “consisting essentially of” the recited ingredient / steps, which allows only the presence of the recited ingredient / steps, excluding other ingredients / steps, in addition to any unavoidable impurities that may result therefrom.

[0024] Numerical values within the specification and claims of this application are to be understood as including both a numerical value that would be the same when rounded to the same number of significant digits for determining the value and a numerical value that differs from the recited value by less than the experimental error of conventional measurement techniques of the type described in this application.

[0025] All ranges disclosed herein include the recited endpoints and are independently combinable (e.g., a range of “2 grams to 10 grams” includes the endpoints, i.e., 2 grams and 10 grams, and all intermediate values).

[0026] The terms "about" and "approximately" can be used to include any numerical value that can vary without changing the basic function of the value. When used in combination with a range, "about" and "approximately" also disclose the range defined by the absolute values of the two endpoints. For example, "about 2 to about 4" also discloses the range of "2 to 4". Generally, the terms "about" and "approximately" can refer to ±10% of the indicated number.

[0027] As used herein, the terms "excitation light" and "excitation wavelength" refer to the input light that is subsequently converted, e.g., light produced by a laser-based illumination source or other light source. The terms "emitted light" and "emission wavelength" refer to the resulting light produced by the converted light, e.g., by a phosphor exposed to the excitation light.

[0028] For reference, red typically refers to light having a wavelength of about 780 nanometers to about 622 nanometers. Green typically refers to light having a wavelength of about 577 nanometers to about 492 nanometers. Blue typically refers to light having a wavelength of about 492 nanometers to about 455 nanometers. Yellow typically refers to light having a wavelength of about 597 nanometers to about 577 nanometers. However, this can be context-dependent. For example, these colors are sometimes used to label various components and distinguish them from each other.

[0029] The present disclosure relates to a light conversion device such as a phosphor wheel that uses an inorganic binder that provides better thermal properties than silicone binders and is significantly lower in cost than ceramic binders.

[0030] A phosphor wheel is used to continuously generate light of different colors. A light-converting (or wavelength-converting) material, such as a phosphor, is used on the phosphor wheel. A phosphor wheel typically has several fan compartments containing different types of phosphors for converting excitation light to green, yellow, or red. Typically, a blue light laser (with a wavelength of approximately 440 nm to 460 nm) is used to excite the phosphor compartments on the phosphor wheel. The phosphor wheel may also have one or more gaps to allow the blue source light to pass through in its unconverted state. Phosphor wheels have two basic structures: reflective and transmissive.

[0031] In a reflective phosphor wheel, the excitation light from a blue laser does not pass through the substrate before stimulating the phosphor. Figures 1A and 1B show a typical structure of a reflective phosphor wheel. A phosphor mixture is prepared by mixing phosphor powder with a binder and depositing it onto a substrate 112. In some embodiments, the substrate is arbitrary.

[0032] The substrate for a phosphor wheel is typically a metal with high thermal conductivity, such as aluminum or aluminum alloys, copper or copper alloys, or another metal with high thermal conductivity. The substrate can also be made from, for example, glass, sapphire, or diamond. The substrate may include a mirror or reflective coating, or may be made from a reflective material, if desired. For example, the reflective material / reflective coating may be made from a metallic material, a dielectric material, or a combination thereof. Examples of metallic materials include the metals and metallic alloys identified above. Examples of dielectric materials include magnesium fluoride, silicon dioxide, tantalum pentoxide, zinc sulfide, and titanium dioxide.

[0033] After curing at a specified or desired temperature, the phosphor mixture takes the form of wavelength conversion elements 111, which are tightly bonded to the substrate. As shown in Figure 1A, there are three wavelength conversion elements, namely, a green section 111a, a red section 111b, and a yellow section 111c. These three sections are located around the circular substrate 112 (from the plan view). Not shown here is a section for blue excitation light that passes through the substrate and is not reflected. As shown in Figure 1B, the substrate 112 is then mounted on a motor 113 to obtain a phosphor wheel 110. In the phosphor wheel, the substrate is rotated during use. It is also conceivable that the substrate may be used in a static (i.e., fixed, non-rotating) configuration. For example, the wavelength conversion elements can be directly bonded to a substrate that acts as a heat sink.

[0034] As shown in Figure 1B, as the substrate 112 is rotated about axis AA, the excitation blue light 114a stimulates the red and green phosphors 111, and the synchrotron radiation 114b is reflected by the substrate 112 and then collected by a subsequent optical system. In this way, the excitation light does not pass through the substrate 112 in order to stimulate the phosphors to produce emitted light.

[0035] A second type of phosphor wheel is the transmissive phosphor wheel. In a transmissive phosphor wheel, the excitation light passes through the substrate before stimulating the phosphor. Figures 2A and 22B show a typical transmissive phosphor wheel structure. Again, three wavelength conversion elements 211, namely the green section 211a, the red section 211b, and the yellow section 211c, are illustrated here. However, instead of a reflective substrate, in a transmissive phosphor wheel, the entire substrate 212 is a transparent substrate coated with a blue dichroic film. Generally, glass, diamond, or sapphire are used as the substrate material. Blue light can pass through the substrate, while red, green, and yellow (RGY) light emitted by the phosphor is reflected.

[0036] As shown in Figure 2B, the excitation blue light 214a first passes through the substrate (i.e., is transmitted from the back side of the phosphor wheel) and then stimulates the phosphor 211. The synchrotron radiation 214b is collected by a subsequent optical system.

[0037] Several performance characteristics, such as converted light output, color, and lifetime, are direct functions of the operating temperature. At higher operating temperatures, converted light output may decrease, color may shift, and phosphor wheel lifetime may decrease. Under normal operating conditions, approximately 50% to 60% of the input power is output as heat, while the remainder is converted into light. At high input power, the heat generation during conversion will cause temperatures exceeding 200 degrees Celsius (200°C).

[0038] A desirable binder for phosphors used to fabricate wavelength conversion elements should ideally possess a combination of several properties. The binder should have high transparency in visible wavelengths, a low refractive index, high bonding hardness, high thermal stability (i.e., high Tg or maximum operating temperature), a relatively low curing / sintering temperature, good compatibility / miscibility with the phosphor, and / or a desirable viscosity. This will improve the thermal endurance of the phosphor wheel at temperatures between 165°C and 300°C.

[0039] In this disclosure, wavelength conversion elements such as the phosphor section of a phosphor wheel include a phosphor and an inorganic binder. The term "inorganic" means that the binder does not contain any carbon.

[0040] The wavelength conversion element may also include one or more fillers, one or more inorganic materials, and one or more dispersants.

[0041] The addition of fillers to inorganic materials improves the bonding strength of the inorganic binder. In particular, the addition of fillers can reduce the shrinkage rate of the composition used to fabricate wavelength conversion elements, reduce or prevent the formation of bubbles or cracks during solidification, thereby reducing the amount and / or effect of stress during use and improving the bonding strength of the composition. Fillers can be selected to have a thermal expansion coefficient as close as possible to (e.g., substantially equivalent to) that of the inorganic material. Similarly, to avoid lamination, fillers can be selected to have a density as close as possible to (e.g., substantially equivalent to) that of the inorganic material. Fillers may have any desired form, such as granular, flake, or fibrous form. Any suitable filler can be used. For example, specifically, the filler may be silica, silicates, aluminates, or phosphoric acid, or diamond powder. Fillers may be metal powders such as aluminum, copper, silver, or gold powder. Fillers may be nitrides such as aluminum nitride or borazon. The filler may be an oxide such as aluminum oxide or boron oxide. The filler may be a metal oxide, metal nitride, or metal sulfide.

[0042] The addition of a dispersant is beneficial in dispersing the filler throughout the binder, thereby avoiding undesirable aggregation or sedimentation. Any suitable dispersant can be used. Specifically, the dispersant may be an organic dispersant such as polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene-co-maleic anhydride, or lignosulfonate. Specifically, as an alternative, the dispersant may be an inorganic dispersant such as hexametaphosphate, silicate, polyphosphate, or fumed silica.

[0043] Preferably, the inorganic binder has a coefficient of thermal expansion (CTE) of about 0.5 to about 25 ppm / °C. In certain embodiments, the inorganic binder is sodium silicate. Sodium silicate has the chemical formula (Na2SiO3). nIt is a common name for the compound, and can be considered a polymer, as seen in the following chemical formula (I). [ka]

[0044] Sodium silicate exists in both anhydrous and hydrated forms: Na2SiO3·nH2O (wherein n=5, 6, 8, or 9). Sodium silicate can be characterized by the weight ratio of silicon dioxide (SiO2) to sodium oxide (Na2O). The SiO2:Na2O weight ratio can vary from 2:1 to 3.75:1. In certain embodiments, the SiO2:Na2O weight ratio is about 2.5:1 to about 3.75:1 or about 2:1 to about 3:1. Sodium silicate is typically supplied as an aqueous solution.

[0045] In other embodiments, the inorganic binder can be made from inorganic materials other than sodium silicate. These inorganic materials may be silicates, aluminates, phosphates, borates, or inorganic sol gels. Examples of inorganic sol gels include sol gels made from silicon dioxide (SiO2) or aluminum oxide (Al2O3).

[0046] Typically, the phosphor and the inorganic binder are mixed together and then applied within the desired area. A paste is formed by applying it to the substrate. The weight ratio of phosphor to inorganic binder is approximately 1:1 to approximately 5:1, meaning that there may be more phosphor than inorganic binder, including approximately 1:1 to approximately 3:1 and approximately 1:1 to approximately 2:1.

[0047] The paste can then be applied, for example, by dispensing, spraying, brushing, or silk-screen printing. For applications where the paste is to be applied by dispensing or silk-screen printing, the paste should have a suitable viscosity of about 0 to about 5,000 cP, including about 0 to about 2,000 centipoise (cP), or about 100 to about 2,000 cP, or about 0 to about 2,500 cP, or about 100 to about 2,500 cP. Viscosity can be measured using a Brookfield DVE SLVTJ0 viscometer or ASTM Measured according to D1084. The inorganic binder itself (i.e., without phosphors) may also have a suitable viscosity of about 0 to about 5,000 cP, including about 0 to about 2,000 centipoise (cP) or about 100 cP to about 800 cP.

[0048] The paste is then cured to obtain a wavelength conversion element. Curing can be carried out by thermosetting at a temperature of approximately 100°C to 500°C, which is lower than that for conventional silicone adhesives.

[0049] The resulting wavelength conversion element can typically have a thickness of approximately 0.05 mm to 0.3 mm. The thickness is measured in the direction of axis AA in Figure 1A.

[0050] Preferably, the inorganic binder is substantially optically transparent (e.g., the inorganic binder has a light transmittance of at least 80%, containing 90% to a maximum of 98%). This can be measured, for example, by using a Lambda 950 spectrophotometer, available from Perkin-Elmer, at a thickness of about 0.1 to about 0.2 millimeters. In contrast, many inorganic binders are opaque. This allows inorganic binders to be used in transmission or reflection phosphor wheels.

[0051] In certain embodiments, an inorganic binder may be applied to a reflective layer or coating applied to a substrate. The reflective layer, as discussed above, may be made from a metallic material, a dielectric material, or a combination thereof. Dielectric mirrors are well known in the art. When the reflective layer is a metallic material, it is usually made from a different metal than the metal used to make the substrate.

[0052] In further embodiments, a smoothing layer can be applied to a wavelength conversion element. The smoothing layer serves to reduce the surface roughness of the final device without the use of mechanical processes such as polishing, which could damage the final device. This reduces scattering, improves wavelength conversion efficiency, and enhances the ability to direct the resulting light in a desired direction. The smoothing layer may be a polymer, or it may be made from a material such as a metal like tungsten, nickel, or cobalt, or a carbide such as boron carbide or silicon carbide.

[0053] Additional protective coatings can also be applied to this device. Such coatings may be transparent, anti-reflective, or spectrally selective coatings, as desired for various applications.

[0054] It is assumed that any combination of such layers / coatings may exist. For example, the phosphor wheel according to this disclosure can be designed using a substrate, a reflective coating applied to the substrate, a wavelength conversion element applied on the reflective coating, a smoothing layer applied on an inorganic binder, and a protective coating applied on the smoothing layer.

[0055] Inorganic binders, particularly sodium silicate, can exhibit higher bonding strength than conventional silicone adhesives. In certain embodiments, the inorganic binders of this disclosure may have an initial bonding strength of at least 100 psi, or at least 200 psi, or about 100 psi to about 600 psi. This property is measured at the maximum temperature to which the adhesive is applied, e.g., 300°C, using two aluminum test plates with the inorganic binder placed between the two plates with a thickness of 0.1 mm and a bonding area of ​​169 square mm.

[0056] Inorganic materials are generally stable over long periods, and therefore, the performance of these devices does not necessarily degrade significantly over time. Organic materials, on the other hand, may exhibit certain gas emissions at high operating temperatures, which can lead to contamination of nearby components within optical devices. In addition, inorganic binders may be more durable than conventional silicone materials under high-power conditions. They exhibit reliable operation under high laser irradiation and temperatures. They can also be flexibly fabricated in various sizes, shapes, and thicknesses. The inorganic binders of this disclosure can also withstand high operating temperatures, i.e., operating temperatures exceeding 200°C. They can be used in high-power laser projection display systems where solid-state laser projectors can be equipped with laser powers ranging from approximately 60 watts to approximately 300 watts, including those exceeding 100 watts. The operating temperature of such devices can reach above 200°C, enabling high luminosity.

[0057] Inorganic binders are envisioned for use in phosphor wheels and laser projection display systems. They can also be used in conjunction with solid-state lighting sources, such as automotive headlights.

[0058] The following examples are provided to illustrate the processes of the present disclosure. The examples are illustrative only and are not necessarily intended to limit the present disclosure to the materials, conditions, or process parameters described therein. [Examples]

[0059] (Example 1) Sodium silicate was used as an inorganic binder in the phosphor wheel along with the phosphor. The inorganic binder had a weight ratio of SiO2:Na2O of 2.5:1. The inorganic binder alone (i.e., pure) had a viscosity of 600 cP. The viscosity of the paste formed by bonding the phosphor and the inorganic binder was 2,000 cP. The paste had an initial bonding strength of 500 psi. The paste was then cured at 200°C for 4 hours. The phosphor wheel was then tested. The phosphor compartment was thermally stable up to 300°C and had a light transmittance of 98%.

[0060] The synchrotron radiation efficiency of this phosphor wheel, which uses sodium silicate as an inorganic binder, was compared to that of a phosphor wheel using an organosilicon binder (i.e., a comparative example). The new phosphor wheel had an efficiency that was only 3% lower than that of the comparative example. (Example 2)

[0061] Silicate was used as an inorganic binder along with the phosphor in the phosphor wheel. The inorganic binder alone (i.e., pure) had a viscosity of 200 cP. The viscosity of the paste formed by bonding the phosphor and the inorganic binder was 1,500 cP. The paste had an initial bonding strength of 200 psi. The paste was then cured at 85°C for 0.3 hours and then at 185°C for 0.75 hours. The phosphor wheel was then tested. The phosphor compartment was thermally stable up to 400°C and had a light transmittance of 98%. The synchrotron radiation efficiency of this new phosphor was compared. It was only 4% lower than the one in question. (Example 3)

[0062] In one exemplary embodiment, the inorganic material used in the inorganic binder is formed from first and second components. The total dissolved solids (TDS) properties of the inorganic material used are provided in the table below. [Table 1]

[0063] The inorganic material was prepared by mixing the first and second components and stirring the mixture at a temperature of approximately 25 to 30°C for a period of approximately 2 to 3 hours. The ratio of the first component to the second component was approximately 1:1 to 7:3.

[0064] An inorganic binder was then prepared by adding a filler and a dispersant to an inorganic material. The inorganic binder was cured in a stepwise process. The first curing step was carried out at a temperature of approximately 60 to 90°C over a period of approximately 0.2 to 1 hour. The second curing step was then carried out at a temperature of approximately 150 to 200°C over a period of approximately 0.4 to 2 hours. It was shown that the cured inorganic binder exhibited excellent bonding strength at the maximum applied temperature due to the high temperature resistance of the inorganic binder.

[0065] This disclosure is described with reference to exemplary embodiments. Modifications and alterations will be recalled to those skilled in the art, in accordance with careful reading and understanding of the foregoing detailed description. This disclosure is intended to be construed as including all such modifications and alterations to the extent that they fall within the scope of the appended claims or their equivalents. For example, this application provides the following items. (Item 1) It is a light conversion device, A wavelength conversion element, wherein the wavelength conversion element is configured to absorb light of an excitation wavelength and generate light of an emission wavelength, and comprises an inorganic binder and a phosphor. A light conversion device equipped with the following features. (Item 2) The above inorganic binder comprises sodium silicate, as described in item 1, for the photoconversion device. (Item 3) The SiO2:Na2O ratio is approximately 2:1 to 3.75:1, as described in item 2 for the light conversion device. (Item 4) The photoconversion device according to item 1, wherein the inorganic binder comprises an inorganic material selected from the group consisting of silicates, aluminates, phosphates, borates, and inorganic sol gels. (Item 5) The light conversion device described in item 1, wherein the weight ratio of the phosphor to the inorganic binder is approximately 1:1 to approximately 5:1. (Item 6) The above inorganic binder is substantially optically transparent, as described in item 1, for the light conversion device. (Item 7) The above inorganic binder has a light transmittance of at least 80%, and is a photoconversion device as described in item 6. A chair. (Item 8) The above inorganic binder is capable of withstanding temperatures exceeding 200°C, as described in item 1 for the optical conversion device. (Item 9) The above inorganic binder is the photoconversion device according to item 1, having a bonding strength of at least 100 psi. (Item 10) The above inorganic binder is a photoconversion device as described in item 1, having a curing temperature of approximately 100°C to approximately 500°C. (Item 11) The above inorganic binder has a viscosity of approximately 0 cP to approximately 2,000 cP, and is used in the photoconversion device described in item 1. (Item 12) The above wavelength conversion element is the optical conversion device described in item 1, having a thickness of approximately 0.05 mm to approximately 3 mm. (Item 13) The optical conversion device according to item 1, further comprising a substrate on which the wavelength conversion element is mounted, the substrate being in the shape of a disk, and further comprising a motor arranged to rotate the substrate around an axis normal to the substrate. (Item 14) It is an optical engine, The optical conversion device described in item 1, A light source arranged to expose the photoconversion device to light of the above excitation wavelength, A light engine equipped with this feature. (Item 15) A method for fabricating a phosphor wheel, Applying a wavelength conversion element containing an inorganic binder and a phosphor to a substrate. Methods that include... (Item 16) The wavelength conversion element is applied to the substrate by dispensing, spraying, brush coating, or silk printing, as described in item 15. (Item 17) The method according to item 15, further comprising curing the inorganic binder described above. (Item 18) The inorganic binder described above is cured at a temperature of approximately 100°C to approximately 500°C, as described in item 17. (Item 19) The inorganic binder described above is the method described in item 15, comprising sodium silicate. (Item 20) A laser projection display system, A laser beam with power of approximately 60W to approximately 300W, A phosphor wheel, wherein the phosphor wheel is Substrate and A wavelength conversion element, wherein the wavelength conversion element is configured to absorb light of an excitation wavelength and generate light of an emission wavelength, and comprises an inorganic binder and a phosphor. A phosphor wheel equipped with A laser projection display system equipped with the following features. (Item 1A) It is a phosphor wheel, A disc-shaped substrate and A motor is arranged such that it rotates the substrate around an axis normal to the substrate, A wavelength conversion element disposed on the substrate, wherein the wavelength conversion element is configured to absorb light of an excitation wavelength and generate light of an emission wavelength, and comprises an inorganic binder and a phosphor. A phosphor wheel equipped with a phosphor. (Item 2A) The inorganic binder is sodium silicate, as described in item 1A, for the phosphor wheel. (Item 3A) The SiO2:Na2O ratio is approximately 2:1 to 3.75:1, as described in item 2A for the phosphor wheel. (Item 4A) The phosphor wheel according to item 1A, wherein the inorganic binder comprises an inorganic material selected from the group consisting of silicates, aluminates, phosphates, borates, and inorganic sol gels. (Item 5A) The phosphor wheel according to item 1A, wherein the weight ratio of the phosphor to the inorganic binder is approximately 1:1 to approximately 5:1. (Item 6A) The inorganic binder is substantially optically transparent, as described in item 1A, for the phosphor wheel. (Item 7A) The inorganic binder is a phosphor wheel according to item 6A, having a light transmittance of at least 80%. (Item 8A) The inorganic binder is capable of withstanding temperatures exceeding 200°C, as described in item 1A, for the phosphor wheel. (Item 9A) The inorganic binder is the phosphor wheel according to item 1A, having a bonding strength of at least 100 psi. (Item 10A) The inorganic binder is the phosphor wheel described in item 1A, having a curing temperature of approximately 100°C to approximately 500°C. (Item 11A) The inorganic binder is the phosphor wheel described in item 1A, having a viscosity of about 0 cP to about 2,000 cP. (Item 12A) The wavelength conversion element is a phosphor wheel as described in item 1A, having a thickness of approximately 0.05 mm to approximately 3 mm. (Item 13A) The inorganic binder is sodium silicate, as described in item 1A, for the phosphor wheel. (Item 14A) It is an optical engine, The phosphor wheel described in item 1A, A light source arranged to expose the wavelength conversion element of the phosphor wheel to light of the excitation wavelength, A light engine equipped with this feature. (Item 15A) A method for fabricating a phosphor wheel, Applying a wavelength conversion element containing an inorganic binder and a phosphor to a disk-shaped substrate, The motors are arranged so as to rotate the substrate around an axis normal to the substrate. thing and Methods that include... (Item 16A) The wavelength conversion element is applied to the substrate by dispensing, spraying, brush coating, or silk printing, as described in item 15A. (Item 17A) The method according to item 15A, further comprising curing the inorganic binder. (Item 18A) The inorganic binder is cured at a temperature of approximately 100°C to approximately 500°C, as described in item 17A. (Item 19A) The inorganic binder is the method described in item 15A, comprising sodium silicate.

Claims

1. It is a phosphor wheel, A disc-shaped substrate and A motor is arranged such that it rotates the substrate around an axis normal to the substrate, A wavelength conversion element disposed on the substrate, wherein the wavelength conversion element is configured to absorb light of an excitation wavelength and generate light of an emission wavelength, and comprises an inorganic binder and a phosphor. A phosphor wheel equipped with a phosphor.

2. The phosphor wheel according to claim 1, wherein the inorganic binder comprises sodium silicate.

3. SiO ２ : Na ２ The phosphor wheel according to claim 2, wherein the ratio of O is approximately 2:1 to approximately 3.75:

1.

4. The phosphor wheel according to claim 1, wherein the inorganic binder comprises an inorganic material selected from the group consisting of silicates, aluminates, phosphates, borates, and inorganic sol gels.

5. The phosphor wheel according to claim 1, wherein the weight ratio of the phosphor to the inorganic binder is about 1:1 to about 5:

1.

6. The phosphor wheel according to claim 1, wherein the inorganic binder is substantially optically transparent.

7. The phosphor wheel according to claim 6, wherein the inorganic binder has a light transmittance of at least 80%.

8. The phosphor wheel according to claim 1, wherein the inorganic binder is capable of withstanding temperatures exceeding 200°C.

9. The phosphor wheel according to claim 1, wherein the inorganic binder has a bonding strength of at least 100 psi.

10. The phosphor wheel according to claim 1, wherein the inorganic binder has a curing temperature of about 100°C to about 500°C.

11. The phosphor wheel according to claim 1, wherein the inorganic binder has a viscosity of about 0 cP to about 2,000 cP.

12. The phosphor wheel according to claim 1, wherein the wavelength conversion element has a thickness of about 0.05 mm to about 3 mm.

13. The phosphor wheel according to claim 1, wherein the inorganic binder comprises sodium silicate.

14. It is an optical engine, The phosphor wheel according to claim 1, A light source arranged to expose the wavelength conversion element of the phosphor wheel to light of the excitation wavelength, A light engine equipped with this feature.

15. A method for fabricating a phosphor wheel, Applying a wavelength conversion element containing an inorganic binder and a phosphor to a disk-shaped substrate, The motors are arranged so as to rotate the substrate around an axis normal to the substrate. Methods that include...

16. The method according to claim 15, wherein the wavelength conversion element is applied to the substrate by dispensing, spraying, brush coating, or silk printing.

17. The method according to claim 15, further comprising curing the inorganic binder.

18. The method according to claim 17, wherein the inorganic binder is cured at a temperature of about 100°C to about 500°C.

19. The method according to claim 15, wherein the inorganic binder comprises sodium silicate.

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