Phosphor wheel with inorganic binder

Abstract

To provide a phosphor wheel with an inorganic binder. [Solution] A light-conversion device is disclosed. The light-conversion device includes a substrate and a wavelength-converting element (111). The wavelength-converting element (111) includes an inorganic binder such as sodium silicate. Also disclosed are a phosphor wheel and a light engine including such a phosphor wheel. Also disclosed is a high-power laser projection display system including a laser having a power of about 60 W to about 300 W and a light-conversion device. The use of an inorganic binder allows for 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 relates generally to solid-state devices and the illumination provided thereby. The devices include wavelength conversion elements that use inorganic binders. These are used in optical devices to produce light of different colors or wavelengths. [Background technology]

[0002] Phosphor wheels are used in various optical devices, such as projection bases or other image generating systems that use digital light processing (DLP) technology. Phosphor wheels include a hub portion, which is a cylinder that acts as a rotor when coupled to a motor. Optically active radial portions, typically metal plates or substrates, are attached to or integrated with the hub portion. Wavelength-converting material (phosphors) on the optically active radial portions generate emitted light at a different wavelength than the incident excitation light. Blue laser illumination sources are commonly used in many laser projectors.

[0003] Solid-state lighting generally refers to light emitted by solid-state electroluminescence, as opposed to thermal radiation (e.g., white light) or fluorescent light. Solid-state lighting generally produces blue light; however, other colors may also be useful / desirable.

[0004] Wavelength-converting materials, such as phosphors, are typically provided in one of two ways. First, in phosphor-containing silicone products, phosphor powder is mixed into a silicone binder or adhesive and then dispensed or printed in the desired pattern. Silicon binders are popular due to their high transparency, high bond 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 blend 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 thermal cure time of 60 minutes at 150°C.

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

[0006] Second, in phosphor-containing ceramic products, the phosphor is mixed with a ceramic binder and sintered to create a solid phosphor-containing ceramic product. Phosphor-containing ceramic products have good operating temperatures up to 300°C. However, sintering temperatures can be well above 1,000°C, and as a result, such products are also very expensive.

[0007] It would therefore be desirable to provide a photoconversion device that is suitable for use in high-power, high-temperature sources (e.g., high-power laser projection systems) without significant reduction in efficiency and operational lifetime, and without any other significant parameter or performance change. Summary of the Invention [Means for solving the problem]

[0008] The present disclosure relates to optical light conversion devices suitable for use in high-power, high-temperature sources. Briefly, an inorganic binder is used in combination with a phosphor to create 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 a specific embodiment, the wavelength converting element includes an inorganic binder and a phosphor (usually in powder form). The substrate can be an annular disk. The annular disk can be made of a reflective material such as a metallic material, or can be made of a non-metallic material or a composite material with a reflective coating. For example, the reflective material / reflective coating can be made of a metallic material, a dielectric material, or a combination thereof.

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

[0011] The inorganic binder may be substantially optically transparent (e.g., the inorganic binder may have a light transmittance of at least 80%, including 90% to 98%). The inorganic binder may be capable of withstanding 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 cure 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 converting element may have a thickness of about 0.05 millimeters (mm) to about 0.3 mm.

[0012] The light conversion device can be used in a phosphor wheel, a light engine, an automobile headlight, or other lighting device. The phosphor wheel can be rotatable about an axis normal to the plane of the substrate. In this case, the assembly can further include a motor that rotates the substrate about this axis. The light engine can also include a light source (e.g., a laser-based illumination source) arranged to apply light of an excitation wavelength to the wavelength conversion element.

[0013] Also disclosed in various embodiments herein is a method for making a phosphor wheel, the method including applying a wavelength converting element to a substrate, the wavelength converting element including an inorganic binder and a phosphor.

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

[0015] Also disclosed herein in various embodiments is a laser projection display system 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 converting element configured to absorb light at an excitation wavelength and generate light at an emission wavelength, the phosphor wheel comprising an inorganic binder and a phosphor, the inorganic binder may be capable of withstanding temperatures exceeding 200°C.

[0016] These and other non-limiting features of the present disclosure are more particularly disclosed below. [Brief explanation of the drawings]

[0017] The following is a brief description of the drawings, which are presented for the purpose of illustrating the exemplary embodiments disclosed herein and are not intended to be limiting thereof.

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

[0019] [Figure 2] Figure 2A is a top view of a conventional transmissive phosphor wheel, and Figure 2B is a side view showing the optical path through it. DETAILED DESCRIPTION OF THE INVENTION

[0020] A more complete understanding of the components, processes, and apparatus disclosed herein can be obtained by reference to the accompanying drawings, which are schematic representations merely for the convenience and ease of illustrating the disclosure, and as such are not intended to illustrate the relative sizes and dimensions of the devices or their components and / or to define or limit the scope of the exemplary embodiments.

[0021] Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure 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 numerical designations refer to components of similar function.

[0022] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0023] As used in this specification and claims, the terms "comprise," "include," "having," "has," "can," "contain," and variations thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the specified ingredients / steps and allow for the presence of other ingredients / steps. However, such descriptions should also be construed as describing a composition or process as "consisting of" and "consisting essentially of" the listed ingredients / steps, which allows for the presence of only the specified ingredients / steps, in addition to any unavoidable impurities that may result therefrom, and excludes other ingredients / steps.

[0024] Numerical values ​​within the specification and claims of this application should be understood to include numerical values ​​that would be identical if rounded to the same number of significant figures to determine the value, and numerical values ​​that differ from the stated value by less than experimental error using conventional measurement techniques of the type described herein.

[0025] All ranges disclosed herein are inclusive of the recited endpoints and are independently combinable (e.g., the range "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 conjunction 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 a range of "2 to 4." In general, 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 input light that is then 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 converted light, e.g., the resulting light produced by a phosphor that has been 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 may depend on the context. For example, these colors are sometimes used to label various components and distinguish them from one another.

[0029] The present disclosure relates to light conversion devices, such as phosphor wheels, that use inorganic binders that provide better thermal properties than silicone binders and are significantly lower in cost than ceramic binders.

[0030] A phosphor wheel is used to continuously generate different colored lights. Light conversion (or wavelength conversion) materials, such as phosphors, are used on the phosphor wheel. The phosphor wheel usually has several fan sections containing different types of phosphors to convert the excitation light to green, yellow, or red. Typically, a blue light laser (having a wavelength of about 440 nm to about 460 nm) is used to excite the phosphor sections on the phosphor wheel. The phosphor wheel can also have one or more gaps to allow blue source light to pass through unconverted. Phosphor wheels have two basic structures: reflective and transmissive.

[0031] In a reflective phosphor wheel, the excitation light of the blue light laser does not pass through a substrate before stimulating the phosphor. Figures 1A and 1B show a typical structure of a reflective phosphor wheel. Phosphor powder is mixed with a binder to create a phosphor mixture that is deposited on a substrate 112. In some embodiments, the substrate is optional.

[0032] The substrate of the phosphor wheel, when present, is typically a metal with high thermal conductivity, such as aluminum or an aluminum alloy, copper or a copper alloy, or another metal with high thermal conductivity. The substrate may also be made of, for example, glass, sapphire, or diamond. The substrate can include a mirror or reflective coating, or can be made of a reflective material, when desired. For example, the reflective material / reflective coating can be made of a metallic material, a dielectric material, or a combination thereof. Examples of metallic materials include the metals and metal 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 a wavelength converting element 111 that is tightly bonded to the substrate. As shown in FIG. 1A, there are three wavelength converting elements: a green section 111a, a red section 111b, and a yellow section 111c. These three sections are located around the periphery of a circular substrate 112 (from a plan view). Not shown here is a section for blue excitation light that passes through the substrate and is not reflected. As shown in FIG. 1B, the substrate 112 is then mounted on a motor 113 to obtain a phosphor wheel 110. In a phosphor wheel, the substrate is rotated during use. It is also envisioned that the substrate can be used in a static (i.e., fixed, non-rotating) configuration. For example, the wavelength converting element can be directly bonded to the substrate, which acts as a heat sink.

[0034] 1B, as the substrate 112 is rotated about axis AA, excitation blue light 114a stimulates the red and green phosphors 111, and emitted light 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 to stimulate the phosphors to produce emitted light.

[0035] The second type of phosphor wheel is a transmissive phosphor wheel. In a transmissive phosphor wheel, excitation light passes through a substrate before stimulating the phosphors. Figures 2A and 22B show a typical transmissive phosphor wheel structure. Again, three wavelength conversion elements 211 are illustrated here: a green section 211a, a red section 211b, and a yellow section 211c. 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. Typically, glass, diamond, or sapphire is used as the substrate material. Blue light can pass through the substrate, while red, green, and yellow (RGY) light emitted by the phosphors is reflected.

[0036] 2B, 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 phosphors 211. Emitted light 214b is collected by a subsequent optical system.

[0037] Some performance characteristics, such as converted light output, color, and lifetime, are a direct function of operating temperature. At higher operating temperatures, converted light output may decrease, color may shift, and phosphor wheel lifetime may be reduced. Under normal operating conditions, approximately 50% to 60% of the input power is output as heat, while the remainder of the input power is converted to light. At high input powers, heat generation during conversion may cause temperatures to exceed two hundred degrees Celsius (200°C).

[0038] A desirable binder for phosphors for fabricating wavelength conversion elements should ideally have a combination of several properties: high transparency at visible wavelengths, a low refractive index, a high bonding hardness, high thermal stability (i.e., a 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 durability of the phosphor wheel at temperatures between 165°C and 300°C.

[0039] In the present disclosure, a wavelength converting element, such as a phosphor section of a phosphor wheel, includes a phosphor and an inorganic binder, the term "inorganic" meaning that the binder does not contain any carbon.

[0040] The wavelength converting 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 inorganic binders. In particular, the addition of fillers can reduce the shrinkage rate of the composition used to fabricate the wavelength conversion element, 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. The filler can be selected to have a thermal expansion coefficient as close as possible to (e.g., substantially the same as) the thermal expansion coefficient of the inorganic material. Similarly, to avoid stratification, the filler can be selected to have a density as close as possible to (e.g., substantially the same as) the density of the inorganic material. The filler can have any desired shape, such as a granular, flaky, or fibrous shape. Any suitable filler can be used. For example, it is specifically contemplated that the filler can be silica, silicate, aluminate, or phosphate, or diamond powder. The filler can be a metal powder, such as aluminum, copper, silver, or gold powder. The filler can be a nitride, 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 for dispersing the filler throughout the binder, thereby avoiding undesirable aggregation or settling. Any suitable dispersant can be used. For example, it is specifically contemplated that the dispersant may be an organic dispersant such as polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene-co-maleic anhydride, or lignosulfonate. Alternatively, it is specifically contemplated that the dispersant may be an inorganic dispersant such as hexametaphosphate, silicate, polyphosphate, or fumed silica.

[0043] Desirably, the inorganic binder has a coefficient of thermal expansion (CTE) of about 0.5 to about 25 ppm / °C. In a particular embodiment, the inorganic binder is sodium silicate. Sodium silicate has the chemical formula (Na2SiO3) nis a common name for a compound of formula (I) which can alternatively be considered a polymer, as can be seen in the following formula (I): [ka]

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

[0045] In other embodiments, the inorganic binder can be made from other inorganic materials besides sodium silicate. These inorganic materials can 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] The phosphor and inorganic binder are typically mixed together and then applied to the desired area. The weight ratio of phosphor to inorganic binder is from about 1:1 to about 5:1, i.e., there can be more phosphor than inorganic binder, including from about 1:1 to about 3:1 and from about 1:1 to about 2:1.

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

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

[0049] The resulting wavelength converting element may typically have a thickness of about 0.05 mm to about 0.3 mm, measured in the direction of axis AA in FIG. 1A.

[0050] Desirably, the inorganic binder is substantially optically transparent (e.g., the inorganic binder has a light transmittance of at least 80%, including 90% up to 98%), as 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, which allows them to be used in transmission or reflection phosphor wheels.

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

[0052] In further embodiments, a smoothing layer can be applied on the wavelength conversion element.The smoothing layer serves to reduce the surface roughness of the final device without using mechanical processes such as polishing, which can damage the final device.This reduces scattering, improves wavelength conversion efficiency, and improves the ability to direct the resulting light in the desired direction.The smoothing layer can be polymeric, or can be made of materials such as metals such as tungsten, nickel, or cobalt, or carbides such as boron carbide or silicon carbide.

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

[0054] It is contemplated that any combination of such layers / coatings may be present. For example, a phosphor wheel according to the present disclosure may be designed with a substrate, a reflective coating applied to the substrate, a wavelength converting element applied over the reflective coating, a smoothing layer applied over the inorganic binder, and a protective coating applied over the smoothing layer.

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

[0056] Inorganic materials are typically stable over long periods of time, and the performance of these devices has not necessarily been found to degrade significantly over time. Organic materials can also exhibit some outgassing at high operating temperatures, which can lead to contamination of nearby components within the optical device. Additionally, inorganic binders can 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 into various sizes, shapes, and thicknesses. The inorganic binders of the present disclosure can also withstand high operating temperatures, i.e., 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 of about 60 watts to about 300 watts, including those exceeding 100 watts. The operating temperatures of such devices can reach temperatures exceeding 200°C, enabling high emission brightness.

[0057] It is envisioned that the inorganic binders can be used in phosphor wheels and laser projection display systems. They can also be used with solid-state lighting sources, such as automobile headlights.

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

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

[0060] The emitted light efficiency of the present phosphor wheel, which uses sodium silicate as the inorganic binder, was compared with that of a phosphor wheel using an organosilicone binder (i.e., the comparative example). The new phosphor wheel had an efficiency 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 combining the phosphor and inorganic binder was 1,500 cP. The paste had an initial bond 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 sections were thermally stable up to 400°C and had a light transmittance of 98%. The emitted light efficiency of this new phosphor was measured in comparative experiments. It was just 4% lower than the example. Example 3

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

[0063] The inorganic material is mixed with the first component and the second component, and the mixture is heated to about 25 to 3000°C. about 30 The mixture was prepared by stirring for a period of about 2 to about 3 hours at a temperature of 0° C. The ratio of the first component to the second component was about 1:1 to about 7:3.

[0064] An inorganic binder was then prepared by adding a filler and a dispersant to the inorganic material. The inorganic binder was cured in a stepwise process. The first curing step was carried out at a temperature of about 60 to about 90°C for a period of about 0.2 to about 1 hour. The second curing step was then carried out at a temperature of about 150 to about 200°C for a period of about 0.4 to about 2 hours. The cured inorganic binder was shown to exhibit excellent bond strength at the highest applied temperature due to the inorganic binder's high temperature resistance.

[0065] The present disclosure has been described with reference to exemplary embodiments. Modifications and alterations will occur to those skilled in the art upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or their equivalents. For example, the present application provides the following: (Item 1) 1. A photoconversion device comprising: A wavelength converting element configured to absorb light at an excitation wavelength and generate light at an emission wavelength, the wavelength converting element comprising an inorganic binder and a phosphor. A photoconversion device comprising: (Item 2) Item 2. The photoconversion device of item 1, wherein the inorganic binder comprises sodium silicate. (Item 3) Item 3. The photoconversion device according to item 2, wherein the ratio of SiO2:Na2O is from about 2:1 to about 3.75:1. (Item 4) Item 2. The photoconversion device of 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) Item 2. The light-conversion device according to item 1, wherein the weight ratio of said phosphor to said inorganic binder is from about 1:1 to about 5:1. (Item 6) Item 10. The photoconversion device of item 1, wherein the inorganic binder is substantially optically transparent. (Item 7) Item 7. The light conversion device according to item 6, wherein the inorganic binder has a light transmittance of at least 80%. Chair. (Item 8) Item 2. The photoconversion device according to item 1, wherein the inorganic binder is capable of withstanding temperatures above 200°C. (Item 9) Item 1. The photoconversion device of item 1, wherein the inorganic binder has a bond strength of at least 100 psi. (Item 10) 2. The photoconversion device according to item 1, wherein the inorganic binder has a curing temperature of about 100°C to about 500°C. (Item 11) 2. The photoconversion device according to item 1, wherein the inorganic binder has a viscosity of about 0 cP to about 2,000 cP. (Item 12) Item 2. The optical conversion device according to item 1, wherein the wavelength conversion element has a thickness of about 0.05 mm to about 3 mm. (Item 13) Item 1, further comprising a substrate on which the wavelength conversion element is mounted, the substrate being disk-shaped, and further comprising a motor arranged to rotate the substrate around an axis normal to the substrate. (Item 14) 1. A light engine, comprising: The photoconversion device according to item 1; a light source arranged to expose the photo-conversion device to light at the excitation wavelength; A light engine comprising: (Item 15) 1. A method for making a phosphor wheel, comprising: Applying a wavelength conversion element containing an inorganic binder and a phosphor to a substrate. A method comprising: (Item 16) Item 16. The method according to item 15, wherein the wavelength converting element is applied to the substrate by dispensing, spraying, brush coating, or silk printing. (Item 17) Item 16. The method of item 15, further comprising curing the inorganic binder. (Item 18) Item 18. The method according to item 17, wherein the inorganic binder is cured at a temperature of about 100°C to about 500°C. (Item 19) Item 16. The method according to item 15, wherein the inorganic binder comprises sodium silicate. (Item 20) 1. A laser projection display system, comprising: A laser beam having a power of about 60 W to about 300 W; A phosphor wheel, the phosphor wheel comprising: A substrate; a wavelength converting element configured to absorb light at an excitation wavelength and generate light at an emission wavelength, the wavelength converting element comprising an inorganic binder and a phosphor; a phosphor wheel comprising: A laser projection display system comprising: (Item 1A) A phosphor wheel, a substrate in the shape of a disk; a motor arranged to rotate the substrate about an axis normal to the substrate; a wavelength converting element disposed on the substrate, the wavelength converting element configured to absorb light at an excitation wavelength and generate light at an emission wavelength, the wavelength converting element comprising an inorganic binder and a phosphor; A phosphor wheel comprising: (Item 2A) Item 1C. The phosphor wheel of item 1A, wherein the inorganic binder comprises sodium silicate. (Item 3A) The phosphor wheel of item 2A, wherein the ratio of SiO2:Na2O is from about 2:1 to about 3.75:1. (Item 4A) Item 1B. The phosphor wheel of 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) Item 1B. The phosphor wheel according to item 1A, wherein the weight ratio of the phosphor to the inorganic binder is about 1:1 to about 5:1. (Item 6A) The phosphor wheel of claim 1A, wherein the inorganic binder is substantially optically transparent. Item 6B. The phosphor wheel of item 6A, wherein the inorganic binder has a light transmittance of at least 80%. (Item 8A) Item 1B. The phosphor wheel of item 1A, wherein the inorganic binder is capable of withstanding temperatures exceeding 200°C. (Item 9A) The inorganic binder has a bond strength of at least 100 psi. Light body wheel. (Item 10A) The phosphor wheel according to Item 1A, wherein the inorganic binder has a curing temperature of about 100°C to about 500°C. (Item 11A) The phosphor wheel according to Item 1A, wherein the inorganic binder has a viscosity of about 0 cP to about 2,000 cP. (Item 12A) Item 1B. The phosphor wheel according to Item 1A, wherein the wavelength conversion element has a thickness of about 0.05 mm to about 3 mm. (Item 13A) Item 1C. The phosphor wheel of item 1A, wherein the inorganic binder comprises sodium silicate. (Item 14A) 1. A light engine, comprising: The phosphor wheel according to item 1A; a light source arranged to expose the wavelength converting element of the phosphor wheel to light at the excitation wavelength; A light engine comprising: (Item 15A) 1. A method for making a phosphor wheel, comprising: applying a wavelength converting element comprising an inorganic binder and a phosphor to a substrate in the shape of a disk; arranging a motor to rotate the substrate about an axis normal to the substrate; A method comprising: (Item 16A) Item 15B, the method according to item 15A, wherein the wavelength converting element is applied to the substrate by dispensing, spraying, brush coating, or silk printing. (Item 17A) The method of claim 15A, further comprising curing the inorganic binder. (Item 18A) The method according to Item 17A, wherein the inorganic binder is cured at a temperature of about 100°C to about 500°C. (Item 19A) The method of claim 15A, wherein the inorganic binder comprises sodium silicate.

Claims

1. 1. A photoconversion device comprising: A wavelength converting element, the wavelength converting element being configured to absorb light at an excitation wavelength and generate light at an emission wavelength, the wavelength converting element including an inorganic binder and a phosphor, the inorganic binder including an inorganic material, a filler, and a dispersant; the inorganic material is selected from the group consisting of silicates, aluminates, phosphates, borates and inorganic sol-gels; the silicate comprises sodium silicate; and The inorganic sol-gel is made of silicon dioxide (SiO 2 ) or aluminum oxide (Al 2 O 3 ); the filler is selected from the group consisting of silica, silicates, aluminates, phosphates, diamond powder, metal powder, nitrides, oxides, and metal sulfides; the metal powder is aluminum powder, copper powder, silver powder, or gold powder; the nitride is aluminum nitride, borazon, or a metal nitride; and the oxide is aluminum oxide, boron oxide, or a metal oxide; the selected filler has a coefficient of thermal expansion that is comparable to the coefficient of thermal expansion of the inorganic material, and the selected filler has a density that is comparable to the density of the inorganic material; the inorganic binder is capable of withstanding operating temperatures exceeding 200°C and has a thermal expansion coefficient of 0.5 ppm / °C to 25 ppm / °C, and the inorganic binder and the phosphor are miscible; Wavelength conversion element A photoconversion device comprising:

2. 10. The light-conversion device of claim 1, wherein the weight ratio of said phosphor to said inorganic binder is 1:1 to 5:

1.

3. The photoconversion device of claim 1, wherein the dispersant is an organic dispersant selected from the group consisting of polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene-co-maleic anhydride, and lignosulfonate, or the dispersant is an inorganic dispersant selected from the group consisting of hexametaphosphate, silicate, polyphosphate, and fumed silica.

4. 10. The photo-conversion device of claim 1, wherein the inorganic material is the inorganic sol-gel, and the inorganic material is used to form the inorganic binder made from a first component and a second component, wherein: The first component has a viscosity of 1 mPa·sec to 50 mPa·sec and a viscosity of 0.8 g / cm 3 to 1.3 g / cm ３ and a solids content greater than 10%; and The second component has a viscosity of 0 mPa·sec to 50 mPa·sec, a viscosity of 0.6 g / cm 3 to 1.0 g / cm ３ and a solids content of greater than 10%. Photoconversion devices.

5. 5. The photo-conversion device of claim 4, wherein the first component is a translucent liquid and the second component is a transparent liquid.

6. A method for making a photoconversion device described in any one of claims 4 to 5, comprising preparing the inorganic material by stirring a mixture of the first component and the second component at a temperature of 25 to 30°C for a period of 2 to 3 hours.

7. The photo-conversion device according to any one of claims 1 to 5, wherein the inorganic binder has a light transmittance of at least 80%.

8. The photo-conversion device according to any one of claims 1 to 3, wherein the inorganic binder has a curing temperature of 100°C to 500°C.

9. The photo-conversion device according to any one of claims 1 to 3, wherein the inorganic binder has a viscosity of 0 cP to 2,000 cP.

10. An optical conversion device described in any one of claims 1 to 3 and 9, wherein the inorganic binder has an initial bond strength of at least 100 psi.

11. The inorganic binder is SiO ２ : Na ２ 10. The photo-conversion device of claim 1, comprising sodium silicate having a weight ratio of 0.

12. The photoconversion device according to any one of claims 1 to 5, a substrate, on which the wavelength converting element is mounted, the substrate being in the shape of a disk; and a motor arranged to rotate the substrate about an axis normal to the substrate; The photoconversion device further comprises:

13. 1. A light engine, comprising: The photoconversion device of claim 1 ; a light source arranged to expose the photo-conversion device to light at the excitation wavelength; A light engine comprising:

14. 1. A method for fabricating a photoconversion device, comprising: applying a wavelength converting element comprising an inorganic binder and a phosphor to a substrate; the inorganic binder comprises an inorganic material, a filler, and a dispersant; the inorganic material is selected from the group consisting of silicates, aluminates, phosphates, borates and inorganic sol-gels; the silicate comprises sodium silicate; and The inorganic sol-gel is made of silicon dioxide (SiO 2 ) or aluminum oxide (Al 2 O 3 ); the filler is selected from the group consisting of silica, silicates, aluminates, phosphates, diamond powder, metal powder, nitrides, oxides, and metal sulfides; the metal powder is aluminum powder, copper powder, silver powder, or gold powder; the nitride is aluminum nitride, borazon, or a metal nitride; and the oxide is aluminum oxide, boron oxide, or a metal oxide; the selected filler has a coefficient of thermal expansion that is comparable to the coefficient of thermal expansion of the inorganic material, and the selected filler has a density that is comparable to the density of the inorganic material; the inorganic binder is capable of withstanding operating temperatures exceeding 200°C and has a thermal expansion coefficient of 0.5 ppm / °C to 25 ppm / °C, and the inorganic binder and the phosphor are miscible; method.

15. 15. The method of claim 14, wherein the weight ratio of the phosphor to the inorganic binder is 1:1 to 5:

1.

16. The method of claim 14, wherein the dispersant is an organic dispersant selected from the group consisting of polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene-co-maleic anhydride, and lignosulfonate, or the dispersant is an inorganic dispersant selected from the group consisting of hexametaphosphate, silicate, polyphosphate, and fumed silica.

17. 15. The method of claim 14, wherein the inorganic material is the inorganic sol-gel, and the inorganic material is used to form the inorganic binder made from a first component and a second component, wherein: The first component has a viscosity of 1 mPa·sec to 50 mPa·sec and a viscosity of 0.8 g / cm 3 to 1.3 g / cm ３ and a solids content greater than 10%; and The second component has a viscosity of 0 mPa·sec to 50 mPa·sec, a viscosity of 0.6 g / cm 3 to 1.0 g / cm ３ and a solids content of greater than 10%. method.

18. 18. The method of claim 17, wherein the inorganic material is prepared by stirring a mixture of the first and second components at a temperature of 25-30° C. for a period of 2-3 hours.

19. The method according to any one of claims 17 to 18, conducting a first cure at a temperature of 60-90°C for a period of 0.2-1 hour; and This is followed by a second cure at a temperature of 150-200°C for a period of 0.4-2 hours. curing the inorganic binder made from the first component and the second component in a stepwise process comprising:

20. The method according to any one of claims 14 to 18, wherein the wavelength converting element is applied to the substrate by dispensing, spraying, brushing or silk printing.

21. The method of any one of claims 14 to 16, further comprising curing the inorganic binder at a temperature of 100°C to 500°C.

22. 1. A laser projection display system, comprising: a laser beam having a power of 60 W to 300 W; 1. A light conversion device that is a phosphor wheel, A substrate; A wavelength converting element, the wavelength converting element being configured to absorb light at an excitation wavelength and generate light at an emission wavelength, the wavelength converting element including an inorganic binder and a phosphor, the inorganic binder including an inorganic material, a filler, and a dispersant; the inorganic material is selected from the group consisting of silicates, aluminates, phosphates, borates and inorganic sol-gels; the silicate comprises sodium silicate; and The inorganic sol-gel is made of silicon dioxide (SiO 2 ) or aluminum oxide (Al 2 O 3 ); the filler is selected from the group consisting of silica, silicates, aluminates, phosphates, diamond powder, metal powder, nitrides, oxides, and metal sulfides; the metal powder is aluminum powder, copper powder, silver powder, or gold powder; the nitride is aluminum nitride, borazon, or a metal nitride; and the oxide is aluminum oxide, boron oxide, or a metal oxide; the selected filler has a coefficient of thermal expansion that is comparable to the coefficient of thermal expansion of the inorganic material, and the selected filler has a density that is comparable to the density of the inorganic material; The inorganic binder can withstand an operating temperature exceeding 200°C and has a thermal expansion coefficient of 0.5 ppm / °C to 25 ppm / °C, and the inorganic binder and the phosphor are miscible. a photoconversion device comprising: A laser projection display system comprising:

23. The laser projection display system of claim 22, wherein the dispersant is an organic dispersant selected from the group consisting of polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene-co-maleic anhydride, and lignosulfonate, or the dispersant is an inorganic dispersant selected from the group consisting of hexametaphosphate, silicate, polyphosphate, and fumed silica.

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