Light conversion device with enhanced inorganic binder

Abstract

A light conversion device, in particular a light conversion device with an enhanced inorganic binder, comprising a layer formed from an inorganic binder comprising: from about 25% to about 80% by weight of a filler; from about 20% to about 75% by weight of an inorganic binder; and from about 0.5% to about 5% by weight of a dispersant. The inorganic binder is resistant to high temperatures, has high light transmittance, has high tensile shear strength, can be coated by a flexible coating method, and has a low curing temperature. Such inorganic binders can be advantageously used in various applications, such as optical channels (300), projection display systems, and optical light conversion devices used in such systems, such as fluorescent wheels (100).

Description

[0001] This patent application is a divisional application of the patent application with application number 2017800957166, filing date September

[0002] 20, 2017, and invention title "Optical Conversion Device with Enhanced Inorganic Binder". Technical Field

[0003] The present disclosure relates to an inorganic binder having certain properties that make it particularly suitable for projection display systems and optical light conversion devices, such as fluorescent wheels, used in such systems. In particular, the inorganic binder of the present disclosure maintains enhanced bond strength at temperatures up to 400 °C. Background Art

[0004] Organic binders (e.g., epoxy resins, polyurethanes, silicones) are widely used for bonding. For example, in phosphor products in silicone, phosphor powder is mixed into a silicone binder or adhesive, and then drop-coated or printed in a desired pattern. Silicone is commonly used for bonding metals, glass, and other materials due to its high transparency, high bond strength, low refractive index, and suitable viscosity. For example, a commonly used binder is selected to be manufactured OE-6336, which has a mixed viscosity of 1,425 centipoise (cP), a transparency of 99.6% at 450 nm and a thickness of 1 mm, a refractive index of 1.4, and a thermal curing time of 60 minutes at 150 °C.

[0005] However, silicone binders / adhesives have poor thermal stability. At temperatures above 200 °C, silicone adhesives degrade, typically starting to turn yellow and gradually starting to burn. This undesirably results in a short service life of the fluorescent wheel, and it has been observed that the light conversion efficiency drops sharply due to thermal quenching (> 10% @ 200 °C). In applications with high brightness (e.g., laser power of 300 W), the operating temperature of the fluorescent wheel is expected to be typically greater than 200 °C, thus making the use of silicone adhesives undesirable. That is, phosphor products in silicone cannot achieve a long service life in high-power laser projectors. In the life tests of such products, it has been determined that the safe operating temperature should be controlled below 150 °C.

[0006] ​Accordingly, there is a desire to provide an inorganic binder that, in addition to having a relatively high temperature resistance (e.g., greater than 200 °C, including 300 °C or above, and up to 400 °C), also exhibits the same desirable properties as organic binders (i.e., high transparency, high bond strength, low refractive index, and suitable viscosity). Such inorganic binders can be advantageously used in various applications such as optical channels, projection display systems, and optical light conversion devices (e.g., fluorescent wheels) used in such systems. Summary of the Invention

[0007] The present disclosure relates to an inorganic binder that can be used in a high reflectivity coating of an optical light conversion device (e.g., a fluorescent wheel) or as an adhesive for joining two elements. The inorganic binder has certain properties that make it particularly suitable for high power lighting systems. For example, in certain embodiments, the inorganic binder is capable of withstanding high temperatures (e.g., greater than 200 °C, including 300 °C or above, and up to 400 °C), has a high light transmittance (e.g., at least 98%), has a high tensile shear strength (e.g., at least 100 psi at 300 °C), can be applied by flexible coating methods (e.g., drop coating, screen printing, spraying), and has a low curing temperature (e.g., below 185 °C).

[0008] In some cases, the composition consists essentially of: from about 25 wt% to about 80 wt% of one or more fillers; from about 20 wt% to about 75 wt% of one or more inorganic binders; and from about 0.5 wt% to about 5 wt% of one or more dispersants.

[0009] The inorganic binder can include a first component (e.g., a translucent liquid) and a second component (e.g., a transparent liquid). The ratio of the first component to the second component can range from about 1:1 to about 7:3. The inorganic binder can be prepared by stirring the first component and the second component. The first component and the second component can be stirred for a period of about 2 hours to about 3 hours. The first component and the second component can be stirred at a temperature of about 25 °C to about 30 °C. In certain embodiments, the viscosity of the first component ranges from about 1 mPa·sec to about 50 mPa·sec, the density ranges from about 0.8 g / cm 3 to about 1.3 g / cm 3 and the solids content is greater than 10%. In some embodiments, the viscosity of the second component ranges from about 0 mPa·sec to about 50 mPa·sec, the density ranges from about 0.6 g / cm 3 to about 1.0 g / cm 3 and the solids content is greater than 10%.

[0010] In some cases, the coefficient of thermal expansion of the filler is within ±20% (±20%) of the coefficient of thermal expansion of the inorganic binder. The density of the filler can also be within ±20% (±20%) of the density of the inorganic binder.

[0011] One or more fillers can be selected from the group consisting of silica, alumina, and boron oxide. The shape of the filler can be granular, flaky, or fibrous. The particle size of the filler can range from about 0.1 micron to about 50 microns.

[0012] In some embodiments, the dispersant is organic (e.g., polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene copoly maleic anhydride, or lignosulfonate). In alternative embodiments, the dispersant is inorganic (e.g., hexametaphosphate, silicate, polyphosphate, or calcined silica).

[0013] A method of forming an inorganic binder according to the present disclosure includes: performing a first curing at a temperature of about 60°C to about 90°C for a period of about 0.2 hours to about 1 hour, and subsequently performing a second curing at a temperature of about 150°C to about 200°C for a period of about 0.4 hours to about 2 hours.

[0014] Also disclosed herein is a light conversion device including: a substrate having an inorganic coating, the inorganic coating comprising: from about 20 wt% to about 80 wt% filler; from about 20 wt% to about 75 wt% inorganic binder; and from about 0.5 wt% to about 5 wt% dispersant. In more specific embodiments, the filler is present in an amount of about 60 wt% to about 75 wt%, and the inorganic binder is present in an amount of about 20 wt% to about 35 wt%.

[0015] The substrate can be in the form of a disk. The light conversion device can further include a motor configured to rotate the substrate about an axis perpendicular to the substrate.

[0016] In some embodiments, the filler is a phosphor (e.g., yttrium aluminum garnet, silicate, or nitride). The particle size of the phosphor can range from about 10 microns to about 30 microns.

[0017] In certain embodiments, the filler is a refractive powder having a particle size ranging from about 0.1 micron to about 150 microns. The resulting inorganic coating can have a high reflectivity (e.g., at least 80%, at least 90%, at least 95%, at least 98%, etc.) for light having a wavelength from about 380 nm to about 800 nm. The light conversion device can further include a phosphor layer applied to the inorganic coating on the substrate.

[0018] A method of forming a light conversion device according to the present disclosure, the method comprising: coating an inorganic coating onto a substrate by spraying, drop coating or screen printing; performing a first curing of the inorganic coating at a temperature of about 85 °C for a period of about 0.25 hours, and subsequently performing a second curing of the inorganic coating at a temperature of about 185

[0019] °C for a period of about 0.75 hours.

[0020] The present disclosure also discloses an optical channel, which includes: a plurality of reflectors joined together by an inorganic binder capable of withstanding a temperature greater than 200 °C, the inorganic binder comprising: from about 25 wt% to about 80 wt% of a filler; from about 20 wt% to about 75 wt% of an inorganic binder; and from about 0.5 wt% to about 5 wt% of a dispersant.

[0021] In a particular embodiment, the filler may be alumina. The particle size of the filler may range from about 0.5 microns to about 10 microns.

[0022] A method of forming an optical channel according to the present disclosure, the method comprising: performing a first curing of the inorganic binder at a temperature of about 85 °C

[0023] for a period of about 0.25 hours, and subsequently performing a second curing of the inorganic binder at a temperature of about 185 °C for a period of about 0.75 hours.

[0024] These and other non-limiting features of the present disclosure are disclosed in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following are brief descriptions of the drawings, which are provided to illustrate the exemplary embodiments disclosed herein and are not intended to limit the invention.

[0026] Figure 1A A schematic diagram of a first exemplary optical light conversion device according to the present disclosure, the optical light conversion device including a substrate and a coating.

[0027] Figure 1B For Figure 1A a side cross-sectional view of the first exemplary optical light conversion device.

[0028] Figure 2A A schematic diagram of a second exemplary optical light conversion device according to the present invention, the optical light conversion device including a substrate, a high reflectivity scattering layer and a phosphor layer.

[0029] Figure 2B For Figure 2A a side cross-sectional view of the second exemplary optical light conversion device.

[0030] Figure 3Schematic diagram of an optical channel according to the present disclosure, the optical channel including a plurality of reflectors joined together by an adhesive. Detailed implementation mode

[0031] A more complete understanding of the components, methods, and devices disclosed herein can be obtained with reference to the accompanying drawings. These drawings are merely schematic descriptions based on convenience and ease of illustration of the present disclosure, and thus are not intended to represent the relative sizes and dimensions of the devices or the various components of the devices and / or are not intended to define or limit the scope of the exemplary embodiments.

[0032] Although specific terms are used in the following description for clarity, these terms are only intended to refer 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, it should be understood that the same reference numerals refer to components having the same function.

[0033] Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" also include plural objects.

[0034] As used in the specification and claims, the terms "comprising", "including", "having", "has", "can", "containing", and their variants are intended herein as open transitional terms, terms, or words that require the presence of the specified components / steps and allow the presence of other components / steps. However, this description should also be interpreted as describing the composition or process as "consisting of the recited components / steps" and "consisting essentially of the recited components / steps", which allows only the presence of the specified components / steps and any inevitable impurities that may result from these components, but does not include other components / steps.

[0035] The numerical values in the specification and claims of the present application should be understood to include: numerical values that are the same when reduced to the same number of significant figures; and numerical values whose difference from the set value is smaller than the experimental error of the conventional measurement techniques of the type described in the present application for determining the value.

[0036] All ranges disclosed herein include the recited end values and can be combined independently (e.g., the range "from 2 grams to 10 grams" includes the end values 2 grams and 10 grams and all intermediate values).

[0037] 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 a range, the terms "about" and "approximately" also disclose the range defined by the absolute values of the two end values. For example, "about 2 to about 4" also discloses the range "from 2 to 4". Generally speaking, the terms "about" and "approximately" can refer to + / - 10% of the indicated number.

[0038] As used herein, the terms "exciting light" and "exciting wavelength" refer to input light that is subsequently converted, such as light generated by a laser-based illumination source or other light source. The terms "emitted light" and "emitted wavelength" refer to the converted light, such as the resulting light generated by a phosphor that has been exposed to the exciting light.

[0039] As used herein, the term "inorganic" means that an "inorganic" object does not contain any carbon. For the avoidance of doubt, the terms "inorganic binder", "inorganic adhesive", and "inorganic coating" of the present disclosure do not contain carbon.

[0040] For reference, red generally refers to light having a wavelength of from about 780 nanometers to about 622 nanometers. Green generally refers to light having a wavelength of from about 577 nanometers to about 492 nanometers. Blue generally refers to light having a wavelength of from about 492 nanometers to about 455 nanometers. Yellow generally refers to light having a wavelength of from about 597 nanometers to about 577 nanometers. However, the above may depend on the context. For example, these colors are sometimes used to label individual parts and to distinguish these parts from each other.

[0041] The present disclosure relates to an inorganic binder that has certain properties that make it particularly suitable for high-power lighting systems. The inorganic binder is a composition containing multiple components. Some performance characteristics, such as converted light output, color, and lifetime, are direct functions of the operating temperature. At higher operating temperatures, the converted light output may decrease, the color may shift, and the service life may be shortened. Under normal operating conditions, about 50% to 60% of the input power is output as heat, while the remainder of the input power is converted into light. At high input powers, the heat generated during conversion will result in high sustained temperatures greater than 200 degrees Celsius (200°C), including 300°C or higher, and up to 400°C.

[0042] In certain embodiments, the inorganic binder of the present disclosure is capable of withstanding high temperatures (e.g., greater than 200°C, including 300°C or higher, and up to 400°C), has a high light transmittance (e.g., at least 98%), has a high tensile shear strength (e.g., at least 100 psi at 300°C), can be coated by flexible coating methods (e.g., drop coating, screen printing, spraying), and has a low curing temperature (e.g., below 185°C).

[0043] The inorganic binder of the present disclosure can be used in high-power lighting systems, such as optical light conversion devices (e.g., fluorescent wheels). The inorganic binder can be used in different layers to provide high reflectivity or to provide a wavelength conversion layer.

[0044] Generally speaking, as described in the various embodiments herein, the inorganic binder comprises or consists essentially of: at least one filler, at least one inorganic adhesive, and at least one dispersant.

[0045] Based on the weight of the inorganic binder, the inorganic binder may comprise from about 25 wt% to about 80 wt% of a filler, including from about 60 wt% to about 75 wt%, or from about 65 wt% to about 75 wt% of the filler. The filler can be used to obtain the functions required for the layer made of the inorganic binder. For example, the filler can be a phosphor to produce a wavelength conversion layer; or it can be a refractive powder to produce a reflective coating. One or more different fillers can be present.

[0046] Based on the weight of the inorganic binder, the inorganic binder may comprise from about 20 wt% to about 75 wt% of an inorganic binder, including from about 20 wt% to about 45 wt%, or from about 25 wt% to about 40 wt% of the inorganic binder.

[0047] Based on the weight of the inorganic binder, the inorganic binder may comprise from about 0.5 wt% to about 5 wt% of a dispersant, including from about 1 wt% to about 4 wt%, or from about 2 wt% to about 3 wt% of the dispersant. One or more dispersants can be used, and these amounts apply to all the dispersants combined.

[0048] In a specific embodiment, the inorganic binder consists essentially of from about 25 wt% to about 80 wt% of one or more fillers, from about 20 wt% to about 75 wt% of one or more inorganic binders, and from about 0.5 wt% to about 5 wt% of one or more dispersants, with these components totaling 100 wt%.

[0049] In other specific embodiments, the inorganic binder consists essentially of from about 60 wt% to about 75 wt% of one or more fillers, from about 20 wt% to about 40 wt% of one or more inorganic binders, and from about 0.5 wt% to about 5 wt% of one or more dispersants, with these components totaling 100 wt%.

[0050] Adding one or more fillers to one or more inorganic binders enhances the bonding strength of the inorganic binder. In particular, adding one or more fillers can reduce the shrinkage rate of the inorganic binder, reduce or prevent the formation of bubbles or cracks during curing, thereby reducing the amount and / or effect of stress during use, and improving the bonding strength of the inorganic binder. The coefficient of thermal expansion of the one or more fillers selected can be within ±20% of the coefficient of thermal expansion of the inorganic binder. Similarly, to avoid delamination, the density of the one or more fillers selected can be within ±20% of the density of the inorganic binder. The one or more fillers can have any desired shape, such as granular, flaky or fibrous. Any suitable one or more fillers can be used. For example, one or more fillers 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 boron nitride. The filler can be an oxide, such as alumina or boron oxide. The filler can be a metal oxide, metal nitride or metal sulfide. The one or more fillers can have any suitable particle size, such as from about 0.1 micron to about 50 microns.

[0051] Adding one or more dispersants facilitates the dispersion of the one or more fillers throughout the binder, thereby avoiding unwanted aggregation or sedimentation. Any suitable one or more dispersants can be used. For example, one or more dispersants can be organic dispersants, such as polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene copoly maleic anhydride or lignosulfonate. Alternatively, one or more dispersants can be inorganic dispersants, such as hexametaphosphate, silicate, polyphosphate or calcined silica.

[0052] As previously mentioned, the inorganic binder can be used in a variety of applications, such as as a coating for forming one or more layers within an optical light conversion device such as a fluorescent wheel. Fluorescent wheels are used to sequentially generate light of different colors. Light conversion (or wavelength conversion) materials such as phosphors are used on the fluorescent wheel. Fluorescent wheels typically have a number of sector segments that contain different types of phosphors to convert the excitation light into green, yellow or red. Typically, a blue laser (having a wavelength of about 440 nm to about 460 nm) is used to excite the phosphor sector segments on the fluorescent wheel. The fluorescent wheel can also have one or more gaps to allow the blue source light to pass through without being converted.

[0053] Figure 1A and Figure 1B shows such a light conversion device that includes a wavelength conversion layer formed of an inorganic binder. In particular, the first exemplary light conversion device is the fluorescent wheel 100. Figure 1A is a schematic diagram of the fluorescent wheel 100, while Figure 1BSide cross-sectional view of the fluorescent wheel 100. The fluorescent wheel 100 includes a substrate 110, and an inorganic binder is applied to the substrate 110 to form a wavelength conversion layer 120. The wavelength conversion layer is an inorganic coating substantially composed of a filler 121, an inorganic binder 122, and a dispersant (not shown). In this particular embodiment, the wavelength conversion layer is substantially composed of: from about 60 wt% to about 75 wt% of the filler, from about 20 wt% to about 45 wt% of the inorganic binder, and from about 0.5 wt% to about 5 wt% of the dispersant.

[0054] The substrate 110 is typically a metal with high thermal conductivity, such as aluminum or aluminum alloy, copper or copper alloy, or other metals with high thermal conductivity. It can also be made of glass, sapphire, or diamond, for example. For illustrative purposes, the wavelength conversion layer 120 is shown separated from the substrate 110, but in use, the inorganic binder is directly applied to the substrate 110, for example, by spraying, drop coating, or screen printing, to form the wavelength conversion layer.

[0055] In this exemplary embodiment of the fluorescent wheel 100, the filler is a phosphor. Suitable phosphors include yttrium aluminum garnet (YAG), silicates, and nitrides. The particle size of the phosphor can range from about 10 microns to about 30 microns. Then, the phosphor filler can be mixed with the dispersant and an inorganic binder (e.g., a liquid transparent inorganic binder) to form the inorganic binder. The inorganic binder can be drop coated, sprayed, or screen printed onto the substrate and then thermally cured and consolidated to form the wavelength conversion layer 120, such as a concentric pattern when the substrate 110 is in the shape of a disk. The curing of the inorganic coating 120 can be carried out in a stepwise manner. For example, in this exemplary embodiment, the first curing step is carried out at a temperature of about 75 °C to about 100 °C for a period of about 0.1 hour to about 1 hour, such as 0.25 hour. Subsequently, the second curing step is carried out at a higher temperature of about 150 °C to about 200 °C for a period of about 0.5 hour to about 1 hour.

[0056] Now turning to Figure 2A and Figure 2B , which describes another optical light conversion device. In particular, the second exemplary light conversion device is another fluorescent wheel 200. Figure 2A Schematic diagram of the fluorescent wheel 200, while Figure 2BIt is a side view cross-sectional view of the fluorescent wheel 200. The fluorescent wheel 200 includes a substrate 210, a reflective layer 220 formed by applying an inorganic binder on the substrate 210, and a phosphor layer 230 applied on the reflective layer 220 on the substrate 210. The inorganic coating includes a filler 221, an inorganic binder 222, and a dispersant (not shown). In particular, in this exemplary embodiment of the fluorescent wheel 200, the inorganic coating consists essentially of: from about 65 wt% to about 75 wt% of a filler, from about 20 wt% to about 35 wt% of one or more inorganic binders, and from about 1 wt% to about 2 wt% of one or more dispersants.

[0057] In this embodiment of the fluorescent wheel 200, one or more fillers include one or more refractive powders. The particle size of one or more refractive powders can range from about 0.1 micrometer to about 150 micrometers. Then, one or more refractive powders can be mixed with one or more dispersants together with one or more inorganic binders (e.g., a liquid transparent inorganic binder) to form an inorganic binder. Then, the inorganic binder can be drop-coated, spray-coated, or screen-printed onto the substrate, and then heat-cured and consolidated on the substrate 210 (such as in a concentric pattern when the shape of the substrate 210 is disc-shaped) to prepare the substrate 210 with a high-reflectivity layer 220 thereon. For example, the inorganic coating 220 can have a high reflectivity to light with wavelengths ranging from about 380 nm to about 800 nm. The curing of the inorganic binder can be carried out in a stepwise manner. For example, in this exemplary embodiment, the first curing step is carried out at a temperature of about 75 °C to about 100 °C for a period of about 0.1 hour to about 1 hour, such as 0.25 hour. Subsequently, the second curing step is carried out at a temperature of about 150 °C to about 200 °C (such as 185 °C) for a period of about 0.5 hour to about 1 hour, such as 0.75 hour.

[0058] The fluorescent wheel 200 further includes a phosphor layer 230 (e.g., a layer of phosphor powder) applied on the high-reflectivity layer 220 on the substrate 210. The phosphor layer 200 can be applied by (e.g.) drop-coating or screen-printing.

[0059] Figure 1A and Figure 1B the fluorescent wheel 100 as well as Figure 2A and Figure 2B both the fluorescent wheel 200 can be established by mounting the substrate on a motor and rotating it at high speed. Generally, the substrate is rotated during use, although the device can be used in a static (non-rotating) configuration, but in such a case, it may not be called a fluorescent wheel. In Figure 1A and Figure 2A the rotation of the fluorescent wheel is described by an arrow rotating around the axis A-A, and the axis A-A passes through each substrate 110, 210 and is perpendicular to the plane of each substrate 110, 210.

[0060] As Figure 1A - 1B and Figure 2A - 2B shown, excitation light 123 (i.e., excitation light or input light) of an excitation wavelength from a light source (not shown) (e.g., a laser-based illumination source) is focused on an inorganic coating, and emission light 124 (i.e., emission light or converted light) of the excitation wavelength is generated by the inorganic coating. In this way, the inorganic coating converts the spectrum from excitation light in a first spectral wavelength range to emission (or re-emission) light in a second, different spectral wavelength range. When light 123 of the excitation wavelength (e.g., a blue laser beam) is focused on the inorganic coating, light 124 of the emission wavelength (e.g., yellow light) will be emitted and reflected by the inorganic coating and can then be collected (e.g.) by a lens. The fluorescent wheel can be made of an inorganic coating including a plurality of color segment sectors (not shown here), each color segment sector for generating light of a specific color, or can be made to emit light of any desired color. For example, the inorganic coating can be configured to absorb blue light and / or generate yellow light and / or green light.

[0061] Now refer to Figure 3 , which describes an exemplary light channel using an inorganic binder as an adhesive. The light channel wheel 300 includes a plurality of reflectors 301, and the plurality of reflectors 301 are arranged to define a hollow channel therebetween. An inorganic binder 305 is applied to join the reflectors together. The inorganic binder contains one or more fillers, one or more inorganic adhesives, and one or more dispersants. In particular, in this exemplary embodiment of the light channel 300, the inorganic binder consists essentially of: from about 60 wt% to about 75 wt% of one or more fillers, from about 20 wt% to about 45 wt% of one or more inorganic adhesives, and from about 2 wt% to about 3 wt% of one or more dispersants.

[0062] In this exemplary embodiment of the light channel 300, the filler is alumina (Al2O3). The particle size of the alumina filler can range from about 0.5 microns to about 10 microns. Then, the alumina filler and one or more dispersants can be combined with one or more inorganic adhesives (e.g., a liquid transparent inorganic adhesive) to form the inorganic binder 305. Then, the inorganic binder 305 can be drop-coated at the joints between adjacent reflectors 301 for joining adjacent reflectors 301. Then, the inorganic binder 305 is thermally cured and consolidated. The curing of the inorganic binder 305 can be carried out in a stepwise method. For example, in this exemplary embodiment, a first curing step is carried out at a temperature of about 85 °C for a period of about 0.25 hours. Subsequently, a second curing step is carried out at a temperature of about 185 °C for a period of about 0.75 hours.

[0063] The inorganic binders / inorganic binder coatings and adhesives of the present disclosure offer many advantages over conventional phosphor light converters in silicone. For example, the phosphor binder coating in the inorganic binder can maintain the light conversion efficiency at temperatures up to at least 200 °C, including 300 °C or above, and up to 400 °C. The coating should have high transparency at visible light wavelengths; low refractive index; high bond strength; high thermal stability (i.e., high Tg or maximum operating temperature); relatively low curing / sintering temperature; good compatibility / miscibility with phosphors; and / or suitable viscosity. This will enhance the heat resistance of the fluorescent wheel at temperatures from 165 °C to 400 °C.

[0064] Ideally, the inorganic binder is substantially optically transparent (e.g., the light transmittance of the inorganic binder is at least 80%, at least 90%, at least 95% or at least 98%. This is measured (e.g.) using a Lambda 950 spectrophotometer available from Perkin-Elmer. In contrast, many organic binders are opaque. This enables the inorganic binder to be used in transmissive or reflective fluorescent wheels.

[0065] The inorganic binder can exhibit greater bond strength than conventional silicone adhesives. In certain embodiments, the initial bond strength of the inorganic binder of the present disclosure can be at least 100 psi, or at least 200 psi, or from about 100 psi to about 600 psi. This property is determined using two aluminum test plates at the highest temperature at which the adhesive is applied (e.g., at 300 °C), with an inorganic binder having a thickness of 0.1 mm and a bond area of 169 mm 2 placed between the two plates.

[0066] It has been found that inorganic adhesives are generally long-term stable, so the performance of these devices does not necessarily degrade significantly over time. In addition, at high operating temperatures, organic materials can exhibit some outgassing. This can cause contamination of nearby components in the optical device. In addition, under high power conditions, the inorganic binder can be more durable than conventional silicone materials. The inorganic binder exhibits reliable operation at high laser irradiance and temperature. The inorganic binder can also be flexibly fabricated into various sizes, shapes and thicknesses. The inorganic binder of the present disclosure can also tolerate high operating temperatures, i.e., operating temperatures above 200 °C. The inorganic binder can be used in high power laser projection display systems, where the laser power equipped in the solid-state laser projector can range from about 60 watts to about 300 watts, including over 100 watts. The operating temperature of such devices can reach greater than 200 °C, including greater than 300 °C, and up to 400 °C to achieve high luminous brightness.

[0067] It is expected that inorganic binders can be used in fluorescent wheels and laser projection display systems. Inorganic binders can also be used in combination with solid-state lighting sources, such as in automotive headlights. Inorganic binders can further be used as adhesives for light channels, light funnels, etc.

[0068] The following examples are provided to illustrate the methods 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 herein.

[0069] Example

[0070] Example 1

[0071] In one exemplary embodiment, one or more inorganic binders are formed from a first component and a second component. The total dissolved solids (TDS) characteristics of the inorganic binders used are provided in the following table:

[0072] Name Appearance Viscosity (mPa·sec) <![CDATA[Density (g / cm 3 )]]> Solid Content First Component Translucent Liquid 1～50 0.8～1.3 >10％ Second Component Transparent Liquid 0～50 0.6～1.0 >10％

[0073] The inorganic binder is prepared by mixing the first component and the second component and stirring for a period of about 2 hours to about 3 hours at a temperature of about 25°C to about 30°C. The ratio of the first component to the second component is about 1:1 to about 7:3.

[0074] Then the inorganic binder is prepared by adding one or more fillers and one or more dispersants to one or more inorganic binders. The inorganic binder is cured in a stepwise manner. The first curing step is carried out for a period of about 0.2 hours to about 1 hour at a temperature of about 60°C to about 90°C. Subsequently, the second curing step is carried out for a period of about 0.4 hours to about 2 hours at a temperature of about 150°C to about 200°C. Due to the high temperature resistance of the inorganic binder, the cured inorganic binder exhibits excellent bonding strength at the maximum application temperature.

[0075] The present disclosure has been described with reference to preferred embodiments. Modifications and changes will occur to those skilled in the art upon reading and understanding the foregoing detailed description. It is intended that the invention be construed to include all such modifications and variations as long as they fall within the scope of the appended claims or their equivalents.

Claims

1. A light conversion device, which includes a layer formed of an inorganic binder, and the inorganic binder includes: From 25% to 80% by weight of a filler, where the filler includes one or more materials selected from the group consisting of: silica, silicate, aluminate, phosphate, diamond powder, metal powder, nitride, oxide, phosphor, refractive powder, and metal sulfide; From 20% to 75% by weight of an inorganic binder; and From 0.5% to 5% by weight of a dispersant, where: The dispersant is an organic dispersant selected from the group consisting of: polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene copolymerized maleic anhydride, and lignosulfonate; or the dispersant is an inorganic dispersant selected from the group consisting of: hexametaphosphate, silicate, polyphosphate, and calcined silica, and wherein the coefficient of thermal expansion of the filler is within ±20% of the coefficient of thermal expansion of the inorganic binder, and wherein the density of the filler is within ±20% of the density of the inorganic binder.

2. The light conversion device according to claim 1, where the inorganic binder is made of a first component and a second component, where the first component is a translucent liquid and the second component is a transparent liquid.

3. The light conversion device according to claim 2, where the weight ratio of the first component to the second component is 1:1 to 7:

3.

4. The light conversion device according to any one of claims 2 and 3, where: The viscosity of the first component ranges from 1 mPa·sec to 50 mPa·sec, the density ranges from 0.8 g / cm 3 to 1.3 g / cm 3 , and the solid content is greater than 10%; and The viscosity of the second component ranges from 0 mPa·sec to 50 mPa·sec, and the density ranges from 0.6 g / cm 3 to 1.0 g / cm 3 , and the solid content is greater than 10%.

5. The light conversion device according to any one of claims 1-4, where the filler at least includes the refractive powder, where the refractive powder has a particle size from 0.1 micron to 150 microns, and where the layer formed of the inorganic binder is a high-reflectivity layer having at least 80% reflectivity for light with wavelengths from 380 nm to 800 nm. The light conversion device further includes: A phosphor layer, which is provided on a layer formed of an inorganic binder.

6. The light conversion device according to claim 5, where the inorganic binder includes: From 65% to 75% by weight of a filler; From 20% to 35% by weight of an inorganic binder; and From 1% to 2% by weight of a dispersant.

7. The light conversion device according to any one of claims 1 to 4, where the filler at least includes a phosphor, where the phosphor is selected from yttrium aluminum garnet (YAG), silicate, and nitride, and where the layer formed of the inorganic binder is a light conversion layer.

8. The light conversion device according to claim 7, where the inorganic binder includes: From 60% to 75% by weight of a filler; From 20% to 45% by weight of an inorganic binder; and A dispersant from 0.5% to 5% by weight.

9. A method of forming a layer formed of an inorganic binder of a light conversion device according to any one of claims 5-8, the method comprising: Performing a first curing of the inorganic binder at a temperature of 75°C to 100°C for a period of 0.1 hour to 1 hour; And Subsequently performing a second curing of the inorganic binder at a temperature of 150°C to 200°C for a period of 0.5 hour to 1 hour.

10. A method of forming a layer formed of an inorganic binder of a light conversion device according to any one of claims 1-4, the method comprising: Performing a first curing of the inorganic binder at a temperature of 60°C to 90°C for a period of 0.2 hour to 1 hour; And Subsequently performing a second curing of the inorganic binder at a temperature of 150°C to 200°C for a period of 0.4 hour to 2 hours.

11. A light conversion device, comprising: A substrate; And An inorganic coating provided on the substrate, the inorganic coating comprising: From 25% to 80% by weight of a filler, wherein the filler includes one or more materials selected from the group consisting of: silica, silicate, aluminate, phosphate, diamond powder, metal powder, nitride, oxide, phosphor, refractive powder, and metal sulfide; From 20% to 75% by weight of an inorganic binder; And From 0.5% to 5% by weight of a dispersant, wherein: the dispersant is an organic dispersant selected from the group consisting of: polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene copolymerized maleic anhydride, and lignosulfonate; or the dispersant is an inorganic dispersant selected from the group consisting of: hexametaphosphate, silicate, polyphosphate, and calcined silica, and wherein the coefficient of thermal expansion of the filler is within ±20% of the coefficient of thermal expansion of the inorganic binder, and wherein the density of the filler is within ±20% of the density of the inorganic binder.

12. The light conversion device according to claim 11, wherein the filler comprises at least a phosphor, wherein the phosphor is selected from yttrium aluminum garnet (YAG), silicate, and nitride, and wherein the inorganic coating forms a light conversion layer.

13. The light conversion device according to claim 11, wherein the filler comprises at least the refractive powder, wherein the refractive powder has a particle size from 0.1 micrometer to 150 micrometers, and wherein the inorganic coating forms a high reflectivity layer.

14. The light conversion device according to claim 13, wherein the inorganic coating has a reflectivity of at least 80% for light with a wavelength from 380 nm to 800 nm.

15. The light conversion device according to any one of claims 13-14, further comprising: A phosphor layer, which is provided on the inorganic coating such that the inorganic coating is interposed between the substrate and the phosphor layer.

16. The light conversion device according to any one of claims 11-15, wherein the substrate is in a disc shape, and the light conversion device further comprises: A motor configured to rotate the substrate about an axis perpendicular to the substrate.

17. A method of forming a light conversion device according to claim 11, the method comprising: Applying the inorganic coating to the substrate; Performing a first curing of the inorganic coating at a temperature of 75°C to 100°C for a period of 0.1 hour to 1 hour; And Subsequently performing a second curing of the inorganic coating at a temperature of 150°C to 200°C for a period of 0.5 hour to 1 hour.

18. An optical channel, comprising: A plurality of reflectors joined together by an inorganic binder capable of withstanding a temperature greater than 200°C, the inorganic binder comprising: From 25% to 80% by weight of a filler, wherein the filler is at least one material selected from the group consisting of: silica, silicate, aluminate, phosphate, diamond powder, metal powder, nitride, oxide, and metal sulfide; From 20% to 75% by weight of an inorganic binder; and from 0.5% to 5% by weight of a dispersant, wherein: the dispersant is an organic dispersant selected from the group consisting of polyvinylpyrrolidone, polyacrylate, gelatin, polyvinyl alcohol, cellulose, styrene copolymaleic anhydride, and lignosulfonate; or the dispersant is an inorganic dispersant selected from the group consisting of hexametaphosphate, silicate, polyphosphate, and calcined silica, and wherein the coefficient of thermal expansion of the filler is within ±20% of the coefficient of thermal expansion of the inorganic binder, and wherein the density of the filler is within ±20% of the density of the inorganic binder.

19. The optical channel according to claim 18, wherein the inorganic binder comprises: from 60 wt% to 75 wt% of a filler; from 20 wt% to 45 wt% of an inorganic binder; and from 3 wt% to 3 wt% of a dispersant.

20. The optical channel according to claim 19, wherein the filler selected from the group is an oxide, and the oxide is alumina.

21. The optical channel according to any one of claims 18 - 20, wherein the inorganic binder is a liquid transparent inorganic binder.

22. A method of forming an optical channel according to claim 18, the method comprising: The first curing of the inorganic binder is carried out for a period of 0.25 hours at a temperature of 85 °C; and subsequently, the second curing of the inorganic binder is carried out for a period of 0.75 hours at a temperature of 185 °C.

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