Wavelength conversion module and projection device

Abstract

A wavelength conversion module includes a ceramic substrate, a ceramic intermediate layer, a ceramic reflective layer, and a wavelength conversion layer. The ceramic intermediate layer is disposed on the ceramic substrate. The ceramic reflective layer is disposed on the ceramic intermediate layer. A coefficient of thermal expansion of the ceramic intermediate layer is between a coefficient of thermal expansion of the ceramic substrate and a coefficient of thermal expansion of the ceramic reflective layer. The wavelength conversion layer is disposed on the ceramic reflective layer. The invention also provides a projection device having the wavelength conversion module. With the wavelength conversion module and the projection device of the invention, the ceramic intermediate layer can avoid separation or gap between the ceramic substrate and the ceramic reflective layer due to a too large difference in the coefficient of thermal expansion, and thus can improve adhesion between the ceramic substrate and the ceramic reflective layer, thereby achieving a longer service life and improved structural reliability of the wavelength conversion module.

Description

Technical Field

[0001] The present invention relates to an optical module and a projection device, and more particularly to a wavelength conversion module and a projection device having the wavelength conversion module. Background Technology

[0002] Currently, the development trend of projection devices is to pursue higher brightness to be suitable for various environments. The phosphor color wheel is the source of brightness in laser projection devices, therefore, the phosphor color wheel needs to have high luminous efficiency, high heat resistance, and the ability to withstand high-energy laser power.

[0003] Conventional fluorescent color wheels used in high-power lasers are primarily made by sintering phosphors mixed with organic adhesives onto inorganic materials, such as ceramics or glass, to create inorganic fluorescent sheets. However, inorganic fluorescent sheets require organic adhesives to attach them to reflective layers or heat-dissipating substrates. Therefore, the fluorescent color wheel is still limited by the temperature resistance, transmittance, and thermal conductivity of the organic adhesives. For example, the visible light transmittance of the organic adhesive must be greater than 90%, but organic adhesives with high transmittance generally have a thermal conductivity of less than 0.5 W / mK. Consequently, the heat generated when the fluorescent sheet is excited by laser light is difficult to conduct to the heat-dissipating substrate due to the poor thermal conductivity of the organic adhesive, resulting in a higher temperature for the fluorescent sheet and consequently a decrease in excitation efficiency and optomechanical brightness. Furthermore, the temperature resistance of the organic adhesive is limited to below 300°C. The heat accumulation caused by prolonged exposure to high-power laser energy may degrade the adhesive, raising concerns about the reliability of the fluorescent color wheel.

[0004] Alternatively, it is conventional to sinter the diffuse reflection layer and phosphor onto a ceramic substrate, but this is limited because the ceramic substrate needs to have a high thermal conductivity. Currently, the commonly used material for ceramic heat dissipation substrates is AlN (aluminum nitride), but when sintering the diffuse reflection layer and phosphor onto an AlN substrate, the thermal expansion coefficients of the phosphor and diffuse reflection layer differ greatly from those of the AlN substrate, making it prone to poor adhesion and cracking.

[0005] The "Background Art" paragraph is only used to help understand the content of this invention. Therefore, the content disclosed in the "Background Art" paragraph may include some prior art that is not known to those skilled in the art. The content disclosed in the "Background Art" paragraph does not mean that the content or the problem to be solved by one or more embodiments of this invention was known or recognized by those skilled in the art before this application was filed. Summary of the Invention

[0006] This invention provides a wavelength conversion module that has better structural reliability.

[0007] The present invention also provides a projection device, which includes the above-mentioned wavelength conversion module, and has better projection quality and product competitiveness.

[0008] Other objects and advantages of the present invention can be further understood from the technical features disclosed herein.

[0009] To achieve one or more of the above-mentioned objectives, or other objectives, an embodiment of the present invention provides a wavelength conversion module, including a ceramic substrate, a ceramic interlayer, a ceramic reflective layer, and a wavelength conversion layer. The ceramic interlayer is disposed on the ceramic substrate. The ceramic reflective layer is disposed on the ceramic interlayer. The coefficient of thermal expansion of the ceramic interlayer is between that of the ceramic substrate and the ceramic reflective layer. The wavelength conversion layer is disposed on the ceramic reflective layer.

[0010] To achieve one, some, or all of the above-mentioned objectives, or other objectives, an embodiment of the present invention provides a projection device, including an illumination system, a light valve, and a projection lens. The illumination system provides an illumination beam and includes a light source module and a wavelength conversion module. The light source module provides an excitation beam. The wavelength conversion module is disposed in the transmission path of the excitation beam to convert the excitation beam into an illumination beam. The wavelength conversion module includes a ceramic substrate, a ceramic intermediate layer, a ceramic reflective layer, and a wavelength conversion layer. The ceramic intermediate layer is disposed on the ceramic substrate. The ceramic reflective layer is disposed on the ceramic intermediate layer. The coefficient of thermal expansion of the ceramic intermediate layer is between the coefficient of thermal expansion of the ceramic substrate and the coefficient of thermal expansion of the ceramic reflective layer. The wavelength conversion layer is disposed on the ceramic reflective layer to receive the excitation beam. The light valve is disposed in the transmission path of the illumination beam to convert the illumination beam into an image beam. The projection lens is disposed in the transmission path of the image beam to project the image beam out of the projection device.

[0011] Based on the above, the embodiments of the present invention have at least one of the following advantages or effects. In the design of the wavelength conversion module of the present invention, a ceramic interlayer is disposed between the ceramic substrate and the ceramic reflective layer, and the coefficient of thermal expansion of the ceramic interlayer is between that of the ceramic substrate and the ceramic reflective layer. Therefore, the ceramic interlayer can prevent separation or gaps between the ceramic substrate and the ceramic reflective layer due to excessive differences in their coefficients of thermal expansion, thereby improving the adhesion between the ceramic substrate and the ceramic reflective layer, thus extending the lifespan of the wavelength conversion module and improving its structural reliability. Furthermore, projection devices using the wavelength conversion module of the present invention can have better projection quality and product competitiveness.

[0012] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a projection device according to an embodiment of the present invention.

[0014] Figure 2 for Figure 1 A cross-sectional schematic diagram of the wavelength conversion element of the projection device.

[0015] Figure 3 This is a cross-sectional schematic diagram of a wavelength conversion element according to another embodiment of the present invention. Detailed Implementation

[0016] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front, or back, are merely for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the present invention.

[0017] Figure 1 This is a schematic diagram of a projection device according to an embodiment of the present invention. Please refer to... Figure 1 In this embodiment, the projection device 10 includes an illumination system 20, a light valve 30, and a projection lens 40. The illumination system 20 provides an illumination beam L1, and includes a light source module 25 and a wavelength conversion module 100a. The light source module 25 provides an excitation beam L'. The wavelength conversion module 100a is disposed on the transmission path of the excitation beam L' and converts the excitation beam L' into a converted beam. Here, the illumination beam L1 includes the excitation beam L' and the converted beam. The light valve 30 is disposed on the transmission path of the illumination beam L1 and converts the illumination beam L1 into an image beam L2. The projection lens 40 is disposed on the transmission path of the image beam L2 and projects the image beam L2 out of the projection device 10. The wavelength conversion module 100a is, for example, a phosphor wheel, to repeatedly enter the transmission path of the excitation beam L'.

[0018] In detail, the light source module 25 used in this embodiment is, for example, a laser diode (LD) or a laser diode bank. Specifically, any light source that meets the size requirements of the actual design can be implemented, and the present invention is not limited thereto. The light valve 30 is, for example, a reflective light modulator such as a liquid crystal on silicon panel (LCoS panel) or a digital micro-mirror device (DMD). In one embodiment, the light valve 30 is, for example, a transparent liquid crystal panel, an electro-optic modulator, a magneto-optic modulator, or an acousto-optic modulator (AOM), etc., a transmissive light modulator, but this embodiment does not limit the type or kind of the light valve 30. The method by which the light valve 30 converts the illumination beam L1 into the image beam L2 is well-documented, and its detailed steps and implementation methods are readily available from common knowledge in the art, and therefore will not be elaborated further. Additionally, the projection lens 40 may include, for example, a combination of one or more optical lenses with refractive power, such as various combinations of non-planar lenses including biconcave lenses, biconvex lenses, concave-convex lenses, convex-concave lenses, plano-convex lenses, and plano-concave lenses. In one embodiment, the projection lens 40 may also include planar optical lenses to convert the image beam L2 from the light valve 30 into a projection beam and project it out of the projection device 10 by reflection or transmission. Therefore, this embodiment does not limit the type or form of the projection lens 40.

[0019] Figure 2 for Figure 1 A cross-sectional schematic diagram of the wavelength conversion element of the projection device. Please refer to... Figure 2 In this embodiment, the wavelength conversion module 100a includes a ceramic substrate 110, a ceramic intermediate layer 120, a ceramic reflective layer 130, and a wavelength conversion layer 140. The ceramic intermediate layer 120 is disposed on the ceramic substrate 110. The ceramic reflective layer 130 is disposed on the ceramic intermediate layer 120. The coefficient of thermal expansion of the ceramic intermediate layer 120 is between that of the ceramic substrate 110 and the ceramic reflective layer 130. In this embodiment, the coefficient of thermal expansion of the ceramic substrate 110 is, for example, 4 x 10⁻⁶ / ℃, while the coefficient of thermal expansion of the ceramic intermediate layer 120 is, for example, 5.5 x 10⁻⁶ / ℃, and the coefficient of thermal expansion of the ceramic reflective layer 130 is, for example, 7 x 10⁻⁶ / ℃. The wavelength conversion layer 140 is disposed on the ceramic reflective layer 130.

[0020] Through the above design, the ceramic interlayer 120 can prevent separation or gaps from forming between the ceramic substrate 110 and the ceramic reflective layer 130 due to excessive differences in their coefficients of thermal expansion. Furthermore, the ceramic interlayer 120 can adjust the sintering compatibility between the ceramic substrate 110 and the ceramic reflective layer 130, thereby increasing their adhesion. In addition, the ceramic interlayer 120 can protect the ceramic substrate 110, preventing hydrolysis under high temperature and high humidity conditions, which could cause the adhesives on the ceramic substrate 110 to detach. Therefore, the wavelength conversion module 100a of this embodiment has a longer service life and higher reliability.

[0021] Furthermore, the ceramic substrate 110 in this embodiment is made of, for example, aluminum nitride. The ceramic intermediate layer 120 and the ceramic reflective layer 130 are made of, for example, ceramic or glass, wherein the ceramic material is, for example, silicon oxide or aluminum oxide, and the glass material is, for example, amorphous silicon oxide, but not limited thereto. The ceramic intermediate layer 120 and the ceramic reflective layer 130 can be formed by mixing at least two ceramic materials with different physical properties, such as silicon oxide mixed with aluminum oxide, or the ceramic intermediate layer 120 and the ceramic reflective layer 130 can also be formed by mixing silicon oxides with different crystal structures. In this embodiment, the stacked structure of the wavelength conversion module 100a is made of inorganic materials. Therefore, the wavelength conversion module 100a of this embodiment has temperature resistance, thermal conductivity, light efficiency, and reliability.

[0022] Furthermore, the ceramic intermediate layer 120 and the ceramic reflective layer 130 each include a plurality of ceramic particles P, which are, for example, ceramic powder, and are made of materials such as silicon oxide, alumina, zirconium oxide, or boron nitride. The particle size of each ceramic particle P is, for example, between 0.1 micrometers and 5 micrometers. In this embodiment, the volume ratio of ceramic particles P to the ceramic intermediate layer 120 is less than the volume ratio of ceramic particles P to the ceramic reflective layer 130. Specifically, the volume ratio of ceramic particles P to the ceramic intermediate layer 120 is, for example, between 0% and 20%. The volume ratio of ceramic particles P to the ceramic reflective layer 130 is, for example, between 40% and 70%. In this embodiment, the reflectivity of the ceramic intermediate layer 120 for the visible light band is less than the reflectivity of the ceramic reflective layer 130 for the visible light band.

[0023] like Figure 2As shown, in this embodiment, the first thickness T1 of the ceramic interlayer 120 is less than the second thickness T2 of the ceramic reflective layer 130. Specifically, the first thickness T1 of the ceramic interlayer 120 is, for example, between 0.1 micrometers and 50 micrometers, and the second thickness T2 of the ceramic reflective layer 130 is, for example, between 0.08 millimeters and 0.2 millimeters. In this embodiment, the thickness T3 of the ceramic substrate 110 is, for example, between 0.3 millimeters and 1 millimeter, and the thickness T4 of the wavelength conversion layer 140 is, for example, between 0.08 millimeters and 0.25 millimeters.

[0024] In this embodiment, the wavelength conversion layer 140 includes a plurality of fluorescent particles 142, the fluorescent particles 142 being made of, for example, yttrium aluminum garnet. The particle size of each fluorescent particle is, for example, between 10 micrometers and 35 micrometers. Specifically, the volume ratio of the fluorescent particles to the wavelength conversion layer 140 is, for example, between 40% and 70%.

[0025] In terms of fabrication, the wavelength conversion module 100a of this embodiment can be manufactured by sequentially sintering a ceramic intermediate layer 120, a ceramic reflective layer 130, and a wavelength conversion layer 140 onto a ceramic substrate 110. Specifically, firstly, an inorganic material mixed with a low concentration of ceramic powder P is coated onto the ceramic substrate 110, and then sintered at high temperature to form the ceramic intermediate layer 120. Here, the low concentration of ceramic powder P refers to its volume concentration being lower than that of the ceramic powder P in the ceramic reflective layer 130. Next, an inorganic material mixed with a high reflectivity ceramic powder P is coated onto the surface of the aforementioned ceramic intermediate layer 120, and then sintered at high temperature to form the ceramic reflective layer 130. Here, high reflectivity refers to a reflectivity greater than 90% for the visible light band, and the material of the high reflectivity ceramic powder P is, for example, titanium oxide, aluminum oxide, zinc oxide, or silicon oxide. Finally, an inorganic material mixed with a wavelength conversion material is coated onto the surface of the aforementioned ceramic reflective layer 130, and then sintered at high temperature to form the wavelength conversion layer 140. Wavelength conversion materials can be made of materials such as yttrium aluminum garnet.

[0026] In this embodiment, the inorganic material is, for example, ceramic. However, in other embodiments, the inorganic material may also be glass. Because inorganic materials such as ceramics or glass have high heat resistance, their sintering temperature can be greater than 500 degrees Celsius. Furthermore, in this embodiment, the sintering temperature of the ceramic intermediate layer 120 is greater than or equal to the sintering temperature of the ceramic reflective layer 130, and the sintering temperature of the ceramic reflective layer 130 is greater than or equal to the sintering temperature of the wavelength conversion layer 140.

[0027] In short, the wavelength conversion module 100a of this embodiment uses a ceramic interlayer 120 to prevent separation or gaps between the ceramic substrate 110 and the ceramic reflective layer 130 due to excessive differences in their coefficients of thermal expansion. This improves the adhesion between the ceramic substrate 110 and the ceramic reflective layer 130, thereby extending the lifespan of the wavelength conversion module 100a and enhancing its structural reliability. Furthermore, the projection device 10 using the wavelength conversion module 100a of this embodiment can achieve better projection quality and product competitiveness.

[0028] It must be noted that the following embodiments use the component reference numerals and some content from the foregoing embodiments, with the same reference numerals used to represent the same or similar components, and descriptions of the same technical content omitted. For explanations of the omitted parts, please refer to the foregoing embodiments; these will not be repeated in the following embodiments.

[0029] Figure 3 This is a cross-sectional schematic diagram of a wavelength conversion element according to another embodiment of the present invention. Please also refer to... Figure 2 and Figure 3 In this embodiment, the wavelength conversion element 100b and Figure 2 Similar to the wavelength conversion element 100a, the difference lies in that the wavelength conversion module 100b of this embodiment further includes an anti-reflective film 150, which is made of, for example, nanoscale silicon oxide and titanium oxide. The anti-reflective film 150 is disposed on the wavelength conversion layer 140, and the wavelength conversion layer 140 is located between the anti-reflective film 150 and the ceramic reflective layer 130.

[0030] In summary, the embodiments of the present invention have at least one of the following advantages or effects. In the design of the wavelength conversion module of the present invention, a ceramic interlayer is disposed between the ceramic substrate and the ceramic reflective layer, and the coefficient of thermal expansion of the ceramic interlayer is between that of the ceramic substrate and the ceramic reflective layer. Therefore, the ceramic interlayer can prevent separation or gaps between the ceramic substrate and the ceramic reflective layer due to excessive differences in their coefficients of thermal expansion, thereby improving the adhesion between the ceramic substrate and the ceramic reflective layer, thus extending the lifespan of the wavelength conversion module and improving its structural reliability. Furthermore, projection devices using the wavelength conversion module of the present invention can have better projection quality and product competitiveness.

[0031] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All simple equivalent variations and modifications made according to the claims and description of the invention are still within the scope of this patent. Furthermore, no embodiment or claim of the present invention needs to achieve all the objectives, advantages, or features disclosed in the invention. In addition, the abstract and headings are only for assisting in patent document searches and are not intended to limit the scope of the invention. Moreover, the terms "first," "second," etc., mentioned in this specification or claims are only used to name elements or distinguish different embodiments or scopes, and are not used to limit the upper or lower limit of the number of elements.

[0032] Explanation of reference numerals in the attached figures

[0033] 10: Projection device

[0034] 20: Lighting System

[0035] 25: Light Source Module

[0036] 30: Light valve

[0037] 40: Projection lens

[0038] 100a, 100b: Wavelength conversion module

[0039] 110: Ceramic substrate

[0040] 120: Ceramic intermediate layer

[0041] 130: Ceramic reflective layer

[0042] 140: Wavelength conversion layer

[0043] 142: Fluorescent particles

[0044] 150: Anti-reflective coating

[0045] L': Excitation beam

[0046] L1: illumination beam

[0047] L2: Image Beam

[0048] P: Ceramic particles

[0049] T1: First thickness

[0050] T2: First thickness

[0051] T3: Thickness

[0052] T4: Thickness.

Claims

1. A wavelength conversion module, characterized in that, The wavelength conversion module includes: Ceramic substrate; A ceramic intermediate layer is sintered and formed on the ceramic substrate; A ceramic reflective layer, sintered and formed on the ceramic intermediate layer, wherein the coefficient of thermal expansion of the ceramic intermediate layer is between the coefficient of thermal expansion of the ceramic substrate and the coefficient of thermal expansion of the ceramic reflective layer; and A wavelength conversion layer is disposed on the ceramic reflective layer; The ceramic substrate is made of aluminum nitride, and the ceramic intermediate layer and the ceramic reflective layer are made of ceramic or glass.

2. The wavelength conversion module according to claim 1, characterized in that, The ceramic intermediate layer and the ceramic reflective layer each comprise a plurality of ceramic particles, and the particle size of each of the plurality of ceramic particles is between 0.1 micrometers and 5 micrometers.

3. The wavelength conversion module according to claim 2, characterized in that, The volume ratio of the plurality of ceramic particles in the ceramic intermediate layer to the ceramic intermediate layer is less than the volume ratio of the plurality of ceramic particles in the ceramic reflective layer to the ceramic reflective layer.

4. The wavelength conversion module according to claim 3, characterized in that, The volume ratio of the plurality of ceramic particles in the ceramic intermediate layer to the ceramic intermediate layer is between 0% and 20%.

5. The wavelength conversion module according to claim 3, characterized in that, The volume ratio of the plurality of ceramic particles in the ceramic reflective layer to the ceramic reflective layer is between 40% and 70%.

6. The wavelength conversion module according to claim 1, characterized in that, The thickness of the ceramic intermediate layer is a first thickness, which is less than the second thickness of the ceramic reflective layer.

7. The wavelength conversion module according to claim 6, characterized in that, The first thickness of the ceramic intermediate layer is between 0.1 micrometers and 50 micrometers.

8. The wavelength conversion module according to claim 6, characterized in that, The second thickness of the ceramic reflective layer is between 0.08 mm and 0.2 mm.

9. The wavelength conversion module according to claim 1, characterized in that, The reflectivity of the ceramic intermediate layer to the visible light band is less than that of the ceramic reflective layer to the visible light band.

10. The wavelength conversion module according to claim 1, characterized in that, The thickness of the ceramic substrate is between 0.3 mm and 1 mm.

11. The wavelength conversion module according to claim 1, characterized in that, The wavelength conversion layer includes a plurality of fluorescent particles, each of which has a particle size between 10 micrometers and 35 micrometers.

12. The wavelength conversion module according to claim 11, characterized in that, In the wavelength conversion layer, the volume ratio of the plurality of fluorescent particles to the wavelength conversion layer is between 40% and 70%.

13. The wavelength conversion module according to claim 1, characterized in that, The wavelength conversion layer has a third thickness, which is between 0.08 mm and 0.25 mm.

14. The wavelength conversion module according to claim 1, characterized in that, The wavelength conversion module also includes: An anti-reflective film is disposed on the wavelength conversion layer, wherein the wavelength conversion layer is located between the anti-reflective film and the ceramic reflective layer.

15. A projection device, characterized in that, The projection device includes: A lighting system for providing a light beam, the lighting system comprising: A light source module is used to provide an excitation beam; and A wavelength conversion module, configured on the transmission path of the excitation beam, is used to convert the excitation beam into the illumination beam. The wavelength conversion module includes: Ceramic substrate; A ceramic intermediate layer is sintered and formed on the ceramic substrate; A ceramic reflective layer, sintered and formed on the ceramic intermediate layer, wherein the coefficient of thermal expansion of the ceramic intermediate layer is between the coefficient of thermal expansion of the ceramic substrate and the coefficient of thermal expansion of the ceramic reflective layer; and A wavelength conversion layer, disposed on the ceramic reflective layer, is used to receive the excitation beam; The ceramic substrate is made of aluminum nitride, and the ceramic intermediate layer and the ceramic reflective layer are made of ceramic or glass. A light valve, disposed in the transmission path of the illumination beam, is used to convert the illumination beam into an image beam; and A projection lens is positioned along the transmission path of the image beam to project the image beam out of the projection device.

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