A curved glass high-reflectivity mirror for HUD and its fabrication method

Abstract

This invention belongs to the field of reflective mirror technology for vehicle-mounted HUDs, specifically relating to a curved glass high-reflectivity mirror for HUDs and its fabrication method. The curved glass high-reflectivity mirror has multiple layers, from bottom to top: a glass substrate, a transition film layer, an Al film layer, a first SiO2 film layer, a Nb2O5 film layer, and a second SiO2 film layer. The reflective mirror produced by this invention has clear imaging, high reflectivity, and excellent thermal stability, wear resistance, and long-term reliability, meeting the high-performance requirements of AR-HUDs. The fabrication method is simple, controllable, and easy for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of reflective mirror technology for vehicle-mounted HUDs, specifically relating to a curved glass high-reflectivity mirror for HUDs and its preparation method. Background Technology

[0002] HUD, short for Head-Up Display, is a system that displays important information such as navigation, speed, and alarms in front of the driver's line of sight without requiring the user to look down, based on the principle of optical reflection. The main design principle of HUD is an off-axis three-mirror optical system, in which the graphic display (PGU) generates the image, a small mirror deflects the light path, a large mirror reflects and amplifies the light, and finally the image is formed by reflection through the windshield into the human eye.

[0003] Automotive HUD technology has undergone three generations of iteration and has now entered a development stage dominated by augmented reality HUDs (AR-HUDs). The imaging quality and optical performance of AR-HUDs depend primarily on the reflective mirror component in its optical system, which directly determines the clarity, brightness uniformity, distortion-free effect, and long-term reliability of the displayed information.

[0004] In the early stages of AR-HUD development and in some low-to-mid-range HUD products, the industry widely used traditional plastics as the substrate for reflectors, with polycarbonate (PC) and cyclic olefin copolymers (COC) being common materials. However, these materials have many insurmountable drawbacks and are no longer suitable for the high-performance requirements of AR-HUDs. Specifically: First, plastics have poor thermal stability and are prone to thermal expansion and contraction, deformation, and even aging and yellowing in automotive environments (-40℃~85℃), leading to a decrease in the accuracy of the reflector surface and image distortion, which seriously affects the display effect. Second, plastics have low surface hardness and poor wear resistance, making them easily scratched, which can damage the reflective film layer and reduce reflectivity and display clarity. Third, plastics have insufficient optical transmittance and surface flatness, which can lead to problems such as poor film adhesion and uneven thickness after coating, making it difficult to achieve the design requirements of high reflectivity. Fourth, plastics have poor chemical resistance and are easily corroded by oil and moisture in the automotive environment, leading to reflector failure and failing to meet the long-term reliability requirements of automotive products (such as 85℃ / 85%RH damp heat testing and high and low temperature cycling testing).

[0005] To address the aforementioned issues, the industry has attempted to use curved glass as the substrate for the reflector. However, the internal residual stress is relatively large, which does not match the thermal expansion coefficient of the high-reflectivity film, making it prone to problems such as film cracking and peeling. Therefore, there is a need for a HUD curved glass high-reflectivity mirror that can solve the above defects and its preparation method. Summary of the Invention

[0006] To address the problems of poor thermal stability, insufficient wear resistance, and low reliability of plastic-based HUD reflectors in existing technologies, as well as poor compatibility between curved glass substrates and film layers, leading to easy film cracking and peeling, this invention provides a curved glass high-reflectivity reflector for HUDs and its preparation method. This reflector provides clear imaging, high reflectivity, and excellent thermal stability, wear resistance, and long-term reliability, meeting the high-performance requirements of AR-HUDs. The preparation method is simple, controllable, and easy for industrial production.

[0007] The technical solution of the present invention is as follows: A curved glass high-reflectivity mirror for HUD, the curved glass high-reflectivity mirror having multiple layers, from bottom to top: a glass substrate, a transition film layer, an Al film layer, a first SiO2 film layer, an Nb2O5 film layer and a second SiO2 film layer.

[0008] Preferably, the transition film is a Cr film.

[0009] Preferably, the thickness of the Cr film is 20 nm.

[0010] Preferably, the refractive index of Nb2O5 is 2.25-2.4, the refractive index of SiO2 is 1.43-1.47, and the refractive index of Al is 6.5-7.5.

[0011] Preferably, the Al film has a thickness of 90 nm, the first SiO2 film has a thickness of 70 nm, the Nb2O5 film has a thickness of 45 nm, and the second SiO2 film has a thickness of 30 nm.

[0012] A method for fabricating a curved glass high-reflectivity mirror for a HUD, comprising the following steps: Step 1: Place the glass substrate into a vacuum multi-cavity magnetron coating machine. Each cavity in the vacuum multi-cavity magnetron coating machine is evacuated to a vacuum level of 1.0 × 10⁻⁶. -3 Pa; Step 2: A transition film is deposited on the surface of the glass substrate using PVD vacuum magnetron sputtering to complete the preparation of the transition film. Step 3: An Al film is deposited on the surface of the transition film layer using PVD vacuum magnetron sputtering to complete the preparation of the Al film layer; Step 4: The first SiO2 film is deposited on the surface of the Al film by PVD vacuum magnetron sputtering to complete the preparation of the first SiO2 film. Step 5: An Nb2O5 film is deposited on the surface of the first SiO2 film using PVD vacuum magnetron sputtering to complete the preparation of the Nb2O5 film. Step 6: A second SiO2 film is deposited on the surface of the Nb2O5 film using PVD vacuum magnetron sputtering to complete the preparation of the second SiO2 film, thus obtaining the curved glass high-reflection mirror used for HUD.

[0013] Furthermore, in step 2, the transition film is a Cr film, a Cr target is used as the sputtering target, the magnetron sputtering cathode voltage is 300V, the discharge current is 20A, the sputtering power is 6KW, the deposition rate of the Cr film is 3A / s, and the deposition thickness is 20nm. In step 3, an Al target is used as the sputtering target material, the magnetron sputtering cathode voltage is 600V, the discharge current is 30A, the sputtering power is 18KW, the deposition rate of the Al film is 45A / s, and the deposition thickness is 90nm.

[0014] Furthermore, in step 4, a Si target is used as the sputtering target material, the magnetron sputtering cathode voltage is 400V, the discharge current is 30A, the sputtering power is 12KW, the deposition rate of the first SiO2 film is 7A / s, and the deposition thickness is 70nm. In step 5, an Nb target is used as the sputtering target material, the magnetron sputtering cathode voltage is 400V, the discharge current is 30A, the sputtering power is 12KW, the deposition rate of the Nb2O5 film is 3A / s, and the deposition thickness is 45nm.

[0015] Furthermore, in step 6, a Si target is used as the sputtering target material, the magnetron sputtering cathode voltage is 300V, the discharge current is 20A, the sputtering power is 6KW, the deposition rate of the second SiO2 film is 3A / s, and the deposition thickness is 30nm.

[0016] Furthermore, the working gas for the vacuum magnetron sputtering is argon. A negative bias is applied to the cathode target in the vacuum chamber, causing the argon to be ionized to form plasma. High-energy argon ions bombard the target surface, causing the target atoms or molecules to be sputtered and deposited on the substrate surface to form a thin film.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention uses curved glass as a substrate, which has excellent thermal stability, surface hardness and optical transmittance compared to traditional plastic substrates. It can effectively avoid problems such as thermal expansion and contraction, deformation, aging and yellowing in the automotive environment, ensure the accuracy of the reflector surface, reduce imaging distortion, and improve wear resistance and chemical resistance, thus meeting the long-term reliability requirements of automotive products. The present invention sets a Cr transition film layer, which effectively alleviates the difference in thermal expansion coefficient between the glass substrate and the Al film layer, reduces film layer stress, improves film layer adhesion, and avoids film layer cracking and peeling, thus solving the problem of poor compatibility between curved glass substrate and film layer. This invention uses an Al film as the main reflective layer, combined with an optical matching structure formed by alternating Nb2O5 and SiO2, which enables the reflector to have an average reflectivity of over 94% in the visible light band at an 8-degree incident angle, significantly improving the display brightness and clarity of the AR-HUD and optimizing the spectral flatness. The preparation method of the present invention adopts PVD vacuum magnetron sputtering, which is simple and controllable, with precise parameters of each film layer, high film density and good uniformity, which is convenient for industrial mass production. Moreover, the preparation process generates no pollutants and meets environmental protection requirements. The reflector structure of this invention is rationally designed, and the various film layers work together to ensure high reflectivity, excellent weather resistance, wear resistance and long-term reliability. It is perfectly suited to the high-performance requirements of AR-HUD and has broad application prospects. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the curved glass high-reflection mirror of the present invention; In the figure: 1-glass substrate, 2-transition film, 3-Al film, 4-first SiO2 film, 5-Nb2O5 film, 6-second SiO2 film. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] See Figure 1 A curved glass high-reflectivity mirror for HUD, the curved glass high-reflectivity mirror having multiple layers, from bottom to top: glass substrate 1, transition film layer 2, Al film layer 3, first SiO2 film layer 4, Nb2O5 film layer 5 and second SiO2 film layer 6.

[0021] In one embodiment of the present invention, the transition film layer 2 is a Cr film layer. The Cr film layer serves as a transition buffer layer between the glass substrate and the Al film layer 3, which can effectively improve interface compatibility, reduce film layer stress, enhance the overall film system bonding force, and prevent the Al film 3 from falling off.

[0022] In a preferred embodiment of the present invention, the thickness of the Cr film is 20 nm, which ensures a smooth transition without affecting the overall optical performance.

[0023] In another embodiment of the present invention, the refractive index of Nb2O5 is 2.25-2.4, the refractive index of SiO2 is 1.43-1.47, and the refractive index of Al is 6.5-7.5. This range of refractive indices enables the mirror to form an excellent optical matching structure in the visible light (400-700nm) band, thereby improving reflectivity.

[0024] In a preferred embodiment of the present invention, the Al film 3 has a thickness of 90 nm, the first SiO2 film 4 has a thickness of 70 nm, the Nb2O5 film 5 has a thickness of 45 nm, and the second SiO2 film 6 has a thickness of 30 nm. The thicknesses of the various film layers work together to enable the reflector to have an average reflectivity of over 94% in the visible light band at an incident angle of 8 degrees.

[0025] This invention optimizes the multilayer film structure of the HUD reflector, using glass as a substrate in conjunction with a transition film, an Al film 3, a first SiO2 film 4, a Nb2O5 film 5, and a second SiO2 film 6 to achieve a highly reflective and stable reflector. At an 8-degree incident angle, the reflector has an average reflectivity of over 94% in the visible light band, significantly improving the brightness, clarity, and color reproduction of AR-HUD display information. This perfectly meets the high-performance imaging requirements of AR-HUD and enhances the driver's user experience.

[0026] A method for fabricating a curved glass high-reflectivity mirror for HUD includes the following steps: Step 1: Place the glass substrate into a vacuum multi-cavity magnetron coating machine. Each cavity in the vacuum multi-cavity magnetron coating machine is evacuated to a vacuum level of 1.0 × 10⁻⁶. -3 Pa; Step 2: The transition film 2 is deposited on the surface of the glass substrate by PVD vacuum magnetron sputtering to complete the preparation of the transition film 2; Step 3: An Al film is deposited on the surface of the transition film layer 2 using PVD vacuum magnetron sputtering to complete the preparation of the Al film. Step 4: The first SiO2 film 4 is deposited on the surface of Al film 3 by PVD vacuum magnetron sputtering, thus completing the preparation of the first SiO2 film 4; Step 5: An Nb2O5 film 5 is deposited on the surface of the first SiO2 film 4 using PVD vacuum magnetron sputtering, thus completing the preparation of the Nb2O5 film 5. Step 6: A second SiO2 film 6 is deposited on the surface of the Nb2O5 film 5 using PVD vacuum magnetron sputtering to complete the preparation of the second SiO2 film 6, thus obtaining the curved glass high-reflection mirror used for HUD.

[0027] In one embodiment of the present invention, in step 2, the transition film layer 2 is a Cr film layer, a Cr target is used as the sputtering target material, the magnetron sputtering cathode voltage is 300V, the discharge current is 20A, the sputtering power is 6KW, the deposition rate of the Cr film layer is 3A / s, and the deposition thickness is 20nm. In step 3, an Al target is used as the sputtering target material, the magnetron sputtering cathode voltage is 600V, the discharge current is 30A, the sputtering power is 18KW, the deposition rate of Al film 3 is 45A / s, the deposition thickness is 90nm, and Al film 3 serves as the main reflective layer, providing the core function of high reflectivity.

[0028] In step 4, a Si target is used as the sputtering target material, the magnetron sputtering cathode voltage is 400V, the discharge current is 30A, the sputtering power is 12KW, the deposition rate of the first SiO2 film layer 4 is 7A / s, and the deposition thickness is 70nm. The first SiO2 film layer 4 can effectively block oxygen, water vapor, and sulfides, prevent the Al film from oxidizing and turning black, and at the same time, it serves as a stress buffer layer to reduce the stress difference between Al and the upper high-refractive-index film. In step 5, an Nb target was used as the sputtering target material. The magnetron sputtering cathode voltage was 400V, the discharge current was 30A, the sputtering power was 12KW, the deposition rate of the Nb2O5 film 5 was 3A / s, and the deposition thickness was 45nm. The Nb2O5 film 5 exhibits high reflectivity, and the alternating formation of optically matched structures with SiO2 further enhances the overall reflectivity and optimizes spectral flatness. In step 6, a Si target is used as the sputtering target material, the magnetron sputtering cathode voltage is 300V, the discharge current is 20A, the sputtering power is 6KW, the deposition rate of the second SiO2 film layer 6 is 3A / s, and the deposition thickness is 30nm. The second SiO2 film layer 6 serves as the outermost protective layer and has advantages such as high hardness, high density, scratch resistance, damp heat resistance, and chemical corrosion resistance. It protects the inner film layer from the harsh automotive environment, thus obtaining the curved glass high-reflection mirror used for HUD.

[0029] Tests showed that the reflector had an average reflectivity of 94.5% in the visible light (400-700nm) band at an 8-degree incident angle. After undergoing 85℃ / 85%RH damp heat testing and high and low temperature cycling testing (-40℃~85℃), the film layer showed no cracking or peeling, and the surface showed no scratches or oxidation blackening. The image was clear and distortion-free, meeting the requirements for AR-HUD use.

[0030] In this invention, the working principle of the magnetron sputtering coating machine is as follows: A negative bias is applied to the cathode target within the vacuum chamber. Under the influence of the high-voltage electric field, the working gas (usually argon, Ar) introduced into the chamber is ionized to form plasma, generating a large number of high-energy argon ions (Ar). + High-energy argon ions, accelerated by an electric field, bombard the surface of a target material, sputtering target atoms or molecules to form gaseous particles. These gaseous particles are deposited on the surface of a glass substrate in a vacuum environment with a certain energy. Through adsorption, migration, nucleation, and growth processes, they eventually form a continuous, dense, and uniform thin film.

[0031] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A curved glass high-reflectivity mirror for HUD, characterized in that, The curved glass high-reflectivity mirror has multiple layers, which, from bottom to top, are: a glass substrate, a transition film layer, an Al film layer, a first SiO2 film layer, a Nb2O5 film layer, and a second SiO2 film layer.

2. The curved glass high-reflectivity mirror for HUD according to claim 1, characterized in that, The transition film is a Cr film.

3. A curved glass high-reflectivity mirror for HUD according to claim 2, characterized in that, The thickness of the Cr film is 20 nm.

4. A curved glass high-reflectivity mirror for HUD according to claim 1, characterized in that, The refractive index of Nb2O5 is 2.25-2.4, the refractive index of SiO2 is 1.43-1.47, and the refractive index of Al is 6.5-7.

5.

5. A curved glass high-reflectivity mirror for HUD according to claim 1, characterized in that, The Al film has a thickness of 90 nm, the first SiO2 film has a thickness of 70 nm, the Nb2O5 film has a thickness of 45 nm, and the second SiO2 film has a thickness of 30 nm.

6. A method for preparing a curved glass high-reflectivity mirror for a HUD as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Place the glass substrate into a vacuum multi-cavity magnetron coating machine. Each cavity in the vacuum multi-cavity magnetron coating machine is evacuated to a vacuum level of 1.0 × 10⁻⁶. -3 Pa; Step 2: A transition film is deposited on the surface of the glass substrate using PVD vacuum magnetron sputtering to complete the preparation of the transition film. Step 3: An Al film is deposited on the surface of the transition film layer using PVD vacuum magnetron sputtering to complete the preparation of the Al film layer; Step 4: The first SiO2 film is deposited on the surface of the Al film by PVD vacuum magnetron sputtering to complete the preparation of the first SiO2 film. Step 5: An Nb2O5 film is deposited on the surface of the first SiO2 film using PVD vacuum magnetron sputtering to complete the preparation of the Nb2O5 film. Step 6: A second SiO2 film is deposited on the surface of the Nb2O5 film using PVD vacuum magnetron sputtering to complete the preparation of the second SiO2 film, thus obtaining the curved glass high-reflection mirror used for HUD.

7. The method for fabricating a curved glass high-reflectivity mirror for a HUD according to claim 6, characterized in that, In step 2, the transition film is a Cr film, a Cr target is used as the sputtering target, the magnetron sputtering cathode voltage is 300V, the discharge current is 20A, the sputtering power is 6KW, the deposition rate of the Cr film is 3A / s, and the deposition thickness is 20nm. In step 3, an Al target is used as the sputtering target material, the magnetron sputtering cathode voltage is 600V, the discharge current is 30A, the sputtering power is 18KW, the deposition rate of the Al film is 45A / s, and the deposition thickness is 90nm.

8. The method for fabricating a curved glass high-reflectivity mirror for a HUD according to claim 6, characterized in that, In step 4, a Si target is used as the sputtering target material, the magnetron sputtering cathode voltage is 400V, the discharge current is 30A, the sputtering power is 12KW, the deposition rate of the first SiO2 film is 7A / s, and the deposition thickness is 70nm. In step 5, an Nb target is used as the sputtering target material, the magnetron sputtering cathode voltage is 400V, the discharge current is 30A, the sputtering power is 12KW, the deposition rate of the Nb2O5 film is 3A / s, and the deposition thickness is 45nm.

9. A method for fabricating a curved glass high-reflectivity mirror for a HUD according to claim 6, characterized in that, In step 6, a Si target is used as the sputtering target material, the magnetron sputtering cathode voltage is 300V, the discharge current is 20A, the sputtering power is 6KW, the deposition rate of the second SiO2 film is 3A / s, and the deposition thickness is 30nm.

10. A method for fabricating a curved glass high-reflectivity mirror for a HUD according to claim 6, characterized in that, The working gas for the vacuum magnetron sputtering is argon. A negative bias is applied to the cathode target in the vacuum chamber, causing the argon to be ionized to form plasma. High-energy argon ions bombard the target surface, causing the target atoms or molecules to be sputtered and deposited on the substrate surface to form a thin film.

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