A method for preparing a low reflectance bracket for a vehicle camera

Abstract

The present application belongs to the technical field of automobile parts manufacturing, and relates to a preparation method of a low reflectivity support for a vehicle-mounted camera, comprising the following steps: (1) preparing a support body comprising a field angle region; (2) performing structured light extinction treatment on the surface of the field angle region to increase the surface roughness or form a light diffusion structure, wherein the structured light extinction treatment comprises setting a sawtooth structure or a gradient refractive index layer; and (3) sequentially coating a water-based sand black primer layer and a water-based elastic topcoat layer on the field angle region subjected to the structured light extinction treatment to form a composite light extinction coating layer. The preparation method of the low reflectivity support for the vehicle-mounted camera provided by the present application can effectively suppress reflection interference while ensuring the mechanical performance and environmental durability of the support.

Description

Technical Field

[0001] This invention belongs to the technical field of automotive parts manufacturing, and relates to a method for preparing a low-reflectivity bracket for an in-vehicle camera. Background Technology

[0002] With the development of autonomous driving technology in automobiles, the image quality of onboard cameras directly affects the reliability of the perception system. Camera mounts are typically located around the camera lens, and light reflection from their surfaces can create stray light that interferes with imaging after entering the lens, potentially leading to misidentification. Current automotive plastic mounts primarily focus on mechanical strength and weather resistance, with surface treatments (such as ordinary painting) mainly for corrosion protection and aesthetics, resulting in high gloss levels. This fails to meet the stringent requirements of extremely low reflectivity in camera areas (typically requiring a gloss level of ≤2 GU at 60°, with high-end requirements ≤0.5 GU). While methods to reduce gloss by applying matte paint exist, the results are still unsatisfactory, and the adhesion, durability, and bonding strength of the paint film to the plastic substrate also face challenges under automotive-grade conditions. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for manufacturing a low-reflectivity bracket for vehicle-mounted cameras, which can effectively suppress reflection interference while ensuring the mechanical performance and environmental durability of the bracket.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for fabricating a low-reflectivity bracket for an automotive camera includes the following steps:

[0006] (1) Fabricate a support body including the field of view (FOV) region;

[0007] (2) The surface of the field of view area is subjected to structured extinction treatment, wherein the structured extinction treatment includes setting a sawtooth structure or a gradient refractive index layer;

[0008] (3) On the field of view area that has undergone structured matte treatment, a water-based sand black primer layer and a water-based elastic topcoat layer are applied in sequence to form a composite matte coating.

[0009] Wherein, after the field of view region undergoes structured matting treatment and is coated with a composite matting coating, its gloss at a 60° measurement angle is no greater than 0.2 GU.

[0010] As a further improvement of the present invention, the support body is injection molded from a composite material of polybutylene terephthalate (PBT), polycarbonate (PC) and glass fiber (GF), and the glass fiber content is 30%.

[0011] As a further improvement of the present invention, in step (3), when coating the primer layer and the topcoat layer, a spraying cover is used to cover the area outside the field of view. The spraying cover is fixed above the support body by the buckle at its bottom in a covering manner.

[0012] As a further improvement of the present invention, the water-based sand black primer is prepared by mixing paint and deionized water in a weight ratio of 10:1 and filtering through a 150-mesh filter; the water-based elastic topcoat is prepared by mixing paint, curing agent and deionized water in a weight ratio of 10:1:1 and filtering through a 300-mesh filter.

[0013] As a further improvement of the present invention, the serrated structure includes: a first serrated unit disposed at the bottom of the field of view region, a second serrated unit disposed on the right side wall of the field of view region, and a third serrated unit disposed on the left side wall of the field of view region, wherein the first serrated unit, the second serrated unit and the third serrated unit adopt different serrated structures.

[0014] Preferably, the tooth width and tooth height of the first sawtooth unit are both smaller than the tooth width and tooth height of the second sawtooth unit and the third sawtooth unit.

[0015] Preferably, the first and second sawtooth units adopt symmetrical sawtooths, and the third sawtooth unit adopts oblique sawtooths and is inclined toward the opening direction of the field of view region.

[0016] Preferably, the serrations of the first serration unit extend along the length direction of the bottom of the field of view region, and the serrations of the second and third serration units extend vertically along the sidewall of the field of view region.

[0017] As a further improvement of the present invention, the gradient refractive index layer includes a transition layer in which the refractive index gradually changes from the support body side to the air side, between the support body and the air, so as to eliminate Fresnel reflection caused by abrupt change in refractive index. The method can be a gradient coating method or a gradient plating method.

[0018] As a further improvement of the present invention, it also includes a staged curing process after coating: first, surface drying at 40°C to 65°C, followed by baking curing at 65°C to 80°C.

[0019] As a further improvement of the present invention, it also includes plasma surface treatment of the back surface area of ​​the support body to make its surface dyne value not less than 36.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention innovatively introduces a micro-structured matting layer on the surface of the lens field of view area of ​​the bracket, physically disrupting the basis of specular reflection. Then, a functional composite coating composed of a specific water-based sand-black primer and a water-based elastic topcoat is precisely applied over this structured surface. This coating system itself possesses high absorption and low gloss characteristics. Through this design, the gloss level in key areas of the bracket is successfully reduced from over 2 GU in conventional parts to below 0.2 GU, far exceeding the current industry level and providing a reliable guarantee for high-definition imaging.

[0022] 2. The present invention adopts a partitioned sawtooth design scheme, which can be based on optical simulation and actual road condition analysis to design different sawtooth size, tooth shape and direction for different light-receiving areas such as bottom, left side wall and right side wall. For example, the bottom uses finer horizontal sawtooth to suppress the reflection of the hood near the engine, and the side wall uses vertical or directional inclined sawtooth to deflect the incident light from the side, thereby achieving the optimal local extinction effect. Attached Figure Description

[0023] Figure 1 This is a perspective view of the present invention.

[0024] Figure 2 for Figure 1 Enlarged view of point A;

[0025] Figure 3 for Figure 1 Enlarged view of point B;

[0026] Figure 4 A perspective view of the spray coating fixture installed according to the present invention;

[0027] In the figure: 1. Support body; 11. Field of view area; 11a. First sawtooth unit; 11b. Second sawtooth unit; 11c. Third sawtooth unit; 2. Spraying cover; 21. Buckle. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the raw materials used in the present invention are all conventional commercially available products; the methods used, unless otherwise specified, are conventional methods in the art.

[0029] Example 1

[0030] Preparation of the scaffold body 1

[0031] A composite material of polybutylene terephthalate (PBT), polycarbonate (PC), and glass fiber (GF) of grade "Teju 6700" was used, with the glass fiber content being 30% (i.e., PBT / PC / GF30). It was injection molded in a mold using an injection molding machine to obtain the desired result. Figure 1 The bracket body 1 is shown. The bracket body 1 is designed with a field of view area 11 for the camera to transmit light.

[0032] Example 2

[0033] Structured matting treatment

[0034] In this embodiment, a serrated structure is machined on the surface of the field of view region 11, as shown in the attached diagram. Figure 2 and attached Figure 3 Specifically, three different serrated units are formed in this area through precision mold etching or CNC machining:

[0035] The first sawtooth unit 11a is located at the bottom of the field of view region 11. Its sawtooth design consists of transverse micro-sawtooths extending along the length of the bottom. The average tooth width is approximately 0.2 mm, the tooth height is approximately 0.15 mm, and the tooth shape is a symmetrical V-shape. Since the bottom directly faces surfaces such as the hood that are prone to near-field reflections, and is close to the lower edge of the camera's imaging core area, finer sawtooths are used to provide more precise light scattering control.

[0036] The second sawtooth unit 11b is located on the right side wall of the field of view region 11. Its sawtooths extend vertically along the side wall. The average tooth width is approximately 0.5 mm, the tooth height is approximately 0.4 mm, and the tooth shape is a symmetrical V-shape. It is mainly used to scatter incident light from the right side of the vehicle.

[0037] The third sawtooth unit 11c is located on the left side wall of the field of view region 11. Its sawtooth is also a vertically extending sawtooth along the side wall, with an average size similar to that of the second sawtooth unit. However, its tooth shape is designed as oblique sawtooth, that is, the sawtooth surface is tilted towards the opening direction of the field of view region (i.e., the opposite direction of the camera lens direction). This design can more effectively guide incident light from a specific angle on the left side to the non-imaging direction.

[0038] Example 3

[0039] Coating with composite matte coating

[0040] 1. Pre-coating treatment: Remove sharp edges and burrs from the bracket body 1, and then wipe the surface with a lint-free cloth dampened with alcohol to remove dirt.

[0041] 2. Install spray painting hood 2, such as Figure 4 As shown, before spraying, a dedicated spraying hood 2 is used to cover the support body 1. The spraying hood 2 has an elastic buckle 21 at the bottom, which can tightly cover the top of the support body 1, precisely exposing the field of view 11 (which has been serrated) to be sprayed, while protecting all other areas from paint contamination. This step is crucial for controlling the paint film boundary and preventing paint overflow.

[0042] 3. Primer Preparation and Spraying: Take 1000g of SW-1701 water-based sand black paint and 100g of deionized water, place them in a mixing tank, and stir at medium speed for about 5 minutes until uniformly mixed. Then filter the mixture through a 150-mesh filter to remove any possible particulate impurities. Test the viscosity of the filtered primer using a viscosity cup (NK-2 type) at 25℃, and adjust the viscosity to 20±5 seconds. Add the prepared primer to the spraying equipment and spray evenly over the exposed field of view to form a primer layer.

[0043] 4. Topcoat preparation and spraying: Take 1000g of TW-0120 water-based elastic coating, 100g of the matching curing agent GW-09, and 100g of deionized water. Mix and stir for about 5 minutes, then filter through a 300-mesh filter. After the primer layer is surface dry, apply the second coat of topcoat to the same area to form the topcoat layer. Control the thickness of the topcoat spraying to ensure that the total thickness of the final composite coating meets the design requirements and that the paint film boundaries are clear.

[0044] 5. Segmented curing: The coated support is sent to the curing line. First, it is surface-dried at 40℃ for approximately 90 minutes. Then, it is transferred to an oven and baked at 65℃ for 3 hours, followed by a further increase to 80℃ for 30 minutes. This staged heating process helps to slowly release internal stress in the paint film and achieve complete cross-linking and curing, ensuring the coating's adhesion, hardness, and durability.

[0045] 6. Backside Plasma Treatment: The area on the back of the bracket body 1 where the additional heating film needs to be attached is treated with an atmospheric plasma treatment device. The surface dyne value after treatment can be increased from about 30 to over 36, significantly increasing the surface energy, thereby ensuring the firmness of the heating film adhesion and meeting the reliability requirements in the automotive environment.

[0046] Multiple tests were performed on the low-reflectivity support (24 samples in total, 01#-24#) prepared in this embodiment. The test methods and results are shown in Table 1.

[0047] Table 1 Performance testing of low reflectivity brackets

[0048]

[0049] From the above test data, we can see that:

[0050] 1. Gloss: The gloss was measured at 60° in the field of view area (the inner surface of the structure surrounding the camera). The test results for the three samples were 0.07 GU, 0.06 GU, and 0.09 GU, respectively, all far below the technical requirement of 0.2 GU, and the data were stable. This fully demonstrates the excellent matting effect of the "serrated structure" and the "SW-1701 / TW-0120 composite coating".

[0051] 2. Other performance: The sample also passed a full set of tests, including 48h salt spray test (no red rust on metal inserts), flocking adhesion (0-1 grade), flocking abrasion resistance (≥3 grade), insert nut pull-out force (≥417N), shear force (≥223N), torque (≥13.6N·m), and back dyne value (≥36), fully meeting the performance requirements of automotive-grade parts.

[0052] Example 4

[0053] Setting of gradient refractive index layer

[0054] 1. Prepare three coating solutions with different refractive indices: Using silica sol as the base liquid, different mass fractions of high refractive index nano-zirconia (ZrO2) powder are added to prepare coating solutions A, B, and C with refractive indices from high to low.

[0055] 2. In the cleaned FOV area of ​​the support, use precision spraying equipment to spray coating liquids A, B and C in sequence. After each layer is sprayed, pre-cured at 80°C for 5 minutes to form a gradient refractive index layer with a total thickness of about 15μm.

[0056] 3. Subsequent Processes: Subsequently, following the steps in Example 3, SW-1701 primer and TW-0120 topcoat are applied onto the gradient layer, followed by staged curing. This structure utilizes the continuous transition of refractive index to eliminate interface reflections, and in conjunction with the upper low-reflection coating, further reduces the overall gloss.

[0057] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a low reflectance mount for a vehicle camera, characterized by, Includes the following steps: (1) Prepare a support body including a field of view region; the support body is injection molded from a composite material of polybutylene terephthalate, polycarbonate and glass fiber, and the glass fiber content is 30%; (2) The surface of the field of view area is subjected to structured extinction treatment to increase its surface roughness or form a light diffusion structure; the structured extinction treatment includes setting a sawtooth structure; (3) On the field of view area after the structured matte treatment, a water-based sand black primer layer and a water-based elastic topcoat layer are applied in sequence to form a composite matte coating; when applying the primer layer and the topcoat layer, a spraying hood is used to cover the area outside the field of view area, and the spraying hood is fixed above the support body by the buckle at its bottom; the water-based sand black primer is prepared by mixing paint and deionized water in a weight ratio of 10:1 and filtering through a 150-mesh filter; the water-based elastic topcoat is prepared by mixing paint, curing agent and deionized water in a weight ratio of 10:1:1 and filtering through a 300-mesh filter. (4) After coating, perform staged curing treatment: first, surface dry at 40℃ to 65℃, then bake and cure at 65℃ to 80℃; The serrated structure includes: a first serrated unit disposed at the bottom of the field of view region, a second serrated unit disposed on the right side wall of the field of view region, and a third serrated unit disposed on the left side wall of the field of view region; the tooth width and tooth height of the first serrated unit are both smaller than the tooth width and tooth height of the second and third serrated units; the first and second serrated units adopt symmetrical serrations, and the third serrated unit adopts oblique serrations and is inclined towards the opening direction of the field of view region; the serrations of the first serrated unit extend along the length direction of the bottom of the field of view region, and the serrations of the second and third serrated units extend vertically along the side wall of the field of view region; It also includes plasma surface treatment of the back surface area of ​​the support body to make its surface dyne value not less than 36; Wherein, after the field of view region undergoes structured matting treatment and is coated with a composite matting coating, its gloss at a 60° measurement angle is no greater than 0.2 GU.

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