WO2023222583A1 - Lidar window, method for preparing the same, and sensor system - Google Patents

Lidar window, method for preparing the same, and sensor system Download PDF

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Publication number
WO2023222583A1
WO2023222583A1 PCT/EP2023/062925 EP2023062925W WO2023222583A1 WO 2023222583 A1 WO2023222583 A1 WO 2023222583A1 EP 2023062925 W EP2023062925 W EP 2023062925W WO 2023222583 A1 WO2023222583 A1 WO 2023222583A1
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WO
WIPO (PCT)
Prior art keywords
layer
lidar
electrically conductive
window
conductive heating
Prior art date
Application number
PCT/EP2023/062925
Other languages
French (fr)
Inventor
Tianxiao REN
Hui Ying YANG
Fan Wang
Bing Huang
Original Assignee
Covestro Deutschland Ag
Wuxi Xin Giant Macro Intelligent Technology Co. Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CN202210540218.0A external-priority patent/CN117129967A/en
Application filed by Covestro Deutschland Ag, Wuxi Xin Giant Macro Intelligent Technology Co. Ltd. filed Critical Covestro Deutschland Ag
Publication of WO2023222583A1 publication Critical patent/WO2023222583A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0006—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means to keep optical surfaces clean, e.g. by preventing or removing dirt, stains, contamination, condensation
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/28—Interference filters
    • G02B5/281—Interference filters designed for the infrared light

Definitions

  • the present invention belongs to the field of LiDAR windows. Specifically, the present invention relates to a LiDAR window, a method for preparing the same, and a sensor system.
  • ADAS Autonomous driving assistance systems
  • the sensors used in ADAS mainly include cameras, millimeter-wave radar, laser radar and ultrasonic radar, etc., which can detect light, heat, pressure or other variables used for monitoring the state of the automobile. They are commonly located on the front grille, front and rear bumpers, pillar cover plates, roof cover plate, side view mirrors or windshield.
  • Laser radar also known as LiDAR (light detection and ranging) detects obstacles and locates objects using laser beams rather than radio waves.
  • LiDAR can emit lower-power, eye-safe infrared pulsed laser beams with a wavelength of 905 nm to determine the time required for a round trip between the laser transmitter and the target, while generating a 3D point cloud image according to the resulting data.
  • the material of the window should be radioparent to infrared rays with a wavelength of 905 nm, and have the highest possible transmittance.
  • LiDAR windows there are mainly two categories of materials for LiDAR windows. One is a glass material, and the other is a plastic material. Considering that LiDAR needs to be installed on the body of the automobile and conforms to the curvy design of the automobile, and given the factor of collision safety, there is a growing number of LiDAR windows using plastic windows. Plastic windows enjoy many advantages over glass windows, for example, light weight, good impact resistance, the ability to be made into a 3D curved surface to match the styling of the automobile, and be integrated with surrounding spare parts.
  • LiDAR works by calculating the flight time to locate and measure distance, it is also required to increase the infrared transmittance as much as possible when the laser beams pass through the plastic window, so that the transmission power can be enhanced to the greatest extent for the purpose of increasing the distance of detection.
  • the LiDAR plastic window In addition to meeting the functional requirement of infrared transmission, the LiDAR plastic window also needs to meet the functional requirements of automotive exterior decoration and surface cleaning.
  • the automotive exterior decoration requirements mainly include: weather resistance, wear and scratch resistance, environmental ageing resistance, and so on.
  • the plastic window is an exposed member, the surface of which would be easily attached with dust and dirt that block the emission and reception of laser beams, thereby affecting the LiDAR efficiency and functions. Therefore, it is critical to remove the dust and dirt from the surface of the LiDAR plastic window in time.
  • LiDAR window which not only meets the requirement of LiDAR infrared optical transmission but also has defrosting and defogging functions, while meeting the requirements for automotive exterior decoration.
  • An objective of the present invention is to provide a LiDAR window which not only meets the requirement of LiDAR infrared optical transmission but also has defrosting and defogging functions, while meeting the requirements for automotive exterior decoration.
  • Another objective of the present invention is to provide a method for preparing the LiDAR window.
  • the present invention provides a LiDAR window, comprising the following layers stacked together in the order of: a protective layer; a substrate prepared from a thermoplastic material having a Vicat softening temperature of not lower than 170°C; an adhesive layer; and an electrically conductive heating layer having a surface square resistance of ⁇ 200 ohm, wherein the LiDAR window has a transmittance to infrared rays with a wavelength of 905 nm of at least 80% at an incidence angle of 0°, as measured in accordance with the method described in ISO 13468-2: 2006; and the LiDAR window has a gloss retention rate of at least 70%, as measured in accordance with ASTM D 1044-05.
  • the present invention provides a method for preparing the aforementioned LiDAR window, comprising the steps of: i) providing a substrate; ii) forming an adhesive layer and a protective layer respectively on two opposite surfaces of the substrate; iii) forming an electrically conductive heating layer on the adhesive layer; and iv) optionally, forming an anti-reflection layer on the electrically conductive heating layer.
  • the present invention provides a sensor system, comprising: a LiDAR sensor emitting lasers with a wavelength of 800 nm to 1,600 nm; and the aforementioned LiDAR window partially or completely surrounding the LiDAR sensor, wherein the protective layer and the LiDAR sensor are disposed towards two opposite sides of the substrate.
  • the present invention provides a vehicle comprising the aforementioned sensor system.
  • the LiDAR window of the present invention can meet the functional requirement of laser signal transmission, while also having defrosting and defogging functions and meeting the requirements for automotive exterior decoration, and can be used in a sensor system.
  • FIG. 1 shows a schematic diagram of structure 1 obtained by combining the LiDAR window prepared in Example 1 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; and 7 represents electrically conductive adhesives and electrodes.
  • FIG. 2 shows a schematic diagram of structure 2 obtained by combining the LiDAR window prepared in Example 2 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; 6 represents an anti-reflection layer; and 7 represents electrically conductive adhesives and electrodes.
  • FIG. 3 shows a schematic diagram of electrode setup according to one embodiment of the present invention, wherein 5 represents an electrically conductive heating layer; 8 represents electrically conductive adhesives; and 9 represents electrodes.
  • an objective of the present invention is to provide a LiDAR window which not only achieves defrosting and defogging functions by heating a large area uniformly, but also meets the requirement of LiDAR infrared optical transmission.
  • the LiDAR window for example, a LiDAR window for automobiles, should meet the following major requirements:
  • Time for heating from 20°C to 40-60°C ⁇ 5 min.
  • the present invention provides a LiDAR window, comprising the following layers stacked together in the order of: a protective layer; a substrate prepared from a thermoplastic material having a Vicat softening temperature of not lower than 170°C; an adhesive layer; and an electrically conductive heating layer having a surface square resistance of ⁇ 200 ohm, wherein the LiDAR window has a transmittance to infrared rays with a wavelength of 905 nm of at least 80% at an incidence angle of 0°, as measured in accordance with the method described in ISO 13468-2: 2006; and the LiDAR window has a gloss retention rate of at least 70%, as measured in accordance with ASTM D 1044-05.
  • the LiDAR window of the present invention further comprises an anti-reflection layer disposed on the electrically conductive heating layer opposite to the adhesive layer.
  • the transmittance to infrared rays is measured in accordance with the method described in ISO13468-2:2006.
  • the LiDAR window according to the present invention comprises a protective layer.
  • the protective layer possesses at least one of the following properties: weather resistance, scratch resistance, chemical resistance, and impermeability.
  • the protective layer is used to protect the entire LiDAR window from environmental and scratch influences, while acting together with the substrate and other layers to fulfill the antireflection effect.
  • the anti-reflection effect refers to reducing the intensity of reflected infrared light, thereby increasing the intensity of transmitted infrared light. In other words, it refers to improving the infrared transmittance of the substrate.
  • the protective layer is formed with an organosilicon coating material, an acrylate coating material, or an organosilicon-acrylate coating material with a refractive index in the range of 1.20-1.55.
  • organosilicon-acrylate coating material herein refers to a mixture of organosilicon and acrylate.
  • the refractive index generally refers to the refractive index at a wavelength of 589 nm.
  • the refractive index described in the description and claims of the present application is measured in accordance with the standard GB/T7962.1-2010 “Test Methods of Colorless Optical Glass” Part 1: Refractive Index and Coefficient of Dispersion.
  • a coating material that can be used as a protective layer in the LiDAR window of the present invention mention may be made of AS4700 (with a refractive index in the range of 1.40-1.44) and SHP 470 FT2050, PHC587C-2, UVHC3000, UVHC5000 from Momentive Performance Materials.
  • the protective layer may be one layer or consist of at least two sublayers.
  • the protective layer may consist of two layers, wherein the first protective layer in contact with the substrate is weather-resistant, and the second protective layer facing toward the external environment is mainly scratch-resistant.
  • the total thickness of the protective layer is in the range of 0.5-20 pm.
  • the protective layer not only has anti-reflection effect but also has excellent abrasion resistance, scratch resistance, salt mist resistance and environmental resistance, which can well protect the substrate and meet the requirements for automotive exterior decoration.
  • the LiDAR window according to the present invention comprises a substrate.
  • the substrate is prepared from a thermoplastic material.
  • the thermoplastic material consists of a polymer resin and optional additives.
  • the additives may be those commonly used in the thermoplastic material, for example, colorants, heat stabilizers, mold release agents, UV absorbers, flame retardants, antistatic agents and/or flow improvers, and they are in conventional additive amounts, with the proviso that the types and amounts of the additives do not adversely affect the objective of the present invention.
  • the substrate is prepared from a thermoplastic material comprising a polymer resin having a Vicat softening temperature of not lower than 180°C.
  • the substrate has a transmittance to infrared rays with a wavelength of 905 nm of at least 70% at an incident angle of 0°.
  • the substrate is prepared from a thermoplastic material with a refractive index in the range of 1.45-1.75.
  • the thermoplastic material has a transmittance to a light in the range of 380-780 nm of less than 25.0%, as measured in accordance with DIN ISO 13468-2:2006 (D65, 10°) at a layer thickness of 4 mm.
  • the substrate is prepared from a thermoplastic material comprising a polymer resin selected from the group consisting of: copolycarbonate (PC), polyetherimide (PEI), polyimide (PI), polysulfone (PSU), polyarylate (PAR), polyethersulfone (PES) and polyphenylsulfone (PPSU).
  • a polymer resin selected from the group consisting of: copolycarbonate (PC), polyetherimide (PEI), polyimide (PI), polysulfone (PSU), polyarylate (PAR), polyethersulfone (PES) and polyphenylsulfone (PPSU).
  • thermoplastic material comprising a polymer resin
  • the polymer resin constitutes a major part of the thermoplastic material, accounting for at least 70 wt. % of the thermoplastic material, relative to the total weight of the thermoplastic material.
  • the polymer resin is selected from a copolycarbonate based on bisphenol A and 1 , 1 -bis(4-hydroxyphenyl)-3 ,3 ,5-trimethylcyclohexane.
  • copolycarbonate examples include the APEC® series from Covestro Polymers (China) Co., Ltd., and the LEXANTM XHT series and SLX series from Saudi Basic Industry Corporation (SABIC) can be used.
  • APEC® series from Covestro GmbH AG, such as APEC® 1895 (having a Vicat softening temperature of 183°C), APEC® 2095 (having a Vicat softening temperature of 202°C), APEC® 2097 (having a Vicat softening temperature of 202°C) and APEC® DP 1-9389 (having a Vicat softening temperature of 218°C).
  • the thickness of the substrate is in the range of 0.5-5 mm.
  • the LiDAR window according to the present invention comprises an adhesive layer.
  • the adhesive layer is used to enhance the adhesion between the substrate and the electrically conductive heating layer, and also has the anti-reflection effect.
  • the adhesive layer is formed with an organosilicon coating material, an acrylate coating material, or an organosilicon-acrylate coating material with a refractive index in the range of 1.20-1.55.
  • organosilicon-acrylate coating material herein refers to a mixture of organosilicon and acrylate.
  • PHC587C-2 As a coating material that can be used as an adhesive layer in the LiDAR window of the present invention, mention may be made of PHC587C-2 (with a refractive index of 1.42) from the company Momentive Performance Materials.
  • the thickness of the adhesive layer is in the range of 0.5-10 pm.
  • the LiDAR window according to the present invention comprises an electrically conductive heating layer.
  • the electrically conductive heating layer is used to provide heating to achieve defrosting and defogging functions.
  • the electrically conductive heating layer comprises tin-doped indium oxide (ITO), wherein the mass ratio of In 2 O 3 : Sn is in the range of 85: 15 to 95: 5.
  • ITO tin-doped indium oxide
  • the tin-doped indium oxide is present in the amount of 90-100 wt.% in the electrically conductive heating layer.
  • the electrically conductive heating layer is composed of tin-doped indium oxide.
  • the tin-doped indium oxide possesses excellent visible-light and near-infrared transmission properties.
  • the tin-doped indium oxide is also a crystal having a crystallization temperature of 350°C. When the temperature increases, the degrees of crystallinity, transparency, and electrical conductivity are also higher.
  • the electrically conductive heating layer can generate a surface square resistance of less than or equal to 200 ohm.
  • the surface square resistance of the electrically conductive heating layer is preferably less than or equal to 150 ohm, more preferably less than or equal to 100 ohm.
  • the thickness of the electrically conductive heating layer is in the range of 50-500 nm.
  • the electrically conductive heating layer can realize uniform heating over a large area.
  • the LiDAR window of the present invention addresses the problem of non-uniform temperature distribution and infrared laser interference caused by heating electrically conductive silver paste and electrically conductive filaments in the prior art.
  • the electrically conductive heating layer in the LiDAR window of the present invention not only does not interfere with the anti-reflection effect of the anti-reflection coating on the external surface, but also can have optical synergistic effect with the anti-reflection coating to fulfill the anti-reflection effect .
  • Anti-reflection layer not only does not interfere with the anti-reflection effect of the anti-reflection coating on the external surface, but also can have optical synergistic effect with the anti-reflection coating to fulfill the anti-reflection effect .
  • the LiDAR window according to the present invention further comprises an antireflection layer disposed on the electrically conductive heating layer opposite to the adhesive layer.
  • the anti-reflection layer can be prepared from a material with a refractive index in the range of 1.3-2.4.
  • the anti-reflection layer can be formed with a material selected from the group consisting of MgF 2 , SiO 2 , AI 2 O 3 , Ti 2 O 3 , Ti 3 O 5 , Nb 2 O 3 , ZrO 2 , and silicon nitride.
  • the thickness of the anti-reflection layer is in the range of 50-600 nm.
  • the anti-reflection layer can be composed of two or more sublayers of the same or different thickness, comprising different materials selected from the group consisting of MgF2, SiO 2 , A1 2 O 3 , Ti 2 O 3 , Ti 3 O 5 , Nb 2 O 3 , ZrO 2 , and silicon nitride, wherein each sublayer has a thickness in the range of 10-300 nm.
  • the anti-reflection layer comprises a SiO 2 layer and a Ti 3 O 5 layer.
  • the anti-reflection layer comprises alternately arranged SiO 2 layers and Ti 3 O 5 layers, wherein each SiO 2 layer has a thickness in the range of 10-60 nm, and each Ti3O5 layer has a thickness in the range of 10-200 nm.
  • the anti-reflection layer includes or consists of the following sublayers:
  • the electrodes are attached to the electrically conductive heating layer so as to be connected to a power supply for heating.
  • Electrodes There is no special requirement for the electrodes.
  • common copper sheets can be used.
  • the electrodes can be attached to the electrically conductive heating layer by bonding with an electrically conductive adhesive, or with a joint of flexible printed circuit (FPC) or metallic leaf spring.
  • FPC flexible printed circuit
  • the present invention provides a method for preparing the LiDAR window, comprising the steps of: i) providing a substrate; ii) forming an adhesive layer and a protective layer respectively on two opposite surfaces of the substrate; iii) forming an electrically conductive heating layer on the adhesive layer; and iv) optionally, forming an anti-reflection layer on the electrically conductive heating layer.
  • Step i providing a substrate
  • the substrate can be purchased or self-prepared.
  • the substrate can be prepared by standard injection molding.
  • the substrate is prepared from a thermoplastic material comprising a polymer resin selected from the group consisting of: copolycarbonate (PC), polyetherimide (PEI), polyimide (PI), polysulfone (PSU), polyarylate (PAR), polyethersulfone (PES) and polyphenylsulfone (PPSU) by standard injection molding.
  • a polymer resin selected from the group consisting of: copolycarbonate (PC), polyetherimide (PEI), polyimide (PI), polysulfone (PSU), polyarylate (PAR), polyethersulfone (PES) and polyphenylsulfone (PPSU) by standard injection molding.
  • the substrate is prepared from a thermoplastic material comprising a copolycarbonate based on bisphenol A and l,l-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane by standard injection molding.
  • Injection molding can be carried out by using a high-precision injection molding machine, more preferably an electric injection molding machine, which makes it possible to precisely control injection stroke, mold stroke, pressure and speed.
  • a high-precision injection molding machine more preferably an electric injection molding machine, which makes it possible to precisely control injection stroke, mold stroke, pressure and speed.
  • the mold temperature is controlled within the range of 90-160°C.
  • Step ii forming an adhesive layer and a protective layer respectively on two opposite surfaces of the substrate
  • the substrate is subjected to destaticizing and/or cleaning treatments prior to the formation of an adhesive layer and a protective layer.
  • Destaticizing can be carried out, for example, by blowing with deionized air (for example, for 10 seconds to 1 minute).
  • Cleaning can be carried out, for example, by washing with isopropanol.
  • the method of applying an adhesive layer and a protective layer is not particularly defined, including but not limited to flow coating, dip coating, spin coating, spray coating, scrape coating and roller coating.
  • an adhesive layer and a protective layer can be formed respectively on the two opposite surfaces of the substrate, by flow coating or other processes.
  • the coating material for forming an adhesive layer is applied onto one surface of the substrate by flow coating, flashed off at room temperature (23-25°C) and 35-55 RH% humidity for 5-30 minutes, followed by baking at the temperature of 100-140°C for 15-60 minutes, to form an adhesive layer on the substrate.
  • the material for forming a protective layer is applied onto the substrate by flow coating, flashed off at room temperature (23-25 °C) and 35-55 RH% humidity for 5-30 minutes, followed by baking at the temperature of 100-140 °C for 15-60 minutes, to form a protective layer on the substrate.
  • Step iii forming an electrically conductive heating layer on the adhesive layer
  • the destaticizing treatment is carried out prior to the formation of an electrically conductive heating layer.
  • Destaticizing can be carried out, for example, by blowing with deionized air (for example, for 10 seconds to 1 minute).
  • the electrically conductive heating layer can be formed by a PVD (Physical Vapor Deposition) process or other processes.
  • the PVD process may be an evaporation process or a magnetron sputtering process.
  • the deposition temperature is in the range of 150-300°C.
  • the coating material for forming an electrically conductive heating layer is applied onto the adhesive layer by the PVD process, and then annealed at 150-250°C for 1-3 hours, followed by condensation to form an electrically conductive heating layer.
  • the material of an electrically conductive heating layer is heated and evaporated so that its atoms or molecules vaporize and escape from the surface to form a vapor flow incident on the surface of the adhesive layer, and annealed at 150-250°C for 1-3 hours, followed by sufficient crystallization to form an electrically conductive heating layer.
  • Step iv forming an anti-reflection layer on the electrically conductive heating layer
  • the LiDAR window further comprises an anti-reflection layer disposed on the electrically conductive heating layer opposite to the adhesive layer
  • the anti-reflection layer is commonly formed on the electrically conductive heating layer by a PVD process.
  • the destaticizing treatment is carried out prior to the formation of the anti-reflection layer.
  • Destaticizing can be carried out, for example, by blowing with deionized air (for example, for 10 seconds to 1 minute).
  • the anti-reflection layer can be formed by a PVD (Physical Vapor Deposition) process or other processes.
  • PVD Physical Vapor Deposition
  • the PVD process may be an evaporation process or a magnetron sputtering process.
  • the deposition temperature is in the range of 150-300°C.
  • the coating material for forming an anti-reflection layer is applied onto the electrically conductive heating layer by the PVD process, and then annealed at 150-250°C for 1-3 hours, followed by condensation to form an anti-reflection layer.
  • the material of an anti-reflection layer is heated and evaporated so that its atoms or molecules vaporize and escape from the surface to form a vapor flow incident on the surface of the electrically conductive heating layer, and annealed at 150-250 °C for 1-3 hours, followed by sufficient crystallization to form an anti-reflection layer.
  • the adhesive layer can be formed prior to, after, or at the same time as the formation of the protective layer.
  • the electrically conductive heating layer can be formed prior to, after, or at the same time as the formation of the protective layer.
  • the anti-reflection layer can be formed prior to, after, or at the same time as the formation of the protective layer.
  • Sensor system and vehicle can be formed prior to, after, or at the same time as the formation of the protective layer.
  • the LiDAR window of the present invention can meet the functional requirement of laser signal transmission, while also having defrosting and defogging functions and meeting the requirements for automotive exterior decoration.
  • the present invention provides a sensor system, comprising: a LiDAR sensor emitting lasers with a wavelength of 800 nm to 1,600 nm; and the aforementioned LiDAR window partially or completely surrounding the LiDAR sensor, wherein the protective layer and the LiDAR sensor are disposed towards two opposite sides of the substrate.
  • the LiDAR sensor emits laser pulses in the range of 800 nm to 1,600 nm, preferably in the range of 820 nm to 1 ,500 nm, more preferably in the range of 850 nm to 1 ,300 nm, and in particular preferably in the range of 880 nm to 930 nm.
  • the distance from the LiDAR sensor to the window is in the range of 0.1 mm to 1000 mm, preferably in the range of 1 mm to 500 mm, more preferably in the range of 10 mm to 300 mm, and in particular preferably in the range of 50 mm to 300 mm.
  • the distance selected is basically contingent on the construction of the sensor system, as it should be selected to adequately protect the sensor from impacts.
  • the present invention provides a vehicle comprising the aforementioned sensor system.
  • infrared transmittance when it comes to infrared transmittance, unless otherwise specified, it generally refers to transmittance to infrared rays with a wavelength of 905 nm.
  • Example 1 The conception, specific structure, and the technical effect of the present invention will be further illustrated hereinafter in conjunction with the Examples and drawings, so that a person of ordinary skill in the art can fully understand the objectives, features and effects of the present invention. It is not difficult for the skilled person to understand that the Examples herein are for the purpose of illustration only, and the scope of the present invention is not limited thereto.
  • Example 1 The conception, specific structure, and the technical effect of the present invention will be further illustrated hereinafter in conjunction with the Examples and drawings, so that a person of ordinary skill in the art can fully understand the objectives, features and effects of the present invention. It is not difficult for the skilled person to understand that the Examples herein are for the purpose of illustration only, and the scope of the present invention is not limited thereto.
  • Example 1 Example 1
  • a LiDAR window was prepared as follows:
  • Step i providing a substrate
  • a plate i.e., substrate having the dimensions of 140 mm x 50 mm x 2 mm was prepared using a copolycarbonate (available from Covestro Polymers (China) Co., Ltd. under the trade name APEC® 2095, having a Vicat softening temperature of 203°C and a refractive index of 1.566), with the mold temperature being controlled at 140°C.
  • a copolycarbonate available from Covestro Polymers (China) Co., Ltd. under the trade name APEC® 2095, having a Vicat softening temperature of 203°C and a refractive index of 1.566
  • Step ii forming a first protective layer on one surface of the substrate
  • an organosilicon coating material (available from Momentive Performance Materials under the trade name SHP470 FT2050) was applied onto the substrate to form a first protective layer with a thickness of 2 pm.
  • This layer mainly has the weather-resistant effect. Specifically, in a clean room, the substrate was first blown with deionized air to remove static electricity, and then the surface of the substrate was washed with isopropanol.
  • the coating material was applied onto one surface of the substrate by flow coating, flashed off at room temperature (23-25°C) and 35-55 RH% humidity for 10 minutes, and then placed in an oven for baking at the temperature of 127°C for 40 minutes to form a first protective layer, i.e., a weather-resistant layer.
  • Step iii forming a second protective layer on the first protective layer
  • an organosilicon coating material (available from Momentive Performance Materials under the trade name AS4700) was applied onto the weather-resistant layer to form a second protective layer with a thickness of 5 pm.
  • the second protective layer mainly has the scratch-resistant effect. Specifically, in a clean room, the substrate was first blown with deionized air to remove static electricity, and then the surface of the substrate was washed with isopropanol.
  • the coating material was applied onto the weather-resistant layer by flow coating, flashed off at room temperature (23-25°C) and 35-55RH% humidity for 10 minutes, and then placed in an oven for baking at the temperature of 127°C for 40 minutes to form a second protective layer, i.e., a scratch-resistant layer.
  • Step iv forming an adhesive layer on the other surface of the substrate opposite to the protective layers
  • an organosilicon coating material (available from Momentive Performance Materials under the trade name PHC587C-2) was applied onto the substrate to form an adhesive layer with a thickness of 7 pm.
  • the substrate was first blown with deionized air to remove static electricity, and then the surface of the substrate was washed with isopropanol. After the isopropanol completely volatilized, the coating material was applied onto the other surface of the substrate by flow coating, flashed off at room temperature (23-25°C) and 35-55 RH% humidity for 10 minutes, and then placed in an oven for baking at the temperature of 127°C for 40 minutes to form an assembly of the substrate and the adhesive layer.
  • Step v forming an electrically conductive heating layer on the adhesive layer
  • ITO in-doped indium oxide in which the mass ratio of In 2 O 3 : Sn is 90: 10, i.e., an n-type semiconducting material
  • an electrically conductive heating layer with a thickness of 400 nm.
  • the assembly of the substrate and the adhesive layer was subjected to destaticizing treatment for 30 seconds.
  • electrically conductive adhesives 3307BC from 3M Company
  • electrodes common copper sheet electrodes
  • FIG. 1 shows a schematic diagram of structure 1 obtained by combining the LiDAR window prepared in Example 1 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; and 7 represents electrically conductive adhesives and electrodes.
  • Example 2 was carried out with reference to Example 1.
  • an anti-reflection layer comprising each sublayer in Table 1 and having a thickness of 203 nm was formed on the conductive heating layer of the assembly prepared in Example 1.
  • anti -reflection target materials were placed on a support in a vacuum chamber, to be coated in sequence. After coating one target material, the device used would automatically switch to another target material according to the input design until the coating process was completed.
  • electrically conductive adhesives 3307BC from 3M Company
  • electrodes common copper sheet electrodes
  • FIG. 2 shows a schematic diagram of structure 2 obtained by combining the LiDAR window prepared in Example 2 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; 6 represents an anti-reflection layer; and 7 represents electrically conductive adhesives and electrodes. Performance Testing
  • Structures 1 and 2 were tested in terms of infrared transmittance, adhesion, heating performance, weather resistance, scratch resistance, salt mist resistance, and environmental resistance, respectively.
  • Structures 1 and 2 were tested for transmittance to infrared rays with a wavelength of 905 nm at 0°, 30°, 60° incident angles with a UV-3600 Plus UV-VIS-NIR spectrophotometer, in accordance with the method described in ISO13468-2:2006.
  • Structures 1 and 2 were tested for adhesion with a cross-cut tester, in accordance with the standard ISO2409 (Test conditions: boiled in water at 98°C for 4 hours and soaked in water at 60°C for 24 hours). The results were rated on a 0-5 scale, with 0 being the best and 5 being the worst. Only the side facing the external environment (A-side) was tested.
  • structures 1 and 2 have good weather resistance.
  • the scratched samples were tested for the gloss retention rate and the infrared transmission retention rate, and the appearance of the samples was observed. The results are shown in Table 5. When the gloss retention rate reaches 80% and the infrared transmission retention rate reaches 95%, it is considered that the sample has good scratch resistance.
  • Structures 1 and 2 were subjected to the salt mist test, in accordance with the standard GB/T2423.17-2008, and then tested for infrared transmittance at 0°, 30°, and 60° incident angles.
  • Structures 1 and 2 were subjected to the environmental test (85°C/85 RH %, 300h) in accordance with the standard GB/T19394-2003, and then tested for infrared transmittance at the incident angles of 0°, 30°, and 60°.
  • Heating was performed using a direct current (DC) voltage of 12V, and surface temperature distribution images were captured using an infrared camera.
  • DC direct current
  • the infrared camera was used to detect the highest and lowest surface temperatures in the effective window area, and the time for increasing the temperature from room temperature to 50°C.
  • the surface square resistance was measured with a HPS2523 coated sheet resistance tester.
  • the principle of operation is as follows: two probes measure the constant current; two probes measure the potential difference; through the built-in formula, the surface square resistance is determined.
  • the method of operation is as follows: connect the tester to a 220V power supply, switch on the power supply, and select the automatic mode; then press the four-point probes against the surface of the sample to be tested, wait until the numbers on the display are stable, and read the numbers.
  • the difference between the highest surface temperature and the lowest surface temperature in the effective window area is 5°C (satisfying the requirement of ⁇ 10°C), and the time required for increasing the temperature from room temperature to 50°C is 5 minutes (satisfying the requirement of ⁇ 5 minutes).
  • the LiDAR window of the present invention is integrated with the heating function. Meanwhile, the LiDAR window can meet the performance requirement of infrared transmission and the use requirement of automotive exterior decoration.

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Abstract

The present invention relates to a LiDAR window, a method for preparing the same, and a sensor system. The LiDAR window comprises the following layers stacked together in the order of: a protective layer, a substrate, an adhesive layer and an electrically conductive heating layer having a surface square resistance of ≤ 200 ohm. The LiDAR window of the present invention can meet the functional requirement of laser signal transmission, while also having defrosting and defogging functions and meeting the requirements for automotive exterior decoration, and can be used in a sensor system.

Description

LIDAR WINDOW, METHOD FOR PREPARING THE SAME, AND SENSOR SYSTEM
TECHNICAL FIELD
The present invention belongs to the field of LiDAR windows. Specifically, the present invention relates to a LiDAR window, a method for preparing the same, and a sensor system.
BACKGROUND ART
With the development of 5G technology and electronic technology and the nation's increasing emphasis on energy conservation and environmental protection, over the past few years, the automotive industry has taken on new development trends: interconnection, autonomous driving, car sharing, and electrification. Autonomous driving assistance systems (abbreviated as ADAS) have gradually become indispensable for future automobiles. They collect environmental data inside and outside the automobile with various sensors, and perform technical processing such as identifying, detecting and tracking static and dynamic objects with on-board computer and algorithm software, so that the driver can perceive potential dangers in the shortest time possible.
The sensors used in ADAS mainly include cameras, millimeter-wave radar, laser radar and ultrasonic radar, etc., which can detect light, heat, pressure or other variables used for monitoring the state of the automobile. They are commonly located on the front grille, front and rear bumpers, pillar cover plates, roof cover plate, side view mirrors or windshield.
Laser radar, also known as LiDAR (light detection and ranging), detects obstacles and locates objects using laser beams rather than radio waves. LiDAR can emit lower-power, eye-safe infrared pulsed laser beams with a wavelength of 905 nm to determine the time required for a round trip between the laser transmitter and the target, while generating a 3D point cloud image according to the resulting data.
When the laser transmitter emits laser beams or laser beams are reflected back, the beams would inevitably pass through the radar window. Thus, it is required that the material of the window should be radioparent to infrared rays with a wavelength of 905 nm, and have the highest possible transmittance.
Currently, there are mainly two categories of materials for LiDAR windows. One is a glass material, and the other is a plastic material. Considering that LiDAR needs to be installed on the body of the automobile and conforms to the curvy design of the automobile, and given the factor of collision safety, there is a growing number of LiDAR windows using plastic windows. Plastic windows enjoy many advantages over glass windows, for example, light weight, good impact resistance, the ability to be made into a 3D curved surface to match the styling of the automobile, and be integrated with surrounding spare parts.
Since LiDAR works by calculating the flight time to locate and measure distance, it is also required to increase the infrared transmittance as much as possible when the laser beams pass through the plastic window, so that the transmission power can be enhanced to the greatest extent for the purpose of increasing the distance of detection.
In addition to meeting the functional requirement of infrared transmission, the LiDAR plastic window also needs to meet the functional requirements of automotive exterior decoration and surface cleaning. The automotive exterior decoration requirements mainly include: weather resistance, wear and scratch resistance, environmental ageing resistance, and so on. The plastic window is an exposed member, the surface of which would be easily attached with dust and dirt that block the emission and reception of laser beams, thereby affecting the LiDAR efficiency and functions. Therefore, it is critical to remove the dust and dirt from the surface of the LiDAR plastic window in time.
At present, some manufacturers wash the surface of the plastic window with specialized sprinklers to remove dust and dirt. Though washing with sprinklers can remove dust and dirt from the surface, the residual water droplets or water film would remain on the surface of the plastic window. These water droplets and water film may give rise to some undesirable optical phenomena such as light refraction, absorption, and reflection, thereby affecting the original optical design of the plastic window. In some extreme weather conditions, for example, rain and snow in winter, ice and frost would accumulate on the surface of the plastic window, impairing the optical design of the plastic window, and further affecting the properties of LiDAR. To counter these phenomena, LiDAR suppliers demand that the plastic window must have defrosting, deicing and accumulated water removal functions.
Some manufacturers remove frost and fog by heating with electrically conductive silver paste or electrically conductive filaments. However, this may lead to non-uniform temperature distribution and/or negative effects on the transmission of laser beams.
Therefore, it is desirable in the art to develop a LiDAR window which not only meets the requirement of LiDAR infrared optical transmission but also has defrosting and defogging functions, while meeting the requirements for automotive exterior decoration.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a LiDAR window which not only meets the requirement of LiDAR infrared optical transmission but also has defrosting and defogging functions, while meeting the requirements for automotive exterior decoration.
Another objective of the present invention is to provide a method for preparing the LiDAR window.
Therefore, according to a first aspect, the present invention provides a LiDAR window, comprising the following layers stacked together in the order of: a protective layer; a substrate prepared from a thermoplastic material having a Vicat softening temperature of not lower than 170°C; an adhesive layer; and an electrically conductive heating layer having a surface square resistance of ≤200 ohm, wherein the LiDAR window has a transmittance to infrared rays with a wavelength of 905 nm of at least 80% at an incidence angle of 0°, as measured in accordance with the method described in ISO 13468-2: 2006; and the LiDAR window has a gloss retention rate of at least 70%, as measured in accordance with ASTM D 1044-05.
According a second aspect, the present invention provides a method for preparing the aforementioned LiDAR window, comprising the steps of: i) providing a substrate; ii) forming an adhesive layer and a protective layer respectively on two opposite surfaces of the substrate; iii) forming an electrically conductive heating layer on the adhesive layer; and iv) optionally, forming an anti-reflection layer on the electrically conductive heating layer.
According to a third aspect, the present invention provides a sensor system, comprising: a LiDAR sensor emitting lasers with a wavelength of 800 nm to 1,600 nm; and the aforementioned LiDAR window partially or completely surrounding the LiDAR sensor, wherein the protective layer and the LiDAR sensor are disposed towards two opposite sides of the substrate.
According to a fourth aspect, the present invention provides a vehicle comprising the aforementioned sensor system.
The LiDAR window of the present invention can meet the functional requirement of laser signal transmission, while also having defrosting and defogging functions and meeting the requirements for automotive exterior decoration, and can be used in a sensor system.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described and explained in detail in conjunction with the figures hereinafter, wherein:
FIG. 1 shows a schematic diagram of structure 1 obtained by combining the LiDAR window prepared in Example 1 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; and 7 represents electrically conductive adhesives and electrodes.
FIG. 2 shows a schematic diagram of structure 2 obtained by combining the LiDAR window prepared in Example 2 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; 6 represents an anti-reflection layer; and 7 represents electrically conductive adhesives and electrodes.
FIG. 3 shows a schematic diagram of electrode setup according to one embodiment of the present invention, wherein 5 represents an electrically conductive heating layer; 8 represents electrically conductive adhesives; and 9 represents electrodes.
DETAILED DESCRIPTION OF THE INVENTION
Various aspects and further objectives, features and advantages of the present invention will be demonstrated in a more comprehensive manner hereinafter.
As noted above, an objective of the present invention is to provide a LiDAR window which not only achieves defrosting and defogging functions by heating a large area uniformly, but also meets the requirement of LiDAR infrared optical transmission.
The LiDAR window, for example, a LiDAR window for automobiles, should meet the following major requirements:
I) Optical requirement
A transmittance to infrared rays with a wavelength of 905 nm of at least 80% at an incidence angle of 0°, as measured in accordance with the method described in ISO 13468-2: 2006.
II) Requirements for Automotive exterior decoration, including, inter alia, adhesion, weather resistance, scratch resistance, salt mist resistance and environmental resistance
III) Heating function requirements
• Surface square resistance: ≤ 200 ohm; Maximum temperature difference in the effective window area: ≤ 10°C;
Minimum temperature attainable: 50°C;
Time for heating from 20°C to 40-60°C: ≤ 5 min.
LiDAR window
According to a first aspect, the present invention provides a LiDAR window, comprising the following layers stacked together in the order of: a protective layer; a substrate prepared from a thermoplastic material having a Vicat softening temperature of not lower than 170°C; an adhesive layer; and an electrically conductive heating layer having a surface square resistance of ≤ 200 ohm, wherein the LiDAR window has a transmittance to infrared rays with a wavelength of 905 nm of at least 80% at an incidence angle of 0°, as measured in accordance with the method described in ISO 13468-2: 2006; and the LiDAR window has a gloss retention rate of at least 70%, as measured in accordance with ASTM D 1044-05.
Preferably, the LiDAR window of the present invention further comprises an anti-reflection layer disposed on the electrically conductive heating layer opposite to the adhesive layer.
In the present application, unless otherwise specified, the gloss is measured in accordance with ASTM D523-2014.
In the present application, unless otherwise specified, the transmittance to infrared rays (or IR transmittance) is measured in accordance with the method described in ISO13468-2:2006.
Protective layer
The LiDAR window according to the present invention comprises a protective layer.
The protective layer possesses at least one of the following properties: weather resistance, scratch resistance, chemical resistance, and impermeability.
Preferably, the protective layer is used to protect the entire LiDAR window from environmental and scratch influences, while acting together with the substrate and other layers to fulfill the antireflection effect.
In the description and claims of the present application, the anti-reflection effect refers to reducing the intensity of reflected infrared light, thereby increasing the intensity of transmitted infrared light. In other words, it refers to improving the infrared transmittance of the substrate.
Preferably, the protective layer is formed with an organosilicon coating material, an acrylate coating material, or an organosilicon-acrylate coating material with a refractive index in the range of 1.20-1.55.
The organosilicon-acrylate coating material herein refers to a mixture of organosilicon and acrylate.
In the description and claims of the present application, unless otherwise specified, the refractive index generally refers to the refractive index at a wavelength of 589 nm.
The refractive index described in the description and claims of the present application is measured in accordance with the standard GB/T7962.1-2010 “Test Methods of Colorless Optical Glass” Part 1: Refractive Index and Coefficient of Dispersion. As a coating material that can be used as a protective layer in the LiDAR window of the present invention, mention may be made of AS4700 (with a refractive index in the range of 1.40-1.44) and SHP 470 FT2050, PHC587C-2, UVHC3000, UVHC5000 from Momentive Performance Materials.
The protective layer may be one layer or consist of at least two sublayers.
For example, the protective layer may consist of two layers, wherein the first protective layer in contact with the substrate is weather-resistant, and the second protective layer facing toward the external environment is mainly scratch-resistant.
Preferably, the total thickness of the protective layer is in the range of 0.5-20 pm.
Preferably, the protective layer not only has anti-reflection effect but also has excellent abrasion resistance, scratch resistance, salt mist resistance and environmental resistance, which can well protect the substrate and meet the requirements for automotive exterior decoration.
Substrate
The LiDAR window according to the present invention comprises a substrate.
The substrate is prepared from a thermoplastic material.
The thermoplastic material consists of a polymer resin and optional additives. The additives may be those commonly used in the thermoplastic material, for example, colorants, heat stabilizers, mold release agents, UV absorbers, flame retardants, antistatic agents and/or flow improvers, and they are in conventional additive amounts, with the proviso that the types and amounts of the additives do not adversely affect the objective of the present invention.
Preferably, the substrate is prepared from a thermoplastic material comprising a polymer resin having a Vicat softening temperature of not lower than 180°C.
Preferably, the substrate has a transmittance to infrared rays with a wavelength of 905 nm of at least 70% at an incident angle of 0°.
Preferably, the substrate is prepared from a thermoplastic material with a refractive index in the range of 1.45-1.75.
Preferably, the thermoplastic material has a transmittance to a light in the range of 380-780 nm of less than 25.0%, as measured in accordance with DIN ISO 13468-2:2006 (D65, 10°) at a layer thickness of 4 mm.
Preferably, the substrate is prepared from a thermoplastic material comprising a polymer resin selected from the group consisting of: copolycarbonate (PC), polyetherimide (PEI), polyimide (PI), polysulfone (PSU), polyarylate (PAR), polyethersulfone (PES) and polyphenylsulfone (PPSU).
In the present application, when it comes to the thermoplastic material comprising a polymer resin, this means that the polymer resin constitutes a major part of the thermoplastic material, accounting for at least 70 wt. % of the thermoplastic material, relative to the total weight of the thermoplastic material.
More preferably, the polymer resin is selected from a copolycarbonate based on bisphenol A and 1 , 1 -bis(4-hydroxyphenyl)-3 ,3 ,5-trimethylcyclohexane.
As examples of the copolycarbonate, the APEC® series from Covestro Polymers (China) Co., Ltd., and the LEXAN™ XHT series and SLX series from Saudi Basic Industry Corporation (SABIC) can be used.
As specific examples for commercial products of the copolycarbonate, mention may be made of the APEC® series from Covestro Deutschland AG, such as APEC® 1895 (having a Vicat softening temperature of 183°C), APEC® 2095 (having a Vicat softening temperature of 202°C), APEC® 2097 (having a Vicat softening temperature of 202°C) and APEC® DP 1-9389 (having a Vicat softening temperature of 218°C).
Preferably, the thickness of the substrate is in the range of 0.5-5 mm.
Adhesive layer
The LiDAR window according to the present invention comprises an adhesive layer.
The adhesive layer is used to enhance the adhesion between the substrate and the electrically conductive heating layer, and also has the anti-reflection effect.
Preferably, the adhesive layer is formed with an organosilicon coating material, an acrylate coating material, or an organosilicon-acrylate coating material with a refractive index in the range of 1.20-1.55.
The organosilicon-acrylate coating material herein refers to a mixture of organosilicon and acrylate.
As a coating material that can be used as an adhesive layer in the LiDAR window of the present invention, mention may be made of PHC587C-2 (with a refractive index of 1.42) from the company Momentive Performance Materials.
Preferably, the thickness of the adhesive layer is in the range of 0.5-10 pm.
Electrically conductive heating layer
The LiDAR window according to the present invention comprises an electrically conductive heating layer.
The electrically conductive heating layer is used to provide heating to achieve defrosting and defogging functions.
Preferably, the electrically conductive heating layer comprises tin-doped indium oxide (ITO), wherein the mass ratio of In2O3: Sn is in the range of 85: 15 to 95: 5.
More preferably, the tin-doped indium oxide is present in the amount of 90-100 wt.% in the electrically conductive heating layer.
Most preferably, the electrically conductive heating layer is composed of tin-doped indium oxide.
The tin-doped indium oxide is a semiconducting material with a conductivity of p=5x 10-4 Ω●cm. The tin-doped indium oxide possesses excellent visible-light and near-infrared transmission properties.
The tin-doped indium oxide is also a crystal having a crystallization temperature of 350°C. When the temperature increases, the degrees of crystallinity, transparency, and electrical conductivity are also higher.
The electrically conductive heating layer can generate a surface square resistance of less than or equal to 200 ohm. Preferably, the surface square resistance of the electrically conductive heating layer is preferably less than or equal to 150 ohm, more preferably less than or equal to 100 ohm.
Preferably, the thickness of the electrically conductive heating layer is in the range of 50-500 nm.
The electrically conductive heating layer can realize uniform heating over a large area.
Driven by a DC power supply, it can generate an electric power of 3-8W at a safe voltage (for example, 12V, DC), and increase the surface temperature from 20°C to 40-60°C in no more than 5 minutes, thereby performing the defrosting and defogging functions. By incorporating a low-resistance electrically conductive heating layer, the LiDAR window of the present invention addresses the problem of non-uniform temperature distribution and infrared laser interference caused by heating electrically conductive silver paste and electrically conductive filaments in the prior art. The electrically conductive heating layer in the LiDAR window of the present invention not only does not interfere with the anti-reflection effect of the anti-reflection coating on the external surface, but also can have optical synergistic effect with the anti-reflection coating to fulfill the anti-reflection effect. Anti-reflection layer
Preferably, the LiDAR window according to the present invention further comprises an antireflection layer disposed on the electrically conductive heating layer opposite to the adhesive layer.
The anti-reflection layer can be prepared from a material with a refractive index in the range of 1.3-2.4. For example, the anti-reflection layer can be formed with a material selected from the group consisting of MgF2, SiO2, AI2O3, Ti2O3, Ti3O5, Nb2O3, ZrO2, and silicon nitride.
Preferably, the thickness of the anti-reflection layer is in the range of 50-600 nm.
The anti-reflection layer can be composed of two or more sublayers of the same or different thickness, comprising different materials selected from the group consisting of MgF2, SiO2, A12O3, Ti2O3, Ti3O5, Nb2O3, ZrO2, and silicon nitride, wherein each sublayer has a thickness in the range of 10-300 nm.
Preferably, the anti-reflection layer comprises a SiO2 layer and a Ti3O5 layer.
Preferably, the anti-reflection layer comprises alternately arranged SiO2 layers and Ti3O5 layers, wherein each SiO2 layer has a thickness in the range of 10-60 nm, and each Ti3O5 layer has a thickness in the range of 10-200 nm.
Preferably, the anti-reflection layer includes or consists of the following sublayers:
Figure imgf000008_0001
When the LiDAR window of the present invention is in use, the electrodes are attached to the electrically conductive heating layer so as to be connected to a power supply for heating.
There is no special requirement for the electrodes. For example, common copper sheets can be used.
The electrodes can be attached to the electrically conductive heating layer by bonding with an electrically conductive adhesive, or with a joint of flexible printed circuit (FPC) or metallic leaf spring.
Method for preparing the LiDAR window
According to a second aspect, the present invention provides a method for preparing the LiDAR window, comprising the steps of: i) providing a substrate; ii) forming an adhesive layer and a protective layer respectively on two opposite surfaces of the substrate; iii) forming an electrically conductive heating layer on the adhesive layer; and iv) optionally, forming an anti-reflection layer on the electrically conductive heating layer.
Step i: providing a substrate
The substrate can be purchased or self-prepared.
For example, the substrate can be prepared by standard injection molding.
Preferably, the substrate is prepared from a thermoplastic material comprising a polymer resin selected from the group consisting of: copolycarbonate (PC), polyetherimide (PEI), polyimide (PI), polysulfone (PSU), polyarylate (PAR), polyethersulfone (PES) and polyphenylsulfone (PPSU) by standard injection molding.
More preferably, the substrate is prepared from a thermoplastic material comprising a copolycarbonate based on bisphenol A and l,l-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane by standard injection molding.
Injection molding can be carried out by using a high-precision injection molding machine, more preferably an electric injection molding machine, which makes it possible to precisely control injection stroke, mold stroke, pressure and speed.
During the injection molding process, the mold temperature is controlled within the range of 90-160°C.
Step ii: forming an adhesive layer and a protective layer respectively on two opposite surfaces of the substrate
Preferably, the substrate is subjected to destaticizing and/or cleaning treatments prior to the formation of an adhesive layer and a protective layer.
Destaticizing can be carried out, for example, by blowing with deionized air (for example, for 10 seconds to 1 minute).
Cleaning can be carried out, for example, by washing with isopropanol.
The method of applying an adhesive layer and a protective layer is not particularly defined, including but not limited to flow coating, dip coating, spin coating, spray coating, scrape coating and roller coating.
For example, an adhesive layer and a protective layer can be formed respectively on the two opposite surfaces of the substrate, by flow coating or other processes.
Preferably, the coating material for forming an adhesive layer is applied onto one surface of the substrate by flow coating, flashed off at room temperature (23-25°C) and 35-55 RH% humidity for 5-30 minutes, followed by baking at the temperature of 100-140°C for 15-60 minutes, to form an adhesive layer on the substrate.
Preferably, the material for forming a protective layer is applied onto the substrate by flow coating, flashed off at room temperature (23-25 °C) and 35-55 RH% humidity for 5-30 minutes, followed by baking at the temperature of 100-140 °C for 15-60 minutes, to form a protective layer on the substrate.
Step iii: forming an electrically conductive heating layer on the adhesive layer
Preferably, the destaticizing treatment is carried out prior to the formation of an electrically conductive heating layer.
Destaticizing can be carried out, for example, by blowing with deionized air (for example, for 10 seconds to 1 minute). The electrically conductive heating layer can be formed by a PVD (Physical Vapor Deposition) process or other processes.
Specifically, the PVD process may be an evaporation process or a magnetron sputtering process.
In the case of using the PVD process, preferably, the deposition temperature is in the range of 150-300°C.
Preferably, the coating material for forming an electrically conductive heating layer is applied onto the adhesive layer by the PVD process, and then annealed at 150-250°C for 1-3 hours, followed by condensation to form an electrically conductive heating layer.
For example, in a vacuum chamber, the material of an electrically conductive heating layer is heated and evaporated so that its atoms or molecules vaporize and escape from the surface to form a vapor flow incident on the surface of the adhesive layer, and annealed at 150-250°C for 1-3 hours, followed by sufficient crystallization to form an electrically conductive heating layer.
Step iv: forming an anti-reflection layer on the electrically conductive heating layer
Under the circumstance that the LiDAR window further comprises an anti-reflection layer disposed on the electrically conductive heating layer opposite to the adhesive layer, the anti-reflection layer is commonly formed on the electrically conductive heating layer by a PVD process.
Preferably, the destaticizing treatment is carried out prior to the formation of the anti-reflection layer.
Destaticizing can be carried out, for example, by blowing with deionized air (for example, for 10 seconds to 1 minute).
The anti-reflection layer can be formed by a PVD (Physical Vapor Deposition) process or other processes.
Specifically, the PVD process may be an evaporation process or a magnetron sputtering process.
In the case of using the PVD process, preferably, the deposition temperature is in the range of 150-300°C.
Preferably, the coating material for forming an anti-reflection layer is applied onto the electrically conductive heating layer by the PVD process, and then annealed at 150-250°C for 1-3 hours, followed by condensation to form an anti-reflection layer.
For example, in a vacuum chamber, the material of an anti-reflection layer is heated and evaporated so that its atoms or molecules vaporize and escape from the surface to form a vapor flow incident on the surface of the electrically conductive heating layer, and annealed at 150-250 °C for 1-3 hours, followed by sufficient crystallization to form an anti-reflection layer.
There is no special requirement for the sequence of forming each layer, so long as the LiDAR window of the present invention can finally be formed. Certainly, it is obvious that the adhesive layer must be formed prior to the formation of the electrically conductive heating layer, and the antireflection layer must be formed after the formation of the electrically conductive heating layer.
The adhesive layer can be formed prior to, after, or at the same time as the formation of the protective layer.
The electrically conductive heating layer can be formed prior to, after, or at the same time as the formation of the protective layer.
The anti-reflection layer can be formed prior to, after, or at the same time as the formation of the protective layer. Sensor system and vehicle
The LiDAR window of the present invention can meet the functional requirement of laser signal transmission, while also having defrosting and defogging functions and meeting the requirements for automotive exterior decoration.
Thus, according to a third aspect, the present invention provides a sensor system, comprising: a LiDAR sensor emitting lasers with a wavelength of 800 nm to 1,600 nm; and the aforementioned LiDAR window partially or completely surrounding the LiDAR sensor, wherein the protective layer and the LiDAR sensor are disposed towards two opposite sides of the substrate.
The LiDAR sensor emits laser pulses in the range of 800 nm to 1,600 nm, preferably in the range of 820 nm to 1 ,500 nm, more preferably in the range of 850 nm to 1 ,300 nm, and in particular preferably in the range of 880 nm to 930 nm.
Advantageously, the distance from the LiDAR sensor to the window is in the range of 0.1 mm to 1000 mm, preferably in the range of 1 mm to 500 mm, more preferably in the range of 10 mm to 300 mm, and in particular preferably in the range of 50 mm to 300 mm. The distance selected is basically contingent on the construction of the sensor system, as it should be selected to adequately protect the sensor from impacts.
According to a fourth aspect, the present invention provides a vehicle comprising the aforementioned sensor system.
In the present application, when it comes to infrared transmittance, unless otherwise specified, it generally refers to transmittance to infrared rays with a wavelength of 905 nm.
In the present application, when it comes to applying a certain material onto a certain layer, unless otherwise specified, it generally refers to completely covering at least one surface of the layer with the material.
In the present application, the terms “comprising” and “including” cover the circumstances further comprising or including other elements not expressly mentioned and the circumstances comprising the elements mentioned.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the field the present invention belongs to. When the definition of a term in the present description conflicts with the meaning as commonly understood by a person of ordinary skill in the field the present invention belongs to, the definition described herein shall prevail.
Unless otherwise specified, all numerical values expressing the amount, infrared transmittance, thickness and the like used in the description and claims should be understood as being modified by the term “about”. Therefore, unless indicated to the contrary, the numerical value parameters described herein are approximate values that may be varied according to the desired properties.
Examples
The conception, specific structure, and the technical effect of the present invention will be further illustrated hereinafter in conjunction with the Examples and drawings, so that a person of ordinary skill in the art can fully understand the objectives, features and effects of the present invention. It is not difficult for the skilled person to understand that the Examples herein are for the purpose of illustration only, and the scope of the present invention is not limited thereto. Example 1
A LiDAR window was prepared as follows:
Step i: providing a substrate
By standard injection molding, a plate (i.e., substrate) having the dimensions of 140 mm x 50 mm x 2 mm was prepared using a copolycarbonate (available from Covestro Polymers (China) Co., Ltd. under the trade name APEC® 2095, having a Vicat softening temperature of 203°C and a refractive index of 1.566), with the mold temperature being controlled at 140°C.
Step ii: forming a first protective layer on one surface of the substrate
By flow coating, an organosilicon coating material (available from Momentive Performance Materials under the trade name SHP470 FT2050) was applied onto the substrate to form a first protective layer with a thickness of 2 pm. This layer mainly has the weather-resistant effect. Specifically, in a clean room, the substrate was first blown with deionized air to remove static electricity, and then the surface of the substrate was washed with isopropanol. After the isopropanol completely volatilized, the coating material was applied onto one surface of the substrate by flow coating, flashed off at room temperature (23-25°C) and 35-55 RH% humidity for 10 minutes, and then placed in an oven for baking at the temperature of 127°C for 40 minutes to form a first protective layer, i.e., a weather-resistant layer.
Step iii: forming a second protective layer on the first protective layer
By flow coating, an organosilicon coating material (available from Momentive Performance Materials under the trade name AS4700) was applied onto the weather-resistant layer to form a second protective layer with a thickness of 5 pm. The second protective layer mainly has the scratch-resistant effect. Specifically, in a clean room, the substrate was first blown with deionized air to remove static electricity, and then the surface of the substrate was washed with isopropanol. After the isopropanol completely volatilized, the coating material was applied onto the weather-resistant layer by flow coating, flashed off at room temperature (23-25°C) and 35-55RH% humidity for 10 minutes, and then placed in an oven for baking at the temperature of 127°C for 40 minutes to form a second protective layer, i.e., a scratch-resistant layer.
Step iv: forming an adhesive layer on the other surface of the substrate opposite to the protective layers
By flow coating, an organosilicon coating material (available from Momentive Performance Materials under the trade name PHC587C-2) was applied onto the substrate to form an adhesive layer with a thickness of 7 pm. Specifically, in a clean room, the substrate was first blown with deionized air to remove static electricity, and then the surface of the substrate was washed with isopropanol. After the isopropanol completely volatilized, the coating material was applied onto the other surface of the substrate by flow coating, flashed off at room temperature (23-25°C) and 35-55 RH% humidity for 10 minutes, and then placed in an oven for baking at the temperature of 127°C for 40 minutes to form an assembly of the substrate and the adhesive layer.
Step v: forming an electrically conductive heating layer on the adhesive layer
By the PVD process, ITO (tin-doped indium oxide in which the mass ratio of In2O3: Sn is 90: 10, i.e., an n-type semiconducting material) was applied onto the adhesive layer to form an electrically conductive heating layer with a thickness of 400 nm. Specifically, prior to PVD, the assembly of the substrate and the adhesive layer was subjected to destaticizing treatment for 30 seconds. Then, in a vacuum chamber, baking was carried out at 200°C for 10 minutes to heat and evaporate the ITO in a container through heating with electron beams, so that the atoms or molecules of the ITO vaporized and escaped from the surface to form a vapor flow incident on the surface of the adhesive layer, followed by annealing at 200°C for 2 hours and condensation, to form an electrically conductive heating layer. The LiDAR window illustrated in FIG. 1 was thus obtained.
Referring to FIG. 3, electrically conductive adhesives (3307BC from 3M Company) and electrodes (common copper sheet electrodes) were attached to the surface of the conductive heating layer. Structure 1 was thus obtained.
FIG. 1 shows a schematic diagram of structure 1 obtained by combining the LiDAR window prepared in Example 1 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; and 7 represents electrically conductive adhesives and electrodes.
Example 2
This Example was carried out with reference to Example 1. By the PVD process, an anti-reflection layer comprising each sublayer in Table 1 and having a thickness of 203 nm was formed on the conductive heating layer of the assembly prepared in Example 1. Specifically, anti -reflection target materials were placed on a support in a vacuum chamber, to be coated in sequence. After coating one target material, the device used would automatically switch to another target material according to the input design until the coating process was completed.
Figure imgf000013_0001
Referring to FIG. 3, electrically conductive adhesives (3307BC from 3M Company) and electrodes (common copper sheet electrodes) were attached to the surface of the electrically conductive heating layer. Structure 2 was thus obtained.
FIG. 2 shows a schematic diagram of structure 2 obtained by combining the LiDAR window prepared in Example 2 with electrodes through electrically conductive adhesives, wherein 1 represents a substrate; 2 represents a second protective layer; 3 represents a first protective layer; 4 represents an adhesive layer; 5 represents an electrically conductive heating layer; 6 represents an anti-reflection layer; and 7 represents electrically conductive adhesives and electrodes. Performance Testing
Structures 1 and 2 were tested in terms of infrared transmittance, adhesion, heating performance, weather resistance, scratch resistance, salt mist resistance, and environmental resistance, respectively.
Infrared transmittance
Structures 1 and 2 were tested for transmittance to infrared rays with a wavelength of 905 nm at 0°, 30°, 60° incident angles with a UV-3600 Plus UV-VIS-NIR spectrophotometer, in accordance with the method described in ISO13468-2:2006.
The test results are summarized in Table 2.
Figure imgf000014_0001
Adhesion
Structures 1 and 2 were tested for adhesion with a cross-cut tester, in accordance with the standard ISO2409 (Test conditions: boiled in water at 98°C for 4 hours and soaked in water at 60°C for 24 hours). The results were rated on a 0-5 scale, with 0 being the best and 5 being the worst. Only the side facing the external environment (A-side) was tested.
The test results are summarized in Table 3.
Figure imgf000014_0002
As can be seen from Table 3, structures 1 and 2 have good adhesion.
Weather resistance
The A-sides of structures 1 and 2 were tested for weather resistance in an Atlas4000 flash light aging chamber, in accordance with the standard SAE J2527-2004 (Xenon Lamp Aging Test in the dry and wet states).
Test conditions: illumination wavelength: 340 nm; radiation intensity: 0.75 w/cm2; dry/wet state duration: 102/18 min; total radiation energy: 4500 KJ; irradiation intensity: 0.55 W/m2.
The results are shown in Table 4, wherein the change in appearance indicates whether there are undesirable phenomena such as chalking, delamination, brittleness, frosting, air bubbles, and stickiness occurring on the surface of the sample.
Figure imgf000015_0001
As can be seen from Table 4, structures 1 and 2 have good weather resistance.
Scratch resistance
The A-sides of structures 1 and 2 were subjected to the Taber abrading wheel test, in accordance with the standard ASTM D 1044-05. Test conditions: 500g load/500 revolutions.
The scratched samples were tested for the gloss retention rate and the infrared transmission retention rate, and the appearance of the samples was observed. The results are shown in Table 5. When the gloss retention rate reaches 80% and the infrared transmission retention rate reaches 95%, it is considered that the sample has good scratch resistance.
Figure imgf000015_0002
As can be seen from Table 5, structures 1 and 2 have good scratch resistance.
Salt mist resistance
Structures 1 and 2 were subjected to the salt mist test, in accordance with the standard GB/T2423.17-2008, and then tested for infrared transmittance at 0°, 30°, and 60° incident angles.
The results are shown in Table 6.
Figure imgf000015_0003
As can be seen from Table 6, structures 1 and 2, after going through the salt mist test, still meet the optical requirement described in the present application. Environmental resistance
Structures 1 and 2 were subjected to the environmental test (85°C/85 RH %, 300h) in accordance with the standard GB/T19394-2003, and then tested for infrared transmittance at the incident angles of 0°, 30°, and 60°.
The results are shown in Table 7.
Figure imgf000016_0001
As can be seen from Table 7, structures 1 and 2, after going through the environmental test, still meet the optical requirement described in the present application.
Heating performance
Heating was performed using a direct current (DC) voltage of 12V, and surface temperature distribution images were captured using an infrared camera.
The results show that, the structures 1 and 2 have uniform surface temperature distribution after the heating.
Meanwhile, the infrared camera was used to detect the highest and lowest surface temperatures in the effective window area, and the time for increasing the temperature from room temperature to 50°C.
The test results are summarized in Table 8.
Figure imgf000016_0002
* : The surface square resistance was measured with a HPS2523 coated sheet resistance tester. The principle of operation is as follows: two probes measure the constant current; two probes measure the potential difference; through the built-in formula, the surface square resistance is determined. The method of operation is as follows: connect the tester to a 220V power supply, switch on the power supply, and select the automatic mode; then press the four-point probes against the surface of the sample to be tested, wait until the numbers on the display are stable, and read the numbers.
As can be seen from the results in Table 8, the difference between the highest surface temperature and the lowest surface temperature in the effective window area is 5°C (satisfying the requirement of ≤ 10°C), and the time required for increasing the temperature from room temperature to 50°C is 5 minutes (satisfying the requirement of ≤ 5 minutes).
The LiDAR window of the present invention is integrated with the heating function. Meanwhile, the LiDAR window can meet the performance requirement of infrared transmission and the use requirement of automotive exterior decoration.
Only exemplary embodiments or examples of the present invention are described above, and they are not intended to limit the present invention. For a person of ordinary skill in the art, the present invention may be modified or changed in various manners. Any modification, equivalent replacement, improvement and the like made without departing from the spirit and principles of the present invention shall fall within the scope of the claims of the present application.

Claims

Claims;
1. A LiDAR window, comprising the following layers stacked together in the order of: a protective layer; a substrate prepared from a thermoplastic material having a Vicat softening temperature of not lower than 170°C; an adhesive layer; and an electrically conductive heating layer having a surface square resistance of ≤ 200 ohm, wherein the LiDAR window has a transmittance to infrared rays with a wavelength of 905 nm of at least 80% at an incidence angle of 0°, as measured in accordance with the method described in ISO 13468-2: 2006; and the LiDAR window has a gloss retention rate of at least 70%, as measured in accordance with ASTM D 1044-05.
2. The LiDAR window of claim 1, further comprising an anti-reflection layer disposed on the conductive heating layer opposite to the adhesive layer.
3. The LiDAR window of claim 1 or 2, wherein the protective layer is formed with an organosilicon coating material, an acrylate coating material, or an organosilicon-acrylate coating material with a refractive index in the range of 1.20-1.55.
4. The LiDAR window of any one of claims 1 to 3, wherein the substrate is prepared from a thermoplastic material with a refractive index in the range of 1.45-1.75.
5. The LiDAR window of any one of claims 1 to 4, wherein the thermoplastic material for preparing the substrate has a transmittance to a light in the range of 380-780 nm of less than 25.0%, as measured in accordance with DIN ISO 13468-2:2006 (D65, 10°) at a layer thickness of 4 mm.
6. The LiDAR window of any one of claims 1 to 5, wherein the substrate is prepared from a thermoplastic material comprising a polymer resin selected from the group consisting of: copolycarbonate (PC), polyetherimide (PEI), polyimide (PI), polysulfone (PSU), polyarylate (PAR), polyethersulfone (PES) and polyphenylsulfone (PPSU); preferably, the polymer resin is selected from a copolycarbonate based on bisphenol A and l,l-bis(4-hydroxyphenyl)-3,3,5- trimethylcyclohexane .
7. The LiDAR window of any one of claims 1 to 6, wherein the adhesive layer is formed with an organosilicon coating material, an acrylate coating material, or an organosilicon-acrylate coating material with a refractive index in the range of 1.20-1.55.
8. The LiDAR window of any one of claims 1 to 7, wherein the electrically conductive heating layer comprises tin-doped indium oxide (ITO), wherein the mass ratio of ImOa: Sn is in the range of 85: 15 to 95: 5; preferably, the tin-doped indium oxide is present in the amount of 90-100 wt.% in the electrically conductive heating layer.
9. The LiDAR window of any one of claims 1 to 8, further comprising an anti-reflection layer disposed on the electrically conductive heating layer opposite to the adhesive layer; preferably, the anti-reflection layer has a refractive index in the range of 1.3-2.4, and a thickness in the range of 50- 600 nm.
10. The LiDAR window of claim 9, wherein the anti -reflection layer is formed with a material selected from the group consisting of MgF2, SiO2 , A12O3, Ti2O3, Ti3O5, NrO2, ZrO 2, and silicon nitride; more preferably, the anti-reflection layer comprises alternately arranged SiO2 layers and Ti3O5 layers, wherein each SiCL layer has a thickness in the range of 10-60 nm, and each Ti3O5 layer has a thickness in the range of 10-200 nm.
11. A method for preparing the LiDAR window of any one of Claims 1 to 10, comprising the steps of: i) providing a substrate; ii) forming an adhesive layer and a protective layer respectively on two opposite surfaces of the substrate; iii) forming an electrically conductive heating layer on the adhesive layer; and iv) optionally, forming an anti-reflection layer on the electrically conductive heating layer.
12. The method of claim 11, wherein the electrically conductive heating layer is formed by a PVD process; preferably, the electrically conducive heating layer is formed by applying a coating material for forming the electrically conductive heating layer onto the adhesive layer by the PVD process, and then annealing at 150-250°C for 1-3 hours, followed by condensation.
13. The method of any one of claims 11 or 12, wherein the anti-reflection layer is formed by a PVD process; preferably, the anti-reflection layer is formed by applying a coating material for forming the anti-reflection layer onto the electrically conductive heating layer by the PVD process, and then annealing at 150-250°C for 1-3 hours, followed by condensation.
14. A sensor system, comprising: a LiDAR sensor emitting lasers with a wavelength of 800 nm to 1,600 nm; and the LiDAR window of any one of Claims 1 to 10 partially or completely surrounding the LiDAR sensor, wherein the protective layer and the LiDAR sensor are disposed towards two opposite sides of the substrate.
15. A vehicle, comprising the sensor system of claim 14.
PCT/EP2023/062925 2022-05-18 2023-05-15 Lidar window, method for preparing the same, and sensor system WO2023222583A1 (en)

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CN202210540218.0A CN117129967A (en) 2022-05-18 2022-05-18 Laser radar window, preparation method thereof and sensor system
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EP22185924 2022-07-20
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3418612A1 (en) * 1983-05-19 1984-11-22 Toyoda Gosei Co., Ltd., Haruhimura, Aichi Exothermic transparent body
US5391795A (en) * 1994-02-18 1995-02-21 General Electric Company Silylated agents useful for absorbing ultraviolet light
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WO2021094248A1 (en) * 2019-11-14 2021-05-20 Covestro Intellectual Property Gmbh & Co. Kg Thermoplastic compositino for lidar sensor system with improved absorption properties
CN113296078A (en) * 2021-07-27 2021-08-24 宁波永新光学股份有限公司 Front-mounted heating optical window of laser radar
CN216083087U (en) * 2021-11-04 2022-03-18 宁波舜宇车载光学技术有限公司 Optical composite window and laser radar

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3418612A1 (en) * 1983-05-19 1984-11-22 Toyoda Gosei Co., Ltd., Haruhimura, Aichi Exothermic transparent body
US5391795A (en) * 1994-02-18 1995-02-21 General Electric Company Silylated agents useful for absorbing ultraviolet light
WO2018108978A1 (en) * 2016-12-15 2018-06-21 Covestro Deutschland Ag Transparently coated polycarbonate component, its production and use
WO2021094248A1 (en) * 2019-11-14 2021-05-20 Covestro Intellectual Property Gmbh & Co. Kg Thermoplastic compositino for lidar sensor system with improved absorption properties
CN113296078A (en) * 2021-07-27 2021-08-24 宁波永新光学股份有限公司 Front-mounted heating optical window of laser radar
CN216083087U (en) * 2021-11-04 2022-03-18 宁波舜宇车载光学技术有限公司 Optical composite window and laser radar

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