Manufacturing method of head-up display reflecting film

Abstract

The invention discloses a method for manufacturing a head-up display reflecting film, which belongs to the field of vehicle display, and comprises the steps of preparing a reflecting layer, calculating parameters of a compensation layer, preparing the compensation layer, forming the head-up display reflecting film and the like, and the manufactured head-up display reflecting film reflects a light beam generated by a display device which is incident at a Brewster angle in a vehicle. The energy of the light beam forming the ghosting is reduced, and the ghosting is eliminated; only right-handed circularly polarized light close to the working wavelength of the display device is reflected for natural light outside a vehicle, and natural light with other wavelengths and polarization directions is transmitted, so that the head-up display reflecting film has high reflectivity and high transmittance.

Description

Technical Field

[0001] The invention relates to the field of vehicle display, and in particular to a method for manufacturing a head-up display reflective film. Background Art

[0002] The car head-up display (HUD) is a visual assisted driving system that can provide the driver with key assisted driving information and project the driving information into a virtual image, which is displayed at a certain distance in front of the driver, so that the driver can obtain information such as vehicle speed, fuel level, real-time navigation, etc. in a head-up state, thereby avoiding the blind spot time caused by the driver lowering his head to check driving information, reducing potential traffic accidents, and ensuring driving safety.

[0003] When the existing head-up display device is used, Figure 1 As shown in the figure, point A is the image source. The light beam emitted by the image source enters the human eye after being reflected by the windshield, forming a virtual image. At the same time, the light beam emitted by the actual object in the outside world can also enter the human eye to form a real image, so as to achieve the display effect of augmented reality. Since the reflectivity of the air-glass interface is low, about 10%, only 10% of the energy of the light beam emitted by the image source can enter the human eye, the energy utilization rate is low, and the brightness is limited; at the same time, Figure 2 as well as Figure 3 As shown, reflection occurs on both sides of the windshield, both forming virtual images and causing ghosting problems, affecting driving safety.

[0004] In the prior art, a reflective film is attached to the inside of the windshield to increase the reflectivity, thereby improving energy utilization and brightness, so that the light emitted by the image source can be clear, but the problem of ghosting cannot be solved. Moreover, when the reflectivity of the reflective film is too high, the energy transmitted by the actual object will be reduced, making it impossible for the light beam of the external object to enter the human eye normally. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a method for manufacturing a head-up display reflective film that can avoid ghosting and ensure that the light beams of external objects and the light of the image source inside the vehicle can effectively reach the human eye.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] A method for manufacturing a head-up display reflective film comprises the following steps:

[0008] Preparation of a reflective layer: cleaning a glass substrate, spin coating SD1 on the surface of the glass substrate as an alignment layer of the substrate, aligning SD1 with ultraviolet light, spin coating a first liquid crystal layer on the alignment layer to form a reflective layer, controlling the thickness of the first liquid crystal layer by the thickness during spin coating, and controlling the longitudinal period of the layer by the concentration of chiral molecule doping;

[0009] Calculate the compensation layer parameters: circularly polarized light is incident on the reflective layer, and the polarization state of the light beam after passing through the reflective layer is The polarization state is The polarization state of the light after passing through the compensation layer is A s1 , A s2 is the strength in the S direction, A p1 , A p2 is the intensity in the P direction, is the phase difference between the S direction and the P direction, the polarization state It can be obtained by measuring the polarization state A is calculated based on the rigorous coupled wave method. s2 is the function distribution A related to R and α s2 (R, α), R is the delay, α is the direction of the optical axis, traverse R and α, where the traversal range of R is 0 to λ, λ is the wavelength of the incident light, and the traversal range of α is 0 to 180 degrees, and find A s2 The values ​​corresponding to R and α at the minimum are the design parameters of the compensation layer;

[0010] Preparation of compensation layer: cleaning the glass substrate, spin coating SD1 on the surface of the glass substrate as the alignment layer of the substrate, aligning SD1 with ultraviolet light, spin coating a second liquid crystal layer on the alignment layer to form a compensation layer, the thickness of the second liquid crystal layer Z = R / △n, △n is the refractive index difference of the liquid crystal material; the optical axis direction α of the compensation layer is controlled by the polarization direction of the ultraviolet light when SD1 is exposed;

[0011] Forming a head-up display reflective film: the reflective layer and the compensation layer are transferred from the glass substrate respectively, and the alignment layer SD1 is washed off, and finally the compensation layer is pasted on the OCA glue with a protective film in the order of the compensation layer at the bottom and the reflective layer at the top.

[0012] Furthermore, in the step of preparing the compensation layer, the thickness of the second liquid crystal layer is controlled by controlling the rotation speed during spin coating, and the relationship between Z and the rotation speed during spin coating is a monotonically decreasing relationship, that is, the faster the rotation speed, the thinner the thickness, and the slower the rotation speed, the thicker the thickness.

[0013] Furthermore, in the step of preparing the compensation layer, the second liquid crystal layer material is not doped with chirped molecules.

[0014] Furthermore, in both the steps of preparing the reflective layer and the steps of preparing the compensation layer, the cleaned glass substrate needs to be heated to remove the chiral agent on the surface of the glass substrate.

[0015] Furthermore, in the steps of preparing the reflective layer and the compensation layer, the glass substrate is cleaned in sequence by glass cleaning agent, water, alcohol and water, and each cleaning is performed by an ultrasonic cleaning machine.

[0016] Furthermore, after each cleaning, the residual substances were rinsed off with deionized water.

[0017] Furthermore, in the step of forming a reflective film, transferring the reflective layer from the glass substrate is specifically performed by sticking an optical adhesive with a protective film on the liquid crystal film, and then tearing off the protective film, the optical adhesive, the reflective layer, and the alignment layer from the glass substrate.

[0018] Furthermore, in the step of forming the reflective film, transferring the compensation layer from the glass substrate is specifically performed by sticking an optical adhesive with a protective film on the liquid crystal film, and then tearing off the protective film, the optical adhesive, the compensation layer, and the alignment layer from the glass substrate.

[0019] Furthermore, in the step of forming the head-up display reflective film, the head-up display reflective film includes a protective film, an optical adhesive, the reflective layer, the compensation layer, the optical adhesive and a protective film which are arranged in sequence.

[0020] Compared with the prior art, the head-up display reflective film manufacturing method of the present invention includes the steps of preparing a reflective layer, calculating compensation layer parameters, preparing a compensation layer, and forming a head-up display reflective film. The manufactured head-up display reflective film reflects the light beam generated by the display device in the vehicle that is incident at the Brewster angle, thereby reducing the energy of the light beam that forms the ghost image and eliminating the ghost image. For the natural light outside the vehicle, only P-polarized light close to the working wavelength of the display device is reflected, and natural light of other wavelengths and polarization directions is transmitted, so that the head-up display reflective film has both high reflectivity and high transmittance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a light path diagram of the head-up display in the background technology;

[0022] Figure 2 It is a light path diagram produced by ghosting in the background technology;

[0023] Figure 3 It is a schematic diagram of ghosting in the background technology;

[0024] Figure 4 This is a flow chart of the manufacturing method of the head-up display reflective film of the present application;

[0025] Figure 5 This is a process diagram of the head-up display reflective film manufacturing method of this application;

[0026] Figure 6 Schematic diagram of the change of polarization state when light passes through the compensation layer;

[0027] Figure 7 This is a light path diagram when the head-up display reflective film is used in this application;

[0028] Figure 8 This is a rendering of the head-up display reflective film manufacturing method of this application.

[0029] In the figure: 10, windshield; 21, compensation layer; 22, reflection layer. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be another intermediate component through which it is fixed. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0033] See also Figure 4 as well as Figure 5 The present application provides a method for manufacturing a head-up display reflective film, comprising the following steps:

[0034] Preparation of the reflective layer 22: cleaning the glass substrate, spin coating SD1 on the surface of the glass substrate as an alignment layer of the substrate, and aligning SD1 with ultraviolet light, spin coating the first liquid crystal layer on the alignment layer to form the reflective layer 22, controlling the thickness of the first liquid crystal layer by the thickness during spin coating, and controlling the longitudinal period of the layer by the concentration of chiral molecule doping;

[0035] Calculate the parameters of the compensation layer 21: circularly polarized light enters the reflective layer 22, and the polarization state of the light beam after passing through the reflective layer 22 is The polarization state is After the light passes through the compensation layer 21, the polarization state is A s1 , A s2 is the strength in the S direction, A p1 , A p2 is the intensity in the P direction, is the phase difference between the S direction and the P direction, the polarization state It can be obtained by measuring the polarization state A is calculated based on the rigorous coupled wave method. s2 is the function distribution A related to R and α s2 (R, α), R is the delay, α is the direction of the optical axis, traverse R and α, where the traversal range of R is 0 to λ, λ is the wavelength of the incident light, and the traversal range of α is 0 to 180 degrees, and find A s2 The values ​​corresponding to R and α at the minimum are the design parameters of the compensation layer;

[0036] Preparation of compensation layer 21: cleaning the glass substrate, spin coating SD1 on the surface of the glass substrate as an alignment layer of the substrate, aligning SD1 with ultraviolet light, spin coating a second liquid crystal layer on the alignment layer to form compensation layer 21, the thickness of the second liquid crystal layer Z = R / △n, △n is the refractive index difference of the liquid crystal material; the optical axis direction α of the compensation layer is controlled by the polarization direction of the ultraviolet light when SD1 is exposed;

[0037] Forming a head-up display reflective film: the reflective layer 22 and the compensation layer 21 are transferred from the glass substrate respectively, and the alignment layer SD1 is washed off, and finally the compensation layer is pasted on the OCA glue with a protective film in the order of the compensation layer at the bottom and the reflective layer at the top.

[0038] Specifically, in the step of preparing the reflective layer 22, the glass substrate is cleaned with a glass cleaning agent, water, alcohol, and water in turn, and each cleaning is performed by an ultrasonic cleaning machine. After each cleaning, deionized water is used to rinse off residual substances. The cleaned glass substrate is heated to remove the chiral agent on the surface of the glass substrate. Specifically, the glass substrate is heated at 90-110°C for 0.5-1.5h. In this embodiment, the glass substrate is placed on a heating table and heated at 100°C for 1h. SD1 is colored, so SD1 needs to be removed in subsequent steps.

[0039] Please continue reading Figure 6 In the step of calculating the parameters of the compensation layer 21, the polarization state of the light beam after passing through the reflective layer 22 is polarization state 1, which can be measured by an ellipsometer, and the intensity A of the polarized light in the S direction and the P direction is s1 and A p1 , and the phase difference between the two The above three values ​​can be obtained by measuring the beam after the beam is emitted by an ellipsometer. The polarization state 1 can be described by the Jones vector as Its polarization state after passing through the compensation layer 21 is polarization state 2, which can be described as The properties of the compensation layer 21 are mainly determined by the delay amount and the direction of the optical axis. The delay amount is the optical path difference between a light beam polarized along the direction of the optical axis and a light beam polarized perpendicular to the direction of the light beam after passing through the wave plate, which is represented by R. The direction of the optical axis is represented by the angle α with the X-axis.

[0040] Designing a reflective layer to eliminate ghosting is actually to design the delay R and the optical axis direction α so that the intensity of the polarized light in the S direction is basically 0. Since the light beam is not incident vertically but at an angle α, we calculate the polarization state after the beam is emitted based on the strict coupled wave method. The polarization state 1 obtained by the measurement is calculated based on the polarization state 1 after passing through the wave plate with a phase delay of R and an angle α between the optical axis and the X axis. Then the intensity of the polarized light in the S direction is A s2 is the function distribution A related to R and α s2 (R, α), traverse R and α by computer, where the traversal range of R is 0 to λ, λ is the wavelength of the incident light, and the traversal range of α is 0 to 180 degrees, and find A s2 The values ​​corresponding to R and α when they are minimum are the design parameters of the compensation layer.

[0041] In the step of preparing the compensation layer 21, the glass substrate is cleaned with a glass cleaning agent, water, alcohol and water in turn, and each cleaning is performed by an ultrasonic cleaning machine. After each cleaning, deionized water is used to rinse off residual substances. The cleaned glass substrate is heated to remove the chiral agent on the surface of the glass substrate. Specifically, the glass substrate is heated at 90-110°C for 0.5-1.5h. In this embodiment, the glass substrate is placed on a heating table and heated at 100°C for 1h. The direction of the bottom layer of the liquid crystal director is determined by ultraviolet exposure on the glass substrate, and then the liquid crystal is spin-coated to form the compensation layer 21. The thickness of the liquid crystal layer is controlled by the thickness during spin coating. The liquid crystal material is not doped with chiral molecules. Therefore, during the process of self-assembly of the liquid crystal, the liquid crystal director of the upper layer will be consistent with the liquid crystal director of the next layer. The delay amount R is controlled by the thickness Z of the liquid crystal layer and the refractive index difference △n of the liquid crystal material. After using a certain liquid crystal material, the refractive index difference △n of the liquid crystal material at a certain wavelength is a certain value, Z=R / △n. The relationship between Z and the rotation speed during spin coating is a monotonically decreasing relationship. The faster the rotation speed, the thinner the thickness, and the slower the rotation speed, the thicker the thickness. The direction of the optical axis α is determined by the polarization direction of the ultraviolet light during exposure. The polarization direction of the bottom layer of liquid crystal director tends to be consistent with the linear polarization direction of the light beam during the exposure link. Therefore, the polarization direction of the compensation layer can be controlled by controlling the linear polarization direction during the exposure link.

[0042] In the step of forming the reflective film, the reflective layer 21 is transferred from the glass substrate by affixing an optical adhesive with a protective film on the liquid crystal film, and then peeling off the protective film, the optical adhesive, the reflective layer 21, and the alignment layer from the glass substrate. The compensation layer 22 is transferred from the glass substrate by affixing an optical adhesive with a protective film on the liquid crystal film, and then peeling off the protective film, the optical adhesive, the compensation layer 22, and the alignment layer from the glass substrate. The head-up display reflective film includes a protective film, an optical adhesive, a reflective layer 21, a compensation layer 22, an optical adhesive, and a protective film arranged in sequence.

[0043] As attached Figure 7 As shown, when the head-up display reflective film is used, the protective film on the side of the head-up display reflective film close to the compensation layer 22 is torn off, and the head-up display reflective film is attached to the inner side of the windshield 10. The display device set in the car is connected to the car control system to obtain the driving parameters of the car, which include information such as vehicle speed, time, gear position, weather, etc. The display device emits the driving parameters in the form of left-handed circularly polarized light.

[0044] When the left-handed circularly polarized light emitted by the display device (image source) enters the windshield 10 at the Brewster angle (56 degrees), the light beam first enters the reflective layer 22. Since the rotation direction of the light beam is the same as the rotation direction of the longitudinal period of the reflective layer 22, about 80% of the energy will be reflected and enter the human eye, and the remaining 20% ​​of the energy will pass through the compensation layer 21 and then enter the interface between the windshield 10 and the air. By controlling the compensation layer 21, the polarization state of the light beam after passing through the compensation layer 21 can be made P polarization. Due to the existence of the Brewster angle, the P-polarized circularly polarized light can completely pass through the windshield 10 without being reflected, so no ghosting will be generated.

[0045] Since the director of the reflective layer 22 forms a spiral structure in the longitudinal direction, the spiral liquid crystal director distribution has two properties. One property is wavelength selectivity. The center position of the wavelength that can be reflected is located near λ, λ=nP cos(θ), where n is the average refractive index of the liquid crystal light, P is the pitch of the spiral liquid crystal, and θ is the propagation angle in the liquid crystal. It has no reaction to other wavelengths. The other property is circular polarization selectivity, which only works on circularly polarized light of one rotation direction. The natural light outside the car is not polarized. After passing through the compensation layer 21, it can be regarded as 50% left-handed circularly polarized light and 50% right-handed circularly polarized light. The left-handed circularly polarized light has the opposite rotation direction to the reflective layer 22 and passes almost completely, while the right-handed circularly polarized light is inevitably reflected, but it is also only reflected near λ, not the entire visible light spectrum range. The light beam generated by the image source is all left-handed circularly polarized light, which can be reflected with a high reflectivity. The high reflectivity film reflects only the right-handed circularly polarized light that is close to the working wavelength of the image source after passing through the compensation layer 21, and transmits the natural light of other wavelengths and polarization directions, thereby avoiding the compatibility problem between high reflectivity and high transmittance. The effect is as follows: Figure 8 shown.

[0046] Compared with the prior art, the head-up display reflective film manufacturing method of the present invention includes the steps of preparing a reflective layer, calculating compensation layer parameters, preparing a compensation layer, and forming a head-up display reflective film. The manufactured head-up display reflective film reflects the light beam generated by the display device in the vehicle that is incident at the Brewster angle, thereby reducing the energy of the light beam that forms the ghost image and eliminating the ghost image. For the natural light outside the vehicle, only P-polarized light close to the working wavelength of the display device is reflected, and natural light of other wavelengths and polarization directions is transmitted, so that the head-up display reflective film has both high reflectivity and high transmittance.

[0047] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which are equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of them belong to the protection scope of the present invention.

Claims

1. A method for manufacturing a head-up display reflective film, characterized in that: The following steps are involved: Preparation of a reflective layer: cleaning a glass substrate, spin coating SD1 on the surface of the glass substrate as an alignment layer of the substrate, aligning SD1 with ultraviolet light, spin coating a first liquid crystal layer on the alignment layer to form a reflective layer, controlling the thickness of the first liquid crystal layer by the thickness during spin coating, and controlling the longitudinal period of the layer by the concentration of chiral molecule doping; Calculate the compensation layer parameters: circularly polarized light is incident on the reflective layer, and the polarization state of the light beam after passing through the reflective layer is The polarization state is The polarization state of the light after passing through the compensation layer is A s1 , A s2 is the strength in the S direction, A p1 , A p2 is the intensity in the P direction, is the phase difference between the S direction and the P direction, the polarization state It can be obtained by measuring the polarization state A is calculated based on the rigorous coupled wave method. s2 is the function distribution A related to R and α s2 (R, α), R is the delay, α is the direction of the optical axis, traverse R and α, where the traversal range of R is 0 to λ, λ is the wavelength of the incident light, and the traversal range of α is 0 to 180 degrees, and find A s2 The values ​​corresponding to R and α at the minimum are the design parameters of the compensation layer; Preparation of compensation layer: cleaning the glass substrate, spin coating SD1 on the surface of the glass substrate as the alignment layer of the substrate, aligning SD1 with ultraviolet light, spin coating a second liquid crystal layer on the alignment layer to form a compensation layer, the thickness of the second liquid crystal layer Z = R / △n, △n is the refractive index difference of the liquid crystal material; The optical axis direction α of the compensation layer is controlled by the polarization direction of the ultraviolet light during exposure to SD1; Forming a head-up display reflective film: the reflective layer and the compensation layer are transferred from the glass substrate respectively, and the alignment layer SD1 is washed off, and finally the compensation layer is pasted on the OCA glue with a protective film in the order of the compensation layer at the bottom and the reflective layer at the top.

2. The method for manufacturing a head-up display reflective film according to claim 1, characterized in that: In the step of preparing the compensation layer, the thickness of the second liquid crystal layer is controlled by controlling the rotation speed during spin coating, and the relationship between Z and the rotation speed during spin coating is a monotonically decreasing relationship. The faster the rotation speed, the thinner the thickness, and the slower the rotation speed, the thicker the thickness.

3. The method for manufacturing a head-up display reflective film according to claim 1, characterized in that: In the step of preparing the compensation layer, the second liquid crystal layer material is not doped with chirped molecules.

4. The method for manufacturing a head-up display reflective film according to claim 1, characterized in that: In both the steps of preparing the reflective layer and the steps of preparing the compensation layer, the cleaned glass substrate needs to be heated to remove the chiral agent on the surface of the glass substrate.

5. The method for manufacturing a head-up display reflective film according to claim 1, characterized in that: In the steps of preparing the reflective layer and the steps of preparing the compensation layer, the glass substrate is cleaned in sequence by glass cleaning agent, water, alcohol and water, and each cleaning is performed by an ultrasonic cleaning machine.

6. The method for manufacturing a head-up display reflective film according to claim 5, characterized in that: Rinse with deionized water to remove any residual material after each cleaning.

7. The method for manufacturing a head-up display reflective film according to claim 1, characterized in that: In the step of forming the reflective film, transferring the reflective layer from the glass substrate is specifically performed by sticking an optical adhesive with a protective film on the liquid crystal film, and then tearing off the protective film, the optical adhesive, the reflective layer, and the alignment layer from the glass substrate.

8. The method for manufacturing a head-up display reflective film according to claim 1, characterized in that: In the step of forming the reflective film, transferring the compensation layer from the glass substrate is specifically performed by sticking an optical adhesive with a protective film on the liquid crystal film, and then tearing off the protective film, the optical adhesive, the compensation layer, and the alignment layer from the glass substrate.

9. The method for manufacturing a head-up display reflective film according to claim 1, characterized in that: In the step of forming the head-up display reflective film, the head-up display reflective film includes a protective film, an optical adhesive, the reflective layer, the compensation layer, the optical adhesive and a protective film which are arranged in sequence.

Images