A head-up display reflection film manufacturing method

Abstract

The application discloses a head-up display reflection film manufacturing method, and belongs to the field of vehicle display. The head-up display reflection film is manufactured through the steps of preparing a reflection layer, calculating compensation layer parameters, preparing a compensation layer, and forming a head-up display reflection film, etc. The head-up display reflection film reflects the light beam generated by the display device which is incident at Brewster's angle in the vehicle, so that the light beam energy forming ghost image is small, and the ghost image is eliminated. The head-up display reflection film only reflects right-handed circularly polarized light with a wavelength close to the working wavelength of the display device for the outside natural light, and transmits the natural light with other wavelengths and polarization directions, so that the head-up display reflection film has high reflectivity and high transmittance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle display, in particular to a head-up display reflection film manufacturing method. BACKGROUND

[0002] The automobile head-up display device (HUD) is a visual auxiliary driving system, which can provide key auxiliary driving information for the driver, and project the driving information into a virtual image displayed at a certain distance in front of the driver, so that the driver can obtain the speed, fuel, real-time navigation and other information in the state of looking straight ahead, thereby avoiding the blind area time caused by the driver looking down to check the driving information, reducing the potential traffic accidents, and ensuring the driving safety.

[0003] The existing head-up display device, when in use, as shown in Figure 1 , point A is the image source, and the light beam emitted by the image source enters the human eye after being reflected by the windshield to form 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, as shown in Figure 2 and Figure 3 , the reflection occurs on the front and back sides of the windshield, both of which form a virtual image, resulting in ghosting problem, which affects the safety of driving.

[0004] In the prior art, a reflection film is attached to the inner side of the windshield to increase the reflectivity, so as to improve the energy utilization rate and brightness, so that the light emitted by the image source can be clear, but the ghosting problem cannot be solved. When the reflectivity of the reflection film is too high, the energy transmitted by the actual object will be reduced, so that the light beam of the object in the outside world cannot normally enter the human eye. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, one of the purposes of the present application is to provide a head-up display reflection film manufacturing method which can avoid ghosting and effectively make the light beams of the objects in the outside world and the light beams of the image sources in the vehicle reach the human eye.

[0006] One of the purposes of the present application is achieved by adopting the following technical solutions:

[0007] A head-up display reflection film manufacturing method, comprising the following steps:

[0008] Preparation of a reflection layer: the glass substrate is cleaned, SDI is spin-coated on the surface of the glass substrate as an alignment layer of the substrate, and the SDI is aligned by ultraviolet light. A first liquid crystal layer is formed on the alignment layer by spin coating, the thickness of the first liquid crystal layer is controlled by the thickness during spin coating, and the longitudinal period of the layer is controlled by the concentration of chiral molecule doping.

[0009] Calculate the compensation layer parameters: When circularly polarized light is incident on the reflective layer, the polarization state of the light beam after passing through the reflective layer is... polarization state is The polarization state of the light after passing through the compensation layer is A s1 A s2 Let A be the intensity in the S direction. p1 A p2 The intensity is in the P direction. The phase difference between the S and P directions, polarization state The polarization state can be obtained through measurement. A was obtained through calculations based on the rigorous coupled-wave method. s2 The function distribution A is related to R and α. s2 (R, α), where R is the delay and α is the optical axis direction. The search iterates through R and α, where R ranges from 0 to λ, where λ is the wavelength of the incident light, and α ranges from 0 to 180 degrees, to find A. s2 The values ​​of R and α at their minimum are the design parameters of the compensation layer;

[0010] Preparation of compensation layer: The glass substrate is cleaned, and SDI is spin-coated on the surface of the glass substrate as the alignment layer of the substrate. The SDI is aligned with ultraviolet light. A second liquid crystal layer is spin-coated on the alignment layer to form a compensation layer. The thickness of the second liquid crystal layer is Z = R / Δn, where Δn 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 SDI exposure.

[0011] Forming the head-up display reflective film: The reflective layer and the compensation layer are transferred from the glass substrate respectively, and the alignment layer SDI is washed off. Finally, they are pasted onto the OCA adhesive with the protective film in the order of compensation layer at the bottom and 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. 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.

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

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

[0015] Further, in the steps of preparing the reflection layer and preparing the compensation layer, the glass substrate is sequentially cleaned by glass cleaning agent, water, alcohol and water, and each cleaning is performed by an ultrasonic cleaner.

[0016] Further, after each cleaning, the residual substances are washed away by deionized water.

[0017] Further, in the step of forming the reflection film, the reflection layer is transferred from the glass substrate by: pasting the optical adhesive with the protective film on the liquid crystal film, and then tearing the protective film, the optical adhesive, the reflection layer and the alignment layer from the glass substrate.

[0018] Further, in the step of forming the reflection film, the compensation layer is transferred from the glass substrate by: pasting the optical adhesive with the protective film on the liquid crystal film, and then tearing the protective film, the optical adhesive, the compensation layer and the alignment layer from the glass substrate.

[0019] Further, in the step of forming the head-up display reflection film, the head-up display reflection film comprises the protective film, the optical adhesive, the reflection layer, the compensation layer, the optical adhesive and the protective film arranged in sequence.

[0020] Compared with the prior art, the head-up display reflection film manufacturing method of the present application comprises the steps of preparing the reflection layer, calculating the compensation layer parameters, preparing the compensation layer and forming the head-up display reflection film, so that the head-up display reflection film manufactured by the method reflects the light beam generated by the display device at the Brewster angle in the vehicle, reduces the light beam energy forming ghosting, and eliminates the ghosting; and only reflects the P-polarized light close to the working wavelength of the display device for the natural light outside the vehicle, and transmits the natural light of other wavelengths and polarization directions, so that the head-up display reflection film has high reflectivity and high transmittance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The optical path diagram of the head-up display in the background art;

[0022] Figure 2 The optical path diagram of the ghosting generation in the background art;

[0023] Figure 3 The ghosting schematic diagram in the background art;

[0024] Figure 4 The flowchart of the head-up display reflection film manufacturing method of the present application;

[0025] Figure 5 The process diagram of the head-up display reflection film manufacturing method of the present application;

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

[0027] Figure 7 A light path diagram for the head-up display reflective film of the present application;

[0028] Figure 8 An effect diagram for the head-up display reflective film manufacturing method of the present application.

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

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0031] It should be noted that when a component is referred to as being "fixed" to another component, it can be directly on the other component or can be fixed thereto through another intermediate component. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or can be connected thereto through another intermediate component. When a component is referred to as being "provided on" another component, it can be directly provided on the other component or can be provided thereon through another intermediate component. The terms "vertical", "horizontal", "left", "right", and the like used herein are for illustrative purposes only.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] Referring to Figure 4 and Figure 5 The head-up display reflective film manufacturing method of the present application comprises the following steps:

[0034] Preparation of the reflective layer 22: the glass substrate is cleaned, SDI is spin-coated on the surface of the glass substrate as the alignment layer of the substrate, and the SDI is aligned by ultraviolet light, the first liquid crystal layer is spin-coated on the alignment layer to form the reflective layer 22, the thickness of the first liquid crystal layer is controlled by the thickness during the spin-coating, and the longitudinal period of the layer is controlled by the concentration of the chiral molecule doping;

[0035] Calculation of the compensation layer 21 parameters: the circularly polarized light is incident on the reflective layer 22, and the polarization state of the light beam after passing through the reflective layer 22 is The polarization state of the light is The polarization state of the light is A s1 , A s2 is the intensity of the S direction, A p1 , A p2 is the intensity of the P direction, is the phase difference between the S direction and the P direction, the polarization state can be obtained by measurement, and the measured polarization state passes through the compensation layer 21, and A s2 is calculated based on the rigorous coupled wave method, A s2 (R, a) is a function distribution related to R and a, R is the retardation, a is the optical axis direction, and a is traversed R and a, wherein the traversal range of R is 0 to λ, λ is the wavelength of the incident light, and the traversal range of a is 0 to 180 degrees, and the value corresponding to R and a when A s2 is the smallest is the design parameter of the compensation layer;

[0036] The compensation layer 21 is prepared: the glass substrate is cleaned, SDI is spin-coated on the surface of the glass substrate as the alignment layer of the substrate, and the SDI is aligned by ultraviolet light, and the second liquid crystal layer is spin-coated on the alignment layer to form the compensation layer 21, the thickness Z of the second liquid crystal layer is R / △n, and △n is the refractive index difference of the liquid crystal material; the optical axis direction a of the compensation layer is controlled by the polarization direction of the ultraviolet light when the SDI is exposed;

[0037] The head-up display reflective film is formed: the reflective layer 22 and the compensation layer 21 are respectively transferred from the glass substrate, and the alignment layer SDI is washed away, and finally pasted on the OCA glue with a protective film in the order of compensation layer below and reflective layer above.

[0038] Specifically, in the step of preparing the reflective layer 22, the glass substrate is sequentially cleaned by glass cleaning agent, water, alcohol and water, and each cleaning is carried out by an ultrasonic cleaning machine. After each cleaning, the residual substances are washed away with deionized water. 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 at 100°C for 1h. The SDI has color, so the SDI needs to be removed in the subsequent steps.

[0039] Please continue to refer to Figure 6 , in the step of calculating the parameters of the compensation layer 21, the polarization state of the light beam passing through the reflective layer 22 is polarization state 1, which can be measured by an ellipsometer, and the intensity of the polarized light A s1 and A p1 , and the phase difference The three values above can be obtained by measuring the light beam after the beam exits the ellipsometer. The polarization state 1 can be described by a Jones vector as The 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 retardation and the direction of the optical axis. The retardation is the optical path difference between the light beam polarized along the direction of the optical axis and the light beam polarized perpendicular to the direction of the optical axis after passing through the wave plate, which is represented by R. The direction of the optical axis is represented by the angle a with the X axis.

[0040] The design of the reflective layer to eliminate ghosting is actually to design the retardation R and the direction of the optical axis a so that the intensity of the S direction polarized light is substantially 0. Since the light beam is not perpendicular to the incident, but is incident at an angle a, we calculate the polarization state after the exit based on the rigorous coupled wave method. The polarization state 1 is obtained by measurement, and the polarization state 2 after the wave plate with a phase retardation of R and an angle a of the optical axis direction with the X axis is calculated. Then the intensity A of the S direction polarized light s2 is a function of R and a distribution A s2 (R, a), which is calculated by computer traversal of R and a, where the traversal range of R is 0 to l, and the traversal range of a is 0 to 180 degrees. Find the value of R and a corresponding to the minimum A s2 The design parameters of the compensation layer are obtained.

[0041] In the preparation of the compensation layer 21, the glass substrate is sequentially cleaned by glass cleaning agent, water, alcohol and water, and each cleaning is performed by an ultrasonic cleaning machine. After each cleaning, the residual substances are washed away with deionized water. 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 at 100°C for 1h. The direction of the liquid crystal director of the bottom layer is determined by ultraviolet exposure on the glass substrate, and then the compensation layer 21 is formed by spin coating liquid crystal. The thickness of the liquid crystal layer is controlled by the thickness during spin coating, and the liquid crystal material is not doped with chiral molecules, so the liquid crystal director of the previous layer is consistent with the liquid crystal director of the layer. The retardation R is controlled by the thickness Z of the liquid crystal layer and the refractive index difference An of the liquid crystal material. After using a certain liquid crystal material, the refractive index difference An of the liquid crystal material at a certain wavelength is a certain value, and Z = R / An. The relationship between Z and the rotation speed during spin coating is a monotonic 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 a is determined by the polarization direction of the ultraviolet light during exposure. The polarization direction of the lowermost liquid crystal director tends to be consistent with the linear polarization direction of the light beam during the exposure link, so the polarization direction of the compensation layer can be controlled by controlling the linear polarization direction during the exposure link.

[0042] In the forming reflective film step, the reflective layer 21 is transferred from the glass substrate by: pasting the optical adhesive with the protective film on the liquid crystal film, and then tearing 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: pasting the optical adhesive with the protective film on the liquid crystal film, and then tearing the protective film, the optical adhesive, the compensation layer 22 and the alignment layer from the glass substrate. The head-up display reflective film comprises the protective film, the optical adhesive, the reflective layer 21, the compensation layer 22, the optical adhesive and the protective film arranged in sequence.

[0043] As shown in the accompanying drawings, when the head-up display reflective film is used, the protective film on the side close to the compensation layer 22 of the head-up display reflective film is torn off, and the head-up display reflective film is pasted on the inner side of the windshield 10. The display device arranged in the vehicle is connected to the automobile control system to obtain the driving parameters of the automobile, including the speed, time, gear, weather and other information. The display device emits the driving parameters in the form of left-handed circularly polarized light. Figure 7

[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 handedness of the light beam is the same as the handedness of the longitudinal period of the reflective layer 22, about 80% of the energy is reflected into the human eye, and the remaining 20% of the energy is emitted into the interface between the windshield 10 and the air after passing through the compensation layer 21. By controlling the compensation layer 21, the polarization state of the light beam after passing through the compensation layer 21 can be P-polarization. Due to the existence of the Brewster angle, the P-polarized circularly polarized light can completely pass through the windshield 10 without reflection, so no ghosting occurs.

[0045] Since the director of the reflective layer 22 has a spiral structure in the longitudinal direction, the spiral liquid crystal director distribution has two properties. One property is wavelength selectivity, which can reflect the wavelength center position near λ, 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. The other property is circular polarization selectivity, which only works on circularly polarized light of one handedness. The natural light outside the vehicle has no polarization, and after passing through the compensation layer 21, it can be considered as 50% left-handed circularly polarized light and 50% right-handed circularly polarized light. The left-handed circularly polarized light, which is opposite in handedness to the reflective layer 22, is almost completely transmitted, while the right-handed circularly polarized light is inevitably reflected, but only near λ, not the entire visible light spectrum. The light beam emitted by the image source is all left-handed circularly polarized light, which can be reflected with high reflectivity. The high reflectivity film only reflects the right-handed circularly polarized light close to the wavelength of the image source after passing through the compensation layer 21, and transmits other wavelengths and polarization directions of natural light, thus avoiding the compatibility problem of high reflectivity and high transmittance. The effect is as follows:​Figure 8 As shown.

[0046] Compared with the prior art, the head-up display reflection film manufacturing method of the present application is prepared by preparing a reflection layer, calculating compensation layer parameters, preparing a compensation layer, and forming a head-up display reflection film, etc. The head-up display reflection film manufactured by the method reflects the light beam generated by the display device incident at Brewster's angle in the vehicle, reduces the light beam energy forming ghost images, and eliminates ghost images. For the natural light outside the vehicle, only the P-polarized light close to the working wavelength of the display device is reflected, and the natural light of other wavelengths and polarization directions is transmitted, so that the head-up display reflection film has high reflectivity and high transmittance.

[0047] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are equivalent modifications and evolutions of the above examples according to the essential technology of the present application, and these are within the protection scope of the present application.

Claims

1. A method for manufacturing a head-up display reflective film, characterized in that, Includes the following steps: Preparation of reflective layer: The glass substrate is cleaned, SDI is spin-coated on the surface of the glass substrate as the alignment layer of the substrate, and the SDI is aligned with ultraviolet light. A first liquid crystal layer is spin-coated on the alignment layer to form a reflective layer. The thickness of the first liquid crystal layer is controlled by the thickness during spin-coating, and the longitudinal period of the layer is controlled by the concentration of chiral molecule doping. Calculate the compensation layer parameters: When circularly polarized light is incident on the reflective layer, the polarization state of the light beam after passing through the reflective layer is... polarization state is The polarization state of the light after passing through the compensation layer is A s1 A s2 Let A be the intensity in the S direction. p1 A p2 The intensity is in the P direction. The phase difference between the S and P directions, polarization state The polarization state can be obtained through measurement. A was obtained through calculations based on the rigorous coupled-wave method. s2 The function distribution A is related to R and α. s2 (R, α), where R is the delay and α is the optical axis direction. The search iterates through R and α, where R ranges from 0 to λ, where λ is the wavelength of the incident light, and α ranges from 0 to 180 degrees, to find A. s2 The values ​​of R and α at their minimum are the design parameters of the compensation layer; Preparation of compensation layer: The glass substrate is cleaned, SDI is spin-coated on the surface of the glass substrate as the alignment layer of the substrate, and the SDI is aligned with ultraviolet light. A second liquid crystal layer is spin-coated on the alignment layer to form a compensation layer. The second liquid crystal layer material does not contain chiral molecules, and the thickness of the second liquid crystal layer is Z = R / Δn, where Δn 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 SDI exposure; Forming the head-up display reflective film: The reflective layer and the compensation layer are transferred from the glass substrate respectively, and the alignment layer SDI is washed off. Finally, they are pasted onto the OCA adhesive with the protective film in the order of compensation layer at the bottom and 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. 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 both the preparation of the reflective layer and the preparation of the compensation layer, the cleaned glass substrate needs to be heated to remove the chiral agent from the surface of the glass substrate.

4. 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 compensation layer, the glass substrate is cleaned sequentially with glass cleaner, water, alcohol and water, and each cleaning is performed by an ultrasonic cleaner.

5. The method for manufacturing a head-up display reflective film according to claim 4, characterized in that: Rinse off any residue with deionized water after each cleaning.

6. 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 process of transferring the reflective layer from the glass substrate specifically involves: applying an optical adhesive with a protective film onto the liquid crystal film, and then peeling the protective film, optical adhesive, reflective layer, and alignment layer off the glass substrate.

7. 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 transfer of the compensation layer from the glass substrate specifically involves: applying an optical adhesive with a protective film onto the liquid crystal film, and then peeling off the protective film, optical adhesive, compensation layer, and 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 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 the protective film arranged sequentially.

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