A reflection film for vehicle and display structure for eliminating ghost

Abstract

This invention discloses a reflective film for automotive applications and a display structure for eliminating ghosting, belonging to the field of automotive displays. It includes a first liquid crystal layer and a second liquid crystal layer. The first liquid crystal layer has a direction pointing in the same direction and a thickness of 1 / 4 waveplate. The second liquid crystal layer is a reflective layer with a spiral structure in the longitudinal direction. The first liquid crystal layer is bonded to the windshield. The reflective film reflects the light beam generated by the display device incident at Brewster's angle inside the vehicle, reducing the energy of the beam that causes ghosting and eliminating it. For natural light from outside the vehicle, it only reflects P-polarized light with a wavelength close to that of the display device, while allowing other wavelengths and polarization directions of natural light to pass through, giving the automotive reflective film both high reflectivity and high transmittance.

Description

Technical Field

[0001] This invention relates to the field of automotive displays, and more particularly to automotive reflective films for eliminating ghosting. Background Technology

[0002] A head-up display (HUD) is a vision-assisted driving system that provides drivers with crucial driving assistance information. It projects driving information as a virtual image and displays it at a certain distance in front of the driver, allowing the driver to obtain information such as vehicle speed, fuel level, and real-time navigation while looking at the road. This avoids blind spot time caused by the driver looking down to check driving information, reduces potential traffic accidents, and ensures driving safety.

[0003] Existing head-up display devices, when in use, such as Figure 1 As shown, point A is the image source. The emitted light beam, after being reflected by the windshield, enters the human eye, forming a virtual image. Simultaneously, light beams emitted by actual objects in the outside world can also enter the human eye, forming a real image, thus achieving an augmented reality display effect. Because the reflectivity of the air-glass interface is low, approximately 10%, only about 10% of the light beam energy emitted by the image source reaches the human eye, resulting in low energy utilization and limited brightness; simultaneously... Figure 2 as well as Figure 3 As shown, the reflection occurs on both the front and rear sides of the windshield, creating a virtual image and causing ghosting, which affects driving safety.

[0004] In existing technologies, reflective films are applied to the inside of windshields to increase reflectivity, thereby improving energy efficiency and brightness, making the light emitted from the image source clear. However, this cannot solve the problem of ghosting. Furthermore, when the reflective film has too high a reflectivity, it will reduce the energy transmitted by actual objects, preventing the light beams from external objects from entering the human eye normally. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, one of the objectives of the present invention is to provide a vehicle reflective film that can avoid ghosting and effectively reach the human eye from both light beams from external objects and light from in-vehicle image sources.

[0006] In order to overcome the shortcomings of the prior art, the second objective of the present invention is to provide a display structure that can avoid ghosting and ensure that the light beams from external objects and the light from the in-vehicle image source can effectively reach the human eye.

[0007] One of the objectives of this invention is achieved through the following technical solution:

[0008] A reflective film for eliminating ghosting in automobiles includes a first liquid crystal layer and a second liquid crystal layer. The first liquid crystal layer has a direction pointing in the same direction and a thickness of 1 / 4 wave plate. The second liquid crystal layer is a reflective layer with a longitudinally spiral structure. The first liquid crystal layer is bonded to the windshield, and the second liquid crystal layer faces an in-vehicle display device. The direction of the light beam generated by the in-vehicle display device is the same as the longitudinal periodic direction of the second liquid crystal layer. Most of the light beam generated by the in-vehicle display device is reflected by the second liquid crystal layer. The liquid crystal layer reflects the light, and the remaining light passes through the first liquid crystal layer and enters the interface between the windshield and the air. The P-light completely passes through the windshield, while the S-light is partially reflected. The reflected S-light becomes right-handed circularly polarized light after passing through the first liquid crystal layer and is reflected by the second liquid crystal layer, thus reducing the energy of the beam that causes the ghosting and eliminating the ghosting. After the natural light from outside the vehicle passes through the windshield, the P-light enters the first liquid crystal layer and becomes left-handed circularly polarized light before passing through the second liquid crystal layer and reaching the human eye. The S-light enters the first liquid crystal layer and becomes right-handed circularly polarized light. Light with a wavelength of λ = nP cos(θ) is reflected, where n is the average refractive index of the liquid crystal, P is the pitch of the spiral liquid crystal, and θ is the angle of light propagation in the liquid crystal. The remaining light passes through the second liquid crystal layer and reaches the human eye.

[0009] Furthermore, the angle at which the light beam generated by the in-vehicle display device enters the first liquid crystal layer is the Brewster angle.

[0010] Furthermore, the angle at which the light beam generated by the in-vehicle display device enters the first liquid crystal layer is 56 degrees.

[0011] Furthermore, the ghosting contrast of the automotive reflective film is greater than or equal to 100.

[0012] Furthermore, the thickness of the first liquid crystal layer is d = λ / Δn / 4, where λ is the center wavelength of the light beam emitted by the display device and Δn is the refractive index difference of the liquid crystal material.

[0013] Furthermore, the pitch of the second liquid crystal layer is n is the average refractive index of the liquid crystal material, and θ is the Brewster angle corresponding to the windshield.

[0014] Furthermore, θ = arcsin(1 / n) glasss ), n glasss The refractive index is the value of the windshield.

[0015] The second objective of this invention is achieved by the following technical solution:

[0016] A display structure includes a windshield and an anti-ghosting automotive reflective film disposed on the inner side of the windshield, wherein the anti-ghosting automotive reflective film is any of the above-mentioned types, a first liquid crystal layer is attached to the surface of the windshield and the first liquid crystal layer is located on the side of the windshield facing the interior of the vehicle, the windshield is inclined, the display structure reflects the light beam generated by the display device incident at Brewster angle inside the vehicle, and the display structure only reflects P-polarized light with a wavelength close to that of the display device to the natural light outside the vehicle, while transmitting natural light of other wavelengths and polarization directions.

[0017] Compared to existing technologies, the first liquid crystal layer of the automotive reflective film for eliminating ghosting in this invention has a pointer in the same direction, and the thickness of the first liquid crystal layer is a 1 / 4 waveplate. The second liquid crystal layer is a reflective layer, and the pointer of the second liquid crystal layer has a spiral structure in the longitudinal direction. The first liquid crystal layer is bonded to the windshield. The reflective film reflects the light beam generated by the display device inside the vehicle at Brewster angle, thereby reducing the energy of the light beam that causes ghosting and eliminating ghosting. For natural light outside the vehicle, it only reflects P-polarized light that is close to the working wavelength of the display device, while transmitting natural light of other wavelengths and polarization directions, so that the automotive reflective film has both high reflectivity and high transmittance. Attached Figure Description

[0018] Figure 1 This is a light path diagram displayed in the background technology.

[0019] Figure 2 The background image shows the optical path diagram of ghosting in the technique.

[0020] Figure 3 This is a schematic diagram of ghosting in the background technology;

[0021] Figure 4 The optical path diagram of the automotive reflective film for eliminating ghosting as described in this application after it is applied to the windshield;

[0022] Figure 5 This is a structural diagram of the automotive reflective film for eliminating ghosting as described in this application;

[0023] Figure 6 This is an illustration of the effect of the automotive reflective film for eliminating ghosting according to this application;

[0024] Figure 7 The reflection curve of the automotive reflective film for eliminating ghosting in this application to natural light.

[0025] In the diagram: 10, windshield; 20, automotive reflective film to eliminate ghosting; 21, first liquid crystal layer; 22, second liquid crystal layer. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be fixed through another intermediate component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may be fixed through another intermediate component. When a component is said to be "set on" another component, it can be set directly on the other component or it may be set through another intermediate component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0028] 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] Please see Figures 4 to 7 This application discloses a display structure for use inside a car, allowing the driver to see vehicle driving parameters without looking down. The display structure includes a display device, a ghosting-eliminating automotive reflective film 20, and a windshield 10.

[0030] The windshield 10 is located at the front of the car and is tilted.

[0031] The display device connects to the vehicle's control system to obtain the vehicle's driving parameters, including speed, time, gear, and weather information. The display device emits the driving parameters in the form of left-handed circularly polarized light.

[0032] The automotive reflective film 20 for eliminating ghosting is a liquid crystal film. The automotive reflective film 20 for eliminating ghosting includes a first liquid crystal layer 21 and a second liquid crystal layer 22. The first liquid crystal layer 21 is attached to the windshield 10 on the side facing the inside of the vehicle, and the second liquid crystal layer 22 is a reflective layer located on the side of the reflective film facing the inside of the vehicle.

[0033] The first liquid crystal layer 21 has a pointer in the same direction and a thickness of 1 / 4 waveplate. Specifically, the thickness of the first liquid crystal layer 21 is d = λ / Δn / 4, where λ is the center wavelength of the light beam emitted by the display device and Δn is the refractive index difference of the liquid crystal material.

[0034] The second liquid crystal layer 22 has a spiral structure in the longitudinal direction, exhibiting circular polarization selectivity and capable of reflecting circularly polarized light in a specific direction within a certain wavelength range. The pitch of the second liquid crystal layer 22 is... n is the average refractive index of the liquid crystal material, and θ is the Brewster angle corresponding to the windshield 10. θ = arcsin(1 / n) glasss ), n glasss The refractive index is the value of the windshield.

[0035] like Figure 5 As shown, when left-handed circularly polarized light emitted from the display device (image source) enters the windshield 10 at a Brewster angle (56 degrees), the beam first enters the second liquid crystal layer 22. Since the direction of rotation of the beam is the same as the direction of rotation of the longitudinal period of the second liquid crystal layer 22, approximately 80% of the energy is reflected into the human eye. The remaining 20% ​​of the energy passes through the first liquid crystal layer 21 and enters the interface between the windshield 10 and the air. Assuming that P-light and S-light each account for 10%, P-light completely passes through the glass, and the energy of S-light reflected is approximately 2%, which becomes right-handed circularly polarized light after passing through the first liquid crystal layer 21. This S-light is reflected by the second liquid crystal layer 22 instead of directly entering the human eye. Ultimately, only 0.4% of the beam energy that enters the human eye to form a ghost image passes through the second liquid crystal layer 22. Even in the worst-case scenario, where all the beam entering the glass-air is S-light, the energy of the beam that ultimately forms a ghost image is only 0.8%. The ghost image contrast ratio is 100, which meets the needs of safe driving. Figure 6 As shown.

[0036] Because the director of the second liquid crystal layer 22 has a helical structure in the longitudinal direction, the helical liquid crystal director distribution has two properties. One property is wavelength selectivity; the center of the reflected wavelength 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 helical liquid crystal, and θ is the propagation angle in the liquid crystal. It has no effect on other wavelengths. The other property is circular polarization selectivity; it only affects circularly polarized light in one direction. Natural light from outside the car is not polarized, equivalent to 50% P-polarized light and 50% S-polarized light. P-light first enters the first liquid crystal layer 21, becoming left-handed circularly polarized light, and almost completely passes through the second liquid crystal layer 22. S-light enters the first liquid crystal layer 21, becoming right-handed circularly polarized light, and is inevitably reflected, but only near λ, not the entire visible light spectrum. Figure 7 As shown. The light beam emitted by the display device (image source) is entirely left-handed circularly polarized light, which can be reflected with high reflectivity. Therefore, the automotive reflective film 20 that eliminates ghosting only reflects P-polarized light, which is close to the operating wavelength of the display device, and transmits natural light of other wavelengths and polarization directions, thus solving the problem of incompatibility between high reflectivity and high transmittance.

[0037] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These are all equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of these fall within the protection scope of the present invention.

Claims

1. A reflective film for automotive applications that eliminates ghosting, characterized in that: The system includes a first liquid crystal layer and a second liquid crystal layer. The first liquid crystal layer has a pointing vector in the same direction and a thickness of 1 / 4 waveplate. The second liquid crystal layer is a reflective layer with a pointing vector in a spiral structure in the longitudinal direction. The first liquid crystal layer is attached to the windshield, and the second liquid crystal layer faces the in-vehicle display device. The direction of rotation of the light beam generated by the in-vehicle display device is the same as the direction of rotation of the longitudinal period of the second liquid crystal layer. Most of the light beam generated by the in-vehicle display device is reflected by the second liquid crystal layer, and the remaining light passes through the first liquid crystal layer and enters the interface between the windshield and the air. The P-light completely passes through the windshield, and the S-light is partially reflected. The reflected S-light becomes right-handed circularly polarized light after passing through the first liquid crystal layer and is reflected by the second liquid crystal layer, thereby reducing the energy of the light beam that causes ghosting and eliminating ghosting. After natural light from outside the vehicle passes through the windshield, P-light enters the first liquid crystal layer and becomes left-handed circularly polarized light, then passes through the second liquid crystal layer to reach the human eye. S-light enters the first liquid crystal layer and becomes right-handed circularly polarized light. Light with wavelength λ = nP cos(θ) is reflected, where n is the average refractive index of the liquid crystal, P is the pitch of the spiral liquid crystal, and θ is the angle of light propagation in the liquid crystal. The remaining light passes through the second liquid crystal layer to reach the human eye.

2. The automotive reflective film for eliminating ghosting according to claim 1, characterized in that: The angle at which the light beam generated by the in-vehicle display device enters the first liquid crystal layer is Brewster's angle.

3. The automotive reflective film for eliminating ghosting according to claim 2, characterized in that: The beam of light generated by the in-vehicle display device enters the first liquid crystal layer at an angle of 56 degrees.

4. The automotive reflective film for eliminating ghosting according to claim 1, characterized in that: The ghosting contrast of the automotive reflective film is greater than or equal to 100.

5. The automotive reflective film for eliminating ghosting according to claim 1, characterized in that: The thickness of the first liquid crystal layer is d = λ / Δn / 4, where λ is the center wavelength of the light beam emitted by the display device and Δn is the refractive index difference of the liquid crystal material.

6. The automotive reflective film for eliminating ghosting according to claim 1, characterized in that: The pitch of the second liquid crystal layer is n is the average refractive index of the liquid crystal material, and θ is the Brewster angle corresponding to the windshield.

7. The automotive reflective film for eliminating ghosting according to claim 1, characterized in that: θ = arcsin(1 / n) glasss ), n glasss The refractive index is the value of the windshield.

8. A display structure, comprising a windshield and an anti-ghosting automotive reflective film disposed on the inner side of the windshield, characterized in that: The ghosting-eliminating automotive reflective film is as described in any one of claims 1-7, wherein the first liquid crystal layer is attached to the surface of the windshield and the first liquid crystal layer is located on the side of the windshield facing the interior of the vehicle, the windshield is tilted, the display structure reflects the light beam generated by the display device incident at Brewster angle inside the vehicle, and the display structure only reflects P-polarized light close to the operating wavelength of the display device from outside the vehicle, while transmitting natural light of other wavelengths and polarization directions.

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