Vehicle reflecting film for eliminating ghosting and display structure

Abstract

The invention discloses an automotive reflecting film for eliminating ghosting and a display structure, and belongs to the field of automotive display, the automotive reflecting film comprises a first liquid crystal layer and a second liquid crystal layer, the directors of the first liquid crystal layer are in the same direction, the thickness of the first liquid crystal layer is 1 / 4 of a wave plate, the second liquid crystal layer is a reflecting layer, and the directors of the second liquid crystal layer are in the same direction. A director of the second liquid crystal layer is of a spiral structure in the longitudinal direction, the first liquid crystal layer is attached to a windshield, and the reflecting film reflects light beams generated by a display device incident at the Brewster angle in a vehicle, so that the energy of the light beams forming double images is reduced, and the double images are eliminated. Only P 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 reflective film for the vehicle has high reflectivity and high transmittance.

Description

Technical Field

[0001] The invention relates to the field of vehicle display, in particular to a vehicle reflective film for eliminating ghosting. 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 of which will form virtual images, resulting in ghosting problems and 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 vehicle 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] In order to overcome the deficiencies of the prior art, a second object of the present invention is to provide a display structure that can avoid ghosting and ensure that both the light beams of external objects and the light of the image source inside the vehicle can effectively reach the human eye.

[0007] One of the purposes of the present invention is achieved by the following technical solution:

[0008] A vehicle reflective film for eliminating ghosting comprises a first liquid crystal layer and a second liquid crystal layer, wherein the director of the first liquid crystal layer is in the same direction, the thickness of the first liquid crystal layer is a 1 / 4 wave plate, the second liquid crystal layer is a reflective layer, the director of the second liquid crystal layer is in a spiral structure in the longitudinal direction, the first liquid crystal layer is attached to the windshield, the second liquid crystal layer faces an in-vehicle display device, the rotation direction of the light beam generated by the in-vehicle display device is the same as the rotation direction of the longitudinal period of the second liquid crystal layer, and most of the light beam generated by the in-vehicle display device is reflected by the second liquid crystal layer. The light is reflected by the liquid crystal layer, and the remaining part of the 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, so that the energy of the light beam forming the ghost image becomes smaller and the ghost image is eliminated. After the natural light outside the vehicle passes through the windshield, the P light enters the first liquid crystal layer and becomes left-handed circularly polarized light, and then passes through the second liquid crystal layer to reach 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 light, P is the pitch of the spiral liquid crystal, and θ is the propagation angle of light in the liquid crystal. The remaining part of the 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 Brewster's 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 vehicle reflective film is greater than or equal to 100.

[0012] Furthermore, the thickness of the first liquid crystal layer is d=λ / Δn / 4, λ is the central 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 is the refractive index of the windshield.

[0015] The second object of the present invention is achieved by adopting the following technical solution:

[0016] A display structure comprises a windshield and a vehicle-use reflective film for eliminating ghosting arranged on the inner side of the windshield, wherein the vehicle-use reflective film for eliminating ghosting is any one of the above-mentioned ones, 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, and the windshield is arranged at an angle, and the display structure reflects a light beam generated by a display device in the vehicle that is incident at a Brewster angle, and the display structure only reflects P-polarized light close to the working wavelength of the display device for natural light outside the vehicle, and transmits natural light of other wavelengths and polarization directions.

[0017] Compared with the prior art, the first liquid crystal layer of the vehicle reflective film for eliminating ghosting of the present invention has its directors in the same direction, the thickness of the first liquid crystal layer is a 1 / 4 wave plate, the second liquid crystal layer is a reflective layer, the directors of the second liquid crystal layer form a spiral structure in the longitudinal direction, the first liquid crystal layer is bonded to the windshield, and the 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 ghosting and eliminating ghosting; 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 vehicle reflective film has both high reflectivity and high transmittance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a light path diagram of the head-up display in the background technology;

[0019] Figure 2 It is a light path diagram produced by ghosting in the background technology;

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

[0021] Figure 4 Light path diagram after the vehicle reflective film for eliminating ghosting in this application is attached to the windshield;

[0022] Figure 5 A structural diagram of a vehicle reflective film for eliminating ghosting in this application;

[0023] Figure 6 The effect diagram of the vehicle reflective film for eliminating ghosting in this application;

[0024] Figure 7 This is the reflection curve of natural light of the vehicle reflective film for eliminating ghosting in this application.

[0025] In the figure: 10, windshield; 20, vehicle reflective film for eliminating double images; 21, first liquid crystal layer; 22, second liquid crystal layer. DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] 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.

[0029] See also Figures 4 to 7 The present application discloses a display structure for use in a car interior, so that the driver can see the driving parameters of the car without lowering his head. The display structure includes a display device, a vehicle reflective film 20 for eliminating ghosting, and a windshield 10.

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

[0031] The display device is connected to the vehicle control system to obtain the driving parameters of the vehicle, including vehicle speed, time, gear position, weather, etc. The display device emits the driving parameters in the form of left-handed circularly polarized light.

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

[0033] The directors of the first liquid crystal layer 21 are in the same direction and the thickness is a quarter wave plate. Specifically, the thickness of the first liquid crystal layer 21 is d=λ / △n / 4, where λ is the central wavelength of the light beam emitted by the display device and △n is the refractive index difference of the liquid crystal material.

[0034] The director of the second liquid crystal layer 22 has a spiral structure in the longitudinal direction, has circular polarization selectivity, and can reflect circularly polarized light of 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 is the refractive index of the windshield.

[0035] like Figure 5 As shown, 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 second liquid crystal layer 22. Since the rotation direction of the light beam is the same as the rotation direction of the longitudinal period of the second liquid crystal 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 first liquid crystal layer 21 and enter 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 reflected by S light is about 2%. After passing through the first liquid crystal layer 21, it becomes right-handed circularly polarized light and will be reflected by the second liquid crystal layer 22 instead of directly entering the human eye. Finally, through the second liquid crystal layer 22, the energy of the light beam that forms the ghost image and enters the human eye is only 0.4%. Even in the worst case, the light beam that enters the glass-air is all S light, and the energy of the light beam that forms the ghost image is only 0.8%. The ghost image contrast is 100, which meets the needs of safe driving, as shown in FIG. Figure 6 shown.

[0036] Since the director of the second liquid crystal 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 response 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, which is equivalent to 50% P polarized light and 50% S polarized light. The P light first enters the first liquid crystal layer 21 and becomes left-handed circularly polarized light, which almost completely passes through the second liquid crystal layer 22. After the S light enters the first liquid crystal layer 21, it becomes right-handed circularly polarized light and is inevitably reflected, but it also only reflects near λ, rather than the entire visible light spectrum range. Figure 7 As shown. The light beams generated by the display device (image source) are all left-handed circularly polarized light, which can be reflected with high reflectivity. Therefore, the vehicle reflective film 20 that eliminates ghosting only reflects P-polarized light close to the working wavelength of the display device for the external natural light, and transmits natural light of other wavelengths and polarization directions, thereby solving the incompatibility problem between high reflectivity and high transmittance.

[0037] 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 vehicle reflective film for eliminating ghosting, characterized in that: It comprises a first liquid crystal layer and a second liquid crystal layer, wherein the director of the first liquid crystal layer is in the same direction, the thickness of the first liquid crystal layer is a 1 / 4 wave plate, the second liquid crystal layer is a reflective layer, the director of the second liquid crystal layer forms a spiral structure in the longitudinal direction, the first liquid crystal layer is attached to the windshield, the second liquid crystal layer faces the in-vehicle display device, the rotation direction of the light beam generated by the in-vehicle display device is the same as the rotation direction 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 part of the light passes through the first liquid crystal layer and is incident on the interface between the windshield and the air, the P light completely passes through the windshield, the S light is partially reflected, and 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, so that the energy of the light beam forming the ghost image becomes smaller, thereby eliminating the ghost image; After the natural light outside the vehicle passes through the windshield, the P light enters the first liquid crystal layer and becomes left-handed circularly polarized light, and then passes through the second liquid crystal layer to reach the human eye. The S light enters the first liquid crystal layer and becomes right-handed circularly polarized light. The light with a wavelength of λ=nP cos(θ) is reflected, 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 of the light in the liquid crystal. The rest of the light passes through the second liquid crystal layer to reach the human eye.

2. The vehicle 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 the Brewster angle.

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

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

5. The vehicle 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 central wavelength of the light beam emitted by the display device, and Δn is the refractive index difference of the liquid crystal material.

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

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

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