A liquid crystal electro-controlled mirror capable of breaking the reflectivity limit

Abstract

This invention relates to a liquid crystal electrically controlled reflector capable of breaking the reflectivity limit, comprising, from front to back, a first liquid crystal device, a second liquid crystal device, a first reflective polarizer, and a second reflective polarizer. The main body of the first liquid crystal device is a first liquid crystal cell sandwiched with a first liquid crystal layer. The first liquid crystal layer is composed of negative liquid crystal doped with dichroic dyes. In its natural state, the negative liquid crystal molecules and the dichroic dye molecules are perpendicularly aligned, while in the driven state, the negative liquid crystal molecules drive the dichroic dye molecules to deflect along a second axis. The second liquid crystal device has a 90° optical rotation function in its natural state, but no optical rotation function in the driven state. This invention not only achieves efficient reflection of two beams of orthogonally polarized states simultaneously in its high-reflectivity operating mode, significantly improving the overall reflectivity, but also reduces the reflectivity to a minimum level in its low-reflectivity operating mode.

Description

Technical Field

[0001] This invention relates to the field of automotive rearview mirrors, and more specifically to a liquid crystal electronically controlled reflector that can overcome the reflectivity limit. Background Technology

[0002] A liquid crystal electronically controlled reflector is an optical device whose reflectivity is adjustable by applying voltage. It has two operating modes: high-reflectivity and low-reflectivity, and is primarily used in automotive rearview mirror systems. When it detects high beams from a vehicle behind, the liquid crystal electronically controlled reflector automatically switches to the low-reflectivity mode, effectively reducing the intensity of reflected incident light, thus preventing driver glare and improving driving safety. Currently, liquid crystal electronically controlled reflectors can also be extended to streaming media rearview mirror systems. By integrating a display module on the optical rear side of the electronically controlled reflector and simultaneously reducing the reflector's reflectivity in display mode, effective separation of the displayed image and the mirrored image is achieved, significantly improving image display quality.

[0003] like Figure 1 As shown, the typical structure of an existing liquid crystal electronically controlled reflector generally consists of an absorptive polarizer 01, a liquid crystal modulation unit 02, a reflective polarizer 03, and a display module 03 arranged from front to back. The reflection function of the liquid crystal electronically controlled reflector is mainly realized by the reflective polarizer 03. However, due to the limitation of the theoretical reflectivity upper limit of 50% for a single-layer reflective polarizer and the optical loss introduced by the absorptive polarizer, it is difficult to make the reflectivity of this liquid crystal electronically controlled reflector reach the 40% threshold required by the national standard in the high-reflectivity working mode. This has become a key technical bottleneck restricting the improvement of product performance. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a liquid crystal electro-controlled reflector that can break through the reflectivity limit. This liquid crystal electro-controlled reflector can not only achieve efficient reflection of two beams of orthogonal polarization simultaneously in its high-reflectivity operating mode, significantly improving the overall reflectivity and thus breaking through the reflectivity limit of the traditional single reflection path, but also reduce the reflectivity to a minimum in its low-reflectivity operating mode. The technical solution adopted is as follows:

[0005] A liquid crystal electrically controlled reflector capable of breaking the reflectivity limit is characterized by comprising a first liquid crystal device, a second liquid crystal device, a first reflective polarizer, and a second reflective polarizer, arranged sequentially from front to back; a first axis and a second axis are defined as two axes parallel to the mirror surface of the liquid crystal electrically controlled reflector and orthogonal to each other; the main body of the first liquid crystal device is a first liquid crystal cell with a first liquid crystal layer sandwiched therebetween, the first liquid crystal layer being composed of negative liquid crystal doped with dichroic dyes, the negative liquid crystal layer of the first liquid crystal layer... In its natural state, the crystal molecules and dichroic dye molecules are vertically aligned. The first liquid crystal layer has a first transmittance T1 for both the first and second axially polarized light. In the driven state, the negative liquid crystal molecules drive the dichroic dye molecules to deflect along the second axis, so that the first liquid crystal layer has a second transmittance T2 for the second axially polarized light, where T2 < T1. The second liquid crystal device has a 90° optical rotation function in its natural state, but no optical rotation function in the driven state. The first reflective polarizer and the second reflective polarizer can transmit the first axially polarized light and reflect the second axially polarized light.

[0006] The first axis or the second axis can be a horizontal axis (0°) or a 45° axis. The first axis polarized light and the second axis polarized light refer to linearly polarized light whose polarization direction (i.e., the electric vector of the light wave) is the first axis and the second axis, respectively.

[0007] In the aforementioned first liquid crystal device, its main body is a first liquid crystal cell with a first liquid crystal layer sandwiched in it. Dichroic dye molecules are mixed in the liquid crystal of the first liquid crystal layer. It can exhibit selective absorption characteristics for polarized light in different directions. It can strongly absorb polarized light whose electric vector is parallel to or at a small angle to the long axis of its dye molecules, while its absorption of polarized light whose electric vector is perpendicular to or at a large angle to the long axis of its dye molecules is weaker.

[0008] The first and second reflective polarizers are optical elements with selective polarization reflection characteristics. They have mutually orthogonal reflection and transmission axes, and can produce specular reflection of the polarization component in the incident light that is aligned with the reflection axis, while allowing the polarization component aligned with the transmission axis to pass through. Both the first and second reflective polarizers are configured to transmit light polarized along a first axial direction and reflect light polarized along a second axial direction; that is, their transmission axis is the first axis, and their reflection axis is the second axis.

[0009] This liquid crystal electro-controlled mirror has two working modes: a high-reflection mode and a low-reflection mode. The high-reflection mode is its default working state, in which both the first liquid crystal device and the second liquid crystal device maintain their natural state. When ambient natural light is incident on the electro-controlled mirror, the incident light can be regarded as including first axially polarized light with a first axial polarization characteristic and second axially polarized light with a second axial polarization characteristic. When the first and second liquid crystal devices are in their natural state, the liquid crystal electro-reflective mirror enters a high-reflectivity operating mode. In this mode, both the first axially polarized light and the second axially polarized light pass through the first liquid crystal layer with a high first transmittance T1. The first axially polarized light matches the transmission axis of the first reflective polarizer and is thus transmitted. After entering the second liquid crystal device, the transmitted light undergoes a 90° polarization rotation, changing its polarization direction from the first axis to the second axis. This polarization state matches the reflection axis of the second reflective polarizer and is thus totally reflected. When the reflected light passes through the second liquid crystal device again, it undergoes a second 90° polarization rotation, restoring its polarization direction from the second axis to the first axis, allowing it to be transmitted through the first reflective polarizer again. This beam then exits through the first liquid crystal device again with a first transmittance T1. Through the aforementioned optical path, the first axially polarized light is reflected inside the liquid crystal electro-reflective mirror and forms a first outgoing beam with first specular reflection characteristics. When the second axially polarized light is incident on the first reflective polarizer, it is totally reflected because its polarization direction matches the reflection axis of the reflective polarizer. The reflected light then exits through the first liquid crystal device with a first transmittance T1. Through the aforementioned optical path, the second axially polarized light is reflected inside the mirror and finally forms a second outgoing beam with second specular reflection characteristics. The overall reflection of the mirror is formed by the superposition of the first and second outgoing beams. Due to the high first transmittance T1, both the first and second outgoing beams exit with high emissivity, thus significantly improving the intensity of their superimposed light. This allows the mirror to significantly overcome the brightness limit of traditional single reflection paths while maintaining overall compactness. When a driving voltage is applied so that both the first and second liquid crystal devices are in the driving state, the liquid crystal electro-reflective mirror enters a low-reflection working mode. In the low-reflection working mode, the incident first axially polarized light still passes through the first liquid crystal layer with a high first transmittance T1. The first axially polarized light matches the transmission axis of the first reflective polarizer and achieves transmission. After the transmitted light enters the second liquid crystal device, it does not undergo a 90° polarization rotation and maintains the polarization direction of the first axis. This polarization state matches the transmission axis of the second reflective polarizer and achieves transmission again. Finally, the light beam penetrates to the light-absorbing substrate on the back of the mirror and is completely absorbed, thereby achieving near-zero reflectivity of the first axially polarized light in the electro-reflective mirror system.The second axially polarized light passes through the first liquid crystal device with a lower second transmittance T2. When the second axially polarized light is incident on the first reflective polarizer, total internal reflection is achieved because the polarization direction is perfectly matched with the reflection axis of the polarizer. When the reflected light passes through the first liquid crystal device again, it exits through the first liquid crystal device with a lower second transmittance T2. Because the second transmittance T2 is low, the intensity of the reflected light of the second axially polarized light is significantly reduced, and only the second axially polarized light is emitted. Moreover, the second axially polarized light is significantly weakened, so that the electronically controlled reflector as a whole exhibits a low-reflection working state.

[0010] As a preferred embodiment of the present invention, it is assumed that the theoretical reflectivity of the electrically controlled reflector in the high-reflection state and the low-reflection state are R0 and R1, respectively. A R B Then R A R B T1 and T2 satisfy the relation: R A =50%×T1 2 +50%×T1 2 =100%×T1 2 R B =50%×T2 2 Based on the properties of existing dichroic dyes, it is possible to design a dye with a first transmittance T1 higher than 75% and a second transmittance T2 lower than 30%. The calculated R... A More than 55%, while R B Below 5%, R A Significantly exceeding the 50% performance limit of existing technologies, while maintaining a low R-value. B It can easily exceed the performance requirements of national standards (in the presence of losses, the high-reflectivity state reflectivity of the electronically controlled reflector will be higher than the theoretical reflectivity R). A The performance is slightly lower, but it still easily exceeds the national standard performance requirements.

[0011] As a further preferred embodiment of the present invention, the first transmittance is at least 70%. Therefore, its R... A The theoretical value can reach 49%, which significantly exceeds the national standard of 40%, meaning that there is still a large design tolerance even when the device has losses.

[0012] As a further preferred embodiment of the present invention, the first transmittance is at least 80%.

[0013] As a further preferred embodiment of the present invention, the second transmittance does not exceed 30%. Therefore, its R... B The theoretical value is less than 9%, which can meet the low reflectivity requirements of most rearview mirrors.

[0014] As a further preferred embodiment of the present invention, the second transmittance does not exceed 20%.

[0015] As a preferred embodiment of the present invention, the first reflective polarizer and the second reflective polarizer are made of reflective polarizing film (RPM). The first reflective polarizer and the second reflective polarizer also employ the multilayer optical thin film structure and its equivalent alternative materials disclosed in Chinese Patent CN1170382A.

[0016] As a preferred embodiment of the present invention, the first liquid crystal cell includes a first front substrate, a first liquid crystal layer, and a first rear substrate. The first front substrate and the first rear substrate are transparent substrates, and the first liquid crystal layer is sandwiched between the first front substrate and the first rear substrate. A first front transparent electrode and a first front alignment layer are provided on the surface of the first front substrate near the first liquid crystal layer, and a first rear transparent electrode and a first rear alignment layer are provided on the surface of the first rear substrate near the first liquid crystal layer. There is an electrode overlap region between the first rear transparent electrode and the first front transparent electrode to form a light control region. The first front alignment layer and the first rear alignment layer are vertical alignment layers. By applying a second axial alignment treatment (such as directional friction that is opposite to each other in the second axial direction) to the first front alignment layer and / or the first rear alignment layer, the first liquid crystal device has an alignment axis in the second axial direction. When the first front transparent electrode and the first rear transparent electrode are in their natural state (meaning there is no voltage applied between the first front transparent electrode and the first rear transparent electrode, or the applied voltage is less than the threshold), the negative liquid crystal molecules and dichroic dye molecules of the first liquid crystal layer are arranged vertically (vertical arrangement means that the angle between the liquid crystal molecules and the cell surface is greater than 85°). Since the long axis of the dichroic dye molecules is perpendicular to or has a large angle with the electric vector of the first axially polarized light and the second axially polarized light, it absorbs less, and both the first axially polarized light and the second axially polarized light have high transmittance when passing through the first liquid crystal layer. When sufficient voltage is applied to the first front transparent electrode and the first rear transparent electrode, the first liquid crystal cell is in a driving state. The negative liquid crystal molecules in the electrode overlapping area are deflected in the second axis. When sufficient voltage is applied, they are deflected into a near-horizontal alignment (the angle between the liquid crystal molecules and the cell surface is less than 30°), which in turn causes the dichroic dye molecules to also be deflected in the second axis into a near-horizontal alignment. The long axis of the dichroic dye molecules is parallel to or has a small angle with the electric vector of the second axially polarized light, and it has a large absorption of the second axially polarized light. The second axially polarized light has a low transmittance when it passes through the first liquid crystal layer.

[0017] As a further preferred embodiment of the present invention, the first front substrate and the first rear substrate are transparent glass substrates or transparent plastic substrates.

[0018] In a preferred embodiment of the present invention, the second liquid crystal device employs a TN (twisted nematic) liquid crystal cell, comprising a second front substrate, a second liquid crystal layer, and a second rear substrate. The second front substrate and the second rear substrate are transparent substrates. The second liquid crystal layer is sandwiched between the second front substrate and the second rear substrate and is composed of positive liquid crystal. A second front transparent electrode and a second front alignment layer are provided on the surface of the second front substrate near the second liquid crystal layer. A second rear transparent electrode and a second rear alignment layer are provided on the surface of the second rear substrate near the second liquid crystal layer. An electrode overlap region exists between the second rear transparent electrode and the second front transparent electrode to form a light control region. The second front alignment layer and the second... The rear alignment layer is a horizontal alignment layer. By applying directional friction with an angle of 90° to the second front alignment layer and the second rear alignment layer, the positive liquid crystal molecules of the second liquid crystal layer are arranged in a twisted alignment of about 90° (i.e., TN alignment) in the natural state (meaning that no voltage is applied between the second front transparent electrode and the second rear transparent electrode, or the applied voltage is less than the threshold). The second liquid crystal device has a 90° optical rotation function. However, when the second liquid crystal device is in the driving state (the second front transparent electrode and the second rear transparent electrode are subjected to sufficient voltage), the positive liquid crystal molecules in the electrode overlap area are fully deflected into a vertical alignment, and the second liquid crystal device has no optical rotation function.

[0019] As a further preferred embodiment of the present invention, the second front substrate and the second rear substrate are transparent glass substrates or transparent plastic substrates.

[0020] As a further preferred embodiment of the present invention, when the second front transparent electrode and the second rear transparent electrode are in their natural state, the liquid crystal molecules of the second liquid crystal layer twist from the first axis to the second axis from front to back, exhibiting a 90° twisted arrangement. This can further optimize the optical rotation effect of the first liquid crystal device and the second liquid crystal device.

[0021] As a preferred embodiment of the present invention, the thickness of the first liquid crystal layer is at least 4 μm.

[0022] As a preferred embodiment of the present invention, the mass ratio of the dichroic dye in the first liquid crystal layer is at least 1%. This allows the first liquid crystal layer to exhibit a significant polarization absorption effect, with a clear distinction between T1 and T2.

[0023] As a preferred embodiment of the present invention, the dichroic dye is a dark-colored organic dye. Specifically, the dichroic dye can be a single dichroic dye, such as a blue or purple dichroic dye, or it can be a combination of two or more dichroic dye molecules, such as a combination of blue, red, and / or yellow dichroic dyes, thereby enabling it to absorb multiple wavelengths of light simultaneously and thus produce a better black effect. Specifically, the dichroic dye can be, but is not limited to, dichroic organic dyes such as azo compounds disclosed in patents such as US4122027A, US4565424A, JP56057850A, and WO2011157614A1.

[0024] For the liquid crystal electronically controlled reflector, the dichroic dye also has the function of adjusting the reflector's hue. As a preferred embodiment of the present invention, the dichroic dye is blue or bluish. Thus, the rearview mirror's hue is designed to be bluish.

[0025] As a preferred embodiment of the present invention, the thickness of the second liquid crystal device does not exceed 1 mm. This ensures that after the first specular reflection and the second specular reflection are superimposed, there will be no obvious ghosting.

[0026] As a further preferred embodiment of the present invention, the thickness of the second liquid crystal device does not exceed 0.6 mm. This ensures that after the first specular reflection and the second specular reflection are superimposed, no obvious ghosting will occur.

[0027] As a preferred embodiment of the present invention, the liquid crystal electro-controlled reflector further includes a drive control system capable of providing drive voltage. The drive lines of the first liquid crystal device and the second liquid crystal device are electrically connected to the corresponding output terminals of the drive control system. The drive control system can simultaneously provide drive voltage to the first liquid crystal device and the second liquid crystal device, realizing simultaneous switching control of the first liquid crystal device and the second liquid crystal device to switch the functional states of the first liquid crystal device and the second liquid crystal device.

[0028] In a preferred embodiment of the present invention, the first liquid crystal device and the first reflective polarizer, the first reflective polarizer and the second liquid crystal device, and the second liquid crystal device and the second reflective polarizer are all bonded together by optical adhesive layers. The optical adhesive layers not only strengthen the structure but also eliminate air gaps between adjacent polarizers and liquid crystal devices, preventing air interface reflections from affecting their function.

[0029] As a preferred embodiment of the present invention, the back of the liquid crystal electronically controlled reflector is provided with a black light-absorbing film layer, such as a black film or plate, or a display device with a black surface.

[0030] As a preferred embodiment of the present invention, the liquid crystal electro-controlled reflector further includes a display module disposed on the rear side of the second reflective polarizer. The display module can be selected from either a liquid crystal display unit or an organic electroluminescent display unit, and its display surface is black or dark and has low reflectivity.

[0031] As a further preferred embodiment of the present invention, the light-emitting surface of the display module is provided with a polarizer, the polarization axis of which matches the first axial direction. When the liquid crystal electronically controlled mirror operates in low-reflection mode, the polarized light (display light) emitted by the display module passes through the mirror optical system with minimal light loss, forming a high-brightness display image. At the same time, due to the significant contrast difference between the low-reflection characteristics of the mirror and the high-brightness characteristics of the display image, interference between the display image and the mirror reflection image is effectively avoided.

[0032] As a further preferred embodiment of the present invention, the liquid crystal electro-controlled reflector has two operating modes: a high-reflection mode and a low-reflection mode. The incident light is decomposed into first axially polarized light with a first axial polarization characteristic and second axially polarized light with a second axial polarization characteristic. In the high-reflection mode, the incident and reflection path of the first axially polarized light is as follows: it passes sequentially through a first liquid crystal device, a first reflective polarizer, and a second liquid crystal device; it is reflected by the second reflective polarizer and then sequentially transmitted through the second liquid crystal device, the first reflective polarizer, and the first liquid crystal device before exiting. The incident and reflection path of the second axially polarized light is as follows: it passes through the first liquid crystal device and is reflected by the first reflective polarizer, and then transmitted through the first liquid crystal device before exiting. In the low-reflection mode, the incident and reflection path of the first axially polarized light is as follows: it passes sequentially through the first liquid crystal device, the first reflective polarizer, the second liquid crystal device, and the polarizer of the display module; the first axially polarized light is absorbed at the polarizer. The incident and reflection path of the second axially polarized light is as follows: it passes through the first liquid crystal device and is absorbed by the first reflective polarizer.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The liquid crystal electro-controlled reflector of the present invention constructs a composite mirror optical system composed of a second liquid crystal modulation unit and a double-reflection polarizer. In the high reflection working mode, it can simultaneously achieve efficient reflection of two beams with orthogonal polarization states, which significantly improves the overall reflection brightness. By using a dye liquid crystal unit with vertical alignment characteristics as the first liquid crystal device, the first liquid crystal device forms an optimized optical match with the double-layer reflection structure, ensuring that the two beams with different polarization directions can maintain high incident and outgoing efficiencies in the high reflection state. This breaks through the reflectivity limit of the traditional single reflection path and easily exceeds the performance requirements of the national standard.

[0035] (2) The liquid crystal electronically controlled reflector of the present invention realizes a dual-path extinction mechanism in the low-reflection working mode. Through optical design, the first polarized beam is penetrated to the back side of the reflector and absorbed. At the same time, the selective absorption characteristics of the dye liquid crystal molecules on the second polarized beam are utilized. The ingenious synergy of the two extinction mechanisms reduces the reflectivity to the lowest level. Attached Figure Description

[0036] Figure 1 This is a typical structural diagram of a liquid crystal electronically controlled reflector in the prior art.

[0037] Figure 2 This is a schematic diagram of the structure of a liquid crystal electronically controlled reflector according to a preferred embodiment of the present invention.

[0038] Figure 3 yes Figure 2 The diagram shows the optical principle of the first liquid crystal device in the liquid crystal electronically controlled mirror under its natural state.

[0039] Figure 4 yes Figure 2 The diagram shows the optical principle of the first liquid crystal device in the liquid crystal electronically controlled mirror under driving conditions.

[0040] Figure 5 yes Figure 2 The diagram shows the optical principle of the second liquid crystal device in the liquid crystal electronically controlled mirror under natural conditions.

[0041] Figure 6 yes Figure 2 The diagram shows the optical principle of the second liquid crystal device in the liquid crystal electronically controlled mirror under driving conditions.

[0042] Figure 7 This is an optical schematic diagram of the liquid crystal electronically controlled reflector in the high-reflectivity working mode of a preferred embodiment of the present invention.

[0043] Figure 8 This is an optical schematic diagram of the liquid crystal electronically controlled reflector in the low-reflection state working mode according to a preferred embodiment of the present invention. Detailed Implementation

[0044] like Figures 2-8As shown, this liquid crystal electronically controlled reflector, capable of breaking the reflectivity limit, includes a first liquid crystal device 1, a second liquid crystal device 2, a first reflective polarizer 3, a second reflective polarizer 4, and a display module 5. The first liquid crystal device 1, the first reflective polarizer 3, the second liquid crystal device 2, the second reflective polarizer 4, and the display module 5 are arranged sequentially from front to back. A first axis 10 and a second axis 20 are defined as two axes parallel to the mirror surface of the liquid crystal electronically controlled reflector and orthogonal to each other. The main body of the first liquid crystal device 1 is a first liquid crystal cell with a first liquid crystal layer 11 sandwiched within it. The first liquid crystal layer 11 is composed of negative liquid crystals doped with dichroic dyes. The negative liquid crystal molecules 110 of the first liquid crystal layer 11... In its natural state, the dichroic dye molecules 1102 are arranged perpendicularly to each other. The first liquid crystal layer 11 has a first transmittance T1 for both the first axially polarized light 100 and the second axially polarized light 200. In the driven state, the negative liquid crystal molecules 1101 drive the dichroic dye molecules 1102 to deflect along the second axis 20, so that the first liquid crystal layer 11 has a second transmittance T2 for the second axially polarized light 200, where T2 < T1. The second liquid crystal device 2 has a 90° optical rotation function in its natural state, but no optical rotation function in the driven state. The first reflective polarizer 3 and the second reflective polarizer 4 can transmit the first axially polarized light 100 and reflect the second axially polarized light 200.

[0045] In this embodiment, the first axis 10 is the horizontal axis (0°).

[0046] In this embodiment, the first reflective polarizer 3 and the second reflective polarizer 4 are optical elements with selective polarization reflection characteristics. They have mutually orthogonal reflection axes 31 and transmission axes 41, and can produce specular reflection of the polarization component in the incident light that is aligned with the direction of the reflection axis 31, while allowing the polarization component aligned with the direction of the transmission axis 41 to pass through. Both the first reflective polarizer 3 and the second reflective polarizer 4 are configured to transmit first axially polarized light 100 and reflect second axially polarized light 200, that is, their transmission axis 41 is the first axis 10, and their reflection axis 31 is the second axis 20.

[0047] In this embodiment, it is assumed that the theoretical reflectivity of the electrically controlled mirror in the high-reflection state and the low-reflection state are R, respectively. A R B Then R A R B T1 and T2 satisfy the relation: R A =50%×T1 2 +50%×T1 2 =100%×T1 2 R B =50%×T2 2Based on the properties of existing dichroic dyes, it is possible to design a dye with a first transmittance T1 higher than 75% and a second transmittance T2 lower than 30%. The calculated R... A More than 55%, while R B Below 5%, R A Significantly exceeding the 50% performance limit of existing technologies, while maintaining a low R-value. B It can easily exceed the performance requirements of national standards (in the presence of losses, the high-reflectivity state reflectivity of the electronically controlled reflector will be higher than the theoretical reflectivity R). A The performance is slightly lower, but it still easily exceeds the national standard performance requirements.

[0048] In this embodiment, the first reflective polarizer 3 and the second reflective polarizer 4 adopt reflective polarizing film (RPM) or adopt the multilayer optical thin film structure and its equivalent alternative materials disclosed in Chinese Patent CN1170382A.

[0049] In this embodiment, the first liquid crystal cell includes a first liquid crystal layer 11, a first front substrate 12, and a first rear substrate 13. The first front substrate 12 and the first rear substrate 13 are transparent substrates (such as transparent glass substrates or transparent plastic substrates). The first liquid crystal layer 11 is sandwiched between the first front substrate 12 and the first rear substrate 13. The surface of the first front substrate 12 near the first liquid crystal layer 11 is provided with a first front transparent electrode 14 and a first front alignment layer 15. The surface of the first rear substrate 13 near the first liquid crystal layer 11 is provided with a first rear transparent electrode 16 and a first rear alignment layer 17. There is an electrode overlap area between the first rear transparent electrode 16 and the first front transparent electrode 14 to form a light control area. The first front alignment layer 15 and the first rear alignment layer 17 are vertical alignment layers. By applying a second axial 20 orientation treatment (such as directional friction in opposite directions on the second axial 20) to the first front alignment layer 15 and / or the first rear alignment layer 17, the first liquid crystal device 1 has an orientation axis 101 of the second axial 20. When the first front transparent electrode 14 and the first rear transparent electrode 16 are in a natural state (meaning no voltage is applied between the first front transparent electrode 14 and the first rear transparent electrode 16, or the applied voltage is less than the threshold), the negative liquid crystal molecules 1101 and dichroic dye molecules 1102 of the first liquid crystal layer 11 are arranged vertically (vertical arrangement means that the angle between the liquid crystal molecules and the cell surface is greater than 85°). Since the long axis of the dichroic dye molecules 1102 has a perpendicular or large angle with the light wave electric vector of the first axially polarized light 100 and the second axially polarized light 200, it absorbs less, and the first axially polarized light 100 and the second axially polarized light 200 have high transmittance when passing through the first liquid crystal layer 11. When sufficient voltage is applied to the first front transparent electrode 14 and the first rear transparent electrode 16, the first liquid crystal cell is in a driving state. The negative liquid crystal molecules 1101 in the electrode overlapping area are deflected on the second axis 20. When sufficient voltage is applied, they are deflected to a near-horizontal alignment (the angle between the liquid crystal molecules and the cell surface is less than 30°), and the dichroic dye molecules 1102 are also deflected to a near-horizontal alignment on the second axis 20. The long axis of the dichroic dye molecules 1102 is parallel to or has a small angle with the electric vector of the second axially polarized light 200, and it has a large absorption of the second axially polarized light 200. The second axially polarized light 200 has a low transmittance when it passes through the first liquid crystal layer 11.

[0050] In this embodiment, the second liquid crystal device 2 adopts a TN (twisted nematic) liquid crystal cell, which includes a second front substrate 21, a second liquid crystal layer 22, and a second rear substrate 23. The second front substrate 21 and the second rear substrate 23 are transparent substrates (such as transparent glass substrates or transparent plastic substrates). The second liquid crystal layer 22 is sandwiched between the second front substrate 21 and the second rear substrate 23, and the second liquid crystal layer 22 is composed of positive liquid crystal. A second front transparent electrode 24 and a second front alignment layer 25 are provided on the surface of the second front substrate 21 near the second liquid crystal layer 22. A second rear transparent electrode 26 and a second rear alignment layer 27 are provided on the surface of the second rear substrate 23 near the second liquid crystal layer 22. There is an electrode overlap region between the second rear transparent electrode 26 and the second front transparent electrode 24 to form a light control region. The second front alignment layer 25... The second rear alignment layer 27 is a horizontal alignment layer. By applying directional friction with an angle of 90° to the second front alignment layer 25 and the second rear alignment layer 27, the positive liquid crystal molecules 221 of the second liquid crystal layer 22 are twisted from front to back from the first axis 10 to the second axis 20 in the natural state (meaning that no voltage is applied between the second front transparent electrode 24 and the second rear transparent electrode 26, or the applied voltage is less than the threshold), presenting a 90° twisted arrangement (i.e., TN arrangement). The second liquid crystal device 2 has a 90° optical rotation function. However, when the second liquid crystal device 2 is in the driving state (the second front transparent electrode 24 and the second rear transparent electrode 26 are subjected to sufficient voltage), the positive liquid crystal molecules 221 in the electrode overlapping area are fully deflected into a vertical arrangement, and the second liquid crystal device 2 has no optical rotation function.

[0051] In this embodiment, the thickness of the first liquid crystal layer 11 is at least 4 μm.

[0052] The main body of the first liquid crystal device 1 is a first liquid crystal cell with a first liquid crystal layer 11 sandwiched between it. Dichroic dye molecules 1102 are mixed in the liquid crystal of the first liquid crystal layer 11. These molecules exhibit selective absorption characteristics for polarized light of different directions. They strongly absorb polarized light whose electric vector is parallel to or at a small angle to the long axis of the dye molecules, while their absorption of polarized light whose electric vector is perpendicular to or at a large angle to the long axis of the dye molecules is weaker. In this embodiment, the dichroic dye is a dark-colored organic dye. Specifically, the dichroic dye can be a single dichroic dye, such as a blue or purple dichroic dye, or a combination of two or more dichroic dye molecules 1102, such as a combination of blue, red, and / or yellow dichroic dyes. This allows it to simultaneously absorb multiple wavelengths of light, resulting in a better-looking black. Specifically, the dichroic dye can be, but is not limited to, the azo compounds and other dichroic organic dyes disclosed in patents such as US4122027A, US4565424A, JP56057850A, and WO2011157614A1. For liquid crystal electronically controlled reflectors, the dichroic dye also has the function of adjusting the reflector's hue; the dichroic dye is blue or bluish. Therefore, the rearview mirror's hue is designed to be bluish.

[0053] In this embodiment, the mass ratio of the dichroic dye in the first liquid crystal layer 11 is at least 1%. This allows the first liquid crystal layer to exhibit a significant polarization absorption effect, with a clear distinction between T1 and T2.

[0054] In this embodiment, the thickness of the second liquid crystal device 2 does not exceed 0.6 mm. This ensures that after the first specular reflection and the second specular reflection are superimposed, there will be no obvious ghosting.

[0055] In this embodiment, the liquid crystal electronically controlled reflector also includes a drive control system (not shown in the figure) capable of providing drive voltage. The drive lines of the first liquid crystal device 1 and the second liquid crystal device 2 are electrically connected to the corresponding output terminals of the drive control system. The drive control system can simultaneously provide drive voltage to the first liquid crystal device 1 and the second liquid crystal device 2, realizing simultaneous switching control of the first liquid crystal device 1 and the second liquid crystal device 2 to switch the functional states of the first liquid crystal device 1 and the second liquid crystal device 2.

[0056] In this embodiment, the display module 5 is selected from either a liquid crystal display unit or an organic electroluminescent display unit, and its display surface is black or dark, exhibiting low reflectivity. A polarizer 51 is provided on the light-emitting surface of the display module 5, and the polarization axis 511 of the polarizer 51 is matched with the first axial direction 10. When the liquid crystal electroluminescent mirror operates in low-reflection mode, the display light 500 emitted by the display module 5 passes through the mirror optical system with minimal light loss, forming a high-brightness display image. Simultaneously, the low reflectivity of the mirror and the high brightness of the display image create a significant contrast difference, effectively avoiding interference between the display image and the mirror reflection image.

[0057] The working principle of this type of liquid crystal electronically controlled reflector is briefly described below:

[0058] This liquid crystal electro-controlled mirror has two working modes: a high-reflection mode and a low-reflection mode. The high-reflection mode is its default working state, in which the first liquid crystal device 1 and the second liquid crystal device 2 both maintain their natural state. When ambient natural light is incident on the electro-controlled mirror, the incident light can be regarded as including a first axially polarized light 100 with a first axial polarization characteristic of 10 and a second axially polarized light 200 with a second axial polarization characteristic of 20.

[0059] When the first liquid crystal device 1 and the second liquid crystal device 2 are in their natural state, the liquid crystal electro-reflective mirror enters a high-reflectivity working mode. In the high-reflectivity working mode, the first axially polarized light 100 and the second axially polarized light 200 both pass through the first liquid crystal layer 11 with a high first transmittance T1. The first axially polarized light 100 matches the transmission axis 41 of the first reflective polarizer 3 and is thus transmitted. After the transmitted light enters the second liquid crystal device 2, it undergoes a 90° polarization rotation, and the polarization direction changes from the first axis 10 to the second axis 20. This polarization state matches the reflection axis 31 of the second reflective polarizer 4 and is thus totally reflected. When the reflected light passes through the second liquid crystal device 2 again, it undergoes a second 90° polarization rotation, and the polarization direction returns from the second axis 20 to the first axis 10, so that it can be transmitted through the first reflective polarizer 3 again. The beam then exits through the first liquid crystal device 1 again with a first transmittance T1. Through the above optical path, the first axially polarized light 100 is reflected inside the liquid crystal electro-reflective mirror and forms a first outgoing beam with a first specular reflection characteristic. When the second axially polarized light 200 is incident on the first reflective polarizer 3, it is totally reflected because its polarization direction matches the reflection axis 31 of the reflective polarizer. The reflected light then exits through the first liquid crystal device 1 with a first transmittance T1. Through the aforementioned optical path, the second axially polarized light 200 is reflected inside the mirror and finally forms a second outgoing beam with second specular reflection characteristics. The overall reflection of the mirror is formed by the superposition of the first and second outgoing beams. Due to the high first transmittance T1, both the first and second outgoing beams exit with high emissivity, thus significantly improving the intensity of their superimposed light. This allows the mirror to significantly overcome the brightness limit of the traditional single reflection path while maintaining overall compactness.

[0060] When a driving voltage is applied so that both the first liquid crystal device 1 and the second liquid crystal device 2 are in the driving state, the liquid crystal electro-reflective mirror enters a low-reflection working mode. In the low-reflection working mode, the incident first axially polarized light 100 still passes through the first liquid crystal layer 11 with a high first transmittance T1. The first axially polarized light 100 matches the transmission axis 41 of the first reflective polarizer 3 to achieve transmission. After the transmitted light enters the second liquid crystal device 2, it does not undergo a 90° polarization rotation and maintains the polarization direction of the first axis 10. This polarization state matches the transmission axis 41 of the second reflective polarizer 4 to achieve transmission again. Finally, the light beam penetrates to the light-absorbing substrate on the back of the mirror and is completely absorbed, thereby achieving a near-zero reflectivity of the first axially polarized light 100 in the electro-reflective mirror system. The second axially polarized light 200 passes through the first liquid crystal device 1 with a lower second transmittance T2. When the second axially polarized light 200 is incident on the first reflective polarizer 3, total internal reflection is achieved because the polarization direction is completely matched with the reflection axis 31 of the polarizer. When the reflected light passes through the first liquid crystal device 1 again, it exits through the first liquid crystal device 1 with a lower second transmittance T2. Because the second transmittance T2 is lower, the intensity of the reflected light of the second axially polarized light 200 is significantly reduced, and only the second axially polarized light 200 is emitted. Moreover, the second axially polarized light 200 is significantly reduced, so that the electronically controlled reflector as a whole presents a low-reflection working state.

[0061] Furthermore, it should be noted that the names of the various parts of the specific embodiments described in this specification may differ. All equivalent or simple variations made to the structure, features, and principles of this invention are included within the scope of protection of this invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the structure of this invention or exceed the scope defined by the claims, all of which should fall within the scope of protection of this invention.

Claims

1. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit, characterized in that: The system includes a first liquid crystal device, a second liquid crystal device, a first reflective polarizer, and a second reflective polarizer, arranged sequentially from front to back. A first axis and a second axis are defined as two axes parallel to the mirror surface of the liquid crystal electro-controlled reflector and orthogonal to each other. The main body of the first liquid crystal device is a first liquid crystal cell with a first liquid crystal layer sandwiched within it. The first liquid crystal layer is composed of negative liquid crystal doped with dichroic dyes. In its natural state, the negative liquid crystal molecules and dichroic dye molecules are vertically aligned. The first liquid crystal layer has a first transmittance T1 for both first-axis and second-axis polarized light. In the driven state, the negative liquid crystal molecules drive the dichroic dye molecules to deflect along the second axis, resulting in a second transmittance T2 for the second-axis polarized light, where T2 < T1. The second liquid crystal device has a 90° optical rotation function in its natural state, but no optical rotation function in the driven state. The first and second reflective polarizers can transmit first-axis polarized light and reflect second-axis polarized light.

2. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: Assume that the theoretical reflectivity of the electrically controlled mirror in the high-reflection state and the low-reflection state are R, respectively. A R B Then R A R B T1 and T2 satisfy the relation: R A =50%×T1 2 +50%×T1 2 =100%×T1 2 R B =50%×T2 2 .

3. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 2, characterized in that: The first transmittance is at least 70%.

4. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 3, characterized in that: The first transmittance is at least 80%.

5. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 2, characterized in that: The second transmittance does not exceed 30%.

6. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 5, characterized in that: The second transmittance does not exceed 20%.

7. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The first liquid crystal cell includes a first front substrate, a first liquid crystal layer, and a first rear substrate. The first front substrate and the first rear substrate are transparent substrates, and the first liquid crystal layer is sandwiched between the first front substrate and the first rear substrate. A first front transparent electrode and a first front alignment layer are provided on the surface of the first front substrate near the first liquid crystal layer, and a first rear transparent electrode and a first rear alignment layer are provided on the surface of the first rear substrate near the first liquid crystal layer. There is an electrode overlap region between the first rear transparent electrode and the first front transparent electrode to form a light control region. The first front alignment layer and the first rear alignment layer are vertical alignment layers. By applying a second axial alignment treatment to the first front alignment layer and / or the first rear alignment layer, the first liquid crystal device has a second axial alignment axis.

8. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The second liquid crystal device employs a TN liquid crystal cell, comprising a second front substrate, a second liquid crystal layer, and a second rear substrate. The second front substrate and the second rear substrate are transparent substrates. The second liquid crystal layer is sandwiched between the second front substrate and the second rear substrate and is composed of positive liquid crystal. A second front transparent electrode and a second front alignment layer are provided on the surface of the second front substrate near the second liquid crystal layer. A second rear transparent electrode and a second rear alignment layer are provided on the surface of the second rear substrate near the second liquid crystal layer. There is an electrode overlap region between the second rear transparent electrode and the second front transparent electrode to form a light control region. The second front alignment layer and the second rear alignment layer are horizontal alignment layers. By applying directional friction with an angle of 90° to the second front alignment layer and the second rear alignment layer, the positive liquid crystal molecules of the second liquid crystal layer are arranged in a twisted alignment of approximately 90° in their natural state, giving the second liquid crystal device a 90° optical rotation function. However, when the second liquid crystal device is in a driven state, the positive liquid crystal molecules in the electrode overlap region are fully deflected into a vertical alignment, and the second liquid crystal device has no optical rotation function.

9. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The thickness of the first liquid crystal layer is at least 4 μm.

10. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The mass ratio of the dichroic dye in the first liquid crystal layer is at least 1%.

11. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The dichroic dye is a dark-colored organic dye.

12. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The dichroic dye is blue or bluish.

13. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The thickness of the second liquid crystal device does not exceed 1 mm.

14. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 13, characterized in that: The thickness of the second liquid crystal device does not exceed 0.6 mm.

15. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The liquid crystal electronically controlled reflector also includes a drive control system capable of providing drive voltage, wherein the drive lines of the first liquid crystal device and the drive lines of the second liquid crystal device are electrically connected to the corresponding output terminals of the drive control system.

16. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The first liquid crystal device and the first reflective polarizer, the first reflective polarizer and the second liquid crystal device, and the second liquid crystal device and the second reflective polarizer are all bonded to each other by optical adhesive layers.

17. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: A black light-absorbing film layer is provided on the back of the liquid crystal electronically controlled reflector.

18. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 1, characterized in that: The liquid crystal electronically controlled reflector also includes a display module, which is disposed behind the second reflective polarizer; the light-emitting surface of the display module is provided with a polarizer, the polarization axis of which matches the first axial direction.

19. A liquid crystal electro-controlled reflector capable of breaking the reflectivity limit according to claim 18, characterized in that: The liquid crystal electro-controlled reflector has two operating modes: a high-reflection mode and a low-reflection mode. It decomposes incident light into first axially polarized light with a first axial polarization characteristic and second axially polarized light with a second axial polarization characteristic. In the high-reflection mode, the incident and reflection path of the first axially polarized light is as follows: it passes sequentially through a first liquid crystal device, a first reflective polarizer, and a second liquid crystal device; it is reflected by the second reflective polarizer and then sequentially transmitted through the second liquid crystal device, the first reflective polarizer, and the first liquid crystal device before exiting. The incident and reflection path of the second axially polarized light is as follows: it passes through the first liquid crystal device and is reflected by the first reflective polarizer, and then transmitted through the first liquid crystal device before exiting. In the low-reflection mode, the incident and reflection path of the first axially polarized light is as follows: it passes sequentially through the first liquid crystal device, the first reflective polarizer, the second liquid crystal device, and the polarizer of the display module; the first axially polarized light is absorbed at the polarizer. The incident and reflection path of the second axially polarized light is as follows: it passes through the first liquid crystal device and is absorbed by the first reflective polarizer.

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