An electronic rearview mirror

Abstract

The present invention relates to an electronic rearview mirror, including a liquid crystal cell, characterized in that: it further includes a polarizing mirror film; the liquid crystal cell is a vertically aligned liquid crystal cell, and a negative liquid crystal layer doped with a dichroic dye is provided in the vertically aligned liquid crystal cell. The vertically aligned liquid crystal cell has a liquid crystal alignment axis capable of determining the deflection direction of negative liquid crystal molecules in an electric field; the polarizing mirror film is disposed at the rear side of the liquid crystal cell, and the polarizing mirror film has a reflective polarization axis parallel to the liquid crystal alignment axis. This kind of electronic rearview mirror not only has a fast response speed and high transmittance, but also can simplify the structure and eliminate the polarizer, thereby avoiding a series of problems caused by the existence of the polarizer.

Description

Technical Field

[0001] The present invention relates to the field of automotive rearview mirrors, and particularly to an electronic rearview mirror. Background Art

[0002] An electronic rearview mirror is a rearview mirror whose mirror reflectivity can be controlled by a circuit. It is generally connected with a light sensor. When it senses the high beam illumination of the vehicle behind, it can reduce the reflection of the rearview mirror through circuit control, thereby avoiding the interference of the high beam on the driver's line of sight and improving driving safety.

[0003] An electronic rearview mirror with a streaming media function is provided with a display screen (such as a liquid crystal display screen, an OLED display screen), and the picture of the display screen can be presented through the mirror surface of the rearview mirror (generally set as a semi-transmissive and reflective mirror).

[0004] The existing electronic rearview mirrors mainly adopt two technologies: liquid crystal (LC) and electrochromic (EC). Among them, the LC electronic rearview mirror mainly controls the reflectivity of the mirror surface through a liquid crystal light valve; the liquid crystal light valve generally needs to be attached with a polarizer, and the interfacial reflection increased by the polarizer will cause certain ghosting and blurring problems in the reflected image. Moreover, the polarizer is generally made of a TAC (triacetyl cellulose) film with poor heat resistance, and the high-temperature environment inside the vehicle is likely to cause the polarizer to deform and cause problems such as mirror image distortion. The EC electronic rearview mirror directly controls the reflectivity of the rearview mirror through its electrochromic layer. Although it does not need to be attached with a polarizer, the EC electronic rearview mirror has a slow response speed and a low transmittance. When it is designed as a streaming media rearview mirror, the brightness loss of the display picture on the electrochromic layer is very large. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an electronic rearview mirror, which not only has a fast response speed and a high transmittance, but also can simplify the structure and eliminate the polarizer, thereby avoiding a series of problems caused by the existence of the polarizer. The adopted technical solution is as follows:

[0006] An electronic rearview mirror includes a liquid crystal cell, and is characterized in that: it further includes a polarizing mirror film; the liquid crystal cell is a vertically aligned liquid crystal cell, and a negative liquid crystal layer doped with a dichroic dye is provided in the vertically aligned liquid crystal cell. The vertically aligned liquid crystal cell has a liquid crystal alignment axis that can determine the deflection direction of the negative liquid crystal molecules in an electric field; the polarizing mirror film is arranged at the rear side of the liquid crystal cell, and the polarizing mirror film has a reflection polarization axis parallel to the liquid crystal alignment axis.

[0007] The above-mentioned negative liquid crystal layer can be formed by pre-dissolving a dichroic dye in a negative liquid crystal and sealing it together with the negative liquid crystal into a liquid crystal cell; the dichroic dye is generally a dark or black organic dye. Specifically, it can be a single dichroic dye, such as a blue or purple dichroic dye, or a combination of two or more dichroic dye molecules, such as a combination of blue, red, and / or yellow dichroic dyes. Thus, it can absorb light of multiple wavelengths simultaneously and present a better black color. 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, WO2011157614A1, etc. As a preferred embodiment of the present invention, the dichroic dye is a black dichroic dye.

[0008] The above-mentioned polarizing mirror film can be a specular reflection film with a specular reflection effect and the reflected light being polarized light, and its reflection polarization axis is the axial direction where the polarization angle of the reflected light is located. For the above-mentioned polarizing mirror film, currently, it can be, but is not limited to, the DBEF and RPM optical films produced by 3M Company; or, it can also be the "multi-layer optical thin film" described in the patent specification with the publication number of CN1170382A and film materials with similar functions. The reflectivity of such polarizing mirror films is generally between 40% and 55%.

[0009] The above-mentioned electronic rearview mirror generally faces the driver. For the convenience of explanation, only the light incident on the rearview mirror vertically (or at a small angle) needs to be analyzed. The external light incident on the electronic rearview mirror is generally natural light, which can be regarded as a mixed light of a first polarized light (polarization angle parallel to the liquid crystal alignment axis) and a second polarized light (polarization angle perpendicular to the liquid crystal alignment axis). Its light path is mainly as follows: The light incident on the rearview mirror first passes through the liquid crystal layer, and then is reflected by the polarizing mirror film. The formed reflected light passes through the liquid crystal layer again and exits. When the liquid crystal cell is in the OFF state (i.e., the natural state), the negative liquid crystal molecules and dichroic dye molecules in the negative liquid crystal layer both exhibit a vertical alignment state. After the external natural light is incident (only considering the case of vertical or small incident angles), the electric field component of the light is perpendicular (or nearly perpendicular) to the dichroic dye molecules. The dichroic dye molecules have almost no polarized light absorption for the incident light and the reflected light. The negative liquid crystal layer has very little polarized light absorption for natural light. After the light is reflected by the polarizing mirror film, it exits as the first polarized light to form a bright-state reflected mirror image. When the liquid crystal cell is in the ON state (i.e., a voltage is applied between the first electrode and the second electrode), the negative liquid crystal molecules in the negative liquid crystal layer tilt or are horizontally arranged along the liquid crystal alignment axis in the electric field, and at the same time drive the dichroic dye molecules to tilt or be horizontally arranged along the liquid crystal alignment axis, so that the negative liquid crystal layer has polarized light absorption along the liquid crystal alignment axis (the negative liquid crystal layer is equivalent to a polarizing film with the absorption axis being the liquid crystal alignment axis). The electric field component of the first polarized light is parallel to the dichroic dye molecules, while the electric field component of the second polarized light is perpendicular to the dichroic dye molecules. Therefore, the first polarized light will be absorbed when passing through the negative liquid crystal layer. Although the second polarized light will not be absorbed by the negative liquid crystal layer, it cannot be reflected by the polarizing mirror film (the polarizing mirror film can only reflect the first polarized light and cannot reflect the second polarized light). Eventually, both the first polarized light and the second polarized light cannot exit the rearview mirror (in fact, because the polarized light absorption rate of the dye and the polarized light reflectivity of the mirror film cannot reach 100%, a part can still exit), forming a dark state.

[0010] In a preferred embodiment, there is an included angle between the polarizing mirror film and the back surface of the liquid crystal cell, and the included angle can make the reflection polarization axis of the polarizing mirror film parallel to the liquid crystal alignment axis. Generally speaking, the polarizing mirror film can be adhered to the rear side of the liquid crystal cell through a transparent adhesive layer (generally required to have no birefringence) and set at a specific angle so that its reflection polarization axis is parallel to the liquid crystal alignment axis.

[0011] As a preferred embodiment of the present invention, the liquid crystal cell includes a first glass plate, the negative liquid crystal layer, and a second glass plate, which are arranged in sequence from front to back. The negative liquid crystal layer is sandwiched between the first glass plate and the second glass plate. On the side of the first glass plate close to the negative liquid crystal layer, a first electrode and a first alignment layer are provided. On the side of the second glass plate close to the negative liquid crystal layer, a second electrode and a second alignment layer are provided. There is an electrode overlap region between the second electrode and the first electrode to form a light control region. Generally speaking, when the negative liquid crystal molecules are under the action of an electric field, the long axis of their molecules tends to be perpendicular to the electric field. Therefore, when a voltage is applied between the first electrode and the second electrode, the negative liquid crystal molecules in the light control region change from a vertical arrangement to an inclined or horizontal arrangement along the liquid crystal orientation axis, and at the same time drive the dichroic dye molecules to change from a vertical state to an inclined or horizontal arrangement along the liquid crystal orientation axis. When light passes through the dichroic dye molecules, the dichroic dye molecules have a relatively high absorption rate for the electric field component of light in the long axis of their molecules, so it has a polarization absorption function. When the dichroic dye molecules are arranged inclined or horizontally on the liquid crystal orientation axis, they have an obvious polarization absorption effect on the linearly polarized light whose electric field component is on the liquid crystal orientation axis. That is to say, the liquid crystal cell has the function of an equivalent polarizing plate in the ON state, and its polarization absorption axis is the liquid crystal orientation axis of the liquid crystal cell.

[0012] Specifically, the first electrode and the second electrode can be transparent electrodes, which are formed by patterning a transparent conductive film (such as an ITO film).

[0013] As a further preferred embodiment of the present invention, both the first alignment layer and the second alignment layer are vertical alignment layers (such as vertical alignment polyimide coatings). The negative liquid crystal molecules (generally nematic liquid crystals) and the dichroic dye molecules generally have a rod-like structure with a long axis of the molecule. Therefore, the negative liquid crystal molecules in the negative liquid crystal layer are vertically aligned in the natural state (OFF state) (the long axis of the molecule is perpendicular to the first glass plate or the second glass plate), and the dichroic dye molecules in the negative liquid crystal layer also present a vertical state (similarly, the long axis of the molecule is perpendicular to the first glass plate or the second glass plate). The liquid crystal orientation axis is generally formed by applying a directional friction to the first alignment layer and the second alignment layer (polymer orientation or other methods can also be used). For example, by applying opposite frictions to the first alignment layer and the second alignment layer on the liquid crystal orientation axis, a pretilt angle can be formed for the negative liquid crystal molecules in the natural state (the pretilt angle is generally about 1°, and the negative liquid crystal layer can be considered to be vertically aligned when the pretilt angle is within 5°).

[0014] The above liquid crystal cell generally maintains a certain thickness (such as 3μm to 20μm) of the negative liquid crystal layer through a spacer design (such as sandwiching spacers with a certain diameter in the negative liquid crystal layer). Thus, the light absorption rates of the liquid crystal cell in the ON state and the OFF state (including the light absorption rate in the OFF state) can be adjusted by the thickness of the negative liquid crystal layer and the dissolution ratio of the dichroic dye in the liquid crystal. As a preferred embodiment of the present invention, the thickness of the negative liquid crystal layer is 4μm to 10μm. By adjusting the light absorption rates of the liquid crystal cell in the ON state and the OFF state and combining with the reflectance of the polarizing mirror film, the overall reflectance of the mirror can be made to be between 30% and 50% (typical value is 40%) in the ON state and between 5% and 20% (typical value is 10%) in the OFF state, meeting the anti-high beam requirements of the rearview mirror.

[0015] As a preferred embodiment of the present invention, the polarizing mirror film is a semi-transmissive and semi-reflective film. When the polarizing mirror film is a semi-transmissive and semi-reflective film, its transmittance is generally between 40% and 60%; the polarizing mirror film can transmit light in another polarization direction, and thus it has a transmission polarization axis orthogonal to the reflection polarization axis. The transmission polarization axis is the other axis where the polarization angle of the transmitted light lies.

[0016] As a further preferred embodiment of the present invention, a display is provided at the rear side of the liquid crystal cell, and a polarizer is provided on the front side of the display. The polarization axis of the polarizer is parallel to the transmission polarization axis of the polarizing mirror film. Such a rearview mirror is generally called a streaming media rearview mirror, and the light of the display can pass through the rearview mirror with very little loss, so that the picture of the display can be presented through the rearview mirror.

[0017] As a still further preferred embodiment of the present invention, the liquid crystal cell is in a long strip shape; the included angle between the liquid crystal alignment axis and the length direction of the liquid crystal cell is 40 - 50°. Thus, both the display picture and the reflection image of the streaming media rearview mirror can have perpendicular polarization components, and the driver can also see the display picture and the reflection image when wearing polarized glasses.

[0018] As a preferred embodiment of the present invention, the electronic rearview mirror further includes a protective lens, the protective lens is attached to the front side of the liquid crystal cell, and a shielding layer capable of shielding the peripheral area of the liquid crystal cell is provided on the protective lens. The protective lens can play a protective role for the liquid crystal cell, and the shielding layer can shield the peripheral area of the liquid crystal cell to make its appearance more beautiful.

[0019] As a preferred embodiment of the present invention, the electronic rearview mirror further includes a light sensor and a control circuit for controlling the liquid crystal cell to be in the OFF state or the ON state. The light sensor is electrically connected to the corresponding signal input terminal of the control circuit. In the driving circuit of the electronic rearview mirror, the control circuit can adopt the common driving method of liquid crystal devices. For example, a square wave driving with a certain voltage (such as 3V - 20V) can be used to achieve the control of the OFF state and the ON state. When the light sensor does not sense the strong light irradiated by the high beam of the vehicle behind, the control circuit controls the liquid crystal cell to be in the OFF state. The negative liquid crystal layer has very little polarization absorption of natural light, and the light almost remains in the natural light state and is reflected in the rearview mirror to form a reflection image. When the light sensor senses the strong light irradiated by the high beam of the vehicle behind, the control circuit controls the liquid crystal cell to be in the ON state, thereby reducing the reflection of the rearview mirror and avoiding the interference of the high beam on the driver's line of sight, improving driving safety.

[0020] As a preferred embodiment of the present invention, the dark state reflectivity of the electronic rearview mirror is not greater than 10%; the bright state reflectivity of the electronic rearview mirror is greater than 40%.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] This kind of electronic rearview mirror not only has a fast response speed and a high transmittance, but also can simplify the structure, eliminate the polarizer, and thus avoid a series of problems caused by the existence of the polarizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of the electronic rearview mirror of Embodiment 1 of the preferred embodiment of the present invention.

[0024] Figure 2 is Figure 1 a schematic optical principle diagram of the shown electronic rearview mirror when the liquid crystal cell is in the OFF state.

[0025] Figure 3 is Figure 1 a schematic optical principle diagram of the shown electronic rearview mirror when the liquid crystal cell is in the ON state.

[0026] Figure 4 is Figure 1 a schematic functional diagram of the polarizing mirror film in the shown electronic rearview mirror.

[0027] Figure 5 is a schematic structural diagram of the electronic rearview mirror of Embodiment 2 of the preferred embodiment of the present invention.

[0028] Figure 6 is Figure 5 a schematic optical principle diagram of the shown electronic rearview mirror when it is in the ON state.

[0029] Figure 7 is Figure 5 the overall external shape diagram of the electronic rearview mirror shown in the figure.

[0030] Figure 8 is the logic block diagram among the light sensor, the control circuit and the liquid crystal cell in the second embodiment of the preferred embodiment of the present invention. Specific embodiments

[0031] Embodiment 1

[0032] As Figures 1-4 shown, this kind of electronic rearview mirror includes a liquid crystal cell 1 and a polarizing mirror film 2; the liquid crystal cell is a vertically aligned liquid crystal cell, which includes a first glass plate 11, a negative liquid crystal layer 12 doped with a dichroic dye and a second glass plate 13 arranged in sequence from front to back. The negative liquid crystal layer 12 is sandwiched between the first glass plate 11 and the second glass plate 13. A first electrode 14 and a first alignment layer 15 are provided on the side of the first glass plate 11 close to the negative liquid crystal layer 12. A second electrode 16 and a second alignment layer 17 are provided on the side of the second glass plate 13 close to the negative liquid crystal layer 12. There is an electrode overlapping area between the second electrode 16 and the first electrode 14 to form a light control area 100; the liquid crystal cell 1 has a liquid crystal alignment axis 101 that can determine the deflection direction of the negative liquid crystal molecules 121 in the electric field; the polarizing mirror film 2 is arranged at the rear side of the liquid crystal cell 1, and the polarizing mirror film 2 has a reflection polarization axis 201 parallel to the liquid crystal alignment axis 101.

[0033] In this embodiment, the negative liquid crystal layer 12 can be formed by pre-dissolving a dichroic dye in a negative liquid crystal and sealing it into the liquid crystal cell 1 together with the negative liquid crystal; the dichroic dye is a black dichroic dye. The negative liquid crystal layer 12 contains negative liquid crystal molecules 121 and dichroic dye molecules 122.

[0034] In this embodiment, the first electrode 14 and the second electrode 16 are transparent electrodes, and the transparent electrodes are formed by patterning a transparent conductive film (such as an ITO thin film).

[0035] In this embodiment, the first alignment layer 15 and the second alignment layer 17 are both vertical alignment layers (such as vertical alignment polyimide coatings). The negative liquid crystal molecules 121 (generally nematic liquid crystals) and the dichroic dye molecules 122 generally have a rod-like structure with a molecular long axis. Thus, the negative liquid crystal molecules 121 of the negative liquid crystal layer 12 are vertically aligned in the natural state (OFF state) (the molecular long axis is perpendicular to the first glass plate 11 or the second glass plate 13), and the dichroic dye molecules 122 in the negative liquid crystal layer 12 are also in a vertical state (similarly, the molecular long axis is perpendicular to the first glass plate 11 or the second glass plate 13). The liquid crystal alignment axis 101 is generally formed by applying a directional rubbing to the first alignment layer 15 and the second alignment layer 17 (polymer orientation and other methods can also be used). For example, by applying an opposite rubbing to the first alignment layer 15 and the second alignment layer 17 along the liquid crystal alignment axis 101, a pretilt angle can be formed in the natural state of the negative liquid crystal molecules 121 (the pretilt angle is generally about 1°, and when the pretilt angle is within 5°, the negative liquid crystal layer 12 can be considered as vertically aligned).

[0036] In this embodiment, there is an angle between the polarizing mirror film 2 and the back surface of the liquid crystal cell 1, and this angle can make the reflection polarization axis 201 of the polarizing mirror film 2 parallel to the liquid crystal alignment axis 101. Generally, the polarizing mirror film 2 can be adhered to the rear side of the liquid crystal cell 1 through a transparent adhesive layer (generally required to have no birefringence) and set at a specific angle to make its reflection polarization axis 201 parallel to the liquid crystal alignment axis 101.

[0037] In this embodiment, the thickness of the negative liquid crystal layer 12 is 4 μm to 10 μm. The liquid crystal cell 1 can maintain a certain thickness of the negative liquid crystal layer 12 (such as 3 μm to 20 μm) through a spacer design (such as sandwiching spacers with a certain diameter in the negative liquid crystal layer 12). Thus, the light absorption rates of the liquid crystal cell 1 in the ON state and the OFF state (including the light absorption rate in the OFF state) can be adjusted by the thickness of the negative liquid crystal layer 12 and the dissolution ratio of the dichroic dye in the liquid crystal. By adjusting the light absorption rates of the liquid crystal cell 1 in the ON state and the OFF state and combining with the reflectivity of the polarizing mirror film 2, the overall reflectivity of the mirror can be made to be between 30% and 50% (typical value is 40%) in the ON state and between 5% and 20% (typical value is 10%) in the OFF state, meeting the anti-high-beam requirements of the rearview mirror.

[0038] In this embodiment, the dark state reflectivity of the electronic rearview mirror is not greater than 10%; the bright state reflectivity of the electronic rearview mirror is greater than 40%.

[0039] In this embodiment, the polarizing mirror film 2 can be a specular reflection film with a specular reflection effect and the reflected light being polarized light. Its reflected polarization axis 201 is the axis where the polarization angle of the reflected light lies. For the above-mentioned polarizing mirror film 2, currently optional but not limited to the DBEF and RPM optical films produced by 3M Company; or, it can also be the "multi-layer optical thin film" described in the patent specification with the publication number CN1170382A and film materials with similar functions. The reflectivity of such polarizing mirror films 2 is generally between 40% and 55%.

[0040] The working principle of this electronic rearview mirror is briefly described below:

[0041] The above-mentioned electronic rearview mirror generally faces the driver directly. For the convenience of explanation, only the light rays incident on the rearview mirror vertically (or at a small angle) need to be analyzed. The external light rays incident on the electronic rearview mirror are generally natural light, which can be regarded as a mixed light of a first polarized light (polarization angle parallel to the liquid crystal alignment axis 101) and a second polarized light (polarization angle perpendicular to the liquid crystal alignment axis 101). Its light path is mainly as follows: The light rays 30 incident on the rearview mirror first pass through the liquid crystal layer, and then are reflected by the polarizing mirror film 2, and the formed reflected light rays 40 pass through the negative liquid crystal layer 12 again and come out.

[0042] When the liquid crystal cell 1 is in the OFF state (i.e., the natural state), the negative liquid crystal molecules 121 and the dichroic dye molecules 122 in the negative liquid crystal layer 12 both show a vertical alignment state. After the external natural light is incident (only considering the case of vertical or small incident angles), the electric field component of the light ray is perpendicular (or nearly perpendicular) to the dichroic dye molecules 122. The dichroic dye molecules 122 have almost no polarized light absorption for both the incident light and the reflected light. The negative liquid crystal layer 12 has very little polarized light absorption for natural light. After the light is reflected by the polarizing mirror film 2, it exits as the first polarized light, forming a bright-state reflection mirror image.

[0043] When the liquid crystal cell 1 is in the ON state (i.e., a voltage is applied between the first electrode 14 and the second electrode 16), the negative liquid crystal molecules 121 of the negative liquid crystal layer 12 are tilted or horizontally arranged in the electric field along the liquid crystal alignment axis 101, and at the same time drive the dichroic dye molecules 122 to be tilted or horizontally arranged along the liquid crystal alignment axis 101, so that the negative liquid crystal layer 12 has polarization absorption along the liquid crystal alignment axis 101. (When light passes through the dichroic dye molecules 122, the dichroic dye molecules 122 have a higher absorption rate for the electric field component of light in the molecular long axis, so it has a polarization absorption function. When the dichroic dye molecules 122 are tilted or horizontally arranged along the liquid crystal alignment axis 101, it has an obvious polarization absorption effect on the linearly polarized light with the electric field component on the liquid crystal alignment axis 101). The electric field component of the first polarized light is parallel to the dichroic dye molecules 122, while the electric field component of the second polarized light is perpendicular to the dichroic dye molecules 122. Therefore, the first polarized light will be absorbed when passing through the negative liquid crystal layer 12. Although the second polarized light will not be absorbed by the negative liquid crystal layer 12, it cannot be reflected by the polarizing mirror film 2 (the polarizing mirror film 2 only reflects the first polarized light and cannot reflect the second polarized light). Finally, both the first polarized light and the second polarized light cannot exit the rearview mirror (in fact, due to the polarization absorption rate of the dye and the polarization reflectivity of the mirror film cannot reach 100%, a part can still exit), forming a dark state.

[0044] Example 2

[0045] Reference Figures 5-8 , in other parts are the same as in Example 1, the difference is that: the electronic rearview mirror of this embodiment further includes a protective lens 3, the protective lens 3 is attached to the front side of the liquid crystal cell 1, and the protective lens 3 is provided with a shielding layer 31 that can shield the peripheral area of the liquid crystal cell 1. The protective lens 3 can protect the liquid crystal cell 1, and the shielding layer 31 can shield the peripheral area of the liquid crystal cell 1, making its appearance more beautiful.

[0046] In this embodiment, the polarizing mirror film 2 is a semi-transmissive and semi-reflective film; a TFT display 4 is provided on the rear side of the liquid crystal cell 1, and a polarizer 41 is provided on the front side of the TFT display 4, and the polarization axis 411 of the polarizer 41 is parallel to the transmission polarization axis 202 of the polarizing mirror film 2. This kind of rearview mirror is generally called a streaming media rearview mirror. The light of the TFT display 4 can pass through the rearview mirror with almost no loss, so that the picture of the TFT display 4 can be presented through the rearview mirror. When the polarizing mirror film 2 is a semi-transmissive and semi-reflective film, its transmittance is generally between 40% and 60%; the polarizing mirror film 2 can transmit light of the other polarization direction, so it has a transmission polarization axis 202 orthogonal to the reflection polarization axis 201, and the transmission polarization axis 202 is the other axis where the polarization angle of the transmitted light is located.

[0047] In this embodiment, the liquid crystal cell 1 is strip-shaped; the angle between the liquid crystal alignment axis 101 and the length direction of the liquid crystal cell 1 is 40-50°. Thus, both the display screen and the reflection mirror image of the streaming media rearview mirror can have a vertical polarization component, and the driver can see the display screen and the reflection mirror image even when wearing polarized glasses.

[0048] The electronic rearview mirror of this embodiment further includes a light sensor 5 and a control circuit 6 for controlling the liquid crystal cell 1 to be in the OFF state or the ON state. The light sensor 5 is electrically connected to the corresponding signal input terminal of the control circuit 6. In the driving circuit of the electronic rearview mirror, the control circuit 6 can adopt the common driving method of liquid crystal devices. For example, a square wave driving with a certain voltage (such as 3V to 20V) can be used to achieve the control of the OFF state and the ON state. When the light sensor 5 does not sense the strong light irradiated by the high beam of the vehicle behind, the control circuit 6 controls the liquid crystal cell 1 to be in the OFF state. The negative liquid crystal layer 12 has very little polarization absorption of natural light, and the light is almost reflected in the rearview mirror in the state of natural light, forming a reflection mirror image; when the light sensor 5 senses the strong light irradiated by the high beam of the vehicle behind, the control circuit 6 controls the liquid crystal cell 1 to be in the ON state, thereby reducing the reflection of the rearview mirror, avoiding the interference of the high beam on the driver's line of sight, and improving the driving safety.

[0049] In addition, it should be noted that for the specific embodiments described in this specification, the names of their various parts and the like can be different. Any equivalent or simple changes made according to the structure, features, and principles of the inventive concept of this invention patent are included in the protection scope of this invention patent. Those skilled in the technical field to which this invention belongs can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the structure of this invention or exceed the scope defined by this claim book, they should all belong to the protection scope of this invention.

Claims

1. An electronic rearview mirror, comprising a liquid crystal cell, characterized in that: It further includes a polarizer film; the liquid crystal cell is a vertically aligned liquid crystal cell, and the vertically aligned liquid crystal cell includes a first glass plate, a negative liquid crystal layer doped with a dichroic dye, and a second glass plate arranged in sequence from front to back. The negative liquid crystal layer is sandwiched between the first glass plate and the second glass plate. A first electrode and a first alignment layer are provided on the side of the first glass plate close to the negative liquid crystal layer, and a second electrode and a second alignment layer are provided on the side of the second glass plate close to the negative liquid crystal layer. There is an electrode overlapping area between the second electrode and the first electrode to form a light control area. The vertically aligned liquid crystal cell has a liquid crystal alignment axis that can determine the deflection direction of the negative liquid crystal molecules in an electric field; the polarizer film is arranged on the rear side of the liquid crystal cell, and the polarizer film has a reflection polarization axis parallel to the liquid crystal alignment axis; there is an included angle between the polarizer film and the back surface of the liquid crystal cell, and the included angle can make the reflection polarization axis of the polarizer film parallel to the liquid crystal alignment axis.

2. An electronic rearview mirror according to claim 1, characterized in that: Both the first alignment layer and the second alignment layer are vertically aligned layers.

3. An electronic rearview mirror according to claim 1, characterized in that: The polarizer film is a semi-transmissive and semi-reflective film.

4. The electronic rearview mirror according to claim 3, characterized in that: A display is provided on the rear side of the liquid crystal cell, and a polarizer is provided on the front side of the display. The polarization axis of the polarizer is parallel to the transmission polarization axis of the polarizer film.

5. An electronic rearview mirror according to claim 3, characterized in that: The liquid crystal cell is in a long strip shape; the included angle between the liquid crystal alignment axis and the length direction of the liquid crystal cell is 40 - 50°.

6. An electronic rearview mirror according to any one of claims 1-5, characterized in that: The electronic rearview mirror further includes a protective lens, and the protective lens is attached to the front side of the liquid crystal cell. A shielding layer capable of shielding the peripheral area of the liquid crystal cell is provided on the protective lens.

7. An electronic rearview mirror according to any one of claims 1-5, characterized in that: The electronic rearview mirror further includes a light sensor and a control circuit for controlling the liquid crystal cell to be in the OFF state or the ON state. The light sensor is electrically connected to the corresponding signal input terminal of the control circuit.

8. An electronic rearview mirror according to any one of claims 1-5, characterized in that: The dark state reflectivity of the electronic rearview mirror is not greater than 10%; the bright state reflectivity of the electronic rearview mirror is greater than 40%.

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