CN219856986U - Electronic rearview mirror - Google Patents

Abstract

The utility model relates to an electronic rearview mirror, which comprises a liquid crystal box and is characterized in that: the liquid crystal display also comprises a polarizer mask; the liquid crystal box is a vertical alignment liquid crystal box, a negative liquid crystal layer doped with dichroic dye is arranged in the vertical alignment liquid crystal box, and the vertical alignment liquid crystal box is provided with a liquid crystal orientation axis capable of determining the deflection direction of negative liquid crystal molecules in an electric field; a polarizer film is disposed on the rear side of the liquid crystal cell, the polarizer film having a reflective polarizing axis parallel to the liquid crystal alignment axis. The electronic rearview mirror has the advantages of high response speed, high transmittance, simplified structure and no polaroid, thereby avoiding a series of problems caused by the existence of the polaroid.

Description

Electronic rearview mirror

Technical Field

The utility model relates to the field of automobile rearview mirrors, in particular to an electronic rearview mirror.

Background

The electronic rearview mirror is a rearview mirror with the mirror surface reflectivity controlled by a circuit, is generally connected with a light sensor, and can reduce the reflection of the rearview mirror by the circuit control when sensing the irradiation of a rear vehicle high beam, thereby avoiding the interference of the high beam to the sight of a driver and improving the driving safety.

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

The existing electronic rearview mirror mainly adopts two technologies of Liquid Crystal (LC) and Electrochromic (EC), wherein the LC electronic rearview mirror mainly controls the reflectivity of a mirror surface through a liquid crystal light valve; the liquid crystal light valve generally needs to be attached with a polaroid, the increased interface reflection of the polaroid can cause the problem of certain ghost image blurring of the reflected mirror image, the polaroid is generally manufactured by a TAC (triacetate) film with poor temperature resistance, and the high-temperature environment in a vehicle can easily deform the polaroid to cause the problems of mirror image distortion and the like. The EC electronic rearview mirror directly controls the reflectivity of the rearview mirror through the electrochromic layer, and although the EC electronic rearview mirror does not need to be pasted with a polaroid, the EC electronic rearview mirror has low response speed and low transmittance, and when the EC electronic rearview mirror is designed into a streaming media rearview mirror, the brightness loss of a display picture on the electrochromic layer is very large.

Disclosure of Invention

The technical problem to be solved by the utility model is to provide the electronic rearview mirror which has the advantages of high response speed, high transmittance, simplified structure and no polaroid, thereby avoiding a series of problems caused by the existence of the polaroid. The technical scheme adopted is as follows:

an electronic rearview mirror comprising a liquid crystal cell, characterized in that: the liquid crystal display also comprises a polarizer mask; the liquid crystal box is a vertical alignment liquid crystal box, a negative liquid crystal layer doped with dichroic dye is arranged in the vertical alignment liquid crystal box, and the vertical alignment liquid crystal box is provided with a liquid crystal orientation axis capable of determining the deflection direction of negative liquid crystal molecules in an electric field; a polarizer film is disposed on the rear side of the liquid crystal cell, the polarizer film having a reflective polarizing axis parallel to the liquid crystal alignment axis.

The negative liquid crystal layer may be formed by dissolving a dichroic dye in a negative liquid crystal in advance and sealing the dye in a liquid crystal cell together with the negative liquid crystal; the dichroic dye is generally a dark or black organic dye, and specifically, it may be a single dichroic dye such as a blue or violet dichroic dye, or a combination of two or more dichroic dye molecules such as a combination of blue, red and/or yellow dichroic dyes, whereby it can absorb light of various wavelengths simultaneously to exhibit better black. Specifically, the dichroic dye may be, but not limited to, a dichroic organic dye such as an azo compound disclosed in US4122027A, US4565424A, JP56057850A, WO2011157614A1 or the like. As a preferred embodiment of the present utility model, the dichroic dye is a black dichroic dye.

The polarizer film may be a specular reflection film having a specular reflection effect and having a polarized light as reflected light, and the reflected polarized light axis is an axial direction in which the polarized angle of the reflected light is located. The polarizer masks described above are currently selected from, but not limited to, DBEF and RPM optical films available from 3M company; alternatively, it may be a "multilayer optical film" as described in the patent specification of CN1170382a and a film material having a similar function, and the reflectance of such a polarizer film is generally between 40% and 55%.

For convenience of explanation, the electronic rearview mirror generally faces the driver, only the light incident on the rearview mirror at a vertical (or small angle) is needed for analysis, the external light incident on the electronic rearview mirror is generally natural light, and can be regarded as the mixed light of the first polarized light (the polarization angle is parallel to the liquid crystal orientation axis) and the second polarized light (the polarization angle is perpendicular to the liquid crystal orientation axis), and the light paths are mainly as follows: the light rays entering the rearview mirror pass through the liquid crystal layer firstly and then are reflected by the polarizer mask, and the formed reflected light rays pass through the liquid crystal layer again. When the liquid crystal cell is in an OFF state (i.e., a natural state), both the negative liquid crystal molecules and the dichroic dye molecules of the negative liquid crystal layer are in a vertical alignment state, after external natural light is incident (only the case of a vertical or small incident angle is considered), the electric field component of the light is vertical (or nearly vertical) to the dichroic dye molecules, the dichroic dye molecules almost have no polarized light absorption on both the incident light and the reflected light, the polarized light absorption of the negative liquid crystal layer on the natural light is very small, and the light is emitted as first polarized light to form a bright reflection mirror image after being reflected by the polarizer mask. When the liquid crystal box is in an ON state (namely, voltage is applied between the first electrode and the second electrode), negative liquid crystal molecules of the negative liquid crystal layer are obliquely or horizontally arranged along a liquid crystal orientation axis in an electric field, and meanwhile, the dichroic dye molecules are driven to be obliquely or horizontally arranged along the liquid crystal orientation axis, so that the negative liquid crystal layer has polarization absorbability ON the liquid crystal orientation axis (the negative liquid crystal layer is equivalent to a polarizer with the absorption axis being the liquid crystal orientation axis), an electric field component of first polarized light is parallel to the dichroic dye molecules, and an electric field component of second polarized light is perpendicular to the dichroic dye molecules, therefore, the first polarized light can be absorbed when passing through the negative liquid crystal layer, the second polarized light can not be absorbed by the negative liquid crystal layer, and can not be reflected by the polarizer film (the polarizer film only reflects the first polarized light, can not reflect the second polarized light), and finally, the first polarized light and the second polarized light can not exit the rearview mirror (actually can not reach 100% due to the polarization absorptivity of the dye and the polarized light of the mirror film or can not partially exit), so as to form a dark state.

In a preferred scheme, an included angle is formed between the polarizer film and the back surface of the liquid crystal box, and the included angle can enable the reflection polarization axis of the polarizer film to be parallel to the liquid crystal orientation axis. In general, the polarizer film may be adhered to the rear side of the liquid crystal cell through a transparent adhesive layer (no birefringence is generally required) and disposed at a specific angle such that its reflective polarizing axis is parallel to the liquid crystal alignment axis.

As a preferable scheme of the utility model, the liquid crystal box comprises a first glass plate, the negative liquid crystal layer and a second glass plate which are sequentially arranged from front to back, wherein the negative liquid crystal layer is clamped between the first glass plate and the second glass plate, a first electrode and a first alignment layer are arranged on the side surface of the first glass plate, which is close to the negative liquid crystal layer, a second electrode and a second alignment layer are arranged on the side surface of the second glass plate, which is close to the negative liquid crystal layer, and an electrode overlapping area is formed between the second electrode and the first electrode to form a light control area. In general, the long axes of the negative liquid crystal molecules tend to be perpendicular to the electric field when the electric field is applied, so that when a voltage is applied between the first electrode and the second electrode, the negative liquid crystal molecules in the light control region are changed from vertical arrangement to inclined or horizontal arrangement along the liquid crystal alignment axis, and meanwhile, the dichroic dye molecules are driven to be changed from vertical state to inclined or horizontal arrangement along the liquid crystal alignment axis. When light passes through the dichroic dye molecules, the dichroic dye molecules have a higher absorptivity to the electric field component of light on the molecular long axis thereof, whereby they have a polarization absorption function. When the dichroic dye molecules are present in an inclined or horizontal arrangement ON the liquid crystal alignment axis, they have a remarkable polarization absorption effect ON linearly polarized light having an electric field component ON the liquid crystal alignment axis, that is, the liquid crystal cell has an equivalent polarizer effect in the ON state, and the polarization absorption axis thereof is the liquid crystal alignment axis of the liquid crystal cell.

Specifically, the first electrode and the second electrode may be transparent electrodes, and are patterned by a transparent conductive film (such as an ITO film).

As a further preferred embodiment of the present utility model, the first alignment layer and the second alignment layer are both vertical alignment layers (such as vertically aligned polyimide coating). The negative liquid crystal molecules (typically nematic liquid crystal) and the dichroic dye molecules are generally rod-shaped structures having a long molecular axis, whereby the negative liquid crystal molecules of the negative liquid crystal layer are vertically aligned (the long molecular axis is perpendicular to the first glass plate or the second glass plate) in a natural state (OFF state), and the dichroic dye molecules in the negative liquid crystal layer are also vertically aligned (the long molecular axis is also perpendicular to the first glass plate or the second glass plate). The liquid crystal alignment axis is generally formed by applying alignment friction to the first alignment layer and the second alignment layer (polymer alignment or the like may be used), for example: the negative liquid crystal molecules can have a pretilt angle in a natural state by applying opposite rubbing to the first alignment layer and the second alignment layer on the liquid crystal alignment axis (the pretilt angle is generally about 1 ° and the pretilt angle is within 5 ° so that the negative liquid crystal layer is considered to be vertically aligned).

The above-mentioned liquid crystal cell generally maintains a certain thickness (e.g., 3 μm to 20 μm) of the negative liquid crystal layer by a spacer design (e.g., a spacer having a certain diameter is interposed in the negative liquid crystal layer), whereby the light absorptance (including the light absorptance in the OFF state) of the liquid crystal cell in the ON state and 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. In a preferred embodiment of the present utility model, the negative liquid crystal layer has a thickness of 4 μm to 10 μm. By adjusting the light absorptivity of the liquid crystal box in the ON state and the OFF state and combining the reflectivity of the polarizer mask, the overall reflectivity of the reflector can be between 30% and 50% (typically 40%) in the ON state and between 5% and 20% (typically 10%) in the OFF state, thereby meeting the requirement of the rearview mirror ON high beam prevention.

As a preferable scheme of the utility model, the polarizer mask is a semi-transparent semi-reflective film. When the polarizer mask is a semi-transparent and semi-reflective film, the transmissivity of the polarizer mask is generally between 40% and 60%; the polarizer film may transmit light of another polarization direction, whereby it has a transmission polarization axis orthogonal to the reflection polarization axis, i.e. another axis at which its transmission polarization angle is located.

As a further preferable scheme of the utility model, the rear side of the liquid crystal box is provided with a display, the front side of the display is provided with a polaroid, and the polarizing axis of the polaroid is parallel to the transmission polarizing axis of the polarizing film. Such a rearview mirror is generally called a streaming rearview mirror, and light of a display can pass through the rearview mirror with little loss, so that a picture of the display can be displayed through the rearview mirror.

As a further preferable mode of the utility model, the liquid crystal cell is in a strip shape; the included angle between the liquid crystal orientation axis and the length direction of the liquid crystal box is 40-50 degrees. Therefore, the display picture and the reflection mirror image of the streaming media rearview mirror have vertical polarized light components, and the display picture and the reflection mirror image can be seen by a driver under the condition of having polarized light glasses.

As a preferable scheme of the utility model, the electronic rearview mirror further comprises a protective lens, wherein the protective lens is attached to the front side of the liquid crystal box, and a shielding layer capable of shielding the peripheral area of the liquid crystal box is arranged on the protective lens. The protective lenses can protect the liquid crystal box, and the shielding layer can shield the peripheral area of the liquid crystal box, so that the appearance of the liquid crystal box is more attractive.

As a preferable scheme of the utility model, the electronic rearview mirror further comprises a light sensor and a control circuit for controlling the liquid crystal box to be in an OFF state or an ON state, wherein the light sensor is electrically connected with a signal input end corresponding to the control circuit. In the driving circuit of the electronic rearview mirror, the control circuit can adopt a common driving mode of a liquid crystal device, for example, square wave driving with a certain voltage (such as 3V-20V) can be adopted to realize control of an OFF state and an ON state. When the light sensor does not sense strong light irradiated by a rear vehicle high beam, the control circuit controls the liquid crystal box to be in an OFF state, the negative liquid crystal layer has very small polarized light absorption on natural light, and the light almost keeps the natural light state to be reflected in the rearview mirror to form a reflection mirror image; when the light sensor senses strong light irradiated by a rear vehicle high beam, the control circuit controls the liquid crystal box to be in an ON state, so that reflection of the rearview mirror is reduced, interference of the high beam to the sight of a driver is avoided, and driving safety is improved.

As a preferable scheme of the utility model, the dark state reflectivity of the electronic rearview mirror is not more than 10%; the bright state reflectivity of the electronic rearview mirror is more than 40%.

Compared with the prior art, the utility model has the following advantages:

the electronic rearview mirror has the advantages of high response speed, high transmittance, simplified structure and no polaroid, thereby avoiding a series of problems caused by the existence of the polaroid.

Drawings

Fig. 1 is a schematic view showing the structure of an electronic rear view mirror according to an embodiment of the present utility model.

Fig. 2 is a schematic view of the optical principle of the electronic rear view mirror shown in fig. 1 in the OFF state of the liquid crystal cell.

Fig. 3 is a schematic view of the optical principle of the electronic rear view mirror shown in fig. 1 in the ON state of the liquid crystal cell.

Fig. 4 is a functional schematic diagram of a polarizer mask in the electronic rear view mirror shown in fig. 1.

Fig. 5 is a schematic structural view of a second electronic rear view mirror according to an embodiment of the present utility model.

Fig. 6 is a schematic view of the optical principle of the electronic rear view mirror shown in fig. 5 in an ON state.

Fig. 7 is an overall external view of the electronic rear view mirror shown in fig. 5.

Fig. 8 is a logic block diagram between the light sensor, the control circuit and the liquid crystal cell in the second embodiment of the present utility model.

Detailed Description

Example 1

As shown in fig. 1 to 4, such an electronic rear view mirror includes a liquid crystal cell 1 and a polarizer film 2; the liquid crystal box is a vertical alignment liquid crystal box and comprises a first glass plate 11, a negative liquid crystal layer 12 doped with a dichroic dye and a second glass plate 13 which are sequentially arranged from front to back, wherein the negative liquid crystal layer 12 is clamped between the first glass plate 11 and the second glass plate 13, a first electrode 14 and a first alignment layer 15 are arranged on the side surface, close to the negative liquid crystal layer 12, of the first glass plate 11, a second electrode 16 and a second alignment layer 17 are arranged on the side surface, close to the negative liquid crystal layer 12, of the second glass plate 13, and an electrode overlapping area exists 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 capable of determining a direction in which negative liquid crystal molecules 121 deflect in an electric field; the polarizer film 2 is disposed on the rear side of the liquid crystal cell 1, and the polarizer film 2 has a reflective polarizing axis 201 parallel to the liquid crystal alignment axis 101.

In the present embodiment, the negative liquid crystal layer 12 may be formed by dissolving a dichroic dye in a negative liquid crystal in advance and sealing 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.

In this embodiment, the first electrode 14 and the second electrode 16 are transparent electrodes, and the transparent electrodes are patterned by a transparent conductive film (such as an ITO film).

In this embodiment, the first alignment layer 15 and the second alignment layer 17 are vertical alignment layers (such as a vertically aligned polyimide coating). The negative liquid crystal molecules 121 (typically nematic liquid crystal) and the dichroic dye molecules 122 are generally rod-shaped structures having long molecular axes, whereby the negative liquid crystal molecules 121 of the negative liquid crystal layer 12 are vertically aligned (the long molecular axes are perpendicular to the first glass plate 11 or the second glass plate 13) in a natural state (OFF state), and the dichroic dye molecules 122 in the negative liquid crystal layer 12 are also vertically aligned (the long molecular axes are also perpendicular to the first glass plate 11 or the second glass plate 13). The liquid crystal alignment axis 101 is generally formed by applying alignment friction to the first alignment layer 15 and the second alignment layer 17 (polymer alignment or the like may be used), for example: the negative liquid crystal molecules 121 can be naturally provided with a pretilt angle (a pretilt angle of about 1 ° and a pretilt angle of 5 ° or less is typical, and the negative liquid crystal layer 12 can be considered to be vertically aligned) by applying opposing rubbing to the first alignment layer 15 and the second alignment layer 17 on the liquid crystal alignment axis 101.

In this embodiment, an angle is formed between the polarizer film 2 and the back surface of the liquid crystal cell 1, and the angle is such that the reflection polarization axis 201 of the polarizer film 2 is parallel to the liquid crystal alignment axis 101. In general, the polarizer film 2 may be adhered to the rear side of the liquid crystal cell 1 through a transparent adhesive layer (no birefringence is generally required) and disposed at a specific angle such that its reflective polarizing axis 201 is parallel to the liquid crystal alignment axis 101.

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 the negative liquid crystal layer 12 at a certain thickness (e.g., 3 μm to 20 μm) by a spacer design (e.g., a spacer having a certain diameter is interposed in the negative liquid crystal layer 12), whereby the light absorptance (including the light absorptance in the OFF state) of the liquid crystal cell 1 in the ON state and 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 absorptivity of the liquid crystal cell 1 in the ON state and the OFF state, and combining the reflectivity of the polarizer mask 2, the overall reflectivity of the reflector can be between 30% and 50% (typically 40%) in the ON state and between 5% and 20% (typically 10%) in the OFF state, so as to meet the far-reaching light prevention requirement of the rearview mirror.

In this embodiment, the dark state reflectance of the electronic rear view mirror is not more than 10%; the bright state reflectivity of the electronic rearview mirror is more than 40 percent.

In this embodiment, the polarizer film 2 may be a specular reflection film having a specular reflection effect and having a polarized light as reflected light, and the reflected polarized light axis 201 thereof is the axial direction in which the polarized angle of the reflected light is located. The polarizer film 2 described above, currently selected but not limited to DBEF and RPM optical films available from 3M company; alternatively, it may be a "multilayer optical film" described in the patent specification of CN1170382a or a film material having a similar function, and the reflectance of such a polarizer film 2 is generally between 40% and 55%.

The working principle of the electronic rearview mirror is briefly described below:

for convenience of description, only the light incident on the electronic rearview mirror from the vertical (or small angle) is needed to be analyzed, and the external light incident on the electronic rearview mirror is generally natural light, which can be regarded as the mixed light of the first polarized light (the polarization angle is parallel to the liquid crystal alignment axis 101) and the second polarized light (the polarization angle is perpendicular to the liquid crystal alignment axis 101), and the light paths are mainly: the light ray 30 entering the rearview mirror passes through the liquid crystal layer first, then is reflected by the polarizer film 2, and the formed reflected light ray 40 passes through the negative liquid crystal layer 12 again.

When the liquid crystal cell 1 is in an OFF state (i.e., a natural state), both the negative liquid crystal molecules 121 and the dichroic dye molecules 122 of the negative liquid crystal layer 12 are in a homeotropic alignment state, and after the external natural light is incident (only the case of a homeotropic or small incident angle is considered), the electric field component of the light is perpendicular (or nearly homeotropic) to the dichroic dye molecules 122, the dichroic dye molecules 122 have almost no polarized light absorption on both the incident light and the reflected light, the polarized light absorption of the negative liquid crystal layer 12 on the natural light is very small, and the light is emitted as the first polarized light after being reflected by the polarizer film 2, forming a bright state reflection mirror image.

When the liquid crystal cell 1 is in an 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 aligned obliquely or horizontally along the liquid crystal alignment axis 101 in an electric field, and simultaneously the dichroic dye molecules 122 are driven to be aligned obliquely or horizontally along the liquid crystal alignment axis 101, so that the negative liquid crystal layer 12 has polarization absorbability ON the liquid crystal alignment axis 101 (when light passes through the dichroic dye molecules 122, the dichroic dye molecules 122 have higher absorptivity to the electric field component ON the long axes of the molecules thereof, thereby having polarization absorbability).

Example 2

Referring to fig. 5 to 8, in the case where the other portions are the same as in the first embodiment, the difference is that: the electronic rearview mirror of the embodiment further comprises a protective lens 3, wherein the protective lens 3 is attached to the front side of the liquid crystal box 1, and a shielding layer 31 capable of shielding the peripheral area of the liquid crystal box 1 is arranged on the protective lens 3. The protective lens 3 can protect the liquid crystal box 1, and the shielding layer 31 can shield the peripheral area of the liquid crystal box 1, so that the appearance is more attractive.

In this embodiment, the polarizer film 2 is a semi-transparent and semi-reflective film; the rear side of the liquid crystal box 1 is provided with a TFT display 4, the front side of the TFT display 4 is provided with a polaroid 41, and the polarizing axis 411 of the polaroid 41 is parallel to the transmission polarizing axis 202 of the polarizer film 2. Such a rear view mirror is generally called a streaming rear view mirror, and the light of the TFT display 4 can pass through the rear view mirror with little loss, so that the picture of the TFT display 4 can be displayed through the rear view mirror. When the polarizer mask 2 is a semi-transparent and semi-reflective film, the transmittance is generally between 40% and 60%; the polarizer film 2 is transmissive to light of another polarization direction, and thus has a transmission polarization axis 202 orthogonal to the reflection polarization axis 201, the transmission polarization axis 202 being the other axis in which the transmitted light is polarized.

In this embodiment, the liquid crystal cell 1 has an elongated shape; the angle between the liquid crystal alignment axis 101 and the longitudinal direction of the liquid crystal cell 1 is 40-50 °. Therefore, the display picture and the reflection mirror image of the streaming media rearview mirror have vertical polarized light components, and the display picture and the reflection mirror image can be seen by a driver under the condition of having polarized light glasses.

The electronic rearview mirror of the embodiment further comprises a light sensor 5 and a control circuit 6 for controlling the liquid crystal box 1 to be in an OFF state or an ON state, wherein the light sensor 5 is electrically connected with a signal input end corresponding to the control circuit 6. In the driving circuit of the electronic rearview mirror, the control circuit 6 can adopt a common driving mode of a liquid crystal device, for example, can adopt square wave driving with a certain voltage (such as 3V-20V) to realize control of an OFF state and an ON state. When the light sensor 5 does not sense strong light irradiated by a far-reaching headlamp of a rear vehicle, the control circuit 6 controls the liquid crystal box 1 to be in an OFF state, the polarized light absorption of the negative liquid crystal layer 12 to natural light is very small, and the light almost keeps the natural light state to be reflected in the rearview mirror to form a reflection mirror image; when the light sensor 5 senses strong light irradiated by the far-reaching headlamp of the rear vehicle, the control circuit 6 controls the liquid crystal box 1 to be in an ON state, so that reflection of the rearview mirror is reduced, interference of the far-reaching headlamp ON the sight of a driver is avoided, and driving safety is improved.

In addition, it should be noted that, in the embodiments described in the present specification, names of various portions may be different, and equivalent or simple changes according to the structure, features and principles of the present utility model are included in the protection scope of the present utility model. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions in a similar manner without departing from the scope of the utility model as defined in the accompanying claims.

Claims (10)

1. An electronic rearview mirror comprising a liquid crystal cell, characterized in that: the liquid crystal display also comprises a polarizer mask; the liquid crystal box is a vertical alignment liquid crystal box, a negative liquid crystal layer doped with dichroic dye is arranged in the vertical alignment liquid crystal box, and the vertical alignment liquid crystal box is provided with a liquid crystal orientation axis capable of determining the deflection direction of negative liquid crystal molecules in an electric field; a polarizer film is disposed on the rear side of the liquid crystal cell, the polarizer film having a reflective polarizing axis parallel to the liquid crystal alignment axis.

2. An electronic rear view mirror as claimed in claim 1, characterized in that: an included angle is formed between the polarizer mask and the back surface of the liquid crystal box, and the included angle can enable the reflection polarizing axis of the polarizer mask to be parallel to the liquid crystal orientation axis.

3. An electronic rear view mirror as claimed in claim 1, characterized in that: the liquid crystal box comprises a first glass plate, a negative liquid crystal layer and a second glass plate which are sequentially arranged from front to back, the negative liquid crystal layer is clamped between the first glass plate and the second glass plate, a first electrode and a first alignment layer are arranged on the side surface, close to the negative liquid crystal layer, of the first glass plate, a second electrode and a second alignment layer are arranged on the side surface, close to the negative liquid crystal layer, of the second glass plate, and an electrode overlapping area exists between the second electrode and the first electrode to form a light control area.

4. An electronic rear view mirror according to claim 3, characterized in that: the first alignment layer and the second alignment layer are vertical alignment layers.

5. An electronic rear view mirror according to any of claims 1-4, characterized in that: the polarizer mask is a semi-transparent and semi-reflective film.

6. An electronic rear view mirror as claimed in claim 5, wherein: the rear side of the liquid crystal box is provided with a display, the front side of the display is provided with a polaroid, and the polarizing axis of the polaroid is parallel to the transmission polarizing axis of the polarizer mask.

7. An electronic rear view mirror as claimed in claim 5, wherein: the liquid crystal box is in a strip shape; the included angle between the liquid crystal orientation axis and the length direction of the liquid crystal box is 40-50 degrees.

8. An electronic rear view mirror according to any of claims 1-4, characterized in that: the electronic rearview mirror further comprises a protective lens, wherein the protective lens is attached to the front side of the liquid crystal box, and a shielding layer capable of shielding the peripheral area of the liquid crystal box is arranged on the protective lens.

9. An electronic rear view mirror according to any of claims 1-4, characterized in that: the electronic rearview mirror further comprises a light sensor and a control circuit for controlling the liquid crystal box to be in an OFF state or an ON state, and the light sensor is electrically connected with a signal input end corresponding to the control circuit.

10. An electronic rear view mirror according to any of claims 1-4, characterized in that: the dark state reflectivity of the electronic rearview mirror is not more than 10%; the bright state reflectivity of the electronic rearview mirror is more than 40%.