Display device and automobile

Abstract

The invention provides a display device and an automobile. The display device comprises a liquid crystal box, a first dimming box, a second dimming box and a backlight module, the first dimming box and the second dimming box are arranged between the backlight module and the liquid crystal box and are provided with four polarizers, the light-transmitting axes of the first polarizer, the second polarizer and the third polarizer are parallel, and the light-transmitting axes of the first polarizer, the second polarizer and the third polarizer are parallel. The light-transmitting axis of the fourth polaroid is perpendicular to the light-transmitting axis of the third polaroid. The first dimming box and the second dimming box each comprise an upper substrate, a lower substrate and a liquid crystal layer, alignment films are arranged on the surfaces, facing the liquid crystal layers, of the upper substrates and the surfaces, facing the liquid crystal layers, of the lower substrates, and the included angle between the alignment direction of the alignment films of the upper substrates and the light-transmitting axis of the first polaroid ranges from 50 degrees to 130 degrees. The included angle between the alignment direction of the alignment film of the lower substrate and the light-transmitting axis of the first polaroid is 50-130 degrees. According to the technical scheme, the asymmetric peep-proof effect can be achieved, the display device has different brightness expressions within a specific observation angle range, and the display device is suitable for vehicle-mounted display application.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to a display device and an automobile. Background Technology

[0002] Traditional display panels installed on the passenger side of a car need to have privacy features to avoid affecting the driver's safe driving and to ensure the driver's safety.

[0003] Currently, in-vehicle privacy display panels mainly rely on liquid crystal dimming boxes to achieve dynamic privacy effects. In the liquid crystal dimming box solution, display panel manufacturers primarily employ two technical approaches: one is based on ECB (Electrically Controlled Birefringence) dimming boxes as a symmetrical privacy solution, and the other is based on TN (Twisted Nematic) dimming boxes as an asymmetrical privacy solution.

[0004] The ECB dimmer box uses a vertical alignment method, which gives it a symmetrical privacy protection effect in all directions and enables strong light control in the area near the central axis.

[0005] However, due to its symmetrical privacy protection feature, this technology offers essentially the same privacy protection capability across all angles, making it impossible to differentiate control based on actual application needs. In automotive applications, the driver and passengers are in different positions, and their privacy protection requirements also differ. The symmetrical privacy protection feature of traditional ECB dimming boxes is insufficient to meet these differentiated privacy protection needs. Furthermore, existing ECB privacy protection technologies often significantly impact display performance at the front viewing angle when achieving privacy protection.

[0006] Therefore, it is necessary to propose a new technical solution to solve the above-mentioned technical problems. Summary of the Invention

[0007] The purpose of the embodiments of this application is to provide a display device and an automobile that aims to solve the technical problem that traditional in-vehicle display devices cannot achieve asymmetric privacy protection.

[0008] This application provides a display device comprising a liquid crystal cell, a first dimming cell, a second dimming cell, and a backlight module. The first dimming cell and the second dimming cell are disposed between the backlight module and the liquid crystal cell. A first polarizer is disposed between the first dimming cell and the backlight module. A second polarizer is disposed between the second dimming cell and the first dimming cell. A third polarizer is disposed between the liquid crystal cell and the second dimming cell. A fourth polarizer is disposed on the surface of the liquid crystal cell facing away from the backlight module. The light transmission axis of the first polarizer and the second polarizer are... The light transmission axis of the first polarizer is parallel to that of the third polarizer, and the light transmission axis of the fourth polarizer is perpendicular to that of the third polarizer. Both the first dimming box and the second dimming box include an upper substrate, a lower substrate, and a liquid crystal layer located between the upper substrate and the lower substrate. An alignment film is disposed on the surface of the upper substrate and the lower substrate facing the liquid crystal layer. The alignment direction of the alignment film of the upper substrate forms an angle of 50 degrees to 130 degrees with the light transmission axis of the first polarizer, and the alignment direction of the alignment film of the lower substrate forms an angle of 50 degrees to 130 degrees with the light transmission axis of the first polarizer.

[0009] In the above-described display device, the alignment direction of the alignment film on the upper substrate of the first dimming box differs from the alignment direction of the alignment film on the lower substrate of the first dimming box by 180 degrees; the alignment direction of the alignment film on the upper substrate of the second dimming box differs from the alignment direction of the alignment film on the lower substrate of the second dimming box by 180 degrees; and the alignment direction of the alignment film on the lower substrate of the first dimming box is the same as the alignment direction of the alignment film on the lower substrate of the second dimming box.

[0010] In the above-described display device, the alignment direction of the alignment film of the upper substrate forms an angle of 70 degrees to 110 degrees with the light transmission axis of the first polarizer, and the alignment direction of the alignment film of the lower substrate forms an angle of 70 degrees to 110 degrees with the light transmission axis of the first polarizer.

[0011] In the aforementioned display device, the ratio of the brightness of the display device on the first side with an azimuth angle of 135 degrees to 170 degrees and an polar angle of 30 degrees to 65 degrees to the brightness of the direct viewing angle is less than 10%, and the ratio of the brightness of the display device on the second side located in the opposite direction of the first side with an azimuth angle of 10 degrees to 45 degrees and an polar angle of 30 degrees to 65 degrees to the brightness of the direct viewing angle is greater than 50%.

[0012] In the aforementioned display device, the ratio of the brightness of the display device in the observation angle range of 150 to 160 degrees azimuth angle and 30 to 65 degrees polar angle on the first side to the brightness of the direct viewing angle is less than 5%, and the ratio of the brightness of the display device in the observation angle range of 20 to 30 degrees azimuth angle and 30 to 65 degrees polar angle on the second side to the brightness of the direct viewing angle is greater than 70%.

[0013] In the above-mentioned display device, thermal expansion compensation grooves are provided in the substrates of the first dimming box and the second dimming box, and the thermal expansion compensation grooves are arc-shaped grooves distributed along the edge of the substrate.

[0014] In the above-mentioned display device, the depth of the thermal expansion compensation groove is 20% to 60% of the substrate thickness.

[0015] In the aforementioned display device, the depth of the central portion of the bottom of the thermal expansion compensation groove is greater than the depth of the portions at both ends of the bottom of the groove.

[0016] In the above-mentioned display device, a positioning and fixing assembly is provided between the first dimming box and the second dimming box. The positioning and fixing assembly includes a plurality of positioning posts and corresponding positioning holes. The positioning posts are distributed in the peripheral edge area of ​​the first dimming box.

[0017] An embodiment of this application also provides a car, the car including a car body and the above-mentioned display device, the display device including a first side and a second side located in the opposite direction to the first side, the first side of the display device being the side close to the driver's seat of the car body.

[0018] The display device provided in the embodiments of this application, through a specific alignment film alignment direction configuration, can effectively solve the technical problem that traditional vehicle display devices cannot achieve asymmetric privacy protection. Specifically, the first dimming box and the second dimming box of the display device both include an upper substrate, a lower substrate, and a liquid crystal layer located between the upper substrate and the lower substrate. An alignment film is disposed on the surface of the upper substrate and the lower substrate facing the liquid crystal layer. The alignment direction of the alignment film of the upper substrate forms an angle of 50 degrees to 130 degrees with the light transmission axis of the first polarizer, and the alignment direction of the alignment film of the lower substrate forms an angle of 50 degrees to 130 degrees with the light transmission axis of the first polarizer.

[0019] Through the above technical solution, the liquid crystal layer exhibits different birefringence effects in different azimuth and polar angles of observation, resulting in varying degrees of polarization changes in light as it passes through the dimming box. This differential change in polarization allows the display device to achieve enhanced privacy protection within a specific viewing angle range, while maintaining relatively good light transmission performance in other angle ranges, thus achieving an asymmetric privacy protection effect.

[0020] Specifically, this technical solution reduces the brightness ratio of the display device on the first side (azimuth angle of 135° to 170° and polar angle of 30° to 65°) to below 10% compared to the brightness at the direct viewing angle, achieving excellent privacy protection. Simultaneously, on the second side (opposite to the first side), within the same azimuth angle of 10° to 45° and polar angle of 30° to 65°, the brightness ratio remains above 50% compared to the direct viewing angle, ensuring a normal viewing experience. This asymmetrical brightness distribution makes the display device particularly suitable for automotive applications, providing effective privacy protection for the driver while maintaining good display quality for passengers.

[0021] Furthermore, this technical solution has the advantage of minimal impact on display performance at the normal viewing angle. Since the alignment direction of the alignment film is adjusted within a specific angular range, it does not significantly affect the propagation of perpendicularly incident light. Therefore, while achieving an asymmetric privacy protection effect, it can maintain the display performance of the device, such as brightness and contrast, at the normal viewing angle, thus meeting the differentiated privacy protection requirements of different viewing positions. Attached Figure Description

[0022] Figure 1 A schematic diagram showing the location of a display device in a car, as provided in an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of a display device provided in an embodiment of this application.

[0024] Figure 3 yes Figure 2 A schematic diagram showing the positional relationship between the first dimming box or the second dimming box and the polarizer in the display device shown.

[0025] Figure 4 A schematic diagram illustrating the asymmetric privacy protection effect of the first and second sides of the display device provided in the embodiments of this application.

[0026] Figure 5 A schematic diagram illustrating the privacy protection effect of the second quadrant viewing area of ​​the display device provided in the embodiments of this application.

[0027] Figure 6 A simulation diagram of the privacy protection capability of the display device provided in this application.

[0028] Figure 7 A simulation diagram illustrating the privacy protection capabilities of an embodiment of the display device provided in this application. Detailed Implementation

[0029] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0030] The terms “first,” “second,” and similar words do not indicate any order, quantity, or importance, but are merely used to distinguish different technical features. The terms “multiple,” and similar words mean two or more, unless otherwise expressly specified.

[0031] The embodiments of this application can be combined with each other.

[0032] Embodiments of this application provide a display device (DA) and an automobile, aiming to solve the technical problem that traditional in-vehicle display devices (DA) cannot achieve asymmetric privacy protection.

[0033] This application defines the required privacy angle range based on the mounting position of the vehicle-mounted display device (DA): azimuth angle from 150 to 160 degrees, and polar angle from 40 to 60 degrees. Figure 5 As shown, the LCD dimming box is adjusted based on the required privacy angle range to achieve the optimal privacy effect within the required privacy angle range, while having minimal impact on the non-privacy angle range.

[0034] Traditional ECB dimming boxes use vertical alignment to achieve symmetrical privacy protection, but this cannot meet the differentiated privacy protection needs of drivers and passengers in automotive applications due to their different positions. An ECB dimming box, short for Electrically Controlled Birefringence Dimming Box, mainly includes key components such as an upper substrate SUB1, a lower substrate SUB2, a liquid crystal layer LC, and an alignment film. The liquid crystal layer LC is located between the two substrates, and the alignment film is applied to the surface of the substrate facing the liquid crystal layer LC to control the initial alignment of the liquid crystal molecules. The working principle of the ECB dimming box is based on the birefringence properties of liquid crystals. By controlling the alignment state of the liquid crystal molecules through an electric field, the transmittance and polarization state of light are adjusted, achieving light control at different viewing angles.

[0035] Regarding the display device (DA) mounted in the passenger seat, due to differences in vehicle size, DA size, mounting position, and angle, the driver's requirements for the anti-spy angle of the DA vary. Figure 1 As shown. For the driver, due to differences in height, weight, and seating position, the required anti-peeping angle of the passenger-side display device DA is approximately 49 to 60 degrees (i.e., in the range of about 11 degrees).

[0036]

[0037] Table 1 In Table 1 above, the driver's position in the driver's seat could be P1 or P2, with P2 located away from the dashboard in front of P1. The passenger's position in the front passenger seat could be P3 or P4, with P4 located away from the display device DA in front of P3. The distance between P1 and the dashboard in front of the driver's seat (P5) is A1, the distance between P2 and P5 is A2, the distance between P3 and the midpoint of display device DA (P6) is B1, the distance between P4 and P6 is B2, the position of display device DA closer to the driver's seat is P7, and the position of display device DA furthest from the driver's seat is P8. α(m1) is the angle between the line connecting P1 and P5 and the line connecting P1 and P7; α(n1) is the angle between the line connecting P1 and P5 and the line connecting P1 and P6; α(o1) is the angle between the line connecting P1 and P5 and the line connecting P1 and P8; α(m2) is the angle between the line connecting P2 and P5 and the line connecting P2 and P7; α(n2) is the angle between the line connecting P2 and P5 and the line connecting P2 and P6; α(o2) is the angle between the line connecting P2 and P5 and the line connecting P2 and P8. α(M1) is the angle between the line connecting P3 and P7 and the line connecting P3 and P6; α(O1) is the angle between the line connecting P3 and P8 and the line connecting P3 and P6; α(M2) is the angle between the line connecting P4 and P7 and the line connecting P4 and P6; and α(O2) is the angle between the line connecting P4 and P8 and the line connecting P4 and P6.

[0038] For a passenger-side display (DA) located to the right of the driver's seat in a left-hand drive vehicle, the driver's field of vision for the passenger-side display (DA) falls within the second quadrant of the display (DA). Based on Figure 1 The azimuth angle of the display device DA shown is approximately 150 to 160 degrees. This application improves the privacy protection effect of the display device DA in the second quadrant of the passenger seat by adjusting the internal configuration of the dimming box. Similarly, the display device DA in the passenger seat located to the left of the driver's seat in a right-hand drive vehicle needs to have a privacy protection effect in the first quadrant of the passenger seat.

[0039] This application achieves an asymmetric privacy effect by adjusting the alignment direction AD of the alignment film in the dimming box, providing optimized privacy performance within a specific viewing angle range. The display device DA is configured to be installed in the passenger seat to provide the driver with an asymmetric privacy effect.

[0040] like Figure 2As shown in the embodiments of this application, the display device DA includes a liquid crystal cell DP, a first dimming cell SLM1, a second dimming cell SLM2, and a backlight module BL. The first dimming cell SLM1 and the second dimming cell SLM2 are disposed between the backlight module BL and the liquid crystal cell DP, and the two dimming cells are stacked to jointly achieve the privacy protection function. The first dimming cell SLM1 and the second dimming cell SLM2 are ECB dimming cells, and the privacy protection effect is achieved by using the principle of electrically controlled birefringence.

[0041] The liquid crystal cell (DP) consists of two substrates and a liquid crystal layer (LC) located between the substrates. The backlight module (BL) provides uniform backlight illumination for the display device (DA) and typically includes optical components such as a light source, light guide plate, reflector, and diffuser.

[0042] A first polarizer POL1 is disposed between the first dimming cell SLM1 and the backlight module BL. A second polarizer POL2 is disposed between the second dimming cell SLM2 and the first dimming cell SLM1. A third polarizer POL3 is disposed between the liquid crystal cell DP and the second dimming cell SLM2. A fourth polarizer POL4 is disposed on the surface of the liquid crystal cell DP facing away from the backlight module BL. The absorption axes LAA1 of the first polarizer POL1, LAA2 of the second polarizer POL2, and LAA3 of the third polarizer POL3 are parallel. The absorption axis LAA4 of the fourth polarizer POL4 is perpendicular to the absorption axis LAA3 of the third polarizer POL3. The transmission axes LTA1 of the first polarizer POL1, LTA2 of the second polarizer POL2, and LTA3 of the third polarizer POL3 are parallel. The transmission axis LTA4 of the fourth polarizer POL4 is perpendicular to the transmission axis LTA3 of the third polarizer POL3. This polarizer configuration ensures that the light produces the desired polarization effect as it passes through each dimming box.

[0043] like Figure 3 As shown, both the first dimming cell SLM1 and the second dimming cell SLM2 include an upper substrate SUB1, a lower substrate SUB2, and a liquid crystal layer LC located between the upper substrate SUB1 and the lower substrate SUB2. Alignment films are disposed on the surfaces of the upper substrate SUB1 and the lower substrate SUB2 facing the liquid crystal layer LC. These alignment films are used to control the initial alignment direction of the liquid crystal molecules. The alignment direction AD of the alignment film is achieved through a triboelectric alignment process or a photo-alignment process. In the triboelectric alignment process, the alignment direction AD of the alignment film is parallel to the alignment grooves on the surface of the alignment film.

[0044] In the technical solution of this application, the alignment direction of the alignment film of the upper substrate SUB1 and the light transmission axis LTA1 of the first polarizer POL1 are at an angle of 50 degrees to 130 degrees, for example, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees, 85 degrees, 90 degrees, 95 degrees, 100 degrees, 105 degrees, 110 degrees, 115 degrees, 120 degrees, 125 degrees, and 130 degrees. The alignment direction AD of the alignment film of the lower substrate SUB2 and the light transmission axis LTA1 of the first polarizer POL1 are at an angle β of 50 degrees to 130 degrees, for example, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees, 85 degrees, 90 degrees, 95 degrees, 100 degrees, 105 degrees, 110 degrees, 115 degrees, 120 degrees, 125 degrees, and 130 degrees. The alignment direction AD setting causes the liquid crystal molecules in the liquid crystal layer LC to deflect at a specific angle, thereby changing the optical properties of the liquid crystal layer LC at different viewing angles.

[0045] In one specific embodiment, the alignment direction of the alignment film on the upper substrate SUB1 forms an angle of 70 to 110 degrees with the light transmission axis LTA1 of the first polarizer POL1, and the alignment direction AD of the alignment film on the lower substrate SUB2 forms an angle of 70 to 110 degrees with the light transmission axis LTA1 of the first polarizer POL1. More specifically, the alignment angle of the alignment film on the upper substrate SUB1 of the first dimming cell SLM1 is 85 degrees, and the alignment angle of the alignment film on the lower substrate SUB2 of the first dimming cell SLM1 is -95 degrees. The alignment angle of the alignment film on the upper substrate SUB1 of the second dimming cell SLM2 is 85 degrees, and the alignment angle of the alignment film on the lower substrate SUB2 of the second dimming cell SLM2 is -95 degrees. This alignment angle setting causes a 5-degree deflection of the liquid crystal molecules in the liquid crystal layer LC.

[0046] This application deflects the alignment direction AD of the upper and lower dimming boxes from 0 to 40 degrees, while keeping the polarization axis of the first polarizer POL1 to the fourth polarizer POL4 unchanged, thereby achieving asymmetric privacy protection and controlling the privacy protection effect of the second quadrant observation zone to the optimal level.

[0047] The alignment direction AD of the alignment film on the upper substrate SUB1 of the first dimming cell SLM1 differs from the alignment direction AD of the alignment film on the lower substrate SUB2 of the first dimming cell SLM1 by 180 degrees. Similarly, the alignment direction AD of the alignment film on the upper substrate SUB1 of the second dimming cell SLM2 differs from the alignment direction AD of the alignment film on the lower substrate SUB2 of the second dimming cell SLM2 by 180 degrees. This configuration ensures the antiparallel alignment of the liquid crystal molecules within each dimming cell. Simultaneously, the alignment direction AD of the alignment film on the lower substrate SUB2 of the first dimming cell SLM1 is the same as the alignment direction AD of the alignment film on the lower substrate SUB2 of the second dimming cell SLM2, allowing the two dimming cells to work together to enhance the privacy protection effect.

[0048] By setting the alignment direction AD of the alignment film of the dimming box as described above, the privacy protection capability of the display device DA in the second and first quadrant observation areas is improved, enabling the display device DA to achieve an asymmetric privacy protection effect. Specifically, the brightness ratio of the display device DA to the brightness of the viewing angle is less than 10% within the observation angle range of 135° to 170° (e.g., 140°, 145°, 150°, 155°, 160°, 165°) on the first side S1 and the polar angle is 30° to 65° (e.g., 35°, 40°, 45°, 50°, 55°, 60°), achieving a strong privacy protection effect. Here, the azimuth angle (Phi, Ψ) refers to the angle of counterclockwise rotation from the reference direction (e.g., the X-axis direction) within the display plane of the display device DA, and the polar angle (Theta, θ) refers to the angle of outward tilt from the normal direction of the display plane of the display device DA.

[0049]

[0050] Table 2 In actual testing, as shown in Table 2, at an observation angle of 150 degrees azimuth and 50 degrees polar angle, the percentage of the side viewing angle brightness to the front viewing angle brightness of the display device DA is less than 6%, a significant improvement compared to the 12.04% of the traditional solution. Simultaneously, the ratio of the brightness of the display device DA to the front viewing angle brightness is greater than 50% within the observation angle range of 10 to 45 degrees (e.g., 15, 20, 25, 30, 35, 40 degrees) and 30 to 65 degrees (e.g., 35, 40, 45, 50, 55, 60 degrees) on the second side S2, located opposite the first side S1. This ensures that the second side S2 also has adequate privacy protection, preventing the light from the display device DA from shining into the passenger side window and thus preventing interference with the driver's view of the passenger side rearview mirror.

[0051] In a more preferred embodiment, such as Figure 5 As shown, the brightness ratio of the display device DA in the observation angle range of 150 to 160 degrees (e.g., 152, 154, 156, 158 degrees) on the first side S1 and 30 to 65 degrees (e.g., 35, 40, 45, 50, 55, 60 degrees) on the first side S1 to the brightness ratio of the viewing angle is less than 5%, and the brightness ratio of the display device DA in the observation angle range of 20 to 30 degrees (e.g., 22, 24, 26, 28 degrees) on the second side S2 and 30 to 65 degrees (e.g., 35, 40, 45, 50, 55, 60 degrees) on the second side S2 to the brightness ratio of the viewing angle is greater than 70%.

[0052] From a technical principle perspective, the aforementioned setting of the alignment direction AD of the alignment film alters the optical properties of the liquid crystal molecules at different viewing angles. When incident light enters the liquid crystal layer LC from a specific angle, the birefringence effect of the liquid crystal molecules causes a change in the polarization state of the light. Because the alignment direction AD of the alignment film has the aforementioned angular range, the liquid crystal layer LC exhibits different optical response characteristics at different azimuth and polar angles of observation, thus achieving an asymmetric privacy protection effect. Figure 7 As shown in regions Z1 and Z2, the anti-peeping capability of the display device after the above-mentioned alignment angle setting in the embodiments of this application in the first quadrant observation range and the second quadrant observation range is compared (e.g.) Figure 6 (As shown) there is a significant improvement.

[0053] Within the dimming box, the liquid crystals on both sides of the lower substrate SUB2 and the upper substrate SUB1 are antiparallel aligned. In this application, the alignment angle of the upper substrate SUB1 is 85 degrees, and the alignment angle of the lower substrate SUB2 is -95 degrees. Alternatively, the alignment angle of the upper substrate SUB1 can be -95 degrees, and the alignment angle of the lower substrate SUB2 can be 85 degrees; or, the alignment angle of the upper substrate SUB1 can be 95 degrees, and the alignment angle of the lower substrate SUB2 can be -85 degrees; or, the alignment angle of the upper substrate SUB1 can be -85 degrees, and the alignment angle of the lower substrate SUB2 can be 95 degrees.

[0054] This application also provides a vehicle, which includes a vehicle body and the aforementioned display device DA. The display device DA includes a first side S1 (corresponding to the second quadrant observation area) and a second side S2 (corresponding to the first quadrant observation area) located in the opposite direction to the first side S1, as shown below. Figure 1 and Figure 4 As shown, the first side S1 of the display device DA is the side closest to the driver's seat of the car body. This configuration allows the display device DA to provide good privacy protection in the driver's direction, while also providing adequate privacy protection in the second side S2 direction to prevent light from shining into the passenger side window, thereby preventing glare from the side window and affecting the driver's view of the rearview mirror.

[0055] In automotive applications, when the display device DA is installed in the passenger seat, the driver is positioned on the first side (S1) of the display device DA, while the second side (S2) of the display device DA faces the passenger side window. Because the display device DA has asymmetrical privacy features, it effectively prevents the driver from being distracted by the displayed content, while ensuring the passenger can view the content normally and preventing light from the display device DA from shining into the passenger side window and affecting the driver's view of the rearview mirror.

[0056] The technical solution of this application realizes the asymmetric anti-peeping function of the vehicle-mounted display device DA, which has a better anti-peeping effect in a specific angle range and meets the needs of practical application scenarios.

[0057] Under different temperature conditions, the alignment state of liquid crystal molecules will change, causing the privacy protection effect to deviate under high or low temperature conditions, and making it impossible to maintain stable privacy protection performance.

[0058] To address the aforementioned technical problems, this application provides thermal expansion compensation grooves in the substrates of the first dimming box SLM1 and the second dimming box SLM2. The thermal expansion compensation grooves are arc-shaped grooves distributed along the edges of the substrate, with a depth ranging from 20% to 60% of the substrate thickness. The thermal expansion compensation grooves are evenly distributed along the four edges of the substrate. When the temperature rises, the substrate thermally expands. The thermal expansion compensation grooves absorb this expansion by deforming, causing the arc-shaped outer wall of the groove to contract inwards, reducing the volume of the groove and thus releasing the stress generated by thermal expansion. When the temperature decreases, the substrate thermally contracts, causing the outer wall of the thermal expansion compensation groove to expand outwards, increasing the volume of the groove and compensating for the spatial changes caused by the substrate contraction.

[0059] The thermal expansion compensation groove employs a gradient depth design at its bottom, with the deepest portion in the center and gradually decreasing in depth towards both ends, forming a smooth transition surface. This gradient depth design enables more uniform stress distribution, preventing substrate cracking caused by stress concentration. The thermal expansion compensation groove also includes stress-guiding grooves, which extend from both ends of the compensation groove towards the central region of the substrate, gradually decreasing in depth until they are flush with the substrate surface. These stress-guiding grooves gradually transfer thermal stress from the edge areas to the central region of the substrate, preventing excessive stress concentration at the edges.

[0060] The outer frames of the first dimming box (SLM1) and the second dimming box (SLM2) are made of materials with a low coefficient of thermal expansion, less than 5 × 10⁻⁶ / ℃, including titanium alloys, Invar alloys, or carbon fiber composites. The outer frame includes a main frame and multiple flexible connecting parts. The main frame is rectangular, and its internal dimensions match the outer contour of the dimming box. Flexible connecting parts are located at the four corners and the midpoints of each side of the main frame. Each flexible connecting part includes an elastic arm and a connecting node. The elastic arms adopt a wavy or serpentine path. The connecting nodes connect the elastic arms to the main frame, and the nodes use a rounded transition to avoid stress concentration.

[0061] The flexible connection absorbs dimensional changes caused by temperature variations through elastic deformation. When the outer frame is subjected to thermal expansion, the elastic arm bends outward, increasing the effective size of the frame. When the outer frame is subjected to thermal contraction, the elastic arm bends inward, decreasing the effective size of the frame. The amount of deformation of the elastic arm is directly proportional to the amount of temperature change. The outer frame also includes temperature compensation adjusting bolts, which are located at the connection nodes of the flexible connection. By adjusting the tightness of the bolts, the prestress state of the elastic arm is changed, thereby adjusting the temperature response characteristics of the flexible connection.

[0062] A buffer layer, made of highly elastic rubber or polyurethane material, is placed between the outer frame and the dimming box. This buffer layer further absorbs the thermal expansion differences between the outer frame and the dimming box, preventing stress transmission caused by thermal expansion mismatch. Multiple vent holes are provided on the surface of the buffer layer to expel gases generated by temperature changes, preventing gas pressure from affecting the thickness of the liquid crystal layer (LC).

[0063] Under vibration during vehicle operation, relative displacement may occur between the first dimming box SLM1 and the second dimming box SLM2, resulting in optical path offset and unstable anti-spy effect.

[0064] To address the aforementioned technical issues, this application provides a positioning and fixing assembly between the first dimming box SLM1 and the second dimming box SLM2. The positioning and fixing assembly includes multiple positioning posts and corresponding positioning holes. The positioning posts are evenly distributed along the outer edge of the first dimming box SLM1. The positioning posts are cylindrical or square. The height of the positioning posts is 80% to 95% of the distance between the first polarizer POL1 and the second polarizer POL2, ensuring that the positioning posts can be effectively inserted into the positioning holes without affecting light transmission. The positioning posts are made of the same material as the dimming box substrate to ensure consistency in the coefficient of thermal expansion and avoid positioning deviations caused by differences in thermal expansion.

[0065] The positioning hole is located at the corresponding position on the second dimming box SLM2. The inner diameter of the positioning hole is 0.02 mm to 0.1 mm larger than the outer diameter of the positioning post, forming a clearance fit. This clearance fit ensures positioning accuracy while allowing for minor thermal expansion adjustments. The depth of the positioning hole is 105% to 120% of the height of the positioning post, ensuring that the positioning post can be fully inserted into the positioning hole. The hole wall is rounded to reduce frictional resistance and stress concentration during the insertion of the positioning post. A buffer groove is provided at the bottom of the positioning hole, with a diameter 1 mm to 3 mm larger than the diameter of the positioning hole. The buffer groove can accommodate machining errors and thermal expansion allowances at the end of the positioning post.

[0066] The locating pin and locating hole are connected using a progressive fit. The upper end of the locating pin has a guide cone surface, the length of which is 0.5 to 1 times the diameter of the locating pin. This guide cone surface guides the locating pin smoothly into the locating hole, reducing alignment difficulties during assembly. A locating section is located in the middle of the locating pin, its diameter matching the inner diameter of the locating hole. The length of the locating section is 60% to 80% of the total length of the locating pin. A locking section is located at the lower end of the locating pin, its diameter being 0.05 mm to 0.2 mm larger than the diameter of the locating section. The locking section forms an interference fit with the bottom area of ​​the locating hole, ensuring reliable positioning.

[0067] The positioning and fixing assembly also includes a buffer pad, which is disposed in the gap between the positioning post and the positioning hole. The buffer pad is annular in shape, with its outer diameter matching the inner diameter of the positioning hole and its inner diameter matching the outer diameter of the positioning post. The buffer pad is made of rubber, silicone, or polyurethane, which have excellent vibration damping properties. Multiple micro-dimples are formed on the surface of the buffer pad to increase its elastic deformation capacity and improve the vibration damping effect.

[0068] The buffer pads are layered along the height of the positioning post. Different layers of buffer pads use materials of varying hardness; the pads near the top of the positioning post have lower hardness, while those near the bottom have higher hardness, creating a gradual hardness distribution. This gradual hardness distribution provides different damping effects for vibrations of different frequencies, improving overall vibration reduction performance. The buffer pads also include radial elastic arms, extending inward from the outer circumference of the pad. The length of the arm is 20% to 40% of the pad radius, and the thickness is 50% to 80% of the pad thickness. These radial elastic arms provide additional elastic support in the radial direction, preventing positioning misalignment due to lateral vibrations.

[0069] The embodiments of this application have been described in detail above. The content of this specification should not be construed as limiting the scope of protection of this application.

Claims

1. A display device, characterized in that, The display device includes a liquid crystal cell, a first dimming cell, a second dimming cell, and a backlight module. The first dimming cell and the second dimming cell are disposed between the backlight module and the liquid crystal cell. A first polarizer is disposed between the first dimming cell and the backlight module. A second polarizer is disposed between the second dimming cell and the first dimming cell. A third polarizer is disposed between the liquid crystal cell and the second dimming cell. A fourth polarizer is disposed on the surface of the liquid crystal cell facing away from the backlight module. The light transmission axes of the first polarizer, the second polarizer, and the third polarizer are parallel, and the light transmission axis of the fourth polarizer is perpendicular to the light transmission axis of the third polarizer. Both the first dimming box and the second dimming box include an upper substrate, a lower substrate, and a liquid crystal layer located between the upper substrate and the lower substrate. An alignment film is disposed on the surface of the upper substrate and the lower substrate facing the liquid crystal layer. The alignment direction of the alignment film of the upper substrate forms an angle of 50 degrees to 130 degrees with the light transmission axis of the first polarizer. The alignment direction of the alignment film of the lower substrate forms an angle of 50 degrees to 130 degrees with the light transmission axis of the first polarizer.

2. The display device according to claim 1, characterized in that, The alignment direction of the alignment film on the upper substrate of the first dimming box differs from the alignment direction of the alignment film on the lower substrate of the first dimming box by 180 degrees. The alignment direction of the alignment film on the upper substrate of the second dimming box differs from the alignment direction of the alignment film on the lower substrate of the second dimming box by 180 degrees. The alignment direction of the alignment film on the lower substrate of the first dimming box is the same as the alignment direction of the alignment film on the lower substrate of the second dimming box.

3. The display device according to claim 1, characterized in that, The alignment direction of the alignment film on the upper substrate forms an angle of 70 to 110 degrees with the light transmission axis of the first polarizer, and the alignment direction of the alignment film on the lower substrate forms an angle of 70 to 110 degrees with the light transmission axis of the first polarizer.

4. The display device according to claim 1, characterized in that, The brightness ratio of the display device at the first side, within an azimuth angle of 135 to 170 degrees and an polar angle of 30 to 65 degrees, to the brightness at the normal viewing angle is less than 10%, and the brightness ratio of the display device at the second side, located in the opposite direction to the first side, within an azimuth angle of 10 to 45 degrees and an polar angle of 30 to 65 degrees, to the brightness at the normal viewing angle is greater than 50%.

5. The display device according to claim 4, characterized in that, The ratio of the brightness of the display device at the viewing angle range of 150 to 160 degrees azimuth and 30 to 65 degrees polar angle on the first side to the brightness at the viewing angle is less than 5%, and the ratio of the brightness of the display device at the viewing angle range of 20 to 30 degrees azimuth and 30 to 65 degrees polar angle on the second side to the brightness at the viewing angle is greater than 70%.

6. The display device according to claim 1, characterized in that, The substrates of the first dimming box and the second dimming box are provided with thermal expansion compensation grooves, which are arc-shaped grooves distributed along the edge of the substrate.

7. The display device according to claim 6, characterized in that, The depth of the thermal expansion compensation groove is 20% to 60% of the substrate thickness.

8. The display device according to claim 6, characterized in that, The depth of the central part of the bottom of the thermal expansion compensation groove is greater than the depth of the two ends of the bottom of the groove.

9. The display device according to claim 1, characterized in that, A positioning and fixing assembly is provided between the first dimming box and the second dimming box. The positioning and fixing assembly includes multiple positioning posts and corresponding positioning holes. The positioning posts are distributed in the outer edge area of ​​the first dimming box.

10. A car, characterized in that, The vehicle includes a vehicle body and a display device as described in any one of claims 1 to 5, the display device including a first side and a second side located in the opposite direction to the first side, the first side of the display device being the side closest to the driver's seat of the vehicle body.

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