Display device, especially for a vehicle, with switchable sharing and private modes

Description

[0001] The invention relates to a display device, in particular for use in a vehicle, which can optionally be operated either in sharing mode or in private mode.

[0002] The number and size of displays, especially in vehicles, are constantly increasing. Vehicle concepts already exist where displays for the passenger are located in or on the instrument panel, either as separate displays or as the passenger section of a door-to-door display.

[0003] For some time now, measures have existed to restrict the free visibility of information displayed on a screen to third parties. Ideally, only the intended viewer should be able to perceive the screen content, while people in the vicinity should not be able to read, recognize, or perceive the displayed information.

[0004] US patent A-2020 / 0073157 describes an LCD display with a controllable viewing angle range, which is equipped with: an LCD display having a plurality of pixels with a transparent substrate layer on which a group of electrodes and further electronic components for controlling the electrodes are arranged for each pixel, a transparent cover layer forming a display area with a liquid crystal layer between the substrate layer and the cover layer, wherein each group of electrodes has a first electrode surface connectable to a ground potential and a third electrode which is electrically isolated from the first electrode surface and connectable to an operating potential, and a control unit comprising, among other things, the electronic components for connecting the third electrode of each pixel or selected pixels to the operating potential and for connecting the first electrode surfaces of each pixel or selected pixels to the ground potential in a sharing mode and in a private mode,This means that information displayed on the LCD screen appears with higher contrast when viewed from a particular angle in split-screen mode than in private mode.

[0005] Another example of an LCD display with a controllable viewing angle range is described in US-A-2013 / 0265514.

[0006] LCD displays that feature In-Plane Switching (IPS) technology have proven to be particularly powerful.

[0007] The object of the invention is to create a display device, in particular for a vehicle, which enables an electronic possibility of selective operation in shared mode or private mode and has IPS technology.

[0008] According to the invention, a display device, particularly for a vehicle, is proposed to solve this problem, which is equipped with an LCD display having a plurality of pixels with a transparent substrate layer on which a group of electrodes and further electronic components for controlling the electrodes are arranged for each pixel, a transparent cover layer forming a display area and with a liquid crystal layer between the substrate layer and the cover layer, wherein each group of electrodes has a first electrode surface connectable to a ground potential and two second electrode surfaces also connectable to the ground potential, which are electrically insulated from each other and from the first electrode surface and are arranged next to each other and aligned with the first electrode surface above or below it, wherein each group of electrodes has a third electrode which is electrically insulated from the first and second electrode surfaces and connectable to an operating potential,and a control unit comprising, among other things, the electronic components for connecting the third electrode of each pixel or selected pixels to the operating potential in split mode and for connecting the first electrode surfaces of each pixel or selected pixels to the ground potential, as well as for connecting the first electrode surface and additionally one of the two second electrode surfaces of each pixel or selected pixels to the ground potential in private mode, whereby, when viewing the display surface from a direction facing one of the two second electrode surfaces of all pixels, the information displayed on the display surface is more visible in split mode than in private mode, in which the one of the two second electrode surfaces of each pixel or selected pixel facing away from said direction of view is connected to the ground potential.This means that the other of the two second electrode surfaces of each pixel or selected pixels, the one facing away from the said viewing direction, is not connected to the ground potential.

[0009] According to the invention, the display device comprises an LCD display with IPS technology. The negative electrode of each pixel is designed as a multi-part unit. By selectively and differently controlling the individual electrodes of each multi-part electrode of the LCD display in IPS technology, the contrast can be influenced when viewing the display area from the viewing direction towards which the respective uncontrolled electrode is facing.

[0010] In the display device concept according to the invention, the positive electrode is the electrode design known from LCD displays using IPS technology, which has two comb structures. The first sections of both comb structures are electrically connected to each other, and the second sections projecting from the first sections alternately follow one another, i.e., lie alternately next to each other. The negative electrode is now designed in multiple parts. It comprises a negative electrode area that substantially fills the area of ​​the pixel. Above or below this first negative electrode area, there exists a further, electrically isolated, two-part negative electrode area with two or more negative electrode sub-areas that are arranged next to each other and are electrically insulated from each other. The electric field that forms within a pixel in the liquid crystal layer is now controlled by the selection of the addressed negative electrode area.The negative electrode sub-areas can be influenced, both in terms of their intensity or strength and their homogeneity across the pixel area. If only one of the two negative electrode sub-areas is activated, an asymmetry arises in the electric field, as its strength is lower in the area of ​​the unactivated negative electrode sub-area than in the rest of the pixel. This affects both light transmission and contrast when viewing the display from the direction facing the unactivated second negative electrode sub-area.

[0011] The invention is explained in more detail below with reference to an exemplary embodiment and the drawing. Specifically, the drawing shows: Fig. 1 Schematic cross-sectional and top-view views of the standard design of an LCD pixel in IPS technology, Fig. 2 Cross-sectional and top-view views of a modification of the pixel design according to an embodiment of the invention when controlled for split-screen mode, Fig. 3 The pixel design according to the embodiment of the invention, however, when controlled for private mode, schematically in cross-sectional and top-view views, Fig. 4 A comparison of the visibility conditions for driver and passenger in the operating modes of the display assigned to the passenger in split-screen mode (left in Fig. 4 ) and in private mode (right in Fig. 4 ) and Fig. 5 a comparison of the visibility conditions for driver and front passenger in the operating modes of the display assigned to the front passenger in split mode (left in Fig. 5 ) and in private mode (right in Fig. 5) with an additional reduction in the backlight intensity of the display assigned to the passenger in private mode operation.

[0012] Privacy screen technologies for restricting or preventing the readability of content displayed on a screen to third parties have been available for many years. These technologies allow the display to be viewed only from a preferred direction, while the information is not visible from any other direction. Known technologies are based on both static and switchable privacy screens. The static option achieves the privacy effect by implementing light control systems (i.e., light control film, prisms, etc.) in the display's backlighting unit. For switchable privacy screens, the backlight design has been extended to support both normal light illumination and privacy screen illumination.These approaches reduce luminance across the viewing angle; however, in dark rooms, the visibility of the image cannot be reduced due to the daylight recalibration of the human eye to low light levels. In this case, the image is still visible even if the luminance is only 0.3 cd / m², resulting in a reduced level of visual protection.

[0013] When this type of privacy screen is used in a vehicle, information on a separate display or display area of, for example, a door-to-door display assigned to the passenger remains at least faintly visible to the driver, which could distract them and thus lead to dangerous situations. The ability to switch to an enhanced privacy mode is therefore of particular safety importance, especially in automotive applications.

[0014] In contrast, other approaches focus primarily on privacy on display panels by converting the pixel design into different electrical drive modes. With this type of approach, an in-cell display cannot be implemented. These approaches reduce the luminance or contrast ratio, but the reduction in image visibility can only be achieved by using a very strong dimming factor in the backlight, which drastically affects the image quality for the intended user.

[0015] These approaches currently on the market are primarily suitable for consumer use and are very effective at creating a privacy effect under normal lighting conditions. However, when the ambient light is relatively dim, as is the case when driving at night, the privacy effect is not as effective because the eye readjusts to lower light levels.

[0016] These approaches have drawbacks in terms of optical performance, as the switchable power optimized for privacy mode drastically reduces the display's performance in normal split-screen operation. This is also a disadvantage in vehicles. Due to the number of displays integrated into a vehicle's instrument panel, they must be matched to provide similar optical performance. A privacy screen technology that cannot deliver comparable optical performance in split-screen mode to the other displays in the vehicle may not be suitable for automotive applications.

[0017] The invention presents a solution for maintaining the added value of displays in the automotive sector, combined with an improved privacy display effect in applications using both discrete and in-cell touch technologies. The pixel design according to the invention guarantees the display performance and in-cell compatibility of the design based on an IPS-like pixel design. The proposed dual-mode pixel design according to the invention offers the following advantages, particularly with regard to its application in a vehicle: In split mode, the pixel behaves like an IPS panel (normal or first pixel control mode). This allows the high optical performance required in automotive applications to be achieved. The pixel control can be switched to private mode (second pixel control mode) to selectively reduce contrast towards the driver's position while maintaining luminance and contrast levels in the passenger's position.

[0018] A display according to an embodiment of the invention uses in-plane switching (IPS) technology and includes, among other things, the following elements: LCD-TFT glass, LCD color filter glass, liquid crystal, alignment layer, electronic control (IC control, routing, TFT, gate on panel)

[0019] Other components, such as a touch panel and a backlight unit, as well as proximity sensors with optional gesture recognition integrated into the display device, may also be present, but these are generally irrelevant to the invention. The polarization filters typically present are also not discussed further here, as they are not important to the invention.

[0020] The color filter glass and IC driver are of conventional types and can be selected according to the desired functionalities and performance of the display. The color gamut, for example, can be adjusted using a color filter. Furthermore, an in-cell IC driver and / or a separate touch panel can be implemented.

[0021] IPS displays are characterized by, among other things, wide viewing angles and optimal color reproduction with very high image quality. The standard IPS pixel design features a thin-film transistor (TFT). The video signal (voltage level) is applied to the pixel electrode to generate a voltage level on the pixel. The voltage difference between ground (Vcom) and the voltage level on the grid then defines the overall voltage level (electric field) in the liquid crystal to produce a defined and well-controlled grayscale.

[0022] Fig. 1This situation illustrates that the electrode design can be multi-domain (V-shaped, two domains, zigzag, etc.), i.e., with multiple electrode surfaces per pixel, the geometry and number of which can vary depending on the design, in order to achieve symmetrical properties with regard to translation and contrast ratio, and also to achieve a low color shift level.

[0023] The standard pixel design of Fig. 1In IPS technology, a conventional TFT panel 10 has a ground electrode or ground-electrode area 12 on each pixel (grounded via the control unit 30). Separated from the ground-electrode area 12 by an electrically insulating insulating layer 14 are the "fingers" 16 of a single electrode 18, which is controlled by a TFT transistor 20 (see the control unit 21). Above and at a distance from the TFT panel 10 is the cover glass 22 of the LCD display 23, with the liquid crystals 24 located between the TFT panel 10 and the cover glass 22.

[0024] In the embodiment of an LCD display 23 according to the invention ( Fig. 2 and 3The pixel design features a single 20-inch TFT with a single-grid, multi-domain electrode design (similar to the standard IPS design). However, the Vcom electrode design (ground electrode or ground electrode area) is extended by a second Vcom electrode area. The second Vcom2 electrode is placed on top of the standard Vcom1, with an insulating layer between them. Vcom2 can be a single domain or dual domain to integrate selective Vcom drive in an asymmetric direction. Vcom1 and Vcom2 can then be tuned to generate a combined electric field similar to the IPS-like drive for operation in split-mode mode. Fig. 2 ) and introduces a selective asymmetry for operation in private mode ( Fig. 3This asymmetry in the electrical control leads to an asymmetry in contrast and luminance performance across the pixel's viewing angle. The pixel's electrode shape can be optimized to achieve minimum contrast at the driver's position.

[0025] In Fig. 2The pixel design is shown when operating in division mode. The ground electrode design comprises a first ground electrode area 12' on which a second ground electrode area 13 is arranged, separated by an insulating layer 14'. On this second ground electrode area, also separated by an insulating layer 14", is the positive electrode 18', which has a comb-like structure and is not subdivided. This third electrode 18' is identical in design to the positive electrode of the standard IPS pixel. The second ground electrode area 13 is subdivided into two ground electrode sub-areas 13' and 13".By selectively controlling (see the further control unit 30) both or one of the two mass electrode partial surfaces 13', 13" next to the first mass electrode surface 12 (with simultaneous control of the third electrode 18') the electric field for the liquid crystals 24 within the pixel is influenced, both with regard to its strength and with regard to its homogeneity (symmetry, asymmetry), as described above, in order to switch between the division mode and the private mode (see . Fig. 3 ) to be able to switch.

[0026] The asymmetry of the Vcom2 ground electrode area of ​​the pixel, divided by the 13' and 13" ground electrode sub-areas, results in a tuned asymmetric contrast ratio. The minimum contrast can be achieved on the horizontal axis and adjusted to the driver's position. In split mode, IPS-like properties are achieved, while in private mode, the asymmetrically reduced contrast reduces the visibility of the image from the side of the display PID, e.g., from the driver's position, but is more than sufficient for the viewer directly in front of the display PID (e.g., passenger) (see the comparison in [reference]). Fig. 4 (with the CID display between driver and passenger and the PID display in front of the passenger).

[0027] The pixel design is compatible with the standard TFT manufacturing process for displays in the automotive sector and also compatible with the segmented Vcom design standardized for in-cell technology.

[0028] By combining the luminance profile of a backlighting unit that is also switchable between private mode and split mode, as described, for example, in WO-A-2023 / 232969, with the contrast and viewing angle restriction profile at the pixel level according to the invention, which is also switchable between private mode and split mode, the requirements for the degree of privacy in the automotive sector can be met, which consist of image visibility and a reduction in the degree of distraction. This is shown in the comparison in Fig. 5 .

[0029] In displays with a switchable privacy function for toggling between split-screen mode and private mode, as provided for in the invention, this switching can be performed both manually and automatically. In automotive applications, automatic switching from split-screen mode to private mode is advantageous when, for example, a camera monitoring the driver detects that the driver is looking towards the passenger display or passenger display area (eye tracking). In such cases, it would also be useful to automatically switch to private mode when "moving images" are displayed on the passenger display or passenger display area. Thus, various approaches exist for the automatic switching from split-screen mode to private mode. Accordingly, resetting to split-screen mode also occurs automatically.The automatic switch to private mode can be omitted in vehicles with seat occupancy detection if no passenger seat occupancy is detected.

[0030] The concept according to the invention can also be combined with non-switchable privacy functions (permanent privacy mode), which, however, is not in accordance with the claimed subject matter. An example of such a privacy concept is described in WO-A-2023 / 057551. REFERENCE MARK LIST

[0031] 10 TFT panel 12 Ground electrode area 12' First ground electrode area 13 Ground electrode area 13' Ground electrode sub-areas 13" Ground electrode sub-areas 14 Electrically insulating layer 14' Insulation layer 14" Insulation layer 16 Finger of an electrode 18 Electrode 18' Third electrode 20 TFT transistor 21 Driver unit for TFT 22 Cover glass 23 LCD display 24 Liquid crystals 30 Driver unit (for Vcom1 and Vcom2)

Claims

1. A display device, in particular for a vehicle, comprising - an LCD display having a plurality of pixels with a transparent carrier layer (10) on which a group of electrodes (12', 13', 13", 18') and also electronic components for actuating the electrodes (12', 13', 13", 18') are arranged per pixel, a transparent cover layer (22) forming a display surface, and a liquid crystal layer (24) between the carrier layer (10) and the cover layer (22), - wherein each group of electrodes (12', 13', 13", 18') comprises a first electrode surface (12') that can be connected to a ground potential and two second electrode surfaces (13', 13") that can also be connected to the ground potential, are electrically insulated from one another and from the first electrode surface (12'), and are arranged above or below the first electrode surface (12') such that they are together aligned therewith, - wherein each group of electrodes (12', 13', 13", 18') comprises a third electrode (18'), which is arranged to be electrically insulated from the first and second electrode surfaces (12', 13', 13") and can be connected to an operating potential, and - an control unit, which comprises the electronic components, inter alia, for connecting the third electrode (18') of each pixel or selected pixels to the operating potential and for connecting the first electrode surfaces (12') of each pixel or selected pixels to the ground potential in a sharing mode and for connecting the first electrode surface (12') and additionally one of the two second electrode surfaces (13', 13") of each pixel or selected pixels to the ground potential in a private mode, - as a result of which information displayed on the display surface of the LCD display, when looking at the display surface from a viewing direction facing one of the two second electrode surfaces (13', 13") of all the pixels, is visible in greater contrast in sharing mode than in private mode, in which the one of the two second electrode surfaces (13', 13") of each pixel or selected pixels which faces away from said viewing direction is connected to the ground potential.