Display device

Abstract

By using IPS technology, a display device that includes a liquid crystal display with multiple pixels and a special split electrode design, can affect the strength and uniformity of the electric field that spreads across the pixel, allowing each pixel to switch from a shared mode with maximum brightness and a symmetrical viewing angle range to a private mode with reduced brightness and an asymmetrical viewing angle range, and vice versa.

Description

[Technical field]

[0001] This PCT application claims priority to German patent application no. 102021126024.8 filed on October 7, 2021 and German patent application no. 102022114155.1 filed on June 3, 2022, the contents of which are incorporated by reference as if they constitute the subject matter of this application.

[0002] The present invention relates to a display device, particularly for use in a vehicle, which can be selectively operated in a shared mode or a private mode. [Background technology]

[0003] The number and size of displays, especially in vehicles, continues to grow, and currently vehicle concepts already exist that feature displays for the passengers in or on the dashboard, either as a separate display from the other displays or as the passenger portion of a door-to-door display.

[0004] For some time now, there have been measures in place to limit the ability of third parties to freely view information displayed on a display surface. Ideally, only the intended viewer should be able to read the screen contents, and anyone nearby should not be able to read, understand, or recognize the displayed information.

[0005] Two examples of liquid crystal displays with controllable viewing angle ranges are described in US Patent Application Publication No. 2020 / 0073157 and US Patent Application Publication No. 2013 / 0265514. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2020 / 0073157 [Patent Document 2] US Patent Application Publication No. 2013 / 0265514

[0007] Liquid crystal displays using the so-called In-Plane-Switching (IPS) technology have proven to be particularly effective. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a display device, particularly for vehicles, using IPS technology, which electronically realizes selective operation in a share mode or a private mode. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention proposes a display device, particularly for a vehicle, which display device, according to a first aspect of the present invention, comprises: a liquid crystal display having a plurality of pixels; A drive unit. the liquid crystal display comprises a transparent carrier layer in which one electrode group per pixel and electronic components for driving the electrodes are arranged, a transparent cover layer constituting a display surface, and a liquid crystal layer between the carrier layer and the cover layer; Each electrode group has a ground electrode surface connectable to a ground potential and at least two comb-tooth electrodes connectable to an operating potential independently of each other, each comb-tooth electrode has a first portion from which a plurality of second portions extend, the two first portions of the two comb-tooth electrodes are parallel to each other, and the second portions of one of the comb-tooth electrodes extend between adjacent second portions of the other of the comb-tooth electrodes, the two comb-tooth electrodes are disposed on the ground electrode surface, and are electrically insulated from each other and from the ground electrode surface; the driving unit in particular comprises the electronic components, and in a private mode connects one of the two comb electrodes of each pixel or selected pixels to the operating potential, and in a share mode connects both comb electrodes of each pixel or selected pixels to the operating potential; As a result, when the display surface is viewed from a viewing direction facing the first portion of one of the two comb-tooth electrodes of all pixels, only the comb-tooth electrodes of each pixel or selected pixels whose first portions do not face the viewing direction are connected to the operating potential, i.e., in the share mode, information displayed on the display surface of the liquid crystal display can be viewed with higher contrast than in the private mode in which the comb-tooth electrodes of each pixel or selected pixels whose first portions face the viewing direction are not connected to the operating potential.

[0010] According to a second aspect of the present invention, in order to solve the above problem, a display device, particularly for a vehicle, is proposed, the display device comprising: a liquid crystal display having a plurality of pixels; A drive unit. the liquid crystal display comprises a transparent carrier layer in which one electrode group per pixel and electronic components for driving the electrodes are arranged, a transparent cover layer constituting a display surface, and a liquid crystal layer between the carrier layer and the cover layer; each electrode group has a first electrode surface connectable to a ground potential and two second electrode surfaces also connectable to said ground potential, the second electrode surfaces being electrically insulated from each other and from said first electrode surface and arranged side by side above or below said first electrode surface so that both coincide with said first electrode surface; each electrode group has a third electrode arranged electrically insulated from the first and second electrode surfaces and connectable to an operating potential; said driving unit in particular comprising said electronic components, in a shared mode, connecting said third electrode of each pixel or selected pixels to said operating potential and connecting said first electrode surface of each pixel or selected pixels to said ground potential, and in a private mode, connecting one of said two second electrode surfaces of each pixel or selected pixels to said ground potential in addition to said first electrode surface, As a result, when the display surface is viewed from a viewing direction facing one of the two second electrode surfaces of all pixels, the one of the two second electrode surfaces of each pixel or a selected pixel that does not face the viewing direction is connected to the ground potential, i.e., in the share mode, information displayed on the display surface of the liquid crystal display can be viewed with higher contrast than in the private mode in which the one of the two second electrode surfaces of each pixel or a selected pixel that does not face the viewing direction is connected to the ground potential.

[0011] According to the present invention, the display device according to both aspects includes a liquid crystal display using IPS technology. However, in this case, in the first aspect, the positive electrode is composed of multiple parts, whereas in the second aspect of the display device according to the present invention, the negative electrode is composed of multiple parts for each pixel. In the IPS technology, by selectively driving each electrode of one electrode composed of multiple parts for each pixel of the liquid crystal display in a different manner, it is possible to affect the contrast when the display surface is viewed from a viewing direction opposite to the non-driven electrode.

[0012] According to a first aspect of the display device according to the invention, a number of pixels each have one ground electrode and a number of positive electrodes that can be driven according to the information to be displayed. The positive electrodes are arranged side by side and are electrically isolated from each other and from the ground electrode. When both positive electrodes are driven by a signal supplied to display the desired information, typically via transistors implemented by TFT technology, the strength of the electric field prevailing in the liquid crystal layer is maximized. This maximizes the contrast and maximizes the light transmittance. In contrast, when only one positive electrode is driven for each pixel or for selected pixels, the electric field strength is reduced, which reduces the contrast and the backlight transmittance. This is particularly effective when the display is viewed from a viewing direction facing the non-driven positive electrodes.

[0013] The optimum effect is obtained when the two positive electrodes each have a comb-tooth structure in which the "teeth" of each comb are interdigitated with each other. Thus, each comb-tooth electrode has a first portion, and the first portions of the two comb-tooth electrodes are parallel to each other. From each first portion, a number of second portions extend, and between two adjacent second portions of one comb-tooth electrode, one of the second portions of the other comb-tooth electrode extends. This electrode design is basically the same as that of an LCD pixel in IPS technology, but there is a crucial difference from the known background art, which is divided into two sub-electrodes that can be driven separately (typically by TFT transistors).

[0014] In a second embodiment of the display device concept according to the present invention, an electrode design known from liquid crystal displays in IPS technology is adopted as the positive electrode, which has two comb-tooth structures, the first parts of both comb-tooth structures being electrically connected to each other, and the second parts protruding from the first parts appear alternately and are arranged in an alternating manner. The negative electrode is composed of a plurality of parts. The negative electrode has a negative electrode surface that substantially occupies the pixel surface. Above or below this first negative electrode surface, there is another negative electrode surface divided in an electrically insulated state, and this negative electrode surface has two or more negative sub-electrode surfaces arranged side by side and electrically insulated from each other. The electric field formed in the liquid crystal layer in the pixel can be influenced by the selection of the negative electrode surface or the negative sub-electrode surface to be driven, both in its strength and in its uniformity in the pixel surface. Specifically, when only one of the two negative sub-electrode surfaces is driven, the electric field strength in the area of ​​the negative sub-electrode surface that is not driven becomes smaller than in the remaining area of ​​the pixel, resulting in an asymmetry in the electric field. This affects both the light transmittance and the contrast when the display surface is viewed from a viewing direction facing the undriven second negative sub-electrode surface.

[0015] The present invention will be described in detail below using two embodiments with reference to the drawings. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view and a schematic top view showing a standard design of an LCD pixel in IPS technology. [Diagram 2] FIG. 2 shows cross-sectional and top views of a modification of the pixel design according to the first embodiment for drive in share mode. [Diagram 3] FIG. 3 is a schematic cross-sectional view and a schematic top view showing a pixel design according to the first embodiment in private mode driving. [Figure 4]FIG. 4 shows cross-sectional and top views of a modified pixel design according to the second embodiment for drive in share mode. [Diagram 5] FIG. 5 is a schematic cross-sectional view and a schematic top view showing a pixel design according to the second embodiment in private mode driving. [Figure 6] FIG. 6 is a diagram showing a comparison of the visibility of the driver and passenger in the passenger display operation modes of share mode (FIG. 6, left) and private mode (FIG. 6, right). [Figure 7] FIG. 7 is a diagram showing a comparison of the visibility of the driver and passenger when the backlight light intensity of the passenger display in private mode operation is further reduced in the passenger display operation modes of share mode (left side of FIG. 7) and private mode (right side of FIG. 7). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Privacy protection techniques have been on the market for many years already to limit / prevent third parties from reading the contents displayed on a display, so that the display can only be viewed from one preferred direction, while the information is hidden in all other directions. The known techniques are based on both fixed and switchable privacy protection. In the fixed case, the privacy protection effect is achieved by integrating a dimming system (i.e. dimming film, prism, etc.) into the backlight unit of the display. For switchable privacy protection, the backlight design has been extended so that both driving the illumination with normal light and privacy protection illumination are supported. These measures reduce the luminance over the entire viewing angle, but in dark spatial situations the visibility of the image cannot be reduced to low light intensities due to the daylight recalibration of the human eye. In this case, the luminance is reduced to 0.3 cd / m 2 Even if only one image is captured, the image will still be visible, leading to a decrease in privacy protection performance.

[0018] In the case of applying such a privacy concept in a vehicle, the information in the display area of ​​a separate display for passengers or, for example, a door-to-door display, is at least slightly perceptible to the driver, which may distract the driver and lead to dangerous situations. Therefore, the possibility of switching to an improved private mode is important with regard to safety, especially in automotive applications.

[0019] Meanwhile, other solutions mainly focus on privacy protection of the display panel by converting the pixel design to a different electrical driving mode. Such solutions do not allow the realization of an in-cell display. These solutions reduce the brightness or contrast ratio, but only when a very strong dimming factor is used for the backlight, the visibility of the image can be reduced, which has a significant impact on the image quality for the target user.

[0020] These existing solutions are mainly suitable for end-user market applications and are very effective in providing privacy protection under normal lighting conditions, but are less effective when the ambient light is relatively low, such as when driving a vehicle at night, because the eyes have readapted to the low light intensity.

[0021] These solutions have a disadvantage in terms of optical performance, since the optimal performance in switchable and private mode significantly degrades the display's performance in normal sharing operation. This also has a disadvantage in vehicles. Based on the number of displays integrated into the vehicle's dashboard, these displays need to be tuned to exhibit similar optical performance. Privacy protection technologies that cannot achieve the same optical performance in sharing mode as the rest of the displays in the vehicle may not be suitable for automotive applications.

[0022] The present invention provides a solution for obtaining added value of displays in the automotive field, combined with improved privacy protection display effect in discrete touch and in-cell touch technology applications, where the pixel design of the present invention ensures display performance and in-cell compatibility of the design based on IPS pixel design. The dual mode pixel design proposed by the present invention has the following advantages, especially for vehicle applications:

[0023] The pixel is IPS-like in share mode (normal mode or first pixel drive mode), which allows it to achieve the high optical performance required in the automotive sector.

[0024] To selectively reduce the contrast towards the driver position while at the same time preserving the brightness and contrast levels at the passenger position, the pixel drive can be switched to a private mode (second pixel drive mode).

[0025] A display according to one embodiment of the invention uses In-Plane-Switching (IPS) technology and comprises, inter alia: ·LCD-TFT Glass LCD color filter glass ·liquid crystal Orientation layer Electronic control unit (IC control unit, routing, TFT, Gate on Panel)

[0026] Other elements may also be provided, such as a touch panel, a backlight unit, a proximity sensor system with gesture recognition, if necessary integrated into the display device, but these are essentially not relevant to the invention. Polarizing filters, which are typically provided, are also not important for the invention and will therefore not be mentioned below.

[0027] The color filter glass and IC control are conventional and can be selected according to the required functionality and performance of the display. The color scale can be set, for example, by color filters. Also, an in-cell IC controlled and / or separate touch panel may be implemented.

[0028] IPS displays are particularly good at wide viewing angles, very high image quality and optimal color rendition. The standard pixel design of an IPS type has a thin film transistor (TFT). A video signal (voltage level) is applied to the pixel's electrode to generate a voltage level at the pixel. The voltage difference between ground (Vcom) and the voltage level on the grid then determines the total voltage level (electric field) within the liquid crystal, producing a clear and well-controlled grey scale.

[0029] This state is shown in Figure 1. Here, the electrode design can be a multi-domain type (V-type, two domains, zigzag, etc.) with multiple electrode surfaces per pixel, although the arrangement and number can vary depending on the design, which can provide symmetry in transmittance and contrast ratio while keeping the color shift level low.

[0030] A standard pixel design in IPS technology, Fig. 1, conventionally comprises a TFT panel 10 on which is disposed one ground electrode or ground electrode plane 12 per pixel (grounded via a drive unit 30). Separated from the ground electrode plane 12 by an electrically insulating insulating layer 14 is a "finger" 16 of a single electrode 18 which is driven via a TFT transistor 20 (see drive unit 21). Above and spaced from the TFT panel 10 is a liquid crystal display cover glass 22, with liquid crystal 24 disposed between the TFT panel 10 and the cover glass 22.

[0031] According to a first aspect of the invention (see Figures 2 and 3), the electrode design, compared to a single-electrode pixel design, is split into two (sub) electrodes. A separate TFT transistor 20', 20" is connected to each sub-electrode (in this embodiment formed as comb-tooth electrodes 26, 28). When the display is operated in share mode, both TFTs are selected when the pixel is driven. Here, standard electric fields are generated for a standard design of the IPS type (see Figure 2).

[0032] In the private mode, when one of the two TFT transistors 20', 20" is blocked by the control unit, the electric field is changed (Figure 3). Here, a single liquid crystal domain orientation is preferred, which leads to asymmetric optical properties. In particular the luminance transmittance of the pixel decreases over the viewing angle as well as the contrast ratio. The pixel electrode shape may now be optimized to the extent that the contrast at the driver position is minimized. The expected asymmetric contrast ratio (CR) is shown in Figure 3, whereas the standard symmetric CR is shown in Figure 2.

[0033] This pixel design, and in particular the electrode design according to this first aspect (first embodiment), differs from the standard IPS design in that the positive electrode to which the driving unit 21 applies a video signal or a signal related to the display of information is divided into several parts. In this embodiment, the electrode 18 is divided into two comb-tooth electrodes 26, 28 which are electrically isolated from each other and can be selectively driven by the TFT transistors 20', 20". FIG. 2 shows how the two comb-tooth electrodes 26, 28 are driven simultaneously, resulting in a relatively strong and uniform electric field within the pixel. In operation of such a pixel, the pixel is driven in share mode. The transmittance and contrast profile of FIG. 2 shows 100% light transmittance and a relatively wide and symmetrical viewing angle range.

[0034] When the pixel is operated in private mode, only one of the two comb electrodes 26, 28 is activated. The electric field formed in the liquid crystal region in the pixel is then weaker and asymmetric. The resulting transmittance is therefore lower and the viewing angle range is narrower and further shifted to one side. Thus, for the situation shown in FIG. 3, a viewer on the left side of the display will have a very limited viewing area of ​​the display. By driving the other comb electrode 26 alone (instead of comb electrode 28 as shown in FIG. 3), the private mode is activated for a viewer on the right side of the display. Thus, the direction of the protection function can be changed by selecting the driving of one of the two comb electrodes 26, 28.

[0035] The design in the second embodiment (FIGS. 4 and 5) consists of a single TFT 20 with a single grid multi-domain electrode design (similar to the IPS standard design). However, the Vcom electrode design (ground electrode or ground electrode plane) is extended by a second Vcom electrode plane. The second Vcom2 electrode is placed on the standard Vcom1 through an insulating layer. Vcom2 can be single domain or dual domain to incorporate selective Vcom drive in asymmetric directions. Vcom1 and Vcom2 can then be tuned to generate a total field similar to IPS drive for Share mode operation (FIG. 4) and a total field with selective asymmetry for Private mode operation (FIG. 5). This asymmetry in electrical drive leads to asymmetry in contrast and brightness performance across the viewing angle of the pixel. Here, the pixel electrode shape may be optimized to minimize contrast at the driver position.

[0036] FIG. 4 shows another pixel design for operation in this share mode. The ground electrode design has a first ground electrode plane 12' on which a second ground electrode plane 13 is arranged, separated by an insulating layer 14', and on which an unsplit positive electrode 18' with a comb-tooth structure is arranged, also separated by an insulating layer 14". The design of this third electrode 18' is similar to that of the positive electrode of a standard IPS pixel. In this embodiment, the second ground electrode plane 13 is split into two sub-ground electrode planes 13', 13". By selectively driving (see drive unit 30) the first ground electrode plane 12 (driven simultaneously with the third electrode 18') and / or the two sub-ground electrode planes 13', 13", the electric field across the liquid crystal in the pixel is influenced, both in strength and uniformity (symmetric, asymmetric) and can be switched between share and private modes (see FIG. 5), as described above.

[0037] The asymmetry of the Vcom2 ground electrode surface of the pixel divided by the sub-ground electrode surfaces 13', 13" adjusts the asymmetric contrast ratio. The minimum contrast is obtained on the horizontal axis and can be adjusted to the driver's position. Here, in the share mode, an IPS-type characteristic is obtained, whereas in the private mode, the asymmetric and lower contrast reduces the visibility of the image from a position to the side of the display PID, e.g. the driver's position, but is generally sufficient for a viewer in front of the display PID (e.g. a passenger) (see comparison in Figure 6 for a CID display between the driver and passenger and a PID display in front of the passenger).

[0038] Both pixel designs are compatible with standard TFT manufacturing processes for displays in the automotive sector and are also compatible with the standardized segmented Vcom design for in-cell technology.

[0039] A backlight unit which can likewise be switched between a private mode and a shared mode (see, for example, DE 102022114153.5 of June 3, 2022, entitled "Anzeigevorrichtung, insbesondere The luminance profile of the 'fuer ein Fahrzeug, zum Anzeigen von Information mit unschaltbarem Teilungs- und Privat-Modus' (see also WO 2005 / 0231111, the contents of which are incorporated herein by reference) combined with the pixel-level contrast and viewing angle limitation profile switchable between private and share modes according to the invention meets the requirements for a level of privacy protection in the automotive field, with respect to image visibility and reduced distraction, as shown in the comparison in FIG. 7.

[0040] In a display with switchable privacy protection to switch between shared and private modes, this switching can be done manually or automatically, as described in the present invention. In automotive applications, it is useful to automatically switch from shared to private mode, for example, when a camera observing the driver detects that the driver looks in the direction of the passenger display or passenger display area (eye tracking). It can also be useful to automatically switch to private mode when a "video" is displayed on the passenger display or passenger display area. Thus, there are various methods for automatically switching from shared to private mode. It is therefore also possible to automatically switch back to shared mode. In vehicles with seat occupancy recognition, the automatic switching to private mode can be omitted if it is detected that no one is in the passenger seat.

[0041] The inventive concept can also be combined with a non-switchable privacy protection function (always private mode). Examples of such privacy protection concepts are described in the PCT patent application entitled "Anzeigevorrichtung, insbesondere fur ein Fahrzeug, zum Anzeigen von Information mit asymmetric Hinterleuchtung" (attorney docket no. 222366WO, filed on the same day as this PCT application) and in the published German patent application nos. 102021126025.6 dated October 7, 2021 and 102022144165.9 dated June 3, 2022, the contents of which are also incorporated by reference as constituting the subject matter of this PCT application. [Explanation of symbols]

[0042] 10 TFT Panel 12 Ground electrode plane 12' First ground electrode surface 13 Ground electrode surface 13' Sub-ground electrode surface 13” Sub-ground electrode surface 14 Electrically insulating insulating layer 14' Insulation layer 14” Insulation Layer 18 electrodes 18' Third electrode 20 TFT transistor 20' TFT transistor 20” TFT transistor 21 TFT drive unit 22 Coverslip 23 Liquid crystal display 24 Liquid crystal 26 comb electrode 28 Comb electrode 30 (for Vcom1 and Vcom2) drive unit

Claims

1. A display device for a vehicle, comprising: a liquid crystal display having a plurality of pixels; Drive unit and Equipped with The liquid crystal display is a transparent carrier layer (10) on which one group of electrodes (12', 13', 13", 18') per pixel and electronic components for driving the group of electrodes (12', 13', 13", 18') are arranged; A transparent covering layer (22) constituting a display surface; a liquid crystal layer (24) between the carrier layer (10) and the covering layer (22); having Each of the electrode groups (12', 13', 13", 18') is a first electrode surface (12') connectable to ground potential; two second electrode surfaces (13', 13") connectable to the ground potential; having the second electrode surfaces (13', 13") are electrically insulated from each other and from the first electrode surface (12'), and are arranged side by side above or below the first electrode surface (12') so as to coincide with the first electrode surface (12'); Each of the electrode groups (12', 13', 13", 18') has a third electrode (18') arranged electrically insulated from the first and second electrode surfaces (12', 13', 13") and connectable to an operating potential; The drive unit is The electronic component is provided In a share mode, the third electrode (18') of each or selected pixel is connected to the operating potential and the first electrode surface (12') of each or selected pixel is connected to the ground potential; In a private mode, in addition to the first electrode surface (12'), one of the two second electrode surfaces (13', 13") of each pixel or selected pixels is connected to the ground potential, As a result, when the display surface is viewed from a viewing direction facing one of the two second electrode surfaces (13', 13") of all pixels, in the share mode, the information displayed on the display surface of the liquid crystal display can be viewed with higher contrast than in the private mode in which the one of the two second electrode surfaces (13', 13") of each pixel or a selected pixel that does not face the viewing direction is connected to the ground potential.

2. A display device for a vehicle, comprising: A liquid crystal display (23) having a plurality of pixels; A drive unit (21) and Equipped with The liquid crystal display (23), a transparent carrier layer (10) on which a group of electrodes (12, 26, 28) per pixel and electronic components for driving the group of electrodes (12, 26, 28) are arranged; A transparent covering layer (22) constituting a display surface; a liquid crystal layer (24) between the carrier layer (10) and the covering layer (22); having Each of the electrode groups (12, 26, 28) a ground electrode surface (12) connectable to a ground potential; At least two comb electrodes (26, 28) that can be connected to an operating potential independently of each other; having Each of the comb-tooth electrodes (26, 28) has a first portion (26', 28'), a plurality of second sections (26", 28") extending from the first section (26', 28'); the two first portions (26', 28') of the two comb-tooth electrodes (26, 28) are parallel to each other; the second portion (26", 28") of one of the two comb-tooth electrodes (26, 28) extends between the adjacent second portions (26", 28") of the other of the two comb-tooth electrodes (26, 28); the two comb-tooth electrodes (26, 28) are disposed on the ground electrode surface (12) while being electrically insulated from each other and from the ground electrode surface (12); The drive unit (21) The electronic component is provided In a private mode, one of the two comb electrodes (26, 28) of each pixel or selected pixels is connected to the operating potential; In a share mode, the two comb electrodes (26, 28) of each pixel or selected pixels are both connected to the operating potential; As a result, when the display surface is viewed from a viewing direction facing the first portion (26', 28') of one of the two comb-tooth electrodes (26, 28) of all pixels, only the comb-tooth electrodes (26, 28) of each of the pixels or selected pixels whose first portions (26', 28') do not face the viewing direction are connected to the operating potential, and the display device allows information displayed on the display surface of the liquid crystal display to be viewed with higher contrast in the share mode than in the private mode in which the comb-tooth electrodes (26, 28) of each of the pixels or selected pixels whose first portions (26', 28') face the viewing direction are not connected to the operating potential.

Images