Screen, structured polarization filter and method for producing such a polarization filter

Abstract

The invention relates to a screen comprising an imaging device (2) that, in order to display image content, has a grid containing pixels PBild that are divided at least into a first group of pixels P1 and a second group of pixels P2, furthermore comprising a first optical element (3) active in each case in front of or behind the pixels P1 of the first group in the viewing direction of an observer, a second optical element (4) active in each case in front of or behind the pixels P2 of the second group in the viewing direction of an observer, and a third, planar optical element (5), wherein material is selected in each case from defined groups for all of the first, second and third optical elements (3, 4, 5) such that in each case the combined effect of the first and third optical element allows the pixels P1 of the first group to emit light in an unrestricted angular range, and such that in each case the combined effect of the second and third optical element causes the pixels P2 of the second group to emit light in a restricted angular range, resulting in different viewing angles on the imaging device (2) for the first group of pixels P1 and for the second group of pixels P2. A structured polarization filter and a method for producing same are also disclosed.

Description

title

[0001] Display screen, structured polarization filter and manufacturing method for such a polarization filter Technical field of the invention

[0002] In recent years, great strides have been made in widening the viewing angle of LCDs. However, there are often situations where the very large viewing area of ​​a screen can be a disadvantage. Information, such as banking details and other personal and sensitive data, is also becoming increasingly available on mobile devices such as notebooks and tablet PCs. Accordingly, people need control over who can see this sensitive data. They must be able to choose between a wide viewing angle – a public mode – in order to share information on their display with others, e.g., when looking at holiday photos or for advertising purposes. On the other hand, they need a narrow viewing angle – in a private mode – if they want to keep the image information confidential.

[0003] A similar problem arises in vehicle construction: The driver must not be distracted by image content, such as digital entertainment programs, when the engine is running, while the passenger also wants to consume these while driving. Therefore, a screen that can switch between the corresponding display modes is required.

[0004] Additional films based on micro-louvres have already been used for mobile displays to achieve visual privacy. However, these films were not switchable or reversible; they always had to be applied and removed manually. They also had to be transported separately from the display when not in use. A major disadvantage of using such louvre films is the associated light loss.

[0005] US Pat. No. 6,765,550 B2 describes such a privacy screen using micro-louvres. The biggest disadvantage here is the mechanical removal or installation of the filter, as well as the loss of light in protected mode.

[0006] US Pat. No. 5,993,940 A describes the use of a film with evenly spaced, small, strip-shaped prisms on its surface to achieve a private mode, i.e., a restricted viewing mode with a narrow viewing angle range. Development and production are technically quite complex.

[0007] In WO 2012 / 033583 A1, switching between unobstructed and restricted view is achieved by controlling liquid crystals between so-called "chromonic" layers. This results in light loss and requires considerable technical effort.

[0008] US 2012 / 0235891 A1 describes a very complex backlight in a screen. According to Figs. 1 and 15, not only multiple light guides are used, but also other complex optical elements such as microlens elements 40 and prism structures 50, which transform the light from the rear illumination on its way to the front illumination. This is expensive and technically complex to implement and also involves light loss. According to the variant shown in Fig. 17 in US 2012 / 0235891 A1, both light sources 4R and 18 produce light with a narrow illumination angle, with the light from the rear light source 18 first being converted at great expense into light with a wide illumination angle. This complex conversion, as already mentioned above, significantly reduces brightness.

[0009] According to JP 2007-155783 A, special optical surfaces 19 are used, which are complex to calculate and manufacture, and which then deflect light into different narrow or wide areas depending on the angle of incidence. These structures resemble Fresnel lenses. Furthermore, there are interference edges that deflect light in undesirable directions. Thus, it remains unclear whether truly meaningful light distributions can be achieved.

[0010] US 2013 / 0308185 A1 describes a special light guide with steps that emits light over a large area in different directions, depending on the direction from which it illuminates from a narrow side. In conjunction with a transmissive image display device, such as an LCD, a screen can be created that can be switched between free and restricted viewing modes. A disadvantage of this is that the restricted viewing effect can only be created for left / right or up / down, but not for left / right / up / down simultaneously, as is necessary for certain payment transactions, for example. Furthermore, even in restricted viewing mode, residual light is still visible from blocked viewing angles.

[0011] The applicant's WO 2015 / 121398 A1 describes a screen with two operating modes, in which scattering particles are present in the volume of the corresponding light guide for switching between the operating modes. However, the polymer scattering particles selected there generally have the disadvantage that light is coupled out of both large surfaces, causing approximately half of the useful light to be emitted in the wrong direction, namely toward the backlight, where it cannot be adequately recycled due to their design. Furthermore, the polymer scattering particles distributed in the volume of the light guide can, under certain circumstances, particularly at higher concentrations, lead to scattering effects that reduce the privacy effect in the protected operating mode.

[0012] The approach of "Electrical Birefringence (EDB)" technology is based on the idea of ​​using the switchable liquid crystals of an additionally applied LC panel to "filter" all light rays that do not exit the imaging layer at a specific beam angle. Disadvantages of this technology include high additional energy and cost requirements and the difficult-to-change + / -40 0 Sweet spot, i.e. the best possible viewing position. The absorption coefficient of the LC structures is also insufficient, since the attenuation of the light intensity increases again for viewing angles greater than the sweet spot, so that the light intensity for viewing angles greater than + / -40 0 up to 3% of the maximum light intensity.

[0013] The aforementioned methods and arrangements generally have the disadvantage that they significantly reduce the brightness of the basic screen and / or require a complex and expensive optical element for mode switching and / or reduce the resolution in the freely viewable, public mode and / or have visual artifacts on very high-resolution displays. Description of the invention

[0014] The object of the invention is therefore to describe a screen with a switchable angular radiation characteristic. Furthermore, a structured polarization filter, including a method for its production, is to be disclosed, wherein such a structured polarization filter can optionally be used in the aforementioned screen.

[0015] This object is achieved in a first embodiment according to the invention by a screen with an image generator which has a grid with pixels Pßiid for displaying image content, which are divided into at least a first group of pixels P1 (which should be visible in a wide angular range) and a second group of pixels P2 (which should be visible in a limited angular range), further comprising a first optical element which is active in the viewing direction of a viewer behind or (preferably) in front of the pixels P1 of the first group, a second optical element which is active in the viewing direction of a viewer in front of or behind the pixels P2 of the second group, and a third, planar optical element arranged in the viewing direction of a viewer in front of or behind the first and the second optical elements, - wherein for all first, second and third optical elements, a material is selected from the group consisting of a) linear polarizer which transmits electric fields along a first preferred direction (wherein the first preferred direction is preferably vertical from the perspective of a standing or sitting observer), b) linear polarizer which transmits electric fields along a second direction perpendicular to the first preferred direction, c) vertical polarizer, d) s-polarizing material, e) p-polarizing material, f) material with no polarization-changing function (such a material can consist of a preferably transparent or translucent placeholder, but it can also be in gaseous form rather than in solid form present, as in the case of air as a material, and thus virtually eliminated), g) two vertical polarizers, between which there is an sp converter, or h) retarder, - wherein for the entirety of first, second and third optical elements, preferably or exclusively the combinations 1. a), b) and c); 2. c), d) and e); 3. c), f) and [a) or b)]; 4. twice f) and once g); 5. a), c) and f); 6. e), c) and f); 7. a), [a) with h)] and a); 8. b), [b) + h)] and b) are permitted, so that the combined effect of the first and third optical elements for the pixels P1 of the first group allows light emission in an unrestricted angular range, and so that the combined effect of the second and third optical elements for the pixels P2 of the second group causes light emission in a restricted angular range, in which the light emitted by the pixels P2 of the second group is emitted in an angular range that is restricted compared to the pixels P1 of the first group, - which causes the viewing angles on the imager to differ for the first group of pixels P1 and for the second group of pixels P2.

[0016] Within the scope of the invention, and in particular with regard to pixels P2 of the second group, "limited angular range" means that the corresponding (possibly standardized) luminance is concentrated to at least 80% or 90% in a defined angular range, while residual light may still exist outside the defined limited angular range, which is generally due to technical reasons. Ideally, such residual light is minimal and generally decreases with increasing angles. The defined angular range can lie in one or more planes that intersect the screen. Preferably, it lies in a plane that contains the bisector of the screen and is particularly preferably arranged parallel to the upper edge of the image generator (from the perspective of a standing or seated viewer) with a maximum tolerance of 10°.

[0017] The operation of the invention consists, among other things, in the pixels of the two groups P1 and P2 having different angular ranges of light emission. This is achieved by the first, second, and third optical elements. These optical effects are coupled with a corresponding control of the respective first and / or second group of pixels P1, P2, which is explained in more detail below, in order to display image content on the screen either with a restricted or an unrestricted angular radiation characteristic, i.e. with optionally different possible viewing angles.

[0018] Materials d) and e) can be, for example, metamaterials. In the case of a retarder h), these can be, for example, fixed liquid crystals, in particular GHLC liquid crystals, which are applied, aligned, and fixed on a transparent substrate. However, it is also possible to use a retarder made of a polymer, although other designs are also conceivable.

[0019] Each vertical polarizer, i.e. material c), if present, can in turn comprise a multitude of light-absorbing transition dipole moments, - wherein the majority (e.g., more than 80%, preferably more than 90%, particularly preferably more than 97%) of the transition dipole moments are permanently, or at least in a first state, aligned with a tolerance of a maximum of 20° (preferably a maximum of 10°) parallel to a second preferred direction selectable for the respective vertical polarizer, which is perpendicular to the first preferred direction (wherein the second preferred direction is preferably also perpendicular to the second direction), or vary around this, so that light incident on such a vertical polarizer is transmitted or at least partially absorbed depending on its polarization state, its plane of incidence, and its angle of incidence. (By virtue of this definition, "vertical polarizer" also explicitly includes polarizers whose second preferred direction is not parallel to the perpendicular bisector of the screen.)

[0020] A material from group c) can, for example, be formed as a laminate of layers of polymer film polarizers. Other manufacturing variants and material designs are possible.

[0021] Alternatively or in combination, a material from group c) can also be produced by photoalignment of molecules or particles. In general, one can Here, we are talking about liquid crystal polymers doped with dye(s). Various approaches are known in the art (e.g., thermosettling LCs and epoxy LCs), which therefore need not be discussed in detail. The following publications are examples in this context:

[0022] N. Saba, M. Jawaid, OY Alothman, MT Paridah, and A. Hassan, “Recent advances in epoxy resin, natural fiber-reinforced epoxy composites and their applications,” Journal of Reinforced Plasticsand Composites, vol. 35, no. 6, 2015.

[0023] C. Carfagna, E. Amendola, and M. Giamberini, “Liquid crystalline epoxy based thermosetting polymers,” Progress in Polymer Science, vol. 22, pp. 1607-1647, 1997.

[0024] V. P. Shibaev and A. Yu. Bobrovsky, “Liquid crystalline polymers: development trends and photocontrollable materials,” Russian Chemical Reviews, vol. 86, pp. 1024- 1072, 2017.

[0025] T. Ikeda, J.-i. Mamiya, and Y. Yu, “Photomechanics of liquid-crystalline elastomers and other polymers,” Angew. Chem. Int. Ed., vol. 46, pp. 506-528, 2007.

[0026] The at least one dye consists of dye molecules, wherein a transition dipole or transition dipole moment is advantageously associated with each dye molecule, i.e. each dye molecule corresponds to a transition dipole or transition dipole moment. Typically, a dye has a mass fraction of 0.01% to 10% (or possibly significantly more, e.g. 80%), preferably of 0.1% to 5%, of the material of the respective layer(s) in the first or second optical element. The thickness of the layers is preferably in the range from 0.2 pm to 50 pm, more preferably in the range from 0.5 pm to 20 pm, all boundary values ​​included. The dyes or dye mixtures in the first and second optical element can also be formed differently in their different layers, if present.

[0027] A preferred embodiment is a mixture of liquid crystals with at least one dye, especially with at least one dichroic dye mixture. Examples of dichroic dyes or dye mixtures that can be used are azomethine dyes, indigoid and thioindigoid dyes, merocyanines, azulene, quinophthalone dyes, perylene dyes, phthaloperine dyes, dioxazine dyes, triphenodioxazine dyes, quinoxaline dyes, triazine dyes, tartrazine, azo- Dyes and anthraquinone dyes are suitable. The preparation of a liquid crystal dye mixture is described, for example, in US Pat. No. 4,695,131 A. Furthermore, the outer surfaces of the layers are preferably treated, for example, brushed, to achieve a homogeneous surface alignment of the transition dipole moments or, if present, of the liquid crystals.

[0028] It is advantageous for the pixels Pßiid to be full-color pixels, monochrome pixels, color subpixels, and / or subdomains of color subpixels. In modern screens, color subpixels often consist of so-called subdomains, which can take on non-rectangular shapes, such as so-called "chevron" shapes. By assigning the pixels Pßiid to subdomains of such color subpixels, parts of these color subpixels can then advantageously be controlled separately.

[0029] If the pixels P11d are each such subdomains of color subpixels, the first group of pixels P1 and the second group of pixels P2 preferably have differing gamma curves and / or differing luminance profiles. With such configurations, it is possible for the pixels P2 of the second group to have, on average, a lower luminance at angles that deviate, for example, by more than 20° from the perpendicular to the image sensor than the pixels P2 of the first group.

[0030] Further design variants provide that pairs of immediately adjacent pixels are color subpixels of the same color, with one color subpixel of each such pair belonging to the first group of pixels P1 and the other color subpixel belonging to the second group of pixels P2. In other words, such a design variant always has a pair of color subpixels of the same color (e.g., RR*GG*BB*RR*GG*BB*, etc.) in one direction, e.g., the horizontal direction from the perspective of a standing or seated observer, where alternately, one pixel P1 belongs to the first group and one pixel P2 belongs to the second group.

[0031] Furthermore, it is possible for the pixels P1, P2 of the first and second groups to alternate in rows, columns, or a checkerboard pattern. Other configurations are possible, as is a random distribution of the pixels P1, P2 of the first and second groups.

[0032] Particular embodiments of the invention provide that the selection of the material effect for all first, second and third optical elements from the aforementioned groups is carried out in a temporally variable or temporally sequential manner.

[0033] Advantageously, the numbers of pixels P1, P2 of the first and second groups differ by no more than 50%. Preferably, the same number of pixels P1 and P2 are present in each of the first and second groups. Alternatively, it is also possible for there to be fewer pixels P2 of the second group than pixels P1 of the first group. In the latter case, the image content perceived within a limited angular range and displayed on the pixels P2 of the second group would have a lower resolution than the image content displayed on the pixels P1 of the first group.

[0034] When controlling a screen in question, appropriate control electronics can ensure that two (nearest) neighboring pixels P1, P2 of the first and second groups each display the same screen content. In this way, an increased resolution can be achieved, at least for the unrestricted angular range.

[0035] Furthermore, the control of a screen can also act in such a way that for a first operating mode B1 for a free viewing mode, either only the pixels P1 of the first group display an image content and the pixels P2 of the second group are switched to black, or that both the pixels P1 of the first group and the pixels P2 of the second group display an image content, while for a second operating mode B2 for a restricted viewing mode, only the pixels P2 of the second group display an image content and the pixels P1 of the first group are switched to black or possibly display a static content.

[0036] Further design variants provide that two (nearest) neighboring pixels P1, P2 of the first and second group together form a parallelogram, a square or a rectangle.

[0037] The invention can also be implemented in a second screen with an image generator which has a grid with pixels Pßiid for displaying image content, which are divided into a first group of pixels P1 and a second group of pixels P2, further comprising a second optical element, which i. comprises a plurality of light-absorbing transition dipole moments, which are in the form of molecules of one and / or in the form of one or more dichroic dyes, ii. wherein the majority of the transition dipole moments are aligned, at least in a first state, with a tolerance of a maximum of 20° parallel to a first preferential direction selectable for the second optical element or vary around this, ill. so that light incident on the second optical element is transmitted or at least partially absorbed depending on its polarization state and its direction of incidence relative to the second optical element, iv. wherein the transition dipole moments are embedded in a liquid crystal layer, Means for selectively generating at least one first electric field (EF1) or a second electric field (EF2), which are divided into a second grid with pixels PLC, wherein the first or the second electric field acts on the liquid crystal layer, so that the transition dipole moments can be varied pixel by pixel with a division into pixels PLC in their orientation and / or their amount between the first and at least one second state, in order to be able to set the second optical element pixel by pixel with a division into pixels PLC alternatively into at least two different states, - wherein the entire first group of pixels P1 each emits or transmits light of a first polarization type, - wherein the entire second group of pixels P2 each emits or transmits light of a second polarization type different from the first polarization type (usually a complementary polarization type, e.g. one can be linearly vertically polarized and the other linearly horizontally polarized), so that the viewing angles for the first group of pixels P1 and for the second group of pixels P2 are different.

[0038] The invention further comprises a structured polarization filter for use in a display screen as described above, wherein such a polarization filter has linearly horizontally and linearly vertically polarized sections arranged alternately in rows, columns, or a checkerboard pattern. Such a polarization filter can, for example, represent the materials of groups a) and b) in a single film and, accordingly, combine the function of the first and second optical elements for selected embodiments of the invention.

[0039] The invention further comprises a manufacturing method for an aforementioned structured polarization filter, comprising the following steps: Preparation of a guest-host liquid crystal mixture (GHLC) comprising at least dichroic color molecules and liquid crystals, - Applying said mixture (guest-host liquid crystal mixture, GHLC) of dichroic color molecules and liquid crystals on a transparent substrate, - aligning an exposure mask (which has, for example, stripes in rows or columns, or a checkerboard pattern) relative to the transparent substrate in a first position, First alignment and subsequent exposure of the mixture of dichroic color molecules and liquid crystals on the transparent substrate using UV light through the exposure mask, - aligning the exposure mask relative to the transparent substrate in a second position different from the first position, - Second alignment and subsequent exposure of the mixture of dichroic color molecules and liquid crystals on the transparent substrate using UV light through the exposure mask.

[0040] This is usually followed by a step of fixing and, if necessary, further chemical treatments.

[0041] It is possible that a transparent display is used to implement the exposure mask, in that its displayed image content corresponds to the This corresponds to an exposure mask, which is located at the two different positions on the display for the various steps. Alternatively, films or plates produced using lithography, for example, can be used as exposure masks.

[0042] It should also be noted that pixels P1 and P2 of the first and second groups, respectively, can also have, for example, left- and right-circularly rotating polarizations. In this case, a retarder, e.g., a quarter-wavelength, would preferably be incorporated into the structure, so that light with the aforementioned circular polarizations is converted into light with two different linear polarizations.

[0043] Further designs provide for the structure to be expanded to include an additional birefringent layer.

[0044] The imager can be an OLED, a microLED, an LCD, a SED, a field emission display (FED), or a vacuum fluorescent display (VFD), each with appropriate control electronics. Other designs are possible.

[0045] Such a screen is advantageously used in a mobile device, a motor vehicle, aircraft, or watercraft, in a payment terminal, or in an access system. Switching between the aforementioned operating modes is possible either over the entire screen or by sections or pixels to protect sensitive data, i.e., to display it in a way that is perceptible to only one viewer, or alternatively, to display image content simultaneously for multiple viewers.

[0046] In principle, the performance of the invention is maintained if the parameters described above are varied within certain limits.

[0047] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention. Short description of the drawings

[0048] The invention is explained in more detail below using exemplary embodiments with reference to the accompanying drawings, which also disclose features essential to the invention. These exemplary embodiments are for illustrative purposes only and are not to be interpreted as restrictive. For example, a description of an embodiment with a large number of elements or components should not be interpreted to mean that all of these elements or components are necessary for implementation. Rather, other embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different exemplary embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments.To avoid repetition, identical or corresponding elements in different figures are designated by the same reference numerals and are not explained more than once. They show: Fig.1 to Fig. 14 show the schematic diagrams (as a section) of exemplary first to fourteenth embodiments of a screen, Fig.15 to Fig.17 show the schematic diagrams (as a section) of exemplary LCD subpixel structures with subpixel domains, Fig.18 the schematic diagram of an OLED pixel structure (as a section), Fig.19 the schematic diagram of a setup for producing a structured polarization filter, as well as Fig.20 shows the schematic diagram of an aligned and exposed GHLC structure, showing a structured polarization filter (as a section). Detailed description of the drawings

[0049] The drawings are not to scale and merely depict schematic diagrams in sections. The following embodiments are merely examples. Modifications in the arrangement and geometry of the pixels are also covered by the invention.

[0050] Fig. 1 shows the schematic diagram of an exemplary first embodiment of a screen, namely a section with six adjacent color subpixels R, R*, B, B*, G, G* of a row. In reality, a large number of such color subpixels R, R*, B, B*, G, G* are present in rows and columns. Such a screen with an image generator 2, which has a grid with pixels Pßiid for displaying image content, which are divided into at least a first group of pixels P1 (which are visible in a wide angular range, wherein according to the conditions in Fig. 1 the color subpixels R, G, B belong to the first group of pixels P1) and a second group of pixels P2 (which are visible in a limited angular range, wherein according to the conditions in Fig. 1 the color subpixels R*, G*, B* belong to the second group of pixels P2), comprises a in the viewing direction of a viewer (this would be the case in Fig.1 look from above at the screen 2) a first optical element 3 which is effective in front of the pixels P1 of the first group, a second optical element 4 which is effective in front of the pixels P2 of the second group in the viewing direction of a viewer, and a third, planar optical element 5 which is arranged in front of the first and the second optical elements 3, 4 in the viewing direction of a viewer. - wherein for all first, second and third optical elements a material is selected from the group consisting of a) linear polarizer which transmits electric fields along a first preferred direction (wherein the first preferred direction is preferably vertical from the perspective of a standing or sitting observer), b) linear polarizer which transmits electric fields along a second direction perpendicular to the first preferred direction, c) vertical polarizer, d) s-polarizing material, e) p-polarizing material, f) material with no polarization-changing function (such a material may also omitted, ie consist of air or a placeholder), g) two vertical polarizers between which there is an sp converter, or h) retarder, - wherein for the totality of first, second and third optical elements, preferably or exclusively the combinations 1. a), b) and c); 2. c), d) and e); 3. c), f) and [a) or b)]; 4. twice f) and once g); 5. a), c) and f); 6. e), c) and f); 7. a), a) with h) and a); 8. b), b) with h) and b) are permitted, whereby in the exemplary first embodiment according to Fig. 1, the combination mentioned under 1 applies, so that the combined effect of the first and third optical elements (3, 5) for the pixels P1 of the first group (i.e. R, G, B) allows light emission in an unrestricted angular range, and so that the combined effect of the second and third optical elements (4, 5) for the pixels P2 of the second group (i.e. R*, G*, B*) allows light emission in a restricted angular range, in which the light emitted by the pixels P2 of the second group is emitted in an angular range that is restricted compared to the pixels P1 of the first group, - whereby the viewing angles on the imager 2 differ for the first group of pixels P1 and for the second group of pixels P2.

[0051] It is advantageous for the pixels Pßiid to be full-color pixels, monochrome pixels, color subpixels, and / or subdomains of color subpixels. In modern screens, color subpixels often consist of so-called subdomains, which can take on non-rectangular shapes, such as so-called "chevron" shapes. By assigning the pixels Pßiid to subdomains of such color subpixels, parts of these color subpixels can then advantageously be controlled separately.

[0052] For this and all other exemplary embodiments, the following applies: Within the scope of the invention, and in particular with regard to pixels P2 of the second group, the term "limited angular range" means that the corresponding (possibly standardized) luminance is concentrated to at least 80% or 90% in a defined angular range, while there may still be residual light outside the defined limited angular range, which is generally due to technical reasons. Ideally, such residual light is minimal and generally decreases with increasing angles. The defined angular range can be in one or more planes, that intersect the screen. It preferably lies in a plane that includes the perpendicular bisector of the screen and is particularly preferably arranged parallel to the upper edge of the image generator 2 (from the perspective of a standing or seated viewer) with a maximum tolerance of 10°.

[0053] The mode of operation of the invention consists, among other things, in the fact that the pixels P1 and P2 of the two groups have different angular ranges of light emission. This is achieved by the combined effects of the first, second, and third optical elements 3, 4, and 5.

[0054] For reasons of clarity, the designators 2 to 5 for the screen and the first, second, and third optical elements are shown only in the drawing Fig. 1. These also apply implicitly to the following drawings Fig. 2 to Fig. 14.

[0055] A vertical polarizer, i.e. material c), if present in one of the embodiments, can in turn comprise a plurality of light-absorbing transition dipole moments, - wherein the majority (e.g., more than 80%, preferably more than 90%, particularly preferably more than 97%) of the transition dipole moments are permanently, or at least in a first state with a tolerance of a maximum of 20°, aligned parallel to a second preferred direction selectable for the respective vertical polarizer, which is perpendicular to the first preferred direction (wherein the second preferred direction is preferably perpendicular to the second direction), or vary around this, so that light incident on such a vertical polarizer is transmitted or at least partially absorbed depending on its polarization state, its plane of incidence, and its angle of incidence. (By virtue of this definition, "vertical polarizer" also explicitly includes polarizers whose second preferred direction is not arranged parallel to the perpendicular bisector of the screen 2.)

[0056] If, for example, the image generator 2 is an LCD or OLED panel, then in this exemplary first embodiment it would have separately controllable double color subpixels, ie there are always adjacent pairs of color subpixels R and R*, G and G*, B and B* for red, green and blue are present. These color subpixels are divided into the first and second groups of pixels P1, P2 as described above. The first optical element 3 comprises a linear polarizer a) which transmits electric fields along a first preferred direction (wherein the first preferred direction is preferably vertical from the perspective of a standing or sitting observer), the second optical element 4 comprises a linear polarizer which transmits electric fields along a second direction perpendicular to the first preferred direction b), and the third optical element 5 comprises a vertical polarizer c), so that the combination a) & c) is optically effective for the pixels P1 of the first group and the combination b) & c) is optically effective for the pixels P2 of the second group.

[0057] The following applies to the first embodiment described above and all the following exemplary embodiments: Due to the effect of the aforementioned combinations of the first and third optical elements 3, 5, the pixels P1 of the first group are visible from (for a standing or sitting observer) at least one direction in a wide angular range, while the pixels P2 of the second group are visible from (for a standing or sitting observer) at least one direction only in a limited angular range due to the effect of the aforementioned combinations of the second and third optical elements 4, 5.Accordingly, the screen can now be switched between a wide and a restricted angle range by controlling at least the pixels P1 of the first group (and optionally also the pixels P2 of the second group) with image content for a wide angle range, and exclusively the pixels P2 of the second group for a restricted angle range, while the pixels P1 of the first group are either (preferably) switched to black, or are controlled with static image content (e.g. a grey or pastel-coloured image, or a static logo on a non-black background), which is also visible on the pixels P2 of the second group, but may also additionally overlay residual light from the pixels P2 of the second group from larger viewing angles in order to improve privacy.Such image content for the pixels P1 of the first group in the latter case will typically be significantly reduced in brightness compared to the image content shown on the pixels P2 of the second group in order to impose only a moderate reduction in contrast on the viewer of the pixels P2 of the second group.

[0058] An advantage of the ratios shown in Fig.1 is that the resolution of the imager 2 is high and is not reduced by the use of the two groups of pixels P1, P2.

[0059] Figure 2 shows a second exemplary embodiment. The first, second, and third optical elements 3, 4, 5 are selected analogously to the first exemplary embodiment. The difference from the situation shown in Figure 1 lies in particular in the fact that the color subpixels R, G, B, R, G, B, etc., alternate and each alternately belong to the first group of pixels P1 and the second group of pixels P2.

[0060] Furthermore, Fig. 3 shows a third exemplary embodiment. Here, similar to Fig. 1, there are always adjacent pairs of color subpixels R and R*, G and G*, B and B* for red, green and blue. The third optical element 5 comprises a vertical polarizer c), while the first optical element 3 comprises an s-polarizing material d) and the second optical element 4 comprises a p-polarizing material e). The materials d) and e) can be metamaterials, for example. Due to the optical effect of the third optical element 5, s-polarized light is transmitted in almost all directions, so that the pixels P1 of the first group are visible from a wide angular range from virtually all directions. In contrast, p-polarized light is transmitted in almost all directions that differ from the main transmission direction of the third optical element 5 by more than approx.25°, are (at least partially) absorbed, so that the pixels P2 of the second group are visible from virtually all directions only from a limited angular range. By switching the use of the pixels P1 and P2 of the first and second groups, it is possible to switch between a public mode and a so-called 4-way privacy mode, i.e., the viewer's perception of the left, right, top, and bottom is inhibited.

[0061] Figure 4 shows a fourth exemplary embodiment. Here, the first, second, and third optical elements are again selected as in Figure 3, but now alternating color subpixels R, G, B, R, G, B, etc. are present. Otherwise, the explanations given for Figure 3 apply.

[0062] An exemplary fifth embodiment is shown in Fig. 5. Neighbouring pairs of colour subpixels R and R*, G and G*, B and B* for red, green and blue is present. The third optical element 5 comprises a linear polarizer a) which transmits electric fields along a first preferred direction (wherein the first preferred direction preferably runs vertically from the perspective of a standing or sitting observer), while the first optical element 3 comprises a material with no polarization-changing function (such a material can also be omitted if necessary, i.e. consist of air or a placeholder) (f) and the second optical element 4 comprises a vertical polarizer c). In this embodiment, the light emission of the pixels P2 of the second group in the vertical direction is only possible in a limited angular range.

[0063] Figure 6 shows an exemplary sixth embodiment. The only difference from the situation according to Figure 5 is that the third optical element 5 here comprises a linear polarizer b), which transmits electric fields along a second direction perpendicular to the first preferred direction. Accordingly, in this embodiment, the light emission of the pixels P2 of the second group in the horizontal direction is only possible within a limited angular range.

[0064] Furthermore, Fig. 7 shows an exemplary seventh embodiment. This is analogous to the situation in Fig. 5, but here alternating color subpixels R, G, B, R, G, B, etc. are present. Otherwise, the explanations given for Fig. 5 apply.

[0065] Accordingly, Fig.8, which shows an exemplary eighth embodiment, corresponds to the conditions according to Fig.6, whereby here correspondingly alternating color subpixels R, G, B, R, G, B, etc. are present.

[0066] Fig. 9 also shows an exemplary ninth embodiment. Here, neighboring pairs of color subpixels R and R*, G and G*, B and B* for red, green, and blue are again present. Only in front of the pixels R*, G*, B*, etc. of the second group of pixels P2 are materials from group g), i.e., two vertical polarizers, between which an sp converter is located. Thus, the pixels P1 of the first group are not restricted in their visibility from all directions in the angular range, while the pixels P2 of the second group are only visible to a limited extent in the angular range from all (oblique) directions, i.e., from above, below, left, and right.

[0067] Furthermore, Fig. 10 shows an exemplary tenth embodiment. This is analogous to the situation in Fig. 9, although here again alternating color subpixels R, G, B, R, G, B, etc. are present.

[0068] Fig. 11 shows an exemplary tenth embodiment. Here, adjacent pairs of color subpixels R and R*, G and G*, B and B* for red, green, and blue are again present. Both the first and the third optical element 3, 5 comprise a linear polarizer a) which transmits electric fields along a first preferred direction (wherein the first preferred direction preferably runs vertically from the perspective of a standing or sitting observer), while the second optical element 4 also comprises such a linear polarizer a), but which is also provided with a retarder h) on the observer side. In the case of the aforementioned retarder h), these can be, for example, aligned, fixed liquid crystals, in particular GHLC liquid crystals. However, it is also possible to use a retarder made of a polymer, although other embodiments are also conceivable.Preferably, all linear polarization filter components of the first and second optical elements 3, 4 are formed as a planar polarization filter, ideally in a single component. Thus, the pixels P1 of the first group are not restricted in their visibility from all directions in the angular range, since only two identical polarization filters of type a) are present in the light path. While the pixels P2 of the second group are only restricted in their visibility from at least one direction in the angular range, because the combination of polarization filter a), retarder h), and another polarization filter a) acts like a dual-cell privacy panel in privacy mode.

[0069] Accordingly, Fig.12, which shows an exemplary twelfth embodiment, corresponds to the conditions according to Fig.1 1 , whereby alternating color subpixels R, G, B, R, G, B, etc. are present here.

[0070] Fig. 13 shows a thirteenth embodiment variant, again with adjacent pairs of color subpixels R and R*, G and G*, B and B*. This corresponds to the situation shown in Fig. 11, but here the existing polarization filters of type a) are replaced by type b), which influences the direction of the viewing angle restriction for the pixels P2 of the second group.

[0071] Finally, Fig.14 shows a fourteenth embodiment variant which corresponds to the conditions according to Fig.13, whereby alternating colour subpixels R, G, B, R, G, B etc. are now present again.

[0072] Figs. 15 to 17 show, in detail, schematic diagrams of exemplary LCD subpixel structures with subpixel domains as pixel Pβiid. These three exemplary configurations show different possibilities for structuring the subpixels or subpixel domains. R, G, B stand for the colors red, green, and blue, respectively. The subpixel domains located under the letters R, G, B in the drawings mentioned always represent the corresponding color in each column. The subpixel structures shown exemplify the typical so-called "chevron structure" of LCD (IPS / FFS) at the subpixel level. Other subpixel structures or types, shape, and number of subpixel domains are also within the scope of the invention.

[0073] Here, all subpixel domains drawn in black belong to the second group of pixels P2, while the subpixel domains drawn in white belong to the first group of pixels P1. In this way, dividing the subpixel domains between the two groups of pixels P1 and P2 does not result in a loss of resolution of image sensor 2, because each subpixel of each color is represented in both groups of pixels P1 and P2. However, as already described above, the subdomains of the color subpixels, i.e., the subpixel domains, must be controllable separately.

[0074] If, as shown in Figs. 15 to 17, the pixels P11d are each such subdomains of color subpixels, the first group of pixels P1 and the second group of pixels P2 advantageously have differing gamma curves and / or differing luminance profiles. With such configurations, it is possible for the pixels P2 of the second group to have, on average, a lower luminance at angles deviating by more than 20° from the perpendicular to the imager than the pixels P1 of the first group.

[0075] Furthermore, Fig. 18 shows a schematic diagram of an exemplary OLED pixel structure in section form. Here, for example, each odd-numbered row could belong to the first group of pixels P1, and each even-numbered row to the second group of pixels P2. In this way, the weightings for the red, green, and blue color components are evenly distributed. between the two groups of pixels P1 and P2. Other configurations are possible.

[0076] For practical implementations, it is advantageous if, where possible, the first and second optical elements 3, 4 are each integrated into a single layer and / or component. For example, materials a) and b), i.e., two different linear polarization filters, can be accommodated on a single substrate and incorporated into the screen. In this regard, a manufacturing method for a structured polarization filter is explained below with reference to the drawings Fig. 19 and Fig. 20, with Fig. 19 in particular depicting the schematic diagram of a structure for manufacturing a structured polarization filter. This manufacturing method comprises the following steps: Preparation of a guest-host liquid crystal mixture 12 (GHLC) comprising at least dichroic color molecules and liquid crystals, - applying said mixture (guest-host liquid crystal mixture) 12 of dichroic color molecules and liquid crystals on a transparent substrate 13, - aligning an exposure mask 11 (which has, for example, stripes in rows or columns, or a checkerboard pattern) relative to the transparent substrate 13 in a first position, First alignment and exposure of the mixture 12 of dichroic color molecules and liquid crystals on the transparent substrate 13 by means of UV light from a UV exposure unit 10 through the exposure mask 11, - aligning the exposure mask 11 relative to the transparent substrate 13 in a second position, - Second alignment and exposure of the mixture 12 of dichroic color molecules and liquid crystals on the transparent substrate 13 by means of UV light from a UV exposure unit 10 through the exposure mask 11.

[0077] This is usually followed by a step of fixing and, if necessary, further chemical and / or mechanical treatments.

[0078] The above-mentioned method can also be modified, for example by combining two (or, if necessary, more than two) of the types of materials a) to h) mentioned.

[0079] It is also possible for a transparent display to be used as the exposure mask 11. In this case, not the display itself, but only the pattern displayed by the display would occupy the aforementioned first and second positions as the exposure mask.

[0080] The result is shown in Fig. 20 in the form of a schematic diagram of an aligned and exposed GHLC structure, representing a structured polarization filter. This example includes linear polarization filters of the type a described above in all odd-numbered columns and linear polarization filters of the type b described above in all even-numbered columns. However, it is a single component, a structured polarization filter, which has linearly vertically and horizontally polarized sections arranged alternately in columns.

[0081] In addition, the materials a) or b) of the first and second optical elements 3, 4 can each be formed as a polarization filter according to the embodiments according to the drawings Fig.11 to Fig.14, which significantly simplifies production.

[0082] Furthermore, it is possible for the pixels P1, P2 of the first and second groups to alternate in rows, columns, or a checkerboard pattern. Other configurations are possible, as is a random distribution of the pixels P1, P2 of the first and second groups.

[0083] Advantageously, the number of pixels P1 and P2 in the first and second groups differs by no more than 50%. Ideally, the number of pixels P1 and P2 in the first and second groups is equal.

[0084] For all of the first to fourteenth embodiments described above, appropriate control electronics can, within the context of controlling a screen in question, ensure that two (nearest) adjacent pixels P1, P2 of the first and second groups each optionally display the same screen content. In this way, an increased resolution can be achieved, at least within the unrestricted angular range.

[0085] A screen as described above is advantageously used in a mobile device, a motor vehicle, aircraft, or watercraft, in a payment terminal, or in an access system. It can be switched between different viewing angles to protect sensitive data, i.e., to display it in a way that is perceptible to only one viewer, or alternatively, to display image content simultaneously for multiple viewers. Switching between viewing angles is usually advantageously achieved purely via software or appropriate control electronics.

Claims

Patent claims 1. A screen with an image generator (2) which, for displaying image content, has a grid with pixels Pβiid which are divided into at least a first group of pixels (P1) and a second group of pixels (P2), further comprising a first optical element (3) acting in front of or behind the pixels (P1) of the first group in the viewing direction of a viewer, a second optical element (4) acting in front of or behind the pixels (P2) of the second group in the viewing direction of a viewer, and a third, planar optical element (5) arranged in front of or behind the first and second optical elements (3, 4) in the viewing direction of a viewer, wherein the first, second and third optical elements (3, 4, 5) consist entirely or partially of a material, each of which consists of a group consisting of a) linear polarizer which transmits electric fields along a first preferred direction, b) linear polarizer,which transmits electric fields along a second direction perpendicular to the first preferred direction, c) vertical polarizer, d) s-polarizing material, e) p-polarizing material, f) material with no polarization-changing function, g) two vertical polarizers between which there is an sp-converter, or h) retarder, wherein for the entirety of first, second and third optical elements the combinations 1. a), b) and c); 2. c), d) and e); 3. c), f) and [a) or b)]; 4. twice f) and once g); 5. a), c) and f); 6. e), c) and f); 7. a), [a) with h)] and a); 8. b), [b) with h)] and b) are permitted, so that the combined effect of the first and third optical elements for the pixels (P1) of the first group allows light emission in an unrestricted angular range, and such that the combined effect of the second and third optical elements causes the pixels (P2) of the second group to emit light in a restricted angular range, in which the light emitted by the pixels (P2) of the second group is emitted in an angular range which is restricted compared to the pixels (P1) of the first group, as a result of which the viewing angles on the image generator (2) for the first group of pixels (P1) and for the second group of pixels (P2) differ.

2. Screen according to claim 1, characterized in that each vertical polarizer, if present, in turn comprises a plurality of light-absorbing transition dipole moments, the majority of these transition dipole moments being permanently or at least in a first state with a tolerance of maximum 20° parallel to or varying around a second preferred direction which can be selected for the respective vertical polarizer and which is perpendicular to the first preferred direction, so that light which is incident on such a vertical polarizer is transmitted or at least partially absorbed depending on its polarization state, its plane of incidence and its angle of incidence.

3. Screen according to claim 1 or 2, characterized in that the pixels Pßiid are each full-color pixels, monochrome pixels, color subpixels and / or partial domains of color subpixels.

4. Screen according to claim 3, characterized in that when the pixels Pßiid are each subdomains of color subpixels, the first group of pixels (P1) and the second group of pixels (P2) have mutually differing gamma curves and / or mutually differing luminance profiles, so that the pixels (P2) of the second group have on average a lower luminance at angles which deviate by more than 20° from the perpendicular to the image generator (2) than the pixels (P1) of the first group.

5. Screen according to claim 1 or 2, characterized in that pairs of immediately adjacent pixels are color subpixels of the same color, wherein of such a pair one color subpixel belongs to the first group of pixels (P1) and the other color subpixel belongs to the second group of pixels (P2).

6. Screen according to one of the preceding claims, characterized in that the pixels (P1, P2) of the first and second groups alternate in rows, columns or in a checkerboard pattern.

7. Screen according to one of the preceding claims, characterized in that the selection of the material effect for all first, second and third optical elements from the groups is carried out in a time-variable or time-sequential manner.

8. Screen according to one of the preceding claims, characterized in that the number of pixels (P1, P2) of the first and second groups differ from each other by at most 50%.

9. Screen according to one of the preceding claims, characterized in that two adjacent pixels (P1, P2) of the first and second groups show the same image content.

10. Screen according to one of the preceding claims, characterized in that for a first operating mode B1 for a free viewing mode, either only the pixels (P1) of the first group display an image content and the pixels (P2) of the second group are switched to black, or that both the pixels (P1) of the first group and the pixels (P2) of the second group display an image content, while for a second operating mode B2 for a restricted viewing mode, only the pixels (P2) of the second group display an image content and the pixels (P1) of the first group are switched to black or show a static image content.

Images