MEMS DISPLAY

Description

[0001] The present invention relates to a display for the optical reproduction of variable information. STATE OF THE ART

[0002] Displays are components of display devices for the visual reproduction of changing information, especially for the presentation of images, videos, or text, whereby the information to be displayed is usually transmitted electronically to the display. Examples of displays include televisions, computer monitors, and digital signage, as well as mobile devices such as tablet computers and smartphones.

[0003] The display market, especially for consumer electronics, is currently dominated by displays in the form of liquid crystal displays (LCDs) and light-emitting diode displays based on solid-state light-emitting diodes (LEDs) or organic light-emitting diodes (OLEDs).

[0004] The optical reproduction of information by displays is based on a spatiotemporal modulation of a light distribution perceived by a viewer. Within the scope of this application, the term "display" is understood to mean a direct-view display. In a direct-view display, the reproduced information is perceptible by directly viewing the display, i.e., by directly viewing those components of the display that generate the spatiotemporal modulation of the light distribution perceived by the viewer. This definition distinguishes it from projection displays, in particular those based on chips with digital micromirror devices (DMDs) for projecting information as a modulated light distribution onto a spaced projection surface on which the reproduced information is displayed and which is intended for viewing by the viewer.

[0005] US Patent 2010 / 0156859 A1 discloses an information display panel for rewriting and displaying information, such as an image, by electrically connecting a display unit with a memory function to a driver circuit substrate, wherein an attachment / detachment mechanism is provided for the detachable connection of the display unit to the driver circuit substrate. The display is detachable and is attached to the attachment / detachment mechanism for connection to a driver circuit. The information display panel is suitable, for example, for use as an electronic price tag.

[0006] KR 2012 0023510 A discloses an optical display device based on an arrangement of microshutters mounted on a substrate and pivotable between a planar and a vertical position, the pivotability being based on the thermal expansion of a bimetal. The microshutters form image pixels and have black or colored surfaces, the substrate having a contrasting surface or being transparent. For example, backlighting of the substrate may be provided.

[0007] US Patent 6,639,572 B1 discloses a low-power, paper-white, direct-view display comprising an arrangement of pivotable micromirrors that are deflected between two states: a first state in which the micromirror partially obscures the background, and a second state in which the micromirror exposes the background. In a particular configuration, a stability mechanism is integrated into the display such that the micromirrors switch between stable states and remain in these stable states until an actuating force is applied to the micromirrors sufficient to overcome an actuating threshold. This bistability allows the display to be de-energized between updates, but requires active control between the two states. The drive electronics are similar to those used in multiplex LCDs.

[0008] US Patent 9,007,676 B1 discloses an electrostatic display based on MEMS technology with an array of rotatable microcantilevers. The transition from white to black pixel color occurs when two microcantilevers covering the pixel area are electrostatically rotated from a position parallel to the substrate plane to a position perpendicular to the substrate plane. Four electrode-pixel control circuits are used to form a row and column matrix. This matrix utilizes a bista stability effect resulting from the difference in voltages required to rotate and hold the microcantilevers in an upright position.

[0009] Furthermore, so-called flip-disc (or flip-dot) displays are known, which are used for display boards with large characters, for example in train stations and airports to display timetables or flight schedules. Flip-disc displays are based on a matrix-shaped arrangement of electromagnetic-mechanical components, which, depending on the control signal via a rotating mechanism, show one of two differently colored sides of a disc. Each disc is mounted on an axle, with the disc or the axle containing a small permanent magnet, and is associated with a controllable magnetic coil. By applying a corresponding electrical polarity to the magnetic coil, the permanent magnet aligns itself in the resulting magnetic field, causing the disc to rotate. REVELATION OF THE INVENTION

[0010] The object of the present invention is to propose an alternative embodiment of a display for the optical reproduction of variable information, which is characterized in particular by low energy consumption and high viewing angle independence.

[0011] This problem is solved by a display according to claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

[0012] The invention includes the technical teaching that the display has a regular arrangement of microleaf elements with actuable leaf sections, which are pivotably designed between a closed and at least one open position, such that the information display is based on a spatiotemporal modulation of the optical reflectivity of the display by actuating the leaf sections, wherein the front and back sides of the leaf sections have a mirror effect for visible light, wherein the display comprises an opaque rear base plate, wherein the rear base plate produces a black color impression, in particular by having a black color coating, a black substrate and / or a light-absorbing interface structure, and wherein the rear base plate has an anti-reflective coating.in particular based on a layer stack of Al₂O₃, Si₃N₄, and SiO₂ thin films or a layer stack of Al₂O₃, Si₃N₄, and MgF₂ thin films. According to the invention, it is also provided that the pivot directions of all leaf sections are the same when pivoting about their pivot axis between the closed and the at least one open position. The invention is based on the idea of ​​using micro-electro-mechanical systems (MEMS) in the form of microleaf elements for light modulation, such that the logic values ​​of the information to be displayed on the display according to the invention are encoded in the position of the actuable leaf sections of the microleaf elements.where each pixel of the display is assigned at least one microleaf element. For example, the value "logic-1" can be represented by the closed position and the value "logic-0" by the (maximally) open position of a leaf segment. The position of the leaf segments determines the local reflectivity of the display. The photometric,

[0013] The effect of the surfaces of the leaf segments and the underlying, rear base plate of the display, which is either concealed or exposed by the leaf segments depending on their position, varies so significantly that a high-contrast visual impression is created for a viewer looking directly at the display, suitable for information reproduction. In addition to purely binary information reproduction with exactly two different leaf segment positions—a closed and a (fully) open position—each individual micro-leaf element can, in principle, also display grayscale values ​​by assuming an intermediate position in which the underlying base plate is only partially concealed.

[0014] According to the invention, the microsheet elements are arranged in a regular matrix form in parallel rows and parallel columns, wherein preferably the entirety of the microsheet elements defines the section of the display designed for information reproduction. Each pixel is assigned one or more microsheet elements.

[0015] The power required to actuate MEMS is typically extremely low. As detailed below, a preferred embodiment of the display according to the invention is based on microsheet elements with electrostatically actuated sheet sections, and matrix-shaped arrays of such microsheet elements (dimensions of 400 x 150 µm² per microsheet element) have been produced on a laboratory scale, which consume only 0.2–2 mW / m² for continuous actuation. The power required for light modulation, i.e., for the spatiotemporal modulation of the reflectivity of the display according to the invention, is therefore low, even with a very large active display area, compared to the power consumption of thin-film transistor (TFT) control in prior art LCD or OLED displays.Furthermore, the microblade elements with electrostatically actuated blade sections can be operated at switching frequencies up to 1 MHz. Due to the low inertial forces involved in the movement of MEMS, the resulting wear is minimal, thus ensuring long-term functionality of the structures.

[0016] In contrast to flip-disc displays of the prior art, the display according to the invention with electrostatically actuated microsheet elements represents a miniaturized solution which has significantly higher resolution and switching frequencies as well as significantly lower energy consumption.

[0017] Conventional thin-film processes can be used to fabricate the microsheet elements, in particular deposition processes, lithography and etching steps, as well as sacrificial layer techniques. Detailed information on the fabrication and function of a regular arrangement of mirror-effect microsheet elements can be found, for example, in Hillmer et al., Jpn. J. Appl. Phys. 57, 08PA07 (2018).

[0018] According to the invention, the front and back surfaces of the sheet sections have a mirror effect for visible light, and the display comprises an opaque rear base plate. According to the invention, the rear base plate creates a black color impression, for example, by having a black coating, a black substrate, and / or a light-absorbing interface structure. In this embodiment, the display is designed as a reflective display that requires front illumination, i.e., illumination from the hemisphere into which the front surface of the display, designed for information reproduction, is directed. In particular, it may be provided to use daylight or ambient light to illuminate the display, i.e., not to assign a dedicated lighting device to the display.Information reproduction is based on the optical contrast between the reflective front surface of the leaf sections and the absorbing, preferably black, color impression of the rear base plate located behind them. The contrast is significantly higher than that of prior art reflective LCDs, since the latter exhibit significant absorption losses due to the polarizers through which the light passes. Thanks to this high contrast, the display according to the invention is particularly suitable for use as a reflective display based on ambient light illumination alone, i.e., without a separate lighting device.

[0019] In particular, the display according to the invention has a front base plate and a rear base plate, the front base plate being translucent, and the microleaf elements being received in a space between the base plates, each microleaf element having a leaf segment and being hinged to one of the base plates by means of an edge-side fastening section, such that each leaf segment can be pivoted from a closed position oriented parallel to the base plates to at least one open position, in particular oriented perpendicular to the base plates. In all embodiments, the front side of the leaf segments is defined as the side which, when the leaf segments are in the closed position, is oriented towards the front base plate, i.e., the side facing a viewer of the display.

[0020] The base plates typically comprise at least one substrate, particularly made of glass, and optionally layers deposited on the substrate, especially those with dedicated photometric functions, such as a black coating. The aforementioned light-absorbing interface structure can, for example, be incorporated into the back of the substrate of the rear base plate in the form of a pyramid array and covered with a black coating.

[0021] The microsheet elements are arranged on the inside of one of the two base plates and are protectively enclosed by them. The base plates are typically plate-shaped, i.e., designed as thin cuboids, but can alternatively be curved bodies, so that the front of the display, intended for information reproduction, is, for example, concave or convex.

[0022] In the reflective display according to the invention, the opaque, blackened, rear base plate has an antireflective coating, in particular based on a layer stack of Al₂O₃, Si₃N₄, and SiO₂ thin films or a layer stack of Al₂O₃, Si₃N₄, and MgF₂ thin films. The antireflective coating ensures higher contrast, as it makes black appear even darker. This effect is also present at very shallow viewing angles and in combination with mirrored leaf elements (see Figure 2b ) thus, a high image contrast is ensured largely independent of the viewer's viewing angle to the display.

[0023] Furthermore, the display according to the invention can be configured for information display in color by having a color filter, in particular in the form of a Bayer filter, preferably such that at least one micro-element is assigned to each color point of the color filter. A Bayer filter is a checkerboard-shaped RGB color filter, which typically has 50% green pixel-shaped color points and 25% each of red and blue pixel-shaped color points. Each pixel of the display is formed, for example, from two green pixels and one red and one blue pixel. In particular, exactly one micro-element can be assigned to each color point of the color filter, i.e., that an individual color point can be switched by activating each micro-element. Alternatively, a group of micro-elements can be assigned to each color point of the color filter, for example, as a redundant safeguard.Furthermore, there may be display applications where a particularly low transmittance is required when the microleaf sections are closed, with the minimum transmittance decreasing as the size of the microleaf elements increases. The minimum transmittance is determined by the areas of the display where adjacent microleaf elements meet. Provided that a reduction in color reproduction quality is acceptable, the size of the microleaf elements can, in such cases, exceed the size of the color pixels of the color display, meaning that each microleaf element can be assigned more than one color pixel. The translucent front base plate houses the color filter.

[0024] Details regarding the structure and updatability of the microsheet elements are described below.

[0025] In a preferred embodiment, the microsheet elements each have a layer structure comprising at least one compression-stressed layer and one tension-stressed layer, wherein the sheet section of each microsheet element also has a suitably stressed compensation layer, such that each microsheet element is subdivided into the following sections: the blade section, which is globally stress-free and has two essentially plane-parallel surfaces, the edge-side fastening section, which is rigidly arranged on one of the base plates, and an intermediate hinge section, which has a residual stress-induced curvature, thereby forming an open position of the micro-blade element.

[0026] In the absence of external actuation, the microleaf elements are in a maximally open position, which results from the curvature of the hinge section between the fastening section (which is fixed to the base plate, particularly by a material bond) and the stress-compensated leaf section, due to the existing residual stresses. For example, the hinge section has a radius of curvature that is between one hundredth and one-third of the length of the longest side of the contour of the respective leaf section.

[0027] The curvature of the hinge section can also be achieved using a single layer in which a stress gradient exists perpendicular to the surface or interface, such that compressive or tensile stresses are present on the opposite sides of the single layer.

[0028] Furthermore, the pivoting of the blade sections between the closed position and the at least one open position is preferably actuated by means of an electrostatic operating principle, for which the associated base plate comprises an electrically conductive electrode layer and at least one electrically insulating insulating layer, wherein the mounting section of each microblade element is arranged on the insulating layer, and the blade sections each have or form an electrode, such that by applying electrical

[0029] Individual microsheet elements and / or groups of microsheet elements can be actuated by voltage signals between the electrodes and the electrode layer.

[0030] Preferably, the leaf sections are pivoted by approximately 90° relative to the closed position in the maximum open position, i.e., essentially orthogonal to the base plates. InIn such a vertical position, maximum light transmission through the respective microsheet element is achieved when light falls perpendicularly onto the base plates, and this position is assumed when the microsheet elements are not subject to any electrostatic force from an applied electrical voltage, so that the hinge sections are rolled up purely according to their mechanical residual stresses.

[0031] Between the fully open and fully closed positions of the micro-blade segments, further intermediate positions can be assumed, representing corresponding grayscale values ​​with respect to transmittance. Starting from the fully open position of the micro-blade segments, a continuously increasing electrical voltage applied between the base plate and the electrodes allows for stepless closing of the micro-blade elements up to a limit voltage at which the micro-blade elements close completely. This variety of specifically adjustable opening angles of the micro-blade segments relative to the base plates can be used for the targeted representation of grayscale values ​​in information reproduction.

[0032] The display according to the invention particularly features an addressing network of narrow, planar lines on one of the base plates, which form electrical connections between the electrode layers of individual microsheet elements or groups of microsheet elements and an edge-side interface for computer-controlled addressing and actuation of the microsheet elements. Such control is particularly provided for the embodiment as a transmissive display, whereas the reflective display, due to the opaque rear base plate, alternatively allows active or direct addressing, in which the control electronics are arranged directly beneath the microsheet elements.

[0033] The sheet sections have, for example, a rectangular contour, in particular a square contour, wherein the edges of the sheet sections have a length in the range of 10 micrometers to 1 millimeter, preferably 100 micrometers to 200 micrometers. The dimensions of the sheet sections can be expediently adapted to the specific requirements of the display in question, in particular with regard to the desired image resolution.

[0034] The display according to the invention is particularly intended for use with an electronic price tag. Electronic price tags are used, for example, in supermarkets and department stores to label goods offered for sale and serve, for instance, to indicate a price, an item name, a corresponding barcode, and additional information, etc. Since the merchandise displays are typically brightly illuminated and the display according to the invention generates a high optical contrast, a reflective display can advantageously be used without an additional lighting device, so that no additional energy is required except for actuating the leaf sections of the microleaf elements.

[0035] Furthermore, the display according to the invention can be used, for example, for various outdoor applications, in particular by utilizing sunlight as sufficient illumination.

[0036] The invention further relates to a display device comprising at least a display for the optical reproduction of variable information according to one of the aforementioned embodiments and a lighting device for homogeneous illumination of the display. The lighting device is designed and arranged for front illumination of the display.

[0037] It is obvious to a specialist that an electronic control unit, particularly one with a microcontroller, is required to control the display and the backlighting. A suitable control unit is also essential if the display is not integrated into a display device with separate backlighting, but is intended solely for operation under daylight or ambient light. PREFERRED EXAMPLES OF THE INVENTION

[0038] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments of the invention, with reference to the figures. The figures show: Fig. 1 a schematic, perspective view of a display according to the invention, Fig. 2a, b schematic cross-sectional partial views of a display according to Fig. 1 , Fig. 3 a schematic cross-sectional view of a first embodiment of the display according to the invention, Fig. 4 schematic cross-sectional view to illustrate the electrostatic actuation, Fig. 5 schematic cross-sectional view to illustrate the residual stresses of a microsheet element, and Fig. 6 calculated reflectivity of base plates with anti-reflective coating.

[0039] Figure 1Figure 1 shows a schematic, perspective view of a display 100 according to the invention for the optical display of variable information. The display 100 has a regular arrangement of microleaf elements 1 with actuable leaf sections 11 arranged on the rear base plate 3. The microleaf elements 1 are arranged in a matrix in rows and columns, and the pivotable leaf sections 11 each have rectangular contours. Each pixel that can be displayed by the display 100 corresponds to a microleaf element 1 or a group of microleaf elements 1. In the section of the display 100 intended for information display, the entirety of the microleaf elements 1, when the leaf sections 11 are closed, forms a substantially complete surface coverage of the rear base plate 3.

[0040] Seven of the leaf sections 11 are shown in a closed position, i.e., parallel to the rear base plate 3, so that the front surfaces 11a of these leaf sections 11 face a viewer of the display 100. The remaining leaf sections 11 are shown in an open position, perpendicular to the rear base plate 3, thus revealing it. The front surface 11a and the back surface 11b of each leaf section 11 are reflective for visible light, and the rear base plate 3 is opaque, creating a black appearance.

[0041] The present display 100 is thus designed as a reflective display, and the information reproduction is based on a spatiotemporal modulation of the optical reflectivity, whereby the optical impression of the associated pixels can be changed between brightly reflective (closed position) and matte black (fully open position) by actuating the leaf sections 11. With sufficient illumination, for example by daylight, the display 100 according to the invention offers an extremely sharp contrast between open and closed leaf sections 11.

[0042] The Figures 2a and 2b show schematic cross-sectional views of a display 100 according to Figure 1 .

[0043] In Figure 2aThe leaf sections 11 of the microleaf elements 1 are shown in an almost closed position, i.e., oriented almost parallel to the rear base plate 3. Due to the reflective effect of the front surfaces 11a, light incident on the front of the microleaf elements 1 is reflected (open arrows) and creates the perception of bright pixels for the viewer.

[0044] In Figure 2bThe leaf sections 11 are in an open position, so that the blackened rear base plate 3 is visible to the viewer. Due to the reflective effect of the front surfaces 11a and back surfaces 11b of the leaf sections 11, the black color impression (dashed arrows) of the exposed pixels of the rear base plate 3 is also produced at shallow viewing angles on the display 100. The advantageously high contrast for the information reproduction of the display 100 according to the invention is thus present over a wide viewing angle range. This is particularly true in combination with an anti-reflective coating of the rear base plate 3, which produces a rich black optical impression even at shallow viewing angles parallel to the pivot axes of the leaf sections 11.

[0045] The Figure 3Figure 1 shows a schematic cross-sectional view of an embodiment of the display 100 according to the invention. The illustration includes sections of the translucent front base plate 2, the rear base plate 3, and a microsheet element 1 received in the space between. The illustration represents a section of a regular arrangement of a plurality of microsheet elements.

[0046] The micro-blade element 1 has the blade section 11 and is hinged to the rear base plate 3 by means of the edge-side mounting section 12, with the blade section 11 always in an open position. The pivot range of the blade section 11 is indicated by the dashed arc and is approximately 120° from the closed position, in which the blade section 11 lies parallel to the rear base plate 3. Alternatively, the pivot range can be limited to approximately 90°, for example. The pivoting movement occurs about a pivot axis, which is perpendicular to the plane of the figure.

[0047] The base plates 2, 3 each comprise a translucent substrate 20, 30, in particular made of glass. Alternatively, for example, the substrates 20, 30 can be made of a flexible material, such as a polymer, and have curved shapes, so that the display 100 has, for example, a concave or convex curvature. The rear base plate 3 further comprises the electrically conductive electrode layer 35 and at least one electrically insulating insulating layer 36, wherein the mounting section 12 of the microsheet element 1 is arranged on the insulating layer 36, and the sheet section 11 forms an electrode, such that the microsheet element 1, i.e., the sheet section 11, can be actuated by applying electrical voltage signals between the microsheet element 1 and the electrode layer 35.The electrode layer 35 is formed from a transparent material, for example, fluorine-doped tin oxide (FTO) or indium tin oxide (ITO). Furthermore, the electrode layer 35 can be formed from a suitable arrangement of silver nanowires, which exhibits higher optical transparency and higher electrical conductivity than an FTO layer.

[0048] Alternatively to the embodiment of the Figure 3 The microsheet elements 1 can be arranged on the front base plate 2, which is then to be provided with the aforementioned layers for electrostatic actuation.

[0049] The Figure 3 Figure 1 shows a reflective display 100, in which the rear base plate 3 is opaque due to the black coating 31. The information display is based on a spatiotemporal modulation of the optical reflectivity of the display 100 by means of updating the page sections 11.

[0050] In Figure 3 The front 11a and the back 11b of the sheet section 11 have a reflective effect for visible light, so that a high contrast with the black color impression of the rear base plate 3 can be achieved. The back of the substrate 30 of the rear base plate 3 has the light-absorbing interface structure 31a in the form of a pyramid pattern, wherein the black color coating 31 fills and covers the interface structure 31a. The interface structure 31a acts as a light trap and ensures a homogeneous black color impression even at shallow viewing angles to the display 100. The exemplary embodiment of the Figure 3 This corresponds, for example, to the one in Figure 1 , 2a and 2b Display type shown.

[0051] Furthermore, the rear base plate 3 comprises the antireflective coating 32, which is deposited on the insulating layer 36 and is itself also electrically insulating. The antireflective coating 32 is based, by way of example, on a layer stack of three thin films. For a rear base plate 3 based on a glass substrate 30, a transparent FTO electrode layer 35, a SiO₂ insulating layer 36, and an antireflective coating 32 based on Al₂O₃, Si₃N₄, and SiO₂ thin films or Al₂O₃, Si₃N₄, and MgF₂ thin films, the optical reflectivity in the visible light spectrum is, for example, less than 2% (see Figure 6 ).

[0052] The front base plate 2 includes the color filter 21. When the microleaf element 1 is closed, the light reflected from the front 11a of the leaf section 11 is filtered accordingly during transmission through the color filter 21, i.e., in particular, emitted as green, red or blue light from the front base plate 2.

[0053] The microsheet element 1 has a gradient layer 1d, which causes the curvature of the microsheet element 1 by creating a pronounced gradient of mechanical residual stresses within the gradient layer 1d. This means that the stress changes in a direction perpendicular to the surface of the gradient layer 1d, thus generating a stress gradient. In the region of the underside, which forms the interface with the rear base plate 3 in the fastening section 12, the gradient layer 1d is in a compressive state, whereas the opposite upper side is in a tensile state. The curvature of the microsheet element 1 in the hinge section 13 occurs according to these stress conditions. Sectional compensation of the curvature is achieved by the tensile compensation layer 1c, forming the planar sheet section 11.

[0054] The displays 100 of all embodiments preferably have addressing networks (not shown here) consisting of electrical conductors, which form electrical connections between individual microsheet elements 1 or groups of microsheet elements 1 and an interface for computer-controlled addressing and actuation of the microsheet elements 1 by means of voltage signals. The electrical conductors are, for example, applied as metallic thin films to or integrated into the rear base plate 3; in particular, the electrode layer 35 can be microstructured, i.e., divided into sections that can be electrically connected independently of one another.

[0055] Another embodiment of a display not covered by the claims, not shown here, can be configured as a reflective or transmissive display in sections, i.e., certain sections of the rear base plate are opaque and other sections are transparent. Information reproduction is then based section by section on a spatiotemporal modulation of the optical reflectivity or optical transmissivity of the display, with separate backlighting devices being assigned to the transparent sections of the rear base plate. To illustrate the electrostatic actuation principle, [Figure 1] shows... Figure 4A schematic cross-sectional view of a display 100 according to the invention. The illustration includes a single microsheet element 1, which is received in the space between the front base plate 2 and the rear base plate 3 and arranged on the latter. The microsheet element 1 forms an electrode and, for this purpose, comprises an electrically conductive material. The specific photometric functions of the front 11a and rear 11b of the sheet section 11 are not shown here for the sake of clarity. The rear base plate 3 comprises the substrate 30, the translucent and electrically conductive electrode layer 35, and the translucent and electrically insulating insulating layer 36. The microsheet element 1 is arranged with its mounting section 12 on the insulating layer 36, and the pivoting movement of the sheet section 11 is effected by a curvature of its hinge section 13.In the depicted state, an electrical actuation voltage Uact is applied between the microsheet element 1 and the electrode 35, such that an electrostatic attraction between the electrode layer 35 and the microsheet element 1 leads to the closing of the sheet section 11 into the depicted horizontal, i.e., closed, position. Two open positions of the sheet section 11 are shown with dashed lines: one oriented essentially orthogonally to the base plates 2, 3, and a semi-open intermediate position in which there is an angle of approximately 45° between the sheet section 11 and the base plates 2, 3. The maximally open position is assumed when the microsheet element 1 and the electrode layer 35 are at the same electrical potential, and in the semi-open intermediate position, a lower actuation voltage Uact is present compared to the closed position.By appropriately varying the applied actuation voltage U act, a large number of partially open intermediate positions with different angles of the blade section 11 relative to the base plates 2, 3 can therefore be set.

[0056] Figure 5 Figure 1 shows a schematic cross-sectional view to demonstrate the residual stresses of a microsheet element 1. For the sake of clarity, the photometric functions of the microsheet element 1 are again not shown. The microsheet element 1 has a compression-stressed layer 1a arranged on the base plate 3, as well as a tension-stressed layer 1b. The effect of this

[0057] Residual stresses arise from the curvature of the microsheet element 1 along the hinge section 13, exemplified here by a rolling angle of approximately 90°. Along the mounting section 12, this curvature is prevented by the bonded connection to the base plate 3, and along the sheet section 11, the tension-stressed compensation layer 1c ensures that the global, i.e., effectively acting, residual stress in sheet section 11 disappears, thus preventing any curvature there. The illustrated layers 1a, 1b, and 1c can, for example, collectively form an electrode of the microsheet element 1, and the optical function of the microsheet element 1 is generated by unstressed layers or layer systems applied to both sides. Figure 3 The differently tensioned layers are not shown in detail for the sake of clarity.

[0058] Especially when using vapor deposition (PVD) or CVD methods, all layers are typically stressed, including, for example, the black coating layer on the microsheet element. In this case, it is advantageous to design the entire layer sequence to compensate for the mechanical stresses in the planar sheet section 11. In principle, two different layers are sufficient for global stress compensation in sheet section 11; see the embodiment of the Figure 3 . However, with regard to design freedom concerning the functionality and dimensions of the microsheet elements, it is advantageous to use more than two layers.

[0059] Figure 6This figure shows the reflectivity of base plates with two different antireflective coatings, based on computational simulations that take into account the spectral variation of the refractive indices and absorption. The spectra each refer to a layer stack deposited on a glass substrate, consisting of an FTO electrode layer, a SiO₂ insulating layer, and an antireflective coating based on a layer stack of Al₂O₃, Si₃N₄, and MgF₂ thin films (Option A) or of Al₂O₃, Si₃N₄, and SiO₂ thin films (Option B). In the visible region of the light spectrum, i.e., at wavelengths from 380 nm to 740 nm, the reflectivity is essentially less than 2%. In combination with back-side blackening of the glass substrate, this results in a black color impression for the observer over a wide viewing angle range.

[0060] The invention is not limited in its implementation to the preferred embodiment described above. Rather, a number of variants are conceivable which make use of the solution shown, even in fundamentally different designs, as long as these variants fall within the scope of protection of the pending claims. Reference symbol list:

[0061] 1000 Display device 100 Display 200 Lighting device 1 Microsheet element 1a Pressure-stressed layer 1b Pull-down-stressed layer 1c Compensation layer 1d Gradient layer 11 Sheet section 11a Front 11b Back 12 Mounting section 13 Hinge section 14 Black paint layer 2 Front base plate 20 Substrate 3 Back base plate 30 Substrate 21 Color filter 31 Black paint coating 31a Interface structure 32 Anti-reflective coating 33 White paint coating 34 Color filter 35 Electrode layer 36 Insulation layer U act actuation voltage

Claims

1. A display (100) for the visual presentation of variable information, comprising a regular array of micro-leaf elements (1) with actuable leaf sections (11), wherein the micro-leaf elements (1) are arranged in a regular matrix formation in parallel rows and parallel columns, and wherein the actuable leaf sections (11) are designed to pivot between a closed position and at least one open position, such that the display of information is based on a spatio-temporal modulation of the optical reflectivity of the display (100) by means of actuation of the leaf sections (11), wherein the front side (11a) and the rear side (11b) of the leaf sections (11) exhibit a mirror-like effect for visible light, wherein the display (100) comprises an opaque rear base plate (3), wherein the rear base plate (3) produces a black colour impression, in particular by the rear base plate (3) comprising a black colour coating (31), a black substrate and / or a light-absorbing interface structure (31a), characterised in that the pivot directions of all leaf sections (11) are the same when pivotling about their pivot axis between the closed position and the at least one open position, and wherein the rear base plate (3) comprises an anti-reflective coating (32), in particular based on a stack of Al2O3 -, Si3 N4 - and SiO2 - thin films or a stack of Al2 O3 -, Si3 N4 - and MgF2 - thin films.

2. Display (100) according to claim 1, characterised in that the display (100) comprises a colour filter (21, 34), in particular in the form of a Bayer filter, preferably such that at least one micro-leaf element (1) is assigned to each colour pixel of the colour filter (21, 34).

3. Display (100) according to one of the aforementioned claims, characterised in that the display (100) comprises a front base plate (2) and a rear base plate (3), wherein the front base plate (2) is designed to be light-transmissive, and wherein the micro-leaf elements (1) are accommodated in a space between the base plates (2, 3), each micro-leaf element (1) comprising a leaf section (11) and being arranged in a hinge-like manner on one of the base plates (2, 3) by means of an edge-side mounting section (12), such that each leaf section (11) can be pivoted from a closed position, oriented parallel to the base plates (2, 3), into at least one open position, in particular one oriented at right angles to the base plates (2, 3).

4. Display (100) according to claim 3, characterised in that the micro-leaf elements (1) each have a layered structure comprising at least one compression-stressed layer (1a) and one tension-stressed layer (1b), wherein the leaf section (11) of each micro-leaf element (1) also comprises a suitably stressed compensation layer (1c), such that each micro-leaf element (1) is divided into the following sections: - the leaf section (11), which is designed to be globally stress-free and has two substantially coplanar surfaces, - the edge-side mounting section (12), which is rigidly mounted on one of the base plates (2, 3), and - an intermediate hinge section (13), which exhibits a curvature induced by internal stress, thereby forming an open position of the micro-leaf element (1).

5. A display (100) according to one of the preceding claims, characterised in that, the pivoting of the leaf sections (11) between the closed position and the at least one open position can be actuated by means of an electrostatic principle, for which purpose the associated base plate (2, 3) comprises an electrically conductive electrode layer (35) and at least one electrically insulating layer (36), wherein the edge-side mounting section (12) of each micro-blade element (1) is arranged on the insulating layer (36), and the leaf sections (11) each comprise or form an electrode, such that individual micro-blade elements (1) and / or groups of micro-blade elements (1) can be actuated by applying electrical voltage signals between the electrodes and the electrode layer (35).

6. A display (100) according to one of the preceding claims, characterised in that the leaf sections (11) have a rectangular contour, in particular a square contour, wherein the edges of the leaf sections (11) have a length in the range from 10 micrometres to 1 millimetre, preferably 100 micrometres to 200 micrometres.

7. A display (100) according to one of the preceding claims, characterised in that the entirety of the micro-leaf elements (1) defines the section of the display (100) designed for information display.

8. Use of a display (100) according to any one of the preceding claims for an electronic price tag.

9. A display device (1000) comprising at least: - a display (100) for the visual display of variable information in accordance with one of claims 1 to 7, and - an illumination device (200) for uniformly illuminating the display (100).