DE102006036867A1 - Information display for tactile or visual perception, includes liquid layer having structure and properties affected locally and reversibly by physical stimulus - Google Patents

Abstract

A stimulus locally affects a functional layer (1, 1a, 1b) comprising a solution, in its optical-, aggregation-, cross-linking- and/or swelling properties. The resultant change persists until further stimulation occurs. Surplus solution is removed or transformed reversibly into hydrogel structures. Local regions of the functional layer undergo change in optical properties, in accordance with shape memory effect. The layer is transformed reversibly from an oil, paraffin or wax, into a solid state.

Description

Technical area

The The invention relates to devices for displaying tactile and / or visual Information that can be rewritten, erased, and described Condition can be maintained without the need for auxiliary power.

State of the art

Small, lightweight, portable and durable if possible low energy consumption should be mobile display devices for the electronic Be the media of the future. They are prerequisite for "Mobile Business. "This Thoughts correspond to the concepts of "electronic paper" and in part futuristic electronic notebooks. Ideally, they are little else than a thin, transparent and flexible film. To achieve such devices is currently a whole series of technical principles, such as electrophoretic, Electrowetting, electrochromic and OLED (organic light-emitting diode) technologies.

These Ads have several disadvantages: they can not provide tactile information represent and need electrical energy to hold their image information. Furthermore Some of them have a complicated and expensive construction.

Object of the invention

task The invention is therefore, devices for displaying more tactile and / or visual information that needs to be rewritten. as well as erasable are and a described condition without the need of Maintain power.

Description and examples

According to the invention Problem solved by the features specified in claim 1. advantageous Embodiments are specified in claims 2 to 11.

core The invention is a substance which by spatially defined action certain environmental variables with preferably energetic character locally in their optical and / or tactile properties changed can be this information without supply of auxiliary power over certain periods save and can be reversibly deleted and rewritten.

The Contains substance in a first possibility either crosslinkable substances or many small polymer networks, e.g. in the form of microgels, or it is through a single polymer network educated. Hydrogels as special water-swellable polymer networks are particularly suitable for the invention because of their properties.

The Substance consists in a second possibility of materials, in the range of room temperature, for example between -20 ° C and + 120 ° C by the effect of temperature to an aggregate state change between liquid and solid or liquid and highly viscous (insignificant flow properties) are stimulated can. Such substances can for example oils and fats, paraffins or alkanes, or waxes. Semi-solid paraffins or soft paraffin, e.g. Melting temperatures between 45 ° C and 65 ° C, petrolatum Vaseline has melting temperatures in the range of 38 ° C and 60 ° C.

hydrogels are polymer networks which, when exposed to aqueous swelling agents, have their volume, change their strength and other properties. They relax the type of polymer chain linkage with each other in chemically and physically networked polymer networks or hydrogels subdivide. For chemically crosslinked polymer networks the individual polymer chains by covalent (chemical) compounds irreversibly linked together. For physically crosslinked polymer networks, the polymer chains are interconnected by physical interactions, the usually solved again can be.

A particular class of hydrogels are those of "smart" character, performing smart or "stimuli-responsive" hydrogels chemically crosslinked polymer networks reversible discontinuous Phase transitions at Influence of certain environmental parameters. As physically crosslinkable polymer networks remove or crosslink (even yellowing or gelling) between them the maximum networked and fully resolved state. Chemically crosslinked Change polymer networks by swelling agent absorption or release their volume, but also mechanical, optical and other properties. The influencing environmental variables can be electrical Field sizes, radiation, Temperature, ion and substance concentrations.

In dependence of the material used different mechanisms for maintaining the described visual and / or tactile information.

Chemically cross-linked polymer networks with volume phase transition behavior, when exceeding or falling below a critical value of a certain environmental quantity, change from a mixed state (the polymer chains "float" in the swelling agent) into a phase-separated state the swelling agent and polymer segregate, so that the swelling agent is released from the polymer network. This is usually reversible, ie, the segregation or phase transition value is reached again, then the gel swells under swelling agent uptake.

A leaves tactile information through a tangible height difference represent, which realized with targeted de-sourcing of certain areas can be. Since hydrogels additionally change their strength during the phase transition, they can also Conveyed softness information become.

As a result the reversible phase transition behavior The hydrogel needs to maintain a swelling state always the corresponding value of the environment size are kept constant. A temperature-sensitive hydrogel with a lower critical mixing temperature (Lower critical solution temperature LCST) is for example at low temperatures swelled and depleted when passing the phase transition temperature. To maintain the de-swollen state, the gel must do the whole Time to be heated. This problem can be bypassed by deprived of the excess swelling agent after the writing process becomes. Would like Swell the swollen hydrogel areas, they can do so because of swelling agent not so that the state described in terms of its source and strength properties is fixed. The representation of visual Information with chemically cross-linked hydrogels is in principle easy to implement, since they are usually in the phase-separated state opaque-opaque, in the swollen state are often transparent. However, the phase-separated, opaque state can not be passed through Fix swelling agent removal. Upon reaching the mixing conditions loses the phase-separated state and the hydrogel is independently transparent from a source operation. A visual information can be but reach through trapped color pigments. In the swollen State, the density of the pigments is low, in the swollen state however high. With appropriate dimensioning one can in extreme cases also between a transparent and an opaque-pigmented state switch back and forth.

Becomes an exposure sequence with light of different Wavelength performed, so can be a color-dependent Description can be achieved by e.g. the pigments accordingly their colors absorb light of the appropriate wavelength and in a corresponding phase transition temperature implement.

Hydrogels and other polymer networks (both physically and chemically crosslinked) may also exhibit shape-memory effects that are mostly due to reversible changes in structure or conformation, such as crystal structure, crystallinity, changes in coordinative bonding equilibrium [ Y. Osada, A. Matsuda, Nature 376 (1995), 219 ; A. Lendlein, S. Kelch, Angew. Chem. 114 (2002), 2138 ]. Shape memory polymers appear to be particularly interesting in terms of transmitting visual information, since it is only necessary for the switching of the optical properties, such as polarity and transparency, a power supply, but not to hold this information.

A another possibility for controlling the degree of swelling and thus the visual or tactile Information content is the targeted storage and retrieval of substances or ions in polymer networks charged via charged groups (e.g. Polyacid or polybasic groups) feature. Such controlling of internal migration can be achieved by applying an electrical Field done. Currently, this process is still problematic.

One Reversible gelling of physical polymer networks is i.a. at Exposure to temperature and high energy radiation (e.g. Radiation, light of certain wavelengths). It is the Temperature-induced gelation is the best known and probably the most common best manageable gelling option.

Physically Crosslinkable polymer networks form when exposed to certain Environment sizes off a polymer solution by gelling, by the individual polymer molecules to a three-dimensional Link network or network. This condition is stable for certain periods of time. Since the gelling process is usually reversible (sol-gel transition behavior), by Acting on a critical environment size, the linking points be separated again, so that the polymer molecules dissolved or have been removed.

Of the tactile information content of display units based on physical crosslinkable polymer networks leaves through space Define defined Ver- or Entnetzen the polymer-containing substance. For this purpose, the individual pixels are controlled by the action of acting as a control variable environment size, that these gel. The uncontrolled pixels continue to exist from the polymer-containing substance or polymer solution.

Between Strength differences naturally exist in the networked and ungelled picture elements. To amplify or representing profiles, reliefs and contours can be the uncrosslinked polymer solution be withdrawn. To illustrate differences in strength also local viscosity changes the polymer solution out.

visual Information can also be obtained through gelable materials with several possibilities represent.

Are located In the gelable substance color pigments, so they can be immobilized by gelling. Will the uncrosslinked medium of liquid Withdrawed display areas, the gelled pixels show the color information the pigments in them, while the other areas ever decolorize after evacuation.

It is still possible to change the optical properties of the polymer-containing substance. at Phase separation or in the formation of heterogeneous structures (this is characterized by the simultaneous formation of a polymer-rich and polymer-poor phase) As a rule, the transparency of the polymer is opaque to opaque. This effect can be exploited with two different effects become.

Becomes by gelling a whole pixel in a heterogeneous structure fixed, it hides the pigments in it due his opacity. The uncrosslinked areas, however, show the color of the pigments, as they are not hidden.

Becomes however, a solution or a matrix (solid substance in which the activatable substances embedded) containing physical microgels in which the pigments are present (e.g., as a core-shell construction where one Gel cover one Pigment core enveloped), stimulated, so hide the gel sheaths because of their cloudiness the included pigments, and the optical properties of the solution or matrix (for example, they may be transparent). In the non-activated areas, the pigments are due to the Transparency of the gel envelopes visible, so that the display unit is there their color.

By a sequential description sequence with media of different Color can be used to create color images. Will the gelation with light certain wavelength carried out, so can a color-dependent Gelation can be achieved by the pigments according to their Colors light the associated wavelength Absorb and convert to a temperature necessary for gelation.

Typical temperature-switchable physically crosslinkable hydrogels, which are also called thermoreversible systems in the case of reversible gelation, are gelatin, pectins and agarose. Their sol-gel transition temperatures can be adjusted by various measures between about 15 ° C and 95 ° C. To these and other physically networkable polymer networks [ K. te Nijenhuis, Thermoreversible Networks, Adv. Polym. Sci. 130, Springer-Verlag Berlin, Heidelberg, New York 1997 ] an overview. There are also polymer networks that are chemically crosslinked and have physically crosslinkable components. By acting on the physically crosslinkable components, additional crosslinking points can be formed or eliminated, so that the degree of crosslinking and thus also the degree of swelling can be influenced.

By Absorption of light of specific wavelength, which is due to the use corresponding dyes are reinforced in the polymer network or at its interfaces can, and the consequent conversion into heat can be temperature-sensitive polymer networks ultimately also be light-sensitive. A direct light sensitivity lies in photochemically crosslinkable polymer networks. These wise For example, photodimerizable chromophores (common Chromophores are based e.g. on Phenylinden, Stilben, Stilbazolium, Acridizinium) on. By dimerization reactions of these groups upon exposure to light of a certain wavelength, crosslinking points become built up between the polymer chains and it creates a polymer network. are the photodimerizations photochemically or thermally reversible, can the gels are dehumidified again.

A initiated by electric field sizes Gellability or removability may possibly occur in polymer networks, possess coordinative bonds to metals as crosslinking points, be achieved. This can e.g. based on that education the metal complexes influenced by an applied electric field becomes. About that In addition, an applied magnetic field can be electrode-specific Cause migration of metal salt ions, so that the number of available for complexing Ion is controllable. Physical polymer networks based on coordinative Bindings are often thermoreversible.

The Influencing with multiple environmental sizes, e.g. with electric Field sizes and temperature, allows writing to one size and deleting the Display information with the other size.

For writing the display units according to the invention Particularly energetic quantities are suitable, such as light, others high-energy radiation, electric field quantities and the temperature.

To the Light-based describing the display unit are all facilities with the ability enough to structure high-energy light.

When electronically controllable imaging light systems are for example Liquid-crystal systems, as used in beamers suitable. Also mirror head systems, as they are also known from high-speed projection systems, are suitable as optoelectronic control.

Also a line laser system is suitable for optoelectronic writing the display unit.

A However, light-based description can also be given by fixed masks or transparent pictures take place. For example, if you put an X-ray image on the projection screen, so on the display unit, the X-ray image projected so that it is described according to the template.

The light-based control can simultaneously as thermal control, based on the conversion of the light into heat by absorption become.

To the Thermal description of the display unit are all facilities with the ability to generate a defined temperature field.

This can be done for example by a picture drum, as they are from Thermo-copiers or laser printers are known forth.

It Furthermore, a resistive control can be used, which from a variety of heating structures, such as resistors or used as resistors Thin film transistors, consists, wherein ideally each pixel is assigned a heating element. Finally, the display unit can also be introduced into an apparatus which can produce a corresponding temperature field. Also this can be punctiform resistors own, but also work in the manner of a heated stamp, which by direct contact of the raised places a corresponding Image generated on the display unit.

To the Describe the display unit with electrical field sizes are suitable electrode arrangements. You can do this, for example, between two Plates, of which at least one of a plurality of individual electrodes is to be laid. However, the display unit itself can also be corresponding Have electrode assemblies in the form of conductive layers.

Especially the presentation of visual information such as contours, reliefs and Textures is due to the softness of the hydrogels directly hardly possible. For that let but use pimples, one of which is a tactile pixel of the Display unit can be assigned.

The Invention is intended to some embodiments be explained in more detail. In the associated Drawings show:

1 the basic structure of a tactile display unit based on a temperature-sensitive chemically crosslinked hydrogel, wherein

1a the blank initial state and

1b represents the described and fixed state,

2 the basic structure of a tactile display unit based on a thermo-reversible gellable hydrogel, wherein

2a the blank initial state and

2 B the described condition as well

2c illustrates the described and fixed state,

3 the basic structure of a tactile or visual display unit with integrated drive electrodes,

4 possible visual operating modes, wherein

4a , b the visual function of pigmented hydrogels as a result of the pigment density change during swelling

4c , d the visual functioning of gellable transparent hydrogels

4e , f illustrate the visual functioning of gellable hydrogels that become opaque upon gelling,

5 the operation of a visual operation of a display unit with integrated drive electrodes and a functional material that changes its strength or viscosity, wherein

5a the blank initial state

5b the state when writing

5c the fixed state
shows,

6 possible pimple forms, wherein

6a rectangular pimples

6b round pimples

6c hexagonal pimples
shows, and

7 possible edge forms with

7a Ninety-degree edges

7b chamfered edges as well

7c rounded edges.

Based on 1 the basic structure and operation of the display unit according to the invention is presented.

The display unit after 1a basically comprises three layers: a structural support ( 4 ), a cover ( 5 ) and an intervening functional layer containing the functional polymers ( 1a - 1d ) and, if necessary, swelling agent ( 2 ) and corresponding storage options ( 3 ) contains. The display unit can be made transparent. The support materials should normally provide mechanical stability, so that, for example, polyamide, polyester, but also polycarbonate or cycloolefins can be used. For the cover ( 5 ) are the same materials. If it has to be flexible, highly elastic materials can be used. Make sure that they are impervious to water vapor.

When Functional polymer can be used, for example, poly (N-isopropylacrylamide) (PNIPAAm) which is a temperature-sensitive chemically cross-linked hydrogel with lower critical solution temperature (LCST) characteristic. The PNIPAAm may e.g. with photolithographic methods to a Array, which consists of many small single actuators, each one Form tactile pixels, be structured.

The functional layer comprises, in addition to the functional polymer, a storage possibility ( 3 ) for swelling agent ( 2 ). The size of the reservoir ( 3 ) can be determined by the spatial distance between the hydrogel actuators ( 1a ) establish.

At low temperatures, eg at room temperature, the PNIPAAm actuator ( 1a ) swollen. If the display unit is locally heated by a descriptive device not shown in detail, the hydrogel actuators ( 1b ) when a volume phase transition temperature PÜT (for PNIPAAm about 34 ° C) is exceeded by swelling agent delivery into the reservoir ( 3 ). Is then the excess swelling agent ( 2 ) from the reservoir ( 3 ) sucked off, then results in the 1b illustrated state. Because the pimples ( 6 ) over the swollen actuators ( 1a ) are higher than those above the swollen Akto ren ( 1b ), results in a height difference that can be felt. By the extraction of the swelling agent ( 2 ), the actuators ( 1b ) no longer swell even when the PÜT falls below, as the reservoir ( 3 ) no swelling agent ( 2 ) can provide more. The tactile information content of the ad is thus frozen. To delete or refresh the content of the advertisement, the missing source means ( 2 ) again.

Next PNIPAAm also have a number of other hydrogels on an LCST characteristic. These are, for example, poly (methyl vinyl ethers) and polymers Base of hydroxypropylcellulose.

temperature Sensitive chemically cross-linked hydrogels with an Upper Critical Solution Temperature (UCST) characteristic swell if exceeded the phase transition temperature and are swollen at low temperatures. A hydrogel with UCST behavior is the copolymer of hydroxyethyl methacrylate (HEMA) and acetoacetoxyethyl Methacrylate (AAEM), which demonstrates this behavior in water-alcohol mixtures shows.

Using a thermo-reversible gelable hydrogel, for example based on gelatin, the functional layer in the unrecorded state initially consists of a gellable solution ( 1c ), which are in the reservoir ( 3 ) ( 2a ). By local heating above the gelling temperature with a corresponding descriptor hydrogel actuators form ( 1d ) out ( 2 B ). After the writing process, the uncrosslinked solution ( 1c ) be evacuated, so that in 2c shown tangible height profile arises. To delete or refresh the content of the advertisement, it is heated above the critical temperature and, if appropriate, the solution removed ( 1c ) again.

In principle, the swollen actuators ( 1a . 1d ) are linked to the tactile information "perceptible" or "sublime" and "soft." Swollen actuators ( 1b ) have the information content "not perceptible" or "hard".

by virtue of The simple feasibility is a control with electrical Field sizes extremely attractive. Although the electrical drivability of hydrogels is problematic is she can for the Display unit according to the invention in certain circumstances be used because the rewriting rates are very small and long enough Recovery times possible are.

One possible embodiment of the electrical control of the display unit is in 3 shown. Is connected to a single electrode ( 7 ) one Voltage is applied, it becomes the counterelectrode ( 8th ) build up an electric field. In the swelling agent ( 2 ) ions are thus enriched between the electrode plates. The hydrogel ( 1a ), which has a polyelectrolytic character, for example, will change its degree of swelling in accordance with the stored ions, so that the resulting height profile over the pebbles ( 6 ) becomes tangible. By removing the excess swelling agent, the described state can be fixed.

A functional principle for the reproduction of primarily visual information with chemically cross-linked hydrogels is shown by the 4a and b. When swollen, the density in the actuator ( 1a ) included color pigments ( 9 ) low, so that the pixel ( 1a ) is transparent or at least little colored. However, if the actuator is depleted (actuator ( 1b ) in 4b ), it has a much higher pigment density and thus a strong color. During the switching process, it is possible that the actuator becomes opaque for a short time due to the phase separation.

The 4c to 4d illustrate two visual principles of pigment-containing gelatable systems. In the 4c arrangement shown consists of a gellable solution ( 1c ), which pigments ( 9 ) contains. By appropriate control, the solution gels to an element ( 1d ) containing the pigments ( 9 ) fixed. After removing the solution ( 1c ), the gelled color structure remains as a positive image.

Will the in 4e shown pigment-containing functional solution ( 1c ) so that the crosslinked areas are opaque or un transparent, the result is a negative image of the described area, ie the areas described do not show the color information of the pigments.

5 illustrates the operation of a display unit for mainly visual information based on reversible gellable materials, but also on substances that can be switched in their state of aggregation between liquid and highly viscous or firmly. The principle is described using the latter materials. The functional material ( 1 ) consists, for example, of soft paraffin and contains color pigments ( 9 ). The temperature of the display unit is raised to 45 ° C so that liquid paraffin ( 1e ) ( 5a ). The color pigments ( 9 ) consist of materials that are influenced by electrical or magnetic field sizes, so attract or repel. As 5b shows arise by activating certain pairs of electrodes ( 7 ) and ( 8th ) local electromagnetic fields in which the in the liquid ( 1e ) floating color pigments ( 9 ) collect. If the temperature is lowered below the melting temperature, the soft paraffin solidifies ( 1f in 5c ) and thus fixes the pigment distribution. By re-heating the display content is deleted again and can be rewritten.

The Hydrogel actuators of a tactile display are suitable because of their Softness only conditionally for transmission tactile information.

The communicable tactile information can be significantly determined by the cover made of harder material used. A smooth film can be used to show differences in the material properties "softness." The mediative impressions range from the softness of fatty tissue to solid surfaces such as wood, and contours are difficult to feel with such films. The palpable edge sharpness, but also the transferable textures are determined by the shape and size of the knobs The knobby material influences the feeling experience with its hardness. 6 ). Pimples with a square layout ( 6a ) have sharp corners and may have the same shape as the underlying hydrogel actuators. In the 6b shown round nubs have no corners. The staggered hexagons after 6c make it possible to achieve a high density of nubs with tangible corners.

As 7 clarified, the nub edges can also be influenced. In the 7a shown knob has sharp edges. A chamfer attenuates the palpable edge sharpness ( 7b ). The same is achievable by rounding the knob edges ( 7c ). Also the knob size and density have a significant influence on the feeling experience. Also important is the nub lift, which is determined by the hydrogel actuators. Differences in the dimple height can be felt from about 100 μm.

When Design policy may apply that sharp-edged, larger nubs Particularly well suited for contour presentation. Smaller rounded ones Allow nubs a greater variety in the texture transmission. Smooth surfaces, which e.g. are achievable by a high Noppendichte allow an improved feeling softness, since hydrogel actuators are next to tactile information the hub also changes their elasticity (Softness). That is for to optimize the respective application.

Become a nub several actuators, e.g. assigned to three actuators, can these are defined in their inclination to be changed.

Furthermore, it is conceivable that the film with Areas of different pimple features is equipped. This can be interesting in particular for illustrative materials.

bubble films can For example, be prepared from polydimethylsiloxane (PDMS). Base substance and hardener is in a relationship mixed by 9: 1. By spin coating at 3000 rpm for 25 s about 30 microns thick film produced on a plane glass slide and at 65 ° C for three hours polymerized. The nubs can be with a Teflon-coated Silicon Molding Master (wet chemical deep etching by ASE-Bosch process, Teflon coating by PECVD) produce. This is the elastomer mixture filled in the stud shapes and degas. Subsequently The mold is pressed onto the PDMS-coated glass slide and allowed to stand for three hours Polymerized 65 ° C. The nubs form a permanent bond with the film.

The Display unit leaves thin, transparent and flexible. The necessary thickness is in addition to aspects of the mechanical Resistance especially after tactile or visual information, that is, the functional layer must be so thick that the necessary change the optical properties or the height difference (a minimum stroke of 100 μm is necessary) is clearly perceptible.

The Display unit leaves for diverse applications use. In addition to the visual "electronic paper" that allows Display principle also the low-energy representation of tactile information. It can be permanently connected to the descriptive mechanism, e.g. as a screen of an electronic book, but she can as well be described by a separate descriptor and used in the described state like an image or a sheet of paper become.

The the latter variant offers many advantages. So can visual as well as tactile information with a device, which for example a Thermo-copier resembles written on the "paper". The information then remains until the deletion or rewriting process receive. The display units are not just for everyday things Demand interesting, but also for many other applications. So can the image-based medical and technical diagnostics Benefit from having visual and tactile information if necessary also shown enlarged can be. By their use as teaching materials can be replaced, but preparations also maps and the like can from the display units according to the invention benefit.

1

functional material

1a

swollen Hydrogelaktor

1b

entquollener Hydrogelaktor

1c

linkable solution

1d

networked hydrogel

1e

liquid paraffin

1f

solid paraffin

2

swelling agent

3

reservoir

4

structural beam

5

cover

6

burl

7

Single electrode

8th

Surface electrode

9

color pigment

Claims (13)

Rewritable device for displaying tactile and / or visual information, characterized in that at least one functional layer made of a functional material (by the action of at least one physical variable that can be controlled in its local action) ( 1 . 1a - 1f ) is changed locally in its optical, aggregate, crosslinking and / or swelling properties, wherein the functional layer can maintain this state until a physical quantity is re-acted, by a) removing the excess swelling agent ( 2 ) or the excess crosslinkable solution ( 1c ) is wholly or partially withdrawn, and / or b) local areas of the functional layer of crosslinkable solution ( 1c ) in a reversible manner into gelled hydrogel structures ( 1d c) local areas of the functional layer are changed in their optical properties according to the nature of the shape memory effect d) the functional layer consists of a liquid oil, paraffin or wax ( 1e ) in a reversible manner into a solidified state ( 1f ) is transferred. Device according to claim 1, characterized in that the material ( 1a - 1d ) consists of temperature-sensitive hydrogels. Device according to claim 1, characterized in that the material ( 1a - 1d ) consists of hydrogels with sensitivities to light of a certain wavelength. Device according to claim 1, characterized in that the material ( 1a - 1d ) consists of hydrogels that are sensitive to electrical and / or magnetic field sizes. Device according to claim 1, characterized in that the material ( 1 . 1e . 1f ) from oils, Fats, alkanes, paraffins, waxes, which are reversible in the range of -20 ° C to + 120 ° C from a liquid in the solid or from the liquid to a highly viscous state exists. Device according to claim 1, characterized in that the functional layer when using chemically crosslinked hydrogels from an array of many individual actuators ( 1a . 1b ), each actuator representing a pixel. Device according to claim 1, characterized in that the functional materials ( 1 . 1a - 1f ) Dyes, in particular color pigments ( 9 ), contain. Device according to claim 7, characterized in that the dyes, in particular color pigments ( 9 ), by the action of at least one controllable in their local effect physical size, in particular electrical and / or magnetic field quantities are moved in liquid materials and thus low-dye and dye-rich areas can be generated. Device according to claim 7 and 8, characterized in that the local distribution of the dyes, in particular color pigments ( 9 ), is fixed by solidification or gelation of the functional materials. Device according to claim 1, characterized in that the cover ( 5 ) has a profiled surface. Device according to claim 1, characterized in that the cover ( 5 ) over pimples ( 6 ). Device according to claim 1, characterized in that the nubs ( 6 ) are adapted to the respective application in terms of their material and geometric properties. Device according to claim 1, characterized in that each knob ( 6 ) at least one actuator ( 1a . 1b . 1d ) and / or the basic geometric relationships, in particular the grid dimension, correspond to each other in integer ratios.