DE102005024921A1 - Elastomer based projection display unit , has color filter section, and buffer section enabling lateral extension of one of contact sections and elastomer section, where electric field is created between contact sections - Google Patents

Abstract

The display unit has an elastomer section (6) arranged between contact sections and between a partial reflective section and one of the contact sections or a additional reflective section. A flexible buffer section enables lateral extension of one of the contact sections and the elastomer section, where an electric field is created between the contact sections, between which the elastomer section is arranged. A color filter section is arranged between one of the contact sections and the partial section. An independent claim is also included for a method for producing light of a pre-set wave length range.

Description

The The invention relates to a display element and a method for generating of light of a given wavelength range with those in the preambles the claims 1 and 17 mentioned features, in particular the invention relates an elastomer-based display element.

The Group of elastomers is characterized by the fact that they are already stretch and flex with little force and without force reset again, their original form taking. They are macromolecules, the only by a few chemical cross-linking bridges with each other are connected.

Out US 4,626,920 is a projection display based on elastomers known. A plurality of pixel electrodes may cause deformation of an elastomeric film upon application of an electric field, whereby the elastomeric film takes the form of a diffraction grating. A reflective layer on top of the elastomer layer reflects incident light into a corresponding projection optics. Elastomer-based display elements are also known from Sheridon et al., SPIE, Vol. 128 (1977), p. 244 and Kornblum et al., Proc SPIE, Vol. 3987 (2000), p. 51.

Out US 2004/0212869 A1 is an electrostrictive (elastomer-based) Light modulator known in which an active layer of an electrostrictive Material (elastomer) deformed by applying an electric field is and thus arranged on the elastomer layer reflective Layer modulated according to incident light.

It Object of the present invention, an elastomer-based display element and a method for generating light of a predetermined wavelength range indicate which one with one (compared to the prior art) high contrast and low power consumption.

These Tasks are performed according to the invention the features of the claims 1 (display element) and 17 (procedure) solved. Preferred embodiments The invention are contained in the subclaims.

To has an inventive display element a first partially reflective layer and a first electrical Contact layer, wherein the first contact layer at least partially translucent is; the display element further comprises an elastomer layer and a second contact layer, wherein the second contact layer is reflective or the display element an additional has reflective layer arranged on the second contact layer, wherein the elastomer layer between the first contact layer and second Contact layer and between the first reflective layer and second Contact layer or the additional reflective layer is arranged. Preferably, between the first contact layer and the first partially reflective layer an at least partially translucent buffer layer of a arranged flexible material and / or a color filter layer and / or the first contact layer is periodically structured.

The The idea of the present patent application is therefore to Ambient light over to couple a first partially reflective layer, wherein a Part of the ambient light reflected and thus not coupled and the coupled portion of the ambient light at a second reflective layer is reflected and that at the second reflective Layer reflected light at least partially the first partially reflective layer happens a second time and with that at the first partially reflective layer reflected part of the ambient light interferes, so by the optical path length, which is the light between first partially reflective layer and the second reflective layer Shift back constructive or destructive interference is realized, thereby the corresponding display element, for example, bright (constructive Interference) or dark (destructive interference) can be. The optical path length the layers lying between the two (partial) mirrors can (the Elastomer layer is always between the two mirrors) by Applying an electric field to the elastomer layer varies be, whereby the brightness or the color perception of the Display element can be controlled. Because the elastomer layer changed upon application of an electric field its thickness. By the Coulomb attraction the charge carrier the elastomer layer is compressed, thus changing the resonance conditions in the display element.

To reduce the current consumption, which is applied to the deformation of the elastomeric layer to the electrical contacts, according to the invention the translucent buffer layer of a flexible material is provided, on which the electrical contact layers and the elastomer layer are arranged. When an electric field is applied to the elastomer layer, both the elastomer layer and the first transparent contact layer are squeezed (thickness decreases), with both the elastomer layer and the first transparent contact layer extending in the lateral direction stretch. This extension in the lateral direction, which is associated with a reduction in film thickness and thus with a change in the interference conditions of the display element is promoted by the flexible buffer layer, which favors the lateral extent of the overlying first contact layer and the elastomer layer due to their flexible properties, so that a smaller electric field for the same layer thickness reduction (same interference effect) is required compared to a display element without flexible buffer layer. As a result, the power consumption and the necessary control voltage of the elastomer-based display element according to the invention can be significantly reduced.

Farther can according to the invention the contrast and the color saturation the elastomer-based display element by a between first partially reflective layer and second reflective layer arranged color filter layer can be increased because the color filter layer a Reflektivitätsabfall a desired one wavelength causes. Another advantage is that through the color filter layer the angle-dependent Color shift can be minimized. The color filter layer is preferably from a pigment dispersion having a thickness between 20 nm and 200 nm. Suitable pigments can For example, from the material classes of phthalocyanines, perylene imides, anthachinones, Quinacridones, diazo dyes, dioxazines. Alternatively, thin layers said pigments and related materials are used.

The Layer structure of the display element according to the invention is preferably on a transparent substrate, for example made of borosilicate glass built up. On the substrate are the first partially reflective Layer and the color filter layer and / or the buffer layer and the first electrical contact layer, the elastomer layer and the arranged second electrical contact layer. The first contact layer preferably consists of polyethylene dioxytiophene. The elastomer layer preferably consists of siloxane-based materials, for example from cross-linked polydimethylsiloxane or related polyalkylsiloxanes or related polyarylsiloxanes.

In a further preferred embodiment the elastomer layer consists of cross-linkable polyurethane or Fluoroelastomer. Similarly, sulfur-crosslinked elastomers are based of butadiene and isoprene and acrylonitrile suitable. Other possible materials for the Elastomer layer are physically cross-linked elastomers. These materials can e.g. from material classes such as block copolymers of polystyrene with either polybutadiene, polyisoprene or polyisobutylene can be selected. The materials mentioned can be through Addition of suitable plasticizers, e.g. Squalane in elastic modulus be modified.

In a further, particularly preferred embodiment of the invention it is provided, the reflectivity of the display element according to the invention by means of a periodically structured first contact layer vary. By applying an electric field between the periodically structured first contact layer and the unstructured second contact layer, between which the elastomer layer is arranged is, the elastomer layer is wavy (periodically) distorted (deformed), which in turn reduces the interference conditions between the two reflective layers (first partially reflective Layer and the second reflective layer, which also deformed lattice-shaped will) change. Also by this design can be a very efficient and high-contrast Structure are generated.

In a particularly preferred embodiment For example, the first contact layer has a grating period between 1 μm and 200 μm. The Buffer layer is preferably made of flexible, chemically crosslinked Elastomers, e.g. Siloxane-based materials, for example from cross-linked polydimethylsiloxane or related polyalkylsiloxanes or related polyarylsiloxanes. Also suitable are crosslinkable Polyurethanes or fluoroelastomers. Likewise, sulfur-crosslinked elastomers based on butadiene and isoprene and acrylonitrile suitable.

The Color filter layer is preferably for a wavelength range permeable between 1 nm and 30 nm educated. Outside this wavelength range is the transmission of the color filter layer less than 10%.

alternative the absorption of the color filter layer can be selected broadband, wherein the color matching by the resonance of the resulting interference filter done, in turn, by electrically controlled layer thickness change can be influenced.

The first partially reflective layer is preferably made of silver, Aluminum, chrome or gold.

The prior art does not disclose an elastomer-based electrostrictive display element based on interference as a coloring mechanism. The use of elastomers represents a significant advance over that of Iridigm Display Corporation ( US 6650455 ) presented concept of an interference display, in which two parallel arranged fully reflective or partially reflective layers lead to interference of coupled light. In this case, the distance of the layers by an electrostatically controlled micromechanics is variable. However, the manufacturing cost of the required (spring) structures and freestanding reflector layers is large. In contrast, the use of a transparent elastomer is an easy-to-use, robust technology that can be realized with significantly reduced process cost.

• – Einkoppeln von Umgebungslicht über eine erste teilweise reflektive Schicht, wobei ein Teil des Umgebungslichts reflektiert und damit nicht eingekoppelt wird,
• – Reflexion des eingekoppelten Lichts an einer zweiten reflektiven Schicht, wobei das an der zweiten reflektiven Schicht reflektierte Licht zumindest teilweise die erste teilweise reflektive Schicht eines zweites Mal passiert und mit dem an der ersten teilweise reflektiven Schicht reflektierten Teil des Umgebungslichts interferiert.

The method according to the invention for producing light of a predetermined wavelength range is characterized by the following method steps:

• Coupling in ambient light over a first partially reflective layer, whereby a part of the ambient light is reflected and thus not coupled in,
• Reflection of the coupled-in light at a second reflective layer, wherein the light reflected at the second reflective layer at least partially passes the first partially reflective layer a second time and interferes with the part of the ambient light reflected at the first partially reflective layer.

Preferably becomes a part of the injected light by means of a color filter layer filtered. Preferably, the second reflective layer is on an elastomeric layer arranged and to the elastomer layer to change its thickness in spatially periodic intervals an electric field is applied, i. the elastomer layer is spatially deformed periodically.

The Invention will be described below with reference to FIGS Embodiments explained in more detail. It demonstrate:

1 a display according to the invention with a continuous first contact layer in a schematic, sectional representation;

2a and 2 B : the schematic representation of the operation of the display element after 1 without applied electric field ( 2a ) and with an applied electric field ( 2 B ) between the contact layers;

3 a display element according to the invention with a periodically structured first contact layer in a schematic, sectional view and

4a and 4b : the operation of the display element after 3 without concern of an electric field ( 4a ) and with an applied electric field ( 4b ).

1 shows an inventive elastomer-based display element in a schematic, sectional view. On the transparent substrate 1 is a partially reflective layer 2 arranged in silver. On the partially reflective layer 2 is a color filter layer 3 arranged from a pigment dispersion. For example, a dispersion of copper phthalocyanine in a thermally or by means of light-crosslinkable acrylate matrix is suitable. On the color filter layer 3 is a transparent buffer layer 4 made of a flexible material.

When Material for the buffer layer becomes chemically cross-linked poly-dimethylsiloxane used, with a typical elastic modulus in the range 10-100 MPa and a layer thickness in the range of 1-20 mm.

On the buffer layer 4 a first electrical contact layer of polyethylenedioxythiophene is arranged, on which the elastomeric layer 6 of physically crosslinking block copolymer poly (co-isoprene-styrene) is arranged. The elastomer is brought by solution of the plasticizer squalane in solution to an elastic modulus in the range 0.5-10 MPa. On the elastomer layer 6 is a second contact layer 7 arranged in silver. The elastomer layer used 6 is for the ambient light 8th transparent. The ambient light 8th is on the light entrance side (over the substrate 1 ) are coupled into the structure according to the invention, wherein at the partially reflective layer 2 a part of the ambient light 8th reflected and another part transmits, that is coupled into the structure of the invention. The ambient light coupled into the structure becomes the reflective contact 7 in turn reflects and passes through the semipermeable layer a second time (at least a portion of this light) 2 therethrough. Due to the interference of the two partial waves (first partial wave that is at the layer 2 reflected ambient light 8th and the second part wave is that at the layer 2 twice transmitted light) certain wavelengths are amplified while other wavelengths are attenuated by destructive interference. Which wavelengths are amplified and which ones are weakened depends on the optical path length through which the layers pass 2 to 7 shaped cavity from. The thickness of the elastomer layer 6 can by applying a voltage between the contacts 5 and 7 varies, that is reduced. According to the applied voltage, a viewer sees the interference light 9 in a wavelength dependent on the applied voltage.

By introducing the elastic, flexible buffer layer 4 can the necessary drive voltage of the device can be greatly reduced because a lower compression force 10 , please refer 2 B , for deformation of the elastomer layer 6 is necessary because the lateral extent of the elastomer layer 6 and the first contact layer 5 through the flexible buffer layer 4 relieved, ie improved. This can (due to the good lateral mobility of the layers 5 and 6 ) the optical path length of the (through the layers 2 to 7 ) trained resonator already with a low electric field, that is to be varied with low control voltages. By the arrangement of the color filter layer 3 In addition, the contrast and the color saturation is improved. Furthermore, angle-dependent color shifts can be minimized.

In the 1 . 3 and 4 is the layer 2 represented by two (drawn) layers. Basically, the layer 2 consist of one layer, but also of several layers, for example of two layers. Insofar, with reference to the layer 2 always the whole of the layer 2 to understand training layers.

3 shows the display element according to the invention according to a second embodiment of the invention with a periodically structured first contact layer 5 , The structure otherwise resembles the display element according to 1 , In contrast to 1 is the contact layer 5 however, not formed continuously, but periodically structured so that the electric field between the contact layers 5 and 7 only in a few, periodically spaced areas in the elastomeric layer 6 is produced. This spatially periodic electric field also leads to a spatially periodic deformation of the elastomer layer 6 and the reflective contact layer disposed thereon 7 , By the local change of the layer thickness of the layer 6 the interference conditions during the application of the electric field ( 4b ) is changed depending on the spatial position, so that the color of the light leaving the display element, as perceived by a viewer, can be controlled by the electric field (as opposed to 4a where no electric field is applied). This also makes it possible to achieve an efficient and energy-saving control of the display element according to the invention.

The layer 5 can be patterned by photolithography, screen printing, ink jet printing, vacuum evaporation of metals or by means of a shadow mask. With a pixel width of 500 .mu.m, at least 10, preferably 20 periods should be present, ie structure sizes in the range 50-20 .mu.m should be generated.

1

substratum

2

first partially reflective layer

3

Color filter layer

4

buffer layer

5

first electrical contact layer

6

elastomer layer

7

second electrical contact layer

8th

ambient light

9

interference light

10

electrostrictive compressive force

Claims (19)

Display element comprising: a first partially reflective layer ( 2 ), a first translucent electrical contact layer ( 5 ), wherein the first contact layer ( 5 ) is at least partially translucent, an elastomeric layer ( 6 ), a second electrical contact layer ( 7 ), wherein the second contact layer ( 7 ) is reflective or the display element has an additional reflective layer and wherein the elastomer layer ( 6 ) between the first contact layer ( 5 ) and second contact layer ( 7 ) and between the first reflective layer ( 2 ) and second contact layer ( 7 ) or the additional reflective layer is arranged. Display element according to claim 1, characterized in that between the first contact layer ( 5 ) and the first partially reflective layer ( 2 ) an at least partially transparent buffer layer ( 4 ) of a flexible material and / or a color filter layer ( 3 ), or that the first contact layer ( 5 ) is periodically structured. Display element according to Claim 1 or 2, characterized in that the first partially reflective layer ( 2 ) on a substrate ( 1 ) is arranged. Display element according to one of the preceding claims, characterized in that the color filter layer ( 3 ) consists of a pigment dispersion. Display element according to claim 4, characterized in that the color filter layer ( 3 ) has a thickness between 20 nm and 200 nm. Display element according to one of the preceding claims, characterized in that the first contact layer ( 5 ) consists of Polyethylendioxythiophen. Display element according to one of the preceding claims, characterized in that the elastomer layer ( 6 ) of siloxane-based materia lien exists. Display element according to claim 7, characterized in that the elastomer layer ( 6 ) consists of cross-linked poly (dimethylsiloxane) or related polyalkylsiloxane or related polyarylsiloxane. Display element according to one of claims 1 to 6, characterized in that the elastomer layer ( 6 ) consists of cross-linkable polyurethane or fluoroelastomer. Display element according to one of the preceding claims, characterized in that the first contact layer ( 5 ) is formed lattice-shaped. Display element according to claim 10, characterized in that the grating period of the first contact layer ( 5 ) is between 1 .mu.m and 200 .mu.m. Display element according to one of the preceding claims, characterized in that the buffer layer ( 4 ) consists of chemically crosslinked elastomers. Display element according to claim 12, characterized in that the buffer layer ( 4 ) consists of siloxane-based materials, crosslinkable polyurethane, a fluoroelastomer or sulfur-crosslinked elastomer based on butadiene. Display element according to claim 13, characterized in that the buffer layer ( 4 ) consists of cross-linked polydimethylsiloxane, related polyalkylsiloxanes, related polyarylsiloxanes, isoprene or acrylonitrile. Display element according to one of the preceding claims, characterized in that the color filter layer ( 3 ) is permeable to a wavelength range between 1 nm and 30 nm. Display element according to one of the preceding claims, characterized in that the first partially reflective layer ( 2 ) consists of silver, aluminum, chromium or gold. Method for producing light of a predetermined wavelength range, comprising the following method steps: - coupling in ambient light ( 8th ) over a first partially reflective layer ( 2 ), whereby a part of the ambient light ( 8th ) is reflected and thus not coupled in, and - reflection of the coupled-in light at a second reflective layer ( 7 ), wherein the at the second reflective layer ( 7 ) reflected light at least partially the first partially reflective layer ( 2 ) a second time and with the first partially reflective layer ( 2 ) reflected part of the ambient light ( 8th ) interferes. A method according to claim 17, characterized in that a part of the injected light by means of a color filter layer ( 3 ) or the second reflective layer ( 7 ) is spatially periodically deformed to form a reflection grating. A method according to claim 17, characterized in that the second reflective layer ( 7 ) on an elastomer layer ( 6 ) and to the elastomer layer ( 6 ) is applied to change its thickness in spatially periodic distances an electric field.