EP1913438A1

EP1913438A1 - Method for producing an electrochromic display

Info

Publication number: EP1913438A1
Application number: EP06792700A
Authority: EP
Inventors: Christoph Brabec; Jens Hauch
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2005-08-08
Filing date: 2006-08-04
Publication date: 2008-04-23
Also published as: WO2007017472A1; US7898728B2; US20100157409A1

Abstract

The invention relates to a method for producing electrochromic displays (1, 10), according to which the functional layers, such as the electrodes (3, 4, 6) and electrochromic layer (5) are configured in a printing process. Said method enables a particularly cost-effective and flexible production of the display.

Description

description

Method for producing an electrochromic display

The present invention relates to a manufacturing method for electrochromic displays with a plurality of functional layers.

Electrochromic displays are usually formed by a system of multiple functional layers. The actual electrochromic or coloring layer may consist of three layers, for example, an ion storage and ion sputtering layer, an electrolyte layer and a layer with the actual electrochromic material.

As electrochromic materials, for example, PEDOTrPSS (poly (3,4-ethylenedioxythiophene)) with PSS (polystyrene sulfonate) as a counterion or PANI (polyaniline) are known, which discolor as a result of oxidation or reduction. A controlled reduction or oxidation takes place in electrochromic displays by applying a voltage which drops across the electrochromic and ion storage layer. Therefore, two electrode layers are to be provided, between which the color system with the electrochromic layer and the ion storage / dispenser and electrolyte is provided. In the recent past, materials have also been developed which combine the functions of the electrolyte and paint system in a single electrochromic layer.

Nevertheless, the production of an electrochromic display requires at least the production of three superimposed layers. At least one of the electrode layers must also have a transparency of at least about 80% in the visible spectrum so that the color change of the electrochromic layer upon application of voltages is visible, thus providing a useful display form. As a suitable material has indium tin oxide (ITO = indium tin oxide) proved, which is semiconductive and transparent. By doping a sufficient conductivity is achieved. A transparent electrode layer is then formed by sputtering ITO mixed oxide on glass or clear, transparent film. This transparent, used as a viewing electrode layer is then covered by other methods with the electrochromic layer and a second electrode. In the production of the various functional layers, it is particularly unfavorable to combine different processing techniques, such as, for example, sputtering the ITO layer with printing or adhesive processes, because in this way the production flow is interrupted.

It is therefore an object of the present invention to provide a simple, uniform production method for electrochromic displays.

This object is achieved by the production method with the method steps according to claim 1 and the electrochromic display with the features of claim 12.

Accordingly, the following process steps are provided for the production of an electrochromic display:

a) applying a first fluid with conductive particles to a substrate by means of a printing process for forming a first electrode layer;

b) applying a second fluid having an electrochromic material on the first electrode layer by means of a printing process for forming an electrochromic layer;

c) applying a third fluid with conductive particles to the electrochromic layer by means of a printing process for forming a second electrode layer. An electrochromic display according to the invention thus has a substrate, a printed semitransparent viewing electrode layer, a printed electrochromic layer and a printed electrode layer, the layers being arranged on top of each other.

According to the invention, all functional layers are formed by means of printing technology. This results in usually very flexible substrates a very cost-effective production of electrochromic displays. The simple structuring of the various layers by printing processes enables production from roll to roll and thus can serve the production of "electronic paper".

Preferably, the first and / or third fluid indium-tin oxide in a transparent suspending agent or a conductive polymer such as PEDOT or PANI. The first or third fluid preferably has silver or gold particles. In a preferred embodiment, a further electrode layer, which preferably has carbon particles, is printed between the electrochromic layer and the first and / or second electrode layer. Preferably, the substrate is transparent or partially transparent. It is then desired a transparency such that color changes in the electrochromic layer through the substrate are perceptible. The fluids are preferably carried out as a suspension or solution.

Screen printing, offset printing or gravure printing methods for forming the functional layers are preferably used as the printing method.

In particularly preferred embodiments of the invention, after at least one of the steps of applying by means of a printing process, a method step for curing the respective formed layer by evaporation, heat radiation, UV light irradiation or a chemical reaction. Preferably, a fluid then comprises crosslinkable polymers which crosslink by UV irradiation and form a printable layer.

The electrode layers preferably have a thickness of between 1 μm and 10 μm, and the electrochromic layer preferably has a thickness of between 10 μm and 200 μm.

Further advantageous embodiments and development of the invention are the subject of the dependent claims and the further description with reference to the figure.

In the following preferred embodiments of the invention are explained in detail. FIG. 1 shows an electrochromic display produced according to the invention.

FIG. 1 (A) shows a completely printed electrochromic display 1. On a substrate 2, which comprises, for example, PET (polyethylene terephthalate), a first electrode 3 made of a silver screen-printing paste is printed on which after drying a second screen printing paste comprising carbon nanoparticles is printed, which forms a second electrode layer 4.

An electrochromic material is printed onto the second electrode layer 4, for example by screen printing, in order to form the electrochromic layer 5. For example, Dow Chemicals offers a screen-printable electrochromic dye under the brand name READ. These READ paints have ion-conducting polymers in which a redox

Group and a dye are coupled directly to an electrolyte molecule.

Printed on the electrochromic layer 5 is a semitransparent viewing electrode 6, wherein, for example, a corresponding screen printing paste has a transparent suspending agent and indium tin oxide particles. This semi-trans- Parente Sichtelektrode 6 Finally, a sealing layer 7 is printed.

By applying a voltage between the silver electrode layer 3 and the transparent viewing electrode 6, the oxidation in the electrochromic material of the electrochromic layer 5 is controlled and the optical properties of this layer arrangement are changed. The carbon electrode layer 4 essentially serves to protect the silver in the first electrode layer 3 from chemical reactions with the electrochromic layer 5.

Preference is given to the printing pastes for successive printing operations, ie directly adjacent, functional layers, orthogonal suspension or solvent used. Thus, for example, the silver printing paste used for the first electrode layer 3 may comprise a polar suspending agent, while the following carbon printing paste for the second electrode layer 4 is based on nonpolar suspending agents. The materials of the printing pastes are chosen such that in the dried state, a sufficiently high mechanical strength occurs to print another functional layer. In order to further increase the production rate of a display according to the invention, it is also possible to use solvents or suspending agents which solidify as a result of UV irradiation. By way of example, materials may be mentioned here which contain mono- and / or polymers and suitable photoinitiators. Polymerization is then started by UV irradiation. Compared to conventional drying Allowing the printed layer can thus achieve an accelerated sequence of process steps.

The electrochromic display 1 shown in FIG. 1 (A) has a clear seal 7, so that a nontransparent substrate 2 can be used. FIG. 1 (B) shows an electrochromic display 10 which has an alternative sequence of the functional layers 3-7.

First, a semipermeable or transparent substrate 8 is provided on which a suspension with ITO is printed. After drying, a transparent or semitransparent electrode layer 6 is thus created, which serves as a viewing electrode. Then, in turn, a suspension with electrochromic material, for example READ material, is printed on. On this electrochromic layer 5, a carbon screen-printing paste is optionally printed by screen printing in structured form. A suspension with, for example, silver or gold nanoparticles is then printed onto this carbon electrode 4 in order to obtain a particularly high conductivity of this second electrode layer 3.

Finally, the layer sequence of transparent electrode layer 6, electrochromic layer 5, carbon electrode layer 4, and silver or gold electrode layer 3 is sealed with a suitable material 7. This can be done for example by lamination with a plastic or by another printing process.

The process according to the invention for the production of these electrochromic displays 1, 10 shown here by way of example is based exclusively on printing processes. Therefore, a particularly simple structuring of the functional layers 3-6 is possible. Furthermore, the application of all layers by means of printing technology processes, such as screen printing, gravure printing, offset printing or flexographic printing, enables the processing of large-area electrochromic displays from roll to roll in a printing process.

With a thickness of the electrode layers of about 10 μm and a thickness of the electrochromic layer of 50 μm, the result is as well the substrate thickness and the seal a flexible electrochromic display assembly.

The indium tin oxide suspension mentioned here for printing the transparent electrolyte layer is only to be understood as an example. In particular, conductive polymers such as PEDOT or PANI can be applied to the corresponding electrochromic layer as a transparent electrode layer.

Claims

claims

1. Method for producing an electrochromic display (1, 10) with the method steps:

a) applying a first fluid with conductive particles to a substrate by means of a printing process for forming a first electrode layer (3, 6);

b) applying a second fluid having an electrochromic material on the first electrode layer (3, 6) by means of a printing process for forming an electrochromic layer (5); and

c) applying a third fluid with conductive particles to the electrochromic layer (5) by means of a printing process for forming a second electrode layer (6, 3).

2. The method according to claim 1, characterized in that at least one of the fluids has a suspension or solution.

3. The method according to any one of claims 1 or 2, characterized in that the first and / or third fluid indium tin oxide in a transparent or semitransparent suspension medium.

4. The method according to at least one of claims 1-3, characterized in that the first and / or third fluid silver and / or gold particles.

5. The method according to at least one of claims 1-4, characterized in that the first and / or third fluid comprises a conductive polymer, in particular PEDOT or PANI.

6. The method according to at least one of claims 1-5, characterized in that before and / or after the application of the second fluid at least one further electrode layer (4) is printed, wherein the first and / or second electrode layer (4) a has higher conductivity than the further electrode layer (3).

7. The method according to claim 6, characterized in that the further electrode layer (4) comprises carbon particles.

8th . Method according to at least one of claims 1 - 7, characterized in that the printing methods are screen printing, offset printing and / or gravure printing methods.

9. The method according to at least one of claims 1-8, characterized in that after at least one of the steps of applying by means of a printing process, a step of curing the respective layer formed by evaporation, heat radiation, UV light irradiation or a chemical reaction takes place.

10. The method according to claim 9, characterized in that at least one fluid has crosslinkable polymers which crosslink by UV irradiation and form a printable layer.

11. The method according to at least one of claims 1 - 10, characterized in that the display (1, 10) is sealed with a sealing layer (7).

12. An electrochromic display (1, 10) comprising a substrate (2, 8), a printed semi-transparent viewing electrode layer (6), a printed electrochromic layer (5) and a printed electrode layer (3), the layers being arranged one on top of the other.

13. An electrochromic display according to claim 12, characterized in that a further printed electrode layer (4) is provided, which has a lower conductivity than the first and / or second electrode layer (3, 6).

14. An electrochromic display or method according to any one of claims 1-13, characterized in that the substrate (8) is transparent or partially transparent.

15. An electrochromic display or method according to any one of claims 1-14, characterized in that the electrode layers (3, 4, 6) each have a thickness in a range between lμm and lOμm, preferably about 5μm.

16. An electrochromic display or method according to any one of claims 1-15, characterized in that the electrochromic layer (5) has a thickness in a range between lOμm and 200μm, preferably about 50μm.