WO1998014824A1

WO1998014824A1 - Electrochromic mirror and method for producing an electrochromic mirror

Info

Publication number: WO1998014824A1
Application number: PCT/DE1997/002241
Authority: WO
Inventors: Michael Rissmann; Thomas Paul
Original assignee: Flachglas Aktiengesellschaft
Priority date: 1996-10-01
Filing date: 1997-09-30
Publication date: 1998-04-09
Also published as: DE19640515A1; AU4771397A

Abstract

The invention relates to an electrochromic mirror consisting of at least the following solid thin films: A transparent support, especially a glass support; a transparent electrode layer; an ion storage layer; a transparent ion conducting layer made of inorganic material; a cathodic electrochromic layer; and a reflecting layer, in which the ions effecting the coloring/decoloring process are protons (H+). The invention is characterized by the fact that the ion storage layer consists either of (Ce¿x?Tiy) Oz; wherein x = 0.3 to 0.7; y = 0.7 to 0.3 and z ≈ 1.5 to 2, or of (NixMey) Oz, wherein Me is a transition metal chosen from Ti, V, Cr., MN, Fe, CO, and x = 0.95 to 0.60, y = 0.05 to 0.40 and z is set according to the value of Ni and that of the transition metal Me. A method for producing an electrochromic mirror is also disclosed.

Description

Electrochromic mirror and method for producing an electrochromic mirror

description

The invention relates to an electrochromic mirror, consisting of at least the following solid thin layers: a transparent support, in particular a glass support; a transparent electrode layer; an ion storage layer; a transparent ion conducting layer made of an inorganic material; a cathodic electrochromic layer and a reflection layer, the ions causing the coloring / decoloring process being protons (H ⁺ ). The order of the ion storage layer and the cathodic electrochromic layer is interchangeable. The ion storage layer can act as a pure storage layer without any noteworthy coloring when the ions are stored or extracted. However, it can also be an anodically coloring electro-chrome layer. It is understood that further auxiliary layers for modifying the optical or electrical properties, adhesive layers, etc., as are known to the person skilled in the art, can be present. It is understood that contact must be made to complete the mirror. For improved durability, an edge seal and a flat protective coating should be provided on the reflective layer. The term "solid thin layers" encompasses thin layers applied by chemical or physical coating processes in the solid state.

Generic electrochromic mirrors are known for example from EP 356 099 B1. WO _x (x 3) is generally used for the cathodically coloring layer. The inorganic ion-conducting layer is electronically insulating, but has good conductivity for the ions causing the coloring or decolorization process. Such ions are in particular lithium ions (Li ⁺ ) and protons (H ⁺ ). In addition to other inorganic materials, silicon dioxide (Si0 ₂ ) has proven to be particularly suitable for ion-conducting layers in the solid materials. The reflection layer typically consists of aluminum, but other metals such as gold or silver are also mentioned. The electrical connections are made to the reflection layer and to the transparent electrode layer. It is proposed, inter alia, in JP-A 61-241 733 to use the oxide or hydroxide of a transition metal, for example Ir, Ni, Cr, V, Ru, Rh, as the material for the ion storage layer. Such layers are particularly intended to achieve a high response speed and desired side reactions can be prevented. US Pat. No. 4,878,743 also recognizes the transition metals as advantageous and preferably Cr ₂ 0 ₃ , NiO or Ir0 ₂ as anodically coloring materials. The electrochromic elements described there are used as rear-view mirrors for motor vehicles.

Another electrochromic element having a different functional principle is disclosed in US Pat. No. 5,111,328. Here lithium ions are used as the ions mediating the transitions between the states of the electrochromic element. A cerium-titanium mixed oxide is used in an ion storage layer for lithium ions, the transparency of which does not change appreciably when filled with these ions.

An electrochromic element that can be used for various types of dimmers and displays is disclosed in US-A 4,664,934. Cr ₂ 0 ₃ , IrO, NiO _x and RhO are again mentioned as typical materials for the anodically coloring layer, and elemental nickel.

Another class of electrochromic elements uses liquid, gel-like or polymeric ion conducting layers. In particular, WO 91/02282 discloses an electrochromic element which works with an ion storage layer based on cerium oxide. The cerium atoms are partially replaced by those with a smaller ion radius, for example titanium atoms, tin atoms and germanium atoms, which is intended to improve the diffusion kinematics of the lithium ions used exclusively there. As an example, (Ce ₀₅ Ti ₀₅ ) O _{2 is} given. In preferred embodiments, a further element is used as an additive, for example niobium or tantalum, which is intended to increase the electronic line by inducing valences. W0 ₃ , Mo0 ₃ , Ti0 ₂ and others can be used as the cathodically coloring layer Connections are used. The transparent electrode layer consists, for example, of tin-doped In ₂ 0 ₃ or fluorine-doped Sn0 ₂ or ZnO. Sputtering or vacuum evaporation from the corresponding oxide is specified as a suitable method for producing the ion storage layer. A similar system, also working with lithium ions, with a (Ce _x Ti _y ) O _z layer is known from DE 41 16 059 AI. Electrochromic mirrors working with polymer-based ion guide layers are complex to manufacture and often not sufficiently UV-resistant.

If an electrochromic element is to be used for mirrors, which are used in particular as glare-free rear-view mirrors in motor vehicles, it must be able to change its reflectivity quickly and uniformly over its surface in order to be able to offer the desired protection against glare from headlights of other vehicles with otherwise high light reflection . The reflection stroke, namely the difference between the reflection maximum and the reflection minimum, should be as high as possible. The mirror must survive a large number of switching cycles and function properly in a wide temperature range and for many years. In addition, it should be possible to manufacture it as inexpensively as possible.

It is the object of the present invention to provide an electrochromic mirror which is optimized for use as a rear-view mirror in motor vehicles.

This object is achieved by an electrochromic mirror according to claim 1. A method for producing such a mirror is specified in claim 16.

According to the invention, in the case of an electrochromic mirror of the type mentioned in the introduction, it is provided that the anodic electro- chrome layer either consists of (Ce _x Ti _y ) O _z , where x = 0.3 to 0.7; y = 0.7 to 0.3; z = 1.5 to 2, or consists of (Ni _x Me _y ) O _z , where Me is at least one transition metal selected from Ti, V, Cr, Mn, Fe, Co and x = 0.95 to 0.60, y = 0.05 to 0.40 and z is set depending on the valence of Ni and that of the transition metal Me.

Surprisingly, the layer structure according to the invention can be used to produce an electrochromic mirror which can be switched sufficiently quickly, which does not require any expensive preconditioning or doping with ions, and which has a high reflection stroke. The mirror according to the invention can be produced inexpensively by means of magnetron sputtering. The protons causing the system's switching ability are built into the layer system in the course of the coating, so that a functional electrochromic mirror is available immediately after manufacture and after a few start switching cycles.

Vanadium and / or chromium are preferably used as the alloy material, that is to say as component Me in the material for the ion storage layer made of (Ni _x Me _y ) O _z . The Ni-Me mixed oxides according to the invention are distinguished from the unalloyed nickel oxide by a higher stability of the mirror, a more homogeneous coloring and a higher storage capacity than would be expected with an arithmetic averaging of the corresponding values of the individual oxides. _In addition, they are much easier to produce than NiO using magnetron cathode reinforcement.

The proportion of vanadium is advantageously set so that 0.05 < _. y <_ 0.35 and preferably y is approximately 0.07. If chromium is used, its proportion should be set so that 0.10 <_ y <_ 0.30 and preferably y is approximately 0.20. The thickness of the ion storage layer is preferably approximately 40 to 300 nm, the layer consisting of (Ce _x Ti _y ) O _z having a thickness of approximately 100 to 300 nm and the layer consisting of (Ni _x Me _y ) O _z having a thickness of approximately 40 to 150 nm.

For the cathodic electrochromic layer, WO _x or MoO _x with x = 3 or TiO _x with x ~ 2 have proven effective.

The cathodic electrochromic layer of W0 _X can typically be 50 to 250 nm, preferably about 110 nm thick.

It is preferred that the transparent electrode layer consists of a transparent metal oxide, in particular of fluorine-doped tin oxide or ITO, and is produced in such a way that a surface resistance of at most 20 ohms is achieved.

It is particularly preferred that the transparent ion conducting layer consists of silicon oxide, silicon nitride, tantalum oxide, aluminum oxide, zirconium oxide, titanium oxide and / or magnesium fluoride. It is within the scope of the invention to use mixtures of these materials instead of a single-layer homogeneous layer made of one of the specified materials, or to construct the ion-conducting layer in multiple layers from these materials or their mixtures.

Silicon nitride has the advantage of a higher refractive index than silicon oxide, which avoids or at least reduces disruptive interference effects.

The transparent ion-conducting layer should have a thickness of approximately 150 to 450 nm and should be produced as error-free as possible to reduce leakage currents.

It is further preferred that the reflection layer made of aluminum or an aluminum alloy. Although silver, gold and NiCr are fundamentally also suitable as materials for the reflection layer, tests have occasionally shown a slight deterioration in properties, in particular due to higher leakage currents, presumably due to a higher diffusion of metal atoms into the layer system. The best results were achieved with aluminum or high-aluminum alloys for the reflective layer. This should have a thickness of approximately 70 to 300 nm.

The mirror according to the invention is preferably coated by means of (magnetron) cathode sputtering (sputtering), it being advantageous to produce the transparent electrode layer in another way. A particular advantage of sputtering the ion storage layer according to the invention is that the required target materials are not ferromagnetic. It is therefore possible to work with conventional systems and with a high coating rate, which helps to reduce the production costs of the mirror.

A particularly preferred method for producing an electrochromic mirror of the construction described above has the following steps:

(a) applying a transparent electrode layer on a transparent support;

(b) applying the cathodic electrochromic layer or the ion storage layer to the transparent electrode layer by sputtering;

(c) applying a transparent ion-conducting layer made of inorganic material to the previously applied layer by sputtering, (d) applying the ion storage layer or the cathodic electrochromic layer to the transparent ion-conducting layer by sputtering;

(e) applying a reflective layer to the previous layer by sputtering;

(f) attaching electrical contacts to the transparent electrode layer and to the reflection layer,

wherein the residual gas during steps (b) to (d) contains water vapor with a partial pressure of 10 ^"6 to 10 ^{" 5} mbar and the process from step (b) to step (e) is carried out without ventilation.

At least four layers are thus applied in succession and without intermediate ventilation in a vacuum. The hydrogen from the residual gas, which is required for coloring, is built into the layer system. The mirror is surprisingly functional after coating and a few switching cycles with high voltages and does not need to be conditioned in a lengthy and complex manner.

The ion conducting layer made of SiO ₂ or the like is preferably produced by means of a double magnetron using the medium-frequency sputtering method if particularly low leakage currents are to be achieved. Layers produced in this way are surprisingly distinguished, despite their relatively high density, by a particularly high conductivity for protons with extremely low electronic conductivity.

A problem with most prior art mirrors is the high leakage current through the system, which is approximately 0.1 A per volt of applied voltage in the range of 1 V to 10 V. is what corresponds to 0.1 to 1 A current through the system. This problem can be caused by defects in the ion-conducting layer, for which Si0 _{2 is} generally used. In the system produced according to the invention, which preferably also uses silicon dioxide, but also silicon nitride or mixtures of the two as material for the ion-conducting layer, these leakage currents do not appear.

The electrical contact is made via the transparent electrode layer and the reflection layer. For example, a resilient contact strip encompassing the edge of the electrochromic mirror can be used for contacting. Other methods of contacting are possible.

The entire system is closed, as is known per se, by a protective coating, e.g. a protective varnish, and an edge seal against environmental influences.

The invention will be explained in more detail below with reference to the accompanying drawing. The drawing figure shows a schematic, perspective view of the basic structure of an electrochromic mirror according to the invention.

A transparent electrode layer 12, which consists of indium tin oxide, tin oxide doped with fluorine or the like, is applied to a transparent carrier 10, usually a glass carrier. This transparent electrode layer 12 is connected to an electrical contact strip 24 which extends along one of the sides of the mirror on the transparent electrode layer 12. The layers 14 and 18 are the two electrochromic functional layers of the electrochromic mirror. The layer 18 consists of a cathodically coloring material, for example WO _x , MoO _x , TiO _x or mixtures thereof. Layers 14 and 18 are through a transparent ion conducting layer 16 is separated, which preferably consists of silicon oxide and / or silicon nitride or the like. This transparent ion-conducting layer 16 is not electronically conductive, but shows a low resistance for protons, which serve as charge carriers in the dyeing / decolorization process. The ion storage layer 14, which may be anodically electrochromic or non-coloring, consists of one of the cerium-titanium or nickel-transition metal (Me) mixed oxides according to the invention; a reflection layer 20 is applied to it, which preferably consists of aluminum. This reflection layer 20 also carries the second of the electrical contacts 26, which again extends over a long side of the electrochromic mirror, diametrically opposite the first electrical contact 24.

This electrochromic mirror is produced according to a preferred method as follows:

The transparent electrode layer 12 is first applied to a glass carrier 10, for example by pyrolysis, hydrolysis, sol-gel technology, sputtering or other customary coating processes. The ion storage layer 14 is applied to the glass substrate coated in such a conductive manner under vacuum by means of magnetron sputtering, then the transparent ion conducting layer 16, the cathodic electrochromic layer 18 and the reflection layer 20, without venting between the individual application steps. Finally, the system is provided with contacts and a protective coating made of a suitable paint.

It is within the scope of the invention to interchange the order of the layers 14 and 18, that is to say to apply the cathodic electrochromic layer 18 as the first layer to the transparent electrode layer and the ion storage layer 14 in the Connection to the ion conducting layer 16.

When choosing the layer thicknesses for the Ce-Ti system or for the Ni-Me system, three important boundary conditions must be met:

1. The ion storage layer and the cathodic electrochromic layer must have a sufficient thickness in order to achieve the desired reflection stroke.

2. The layer thicknesses of the cathodic electrochromic layer, the ion storage layer, the transparent ion-conducting layer and the transparent electrode layer must be coordinated with one another in such a way that the highest possible reflection can be achieved in the decolored state. Interference effects can be used for this.

3. The thicknesses of the ion storage layer and the cathodic electrochromic layer must be matched to one another, so that they have appropriate capacities to accommodate the protons which effect the coloring / decolorization process.

Taking into account the conditions mentioned, the following layer thicknesses have proven to be advantageous:

(Ni _x Me _y ) O _z : 40 to 150 nm

SiO _x : 200 to 450 nm

W0 _X : 50 to 75 nm

AI: 100 to 200 nm

respectively. (Ce _x Ti _y ) O _z : 100 to 300 nm

SiO _x : 200 to 450 nm

WO _x : 100 to 200 nm

AI: 100 to 200 nm

Examples

For the examples described below, glass was used as the support, coated with ITO as the electrode layer, the surface resistance of which was 10 ohms. The dimensions of the carrier were 10 cm x 10 cm or 20 cm x 5 cm. The substrate thus obtained was cleaned in an ultrasonic bath. An edge strip for later contacting the ITO layer (after the coating) was masked with vacuum-compatible adhesive tape. The substrate was then fed to the coating process by magnetron sputtering. The coating system was evacuated so that a water vapor partial pressure of 10 ⁶ - 10 ⁵ mbar was established.

Example 1 (Ce Ti O, system)

A Ce (50) Ti (50) alloy was used as the target for the sputtering process to apply a (Ce ₀₅ Ti ₀₅ ) O _z layer (z <1.75) as the ion storage layer 14. Argon was set at a flow of 300 ml / min as sputter gas and oxygen at a flow of 33 ml / min as reactive gas. The cathode current was set to I = 15.2 A at a cathode voltage of U = 330 V. A (Ce ₀₅ Ti ₀₅ ) O _z layer with a thickness of 125 nm was produced.

An Si0 ₂ layer was then applied to the (Ce ₀₅ Ti ₀₅ ) O _z layer as a transparent ion-conducting layer 16. The targets of the double cathode operated with medium frequency consisted of silicon. Argon was used as sputtering gas with Flow of 380 ml / min, oxygen set as a reactive gas with a flow of 47 ml / min. The cathode current was set to I = 8 A at a cathode voltage of U = 750 V. An Si0 ₂ layer with a thickness of 220 nm was produced.

Tungsten was used as a target for the sputtering process to apply a W0 ₃ layer as the cathodic electrochromic layer 18. Argon was set at a flow of 190 ml / min as sputtering gas and oxygen at a flow of 200 ml / min as reactive gas. The cathode current was set to I = 8 A at a cathode voltage of U = 666 V. A W0 ₃ layer with a thickness of 110 nm was produced.

Finally, a reflection layer 20 with aluminum as a target was applied. Argon was set as the sputtering gas at a flow of 60 ml / min. The cathode current was set to I = 6 A at a cathode voltage of U = 527 V. An aluminum layer with a thickness of 200 nm was produced.

After removing the masking tape from the ITO layer, contact springs were clamped onto the ITO layer and the aluminum layer. After contacting, the electrochromic reflective layer system was switched with different voltages. Its reflection and switching time were measured.

Switching voltage reflection change switching time (s) (V) (stroke) for 90% stroke

5 64% to 12% 9

(light-dark)

-5 12% to 64% 9

(dark bright) Example 2 (NiXr O.-Systeml

To apply a (Ni _{0 8} Cr ₀₂ ) O _z layer as the ion storage layer 14, a Ni (80) Cr (20) alloy was used as the target for the sputtering process. An argon-hydrogen mixture of 90% by volume argon and 10% by volume hydrogen (H ₂ ) and with a flow of 200 ml / min was set as sputtering gas, and oxygen as a reactive gas with a flow of 120 ml / min. The cathode current was set to I = 10 A at a cathode voltage of U = 427 V. A (Ni _{0 8} Cr _{0 2} ) O _z layer with a thickness of 100 nm was produced.

A Si0 were then incubated with the process parameters as in Example 1 on the _z (Ni Cr _{0 8} _{0 2)} O layer ₂ layer of 220 nm thickness, a W0 ₃ - layer 50 nm thick and a Alumini ^¬ umschicht with 100 nm Thickness generated.

Contact was also made according to Example 1.

The following results were achieved with the layer system:

5 65% to 15% 11

(light-dark)

-5 15% to 65% 10

(dark bright)

Example 3 [(Ni „V _y ) 0, system]

The cathodic electrochromic layer 18 was first applied to the substrate, specifically a WO ₃ layer with a thickness of 50 nm. The process parameters corresponded to those of the Example 1. Then, again according to example 1, an SiO ₂ layer with a thickness of 225 nm was produced.

To apply a (Ni _{0 93} V _{0 07} ) O _z layer as the ion storage layer 14, a Ni (93) V (7) alloy was used as the target for the sputtering process. An argon-hydrogen mixture of 90% by volume argon and 10% by volume hydrogen (H ₂ ) and with a flow of 200 ml / min was set as the sputter gas, and oxygen as the reactive gas with a flow of 100 ml / min. The cathode current was set to I = 10 A at a cathode voltage of U = 386 V. A (Ni _{0 93} Cr _{0 07} ) O _z layer with a thickness of 70 nm was produced.

Finally, using the process parameters from Example 1, an aluminum layer with a thickness of 100 nm was produced.

Contact was also made according to Example 1.

The following results were achieved with the layer system:

5 79% to 12% 11

(light-dark)

-5 12% to 79% 15

(dark bright)

The features of the invention disclosed in the above description, in the drawing and in the claims can be essential for realizing the invention both individually and in any combination.

Claims

claims

1. Electrochromic mirror, consisting of at least the following solid thin layers:

a transparent carrier (10), in particular a glass carrier; a transparent electrode layer (12); an ion storage layer (14); a transparent ion-conducting layer (16) made of an inorganic material; a cathodic electrochromic layer (18); and a reflective layer (20);

the ions causing the coloring / decoloring process are protons (H ⁺ ),

characterized in that the ion storage layer (14)

either consists of (Ce _x Ti _y ) O _z , where x = 0.3 to 0.7; y = 0.7 to 0.3; z = 1.5 - 2,

or consists of (Ni _x Me _y ) O _z , where Me is at least one transition metal selected from Ti, V, Cr, Mn, Fe, Co and x = 0.95 to 0.60, y = 0.05 to 0, 40 and z is set depending on the valence of Ni and that of the transition metal Me.

2. Electrochromic mirror according to claim 1, characterized in that the transition metal Me is chromium (Cr) and / or vanadium (V).

3. electrochromic mirror according to claim 2, characterized in that the proportion of vanadium is adjusted so that 0.05 <_ y <_ 0.35 and preferably y is approximately 0.07.

4. electrochromic mirror according to claim 2, characterized in that the proportion of chromium is set so that 0.10 <_ y <_ 0.30 and preferably y is approximately 0.20.

5. Electrochromic mirror according to one of the preceding claims, characterized in that the thickness of the ion storage layer (14) is approximately 40 to 300 nm.

6. electrochromic mirror according to claim 5, characterized in that the (Ce _x Ti _y ) O _z existing ion storage layer (14) has a thickness of about 100 to 300 nm.

7. Electrochromic mirror according to claim 5, characterized in that the (Ni _x Me _y ) O _z existing ion storage layer (14) has a thickness of approximately 40 to 150 nm.

8. Electrochromic mirror according to one of claims 1 to 7, characterized in that the cathodic electrochromic layer (18) consists of W0 _X or MoO _x with x «3 or TiO _x with x« 2.

9. electrochromic mirror according to claim 8, characterized in that the cathodic electrochromic layer (18) of WO _x 50 to 250 nm, preferably about 110 nm thick.

10. Electrochromic mirror according to one of the preceding claims, characterized in that the transparent electrode layer (12) consists of a transparent metal oxide, in particular of fluorine-doped tin oxide or of indium-tin oxide (ITO), and is made such that a sheet resistance of maximum 20 ohms is reached.

11. Electrochromic mirror according to one of the preceding claims, characterized in that the transparent ion-conducting layer (16) consists of silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, titanium oxide, aluminum oxide and / or magnesium fluoride.

12. Electrochromic mirror according to one of the preceding claims, characterized in that the transparent ion-conducting layer (16) has a thickness of 150 to 450 nm.

13. Electrochromic mirror according to one of the preceding claims, characterized in that the reflection layer

(20) consists of aluminum or an aluminum alloy.

14. Electrochromic mirror according to one of the preceding claims, characterized in that the reflection layer (20) has a thickness of approximately 70 to 300 nm.

15. Electrochromic mirror according to one of the preceding claims, characterized in that the ion storage layer (14), the transparent ion conducting layer (16), the cathodic electrochromic layer (18) and the reflection layer (20) are applied by means of magnetron sputtering.

16. A method for producing an electrochromic mirror according to one of the preceding claims, comprising the following steps:

(a) applying a transparent electrode layer (12) to a transparent carrier (10);

(b) applying the cathodic electrochromic layer (18) or the ion storage layer (14) to the transparent electrode layer (12) by sputtering;

(c) applying a transparent ion-conducting layer (16) made of inorganic material to the previously applied layer (14, 18) by sputtering,

(d) applying the ion storage layer (14) or the cathodic electrochromic layer (18) to the transparent ion conducting layer (16) by sputtering;

(e) applying a reflective layer (20) to the previous layer (14, 18) by sputtering; (f) attaching electrical contacts (24, 26) to the transparent electrode layer (12) and to the reflection layer (20),

wherein the residual gas during the steps (b) to (d) contains water vapor with a partial pressure of 10 ^"s to 10 ^{" 5} mbar and the process from step (b) to step (e) is carried out without aeration.

17. The method according to claim 16, characterized in that the ion conducting layer (16) is produced by means of double magnetron according to the medium frequency sputtering method.