CA1068950A

CA1068950A - Variable light transmissive electro-optical lenses

Info

Publication number: CA1068950A
Application number: CA261,172A
Authority: CA
Inventors: Robert H. Postal; Donald J. Berets
Original assignee: American Cyanamid Co
Current assignee: Wyeth Holdings LLC
Priority date: 1975-10-23
Filing date: 1976-09-14
Publication date: 1980-01-01
Also published as: DE2644528A1; IT1074718B; SE7611791L; GB1563929A; FR2328979A1; NL7611746A; FR2328979B1; BE847562A; BR7606988A; JPS5254455A; CH608623A5

Abstract

ABSTRACT OF THE DISCLOSURE
Disclosed is a variable light transmissive electro-optical device comprising an optical lens coated with a layer of solid persistent electrochromic material and an ion-conducting layer in contact with a pair of electrodes and a dc voltage source. The light absorption of the electrochromic material can be varied by application of an electrical field whereby the light transmitted through the optical lens can be regulated.

Description

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Background of the Invention The invention relates to electro-optical lenses whose electromagnetic radiation absorption characteristics can be selectively altered by influence of a suitably controlled electric field. In particular, the invention relates to electro-optical ophthalmic lenses whose light transmissive pxoperties can be varied by application of electricity.
In U.S. patent Nos. 3,521,941, 3,578,843, 3,704,057, 3,708,220 and 3,829,196, electro-optical devices are disclosed which exhibit a phenomenon termed in the art as persistent electrochromism. This phenomenon is characterized by the alteration of the electromagnetic radiation absorption characteristics of the persistent electrochromic material by the influence of an electric field. Such devices commonly are employed in sandwich arrangement, with a persistent electrochromic material layer and an ion-conducting layer sandwiched between two electrodes. Coloration is induced by charging the electro-chromic layer negative with respect to the counter-electrode, employing an external potential. The counter-electrode can be the same as the persistent electrochromic material or different. By reversing the original polarity of the field or by applying a new field, the visible coloratlon can be erased. This procedure of color induction and erasure is defined as cycling.
Prior methods for reducing light transmission through optical lenses employed as eyeglasses are capable of achieving desirable degrees of light reduction~ However, these sunglass lenses generally are not adjustable or variable with regard to their light transmissive properties.
Recent developments have produced what is known as a photo-6~39SI~
.
chromic lens which is self adJustable. A layer w~ithin the lens s-tructure is induced by electromagnetic radiation to alter its light absorption properties. An increasing degree of ambient brightness results in darker coloration o~ the lens, thereby reducing light transmission -through the lens. However, such a system suffers from several inherent disadvantages. Photochromic systems with fast switching speeds tend to be unstable, whereas the most stable systems tend to have slow switching speeds. In particular, erasure upon removing a photochromic ophthalmic lens from brlght light to relative darkness is quite slow. Application of photochromic lenses in eyewear specifically could prove hazardous if the -wearer suddenly passes from bright to dim light. A person stepping from bright sunlight into a building or a driver passing into a tunnel while wearing photochromic glasses would remain "in the dark" for many critical seconds. Also, since colorless photochromic systems can be activated only by a change in electromagnetic radiation in the W portion of the spectrum, the system is largely inoperative when the wearer is screened by a W
filter such as a glass window. The ligh-t-induced coloration of the lenses is entirely outside the control of the wearer. ~he degree of light trans-mission cannot be adjusted and depends solely on the degree of ambient electromagnetic radiation.
Hence, for safety, convenience and efficiency, an optical lens is needed which can control the light transmissive properties of the lens either automatically or independently, with ~uick cycling speed, and with selective adjustment of the degree of light transmission.
In accordance with this invention there is provided an electro-optical lens device comprising an optical lens coated with a layer of solid persistent electrochromic material, an ion-conducting layer, a pair of electrodes in contac~ wi-th these layers, and means for applying direct current voltage to said pair of electrodes to create an electric ~ -field across said layers, said electric field being of such a polarity to ~ _ 2 -~ 95~ ~ ~

alter light abs~rption characteristics of said mate~ial~ ~hereb~ said .
absorption may be varied ~rom substantially no absorptl~n to a desired degree o~ absorption~ so as to vary the amount o~ light transmitted throu~h said lens. :
The variable light transmissive optical lens , _ 2a -. - : .

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structure of the present invention is formed by coating a layer of solid persistent electrochromic material and an ion-conducting layer on an optical lens. A pair of elec-trodes connected to a dc power source is placed in contact with the electrochromic and ion-conducting layers, so that an electric field may be applied across the material. , Accordingly, the electrochromic material can be selectively colored or erased to a desired degree of light absorptivity.
This novel lens can be incorporated into an eyeglass struc-ture with appropriate connections to a source of electrical power to effect the desired change in transmission.
Detailed Description of the Invention As used herein, a "persistent electrochromic material" is defined as a material responsive to the appli-cation of an electric field of a given polarity to change from a first persistent state in which it i5 essentially non-absorptive of electromagnetic radiation in a given wavelength region, to a second persistent state in which it is absorptive of electromagnetic radiation in the given wavelength region, and once in said second state, is responsive to the application of an electric field of the opposite polarity to return to its first state. Certain of such materials can also be responsive to a short circuiting condition, in the absence o~ an electric field, so as to return to the initial state.
By "persistent" is meant the ability of the material to remain in the absorptive state to which it is changed, ater removal of the electric field, as distin-guished from a substantially instantaneous reversion to the initial state, as in the case of the Franz-Keldysh effect.
The invention may be further understood from the . :~ ~ . . . : .

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following more particular description of a preferred embodiment of the invention, as illustrated in the accom-panying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed on illustrating principles of the invention.
~ig. 1 is a pictorial view of a pair of eyeglasses including the variable light transmissive lenses according to the invention.
Fig. 2 illustrates, in partial cross section, a lens structure as described and claimed.
Referring to elements of the invention as embodied in the drawings, numeral 36 in Fig. 1 generally represents a pair of electrochromic eyeglasses which comprises a standard assembly with temple support arms 48 hingedly attached to a lens frame unit 54. The basic appearance of the eyeglasses corresponds to standard commercial eye wear. `
However, in place of a simple optical lens, the electro-optical lens of the present invention is inserted. The operation of the variable light transmissive lenses requires the application of an electric field across the electro-chromic layer coated on the lens. Miniature batter~v 34 in the temple support arm provides dc voltage, preferably about 1 - 5 volts. The battery i5 connected through con-ducting wires 42 and 44 to the lens units to control the light absorption thereof. Pushbutton switches 30 and 32 and 50 and 52 are included in the circuit to allow selective operator control of cycling - lens coloration and erasure.
Individual sets of pushbutton control switches are provided for each o~ lenses 38 and 40, so that separate control of each lens is possible. An operator, by depressing the respective coloration or erasure button can readily adjust :.. : . . .. : .

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the light transmission of each lens as desired. Separate controls adapt the glasses to multiple specialized uses. ~ !
For example, selective darkening of one lens while main-taining maximum transmission to the other eye would prove convenient and beneficial to such as microscopists, photo-graphers and sharpshooters etc., who are normally required to close or block one eye during operation.
Coloration and erasure also can be accomplished automatically according to ambient light levels by utili-zation of photocell 46 which is built into the lens frame and integrated into the switching circuitry.
Fig. 2 shows a cross section of the layered lens structure of the invention. Numeral 18 represents the actual optical lens substrate which is coated with light modulating layers. The layers, successively deposited comprise a transparent conductive material 16 such as SnO2, a persistent electrochromic material 14 such as WO3 or MoO3, an ion conducting layer 12 such as SiOx or ~-alumina, and transparent counter-electrode 10 of conductive material such as Au or a transparent oxide. The layers may be ~ -deposited by known vacuum deposition techniques. A source ; of dc potential 22 is coupled to electrodes 16 and 10 ;
through a reversing switch indicated by 20. As shown, with the switch arm in the position to produce coloration, the positive terminal of the source is connected to the outer or gold electrode while the negative terminal is connected to the tin oxide layer on the optical lens substrate.
Once complete coloration is induced, typically in a matter of seconds, switch 20 may be opened/ disconnecting the battery from the device entirely, and the device will remain in its darkened state without further application ^
of power. To erase a previously darkened surface, the - .
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switch arm is thrown to the erase contacts, across which is connected a potentiometer 24. As shown, the potentio-meter contact or slider is movable from a point at which the electrodes 16 and 10 are short circuited to a point at which full battery voltage, of polarity opposite to the coloration condition, is applied between them. Any number of reverse voltage values may be obtained between the two extremes.
In the position illustrated in the drawing, a ;
"bleach" voltage of a value less than battery voltage is applied across the electrodes, setting up a corresponding electric field. Under the influence of this field, the device returns to its initial uncolored state. The rapidity with which the bleaching occurs is determined by the magnitude of the voltage; the higher the voltage, the faster the bleaching process is completed. At the higher bleaching voltages, it has been found that the bleaching process is even faster than the coloring operation. Once ~ -th`e bleaching is completed, the switch may be opened to 2a disconnect the battery from the device and minimize power drain.
It has also been found that, notwithstanding the - absence of an electric field, when the potentiometer is in its short circuiting position, certain of the pexsistent electrochromic materials nevertheless will return completel~
and positively from the colored to the bleached state. The rate at which the bleaching occurs, however, is somewhat slower than when the material is subjected to an electric field.
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The materials which form the electrochromic materials of the device in general are electrical insulators 10689 5~ :

or semiconductors. Thus are excluded those metals, metal alloys, and other metal-containing compounds which are -relatively good electrical conductors. Suitable materials are as described in U.S. Patent 3,521,941. These include S materials aontaining a transition metal element ~including Lanthanide and Actinide series elements), and materials containing non-alkali metal elements such as copper.
Preferred materials of this class are films of transition metal compounds in which the transition metal may exist in any oxidation state from ~2 to +8. Examples of these are: transition metal oxides, transition metal oxysulfides, transition metal halides, selenides, tellurides, chromates, -molybdates, tungstates, vanadates, niobates, tantalates, titanates, stannates, and the like. ;
When the persistent electrochromic materials are -employed as films, thickness desirably will be in the range of from about 0.1-100 microns. However, since a small potential will provide an enormous field strength across very thin films, the latter, i.e., 0.1-10 microns, are preferred over thicker ones. Optimum thickness will also be determined by the nature of the particular compound being laid down as a film and by the film-forming method since the particular compound and film-forming method may place physical (e.g., non-uniform film surface) and economic limitations on manufacture of the devices.
When tungsten oxide is employed as the electro-chromic imaging material and an electric field is applied ~ between the electrodes, a blue coloration of the previously ; transparent electrochromic layer occurs, i.e., the per-sistent electrochromic layer becomes absorptive of electro-magnetic radiation over a band encompassing the red end of the visible spectrum, thereby rendering the imaging layer ; - 7 -: ' ~,~6~g50 ~ ~

blue in appearance. Prior to the application of the electric field, the electrochromic imaging layer was essentially non-absorbent and thus transparent .
Ion-Conducting Layer The layer should be substan-tially -transparent.
One embodiment employs a solution of ~2S04 in glycerin.
Other suitable ion-conductors are as disclosed in U.S. Patent ~os. 3,704,057 and 3,708,220.
~n a preferred embodiment the ion-conducting layer is an inorganic or other solid material, e.g. silicon oxide, calcium fluoride, magnesium fluoride, or the like, metal oxides and sulfides, synthetic resin films, or the like, as disclosed in U.S. Patent No. 3,521,941.
Electrodes Virtually any material exhibiting elec-trical conductivity may be used for an electrode. The same material may be used for both electrodes or each electrode may be of a different material, or mixtures or alloys of different materials. Typical electrode materials are the metals, e.g., gold, silver, aluminum, and conducting non-metals such as carbon, suitably doped tin or indium oxide, and the like. As already indicated, both of the electrodes should be of an optical quality effective for transmission of the electrochromic change. ;
The negative and positive electrodes need only be in electrical contact with the film. Any type and arrangement of electrodes ~; and film effective to impose an electric field on the film when the ; electrodes are connected to a voltage source, will be suitable. Thus, the electrodes may be spaced conducting strips deposited on or imbedded in the film at the lens periphery or they may be conducting layers between which the film is inserted.
While the invention has been particularly shown and described ;~- 30 with reference to preferred embodiments _ 8 -,~ 1 ~ ' ~ ' ~.~168~

thereof, it will be understood by those skilled in the art that various alterations in form and detail may be made therein without departing from the spirit and scope of the invention. For example the circuitry and switching arrange-ments can be changed to suit ease of operation or cosmeticdesign. Also, since power application is needed only to color and bleach the devlce, a source of continuous power within the eyeglass structure is not a necessity. A remote power supply can be utilized to accomplish desired cycl~ng.
Such can be portable and, for example, be conveniently , incorporated-into an eyeglass case. The glasses may take various forms such as ~elding goggles, laser protective goggles, eyeglasses, sunglasses or special glasses for microscopists~ photographers or sharpshooters. `

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electro-optical lens device comprising an optical lens coated with a layer of solid persistent electro-chromic material, an ion-conducting layer, a pair of elec-trodes in contact with these layers, and means for applying direct current voltage to said pair of electrodes to create an electric field across said layers, said electric field being of such a polarity to alter light absorption characteristics of said material, whereby said absorption may be varied from substantially no absorption to a desired degree of absorption, so as to vary the amount of light transmitted through said lens.

2. The electro-optical device of Claim 1 compri-sing a laminar structure of said optical lens successively coated with a first transparent electrode layer, a solid persistent electrochromic film an ion-conducting layer and a second transparent electrode layer.

3. The device of Claim 2 wherein said persistent electrochromic material is W03.

4. The device of Claim 2 wherein said persistent electrochromic material is MoO3.

5. The device of Claim 2 including control means coupled to said electrodes for selectively applying across said electrodes a potential of one polarity a potential of the opposite polarity, and an effective short circuit.

6. A pair of ophthalmic glasses comprising:
first and second lenses mounted in a frame, said lenses each comprising an electro-optical lens as in Claim 1, and means at least partially disposed within said frame for accommodating application of direct current voltage to said pair of electrodes to create an electric potential across the persistent electrochromic material of one polarity and a potential of the opposite polarity, whereby the persistent electrochromic material can be varied in coloration so as to vary the amount of light transmitted through said lens.

7. The pair of glasses of Claim 6 including a photocell control means to adjust light transmissive properties of said lenses according to the degree of ambient light.

8. The pair of glasses of Claim 6 including individual control means for each respective lens, so that light transmission through each lens can be independently adjusted.

9. The pair of glasses of Claim 6 including a direct current power source disposed within said frame.