Particle removal from electrochromic films using non-aqueous fluids

Abstract

Several of the films that comprise various energy producing or control devices, for example, electrochromic devices, lithium batteries, and photovoltaic cells, are sensitive to moisture in some way. They may be especially vulnerable to moisture at particular stages during their fabrication. It may also be highly desirable during fabrication to be able to wash particulates from the surface. The particulates may be generated some aspect of the fabrication process, or they may arise from the environment in which the fabrication takes place. This invention shows ways to remove said particles from the surface without incurring the damage associated with typical washing processes, resulting in higher manufacturing yields and better device performance.

Claims

1. A method of forming an electrochromic device comprising: depositing a first conductive layer over a substrate; depositing a first electrode layer over the first conductive layer, wherein the first electrode layer is one of an electrochromic layer or a counter electrode layer; depositing an ion conductor layer over the first electrode layer, wherein a film stack includes the first conductive layer, the first electrode layer, and the ion conductor layer; exposing the ion conductor layer to a non-aqueous liquid to remove particulate material having a size between about 0.1 m and about 1000 m, wherein the non-aqueous liquid is selected from the group consisting of a hydrofluorocarbon, a fluorocarbon, a polymeric fluorinated solvent, and a fluoride surfactant; depositing a second electrode layer over the film stack after exposing the ion conductor layer to the non-aqueous liquid, wherein the second electrode layer is the other of the electrochromic layer or the counter electrode layer; and depositing a second conductive layer on the second electrode layer, wherein the electrochromic device has a defect density of less than 1 defect/m.sup.2, and wherein the electrochromic device is configured for use in a window.

2. The method of claim 1, wherein the non-aqueous liquid is delivered to a surface of the substrate in the form of a stream or jet of sufficient velocity to dislodge at least some of the particulate material from the surface on which it impinges.

3. The method of claim 1, wherein the temperature of the non-aqueous liquid and of a surface of the substrate are independently controlled.

4. The method of claim 1, wherein the non-aqueous liquid comprises less than about 0.1% of water.

5. The method of claim 1, wherein the first electrode layer is the electrochromic layer, and the second electrode layer is the counter electrode layer.

6. The method of claim 1, wherein the non-aqueous liquid is non-polar.

7. The method of claim 1, wherein the non-aqueous liquid is polar.

8. The method of claim 1, wherein the non-aqueous liquid comprises a fluorocarbon, hydrofluorocarbon, or a polymeric fluorinated solvent.

9. The method according to claim 1, wherein an energy is applied, the energy selected from the group consisting of ultrasonic agitation of the liquid, bubble jet agitation, and thermal heating of the liquid.

10. The method of claim 1, further comprising lithiating the electrochromic layer, the ion conductor layer, or the counter electrode layer.

11. The method of claim 1, further comprising patterning the film stack before exposing the film stack to the non-aqueous liquid.

12. The method of claim 1, wherein the defect density is less than 1 short circuit/m.sup.2.

13. The method of claim 1, wherein the defect density is less than 1 visible defect/m.sup.2.

14. The method of claim 1, wherein the non-aqueous liquid has a fluoride concentration, by weight, based on active content, ranging between about 1 ppm and about 50,000 ppm.

15. The method of claim 1, wherein the fluoride surfactant includes: RfSO.sub.3.sup.M.sup.+, where the Rf is a C1 to C12 perfluoroalkyl group, and M.sup.+is a cation, a H.sup.30 atom or an ammonia group; or RfSO.sub.2N.sup.R.sup.1M.sup.+, where the Rf is a C1 to C12 perfluoroalkyl group; R.sup.1 is H, an alkyl group, a hydroxyalkyl group, an alkylamine oxide group, an alkylcarboxylate group or aminoalkyl group; and M.sup.+is a cation, a H.sup.+atom or an ammonia group.

16. A method of forming an electrochromic device comprising: depositing a first conductive layer over a substrate; depositing a first electrode layer over the first conductive layer, wherein the first electrode layer is one of an electrochromic layer or a counter electrode layer; depositing an ion conductor layer over the first electrode layer, wherein a film stack includes the first conductive layer, the first electrode layer, and the ion conductor layer; exposing the ion conductor layer to a non-aqueous liquid to remove particulate material having a size between about 0.1 m and about 1000 m, wherein the non-aqueous liquid is selected from the group consisting of a hydrofluorocarbon, a fluorocarbon, a polymeric fluorinated solvent, and a fluoride surfactant; depositing a second electrode layer over the ion conductor layer after exposing the film stack to the non-aqueous liquid, wherein the second electrode layer is the other of the electrochromic layer or the counter electrode layer; and depositing a second conductive layer on the second electrode layer, wherein the electrochromic device has a defect density of less than 1 defect/m.sup.2, wherein the electrochromic device is configured to be part of an insulated glass unit, and wherein the electrochromic device is configured for use in a window.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a particular washer concept.

(2) FIG. 2 provides for a process flow chart.

DETAILED DESCRIPTION

(3) In one embodiment is method of preparing a substrate or the surface of a substrate for the receipt of a film or coating material to be deposited in communication with the substrate. In another embodiment is a method of preparing a substrate for the receipt of a film or coating material to be deposited in communication with the substrate, where the substrate is at least partially contaminated with particulate matter. In some embodiments, the particulate material comprises material removed from the surface of the substrate in a prior process step (e.g. particulate defects). In some embodiments, at least about 90% of a particulate material having a size greater than 2 m is removed from the surface of the substrate.

(4) In another embodiment is a method of removing particles from a substrate surface, or a surface of a film stack deposited therein, without affecting the appearance of a device comprising the substrate or film stack. In some embodiments, the device is an electrochromic device, an LCD panel, a photovoltaic device, a thermochromic device, a battery, or any other equivalent device that employs at least one thin film in its operation. In some embodiments the method employs removing particulate defects with a non-aqueous solution, provided that the non-aqueous solution used does not substantially interact with the substrate or the films deposited on the substrate.

(5) In general, the method employs exposing the surface to be cleaned to a non-aqueous fluid, particularly with the addition of some source of energy to enable this fluid to dislodge particles from the surface. The surface may include any substrate, including those comprised of glass, polymers, organic or inorganic thin films (including those films that make up the various layers of electrochromic devices, photovoltaic devices, thermochromic devices, LCDs, etc.). A stream of non-aqueous fluid may be directed at a specific angle incident to the surface of the substrate and provided at a specific pressure, force, or energy to best effect removal of particular matter. Any stream angle or pressure, force, or energy may be employed provided it does not cause damage to the surface of the substrate or any underlying layers that are present. Other forms of energy may be introduced into the liquid to dislodge particulates, for example ultrasonic vibration, bubble jet impact, laser-induced thermal shock, vapor condensation, and motion of brushes.

(6) In some embodiments the particular matter is made of a material that is the same as a material of the underlying substrate. Without wishing to be bound by any particular theory, it is believed that any particulate matter left behind could create visible defects in any completed device (e.g. electrochromic device) or could create short circuits in a device (e.g. a battery or smart window).

(7) In some embodiments, the particles to be removed have a size ranging from between about 1 m to about 1 mm. In other embodiments, the particulate material has a size ranging from between about 1 m to about 500 m. In other embodiments, the particulate material has a size ranging from between about 1 m to about 250 m. In yet other embodiments, the particles to be removed have a size ranging from between about 2 m to about 200 m. In some embodiments, between about 70% and about 95% of particles having a size between about 2 m and about 200 m are removed.

(8) By way of example, in some embodiments a conductive layer is deposited on a glass substrate, and material is removed from the conductive layer in a process to pattern a shape into the conductive layer. The material ejected from by patterning process (which is of itself comprised largely of the material constituting the conductive oxide layer itself) could be left behind on the surface of the conductive layer and is desirable to be removed.

(9) In some embodiments, the non-aqueous fluid stream is directed toward the surface to be prepared through a bubble jet. A bubble jet employs a high energy jet of liquid from a special nozzle to force particles away from the surface in such a manner that the particles may be flushed away and removed or collected. The bubble jet does this in a manner that does not damage the surface being prepared or any of the underlying layers or film sticks beneath the surface being prepared.

(10) In other embodiments, the non-aqueous fluid is applied to a surface and then brushes or air streams are used to flush and remove or loosen particulate matter. The non-aqueous fluid may also be applied and energy supplied from ultrasonic transducers to affect mechanical energy transfer to the particulate matter and ultimately flushing or loosening of the material from the substrate or surface to be prepared.

(11) The person of ordinary skill in the art would be able to envision other means through which mechanical energy may be applied, in conjunction with the non-aqueous fluid, to affect a flushing or loosening of particulate matter from the substrate or surface to be prepared by transferring the applied mechanical or kinetic energy to the particulate matter.

(12) Fluids having low surface energies, for example, 3M Novec 7300, are used to advantage because this property assists in keeping particles removed from a surface in suspension. Proper surfactants added to a higher surface energy non-interacting non-aqueous fluid may be used to advantage for the same purpose.

(13) The non-aqueous fluid may be any fluid that does not interact with the substrate or surface being prepared or any layer in communication with the surface being prepared. In some embodiments, the non-aqueous liquid is a non-polar organic liquid. In other embodiments, the non-aqueous liquid is a polar organic liquid. In other embodiments, the non-aqueous liquid is an organic liquid having a polar moment with a specified range. In other embodiments, the non-aqueous liquid is a polar protic solvent. In yet other embodiments, non-aqueous liquid is a polar aprotic solvent.

(14) In some embodiments, the non-aqueous fluid contains a certain percentage of water. For example, the non-aqueous solution may be a mixture of a non-aqueous organic liquid and water, where the solution may contain up to 0.01% water, provide that the non-aqueous organic liquid and water are miscible. If the non-aqueous liquid contains water, the water is preferred to be deionized water or distilled water.

(15) In some embodiments, the non-aqueous liquid is selected from one that is non-flammable. In some embodiments, the non-aqueous liquid is selected from one that is relatively non-toxic. In some embodiments, the non-aqueous liquid is selected from one that is recyclable (e.g. where the particulate matter could be removed from the liquid, and the liquid reused in subsequent processing). In yet other embodiments, the non-aqueous liquid is an oil with a high flash point, such as those commonly used to store lithium.

(16) In some embodiments, the non-aqueous liquid is pentane, hexane, cyclohexane, benzene, toluene, chloroform or diethyl ether, or mixtures thereof. In other embodiments, the non-aqueous liquid is dichlormethane, tetrahydrofuran, or ethyl acetate or mixtures thereof. In yet other embodiments, the non-aqueous liquid is t-butanol, n-propanol, ethanol, methanol, terpineol, acetic acid, or mixtures thereof, with or without the addition of water.

(17) In some embodiments, the non-aqueous liquid is selected based on the material comprising the particulate defect, such that chemical or physical interactions may exist between the particulate matter and the liquid to assist in the removal of the particulate matter from the surface being prepared. For example, van der Waals forces or hydrogen bonds may temporarily exist between the liquid and the particulate matter aiding in the flushing or loosening of the matter from the surface being prepared (and, in some examples, this would allow lowering of the mechanical energy supplied to the surface or liquid stream). One skilled in the art will be able to select an appropriate liquid and mechanical energy supplied to best flush or loosen materials off the substrate or surface and to prevent damage to the surface or layers in communication with the surface.

(18) In some embodiments, the non-aqueous liquid is a halogenated liquid. In some embodiments, the halogen is fluorine. In some embodiments, the non-aqueous liquid is a hydrofluorocarbon liquid. In other embodiments, the non-aqueous liquid comprises a fluorocarbon. In yet other embodiments, the non-aqueous liquid is a polymeric fluorinated solvent. In yet further embodiments, the non-aqueous liquid comprises a surfactant. In yet further embodiments, the non-aqueous liquid is composed of a non-interacting fluid with the addition of a different surfactant.

(19) Preferred non-aqueous liquids will have at least one of the following properties: (1) only minimally interacts with the surface being prepared; (2) leaves minimal stains or deposits; (3) is readily removable; (4) is relatively non-toxic or non-carcinogenic; (5) low interaction with the environments (e.g. ozone depletion; greenhouse effect); (6) non-flammable or of low flammability; (7) relatively non-corrosive; (8) cost effective; and (9) provides little interaction with upstream or downstream processes (e.g. common washer construction materials).

(20) One example of a family of hydrofluorocarbon liquids is available from 3M under the trade name Novec. Four examples of 3M Novec liquids include 7300, 7200, 7100, and 71IPA. Applicants have found that 71IPA was found to increase film marks similar to those marks left behind from water. However, Applicants have observed that no marks were left from the other liquids in this group. In addition, Applicants have found these liquids to have a suitable low toxicity and are non-flammable, or weakly flammable, making integration into the industrial environment safer than many hydrocarbon based liquids. Moreover, Applicants have found that the fluorocarbon based liquids mark less, cause less bleaching to the surface material to which it is applied, or alter the color or optical density of the surface or dynamic switching rate of any film layers in communication thereof.

(21) In other embodiments, the non-aqueous liquid comprises 3M Novec 4200, 3M FC-4434, 3M Novec4300, 3M FC-4432, 3M Novec fluid HFE-7000, 3M Novec fluid HFE-7100, 3M Novec fluid HFE-7200, 3M Novec fluid HFE-7500, 3M Novec fluid HFE-71IPA, 3M Fluorinert FC-72, 3M Fluorinert FC-84, 3M Fluorinert FC-77, 3M Fluorinert FC-3255, 3M Fluorinert FC-3283, 3M Fluorinert FC-40, 3M Fluorinert FC-43, 3M Fluorinert FC-70, and/or 3M FC-4430. In an exemplary embodiment, the non-aqueous liquid comprises 3M Novec 4200, 3M FC-4434, 3M Novec 4300, 3M FC-4432, 3M Novec fluid HFE-7000, 3M Novec fluid HFE-7100, 3M Novec fluid HFE-7200, 3M Novec fluid HFE-7500, 3M Fluorinert FC-72, 3M Fluorinert FC-84, 3M Fluorinert FC-77, 3M Fluorinert FC-3255, 3M Fluorinert FC-3283, 3M Fluorinert FC-40, 3M Fluorinert FC-43, 3M Fluorinert FC-70, and/or 3M FC-4430. In some embodiments, the liquid has a fluoride concentration, by weight, based on active content, ranging between about 1 ppm and about 50,000 ppm. For example, such fluoride concentration may range between about 100 ppm and about 5000 ppm. has a fluoride concentration, by weight, based on active content, ranging between about 1 ppm and about 50,000 ppm. For example, such fluoride concentration may range between about 100 ppm and about 5000 ppm.

(22) Other non-aqueous liquids include a fluoride surfactant that may be or contain a composition according to the formula: RfSO.sub.3.sup.M.sup.+, where the Rf is a C1 to C12 perfluoroalkyl group, and M.sup.+ is a cation, a H.sup.+ atom or an ammonia group. In some embodiments, the fluoride surfactant may be or contain a composition according to the formula: RfSO.sub.2N.sup.R.sup.1M.sup.+, where the Rf is a C1 to C12 perfluoroalkyl group; R.sup.1 is H, an alkyl group, a hydroxyalkyl group, an alkylamine oxide group, an alkylcarboxylate group or aminoalkyl group; and M.sup.+ is a cation, a H.sup.+ atom or an ammonia group. The alkyl, hydroxylalkyl, alkylamine oxide, alkylcarboxylate or aminoalkyl groups of R groups may have from 1 to 6 carbon atoms. The hydroxylalkyl group may have the formula (CH.sub.2)x-OH, where x is an integer from 1 to 6.

(23) Other non-aqueous liquids include a fluoride surfactant may be or contain a composition according to the formula: Rf-Q-R.sup.1SO.sub.3.sup.M.sup.+, where the Rf is a C1 to C12 perfluoroalkyl group; R.sup.1 is alkylene of the formula CnH2n(CHOH)oCmH2m-, the n and m are independently 1 to 6 and o is 0 to 1, and is optionally substituted by a catenary oxygen or nitrogen group; M.sup.+ is a cation; Q is O or SO.sub.2NR.sup.2; and the R.sup.2 is an H, alkyl, aryl, hydroxyalkyl, aminoalkyl, or sulfonatoalkyl group, optionally containing one or more catenary oxygen or nitrogen heteroatoms. The alkyl, aryl, hydroxyalkyl, aminoalkyl, or sulfonatoalkyl group may have from 1 to 6 carbon atoms. The hydroxyalkyl group may be of the formula C.sub.pH.sub.2pOH, where the p is an integer from 1 to 6. The aminoalkyl group may be of the formula C.sub.pH.sub.2pNR.sup.3R.sup.4, where the p is an integer of 1 to 6 and R.sup.3 and R.sup.4 are independently H or alkyl groups of 1 to 6 carbon atoms. The R.sup.1 group is CnH2nCH(OH)CmH2m-, and the n and m are independently 1 to 6.

(24) In some embodiments, the non-aqueous liquid is recovered or recycled. For example, the solvent may be filtered to remove particles above a certain size by methods such as vacuum or atmospheric distillation, sub-micro filtration, or sorption filtration.

(25) In one test of non-aqueous liquid exposure, a device substrate was paused on a horizontal conveyor after an electrochromic (EC) layer had been deposited. Several non-aqueous liquids were applied to the surface of the EC film, in quantities of approximately 1 cm.sup.3, and allowed to pool on the surface for about 10 seconds. These liquids were applied in locations that were carefully measured and recorded, to allow subsequent observation of the exact locations treated. After about 10 seconds of elapsed time, an air jet was used to blow the pool of liquid across the device. At this point, no marks associated with the liquids were visible on the surface. This substrate was then further processed. After processing, this device (an electrochromic device) was colored and bleached according to standard test protocols, and the measured locations at which the test liquids had been applied were carefully monitored.

(26) Five liquids were used in this experiment: deionized water (control); 3M Novec 7300; 3M Novec 7200; 3M Novec 7100; and 3M Novec 71IPA. The presence of water in the test as a control insured that this particular film stack did in fact exhibit its characteristic sensitivity to water, and so assured us that were dealing with a film stack that behaved in the expected manner. The results are shown in the following Table A:

(27) TABLE-US-00001 Liquid: Test 1 Test 2 DI water very strongly marked not used Novec 71IPA strongly marked strongly marked Novec 7100 no visible marks no visible marks Novec 7200 no visible marks no visible marks Novec 7300 no visible marks no visible marks

(28) Test 2: Test 2 was a repeat of Test 1, except that water was not used as the control. The marking of the electrochromic device produced by 3M Novec 71IPA was so similar to that of water that the water was omitted to allow a larger area of the device to be exposed to each of the four 3M Novec non-aqueous solvents. In each case, the non-polar, highly inert, pure Novec fluorinated solvents, left no marks at all visible in the electrochromic device during coloring or bleaching. The water left mottled light areas with dark edges around the original pool location, and dark-edged light streaks in areas over which the liquid had been blown by the applied air jets. These defects showed up at various points in the coloring and bleaching cycles, as well as in the final fully colored state, and were characterized by differences in switching rate, as well as ultimate optical density. Novec 71IPA, which is a combination of Novec 7100 and isopropanol (IPA), showed behavior very similar to that of water, but a little less strongly marked. Novec 7100, along with Novec 7200 and Novec 7300, showed no marking of the electrochromic devices at all, while bleaching, coloring, or in transition. The lack of transitional defects is a critical point, since lowered switching speed is the first indication of an interaction between the cleaning fluid and the electrochromic device.

(29) A flat glass washer using bubble jet energy and 3M Novec 7300 has been designed and constructed to demonstrate the effectiveness of this method of particle removal, without damage the electrochromic films. A drawing of this system is found in FIG. 1.

(30) Process flow diagram showing alternate locations for patterning and non-aqueous cleaning of particulate debris. The cleaning step can be inserted wherever particulate removal helps yield and quality. The process flow using patterning/cleaning step B only is preferred.