Patent Application
20170305787
The disclosure relates generally to patterned ion-exchanged substrates and methods for making such substrates, and more particularly to methods for making patterned chemically-strengthened glass sheets using poling techniques and ion exchange processes.
Glass sheets are commonly used in a wide variety of applications, including various electronics, such as cell phones, laptops, electronic tablets, televisions, and computer monitors, as well as appliances such as refrigerators, dishwashers, ovens, and microwaves. Other non-limiting applications include architectural elements, e.g., elevator wall panels; furniture elements, such as furniture panels; and decorative or functional elements for automobiles, such as windshields, sunroofs, and door or pillar panels. For various applications, it can often be advantageous to employ chemically-strengthened glass sheets, such as Gorilla® Glass from Corning Incorporated. For example, chemically-strengthened glasses have wide-spread application in touch panels and portable display devices due to their improved strength and damage resistance. In particular, glass cover sheets for electronic devices are often chemically-strengthened to withstand a high level of contact and resist potential damage.
Chemically-strengthened glass sheets can have improved damage resistance due to surface compression layers formed in the glass substrate due to ion exchange. The surface compression can be balanced by a tensile region in the interior of the substrate. However, the magnitude of compressive stress and the elastic energy stored in the interior tensile region of the glass can make mechanical cutting of the substrates difficult. For example, when the compressive layer is punctured, e.g., by cutting or impact, the integral energy of the glass may be released and can result in fragmentation of the glass.
Applicant has conducted various studies relating to mechanical cutting of chemically-strengthened glass. Emerging methods for cutting chemically-strengthened glasses include limiting the central tensile stress to keep the glass from shattering. Such methods may be successful with strengthened glasses having lower compressive stress and/or smaller depth of layer of compressive stress (DOL), such as soda-lime glasses. However, chemically-strengthened glasses such as Gorilla® Glass can have a high central tension that poses problems for mechanical cutting. Laser techniques for cutting chemically-strengthened glass sheets have also been studied by Applicant, but these techniques can still be limited in terms of commercial readiness and/or availability.
As such, most chemically-strengthened glass articles are made by a piece-part process, e.g., the part is cut from a sheet of glass and edge-finished to shape before it is chemically strengthened, such as by ion exchange. Such processes can, however, have ramifications in terms of production cost and/or complexity. Accordingly, it would be advantageous to provide methods for making chemically-strengthened glass substrates that can be subsequently cut using conventional mechanical cutting methods.
Moreover, from a safety standpoint, while chemically-strengthened glass often breaks into smaller pieces upon mechanical impact as compared to non-chemically-strengthened glass, these fragments can still have sharp corners, which can pose potentially safety concerns to the customer. In particular, for automobile applications, it may be desirable to avoid sharp broken glass fragments upon impact or collision to avoid secondary injuries to the driver and/or passengers due to glass breakage. It would thus also be advantageous to provide chemically-strengthened glass substrates that exhibit a desired or controllable breakage pattern to minimize safety concerns during customer usage.
The disclosure relates, in various embodiments, to methods for chemically-strengthening a glass substrate, the methods comprising applying a first electrode to at least one first region on a first surface of a glass substrate and applying a second electrode to at least one second region on a second surface of the glass substrate, wherein the glass substrate comprises metal ions; applying voltage between the first and second electrodes sufficient to cause at least a portion of the metal ions to migrate away from the at least one first region on the first surface; and chemically strengthening the glass substrate by ion exchange. In additional embodiments, the metal ions can be chosen from alkali metal ions, alkaline earth metal ions, transition metal ions, and combinations thereof. According to various embodiments, the methods can further comprise bringing the glass substrate to a temperature less than the glass transition temperature of the glass substrate before applying voltage. In certain embodiments, the glass substrate can be chemically strengthened by immersion in a molten salt bath. According to further embodiments, the first region can comprise a portion of the first surface and/or can define a pattern on the first surface, which can be random or repeating, e.g., comprising repeating shapes chosen from circles, squares, rectangles, triangles, hexagons, and other polygons.
The disclosure also relates to chemically-strengthened glass substrates made using the methods disclosed herein, such as glass substrates comprising a first surface having at least one non-chemically-strengthened region and a second surface having at least one chemically-strengthened region, wherein the at least one chemically-strengthened region comprises metal ions, and wherein the at least one non-chemically-strengthened region is substantially free of the metal ions. According to some embodiments, the metal ions can be chosen from alkali metal ions, alkaline earth metal ions, transition metal ions, and combinations thereof. In certain embodiments, the first surface can comprise a plurality of first chemically-strengthened regions comprising the metal ions, separated at least in part by the at least one non-chemically-strengthened region substantially free of the metal ions. According to various embodiments, the first surface of the glass substrate can be non-chemically-strengthened and can be substantially free of the metal ions, whereas the opposing second surface can be chemically-strengthened and can comprise the metal ions. Also disclosed herein are glass substrates comprising at least one surface having a plurality of chemically-strengthened regions separated at least in part by at least one non-chemically-strengthened region, wherein the plurality of chemically-strengthened regions comprise metal ions, and wherein the at least one non-chemically-strengthened region does not comprise the metal ions.
Further disclosed herein are methods for ion exchange of a substrate, the methods comprising applying a first electrode to at least one first region on a first surface of a substrate and applying a second electrode to at least one second region on a second surface of the substrate, wherein the substrate comprises mobile ions; applying voltage between the first and second electrodes sufficient to cause at least a portion of the mobile ions to migrate away from the at least one first region on the first surface; and treating the substrate by ion exchange. Still further disclosed herein are substrates comprising a first surface having at least one non-ion-exchanged region and a second surface having at least one ion-exchanged region, wherein the at least one ion-exchanged region comprises mobile ions, and wherein the at least one non-ion-exchanged region is substantially free of the mobile ions. According to various embodiments, the substrate can be chosen from glass, glass-ceramic, and ceramic substrates. The mobile metal ions can, in certain embodiments, be metal ions chosen from alkali metal ions, alkaline earth metal ions, transition metal ions, and combinations thereof.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the methods as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present various embodiments of the disclosure, and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure and together with the description serve to explain the principles and operations of the disclosure.
The following detailed description can be further understood when read in conjunction with the following drawings.
Methods
Disclosed herein are methods for chemically-strengthening a glass substrate, the methods comprising applying a first electrode to at least one first region on a first surface of the glass substrate and applying a second electrode to at least one second region on a second surface of the glass substrate, wherein the glass substrate comprises metal ions; applying voltage between the first and second electrodes sufficient to cause at least a portion of the metal ions to migrate away from the at least one first region on the first surface; and chemically strengthening the glass substrate by ion exchange.
Methods according to the disclosure will be discussed herein with reference to
According to methods disclosed herein, a substrate G1 can be processed using a thermal poling treatment to produce one or more regions on a surface of the substrate comprising a layer with a modified composition substantially depleted of mobile ions, e.g., metal cations. As used herein, the terms “substantially free,” “substantially depleted,” “substantially devoid,” and variations thereof are intended to denote that the specified region(s) of the substrate do not comprise any, or comprise only nominal amounts of mobile ions such as alkali metal ions, alkaline earth metal ions, and/or transition metal ions. For example, “substantially free” and variations thereof can denote that the region comprises less than about 3% by weight of alkali, alkaline earth, and/or transition metal ions, such as less than about 2%, less than about 1%, less than about 0.5%, less than about 0.2%, or less than about 0.1% by weight.
The thermal poling process TP can be carried out by placing electrodes in contact with opposing surfaces of the substrate and applying voltage, e.g., DC voltage or AC voltage with a DC bias, between the electrodes. The surface subjected to positive DC bias is referred to herein as the “anode side” or “anodic” surface of the substrate. For purposes of discussion, this surface is also referred to as the “first” surface, although this is not intended to be limiting on the appended claims. The first electrode or anode A can, in various embodiments, comprise any material that is more conductive than the substrate at the poling temperature, which can provide enhanced field uniformity over the surface. It can also be advantageous to select a material for the anode that is sufficiently resistance to oxidation to minimize or prevent the formation of oxide compounds at the interface between the anode and the substrate surface, which could otherwise cause the substrate to stick to the electrode. Non-limiting exemplary anode materials include, but are not limited to, noble metals such as Au, Ag, Pt, and Pd; metals such as Cu and Al; metal alloys; and oxidation-resistant conductive films such as TiN and TiAlN, to name a few. In certain embodiments, graphite can also be used as an anode material.
The surface subjected to negative DC bias is referred to herein as the “cathode side” or “cathodic” surface of the substrate. For purposes of discussion, this surface is also referred to as the “second” surface, although this is not intended to be limiting on the appended claims. The first electrode or cathode C can also comprise any material that is more conductive than the substrate at the poling temperature, which can provide enhanced field uniformity over the surface. It can also be advantageous to select a material for the cathode that is capable of accepting ions from the substrate. Non-limiting exemplary cathode materials include, but are not limited to, graphite, spinel, phosphates, metals, metal alloys, or other suitable cathode materials, to name a few. In certain embodiments, the metals and films disclosed above with respect to the anode can also be used as materials for the cathode, and vice versa.
The first and second electrodes can, in some embodiments, be separate components that can be brought into contact with the substrate surfaces, which can then be separated after processing without complex removal steps. The electrodes can be a bulk material, or they can take the form of a thin film, such as a conductive thin film deposited on the substrate surface(s). The first and second electrodes can cover all or part of the surface with which they are in contact. For example, in some embodiments, the first electrode (or anode) can contact one or more portions, or first regions, of the first surface. These first region(s) can, for example, define a “line” or boundary between other regions not in contact with the anode, the line having any dimension desired for later processing or use, e.g., mechanical cutting or desired breakage profile upon physical impact. The at least one first region can also have other shapes, e.g., circles, squares, rectangles, triangles, and other polygons, without limitation. In additional embodiments, the at least one first region can comprise the entire first surface.
According to various embodiments, the at least one first region can define a pattern on the first surface, which can be random or arranged, repetitive or non-repetitive. For instance, the electrode can comprise a template or grid defining various “openings” which are not contacted with the anode. These openings can be of any shape and/or size, without limitation. According to various aspects, the openings can have a shape chosen from circles, squares, rectangles, diamonds, triangles, hexagons, and other polygons, to name a few. The patter can, in some embodiments, be selected from the group consisting of regular, repeating, or periodic patterns (e.g., lines, gratings, arrays, channels, concentric features, circles, squares, rectangles, triangles, hexagons, and combinations thereof); engineered, designed, or hierarchical structures (e.g., lenses, gratings, waveguides, and light-guiding circuitry); irregular, random, pseudo-random or aperiodic patterns; or any of the like, and combinations thereof.
An exemplary pattern is depicted in
The second electrode (or cathode) can be patterned in a manner similar to the first electrode to create corresponding regions on an opposing second surface. In other embodiments, the entire second surface can be covered by the second electrode, e.g., as illustrated in
According to various embodiments, it may be advantageous to substantially match the curvature and/or flatness of the substrate and the electrodes to provide intimate contact at the interface. However, in some embodiments, initial contact may not be intimate and there may be a difference in curvature between the substrate and the electrodes, e.g., in the case of a machined metal electrode with a substantially flat surface and a substrate with a degree of curvature, and vice versa. In such instances, an electrostatic charge at the interface can pull the two surfaces into intimate contact when voltage is applied.
The methods disclosed herein can further include a step of bringing the substrate, e.g., the anode/substrate/cathode stack, to a predetermined temperature before application of voltage. In certain embodiments, the substrates comprising glass can be heated or cooled to any temperature below the Tg of the substrate, this temperature varying depending on the selected substrate composition and/or the desired thermal poling effect to be achieved. Thermal poling can thus be carried out at any temperature ranging from room temperature (about 25° C.), e.g., little or no heat applied, up to a temperature below Tg (which will vary depending on the composition). According to non-limiting examples, the substrate can be heated to a temperature ranging from about 100° C. to about 350° C., such as from about 125° C. to about 325° C., from about 150° C. to about 300° C., from about 175° C. to about 275° C., or from about 200° C. to about 250° C., including all ranges and subranges therebetween. In further embodiments, the substrate can be allowed to equilibrate at a given temperature for a time period sufficient to ensure temperature uniformity across the substrate, e.g., from about 5 minutes to about 60 minutes, such as from about 10 minutes to about 45 minutes, or from about 15 minutes to about 30 minutes, including all ranges and subranges therebetween.
After assembly, heating and/or, equilibrating, voltage can be applied to the electrodes (or substrate-electrode stack) such that the anode is positively biased relative to the substrate. According to various embodiments a DC voltage or an AC voltage with a DC bias may be applied to the stack. The voltage can be applied for a time period ranging, for example, from less than about a minute to several hours or more. In certain embodiments, the time period can range from about 1 minute to about 60 minutes, such as from about 5 minutes to about 45 minutes, from about 10 minutes to about 30 minutes, or from about 15 minutes to about 20 minutes, including all ranges and subranges therebetween. The magnitude of voltage can vary depending, e.g., upon the substrate composition and/or the desired processing time, to name a few factors. By way of a non-limiting example, the voltage can range from about 100V to about 10,000V, such as from about 500V to about 9,000V, from about 1,000V to about 8,000V, from about 2,000V to about 7,000V, from about 3,000V to about 6,000V, or from about 4,000V to about 5,000V, including all ranges and subranges therebetween. In certain embodiments, voltages less than about 1,000V may be used, for instance, less than about 900V, less than about 800V, less than about 700V, less than about 600V, less than about 500V, less than about 400V, less than about 300V, less than about 200V, or less than about 100V, including all ranges and subranges therebetween.
Voltage may be applied in one or more discrete steps to achieve the maximum desired value or ramped in a controlled/current-limited manner up to the desired value. These approaches may be advantageous and may potentially circumvent any potential thermal dielectric breakdown of the substrate due to the passage of too much current through the substrate, particularly in the case of low-resistivity substrates. These approaches can therefore allow for a higher final poling voltage and potentially thicker surface barrier layers. However, it is also envisioned that voltage can be applied all at once, e.g., an “instant-on” approach. Because breakdown strength can vary with substrate composition, this approach can be suitable for certain compositions and can, in some embodiments, present a more convenient alternative.
After poling the substrate for a predetermined period of time, the substrate can be cooled, e.g., to a temperature ranging from about 25° C. to about 100° C., such as from about 30° C. to about 80° C., or from about 40° C. to about 60° C., including all ranges and subranges therebetween. The voltage may be removed prior to the cooling step or, in some embodiments, the voltage can be removed after the substrate is cooled. After cooling the substrate can be further processed, for instance, the substrate can be separated from the electrodes and then chemically strengthened.
Apparatuses suitable for thermal poling can comprise any system capable of simultaneously supplying and maintaining heat and voltage to a substrate-electrode stack in a controlled manner. In certain embodiments, the apparatus can also avoid practical problems such as leakage current paths or arcing. In additional embodiments, the apparatus can also control the process atmosphere, for example, maintain a vacuum, or provide an atmosphere comprising an inert gas (e.g., N2) or a permeable gas (e.g., He). According to various embodiments, an inert or permeable gas atmosphere may be desirable to minimize atmospheric effects on the substrate-electrode interface (e.g., oxidation) and/or occluded gas at the substrate-electrode interface.
As discussed herein, voltage can be applied to the electrodes such that the anodic surface is positively biased relative to the substrate. The positive bias can induce an ion migration at the anodic interface, such that mobile ions (e.g., alkali, alkaline earth, and/or transition metal ions) migrate away from the anodic surface and towards the cathodic surface. The anodic surface can thus, after poling, comprise a layer (blocking or barrier layer) that is substantially free of such mobile ions. Portions of the substrate surface not in contact with the anode will not or will not substantially develop the same barrier layer. As such, when the surface is chemically strengthened by ion exchange, the treated anodic surfaces comprising the barrier layer will be devoid or substantially devoid of mobile cations for the ion exchange process, which is discussed in more detail below. However, the portions of the substrate surface that do not comprise the barrier layer can have available ions for ion exchange. Thus, the first region(s) (e.g., anodic surface region(s)) may not be chemically strengthened by the ion exchange process, whereas the other regions of the substrate (e.g., untreated and/or cathodic region(s)) can be chemically strengthened by ion exchange.
Accordingly, referring to
After thermal poling, the patterned substrate G2 can be treated by ion exchange. Ion exchange can provide various advantages, e.g., chemical strengthening of a substrate, alteration of optical properties and/or fracture behavior of a substrate, and/or dimensional correction of a substrate, such as correcting or reducing warping in the substrate. During the ion exchange process, ions within a substrate, e.g., a glass sheet, at or near the surface of the substrate may be exchanged for larger ions, for example, from a salt bath. The incorporation of the larger ions into the substrate can strengthen the substrate by creating a compressive stress in a near surface region. A corresponding tensile stress can be induced within a central region of the substrate to balance the compressive stress.
Ion exchange may be carried out, for example, by immersing the substrate in a molten salt bath for a predetermined period of time. Exemplary salt baths include, but are not limited to, KNO3, LiNO3, NaNO3, RbNO3, AgNO3, K2SO4, LiSO4, NaSO4, LiCl, NaCl, KCl and combinations thereof. Other molten salts comprising ions chosen from Cu+, Rb+, Cs+, or Th+ can also be used. The temperature of the molten salt bath and treatment time period can vary. It is within the ability of one skilled in the art to determine process variables such as time and temperature according to the desired application. By way of a non-limiting example, the temperature of the molten salt bath may range from about 350° C. to about 800° C., such as from about 400° C. to about 600° C., or from about 450° C. to about 500° C., including all ranges and subranges therebetween. The treatment time period may range from about 0.2 to about 24 hours, such as from about 4 hours to about 12 hours, or from about 6 hours to about 10 hours, including all ranges and subranges therebetween. However, other temperature and time combinations are envisioned and are intended to fall within the scope of the disclosure. By way of a non-limiting example, the substrate can be submerged in a KNO3 bath, for example, at about 450° C. for about 6 hours, to obtain a K-enriched layer which imparts a surface compressive stress. Of course, while ion exchange is discussed herein using molten salt baths as a non-limiting example, it is to be understood that any other method for ion exchanging, e.g., chemically strengthening, the substrate is possible and envisioned as falling within the scope of the disclosure.
According to various embodiments, the chemically-strengthened regions of the substrate may have a compressive stress greater than about 100 MPa and a depth of layer of compressive stress (DOL) greater than about 10 microns. In further embodiments, the substrate may have a compressive stress greater than about 500 MPa and a DOL greater than about 15 microns, or a compressive stress greater than about 750 MPa and a DOL greater than about 40 microns.
Ion-Exchanged Substrates
Disclosed herein are glass substrates comprising a first surface having at least one non-chemically-strengthened region and a second surface having at least one chemically-strengthened region, wherein the at least one chemically-strengthened region comprises metal ions, and wherein the at least one non-chemically-strengthened region is substantially free of the metal ions. In certain embodiments, the first surface can comprise a plurality of first chemically-strengthened regions comprising the metal ions and separated at least in part by the at least one non-chemically-strengthened region substantially free of the metal ions.
Also disclosed herein are glass substrates comprising at least one surface having a plurality of chemically-strengthened regions separated at least in part by at least one non-chemically-strengthened region, wherein the plurality of chemically-strengthened regions comprise metal ions, and wherein the at least one non-chemically-strengthened region does not comprise the metal ions. Further disclosed herein are substrates comprising a first surface having at least one non-ion-exchanged region and a second surface having at least one ion-exchanged region, wherein the at least one ion-exchanged region comprises mobile ions, and wherein the at least one non-ion-exchanged region is substantially free of the mobile ions.
The substrate, before processing, can be chosen from any untreated or starting material (“parent” composition) comprising mobile ions such as metal ions chosen from alkali, alkaline earth, and/or transition metal ions (see, e.g., G1 in
For example, glass batch materials can be melted according to any method known in the art, such as adding the batch materials to a melting vessel and heating to a temperature ranging from about 1100° C. to about 1700° C., such as from about 1200° C. to about 1650° C., from about 1250° C. to about 1600° C., from about 1300° C. to about 1550° C., from about 1350° C. to about 1500° C., or from about 1400° C. to about 1450° C., including all ranges and subranges therebetween. The batch materials may, in certain embodiments, have a residence time in the melting vessel ranging from several minutes to several hours, depending on various variables, such as the operating temperature and the batch size. For example, the residence time may range from about 30 minutes to about 8 hours, from about 1 hour to about 6 hours, from about 0.2 hours to about 5 hours, or from about 3 hours to about 4 hours, including all ranges and subranges therebetween.
The term “glass batch materials” and variations thereof is used herein to denote a mixture of glass precursor components which, upon melting, react and/or combine to form a glass. The glass batch materials may be prepared and/or mixed by any known method for combining glass precursor materials. For example, in certain non-limiting embodiments, the glass batch materials can comprise a dry or substantially dry mixture of glass precursor particles, e.g., without any solvent or liquid. In other embodiments, the glass batch materials may be in the form of a slurry, for example, a mixture of glass precursor particles in the presence of a liquid or solvent. According to various embodiments, suitable batch materials may comprise glass precursor materials, such as silica, alumina, and various additional oxides, such as sodium, potassium, lithium, cesium, magnesium, calcium, strontium, barium, boron, tin, and/or titanium oxides. For instance, the glass batch materials may comprise a mixture of silica and/or alumina with one or more additional oxides. In various embodiments, the glass batch materials can comprise from about 45 to about 95 wt % collectively of alumina and/or silica and from about 5 to about 55 wt % collectively of at least one oxide of sodium, potassium, lithium, cesium, magnesium, calcium, strontium, barium, boron, tin, and/or titanium.
The melted glass can subsequently undergo various additional processing steps, including fining to remove bubbles, and stirring to homogenize the glass melt, to name a few. The molten glass can then be processed to produce a glass ribbon according to any method known in the art, including, e.g., fusion draw, slot draw, or float methods. A pull roll assembly can deliver the drawn glass ribbon for further processing by additional apparatuses. For example, the glass ribbon can be further processed by a traveling anvil machine (TAM), which can include a mechanical scoring device for scoring the glass ribbon. The scored glass can then be separated into pieces of glass sheet, machined, polished, and/or otherwise processed using various methods and devices known in the art.
Of course, other substrates, such as glass-ceramic and ceramic substrates, can also be made by processing any suitable batch materials using conventional methods or can be otherwise provided or purchased. For example, ceramic substrates can be produced by combining inorganic ceramic batch materials, forming a green body, and firing the green body according to a desired firing schedule to provide a ceramic substrate. A substrate G1 formed from these exemplary batch materials can comprise, in some embodiments, at least about 3% by weight of at least one mobile ion, e.g., metal ions chosen from alkali, alkaline earth, and transition metal ions, such as Na, K, Li, Cs, Mg, Ca, Sr, Ba, or Ag. According to various non-limiting embodiments, the substrate G1 can comprise from about 3% to about 20% by weight of mobile ions, such as from about 4% to about 18%, from about 5% to about 16%, from about 6% to about 15%, from about 7% to about 14%, from about 8% to about 13%, from about 9% to about 12%, or from about 10% to about 11% by weight, including all ranges and subranges therebetween.
The substrate G1 is not limited in terms of dimensions, e.g., height, length, thickness, and so on. In some embodiments, the substrate can be a sheet, such as a rectangular or square glass sheet. According to various embodiments, the substrate can have a thickness of less than about 5 mm, such as less than about 4 mm, less than about 3 mm, less than about 2 mm, or less than about 1 mm, including all ranges in between. For instance, the thickness can range from about 0.05 mm to about 3 mm, from about 0.1 mm to about 2.5 mm, from about 0.3 mm to about 2 mm, from about 0.5 mm to about 1.5 mm, or from about 0.7 mm to about 1 mm, including all ranges and subranges therebetween. The substrate is furthermore not limited in terms of shape and can, for example, comprise one or more planar or non-planar surfaces. The substrate may have a single radius of curvature or multiple radii, such as two, three, four, five, or more radii. The radius of curvature may, in some embodiments, range from about 50 mm to about 1,000 mm, such as from 100 mm to about 500 mm, or from about 200 mm to about 300 mm, including all ranges and subranges therebetween
As discussed above, the substrate G1 can be thermally poled using a variety of methods and configurations to obtain a desired ion exchange, e.g., compressive stress, pattern on one or more of the surfaces. In some embodiments, such as that illustrated in
According to additional embodiments, during the ion exchange process, all or a part of the second surface can be treated to block ion exchange. For instance, one or more thin films can be applied to the surface as a barrier layer to ion exchange. Suitable films can include oxide coatings, e.g., ZnO, ITO, ZrO, and other materials known to impede or block the ion exchange process. The film can, in some embodiments, be a thin film with a thickness less than about 100 nm, such as less than about 30 nm, or less than about 10 nm, including all ranges and subranges therebetween. Accordingly, while the anodic (first) surface can have an intrinsic barrier layer created by thermal poling, the cathodic (second) surface can, in some embodiments, have an extrinsic, e.g., applied, barrier layer. Of course, the first surface can also be similarly treated after thermal poling if so desired. It should be noted, however, that extrinsically blocked surfaces, while avoiding ion exchange, and thus the incorporation of ions M2 from the ion exchange process, can still comprise the mobile ions M1 originally present in the substrate. In contrast, intrinsic barrier layers created, e.g., by thermal poling, can be substantially devoid of both the original mobile ions M1 and the ions M2 that would otherwise be introduced by ion exchange.
The substrate can, in various embodiments, comprise at least one surface having at least one chemically-strengthened region and at least one non-chemically-strengthened region. For instance, at least one surface can comprise a plurality of chemically-strengthened regions separated at least in part by one or more non-chemically strengthened regions. The opposing surface can be chemically-strengthened, non-chemically-strengthened, or a combination thereof. For example, application of extrinsic barrier layers, e.g., thin oxide films or any other suitable blocking means, to the entire second surface can yield a substrate having one surface comprising a plurality of chemically-strengthened regions separated by at least one non-chemically-strengthened region and an opposing non-chemically-strengthened surface. Various combinations of electrode configurations and/or subsequent application of barrier layers can yield numerous combinations of surfaces with different arrangements of chemically-strengthened and non-chemically-strengthened regions, all of which are envisioned as falling within the scope of the disclosure and appended claims.
Of course it is also possible to use alternative or additional techniques for selective ion exchange including, for example, the extrinsic barrier layer methods discussed above, as well as, e.g., thermal treatment of a chemically-strengthened surface after ion exchange. Local heat treatment can increase the local temperature to above the annealing point. At high temperatures, surface compressive stress can relax. Thus, low compressive stress patterns can be created on a chemically-strengthened surface. Another alternative approach comprises using field-assisted ion exchange processes to achieve a patterned ion-exchanged surface. A patterned electrode can be used as a reservoir for the ion to be exchanged into the substrate (e.g., a silver electrode can be used for Ag-for-Na ion exchange). The patterned electrode can be subjected to heat and voltage similar to that described above for thermal poling methods. However, instead of creating a barrier layer, the substrate can instead be selectively ion exchanged only where the electrode is in contact with the substrate, e.g., the electrode “guest” ions can be driven into the substrate by the field-assisted mechanism. The above approaches can be employed multiple times, in any combination, and without limitation, to achieve a desired compressive stress pattern on one or more of the substrate surfaces.
The ion-exchanged substrates disclosed herein can have various advantages as compared to traditional chemically-strengthened substrates. For instance, the disclosed substrates can be processed by manufacturers as full sheets instead of as piece-parts. According to various embodiments, the disclosed substrates can be cut using conventional mechanical methods such as scoring and cutting and may not require the use of specialized equipment for end-use processing. The disclosed methods can also provide for low cost and/or high throughput manufacturing due to the relatively low temperatures, relatively low voltages, relatively low consumption of electrical energy, and/or relatively short processing times. Moreover, in the case of machined press-contact electrodes, a desired pattern can be applied to multiple substrates using a simple apparatus and a single process step. Finally, the methods disclosed herein can be compatible with conventional ion exchange methods and equipment, thus avoiding additional expense and/or complexity. Of course, the substrates and methods disclosed herein may not have one or all of the above-disclosed advantages but are still intended to fall within the scope of the appended claims.
It will be appreciated that the various disclosed embodiments may involve particular features, elements or steps that are described in connection with that particular embodiment. It will also be appreciated that a particular feature, element or step, although described in relation to one particular embodiment, may be interchanged or combined with alternate embodiments in various non-illustrated combinations or permutations.
It is also to be understood that, as used herein the terms “the,” “a,” or “an,” mean “at least one,” and should not be limited to “only one” unless explicitly indicated to the contrary. Thus, for example, reference to “a region” includes examples having two or more such regions unless the context clearly indicates otherwise. Likewise, a “plurality” or an “array” is intended to denote “more than one.” As such, a “plurality” or “array” of regions includes two or more such regions, such as three or more such regions, etc.
Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
The terms “substantial,” “substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, as defined above, “substantially similar” is intended to denote that two values are equal or approximately equal.
Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred.
While various features, elements or steps of particular embodiments may be disclosed using the transitional phrase “comprising,” it is to be understood that alternative embodiments, including those that may be described using the transitional phrases “consisting” or “consisting essentially of,” are implied. Thus, for example, implied alternative embodiments to a method that comprises A+B+C include embodiments where a method consists of A+B+C and embodiments where a method consists essentially of A+B+C.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope of the disclosure. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the disclosure may occur to persons skilled in the art, the disclosure should be construed to include everything within the scope of the appended claims and their equivalents.
The following Example is intended to be non-restrictive and illustrative only, with the scope of the invention being defined by the claims.
An exemplary method was carried out using square sheets of non-chemically strengthened alkali aluminosilicate glass from Corning Incorporated (101.6 mm×101.6 mm×1.0 mm). The Visqueen protective film was removed from the surface and the sample was washed using a standard 4% Semiclean KG process on the Big Dipper. A bulk high-purity platinum monolith was obtained and polished to an optical finish. The monolith was placed in simple contact with the glass surface for use as the anode. On the opposing side, a graphite foil (Grafoil®) was placed in simple contact with the surface for use as the cathode. Both the anode and the cathode measured 63.5 mm×63.5 mm and thus did not cover the entire glass surface on either side of the sample, such that portions of each surface remained unpoled.
The anode, glass sheet, and cathode were loosely stacked and placed in a chamber with an inert nitrogen atmosphere. The stack was heated to 250° C. and allowed to equilibrate at this temperature for 15 minutes. DC voltage (+400V) was applied to the anode, with current limited to a maximum of 1 mA. An initial increase in current was observed, followed by a slow decay as a depletion (barrier) layer formed on the anodic surface. Voltage was applied to the stack for a period of 15 minutes, after which the heater was shut off and the stack was allowed to cool under voltage to a temperature below 100° C. The voltage was then discontinued, the chamber was vented, and the stack was manually separated.
Sections of the glass sheet comprising both poled (e.g., between the electrodes) and unpoled (e.g., outside of the electrodes) regions were cut from the sample. The poled and unpoled regions were analyzed for the presence of a barrier layer. The results of these analyses are presented in
The sample was subsequently chemically-strengthened by a standard ion exchange process. The glass was immersed in a molten salt bath of 100% KNO3 at 420° C. for 5.5 hours and subsequently rinsed. The glass was then analyzed using scanning electron microscopy (SEM) and an electron microprobe analysis (EMPA).
Compressive stress (CS) and depth of layer (DOL) were measured for each of the four regions depicted in
The measured CS and DOL for the unpoled regions were within the expected range, while the poled anodic region had no measurable CS or DOL, thus confirming the inhibition of ion-exchange. The poled cathodic surface showed CS and DOL values close to that of the unpoled regions, albeit slightly lower. This discrepancy is, however, suspected to be a measurement artifact due to low signal-to-noise ratio and/or imperfect optical measurement conditions possibly due to graphite residues on the glass sheet (particularly in light of the fact that the K2O profile for this region matched those of the unpoled regions as measured by EMPA (see
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 62/059,516 filed Oct. 3, 2014 the content of which is relied upon and incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US15/53454 | 10/1/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62059516 | Oct 2014 | US |
