PATENT DOCUMENT

Publication Number: US-10189743-B2
Application Number: US-89582310-A
Country: US
Kind Code: B2

Title: Enhanced strengthening of glass

Abstract:
Apparatus, systems and methods for improving strength of a thin glass member for an electronic device are disclosed. In one embodiment, the glass member can have improved strength by using multi-bath chemical processing. The multi-bath chemical processing allows greater levels of strengthening to be achieved for glass member. In one embodiment, the glass member can pertain to a glass cover for a housing of an electronic device.

Claims:
What is claimed is: 
     
       1. A method for strengthening a piece of glass, said method comprising:
 enhancing the piece of glass by placing the piece of glass in a first sodium solution for a first period of time to migrate sodium ions into the piece of glass; and 
 following the enhancing, chemically strengthening the piece of glass by placing the piece of glass in a potassium solution for a second period of time to exchange potassium ions for sodium ions in the piece of glass, the first period of time being less than the second period of time; 
 following the chemically strengthening, back exchanging the piece of glass by placing the piece of glass in a second sodium solution for a third period of time to back exchange sodium ions for potassium ions to move a compressive maximum inward approximately 70 microns from an outer edge of the piece of glass; and 
 following the back exchanging, post-processing the piece of glass by polishing the piece of glass, wherein: 
 the piece of glass is a cover glass for a portable electronic device; and 
 the piece of glass has a thickness of less than 1.0 mm. 
 
     
     
       2. The method as recited in  claim 1 , wherein the portable electronic device is a mobile phone. 
     
     
       3. The method as recited in  claim 1 , wherein the first sodium solution is a heated sodium solution. 
     
     
       4. The method as recited in  claim 1 , wherein the potassium solution includes a heated potassium solution. 
     
     
       5. The method as recited in  claim 4 , wherein the second sodium solution is a heated sodium solution. 
     
     
       6. The method as recited in  claim 1 , wherein the enhancing of the piece of glass allows the chemical strengthening to be more effective. 
     
     
       7. The method of  claim 1 , wherein the exchange of potassium ions for sodium ions in the piece of glass forms a compression layer near the outer edge of the piece of glass having a depth of approximately 50 microns. 
     
     
       8. A glass strengthening system for glass articles, comprising:
 a first bath station providing a first sodium solution, the first bath station serving to receive a glass article for a first period of time and to migrate sodium ions from the first sodium solution into the glass article to make it more susceptible to chemical strengthening; 
 a second bath station providing a potassium solution, the second bath station serving to receive the glass article for a second period of time following the first bath station and to exchange potassium ions for sodium ions within the glass article, the first period of time being less than the second period of time; and 
 a third bath station providing a second sodium solution, the third bath station serving to receive the glass article for a third period of time following the second bath station and to back exchange potassium ions for sodium ions within the glass article to move a compressive maximum inward approximately 70 microns from an outer edge of the glass article, wherein: 
 the glass article has a thickness of less than 1.0 mm, and 
 the glass article is a cover glass for a portable electronic device. 
 
     
     
       9. The glass strengthening system as recited in  claim 8 , wherein:
 the first sodium solution is heated to a first predetermined temperature; and 
 the potassium solution is heated to a second predetermined temperature. 
 
     
     
       10. The glass strengthening system as recited in  claim 8 , wherein the glass article is alumina silicate glass. 
     
     
       11. The glass strengthening system as recited in  claim 8 , wherein the portable electronic device is a mobile phone. 
     
     
       12. A method for processing a glass piece to improve its strength, the method comprising:
 submerging the glass piece in a first heated sodium bath for a first period of time to migrate sodium ions from the first heated sodium bath into exposed surfaces of the glass piece; 
 following submerging the glass piece in the first heated sodium bath, submerging the glass piece in a heated potassium bath for a second period of time to exchange potassium ions in the heated potassium bath for sodium ions in the glass piece to form a strengthened layer, the first period of time being less than the second period of time; 
 wherein a depth of the strengthened layer of the glass piece depends on the second period of time in the heated potassium bath; 
 following the submerging the glass piece in the heated potassium bath, submerging the glass piece in a second heated sodium bath for a third period of time to back exchange sodium ions in the second heated sodium bath for potassium ions in the strengthened layer of the glass piece to move a compressive maximum inward approximately 70 microns from an outer edge of the glass piece; and 
 attaching the glass piece to a portable electronic device, the glass piece serving as a portion of an outer surface of a housing of the portable electronic device. 
 
     
     
       13. The method as recited in  claim 12 , wherein the portable electronic device is a mobile phone. 
     
     
       14. The method as recited in  claim 12 , wherein the glass piece has a thickness of not more than 1.0 mm. 
     
     
       15. The method as recited in  claim 12 , wherein the glass piece is a cover glass for the portable electronic device. 
     
     
       16. A method for processing a glass piece to improve its strength, the method comprising:
 submerging the glass piece in a first heated sodium bath for a first period of time to migrate sodium ions from the first heated sodium bath into the glass piece, the first heated sodium bath having a temperature of about 350-450 degrees Celsius; 
 subsequent to submerging the glass piece in the first heated sodium bath, submerging the glass piece in a heated potassium bath for a second period of time to chemically strengthen the glass piece by exchanging potassium ions in the heated potassium bath for sodium ions in the glass piece; 
 subsequent to submerging the glass piece in the heated potassium bath, submerging the glass piece in a second heated sodium bath for a third period of time to back exchange sodium ions in the second heated sodium bath for potassium ions in the glass piece to move a compressive maximum inward approximately 70 microns from an outer edge of the glass piece; and 
 attaching the glass piece to a portable electronic device, the glass piece serving as a portion of an outer surface of a housing of the portable electronic device. 
 
     
     
       17. The method of  claim 16 , wherein the first period of time is approximately between 4-8 hours and the second period of time is approximately between 6-20 hours. 
     
     
       18. The method of  claim 16 , wherein the heated potassium bath has a temperature of approximately between 300 to 500 degree Celsius. 
     
     
       19. The method of  claim 16 , wherein the third period of time is approximately between 1-30 minutes and the second heated sodium bath has a temperature of approximately between 300 to 500 degree Celsius. 
     
     
       20. The method of  claim 16 , wherein following migrating sodium ions from the first heated sodium bath into the glass piece, the glass piece is able to be chemically strengthened to an extent greater than it would be without migrating the sodium ions.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 61/374,988, filed Aug. 18, 2010, and entitled “ENHANCED GLASS STRENGTHENING OF GLASS”, which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Conventionally, some portable electronic devices use glass as a part of their devices, either internal or external. Externally, a glass part can be provided as part of a housing, such a glass part is often referred to as a cover glass. The transparent and scratch-resistance characteristics of glass make it well suited for such applications. Internally, glass parts can be provided to support display technology. More particularly, for supporting a display, a portable electronic device can provide a display technology layer beneath an outer cover glass. A sensing arrangement can also be provided with or adjacent the display technology layer. By way of example, the display technology layer may include or pertain to a Liquid Crystal Display (LCD) that includes a Liquid Crystal Module (LCM). The LCM generally includes an upper glass sheet and a lower glass sheet that sandwich a liquid crystal layer therebetween. The sensing arrangement may be a touch sensing arrangement such as those used to create a touch screen. For example, a capacitive sensing touch screen can include substantially transparent sensing points or nodes dispersed about a sheet of glass. 
     Unfortunately, however, use of glass with portable electronic devices requires that the glass be relatively thin. Generally speaking, the thinner the glass the more susceptible the glass is to damage when the portable electronic device is stressed or placed under a significant force. Chemically strengthening has been used to strengthen glass. While chemically strengthening is effective, there is a continuing need to provide improved ways to strengthen glass, namely, thin glass. 
     SUMMARY 
     The invention relates generally to increasing the strength of glass. Through multi-bath chemical processing greater levels of strengthening can be achieved for glass articles. The multi-bath chemical processing can be achieved through the use of successive chemical baths. The use of multi-bath chemical processing for a glass article can enhance the effectiveness of the chemical strengthening process. Accordingly, glass articles that have undergone multi-bath chemical processing are able to be not only thin but also sufficiently strong and resistant to damage. The strengthened glass articles are well suited for use in consumer products, such as consumer electronic devices (e.g., portable electronic devices). 
     The invention can be implemented in numerous ways, including as a method, system, device, or apparatus. Several embodiments of the invention are discussed below. 
     As a method for strengthening a piece of glass, one embodiment can, for example, include at least obtaining a piece of glass that is to be chemically strengthened, enhancing the glass to make it more susceptible to chemical strengthening, and subsequently chemically strengthening the enhanced glass. 
     As a glass strengthening system for glass articles, one embodiment can, for example, includes at least a first bath station providing a sodium solution, and a second bath station providing a potassium solution. The first bath station serves to receive a glass article and to introduce sodium ions into surfaces of the glass article. The second bath station serves to receive the glass article following the first bath station and to exchange potassium ions for sodium ions within the glass article. 
     As a method for processing a glass piece to improve its strength, one embodiment can, for example, include at least: submerging the glass piece in a heated sodium bath, determining whether the glass piece should be removed from the heated sodium bath, subsequently submerging the glass piece in a heated potassium bath, determining whether the glass piece should be removed from the heated potassium bath, and performing post-processing on the glass piece following removal of the glass piece from the heated potassium bath. 
     A method for processing a glass piece to improve its strength, another embodiment can, for example, include at least: submerging the glass piece in a heated sodium bath; removing the glass piece from the heated sodium bath after being in the heated sodium solution for a first duration; subsequently submerging the glass piece in a heated potassium bath; removing the glass piece from the heated potassium bath after being in the heated potassium solution for a second duration; and performing post-processing on the glass piece following removal of the glass piece from the heated potassium bath. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  is a flow diagram of a glass strengthening process according to one embodiment. 
         FIG. 2  illustrates a glass strengthening system according to one embodiment. 
         FIG. 3  is a flow diagram of a glass piece process according to one embodiment. 
         FIG. 4  illustrates a glass strengthening system according to another embodiment. 
         FIG. 5  is a flow diagram of a back exchange process according to one embodiment. 
         FIGS. 6A and 6B  are diagrammatic representations of electronic device according to one embodiment. 
         FIGS. 7A and 7B  are a diagrammatic representation of an electronic device according to another embodiment. 
         FIG. 8  is flow diagram which illustrates a method of chemically strengthening glass, e.g., a glass cover, according to one embodiment. 
         FIG. 9A  is a cross-sectional diagram of a glass cover which has been chemically treated according to one embodiment. 
         FIG. 9B  is a cross-sectional diagram of a glass cover which has been chemically treated, as shown to include a chemically treated portion in which potassium ions have been implanted according to one embodiment. 
         FIG. 10  is a diagrammatic representation of a chemical treatment process that involves submerging a glass cover in an ion bath according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     The invention relates generally to increasing the strength of glass. Through multi-bath chemical processing greater levels of strengthening can be achieved for glass articles. The multi-bath chemical processing can be achieved through the use of successive chemical baths. The use of multi-bath chemical processing for a glass article can enhance the effectiveness of the chemical strengthening process. Accordingly, glass articles that have undergone multi-bath chemical processing are able to be not only thin but also sufficiently strong and resistant to damage. The strengthened glass articles are well suited for use in consumer products, such as consumer electronic devices (e.g., portable electronic devices). 
     Embodiments of the invention can relate to apparatus, systems and methods for improving strength of a thin glass member for a consumer product, such as a consumer electronic device. In one embodiment, the glass member may be an outer surface of a consumer electronic device. For example, the glass member may, for example, correspond to a glass cover that helps form part of a display area of the electronic device (i.e., situated in front of a display either as a separate part or integrated within the display). As another example, the glass member may form a part of a housing for the consumer electronic device (e.g., may form an outer surface other than in the display area). In another embodiment, the glass member may be an inner component of a consumer electronic device. For example, the glass member can be a component glass piece of a LCD display provided internal to the housing of the consumer electronic device. 
     The apparatus, systems and methods for improving strength of thin glass are especially suitable for glass covers or displays (e.g., LCD displays), particularly those assembled in small form factor electronic devices such as handheld electronic devices (e.g., mobile phones, media players, personal digital assistants, remote controls, etc.). The glass can be thin in these small form factor embodiments, such as less than 3 mm, or more particularly between 0.3 and 2.5 mm. The apparatus, systems and methods can also be used for glass covers or displays for other devices including, but not limited to including, relatively larger form factor electronic devices (e.g., portable computers, tablet computers, displays, monitors, televisions, etc.). The glass can also be thin in these larger form factor embodiments, such as less than 5 mm, or more particularly between 0.3 and 3 mm. 
     Embodiments of the invention are discussed below with reference to  FIGS. 1-10 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. The illustrations provided in these figures are not necessarily drawn to scale; instead, the illustrations are presented in a manner to facilitate presentation. 
       FIG. 1  is a flow diagram of a glass strengthening process  100  according to one embodiment. The glass strengthening process  100  serves to chemically strengthen a piece of glass such that it is better suited for its particular usage. 
     The glass strengthening process  100  can enhance  104  the glass for subsequent chemical strengthening. In one implementation, the glass can be enhanced  104  chemically through chemical processing. Specifically, the glass can be placed in a sodium solution so that sodium ions can migrate from the sodium solution into the glass, namely into the exposed surfaces of the glass. 
     After the glass has been enhanced  104 , the enhanced glass can be chemically strengthened  106 . In one implementation, the enhanced glass can be chemically strengthened  106  through chemical processing. Specifically, the enhanced glass can be placed in a potassium solution so that potassium ions from the potassium solution can be exchanged for sodium ions within the enhanced glass. 
     By enhancing  104  the glass, the glass becomes more susceptible to chemical strengthening  106 . In other words, the glass can be strengthened to a greater extent when the glass has been enhanced  104 . Following block  106 , the piece of glass has been chemically strengthened. Due to the enhancement of the glass, the glass is able to be chemically strengthened to a greater extent. Following the chemical strengthening, the glass strengthening process  100  can end. 
       FIG. 2  illustrates a glass strengthening system  200  according to one embodiment. The glass strengthening system  200  receives a glass article  202  to be strengthened through chemical processing. The glass article  202  is provided to a first bath station in which a first bath  204  is provided. The glass article  202  can be inserted (e.g., immersed) into the first bath  204  which includes a sodium solution  206 . Next, the glass article  202  is removed from the first bath station and provided to a second bath station. The second bath station provides a second bath  208 . The glass article can be inserted (e.g., immersed) into the second bath  208  which includes a potassium solution  210 . Later, the glass article  202  is removed from the second bath  208 . At this point, the glass article has been first enhanced and then strengthened. Since the glass article was enhanced, the glass article is able to be chemically strengthened to a greater extent than would otherwise have been determined if the glass article were not first enhanced. 
     Furthermore, following removal of the glass article from the second bath  208 , post-processing can be performed on the glass article. Post-processing can vary widely dependent on intended application for the glass article. However, post-processing can, for example, include one or more of rinsing, polishing, annealing and the like. 
     The sodium solution  206  within the first bath  204  can be heated to a predetermined temperature, and the glass article  202  can be immersed within the first bath  204  for a predetermined period of time. The degree of enhancement of the glass article  202  is dependent on: (1) type of glass, (2) concentration of bath (e.g., Na concentration), (3) time in the first bath  204 , and (4) temperature of the first bath  204 . Likewise, the potassium solution  210  within the second bath  208  can be heated to a predetermined temperature, and the glass article  202  can be immersed within the second bath  208  for a predetermined period of time. The degree of chemically strengthening provided by the second bath  208  to the glass article is dependent on: (1) type of glass, (2) concentration of bath (e.g., K concentration), (3) time in the second bath  208 , and (4) temperature of the second bath  208 . 
     In one implementation, the glass for the glass article can, for example, be alumina silicate glass or soda lime glass. Also, glass from different suppliers, even if the same type of glass, can have different properties and thus may require different values. The first bath  204  can be a sodium (Na) bath or a sodium nitrate (NaNO3) bath, in either case with a sodium concentration of 30%-100% mol. In another embodiment the first bath  204  can be a sodium nitrate (NaNO3) and potassium nitrate (KNO3) bath. The time for the glass article  202  to remain immersed in the first bath  204  can be about 4-8 hours and the temperature for the first bath  204  can be about 350-450 degrees Celsius. The time for the glass article  202  to remain immersed in the second bath  208  can be about 6-20 hours and the temperature for the second bath  208  can be about 300-500 degrees Celsius. 
       FIG. 3  is a flow diagram of a glass piece process  300  according to one embodiment. The glass piece process  300  serves to process a piece of glass such that is more suitable for subsequent use in a consumer product. 
     The glass piece process  300  initially obtains  302  a piece of glass. The glass piece can be submerged  304  in a heated sodium bath. A decision  306  can then determine whether the glass piece should be removed from the heated sodium bath. For example, the heated sodium bath can be maintained at a predetermined temperature and the glass piece can be submerged within the heated sodium for a predetermined period of time. As an example, the decision  306  can determine that the glass piece should be removed from the heated sodium bath after the glass piece has been immersed in the heated sodium bath for the predetermined amount of time. 
     Once the decision  306  determines that the glass piece is to be removed from the heated sodium bath, the glass piece can then be submerged  308  into a heated potassium bath. A decision  310  can then determine whether the glass piece should be removed from the heated potassium bath. The heated potassium bath can, for example, be maintained at a predetermined temperature and the glass piece can be submerged within the heated potassium bath for a predetermined period of time. 
     Once the decision  310  determines that the glass piece is to be removed from the potassium bath, post-processing on the glass piece can be performed  312 . The post-processing can vary depending upon application. For example, the post-processing can include one or more of: polishing, grinding, heating, annealing, cleaning and the like for the glass piece. Typically, the post-processing is performed on the glass piece to make the glass piece more suitable for its intended usage. 
     Following the performing  312  of the post-processing, the glass piece can be utilized  314  in a consumer product. The glass piece can be used as an outer portion of a housing for the consumer product, or can be used as an internal component (e.g., LCD glass panel) glass piece. For example, the consumer product can be a consumer electronics product, such as a portable electronic device. Following the block  314 , the glass piece process  300  can end. 
     The predetermined temperature for use with the heated potassium bath can be the same or different than the predetermined temperature for use with the heated sodium bath. The predetermined period of time for use with the heated potassium bath can be the same or different than the predetermined period of time for use with the heated sodium bath. For example, the glass piece can be immersed in a heated sodium bath at a temperature of about 350-450 degrees Celsius for a predetermined amount of time of about 4-8 hours. Also, for example, the glass piece can be immersed in a heated potassium bath at a temperature of about 300-500 degrees Celsius for a predetermined amount of time of about 6-20 hours. 
     According to another embodiment, glass processing can further include an additional bath. The additional bath can be provided to provide a small amount of back exchange of ions at the surfaces of a glass piece (glass article). The back exchange can serve to exchange potassium ions from the glass piece for sodium ions. This back exchange process can be useful to move a compressive maximum inward from the outer edges (10-70 micrometers) as defects or cracks proximate the edges reside slightly inward from the edges and are weak points that render the glass piece more susceptible to causing damage to the glass member. 
       FIG. 4  illustrates a glass strengthening system  400  according to another embodiment. The glass strengthening system  400  receives a glass article  402  to be strengthened through chemical processing. The glass article  402  is provided to a first bath station where a first bath  404  is provided. The glass article  402  can be inserted (e.g., immersed) into the first bath  404  which includes a sodium solution  406 . Next, the glass article  402  is removed from the first bath station and provided to a second bath station. The second bath station provides a second bath  408 . The glass article can be inserted (e.g., immersed) into the second bath  408  which includes a potassium solution  410 . Later, the glass article  402  is removed from the second bath  408 . At this point, the glass article has been first enhanced and then strengthened. Since the glass article was enhanced, the glass article is able to be chemically strengthened to a greater extent. 
     Additionally, after the glass article  402  has been removed from the second bath  408 , the glass article can be provided to a third bath station where a third bath  412  is provided. The glass article  402  can be inserted (e.g., immersed) into the third bath  412  which includes a sodium solution  414 . Here, potassium ions from the glass article exchange with sodium ions in the sodium solution. This can be referred to as a back exchange because some ions previously exchanged with the glass article are effectively unexchanged or returned. Subsequently, the glass article  402  is removed from the third bath  412 . 
     The sodium solution  406  within the first bath  404  can be heated to a predetermined temperature, and the glass article  402  can be immersed within the first bath  404  for a predetermined period of time. The degree of enhancement of the glass article is dependent on at least: (1) type of glass, (2) concentration of bath (e.g., Na concentration), (3) time in the first bath  402 , and (4) temperature of the first bath  402 . Likewise, the potassium solution  410  within the second bath  408  can heated to a predetermined temperature, and the glass article  402  can be immersed within the second bath  408  for a predetermined period of time. Still further, the sodium solution  414  within the third bath  412  can heated to a predetermined temperature, and the glass article  402  can be immersed within the third bath  412  for a predetermined period of time. 
     The predetermined period of time for use with the second bath  408  can be the same or different than the predetermined period of time for use with the first bath  404  or the third bath  412 . The predetermined period of time for use with the third bath  412  can be the same or different than the predetermined period of time for use with the first bath  404  or the second bath  408 . Typically, the predetermined period of time for use with the third bath  412  is substantially less than the predetermined period of time for use with the first bath  404 . 
     Furthermore, following removal of the glass article from the third bath  412 , post-processing can be performed on the glass article. Post-processing can vary widely dependent on intended application for the glass article. However, post-processing can, for example, include one or more of rinsing, polishing, annealing and the like. 
     The sodium solution  406  within the first bath  404  can be heated to a predetermined temperature, and the glass article  402  can be immersed within the first bath  404  for a predetermined period of time. The degree of enhancement of the glass article  402  is dependent on: (1) type of glass, (2) concentration of bath (e.g., Na concentration), (3) time in the first bath  404 , and (4) temperature of the first bath  404 . Likewise, the potassium solution  410  within the second bath  408  can heated to a predetermined temperature, and the glass article  402  can be immersed within the second bath  408  for a predetermined period of time. The degree of chemically strengthening provided by the second bath  408  to the glass article is dependent on: (1) type of glass, (2) concentration of bath (e.g., K concentration), (3) time in the second bath  408 , and (4) temperature of the second bath  408 . 
     In one implementation, the glass for the glass article can, for example, be alumina silicate glass or soda lime glass. Also, glass from different suppliers, even if the same type of glass, can have different properties and thus may require different values. The first bath  404  can be a sodium (Na) bath or a sodium nitrate (NaNO3) bath, in either case with a sodium concentration of 30%-100% mol. The time for the glass article  402  to remain immersed in the first bath  404  can be about 4-8 hours and the temperature for the first bath  404  can be about 350-450 degrees Celsius. The time for the glass article  402  to remain immersed in the second bath  408  can be about 6-20 hours and the temperature for the second bath  408  can be about 300-500 degrees Celsius. The third bath  412  can be a sodium (Na) bath or a sodium nitrate (NaNO3) bath, in either case with a sodium concentration of 30%-100% mol. The time for the glass article  402  to remain immersed in the third bath  412  can be about 1-30 minutes and the temperature for the third bath  412  can be about 350-450 degrees Celsius. 
       FIG. 5  is a flow diagram of a back exchange process  500  according to one embodiment. The back exchange process  500  provides additional, optional processing that can be used with the glass piece process  300  illustrated in FIG.  3 . For example, the back exchange process  500  can be optionally used following block  310  and prior to block  312  of the glass piece process  300 . 
     The back exchange process  500  provides an additional bath for providing back exchange of sodium into the glass piece. According to the back exchange process  500 , the glass piece can be submerged  502  into a heated sodium bath. A decision  504  can then determine whether the glass piece should be removed from the heated sodium bath. For example, the heated sodium bath can be maintained at a predetermined temperature and the glass piece can be submerged within the heated sodium bath for a predetermined period of time. As an example, the decision  504  can determine that the glass piece should be removed from the heated sodium bath after the glass piece has been immersed in the heated sodium bath for the predetermined amount of time. 
     Once the decision  504  determines that the glass piece is to be removed from the heated sodium bath, the processing of the glass piece can then return to perform pre-processing at block  312  and subsequent operations of the glass piece process  300  illustrated in  FIG. 3 . 
     In the back exchange process  500 , the heated sodium bath can be heated to a predetermined temperature, and the glass piece can be immersed within the heated sodium bath for a predetermined period of time. The extent of the back exchange fir the glass piece can be dependent on: (1) type of glass, (2) concentration of bath (e.g., Na concentration), (3) time in the sodium bath, and (4) temperature of the sodium bath. In one implementation, the glass for the glass piece can, for example, be alumina silicate glass or soda lime glass. Also, glass from different suppliers, even if the same type of glass, can have different properties and thus may require different values. The heated sodium bath can be a sodium (Na) bath or a sodium nitrate (NaNO3) bath, in either case with a sodium concentration of 30%-100% mol. The predetermined period of time for the glass piece to remain immersed in the heated sodium bath for back exchange can be about 1-30 minutes and the temperature for the heated sodium bath can be about 350-450 degrees Celsius. 
     As previously discussed, glass covers can be used as an outer surface of portions of a housing for electronic devices, such as portable electronic devices. Those portable electronic devices that are small and highly portable can be referred to as handheld electronic devices. A handheld electronic device may, for example, function as a media player, phone, internet browser, email unit or some combination of two or more of such. A handheld electronic device generally includes a housing and a display area. 
       FIGS. 6A and 6B  are diagrammatic representations of electronic device  600  according to one embodiment.  FIG. 6A  illustrates a top view for the electronic device  600 , and  FIG. 6B  illustrates a cross-sectional side view for electronic device  600  with respect to reference line A-A′. Electronic device  600  can include housing  602  that has glass cover window  604  (glass cover) as a top surface. Cover window  604  is primarily transparent so that display assembly  606  is visible through cover window  604 . Cover window  604  can be chemically strengthened using the multi-bath chemical processing described herein. Display assembly  606  can, for example, be positioned adjacent cover window  604 . Housing  602  can also contain internal electrical components besides the display assembly, such as a controller (processor), memory, communications circuitry, etc. Display assembly  606  can, for example, include a LCD module. By way of example, display assembly  606  may include a Liquid Crystal Display (LCD) that includes a Liquid Crystal Module (LCM). In one embodiment, cover window  604  can be integrally formed with the LCM. Housing  602  can also include an opening  608  for containing the internal electrical components to provide electronic device  600  with electronic capabilities. In one embodiment, housing  602  may need not include a bezel for cover window  604 . Instead, cover window  604  can extend across the top surface of housing  602  such that the edges of cover window  604  can be aligned (or substantially aligned) with the sides of housing  602 . The edges of cover window  604  can remain exposed. Although the edges of cover window  604  can be exposed as shown in  FIGS. 6A and 6B , in alternative embodiment, the edges can be further protected. As one example, the edges of cover window  604  can be recessed (horizontally or vertically) from the outer sides of housing  602 . As another example, the edges of cover window  604  can be protected by additional material placed around or adjacent the edges of cover window  604 . 
     Cover window  604  may generally be arranged or embodied in a variety of ways. By way of example, cover window  604  may be configured as a protective glass piece that is positioned over an underlying display (e.g., display assembly  606 ) such as a flat panel display (e.g., LCD) or touch screen display (e.g., LCD and a touch layer). Alternatively, cover window  604  may effectively be integrated with a display, i.e., glass window may be formed as at least a portion of a display. Additionally, cover window  604  may be substantially integrated with a touch sensing device such as a touch layer associated with a touch screen. In some cases, cover window  604  can serve as the outer most layer of the display. 
       FIGS. 7A and 7B  are diagrammatic representations of electronic device  700  according to another embodiment of the invention.  FIG. 7A  illustrates a top view for electronic device  700 , and  FIG. 7B  illustrates a cross-sectional side view for electronic device  700  with respect to reference line B-B′. Electronic device  700  can include housing  702  that has glass cover window  704  (glass cover) as a top surface. In this embodiment, cover window  704  can be protected by side surfaces  703  of housing  702 . Here, cover window  704  does not fully extend across the top surface of housing  702 ; however, the top surface of side surfaces  703  can be adjacent to and aligned vertically with the outer surface of cover window  704 . Since the edges of cover window  704  can be rounded for enhanced strength, there may be gaps  705  that are present between side surfaces  703  and the peripheral edges of cover window  704 . Gaps  705  are typically very small given that the thickness of cover window  704  is thin (e.g., less than 3 mm). However, if desired, gaps  705  can be filled by a material. The material can be plastic, rubber, metal, etc. The material can conform in gap  705  to render the entire front surface of electronic device  700  flush, even across gaps  705  proximate the peripheral edges of cover window  704 . The material filling gaps  705  can be compliant. The material placed in gaps  705  can implement a gasket. By filling the gaps  705 , otherwise probably undesired gaps in the housing  702  can be filled or sealed to prevent contamination (e.g., dirt, water) forming in the gaps  705 . Although side surfaces  703  can be integral with housing  702 , side surface  703  could alternatively be separate from housing  702  and, for example, operate as a bezel for cover window  704 . 
     Cover window  704  is primarily transparent so that display assembly  706  is visible through cover window  704 . Display assembly  706  can, for example, be positioned adjacent cover window  704 . Housing  702  can also contain internal electrical components besides the display assembly, such as a controller (processor), memory, communications circuitry, etc. Display assembly  706  can, for example, include a LCD module. By way of example, display assembly  706  may include a Liquid Crystal Display (LCD) that includes a Liquid Crystal Module (LCM). In one embodiment, cover window  704  is integrally formed with the LCM. Housing  702  can also include an opening  708  for containing the internal electrical components to provide electronic device  700  with electronic capabilities. 
     The front surface of electronic device  700  can also include user interface control  708  (e.g., click wheel control). In this embodiment, cover window  704  does not cover the entire front surface of electronic device  700 . Electronic device  700  essentially includes a partial display area that covers a portion of the front surface. 
     Cover window  704  may generally be arranged or embodied in a variety of ways. By way of example, cover window  704  may be configured as a protective glass piece that is positioned over an underlying display (e.g., display assembly  706 ) such as a flat panel display (e.g., LCD) or touch screen display (e.g., LCD and a touch layer). Alternatively, cover window  704  may effectively be integrated with a display, i.e., glass window may be formed as at least a portion of a display. Additionally, cover window  704  may be substantially integrated with a touch sensing device such as a touch layer associated with a touch screen. In some cases, cover window  704  can serve as the outer most layer of the display. 
     As noted above, the electronic device can be a handheld electronic device or a portable electronic device. The invention can serve to enable a glass cover to be not only thin but also adequately strong. Since handheld electronic devices and portable electronic devices are mobile, they are potentially subjected to various different impact events and stresses that stationary devices are not subjected to. As such, the invention is well suited for implementation of glass surfaces for handheld electronic device or a portable electronic device that are designed to be thin. 
     The strengthened glass, e.g., glass covers or cover windows, is particularly useful for thin glass applications. For example, the thickness of a glass cover being strengthen can be between about 0.5-2.5 mm. In other embodiments, the strengthening is suitable for glass products whose thickness is less than about 2 mm, or even thinner than about 1 mm, or still even thinner than about 0.6 mm. 
     Chemically strengthening glass, e.g., glass covers or cover windows, can be more effective for edges of glass that are rounded by a predetermined edge geometry having a predetermined curvature (or edge radius) of at least 10% of the thickness applied to the corners of the edges of the glass. In other embodiments, the predetermined curvature can be between 20% to 50% of the thickness of the glass. A predetermined curvature of 50% can also be considered a continuous curvature, one example of which is illustrated in  FIG. 3E . 
     In one embodiment, the size of the glass cover depends on the size of the associated electronic device. For example, with handheld electronic devices, the size of the glass cover is often not more than five (5) inches (about 12.7 cm) diagonal. As another example, for portable electronic devices, such as smaller portable computers or tablet computers, the size of the glass cover is often between four (4) (about 10.2 cm) to twelve (12) inches (about 30.5 cm) diagonal. As still another example, for portable electronic devices, such as full size portable computers, displays (including televisions) or monitors, the size of the glass cover is often between ten (10) (about 25.4 cm) to twenty (20) inches (about 50.8 cm) diagonal or even larger. 
     However, it should be appreciated that with larger screen sizes, the thickness of the glass layers may need to be greater. The thickness of the glass layers may need to be increased to maintain planarity of the larger glass layers. While the displays can still remain relatively thin, the minimum thickness can increase with increasing screen size. For example, the minimum thickness of the glass cover can correspond to about 0.3 mm for small handheld electronic devices, about 0.5 mm for smaller portable computers or tablet computers, about 1.0 mm or more for full size portable computers, displays or monitors, again depending on the size of the screen. However, more generally, the thickness of the glass cover can depend on the application and/or the size of electronic device. 
     As discussed above, glass cover or, more generally, a glass piece may be chemically treated such that surfaces of the glass are effectively strengthened. Through such strengthening, glass pieces can be made stronger so that thinner glass pieces can be used with consumer electronic device. Thinner glass with sufficient strength allows for consumer electronic device to become thinner. 
       FIG. 8  illustrates a process  800  of chemically treating surfaces of a glass piece in accordance with one embodiment. The process  800  can represent processing associated with chemical strengthening at a second bath station or a potassium bath as discussed above, according to one embodiment. The process  800  of chemically treating surfaces, e.g., edges, of a glass piece can begin at step  802  in which the glass piece is obtained. The glass piece may be obtained, in one embodiment, after a glass sheet is singulated into glass pieces, e.g., glass covers, and the edges of the glass pieces are manipulated to have a predetermined geometry. It should be appreciated, however, that a glass piece that is to be chemically treated may be obtained from any suitable source. 
     In step  804 , the glass piece can be placed on a rack. The rack is typically configured to support the glass piece, as well as other glass pieces, during chemical treatment. Once the glass piece is placed on the rack, the rack can be submerged in a heated ion bath in step  806 . The heated ion bath may generally be a bath which includes a concentration of ions (e.g., Alkali metal ions, such as Lithium, Cesium or Potassium). It should be appreciated that the concentration of ions in the bath may vary, as varying the concentration of ions allows compression stresses on surfaces of the glass to be controlled. The heated ion bath may be heated to any suitable temperature to facilitate ion exchange. 
     After the rack is submerged in the heated ion bath, an ion exchange is allowed to occur in step  808  between the ion bath and the glass piece held on the rack. A diffusion exchange occurs between the glass piece, which generally includes Na +  ions, and the ion bath. During the diffusion exchange, Alkali metal ions, which are larger than Na +  ions, effectively replace the Na +  ions in the glass piece. In general, the Na +  ions near surface areas of the glass piece may be replaced by the Alkali ions, while Na +  ions are essentially not replaced by Alkali ions in portions of the glass which are not surface areas. As a result of the Alkali ions replacing Na +  ions in the glass piece, a compressive layer is effectively generated near the surface of the glass piece. The Na +  ions which have been displaced from the glass piece by the Alkali metal ions become a part of the ion solution. 
     A determination can be made in step  810  as to whether a period of time for submerging the rack in the heated ion bath has ended. It should be appreciated that the amount of time that a rack is to be submerged may vary widely depending on implementation. Typically, the longer a rack is submerged, i.e., the higher the exchange time for Alkali metal ions and Na +  ions, the deeper the depth of the chemically strengthened layer. For example, with thickness of the glass sheet being on the order of 1 mm, the chemical processing (i.e., ion exchange) provided in the ion bath can be provide into the surfaces of the glass pieces 10 micrometers or more. For example, if the glass pieces are formed from soda lime glass, the depth of the compression layer due to the ion exchange can be about 10 microns. As another example, if the glass pieces are formed from alumino silicate glass, the depth of the compression layer due to the ion exchange can be about 50 microns. 
     If the determination in step  810  is that the period of time for submerging the rack in the heated ion bath has not ended, then process  800  flow can return to step  817  in which the chemical reaction is allowed to continue to occur between the ion bath and the glass piece. Alternatively, if it is determined that the period of time for submersion has ended, then the rack can be removed from the ion bath in step  812 . Upon removing the rack from the ion bath, the glass piece may be removed from the rack in step  814 , and the process  800  of chemically treating surfaces of a glass piece can be completed. However, if desired, the glass piece can be polished. Polishing can, for example, remove any haze or residue on the glass piece following the chemical treatment. 
     A glass cover which has undergone a chemical strengthening process generally includes a chemically strengthened layer, as previously mentioned.  FIG. 9A  is a cross-sectional diagram of a glass cover which has been chemically treated such that a chemically strengthened layer is created according to one embodiment. A glass cover  900  includes a chemically strengthened layer  928  and a non-chemically strengthened portion  926 . Although the glass cover  900  is, in one embodiment, subjected to chemical strengthening as a whole, the outer surfaces receive the strengthening. The effect of the strengthening is that the non-chemically strengthened portion  926  is in tension, while the chemically strengthened layer  928  is in compression. While glass cover  900  is shown as having a rounded edge geometry  902 , it should be appreciated that glass cover  900  may generally have any edge geometry, though rounded geometries at edges may allow for increased strengthening of the edges of glass cover  900 . Rounded edge geometry  902  is depicted by way of example, and not for purposes of limitation. 
     Chemically strengthened layer  928  has a thickness (y) which may vary depending upon the requirements of a particular system in which glass cover  900  is to be utilized. Non-chemically strengthened portion  926  generally includes Na +  ions  934  but no Alkali metal ions  936 . A chemical strengthening process causes chemically strengthened layer  928  to be formed such that chemically strengthened layer  928  includes both Na +  ions  934  and Alkali metal ions  936 . 
       FIG. 10  is a diagrammatic representation of a chemical treatment process that involves submerging a glass cover in an ion bath according to one embodiment. When glass cover  1000 , which is partially shown in cross-section, is submerged or soaked in a heated ion bath  1032 , diffusion occurs. As shown, Alkali metal ions  1034  which are present in glass cover  1000  diffuse into ion bath  1032  while Alkali metal ions  1036  (e.g., potassium (K)) in ion bath  1032  diffuse into glass cover  1000 , such that a chemically strengthened layer  1028  is formed. In other words, Alkali metal ions  1036  from ion bath  1032  can be exchanged with Na +  ions  1034  to form chemically strengthened layer  1028 . Alkali metal ions  1036  typically would not diffuse into a center portion  1026  of glass cover  1000 . By controlling the duration (i.e., time) of a chemical strengthening treatment, temperature and/or the concentration of Alkali metal ions  1036  in ion bath  1032 , the thickness (y) of chemically strengthened layer  1028  may be substantially controlled. 
     The concentration of Alkali metal ions in an ion bath may be varied while a glass cover is soaking in the ion bath. In other words, the concentration of Alkali metal ions in a ion bath may be maintained substantially constant, may be increased, and/or may be decreased while a glass cover is submerged in the ion bath without departing from the spirit or the scope of the present invention. For example, as Alkali metal ions displace Na +  ions in the glass, the Na +  ions become part of the ion bath. Hence, the concentration of Alkali metal ions in the ion bath may change unless additional Alkali metal ions are added into the ion bath. 
     The techniques describe herein may be applied to glass surfaces used by any of a variety of electronic devices including but not limited handheld electronic devices, portable electronic devices and substantially stationary electronic devices. Examples of these include any known consumer electronic device that includes a display. By way of example, and not by way of limitation, the electronic device may correspond to media players, mobile phones (e.g., cellular phones), PDAs, remote controls, notebooks, tablet PCs, monitors, all in one computers and the like. 
     The various aspects, features, embodiments or implementations of the invention described above can be used alone or in various combinations. 
     Additional details on strengthening edges of glass articles can be found in: (i) U.S. Provisional Patent Application No. 61/156,803, filed Mar. 2, 2009 and entitled “Techniques for Strengthening Glass Covers for Portable Electronic Devices”, which is herein incorporated by reference; and (ii) International Patent Application No. PCT/US2010/025979, filed Mar. 2, 2010 and entitled “Techniques for Strengthening Glass Covers for Portable Electronic Devices”, which is herein incorporated by reference. 
     Additional details on chemical strengthening processing using different chemical baths can be found in U.S. Provisional Patent Application No. 61/301,585, filed Feb. 4, 2010 and entitled “Techniques for Strengthening Glass Covers for Portable Electronic Devices,” which is hereby incorporated herein by reference. 
     Although only a few embodiments of the invention have been described, it should be understood that the invention may be embodied in many other specific forms without departing from the spirit or the scope of the present invention. By way of example, the steps associated with the methods of the invention may vary widely. Steps may be added, removed, altered, combined, and reordered without departing from the spirit of the scope of the invention. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. 
     While this specification contains many specifics, these should not be construed as limitations on the scope of the disclosure or of what may be claimed, but rather as descriptions of features specific to particular embodiment of the disclosure. Certain features that are described in the context of separate embodiments can also be implemented in combination. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.

Metadata:
Filing Date: 20100930
Publication Date: 20190129
Grant Date: 20190129
Priority Date: 20100818
Inventors: ZADESKY, STEPHEN PAUL
PREST, CHRISTOPHER
WEBER, DOUGLAS
Assignee: APPLE INC
CPC Classifications: [{"code": "H04M1/185", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/001", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/0266", "inventive": false, "first": false, "tree": "[]"}, {"code": "C03C21/001", "inventive": true, "first": true, "tree": "[]"}, {"code": "C03C21/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/185", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0266", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/001", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/185", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0266", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 44533167