WO2013134159A2

WO2013134159A2 - Sapphire laminates

Info

Publication number: WO2013134159A2
Application number: PCT/US2013/028938
Authority: WO
Inventors: Christopher D. Prest; Dale N MEMERING; David A. Pakula; Richard Hung Minh Dinh; Vincent Yan
Original assignee: Apple Inc.
Priority date: 2012-03-06
Filing date: 2013-03-04
Publication date: 2013-09-12
Also published as: WO2013134159A3

Abstract

Various sapphire and laminate structures are discussed herein. One embodiment may take the form of a sapphire structure having a first sapphire sheet with a first sapphire plane type forming the major surface and a second sapphire sheet having a second different sapphire plane type forming the major surface. The first and second sapphire sheets are fused together to form the sapphire structure.

Description

SAPPHIRE LAMINATES

Cross-Reference to Related Applications

This application claims priority to U.S. Provisional Patent Application No. 61/607,401 , filed March 6, 2012, and entitled, "Sapphire Laminates," the contents of which are incorporated herein by reference in their entirety.

Technical Field

The present application relates generally to sapphire and, more particularly, to thin sapphire laminates.

Background

Corundum is a crystalline form of aluminum oxide and is found in various different colors, all of which are generally commonly referred to as sapphire except for red corundum which is commonly known as ruby and pinkish-orange corundum which is known as padparadscha. Transparent forms of corundum are considered precious stones or gems. Generally, corundum is extraordinarily hard with pure corundum defined to have 9.0 Mohs and, as such, is capable of scratching nearly all other minerals. For the present purposes, the terms "corundum" and "sapphire" may be used interchangeably to refer generally to the crystalline form of aluminum oxide.

As may be appreciated, due to certain characteristics of corundum, including its hardness and transparent characteristics, among others, it may be useful in a variety of different applications. However, the same characteristics that are beneficial for particular applications commonly increase both the cost and difficulty in processing and preparing the sapphire for those applications. As such, beyond costs associated with it being a precious stone, the costs of preparing the corundum for particular uses is often prohibitive. For example, the sapphire's hardness makes cutting and polishing the material both difficult and time consuming when conventional processing techniques are implemented. Further, conventional processing tools such as cutters experience relatively rapid wear when used on corundum.

Summary

Various sapphire structure and laminate structures are discussed herein. One embodiment may take the form of a sapphire structure having a first sapphire sheet with a first sapphire plane type forming the major surface and a second sapphire sheet having a second different sapphire plane type forming the major surface. The first and second sapphire sheets are fused together to form the sapphire. Another embodiment may take the form of a sapphire laminate having a first sapphire sheet and a second sapphire sheet fused to the first sapphire sheet. The first and second sapphire sheets have the same crystal orientation with respect to their major surfaces, but different crystal orientations with respect to their edges. That is, the first and second sapphire sheets may have a common sapphire plane forming the major surface and different sapphire planes forming the secondary surfaces.

Yet another embodiment may take the form of a glass structure having a glass sheet and a sapphire sheet adhered to the glass sheet. The glass structure is less than or approximately equal to 1 mm thick.

Still another embodiment may take the form of a method of manufacturing a laminate structure. The method includes lapping and polishing a first side of a sapphire sheet and adhering the sapphire sheet to a glass sheet. The method also includes lapping and polishing a second side of the sapphire sheet and chemically strengthening the glass sheet.

Further still, another embodiments may include the use of a sapphire outer surface with a glass inner surface for the display of a consumer electronics device, where the two sapphire surfaces are laminated together with the glass providing support for the display and the sapphire providing scratch resistance and durability advantages.

While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following Detailed Description. As will be realized, the embodiments are capable of modifications in various aspects, all without departing from the spirit and scope of the embodiments. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

Brief Description of the Drawings

FIG. 1 illustrates an electronic device having a sapphire cover plate.

FIG. 2. illustrates two sheets of sapphire each having a different plane on the major surface prior to joining them together to form a sapphire structure.

FIG. 3 illustrates the two sheets of sapphire of FIG. 2 joined together to form a sapphire structure.

FIG. 4 is a flow chart illustrating the steps for creating the sapphire structure with two sapphire sheets. FIG. 5 illustrates two sheets of sapphire each having the same plane on the major surface but being oriented differently so that different planes are adjacent each other on the edge surface.

FIG. 6 illustrates the two sheets of sapphire of FIG. 5 joined together to form a sapphire structure.

FIG. 7. illustrates a sapphire sheet and a glass sheet prior to laminating the glass sheet with the sapphire sheet.

Fig. 8 illustrates a sapphire structure having a glass sheet in between two sapphire sheets.

Detailed Description

Sapphire laminates are discussed herein that take advantage of the characteristics of sapphire. In particular, sapphire is anisotropic and the crystalline structure of sapphire has multiple different planes. Although each plane exhibits significant hardness over other minerals, some planes may have additional, different characteristics. For example, while C- plane sapphire may be harder than other sapphire planes, A-plane sapphire may have a higher modulus of rupture than other planes. R-plane and M-plane sapphire may provide other advantages.

In some embodiments, two sapphire sheets having different sapphire planes are fused together to take advantage of the different characteristics of the different planes. In other embodiments, a secondary orientation of the sapphire sheets is controlled so that the edges may have different planes. In other embodiments a sapphire sheet maybe laminated over another material. For example, in one embodiment, a sapphire sheet may be adhered to a glass sheet.

Further, handling and processing sapphire sheets that are approximately one millimeter or less is difficult as it requires increased care to prevent breakage. More particularly, handling sapphire sheets less than approximately 0.5 millimeters (such as 0.4 millimeter sheets) typically results in increased breakage of the sapphire sheets. In accordance with techniques discussed herein, sapphire structures and/or sapphire laminates on glass allow creation of sheets of approximately one millimeter or less in thickness. Moreover, in the case of laminating glass with sapphire, the use of glass may provide cost savings over using sapphire, as sapphire is generally more expensive to obtain and/or process than glass. The sapphire laminate provides increased hardness to prevent wear, scratching and/or damage to the glass. Turning to FIG. 1 , an example electronic device 100 is illustrated in which a sapphire structure or laminate may be implemented. For example, a sapphire laminate 102 may be utilized as a cover glass and/or back plate of the device 100. Additionally, or alternatively, a sapphire laminate may be utilized as a cover and/or lens for a camera of the device. It should be appreciated that the sapphire laminates may be utilized in various different devices. For example, they may be used for windows, mirrors, cover glass, lenses and so forth in cameras, computers, mobile devices, watches, display devices, touch screens and clocks among other things.

FIG. 2 illustrates two sapphire sheets prior to fusing or adhering the sheets together. Each sheet may have a different plane in the major surface of the sheet. For example, a top sheet 104 may be a C-plane sheet and a lower sheet 106 may be an A-plane sheet. The C- plane may provide increased hardness, while the A-plane may provide a higher modulus of rupture. Thus, the combination of the two sheets may improve the hardness of the A-plane sheet and the strength of the C-plane sheet to provide an improved sapphire sheet over a sapphire sheet having only a single plane in the major surface. FIG. 3 shows the two sapphire sheets combined together to form the sapphire structure 108.

FIG. 4 is a flowchart illustrating a method 1 10 for fusing two sapphire sheets together. Initially, a first side of a first sapphire sheet is lapped and polished (Block 1 12). A first side of a second sheet is then lapped and polished (Block 1 14). The first sides of the first and second sapphire sheets are polished to help reduce the likelihood of any defects or incongruities that may influence the optical properties of the sheets. The lapped and polished sides of the first and second sapphire sheets are then fused together to form a sapphire laminate (Block 1 16). The fusing of the sapphire sheets may occur at, near or above the melting temperature of sapphire. In some embodiments, the two sheets may be adhered together using an adhesive instead of being fused. In embodiments where adhesive is utilized, the adhesive may have an index of refraction approximately equal to or near that of sapphire to help eliminate or reduce any refraction that may occur as light passes through from one sapphire sheet, through the adhesive and into the other sapphire sheet.

Once the two sheets are joined together to form the sapphire laminate, the exposed surfaces of the sapphire laminate may be lapped and polished (Block 118). Both exposed surfaces of the sapphire laminate may be lapped and polished simultaneously. That is, the sapphire laminate may be immersed in an abrasive and/or polishing slurry with a polishing pad on each side. The sapphire structure may also be mechanically modified to help reduce the likelihood of chipping or fracturing. (Block 120). For example, the edges may be beveled or chamfered. Further, the sapphire structure may be treated with oleophobic coating and/or printed with ink (Block 122).

It should be appreciated that in some embodiments, one or more steps may be omitted and/or the order that the steps are performed may be changed. For example, in one embodiment, there is not post lamination lapping. That is, the individual sheets may be fully finished prior to lamination.

The resulting sapphire laminate may achieve both superior hardness and strength due to the use of multiple planes. The combination of these characteristics may allow the sapphire laminate to be handled at thicknesses less than one millimeter with a reduced likelihood of breakage. In one example, each sapphire sheet may have a thickness of approximately one millimeter to help reduce the likelihood of breakage through handling prior to creation of the sapphire laminate. After the sapphire laminate has been formed, it may be lapped and polished to a thickness less than one millimeter. The hardness and strength provided by the laminate may permit further handling with a reduced risk of breakage. The thinner laminate may be useful to help reduce the depth or thickness of products implementing the sapphire laminate.

FIG. 5 illustrates another embodiment that takes the form of two sheets having the same plane of sapphire in their major surfaces. As used herein, the term major surface refers to the predominate plane of a sheet (e.g., the top or bottom surface of a sapphire sheet). In particular, two A-plane sheets of sapphire 130, 132 are shown. In this embodiment the A-plane sheets 130, 132 may be rotated relative to each other so that the edges 134, 136 are oriented to different planes. For example, the top sheet may have a C- plane along a right edge and the bottom sheet may have an M-plane along the right side. That is, a long axis of the top sheet 130 may be oriented in the C-plane, whereas the long axis of the bottom sheet 132 may be oriented in the M-plane. As such, a longitudinal axis of the sheets (as well as the axial axis) may be oriented at specific angles relative to the crystalline structure of the sapphire. In some embodiments, the edge of the sheets may not directly align with the crystalline structure. For example, the edge may be offset 10 degrees from the C-plane.

Providing a diversity of planes along the edge may help improve the resilience of the edge of the sapphire structure. For example, as the edges may have different sapphire planes that may fracture along different lines and further may provide different hardness and strength characteristics, it is believed that the edges may be more resistant to breakage. More specifically, if one plane is more resistant to chipping while another is preferable for strength considerations, lamination of the sheets together provides an edge that may advantageously have reduced chipping and increased strength. FIG. 6 shows the sapphire structure 138 after the two sheets have been fused together.

FIG. 7 illustrates yet another embodiment with a sapphire sheet 140 and a glass sheet 142. One side 144 of the sapphire sheet 140 is lapped and polished. The glass sheet may also be polished. The polished side of the sapphire is then adhered to the glass sheet with adhesive. An adhesive having an index of refraction that is in between the index of refraction of sapphire and the index of refraction of glass may be used to help reduce any optical effects that may occur at or along the interface between the sapphire and the glass. Generally, a thin and hard bond is desired to be achieved by the optically clear adhesive. Some epoxies and liquid optically clear adhesives ("LOCAs") may be used as adhesives.

Although the embodiment is discussed as a sapphire laminate on glass, it should be appreciated that a sapphire laminate may be applied to a steel back plate, a plastic back plate or other material. In these embodiments, a thin hard bond achievable using epoxies and LOCAs may still be desired.

The second side of the sapphire (e.g., the exposed side of the sapphire) may then be further lapped and polished. The glass may also be lapped and polished. The lapping and polishing of glass and sapphire may be done in a single double-lapping procedure. As glass is softer than the sapphire, it will generally be thinned more quickly than the sapphire during the lapping process. To counteract the quicker lapping of the glass, in some embodiments, the glass layer may initially be much thicker than the sapphire, or the lapping pads may be of a different material. After lapping and polishing the combined sapphire and glass, the total thickness may be less than approximately one millimeter. In some embodiments, the total thickness may be less than or approximately one millimeter or less (e.g., approximately 0.9, 0.8, 0.7, 0.6, 0.5, or 0.4 millimeters or less). Lapping the glass and the sapphire sheets together may minimize the yield challenges associated with lapping and polishing a thin sapphire sheet alone. That is, sapphire sheets may be less susceptible to damage when lapped together with the glass.

A computer numerical control process may be performed on the sapphire laminated glass prior to lapping and polishing. Additionally, an edge polish may be performed for the adhesive and joint to smooth the joint and to further eliminate any visible effects resulting from the joinder of the glass and the sapphire.

In some embodiments, the glass may be chemically strengthened. The chemical strengthening may be performed prior to or after the glass and the sapphire are adhered together, since the sapphire will be mostly unaffected by the glass chemical strengthening process. Generally, the glass may be chemically strengthened after the glass has been polished. In some embodiments, a minor re-polish may be performed after the chemical strengthening. Further, the glass and the sapphire may be mechanically modified, for example, to have chamfered edges.

Utilizing a glass substrate for the sapphire may provide increased resiliency for the sapphire. That is, the glass may help reduce the likelihood of breakage of the sapphire sheet by reinforcing the sapphire. Additionally, the use of the glass substrate may allow for thinner sheets of sapphire to be utilized which may provide cost savings as less sapphire will be used on a per device basis and more sapphire sheets may be harvested from the boule as they may be sliced thinner.

Fig. 8 illustrates a sapphire structure 150 having a glass sheet 152 in between two sapphire sheets 154, 156. The sapphire structure 150 may be configured to serve in a variety of different capacities. For example, the sapphire structure 150 may serve as a cover glass in a consumer electronic device, such as a smart phone, a tablet computer, a camera, and so forth. In some implementations, it may be advantageous for the sapphire structure to be thin. As such, it may be approximately 1 .5 mm or thinner. For example, the sapphire structure may be approximately 1 .4 mm, 1 .3 mm, 1 .2 mm, 1 .1 mm, 1 .0 mm, or thinner. Additionally, the various sheets may be adhered together in any suitable manner to form the structure.

In some embodiments, the sapphire sheets 154, 156 may have the same crystallographic orientation in their major surfaces. That is, each of the sapphire sheets may each be C-plane or A-plane sapphire. Although, in alternative embodiments, the sapphire sheets may each have different orientations in their major surface. For example, a first sheet 154 may be C-plane sapphire and the second sheet 156 may be A-plane sapphire.

Further, as discussed above, a secondary orientation of the sapphire sheets may vary with respect to each other to take advantage of the unique characteristics of the different planes of sapphire. For example, the first sheet 154 may have a secondary orientation that provides chipping resistance, whereas the second sheet 156 may have an orientation that is advantageous for strength. It should be appreciated that the secondary orientations may be selected to provide specific characteristics to a particular side or edge of the sapphire structure, as discussed above. Additionally, it should be appreciated that the secondary orientation may be offset an angle from the edge of the structure in some embodiments. That is, the crystallographic orientation of the sapphire sheets may be at an angle relative to the edge of the structure. For example, it may be offset an angle approximately 45 degrees from the long side of the structure. It should be appreciated that the offset angle may be any suitable angle between 0 and 90 degrees.

The foregoing describes some example embodiments of sapphire structure and laminates. Although the foregoing discussion has presented specific embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the embodiments. In particular, certain processes and/or treatments described above with respect one embodiment may be implemented with other embodiments. Accordingly, the specific embodiments described herein should be understood as examples and not limiting the scope thereof.

Claims

CLAIMS: We claim:

1 . A sapphire structure comprising:

a first sapphire sheet having a first sapphire plane type forming the major surface; and

a second sapphire sheet having a second sapphire plane type forming the major surface, the second sapphire sheet fused to the first sapphire sheet to form the sapphire structure.

2. The sapphire structure of claim 1 , wherein the first sapphire sheet comprises a C-plane sheet.

3. The sapphire structure of claim 1 , wherein the second sapphire sheet comprises an A-plane sheet.

4. The sapphire structure of claim 1 , wherein at least one edge of the sapphire structure is parallel to a sapphire plane.

5. The sapphire structure of claim 1 , wherein at least one edge of the sapphire structure comprises a first sheet edge oriented at a first angle with respect to the crystal planes and a second sheet edge oriented at a second angle with respect to the crystal planes.

6. The sapphire structure of claim 5, wherein at least one edge of the sapphire structure is oriented parallel to a C-plane.

7. The sapphire structure of claim 1 , wherein the sapphire structure is less than 1 mm thick.

8. The sapphire structure of claim 1 , comprising a chamfered edge, wherein the chamfered edge comprises one of a rounded chamfer or an angled chamfer.

9. A sapphire structure comprising:

a first sapphire sheet; and

a second sapphire sheet fused to the first sapphire sheet, the first and second

sapphire sheets having a common sapphire plane type forming the major surface and wherein at least the matching edges of the two sheets have different crystal log raphic orientations.

10. The sapphire structure of claim 9, wherein the first and second sapphire sheets have one of a C-plane or A-plane oriented major surface.

1 1 . The sapphire structure of claim 9, wherein the at least one edge of the sapphire structure is oriented parallel to at least one of a C-plane, an A-plane or an m-plane.

12. A glass assembly comprising:

a glass sheet; and a sapphire sheet adhered to the glass sheet, wherein the assembly is less than or approximately equal to 1 mm thick.

13. The glass assembly of claim 12, wherein the sapphire sheet is adhered to a first side of the glass sheet, wherein the glass assembly further comprises a second sapphire sheet adhered to a second side of the glass sheet.

14. The glass assembly of claim 13, wherein the total thickness of the glass assembly is less than 1 .5 mm thick.

15. The glass assembly of claim 13, wherein the sapphire sheet and the second sapphire sheet have a common sapphire plane type forming the major surface.

16. The glass assembly of claim 15, wherein the sapphire sheet and the second sapphire sheet have one of a C-plane or A-plane oriented major surface.

17. The glass assembly of claim 13, wherein matching edges of the sapphire sheet and the second sapphire sheet have different crystal log raphic orientations.

18. A method of manufacturing a glass assembly comprising:

lapping and polishing a first side of a sapphire sheet;

adhering the sapphire sheet to a glass sheet;

lapping and polishing a second side of the sapphire sheet; and

chemically strengthening the glass sheet.

19. The method of manufacturing of claim 18 further comprising applying an oleophobic or ink mask coating on at least one of the glass or the sapphire sheets

20. The method of claim 18 further comprising polishing the glass sheet.