Electronic device having a glass component with crack hindering internal stress regions

A component for an electronic device including an internal compressive stress region is disclosed herein. The internal compressive stress region may be created in a glass portion of the component or in a glass ceramic portion of the component. Electronic devices comprising the components and method for making the components are also disclosed.

FIELD

The described embodiments relate generally to glass components for an electronic device. More specifically, the described embodiments relate to glass components that include internal compressive stress regions that may hinder crack propagation through the glass component.

BACKGROUND

Electronic devices often include transparent exterior components. For example, transparent cover members both protect and allow viewing of a display within the device. However, some traditional glass cover members may be susceptible to cracking when subjected to severe impact, such as when the electronic device is dropped.

Embodiments described herein are directed to electronic device components that may have advantages as compared to some traditional glass components. The techniques described herein are generally directed to components that may include a residual internal compressive stress region in a glass or glass ceramic portion. The components described herein may have improved resistance to cracking and therefore provide enhanced durability of the components and electronic devices including the components. In general, the components formed using the described techniques may not suffer from the drawbacks associated with some traditional glass components for electronic devices.

SUMMARY

Embodiments described herein relate to components for electronic devices which include a crack hindering residual internal compressive stress region. The internal compressive stress region may be located in a glass or glass ceramic portion of the component. As examples, the component may be a glass component, such as a monolithic glass component formed of a single piece of glass or a glass laminate. As an additional example, the component may comprise an internal glass ceramic portion and external glass portions. The components may be transparent, translucent, or opaque.

In embodiments, the component comprises a residual internal compressive stress region. The residual internal compressive stress region is present in the absence of an external load or force. The presence of a residual internal compressive stress region in the component may strengthen the component against cracking. Therefore, a glass component including a residual internal compressive stress region may be referred to as a strengthened glass component. The term strengthened glass component may also be used to refer to a component comprising both glass and glass ceramic portions. For brevity, a residual compressive stress region may be referred to herein as a compressive stress region and a residual tensile stress region may be referred to herein as a tensile stress region.

The internal compressive stress region of the component may act to hinder movement of a crack through a thickness of the component, thereby limiting damage to the component. For example, the internal compressive stress in this region may prevent a crack from passing through the region. In some cases the crack may continue to move through the component, but may move in a different direction. For example, the crack may at least partially reverse direction by moving away from the internal compressive stress region. Therefore, the residual internal compressive stress region may deflect a crack propagating through an internal tensile stress region in the component. The internal compressive stress region may be in the form of a layer.

In embodiments, the component further comprises at least one external compressive stress region. The external compressive stress region may provide an initial barrier to generation and/or movement of cracks from a surface of the component into an internal portion of the component. The external compressive stress region may be positioned along at least one external surface of the component. In embodiments, an external compressive stress region may be positioned along front, back, and side surfaces of the component. The component further comprises an internal tensile stress region located between the internal compressive stress region and the external compressive stress region. The internal tensile stress region may be inward from the external compressive stress region along a thickness of the component and the internal compressive stress region may be inward from the internal tensile stress region along a thickness of the component. The external compressive stress region and/or the internal tensile stress region may be in the form of a layer.

As an example, a strengthened glass component for an electronic device may comprise a surface at least partially defining an exterior of the electronic device and a compressive stress region extending from the surface to a first depth in the component. The surface further defines an exterior of the component. The compressive stress region may therefore be referred to as an external compressive stress region. The component may further comprise an internal tensile stress region inward from the external compressive stress region and an internal compressive stress region inward from the internal tensile stress region. The internal tensile stress region may extend from the first depth to a second depth in the component and the internal compressive stress region may extend from the second depth to a third depth in the component. In further embodiments, the internal tensile stress region is a first internal tensile stress region and the component further comprises a second internal tensile stress region inward from the internal compressive stress region and extending from the third depth to a fourth depth in the component.

In additional embodiments, the component comprises multiple internal compressive stress regions and/or external compressive stress regions. For example, a strengthened glass component for an electronic device may comprise: a first external surface defining at least a portion of an exterior of the electronic device, a first external compressive stress region along the first external surface, a first internal tensile stress region inward from the first external compressive stress region, and an internal compressive stress region inward from the first internal tensile stress region. The strengthened glass component may further comprise: a second external surface opposite to the first external surface, a second external compressive stress region along the second external surface, and a second internal tensile stress region inward from the second external compressive stress region. In further embodiments, the component comprises a third internal tensile stress region between the first internal compressive stress region and the second internal compressive stress region.

In embodiments, a method for making a component comprising an internal compressive stress region comprises creating an internal compressive stress region, an external compressive stress region, and an internal tensile stress region in the component. The external compressive stress region may be along at least one surface of the component. The internal tensile stress region may be inward from the external compressive stress region. The internal tensile stress region may also be positioned between the external and the internal compressive stress regions. The internal compressive stress region is inward from the external compressive stress region and the internal tensile stress region. In further embodiments, the method comprises creating another internal tensile stress region inward from the internal compressive stress region of the glass component

For example, a method of strengthening a glass component comprises forming an external compressive stress region extending from a surface to a first depth in the glass component. The method further comprises forming an internal tensile stress region extending from the first depth to a second depth in the glass component and forming an internal compressive stress region extending from the second depth to a third depth in the glass component.

Several techniques can create an internal compressive stress region in the component. For example, an exchange of ions in a glass or a glass ceramic component can create an internal compressive stress region. As another example, crystallizing a portion of a glass component to form a glass ceramic can create an internal compressive stress region. In additional examples, glass layers having different compositions and/or properties can be used to create an internal compressive stress region in a glass laminate component. In embodiments, the glass laminate component comprises a first outer layer formed from a first glass material, an inner layer formed from a second glass material, and a second outer layer formed from a third glass material. For example, the glass laminate component may comprise outer layers each having a higher coefficient of thermal expansion than that of the inner layer. As another example, the inner layer of the glass laminate may have a greater tendency to expand in response to ion exchange than the outer layers.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred implementation. To the contrary, the described embodiments are intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the disclosure and as defined by the appended claims.

The current description is generally directed to components for electronic devices, which incorporate one or more internal compressive stress regions. The internal compressive stress region may be located in an internal glass portion or in an internal glass ceramic portion of the component. The component may further comprise an external compressive stress region and an internal tensile stress region between the external compressive stress region and the internal compressive stress region.

The presence of one or more internal compressive stress regions may reduce or hinder the propagation of cracks or defects within the glass component. In some implementations, the internal compressive stress regions may improve the durability and/or impact resistance of the glass component. The techniques and examples described herein may be used to create glass components for a cover glass of an electronic device, enclosure components of an electronic device, and other glass articles that may form at least a portion of an external surface of the electronic device. In some instances, the glass component may be internal to the electronic device or an electronic device enclosure.

As described in more detail herein, the internal compressive stress regions may be formed any number of different ways. In some example embodiments, the internal compressive stress region may be created, at least in part, due to an ion exchange process. The internal compressive stress region may also be created by crystallization of a portion of a glass component to form a glass ceramic. As an additional example, the internal compressive stress region may be created in an inner layer of a glass laminate having different thermal expansion and/or ion expansion properties than outer layers of the glass laminate. Electronic devices including the components and methods for making the components are also disclosed herein.

FIG. 1Adepicts a front view of a simplified example of an electronic device. As shown inFIG. 1A, the electronic device100includes a housing110and a cover member120. The housing110may be formed from one or more metal or metallic components, a glass component, a ceramic component, or a combination thereof. The housing110may include a side surface116. As an example, the side surface116may be defined by one or more metal components. In one example, the side surface116is formed from a series of metal segments that are separated by polymer or dielectric segments that provide electrical isolation between adjacent metal segments. As additional examples, the side surface116may be defined by one or more glass components, a glass ceramic component, or a component including a glass and a glass ceramic.

The cover member120may be formed from a glass, a ceramic, or a combination thereof. As shown, cover member120defines a front surface122, which may form at least a portion of an exterior of the electronic device100. For example, the front surface122of the cover member120may define at least a portion of the front surface of the electronic device100. The cover member120may be coupled to the housing110using a fastener or fastening technique. For example, the cover member120may be coupled to the housing110using an adhesive, an engagement feature, a fastener, or a combination of any of these. As discussed herein, the cover member120may include an internal compressive stress region. However, the description provided is not limited to cover members and the principles described herein are applicable to other electronic device components, such as components of the housing110.

The cover member120may be positioned over a display that is configured to produce a graphical output that is viewable through a transparent window region of the cover member. For purposes of the following disclosure, the cover member120is described as a sheet of glass. However, the cover member120may be formed from multiple layers that include glass sheets, polymer sheets, and/or various coatings and layers. In some instances, a touch-sensitive layer (e.g., a capacitive touch sensor) is attached to the cover member120and positioned between the cover member120and the display.

FIG. 1Bdepicts a back view of the electronic device100ofFIG. 1A. The housing110further comprises back surface114and side surface116. In embodiments, the electronic device100may further include a second cover member, which forms at least a portion of the back surface114of the electronic device100. The second cover member may be formed from a glass material that may include an internal compressive stress region, as described herein. The second or rear cover member may be partially transparent, formed from a transparent glass sheet, or may be opaque. In some cases, the second or rear cover includes one or more openings for a camera, light source, or other optical component.

In some embodiments, the electronic device100may be a mobile telephone, a notebook computing device (e.g., a notebook), a tablet computing device (e.g., a tablet), a portable media player, a wearable device, or another type of portable device. The electronic device100may also be a desktop computer system, computer component, input device, or virtually any other type of electronic product or device component.

As shown inFIG. 2, cover member220may define a front surface222, a back surface224, and a side surface226extending between the front surface222and the back surface224. As shown, cover member220is generally rectangular and defines a length, L, a width, W, and a thickness, T. The thickness T of cover member220may be from 0.3 mm to 3 mm, 0.1 mm to 2 mm, or from 25 μm to 1 mm. While cover member220is depicted as being generally rectangular in shape for purposes of illustration, the cover member shape shown is not intended to be limiting. In addition, while the edges228between the front surface222and the side surface226and between the back surface224and the side surface226are shown as rounded, the shape shown is not intended to be limiting.

As an example, the cover member220may be at least partially transparent. For example, the cover member220may have a transmittance in the visible spectrum of at least 50% or at least 75%. The cover member220may define one or more transparent portions to allow viewing of a display within the electronic device and/or function as a window for a camera or an optical sensor. In other examples, the cover member120may be translucent or opaque over a portion or all of the area of the component. The cover member120may also include one or more regions that are covered with a decoration or an opaque coating.

In embodiments, the cover member220includes an aluminosilicate glass or glass ceramic or a boroaluminosilicate glass or glass ceramic. As used herein, an aluminosilicate glass or glass ceramic includes the elements aluminum, silicon, and oxygen, but may further include other elements. Similarly, a boroaluminosilicate glass or glass ceramic includes the elements boron, aluminum, silicon, and oxygen, but may further include other elements. For example, an aluminosilicate glass or glass ceramic or a boroaluminosilicate glass or glass ceramic may further include monovalent or divalent ions which compensate charges due to replacement of silicon ions by aluminum ions. Suitable monovalent ions include, but are not limited to, alkali metal ions such as Li+, Na+, or K+. Suitable divalent ions include alkaline earth ions such as Ca2+or Mg2+. In embodiments, the aluminosilicate glass may comprise greater than 0.1 mol % Li2O or greater than 1 mol % Li2O. In additional embodiments, the base composition may comprise from 0.1% to 10% lithium by weight of the base glass.

FIG. 3Ashows a simplified cross-section view of an example cover member320having an internal and an external compressive stress region. The cross-section is taken along line A-A inFIG. 2and hatching is used to indicate regions of compressive stress. The cover member320includes an internal compressive stress region342, an external compressive stress region344, and an internal tensile stress region354.

As shown inFIG. 3A, external compressive stress region344extends along the front surface322, the back surface324, and the side surface326of the cover member320. External compressive stress region344may also extend around the edge between the front surface322and the side surface326. The external compressive stress region344may extend from front surface322or back surface324to a first depth D1. The external compressive stress region344may take the form of a layer and be referred to as an external compressive stress layer.

The cover member320further includes an internal tensile stress region354inward from the external compressive stress region344. As shown, the internal tensile stress region354is located between external compressive stress region344and internal compressive stress region342. The internal tensile stress region354may extend from the first depth D1to a second depth D2. The internal tensile stress region354may take the form of a layer and be referred to as an internal tensile stress layer.

The cover member320further includes internal compressive stress region342inward from the internal tensile stress region354. As shown, the internal compressive stress region342may extend from the second depth D2to a third depth D3. As shown, an internal compressive stress region342may be centrally located in the cover member320. As an example, a centrally located stress region may include locations about halfway between front surface322and back surface324and about halfway between opposing side surfaces326. As used herein, a stress region is inward of another stress region when at least a portion of the stress region is closer to the central portion of the cover member than the other stress region. The external compressive stress region344may take the form of a layer and be referred to as an external compressive stress layer.

FIG. 3Bshows an example of the variation of residual stress with thickness for the cover member ofFIG. 3A. The cover member320includes an internal compressive stress region342, an internal tensile stress region354, and an external compressive stress region344. The internal tensile stress region354is inward from the external compressive stress region344and the internal compressive stress region342is inward from the internal tensile stress region354. As shown inFIG. 3B, a level of the compressive stress is greater in external compressive stress region344than in internal compressive stress region342.

In additional embodiments, the external compressive stress region may comprise a first external compressive stress region and a second external compressive stress region. For example, a first external compressive stress region may be formed along a first external surface of the cover member and a second external compressive stress region may be formed along a second external surface of the cover member. The second external surface may be generally opposite to the first external surface.

FIG. 3Cshows a partial cross-section of a cover member320including a first external compressive stress region and a second external compressive stress region. The first external compressive stress region344amay be formed along front surface322and the second external compressive stress region344bmay be formed along back surface324. The cover member may further comprise a first internal tensile stress region354ainward from the first internal compressive stress region344aand a second internal tensile stress region354binward from the second external compressive stress region344b. In addition, the cover member320may comprise an internal compressive stress region342inward from the first internal tensile stress region354a. The internal compressive stress region342may also be inward from the second internal tensile stress region354b.

FIG. 3Dshows an example of the variation of residual stress with thickness for the cover member320ofFIG. 3C. The cover member320includes an internal compressive stress region342inward from first and second internal tensile stress regions354aand354b. First and second internal tensile stress regions354aand354bare inward from first and second external compressive stress regions344aand344b. The first and the second external compressive stress regions344a,344bmay be substantially similar or may differ. The first and the second internal tensile stress regions354a,354bmay also be substantially similar or may differ. As shown inFIG. 3D, a level of the compressive stress is greater in external compressive stress regions344a,344bthan in internal compressive stress region342. In embodiments, a maximum level of the compressive stress in the external compressive stress regions344a,344bmay be from 3 to 10 times or from 5 to 10 times a maximum level of the compressive stress in the internal compressive stress regions. In embodiments, the surface compressive stress of each of external compressive stress regions344aand344bmay be from 400 MPa to 800 MPa or from 600 MPa to 800 MPa. As shown inFIG. 3D, thickness of the internal compressive stress region342may be greater than a depth of the external compressive stress region344. In embodiments, the depth of each of the first and the second compressive stress regions344aand344bmay be from 5 microns to 50 microns.

FIG. 4Ashows a simplified cross-section view of another example cover member420having an internal and an external compressive stress region. The cover member420includes an internal compressive stress region442, external compressive stress region444, and internal tensile stress regions452and454.

As shown inFIG. 4A, external compressive stress region444extends from front surface422and back surface424to a first depth D1. As shown, the depth of the external compressive stress region444may be substantially equal around the cover member420. In further embodiments, the external compressive stress region444may vary around the cover member420. For example, a first external compressive stress region may be formed along a first external surface of the cover member and a second external compressive stress region may be formed along a second external surface of the cover member. The second external surface may be generally opposite to the first external surface. For example, the first external surface may correspond to front surface422and the second external surface may correspond to back surface424. The external compressive stress region444may take the form of a layer and be referred to as an external compressive stress layer.

The cover member420further includes internal tensile stress region454. As shown, internal tensile stress region454is located inward from external compressive stress region444. Internal tensile stress region454is also located between external compressive stress region444and internal compressive stress region442. The internal tensile stress region454may extend from the first depth D1to a second depth D2. The internal tensile stress region454may take the form of a layer and be referred to as an internal tensile stress layer.

The cover member420further includes internal compressive stress region442. As shown, the internal compressive stress region442is inward from internal tensile stress region454. As shown, the internal compressive stress region442extends from the second depth D2to a third depth D3.The internal compressive stress region442may take the form of a layer and be referred to as an internal compressive stress layer.

The cover member420further includes internal tensile stress region452. As shown, internal tensile stress region452is located inward from internal compressive stress region442. The internal tensile stress region452may take the form of a layer and be referred to as an internal tensile stress layer.

FIG. 4Bshows an example of the variation of residual stress with thickness for the cover member420ofFIG. 4A. The cover member420includes an internal tensile stress region452, an internal compressive stress region442, an internal tensile stress region454, and an external compressive stress region444. As shown inFIG. 4B, a level of the compressive stress is greater in external compressive stress region444than in internal compressive stress region442.

FIG. 4Cshows a partial cross-section of another cover member420including an internal compressive stress region and first and second external compressive stress regions. The first external compressive stress region444ais formed along front surface422and the second external compressive stress region444bis formed along back surface424. The cover member420further comprises a first internal tensile stress region454ainward from the first internal compressive stress region444aand a second internal tensile stress region454binward from the second external compressive stress region444b. In addition, the cover member420comprises a first internal compressive stress region442ainward from the first internal tensile stress region454aand a second internal compressive stress region442binward from the second internal tensile stress region454b. Third internal tensile stress region452may also be inward from both first internal compressive stress region442aand second internal compressive stress region442b.

FIG. 4Dshows an example of the variation of residual stress with thickness for the cover member420ofFIG. 4C. The cover member420includes an internal tensile stress region452inward from internal compressive stress regions442aand442b. Internal compressive stress regions442aand442bare inward from internal tensile stress regions454aand454band internal tensile stress regions454aand454barea are inward from external compressive stress regions444aand444b. As shown inFIG. 4D, a level of the compressive stress is greater in external compressive stress regions444a,444bthan in internal compressive stress regions442a,442b. In embodiments, a maximum level of the compressive stress in the external compressive stress regions444a,444bmay be from 3 to 10 times or from 5 to 10 times a maximum level of the compressive stress in the internal compressive stress regions442a,442b. In embodiments, the surface compressive stress of each external compressive stress regions444a,444bmay be from 400 MPa to 800 MPa or from 600 MPa to 800 MPa. A thickness of the internal compressive stress region442a,442bmay be greater than a depth of the external compressive stress regions444a,444b. In embodiments, the depth of each of the external compressive stress regions444a,444bmay be from 5 microns to 50 microns.

In embodiments, an ion exchange process may create an internal compressive stress region in a component. For example, alkali metal ions in a glass portion of the component may be exchanged for larger alkali metal ions at a temperature below the strain point of the glass. The ion exchange process may also create an external compressive stress region along an external surface of the component and an internal tensile stress region inward from the external compressive stress region. The internal compressive stress region is inward from the internal tensile stress region. In further embodiments, the component further comprises another internal tensile stress region inward from the internal compressive stress region.

For example, the component may comprise an external compressive stress region including third alkali metal ions having a third size, an internal tensile stress region including first alkali metal ions having a first size, and an internal compressive stress region including second alkali metal ions having a second size. The second alkali metal ions and the third alkali metal ions may be introduced into the component by ion exchange. The second size may be greater than the first size and the third size may be greater than the second size. Further, the external compressive stress region may be enriched in the third alkali metal ions compared to the internal tensile stress region and the internal compressive stress region may be enriched in the second alkali metal ions as compared to the internal tensile stress region. In embodiments, the internal compressive stress region, although enriched in the second alkali metal ions, further comprises the first metal alkali metal ions.

As an additional example, a strengthened glass component may comprise a first and a second external compressive stress region, the first external compressive stress region along a first external surface and the second external compressive stress region along a second external surface. The first and the second external compressive stress regions each include third alkali metal ions having a third size. The strengthened glass component further comprises a first and a second internal tensile stress region, the first internal tensile stress region inward from the first external compressive stress region and the second internal tensile stress region inward from the second external compressive stress region. The first and the second internal tensile stress region each include first alkali metal ions having a first size. The strengthened glass component further comprises an internal compressive stress region inward from the first and the second internal tensile stress regions. The internal compressive stress region includes second alkali metal ions having a second size.

As a further example, the internal compressive stress region may be a first internal compressive stress region and the component may further comprise a second internal compressive stress region and a third internal tensile stress region. The third internal tensile stress region comprises the first alkali metal ions and the first and the second internal compressive stress regions are enriched in the second alkali metal ions as compared to the first, second, and third internal tensile stress regions. In embodiments, the first and second internal compressive stress regions, although enriched in the second alkali metal ions, further comprise the first metal alkali metal ions. The second size may be greater than the first size and the third size may be greater than the second size.

In embodiments, the component includes an ion exchangeable glass or glass ceramic. Ion exchangeable glasses include, but are not limited to, soda lime glasses, aluminosilicate glasses, and aluminoborosilicate glasses. Ion exchangeable glass ceramics include, but are not limited to, aluminosilicate glass ceramics and aluminoborosilicate glass ceramics.

FIG. 5Ashows a detailed view of the inset1-1ofFIG. 3Afor an example glass cover member520having an internal compressive stress region created at least in part by an ion exchange process. The glass cover member520comprises an outer portion538, portion536inward from outer portion538, and inner portion532inward from portion536. As shown inFIG. 5A, inner portion532may be centrally located. A first part of outer portion538is adjacent front surface522; a second part of outer portion538is adjacent back surface524. The side surface of the cover member is not shown in this field of view. The alkali metal ions present in the glass cover member are schematically illustrated, but the glass network is not shown.

Prior to the ion exchange process, the cover member may be an ion exchangeable glass comprising first alkali metal ions561. As schematically shown inFIG. 5A, inner portion532of the cover member520includes first alkali metal ions561and second alkali metal ions562. The first alkali metal ions561have a first size and the second alkali metal ions562have a second size greater than the first size. The second alkali metal ions562may have been introduced by the ion exchange process. Inner portion532is enriched in the second alkali metal ions562as compared to portion536. The inner portion532may also be enriched in the second alkali metal ions562as compared to portion538.

Portion536of the cover member520includes first alkali metal ions561. Portion536may be depleted of the second alkali metal ions562and enriched in the first alkali metal ions561as compared to inner portion532. The portion536may also be enriched in the first alkali metal ions561as compared to portion538. The first alkali metal ions may comprise first alkali metal ions present in the glass prior to the ion exchange process and additional first alkali metal ions introduced during the ion exchange process.

Outer portion538of the cover member520comprises third alkali metal ions563having a third size greater than the first size and is enriched in the third alkali metal ions563as compared to portion536. Outer portion538may also be enriched in the third alkali metal ions563as compared to portion532. The second alkali metal ions562and the third alkali metal ions563may have been introduced by the ion exchange process. Outer portion538may further include first alkali metal ions561. The first alkali metal ions561may comprise first alkali metal ions present in the glass prior to the ion exchange process and additional first alkali metal ions introduced during the ion exchange process.

As an example, the first alkali metal ions561(M1+) are lithium ions, the second alkali metal ions562(M2+) are sodium ions, and the third alkali metal ions563(M3+) are potassium ions. In embodiments, the outer portion538of the cover is enriched in potassium ions and the inner portion532is enriched in sodium ions as compared to the portion536.

FIG. 5Bshows an example of the variation of residual stress along the thickness of the glass cover member520ofFIG. 5A. The glass cover member520includes internal compressive stress region542. Internal compressive stress region542may be located in inner portion532of the glass cover member520and created because inner portion532is enriched in the second alkali metal ions as compared to portion536.

The glass cover member520further includes external compressive stress region544. External compressive stress region544may be located in outer portion538of the glass cover member520and created because outer portion538is enriched in the third alkali metal ions563as compared to portion536. As shown inFIG. 5B, a level of the compressive stress is greater in external compressive stress region544than in internal compressive stress region542.

The glass cover member520further comprises internal tensile stress region554between external compressive stress region544and internal compressive stress region542. The tensile stress in internal tensile stress region554at least partially balances the compressive stress in the glass cover member520. Internal tensile stress region554is at least partially located in portion536of the glass cover member520. In some embodiments, the internal tensile stress region554may extend slightly into inner portion532and/or outer portion538of the glass cover member520.

Therefore, the internal compressive stress region542of the glass cover member520ofFIGS. 5A-5Bmay comprise first alkali metal ions561and second alkali metal ions562and may be enriched in the second alkali metal ions562as compared to internal tensile stress region554. Internal tensile stress region554may comprise first alkali metal ions561. Second alkali metal ions562and/or third alkali metal ions563may be present in internal tensile stress region554, but to a lesser amount as compared to the external compressive stress region544and the internal compressive stress region542. External compressive stress region544may comprise first alkali metal ions561and third alkali metal ions563and may be enriched in the third alkali metal ions563as compared to internal tensile stress region554.

FIG. 6illustrates a flowchart of an example process600for making an internal compressive stress region in a component using multiple ion exchange operations. Process600further creates an external compressive stress region and an internal tensile stress region. For example, process600may be used to form the glass cover member ofFIGS. 5A-5B.

Process600includes multiple ion exchange operations. During each ion exchange operation, alkali metal ions in the component may be exchanged for alkali metal ions in a bath. Alkali metal ions from the bath are thus introduced into the component. The bath may comprise a molten ionic salt. The bath temperature may be from the melting point of the salt to approximately 600° C.

The temperature of the bath may be below a strain point or a glass transition point of a glass portion of the component, so that exchanging the alkali metal ions in the component with larger alkali metal ions tends to cause an expansion of an ion-exchanged portion of the component. However, expansion of the ion-exchanged portion of the component may be constrained by other portions of the component which are not ion exchanged. As a result, a compressive stress region, such as a biaxial residual compressive stress region, may be created in the ion-exchanged portion. For example, the ion-exchanged portion may be in the form of an ion-exchanged layer.

The process600may include operation602of exchanging first alkali metal ions in an ion exchangeable portion of the component with second alkali metal ions. The first alkali metal ions have a first size and the second alkali metal ions have a second size larger than the first size. The first alkali metal ions may be exchanged for the second alkali metal ions by immersing the component in a bath comprising the second alkali metal ions. The second alkali metal ions are thus introduced into the component.

For example, operation602may be a first ion exchange operation which forms a first ion exchange layer which extends throughout a thickness of the glass component. As another example, the first ion exchange layer may extend to a first exchange depth which is less than half a thickness of the glass component. For example, the first alkali metal ions may be lithium ions, the second alkali metal ions may be sodium ions, and the first ion exchange layer may comprise sodium ions which have been introduced into the glass via the first ion exchange operation.FIG. 7Bschematically illustrates an example distribution of the first and second alkali metal ions after operation602.

The process600may further include operation604of exchanging second alkali metal ions in the component with first alkali metal ions. Operation604may follow operation602. Operation604may be a second ion exchange which forms a second ion exchange layer. The second ion exchange layer extends to a second exchange depth less than the first exchange depth. The second ion exchange may comprise immersing the component in a bath comprising the first alkali metal ions. First alkali metal ions may thus be re-introduced into the component. For example, the second ion exchange layer may be depleted of sodium ions and enriched in lithium ions as compared to the first ion exchange layer.

In addition, process600may include operation606of exchanging second alkali metal ions in the component with third alkali metal ions. Operation606may further include exchanging first alkali metal ions in the component with the third alkali metal ions. Ion exchange operation606may be a third ion exchange which forms a third ion exchange layer. The third ion exchange layer extends to a third exchange depth less than the second exchange depth. Operation606may comprise immersing the component in a bath comprising the third alkali metal ions. Operation606may follow operation604or may occur concurrently with operation604, in which case the bath may comprise the first alkali metal ions and the third alkali metal ions. For example, the third alkali metal ions may be potassium ions and the third ion exchange layer may be enriched in potassium ions as compared to the second ion exchange layer.FIG. 7Bschematically illustrates an example distribution of the first, second, and third alkali metal ions after operations604and606.

FIGS. 7A, 7B, and 7Cschematically illustrate three stages in an example process for creating an internal compressive stress region in a glass cover using multiple ion exchange operations.FIG. 7Ashows a detailed view of a part of a glass cover member720prior to the first ion exchange. The glass cover member720comprises first alkali metal ions761distributed across the thickness of the glass cover member720. The field of view ofFIGS. 7A-7Cshows front surface722and back surface724, but not the side surface of the glass cover member.

FIG. 7Bshows the glass cover member720ofFIG. 7Afollowing an exchange of at least some of the first alkali metal ions761with second alkali metal ions762having a second size greater than the first size. For example,FIG. 7Bmay show the glass cover member after operation602of process600. As shown, the first ion exchange occurs throughout the thickness of the glass cover member720. However, a greater amount of exchange occurs near front surface722and back surface724, so that the glass cover member720is depleted of the first alkali metal ions761and enriched in the second alkali metal ions762near the front surface722and the back surface724. For example, the glass cover member720may be substantially depleted of first alkali metal ions761in portion737of the glass cover member720. A remainder portion733of the glass cover member720comprises the first alkali metal ions761and the second alkali metal ions762.

FIG. 7Cshows the glass cover member720ofFIG. 7Bafter a second and a third ion exchange which occur concurrently. For example,FIG. 7Cmay show the glass cover member after operations604and606of process600. During the second ion exchange, at least some of the second alkali metal ions762are exchanged for first alkali metal ions761to a second exchange depth DE2less than half the thickness of the glass cover member720. During the third ion exchange, at least some third alkali metal ions763having a third size larger than the second size are exchanged for second alkali metal ions762, first alkali metal ions761, or a combination thereof to third exchange depth DE3which is less than DE2. For example, the glass cover member720may be immersed in a bath comprising the first alkali metal ions761and the third alkali metal ions763to achieve the second and third ion exchanges.

As a result, inner portion732of the glass cover member720comprises the first alkali metal ions761and the second alkali metal ions762. Portion736comprises the first alkali metal ions761and is depleted of the second alkali metal ions762as compared to inner portion732. Outer portion738of the glass cover member720comprises the third alkali metal ions763and the first alkali metal ions761and is enriched in the third alkali metal ions763as compared to portion736. The composition profile ofFIG. 7Ccan produce an internal compressive stress region in portion732, as previously discussed with respect toFIGS. 5A and 5B.

FIG. 8Ashows a detailed view of the inset2-2ofFIG. 4Afor an example glass cover member820having internal compressive stress regions created at least in part by an ion exchange process. The glass cover member820comprises outer portion838, portion836inward from outer portion838, portion834inward from portion836, and inner portion832. A first part of outer portion838is adjacent front surface822; a second part of outer portion838is adjacent back surface824. The side surface of the glass cover member820is not shown in this field of view. Prior to the ion exchange process, the glass cover member820may comprise an ion exchangeable glass comprising first alkali metal ions861.

As shown inFIG. 8A, an inner portion832of the glass cover member820comprises first alkali metal ions861after the ion exchange process. The first alkali metal ions861may comprise first alkali metal ions861present in the glass prior to the ion exchange process. The first alkali metal ions861have a first size.

Portion834of the glass cover member820comprises first alkali metal ions861and second alkali metal ions862. The second alkali metal ions862have a second size greater than the first size. The second alkali metal ions862may have been introduced by the ion exchange process. Portion834is enriched in the second alkali metal ions862and depleted of the first alkali metal ions861as compared to portion832. Portion834may also be enriched in the second alkali metal ions862as compared to portion836.

Portion836of the glass cover member820comprises first alkali metal ions861. Portion836may be depleted of the second alkali metal ions862and enriched in the first alkali metal ions861as compared to portion834. Portion836may also be enriched in the first alkali metal ions861as compared to portion838. The first alkali metal ions861may comprise first alkali metal ions861present in the glass prior to the ion exchange process and additional first alkali metal ions861introduced during the ion exchange process.

Outer portion838of the glass cover member820comprises first alkali metal ions861and third alkali metal ions863having a third size greater than the first size. Outer portion838is enriched in the third alkali metal ions863as compared to portion836. Outer portion838may also be enriched in the third alkali metal ions863as compared to portions834and832.

As an example, the first alkali metal ions861(M1+) are lithium ions, the second alkali metal ions862(M2+) are sodium ions, and the third alkali metal ions863(M3+) are potassium ions. In embodiments, the outer portion838of the cover is enriched in potassium ions as compared to the portion836and the portion834is enriched in sodium ions as compared to the portions832and836.

FIG. 8Bshows an example of the variation of residual stress along the thickness of the glass cover member820ofFIG. 8A. The glass cover member820includes internal compressive stress region842. Internal compressive stress region842may be located in portion834of the glass cover member820and created because portion834is enriched in the second alkali metal ions862as compared to portion836and inner portion832.

The glass cover member820further includes external compressive stress region844. External compressive stress region844may be located in outer portion838of the glass cover member820and created because outer portion838is enriched in the third alkali metal ions863as compared to portion836. As shown inFIG. 8B, a level of the compressive stress is greater in external compressive stress region844than in internal compressive stress region842.

The glass cover member820further comprises internal tensile stress region854between external compressive stress region844and internal compressive stress region842. The tensile stress in internal tensile stress region854at least partially balances the residual compressive stress in the glass cover member820. Internal tensile stress region854is at least partially located in portion836of the glass cover member820. In some embodiments, internal tensile stress region854may extend slightly into inner portion832and/or outer portion838of the glass cover member. The glass cover member820further comprises internal tensile stress region852inward from internal compressive stress region842. The tensile stress in internal tensile stress region852at least partially balances compressive stress in the glass cover member820and is at least partially located in inner portion832of the glass cover member820.

Therefore, the internal compressive stress region842of the glass cover member820ofFIGS. 8A-8Bmay include second alkali metal ions and may be enriched in the second alkali metal ions as compared to internal tensile stress regions854and852. Internal tensile stress regions854and852may include first alkali metal ions. Internal compressive stress region842may further include first alkali metal ions, but may be depleted in the first alkali metal ions as compared to internal tensile stress regions854and852.

External compressive stress region844may comprise third alkali metal ions and may be enriched in the third alkali metal ions as compared to internal tensile stress region854. External compressive stress region844may further comprise first alkali metal ions, but may be depleted in the first alkali metal ions as compared to internal tensile stress region854.

FIGS. 9A, 9B, and 9Cschematically illustrate three stages in an example process for creating an internal compressive stress region in a component using multiple ion exchange operations. For example, the process may be used to produce the component ofFIGS. 8A and 8B.FIG. 9Ashows the glass cover member920prior to ion exchange; the glass cover member920comprises first alkali metal ions961distributed across the thickness of the glass cover member920. The field of view ofFIGS. 9A-9Cshows front surface922and back surface924of the glass cover member920, but not the side surface.

FIG. 9Bshows the glass cover member920after a first ion exchange. During the first ion exchange at least some of the first alkali metal ions961are exchanged with second alkali metal ions962having a second size greater than the first size to a first ion exchange depth DE1less than half the thickness of the glass cover member920. As shown, the exchange does not occur throughout the thickness of the glass cover member920but occurs in portions933. A greater amount of exchange occurs near front surface922and back surface924, so that the glass cover member920is depleted of the first alkali metal ions961and enriched in the second alkali metal ions962near the front surface922and the back surface944. A remainder portion931of the glass cover member920is not substantially ion exchanged and comprises the first alkali metal ions961, but comprises few, if any, of the second alkali metal ions962.

FIG. 9Cshows the glass cover member920after a second and a third ion exchange which occur concurrently. During the second ion exchange, at least some of the second alkali metal ions962are exchanged for first alkali metal ions961to a second exchange depth DE2less than the first ion exchange depth DE1. During the third ion exchange, at least some of the third alkali metal ions963having a third size larger than the second size are exchanged for second alkali metal ions962, first alkali metal ions961, or a combination thereof to a third exchange depth DE3which is less than DE2. For example, the glass cover member920may be immersed in a bath comprising the first alkali metal ions961and the third alkali metal ions963to achieve the desired ion exchange.

As a result, inner portion932of the glass cover member920comprises the first alkali metal ions961. Portion934of the glass cover member920comprises the first alkali metal ions961and the second alkali metal ions962. Portion936comprises the first alkali metal ions and is depleted of the second alkali metal ions as compared to portion934. Outer portion938of the glass cover member920comprises the third alkali metal ions963and the first alkali metal ions961and is enriched in the third alkali metal ions963as compared to portion936. The composition profile ofFIG. 9Ccan produce an internal compressive stress region within portion934, as previously discussed with respect toFIGS. 8A and 8B.

In embodiments, crystallizing an internal portion of a glass component to form a glass ceramic can create an internal compressive stress region in the component. Selective crystallization of an internal portion of a glass component can create an internal glass ceramic portion having different properties than external portions of the cover member and an internal compressive stress region in the internal glass ceramic portion. For example, if the crystals have a lower coefficient of thermal expansion than the glass from which they are formed, the internal glass ceramic portion of the component tends to contract less than the external glass portions when cooled from a crystallization temperature. As a result, compressive stresses can form in the internal glass ceramic portion of the component. The glass component may be ion exchangeable as well as crystallizable.

As an example, a component comprises an internal compressive stress region located in the internal glass ceramic portion. The component further comprises an external compressive stress region along an external surface of the component and an internal tensile stress region inward from the external compressive stress region. The external compressive stress region can be formed by an ion exchange operation in the external glass portion of the component.

The external portions of the component may each include a sufficiently low volume of crystals to be considered a glass. The external glass portion of the component may comprise first alkali metal ions. The external compressive stress region may include second alkali metal ions having a second size greater than the first size. The second alkali metal ions may have been introduced by an ion exchange operation. The internal compressive stress region may include the first alkali metal ions. For example, the first alkali metal ions may be lithium ions and the second alkali ions may be potassium ions.

As another example, a strengthened glass component comprises an internal glass ceramic portion, a first external glass portion, and a second external glass portion. The first external glass portion and the second external glass portion may each comprise an aluminosilicate or an aluminoborosilicate glass including first alkali metal ions having a first size. For example, the first alkali metal ions may be lithium ions.

The strengthened glass component may comprise a first and a second external compressive stress region, the first external compressive stress region along a first external surface and the second external compressive stress region along a second external surface. The first external compressive stress region is located in the first external glass portion and the second external compressive stress region is located in the second external glass portion. The first and the second external compressive stress regions can be formed by an ion exchange operation to introduce second alkali metal ions in the first and second external glass portions of the component. For example, the second alkali metal ions may be potassium ions.

The strengthened glass component may further comprise a first and a second internal tensile stress region, the first internal tensile stress region inward from the first external compressive stress region and the second internal tensile stress region inward from the second external compressive stress region. The first and second internal tensile stress regions may each include first alkali metal ions having a first size.

The strengthened glass component may further comprise an internal compressive stress region inward from the first and the second internal tensile stress regions. The internal compressive stress region includes the glass ceramic. The internal compressive stress region may also include the first alkali metal ions.

In embodiments, the glass component is capable of crystallization to form an internal glass ceramic portion. For example, the glass may be an aluminosilicate glass capable of forming an aluminosilicate glass ceramic or a boroaluminosilicate glass capable of forming a boroaluminosilicate glass ceramic. For example, the glass ceramic may be a lithium aluminosilicate (LAS). In embodiments, the internal glass ceramic portion may include a residual glass phase and crystals of one or more crystalline phases. The volume percentage of the crystals may be low enough to prevent cracking of the residual glass phase during cooling of the glass ceramic to room temperature (e.g., about 20° C.) but high enough to create a residual compressive stress. The crystals may be small enough so that the cover member remains transparent to visible radiation.

FIG. 10Ashows a detailed view of the inset1-1ofFIG. 3Afor an example cover member having an internal compressive stress region created at least in part by forming an internal glass ceramic portion within the cover member. The cover member1020comprises internal glass ceramic portion1032; portion1032comprises a glass ceramic. The glass ceramic may include a residual glass phase and one or more crystalline phases. Crystals1072inFIG. 10Arepresent the crystalline phase; the crystals1072are not necessarily shown to scale. In an embodiment, the glass ceramic includes first alkali metal ions1061having a first size. For convenience, first alkali metal ions1061having a first size are shown in the residual glass phase1074. However, first alkali metal ions1061may also be present in the crystals1072.

As examples, glass ceramic portion1032may have a volume percentage of crystals1072greater than or equal to 30% and less than 100%, greater than or equal to 50% and less than 100%, or greater than or equal to 75% and less than 100%. The crystals1072may have an average size of less than about 50 nm to provide transparency to visible radiation.

In embodiments, the glass ceramic is an aluminosilicate glass ceramic or an aluminoborosilicate glass ceramic. The residual glass portion may be an aluminosilicate glass or an aluminoborosilicate glass. As an example, the glass from which the glass ceramic is formed may be a lithium aluminosilicate glass and the glass ceramic may be a lithium aluminosilicate glass ceramic. Lithium aluminosilicate glasses can form several types of crystals, including β quartz solid solution crystals, β spodumene solid solution crystals, and keatite solid solution crystals. The resulting crystals may have a coefficient of thermal expansion which is close to zero or even less than zero.

The cover member1020ofFIG. 10Aalso comprises an outer portion1038and portion1036. Outer portion1038and portion1036may cooperate to form an external glass portion of the cover member. Both outer portion1038and portion1036may comprise a glass, such as an aluminosilicate or an aluminoborosilicate glass. The aluminosilicate or an aluminoborosilicate glass may include first alkali metal ions1061having a first size. Portion1036may include the first alkali metal ions1061. Outer portion1038may further comprise second alkali metal ions1062having a second size. The second alkali metal ions1062may be introduced into the outer portion1038through an ion exchange process.

FIG. 10Bshows an example of the variation of residual stress with position in the sample for the cover member1020ofFIG. 10A. The cover member1020comprises external compressive stress region1044located along surfaces1022and1024The cover member1020further comprises an internal tensile stress region1054inward of external compressive stress region1044. The cover member1020further comprises an internal compressive stress region1042inward of internal tensile stress region1054.

External compressive stress region1044is in outer portion1038of the cover member1020. The tensile stress in internal tensile stress region1054balances the residual compressive stress in the glass cover member1020and is at least partially located in portion1036of the cover member. In some embodiments, the internal tensile stress region1054may extend slightly into inner portion1032and/or outer portion1038of the cover member1020. As shown inFIG. 10B, a level of the compressive stress is greater in external compressive stress region1044than in internal compressive stress region1042. The internal compressive stress region1042is located in inner glass ceramic portion1032.

FIG. 11illustrates a flowchart of an example process1100for making an internal compressive stress region in a component using a combination of selective crystallization of a glass ceramic and ion exchange. Process1100further creates an external compressive stress region and an internal tensile stress region. For example, process1100may be used to form the glass cover member ofFIGS. 10A-10B.

The process1100may include operation1102of forming a glass ceramic in an internal portion of a glass component. Operation1102includes the operation of forming crystals of the glass ceramic in the internal portion of the glass component. In embodiments, the operation of forming crystals of the glass ceramic may include the operation of creating crystal nuclei followed by the operation of growing the crystal nuclei to form crystals of a desired size. The operation of creating the crystal nuclei may comprise heating the internal portion of the glass component to a first temperature at which crystal nuclei form. The operation of growing the crystal nuclei may comprise heating the internal portion to a second temperature. The second temperature may be greater than the first temperature.

The internal portion of the glass component may be heated at least in part using a beam of radiation, such as a beam of light. For example, a laser may be used to heat the internal portion to a sufficient temperature to nucleate and/or grow crystals in the glass. An adjacent portion of the glass component may be heated to a lesser extent. For example, nucleation and/or growth of crystals in the adjacent portion of the glass component may occur to a lesser extent. For example, the volume percentage of crystals in the adjacent portion may be less than in the adjacent portion of the glass. For example, a volume percentage of crystals in the internal portion may be at least 25%, 50% or 75% higher than in an external portion of the component. The beam of radiation may be used in conduction with one or more additional heat sources (e.g., a furnace).

Process1100may further include operation1104of exchanging first alkali metal ions in an outer portion of the component with second alkali metal ions. The first alkali metal ions have a first size and the second alkali metal ions have a second size larger than the first size. The first alkali metal ions may be exchanged for the second alkali metal ions by immersing the component in a bath comprising the second alkali metal ions. For example, the exchange of ions may form an ion exchange layer which extends to an exchange depth less than a depth of the glass ceramic portion of the component.

FIGS. 12A, 12B, and 12Cschematically illustrate three stages in an example process for creating an internal compressive stress region in a component using a combination of selective crystallization of a glass ceramic and ion exchange.FIGS. 12A and 12Billustrate example operations of forming crystals of the glass ceramic using a beam of radiation. Prior to exposing a cover member to the beam of radiation, the cover member comprises a glass including a first alkali metal ion1261throughout a thickness of the glass component. The entirety of cover member1220is not shown inFIGS. 12A-12Cin order to provide a more detailed view.

FIG. 12Aillustrates an example of forming crystals of the glass ceramic in an internal portion of the glass component. InFIG. 12A, beam1282heats inner portion1232of cover member1220. As a result, crystals1272form in inner portion1232, but not in portions1235. As shown inFIG. 12A, beam1282may be a broad beam configured to deliver energy to a relatively large area. The beam1282may be provided by a laser, such as a gas laser, a chemical laser, a solid state laser, a fiber laser, a photonic crystal laser, or a semiconductor laser. The beam1282may deliver energy to the component through side surface1226, which joins front surface1222and back surface1224.

FIG. 12Billustrates another example of forming crystals of the glass ceramic in an internal portion of the glass component using a beam of radiation. As inFIG. 12A, beam1282heats inner portion1232of cover member1220. As a result, crystals1272form in inner portion1232, but not in portions1235. As shown inFIG. 12B, the beam1282may be focused to create focused beam1284which can deliver energy to a narrower beam spot. One or more lenses may be used to focus beam1282. The focused beam1284may deliver energy to the component through a surface of the component, such as front surface1222. The focused beam1284may be moved over the cover member1220to form crystals1274in inner portion1232.

FIG. 12Cillustrates the cover member1220after the operation of ion exchanging first alkali metal ions in an outer portion of the component with second alkali metal ions. The first alkali metal ions have a first size and the second alkali metal ions have a second size larger than the first size. For example, the exchange of ions may form an ion exchange layer which extends to an exchange depth DE1less than a depth of the glass ceramic portion of the component.

As a result, inner portion1232of the glass cover member1220comprises crystals1272of the glass ceramic and first alkali metal ions1261. Outer portion1238of the glass cover member1220comprises the first alkali metal ions1261and the second alkali metal ions1262. Portion1236comprises the first alkali metal ions1261and is depleted of the second alkali metal ions1262as compared to outer portion1238. The composition and phase profile ofFIG. 12Ccan produce an internal compressive stress region within inner portion1232, as previously discussed with respect toFIGS. 10A and 10B.

FIG. 13Ashows a detailed view of the inset2-2ofFIG. 4Afor an example cover member1320having an internal compressive stress region created at least in part by forming a glass ceramic region within the cover member1320. The cover member1320comprises portion1334including crystals1372of the glass ceramic. The cover member1320ofFIG. 13Aalso comprises an outer portion1338, portion1336inward from outer portion1338, and inner portion1332. Outer portion1338, portion1336, and inner portion1332each may comprise a glass, such as an aluminosilicate or an aluminoborosilicate glass. Portion1336may comprise first alkali metal ions having a first size. The outer portion1338may further comprise second alkali metal ions having a second size and may be enriched in the second alkali metal ions as compared to portion1336. The second alkali metal ions may be introduced into the outer portion1338through an ion exchange process.

FIG. 13Bshows an example of the variation of residual stress with position in the sample for the glass cover member ofFIG. 13A. Internal compressive stress region1342may be located in portion1334and created by formation of the glass ceramic. External compressive stress region1344may be located in outer portion1338and created as a result of an ion exchange operation. As shown inFIG. 13B, a level of the compressive stress is greater in external compressive stress region1344than in internal compressive stress region1342.

The cover member1320further comprises an internal tensile stress region1354between the internal compressive stress region1342and the external compressive stress region1344. The tensile stress in internal tensile stress region1354at least partially balances the residual compressive stress in the cover member1320. Internal tensile stress region1354is at least partially located in portion1336of the cover member1320. In some embodiments, the internal tensile stress region1354may extend slightly into inner portion1332and/or outer portion1338of the glass cover member1320. The cover member1320further comprises internal tensile stress region1352inward from internal compressive stress region1342. The tensile stress in internal tensile stress region1352at least partially balances the residual compressive stress in the glass cover member. Internal tensile stress region1352is at least partially located in inner portion1332of the cover member1320.

In embodiments, at least one of the internal compressive stress regions may be created in a laminate component comprising layers having different compositions and/or properties. In further embodiments, an internal compressive stress region may be created in an inner layer of a glass component having different thermal expansion and/or ion expansion properties than outer layers of the glass component. As another example, the glass laminate component comprises a first outer layer formed from a first glass material, an inner layer formed from a second glass material, and a second outer layer formed from a third glass material. Alternately, each of these glass materials may be referred to as a glass. The second glass material may be the same as or different from the third glass material. Each of the inner layer, the first outer layer, and the second outer layer may have a thickness.

The glass component may further comprise an external compressive stress region, an internal tensile stress region inward from the external compressive stress region, and an internal compressive stress region inward from the internal tensile stress region. As an example, the first outer layer of the component includes the external compressive stress region. The second outer layer of the component may also include the external compressive stress region. The external compressive stress region may extend from a surface of the glass component to a first depth in the component. The internal compressive stress layer may be located in the inner layer. For example, the internal compressive stress layer may extend from the second depth to the third depth. The internal tensile stress layer may extend from the first depth to the second depth.

The first outer layer of the component may extend from a first surface to the second depth in the component, with an interface between the first outer layer of the component and the inner layer of the component located at the second depth. The second outer layer of the component may extend from a second surface to the third depth in the component, with an interface between the second outer layer of the component and the inner layer of the component located at the third depth.

In further embodiments, the glass component may comprise a first external compressive stress region and a second external compressive stress region and an internal compressive stress region. For example, the first external compressive stress region extends from a first surface to a first depth in the component and the second external compressive stress region extends from a second surface to a fourth depth in the component. The glass component may further comprise a first internal tensile stress region extending from the first depth to a second depth in the component, an internal compressive stress region extending from the second depth to a third depth in the component, and a second internal tensile stress region extending from the fourth depth to the third depth of the component. The first outer layer may include the first external compressive stress region and the first internal tensile stress region. The second outer layer may include the second external compressive stress region and the second internal tensile stress region. The inner layer may include the internal compressive stress region.

In an example, the first outer layer of the component extends from the first surface to the second depth in the component, with an interface between the first outer layer of the component and the inner layer of the component located at the second depth. The second outer layer of the component extends from the second surface to the third depth in the component, with an interface between the second outer layer of the component and the inner layer of the component located at the third depth.

FIG. 14Aillustrates formation of an internal compressive stress region in an example glass laminate cover member1420. As shown inFIG. 14A, the glass laminate cover member1420comprises inner layer1425and outer layers1427. The inner layer1425may join each of the outer layers1427at interface1426. Inner layer1425may be formed from a first glass material and each of the outer layers1427may be formed of a second glass material. Each outer layer1427may comprise an outer portion1438and a portion1436inward from the outer portion1438. Although outer portion1438and portion1436are both formed from the second glass material, the composition of outer portion1438may differ from that of the second glass material due to ion exchange.

FIG. 14Bshows an example of the variation of residual stress with position in the sample for the glass laminate cover member1420ofFIG. 14A. The glass laminate cover member1420has an internal compressive stress region1442located in inner layer1425. The internal compressive stress region1442is created as a result of differences in one or more properties between the first glass material and the second glass material. An external compressive stress region1444is located in outer portion1438along surfaces1422and1424. The external compressive stress region1444may be created by an ion exchange. An internal tensile stress region1454is located between the internal compressive stress region1442and the external compressive stress region1444. As shown inFIG. 14B, a level of the compressive stress is greater in the external compressive stress region1444than in internal compressive stress region1442.

In embodiments, the laminate may comprise outer layers each having a higher coefficient of thermal expansion than that of an inner layer. As an example, the first glass material has a first coefficient of thermal expansion, the second glass material has a second coefficient of thermal expansion, and the third glass material has a third coefficient of thermal expansion. The first coefficient of thermal expansion may be lower than the second coefficient of thermal expansion and lower than the third coefficient of thermal expansion. The second coefficient of thermal expansion may be the same as or different from the third coefficient of thermal expansion. For example, the outer layers may have a coefficient of thermal expansion greater than that of the inner layer by at least 10%, 25%, or 50%. In embodiments, the first glass material may be a borosilicate glass and the second and third glass materials may be aluminosilicate glasses. The difference between the coefficient of thermal expansion of the outer layers and the inner layer may create a compressive stress region in the inner layer upon cooling of the laminate from a lamination temperature. The difference between the coefficient of thermal expansion of the outer layers and the inner layer may be limited to prevent cracking at the interface between the outer layers and the inner layer.

FIGS. 15A and 15Bschematically illustrate two stages in an example process for creating an internal compressive stress region in a glass laminate cover member1520. In this example, the first glass material of inner layer1525has a lower coefficient of thermal expansion than the second glass material of the outer layers1527.FIG. 15Aillustrates the glass laminate cover member1520after formation of the laminate. As an example, the layers of the laminate may be directly bonded to each other without an interstitial bonding agent. As another example, the glass laminate may include an interstitial bonding agent between layers such as a glass frit. As shown inFIG. 15A, the second glass material comprises a first alkali metal ion1561having a first size. After the inner layer1525is laminated between the outer layers1527at a lamination temperature, the glass laminate cover member1520is cooled to a lower temperature, such as room temperature. Cooling of the glass laminate cover member1520creates an internal compressive stress region in inner layer1525(indicated by the arrows facing each other) and an external tensile stress region in the outer layer1527(indicated by the arrows facing away from each other).

FIG. 15Bshows the glass laminate cover member1520ofFIG. 15Aafter an ion exchange operation. In the ion exchange operation, at least some of the first alkali metal ions1561in each of the outer layers1527are exchanged with second alkali metal ions1562having a second size greater than the first size. The ion exchange occurs to a depth less than a thickness of each of the outer layers1527. Outer portion1538of glass laminate cover member1520is enriched in the second alkali metal ions1562as compared to portion1536. As indicated by the arrows, the ion exchange creates external compressive stress regions; each external compressive stress region is located in an outer portion1538of each of the outer layers1527adjacent a surface1522,1524of the glass component. The ion exchange also creates internal tensile stress regions, each of the internal tensile stress regions at least partially located in one of the outer layers between one of the external compressive stress regions and the internal compressive stress region.

In additional embodiments, the laminate may comprise an inner layer having a greater tendency to expand in response to ion exchange than the outer layers. For example, the inner layer may have a larger network dilation coefficient than the outer layers. As an example, the first glass material may have a first network dilation coefficient, the second glass material may have a second network dilation coefficient, and the third glass material may have a third network dilation coefficient. The first network dilation coefficient may be greater than the second network dilation coefficient and the third network dilation coefficient. The second network dilation coefficient may be the same as or different from the third network dilation coefficient. The network dilation coefficient, also known as the linear network dilation coefficient, may be given by

B=13⁢1V⁢∂V∂C,
where V is the molar volume and C is the local concentration of the substituted alkali metal ion. For example, the inner layer may have a linear network dilation coefficient greater than that of the outer layers of at least 10%, 25%, or 50%. The greater tendency for expansion in response to ion exchange can create a compressive stress region in the inner layer after ion exchange of the laminate.

FIGS. 16A, 16B, and 16Cschematically illustrate three stages in an example process for creating an internal compressive stress region in a glass laminate cover member1620. In this example, the inner layer1625has a greater tendency to expand in response to ion exchange than the outer layers1627.FIG. 16Aillustrates the glass laminate cover member1620after formation of the laminate. As shown inFIG. 16A, both the inner layer and the outer layers comprise first alkali metal ions1661.

FIG. 16Billustrates the glass laminate cover member1620after a first ion exchange operation in which at least some of the first alkali metal ions are exchanged with second alkali metal ions1662having a second size greater than the first size to a depth greater than a thickness of the outer glass layer1627. As indicated by the arrows, the ion exchange creates an internal compressive stress region.

FIG. 16Cillustrates the glass laminate cover member1620after a second ion exchange operation in which at least some of the second alkali metal ions1662are exchanged with third alkali metal ions1663having a third size greater than the second size. The second ion exchange occurs to a depth less than a thickness of the outer layer1627. Outer portion1638of glass laminate cover member1620is enriched in the third alkali metal ions1663as compared to portion1636. As indicated by the arrows, the ion exchange creates external compressive stress regions; each external compressive stress region is located in an outer portion1638of each of the outer glass layers1627adjacent a surface1624,1622of the glass component. The ion exchange also creates internal tensile stress regions, each of the internal tensile stress regions at least partially located in one of the outer glass layers between one of the external compressive stress regions and the internal compressive stress region.

FIG. 17is a block diagram of example components of an example electronic device. The schematic representation depicted inFIG. 17may correspond to components of the devices depicted inFIG. 1A-16Cas described above. However,FIG. 17may also more generally represent other types of electronic devices with a strengthened glass component as described herein.

In embodiments, an electronic device1700may include sensors1720to provide information regarding configuration and/or orientation of the electronic device in order to control the output of the display. For example, a portion of the display1714may be turned off, disabled, or put in a low energy state when all or part of the viewable area of the display1714is blocked or substantially obscured. As another example, the display1714may be adapted to rotate the display of graphical output based on changes in orientation of the device1700(e.g., 90 degrees or 180 degrees) in response to the device1700being rotated. As another example, the display1714may be adapted to rotate the display of graphical output in response to the device1700being folded or partially folded, which may result in a change in the aspect ratio or a preferred viewing angle of the viewable area of the display1714.

The electronic device1700also includes a processor1704operably connected with a computer-readable memory1702. The processor1704may be operatively connected to the memory1702component via an electronic bus or bridge. The processor1704may be implemented as one or more computer processors or microcontrollers configured to perform operations in response to computer-readable instructions. The processor1704may include a central processing unit (CPU) of the device1700. Additionally and/or alternatively, the processor1704may include other electronic circuitry within the device1700including application specific integrated chips (ASIC) and other microcontroller devices. The processor1704may be configured to perform functionality described in the examples above. In addition, the processor or other electronic circuitry within the device may be provided on or coupled to a flexible circuit board in order to accommodate folding or bending of the electronic device. A flexible circuit board may be a laminate including a flexible base material and a flexible conductor. Example base materials for flexible circuit boards include, but are not limited to, polymer materials such as vinyl (e.g., polypropylene), polyester (e.g., polyethylene terephthalate (PET), biaxially-oriented PET, and polyethylene napthalate (PEN)), polyimide, polyetherimide, polyaryletherketone (e.g., polyether ether ketone (PEEK)), fluoropolymer and copolymers thereof. A metal foil may be used to provide the conductive element of the flexible circuit board.

The memory1702may include a variety of types of non-transitory computer-readable storage media, including, for example, read access memory (RAM), read-only memory (ROM), erasable programmable memory (e.g., EPROM and EEPROM), or flash memory. The memory1702is configured to store computer-readable instructions, sensor values, and other persistent software elements.

The electronic device1700may include control circuitry1706. The control circuitry1706may be implemented in a single control unit and not necessarily as distinct electrical circuit elements. As used herein, “control unit” will be used synonymously with “control circuitry.” The control circuitry1706may receive signals from the processor1704or from other elements of the electronic device1700.

As shown inFIG. 17, the electronic device1700includes a battery1708that is configured to provide electrical power to the components of the electronic device1700. The battery1708may include one or more power storage cells that are linked together to provide an internal supply of electrical power. The battery1708may be operatively coupled to power management circuitry that is configured to provide appropriate voltage and power levels for individual components or groups of components within the electronic device1700. The battery1708, via power management circuitry, may be configured to receive power from an external source, such as an alternating current power outlet. The battery1708may store received power so that the electronic device1700may operate without connection to an external power source for an extended period of time, which may range from several hours to several days. The battery1708may be flexible to accommodate bending or flexing of the electronic device. For example, the battery1708may be mounted to a flexible housing or may be mounted to a flexible printed circuit. In some cases, the battery1708is formed from flexible anodes and flexible cathode layers and the battery cell is itself flexible. In some cases, individual battery cells are not flexible, but are attached to a flexible substrate or carrier that allows an array of battery cells to bend or fold around a foldable region of the device.

In some embodiments, the electronic device1700includes one or more input devices1710. The input device1710is a device that is configured to receive input from a user or the environment. The input device1710may include, for example, a push button, a touch-activated button, capacitive touch sensor, a touch screen (e.g., a touch-sensitive display or a force-sensitive display), capacitive touch button, dial, crown, or the like. In some embodiments, the input device1710may provide a dedicated or primary function, including, for example, a power button, volume buttons, home buttons, scroll wheels, and camera buttons.

The device1700may also include one or more sensors1720, such as a force sensor, a capacitive sensor, an accelerometer, a barometer, a gyroscope, a proximity sensor, a light sensor, or the like. The sensors1720may be operably coupled to processing circuitry. In some embodiments, the sensors1720may detect deformation and/or changes in configuration of the electronic device and be operably coupled to processing circuitry which controls the display based on the sensor signals. In some implementations, output from the sensors1720is used to reconfigure the display output to correspond to an orientation or folded/unfolded configuration or state of the device. Example sensors1720for this purpose include accelerometers, gyroscopes, magnetometers, and other similar types of position/orientation sensing devices. In addition, the sensors1720may include a microphone, acoustic sensor, light sensor, optical facial recognition sensor, or other types of sensing device.

In some embodiments, the electronic device1700includes one or more output devices1712configured to provide output to a user. The output device1712may include display1714that renders visual information generated by the processor1704. The output device1712may also include one or more speakers to provide audio output. The output device1712may also include one or more haptic devices that are configured to produce a haptic or tactile output along an exterior surface of the device1700.

The display1714may include a liquid-crystal display (LCD), light-emitting diode, organic light-emitting diode (OLED) display, an active layer organic light emitting diode (AMOLED) display, organic electroluminescent (EL) display, electrophoretic ink display, or the like. If the display1714is a liquid-crystal display or an electrophoretic ink display, the display1714may also include a backlight component that can be controlled to provide variable levels of display brightness. If the display1714is an organic light-emitting diode or organic electroluminescent type display, the brightness of the display1714may be controlled by modifying the electrical signals that are provided to display elements. In addition, information regarding configuration and/or orientation of the electronic device may be used to control the output of the display as described with respect to input devices1710. In some cases, the display is integrated with a touch and/or force sensor in order to detect touches and/or forces applied along an exterior surface of the device1700.

The electronic device1700may also include a communication port1716that is configured to transmit and/or receive signals or electrical communication from an external or separate device. The communication port1716may be configured to couple to an external device via a cable, adaptor, or other type of electrical connector. In some embodiments, the communication port1716may be used to couple the electronic device to a host computer.

The electronic device1700may also include at least one accessory1718, such as a camera, a flash for the camera, or other such device. The camera may be connected to other parts of the electronic device1700such as the control circuitry1706.