阅读说明：本技术 耐刮擦及抗损伤的迭层玻璃制品 (Scratch and mar resistant laminated glass article ) 是由 蒂莫西·迈克尔·格罗斯 查伦·玛丽·史密斯 于 2020-03-20 设计创作，主要内容包括：揭示一种耐刮擦及抗损伤的迭层玻璃制品。根据一个态样,迭层玻璃制品可以包括可离子交换的核心玻璃组成物所形成的玻璃核心层,并且包括核心玻璃弹性模量E-(C)与直接熔合至玻璃核心层的至少一个玻璃包覆层。至少一个玻璃包覆层可以由可离子交换的包覆玻璃组成物所形成,并且包括包覆玻璃弹性模量E-(CL),可离子交换的包覆玻璃组成物是与可离子交换的核心玻璃组成物不同。迭层玻璃制品可以具有总厚度T,而至少一个玻璃包覆层可以具有小于总厚度T的30％的厚度T-(CL)。E-(C)可以大于E-(CL)至少5％。(A scratch and mar resistant laminated glass article is disclosed. According to one aspect, a laminated glass article may include a glass core layer formed from an ion-exchangeable core glass composition and including a core glass modulus of elasticity E C And at least one glass cladding layer fused directly to the glass core layer. At least one glass cladding layer may be formed from an ion-exchangeable cladding glass composition and include a cladding glass elastic modulus E CL The ion-exchangeable clad glass composition is different from the ion-exchangeable core glass composition. The laminated glass article may have a total thickness T and the at least one glass cladding layer may have a thickness T that is less than 30% of the total thickness T CL 。E C May be greater than E CL At least 5%.)

1. A laminated glass article comprising:

a glass core layer formed of an ion-exchangeable core glass composition, and a glass comprising a core glass elastic modulus E_C(ii) a And

at least one glass cladding layer fused directly to the glass core layer, the at least one glass cladding layer being formed of an ion-exchangeable cladding glass composition, and comprising a cladding glass elastic modulus E_CLAn ion-exchangeable clad glass composition different from the ion-exchangeable core glass composition, wherein:

the laminated glass article has a total thickness T and the at least one glass cladding layer has a thickness T that is less than 30% of the total thickness T_CL(ii) a And

E_Cgreater than E_CLAt least 5%.

2. The laminated glass article of claim 1, wherein E_CLIs less than or equal toEqual to 76.5 Gpa.

3. The laminated glass article of claim 2, wherein E_CLGreater than or equal to 60 GPa.

4. The laminated glass article of claim 1, wherein E_CAnd E_CLThe difference therebetween is greater than or equal to 5 GPa.

5. The laminated glass article of claim 1, wherein the thickness T of the at least one glass cladding layer_CLLess than or equal to 5% of the total thickness T.

6. The laminated glass article of claim 1, wherein a core glass refractive index n of the glass core layer_CRefractive index n of the clad glass being larger than the at least one glass cladding layer_CL。

7. The laminated glass article of claim 6, wherein the cladding glass has a refractive index n_CLGreater than or equal to 1.45 and less than or equal to 1.55.

8. The laminated glass article of claim 1, wherein the at least one glass cladding layer comprises a first glass cladding layer and a second glass cladding layer, wherein:

the first glass cladding layer is fused directly to the first surface of the glass core layer; and

the second glass cladding layer is fused directly to a second surface of the glass core layer, the second surface of the glass core layer being opposite the first surface of the glass core layer.

9. The laminated glass article of claim 1, wherein:

the glass core layer has a core coefficient of thermal expansion CTE at a temperature of 20 ℃ to 300 DEG C_C；

At least one ofThe glass cladding layer has a cladding coefficient of thermal expansion CTE at 20 ℃ to 300 DEG C_CL(ii) a And

CTE_Cgreater than or equal to CTE_CL。

10. The laminated glass article of claim 9, wherein due to CTE_CAnd CTE_CLThe difference between the compressive stress in the at least one glass cladding layer is greater than 100MPa and extends from a surface of the at least one glass cladding layer through a thickness of the at least one glass cladding layer.

11. The laminated glass article of claim 1, wherein the laminated glass article is ion exchange strengthened such that the laminated glass article comprises a compressive stress region extending from a surface of the at least one glass cladding layer to a total thickness T of the laminated glass article to a depth of compression DOC.

12. The laminated glass article of claim 11, wherein:

the laminated glass product has a surface compressive stress CS on the surface of the at least one glass cladding layer₀(ii) a And

the depth of compression DOC is equal to or greater than 10% of the total thickness T.

13. The laminated glass article of claim 11, wherein:

the glass core layer has a core coefficient of thermal expansion CTE of 20 ℃ to 300 ℃_C；

Coating coefficient of thermal expansion CTE of at least one glass coating layer_CLIs 20 ℃ to 300 ℃; and

CTE_Cgreater than or equal to CTE_CL。

14. The laminated glass article of claim 11, wherein the laminated glass article has a Knoop scratch initiation threshold greater than or equal to 2N and less than or equal to 8N.

15. A laminated glass article comprising:

a glass core layer formed from an ion-exchangeable core glass composition; and

at least one glass cladding layer fused directly to the glass core layer at an interface region, the at least one glass cladding layer being formed from an ion-exchangeable cladding glass composition different from the ion-exchangeable core glass composition, wherein:

the laminated glass article has a total thickness T and at least one glass cladding layer has a thickness T that is less than or equal to 30% of the total thickness T_CL；

The laminated glass article is ion exchange strengthened such that the laminated glass article comprises a compressive stress region extending from a surface of the at least one glass cladding layer to a total thickness T to a depth of compression DOC of the laminated glass article;

K₂o and Na₂The concentration of at least one of O decreases from the surface of the at least one glass cladding layer to the cladding side of the interface region; and

K₂o and Na₂The concentration of at least one of O decreases from the core side of the interface region in a direction toward the centerline of the glass core layer, where K is₂O and Na₂The concentration of at least one of O is higher on the clad side of the glass core layer than the concentration of the same component on the core side of the interface region.

16. The laminated glass article of claim 15, wherein:

the at least one glass cladding layer comprises at least one glass former and the concentration of the at least one glass former is substantially constant from the surface of the at least one glass cladding layer to the cladding side of the interface region; and

the glass core layer includes at least one glass former and a concentration of the at least one glass former is substantially constant from a core side of the interphase region to a middle region of the glass core layer.

17. The laminated glass article of claim 15, wherein:

the at least one glass cladding layer comprises at least one glass modifier and the concentration of the at least one glass modifier is substantially constant from the surface of the at least one glass cladding layer to the cladding side of the interfacial region; and

the glass core layer comprises at least one glass modifier and a concentration of the at least one glass modifier is substantially constant from a core side of the interphase region to a middle region of the glass core layer.

18. The laminated glass article of claim 15, wherein:

the glass core layer has a core coefficient of thermal expansion CTE of 20 ℃ to 300 ℃_C；

The at least one glass cladding layer has a cladding coefficient of thermal expansion CTE of 20 ℃ to 300 ℃_CL(ii) a And

CTE_Cgreater than or equal to CTE_CL。

19. The laminated glass article of claim 18, wherein due to CTE_CAnd CTE_CLThe difference between the compressive stress in the at least one glass cladding layer is greater than 100MPa and extends from a surface of the at least one glass cladding layer and through a thickness of the at least one glass cladding layer.

20. The laminated glass article of claim 15, wherein:

the glass core layer comprises a core glass elastic modulus E_C(ii) a And

the at least one glass cladding layer comprises a cladding glass elastic modulus E_CLIn which E_CGreater than E_CL。

21. The laminated glass article of claim 15, wherein E_CAnd E_CLThe difference therebetween is greater than or equal to 5 GPa.

22. The laminated glass article of claim 15, wherein a core glass refractive index n of the glass core layer_CRefractive index n of the clad glass being larger than the at least one glass cladding layer_CL。

23. The laminated glass article of claim 22, wherein the cladding glass has a refractive index n_CLGreater than or equal to 1.45 and less than or equal to 1.55.

24. The laminated glass article of claim 15, wherein the depth of compression DOC is greater than or equal to 10% of the total thickness T.

25. The laminated glass article of claim 15, wherein the thickness T_CLLess than or equal to 10% of the total thickness T.

Technical Field

This specification relates generally to laminated glass articles and more particularly to laminated glass articles that are resistant to scratching and damage caused by dropping.

Background

Glass articles, such as cover glasses, glass backplanes, and the like, are utilized in consumer and commercial electronic devices, such as LCD and LED displays, computer screens, Automated Teller Machines (ATMs), and the like. Some of these glass articles may include a "touch" function, requiring the glass article to be contacted by various objects, including a user's finger and/or a stylus device, and thus the glass must be sufficiently strong to ensure that conventional contact is not damaged (e.g., scratched). In fact, scratches introduced into the surface of the glass article may reduce the strength of the glass article, since the scratches may serve as starting points for cracks leading to catastrophic breakage of the glass.

Moreover, such glass articles may also be incorporated into portable electronic devices (e.g., mobile phones, personal media players, laptop computers, and tablet computers). Glass articles incorporated into these devices may be susceptible to severe impact damage during shipping and/or use of the associated device. For example, strong impact damage may include damage caused by dropping the device. Such damage may result in breakage of the glass.

Thus, there is a need for alternative glass articles that are resistant to scratching and to damage caused by dropping.

Disclosure of Invention

According to a first aspect, a laminated glass article may include a glass core layer formed from an ion-exchangeable core glass composition and including a core glass modulus of elasticity E_CAnd at least one glass cladding layer fused directly to the glass core layer. At least one glass cladding layer may be formed from an ion-exchangeable cladding glass composition and include a cladding glass elastic modulus E_CLThe ion-exchangeable clad glass composition is different from the ion-exchangeable core glass composition. The laminated glass article may have a total thickness T and the at least one glass cladding layer may have a thickness T that is less than 30% of the total thickness T_CL。E_CMay be greater than E_CLAt least 5%.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein E_CLIs less than or equal to 76.5 GPa.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein E_CLIs greater than or equal to 60 GPa.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein E_CAnd E_CLThe difference therebetween is greater than or equal to 5 GPa.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein at least one glass cladding layer has a thickness T_CLIs less than or equal to 5% of the total thickness T.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein a core glass refractive index n of the glass core layer_CIs a refractive index n of the clad glass greater than at least one glass cladding layer_CL。

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein the clad glass has a refractive index of greater than or equal to 1.45 and less than or equal to 1.55.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein the at least one glass cladding layer comprises a first glass cladding layer and a second glass cladding layer. The first glass cladding layer may be fused directly to the first surface of the glass core layer and the second glass cladding layer may be fused directly to the second surface of the glass core layer, the second surface of the glass core layer being opposite the first surface of the glass core layer.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein the glass core layer has a core coefficient of thermal expansion CTE at a temperature of 20 ℃ to 300 ℃_CAt least one glass cladding layer having a cladding coefficient of thermal expansion CTE at 20 ℃ to 300 DEG C_CLAnd CTE of_CIs greater than or equal to CTE_CL。

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein the CTE is due to_CAnd CTE_CLThe difference therebetween, the compressive stress in the at least one glass cladding layer is greater than 100MPa and extends from a surface of the at least one glass cladding layer through a thickness of the at least one glass cladding layer.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein the laminated glass article is ion-exchange strengthened such that the laminated glass article comprises a compressive stress region extending from a surface of the at least one glass cladding layer into a total thickness T of the laminated glass article to a depth of compression DOC.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein the laminated glass article has a surface compressive stress CS at a surface of at least one glass cladding layer₀And the depth of compression DOC is greater than or equal to 10% of the total thickness T.

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein the glass core layer has a core coefficient of thermal expansion CTE from 20 ℃ to 300 ℃_CAt least one glass cladding layer having a cladding coefficient of thermal expansion CTE at 20 ℃ to 300 DEG C_CLAnd CTE of_CIs greater than or equal to CTE_CL。

Another aspect includes a laminated glass article according to any of the preceding aspects, wherein a Knoop scratch initiation threshold of the laminated glass article is greater than or equal to 2N and less than or equal to 8N.

According to a second aspect, a laminated glass article may include a glass core layer formed from an ion-exchangeable core glass composition and at least one glass cladding layer fused directly to the glass core layer at an interface region. At least one glass cladding layer may be formed from an ion-exchangeable cladding glass composition that is different from the ion-exchangeable core glass composition. The laminated glass article may have a total thickness T and the at least one glass cladding layer may have a thickness T that is less than or equal to 30% of the total thickness T_CL. The laminated glass article may be ion-exchange strengthened such that the laminated glass article comprises a compressive stress region extending from a surface of the at least one glass cladding layer into a total thickness T of the laminated glass article to a depth of compression DOC. K₂O and Na₂The concentration of at least one of O may decrease from the surface of the at least one glass cladding layer to the cladding side of the interface region. K₂O and Na₂The concentration of at least one of O may decrease from the core side of the interfacial region in a direction toward the centerline of the glass core layer. K on the cladding side of the interface region₂O and Na₂The concentration of at least one of O is less than the concentration of the same component on the core side of the interfacial region.

Another aspect includes a laminated glass article according to the second aspect, wherein the at least one glass cladding layer includes at least one glass former, and a concentration of the at least one glass former is substantially constant from a surface of the at least one glass former to a cladding layer side of the interface region. The glass core layer may include at least one glass forming agent, and a concentration of the at least one glass forming agent is substantially constant from a core side of the interphase region to a middle region of the glass core layer.

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein the at least one glass cladding layer includes at least one glass modifier, and a concentration of the at least one glass modifier is substantially constant from a surface of the at least one glass cladding layer to a cladding side of the interface region. The glass core layer may include at least one glass modifier, and the concentration of the at least one glass modifier is substantially constant from the core side of the interphase region to the middle region of the glass core layer.

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein the glass core layer has a core coefficient of thermal expansion CTE from 20 ℃ to 300 ℃_CAt least one glass cladding layer having a cladding coefficient of thermal expansion CTE at 20 ℃ to 300 DEG C_CLAnd CTE of_CIs greater than or equal to CTE_CL。

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein CTE is due to_CAnd CTE_CLThe difference therebetween, the compressive stress in the at least one glass cladding layer is greater than 100MPa and extends from a surface of the at least one glass cladding layer through a thickness of the at least one glass cladding layer.

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein the glass core layer includes a core glass modulus of elasticity E_CAnd at least one of the glass cladding layers comprises a cladding glass elastic modulus E_CLIn which E_CIs greater than E_CL。

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein E_CAnd E_CLThe difference therebetween is greater than or equal to 5 GPa.

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein a core glass refractive index n of the glass core layer_CIs a refractive index n of the clad glass greater than at least one glass cladding layer_CL。

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein the clad glass has a refractive index of greater than or equal to 1.45 and less than or equal to 1.55.

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein DOC is greater than or equal to 10% of the total thickness T.

Another aspect includes a laminated glass article according to the second aspect and any other aspect thereof, wherein the thickness T_CLIs less than or equal to 10% of the total thickness T.

Additional features and advantages of the laminated glass articles described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description describe various embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

Drawings

Fig. 1 schematically illustrates a cross-section of a laminated glass article according to one or more embodiments described and illustrated herein;

fig. 2 schematically illustrates an interface region of a laminated glass article according to one or more embodiments shown and described herein;

fig. 3 schematically illustrates an apparatus for forming a laminated glass article according to one or more embodiments shown and described herein;

FIG. 4 is a graph depicting Na for the depicted and ion exchanged samples of laminated glass articles₂Concentration of O (Y-coordinate) as a function of depth (X-coordinate);

FIG. 5 is a graph illustrating Na for ion-exchanged samples of laminated glass articles₂Concentration of O (Y-coordinate) as a function of depth (X-coordinate);

FIG. 6 illustrates Al for the illustrated and ion-exchanged samples of laminated glass articles₂O₃Concentration (Y coordinate) and depth ofA function of degrees (X-coordinate);

FIG. 7 is a graph illustrating Na for ion-exchanged samples of laminated glass articles₂O、K₂O and Al₂O₃As a function of the concentration (Y-coordinate) and depth (X-coordinate);

fig. 8 illustrates compressive stress (Y-coordinate) as a function of depth (X-coordinate) for an ion-exchanged sample of a laminated glass article.

Detailed Description

Reference will now be made in detail to embodiments of the laminated glazing, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. One embodiment of a laminated glass article is schematically illustrated in cross-section in figure 1 and is generally indicated throughout the drawings by reference numeral 100. The laminated glass article generally includes a glass core layer formed from an ion-exchangeable core glass composition and includes a core glass modulus of elasticity, EC, and at least one glass cladding layer fused directly to the glass core layer. The at least one glass cladding layer may be formed from an ion-exchangeable cladding glass composition and include a cladding glass elastic modulus ECL, the ion-exchangeable cladding glass composition being different from the ion-exchangeable core glass composition. The laminated glass article may have a total thickness T and the at least one glass cladding layer may have a thickness TCL that is less than 30% of the total thickness T. The EC may be at least 5% greater than the ECL. Various embodiments of laminated glass articles and methods of forming laminated glass articles will be described in more detail with particular reference to the claims.

Ranges expressed herein may be from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed in an approximate manner using the antecedent "about," it will be appreciated that the particular value will form another embodiment. It will be further understood that each endpoint of a range is distinct and separate from the other endpoint.

Directional terminology used herein (e.g., upper, lower, right, left, front, rear, top, bottom) is only true for the illustrations referenced in the drawings and is not intended to imply absolute orientation.

Unless expressly stated otherwise, it is not intended that any method described herein be construed as necessarily requiring that its steps be performed in a particular order, nor that it require any particular orientation of the apparatus. Thus, where a method claim does not actually recite an order to its steps, or any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, or a specific order or orientation to components of an apparatus is not recited, it is not intended that an order or orientation be inferred, in any respect. This applies to any possibly non-express basis for explanation, including: logical events for the arrangement of steps, operational flows, orders of parts, or orientations of parts; general meaning derived from grammatical organization or punctuation; and the number or type of embodiments described in the specification.

As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects having two or more components, unless the context clearly indicates otherwise.

The term "CTE" as used herein refers to the coefficient of thermal expansion of the glass composition averaged over a temperature range of about 20 ℃ to about 300 ℃.

The elastic modulus (also referred to as young's modulus) of the different layers of the glass laminate is provided in gigapascals (GPa) units. The elastic modulus of the glass was determined by resonance ultrasonic spectroscopy on a large number of samples of each glass laminate composition.

The term "softening point" as used herein refers to a viscosity of the glass composition of 1X 10^7.6The temperature of poise.

As used herein, the term "annealing point" refers to a viscosity of the glass composition of 1X 10¹³The temperature of poise.

The term "strain point" as used herein "And "Tstrain" means that the viscosity of the glass composition is 3X 10¹⁴The temperature of poise.

Surface Compressive Stress (CS) and depth of compression (DOC) were measured using Refracted Near Field (RNF) measurements as described in U.S. patent No. 8,854,623B2 entitled Systems and methods for measuring a profile characterization of a glass sample.

The phrases "depth of compression" and "DOC" refer to the location in the glass where compressive stress is converted to tensile stress.

The concentration profiles of the various constituent components in the glass were measured by Electron Probe Microanalysis (EPMA).

Embodiments described herein provide laminated glass articles having high scratch resistance and also exhibiting improved resistance to breakage from dropping. More specifically, embodiments described herein include laminated glass articles including glass cladding layers and glass core layers having different properties to facilitate different properties. Specifically, when subjected to sharp contact, the glass cladding layer has high scratch resistance and high crack formation resistance, while the glass core layer is easily ion-exchange strengthened, resulting in a deep depth of compression, improving resistance to breakage caused by dropping. In addition, the glass used for the glass cladding layer and the glass core layer is selected so that stress can be generated by cooling after the glass is formed.

Referring now to fig. 1, a laminated glass article 100 is schematically illustrated in cross-section. The laminated glass article 100 generally comprises a glass core layer 102 and at least one glass cladding layer 104 a. In the embodiment of the laminated glass article 100 shown in fig. 1, the laminated glass article includes a first glass cladding layer 104a and a second glass cladding layer 104b positioned on opposite sides of the glass core layer 102. While fig. 1 schematically illustrates the laminated glass article 100 as a laminated glass sheet, it is to be understood that other configurations and physical dimensions are contemplated and possible. For example, the laminated glass article may have a non-planar configuration (e.g., a curved glass sheet or the like). Alternatively, the laminated glass article may be a laminated glass tube, container, or the like.

In the embodiments of the laminated glass article 100 described herein, the glass core layer 102 generally comprises a first major surface 103a and a second major surface 103b opposite the first major surface 103 a. The first glass cladding layer 104a is fused to the first major surface 103a of the glass core layer 102 and the second glass cladding layer 104b is fused to the second major surface 103b of the glass core layer 102.

In the embodiments described herein, the glass cladding layers 104a, 104b are fused to the glass core layer 102 without requiring additional non-glass materials (e.g., adhesives, coating layers, or the like) to be disposed between the glass core layer 102 and the glass cladding layers 104a, 104 b. Thus, in some embodiments, the glass cladding layers 104a, 104b are fused directly to the glass core layer 102 and/or are directly adjacent to the glass core layer 102.

Referring now to fig. 2, an enlarged view of the interface between the glass core layer 102 and the glass cladding layers 104a, 104b is schematically illustrated. In an embodiment, the laminated glass article 100 includes interface regions 106a, 106b at the interface between the glass core layer 102 and the glass cladding layers 104a, 104 b. When the glass core layer 102 and the glass cladding layers 104a, 104b are fused together, interface regions 106a, 106b are formed. The interface regions 106a, 106b are thin layers composed of a mixture of a cladding composition forming the glass cladding layers 104a, 104b and a core composition forming the glass core layer 102. For example, interface regions 106a, 106b may comprise intermediate glass layers and/or diffusion layers formed at the interface of the glass core layer and the glass cladding layer (e.g., by diffusing one or more constituents of the glass core layer and the glass cladding layer into the diffusion layers). In some embodiments, the laminated glass article 100 comprises a glass-to-glass laminate (e.g., an in-situ fused multilayer glass-to-glass laminate) in which the interface between directly adjacent glass layers is a glass-to-glass interface.

Referring again to fig. 1, in the embodiments described herein, the total thickness T of the laminated glass article 100 is the sum of the thickness of the glass core layer 102 and the thickness of each of the glass cladding layers 104a, 104b along the Z-direction of the coordinate axes depicted in fig. 1. In an embodiment, the total thickness T of the laminated glass article may be greater than or equal to 0.5mm and less than or equal to 3 mm. In some embodiments, the total thickness T of the laminated glass article may be greater than or equal to 0.8mm and less than or equal to 1.5 mm. In some embodiments, the total thickness T of the laminated glass article may be greater than or equal to 0.9mm and less than or equal to 1.0 mm.

In an embodiment, the thickness of each glass cladding layer 104a, 104b is less than 30% of the total thickness T of the laminated glass article. In embodiments, the thickness of each glass cladding layer 104a, 104b may be less than or equal to 25% of the total thickness T of the laminated glass article, or even less than or equal to 20% of the total thickness T of the laminated glass article. In other embodiments, the thickness of each glass cladding layer 104a, 104b may be less than or equal to 15% of the total thickness T of the laminated glass article. In an embodiment, the thickness of each glass cladding layer 104a, 104b is less than or equal to 10% of the total thickness T of the laminated glass article. In embodiments, the thickness of each glass cladding layer 104a, 104b may be less than or equal to 8% of the total thickness T of the laminated glass article, or even less than or equal to 6% of the total thickness T of the laminated glass article. In other embodiments, the thickness of each glass cladding layer 104a, 104b may be less than or equal to 5% of the total thickness T of the laminated glass article. A glass cladding layer having a thickness less than 30% of the total thickness T of the laminated glass article facilitates ion exchange strengthening of the glass core layer 102 through the glass cladding layers 104a, 104 b.

In the embodiments of the laminated glass article 100 described herein, the glass core layer 102 is formed from an ion-exchangeable core glass composition, and the glass cladding layers 104a, 104b are formed from ion-exchangeable cladding glass compositions. However, the composition of the glass cladding layers 104a, 104b is different from the composition of the glass core layer 102 to obtain specific properties in the final laminated glass article.

For example, the glass core layer 102 and the glass cladding layers 104a, 104b may have different free volumes, resulting in different properties for the glass core layer 102 and the glass cladding layers 104a, 104 b. The phrase "free volume" as used herein refers to the space in a glass structure not occupied by atoms or structural units. In particular, the glass cladding layers 104a, 104b may have a relatively high free volume compared to the glass core layer 102. The relatively high free volume in the glass cladding layers 104a, 104b results in densification (i.e., scratching) and less shear of the glass during a sharp impact event, while reducing subsurface damage to the glass and reducing residual stress in the glass. However, a relatively high free volume in the glass does not necessarily improve the resistance to damage caused by dropping. This is because glasses with relatively high free volume generally have lower surface compression after ion exchange strengthening compared to glasses with relatively low free volume.

Thus, in the embodiments described herein, the glass core layer 102 has a lower free volume than the glass cladding layers 104a, 104 b. When the glass core layer 102 is strengthened by ion exchange, the relatively low free volume of the glass core layer 102 helps to achieve a higher compressive stress in the glass core layer 102. The compressive stress in the glass core layer 102 (e.g., at the edges of the glass core layer) improves the resistance of the laminated glass article 100 to damage caused by dropping.

As previously described, a laminated glass article 100 having improved scratch resistance and improved resistance to drop-induced damage may be obtained by using a glass having a relatively high free volume for the glass cladding layers 104a, 104b and a glass having a relatively low free volume for the glass core layer 102.

The free volume of glass is related to the elastic modulus of the glass. More specifically, it is generally understood that the modulus of elasticity of glass decreases with increasing free volume and increases with decreasing free volume. Thus, in the embodiments described herein, the elastic modulus E of the glass core layer 102_CIs greater than the elastic modulus E of the glass cladding layers 104a, 104b_CL. In some embodiments, the elastic modulus E of the glass core layer 102_CIs greater than the elastic modulus E of the glass cladding layers 104a, 104b_CLAt least 5%. For example, in some embodiments, the elastic modulus of the glass core layer 102Quantity E_CIs greater than the elastic modulus E of the glass cladding layers 104a, 104b_CLAt least 10%, or even more than the modulus of elasticity E of the glass cladding layers 104a, 104b_CLAt least 15%. In other embodiments, the elastic modulus E of the glass core layer 102_CIs greater than the elastic modulus E of the glass cladding layers 104a, 104b_CLAt least 20%, or even more than the modulus of elasticity E of the glass cladding layers 104a, 104b_CLAt least 25%.

In some embodiments, the elastic modulus E of the glass core layer 102_CAnd the elastic modulus E of the glass cladding layers 104a and 104b_CLThe difference between is greater than or equal to 5GPA, or even greater than or equal to 10 GPA. For example, in some of these embodiments, the elastic modulus E of the glass core layer 102_CAnd the elastic modulus E of the glass cladding layers 104a and 104b_CLThe difference between these is greater than or equal to 15GPA, or even greater than or equal to 20 GPA. In some other embodiments, the elastic modulus E of the glass core layer 102_CAnd the elastic modulus E of the glass cladding layers 104a and 104b_CLThe difference between is greater than or equal to 25GPA, or even greater than or equal to 30 GPA.

In some embodiments, the glass cladding layers 104a, 104b have an elastic modulus E_CLIs less than or equal to 76.5GPa, and the elastic modulus E of the glass core layer 102_CIs greater than 76.5 GPa. For example, in some embodiments, the glass cladding layers 104a, 104b have an elastic modulus E_CLIs less than or equal to 76.5GPa and greater than or equal to 60GPa, and the elastic modulus E of the glass core layer 102_CIs greater than 76.5GPa and less than or equal to 90 GPa. In some embodiments, the glass cladding layers 104a, 104b have an elastic modulus E_CLIs less than or equal to 71.5GPa, and the elastic modulus E of the glass core layer 102_CIs greater than 76.5 GPa.

Like the modulus of elasticity, the free volume of a glass is also related to the refractive index n of the glass. In the embodiments described herein, the core refractive index n of the glass core layer 102_CIs larger than the cladding refractive index n of the glass cladding layers 104a, 104b_CL. For example, in an embodiment, the cladding refractive index n_CLIs greater than or equal to 1.45 and less than or equal to 1.55, or even greater than or equal to 1.48 and less than or equal to 1.505. In these embodiments, the core refractive index n_CIs greater than or equal to 1.50 and less than or equal to 1.60, or even greater than or equal to 1.506 and less than or equal to 1.55.

As described above, the glass core layer 102 and the glass cladding layers 104a and 104b are formed of glass compositions that can be strengthened by ion exchange. The presence of alkali metal oxides in the glass core layer 102 and the glass cladding layers 104a, 104b helps to strengthen the glass by ion exchange. Specifically, alkali metal ions (e.g., potassium ions, sodium ions, lithium ions, and the like) have sufficient mobility in the glass to facilitate ion exchange. The laminate glass article may be strengthened by ion exchange by melting KNO at a temperature of 350 ℃ to 500 ℃₃Molten NaNO₃Or combinations thereof, for less than about 30 hours or even less than about 20 hours for the laminated glass article 100.

In embodiments where the laminated glass article 100 is strengthened by ion exchange, the laminated glass article has a surface compressive stress CS₀And a compressive stress region extending from the surfaces 108a, 108b of the laminated glass article 100 into the total thickness T to a depth of compression DOC. In some of these embodiments, the surface compressive stress is greater than or equal to 200MPa or even greater than or equal to 500 MPa. In some of these embodiments, the surface compressive stress may be greater than or equal to 600MPa or even greater than or equal to 700 MPa.

In embodiments described herein, the laminated glass article includes a compressive stress region extending from a surface of the at least one glass cladding layer into a total thickness T of the laminated glass article to a depth of compression. In some embodiments, the compressive stress region may have a depth of compression greater than or equal to 10% of the total thickness T of the laminated glass article 100. In some embodiments, the compressive depth of the compressive stress region may be greater than or equal to 15% of the total thickness T of the laminated glass article 100, or even greater than or equal to 20% of the total thickness T of the laminated glass article 100. In other embodiments, the compressive depth of the compressive stress region may be greater than or equal to 25% of the total thickness T of the laminated glass article 100, or even greater than or equal to 30% of the total thickness T of the laminated glass article 100.

As described above, the laminated glass article 100 is configured such that the glass core layer 102 can be ion-exchange strengthened through the glass cladding layers 104a, 104 b. Further, the laminated glass article 100 is configured such that the glass core layer 102 has a lower free volume (i.e., a greater modulus of elasticity and a greater index of refraction) than the glass cladding layers 104a, 104 b. The glass core layer 102 and the glass cladding layers 104a, 104b have different compositional properties to achieve these properties. The compositional features of each glass composition, after strengthening by ion exchange, produce a unique alkali ion diffusion profile throughout the thickness of the laminated glass article.

Referring again to FIG. 2, prior to ion exchange strengthening, the various constituents of the glass network of the glass cladding layers 104a, 104b (e.g., glass formers (e.g., SiO)₂And B₂O₃) Intermediate (e.g., Al)₂O₃) And modifiers (e.g., CaO, Na)₂O, etc.)) are generally uniformly distributed from the surfaces 108a, 108b of the laminated glass article 100 to the respective interface regions 106a, 106 b. For example, the glass capping layers 104a, 104b include at least one glass former at a concentration that is substantially constant from the surfaces 108a, 108b of the laminated glass article 100 to the clad side of the interface regions 106a, 106 b. In addition, the glass cladding layers 104a, 104b include at least one modifier (e.g., Na)₂O and/or another alkali metal oxide) and the concentration of the modifying agent is substantially constant from the surfaces 108a, 108b of the laminated glass article 100 to the clad side of the interfacial regions 106a, 106 b.

Similarly, the various compositional components of the glass network of the glass core layer 102 (e.g., glass formers (e.g., SiO)₂And B₂O₃) Intermediate (e.g., Al)₂O₃) And modifiers (e.g., CaO, Na)₂O, etc.)) is generally uniformly distributed from the respective interface regions 106a, 106b to the glass coreCenter line segment C of layer 102_L. For example, the glass core layer 102 includes at least one glass forming agent at a concentration that is from the core side of the interphase region to a centerline segment C of the glass core layer 102_LIs substantially constant. In addition, glass core layer 102 includes at least one modifier (e.g., Na)₂O and/or another alkali metal oxide) and the concentration of the glass modifier is from the core side of the interfacial region to the centerline segment C of the glass core layer 102_LIs substantially constant.

However, after ion exchange, alkali metal oxides (e.g., K)₂O and/or Na₂O) varies with depth from the surfaces 108a, 108b of the laminated glass article 100 in the glass core layer 102 and the glass cladding layers 104a, 104 b. Specifically, K₂O and Na₂The concentration of at least one of O is gradually decreasing from the surface 108a, 108b of the laminated glass article 100 through the glass cladding layers 104a, 104b to the cladding side of the interface regions 106a, 106 b. That is, Na in the glass coating layers 104a and 104b₂O and/or K₂The concentration of O has a negative slope as a function of distance from the surfaces 108a, 108 b. For example, in some embodiments, Na in the glass cladding layers 104a, 104b₂The slope of the O concentration may range from about-5 mol%/μm to about-18 mol%/μm, with K in the glass cladding layers 104a, 104b₂The slope of the O concentration may range from about-3 mole%/μm to about-12 mole%/μm.

Similarly, K₂O and Na₂The concentration of at least one of O is from the core side of the interface regions 106a, 106b along the centerline segment C of the glass core layer 102_LAnd decreases. However, in the embodiments described herein, K at the clad side of the interface regions 106a, 106b₂O and Na₂The concentration of at least one of O is less than the concentration of the same constituent component at the core side of the interfacial regions 106a, 106 b.

Although the concentration of alkali metal oxide in the glass cladding layer changes due to ion exchange strengthening, it is understood that the concentration of the other components of the glass network, i.e., the glass forming agents, the intermediates, and the non-migratory modifiers (e.g., alkaline earth metal oxides (CaO, MgO, etc.)), remain substantially the same (i.e., substantially uniform through the thickness of the glass cladding layer, and substantially uniform through the thickness of the glass core layer).

As described above, in embodiments where the laminated glass article is separated from the continuous glass ribbon, the separation may expose the glass core layer along at least one edge of the laminated glass article and a central tension in the glass core layer. In embodiments where the laminated glass article includes a glass core layer formed from ion-exchangeable glass, ion-exchange strengthening may be performed for an exposed edge of the laminated glass article having an exposed central tension to generate a compressive stress in a surface of the exposed glass core layer extending to a depth of compression. The surface compressive stress in the exposed glass core layer relieves the center tension at the exposed edge and reduces the risk of breakage of the laminated glass article from the exposed edge. In these embodiments, the laminated glass article may have a surface compressive stress along the entire exposed edge (i.e., in the glass cladding layer and the glass core layer).

Referring again to fig. 1, in some embodiments, the laminated glass article 100 may be formed such that there is a mismatch between the Coefficients of Thermal Expansion (CTE) of the glass core layer 102 and the glass cladding layers 104a, 104 b. This mismatch in the CTEs of the glass core layer 102 and the glass cladding layers 104a, 104b results in the formation of compressive stresses extending from the surfaces 108a, 108b of the laminated glass article 100 into the thickness of the laminated glass article. For example, in some embodiments described herein, the glass cladding layers 104a, 104b are formed from a material having an average cladding coefficient of thermal expansion CTE_CLThe glass core layer 102 is formed of a glass having an average core coefficient of thermal expansion CTE_COf different glass compositions. CTE (coefficient of thermal expansion)_CIs greater than CTE_CL(i.e., CTE)_C>CTE_CL) Resulting in compressive stress on the glass cladding layers 104a, 104 b.

The compressive stress in the cladding due to the CTE difference between the core and the cladding can be approximated using the following equation:

wherein t is_coreIs the core thickness, T_CladIs the coating thickness, alpha_cladIs to coat the coefficient of thermal expansion, alpha_coreIs the core coefficient of thermal expansion,. DELTA.T is the effective temperature difference, E_coreIs the elastic modulus of the core, E_cladIs the modulus of elasticity, v, of the coating_coreIs the Poisson's ratio of the core, and v_cladIs the poisson's ratio for the cladding. In general, α_clad< Δ T and α_coreΔ T < 1, thus:

for example, in some embodiments, the glass cladding layer is formed from a glass having an average value in the range of 20 ℃ to 300 ℃ of less than or equal to about 72 x 10^-7Average coating CTE per degree C_CLThe glass composition of (1). In some embodiments, the average clad CTE of the clad glass composition_CLThe average value in the range of 20 ℃ to 300 ℃ may be less than or equal to about 70 x 10^-7V. C. In other embodiments, the average clad CTE of the clad glass composition_CLThe average value in the range of 20 ℃ to 300 ℃ may be less than or equal to about 65 x 10^-7V. C. In other embodiments, the average clad CTE of the clad glass composition_CLIn the range of 20 ℃ to 300 ℃The average value in the enclosure may be less than or equal to 60 x 10^-7The temperature may be less than or equal to about 55 x 10 or even an average value in the range of 20 ℃ to 300 ℃^-7/℃。

However, the glass core layer may be formed of a glass having a thickness of more than 72 × 10 in the range of 20 ℃ to 300 ℃^-7A/° c average coefficient of thermal expansion. In some of these embodiments, the average core CTE of the core glass composition of the glass core layer_CCan be greater than or equal to about 75 x 10 over the range of 20 ℃ to 300 ℃^-7V. C. In other embodiments, the average core CTE of the glass composition of the glass core layer_CThe average value in the range of 20 ℃ to 300 ℃ may be greater than or equal to about 80 x 10^-7V. C. In other embodiments, the average core CTE of the glass composition of the glass core layer_CThe average value in the range of 20 ℃ to 300 ℃ may be greater than or equal to about 90X 10^-7/℃。

In the embodiments described herein, the CTE difference between the glass core layer 102 and the glass cladding layers 104a, 104b (i.e., | CTE |)_C-CTE_CLL) is sufficient to create compressive stress in the cladding layer. In some embodiments, the CTE difference between the glass core layer 102 and the glass cladding layers 104a, 104b is sufficient to produce a compressive stress in the glass cladding layers 104a, 104b of greater than or equal to 100MPa extending from the surface of the glass cladding layers 104a, 104b and through the thickness of the glass cladding layers 104a, 104 b. In some embodiments, the compressive stress in the glass cladding layers 104a, 104b due to the CTE difference is greater than or equal to 120MPa, or even greater than or equal to 150 MPa.

In some embodiments, the CTE difference between the glass core layer and the glass cladding layer is greater than or equal to about 5 x 10^-7/° c, or even 10 × 10^-7V. C. In some other embodiments, the CTE difference between the glass core layer and the glass cladding layer is greater than or equal to about 20 x 10^-7/° c, or even 30 × 10^-7V. C. In other embodiments, the CTE difference between the glass core layer and the glass cladding layer is greater than or equal to about 40 x 10^-7/° c, or even 50 x 10^-7/℃。

In embodiments where the laminated glass article 100 is formed from a core glass composition and a clad glass composition having a CTE difference that produces a compressive stress extending through the thickness of the glass cladding layers 104a, 104b, the laminated glass article 100 may also be ion exchanged to strengthen the properties of the laminated glass article 100. The combination of the CTE difference between the glass core layer 102 and the glass cladding layers 104a, 104b and the ion exchange strengthening results in a unique stress profile and this example is illustrated in figure 8. As shown in fig. 8, the profile of the compressive stress in the glass cladding layer (region "a") is the sum of the stress profile due to the CTE difference between the glass cladding layer and the glass core layer and the stress profile due to ion exchange. The compressive stress in the region from the surface of the glass to the core clad interface at 50 μm includes compressive stress due to CTE difference between the glass core layer and the glass clad layer and compressive stress due to ion exchange strengthening. The glass core layer (i.e., the portion of the laminate greater than 50 μm in depth) is also subjected to compressive stress. However, the stress in the glass core layer is caused by ion exchange through the glass core layer to strengthen the glass cladding layer.

In some embodiments, the glass core layer may be formed from one of the ion-exchangeable core glass compositions listed in table 1A and table 1B below. However, it is understood that other compositions of the glass core layer 102 are contemplated and possible.

Table 1A: exemplary glass core layer compositions

Table 1B: exemplary glass core layer compositions

In some embodiments, the glass cladding layer may be formed from one or more ion-exchangeable cladding glass compositions listed in table 2A and table 2B below. However, it is understood that other compositions of the glass cladding layers 104a, 104b are contemplated and possible.

Table 2A: exemplary clad glass compositions

Table 2B: exemplary clad glass compositions

Various processes, including but not limited to a laminate slot draw process, a laminate float process, or a fusion laminate process, may be used to make the laminated glass articles described herein. Each of these lamination processes generally involves flowing a first molten glass composition, flowing a second molten glass composition, and contacting the first molten glass composition with the second molten glass composition at a temperature greater than the glass transition temperature of either glass composition to form an interface between the two compositions, while allowing the first and second molten glass compositions to fuse together at the interface as the glass cools and solidifies.

In one particular embodiment, the laminated glass article 100 described herein may be formed by a fusion lamination process (e.g., the process described in U.S. patent No. 4,214,886, and incorporated herein by reference). By way of example with reference to fig. 3, a laminate fusion draw apparatus 200 for forming a laminated glass article includes an upper overflow distributor or isopipe 202 positioned above a lower overflow distributor or isopipe 204. The upper overflow distributor 202 includes a trough 210, and the molten glass cladding composition 206 is fed into the trough 210 by a melter (not shown). Similarly, lower overflow distributor 204 includes trough 212, and molten glass core composition 208 is fed into trough 212 by a melter (not shown).

As the molten glass core composition 208 fills the trough 212, it flows out of the trough 212 and over the outer forming surfaces 216, 218 of the lower overflow distributor 204. The outer forming surfaces 216, 218 of lower overflow distributor 204 converge at root 220. Thus, the molten glass core composition 208 flowing over the outer forming surfaces 216, 218 is brought into registration at the root 220 of the underflow distributor 204, thereby forming the glass core layer 102 of the laminated glass article.

At the same time, the molten glass cladding composition 206 overflows the trough 210 formed in the overflow distributor 202 and flows over the outer forming surfaces 222, 224 of the overflow distributor 202. The molten glass cladding composition 206 is deflected outward by the upper overflow distributor 202 such that the molten glass cladding composition 206 flows around the lower overflow distributor 204 and contacts the molten glass core composition 208 flowing over the outer forming surfaces 216, 218 of the lower overflow distributor, fusing to the molten glass core composition and around the glass core layer 102 to form the glass cladding layers 104a, 104 b.

Although fig. 3 schematically illustrates a particular apparatus for forming a flat laminated glass article (e.g., a sheet or ribbon), it should be understood that other geometric configurations are possible. For example, a cylindrical laminated glass article may be formed using the apparatus and method described in U.S. patent No. 4,023,953.

In some embodiments, as described above, the average core coefficient of thermal expansion CTEC of the molten glass core composition 208 is substantially greater than the average cladding coefficient of thermal expansion CTECL of the molten glass cladding composition 206. Thus, as the glass core layer 102 and the glass cladding layers 104a, 104b cool, the difference in the coefficients of thermal expansion of the glass core layer 102 and the glass cladding layers 104a, 104b causes compressive stress to be generated in the glass cladding layers 104a, 104 b. The compressive stress increases the strength of the resulting laminated glass article.

Knoop Scratch Threshold (KST) as described herein was determined using a Knoop diamond indenter. The scratch threshold is determined by first determining the load range at which the transverse crack starts. Once the load range is determined, a series of 5mm long scratches are made at increasing constant loads using a speed of 4mm/s to identify the Knoop scratch threshold, with three or more scratches per load. A transverse crack is a sustained crack defined as greater than twice the width of the groove.

In embodiments described herein, the Knoop scratch threshold of the glass laminate is greater than or equal to 2 newtons (N). In some embodiments, the Knoop scratch threshold of the glass laminate is greater than or equal to 4N, or even greater than or equal to 6N. In embodiments, the Knoop scratch threshold of the glass laminates described herein is greater than or equal to 2N and less than or equal to 8N, or even greater than or equal to 4N and less than or equal to 8N. In some of these embodiments, the Knoop scratch threshold of the glass laminates described herein is greater than or equal to 2N and less than or equal to 4N, or even greater than or equal to 4N and less than or equal to 6N. In other embodiments, the Knoop scratch threshold of the glass laminates described herein is greater than or equal to 6N and less than or equal to 8N.

The laminated glass articles described herein may be used in a variety of applications, including, for example, automotive glass, architectural, appliance, and consumer electronics (e.g., cover glass) applications. The combination of a thin ion-exchangeable glass cladding layer having a relatively low modulus of elasticity and an ion-exchangeable glass core layer having a relatively high modulus of elasticity provides the laminated glass article with improved resistance to surface damage (e.g., scratch resistance), as well as improved resistance to sharp impact damage (e.g., drop-induced damage and breakage).

Examples of the invention

The examples described herein will be further clarified by the following examples.

Example 1

A three-layer laminated glass article was formed having a core glass composition C1 (table 1) and a clad glass composition CL1 (table 2A). The glass cladding layer has a thickness of about 25 μm to about 50 μm, and the glass core layer has a thickness of about 750 μm to about 800 μm. It is understood that the variation in the thickness of the glass cladding layer and the glass core layer is due to the laboratory scale equipment used to manufacture the laminated glass article for testing. The elastic modulus of the glass core layer was 76.67GPa, and the CTE was 84X 10-⁷V. C. Modulus of elasticity of glass coating layerIs 67.78GPa and the CTE is 49.6 x 10^-7V. C. The compressive stress in the glass cladding layer due to the CTE mismatch between the glass cladding layer and the glass core layer was determined to be about 150MPa depending on the values of the elastic modulus, poisson's ratio, and CTE of each glass. For the purposes of this calculation, Δ T is estimated as the difference between the lower strain point temperature and room temperature.

A sample of the laminated glass article was prepared by immersing the sample in 100% NaNO at 430 deg.C₃Or 20% by weight of NaNO₃80% by weight of KNO₃The molten salt bath of (2) is subjected to ion exchange strengthening for 2.5 hours, 7 hours, or 24 hours. After the ion exchange process, the laminated glass article was analyzed using Electron Probe Microanalysis (EPMA) to determine various compositional constituents of the glass, including Na₂O and K₂O) as a function of depth from the surface of the laminated glass article. The results of the analysis are graphically shown in fig. 4 to 7.

FIG. 4 shows Na₂O concentration and laminated glass article shown and 100% NaNO at 430 deg.C₃Ion exchange for 2.25 hours, 7 hours, and 24 hours. FIG. 5 shows Na₂Concentration of O and 20 wt% NaNO at 430 deg.C₃80% by weight of KNO₃As a function of depth of the laminated glass article after 2.25 hours, 7 hours, or 24 hours of ion exchange. As shown in FIG. 4, the glass is coated with Na as shown₂The concentration of O is about 4% by weight, while Na of the glass core layer is shown as₂The concentration of O is about 10.0 wt%. The increase in the concentration of the clad glass from less than 4 wt.% to about 6 wt.% is believed to be due to the densification of the clad glass during the glass drawing process in which the glass core composition is contacted with the glass cladding composition at a temperature greater than 1000 ℃.

Data from the ion exchange process at 430 ℃ are shown in FIGS. 4 and 5 as Na₂O diffuses into and through the glass cladding layer and into the glass core layer, thereby increasing Na in the glass cladding layer and the glass core layer₂The concentration of O.These data indicate ion exchange through the glass cladding layer and into the glass core layer. The data also generally represent Na in the glass coating₂The concentration of O generally decreases with increasing distance from the surface (i.e., depth of 0) of the laminated glass article, while Na in the glass core layer₂The concentration of O generally decreases as the distance from the clad core interface (i.e., 25 μm to 50 μm) to the centerline segment of the laminated glass article increases.

FIG. 6 shows Al₂O₃With SiO₂Concentration of (D) with the laminated glass article shown and 100% NaNO at 430 deg.C₃As a function of the depth of the laminated glass article after 24 hours of ion exchange. These data generally represent the non-alkali composition (e.g., Al) throughout the thickness of the laminated glass article, before and after ion exchange₂O₃With SiO₂) The concentration of (c) is kept constant. These data support the assumption that the ion exchange process will go through the thickness of the glass cladding layer and into the glass core layer (i.e., the data indicates that there is not a significant diffusion of the glass composition at the core cladding interface, but only that the ion exchanged composition appears to be concentrated, which occurs on both sides of the interface).

FIG. 7 is a graph showing 20 wt% NaNO at 390 deg.C₃With 80% by weight of KNO₃Al of the laminated glass article after ion exchange in the mixed salt bath for 8 hours₂O₃、Na₂O and K₂Concentration of O as a function of depth. Comparing fig. 4,6, and 7, it can be seen that Al in the laminated glass article was present before ion exchange and after ion exchange in the mixed salt bath at 390 ℃₂O₃Is constant throughout the thickness of the laminated glass article while Na in the glass core layer after ion exchange₂The concentration of O increases. The data also show, although due to K₂O has a relative ratio to Na₂Lower mobility of O, K₂Diffusion degree of O to Na₂O is smaller but some diffusion still occurs at the core clad interface. Thus, these data support that ion exchange will pass through the glass coating and into the glassAssumption of glass core layer.

80 wt.% KNO at 390 ℃ for a second set of samples₃With 20% by weight of NaNO₃For 4 hours or 16 hours in the molten salt bath. A Refractive Near Field (RNF) technique is then used to determine the compressive stress as a function of the depth of compression from the surface of the laminated glass article. The results are illustrated in fig. 8. As shown in fig. 8, the surface compressive stress of the glass cladding layer is greater than 400MPa, while the compressive stress of the entire glass cladding layer is generally greater than 200 MPa. It should be noted that the value of the surface compressive stress is inferred from the RNF profile, not directly measured. The compressive stress in the glass cladding layer is due to ion exchange and CTE difference between the glass core layer and the glass cladding layer. Fig. 8 also shows that the compressive stress in the glass core layer is the maximum closest to the core cladding interface and decreases with increasing distance, ultimately becoming a tensile stress within the thickness of the glass cladding layer.

Example 2

The ion-exchange properties of the glass core layers and glass compositions of the glass cladding layers identified in tables 1A, 1B, 2A, and 2B were evaluated to determine the effect of free volume on ion exchange. Specifically, a 1mm thick coupon of each glass composition was annealed, followed by 100% KNO at 410 ℃₃For 4 hours in the molten salt bath. After ion exchange, the samples were analyzed using a basic stress meter (FSM) instrument to determine the surface compressive stress and depth of compression caused by the ion exchange. The results are reported in tables 3A, 3B, 4A, and 4B.

Table 3A: ion exchange characteristics of exemplary glass core layer compositions

Table 3B: ion exchange characteristics of exemplary glass core layer compositions

	C8	C9	C10	C11	C12	C13
							Compressive stress (MPa)	1201	1201	1195	1242	1235	1265
Depth of compression (μm)	11	13	6	12	10	12

Table 4A: ion exchange characteristics of exemplary glass cladding compositions

Table 4B: ion exchange characteristics of exemplary glass cladding compositions

As shown in tables 3A-4B, the glass core compositions achieved higher surface compressive stress, while exhibiting that glasses with lower free volume (i.e., glasses with higher refractive index) achieved higher compressive stress under the same ion exchange conditions.

Those skilled in the art will appreciate that various modifications and changes may be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, the description is intended to cover the modifications and variations of the various embodiments described herein that are within the scope of the appended claims and their equivalents.