CN111295282A

CN111295282A - Display module with quasi-static and dynamic impact resistance

Info

Publication number: CN111295282A
Application number: CN201880071470.3A
Authority: CN
Inventors: 诗露·百贝; 蒂莫西·迈克尔·格罗斯; 尤瑟夫·凯耶德·卡鲁什; 山姆·萨默·佐比
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2017-10-11
Filing date: 2018-10-09
Publication date: 2020-06-16
Also published as: TWI779112B; WO2019074935A1; KR20200068706A; JP2020536773A; EP3694708A1; JP7208986B2; TW201923427A

Abstract

A display module includes: a glass-containing cover element having a thickness of from about 25 μ ι η to about 200 μ ι η, an elastic modulus of from about 20GPa to 140GPa, and first and second major surfaces; a stack, the stack comprising: (a) a substrate comprising a component having a glass composition and a thickness of from about 100 μ ι η to 1500 μ ι η, and (b) a first adhesive joining the stack to the second major surface of the cover element, the first adhesive comprising an elastic modulus of from about 0.001GPa to about 10GPa and a thickness of from about 5 μ ι η to about 50 μ ι η. Additionally, the display module includes an impact resistance characterized by a tensile stress at the second major surface of the cover element of less than about 3700Mpa upon impact of the cover element in a quasi-static indentation test.

Description

Display module with quasi-static and dynamic impact resistance

Cross Reference to Related Applications

This application is entitled to priority from U.S. provisional application No. 62/571,017 filed 2017, 10, 11, § 119, the content of which is the basis of this application and is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates generally to bendable display modules and articles of manufacture, and in particular, bendable display modules including a cover comprising glass.

Background

The concept of flexible versions of products and components that are traditionally rigid in nature is used for new applications. For example, flexible electronic devices may offer thin, lightweight, and flexible properties that provide opportunities for new applications including curved displays and wearable devices. Many of these flexible electronic devices incorporate a flexible substrate for holding and mounting the electronic components of the devices. Metal foils have some advantages, including thermal stability and chemical resistance, but suffer from high cost and lack of optical transparency. Polymeric foils have several advantages, including low cost and impact resistance, but suffer from marginal optical clarity, lack of thermal stability, limited hermeticity, and cyclic fatigue performance.

Some of these electronic devices may also use flexible displays. Optical transparency and thermal stability are often desirable properties for flexible display applications. Furthermore, the flexible display should have a high resistance to fatigue and puncture, including failure resistance at small bending radii, especially for flexible displays with touch screen functionality and/or being foldable. In addition, flexible displays should be easy to bend and fold by the consumer, depending on the intended application for the display.

Some flexible glasses and glass-containing materials provide many desirable properties for flexible and foldable substrates and display applications. However, efforts to use glass materials for these applications have been difficult to date. In general, glass substrates can be manufactured to very low thickness levels (<25 μm) to achieve increasingly smaller bend radii. These "thin" glass substrates suffer from limited puncture resistance. At the same time, thicker glass substrates (>150 μm) can be made with better puncture resistance, but these substrates lack suitable fatigue resistance and mechanical reliability after bending.

In addition, as these flexible glass materials are used as cover elements in modules that also contain electronic components (e.g., thin film transistors ("TFTs"), touch screens, etc.), additional layers (e.g., polymeric electronic device panels), and adhesives (e.g., epoxies, optically clear adhesives ("OCAs")), the interaction between these various components and the components can lead to increasingly complex stress states that exist during use of the module within the final product (e.g., electronic display device). These complex stress states may result in increased stress levels and/or stress concentration factors experienced by these cover elements. As such, these cover elements may be susceptible to cohesive and/or layered failure modes within the module. In addition, these complex interactions may result in increased bending forces to bend and fold the cover element by the consumer.

Therefore, what is needed are flexible, glass-containing materials and module designs that utilize these materials in a variety of electronic device applications, particularly for flexible electronic display device applications and more particularly for foldable display device applications.

Disclosure of Invention

According to a first aspect of the present invention, there is provided a display module comprising: a cover element having a thickness of from about 25 μm to about 200 μm and a cover element elastic modulus of from about 20GPa to about 140GPa, the cover element further comprising a component having a glass composition, a first major surface, and a second major surface; and a stack, the stack comprising: (a) a substrate comprising a component having a glass composition and a thickness of from about 100 μ ι η to 1500 μ ι η, and (b) a first adhesive joining the stack to the second major surface of the cover element, the first adhesive comprising an elastic modulus of from about 0.001GPa to about 10GPa and a thickness of from about 5 μ ι η to about 50 μ ι η. Additionally, the display module includes an impact resistance characterized by a tensile stress of less than about 4700Mpa at the second major surface of the cover element after impact to the cover element in a quasi-static indentation test.

According to a second aspect of the present invention, there is provided a display module comprising: a cover element having a thickness of from about 25 μm to about 200 μm and a cover element elastic modulus of from about 20GPa to about 140GPa, the cover element further comprising a component having a glass composition, a first major surface, and a second major surface; and a stack, the stack comprising: (a) a substrate comprising a component having a glass composition and a thickness of from about 100 μ ι η to 1500 μ ι η, and (b) a first adhesive joining the stack to the second major surface of the cover element, the first adhesive comprising an elastic modulus of from about 0.001GPa to about 10GPa and a thickness of from about 5 μ ι η to about 50 μ ι η. Additionally, the display module includes an impact resistance characterized by a tensile stress of less than about 4000MPa at the first major surface of the cover element and a tensile stress of less than about 12000MPa at the second major surface of the cover element upon impact to the cover element in a pen drop test.

According to a third aspect of the present invention, there is provided a display module comprising: a cover element having a thickness of from about 25 μm to about 200 μm and a cover element elastic modulus of from about 20GPa to about 140GPa, the cover element further comprising a component having a glass composition, a first major surface, and a second major surface; and a stack, the stack comprising: (a) a substrate comprising a component having a glass composition and a thickness of from about 100 μ ι η to 1500 μ ι η, and (b) a first adhesive joining the stack to the second major surface of the cover element, the first adhesive comprising an elastic modulus of from about 0.001GPa to about 10GPa and a thickness of from about 5 μ ι η to about 50 μ ι η. The display module includes an impact resistance characterized by a tensile stress of less than about 4700Mpa at the second major surface of the cover element after impact on the cover element in a quasi-static indentation test. In addition, the display module includes a hardness of about 750N/mm or greater, the hardness measured during a quasi-static indentation test.

Additional features and advantages 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 as described herein, including the detailed description which follows, the claims, as well as the appended drawings. For example, various features are combined according to the following embodiments.

Embodiment 1. a display module, comprising:

a cover element having a thickness of from about 25 μm to about 200 μm and a cover element elastic modulus of from about 20GPa to about 140GPa, the cover element further comprising a component having a glass composition, a first major surface, and a second major surface; and

a stack, the stack comprising:

a substrate comprising a component having a glass composition and a thickness of from about 100 μm to 1500 μm, and

a first adhesive joining the stack to the second major surface of the cover element, the first adhesive comprising an elastic modulus from about 0.001GPa to about 10GPa and a thickness from about 5 μm to 50 μm.

Wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4700Mpa at the second major surface of the cover element after impact on the cover element in a quasi-static indentation test.

Embodiment 2. the display module of embodiment 1, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 3200Mpa at the second major surface of the cover element after an impact on the cover element in a quasi-static indentation test.

Embodiment 3. the display module of embodiment 2 or embodiment 3, wherein the first adhesive further comprises a thickness of from about 5 μ ι η to about 25 μ ι η, and the cover element further comprises a thickness of from about 50 μ ι η to about 150 μ ι η.

Embodiment 4. the display module of any one of embodiments 1 to 3, wherein the first adhesive comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, optically clear adhesives, Pressure Sensitive Adhesives (PSAs), polymeric foams, natural or synthetic resins.

Embodiment 5. the display module of any one of embodiments 1 to 4, wherein the stack further comprises:

(c) an interlayer having a thickness of from about 25 μm to about 200 μm and an interlayer elastic modulus of from about 20GPa to about 140GPa, the interlayer further comprising a component having a glass composition;

and

(d) a second adhesive joining the interlayer to the substrate, the second adhesive comprising a modulus of elasticity from about 0.001GPa to about 10GPa and a thickness from about 5 μm to about 50 μm.

Embodiment 6. the display module of embodiment 5, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4200Mpa at the second major surface of the cover element after an impact on the cover element in a quasi-static indentation test.

Embodiment 7 the display module of embodiment 6, wherein each of the first adhesive and the second adhesive further comprises a thickness from about 5 μ ι η to about 25 μ ι η, and each of the cover element and the interlayer comprises a thickness from about 75 μ ι η to about 150 μ ι η.

Embodiment 8 the display module of any one of embodiments 5 to 7, wherein each of the first and second adhesives comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural or synthetic resins.

Embodiment 9. a display module, comprising:

a stack, the stack comprising:

a first adhesive joining the stack to the second major surface of the cover element, the first adhesive comprising an elastic modulus from about 0.001GPa to about 10GPa and a thickness from about 5 μm to about 50 μm,

wherein the display module includes an impact resistance characterized by a tensile stress of less than about 4000MPa at the first major surface of the cover element and a tensile stress of less than about 12000MPa at the second major surface of the cover element upon impact to the cover element in a pen drop test.

Embodiment 10 the display module of embodiment 9, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4000MPa at the first major surface of the cover element and a tensile stress of less than about 9000MPa at the second major surface of the cover element upon an impact to the cover element in a pen drop test.

Embodiment 11 the display module of embodiment 10, wherein the first adhesive further comprises a thickness of from about 5 μ ι η to about 25 μ ι η, and the cover element further comprises a thickness of from about 50 μ ι η to about 150 μ ι η.

Embodiment 12 the display module of any one of embodiments 9 to 11, wherein the first adhesive comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural or synthetic resins.

Embodiment 13 the display module of any one of embodiments 9 to 12, wherein the stack further comprises:

an interlayer having a thickness of from about 25 μm to about 200 μm and an interlayer elastic modulus of from about 20GPa to about 140GPa, the interlayer further comprising a component having a glass composition; and

a second adhesive joining the interlayer to the substrate, the second adhesive comprising a modulus of elasticity from about 0.001GPa to about 10GPa and a thickness from about 5 μm to about 50 μm.

Embodiment 14 the display module of embodiment 13, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4000MPa at the first major surface of the cover element and a tensile stress of less than about 11000MPa at the second major surface of the cover element after an impact to the cover element in a pen drop test.

Embodiment 15 the display module of embodiment 14, wherein each of the first adhesive and the second adhesive further comprises a thickness from about 5 μ ι η to about 25 μ ι η, and each of the cover element and the interlayer comprises a thickness from about 50 μ ι η to about 150 μ ι η.

Embodiment 16 the display module of any of embodiments 13-15, wherein each of the first and second adhesives comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural or synthetic resins.

Embodiment 17. a display module, comprising:

a stack, the stack comprising:

a substrate comprising a component having a glass composition and a thickness of from about 100 μm to about 1500 μm, and

wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4700MPa at the second major surface of the cover element after an impact on the cover element in a quasi-static indentation test, and

further wherein the display member comprises a hardness of about 750N/mm or greater, the hardness measured during the quasi-static indentation test.

Embodiment 18 the display module of embodiment 17, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 3200Mpa at the second major surface of the cover element after an impact on the cover element in a quasi-static indentation test, and further wherein the display component comprises a hardness of about 1000N/mm or greater, the hardness measured in the quasi-static indentation test.

Embodiment 19 the display module of embodiment 18, wherein the first adhesive further comprises a thickness of from about 5 μ ι η to about 25 μ ι η, and the cover element further comprises a thickness of from about 50 μ ι η to about 150 μ ι η.

Embodiment 20 the display module of embodiment 19, wherein the first adhesive comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural or synthetic resins.

Embodiment 21. a display module, comprising:

a stack, the stack comprising:

a substrate comprising a thickness of from about 100 μm to 1500 μm, and

And further wherein the display module comprises at least one of:

impact resistance characterized by a tensile stress at the second major surface of the cover element of less than about 4700Mpa upon impact to the cover element in a quasi-static indentation test;

an impact resistance characterized by a tensile stress at the first major surface of the cover element of less than about 4000MPa after an impact on the cover element in a pen drop test,

and a tensile stress of less than about 12000Mpa at the second major surface of the cover element; and

a hardness of about 750N/mm or greater, the hardness measured during the quasi-static indentation test.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments and together with the description serve to explain the principles and operations of the various embodiments. Directional terminology used herein (e.g., upper, lower, right, left, front, rear, top, bottom) is made with reference to the figures as drawn only and is not intended to imply absolute orientation.

Drawings

FIG. 1A is a cross-sectional view of a three-layer display module according to some aspects of the present invention.

Fig. 1B is a cross-sectional view of a five-layer display module according to some aspects of the present invention.

FIG. 2 depicts a display module within a pen drop test apparatus for measuring quasi-static and dynamic impact resistance according to some aspects of the present invention.

Fig. 3A is a plot of maximum principal stress at the second major surface of a cover element of a display module versus module-controlled load subjected to a modeled quasi-static indentation test at a peak load of up to 60N, according to some aspects of the present disclosure.

Fig. 3B is a load versus deflection curve for a display module subjected to a modeled quasi-static indentation test with a peak load of up to 60N, according to some aspects of the present disclosure.

FIG. 4 is a plot of peak fault load for a portion of the module schematically depicted in FIG. 3A and tested in a quasi-static indentation test.

Fig. 5A is a plot of maximum principal stress at the second major surface of a cover element of a display module versus distance from an impact location modeled in a pen drop test having a pen drop height of 25cm, according to some aspects of the present invention.

Fig. 5B is a plot of maximum principal stress at a first major surface of a cover element of a display module versus distance from an impact location as modeled in a pen drop test having a pen drop height of 25cm, according to some aspects of the present invention.

Fig. 6A and 6B are plots of maximum principal stress and deformation, respectively, at a second major surface of a cover element of a display module versus time from impact modeled in a pen drop test having a pen drop height of 25cm, according to some aspects of the present invention.

Fig. 7 is a bar graph of the maximum principal stress at the second major surface of the cover element of the display module depicted in fig. 3A-6B along with an increase in the percentage of each of these stress values over the lowest maximum principal stress observed in the sample.

Detailed Description

Reference will now be made in detail to the embodiments in accordance with the claims, 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. Ranges may be expressed herein as 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 as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. Whether or not a value or endpoint of a range is stated in the specification as "about," the value or endpoint of the range is intended to include two embodiments: embodiments modified by "about" and embodiments not modified by "about". It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

The term "substantially" and variations thereof as used herein is intended to indicate that the feature being described is equal to or approximately equal to the value or description. For example, a "substantially planar" surface is intended to mean a flat or substantially flat surface. Further, "substantially" is intended to mean that two values are equal or approximately equal. In some embodiments, "substantially" may represent values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

Among other features and benefits, the display modules and articles of the present invention provide unexpectedly high quasi-static and dynamic impact resistance. These modules achieve these impact resistance levels via the design of the adhesive and the thickness of the cover element, along with the number of layers within the module. Additionally, the enhancement of the impact resistance properties associated with these modules may also contribute to mechanical reliability and puncture resistance. With respect to mechanical reliability, the display modules of the present invention are configured to avoid failure of their glass-containing cover elements upon flexing, bending or other deformation of the module. For example, the display module may be used as one or more of: a cover on the user facing portion of the foldable electronic display device (where puncture resistance is particularly desirable); a substrate module internally disposed within the device itself, on which the electronic components are disposed; or elsewhere in the display device. Alternatively, the display module of the invention may be used in devices without a display, but using a device that may be glass or a glass-containing layer to obtain its beneficial properties and which layer is folded or bent to a tight bend radius in a similar manner as in a foldable display. Puncture resistance is particularly beneficial when the display module is used on the exterior of the device at a location with which a user will interact.

More particularly, the display modules and articles of the present invention may achieve some or all of the foregoing advantages via control of the material properties and thicknesses of the cover elements, adhesives, and interlayers used within the modules. For example, these display modules may exhibit enhanced impact resistance as characterized by reduced tensile stress measured via increased thickness of the interlayer, increased elastic modulus of the interlayer, and/or increased elastic modulus of the first adhesive in a modeled or actual quasi-static indentation or dynamic pen drop test at a major surface of the cover element. These lower tensile stresses associated with quasi-static and dynamic loading can lead to improved module reliability, in particular in terms of the failure resistance of the cover element, since the module is subject to application-driven impact evolution. Further, embodiments and concepts in the present invention provide a framework for those skilled in the art to design display modules to reduce tensile stresses at the major surfaces of the cover elements, which may contribute to the reliability, manufacturability, and suitability of these modules for use in a variety of stresses including varying degrees and amounts of bending and folding evolution.

Referring to FIG. 1A, a display module 100a is depicted in exemplary form as a three-layer module in accordance with some aspects of the present invention. The module 100a includes a cover member 50, a first adhesive 10a, and a substrate 60. In addition, reference is made to a stack 90a, which includes an adhesive 10a and a substrate 60. Additionally, the cover element 50 has a thickness 52, a first major surface 54, and a second major surface 56. The thickness 52 may range from about 25 μm to about 200 μm, for example, from about 25 μm to about 175 μm, from about 25 μm to about 150 μm, from about 25 μm to about 125 μm, from about 25 μm to about 100 μm, from about 25 μm to about 75 μm, from about 25 μm to about 50 μm, from about 50 μm to about 175 μm, from about 50 μm to about 150 μm, from about 50 μm to about 125 μm, from about 50 μm to about 100 μm, from about 50 μm to about 75 μm, from about 75 μm to about 175 μm, from about 75 μm to about 150 μm, from about 75 μm to about 125 μm, from about 75 μm to about 100 μm, from about 100 μm to about 175 μm, from about 100 μm to about 150 μm, from about 100 μm to about 125 μm, from about 125 μm to about 120 μm, from about 175 μm to about 175 μm, and from about 175 μm to about 175 μm. In other aspects, the thickness 52 may range from about 25 μm to 150 μm, from about 50 μm to 100 μm, or from about 60 μm to 80 μm. The thickness 52 of the cover member 50 can also be set at other thicknesses or thickness ranges between the aforementioned ranges. Some aspects of the display module 100a incorporate cover elements 50 having a relatively low thickness, for example, from about 75 μm to about 125 μm, as compared to the thickness of other glass cover elements used in these electronic device applications. The use of these cover elements 50 having relatively low thickness values unexpectedly provides an enhanced degree of resistance to both static and dynamic impacts, as manifested in reduced tensile stresses observed at the first and second

major surfaces

54, 56 of the cover element 50 following an impact in a quasi-static indentation or pen-drop test.

The display module 100a depicted in fig. 1A includes a cover element 50 having a cover element elastic modulus from about 20GPa to 140GPa, e.g., from about 20GPa to about 120GPa, from about 20GPa to about 100GPa, from about 20GPa to about 80GPa, from about 20GPa to about 60GPa, from about 20GPa to about 40GPa, from about 40GPa to about 120GPa, from about 40GPa to about 100GPa, from about 40GPa to about 80GPa, from about 40GPa to about 60GPa, from about 60GPa to about 120GPa, from about 60GPa to about 100GPa, from about 80GPa to about 120GPa, from about 80GPa to about 100GPa, and from about 100GPa to about 120 GPa. The cover element 50 may be or include at least one component having a glass composition. In the latter case, the cover element 50 may include one or more layers comprising a glass-containing material, for example, the component 50 may be a polymer/glass composite having second phase glass particles disposed in a polymeric matrix. In some aspects, the cover element 50 is a glass component characterized by an elastic modulus from about 50GPa to about 100GPa or any elastic modulus value or range of values between these limits. In other aspects, the cover element elastic modulus is about 20GPa, 30GPa, 40GPa, 50GPa, 60GPa, 70GPa, 80GPa, 90GPa, 100GPa, 110GPa, 120GPa, 130GPa, 140GPa or any elastic modulus value or range of values between these values.

In certain aspects of the display module 100a depicted in fig. 1A, the cover element 50 may comprise a glass layer. In other aspects, the cover element 50 may include two or more glass layers. Thus, the thickness 52 reflects the sum of the thicknesses of the individual glass layers that make up the cover element 50. In those aspects in which the cover element 50 includes two or more separate glass layers, each of the separate glass layers has a thickness of 1 μm or more. For example, the cover element 50 used in the module 100a may include three layers of glass, each having a thickness of about 8 μm, such that the thickness 52 of the cover element 50 is about 24 μm. However, it should also be understood that the cover element 50 may include other non-glass layers (e.g., flexible polymer layers) sandwiched between multiple glass layers. In other implementations of the module 100a, the cover element 50 may include one or more layers comprising a glass-containing material, for example, the component 50 may be a polymer/glass composite having second phase glass particles disposed in a polymeric matrix.

In FIG. 1A, including the containing glassThe display module 100a of the cover element 50 of glass material may be made from alkali-free aluminosilicate, borosilicate, boroaluminosilicate, and silicate glass compositions. The cover element 50 may also be made from alkali-containing aluminosilicate, borosilicate, boroaluminosilicate, and silicate glass compositions. In certain aspects, an alkaline earth modifier may be added to any of the aforementioned compositions for covering the element 50. In some aspects, a glass composition according to the following is suitable for the cover element 50 having one or more glass layers: SiO 2₂50% to 75% (in mol%); al (Al)₂O₃5% to 20%; b is₂O₃8% to 23%; 0.5 to 9 percent of MgO; CaO, 1% to 9%; SrO, 0 to 5%; BaO, 0 to 5%; SnO₂0.1% to 0.4%; ZrO (ZrO)₂0 to 0.1%; and Na₂O, 0 to 10%, K₂O, 0 to 5% and Li₂O, 0 to 10 percent. In some aspects, a glass composition according to the following is suitable for the cover element 50 having one or more glass layers: SiO 2₂64% to 69% (in mol%); al (Al)₂O₃5% to 12%; b is₂O₃8% to 23%; 0.5 to 2.5 percent of MgO; CaO, 1% to 9%; SrO, 0 to 5%; BaO, 0 to 5%; SnO₂0.1% to 0.4%; ZrO (ZrO)₂0 to 0.1%; and Na₂O, 0 to 1%. In other instances, the following compositions are suitable for covering element 50: SiO 2₂67.4% (in mol%); al (Al)₂O₃，～12.7％；B₂O₃，～3.7％；MgO，～2.4％；CaO，0％；SrO，0％；SnO₂-0.1%; and Na₂O, 13.7 percent. In further aspects, the following compositions are also suitable for the glass layers used in the cover element 50: SiO 2₂68.9% (in mol%); al (Al)₂O₃，10.3％；Na₂O, 15.2%; 5.4 percent of MgO; and SnO₂0.2 percent. In other aspects, the cover element 50 can use the following glass composition ("glass 1"): SiO 2₂65% (in mol%); b is₂O₃，～5％；Al₂O₃，～14％；Na₂O，～14 percent; and MgO, 2 mol%. In further aspects, the following compositions are also suitable for the glass layers used in the cover element 50: SiO 2₂68.9% (in mol%); al (Al)₂O₃，10.3％；Na₂O, 15.2%; 5.4 percent of MgO; and SnO₂0.2 percent. Various criteria may be used to select a composition for the cover element 50 comprising a glass material, including but not limited to ease of manufacturing low thickness levels while minimizing incorporation defects; a region prone to compressive stress to counteract tensile stress generated during bending; optical transparency; and corrosion resistance.

The cover element 50 used in the collapsible module 100a may take a variety of physical forms and shapes. From a cross-sectional perspective, the component 50, as a single layer or multiple layers, may be flat or planar. In some aspects, the component 50 may be manufactured in a non-linear, sheet-like form, depending on the end application. As an example, a mobile display device having an oval display and bezel may use a cover element 50 having a generally oval, laminar form.

Referring again to fig. 1A, the display module 100a further includes: a stack 90a having a thickness 92a from about 100 μm to 1600 μm; and a first adhesive 10a configured to join the stack 90a to the second major surface 56 of the cover element 50, the first adhesive 10a characterized by a thickness 12a and an elastic modulus from about 0.001GPa to about 10GPa, e.g., from about 0.001GPa to about 8GPa, from about 0.001GPa to about 6GPa, from about 0.001GPa to about 4GPa, from about 0.001GPa to about 2GPa, from about 0.001GPa to about 1GPa, from about 0.01GPa to about 8GPa, from about 0.01GPa to about 6GPa, from about 0.01GPa to about 4GPa, from about 0.01GPa to about 2GPa, from about 0.1 to about 8GPa, from about 0.1GPa to about 6GPa, from about 0.1GPa to about 4GPa, from about 0.2GPa to about 8GPa, from about 0.2 to about 6GPa, and from about 0.5 GPa. According to some implementations of the first aspect of the display module 100a, the first adhesive 10a is characterized by an elastic modulus of about 0.001GPa, 0.002GPa, 0.003GPa, 0.004GPa, 0.005GPa, 0.006GPa, 0.007GPa, 0.008GPa, 0.009GPa, 0.01GPa, 0.02GPa, 0.03GPa, 0.04GPa, 0.05GPa, 0.1GPa, 0.2GPa, 0.3GPa, 0.4GPa, 0.5GPa, 0.6GPa, 0.7GPa, 0.8GPa, 0.9GPa, 1GPa, 2GPa, 3GPa, 4GPa, 5GPa, 6GPa, 7, 8GPa, 9GPa, 10GPa, or any amount or range of amounts or amounts between values of these elastic moduli.

Referring again to the display module 100a depicted in FIG. 1A, the first adhesive 10a is characterized by a thickness 12a from about 5 μm to about 60 μm, e.g., from about 5 μm to about 50 μm, from about 5 μm to about 40 μm, from about 5 μm to about 30 μm, from about 5 μm to about 20 μm, from about 5 μm to about 15 μm, from about 5 μm to about 10 μm, from about 10 μm to about 60 μm, from about 15 μm to about 60 μm, from about 20 μm to about 60 μm, from about 30 μm to about 60 μm, from about 40 μm to about 60 μm, from about 50 μm to about 60 μm, from about 55 μm to about 60 μm, from about 10 μm to about 50 μm, from about 10 μm to about 40 μm, from about 10 μm to about 30 μm, from about 10 μm to about 20 μm, from about 20 μm to about 50 μm, From about 30 μm to about 50 μm, from about 40 μm to about 50 μm, from about 20 μm to about 40 μm, and from about 20 μm to about 30 μm. Other embodiments have the first adhesive 10a characterized by a thickness 12a of about 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, or any thickness or range of thicknesses between these thickness values. In some aspects, the thickness 12a of the first adhesive 10a is from about 5 μm to 50 μm. Some aspects of the display module 100a incorporate an adhesive 10a having a relatively low thickness, e.g., from about 5 μm to about 25 μm, as compared to the thickness of known adhesives used in these electronic device applications. The use of these adhesives 10a having relatively low thickness values unexpectedly provides enhanced resistance to registered static and dynamic impacts, as manifested by reduced tensile stresses observed at the first and second

major surfaces

54, 56 of the cover element 50 following an impact in a quasi-static indentation or pen drop test.

In some embodiments of the display module 100a depicted in fig. 1A, the first adhesive 10a is further characterized by a poisson's ratio of from about 0.1 to about 0.5, e.g., from about 0.1 to about 0.45, from about 0.1 to about 0.4, from about 0.1 to about 0.35, from about 0.1 to about 0.3, from about 0.1 to about 0.25, from about 0.1 to about 0.2, from about 0.1 to about 0.15, from about 0.2 to about 0.45, from about 0.2 to about 0.4, from about 0.2 to about 0.35, from about 0.2 to about 0.3, from about 0.2 to about 0.25, from about 0.25 to about 0.45, from about 0.25 to about 0.4, from about 0.25 to about 0.35, from about 0.25 to about 0.45, from about 0.45 to about 0.45, from about 0.35, from about 0.45 to about 0.35, from about 0.45, and from about 0.35. Other embodiments include a first adhesive 10a characterized by a poisson's ratio of about 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or any poisson's ratio or range of ratios between these values. In some aspects, the poisson's ratio of the first adhesive 10a is from about 0.1 to about 0.25.

As summarized above, the display module 100a depicted in fig. 1A includes an adhesive 10a having certain material properties (e.g., an elastic modulus from about 0.001GPa to 10 GPa). Example adhesives that may be used as adhesive 10a in module 100a include optically clear adhesives (e.g., hangao corporation

Liquid OCA), epoxy, and other bonding materials as understood by those skilled in the art as being suitable for bonding the stack 90a (e.g., the substrate 60) to the second major surface 56 of the cover element 50. Other example adhesives that may be used as adhesive 10a in module 100a include one or more of the following: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural resins, and synthetic resins.

Referring again to fig. 1A, the stack 90a of foldable modules 100a further includes a substrate 60 comprising a component having a glass composition, a first major surface 64 and a second major surface 66, and a thickness 62. As a result of including components having glass compositions, in some embodiments, the substrate 60 may have an elastic modulus from about 20GPa to 140GPa, e.g., from about 20GPa to about 120GPa, from about 20GPa to about 100GPa, from about 20GPa to about 80GPa, from about 20GPa to about 60GPa, from about 20GPa to about 40GPa, from about 40GPa to about 120GPa, from about 40GPa to about 100GPa, from about 40GPa to about 80GPa, from about 40GPa to about 60GPa, from about 60GPa to about 120GPa, from about 60GPa to about 100GPa, from about 80GPa to about 120GPa, from about 80GPa to about 100GPa, and from about 100GPa to about 120 GPa. The substrate 60 can be or include at least one component having a glass composition. In the latter case, the substrate 60 may include one or more layers comprising a glass-containing material, for example, the substrate 60 may be a polymer/glass composite having second phase glass particles disposed in a polymeric matrix. In some aspects, the substrate is a glass component characterized by an elastic modulus from about 50GPa to about 100GPa or any value or range of values between these limits. In other aspects, the substrate 60 has an elastic modulus of about 20GPa, 30GPa, 40GPa, 50GPa, 60GPa, 70GPa, 80GPa, 90GPa, 100GPa, 110GPa, 120GPa, 130GPa, 140GPa or any value or range of values therebetween. Additionally, in some embodiments, the substrate 60 is substantially similar to the cover element 50, or the same as the cover element 50, with respect to the glass composition.

In the embodiment of the display module 100a depicted in fig. 1A, the substrate 60 has a thickness 62 of from about 100 μm to about 1500 μm, for example, from about 100 μm to about 1250 μm, from about 100 μm to about 1000 μm, from about 100 μm to about 750 μm, from about 100 μm to about 500 μm, from about 100 μm to about 400 μm, from about 100 μm to about 300 μm, from about 100 μm to about 200 μm, 500 μm to about 1500 μm, for example, from about 500 μm to about 1250 μm, from about 500 μm to about 1000 μm, from about 500 μm to about 750 μm, from about 750 μm to about 1500 μm, from about 750 μm to about 1250 μm, from about 750 μm to about 1000 μm, from about 1000 μm to about 1500 μm, from about 1000 μm to 1250 μm, or any thickness or range between these values. Additionally, in some embodiments, the display module 100a may be bent, flexed, or otherwise mechanically deformed to some extent, for example, to a bend radius of about 10mm or greater or 5mm or greater, given the thickness 62 of the substrate 60.

In some implementations, suitable materials that may be used as the substrate 60 in the module 100a include various thermoset and thermoplastic materials, such as polyimides, suitable for mounting the electronic device 102 and that possess high mechanical integrity and flexibility when subjected to the bending associated with the foldable electronic device module 100 a. For example, the substrate 60 may be an organic light emitting diode ("OLED") display panel. The material selected for the substrate 60 may also exhibit high thermal stability to resist changes and/or degradation in material properties associated with the application environment of the module 100a and/or its processing conditions.

The stack 90a of display modules 100a shown in fig. 1A may also include one or more electronic devices (not shown) coupled to the substrate 60. These electronic devices may be known electronic devices used in known OLED-containing display devices. For example, the substrate 60 of the stack 90a may include one or more electronic devices in the form and structure of touch sensors, polarizers, etc., as well as other electronic devices, along with adhesives or other compounds for bonding these devices to the substrate 60. Additionally, these electronic devices may be located within the substrate 60 and/or on one or more of its

major surfaces

64, 66.

As also depicted in fig. 1B, display module 100B is shown in exemplary form as a five-layer module having a stack 90a, the stack 90a further including (also, i.e., in addition to the first adhesive 10a and the substrate 60) an interlayer 70 having a thickness 72 of from about 25 μm to about 200 μm and an interlayer elastic modulus of from about 20GPa to about 140GPa, the interlayer 70 further including a component having a glass composition; and (d) a second adhesive 10b bonding the interlayer 70 to the substrate 60, the second adhesive 10b comprising an elastic modulus from about 0.001GPa to about 10GPa and a thickness 12b from about 5 μm to about 50 μm. Unless otherwise indicated, the interlayer 70 may be configured with the same or similar composition, thickness, and modulus of elasticity as the cover element 50. In addition, the second adhesive 10b may be configured with a composition, thickness, and modulus of elasticity that are the same as or similar to those of the first adhesive 10a, unless otherwise indicated. More generally, the configuration of the

display modules

100a, 100b demonstrates that display modules having any number of layers can be used in accordance with the principles of the present invention.

Referring now to FIG. 2, a pen drop test device 200 is depicted. As used herein, a "pen drop test" is conducted by the pen drop device 200 to evaluate the impact resistance of the display modules 100a, 100B (see fig. 1A and 1B), as characterized by the stress state observed at the

major surfaces

54, 56 of the cover element. As described and mentioned herein, the pen drop test is a dynamic test conducted such that the

display module

100a, 100b sample is tested by a load (i.e., from a pen dropping at a fixed height of 25 cm) applied to the exposed surface (i.e., major surface 54) of the cover element 50. The opposite side of the display modules 100a, 100B, for example, at the major surface 66 (see fig. 1A and 1B), is supported by an aluminum plate (6063 aluminum alloy, polished to surface roughness, e.g., with 400 sandpaper). A tube is used to guide the pen to the sample according to the pen drop test and is placed in contact with the top surface of the sample such that the longitudinal axis of the tube is substantially perpendicular to the top surface of the sample. Each tube had an outer diameter of 2.54cm (1 inch), an inner diameter of 1.4cm (nine sixteenths of an inch), and a length of 90 cm. For each test, an acrylonitrile butadiene ("ABS") spacer was used to hold the pen at a desired height (of the sphere above the surface of the substrate) of 25 cm. After each drop, the tube is repositioned relative to the sample to guide the pen to a different impact location on the sample. The pen used in the pen drop test had a 0.35mm diameter ball point tip 212, and a weight of 5.7 grams (because of the cap included). According to the pen drop test depicted in fig. 2, the pen is dropped with a cap attached to the tip (i.e., the end opposite the tip) so that the sphere point 212 can interact with the test specimen (i.e., the

display module

100a, 100 b).

Advantageously, the pen drop test performed with the pen drop test apparatus depicted in fig. 2 was modeled using FEA techniques to estimate the tensile stress generated at the

major surfaces

54, 56 of the cover element 50 based on a fixed pen drop height of 25 cm. Certain assumptions are made in making this modeling process, as will be further understood by those skilled in the art of the present disclosure. In particular, it is assumed that the cover element 50 and the substrate 60 have an elastic modulus of 71GPa and a Poisson's ratio of 0.22. In addition, a typical optical adhesive is assumed to exhibit an elastic modulus of 0.3GPa and a poisson's ratio of 0.49 for the first and second adhesives. Further with respect to pen drop test modeling, the following additional assumptions were made: modeling the pen tip 212 as a rigid body without deformation of the pen tip; using a quarter symmetric truncated block of module 100 a; assume that all interfaces in module 100a are perfectly combined during analysis, with no delamination; the aluminum support plate referenced with respect to the pen drop test apparatus 200 was modeled as a rigid body aluminum plate; assuming no frictional contact between the module 100a and the aluminum support plate; assume that the pen tip 212 does not penetrate the cover element 50 of the module 100 a; using linear elastic or superelastic material properties of the components of module 100 a; using a large deformation method; and module 100a is at room temperature during the simulated test.

In certain implementations of the display module 100a, 100B (see fig. 1A and 1B), the module can exhibit impact resistance characterized by a tensile stress of less than about 4000MPa at the first major surface 54 of the cover element 50 and a tensile stress of less than about 12000MPa at the second major surface 56 of the cover element 50 upon impact to the cover element in a pen drop test, as modeled at a pen drop height of 25cm (see fig. 2). Unexpectedly, as understood via this modeling of the pen drop test, the

thicknesses

12a, 12b of the

adhesives

10a, 10b and the thickness 52 of the cover element 50 can be adjusted to further enhance the impact resistance of the module 100a such that upon impact to the cover element in the pen drop test, a tensile stress of less than about 4000MPa at the first major surface 54 of the cover element 50 and a tensile stress of less than about 9000MPa at the second major surface 56 of the cover element 50. Aspects of the display module 100a may also incorporate a first adhesive 10a having a relatively low thickness 12a, for example, from about 5 μm to about 25 μm, as compared to the thickness of known adhesives used in these electronic device applications. Similarly, the display module 100a may also incorporate a cover element 50 having a relatively low thickness 52, for example, from about 75 μm to about 150 μm, as compared to the thickness of other glass-containing cover elements used in these electronic device applications. By this modeling and design of the first adhesive 10a and the cover element 50, the tensile stress at the first major surface 54 of the cover element 50 may be reduced to less than about 4000MPa, 3900MPa, 3800MPa, 3700MPa, 3600MPa, 3500MPa, 3400MPa, 3300MPa, 3200MPa, 3100MPa, 3000MPa, and lower. Similarly, the tensile stress at the second major surface 56 of the cover element 50 can be reduced to less than about 12000MPa, 11000MPa, 10000MPa, 9000MPa, 8000MPa, 7500MPa, 7000MPa, 6500MPa, 6000MPa, 5500MPa, 5000MPa, 4500MPa, 4000MPa, 3500MPa, 3000MPa, and lower.

Referring again to FIG. 2, a pen drop test device 200 is depicted. As used herein, a "quasi-static indentation test" is performed with the pen drop device 200 to evaluate the impact resistance of the display modules 100a, 100B (see fig. 1A and 1B), as characterized by the stress state observed at the

major surfaces

54, 56 of the cover element. As described and referenced herein, the quasi-static indentation test is a quasi-static test conducted such that the

display module

100a, 100b sample passes a constant load test of 60N applied to the exposed surface (i.e., major surface 54) of the cover member 50. The opposite side of the display modules 100a, 100B, for example, at the major surface 66 (see fig. 1A and 1B), is supported by an aluminum plate (6063 aluminum alloy polished to surface roughness with 400 sandpaper). The pen used in the quasi-static indentation test had a 0.5mm diameter ball point tip 212, and a weight of 5.7 grams (because of the cap included). According to the quasi-static indentation test depicted in fig. 2, a straight line is applied to the exposed surface of the cover element 50 with a constant load of 60N or with successively higher loads starting at 5N until failure.

Advantageously, quasi-static indentation tests as performed with the pen drop test apparatus depicted in fig. 2 were modeled using FEA techniques to estimate the tensile stress generated at the

major surfaces

54, 56 of the cover element 50 based on an applied load of 60N. Certain assumptions are made in making this modeling process, as will be further understood by those skilled in the art of the present disclosure. In particular, it is assumed that the cover element 50 and the substrate 60 have an elastic modulus of 71GPa and a Poisson's ratio of 0.22. In addition, a typical optical adhesive is assumed to exhibit an elastic modulus of 0.3GPa and a poisson's ratio of 0.49 for the first and second adhesives. Further with respect to quasi-static test modeling, the following additional assumptions were made: modeling the pen tip 212 as a rigid body without deformation of the pen tip; using quarter symmetric blocks of the

modules

100a, 100 b; assuming that all interfaces in the

modules

100a, 100b are perfectly combined during analysis, there is no delamination; the aluminum support plate referenced with respect to the pen drop test apparatus 200 was modeled as a rigid body aluminum plate; assuming no frictional contact between the

modules

100a, 100b and the aluminum support plate; assuming that the pen tip 212 does not penetrate the cover element 50 of the

module

100a, 100 b; using linear elastic or superelastic material properties of the components of the

modules

100a, 100 b; using a large deformation method; and the

modules

100a, 100b are at room temperature during the simulated testing.

In certain implementations of the display module 100a, 100B (see fig. 1A and 1B), the module can exhibit impact resistance characterized by a tensile stress at the second major surface 56 of the cover element 50 of less than about 4700Mpa when subjected to an impact on the cover element in a quasi-static indentation test, modeled at a fixed load of 60N (see fig. 2). Unexpectedly, it is understood via this modeling of quasi-static indentation testing that the

thicknesses

12a, 12b of the

adhesives

10a, 10b and the thickness 52 of the cover element 50 can be adjusted to further enhance the impact resistance of the

modules

100a, 100b such that a tensile stress of less than about 3200MPa at the second major surface 56 of the cover element 50 upon impact to the cover element in the quasi-static indentation test. Aspects of the display module 100a may also incorporate a first adhesive 10a having a relatively low thickness 12a, for example, from about 5 μm to about 25 μm, as compared to the thickness of known adhesives used in these electronic device applications. Similarly, the display module 100a may also incorporate a cover element 50 having a relatively low thickness 52, for example, from about 75 μm to about 150 μm, as compared to the thickness of other glass-containing cover elements used in these electronic device applications. By this modeling and design of the first adhesive 10a and the cover element 50, the tensile stress at the second major surface 56 of the cover element 50 can be reduced to less than about 4700MPa, 4600MPa, 4500MPa, 4400MPa, 4300MPa, 4200MPa, 4100MPa, 4000MPa, 3900MPa, 3800MPa, 3700MPa, 3600MPa, 3500MPa, 3400MPa, 3300MPa, 3200MPa, 3100MPa, 3000MPa, and lower.

Still referring to fig. 1A and 1B, in certain aspects of the invention, the cover element 50 of the display modules 100a, 100B may comprise a glass layer or member having one or more compressively stressed regions (not shown) extending from the first and/or second

major surfaces

54, 56 to a selected depth in the cover element 50. Additionally, in certain aspects of the

modules

100a, 100b, edge compressive stress regions (not shown) extending from edges (e.g., orthogonal or substantially orthogonal to the major surfaces 54, 56) of the component 50 to a selected depth may also be created. For example, the compressive stress region(s) (and/or edge compressive stress regions) contained in the glass cover element 50 can be formed by an ion exchange ("IOX") process. As another example, the glass cover element 50 may include various tailored glass layers and/or regions that may be used to create one or more of these compressive stress regions via a mismatch in the Coefficients of Thermal Expansion (CTE) associated with these layers and/or regions.

In those aspects of the

display modules

100a, 100b having the cover element 50 with one or more compressive stress regions formed by the IOX process, the compressive stress region(s) may comprise a plurality of ion-exchangeable metal ions and a plurality of ion-exchanged metal ions selected to generate a compressive stress in the compressive stress region(s). In some aspects of the module 100a containing a compressive stress region, the ion-exchanged metal ions have an atomic radius that is greater than an atomic radius of the ion-exchangeable metal ions. Ion-exchangeable ions (e.g. Na)⁺Ions) are present in the glass cover member 50 before being subjected to the ion exchange process. The ions may be exchanged for ions (e.g., K)⁺Ions) are incorporated into the glass cover member 50, replacing some of the ion-exchangeable ions in the region within the component 50 that eventually becomes the compressive stress region. Ion exchange of ions (e.g. K)⁺Ions) into the cover element 50 may be subjected to immersion (e.g., prior to forming the complete module 100 a) of the component 50 in a solution containing ion-exchanging ions (e.g., molten KNO)₃Salt) in a molten salt bath. In this example, K⁺The ion has a ratio of Na to⁺The ions have a large atomic radius and tend to create local compressive stress in the glass cover member 50 (where present), for example, in the region of compressive stress.

Depending on the ion exchange process conditions for the cover element 50 used in the display modules 100a, 100B depicted in fig. 1A and 1B, ion-exchanged ions may be imparted from the first major surface 54 of the cover element 50 down to a first ion exchange depth (not shown, "DOL"), establishing an ion exchange compression depth "DOC"). As used herein, DOC means the depth to which the stress in a chemically strengthened alkali aluminosilicate glass article described herein changes from compression to tension. Depending on the ion exchange process, DOC can be measured by a surface stress meter (FSM — using a commercially available instrument such as FSM-6000 manufactured by Orihara industrialco, Ltd. (japan)) or scattered light polarizer (SCALP). The DOC is measured using a FSM with the stress in the glass article being generated by the exchange of potassium ions into the glass article. The DOC is measured using the SCALP with the stress created by the exchange of sodium ions into the glass article. Where the stress in the glass article is generated by exchange to both potassium and sodium ions within the glass, the DOC is measured by SCALP, which, since it is believed, the exchange depth of sodium indicates the DOC and the exchange depth of potassium ions indicates a change in the magnitude of the compressive stress (but not a change in the stress from compression to tension); the depth of exchange of potassium ions in these glass articles was measured by FSM. Compressive stress (including surface CS) is measured by FSM. Surface stress measurements rely on accurate measurements of Stress Optical Coefficients (SOC) related to the birefringence of the glass. SOC was in turn measured according to procedure C (Glass dish Method) described in ASTM Standard C770-16, entitled "Standard Test Method for measuring of Glass Stress-optical Coefficients", the contents of which are incorporated herein by reference in their entirety. Similarly, a second compressive stress region may be created in the component 50 from the second major surface 56 down to a second ion exchange depth. Compressive stress levels well in excess of 100MPa within the DOL can be achieved by these IOX processes, up to 2000 MPa. The compressive stress level in the compressive stress region(s) within the cover element 50 may be used to counteract the tensile stress generated in the cover element 50 after bending of the foldable electronic device module 100 a.

Referring again to fig. 1A and 1B, in some implementations, the display modules 100a, 100B can include one or more edge compressive stress regions in the cover element 50 at edges orthogonal to the first and second

major surfaces

54, 56, each defined by a compressive stress of 100MPa or greater. It will be appreciated that these edge compressive stress regions may be created in the cover element 50 at any of its edges or surfaces distinct from its major surfaces, depending on the shape or form of the component 50. For example, in some implementations of

display modules

100a, 100b having an elliptical cover element 50, the edge compressive stress region may be created inward from an outer edge of the component that is orthogonal (or substantially orthogonal) to a major surface of the component. IOX processes, similar in nature to the processes used to create compressive stress regions near

major surfaces

54, 56, may be deployed to create these edge compressive stress regions. More particularly, any of these edge compressive stress regions in the cover element 50 may be used to counteract tensile stresses generated at the edges of the component via, for example, quasi-static or dynamic impacts to the cover element 50 (and

modules

100a, 100b) across any of its edges and/or uneven bending of the cover element 50 at its

major surfaces

54, 56. Alternatively, or in addition to this, without being bound by theory, any of these edge compressive stress regions used in the cover element 50 may counteract adverse effects from impact or friction at or against the edges of the component 50 within the

modules

100a, 100 b.

Referring again to fig. 1A and 1B, in those aspects of the display modules 100a, 100B having a cover element 50 (having one or more compressive stress regions formed via a mismatch in the CTE of the regions or layers within the component 50), these compressive stress regions are created by trimming of the structure of the component 50. For example, a CTE difference within the component 50 may create one or more regions of compressive stress within the component. In one example, the cover element 50 may include a core region or layer sandwiched by cladding regions or layers that are each substantially parallel to the

major surfaces

54, 56 of the component. In addition, the core layer is adapted for a CTE that is greater than the CTE of the cladding regions or layers (e.g., controlled by the composition of the core and cladding regions or layers). Upon cooling the cover element 50 from its manufacturing process, the CTE difference between the core region or layer and the cladding regions or layers causes a non-uniform volumetric shrinkage upon cooling, resulting in the creation of residual stresses in the cover element 50 that are manifested in the creation of compressive stress regions underlying the

major surfaces

54, 56 within the cladding regions or layers. In other words, the core region or layer and the cladding regions or layers are brought into intimate contact with each other at elevated temperatures; and then cooling these layers or regions to a low temperature such that the large volumetric change of the high CTE core region (or layer) relative to the low CTE cladding region (or layer) creates a region of compressive stress in the cladding region or layer within the cover element 50.

Referring again to the cover element 50 in the modules 100a, 100B depicted in fig. 1A and 1B having CTE-generated compressive stress regions that reach down from the first major surface 54 to a first CTE region depth and from the second major surface 56 to a second CTE region depth, respectively, thus establishing a CTE-related DOL for each of the compressive stress regions associated with the respective

major surfaces

54, 56 and within the cladding layer or region. In some aspects, the compressive stress level in these compressive stress regions may exceed 150 MPa. Maximizing the difference in CTE values between the core region (or layer) and the clad region (or layer) may increase the magnitude of the compressive stress generated in the compressive stress region after the cooling component 50 is manufactured. In certain implementations of the

display modules

100a, 100b having the cover element 50 (with these CTE-dependent compressive stress regions), the cover element 50 uses a core region and a cladding region having a thickness ratio greater than or equal to 3 for the sum of the core region thickness divided by the cladding region thickness. Thus, maximizing the size of the core region and/or its CTE relative to the size and/or CTE of the cladding region may serve to increase the amount of compressive stress level observed in the compressive stress region of the

display module

100a, 100 b.

Among other advantages, depending on the nature of the impact, a compressive stress region (e.g., generated via the IOX or CTE related approach outlined in the preceding paragraph) may be used within the cover element 50 to counteract the tensile stress generated in the component after quasi-static or dynamic impact to the display modules 100a, 100B (see fig. 1A and 1B), particularly to achieve maximum tensile stress on one of the

major surfaces

54, 56. In certain aspects, the compressive stress region can include a compressive stress of about 100MPa or greater at the

primary surfaces

54, 56 of the cover element 50. In some aspects, the compressive stress at the major surface is from about 600MPa to about 1000 MPa. In other aspects, the compressive stress may exceed 1000MPa, up to 2000MPa, at the primary surface, depending on the process used to create the compressive stress in the cover element 50. In other aspects of the invention, the compressive stress may also range from about 100MPa to about 600MPa at the major surfaces of the component 50. In additional aspects, the compressive stress region(s) within the covering element 50 of the

modules

100a, 100b can exhibit a compressive stress from about 100MPa to about 2000MPa, e.g., from about 100MPa to about 1500MPa, from about 100MPa to about 1000MPa, from about 100MPa to about 800MPa, from about 100MPa to about 600MPa, from about 100MPa to about 400MPa, from about 100MPa to about 200MPa, from about 200MPa to about 1500MPa, from about 200MPa to about 1000MPa, from about 200MPa to about 800MPa, from about 200MPa to about 600MPa, from about 200MPa to about 400MPa, from about 400MPa to about 1500MPa, from about 400MPa to about 1000MPa, from about 400MPa to about 800MPa, from about 400MPa to about 600MPa, from about 600MPa to about 1500MPa, from about 600MPa to about 1000MPa, from about 600MPa to about 800MPa, from about 800MPa to about 1500MPa, from about 800MPa to about 1000MPa, and from about 1000MPa to about 1000 MPa.

Within this compressive stress region used in the cover element 50 of the display module 100a, 100B (see fig. 1A and 1B), the compressive stress may remain constant, decreasing or increasing with depth from the major surface down to one or more selected depths. Thus, various compressive stress distributions may be used in the compressive stress region. Additionally, the depth of each of the compressive stress regions may be set at approximately 15 μm or less from the

major surfaces

54, 56 of the cover element 50. In other aspects, the depth of the compressive stress region(s) can be set such that it is approximately 1/3 or less of the thickness 52 of the

cover element

50, or 20% or less of the thickness 52 of the cover element 50, from the first and/or second

major surfaces

54, 56.

Referring again to fig. 1A and 1B, the display modules 100a, 100B may include a cover element 50 comprising a glass material having one or more regions of compressive stress, the cover element 50 having a maximum defect size of 5 μm or less at the first major surface 54 and/or the second major surface 56. The maximum flaw size can also be maintained to a flaw size range of about 2.5 μm or less, 2 μm or less, 1.5 μm or less, 0.5 μm or less, 0.4 μm or less, or even less. Reducing the flaw size in the compressive stress region of the glass cover element 50 may further reduce the propensity of the component 50 to fail by crack propagation after a tensile stress is applied to the display modules 100a, 100B (see fig. 1A, 1B, and 2) by means of an impact-related force. Further, some aspects of

modules

100a, 100b may include surface regions having a controlled flaw size distribution (e.g., flaw sizes of 0.5 μm or less at first major surface 54 and/or second major surface 56) without the use of one or more compressive stress regions.

Referring again to fig. 1A and 1B, other implementations of the display modules 100a, 100B may include the cover element 50 comprising a glass material subjected to various etching processes suitable to reduce the flaw size and/or improve flaw distribution within the component 50. These etching processes can be used to control the distribution of defects within the cover element 50 in the immediate vicinity of its

major surfaces

54, 56 and/or along its edges (not shown). For example, an etching solution containing about 15 vol% HF and 15 vol% HCl may be used to lightly etch the surface of the cover member 50 with the glass composition. Those skilled in the art will appreciate that the time and temperature of the light etch may be set according to the composition of the component 50 and the desired level of material removal from the surface of the cover member 50. It should also be understood that some surfaces of the component 50 may be left in an unetched state by using a masking layer or the like for those surfaces during the etching procedure. More particularly, such a light etch may beneficially improve the strength of the cover element 50. In particular, the cutting or singulation process used to cut through the glass structure ultimately used as the cover element 50 may leave flaws and other defects in the surface of the component 50. These flaws and defects may propagate and cause glass failure during the application of stress to the

modules

100a, 100b containing the component 50 from the application environment and use. By virtue of lightly etching one or more edges of feature 50, the selective etching process may remove at least some of these imperfections and defects, thereby increasing the strength and/or fracture resistance of the lightly etched surface. Additionally or alternatively, the mild etching step may be performed after chemical annealing (e.g., ion exchange) of the cover element 50. This light etching after the chemical tempering may reduce any defects introduced by the chemical tempering process itself and may thus increase the strength and/or fracture resistance of the cover element.

It should also be understood that the cover element 50 used in the display modules 100a, 100B depicted in fig. 1A and 1B may include any one or more of the aforementioned strength enhancement features: (a) a compressive stress region associated with the IOX; (b) a region of compressive stress related to CTE; and (c) an etched surface having a smaller defect size. These strength enhancing features may be used to counteract or partially counteract tensile stresses generated at the surface of the cover element 50 associated with the application environment, use, and handling of the

display modules

100a, 100 b.

In some implementations, the display modules 100a, 100B depicted in fig. 1A and 1B can be used in a display, printed circuit board, housing, or other feature associated with an end product electronic device. For example, the

display modules

100a, 100b may be used in electronic display devices containing numerous thin film transistors ("TFTs"), or LCD or OLED devices containing low temperature polysilicon ("LTPS") backplanes. For example, when the

display modules

100a, 100b are used in a display, the

modules

100a, 100b may be substantially transparent. Additionally, with respect to quasi-static or dynamic impacts, the

modules

100a, 100b may have desirable impact resistance, as described in the preceding paragraphs. In some implementations, the

display modules

100a, 100b are used in a wearable electronic device, such as a watch, wallet, or bracelet. As used herein, "foldable" includes fully folded, partially folded, bent, flexed, discretely bent, and multiple fold capabilities; in addition, the device may be folded such that the display is on the outside of the device when folded, or on the inside of the device when folded.

Examples

In this embodiment, the comparative display module (comparative example 1) and the display modules resulting from aspects of the invention (e.g., examples 1-1 to 1-4, 2-1, and 2-2) were modeled to withstand simulated quasi-static and dynamic impacts according to the quasi-static indentation test and the pen-drop test. Further, actual quasi-static indentation tests were performed on some of the samples to obtain peak fault load values, recognizing that the actual indentation loads were varied until faulty. The results of these modeling and experimental measurements are depicted in fig. 3A-7. Additionally, the legend in these diagrams describes the configuration of the modeled and/or tested display modules. For example, comparative example 1 was configured with a glass cover element having a thickness of 100 μm, a first adhesive comprising a PSA material having a thickness of 100 μm, and a substrate containing a glass 1 composite having a thickness of 1.1 mm. Although the substrate was modeled at a thickness of 1.1mm, this is to show the effect of the adhesive layer on the stack. The substrate need not have a thickness of 1.1 mm; rather, as noted elsewhere, the substrate may have a thickness of less than 1.1mm, for example as described above with respect to substrate 62, and these trends will still be similar to those observed with 1.1mm thick glass substrates.

Referring to fig. 3A, a plot of maximum principal stress at the second major surface of a cover element of a display module versus module-controlled load in a modeled quasi-static indentation test subjected to peak loads up to 60N is provided, in accordance with some aspects of the present invention. As is apparent from this figure, the three-layer display modules (examples 1-1 to 1-4) having a first adhesive (having a smaller thickness from about 15 μm to about 50 μm) demonstrated the lowest maximum principal stress level at the second major surface of the cover element compared to the module having a maximum first adhesive thickness of about 100 μm (comparative example 1). In addition, the three-layer display modules (examples 1-1 to 1-4) demonstrated lower maximum principal stress levels at the second principal surface of the cover element as compared to the five-layer display modules (examples 2-1 to 2-2). Furthermore, the display module with a slightly thicker cover element (example 1-4, cover element thickness 130 μm) demonstrated the lowest maximum principal stress level at the second main surface of the cover element compared to a comparably configured display module with a slightly thinner cover element (example 1-2, cover element thickness 100 μm).

Without being limited by theory, and in view of the results illustrated in fig. 3A, the relatively softer first adhesive material comprising a Pressure Sensitive Adhesive (PSA) material facilitates localized bending of the display glass under the piercing tip of the testing device. The small radius of the tip (see fig. 2, radius 0.5mm) tends to result in highly localized bending that produces high tensile stress on the major surface of the cover element. Since the bending stress is related to the overall stiffness of the module, it is further believed that increasing the stiffness of the module may result in improved impact performance.

Referring now to FIG. 3B, a graph of load versus deformation for a display module subjected to modeled quasi-static indentation test control of peak load up to 60N previously used to produce the results in FIG. 3A is provided. In addition, the slope of the load versus deformation curve in 3B is a measure of the hardness of the display module. Given the results shown earlier in fig. 3A, it is clear that a module with a higher hardness value as shown in fig. 3B tends to perform better in terms of reduced maximum principal stress at the second main surface of the cover element. In other words, the maximum tensile stress at the second main surface of the cover element observed from the quasi-static indentation test is inversely proportional to the hardness of the module.

Referring now to fig. 4, a plot of experimentally determined peak fault load for a portion of the module schematically depicted in fig. 3A and 3B and modeled by a quasi-static indentation test is provided. In particular, two three-layer modules (examples 1-2 and 13) and two five-layer modules (examples 2-1 and 2-2) were subjected to actual quasi-static indentation tests with increased applied loads (constant loads other than 60N) to produce an average failure load. Fracture microscopic analysis of these samples revealed that all experienced biaxial failure mechanisms. In addition, it is apparent from the results shown in fig. 4 that the three-layer display module exhibits a significantly higher peak failure load than the five-layer display module. It is believed that this result is due to the fact that: given the relatively low amount of adhesive present in these designs (i.e., one adhesive for a 3-layer module and two adhesives for a 5-layer module), the three-layer display module is harder than its five-layer counterpart.

Referring now to fig. 5A and 5B, there is provided a plot of maximum principal stress at the second and first major surfaces, respectively, of the cover elements of the same display module depicted in fig. 3A and 3B, modeled in a pen drop test having a pen drop height of 25cm, versus distance from the impact location. As is generally evident from fig. 5A and 5B, the tensile stress at the second major surface of the cover element is significantly higher in magnitude relative to the tensile stress observed at the first major surface for a same pen drop height of 25 cm. Without being bound by theory, it is believed that the higher tensile stress observed at the second major surface of the cover element is due to biaxial bending of the cover element, and the slightly lower tensile stress at the first major surface is associated with hertzian contact with the pen tip from the pen drop test (see fig. 2).

Referring again to fig. 5A and 5B, the spatial variation of the tensile stress at the second and first major surfaces of the cover element is depicted, which results from a simulated pen drop test with a pen drop height of 25 cm. In particular, display modules having a thinner first adhesive thickness level (e.g., examples 1-1 to 1-3, thicknesses from about 15 μm to 50 μm) experience lower tensile stress at both major surfaces than display modules having a larger first adhesive thickness (i.e., comparative example 1, thickness of 100 μm). In addition, the three-layer display modules (examples 1-1 to 1-4) demonstrated lower maximum principal stress levels at both major surfaces of the cover element, as produced from the pen drop test, as compared to the five-layer display modules (examples 2-1 to 2-2). Furthermore, the display module with a slightly thicker cover element (example 1-4, cover element thickness 130 μm) demonstrated a lower maximum principal stress level at both main surfaces of the cover element compared to a comparably configured display module with a slightly thinner cover element (example 1-2, cover element thickness 100 μm).

Referring now to fig. 6A and 6B, there is provided a plot of maximum principal stress and deformation, respectively, at the second major surface of the cover element of the same display module as depicted in fig. 3A and 3B versus time of self-impact as modeled in a pen drop test having a pen drop height of 25 cm. In particular, fig. 6A and 6B show that the maximum tensile stress observed at the second major surface occurs when the display module undergoes its maximum deformation associated with a pen drop at 25 cm. The maximum tensile stress observed at the second main surface of the cover element is therefore a function of the overall stiffness of the display module.

Referring now to fig. 7, a bar graph is provided of the maximum principal stress at the second major surface of the cover element of the same group of display modules depicted in fig. 3A-3B along with an increase in the percentage of each of these stress values over the lowest maximum principal stress observed in the sample. That is, the display module with the best performance (i.e., the lowest observed maximum principal stress at the second major surface of the cover element, 7700MPa), example 1-1, served as the baseline for this chart. In particular, display modules with adhesives including PSA and a thickness of 15 μm exhibit the best performance. The graph in fig. 7 further demonstrates that increasing the thickness of the adhesive (e.g., comparative example 1, thickness-100 μm) results in an increase in tensile stress of about 59% over the baseline condition. The graph in fig. 7 also confirms that the three-layer display modules (examples 1-1 to 1-4) exhibit a lower maximum principal stress level at the second major surface of the cover element compared to the five-layer display modules (examples 2-1 to 2-2).

It will be apparent to those skilled in the art that various modifications and variations can be made to the foldable electronic device module of the present invention without departing from the spirit or scope of the claims.

Claims

1. A display module, comprising:

a stack, the stack comprising:

(a) a substrate comprising a component having a glass composition and a thickness of from about 100 μm to 1500 μm, and

(b) a first adhesive joining the stack to the second major surface of the cover element, the first adhesive comprising an elastic modulus from about 0.001GPa to about 10GPa and a thickness from about 5 μm to 50 μm,

wherein the display module comprises one or more of:

impact resistance characterized by a tensile stress at the second major surface of the cover element of less than about 4700Mpa upon impact to the cover element in a quasi-static indentation test; or

2. The display module of claim 1, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 3200Mpa at the second major surface of the cover element after an impact on the cover element in a quasi-static indentation test.

3. The display module of claim 2, wherein the first adhesive further comprises a thickness from about 5 μ ι η to about 25 μ ι η, and the cover element further comprises a thickness from about 50 μ ι η to about 150 μ ι η.

4. The display module of any one of claims 1 to 3, wherein the first adhesive comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural or synthetic resins.

5. The display module of any one of claims 1 to 4, wherein the stack further comprises:

(c) an interlayer having a thickness of from about 25 μm to about 200 μm and an interlayer elastic modulus of from about 20GPa to about 140GPa, the interlayer further comprising a component having a glass composition; and

6. The display module of claim 5, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4200MPa at the second major surface of the cover element after an impact on the cover element in a quasi-static indentation test.

7. The display module of claim 6, wherein each of the first adhesive and the second adhesive further comprises a thickness from about 5 μm to about 25 μm, and each of the cover element and the interlayer comprises a thickness from about 75 μm to about 150 μm.

8. The display module of any one of claims 5 to 7, wherein each of the first and second adhesives comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural or synthetic resins.

9. The display module of any one of claims 5-8, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4000MPa at the first major surface of the cover element and a tensile stress of less than about 11000MPa at the second major surface of the cover element upon impact to the cover element in a pen drop test.

10. The display module of claim 9, wherein each of the first adhesive and the second adhesive further comprises a thickness from about 5 μ ι η to about 25 μ ι η, and each of the cover element and the interlayer comprises a thickness from about 50 μ ι η to about 150 μ ι η.

11. The display module of any one of claims 1-10, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 4000MPa at the first major surface of the cover element and a tensile stress of less than about 9000MPa at the second major surface of the cover element upon impact to the cover element in a pen drop test.

12. The display module of any one of claims 1-11, further comprising a hardness of about 750N/mm or greater as measured during the quasi-static indentation test.

13. The display module of claim 12, wherein the display module comprises an impact resistance characterized by a tensile stress of less than about 3200MPa at the second major surface of the cover element after an impact on the cover element in a quasi-static indentation test, and further wherein the display module comprises a hardness of about 1000N/mm or greater as measured during the quasi-static indentation test.

14. The display module of claim 13, wherein the first adhesive further comprises a thickness from about 5 μ ι η to about 25 μ ι η, and the cover element further comprises a thickness from about 50 μ ι η to about 150 μ ι η.

15. The display module of claim 14, wherein the first adhesive comprises one or more of: epoxy resins, urethanes, acrylates, acrylic acids, styrene copolymers, polyisobutylene, polyvinyl butyral, ethylene vinyl acetate, sodium silicate, Optically Clear Adhesives (OCA), Pressure Sensitive Adhesives (PSA), polymeric foams, natural or synthetic resins.