Patent Application
20230295034
This application claims priority to Korean Patent Application No. 10-2022-0034255 filed on Mar. 18, 2022, in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. 119, the content of which in its entirety is herein incorporated by reference.
The present disclosure relates to a glass composition, a glass article prepared therefrom, and a display device.
Glass articles are widely used in electronic devices including display devices, building materials, or the like. For example, glass articles are applied to substrates of flat panel display devices such as a liquid crystal display device (LCD), an organic light emitting display device (OLED), an electrophoretic display device, or the like. Glass articles are also applied to cover a window protecting a flat panel display device.
As the use of portable electronic devices such as smartphones and tablet personal computers (PCs) increases, glass articles applied to the portable electronic devices are also frequently exposed to external impacts and shock. Accordingly, the development of glass articles has focused on those glass articles that are capable of withstanding an external shock and that are thin for portability.
Recently, for convenience of a user, foldable display devices have been developed. The glass articles applied to a foldable display device preferably have a strength capable of withstanding an external shock and also have a small thickness to relieve bending stress when being folded. Accordingly, there is an ongoing need to improve the strength of thin glass articles, for example by changing a component ratio and/or a preparation process condition of a composition of the glass article.
Aspects provide a glass composition having a particular composition ratio, a glass article prepared therefrom, and a display device including the glass article.
However, aspects and embodiments are not restricted to those set forth herein. The above and other aspects and embodiments will become more apparent to one of ordinary skill in the art by referencing the detailed description.
According to an aspect, a glass article includes a glass composition, wherein the glass composition includes:
0.1<Al2O3/R2O<0.5 Mathematical Expression 1
wherein (R2O) represents a total mole percent of Na2O and Li2O combined, and (Al2O3) represents mole percent of Al2O3.
In one or more embodiments, based on 100 mole percent total of the glass composition, the glass composition may include about 67.2 mol % of SiO2, about 6.3 mol % of Al2O3, about 5.1 mol % of Na2O, about 18.7 mol % of Li2O, wherein a ratio of (Al2O3)/(R2O) is 0.27.
In one or more embodiments, the glass composition may further include 0 mol % to about 1 mol % of K2O, based on 100 mole percent total of the glass composition.
In one or more embodiments, based on 100 mole percent total of the glass composition, the glass composition may include about 67.2 mol % of SiO2, about 6.3 mol % of Al2O3, about 5.0 mol % of Na2O, about 18.7 mol % of Li2O, about 0.1 mol % of K2O, wherein a ratio of (Al2O3)/(R′2O) is 0.26, and wherein (R′2O) represents a total mole percent of Na2O, Li2O, and K2O combined.
In one or more embodiments, a coefficient of thermal expansion (CTE) of the glass composition may be about 75×10−7K−1 to about 85×10−7K−1.
In one or more embodiments, a glass transition temperature (Tg) of the glass article may be about 450° C. to about 550° C.
In one or more embodiments, a density of the glass article may be about 2.4 grams per cubic centimeter (g/cm3) to about 2.6 g/cm3.
In one or more embodiments, an elastic modulus of the glass article may be about 75 gigapascal (GPa) to about 85 GPa.
In one or more embodiments, a Poisson's ratio of the glass article may be about 0.3 to about 0.4.
In one or more embodiments, a hardness of the glass article may be about 5.5 GPa to about 6.5 GPa.
In one or more embodiments, a fracture toughness of the glass article may be about 1.0 megapascal square root meters (MPa*m0.5) to about 1.5 MPa*m0.5.
In one or more embodiments, a brittleness of the glass article may be about 4.5 μm−0.5 to about 5.5 μm−0.5.
According to another aspect, a glass composition comprises about 60 mol % to about 75 mol % of SiO2, about 3 mol % to about 10 mol % of Al2O3, about 3 mol % to about 10 mol % of Na2O, about 10 mol % to about 25 mol % of Li2O, 0 mol % to about 1 mol % of P2O5, and about 1 mol % to about 5 mol % of ZrO2, wherein each amount is based on 100 mole percent total of the glass composition, and wherein Mathematical Expression 1 is satisfied:
0.1<Al2O3/R2O<0.5 Mathematical Expression 1
wherein (R2O) represents a total mole percent of Na2O and Li2O combined, and (Al2O3) represents mole percent of Al2O3.
In one or more embodiments, based on 100 mole percent total of the glass composition, the glass composition may include about 67.2 mol % of SiO2, about 6.3 mol % of Al2O3, about 5.1 mol % of Na2O, about 18.7 mol % of Li2O, and a ratio of (Al2O3)/(R2O) is 0.26.
In one or more embodiments, the glass composition may further comprise 0 mol % to about 1 mol % of K2O, based on 100 mole percent total of the glass composition.
In one or more embodiments, based on 100 mole percent total of the glass composition, the glass composition may include about 67.2 mol % SiO2, about 6.3 mol % of Al2O3, about 5.0 mol % of Na2O, about 18.7 mol % of Li2O, about 0.1 mol % of K2O, wherein a ratio of (Al2O3)/(R′2O) is 0.26, and wherein (R′2O) represents a total mole percent of Na2O, Li2O, and K2O combined.
In one or more embodiments, a total amount of Na2O and Li2O may be about 20 mol % to about 25 mol %, based on 100 mole percent total of the glass composition.
According to another aspect, a display device includes a display panel including a plurality of pixels, a cover window disposed on the display panel, and an optically clear coupling layer disposed between the display panel and the cover window, wherein the cover window includes a glass composition, wherein the glass composition includes about 60 mol % to about 75 mol % of SiO2, about 3 mol % to about 10 mol % of Al2O3, about 3 mol % to about 10 mol % of Na2O, about 10 mol % to about 25 mol % of Li2O, 0 mol % to about 1 mol % of P2O5, and about 1 mol % to about 5 mol % of ZrO2, wherein each amount is based on 100 mole percent total of the glass composition, wherein a thickness of the cover window is in a range of about 20 micrometers to about 100 micrometers, and wherein the glass composition satisfies Mathematical Expression 1:
0.1<Al2O3/R2O<0.5 Mathematical Expression 1
wherein (R2O) represents a total mole percent of Na2O and Li2O combined, and (Al2O3) represents mole percent of Al2O3.
In one or more embodiments, in the cover window, the glass composition may further include 0 mol % to about 1 mol % of K2O, based on 100 mole percent total of the glass composition.
In one or more embodiments, in the cover window, the glass composition may include a total amount of Na2O and Li2O from about 20 mol % to about 25 mol %, based on 100 mole percent total of the glass composition.
In a glass composition according to one or more embodiments, respective components may include particular composition ratios, and a glass article prepared from the glass composition may have an excellent mechanical strength, surface strength, and shock resistance properties while having flexibility. In particular, the glass article may have excellent flexibility and enough strength to be use in a foldable display device.
These and/or other aspects and features will become more apparent and more readily appreciated from the following detailed description, taken in conjunction with the accompanying drawings, in which:
The present subject matter will now be described in further detail and with reference to the accompanying drawings, wherein one or more exemplary embodiments are shown. The subject matter may, however, be embodied in various different forms and should not be construed as being limited to the exemplary embodiments provided herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those having ordinary skill in the art.
It will also be understood that when a layer is referred to as being “on” another layer or substrate, the layer may be directly on the other layer or substrate, or one or more intervening layers may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.
It will be understood that when an element is referred to as being related to another element such as being “coupled” or “connected” to another element, it can be directly coupled or connected to the other element or intervening elements may be present therebetween. In contrast, it should be understood that when an element is referred to as being related to another element such as being “directly coupled” or “directly connected” to another element, there are no intervening elements present. Other expressions that explain the relationship between elements, such as “between,” “directly between,” “adjacent to,” or “directly adjacent to,” should be construed in the same way.
The same reference numbers indicate the same components throughout the specification.
It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer, or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, “a”, “an,” “the,” and “at least one” do not denote a limitation of quantity, and are intended to include both the singular and plural, unless the context clearly indicates otherwise. For example, “an element” has the same meaning as “at least one element,” unless the context clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below.
“About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10% or 5% of the stated value.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.
Each of the features of the various exemplary embodiments may be combined or combined with each other, in part or in whole, and technically various interlocking and driving are possible. Each exemplary embodiment may be implemented independently of each other or may be implemented together in an association.
Hereinafter, exemplary embodiments will be described in further detail and with reference to the accompanying drawings.
A glass article may be used as a cover window for protecting a display panel, as a substrate for a display panel, as a substrate for a touch panel, as an optical member such as a light guide plate, or the like, in electronic devices including displays, such as refrigerators and washing machines including display screens, as well as tablet personal computers (PCs), laptop computers, smartphones, electronic books, televisions, and PC monitors. The glass article may also be used as a cover glass of instrument dashboards of vehicles, a cover glass for solar cells, an interior building material, a window of buildings or houses, or the like.
Some glass articles desirably have a high strength. For example, a glass article for a window preferably has sufficient strength so as not to be easily damaged by an external impact or shock, while also having a small thickness (i.e., a thin article) to provide a high transmissivity and a lighter weight. A glass article with increased strength may be prepared by a method such as chemical strengthening (e.g., chemical tempering) and/or thermal strengthening (e.g., thermal tempering). Exemplary shapes of strengthened glasses are illustrated in
Referring to
Each of the glass articles 100 to 103 may have a rectangular planar shape in plan view. However, each shape of embodiments of glass articles 100 to 103 is not limited thereto, and may have various shapes such as a rectangular shape with rounded corners, a square shape, a circular shape, or an elliptical shape. In the following exemplary embodiments, it will be described by way of example that each of the glass articles 100 to 103 is a flat panel plate having a rectangular planar shape in plan view, but embodiments are not limited thereto.
Referring to
In
In one or more embodiments, the display device 500 may have a rectangular planar shape in plan view. The display device 500 may have a rectangular planar shape with vertical corners or a rectangular planar shape with rounded corners in plan view. The display device 500 may include two shorter sides disposed in the first direction DR1 and two longer sides disposed in the second direction DR2 in plan view. As noted before, a third direction DR3 may be a thickness direction of the display device 500.
The display device 500 may include a display area DA and a non-display area NDA. In plan view, a shape of the display area DA may correspond to the shape of the display device 500. For example, when the display device 500 has a rectangular planar shape in plan view, the display area DA may also have a rectangular planar shape.
The display area DA may be an area displaying an image by including a plurality of pixels (PX in
The non-display area NDA may be an area that does not display an image because it does not include pixels. The non-display area NDA may be disposed around the perimeter of the display area DA, as shown in
In one or more embodiments, the display device 500 may be maintained in both a folded state and an unfolded state. The display device 500 may be folded in an in-folding manner in which the display area DA is disposed inside the folded display device 500 as illustrated in
In one or more embodiments, the display device 500 may be a foldable device. The term “foldable device” as used herein refers to a device that may be folded, and is used as the meaning including not only a folded device, but also a device that may have both a folded state and an unfolded state, and wherein the foldable device may be transitioned from a folded state to an unfolded state, and back again from an unfolded state to a folded state. In addition, folding typically includes folding at an angle of about 180° relative to the second direction D2, but is not limited thereto, and when a folding angle exceeds 180° or is less than 180°, for example, 90° or greater and less than 180°, or 120° or greater and less than 180°, it may be understood that the display device is in a folded state. In addition, when the display device is in a bent state out of an unfolded state even though it is not completely folded, the display device may be referred to as being in the folded state. For example, even though the display device is bent at an angle of 90° or less, as long as the display device has a maximum folding angle that is 90° or greater, it may be expressed that the display device is in the folded state in order to be distinguished from the unfolded state. A radius of curvature of the display device when being folded may be about 5 millimeters (mm) or less, and may be preferably in the range of about 1 mm to about 2 mm, or may be about 1.5 mm, but is not limited thereto.
In one or more embodiments, the display device 500 may include a folding area FDA, a first non-folding area NFA1, and a second non-folding area NFA2. The folding area FDA may be an area in which the display device 500 is folded, and the first non-folding area NFA1 and the second non-folding area NFA2 each may be areas in which the display device 500 is not folded.
The first non-folding area NFA1 may be disposed on one side, for example, the upper portion of the folding area FDA. The second non-folding area NFA2 may be disposed on the other portion, for example, the lower portion of the folding area FDA. The folding area FDA may be an area curved with a predetermined curvature.
In one or more embodiments, the folding area FDA of the display device 500 may be determined at a specific position. The number of folding areas FDA determined at a specific position in the display device 500 may be one or two or more. In another embodiment, a position of the folding area FDA is not specified in the display device 500, and may be freely set in various areas.
In one or more embodiments, the display device 500 may be folded in the second direction DR2. Accordingly, a length of the display device 500 in the second direction DR2 may be reduced by approximately half when the display device 500 is completely folded, and thus, a user may conveniently carry the display device 500 in a pocket, purse, backpack, briefcase, or other conveyance.
In one or more embodiments, a direction in which the display device 500 is folded is not limited to the second direction DR2. For example, the display device 500 may be folded in the first direction DR1. In this case, a length of the display device 500 in the first direction DR1 may be reduced by approximately half when the display device 500 is completely folded.
It has been illustrated in
Referring to
The display panel 200 may be, for example, a self-luminous display panel such as an organic light emitting display panel (OLED), an inorganic electroluminescent (EL) light emitting display panel, a quantum dot light emitting display panel (QED), a micro LED display panel (micro-LED), a nano LED display panel (nano-LED), a plasma display panel (PDP), a field emission display panel (FED), or a cathode ray tube (CRT) display panel, or may be a light-receiving display panel such as a liquid crystal display panel (LCD) and an electrophoretic display panel (EPD).
The display panel 200 may include a plurality of pixels PX, and may display an image using light emitted from each pixel PX. The display device 500 may further include a touch member (not illustrated). In one or more embodiments, the touch member may be internalized in the display panel 200. For example, the touch member may be directly formed on a display member of the display panel 200, such that the display panel 200 itself may perform a touch function. In another embodiment, the touch member may be prepared separately from the display panel 200 and then attached to an upper surface of the display panel 200 by the optically clear coupling layer 300.
The glass article 100 protecting the display panel 200 is disposed on or above the display panel 200. The glass article 100 has a larger size than the display panel 200, such that side surfaces thereof may protrude further out than side surfaces of the display panel 200, but embodiments are not limited thereto. The display device 500 may further include a printing layer (not illustrated) disposed on at least one surface of the glass article 100 at an edge portion of the glass article 100. The printing layer may prevent a bezel area or region of the display device 500 from being viewed externally, and may selectively or optionally perform a decorative function in some cases.
The optically clear coupling layer 300 is disposed between the display panel 200 and the glass article 100. The optically clear coupling layer 300 serves to fix or bond the glass article 100 onto the display panel 200. The optically clear coupling layer 300 may include an optical clear adhesive (OCA), an optical clear resin (OCR), or the like.
Hereinafter, the glass article 100 strengthened as described above will be described in further detail.
Referring to
The first surface US and the second surface RS oppose each other in the thickness direction. When the glass article 100 serves to transmit light like a cover window of a display, the light may mainly enter any one of the first surface US and the second surface RS and be then transmitted through the other of the first surface US and the second surface RS.
A thickness t of the glass article 100 may be defined as a distance between the first surface US and the second surface RS. The thickness t of the glass article 100 may be in the range of about 20 μm to about 100 μm, but is not limited thereto. In one or more embodiments, the thickness t of the glass article 100 may be about 80 μm or less. In another embodiment, the thickness t of the glass article 100 may be about 75 μm or less. In still another embodiment, the thickness t of the glass article 100 may be about 70 μm or less. In still another embodiment, the thickness t of the glass article 100 may be about 60 μm or less. In still another embodiment, the thickness t of the glass article 100 may be about 65 μm or less. In still another embodiment, the thickness t of the glass article 100 may be about 50 μm or less. In still another embodiment, the thickness t of the glass article 100 may be about 30 μm or less. In some specific embodiments, the thickness t of the glass article 100 may be in the range of about 20 μm to about 80 μm, about 20 μm to about 70 μm, about 20 μm to about 60 μm, about 20 μm to about 50 μm, or may have a value of about 30 μm. The glass article 100 may have a uniform thickness t, but is not limited thereto, and may have a different thickness t for each region.
The glass article 100 may be strengthened or tempered to have a predetermined stress profile therein. The occurrence of cracks, propagation of cracks, damage, and the like, due to an external impact and shock are better prevented in the strengthened glass article 100 than in the glass article 100 before being strengthened. The glass article 100 strengthened through a strengthening process may have various stresses for each region. For example, compressive regions CSR1 and CSR2 in which compressive stresses act, may be disposed in the vicinity of surfaces of the glass article 100, that is, in the vicinity of the first surface US and the second surface RS, and a tensile region CTR in which a tensile stress acts may be disposed inside the glass article 100. Stress values of boundaries DOC1 and DOC2 between the compressive regions CSR1 and CSR2 and the tensile region CTR may be 0. A stress value of the compressive stress in one compressive region CSR1 or CSR2 may change depending on a position (i.e., a depth of a point from the respective surfaces). In addition, the tensile region CTR may have different stress values depending on a depth from the surfaces US or RS.
Positions of the compressive regions CSR1 and CSR2, stress profiles within the compressive regions CSR1 and CSR2, compressive energy of the compressive regions CSR1 and CSR2, tensile energy of the tensile region CTR, or the like, within the glass article 100 may have a significant influence on mechanical properties such as a surface strength of the glass article 100.
Referring to
The first compressive region CSR1 and the second compressive region CSR2 serve to resist an external impact or shock to mitigate the occurrence of cracks in the glass article 100 or damage to the glass article 100. As maximum compressive stresses CS1 and CS2 of the first compressive region CSR1 and the second compressive region CSR2 increase, a strength of the glass article 100 generally increases. Since the external impact or shock is normally transferred through the surfaces US and RS of the glass article 100, it is advantageous in terms of durability to have the maximum compressive stresses CS1 and CS2 on the surfaces of the glass article 100. From such a point of view, the compressive stress of the first compressive region CSR1 and the second compressive region CSR2 is greatest at the surfaces of the glass article and tends to decrease toward the inside of the glass article.
The first compressive depth DOC1 and the second compressive depth DOC2 prevent cracks or grooves formed in the first surface US and the second surface RS from propagating into the tensile region CTR inside the glass article 100. As the first compressive depth DOC1 and the second compressive depth DOC2 become greater, the propagation of the cracks and the like may be better prevented. Points corresponding to the first compressive depth DOC1 and the second compressive depth DOC2 correspond to the boundaries between the compressive regions CSR1 and CSR2 and the tensile region CTR, and have a stress value of 0.
Throughout the glass article 100, the tensile stress of the tensile region CTR may be balanced with the compressive stress of the compressive regions CSR1 and CSR2. That is, the sum (i.e., compressive energy) of the compressive stresses and the sum (i.e., tensile energy) of the tensile stresses in the glass article 100 may be the same as each other. Stress energy accumulated in one region having a constant width in the thickness t direction in the glass article 100 may be calculated as a value obtained by integrating a stress profile. When the stress profile in the glass article 100 having a thickness t is expressed as a function f(x), Equation 1 may be satisfied.
∫0tƒ(x)dx=0 Equation 1
As a magnitude of the tensile stress inside the glass article 100 increases, there is a risk that fragments will be more violently released and crushing will occur from the inside of the glass article 100, when the glass article 100 is broken. A maximum tensile stress that satisfies a fragility criterion of the glass article 100 may satisfy Equation 2, but is not limited thereto.
CT
1≤−38.7×ln(t)+48.2 Equation 2
wherein CT1 is maximum tensile stress.
In some embodiments, a maximum tensile stress CT1 may be about 100 megapascal (MPa) or less, or about 85 MPa or less. Meanwhile, it may be preferable in improving mechanical properties, such as a strength, that the maximum tensile stress CT1 is about 75 MPa or greater. In one or more embodiments, the maximum tensile stress CT1 may be about 75 MPa or greater and about 85 MPa or less, but is not limited thereto.
The maximum tensile stress CT1 of the glass article 100 may be positioned at a central portion of the glass article 100 in the thickness t direction. For example, the maximum tensile stress CT1 of the glass article 100 may be positioned at a depth in the range of 0.4t to 0.6t or in the range of 0.45t to 0.55t or be positioned at a depth of about 0.5t.
Meanwhile, it is preferable that the compressive stresses and the compressive depths DOC1 and DOC2 are great in order to increase a strength of the glass article 100, but as the compressive energy increases, the tensile energy also increases, such that the maximum tensile stress CT1 may also increase. It is preferable to adjust the stress profile so that the maximum compressive stresses CS1 and CS2 and the compressive depths DOC1 and DOC2 are greater and the compressive energy is smaller in order to satisfy the fragility criterion while having a high strength. To this end, the glass article 100 may be prepared by a glass composition including specific components in a predetermined amount. According to a composition ratio of the components included in the glass composition, the prepared glass article 100 may have an excellent strength and, at the same time, may have flexible properties and physical properties so as to be able to be applied to a foldable display device.
According to one or more aspects, the glass composition forming the glass article 100 includes about 60 mol % to about 75 mol % of SiO2, about 3 mol % to about 10 mol % of Al2O3, about 3 mol % to about 10 mol % of Na2O, about 10 mol % to about 25 mol % of Li2O, 0 mol % to about 1 mol % of P2O5, and about 1 mol % to about 5 mol % of ZrO2, wherein each amount is based on 100 mole percent total of the glass composition. Here, a “content of any component is 0 mol %” means that the glass component does not substantially contain the corresponding component. A phrase “glass composition substantially does not contain a specific component” means that the specific composition is not intentionally contained in a raw material or the like, and includes, for example, a case where the glass composition unavoidably contains a trace (e.g., 0.1 mol % or less) of impurities.
Respective component of the glass composition will be described in further detail below.
Without wishing to be bound to theory, SiO2 may serve to constitute a skeleton of the glass, improve chemical durability, and reduce the occurrence of cracks when a scratch (indentation) occurs on a glass surface. SiO2 may be a network former oxide forming a network of the glass, and the glass article 100 prepared to include SiO2 may have a decreased coefficient of thermal expansion and an improved mechanical strength. In order to sufficiently perform the role as described above, a content of SiO2 is about 60 mol % or greater, based on 100 mole percent total of the glass composition. In order to exhibit sufficient meltability, a content of SiO2 in the glass composition is about 75 mol % or less, based on 100 mole percent total of the glass composition.
Without wishing to be bound to theory, Al2O3 serves to improve friability of the glass. In other words, Al2O3 may serve to allow a smaller number of fragments to occur when the glass breaks. Al2O3 may be an intermediate oxide forming a bond with SiO2 forming a network structure. In addition, Al2O3 may act as an active component improving ion exchange performance at the time of chemical strengthening and increasing a surface compressive stress after the chemical strengthening. When a content of Al2O3 is about 3 mol % or greater, based on 100 mole percent total of the glass composition, Al2O3 may effectively perform the function as described above. Meanwhile, in order to maintain acid resistance and meltability of the glass, it is preferable that the content of Al2O3 is about 10 mol % or less, based on 100 mole percent total of the glass composition.
Without wishing to be bound to theory, Na2O serves to form a surface compressive stress by ion exchange and improves meltability of the glass. Na2O may form non-bridging oxygen in a SiO2 network structure by forming an ionic bond with oxygen of SiO2 forming the network structure. An increase in the non-bridging oxygen may improve flexibility of the network structure, and the glass article 100 may have physical properties that it is applicable to the foldable display device. It is preferable in effectively performing the role as described above that a content of Na2O is about 3 mol % or greater, based on 100 mole percent total of the glass composition. However, in terms of acid resistance of the glass article 100, it is preferable that the content of Na2O is about 10 mol % or less, based on 100 mole percent total of the glass composition.
Without wishing to be bound to theory, Li2O serves to form a surface compressive stress by ion exchange, and improves meltability of the glass, similar to Na2O described above. Li2O may form non-bridging oxygen in the SiO2 network structure by forming an ionic bond with oxygen of SiO2 forming the network structure. An increase in the non-bridging oxygen may improve flexibility and a shock absorption function of the network structure, and the glass article 100 may have physical properties that it is applicable to the foldable display device. It is preferable in effectively performing the role as described above that a content of Li2O is about 10 mol % or greater, based on 100 mole percent total of the glass composition. However, in terms of heat resistance of the glass article 100, it is preferable that the content of Li2O is about 25 mol % or less, based on 100 mole percent total of the glass composition.
Without wishing to be bound to theory, ZrO2 may improve transmissivity and a surface strength of the glass, and increases resistance to surface crack expansion. ZrO2 may be an intermediate oxide forming a bond with SiO2 forming a network structure. ZrO2 is bonded to a portion where a bond is broken by Li2O and Na2O in the SiO2 network structure to increase fracture toughness of the glass and increase a repulsive force against bending. ZrO2 may meaningfully perform the function as described above when a content thereof is about 1 mol % or greater, based on 100 mole percent total of the glass composition. However, in terms of flexibility of the glass article 100, it is preferable that the content of ZrO2 is about 5 mol % or less, based on 100 mole percent total of the glass composition.
Without wishing to be bound to theory, P2O5 improves ion exchange performance and chipping resistance. P2O5 may also be a network former oxide forming a network structure together with SiO2. P2O5 may form a chain structure similar to that of a polymer to have excellent ion mobility, and thus, may absorb a shock while positions of atoms are changed at the time of the shock. P2O5 may be omitted (0 mol %), but may meaningfully perform the function as described above when a content thereof is about 0.1 mol % or greater, based on 100 mole percent total of the glass composition. It is preferable that P2O5 has a content of about 1 mol % or less, based on 100 mole percent total of the glass composition, in terms of chemical resistance of the glass article.
According to one or more aspects, the glass composition satisfies Mathematical Expression 1:
0.1<Al2O3/R2O<0.5 Mathematical Expression 1
wherein, in Mathematical Expression 1,
In other words, in Mathematical Expression 1, R may be Na or Li. In other embodiments, R may be Na, Li, or K.
As described herein, the glass article 100 prepared by the glass composition according to one or more embodiments may have properties and physical properties that are applicable to the foldable display device. For example, the glass article 100 may have a flexible property to be able to be folded and unfolded, and may have impact resistance and chemical resistance properties that are sufficient for use as the cover window of the display device 500. In a network structure formed by SiO2 and Al2O3 included in the glass composition, Na2O and Li2O are added, such that a network structure having flexibility may be formed. By the addition of Na2O and Li2O, Na ions or Li ions form ionic bonds with oxygen between bonds forming the network structure, for example, inter-SiO2 bonds, such that the non-bridging oxygen may increase. The increase in the non-bridging oxygen in the network structure means that the bond of the network structure is broken or becomes an open state, and the network structure of the glass may have greater flexibility. The glass composition may include Na2O in an amount of about 3 mol % or greater and Li2O in an amount of about 10 mol % or greater so that the prepared glass article 100 may have sufficient flexibility.
The glass composition includes relatively greater amounts of Na2O and Li2O, and may thus have a lower mechanical strength. The glass composition includes Al2O3 in order to offset for the lower mechanical strength, and a ratio of the molar content of Al2O3 to the molar content of R2O (the sum of the molar contents of Na2O and Li2O) is adjusted in the range of 0.1 to 0.5 according to Mathematical Expression 1, such that the mechanical strength may be added to the network structure. In the glass composition, the ratio of the molar content of Al2O3 to the molar content of R2O (the sum of the molar contents of Na2O and Li2O) or an “R ratio” is in the range of 0.1 to 0.5.
When the ratio (R ratio) of the molar content of Al2O3 to the molar content of R2O (the sum of the molar contents of Na2O and Li2O) included in the glass composition is 0.1 or greater, the molar contents of Na2O and Li2O are increased, and the increased Na2O and Li2O may break the network structure of SiO2 to increase an interatomic distance in the network structure. Accordingly, extra space may be formed in the network structure of SiO2, such that flexibility and shock absorption properties may be improved.
On the other hand, when the ratio (R ratio) of the molar content of Al2O3 to the molar content of R2O (the sum of the molar contents of Na2O and Li2O) included in the glass composition becomes larger, portions where Na2O and/or Li2O break the network structure of SiO2 may increase, and chemical durability of the glass may deteriorate. Accordingly, it is preferable that the ratio (R ratio) of the molar content of Al2O3 to the molar content of R2O (the sum of the molar contents of Na2O and Li2O) is 0.5 or less in terms of chemical durability of the glass article.
When the ratio (R ratio) of the molar content of Al2O3 to the molar content of R2O (the sum of the molar contents of Na2O and Li2O) included in the glass composition has a value between 0.1 and 0.5, the flexibility, strength, and shock absorption properties of the glass article 100 may be improved.
In one or more embodiments, the glass composition may include about 67.2 mol % of SiO2, about 6.3 mol % of Al2O3, about 5.1 mol % of Na2O, and about 18.7 mol % of Li2O, wherein each amount is based on 100 mole percent total of the glass composition, and wherein a ratio of (Al2O3)/(R2O) is 0.26 according to Mathematical Expression 1.
The glass composition may further include additional components such as one or more of Y2O3, La2O3, Nb2O5, Ta2O5, Gd2O3, or a combination thereof, if desired, in addition to the components mentioned above. In addition, the glass composition may further include traces of Sb2O3, CeO2, and/or As2O3 as clarifiers.
Meanwhile, the glass composition may further include K2O to improve bending reliability of the glass article. K2O may replace Na with K to increase a compressive stress of the glass. Accordingly, K2O may contribute to realizing the flexible glass article 100 by improving folding reliability and the bending reliability of the glass article. K2O may be omitted (0 mol %), but may meaningfully perform the function as described above when a content thereof is about 0.1 mol % or greater. However, in terms of meltability of the glass article 100, it may be preferable that the content of K2O is about 1 mol % or less.
When the glass composition includes K2O, in Mathematical Expression 1 of the glass composition, R may further include K. That is, the molar content of R2O in the total weight of the glass composition may be the sum of the molar content of Na2O, the molar content of Li2O, and the molar content of K2O. In other aspects, R′2O represents a total mole percent of Na2O, Li2O, and K2O combined, wherein R′2O may be used interchangeably with R2O to satisfy Mathematical Expression 1. In one or more embodiments, a total amount of Na2O, Li2O, and K2O in the glass composition may be in the range of about 20 mol % to about 25 mol %, based on 100 mole percent total of the glass composition. In one or more embodiments, the glass composition may include about 67.2 mol % of SiO2, about 6.3 mol % of Al2O3, about 5.0 mol % of Na2O, about 18.7 mol % of Li2O, and about 0.1 mol % of K2O, and a ratio of (Al2O3)/(R′2O) is 0.26, wherein (R′2O) represents a total mole percent of Na2O, Li2O, and K2O combined.
The glass composition having the above-described composition may be formed into a sheet glass shape by various methods known in the art. When the glass composition is formed into the sheet glass shape, the glass composition in the sheet glass shape may be further processed to be prepared as the glass article 100 applicable to the display device 500. However, the present disclosure is not limited thereto, and the glass composition is not formed into the sheet glass shape, and may be directly formed into the glass article 100 applicable to an article without an additional forming process.
Hereinafter, a process in which the glass composition is formed into the sheet glass shape and the glass is processed into the glass article 100 will be described in further detail, but embodiments are not limited thereto.
Referring to
The forming step (S1) may include a step of preparing the glass composition and a step of forming the glass composition. The glass composition may have the composition and the components as described herein. A detailed description of the glass composition will be omitted. The glass composition may be formed into the sheet glass shape by a method such as a float process, a fusion draw process, or a slot draw process.
A glass formed into a flat panel plate shape may be cut through the cutting step (S2). The glass formed into the flat panel plate shape may have a different size than the final glass article 100. For example, glass forming may be performed in a state of a large-area substrate as a mother substrate 10a including a plurality of glass articles, and the mother substrate 10a may be cut into a plurality of glass cells 10 to prepare the plurality of glass articles. For example, even though the final glass article 100 has a size of about 15.24 centimeters (i.e., about 6 inches), when the glass is formed in a size several to hundreds of times the size of the final glass article 100, for example, 304.8 cm (120 inches), and then cut, twenty glasses formed in the flat panel plate shape may be obtained at once. In this case, process efficiency may be improved as compared with a case of separately forming individual glass articles. In addition, even though a glass corresponding to a size of one glass article is formed, when the final glass article has various planar shapes, the glass may be prepared in a desired shape through a cutting process.
The cutting of the glass 10a may be performed using a cutting knife 20, a cutting wheel, a laser, or the like.
The cutting step (S2) of the glass may be performed before the strengthening step (S5) of the glass. The glass in a mother substrate 10a unit may be strengthened at once and then cut to a size of the final glass article, but in this case, cut surfaces (e.g., side surfaces of the glass) may be in a non-strengthened state, and thus, it may be preferable to first complete the cutting of the glass and then perform the strengthening step (S5). Accordingly, the strengthening step S5 may be performed after cutting is completed.
A polishing step before strengthening may be performed between the cutting step (S2) of the glass and the strengthening step (S5) of the glass. The polishing step may include the side surface polishing step (S3) and the surface polishing step before strengthening (S4). In one or more embodiments, the side surface polishing step (S3) is first performed and the surface polishing step before strengthening (S4) is then performed, but this order may also be reversed.
Here, specimens having 5 g of each composition were manufactured, and glass transition temperatures (Tg) of the specimens were confirmed using a differential thermal analyzer (DTA) while raising temperatures of the specimens to a glass transition temperature range at a rate of 10 K/min. Specimens having a size of 10×10×13 mm3 were manufactured for each composition, and coefficients of thermal expansion of the specimens were confirmed using a thermal mechanical analyzer (TMA) while raising temperatures of the specimens to a glass transition temperature range at a rate of 10 K/min.
Specimens having a size of 10×20×3 mm3 were manufactured for each composition, and elastic moduli and Poisson ratios of the specimens were confirmed using an elastic modulus tester by confirming stresses and strains of the specimens.
Hardness and fracture toughness of specimens were calculated by Equations (3) and (4) by applying a load of 4.9 N to the specimens for 30 seconds with a Vickers hardness tester using a diamond tip having a size of 19 μm.
Here, HV refers to a Vickers hardness, F refers to a load, and a refers to an indentation length.
Here, KIC refers to a fracture toughness, ϕ refers to a constraint index (ϕ≈3), HV refers to a Vickers hardness, K refers to a constant (=3.2), c refers to a crack length, and a refers to an indentation length.
Brittleness of specimens were calculated by Equation (5) by applying a load of 4.9 N to the specimens for 30 seconds using a Vickers hardness tester.
Here, B refers to a brittleness, g refers to a constant (2.39 N1/4/um1/2), P refers to an indentation load, a refers to an indentation length, and C refers to a crack length.
The side surface polishing step (S3) is a step of polishing side surfaces of the cut glass 10. In the side surface polishing step (S3), the side surfaces of the glass 10 are polished to allow the side surfaces of the glass cells 10 to have smooth surfaces. In addition, the respective side surfaces of the glass cells 10 may have uniform surfaces through the side surface polishing step (S3). More specifically, the cut glass cells 10 may include one or more cut surfaces. Two of four side surfaces of some cut glass cells 10 may be cut surfaces. Three of four side surfaces of some other cut glass cells 10 may be cut surfaces. All of four side surfaces of some other cut glass cells 10 may be cut surfaces. The surface roughness or the like may be different from each other when the side surface is a cut surface and when the side surface is an uncut surface. In addition, the cut surfaces may have a different surface roughness. Accordingly, by polishing the respective side surfaces through the side surface polishing step (S3), the respective side surfaces may have a uniform surface roughness or the like. Furthermore, when there is a small crack on the side surface, the small crack may be removed through the side surface polishing step (S3).
The side surface polishing step (S3) may be performed concurrently or simultaneously on a plurality of cut glass cells 10. That is, in a state in which the plurality of cut glass cells 10 are stacked, the stacked glass cells 10 may be polished simultaneously.
The side surface polishing step (S3) may be performed by a mechanical polishing method and/or a chemical mechanical polishing method using a polishing device 30. In one or more embodiments, two opposing side surfaces of the cut glass cells 10 may be polished simultaneously, and then, the other two opposing side surfaces of the cut glass cells 10 may be polished simultaneously, but embodiments are not limited thereto.
The surface polishing step (S4) before strengthening may be performed in order to allow each glass cell 10 to have a uniform surface. The surface polishing step before strengthening (S4) may be performed for each cut glass cell 10, but when a chemical mechanical polishing device 40 is sufficiently greater than the glass cells 10, a plurality of glass cells 10 may be horizontally arranged, and surfaces of the plurality of glass cells 10 may then be polished simultaneously.
The surface polishing step (S4) before strengthening may be performed by a chemical mechanical polishing method. Specifically, a first surface and a second surface of the cut glass cells 10 are polished using the chemical mechanical polishing device 40 and a polishing slurry. The first surface and the second surface may be polished simultaneously or any one of the first surface and the second surface may be first polished and the other of the first surface and the second surface may then be polished.
After the surface polishing step (S4) before strengthening, the strengthening step (S5) is performed. The strengthening step (S5) may be performed by chemical strengthening and/or thermal strengthening. When the glass cell 10 has a small thickness of about 2 mm or less, and furthermore, about 0.75 mm or less, a chemical strengthening method may be suitably applied in order to precisely control a stress profile.
After the strengthening step (S5), the surface polishing step after strengthening (S6) may be optionally further performed. The surface polishing step after strengthening (S6) may serve to remove fine cracks on the surface of the strengthened glass cell 10 and control compressive stresses of the first surface and the second surface of the strengthened glass cell 10. For example, a floating method, which is one of methods of preparing a sheet glass, is performed in a manner of pouring a glass composition into a tin bath, in this case, a surface in contact with the tin bath and a surface that is not in contact with the tin bath may have different compositions. Accordingly, after the strengthening step (S5) of the glass cell 10, a deviation of a compressive stress between the surface in contact with the tin bath and a surface that is not in contact with the tin bath may occur, but by removing the surface of the glass cell 10 to an appropriate thickness by polishing, the deviation of the compressive stress between the surface in contact with the tin bath and a surface that is not in contact with the tin bath may be decreased.
The surface polishing step after strengthening (S6) may be performed by a chemical mechanical polishing method. Specifically, a first surface and a second surface of the strengthened glass cell 10, which is a glass cell 10 to be processed, are polished using the chemical mechanical polishing device 60 and a polishing slurry. A polishing thickness may be adjusted, for example, in the range of about 100 nm to about 1,000 nm, but is not limited thereto. Polishing thicknesses of the first surface and the second surface may be the same as each other or be different from each other.
Although not illustrated in
The glass article 100 prepared through the above-described process may include a component ratio similar to that of the glass composition. For example, the glass article 100 may include about 60 mol % to about 75 mol % of SiO2, about 3 mol % to about 10 mol % of Al2O3, about 3 mol % to about 10 mol % of Na2O, about 10 mol % to about 25 mol % of Li2O, 0 mol % to about 1 mol % of P2O5, and about 1 mol % to about 5 mol % of ZrO2, wherein each amount is based on 100 mole percent total of the glass article. In addition, a glass article 100 according to another embodiment may further include K2O in an amount of 0 mol % to about 1 mol %, based on 100 mole percent total of the glass article in addition to the above-described component ratio. The glass composition for preparing the glass article 100 satisfies Mathematical Expression 1:
0.1<Al2O3/R2O<0.5 Mathematical Expression 1
wherein, (R2O) represents a total mole percent of Na2O and Li2O combined, and (Al2O3) represents mole percent of Al2O3.
In addition, when the glass article further includes K2O, (R2O) in Mathematical Expression 1 may be expressed as (R′2O), which represents a total mole percent of Li, Na, and K combined.
The glass article 100 prepared from the above-described glass composition has a thickness in the range of about 20 μm to about 100 μm.
In one or more embodiments, the glass article 100 prepared from the above-described glass composition has a thickness in the range of about 20 μm to about 100 μm and may satisfy one or more of the following properties:
Hereinafter, one or more exemplary embodiments will be described through the Preparation Examples and Experimental Examples.
A plurality of glass base materials having various compositions were prepared according to Table 1 and were divided into Examples 1 to 4, and a glass article was prepared by processing according to the method described above was then performed for each sample. Glass articles for each sample were prepared as articles having a thickness of 50 μm.
The compositions of glass articles for each of Examples 1 to 4 are shown in Table 1. In addition, the properties such as density, glass transition temperature (Tg), hardness, fracture toughness, brittleness, elastic modulus, coefficient of thermal expansion (CTE), and Poisson's ratio of the glass articles for each sample were measured and shown in Table 2.
Referring to Tables 1 and 2, Example 1 was a glass article made of a glass composition including Li2O, ZrO2, and P2O5. In addition, Examples 2 to 4 were glass articles made of glass compositions that do not contain Li2O, ZrO2, or P2O5.
It can be seen that a glass transition temperature of Example 1 is 478° C., which was significantly lower than the glass transition temperatures of Examples 2 to 4. This may mean that meltability and processability of a glass in Example 1 were excellent.
In addition, it could be seen that a fracture toughness of Example 1 was 1.21 MPa*m0.5 and a brittleness of Example 1 was 5.05 μm−0.5. On the other hand, the fracture toughness of Examples 2 to 4 were 0.7 MPa*m° 5 or less, and the brittleness of Examples 2 to 4 were 7.71 μm−0.5 or greater. Accordingly, it can be seen that Example 1 has excellent shock resistance properties as compared with Examples 2 to 4.
In addition, it could be seen that an elastic modulus of Example 1 was 81.6 GPa and a Poisson's ratio of Example 1 was 0.353. On the other hand, the elastic modulus of Examples 2 to 4 were 74 GPa or less, and the Poisson's ratios of Examples 2 to 4 were 0.215 or less. Accordingly, it can be seen that Example 1 has excellent flexibility as compared with Examples 2 to 4.
While the present disclosure has been illustrated and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various suitable changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims and equivalents thereof. The exemplary embodiments should be considered in a descriptive sense only and not for purposes of limitation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0034255 | Mar 2022 | KR | national |
