CN117956865A

CN117956865A - Flexible cover window with improved strength and surface hardness

Info

Publication number: CN117956865A
Application number: CN202311407638.2A
Authority: CN
Inventors: 鲜于国贤; 河泰周; 吴再锡
Original assignee: UTI Inc
Current assignee: UTI Inc
Priority date: 2022-10-28
Filing date: 2023-10-27
Publication date: 2024-04-30

Abstract

The present disclosure relates to flexible cover windows having improved strength and surface hardness. Disclosed is a glass-based flexible cover window having improved strength and surface hardness, including a planar portion formed to correspond to a planar area of a flexible display and a folded portion formed to be connected to the planar portion, the folded portion being formed to correspond to a folded area of the flexible display, wherein the flexible cover window includes a flat glass substrate or a glass substrate having an uneven pattern embossed or scored thereon, an adhesive buffer layer formed at a front surface of the glass substrate, a protective film layer formed on the adhesive buffer layer, and a hard coating layer formed on the protective film layer, and the adhesive buffer layer and the protective film layer are alternately stacked at least n times, wherein n is a natural number equal to or greater than 1.

Description

Flexible cover window with improved strength and surface hardness

Cross Reference to Related Applications

The present application claims priority from korean patent application nos. 10-2022-0141196 and 10-2023-013686, filed on the korean intellectual property office on 10-28 and 10-12 of 2022 and 2023, respectively, the disclosures of which are incorporated herein by reference in their entireties.

Technical Field

The present invention relates to a flexible cover window, and more particularly, to a flexible cover window having improved strength and surface hardness, which is configured such that the impact strength and surface hardness of the flexible cover window are excellent while improving the aesthetic sense of the flexible cover window.

Background

With the recent rapid development of electric and electronic technologies and the new demand of the age and the increase of various demands of consumers, various types of display products have been manufactured. Among them, researches on a flexible display capable of being folded and unfolded have been actively conducted.

First, studies on folding flexible displays are performed, and studies on bending, curling, and stretching of flexible displays are now being performed. Not only the display panel but also the cover window configured to protect the display panel must be flexible, and thus the cover window must be flexible and not wrinkled at a folding region thereof after repeated folding, and no image distortion must occur.

For conventional cover windows for flexible displays, a polymer film such as a PI film or a PET film is attached to the surface of the display panel. However, since the simple polymer film has low mechanical strength, the polymer film is only used to prevent scratches on the display panel. In addition, the polymer film has low impact resistance and low transmittance. In addition, polymeric films are relatively expensive.

As the number of times the display is folded increases, the folded region of the polymer film is wrinkled, whereby the folded region of the polymer film is damaged. For example, polymeric films are squeezed or torn upon evaluation of the fold limit (typically 200,000 times).

In recent years, various studies have been made on glass-based cover windows in order to overcome the limitations of polymer film cover windows.

Such glass-based cover windows require substantial physical properties. For example, image distortion must not occur, and the glass-based cover window must have sufficient strength and surface hardness for repeated contact and specific pressure of the stylus pen while satisfying folding characteristics.

In order to meet the strength characteristics of the flexible cover window, the glass must have a specific thickness or greater. On the other hand, in order to satisfy the folding characteristics of the flexible cover window, the glass must have a specific thickness or less. Therefore, research into an optimal thickness and structure of a flexible cover window that does not undergo image distortion while satisfying both strength characteristics and folding characteristics is required.

In korean patent application No. 10-2021-0102841, a protective film layer having a hard coating layer 400 formed at the front surface of a glass substrate is used as an adhesive buffer layer to improve a flexible cover window. However, in order to improve usability of the flexible cover window in daily life, in order to extend the life of the apparatus having the flexible cover window applied thereto, and in order to improve economy, it is necessary to further study the cover window having an appropriate thickness to ensure strength while maintaining aesthetic feeling and while having further improved folding characteristics.

Disclosure of Invention

The present invention has been made in view of the above-mentioned problems and technical problems that have been set forth in the past.

An object of the present invention is to provide a flexible cover window configured such that an adhesive buffer layer and a protective film layer connected to the adhesive buffer layer are formed at least once on a glass substrate having a predetermined shape, thereby being excellent in folding characteristics and aesthetic feeling while being improved in strength and surface hardness.

1. Flat structure

The present invention provides a glass-based flexible cover window having improved strength and surface hardness, the glass-based flexible cover window including a planar portion formed to correspond to a planar area of a flexible display and a folded portion formed to be connected to the planar portion, the folded portion being formed to correspond to a folded area of the flexible display, wherein the flexible cover window includes a flat glass substrate, an adhesive buffer layer formed on a front surface of the glass substrate, a protective film layer formed on the adhesive buffer layer, and a hard coat layer formed on the protective film layer, and the adhesive buffer layer and the protective film layer are alternately stacked at least n times, wherein n is a natural number equal to or greater than 1.

The planar portion and the folded portion of the glass substrate may have the same thickness.

At least one surface of the folded portion of the glass substrate may include an inclined portion, whereby the thickness of the folded portion may be smaller than that of the planar portion.

The inclined portion of the folded portion may be any one of the following: a forward-type inclined portion configured such that the inclined portion is formed at a rear surface of the glass substrate; a reverse-type inclined portion configured such that the inclined portion is formed at a front surface of the glass substrate, the reverse-type inclined portion being a reversal of the forward-type inclined portion; and a double-sided inclined portion configured such that the inclined portion is formed at the front and rear surfaces of the glass substrate.

The double-sided inclined portion may be configured such that a depth of the inclined portion formed at the front surface and a depth of the inclined portion formed at the rear surface are equal to or different from each other.

The adhesive buffer layer may include an Optically Clear Resin (OCR) CLEAR RESIN.

The protective film layer may include at least one selected from the group consisting of: polyethylene terephthalate (PET), transparent Polyimide (TPI), polyurethane (PU), polypropylene (PP), polyethylene naphthalate (PEN), and Polycarbonate (PC).

The strength of the protective film layer at the planar portion and the strength of the protective film layer at the folded portion may be equal to or different from each other.

The thickness of the protective film layer may be 1 μm to 100 μm.

The flexible cover window may be configured such that an elastic buffer layer is optionally formed on the rear surface of the glass substrate.

The elastic buffer layer may include an optically transparent resin (OCR).

When the adhesive buffer layer and the protective film layer are alternately stacked at least n+1 times in the stacking direction, the compositions of the n-th adhesive buffer layer and the (n+1) -th adhesive buffer layer may be the same or different from each other, and the compositions of the n-th protective film layer and the (n+1) -th protective film layer may be the same or different from each other, where n is a natural number equal to or greater than 1.

When the adhesive buffer layer and the protective film layer are alternately stacked at least n+1 times in the stacking direction, the thickness of the n-th adhesive buffer layer may be smaller than the thickness of the (n+1) -th adhesive buffer layer, and the thickness of the n-th protective film layer may be smaller than the thickness of the (n+1) -th protective film layer, where n is a natural number equal to or greater than 1.

2. Uneven structure

Further, the present invention provides a glass-based flexible cover window having improved strength and surface hardness, the glass-based flexible cover window including a planar portion formed to correspond to a planar area of a flexible display and a folded portion formed to be connected to the planar portion, the folded portion being formed to correspond to a folded area of the flexible display, wherein the flexible cover window includes a glass substrate having an uneven pattern formed with embossments or scores, an adhesive buffer layer formed at a front surface of the glass substrate, a protective film layer formed on the adhesive buffer layer, and a hard coating layer formed on the protective film layer, and the adhesive buffer layer and the protective film layer are alternately stacked at least n times, wherein n is a natural number equal to or greater than 1.

The planar portion and the folded portion of the glass substrate may have the same thickness, and the embossed or scored uneven pattern may be formed on the front surface, the rear surface, or both surfaces of the glass substrate.

The planar portion and the folded portion of the glass substrate may have the same thickness, and the embossed or scored uneven pattern may be formed at the folded portion of the glass substrate or at both the planar portion and the folded portion of the glass substrate.

At least one surface of the folded portion of the glass substrate may include an inclined portion, whereby the thickness of the folded portion may be smaller than that of the planar portion, and an embossed or scored uneven pattern may be formed on the front surface, the rear surface, or both surfaces of the glass substrate.

At least one surface of the folded portion of the glass substrate may include an inclined portion, whereby the thickness of the folded portion may be smaller than the thickness of the planar portion, and an embossed or scored uneven pattern may be formed at the folded portion of the glass substrate or at both the planar portion and the folded portion of the glass substrate.

The thickness of the planar portion of the glass substrate may be 10 μm to 300 μm, and the thickness of the folded portion of the glass substrate may be 5 μm to 100 μm.

The adhesive buffer layer may include an optically transparent resin (OCR).

The thickness of the protective film layer may be 1 μm to 100 μm.

The elastic buffer layer may include an optically transparent resin (OCR).

Drawings

FIGS. 1A to 2H are schematic views of a flexible cover window according to the present invention; and

Fig. 3 to 12L are partial schematic views of flexible cover windows in which various types of glass according to embodiments of the present invention are applied.

Detailed Description

Hereinafter, the present invention will be described with reference to fig. 1A to 12L.

In the present invention, the folding area of the display is an area of the display in which the display is folded in half or an area of the display in which the display is bent or curled. Further, in the present invention, a folding area of the cover window corresponding to a folding area of the display is referred to as a "folded portion" of the cover window, and a planar area of the cover window other than the folded portion is referred to as a "planar portion" of the cover window.

In the present invention, a flat glass substrate means a glass substrate such as: which is configured such that no embossed or scored uneven pattern described herein, i.e., a glass substrate having a smooth surface, is formed on the glass surface.

In the present invention, the front surface means a surface facing upward in the drawing. In the present invention, the rear surface means a surface opposite to the front surface, the rear surface being an opposite surface to the touch, i.e., a surface in a direction toward the display panel, the rear surface being a surface facing downward in the drawing.

1. Flat structure

The present invention provides a glass-based flexible cover window having improved strength and surface hardness, the glass-based flexible cover window including a planar portion formed to correspond to a planar area of a flexible display and a folded portion formed to be connected to the planar portion, the folded portion being formed to correspond to a folded area of the flexible display, wherein the flexible cover window includes a flat glass substrate 100, an adhesive buffer layer 200 formed on a front surface of the glass substrate 100, a protective film layer 300 formed on the adhesive buffer layer 200, and a hard coat layer 400 formed on the protective film layer 300, and the adhesive buffer layer 200 and the protective film layer 300 are alternately stacked at least n times, wherein n is a natural number equal to or greater than 1.

In the flexible cover window according to the present invention, the adhesive buffer layer 200 and the protective film layer 300 connected to the adhesive buffer layer 200 are formed at least once, and the hard coat layer 400 is formed at the uppermost end. Accordingly, the inherent aesthetic feeling and touch feeling of glass are maintained, and high pen drop (pen drop) characteristics and puncture characteristics are exhibited, whereby excellent strength and surface hardness can be provided.

Further, the flexible cover window according to the present invention may be formed in a thin film shape using the flat glass substrate 100 and the predetermined protective film layer 300, whereby excellent strength and surface hardness may be provided while satisfying folding characteristics.

1.1. Planar structure/one-time stacking

Fig. 1A to 1D are schematic views of flexible cover windows, each of which includes a flat glass substrate 100 and is configured such that an adhesive buffer layer 200 and a protective film layer 300 are alternately stacked once.

1.1.1. The flat structure/primary stack/flat portion and the folded portion have the same thickness

The flexible cover window according to one embodiment shown in fig. 1A is flat and configured such that the flat portion and the folded portion have the same thickness.

No embossed or scored uneven pattern is formed on the glass substrate 100, whereby the surface of the glass substrate is smooth and flat.

At the glass substrate 100, the thickness of the planar portion and the thickness of the folded portion may be equal to each other.

No embossed or scored uneven pattern is formed on the glass substrate 100, whereby the surface of the glass substrate is smooth and flat, and the thickness of the flat portion and the thickness of the folded portion may be equal to each other.

The thickness of the glass substrate 100, i.e., the thickness of each of the planar portion and the folded portion, may be 10 μm to 300 μm. If the thickness is less than 10 μm, strength and manufacturing workability may be reduced, which is undesirable. If the thickness exceeds 300 μm, folding characteristics may be lowered, which is also undesirable. Specifically, the thickness of the glass substrate 100 may be 20 μm to 200 μm.

The flexible cover window shown in fig. 1A is configured to have a structure in which a glass substrate 100, an adhesive buffer layer 200, a protective film layer 300, and a hard coat layer 400 are sequentially stacked.

An adhesive buffer layer 200 is formed at the front surface of the glass substrate 100, whereby the glass substrate 100 and the protective film layer 300 are adhered to each other. While maintaining an appropriate thickness and elasticity by the adhesive buffer layer 200, deformation at the folded portion is minimized, whereby impact resistance and durability can be improved.

The adhesive buffer layer 200 may include a transparent resin, such as an optically transparent resin (OCR), having a refractive index approximately equal to that of glass in which the adhesive buffer layer is applied. Examples of transparent resins may include, but are not limited to, acrylics, epoxies, silicones, urethanes, urethane composites, urethane-acrylic composites, hybrid sol-gels, and silicones.

The thickness of the adhesive buffer layer 200 may be appropriately adjusted in the range of 1 μm to 50 μm according to the composition and thickness of the protective film layer 300. When bonding is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the adhesive buffer layer 200, whereby impact resistance and durability can be improved.

The adhesive buffer layer 200 may have a strength of 0.01GPa to 1GPa in order to minimize deformation at an interface after an impact such as a pen down while improving surface hardness and adhesion to the glass substrate 100, thereby improving overall durability.

The protective film 300 is formed on the adhesive buffer layer 200, and the thickness or physical properties of the protective film can be adjusted, whereby scratches on the cover window can be prevented, and at the same time, impact resistance, strength, and folding properties can be improved.

The protective film 300 is not limited as long as the protective film is made of a transparent rigid resin. For example, the protective film layer 300 may be made of at least one selected from the group consisting of polyethylene terephthalate (PET), transparent Polyimide (TPI), polyurethane (PU), polypropylene (PP), polyethylene naphthalate (PEN), and Polycarbonate (PC). In particular, the protective film layer 300 may be made of PET or TPI having excellent transparency and flexibility. More specifically, the protective film layer 300 may be made of TPI having excellent heat resistance, chemical resistance and durability, whereby the inherent beauty of glass may be maintained and an appropriate thickness to ensure strength while minimizing loosening or buckling problems that leave marks in a folded region after repeated folding. In particular, when used simultaneously with the hard coat layer 400, the surface hardness of TPI is about 5H to 6H, which will be described below, and thus TPI may also have excellent surface hardness characteristics compared to PET having a surface hardness of 3H to 4H.

The strength of the protective film 300 at the planar portion and the strength of the protective film 300 at the folded portion may be equal to or different from each other.

The thickness of the protective film 300 may be 1 μm to 100 μm. Within the above thickness range, surface hardness of 3H to 6H can be ensured while maintaining the texture and touch inherent to glass, whereby strength can be increased while being thin, and folding characteristics can also be satisfied. If the thickness exceeds 100 μm, which exceeds the above range, the thickness of the cover window increases, and thus the intended effect of the present invention may not be obtained, which is undesirable. If the thickness is less than 1 μm, the workability may be lowered, and the desired impact resistance may not be obtained, which is also undesirable. Specifically, the thickness of the protective film layer 300 may be 1 μm to 50 μm, more specifically 10 μm to 50 μm.

The hard coat layer 400 is formed on the protective film 300 so that impact force (e.g., a pen-down) is received and dispersed, thereby contributing to improved impact resistance to the pen-down and puncture, improved folding characteristics, and increased strength and surface hardness.

The hard coat layer (H/C) 400 may be formed by applying, for example, an acrylic resin, an epoxy resin, or a silicone resin that exhibits a relatively high hardness when hardened. The hard coat layer 400 may be endowed with an anti-fingerprint (AF) or anti-reflection (AR) function as needed. For example, an anti-fingerprint (AF) or anti-reflection (AR) function may be achieved by synthesizing a resin having such a function or by forming various patterns.

The thickness of the hard coating layer 400 may be 1 μm to 30 μm. If the thickness of the hard coat layer 400 is less than 1 μm, deviating from the above range, it is difficult to achieve impact force bearing and dispersing effects, which is undesirable. If the thickness of the hard coat layer 400 exceeds 30 μm, the thickness of the cover window increases, and it is difficult to achieve the effect as a thin plate, which is also undesirable.

Referring to fig. 1B showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100 so as to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

The elastic buffer 500 may include a transparent resin such as an optically transparent resin (OCR) having a refractive index approximately equal to that of glass in which the elastic buffer is applied. Examples of transparent resins may include, but are not limited to, acrylics, epoxies, silicones, urethanes, urethane composites, urethane-acrylic composites, hybrid sol-gels, and silicones.

The elastic buffer layer 500 may have a strength of 0.01GPa to 1GPa in order to minimize deformation at an interface after an impact such as a pen down while improving surface hardness and adhesion to the glass substrate 100, thereby improving overall durability.

The thickness of the elastic buffer layer 500 may be appropriately adjusted in a range of 1 μm to 50 μm according to the composition and thickness of the elastic buffer layer 500. When bonding is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the elastic buffer layer 500, whereby impact resistance and durability can be improved.

However, when the uneven pattern is not formed on the rear surface of the glass substrate or when the inclined portion is not formed on the rear surface of the glass substrate, it is preferable that the elastic buffer layer 500 is not formed on the rear surface of the glass substrate so that the glass substrate is formed in a thin film shape to improve the folding characteristics thereof.

1.1.2. The planar structure/primary stack/planar portion and the folded portion have different thicknesses

The flexible cover window according to one embodiment shown in fig. 1C is flat and configured such that an inclined portion is positioned on the rear surface, whereby the flat portion and the folded portion have different thicknesses.

At least one surface of the folded portion of the glass substrate 100 includes an inclined portion, whereby the thickness of the folded portion may be smaller than that of the planar portion.

No embossed or scored uneven pattern is formed on the glass substrate 100, whereby the surface of the glass substrate is smooth and flat, and at least one surface of the folded portion of the glass substrate 100 includes an inclined portion, whereby the thickness of the folded portion may be smaller than that of the planar portion.

The shape of the inclined portion formed at the folded portion of the glass substrate 100 is not limited as long as the inclined portion is formed to be recessed in the thickness direction from the outer surface of the folded portion. For example, the inclined portion may have a shape extending in a straight line or a curved line such that the thickness of the folded portion increases from the middle planar portion of the glass toward the edge portion of the glass. However, in a broad sense, the shape of the inclined portion may also include a shape in which a middle plane portion of the glass and an edge portion of the glass extend perpendicularly to each other.

In connection with this, the inclined portion of the glass shown in fig. 1C is a forward-direction inclined portion, in which the inclined portion is formed at the rear surface so as to have a shape extending in a straight line such that the thickness of the folded portion increases from the middle plane portion in a direction toward the edge portion.

The inclined portion formed at the folded portion of the glass substrate 100 may be positioned at the rear surface, the front surface, or both. Specifically, when the inclined portion is formed at the rear surface of the glass substrate 100, the inclined portion may be a forward-type inclined portion. When the inclined portion is formed at the front surface of the glass substrate 100, the inclined portion may be a reverse-type inclined portion, which is a reverse of the forward-type inclined portion. When the inclined parts are formed at the front and rear surfaces of the glass substrate 100, the inclined parts may be double-sided inclined parts.

The depth h ₂ of the inclined portion formed at the folded portion of the glass substrate 100 may be appropriately selected according to the thickness h ₁ of the glass substrate 100. For example, in the forward-type inclined portion or the reverse-type inclined portion, the depth of the inclined portion may be 5% to 70%, specifically 10% to 50%, more specifically 15% to 40% of the thickness of the glass (i.e., the thickness of the planar portion). In the double-sided inclined portion, the depth of the inclined portion may be 5% to 35% of the thickness of the glass (i.e., the thickness of the planar portion), specifically 10% to 30%.

If the depth of the inclined portion formed at the folded portion is too large, and the thickness of the folded portion is too small from the above range, in this case, the folding performance is good, but the strength may be lowered, and wrinkles may be easily generated, which is undesirable. If the depth of the inclined portion is too small, the thickness of the folded portion is too large, in which case the flexibility, resilience, and elasticity are reduced upon folding, resulting in poor folding performance, which is also undesirable.

In the reverse-type inclined portion in which the inclined portion is formed at the front surface of the glass substrate 100, the adhesive buffer layer 200 is formed thicker at the folded portion, thereby causing impact absorption, as compared with in the forward-type inclined portion in which the inclined portion is formed at the rear surface of the glass substrate 100, whereby the pen-down characteristics and impact resistance may be excellent.

In the double-sided type inclined portion in which inclined portions are formed at the front and rear surfaces of the glass substrate 100, the depth of the inclined portion at the front surface (the depth of the front portion) and the depth of the inclined portion at the rear surface (the depth of the rear portion) may be equal to or different from each other. Specifically, in the double-sided type inclined portion, the depth of the front portion may be equal to the depth of the rear portion, the depth of the front portion may be greater than the depth of the rear portion, or the depth of the front portion may be less than the depth of the rear portion.

At the glass substrate 100, the thickness of the folded portion may be 5 μm to 100 μm, and the thickness of the planar portion may be 10 μm to 300 μm. If the thickness of the folded portion is less than 5 μm or the thickness of the planar portion is less than 10 μm, strength and manufacturing workability may be lowered, which is not desirable. If the thickness of the folded portion exceeds 100 μm or the thickness of the planar portion exceeds 300 μm, folding characteristics may be degraded, which is also undesirable. Specifically, the thickness of the folded portion may be 10 μm to 80 μm, and the thickness of the planar portion may be 50 μm to 200 μm.

The glass substrate 100 may be made of chemically tempered glass.

The flexible cover window shown in fig. 1C is configured to have a structure in which a glass substrate 100, an adhesive buffer layer 200, a protective film layer 300, and a hard coat layer 400 are sequentially stacked. The adhesive buffer layer 200, the protective film layer 300, and the hard coat layer 400 may have the same shape as previously described.

Referring to fig. 1D showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100 so as to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

When the uneven pattern is formed at the rear surface of the glass substrate or when the inclined part is formed at the rear surface of the glass substrate, the elastic buffer layer 500 is preferably formed on the rear surface of the glass substrate to improve impact resistance and durability and to protect the uneven pattern and the inclined part.

The elastic buffer 500 may have the same shape as previously described.

1.2. Planar structure/(n+1) times stack

Fig. 1E and 1F are schematic views of flexible cover windows, each of which includes a flat glass substrate 100 and is configured such that an adhesive buffer layer 200 and a protective film layer 300 are alternately stacked twice.

The flexible cover window according to the present invention is configured such that the adhesive buffer layer 200 and the protective film layer 300 are alternately stacked at least n+1 times, where n is a natural number equal to or greater than 1, thereby improving rigidity against falling down and puncture while maintaining inherent aesthetic feeling and tactile sensation of glass, and thus excellent strength and surface hardness can be ensured.

1.2.1. The planar structure/(n+1) times stack/planar portion and the folded portion have the same thickness

The flexible cover window according to one embodiment shown in fig. 1E is flat and configured such that the flat portion and the folded portion have the same thickness.

The thickness of the glass substrate 100 (i.e., the thickness of each of the planar portion and the folded portion) may be 10 μm to 300 μm. If the thickness is less than 10 μm, strength and manufacturing workability may be reduced, which is undesirable. If the thickness exceeds 300 μm, folding characteristics may be lowered, which is also undesirable. Specifically, the thickness of the glass substrate 100 may be 20 μm to 200 μm.

An adhesive buffer layer 200 is formed on the front surface of the glass substrate 100, whereby the glass substrate 100 and the protective film layer 300 are adhered to each other. While maintaining an appropriate thickness and elasticity by the adhesive buffer layer 200, deformation at the folded portion is minimized, whereby impact resistance and durability can be improved.

The flexible cover window shown in fig. 1E is configured to have a structure in which a glass substrate 100, a first adhesive buffer layer 200, a first protective film layer 300, a second adhesive buffer layer 210, a second protective film layer 310, and a hard coat layer 400 are sequentially stacked.

When the adhesive buffer layer and the protective film layer are alternately stacked at least n+1 times in the stacking direction, the compositions of the n-th adhesive buffer layer and the (n+1) -th adhesive buffer layer may be the same or different from each other, and the compositions of the n-th protective film layer and the (n+1) -th protective film layer may be the same or different from each other, where n is a natural number equal to or greater than 1. By adjusting the composition of the alternately stacked layers, folding characteristics can be ensured while achieving appropriate strength.

Each of the first adhesive buffer layer 200 and the second adhesive buffer layer 210 may include a transparent resin, such as an optically transparent resin (OCR), having a refractive index approximately equal to that of glass in which the respective adhesive buffer layers are applied. Examples of transparent resins may include, but are not limited to, acrylics, epoxies, silicones, urethanes, urethane composites, urethane-acrylic composites, hybrid sol-gels, and silicones.

In one embodiment, the first adhesive buffer layer 200 may be made of OCR, and the second adhesive buffer layer 210 may be made of OCR.

The first protective film 300 or the second protective film 310 is not limited as long as the protective film is made of a transparent rigid resin. For example, the first protective film layer 300 or the second protective film layer 310 may be made of at least one selected from the group consisting of polyethylene terephthalate (PET), transparent Polyimide (TPI), polyurethane (PU), polypropylene (PP), polyethylene naphthalate (PEN), and Polycarbonate (PC). In particular, the first protective film layer 300 or the second protective film layer 310 may be made of PET or TPI having excellent transparency and flexibility. More specifically, the first protective film 300 or the second protective film 310 may be made of TPI having excellent heat resistance, chemical resistance, and durability, whereby the inherent beauty of glass may be maintained and an appropriate thickness to ensure strength while minimizing loosening or buckling problems that leave marks at a folding region after repeated folding. In particular, when used simultaneously with the hard coat layer 400, the TPI has a surface hardness of about 5H to 6H, which will be described below, and thus the TPI may also have excellent surface hardness characteristics compared to PET having a surface hardness of 3H to 4H.

In one embodiment, the first protective film layer 300 may be made of PET, and the second protective film layer 310 may be made of PET. In another embodiment, the first protective film layer 300 may be made of PET, and the second protective film layer 310 may be made of TPI. In yet another embodiment, the first protective film layer 310 may be made of TPI, and the second protective film layer 320 may be made of TPI. However, if the first protective film layer is made of TPI and the second protective film layer is made of PET, that is, if a different type of protective film layer is used and TPI is formed in the window, the modulus difference between TPI and PET increases, whereby the degree of stretching or deformation increases with external conditions, resulting in a loss of strength, which is undesirable.

When the adhesive buffer layer 200 and the protective film layer 300 are alternately stacked at least n+1 times in the stacking direction, the thickness of the n-th adhesive buffer layer 200 may be smaller than the thickness of the (n+1) -th adhesive buffer layer 210, and the thickness of the n-th protective film layer 300 may be smaller than the thickness of the (n+1) -th protective film layer 310, where n is a natural number equal to or greater than 1. The folding characteristics can be ensured by adjusting the thickness of the alternately stacked layers while achieving appropriate strength.

The thickness of the first adhesive buffer layer 200 or the second adhesive buffer layer 210 may be appropriately adjusted in the range of 1 μm to 50 μm according to the composition and thickness of the protective film layer. When bonding is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the adhesive buffer layer, whereby impact resistance and durability can be improved.

In one embodiment, the thickness of the first adhesive buffer layer 200 may be less than the thickness of the second adhesive buffer layer 210 within the above-described thickness range.

The thickness of the first protective film 300 or the second protective film 310 may be 1 μm to 100 μm. Within the above thickness range, the surface hardness of 3H to 6H can be ensured while maintaining the inherent texture and feel of the glass, whereby strength can be increased while being thin, and folding characteristics can also be satisfied. If the thickness exceeds 100 μm, which exceeds the above range, the thickness of the cover window increases, and thus the intended effect of the present invention may not be obtained, which is undesirable. If the thickness is less than 1 μm, the workability may be lowered, and the desired impact resistance may not be obtained, which is also undesirable. Specifically, the thickness of the first protective film 300 or the second protective film 310 may be 1 μm to 50 μm, more specifically 10 μm to 50 μm.

In one embodiment, the thickness of the first protective film 300 may be less than the thickness of the second protective film 310 within the above-described thickness range.

The hard coating layer 400 is formed on the second protective film layer 310 such that impact force such as a pen is supported and dispersed, thereby contributing to improved impact resistance against the pen and puncture, improved folding characteristics, and increased strength and surface hardness.

The hard coat layer (H/C) 400 may be formed by applying, for example, an acrylic resin, an epoxy resin, or a silicone resin that exhibits a relatively high hardness upon hardening. The hard coat layer 400 may be endowed with an anti-fingerprint (AF) or anti-reflection (AR) function as needed. For example, an anti-fingerprint (AF) or anti-reflection (AR) function may be achieved by synthesizing a resin having such a function or by forming various patterns at a functional layer.

The thickness of the hard coating layer 400 may be 1 μm to 30 μm. If the thickness of the hard coat layer 400 is less than 1 μm, deviating from the above range, it is difficult to achieve impact force supporting and dispersing effects, which is undesirable. If the thickness of the hard coat layer 400 exceeds 30 μm, the thickness of the cover window increases, and it is difficult to achieve the effect as a thin plate, which is also undesirable.

Referring to fig. 1F showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

The elastic buffer 500 may include a transparent resin such as an optically transparent resin (OCR) having a refractive index approximately equal to that of glass to which the elastic buffer is applied. Examples of transparent resins may include, but are not limited to, acrylics, epoxies, silicones, urethanes, urethane composites, urethane-acrylic composites, hybrid sol-gels, and silicones.

The elastic buffer layer 500 may have a strength of 0.01GPa to 1GPa in order to minimize deformation at an interface after an impact such as a pen down while increasing surface hardness and adhesion to the glass substrate 100, thereby improving overall durability.

The thickness of the elastic buffer layer 500 may be appropriately adjusted in the range of 1 μm to 50 μm according to the composition and thickness of the elastic buffer layer 500. When bonding is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the elastic buffer layer 500, whereby impact resistance and durability can be improved.

However, when the uneven pattern is not formed at the rear surface of the glass substrate, or when the inclined portion is not formed at the rear surface of the glass substrate, it is preferable that the elastic buffer layer 500 is not formed on the rear surface of the glass substrate so that the glass substrate is formed in a thin film shape to improve the folding characteristics thereof.

1.2.2. The planar structure/(n+1) times stack/planar portion and the folded portion have different thicknesses

The flexible cover window according to one embodiment shown in fig. 1G is flat and configured such that the inclined portion is located at the rear surface, whereby the flat portion and the folded portion have different thicknesses.

No embossed or scored uneven pattern is formed on the glass substrate 100, whereby the surface of the glass substrate is smooth and flat, and at least one surface of the folded portion includes an inclined portion, whereby the thickness of the folded portion may be less than the thickness of the planar portion.

The shape of the inclined portion formed at the folded portion of the glass substrate 100 is not limited as long as the inclined portion is formed so as to be recessed in the thickness direction from the outer surface of the folded portion. For example, the inclined portion may have a shape extending along a straight line or a curved line such that the thickness of the folded portion increases from the middle planar portion of the glass toward the edge portion of the glass. However, in a broad sense, the shape of the inclined portion may also include a shape in which a middle plane portion of the glass and an edge portion of the glass extend perpendicularly to each other.

In this connection, the inclined portion of the glass shown in fig. 1G extends along a straight line such that the thickness of the folded portion increases from the middle plane portion in a direction toward the edge portion.

The inclined portion formed at the folded portion of the glass substrate 100 may be located at the rear surface, the front surface, or both surfaces. Specifically, when the inclined portion is formed at the rear surface of the glass substrate 100, the inclined portion may be a forward-type inclined portion. When the inclined portion is formed at the front surface of the glass substrate 100, the inclined portion may be a reverse-type inclined portion, which is a reverse of the forward-type inclined portion. When the inclined parts are formed at the front and rear surfaces of the glass substrate 100, the inclined parts may be double-sided inclined parts.

If the depth of the inclined portion formed at the folded portion is too large, deviating from the above range, the thickness of the folded portion is too small, in which case the folding performance is good, but the strength may be lowered, and wrinkles may be easily generated, which is undesirable. If the depth of the inclined portion is too small, the thickness of the folded portion is too large, in which case flexibility, resilience, and elasticity are reduced at the time of folding, resulting in poor folding performance, which is also undesirable.

In the reverse-type inclined portion in which the inclined portion is formed at the front surface of the glass substrate 100, the adhesive buffer layer 200 is formed thicker at the folded portion to cause impact absorption, as compared with in the forward-type inclined portion in which the inclined portion is formed at the rear surface of the glass substrate 100, whereby the pen-down property and impact resistance may be excellent.

The glass substrate 100 may be made of chemically tempered glass.

The flexible cover window shown in fig. 1G is configured to have a structure in which a glass substrate 100, a first adhesive buffer layer 200, a first protective film layer 300, a second adhesive buffer layer 210, a second protective film layer 310, and a hard coat layer 400 are sequentially stacked. The first adhesive buffer layer 200, the first protective film layer 300, the second adhesive buffer layer 210, the second protective film layer 310, and the hard coat layer 400 may have the same shape as previously described.

The adhesive buffer layer 200 is formed on the front surface of the glass substrate 100, whereby the glass substrate 100 and the protective film layer 300 are adhered to each other. The deformation at the folded portion is minimized while maintaining the proper thickness and elasticity by the adhesive buffer layer 200, whereby impact resistance and durability can be improved.

Referring to fig. 1H showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100 to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

The elastic buffer 500 may have the same shape as previously described.

When the uneven pattern is formed at the rear surface of the glass substrate, or when the inclined portion is formed at the rear surface of the glass substrate, it is preferable to form the elastic buffer layer 500 on the rear surface of the glass substrate to improve impact resistance and durability and to protect the uneven pattern and the inclined portion.

2. Uneven structure

Meanwhile, the present invention provides a glass-based flexible cover window having improved strength and surface hardness, the flexible cover window including a planar portion formed to correspond to a planar area of a flexible display and a folded portion formed to be connected to the planar portion, the folded portion being formed to correspond to a folded area of the flexible display, wherein the flexible cover window includes a glass substrate 100 having an embossed or scored uneven pattern formed thereon, an adhesive buffer layer 200 formed at a front surface of the glass substrate 100, a protective film layer 300 formed on the adhesive buffer layer 200, and a hard coating layer 400 formed on the protective film layer 300, and the adhesive buffer layer 200 and the protective film layer 300 are alternately stacked at least n times, wherein n is a natural number equal to or greater than 1.

In the flexible cover window according to the present invention, the adhesive buffer layer 200 and the protective film layer 300 connected to the adhesive buffer layer 200 are formed at least once, and the hard coating layer 400 is formed at the uppermost end. Accordingly, the inherent aesthetic feeling and touch feeling of glass are maintained, and high pen-down characteristics and puncture characteristics are exhibited, whereby excellent strength and surface hardness can be provided.

Further, the flexible cover window according to the present invention may be formed in a film shape using a predetermined protective film layer 300, whereby excellent strength and surface hardness may be provided while satisfying folding characteristics.

Further, in the flexible cover window according to the present invention, the glass substrate 100 having the embossed or scored uneven pattern formed thereon is used, the rigidity against drop is increased, and thus excellent strength and surface hardness can be provided while satisfying the folding characteristics. Since the impact is effectively dispersed or absorbed by the uneven pattern, impact resistance is improved and screen deformation or resolution degradation is minimized, whereby a high quality flexible cover window can be provided.

2.1. Uneven structure/one-time stacking

Fig. 2A to 2D are schematic views of flexible cover windows, each of which includes a glass substrate 100 having an embossed uneven pattern formed thereon, and is configured such that an adhesive buffer layer 200 and a protective film layer 300 are alternately stacked once.

2.1.1. Uneven structure/primary stack/planar portion and folded portion having the same thickness

The flexible cover window according to one embodiment shown in fig. 2A is configured such that the embossed uneven pattern is located at the front surface of the folded portion of the glass substrate 100, and such that the planar portion and the folded portion have the same thickness.

An embossed uneven pattern or a scribed uneven pattern may be formed at the glass substrate 100, and may be formed using a dry etching process or a wet etching process. The etching process may use methods known in the art to which the present invention pertains. For example, an embossed or scored uneven pattern may be formed at the glass substrate 100 by a method comprising: a first step of forming a resist layer on the glass substrate 100; a second step of patterning the resist layer to form a resist pattern layer for forming an embossed or scored uneven pattern on the glass substrate 100; a third step of forming an embossed or scored uneven pattern using the resist pattern layer as a mask; and a fourth step of removing the resist pattern layer. Subsequently, the glass substrate 100 having the embossed or scored uneven pattern formed thereon may be strengthened as the case may be.

The shape of the embossed or scored uneven pattern formed at the glass substrate 100 is not limited, but may have a side surface perpendicular or inclined to a direction toward the front surface or the rear surface of the glass substrate 100, and may be a regular continuous pattern or an irregular pattern vertically and horizontally arranged at the glass substrate 100.

The horizontal sectional shape of the embossed or scored uneven pattern may be at least one of a polygonal shape, an elliptical shape, and a circular shape, or a combination thereof, and the embossed or scored uneven pattern may be formed in a grid arrangement pattern or a cross arrangement pattern to improve folding characteristics and uniformly disperse impact force.

The height h ₃ of the embossed or scored uneven pattern may be 1% to 50%, specifically 10% to 30%, of the thickness h ₁ of the glass substrate 100. If the height is less than the above range, the impact force dispersing effect is not remarkable, which is not desirable. If the height is greater than the above range, the overall strength may be lowered, which is also undesirable.

The width W ₁ of the embossed or scored uneven pattern may be 20 μm to 2000 μm, and the interval W ₂ of the uneven pattern may be 30 μm to 4000 μm. If the width of the uneven pattern is greater than the above range, folding characteristics may be degraded, and if the width of the uneven pattern is less than the above range, pen down characteristics may be degraded, which is undesirable. If the interval of the uneven patterns is greater than the above range, the pen-down characteristics may be degraded, and if the interval of the uneven patterns is less than the above range, the folding characteristics may be degraded, which is also undesirable. In particular, the width of the embossed or scored uneven pattern may be 100 μm to 1000 μm, and the interval of the uneven pattern may be 100 μm to 2000 μm.

The planar portion and the folded portion of the glass substrate 100 may have the same thickness, and the embossed or scored uneven pattern may be formed on the front surface, the rear surface, or both surfaces of the glass substrate 100.

In general, the back side of the glass substrate 100 (i.e., the side opposite to the side on which the impact is applied) is more susceptible to the impact of a pen down. Accordingly, when the uneven pattern is formed at the rear surface of the glass substrate 100, the impact may be more effectively dispersed or absorbed by the uneven pattern, compared to when the uneven pattern is formed at the front surface of the glass substrate 100, whereby the impact resistance may be improved.

When uneven patterns are formed on both surfaces of the glass substrate 100, impact force is mainly absorbed by the uneven patterns formed on the front surface, and impact force transmitted into the glass substrate 100 is absorbed by the uneven patterns formed on the rear surface, whereby impact resistance can be further improved.

When the uneven patterns are formed on both surfaces of the glass substrate 100, the intervals, the heights, etc. of the uneven patterns formed at the front and rear surfaces may be equal to or different from each other according to specifications, uses, etc. of the product.

The planar portion and the folded portion of the glass substrate 100 may have the same thickness, and the embossed or scored uneven pattern may be formed at the folded portion of the glass substrate 100 or at both the planar portion and the folded portion of the glass substrate 100.

When the uneven pattern is formed at the planar portion and the folded portion of the glass substrate 100, the impact is effectively distributed or absorbed by the uneven pattern over a larger area, compared to when the uneven pattern is formed only at the folded portion of the glass substrate 100, whereby the impact resistance can be improved.

The planar portion and the folded portion of the glass substrate 100 may have the same thickness, the embossed or scored uneven pattern may be formed at the front surface, the rear surface, or both surfaces of the glass substrate 100, and the embossed or scored uneven pattern may be formed at the folded portion of the glass substrate 100 or at both the planar portion and the folded portion of the glass substrate 100.

The flexible cover window shown in fig. 2A is configured to have a structure in which a glass substrate 100, an adhesive buffer layer 200, a protective film layer 300, and a hard coat layer 400 are sequentially stacked.

The adhesive buffer layer 200 may include a transparent resin, such as an optically transparent resin (OCR), having a refractive index approximately equal to that of glass to which the adhesive buffer layer is applied. Examples of transparent resins may include, but are not limited to, acrylics, epoxies, silicones, urethanes, urethane composites, urethane-acrylic composites, hybrid sol-gels, and silicones.

The thickness of the adhesive buffer layer 200 may be appropriately adjusted in the range of 1 μm to 50 μm according to the composition and thickness of the protective film layer 300. When the adhesion is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the adhesive buffer layer 200, whereby impact resistance and durability can be improved.

The adhesive buffer layer 200 may have a strength of 0.01GPa to 1GPa to minimize deformation at the interface upon impact (e.g., a pen down) while increasing surface hardness and adhesion to the glass substrate 100 to improve overall durability.

The protective film 300 is formed on the adhesive buffer layer 200, and the thickness or physical properties of the protective film can be adjusted, whereby scratches on the cover window can be prevented, and impact resistance, strength, and folding properties can be simultaneously improved.

The protective film 300 is not limited as long as the protective film is made of a transparent rigid resin. For example, the protective film layer 300 may be made of at least one selected from the group consisting of polyethylene terephthalate (PET), transparent Polyimide (TPI), polyurethane (PU), polypropylene (PP), polyethylene naphthalate (PEN), and Polycarbonate (PC). In particular, the protective film layer 300 may be made of PET or TPI having excellent transparency and flexibility. More specifically, the protective film layer 300 may be made of TPI having excellent heat resistance, chemical resistance and durability, whereby the inherent aesthetic feeling of glass may be maintained and an appropriate thickness to ensure strength while minimizing loosening or buckling problems that leave marks at the folded region after repeated folding. In particular, the TPI has a surface hardness of about 5H to 6H when used simultaneously with the hard coating 400, which will be described below, and thus may also have excellent surface hardness characteristics compared to PET having a surface hardness of 3H to 4H.

The strength of the protective film 300 at the planar portion and the strength of the protective film 300 at the folded portion may be the same or different from each other.

The thickness of the protective film 300 may be 1 μm to 100 μm. Within the above thickness range, surface hardness of 3H to 6H can be ensured while maintaining the texture and touch inherent to glass, whereby strength can be increased while being thin, and folding characteristics can also be satisfied. If the thickness exceeds 100 μm (which exceeds the above range), the thickness of the cover window increases, and thus the intended effect of the present invention may not be obtained, which is undesirable. If the thickness is less than 1 μm, the workability may be lowered, and the desired impact resistance may not be obtained, which is also undesirable. Specifically, the thickness of the protective film layer 300 may be 1 μm to 50 μm, more specifically 10 μm to 50 μm.

The hard coat layer 400 is formed on the protective film layer 300 such that impact force (e.g., a pen down) is supported and dispersed, thereby contributing to improved impact resistance to pen down and puncture, improved folding characteristics, and increased strength and surface hardness.

The hard coat layer (H/C) 400 may be formed by applying, for example, an acrylic resin, an epoxy resin, or a silicone resin that exhibits a relatively high hardness upon hardening. The hard coat layer 400 may be endowed with an anti-fingerprint (AF) or anti-reflection (AR) function as needed. For example, an anti-fingerprint (AF) or anti-reflection (AR) function may be achieved by synthesizing a resin having such a function or by forming various patterns on a functional layer.

The thickness of the hard coating layer 400 may be 1 μm to 30 μm. If the thickness of the hard coat layer 400 is less than 1 μm (which deviates from the above range), it is difficult to achieve the impact force supporting and dispersing effect, which is undesirable. If the thickness of the hard coating 400 exceeds 30 μm, the thickness of the cover window increases and it is difficult to achieve the effect as a thin plate, which is also undesirable.

Referring to fig. 2B showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

The elastic buffer 500 may include a transparent resin, such as an optically transparent resin (OCR), having a refractive index approximately equal to that of glass to which the elastic buffer is applied. Examples of transparent resins may include, but are not limited to, acrylics, epoxies, silicones, urethanes, urethane composites, urethane-acrylic composites, hybrid sol-gels, and silicones.

The elastic buffer layer 500 may have a strength of 0.01GPa to 1GPa to minimize deformation at the interface upon impact (e.g., a pen down) while increasing surface hardness and adhesion to the glass substrate 100 to improve overall durability.

The thickness of the elastic buffer layer 500 may be appropriately adjusted in the range of 1 μm to 50 μm according to the composition and thickness of the elastic buffer layer 500. When the adhesion is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the elastic buffer layer 500, whereby impact resistance and durability can be improved.

2.1.2. Uneven structure/primary stack/planar portion and folded portion having different thickness

The flexible cover window according to one embodiment shown in fig. 2C is configured such that an embossed uneven pattern is formed at the front surface of the folded portion of the glass substrate 100 and such that the inclined portion is located at the rear surface, whereby the planar portion and the folded portion have different thicknesses.

The embossed uneven pattern or the scribed uneven pattern may be formed on the glass substrate 100, and may be formed using a dry etching process or a wet etching process. The etching process may use methods known in the art to which the present invention pertains. For example, an embossed or scored uneven pattern may be formed at the glass substrate 100 by a method comprising the steps of: a first step of forming a resist layer on a glass substrate 100; a second step of patterning the resist layer to form a resist pattern layer for forming an embossed or scored uneven pattern on the glass substrate 100; a third step of forming an embossed or scored uneven pattern using the resist pattern layer as a mask; and a fourth step of removing the resist pattern layer. Subsequently, the glass substrate 100 having the embossed or scored uneven pattern formed thereon may be strengthened as the case may be.

The horizontal sectional shape of the embossed or scored uneven pattern may be at least one of a polygonal shape, an elliptical shape, and a circular shape, or a combination thereof, and the embossed or scored uneven pattern may be formed in a mesh arrangement or a cross arrangement pattern to improve folding characteristics and uniformly disperse impact force.

The width W ₁ of the embossed or scored uneven pattern may be 20 μm to 2000 μm, and the interval W ₂ of the uneven pattern may be 30 μm to 4000 μm. If the width of the uneven pattern is greater than the above range, folding characteristics may be degraded, whereas if the width of the uneven pattern is less than the above range, pen-down characteristics may be degraded, which is undesirable. If the interval of the uneven patterns is greater than the above range, the pen-down characteristic may be degraded, whereas if the interval of the uneven patterns is less than the above range, the folding characteristic may be degraded, which is also undesirable. In particular, the width of the embossed or scored uneven pattern may be 100 μm to 1000 μm, and the interval of the uneven pattern may be 100 μm to 2000 μm.

The shape of the embossed or scored uneven pattern formed at the glass substrate 100 is not limited, but may have a side surface perpendicular or inclined to a direction toward the front surface or the rear surface of the glass substrate 100, and may be a regular continuous pattern or an irregular pattern vertically and horizontally arranged on the glass substrate 100.

The shape of the inclined portion formed at the folded portion of the glass substrate 100 is not limited as long as the inclined portion is formed to be recessed from the outer surface of the folded portion in the thickness direction. For example, the inclined portion may have a shape extending along a straight line or a curved line such that the thickness of the folded portion increases from the middle planar portion of the glass toward the edge portion of the glass. However, in a broad sense, the shape of the inclined portion may also include a shape in which a middle plane portion of the glass and an edge portion of the glass extend perpendicularly to each other.

In this connection, the inclined portion of the glass shown in fig. 2C extends in a straight line such that the thickness of the folded portion increases from the middle plane portion in a direction toward the edge portion.

The inclined portion formed at the folded portion of the glass substrate 100 may be located at the rear surface, the front surface, or both surfaces. Specifically, when the inclined portion is formed at the rear surface of the glass substrate 100, the inclined portion may be a forward-type inclined portion. When the inclined portion is formed at the front surface of the glass substrate 100, the inclined portion may be a reverse inclined portion, which is a reverse of the forward inclined portion. When the inclined parts are formed at the front and rear surfaces of the glass substrate 100, the inclined parts may be double-sided inclined parts.

If the depth of the inclined portion formed at the folded portion is too large (which deviates from the above range), the thickness of the folded portion is too small, in which case the folding performance is good, but the strength may be lowered, and wrinkles may be easily generated, which is undesirable. If the depth of the inclined portion is too small, the thickness of the folded portion is too large, in which case flexibility, resilience, and elasticity are reduced upon folding, resulting in poor folding performance, which is also undesirable.

In the reverse type inclined portion in which the inclined portion is formed at the front surface of the glass substrate 100, the adhesive buffer layer 200 is formed thicker at the folded portion than in the forward type inclined portion in which the inclined portion is formed at the rear surface of the glass substrate 100 to cause impact absorption, whereby the pen-down characteristic and impact resistance may be excellent.

In the double-sided inclined portion in which the inclined portion is formed at the front surface and the rear surface of the glass substrate 100, the depth of the inclined portion at the front surface (depth of the front portion) and the depth of the inclined portion at the rear surface (depth of the rear portion) may be the same as or different from each other. Specifically, in the double-sided type inclined portion, the depth of the front portion may be equal to the depth of the rear portion, the depth of the front portion may be greater than the depth of the rear portion, or the depth of the front portion may be less than the depth of the rear portion.

At least one surface of the folded portion of the glass substrate 100 includes an inclined portion, whereby the thickness of the folded portion may be smaller than that of the planar portion, and an embossed or scored uneven pattern may be formed on the front surface, the rear surface, or both surfaces of the glass substrate 100.

In general, the back side (i.e., the side opposite to the side to which the impact is applied) of the glass substrate 100 is more susceptible to the impact of the pen down. Accordingly, when the uneven pattern is formed on the rear surface of the glass substrate 100, the impact can be more effectively dispersed or absorbed by the uneven pattern than when the uneven pattern is formed on the front surface of the glass substrate 100, whereby the impact resistance can be improved.

When the uneven patterns are formed on both surfaces of the glass substrate 100, the intervals, the heights, etc. of the uneven patterns formed on the front and rear surfaces may be the same or different from each other according to specifications, uses, etc. of the product.

At least one surface of the folded portion of the glass substrate 100 includes an inclined portion, whereby the thickness of the folded portion may be smaller than the thickness of the planar portion, and an embossed or scored uneven pattern may be formed at the folded portion of the glass substrate 100 or at both the planar portion and the folded portion of the glass substrate 100.

When the uneven pattern is formed at the planar portion and the folded portion of the glass substrate 100, the impact is effectively distributed or absorbed over a larger area by the uneven pattern, compared to when the uneven pattern is formed only at the folded portion of the glass substrate 100, whereby the impact resistance can be improved.

At least one surface of the folded portion of the glass substrate 100 includes an inclined portion, whereby the thickness of the folded portion may be smaller than the thickness of the planar portion, an embossed or scored uneven pattern may be formed at the front surface, the rear surface, or both surfaces of the glass substrate 100, and an embossed or scored uneven pattern may be formed at the folded portion of the glass substrate 100 or at both the planar portion and the folded portion of the glass substrate 100.

The glass substrate 100 may be made of chemically tempered glass.

The flexible cover window shown in fig. 2C is configured to have a structure in which the glass substrate 100, the adhesive buffer layer 200, the protective film layer 300, and the hard coat layer 400 are sequentially stacked. The adhesive buffer layer 200, the protective film layer 300, and the hard coat layer 400 may have the same shape as previously described.

Referring to fig. 2D showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

The elastic buffer 500 may have the same shape as previously described.

When the uneven pattern is formed on the rear surface of the glass substrate or when the inclined portion is formed on the rear surface of the glass substrate, it is preferable to form the elastic buffer layer 500 on the rear surface of the glass substrate to improve impact resistance and durability and to protect the uneven pattern and the inclined portion.

2.2. Uneven structure/(n+1) times stacking

Fig. 2E and 2F are schematic views of flexible cover windows, each including a glass substrate 100 having an uneven pattern of embossments formed thereon and configured such that an adhesive buffer layer and a protective film layer are alternately stacked twice.

The flexible cover window according to the present invention is configured such that the adhesive buffer layer and the protective film layer are alternately stacked at least n+1 times, where n is a natural number equal to or greater than 1, thereby increasing rigidity against pen down and puncture while maintaining the inherent aesthetic feeling and touch feeling of glass, and thus excellent strength and surface hardness can be ensured.

In general, as the number of composite layers making up the flexible cover window increases, the elongation must be higher and the modulus must be lower. Elongation is the ratio of the maximum length that the glass can be stretched until the glass is damaged when an external force is applied to the glass, and modulus is the elastic modulus indicating the degree of deformation of the glass when an external force is applied to the glass. High modulus means that the glass resists deformation strongly, and low modulus means that the glass is easily deformed.

In the flexible cover window according to the present invention, the specific adhesive buffer layer and the specific protective film layer are alternately stacked at least n+1 times, where n is a natural number equal to or greater than 1. Thus, even if many composite layers are provided, the elongation may be high and the modulus may be low.

2.2.1. Uneven structure/(n+1) times stacking/planar portion and folded portion have the same thickness

The flexible cover window according to one embodiment shown in fig. 2E includes a glass substrate 100 having an embossed uneven pattern formed thereon and configured such that a planar portion and a folded portion have the same thickness or different thicknesses, and has a structure in which a first adhesive buffer layer 200, a first protective film layer 300, a second adhesive buffer layer 210, a second protective film layer 310, and a hard coat layer 400 are sequentially stacked.

The flexible cover window according to the embodiment shown in fig. 2E is configured such that the embossed uneven pattern is located at the front surface of the folded portion of the glass substrate 100 and such that the planar portion and the folded portion have the same thickness.

The embossed uneven pattern or the scribed uneven pattern may be formed at the glass substrate 100, and may be formed using a dry etching process or a wet etching process. The etching process may use methods known in the art to which the present invention pertains. For example, an embossed or scored uneven pattern may be formed at the glass substrate 100 by a method comprising the steps of: a first step of forming a resist layer on a glass substrate 100; a second step of patterning the resist layer to form a resist pattern layer for forming an embossed or scored uneven pattern on the glass substrate 100; a third step of forming an embossed or scored uneven pattern using the resist pattern layer as a mask; and a fourth step of removing the resist pattern layer. Subsequently, the glass substrate 100 having the embossed or scored uneven pattern formed thereon may be strengthened as the case may be.

The width W ₁ of the embossed or scored uneven pattern may be 20 μm to 2000 μm, and the interval W ₂ of the uneven pattern may be 30 μm to 4000 μm. If the width of the uneven pattern is greater than the above range, folding characteristics may be degraded, whereas if the width of the uneven pattern is less than the above range, pen-down characteristics may be degraded, which is undesirable. If the interval of the uneven patterns is greater than the above range, the pen-down characteristics may be degraded, whereas if the interval of the uneven patterns is less than the above range, the folding characteristics may be degraded, which is also undesirable. In particular, the width of the embossed or scored uneven pattern may be 100 μm to 1000 μm, and the interval of the uneven pattern may be 100 μm to 2000 μm.

The flexible cover window shown in fig. 2E is configured to have a structure in which the glass substrate 100, the first adhesive buffer layer 200, the first protective film layer 300, the second adhesive buffer layer 210, the second protective film layer 310, and the hard coat layer 400 are sequentially stacked.

When the adhesive buffer layer and the protective film layer are alternately stacked at least n+1 times in the stacking direction, the compositions of the n-th adhesive buffer layer and the (n+1) -th adhesive buffer layer may be the same or different from each other, and the compositions of the n-th protective film layer and the (n+1) -th protective film layer may be the same or different from each other, where n is a natural number equal to or greater than 1. The folding characteristics can be ensured while achieving appropriate strength by adjusting the composition of the alternately stacked layers.

Each of the first adhesive buffer layer 200 and the second adhesive buffer layer 210 may include a transparent resin, such as an optically transparent resin (OCR), having a refractive index approximately equal to that of glass to which the respective adhesive buffer layer is applied. Examples of transparent resins may include, but are not limited to, acrylics, epoxies, silicones, urethanes, urethane composites, urethane-acrylic composites, hybrid sol-gels, and silicones.

The first protective film 300 or the second protective film 310 is not limited as long as the protective film is made of a transparent rigid resin. For example, the first protective film layer 300 or the second protective film layer 310 may be made of at least one selected from the group consisting of polyethylene terephthalate (PET), transparent Polyimide (TPI), polyurethane (PU), polypropylene (PP), polyethylene naphthalate (PEN), and Polycarbonate (PC). In particular, the first protective film layer 300 or the second protective film layer 310 may be made of PET or TPI having excellent transparency and flexibility. More specifically, the first protective film layer 300 or the second protective film layer 310 may be made of TPI having excellent heat resistance, chemical resistance, and durability, thereby maintaining inherent beauty of glass and having an appropriate thickness to secure strength while minimizing loosening or buckling problems that leave marks at a folding region after repeated folding. In particular, the TPI has a surface hardness of about 5H to 6H when used simultaneously with the hard coating 400, which will be described below, and thus may also have excellent surface hardness characteristics compared to PET having a surface hardness of 3H to 4H.

In one embodiment, the first protective film layer 300 may be made of PET, and the second protective film layer 310 may be made of PET. In another embodiment, the first protective film layer 300 may be made of PET, and the second protective film layer 310 may be made of TPI. In further embodiments, the first protective film layer 310 may be made of TPI, and the second protective film layer 320 may be made of TPI. However, if the first protective film layer is made of TPI and the second protective film layer is made of PET, that is, if a different type of protective film layer is used and TPI is formed inside the window, the difference in modulus between TPI and PET increases, whereby the degree of stretching or deformation increases according to external conditions, resulting in a loss of strength, which is undesirable.

When the adhesive buffer layer 200 and the protective film layer 300 are alternately stacked at least n+1 times in the stacking direction, the thickness of the n-th adhesive buffer layer 200 may be smaller than the thickness of the (n+1) -th adhesive buffer layer 210, and the thickness of the n-th protective film layer 300 may be smaller than the thickness of the (n+1) -th protective film layer 310, where n is a natural number equal to or greater than 1. The folding characteristics can be ensured while achieving appropriate strength by adjusting the thickness of the alternately stacked layers.

The thickness of the first adhesive buffer layer 200 or the second adhesive buffer layer 210 may be appropriately adjusted in the range of 1 μm to 50 μm according to the composition and thickness of the protective film layer. When the adhesion is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the adhesive buffer layer, whereby impact resistance and durability can be improved.

In one embodiment, within the above thickness ranges, the thickness of the first adhesive buffer layer 200 may be less than the thickness of the second adhesive buffer layer 210.

The thickness of the first protective film 300 or the second protective film 310 may be 1 μm to 100 μm. Within the above thickness range, surface hardness of 3H to 6H can be ensured while maintaining the texture and touch inherent to glass, whereby strength can be increased while being thin, and folding characteristics can also be satisfied. If the thickness exceeds 100 μm (which exceeds the above range), the thickness of the cover window increases, and thus the intended effect of the present invention may not be obtained, which is undesirable. If the thickness is less than 1 μm, the workability may be lowered, and the desired impact resistance may not be obtained, which is also undesirable. Specifically, the thickness of the first protective film 300 or the second protective film 310 may be 1 μm to 50 μm, more specifically 10 μm to 50 μm.

In one embodiment, within the above thickness range, the thickness of the first protective film 300 may be smaller than the thickness of the second protective film 310.

The hard coating layer 400 is formed on the second protective film layer 310 such that impact force such as a pen drop is supported and dispersed, thereby contributing to improved impact resistance to pen drop and puncture, improved folding characteristics, and increased strength and surface hardness.

The hard coat layer (H/C) 400 may be formed by applying, for example, an acrylic resin, an epoxy resin, or a silicone resin that exhibits a relatively high hardness upon hardening. The hard coat layer 400 may be endowed with an anti-fingerprint (AF) or anti-reflection (AR) function, as needed. For example, an anti-fingerprint (AF) or anti-reflection (AR) function may be achieved by synthesizing a resin having such a function or by forming various patterns at a functional layer.

The thickness of the hard coating layer 400 may be 1 μm to 30 μm. If the thickness of the hard coat layer 400 is less than 1 μm (which deviates from the above range), it is difficult to achieve impact force supporting and dispersing effects, which is undesirable. If the thickness of the hard coating 400 exceeds 30 μm, the thickness of the cover window increases and it is difficult to achieve the effect as a thin plate, which is also undesirable.

Referring to fig. 2F showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

The thickness of the elastic buffer layer 500 may be appropriately adjusted in the range of 1 μm to 50 μm according to the composition and thickness of the elastic buffer layer 500. When adhesion is performed within the above range, deformation at the folded portion is minimized while maintaining an appropriate thickness and elasticity by the elastic buffer layer 500, whereby impact resistance and durability can be improved.

2.2.2. Uneven structure/(n+1) times stacking/planar portion and folded portion have different thicknesses

The flexible cover window according to one embodiment shown in fig. 2G is configured such that the embossed uneven pattern is located at the front surface of the folded portion of the glass substrate 100 and the inclined portion is located at the rear surface, whereby the planar portion and the folded portion have different thicknesses.

The width W ₁ of the embossed or scored uneven pattern may be 20 μm to 2000 μm, and the interval W ₂ of the uneven pattern may be 30 μm to 4000 μm. If the width of the uneven pattern is greater than the above range, folding characteristics may be degraded, whereas if the width of the uneven pattern is less than the above range, pen-down characteristics may be degraded, which is undesirable. If the interval of the uneven patterns is greater than the above range, the pen-down characteristics may be degraded, whereas if the interval of the uneven patterns is less than the above range, the folding characteristics may be degraded, which is also undesirable. In particular, the width of the embossed or scored uneven pattern may be 100 μm to 1000 μm and the spacing of the uneven pattern may be 100 μm to 2000 μm

The shape of the inclined portion formed at the folded portion of the glass substrate 100 is not limited as long as the inclined portion is formed to be recessed from the outer surface of the folded portion in the thickness direction. For example, the inclined portion may have a shape extending along a straight line or a curved line such that the thickness of the folded portion increases from the middle plane portion of the glass toward the edge portion of the glass. However, in a broad sense, the shape of the inclined portion may also include a shape in which a middle plane portion of the glass and an edge portion of the glass extend perpendicularly to each other.

In connection with this, the inclined portion of the glass shown in fig. 2G extends along a straight line such that the thickness of the folded portion increases from the middle plane portion in a direction toward the edge portion.

If the depth of the inclined portion formed at the folded portion is too large (which deviates from the above range), the thickness of the folded portion is too small, in which case the folding performance is good, but the strength may be lowered, and wrinkles may be easily generated, which is undesirable. If the depth of the inclined portion is too small, the thickness of the folded portion is too large, in which case the flexibility, resilience, and elasticity are reduced upon folding, resulting in poor folding performance, which is also undesirable.

In the double-sided inclined portion in which the inclined portion is formed at the front surface and the rear surface of the glass substrate 100, the depth of the inclined portion at the front surface (the depth of the front portion) and the depth of the inclined portion at the rear surface (the depth of the rear portion) may be equal to or different from each other. Specifically, in the double-sided type inclined portion, the depth of the front portion may be equal to the depth of the rear portion, the depth of the front portion may be greater than the depth of the rear portion, or the depth of the front portion may be less than the depth of the rear portion.

When the uneven patterns are formed on both surfaces of the glass substrate 100, the intervals, the heights, etc. of the uneven patterns formed on the front and rear surfaces may be equal to or different from each other according to specifications, uses, etc. of the product.

When the uneven pattern is formed at the planar portion and the folded portion of the glass substrate 100, the impact is effectively dispersed or absorbed over a larger area by the uneven pattern, compared to when the uneven pattern is formed only at the folded portion of the glass substrate 100, whereby the impact resistance can be improved.

The glass substrate 100 may be made of chemically tempered glass.

The flexible cover window shown in fig. 2G is configured to have a structure in which the glass substrate 100, the first adhesive buffer layer 200, the first protective film layer 300, the second adhesive buffer layer 210, the second protective film layer 310, and the hard coat layer 400 are sequentially stacked. The first adhesive buffer layer 200, the first protective film layer 300, the second adhesive buffer layer 210, the second protective film layer 310, and the hard coat layer 400 may have the same shape as previously described.

The adhesive buffer layer 200 is formed on the front surface of the glass substrate 100, whereby the glass substrate 100 and the protective film layer 300 are adhered to each other. The deformation of the folded portion is minimized while maintaining the proper thickness and elasticity by the adhesive buffer layer 200, whereby impact resistance and durability can be improved.

Referring to fig. 2H showing an embodiment, according to circumstances, an elastic buffer layer 500 may be optionally formed on the rear surface of the glass substrate 100 to minimize deformation at the folded portion while maintaining an appropriate thickness and elasticity, whereby impact resistance and durability may be improved.

The elastic buffer 500 may have the same shape as previously described.

When the uneven pattern is formed on the rear surface of the glass substrate or when the inclined portion is formed on the rear surface of the glass substrate, it is preferable to form the elastic buffer layer 500 on the rear surface of the glass substrate to improve impact resistance and durability and protect the uneven pattern and the inclined portion.

Tables 1 to 4 below show the configuration of a flexible cover window according to one embodiment of the present invention. The configurations of flexible cover windows including glass described in the following embodiments may be applied to type I to type IV flexible cover windows.

TABLE 1

Type(s)	Elastic buffer layer	Glass thickness	Adhesive buffer layer	Protective film layer	Hard coat layer
						I	OCR	30 Μm or 50 μm	OCR	PET or TPI	H/C

TABLE 2

Type(s)	Elastic buffer layer	Glass thickness	Adhesive buffer layer	Protective film layer	Hard coat layer
						II	Without any means for	30 Μm or 50 μm	OCR	PET or TPI	H/C

TABLE 3

(Excluding the case where the nth protective film layer is made of TPI and the (n+1) th protective film layer is made of PET.)

TABLE 4

< Example >

The following table shows an embodiment of a glass substrate applied to a flexible cover window according to the present invention, and fig. 3 to 12L are partial schematic views of a flexible cover window to which a glass substrate according to an embodiment of the present invention is applied.

In the embodiment shown in fig. 3 to 12L, three points (see the circular portion of fig. 3) located at the upper side indicate that the adhesive buffer layer 200 and the protective film layer 300 may be alternately stacked at least n times. In one embodiment, the adhesive buffer layer and the protective film layer may be alternately stacked once or twice, as shown in fig. 3. The number of stacking times is written at the end of the embodiment number. For example, examples 1-1-1 means that the adhesive buffer layer and the protective film layer are alternately stacked once, and examples 1-1-2 means that the adhesive buffer layer and the protective film layer are alternately stacked twice.

In the embodiment shown in fig. 3 to 12L, a hard coat layer (not shown in fig. 3 to 12L) is located at the uppermost end of each flexible cover window in which an adhesive buffer layer and a protective film layer are alternately stacked once or twice.

In the embodiment shown in fig. 3 to 12L, an elastic buffer layer may be optionally formed on the rear surface of the glass substrate. In one example, for a glass substrate having an uneven pattern formed at a rear surface thereof or an inclined portion formed at a rear surface thereof, it is preferable to form an elastic buffer layer on the rear surface of the glass substrate to improve impact resistance and durability and to protect the uneven pattern and the inclined portion. In another example, for a glass substrate having no uneven pattern formed at its rear surface or no inclined portion formed at its rear surface, it is preferable that an elastic buffer layer is not formed on the rear surface of the glass substrate so that the glass substrate is formed in a film shape to improve its folding characteristics.

TABLE 5

TABLE 6

TABLE 7

TABLE 8

TABLE 9

Experimental example 1 ]

The conditions of the flexible cover windows according to comparative example 1, examples 1-1-1 and examples 1-1-2 are shown in table 10, and the pen-down characteristics and the puncture characteristics of the flexible cover windows were measured. The measured pen down and puncture characteristics of the flexible cover window are shown in table 11. The pen-down characteristic was measured by dropping a pen having a weight of 13g and a tip size of 0.5mm, and the puncture characteristic was measured by dropping a pen having a tip size of 0.5mm at a dropping speed of 0.5 mm/min.

TABLE 10

TABLE 11

In table 10, comparative example 1 has a configuration including only glass, and examples 1-1-1 have a configuration in which an adhesive buffer layer and a protective film layer are alternately stacked once and a hard coat layer is formed at the uppermost end, as shown in fig. 3. Examples 1-1-2 have a configuration in which an adhesive buffer layer and a protective film layer are alternately stacked twice and a hard coat layer is formed at the uppermost end, as shown in fig. 3.

According to table 11, the pen-down test and the puncture test are experiments for evaluating durability, strength, surface hardness, and the like of glass, and it can be seen that the flexible cover window according to examples 1-1-2, in which the protective film layers are stacked twice, can resist impact when the pen is dropped from a height of at least 15cm, and is not damaged before a force of at least 3kgf is applied thereto, thereby exhibiting excellent strength and surface hardness.

Experimental example 2

Meanwhile, the conditions of the flexible cover windows according to comparative example 2, example 2-11-2 and example 2-12-2 are shown in table 12, and the pen-down characteristics and puncture characteristics of the flexible cover windows were measured. The measured pen down and puncture characteristics of the flexible cover window are shown in table 12. The pen-down characteristic was measured by dropping a pen having a weight of 13g and a tip size of 0.5mm, and the puncture characteristic was measured by dropping a pen having a tip size of 0.5mm at a dropping speed of 0.5 mm/min.

TABLE 12

TABLE 13

In table 12, comparative example 2 has a configuration including glass and an elastic buffer layer formed on the rear surface of the glass. Examples 2-11-2 have a configuration in which an adhesive buffer layer and a protective film layer were alternately stacked twice and a hard coat layer was formed at the uppermost end, as shown in fig. 6I. Examples 2-12-2 have a configuration in which an adhesive buffer layer and a protective film layer were alternately stacked twice and a hard coat layer was formed at the uppermost end, as shown in fig. 6D.

In table 12, the glass thickness is expressed as 150/50 μm, which means that in the glass configured such that the thickness of the planar portion and the thickness of the folded portion are different from each other, the thickness of the planar portion is 150 μm, and the thickness of the folded portion on which the uneven structure is formed is 50 μm.

The shape, height, width and interval of the uneven patterns formed at the glass substrate shown in table 12 may be selected from the foregoing.

The shape and depth of the inclined portion formed at the folded portion of the glass substrate shown in table 12 may be selected from the foregoing.

From table 13, it can be seen that the flexible cover window according to example 2-12-2 can resist impact when the pen is dropped from a height of at least 30cm and is not damaged before a force of at least 10kgf is applied thereto, thereby exhibiting excellent strength and surface hardness.

As is apparent from the above description, the flexible cover window according to the present invention is configured such that the adhesive buffer layer and the protective film layer joined with the adhesive buffer layer are formed at least once and the hard coat layer is formed at the uppermost end. Accordingly, the inherent aesthetic feeling and touch feeling of the glass are maintained, and high pen-down characteristics and puncture characteristics are exhibited, whereby excellent strength and surface hardness can be provided.

Further, the flexible cover window according to the present invention may be formed in a film shape using a predetermined protective film layer, whereby excellent strength and surface hardness may be provided while satisfying folding characteristics.

Further, in the flexible cover window according to the present invention, a glass substrate having a predetermined shape is used to disperse impact force, thereby improving impact resistance and increasing rigidity against a pen-down, and thus excellent strength and surface hardness can be provided while satisfying folding characteristics.

Claims

1. A glass-based flexible cover window having improved strength and surface hardness, comprising a planar portion formed to correspond to a planar area of a flexible display and a folded portion formed to connect to the planar portion, the folded portion formed to correspond to a folded area of the flexible display, wherein the flexible cover window comprises:

A flat glass substrate;

An adhesive buffer layer formed at a front surface of the glass substrate;

a protective film layer formed on the adhesive buffer layer; and

A hard coat layer formed on the protective film layer, and

The adhesive buffer layer and the protective film layer are alternately stacked at least n times, where n is a natural number equal to or greater than 1.

2. A glass-based flexible cover window having improved strength and surface hardness, comprising a planar portion formed to correspond to a planar area of a flexible display and a folded portion formed to connect to the planar portion, the folded portion formed to correspond to a folded area of the flexible display, wherein the flexible cover window comprises:

a glass substrate having an uneven pattern formed with embossments or scores;

An adhesive buffer layer formed at a front surface of the glass substrate;

a protective film layer formed on the adhesive buffer layer; and

A hard coat layer formed on the protective film layer, and

3. The flexible cover window according to claim 1 or 2, wherein the planar portion and the folded portion of the glass substrate have the same thickness.

4. The flexible cover window of claim 2, wherein

The planar portion and the folded portion of the glass substrate have the same thickness, and

The embossed or scored uneven pattern is formed at the front surface, rear surface, or both surfaces of the glass substrate.

5. The flexible cover window of claim 2, wherein

The embossed or scored uneven pattern is formed at the folded portion of the glass substrate or at both the planar portion and the folded portion of the glass substrate.

6. The flexible cover window according to claim 1 or 2, wherein at least one surface of the fold of the glass substrate comprises a bevel, whereby the thickness of the fold is less than the thickness of the planar portion.

7. The flexible cover window of claim 6, wherein the inclined portion of the fold is any one of:

a forward-type inclined portion configured such that the inclined portion is formed at a rear surface of the glass substrate;

a reverse-type inclined portion configured such that the inclined portion is formed at the front surface of the glass substrate, the reverse-type inclined portion being an inverse of the forward-type inclined portion; and

A double-sided inclined portion configured such that the inclined portion is formed at the front surface and the rear surface of the glass substrate.

8. The flexible covering window according to claim 7, wherein the double-sided inclined portion is configured such that a depth of the inclined portion formed at the front surface and a depth of the inclined portion formed at the rear surface are equal to or different from each other.

9. The flexible cover window of claim 2, wherein

At least one surface of the folded portion of the glass substrate includes an inclined portion, whereby a thickness of the folded portion is smaller than a thickness of the planar portion, and

10. The flexible cover window of claim 2, wherein

11. The flexible cover window of claim 2, wherein

The planar portion of the glass substrate has a thickness of 10 μm to 300 μm, and

The thickness of the folded portion of the glass substrate is 5 μm to 100 μm.

12. The flexible cover window of claim 1 or 2, wherein the adhesive buffer layer comprises Optically Clear Resin (OCR).

13. The flexible cover window of claim 1 or 2, wherein the protective film layer comprises at least one selected from the group consisting of: polyethylene terephthalate (PET), transparent Polyimide (TPI), polyurethane (PU), polypropylene (PP), polyethylene naphthalate (PEN), and Polycarbonate (PC).

14. The flexible cover window according to claim 1 or 2, wherein the strength of the protective film layer at the planar portion and the strength of the protective film layer at the folded portion are equal to or different from each other.

15. The flexible cover window according to claim 1 or 2, wherein the protective film layer has a thickness of 1 μιη to 100 μιη.

16. The flexible cover window according to claim 1 or 2, wherein the flexible cover window is configured such that an elastic buffer layer is optionally formed on the rear surface of the glass substrate.

17. The flexible cover window of claim 16, wherein the elastic buffer layer comprises optically transparent resin (OCR).

18. The flexible cover window according to claim 1 or 2, wherein

When the adhesive buffer layer and the protective film layer are alternately stacked at least n +1 times in the stacking direction,

The n-th adhesive buffer layer and the (n+1) -th adhesive buffer layer have the same or different compositions from each other, and

The n-th protective film layer and the (n+1) -th protective film layer have the same or different compositions from each other, where n is a natural number equal to or greater than 1.

19. The flexible cover window according to claim 1 or 2, wherein

The thickness of the nth adhesive buffer layer is smaller than the thickness of the (n+1) th adhesive buffer layer, and

The thickness of the nth protective film layer is smaller than that of the (n+1) th protective film layer, wherein n is a natural number equal to or greater than 1.