Flexible cover window with improved strength

Abstract

A flexible cover window with improved strength is disclosed. The flexible cover window includes a planar portion formed to correspond to the planar area of ​​a flexible display and a folded portion formed to connect to the planar portion, the folded portion being formed to correspond to the folded area of ​​the flexible display. The flexible cover window includes a glass substrate and a polyimide (PI) coating formed on the glass substrate. The PI coating is formed on the glass substrate by direct coating, thereby reducing the overall thickness of the flexible cover window while maintaining the inherent texture of the glass, thereby improving the aesthetics of the flexible cover window.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from Korean Patent Application No. 10-2021-0102768 filed on August 4, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a flexible cover window, and more particularly to a flexible cover window with improved strength, wherein the flexible cover window with improved strength is configured so that the strength characteristics of the flexible cover window are improved and the inherent texture of the glass is maintained while the overall thickness of the flexible cover window is reduced, thereby improving the aesthetics of the flexible cover window. Background Art

[0004] Description of Related Technology

[0005] Recently, with the rapid development of electrical and electronic technologies and the increase in new demands of the times and various needs of consumers, various types of display products have been manufactured, among which research on flexible displays that can be folded and unfolded has been actively conducted.

[0006] Initially, research on folding flexible displays was conducted, and now research on rolling and stretching flexible displays is underway. Not only the display panel but also the flexible cover window configured to protect the display panel must be flexible.

[0007] Such a flexible cover window must be substantially flexible and must be free of wrinkles at its folded areas after repeated folding and must not suffer from image distortion.

[0008] For a conventional cover window for a flexible display, a polymer film, such as a PI film or a PET film, is attached to the surface of a display panel.

[0009] However, due to the low mechanical strength of polymer films, polymer films are only used to prevent scratches on display panels. In addition, polymer films have low impact resistance and low transmittance. In addition, polymer films are relatively expensive.

[0010] As the number of folding times of the display increases, the folded region of the polymer film wrinkles, thereby damaging the folded region of the polymer film. For example, the polymer film is squeezed or torn during folding limit evaluation (typically 200,000 times).

[0011] In recent years, various studies on glass-based cover windows have been conducted to overcome the limitations of polymer film cover windows.

[0012] Such a glass-based cover window requires basic physical properties. For example, image distortion must not occur, and the glass-based cover window must be strong enough to withstand repeated contact and specific pressure of a stylus pen, while also satisfying folding characteristics.

[0013] To meet the strength requirements of flexible cover windows, the glass must have a specific thickness or greater. On the other hand, to meet the folding requirements of flexible cover windows, the glass must have a specific thickness or less. Therefore, research is needed to find the optimal thickness and structure for flexible cover windows that meet both strength and folding requirements while preventing image distortion.

[0014] Furthermore, in the case where the glass has a certain thickness or less, the inherent quality of the strengthened glass deteriorates, which must also be considered.

[0015] Therefore, there is a need for a technology capable of providing a flexible cover window having an appropriate thickness required to ensure strength and satisfying folding characteristics while maintaining the inherent aesthetics of tempered glass. Summary of the Invention

[0016] The present invention has been made in view of the above problems, and an object of the present invention is to provide a flexible cover window configured such that a PI coating is formed on a glass substrate, thereby improving the strength of the flexible cover window.

[0017] According to the present invention, the above and other objects can be achieved by providing a glass-based flexible cover window with improved strength, wherein the glass-based flexible cover window with improved strength includes 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 and a polyimide (PI) coating formed on the glass substrate.

[0018] The PI coating layer may be formed on one surface or opposite surfaces of the glass substrate. In addition, the PI coating layer may have a thickness of 1 μm to 50 μm.

[0019] In addition, the PI coating layer may be formed by coating the glass substrate with a coating solution including 100 parts by weight of polyimide (PI) and 2 to 10 parts by weight of a primer.

[0020] In addition, the PI coating layer may be formed on the front surface, the back surface, and the side surfaces of the glass substrate to wrap the glass substrate.

[0021] In addition, the PI coating layer may be formed on the glass substrate by coating, and then UV curing may be performed. The PI coating layer may be formed on the glass substrate by any one of bar coating, slot die coating, and dip coating.

[0022] The flexible cover window may further include a functional layer formed on the PI coating layer formed on the front surface of the glass substrate.

[0023] The flexible cover window may further include a buffer layer formed between the rear surface of the glass substrate and the display panel.

[0024] Furthermore, the PI coating layer may be made of a material configured such that the PI coating layer has the same strength or different strengths at the planar portion and the folded portion.

[0025] Meanwhile, the glass substrate may be integrally formed, may be formed such that the folded portion is thinner than the planar portion, or may be formed such that the folded portion is divided into two or more sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0027] Figures 1 to 6 are schematic diagrams showing various embodiments of flexible cover windows with improved strength according to the present invention. DETAILED DESCRIPTION

[0028] The present invention relates to a flexible cover window, and more particularly to a flexible cover window configured such that a PI coating is formed on a glass substrate, thereby improving surface hardness, pen drop characteristics, and folding characteristics of the flexible cover window.

[0029] Furthermore, in the flexible cover window according to the present invention, the PI coating is formed on the glass substrate by direct coating, thereby reducing the overall thickness of the flexible cover window while maintaining the inherent texture of the glass and thus improving the aesthetics of the flexible cover window.

[0030] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Figures 1 to 6 are schematic diagrams showing various embodiments of flexible cover windows with improved strength according to the present invention.

[0031] As shown, the flexible cover window with improved strength according to the present invention is a glass-based flexible cover window, which includes 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 and a PI coating 200 formed on the glass substrate 100.

[0032] In the present invention, the front surface refers to the surface that can be touched by the user, the surface that the touch pen contacts, and the upper surface in the figure. In addition, in the present invention, the back surface (which is the surface opposite to the front surface) refers to the surface opposite to the touched surface, that is, the surface facing in the direction toward the display panel, and the lower surface in the figure.

[0033] In the present invention, the folding area of ​​the display is the area of ​​the display where the display is folded into two parts or the area of ​​the display where the display is bent or rolled. In addition, in the present invention, the folding area of ​​the flexible cover window corresponding to the folding area of ​​the display is referred to as the "folding portion" of the flexible cover window, and the plane area of ​​the flexible cover window other than the folding portion is referred to as the "plane portion" of the flexible cover window.

[0034] Particularly, the flexible cover window according to the present invention is a glass-based flexible cover window, and uses a chemically strengthened glass substrate 100 .

[0035] The glass substrate 100 according to the present invention may be completely flat (the thicknesses of the folded portion and the flat portion are equal to each other), or the folded portion may be divided into two or more pieces, whereby the glass substrate 100 may have a two-segment structure or a three-segment structure.

[0036] Furthermore, the folded portion can be formed to have a smaller thickness than the planar portion, that is, the folded portion can be formed to be thinner than the planar portion. Generally speaking, the thickness of the planar portion of the flexible cover window is 30μm to 300μm, and the thickness of the folded portion of the flexible cover window is approximately 10μm to 100μm. In other words, a very thin sheet of glass is processed to form the folded portion. The folded portion can be formed to have a uniform thickness, or it can be formed to have a thickness that gradually increases from the center to the edge of the folded area. In other words, the folded portion can be formed in a straight line or a curved line.

[0037] Furthermore, in order to improve the strength characteristics and folding characteristics of the glass substrate 100 , etching patterns may be formed in both the folded portion and the flat portion or only in the folded portion.

[0038] The flexible cover window according to the present invention is formed over the entire surface of the flexible display panel to protect the flexible display panel. Alternatively, the flexible cover window can also be provided on a clear polyimide (CPI) cover to protect the CPI cover.

[0039] As one embodiment of the present invention, Figure 1 As shown in , the flexible cover window with improved strength according to the present invention includes a glass substrate 100 and a polyimide (PI) coating layer 200 formed on a front surface of the glass substrate 100 , wherein a functional layer 300 is formed on the PI coating layer 200 .

[0040] The PI coating 200 can be formed on one or both surfaces of the glass substrate 100. As a result, the surface hardness of the flexible cover window is improved, the folding properties of the flexible cover window are improved, and impact forces applied to the flexible cover window are evenly dispersed. In particular, impact forces such as those caused by a falling pen are dispersed or absorbed.

[0041] In general, when a glass material is used to manufacture a flexible cover window, the thickness of the glass substrate 100 must be small. However, in order to ensure strength characteristics, the glass substrate 100 must have a certain thickness or more.

[0042] For example, if the curvature radius when folded must meet a minimum of 0.5 mm, the thickness of the flexible cover window can be 200 μm or less, preferably 20 μm to 100 μm. As the thickness of the flexible cover window decreases, the strength of the flexible cover window also decreases. In particular, if an object with a small cross-sectional area collides with the upper surface (front surface) of the glass substrate 100, that is, when a pen is dropped, the entire glass substrate 100 may be deformed or damaged around the portion where the pen contacts the glass substrate 100.

[0043] In particular, flexible cover windows with thinned folded areas have a very low thickness, resulting in very weak pen-drop resistance. Furthermore, the thickness difference between the folded area and each flat area creates a stress difference, which can cause ripples in the glass substrate 100. Consequently, the flexible cover window has very low impact resistance.

[0044] In the present invention, the PI coating layer 200 is completely formed on one surface or opposite surfaces of the glass substrate 100 to improve impact resistance by improving pen-drop resistance at the folded portion and to improve folding characteristics while improving the overall strength of the glass substrate 100 .

[0045] In particular, the thickness or physical properties of the PI coating layer 200 are adjusted, and the PI coating layer 200 is formed by directly coating on the glass substrate 100 to disperse or absorb impact force without performing troublesome works such as a mask process or an etching process, so that a specific pattern or folding portion is formed on the glass substrate 100 to improve strength characteristics and folding characteristics as in the conventional art, and thus process simplification is achieved.

[0046] The PI coating layer 200 is formed on the glass substrate 100 by any one of bar coating, slot die coating, and dip coating, and is UV-cured after coating.

[0047] In one embodiment of the present invention, a coating solution containing PI is applied to the glass substrate 100 and UV-cured at 200° C. to 300° C. for about one hour to form the PI coating layer 200 .

[0048] The PI coating 200 according to the present invention is formed by coating a glass substrate 100 with a coating solution containing 100 parts by weight of polyimide (PI) and 2 to 10 parts by weight of a primer. That is, a solvent-free coating solution is used to prevent the glass substrate 100 from being stained or the thickness uniformity of the glass substrate 100 from deteriorating during hardening.

[0049] A silane coupling agent that improves coupling in an undiluted PI solution is used as a primer. For example, a silane coupling agent having a reactive group such as ethoxy, methoxy, dialkoxy, or trialkoxy can be used.

[0050] In order to increase the adhesion to the glass substrate 100, as described above, PI is mixed with a primer, and the mixture is applied to the glass substrate 100 by direct coating and hardened to form the PI coating layer 200. Therefore, the close contact between the PI coating layer 200 and the glass substrate 100 is excellent, thereby minimizing the deformation of the flexible cover window at its interface even due to an impact such as a falling pen, while improving the overall durability of the flexible cover window.

[0051] Generally, when a flexible cover window is subjected to an impact, such as a pen drop, the impact transmitted vertically is stronger than the impact transmitted horizontally. The PI coating 200 according to the present invention is formed over the entire surface of the glass substrate 100. Therefore, it can effectively disperse or absorb the vertical impact and support the glass substrate 100, thereby significantly improving the pen drop resistance characteristics.

[0052] In conventional flexible cover windows, a separate protective film is applied to the glass substrate 100 to enhance the low resistance to pencil drop. However, in the flexible cover window according to the present invention, the PI coating 200 is formed on the glass substrate 100 by direct coating, thereby reducing the overall thickness of the flexible cover window while maintaining the inherent texture of the glass and thus improving the aesthetics of the flexible cover window.

[0053] Furthermore, in the present invention, the functional layer 300 may be formed on the PI coating layer 200 formed on the front surface of the glass substrate 100 .

[0054] Since the front surface of the flexible cover window is touched, the functional layer 300 can be implemented by a surface protection layer having further enhanced strength. In the case of using the functional layer 300 as a surface protection layer, a material containing a high content of a resin having a relatively high hardness when hardened, such as an acrylic or epoxy resin, can be used.

[0055] Furthermore, the functional layer 300 may be provided with anti-fingerprint (AF) or anti-reflective (AR) functions as needed. Resins having such functions may be combined, or various patterns such as moth-eye patterns may be formed on the functional layer 300 to achieve such functions.

[0056] An adhesive layer is formed on the back surface of the flexible cover window, i.e., the back surface of the glass substrate or the back surface of the PI coating, to adhere to the flexible display panel. The adhesive layer can be formed to have an optically clear adhesive (OCA) structure or an OCA / support film layer / OCA structure.

[0057] Here, at least one of polyethylene terephthalate (PET), polypropylene (PP), polyethylene naphthalate (PEN), and polycarbonate (PC) may be used as the support film layer, and the support film layer may have a plurality of layers formed through the medium of OCA.

[0058] When the adhesive layer is composed of a single OCA layer, the thickness of the adhesive layer may be approximately 10 μm to 50 μm. When the adhesive layer is formed to have an OCA / support film layer / OCA structure, the upper OCA may be formed to have a thickness of 10 μm to 50 μm, the support film layer may be formed to have a thickness of 10 μm to 50 μm (haze of 3.0 or less), and the lower OCA may be formed to have a thickness of 10 μm to 75 μm.

[0059] When an adhesive layer is formed on the back surface of a glass substrate to have an OCA / support film layer / OCA structure, micro deformation caused by the difference in elongation between the glass substrate and the display panel can be absorbed, thereby preventing delamination or warping at the folding portion, and thus improving the life of the flexible cover window and minimizing image distortion at the folding portion.

[0060] The upper surface of the adhesive layer is covered with a cover film, and the cover film is removed so that the adhesive layer adheres to the surface of the display panel. At this time, in order to minimize bubble capture between the display panel and the flexible cover window (adhesive layer), it is preferred to spray water on the surface of the display panel and laminate the display panel and the flexible cover window.

[0061] In an embodiment of the present invention, Figures 1 to 6 As shown in FIG, the PI coating layer 200 is formed on the front surface of the glass substrate 100 (the upper surface of the glass substrate 100 in the figure).

[0062] Figure 1It is shown that the PI coating layer 200 is formed on the front surface of the glass substrate 100 and the functional layer 300 is formed on the PI coating layer 200. Impact applied to the front surface (touch surface) of the glass substrate 100 is dispersed or absorbed by the PI coating layer 200. In addition, the PI coating layer 200 is formed over the entire surface of the glass substrate 100 to support the glass substrate 100.

[0063] In another embodiment of the present invention, Figure 2 As shown in FIG, the PI coating layer 200 may be formed on opposite surfaces, i.e., the front surface and the back surface, of the glass substrate 100. Impact is mainly absorbed by the PI coating layer 200 formed on the front surface of the glass substrate 100 (which is a surface including a contact portion to which impact is applied), and impact transmitted to the inside of the glass substrate 100 is absorbed by the PI coating layer 200 formed on the back surface of the glass substrate 100.

[0064] Here, the PI coating layer 200 formed on the front surface of the glass substrate 100 and the PI coating layer 200 formed on the back surface of the glass substrate 100 may be made of different materials and, at the same time, have different strengths and thicknesses.

[0065] Furthermore, in the present invention, the PI coating layer 200 may be formed to have a thickness of 1 μm to 50 μm, which is a thickness required to effectively absorb or disperse impact in consideration of the overall thickness and folding properties of the flexible cover window.

[0066] If the thickness of the PI coating 200 is less than the above thickness range, the impact dispersion effect may be insignificant. If the thickness of the PI coating 200 is greater than the above thickness range, the thickness of the flexible cover window may increase, and thus the folding properties of the flexible cover window may deteriorate.

[0067] In the case where the PI coating layer 200 is formed over the entire surface of the glass substrate 100 , as described above, vertical impact such as a pen drop is supported or dispersed, whereby the pen drop resistance, folding characteristics, and overall strength characteristics of the flexible cover window are improved.

[0068] In another embodiment of the present invention, Figure 3 As shown in FIG, the PI coating layer 200 may be formed on the side surfaces of the glass substrate 100 as well as the front and back surfaces of the glass substrate 100 to wrap the glass substrate 100. That is, the PI coating layer 200 is formed to extend from the front and back surfaces of the glass substrate 100 to the side surfaces of the glass substrate 100.

[0069] Therefore, the entire area of ​​the glass substrate 100 is wrapped by the PI coating layer 200 , thereby improving the strength of the glass substrate 100 while preventing the glass substrate 100 from falling apart.

[0070] In another embodiment of the present invention, Figure 4 As shown in FIG, a buffer layer 400 may be further formed between the back surface of the PI coating layer 200 and the flexible display panel.

[0071] The buffer layer 400 enhances the impact resistance of the glass substrate 100 to prevent the glass substrate 100 from being scattered. To this end, the buffer layer 400 is formed to have a thickness of 1 μm to 40 μm.

[0072] A transparent resin having a refractive index almost the same as that of glass (refractive index of 1.5), such as an optically clear resin (OCR), may be used as the buffer layer 400. For example, acrylic, epoxy, silicone, urethane, urethane composite, urethane acrylic composite, sol-gel hybrid material, or siloxane-based material may be used.

[0073] The PI coating 200 according to the present invention is made of a material different from that used for the buffer layer 400, so that the strength of the PI coating 200 is different from that of the buffer layer 400, thereby effectively dispersing or absorbing impact applied to the glass substrate 100 and stably supporting the glass substrate 100.

[0074] Furthermore, the PI coating 200 is made of a material configured such that the PI coating 200 has the same strength or different strengths at a planar portion and a folded portion, thereby enhancing strength characteristics and folding characteristics of the flexible cover window according to specifications of products in various environments.

[0075] In another embodiment of the present invention, Figure 5 As shown in FIG, the folded portion of the glass substrate 100 is formed to be thinner than the flat portion of the glass substrate 100, the PI coating 200 is formed on the glass substrate 100, and the functional layer 300 is formed on the PI coating 200. Therefore, the folding property of the flexible cover window and the strength property of the flexible cover window are further improved.

[0076] exist Figure 5 In the embodiment, the thinned folded portion is formed to be located at the back surface of the glass substrate 100. The thinned folded portion may be formed on the front surface, the back surface, or opposite surfaces of the glass substrate 100 according to the specifications of the product.

[0077] In yet another embodiment of the present invention, Figure 6As shown in FIG, the folded portion of the glass substrate 100 is divided into two or more sections, whereby the glass substrate 100 has a three-section structure. The PI coating 200 is formed to wrap the divided glass substrate 100. Therefore, the folding characteristics of the flexible cover window and the strength characteristics of the flexible cover window are further improved.

[0078] In the present invention, as described above, the PI coating layer 200 is formed on the glass substrate 100, whereby an impact such as a falling pen is further dispersed or absorbed, and thus the impact resistance is further improved.

[0079] In addition, by appropriately adjusting the thickness and physical properties of the PI coating 200 according to the present invention, the occurrence of cracks at the folded portion can be minimized according to the specifications of the product, and the PI coating 200 is uniformly formed on the entire glass substrate 100, thereby ensuring the flatness of the portion of the flexible cover window adjacent to the display panel.

[0080] Furthermore, the elastic force of the flexible cover window at the surface where the flexible cover window adjoins the display panel is enhanced by the buffer layer 400 according to the present invention, thereby improving the impact resistance of the flexible cover window and preventing the glass substrate 100 from being scattered when the glass substrate 100 is broken.

[0081] Furthermore, in the present invention, the flexible cover window is made of a composite material including glass and a resin material, thereby enhancing the flexibility, restoring force, elasticity and strength characteristics of the flexible cover window by the resin material while maintaining the texture of the glass to the greatest extent.

[0082] Table 1 below shows data on the pen-drop resistance characteristics and measured hardness of the flexible cover window according to one embodiment of the present invention and the flexible cover window according to a comparative example.

[0083] [Table 1]

[0084] Pencil drop resistance Measured hardness Comparative Example 1 (bare) 1cm to 2cm 4H Comparative Example 2 2cm to 3cm 3H Comparative Example 3 10cm B Example 10cm or larger 3H

[0085] In Comparative Example 1, a glass substrate (bare) having a thickness of 30 μm was used. In Comparative Example 2, a hard coating layer having a thickness of about 2 μm was formed on a glass substrate having a thickness of 30 μm. In Comparative Example 3, a protective film such as CPI or TPU was formed on a glass substrate having a thickness of 30 μm.

[0086] In an embodiment of the present invention, a PI coating layer having a thickness of 2 μm was formed on a glass substrate having a thickness of 30 μm (the weight ratio of PI to the primer was 100:5).

[0087] As shown in Table 1 above, it can be seen that, for the Examples of the present invention, the pen drop resistance characteristic is significantly improved to 10 cm or more, and the hardness is improved to 3H or more.

[0088] In the flexible cover window according to the present invention, as described above, the PI coating is formed on the glass substrate, thereby improving the strength characteristics of the flexible cover window and maintaining the inherent texture of the glass while reducing the total thickness of the flexible cover window, thereby improving the aesthetics of the flexible cover window.

[0089] As is apparent from the above description, the present invention relates to a flexible cover window, and more particularly to a flexible cover window configured such that a PI coating is formed on a glass substrate, thereby improving the surface hardness, pen-drop resistance and folding properties of the flexible cover window.

[0090] Conventional flexible cover windows typically require a separate protective film to enhance the low resistance to pencil drop. However, in the flexible cover window according to the present invention, a PI coating is directly applied to the glass substrate, thereby reducing the overall thickness of the flexible cover window while maintaining the inherent texture of the glass and improving its aesthetics.

[0091] Furthermore, in the present invention, to enhance adhesion to the glass substrate, PI is mixed with a primer, applied to the glass substrate by direct coating, and hardened to form a PI coating. This ensures excellent close contact between the PI coating and the glass substrate, minimizing deformation of the flexible cover window at its interface even from impacts such as a falling pen, while also improving the overall durability of the flexible cover window.

[0092] Furthermore, the flexible cover window according to the present invention is realized using a combination of glass and resin materials, thereby enhancing flexibility, resilience, elasticity, and strength characteristics through the resin material while maximally maintaining the texture of the glass. In particular, the resin material absorbs impacts such as those from a falling pen, thereby further improving impact resistance.

[0093] Although the present invention has been described in detail based on specific embodiments, those skilled in the art will appreciate that the invention is not limited thereto and that various modifications, additions and substitutions are possible without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A glass-based flexible cover window with improved strength, comprising 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 formed to correspond to a folded area of ​​the flexible display, wherein the planar portion of the flexible cover window has a thickness of 30 μm to 300 μm, and the folded portion of the flexible cover window has a thickness of 10 μm to 100 μm, wherein the flexible cover window comprises: Glass substrate; as well as forming a polyimide (PI) coating on the glass substrate, wherein the polyimide (PI) coating comprises a front PI coating formed on the front surface of the glass substrate and a back PI coating formed on the back surface of the glass substrate, wherein the glass-based flexible cover window further comprises a functional layer formed on the front PI coating formed on the front surface of the glass substrate, and the functional layer comprises acrylic or epoxy resin, wherein the front PI coating is directly coated on the front surface of the glass substrate, and the back PI coating is directly coated on the back surface of the glass substrate, wherein the front PI coating and the back PI coating are made of different materials to have different strengths, wherein the front PI coating and the back PI coating have different thicknesses, The glass-based flexible cover window further includes a buffer layer formed between the back surface of the glass substrate and the display panel. Wherein, as the material of the buffer layer, silicone, polyurethane, polyurethane composite material or polyurethane acrylic composite material different from the material of the functional layer is used, and The strength of the buffer layer is different from the strength of the polyimide (PI) coating. 2 . The flexible cover window according to claim 1 , wherein the PI coating has a thickness of 1 μm to 50 μm. 3 . The flexible cover window according to claim 1 , wherein the PI coating layer is formed by coating the glass substrate with a coating solution comprising 100 parts by weight of polyimide (PI) and 2 to 10 parts by weight of a primer. 4 . The flexible cover window according to claim 1 , wherein the PI coating is formed on the front surface, the back surface, and the side surfaces of the glass substrate to wrap the glass substrate. The flexible cover window according to claim 1 , wherein the PI coating is formed on the glass substrate by coating and then UV-cured. The flexible cover window according to claim 5 , wherein the PI coating is formed on the glass substrate by any one of bar coating, slot die coating, and dip coating. The flexible cover window according to claim 1 , wherein the PI coating is made of a material configured such that the PI coating has the same strength or different strengths at the planar portion and the folded portion.

8. The flexible cover window according to any one of claims 1 to 7, wherein the glass substrate is integrally formed. 9 . The flexible cover window according to claim 8 , wherein the glass substrate is formed such that the folded portion is thinner than the planar portion. 10 . The flexible cover window according to claim 1 , wherein the glass substrate is formed such that the folded portion is divided into two or more sections.

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