Flexible folding cover plate, preparation method and display module

Abstract

The invention provides a flexible folding cover plate, a preparation method and a display module. The flexible folding cover plate comprises a hardened coating, a flexible substrate layer and an ink layer, the hardened coating is arranged on one side of the flexible substrate layer, and the ink layer is arranged on the side, away from the hardened coating, of the flexible substrate layer. Through the design, the high ductility of the hardened coating is improved, and meanwhile, the ink layer is directly arranged at the preset position of the flexible substrate layer, so that the reliability problem of the flexible folding cover plate in various display forms, such as the coating cracking problem or the ink falling problem, can be improved.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a flexible folding cover, a preparation method and a display module. Background Art

[0002] As an important component of the bendable flexible display module, the flexible folding cover is arranged on the outermost side of the flexible display panel. With the continuous development of display technology, display modules with good bending performance are increasingly favored by the market, which in turn puts forward higher requirements for the bending performance of the flexible folding cover. When the flexible folding cover of the existing flexible display module is bent at low temperature, there is a problem that the hardened coating of the cover cracks or the ink falls off before the expected number of bends. Summary of the invention

[0003] In view of this, the purpose of the present application is to provide a flexible folding cover plate and a preparation method thereof. The flexible folding cover plate prepared by the preparation method avoids the above-mentioned problems of cracking of the hardened coating and falling off of the ink.

[0004] Based on the above objectives, the present application provides a flexible folding cover, which includes:

[0005] Hard coating, flexible base layer and ink layer,

[0006] The hardening coating is disposed on one side of the flexible base layer.

[0007] The ink layer is disposed on a side of the flexible substrate layer away from the hardening coating layer.

[0008] In one embodiment, the ductility of the hardened coating is greater than or equal to 10%.

[0009] Preferably, the ductility of the hardened coating is between 10% and 20%.

[0010] Preferably, the ductility of the hardened coating is between 10 and 15%.

[0011] In one embodiment, the thickness of the flexible substrate layer is less than or equal to 30 μm.

[0012] Preferably, the thickness of the flexible substrate layer is between 15 and 30 μm.

[0013] Preferably, the thickness of the flexible substrate layer is between 25 μm and 30 μm.

[0014] In one embodiment, the material of the flexible base layer is selected from at least one of transparent polyimide, polyethylene terephthalate, polyimide, cycloolefin polymer, cycloolefin copolymer or ultra-thin glass.

[0015] In one embodiment, the hardened coating comprises an acrylic polymer.

[0016] Preferably, the hardened coating comprises or a high-functional acrylic polymer, wherein the high-functional group is a functional group ≥ 6,

[0017] Preferably, the main chain structure of the acrylic resin polymer includes a polyester chain or a fatty chain.

[0018] In one embodiment, the ink layer is disposed in an edge region of the flexible substrate layer on a side away from the hardening coating layer, so as to cover a frame region therebelow.

[0019] Preferably, the ink layer comprises polyurethane ink, and the proportion of solvents having a boiling point greater than 80° C. in the polyurethane ink is less than 35%.

[0020] Based on the same concept, the present application provides a method for preparing a flexible folding cover, which comprises the following steps:

[0021] providing a flexible base layer;

[0022] Ink is disposed on the surface of one side of the flexible substrate layer and dried to form an ink layer, wherein the proportion of a solvent having a boiling point greater than 80° C. in the ink is less than 35%.

[0023] In one embodiment, the ink comprises polyurethane ink, wherein the proportion of solvents having a boiling point greater than 80° C. is less than 35%.

[0024] Preferably, the solvent with a boiling point greater than 80° C. includes at least one of a ketone solvent and an alkane solvent.

[0025] In one embodiment, a hardening coating is provided on one surface of the flexible base layer.

[0026] Preferably, the surface of one side of the flexible substrate layer is coated with micro-dimpled coating or slit coating, and then cured to obtain a hardened coating.

[0027] Based on the same inventive concept, the present application also discloses a display module, which includes the above-mentioned flexible cover plate.

[0028] Compared with the prior art, the flexible folding cover provided in the present application improves and optimizes the laminated structure of the folding cover, omits the primer layer, and allows the ink to be directly prepared on the base layer, thereby avoiding the problem of ink adhesion failure caused by peeling of the primer layer and the base layer of the flexible folding cover. The ductility is improved by optimizing the material and thickness of the hardened coating, avoiding the risk of breakage / cracking or even rupture at the bend when bending, and the problem of visual cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 is a cross-sectional schematic diagram of an existing flexible folding cover;

[0031] Figure 2 A schematic top view of a flexible folding cover according to an embodiment of the present application;

[0032] Figure 3 for Figure 2 Schematic diagram of the cross section of the flexible folding cover at AA;

[0033] Figure 4 A schematic cross-sectional view of a display module equipped with a flexible folding cover according to an embodiment of the present application;

[0034] Figure 5 Schematic diagram of the process of preparing the flexible folding cover according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0036] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should be the usual meanings understood by people with ordinary skills in the field to which the present application belongs. The "first", "second" and similar words used in the embodiments of the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0037] As described in the background technology, the existing flexible display module has the technical problem of poor bending performance. The inventor of the present application decomposed the structure of the flexible display module during the research and development process and found that the current flexible display module includes a flexible folding cover plate, which is in contact with the display panel and the support member through optical adhesive (OCA). Figure 1 As shown, the folding cover 100 includes a base layer 110. Currently, the base layer 110 has a thickness of 50 μm. A first coating layer (also called a hardening coating layer) 120 is provided on one side of the base layer, and a second coating layer (also called a base coating layer, the thickness of which is usually nanometers) 130 is provided on the other side opposite to the hardening coating layer. An ink layer 140 is provided on the second coating layer. For example, the ink layer is located at the edge of the second coating layer and covers the frame area below it after curing. When preparing the ink layer, liquid ink needs to be provided (such as printed) to a preset area (such as the edge) of the second coating layer. The ink is then baked and cured in an oven to set the shape. After the baking and curing process, the high boiling point (boiling point greater than 80°C) solvent in the ink is not completely volatilized, resulting in part of the high boiling point solvent remaining on the base coating. The remaining high boiling point solvent will corrode the base coating, so that the solvent will penetrate into the second coating and contact the base layer, resulting in reduced adhesion between the second coating and the base layer. In this way, when folding inward or outward during use, the second coating and the base layer will peel off. Because the thickness of the base coating is relatively thin, the ink will visually appear to fall off. In addition, the current first coating / hardened coating is easy to break / crack at the bend when bent in low temperature (such as minus 20°C or below), and cracks appear visually.

[0038] In order to solve the above problems, the inventors have designed a flexible folding cover, a preparation method and a display module, which can achieve the effect of improving the comprehensive performance of the flexible folding cover. By improving the hardening coating, the thickness is optimized and the ductility is improved, avoiding cracking when bending / folding in low temperature environments. By improving the ink composition of the ink layer, the adhesion of the ink is improved, and it is directly set / printed on the base layer to improve the problem of ink falling off when bending.

[0039] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0040] The flexible folding cover provided in the embodiment of the present application is described in detail below.

[0041] like Figure 2 The figure is a schematic top view of a flexible folding cover plate according to an embodiment of the present application; Figure 3 for Figure 2 Schematic diagram of the cross section of the flexible folding cover at AA.

[0042] The flexible folding cover 200 comprises:

[0043] Flexible base layer 210,

[0044] A hardening coating 220 is disposed on one side of the flexible base layer 210. The hardening coating 220 includes at least an acrylic resin polymer.

[0045] An ink layer 240 is provided on the side of the flexible substrate layer 210 away from the hardening coating layer 220. Preferably, the hardening coating layer has high ductility, and its ductility is ≥10%. Ductility can be described as the ratio of the deformation of the product after stretching to the initial length of the product. In this embodiment, by optimizing the formula of the hardening coating layer, the ductility is improved while ensuring that its hardness is not reduced (the ductility of the current hardening coating layer is mostly around 5%). Preferably, its ductility is between 10 and 20% (such as 10%, 11%, 16%, 17%, 18%, 19%, 20%) or 10 to 15% (such as 10%, 11%, 12%, 13%, 14%, 15%). The ink layer is directly set at a preset position of the flexible substrate layer to improve the adhesion of the ink to avoid the problem of ink falling off during bending. This can improve the reliability of the cover material in various display forms.

[0046] The material of the flexible substrate layer can be selected from at least one of colorless transparent polyimide (CPI), polyimide (PI), polyethylene terephthalate (PET), cycloolefin polymer (COP) or cycloolefin copolymer (COC). In one embodiment, the flexible substrate layer can also be ultra-thin glass.

[0047] The thickness of the flexible substrate layer is less than or equal to 30 μm (in the z direction). Furthermore, the thickness of the flexible substrate layer is between 5 and 30 μm, such as the thickness of the flexible substrate layer is 20 μm, 25 μm, and 30 μm. By optimizing the thickness of the flexible substrate layer and reducing the thickness of the flexible substrate layer (the current conventional thickness of the flexible substrate layer is about 50 μm), the continuity of the hardened coating is improved. Preferably, the flexible substrate layer is selected from CPI, PET material or ultra-thin glass (UTG, Ultra-Thin Glass). Ultra-thin glass generally refers to a thickness of less than 1 mm. As the thickness continues to decrease, it can gradually have the characteristics of being able to bend and fold. Ultra-thin glass has the advantages of being thin, having a large transmittance in the visible light range, and being resistant to high temperatures.

[0048] The ductility of the hardened coating is ≥10%, which is more than doubled compared to the current hardened coating ductility (the current hardened coating ductility is 5%). The performance reliability of the display module equipped with it is improved, and the bending reliability is improved in low temperature (such as minus 20°C or below). It has been verified through experiments that the improvement has been improved from the current 5000 times of NG (that is, 5000 times of defective) to 20,000 times of bending without abnormality (when bending, in order to ensure that the bending conditions before and after the improvement are consistent, the bending can be performed by a bending fixture), which can expand the application range of flexible displays. Preferably, the thickness of the hardened coating is between 3 and 10μm (such as the thickness of the hardened coating is 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm). When the thickness of the hardened coating is greater than 10μm, the flexibility becomes poor and cracking is easily caused (that is, it cannot meet the requirements of the bending test). In this way, reducing the thickness of the hardened coating is also conducive to improving the ductility. The ductility of 3um thickness is better than that of 10um.

[0049] The hardened coating uses a polymer blended with an acrylate system resin and a main resin of a specific structure. The main resin of the specific structure preferably selects a resin with a longer main chain and a higher molecular weight with a functionality ≥ 6. The mechanical properties of the hardened coating can be guaranteed (its hardness is guaranteed) by selecting a resin with a functionality ≥ 6. The main chain structure selects a polyester chain and a fatty chain, and its molecular chain is more flexible and the molecular movement is easier (its flexibility is guaranteed). Through such a design, a flexible screen folding cover is obtained that takes into account weather resistance, mechanical properties and flexibility at the same time, meets the requirements of folding occasions, and expands the scope of application. The hardened coating includes a high molecular weight or high functional group acrylate polymer, wherein the high functional group is a functionality ≥ 6. Furthermore, the hardened coating uses a polymer blended with an acrylate system resin and a main resin of a specific structure, and the thickness is optimized, and the thickness is between 3 and 10 μm. In this way, the mechanical properties are guaranteed while meeting the bending flexibility, and the service life of the product equipped with it is extended in disguise.

[0050] Preferably, the hardening coating includes an acrylic resin polymer, which improves the verification, such as using an acrylic polymer with a longer main chain, a large molecular weight or a high functional group. Preferably, the main chain structure includes a polyester chain or a fatty chain. By improving the ductility of the hardening coating, the problem of cracking of the hardening coating when folded can be improved. The hardening coating can be coated on the flexible substrate layer during preparation and obtained by curing.

[0051] The ink layer is directly arranged on the side of the flexible substrate layer away from the hardening coating. The (liquid) ink is directly printed (such as screen printing) on ​​a preset position of the flexible substrate layer (such as a frame area, the width of the ink in the x direction is the same or approximately the same as the width of the frame area), avoiding the current bad occurrence that the base coating is eroded by a high boiling point solvent after printing the ink, resulting in a decrease in adhesion, causing it to peel off from the substrate layer. In one embodiment, the ink uses polyurethane ink and the proportion of high boiling point (such as a boiling point greater than 80°C) solvent is less than 35% (such as the proportion of high boiling point solvent is 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%), so as to reduce the influence of solvent residue on the substrate material, thereby improving the adhesion of the ink. In this embodiment, polyurethane ink is used and the proportion of high boiling point solvent is less than 35%, so that the current baking equipment can be used in the baking stage, reducing the requirements for the production line, and can be quickly switched to improve production efficiency.

[0052] like Figure 4 The figure shows a method for preparing the flexible folding cover according to an embodiment of the present application.

[0053] The preparation method comprises the following steps:

[0054] A flexible substrate layer is provided; the material of the flexible substrate layer can be selected from colorless transparent polyimide (Colorless Polyimide, CPI), polyimide (Polyimide, PI), polyethylene terephthalate (Polyethylene Terephthalate, PET) or ultra-thin glass.

[0055] Liquid ink is arranged on the surface of one side of the flexible substrate layer, and an ink layer is formed by drying. During preparation, liquid ink is coated / printed (such as screen printing) on ​​a preset area (such as a frame area) on the side of the flexible substrate layer away from the hardened coating (such as liquid ink is arranged on the edge of the flexible substrate layer), and the proportion of high boiling point solvents in the liquid ink is less than 35%. After baking with a baking device, the proportion of high boiling point solvents is reduced (the lower the proportion of high boiling point solvents in the ink material, the better, at least ensure that it is less than 35%), and the influence of solvent residues on the substrate material is reduced, thereby improving the adhesion of the ink. High boiling point means a boiling point greater than 80°C. High boiling point solvents may include ketone solvents and alkane solvents. In this way, the adhesion performance of the ink can be improved, and the ink can be improved from falling off after standing for 3 days to adhesion being effective for up to half a year, thereby improving the competitiveness of smart portable products equipped with it.

[0056] In one embodiment, the ink is a polyurethane ink, wherein the proportion of high boiling point (meaning boiling point greater than 80° C.) solvent is less than 35%. Preferably, the proportion of ketone solvents and alkane solvents in the ink is less than 35%. Polyurethane ink is an ink with polyurethane resin as the main component. Polyurethane resin has good adhesion and wear resistance, and polyurethane ink can form a solid coating during printing.

[0057] In one embodiment, a hardened coating is formed on one side of the flexible substrate layer (such as CPI or PET), and the thickness of the hardened coating is between 3 and 10 μm. This step can be performed by micro-dimpled coating or slit coating, and the hardened coating with a thickness of between 3 and 10 μm is obtained by curing. The hardness of the hardened coating is 4H or above, referring to the Mohs hardness.

[0058] like Figure 4 The figure shows a cross-sectional schematic diagram of a display module according to an embodiment of the present application, in which a flexible folding cover plate 200 is provided with an ink layer 240 on one side thereof, which is attached to a polarizing layer 250 (such as a polarizer) through an optical adhesive 241 (Optically Clear Adhesive, OCA), and the polarizing layer 250 is stacked on a touch layer 260, and the touch layer 260 is stacked on a flexible display panel 270. It is understood that the display module may also include a supporting component (not shown) for supporting the flexible display panel 270. In one embodiment, the polarizing layer 250 may be a COE (color filter on TFE) layer, which can reduce the thickness of the display module.

[0059] The embodiment of the present application provides a display module, which includes a display panel and a flexible folding cover plate, and the display panel includes a light-emitting surface and a backlight surface. The light-emitting surface is used to display images, and the backlight surface is the other side arranged opposite to the light-emitting surface along the thickness direction of the display module. The display panel can be an organic light-emitting diode (OLED) display panel. The flexible folding cover plate is arranged on the light-emitting surface of the display panel, and the flexible folding cover plate is used to protect the display panel. The display module can be used in devices such as mobile phones, laptops, and tablet computers.

[0060] Although the present application has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations of these embodiments will be apparent to those skilled in the art in light of the foregoing description.

[0061] It should be noted that the above describes some embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the above embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0062] The embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A flexible folding cover, characterized in that: include: Hard coating, flexible base layer and ink layer; The hardening coating is disposed on one side of the flexible base layer; The ink layer is disposed on a side of the flexible substrate layer away from the hardening coating layer.

2. The flexible folding cover according to claim 1, characterized in that: The ductility of the hardened coating is greater than or equal to 10%; Preferably, the ductility of the hardened coating is between 10% and 20%; Preferably, the ductility of the hardened coating is between 10 and 15%.

3. The flexible folding cover according to claim 1 or 2, characterized in that: The thickness of the flexible substrate layer is less than or equal to 30 μm; Preferably, the thickness of the flexible substrate layer is between 15 and 30 μm; Preferably, the thickness of the flexible substrate layer is between 25 μm and 30 μm.

4. The flexible folding cover according to claim 1, characterized in that: The material of the flexible base layer includes at least one of transparent polyimide, polyethylene terephthalate, polyimide, cyclic olefin polymer, cyclic olefin copolymer or ultra-thin glass.

5. The flexible folding cover according to claim 1, characterized in that: The hardened coating comprises an acrylate polymer; Preferably, the hardened coating comprises a high-functionality acrylic polymer, wherein the high-functionality is a functionality ≥ 6; Preferably, the main chain structure of the acrylic resin polymer includes a polyester chain or a fatty chain.

6. The flexible folding cover according to claim 1, characterized in that: The ink layer is disposed in an edge region of the flexible substrate layer on a side away from the hardening coating layer, and is used to cover a frame region therebelow; Preferably, the ink layer comprises polyurethane ink, and the proportion of solvents having a boiling point greater than 80° C. in the polyurethane ink is less than 35%.

7. A method for preparing a flexible folding cover, characterized in that: The following steps are involved: providing a flexible base layer; Ink is coated on the surface of one side of the flexible substrate layer and dried to form an ink layer, wherein the proportion of the solvent with a boiling point greater than 80° C. in the ink is less than 35%.

8. The method for preparing the flexible folding cover according to claim 7, characterized in that: The ink includes polyurethane ink, wherein the proportion of solvents having a boiling point greater than 80° C. is less than 35%; Preferably, the solvent with a boiling point greater than 80° C. includes at least one of a ketone solvent and an alkane solvent.

9. The method for preparing the flexible folding cover according to claim 8, characterized in that: forming a hardened coating on a surface of one side of the flexible base layer; Preferably, the surface of one side of the flexible substrate layer is cured by micro-dimple coating or slit coating to obtain a hardened coating.

10. A display module, characterized in that: It comprises the flexible folding cover plate as claimed in any one of claims 1 to 6.

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