Cover plate, polyurethane composition system, preparation method of cover plate and display device

Abstract

The invention discloses a cover plate, a polyurethane composition system, a preparation method of the cover plate and a display device. The cover plate comprises a substrate, a functional coating and an ink layer, the substrate comprises a first surface and a second surface which are oppositely arranged in the thickness direction of the cover plate; the functional coating at least covers the first surface and / or the second surface of the substrate; the ink layer at least covers part of the surface of the functional coating; wherein the functional coating and the ink layer are made of different polyurethane materials, and the functional coating and the ink layer are connected at least through covalent bonds. The problems of ink falling of the ink layer on the cover plate in the UV cutting process and degradation of the bending performance of the functional coating can be solved at the same time.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to a cover plate, a polyurethane composition system, a method for preparing the cover plate, and a display device. Background Technology

[0002] With the recent development of display technology, foldable displays, rollable displays, and stretchable displays have been developed. Therefore, in order to protect these different types of displays, research is actively underway on ultra-thin glass (UTG) with improved flexibility. The bending resistance of UTG increases as the glass thickness decreases, but thinner glass means poorer impact resistance.

[0003] To improve impact resistance, films or coatings are typically applied to the UTG surface to form a flexurally resistant organic film. For example, a modified polyurethane coating can be applied to the surface of the UTG substrate to enhance its scratch and impact resistance. Ink is usually printed on the coating and the UTG substrate to achieve functions such as light shielding and marking. The UTG substrate with the coating and ink printing completed typically requires precision cutting using an ultraviolet (UV) laser to shape it into components that conform to the dimensions of the end product.

[0004] However, the ink layer on current UTG substrates suffers from ink shedding after UV cutting, which leads to decreased processing yield, product performance failure, and increased production costs. Simultaneously, the poor mechanical compatibility between the coating and ink layer on current UTG substrates results in decreased elongation at break and deteriorated bending performance of the coating. This makes the coating-ink interface prone to cracking during dynamic bending tests, failing to meet the requirements of flexible applications. Therefore, it is necessary to simultaneously address the issues of ink shedding during UV cutting and the deterioration of coating bending performance on UTG substrates. Summary of the Invention

[0005] This application provides a cover plate, a polyurethane composition system, a method for preparing the cover plate, and a display device, which aim to prevent ink layer on the cover plate from falling off during UV cutting and to improve the bending performance of the functional coating.

[0006] In a first aspect, this application provides a cover plate, the cover plate comprising: The substrate includes a first surface and a second surface disposed opposite to each other along the thickness direction of the cover plate; A functional coating covers at least the first surface and / or the second surface of the substrate; An ink layer covers a portion of the surface of the functional coating; The functional coating and the ink layer are made of different polyurethane materials, and the functional coating and the ink layer are connected by at least covalent bonds.

[0007] Optionally, the material of the functional coating includes a modified polyurethane material having a first active functional group, and the material of the ink layer includes a polyurethane material having a second active functional group, wherein the first active functional group and the second active functional group are complementary functional groups.

[0008] Optionally, the first active functional group includes at least one of hydroxyl, amino, and epoxy groups, and the second active functional group includes at least one of isocyanate, carboxyl, and siloxane groups.

[0009] Optionally, the cover plate further includes a surface pretreatment layer located between the functional coating and the substrate; the content of hydroxyl groups on the surface pretreatment layer is greater than the content of hydroxyl groups on the substrate.

[0010] Optionally, the glass transition temperature range of the functional coating is -20°C to 10°C.

[0011] Secondly, this application also provides a polyurethane composition system, the polyurethane composition system comprising a modified polyurethane coating composition and a polyurethane ink composition, wherein the modified polyurethane coating composition is configured to produce the functional coating described above, and the polyurethane ink composition is configured to produce the ink layer described above. The modified polyurethane coating composition contains hydroxyl-terminated polyurethane resin, and the polyurethane ink composition contains waterborne polyurethane resin.

[0012] Optionally, the modified polyurethane coating composition includes the hydroxyl-terminated polyurethane resin, a modifier, and a first solvent; The number-average molecular weight of the hydroxyl-terminated polyurethane resin ranges from 1000 g / mol to 5000 g / mol, the modifier contains at least one of epoxy and amino groups, and the first solvent includes at least one of ester solvents.

[0013] Optionally, in the modified polyurethane coating composition, the mass fraction of the hydroxyl-terminated polyurethane resin ranges from 30% to 45%, the mass fraction of the modifier ranges from 3% to 8%, and the solid content of the first solvent ranges from 30% to 50%.

[0014] Optionally, the modifier includes at least one of ethylene glycol diglycidyl ether and diethylenetriamine, and the first solvent includes at least one of ethyl acetate and propylene glycol methyl ether acetate.

[0015] Optionally, the polyurethane ink composition includes the aqueous polyurethane resin, a crosslinking agent, a pigment, and a second solvent; The number-average molecular weight of the waterborne polyurethane resin ranges from 2000 g / mol to 6000 g / mol, and the crosslinking agent contains isocyanate groups.

[0016] Optionally, in the polyurethane ink composition, the waterborne polyurethane resin has a mass fraction ranging from 40% to 60%, the crosslinking agent has a mass fraction ranging from 5% to 12%, the pigment has a mass fraction ranging from 10% to 20%, and the second solvent has a solid content ranging from 30% to 45%.

[0017] Optionally, the crosslinking agent includes at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate, the pigment includes at least one of carbon black and titanium dioxide, and the second solvent includes deionized water.

[0018] Optionally, the raw material of the hydroxyl-terminated polyurethane resin is composed of a first polyol, a first ester compound containing a diisocyanate group, and a first chain extender; the raw material of the waterborne polyurethane resin is composed of a second polyol, a second ester compound containing a diisocyanate group, a second chain extender, and a neutralizing agent; or, the raw material of the waterborne polyurethane resin is composed of the second polyol, the second ester compound, and the second chain extender.

[0019] Optionally, the first polyol includes any one or more of polytetrahydrofuran ether diol, polypropylene glycol, polybutylene adipate diol, and polyethylene adipate diol; the first ester compound includes any one or more of isophorone diisocyanate, diphenylmethane diisocyanate, and toluene diisocyanate; and the first chain extender includes any one or more of 1,4-butanediol and ethylene glycol. The second polyol includes one or more of polytetrahydrofuran ether diol, polybutylene adipate diol, and methoxy polyethylene glycol; the second ester compound includes one or more of isophorone diisocyanate, toluene diisocyanate, and dicyclohexylmethane diisocyanate; the second chain extender includes one or more of dimethylolpropionic acid, dimethylolbutyric acid, N-methyldiethanolamine, 1,4-butanediol, ethylene glycol, and 1,6-butanediol; and the neutralizing agent includes one or more of dimethylethanolamine, triethylamine, and acetic acid.

[0020] Thirdly, this application also provides a method for preparing a cover plate, comprising the following steps: A substrate is provided; wherein the substrate includes a first surface and a second surface disposed opposite to each other along the thickness direction of the substrate; The modified polyurethane coating composition and the polyurethane ink composition are configured in the polyurethane composition system described above; The modified polyurethane coating composition is applied at least to the first surface and / or the second surface of the substrate, and the modified polyurethane coating composition is cured to form a functional coating; and The polyurethane ink composition is printed onto a portion of the surface of the functional coating, and the polyurethane ink composition is cured to form an ink layer; wherein the functional coating and the ink layer are connected by at least covalent bonds.

[0021] Optionally, the curing treatment of the modified polyurethane coating composition includes the following steps: The modified polyurethane coating is cured at 80°C to 120°C for 30 to 60 minutes. The curing process of the polyurethane ink composition includes the following steps: The polyurethane ink composition is cured at 60°C to 100°C for 20 to 40 minutes.

[0022] Fourthly, this application also provides a display device, the display device including a display panel and the cover plate described above, the cover plate being located on at least one side of the display panel.

[0023] The cover plate, polyurethane composition system, cover plate preparation method, and display device provided in this application construct a homologous system of polyurethane coating and polyurethane ink by selecting different polyurethane materials for the functional coating and ink layer in the cover plate. This enhances the microscopic chemical bonding and physical anchoring force at the contact interface between the functional coating and the ink layer, solving the problem of ink detachment after UV cutting of the cover plate. Simultaneously, since both the functional coating and ink layer in the cover plate are made of polyurethane, the mechanical adjustability of polyurethane can be utilized to reduce the difference in mechanical properties between the ink layer and the functional coating. This allows the elongation at break and flexibility of the functional coating to match those of the ink layer, thereby avoiding the problem of deterioration in the bending performance of the functional coating due to the difference in mechanical properties between the ink layer and the functional coating.

[0024] Therefore, this application can simultaneously solve the problems of ink loss from the cover plate during UV cutting and the deterioration of the bending performance of the functional coating. In other words, this application can both prevent ink loss from the cover plate during UV cutting and improve the bending performance of the functional coating. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of an exemplary ultrathin glass composite structure; Figure 2 This is a schematic diagram of the structure of a cover plate provided in an embodiment of this application; Figure 3 This is a schematic flowchart of a method for preparing a cover plate according to an embodiment of this application; Figures 4a to 4c This is a schematic diagram of the three UV cutting test results of the experimental cover plate in Embodiment 1 of this application; Figures 5a to 5c This is a schematic diagram of the three UV cutting test results of the second comparative cover plate in Comparative Example 2 of this application; Figure 6 This is a schematic diagram of the structure of a display device provided in an embodiment of this application.

[0027] Explanation of reference numerals in the attached figures: 1. Ultra-thin glass; 2. Modified polyurethane coating; 3 (3') Ink layer; 4. Cover plate; 5. Substrate; 6. Functional coating; 7. First surface; 8. Second surface; 9. Side surface; 10. Third surface; 11. Display device; 12. Display panel. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] like Figure 1 As shown, in applications of ultra-thin glass (UTG) 1, such as using UTG as a cover plate for flexible display panels, a modified polyurethane coating 2 needs to be applied to the surface of the UTG 1 to improve its scratch and impact resistance. Then, an ink layer 3' is printed on the same side of the modified polyurethane coating 2 and the UTG 1 to achieve functions such as light shielding and marking. The UTG after printing the modified polyurethane coating 2 and ink layer 3' typically requires precision cutting using an ultraviolet (UV) laser to shape it into components that conform to the dimensions of the final product. Specifically, the UV cutting locations are as follows... Figure 1 As shown.

[0030] Currently, modified polyurethane coatings are typically used in combination with polyester ink layers for UTG. However, this combination has several drawbacks, including ink fading after UV cutting, decreased elongation at break, and deterioration of bending performance.

[0031] Regarding the issue of ink detachment after UV cutting, the inventors discovered through research that the interface between the polyester ink layer and the modified polyurethane coating lacks strong chemical interaction. Specifically, although the surface of the modified polyurethane coating contains active groups such as hydroxyl (-OH) and amino (-NH2), the polyester molecules in the polyester ink layer only contain ester groups (-COO-), preventing the polyester ink layer from forming covalent bonds with the modified polyurethane coating. This results in a weak van der Waals bond between the two. Simultaneously, due to the high rigidity of the polyester molecular chain and poor interfacial wettability with the modified polyurethane coating, their physical adsorption force is weak. Therefore, during UV cutting, the cutting mechanical force easily disrupts the weak bonding force at the interface between the polyester ink layer and the modified polyurethane coating, causing the ink layer to detach from the surface of the modified polyurethane coating, resulting in a UTG product yield of only 70%-80%.

[0032] To address the issues of decreased elongation at break and deteriorated bending performance of the coating, the inventors discovered that polyester inks typically have a glass transition temperature (Tg) above 50°C, and the polyester molecular chains exhibit poor flexibility and low elongation at break. In contrast, modified polyurethane coatings have a relatively higher elongation at break, resulting in a significant difference in the mechanical properties between the polyester ink layer and the modified polyurethane coating. Furthermore, after printing the polyester ink layer onto the modified polyurethane coating, the rigid polyester ink layer restricts the movement of the molecular chains in the modified polyurethane coating, leading to a decrease in the elongation at break of the composite structure formed by the polyester ink layer and the modified polyurethane coating. This makes the UTG (Ultra-Tempered Grating) prone to interfacial cracking between the coating and ink layers during dynamic bending tests, thus failing to meet the requirements for flexible applications.

[0033] In summary, the root causes of ink fading after UV cutting and the decrease in elongation at break and deterioration of bending performance of the coating are directly related to insufficient interfacial micro-adhesion and mismatch in mechanical properties. In other words, current methods for achieving micro-adhesion between the coating and ink layers are limited to a single type (weak physical force) and have poor mechanical compatibility, failing to simultaneously address both ink fading and deterioration of coating bending performance after UV cutting.

[0034] To simultaneously address the issues of ink fading and coating bending performance degradation after UV cutting, this application improves the raw materials for both the coating and ink layers, constructing a homologous system for the polyurethane coating and ink layers. By enhancing the microscopic chemical bonding and physical anchoring force at the contact interface between the polyurethane coating and ink layers, the ink fading problem after UV cutting is solved. Furthermore, by utilizing the mechanical adjustability of the polyurethane system, a match is achieved between the elongation at break and the flexibility of the coating and ink layers, preventing the ink material from reducing the bending performance of the coating. Therefore, this application can improve the yield (≥95%) and bending reliability of UTG composite structures (400,000 bends without cracking at a bending radius R of 1.8 mm).

[0035] like Figure 2 As shown, this application embodiment provides a cover plate 4, which includes a substrate 5, a functional coating 6, and an ink layer 3. The substrate 5 includes a first surface 7 and a second surface 8 disposed opposite to each other along the thickness direction of the cover plate 4. The functional coating 6 covers at least the first surface 7 and / or the second surface 8 of the substrate 5. The ink layer 3 covers a portion of the surface of the functional coating 6. The functional coating 6 and the ink layer 3 are made of different polyurethane materials, and the functional coating 6 and the ink layer 3 are connected at least by covalent bonds.

[0036] It is understandable that the functional coating 6 is a polyurethane coating and the ink layer 3 is a polyurethane ink layer 3. The two are homologous systems, which allows the active groups in the polyurethane molecules of the functional coating 6 and the active groups in the polyurethane molecules of the ink layer 3 to form covalent bonds through chemical reactions, thereby connecting the functional coating 6 and the ink layer 3 at least through covalent bonds.

[0037] In some embodiments, the functional coating 6 and the ink layer 3 are further bonded by a composite microstructure through intermolecular hydrogen bonds, van der Waals forces and mechanical anchoring.

[0038] In some embodiments, substrate 5 includes ultrathin glass (UTG), but is not limited thereto.

[0039] It should be noted that the material of the substrate 5 is not limited in the embodiments of this application; only ultra-thin glass is used as an example for illustration.

[0040] In some embodiments, such as Figure 2 As shown, the substrate 5 also includes a side surface 9 connected between the first surface 7 and the second surface 8, and a functional coating 6 covers the first surface 7 and the side surface 9 of the substrate 5. The functional coating 6 has a third surface 10 disposed on the same side as the second surface 8, and the ink layer 3 covers at least the third surface 10.

[0041] In some embodiments, the ink layer 3 covers the third surface 10 of the functional coating 6 and extends to the edge of the second surface 8 of the substrate 5.

[0042] It is understandable that the distribution range of the ink layer 3 can be adjusted according to actual needs, and this application does not limit it. Furthermore, the cover plate 4 provided in the embodiments of this application is a cover plate that has undergone UV cutting.

[0043] In some embodiments, the material of the functional coating 6 includes a modified polyurethane material having a first active functional group, and the material of the ink layer 3 includes a polyurethane material having a second active functional group, wherein the first active functional group and the second active functional group are complementary functional groups.

[0044] It should be noted that the first and second active functional groups being complementary functional groups means that the first and second active functional groups can interact specifically with each other, such as forming covalent bonds through chemical reactions, but are not limited to this. Furthermore, unreacted first active groups are present in the functional coating 6, and unreacted second active groups are present in the ink layer 3.

[0045] Understandably, polyurethane (PU) is a polymer material directly synthesized from isocyanates and polyols through an addition polymerization reaction, with urethane bonds (-NHCOO-) as the basic structural units of its molecular chain. Its basic properties are determined by the type of raw materials (such as aromatic / aliphatic isocyanates, polyester / polyether polyols), but no additional functional groups or modifying components are introduced. Modified polyurethane (MPU), on the other hand, is a polyurethane derivative that uses ordinary polyurethane as a matrix and introduces other functional components or alters the molecular chain structure through chemical modification or physical blending, thereby optimizing or endowing it with new properties. The core purpose of modification is to compensate for the performance shortcomings of ordinary PU or to endow it with special functions.

[0046] In some embodiments, the first active functional group includes at least one of hydroxyl (-OH), amino (-NH2) and epoxy (-C2H3O-), and the second active functional group includes at least one of isocyanate (-NCO), carboxyl (-COOH) and siloxane (-Si-O-).

[0047] Specifically, hydroxyl groups can undergo nucleophilic addition reactions with isocyanate groups to form urethane bonds (-NHCOO-); hydroxyl groups can undergo esterification reactions with carboxyl groups to form ester bonds (-COO-); hydroxyl groups can undergo hydrolysis-condensation reactions with siloxane groups, where the siloxane group first hydrolyzes to a silanol group (-Si-OH), and then undergoes dehydration condensation with the hydroxyl group to form a silyl ether bond (-Si-OC-); amino groups can undergo nucleophilic addition reactions with isocyanate groups to form urea bonds (-NHCONH-); amino groups and carboxyl groups can first form an ammonium carboxylate salt, and then undergo high-temperature dehydration to form an amide bond (-CONH-); amino groups and siloxane groups can undergo alcohol removal condensation reactions to form Si-N bonds; after ring opening of the epoxy group, a hydroxyl group is formed, which then undergoes an addition reaction with the isocyanate group to form a heterocyclic structure containing urethane bonds; the carboxyl group can provide hydrogen ions to promote ring opening of the epoxy group, forming ester bonds and hydroxyl groups; after hydrolysis of the siloxane group to form a silanol group, it undergoes a condensation reaction with the hydroxyl group generated by ring opening of the epoxy group to form a Si-OC bond.

[0048] It is understood that the functional coating 6 and the ink layer 3 can be connected by at least one of the following: urethane bond (-NHCOO-), ester bond (-COO-), silyl ether bond (-Si-OC-), urea bond (-NHCONH-), amine bond (-CONH-), Si-N bond, heterocyclic structure containing urethane bond, and Si-OC bond, and the connecting bond (covalent bond) is obtained by the reaction of the first active group and the second active group.

[0049] In some embodiments, the functional coating 6 of the modified polyurethane material is prepared from a hydroxyl-terminated polyurethane resin, a modifier, and a solvent, and the modifying additive contains at least one of epoxy and amino groups.

[0050] When the modifying additive contains epoxy groups, on the one hand, the epoxy groups in the modifier react with the hydroxyl groups of the terminal hydroxyl polyurethane to increase the crosslinking density of the functional coating 6 and enhance the mechanical properties of the functional coating 6 itself. On the other hand, more epoxy-based active functional groups are introduced onto the surface of the functional coating 6, providing more reactive sites for the subsequent polyurethane ink layer 3 to form more covalent bonds. Therefore, the embodiments of this application represent a targeted improvement for the interfacial bonding between the functional coating 6 and the ink layer 3, solving the defect of existing formulations that cannot simultaneously achieve scratch resistance and ink adhesion.

[0051] Understandably, when modified additives contain amino groups, they have similar advantages to epoxy groups and can also solve the problem that existing formulations cannot simultaneously achieve scratch resistance and ink adhesion.

[0052] In some embodiments, the ink layer 3 of the polyurethane material is prepared from an aqueous polyurethane resin, a crosslinking agent, a pigment, and a solvent.

[0053] It should be noted that the raw material formulations for functional coating 6 and ink layer 3 will be described in detail below.

[0054] In some embodiments, the cover plate 4 further includes a surface pretreatment layer (not shown) located between the functional coating 6 and the substrate 5; the content of hydroxyl (-OH) on the surface pretreatment layer is greater than the content of hydroxyl on the substrate 5.

[0055] In one specific embodiment, the pretreatment layer is obtained by plasma etching the surface of the substrate 5, which introduces more hydroxyl groups to enhance the covalent bonding with the functional coating 6.

[0056] Specifically, the surface of the UTG substrate 5 itself has a small amount of hydroxyl groups, but the hydroxyl group density is low. When the surface of the UTG substrate 5 is treated with oxygen plasma or argon plasma, the high-energy particles in the plasma (such as oxygen free radicals and ions) will break the Si-O-Si bonds on the surface of the UTG substrate 5, causing it to react with water vapor in the air or oxygen source in the treatment process to form a large number of hydroxyl groups, thereby effectively increasing the density of hydroxyl groups.

[0057] Understandably, the surface pretreatment layer is equivalent to the surface structure of the first surface 7 of the substrate 5, which is used to increase the hydroxyl content of the first surface 7 of the substrate 5. These hydroxyl groups can react with the first active functional group in the functional coating 6 to form covalent bonds, thereby making the covalent bonding force between the substrate 5 and the functional coating 6 stronger.

[0058] Of course, in other embodiments, the surface pretreatment layer can also be obtained by pretreating the surface of the substrate 5 using other methods, and this application does not limit this.

[0059] In some embodiments, the glass transition temperature range of the functional coating 6 is -20°C to 10°C. The low glass transition temperature of the functional coating 6 indicates that it possesses excellent flexibility, low-temperature adaptability, and interfacial adhesion, which is beneficial for improving the bending performance of the cover plate 4.

[0060] In some embodiments, the thickness of the functional coating 6 ranges from 20 micrometers to 40 micrometers.

[0061] In some embodiments, the thickness of the ink layer 3 ranges from 1 micrometer to 10 micrometers.

[0062] In some embodiments, the cover plate 4 can be applied in a flexible display device as a protective cover for the flexible display panel. In this case, the ink layer 3 is disposed corresponding to the non-display area of ​​the display panel.

[0063] In this embodiment, by selecting different polyurethane materials for the functional coating 6 and the ink layer 3 in the cover plate 4, a homologous system of polyurethane coating and polyurethane ink is constructed. This enhances the microscopic chemical bonding and physical anchoring force at the contact interface between the functional coating 6 and the ink layer 3, solving the problem of ink detachment from the ink layer 3 after UV cutting of the cover plate 4. Simultaneously, since both the functional coating 6 and the ink layer 3 in the cover plate 4 are made of polyurethane, the mechanical adjustability of polyurethane can be utilized to reduce the difference in mechanical properties between the ink layer 3 and the functional coating 6. This allows the elongation at break and flexibility of the functional coating 6 to match those of the ink layer 3, thereby avoiding the problem of deterioration in the bending performance of the functional coating 6 due to the difference in mechanical properties between the ink layer 3 and the functional coating 6.

[0064] Therefore, the embodiments of this application can simultaneously solve the problems of ink layer 3 on cover plate 4 losing ink during UV cutting and the deterioration of the bending performance of functional coating 6. In other words, this application can both prevent ink layer 3 on cover plate 4 from losing ink during UV cutting and improve the bending performance of functional coating 6.

[0065] This application also provides a polyurethane composition system for preparing the functional coating and ink layer in the cover plate described in the foregoing embodiments. The polyurethane composition system includes a modified polyurethane coating composition and a polyurethane ink composition, wherein the modified polyurethane coating composition is configured to form the functional coating 6 described in the foregoing embodiments, and the polyurethane ink composition is configured to form the ink layer 3 described in the foregoing embodiments.

[0066] The modified polyurethane coating composition contains hydroxyl-terminated polyurethane resin (HTPU), and the polyurethane ink composition contains waterborne polyurethane resin (WPU).

[0067] Understandably, both hydroxyl-terminated polyurethane resins and waterborne polyurethane resins are polyurethane derivatives.

[0068] In some embodiments, the modified polyurethane coating composition includes a hydroxyl-terminated polyurethane resin, a modifier, and a first solvent. The hydroxyl-terminated polyurethane resin has a number-average molecular weight ranging from 1000 g / mol to 5000 g / mol, the modifier contains at least one of epoxy and amino groups, and the first solvent includes at least one of ester solvents.

[0069] Understandably, number-average molecular weight reflects the average length of the molecular chains of hydroxyl-terminated polyurethane resins. In this application, the number-average molecular weight of the hydroxyl-terminated polyurethane resin is limited to between 1000 g / mol and 5000 g / mol, which balances excellent processing flowability with controllable crosslinking and curing properties, while also being suitable for low-viscosity, high-activity applications.

[0070] It should be noted that the modifier contains at least one of epoxy and amino groups. On the one hand, the epoxy and / or amino groups in the modifier react with the hydroxyl groups of the terminal hydroxyl polyurethane to increase the crosslinking density of the functional coating 6 and enhance the mechanical properties of the functional coating 6 itself. On the other hand, introducing more epoxy and / or amino active functional groups onto the surface of the functional coating 6 provides more reactive sites for the subsequent polyurethane ink layer 3, enabling the formation of more covalent bonds.

[0071] In some embodiments, the mass fraction of hydroxyl groups in the hydroxyl-terminated polyurethane resin ranges from 2% to 5%.

[0072] Understandably, hydroxyl groups are the active functional groups of hydroxyl-terminated polyurethane resins. When the content of hydroxyl groups is too high, the crosslinking point density between the hydroxyl-terminated polyurethane resin and the modifier is too large, which leads to an increase in the hardness and tensile strength of the cured functional coating 6, but a decrease in its flexibility and brittleness. When the content of hydroxyl groups is too low, the crosslinking points between the hydroxyl-terminated polyurethane resin and the modifier are insufficient, resulting in incomplete curing and a significant reduction in the mechanical strength of the formed functional coating 6. Therefore, in this embodiment, the mass fraction of hydroxyl groups in the hydroxyl-terminated polyurethane resin is controlled to be 2% to 5%, which can balance the mechanical strength and flexible bending performance of the functional coating 6.

[0073] In some embodiments, in the modified polyurethane coating composition, the mass fraction of the hydroxyl-terminated polyurethane resin ranges from 30% to 45%, the mass fraction of the modifier ranges from 3% to 8%, and the solid content of the first solvent ranges from 30% to 50%.

[0074] In some embodiments, the modifier includes at least one of ethylene glycol diglycidyl ether and diethylenetriamine, but is not limited thereto.

[0075] In some embodiments, the first solvent includes at least one of ethyl acetate and propylene glycol methyl ether acetate, but is not limited thereto.

[0076] In one specific embodiment, the modified polyurethane coating composition includes a hydroxyl-terminated polyurethane resin with a number average molecular weight of 3000 and a hydroxyl content of 3.5 wt%, an addition amount of 5 wt% of ethylene glycol diglycidyl ether (modifier), and an ethyl acetate (solvent) with a solid content of 40 wt%.

[0077] Understandably, the hydroxyl content is relative to the hydroxyl-terminated polyurethane resin, and the amount of modifier added and the solid content of the solvent are relative to the modified polyurethane coating composition.

[0078] In some embodiments, the raw material for the hydroxyl-terminated polyurethane resin consists of a first polyol, a first ester compound containing a diisocyanate group, and a first chain extender.

[0079] Understandably, hydroxyl-terminated polyurethane resins belong to polyurethane prepolymers.

[0080] In some embodiments, the raw material for the hydroxyl-terminated polyurethane resin comprises the following components in parts by weight: First polyol, 60 to 80 parts; First ester compound, 20 to 30 parts; and First chain extender, 1 to 8 parts.

[0081] In some embodiments, the first polyol includes, but is not limited to, any one or more of polytetrahydrofuran ether diol, polypropylene glycol, polybutylene adipate diol, and polyethylene adipate diol.

[0082] In some embodiments, the first ester compound includes, but is not limited to, any one or more of isophorone diisocyanate (IPDI), diphenylmethane diisocyanate, and toluene diisocyanate.

[0083] In some embodiments, the first chain extender includes any one or more of 1,4-butanediol and ethylene glycol, but is not limited thereto.

[0084] Understandably, the first chain extender is a small molecule chain extender, which is a class of low molecular weight compounds with a molecular weight of less than 500 g / mol and containing two or more active functional groups. Its core function is to react with the active end groups of polyurethane prepolymers (such as NCO-terminated prepolymers and OH-terminated prepolymers) to extend the molecular chain length, increase the molecular weight of the resin, and at the same time regulate the crosslinking density and mechanical properties of the material.

[0085] In some embodiments, the raw material composition of the hydroxyl-terminated polyurethane resin is shown in Table 1.

[0086] Table 1

[0087] For example, in one specific embodiment, the raw materials for the hydroxyl-terminated polyurethane resin consist of 70 parts by weight of polytetrahydrofuran ether diol, 25 parts by weight of isophorone diisocyanate, and 5 parts by weight of 1,4-butanediol.

[0088] In some embodiments, the synthesis process (i.e., reaction stage) of hydroxyl-terminated polyurethane resin includes four stages: raw material preheating, prepolymerization reaction, chain extension reaction, and cooling discharge. The experimental conditions for each stage are shown in Table 2.

[0089] Table 2

[0090] In some embodiments, the polyurethane ink composition comprises an aqueous polyurethane resin, a crosslinking agent, a pigment, and a second solvent. The number-average molecular weight of the aqueous polyurethane resin ranges from 2000 g / mol to 6000 g / mol, and the crosslinking agent contains isocyanate groups.

[0091] Understandably, when the number average molecular weight of waterborne polyurethane resin is limited to 2000 g / mol to 6000 g / mol, it can balance water dispersion stability, processability, and post-curing basic properties, while also being suitable for low-viscosity, thin-coat, and fast-curing applications.

[0092] In some embodiments, the mass fraction of carboxyl groups in the aqueous polyurethane resin ranges from 1% to 3%.

[0093] It should be noted that the mass fraction of carboxyl groups in the waterborne polyurethane resin determines its water dispersion stability, film-forming properties, and application suitability. Specifically, carboxyl groups are hydrophilic groups in waterborne polyurethane resins. During synthesis, they are neutralized by a neutralizing agent (such as triethylamine) to generate carboxylate ions, which stabilize the polyurethane particles in the aqueous phase through electrostatic repulsion, preventing stratification and flocculation. Simultaneously, carboxyl groups are highly polar and act as active groups. After the ink layer forms a film, they can form hydrogen bonds or ionic bonds with hydroxyl and amino groups in the functional coating, improving the adhesion between the ink layer and the functional coating. Therefore, in this application embodiment, by controlling the mass fraction of carboxyl groups in the waterborne polyurethane resin to 1% to 3%, both water dispersion stability and water resistance can be achieved, while also improving the adhesion between the ink layer and the functional coating.

[0094] In some embodiments, in the polyurethane ink composition, the waterborne polyurethane resin has a mass fraction ranging from 40% to 60%, the crosslinking agent has a mass fraction ranging from 5% to 12%, the pigment has a mass fraction ranging from 10% to 20%, and the second solvent has a solid content ranging from 30% to 45%.

[0095] In some embodiments, the crosslinking agent includes at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate, but is not limited thereto.

[0096] In some embodiments, the pigment includes at least one of carbon black and titanium dioxide, but is not limited thereto.

[0097] In some embodiments, the second solvent comprises deionized water.

[0098] In one specific embodiment, the polyurethane ink composition comprises an aqueous polyurethane resin with a number average molecular weight of 4000 and a carboxyl content of 2 wt%, an addition amount of 8 wt% of hexamethylene diisocyanate trimer (crosslinking agent), an addition amount of 15 wt% of carbon black (pigment), and a solid content of 35 wt% of deionized water (solvent).

[0099] Understandably, the carboxyl content is relative to the waterborne polyurethane resin, while the amount of crosslinking agent and pigment added, as well as the solid content of the solvent, are relative to the polyurethane ink composition.

[0100] In some embodiments, the raw materials for the waterborne polyurethane resin consist of a second polyol, a second ester compound containing a diisocyanate group, a second chain extender, and a neutralizing agent. Alternatively, the raw materials for the waterborne polyurethane resin consist of a second polyol, a second ester compound, and a second chain extender.

[0101] Understandably, waterborne polyurethane resins also belong to polyurethane prepolymers.

[0102] In some embodiments, the second chain extender includes at least one of a hydrophilic chain extender and a small molecule chain extender.

[0103] In some embodiments, the raw material of the waterborne polyurethane resin comprises the following components in parts by weight: Second polyol, 50 to 70 parts; Second ester compound, 20 to 30 parts; Hydrophilic chain extender, 4 to 8 parts; Small molecule chain extender, 3 to 7 parts; and Neutralizing agent, 2 to 4 parts.

[0104] In another embodiment, the raw material for the waterborne polyurethane resin comprises the following components in parts by weight: Second polyol, 50 to 70 parts; Second ester compound, 20 to 30 parts; and Small molecule chain extender, 10 to 20 parts.

[0105] In some embodiments, the second polyol in the raw materials of the waterborne polyurethane resin includes, but is not limited to, any one or more of polytetrahydrofuran ether diol, polybutylene adipate diol, and methoxy polyethylene glycol.

[0106] In some embodiments, the second ester compound includes, but is not limited to, any one or more of isophorone diisocyanate, toluene diisocyanate, and dicyclohexylmethane diisocyanate.

[0107] In some embodiments, the hydrophilic chain extender includes any one or more of dimethylolpropionic acid, dimethylolbutyric acid, and N-methyldiethanolamine, but is not limited thereto.

[0108] In some embodiments, the neutralizing agent includes, but is not limited to, any one or more of dimethylethanolamine (DMEA), triethylamine (TEA), and acetic acid (CH3COOH).

[0109] In some embodiments, the small molecule chain extender includes any one or more of 1,4-butanediol, ethylene glycol, and 1,6-butanediol, but is not limited thereto.

[0110] In some embodiments, the raw material composition of the waterborne polyurethane resin is shown in Table 3.

[0111] Table 3

[0112] For example, in one specific embodiment, the raw materials of the waterborne polyurethane resin consist of 60 parts by weight of polytetrahydrofuran ether diol, 25 parts by weight of isophorone diisocyanate, 6 parts by weight of dimethylolpropionic acid, 4 parts by weight of dimethylethanolamine and 5 parts by weight of 1,4-butanediol.

[0113] In some embodiments, the synthesis process (i.e., reaction stage) of the waterborne polyurethane resin includes four stages: prepolymer preparation, cooling and neutralization, water dispersion and curing. The experimental conditions for each stage are shown in Table 4.

[0114] Table 4

[0115] In this embodiment, the modified polyurethane coating composition and polyurethane ink composition in the polyurethane composition system can be used to prepare the functional coating and ink layer in the aforementioned embodiments, respectively. This improves the microscopic chemical bonding force and physical anchoring force at the contact interface between the functional coating and the ink layer, solving the problem of ink detachment after UV cutting of the cover plate. Simultaneously, the mechanical properties of the prepared functional coating and ink layer are similar, achieving a match between the elongation at break and flexibility of the functional coating and the ink layer, thereby avoiding the problem of deteriorated bending performance of the functional coating due to differences in mechanical properties between the ink layer and the functional coating.

[0116] like Figure 3 As shown, this application embodiment also provides a method for preparing the cover plate described in the foregoing embodiment, the method comprising steps S301 to S30: S301: Provide a substrate; wherein the substrate includes a first surface and a second surface disposed opposite to each other along the thickness direction of the substrate.

[0117] Specifically, step S301 further includes cleaning and pre-treating the substrate surface, so that the first surface and side surface of the substrate are formed with the surface pre-treatment layer described in the foregoing embodiments.

[0118] S302: Configuring modified polyurethane coating compositions and polyurethane ink compositions in polyurethane composition systems.

[0119] For example, the modified polyurethane coating composition includes a hydroxyl-terminated polyurethane resin with a number average molecular weight of 3000 and a hydroxyl content of 3.5 wt%, an addition amount of 5 wt% of ethylene glycol diglycidyl ether (modifier), and ethyl acetate (solvent) with a solid content of 40 wt%.

[0120] The raw materials for the hydroxyl-terminated polyurethane resin consist of 70 parts by weight of polytetrahydrofuran ether diol, 25 parts by weight of isophorone diisocyanate, and 5 parts by weight of 1,4-butanediol.

[0121] For example, the polyurethane ink composition includes an aqueous polyurethane resin with a number average molecular weight of 4000 and a carboxyl content of 2 wt%, an addition amount of 8 wt% of hexamethylene diisocyanate trimer (crosslinking agent), an addition amount of 15 wt% of carbon black (pigment), and a solid content of 35 wt% of deionized water (solvent).

[0122] The raw materials for the waterborne polyurethane resin consist of 60 parts by weight of polytetrahydrofuran ether diol, 25 parts by weight of isophorone diisocyanate, 6 parts by weight of dimethylolpropionic acid, 4 parts by weight of dimethylethanolamine and 5 parts by weight of 1,4-butanediol.

[0123] S303: The modified polyurethane coating composition is applied to at least the first and / or second surfaces of a substrate, and the modified polyurethane coating composition is cured to form a functional coating.

[0124] Specifically, the curing treatment of the modified polyurethane coating composition includes the following steps: The modified polyurethane coating was cured at 80°C to 120°C for 30 to 60 minutes.

[0125] S304: A polyurethane ink composition is printed at least on a portion of the surface of a functional coating, and the polyurethane ink composition is cured to form an ink layer; wherein the functional coating and the ink layer are connected at least by covalent bonds.

[0126] Specifically, the curing process for the polyurethane ink composition includes the following steps: The polyurethane ink composition is cured at 60°C to 100°C for 20 to 40 minutes.

[0127] S305: Cut the substrate with the functional coating and ink layer to form a cover plate of the target size.

[0128] Specifically, a UV laser is used to cut the substrate with the functional coating and ink layer.

[0129] In one specific embodiment, such as Figure 1 As shown, the substrate 5 also includes a side surface 9 connected between the first surface 7 and the second surface 8, and a functional coating 6 covers the first surface 7 and the side surface 9 of the substrate 5. The functional coating 6 has a third surface 10 disposed on the same side as the second surface 8, and the ink layer 3 covers at least the third surface 10.

[0130] In this embodiment, by selecting different polyurethane materials for the functional coating and ink layer in the cover plate, a homologous system of polyurethane coating-polyurethane ink is constructed. This enhances the microscopic chemical bonding and physical anchoring force at the contact interface between the functional coating and the ink layer, solving the problem of ink detachment after UV cutting of the cover plate. Simultaneously, since both the functional coating and ink layer in the cover plate are made of polyurethane, the mechanical adjustability of polyurethane can be utilized to reduce the difference in mechanical properties between the ink layer and the functional coating. This allows the elongation at break and flexibility of the functional coating to match those of the ink layer, thereby avoiding the problem of deterioration in the bending performance of the functional coating due to the difference in mechanical properties between the ink layer and the functional coating.

[0131] Therefore, the embodiments of this application can simultaneously solve the problems of ink loss from the cover plate during UV cutting and the deterioration of the bending performance of the functional coating. In other words, this application can both prevent ink loss from the cover plate during UV cutting and improve the bending performance of the functional coating.

[0132] This application also provides an embodiment and two comparative examples, and performs UV cutting and tensile tests on the cover plates provided in the embodiment and comparative examples, thereby verifying the improvement of the cover plates provided in this application in terms of UV cutting ink smudging and bending performance degradation.

[0133] Example 1 Example 1 provides as follows Figure 2 The experimental cover plate shown has a substrate of 60 micrometers thick ultrathin glass, and the functional coating and ink layer in the experimental cover plate are prepared by modified polyurethane coating composition and polyurethane ink composition respectively according to the preparation method described in the foregoing embodiments.

[0134] Specifically, the modified polyurethane coating composition includes a hydroxyl-terminated polyurethane resin with a number average molecular weight of 3000 and a hydroxyl content of 3.5 wt%, ethylene glycol diglycidyl ether (modifier) ​​with an addition amount of 5 wt%, and ethyl acetate (solvent) with a solid content of 40 wt%.

[0135] The raw materials for the hydroxyl-terminated polyurethane resin consist of 70 parts by weight of polytetrahydrofuran ether diol, 25 parts by weight of isophorone diisocyanate, and 5 parts by weight of 1,4-butanediol.

[0136] Specifically, the polyurethane ink composition includes an aqueous polyurethane resin with a number average molecular weight of 4000 and a carboxyl content of 2 wt%, an addition amount of 8 wt% of hexamethylene diisocyanate trimer (crosslinking agent), an addition amount of 15 wt% of carbon black (pigment), and a solid content of 35 wt% of deionized water (solvent).

[0137] The raw materials for the waterborne polyurethane resin consist of 60 parts by weight of polytetrahydrofuran ether diol, 25 parts by weight of isophorone diisocyanate, 6 parts by weight of dimethylolpropionic acid, 4 parts by weight of dimethylethanolamine and 5 parts by weight of 1,4-butanediol.

[0138] Comparative Example 1 Comparative Example 1 provides a first control cover plate, which differs from the experimental cover plate in that it does not have an ink layer, but has the same structure otherwise.

[0139] Comparative Example 2 Comparative Example 2 provides a second control cover plate, which differs from the experimental cover plate in that the material of the ink layer is replaced with commercially available polyester ink (model: TOYO Ink TC-FD6000).

[0140] This application conducted three repeated UV cutting tests on the experimental cover plate provided in Example 1 and the second comparative cover plate provided in Comparative Example 2, respectively. The cutting locations are as follows: Figure 1 As shown. The ink smudge width was measured after cutting, and the measurement results are as follows: Figure 4a , Figure 4b and Figure 4c As shown, after three repeated UV cuts, the ink layer 3 of the experimental cover plate had an ink loss width of 0 in all cases; Figure 5a , Figure 5b and Figure 5c As shown, after three repeated UV cuts, the ink fading widths of the second comparison cover plate were 37 micrometers (μm), 38 micrometers, and 34 micrometers, respectively. This demonstrates that, compared to the modified polyurethane coating-polyurethane ink system, the modified polyurethane coating-polyurethane ink homologous system provided in this application can effectively solve the problem of ink fading during UV cutting.

[0141] This application also conducted tensile tests on the experimental cover plate provided in Example 1, the first comparative cover plate provided in Comparative Example 1, and the second comparative cover plate provided in Comparative Example 2. The elastic modulus, elongation at break, tensile strength, and stress at the fracture point of each cover plate are shown in Table 5.

[0142] Specifically, the thickness, width, gauge length, and tensile speed of the experimental cover plate, the first comparison cover plate, and the second comparison cover plate are shown in Table 5, and the tensile test standard is GB / T528-2009.

[0143] Table 5

[0144] As shown in Table 5, after setting a polyurethane ink layer on the UTG substrate with a modified polyurethane functional coating, the elastic modulus, elongation at break, and tensile strength of the experimental cover plate (UTG composite structure) were significantly improved. This indicates that the polyurethane ink layer and the modified polyurethane functional coating can effectively enhance the rigidity, toughness, and tensile strength of the cover plate.

[0145] After a polyester ink layer was applied to the UTG substrate with the modified polyurethane functional coating, the mechanical properties of the second control cover were all lower than those of the first control cover without an ink layer and the experimental cover with a polyurethane ink layer, indicating that polyester ink is not suitable as a reinforcing coating for UTG.

[0146] like Figure 6 As shown, this application embodiment also provides a display device 11, which includes a display panel 12 and a cover plate 4 as described in the foregoing embodiment, with the cover plate 4 located at least on one side of the display panel 12.

[0147] In some embodiments, the cover plate 4 is located on the light-emitting side of the display panel 12, the display panel 12 includes a display area and a non-display area, and the ink layer 3 is disposed corresponding to the non-display area of ​​the display panel 12.

[0148] In some embodiments, the display panel 12 is a flexible OLED panel, but is not limited thereto.

[0149] In this embodiment, since the materials of the functional coating 6 and the ink layer 3 on the cover plate 4 are selected from different polyurethane materials, a homologous system of polyurethane coating-polyurethane ink is constructed, which improves the adhesion and mechanical compatibility between the ink layer 3 and the functional coating 6 on the cover plate 4, which is beneficial to improving the yield and bending reliability of the cover plate 4, thereby improving the yield and bending reliability of the display device 11.

[0150] The foregoing has provided a detailed description of a cover plate, a polyurethane composition system, a method for preparing the cover plate, and a display device provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A cover plate, characterized in that, include: The substrate includes a first surface and a second surface disposed opposite to each other along the thickness direction of the cover plate; A functional coating that at least covers the first surface and / or the second surface; An ink layer covers a portion of the surface of the functional coating; The functional coating and the ink layer are made of different polyurethane materials, and the functional coating and the ink layer are connected by at least covalent bonds.

2. The cover plate according to claim 1, characterized in that, The material of the functional coating includes a modified polyurethane material having a first active functional group, and the material of the ink layer includes a polyurethane material having a second active functional group, wherein the first active functional group and the second active functional group are complementary functional groups.

3. The cover plate according to claim 2, characterized in that, The first active functional group includes at least one of hydroxyl, amino and epoxy groups, and the second active functional group includes at least one of isocyanate group, carboxyl group and siloxane group.

4. The cover plate according to claim 1, characterized in that, The cover plate further includes a surface pretreatment layer located between the functional coating and the substrate; the hydroxyl content on the surface pretreatment layer is greater than the hydroxyl content on the substrate.

5. The cover plate according to any one of claims 1 to 4, characterized in that, The glass transition temperature range of the functional coating is -20°C to 10°C.

6. A polyurethane composition system, characterized in that, The polyurethane composition system includes a modified polyurethane coating composition and a polyurethane ink composition, wherein the modified polyurethane coating composition is configured to form the functional coating as described in claim 1, and the polyurethane ink composition is configured to form the ink layer as described in claim 1. The modified polyurethane coating composition contains hydroxyl-terminated polyurethane resin, and the polyurethane ink composition contains waterborne polyurethane resin.

7. The polyurethane composition system according to claim 6, characterized in that, The modified polyurethane coating composition comprises the hydroxyl-terminated polyurethane resin, a modifier, and a first solvent; The number-average molecular weight of the hydroxyl-terminated polyurethane resin ranges from 1000 g / mol to 5000 g / mol, the modifier contains at least one of epoxy and amino groups, and the first solvent includes at least one of ester solvents.

8. The polyurethane composition system according to claim 7, characterized in that, In the modified polyurethane coating composition, the mass fraction of the hydroxyl-terminated polyurethane resin ranges from 30% to 45%, the mass fraction of the modifier ranges from 3% to 8%, and the solid content of the first solvent ranges from 30% to 50%.

9. The polyurethane composition system according to claim 7, characterized in that, The modifier includes at least one of ethylene glycol diglycidyl ether and diethylenetriamine, and the first solvent includes at least one of ethyl acetate and propylene glycol methyl ether acetate.

10. The polyurethane composition system according to claim 6, characterized in that, The polyurethane ink composition includes the aqueous polyurethane resin, a crosslinking agent, a pigment, and a second solvent; The number-average molecular weight of the waterborne polyurethane resin ranges from 2000 g / mol to 6000 g / mol, and the crosslinking agent contains isocyanate groups.

11. The polyurethane composition system according to claim 10, characterized in that, In the polyurethane ink composition, the waterborne polyurethane resin has a mass fraction ranging from 40% to 60%, the crosslinking agent has a mass fraction ranging from 5% to 12%, the pigment has a mass fraction ranging from 10% to 20%, and the second solvent has a solid content ranging from 30% to 45%.

12. The polyurethane composition system according to claim 10, characterized in that, The crosslinking agent includes at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate, the pigment includes at least one of carbon black and titanium dioxide, and the second solvent includes deionized water.

13. The polyurethane composition system according to any one of claims 6 to 12, characterized in that, The raw materials of the hydroxyl-terminated polyurethane resin are composed of a first polyol, a first ester compound containing a diisocyanate group, and a first chain extender; the raw materials of the waterborne polyurethane resin are composed of a second polyol, a second ester compound containing a diisocyanate group, a second chain extender, and a neutralizing agent, or the raw materials of the waterborne polyurethane resin are composed of the second polyol, the second ester compound, and the second chain extender.

14. The polyurethane composition system according to claim 13, characterized in that, The first polyol includes any one or more of polytetrahydrofuran ether diol, polypropylene glycol, polybutylene adipate diol, and polyethylene adipate diol; the first ester compound includes any one or more of isophorone diisocyanate, diphenylmethane diisocyanate, and toluene diisocyanate; and the first chain extender includes any one or more of 1,4-butanediol and ethylene glycol. The second polyol includes one or more of polytetrahydrofuran ether diol, polybutylene adipate diol, and methoxy polyethylene glycol; the second ester compound includes one or more of isophorone diisocyanate, toluene diisocyanate, and dicyclohexylmethane diisocyanate; the second chain extender includes one or more of dimethylolpropionic acid, dimethylolbutyric acid, N-methyldiethanolamine, 1,4-butanediol, ethylene glycol, and 1,6-butanediol; and the neutralizing agent includes one or more of dimethylethanolamine, triethylamine, and acetic acid.

15. A method for preparing a cover plate, characterized in that, Includes the following steps: A substrate is provided; wherein the substrate includes a first surface and a second surface disposed opposite to each other along the thickness direction of the substrate; Configure the modified polyurethane coating composition and the polyurethane ink composition in the polyurethane composition system according to any one of claims 6 to 14; The modified polyurethane coating composition is applied at least to the first surface and / or the second surface of the substrate, and the modified polyurethane coating composition is cured to form a functional coating; and The polyurethane ink composition is printed onto a portion of the surface of the functional coating, and the polyurethane ink composition is cured to form an ink layer; wherein the functional coating and the ink layer are connected by at least covalent bonds.

16. The method for preparing the cover plate according to claim 15, characterized in that, The curing treatment of the modified polyurethane coating composition includes the following steps: The modified polyurethane coating is cured at 80°C to 120°C for 30 to 60 minutes. The curing process of the polyurethane ink composition includes the following steps: The polyurethane ink composition is cured at 60°C to 100°C for 20 to 40 minutes.

17. A display device, characterized in that, It includes a display panel and a cover plate as described in any one of claims 1 to 5, the cover plate being located on at least one side of the display panel.

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