Alignment film material, alignment film, display panel and display device

Abstract

The embodiment of the invention discloses an alignment film material, an alignment film, a display panel and a display device.The alignment film material comprises 1.14%-1.52% of soluble polyimide and 1.9%-2.47% of polyamide acid, the alignment film material takes a compound system of the soluble polyimide and the polyamide acid as a main body material for film forming, and the main body material is matched with a proper proportion, so that the alignment film material is prepared. The coating property and stability of the alignment film material can be effectively improved, then the film forming quality and performance of the alignment film are improved, and the problems that the edge of the alignment film is poor, and display on the periphery of a display panel is uneven are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to an alignment film material, an alignment film, a display panel and a display device. BACKGROUND

[0002] A liquid crystal display (LCD) panel usually needs to be provided with an alignment film on a substrate to realize alignment of liquid crystals. A commonly used alignment film material is polyimide (PI), and the conventional polyimide has poor coating property. In some processes, a precursor of polyimide, polyamic acid (PAA), is first coated on the substrate, and then cured by a high-temperature imidization method to form a polyimide alignment film. Although polyamic acid has good coating property, it has poor stability, and the edge of the film layer is prone to shrinkage and deformation during the curing process, resulting in edge defects of the alignment film. Therefore, the existing alignment film material cannot balance the coating property and stability, and has poor film forming quality, which easily leads to display unevenness (Mura) of the display product. SUMMARY

[0003] The present application provides an alignment film material, an alignment film, a display panel and a display device, which can effectively improve the coating property and stability of the alignment film material, improve the film forming quality and performance of the alignment film, and improve the edge defects of the alignment film and the display unevenness of the display panel.

[0004] The present application provides an alignment film material, which comprises, in mass percentage: a soluble polyimide 1.14% to 1.52%; and a polyamic acid 1.9% to 2.47%.

[0005] In some embodiments, the alignment film material further comprises, in mass percentage: a bridging agent 0.19% to 0.38%.

[0006] In some embodiments, the bridging agent comprises at least one of a silane coupling agent, a titanate coupling agent and a phosphorus-based coupling agent.

[0007] In some embodiments, the alignment film material further comprises a solvent composition, and the solvent composition comprises a first solvent and a second solvent, wherein the boiling point of the first solvent is higher than the boiling point of the second solvent, and the surface tension of the first solvent is lower than the surface tension of the second solvent.

[0008] The present application also provides an alignment film formed by the alignment film material as described above. The alignment film comprises a first polymer layer and a second polymer layer, and the first polymer layer and the second polymer layer are connected by a chemical bond.

[0009] In some embodiments, the first polymer layer comprises the soluble polyimide, and the second polymer layer comprises a polyimide formed after dehydration of the polyamide acid, the structure of the polyimide being the same as or different from the structure of the soluble polyimide.

[0010] The present application also provides a display panel, comprising: a first substrate and a second substrate arranged oppositely; a liquid crystal layer arranged between the first substrate and the second substrate; a first alignment film arranged on a side of the first substrate close to the liquid crystal layer; and a second alignment film arranged on a side of the second substrate close to the liquid crystal layer; wherein the first alignment film comprises the alignment film as described above, and the second alignment film comprises the alignment film as described above.

[0011] In some embodiments, the first alignment film is configured to generate a first pre-tilt angle for liquid crystal molecules close thereto, the second alignment film is configured to generate a second pre-tilt angle for liquid crystal molecules close thereto, and the direction of the first pre-tilt angle is different from the direction of the second pre-tilt angle.

[0012] In some embodiments, the first alignment film comprises a first polymer layer and a second polymer layer, the first polymer layer is located on a side of the second polymer layer away from the substrate, the first polymer layer comprises a first soluble polyimide, and the second polymer layer comprises a first polyimide formed after dehydration of a first polyamide acid, the structure of the first polyimide being the same as or different from the structure of the first soluble polyimide; the second alignment film comprises a third polymer layer and a fourth polymer layer, the third polymer layer is located on a side of the fourth polymer layer away from the substrate, the third polymer layer comprises a second soluble polyimide, and the fourth polymer layer comprises a second polyimide formed after dehydration of a second polyamide acid, the structure of the second polyimide being the same as or different from the structure of the second soluble polyimide; wherein the structure of the first soluble polyimide is the same as or different from the structure of the second soluble polyimide, and / or the structure of the first polyamide acid is the same as or different from the structure of the second polyamide acid.

[0013] The present application also provides a display device comprising the display panel as described above.

[0014] The application provides an alignment film material, an alignment film, a display panel and a display device, the alignment film material comprises 1.14%-1.52% of soluble polyimide and 1.9%-2.47% of polyamide acid 1.9%-2.47%; the alignment film material is a complex system of soluble polyimide and polyamide acid as a main body material for film formation, and is matched with a proper ratio, so that the coating property and stability of the alignment film material can be effectively improved, the film formation quality and performance of the alignment film are improved, and the edge defects of the alignment film and the display panel and the display panel are improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is a residual direct current voltage (RDC)-release time curve diagram of two alignment films; Figure 2 is an edge picture of two alignment films; Figure 3 is a schematic diagram of an alignment film structure provided by the application; Figure 4 is a schematic diagram of a display panel structure provided by the application; Figure 5 is a schematic diagram of a first soluble polyimide and a second soluble polyimide provided by the application; Figure 6 is an ion adsorption schematic diagram of a display panel using a prior art alignment film; Figure 7 is Figure 6 is a schematic diagram of a Best Vcom Shift test of a display panel over time; Figure 8 is an ion adsorption schematic diagram of a display panel using an alignment film provided by the application; Figure 9 is Figure 8 is a schematic diagram of a Best Vcom Shift test of a display panel over time.

[0017] Legend of the drawings: 10, display panel; 100, alignment film; 101, first polymer layer; 102, second polymer layer; 110, first alignment film; 120, second alignment film; 210, first substrate; 220, second substrate; 230, liquid crystal layer; 240, ion. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0019] The present application provides an alignment film material, which comprises, in mass percentage: 1.14% to 1.52% of soluble polyimide, and 1.9% to 2.47% of polyamic acid.

[0020] In the present application, the main material part of the alignment film material adopts a compound system of soluble polyimide and polyamic acid. The soluble polyimide is a polyimide modified by molecular structure, which improves its solubility in organic solvents by introducing flexible chain segments, asymmetric structures or substituents, etc. At the same time, the soluble polyimide contains a ring-closed polyimide structure, which is stable in structure and has good thermal stability and ultraviolet light (UV) stability, but the adhesion is weak. The polyamic acid is a precursor of polyimide, which contains a large number of polar groups such as carboxyl and amino groups on the molecular chain, and has good coating properties, but the thermal stability and ultraviolet light (UV) stability are weak. The compound of soluble polyimide and polyamic acid has complementary performance, which can synergistically improve the coating properties and stability of the whole alignment film material, improve the film forming quality of the alignment film, and improve the edge defects of the alignment film and the display unevenness (Mura) of the display product. Especially for curved display products, the compound system of soluble polyimide and polyamic acid is beneficial to the improvement of the coating properties and stability of the edge of the curved display product, and then improves the film forming quality of the edge curved surface of the curved display product, so as to improve the display quality.

[0021] In the alignment film material of the present application, the mass percentage of soluble polyimide is 1.14% to 1.52%, for example, the mass percentage of soluble polyimide can be 1.14%, 1.20%, 1.25%, 1.30%, 1.35%, 1.40%, 1.45%, 1.50%, 1.52%, etc.; the mass percentage of polyamic acid is 1.9% to 2.47%, for example, the mass percentage of polyamic acid can be 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.47%, etc. When the content of soluble polyimide and polyamic acid is within the above range, the uniformity of coating can be guaranteed, and the relative stability of the film layer during the curing process can be guaranteed, the edge defects can be improved, the formed alignment film has good film forming quality, so as to meet the needs of display products, and avoid the display unevenness (Mura) of the display product.

[0022] In some embodiments, the alignment membrane material further includes, by weight percentage, 0.19% to 0.38% of a crosslinking agent. The crosslinking agent can be a small molecule compound having two or more reactive functional groups. During the synthesis of the alignment membrane (typically high-temperature imidization), the active functional groups on the crosslinking agent (such as epoxy groups, hydroxyl groups, amino groups, unsaturated double bonds, etc.) react chemically with specific functional groups (such as terminal amino groups, carboxyl groups, or active sites on the main chain) on the polymer molecular chains of soluble polyimide, polyamic acid, etc. This chemical reaction introduces stable covalent bond "bridges," connecting the originally relatively loose linear or branched polymer chains bound by van der Waals forces into a three-dimensional network structure, thereby improving the compactness of the membrane layer.

[0023] Furthermore, the crosslinking agent may include at least one of silane coupling agents, titanate coupling agents, and phosphorus-based coupling agents, but is not limited thereto.

[0024] In the alignment membrane material of this application, the mass percentage of the crosslinking agent ranges from 0.19% to 0.38%. For example, the mass percentage of the crosslinking agent can be 0.19%, 0.25%, 0.30%, 0.35%, 0.38%, etc. When the content of the crosslinking agent is within the above range, it can ensure that the alignment membrane has good density, so as to avoid excessive crosslinking agent affecting the coating properties and toughness of the alignment membrane material, while insufficient crosslinking agent results in poor membrane density.

[0025] In this application, the alignment film formed by the alignment film material containing a compound system of soluble polyimide and polyamic acid and a crosslinking agent has good film quality and high film density. When used in a liquid crystal display panel, it can block impurity ions from entering the liquid crystal layer, reduce the total amount of impurity ions in the liquid crystal layer, thereby reducing the accumulation of impurity ions at the alignment film interface, improving the migration and release rate of impurity ions, improving the voltage retention capability (VHR) of the liquid crystal layer, reducing residual DC voltage (RDC), improving problems such as ion retention, and improving the display quality of the display panel.

[0026] Please refer to Figure 1 , Figure 1 This is a comparison of the residual DC voltage (RDC)-release time curves for display panels using alignment film material a and alignment film material b. Alignment film material a contains a crosslinking agent, while alignment film material b does not. All other components of alignment film materials a and b are identical. Figure 1It can be seen that the total amount of ions in the liquid crystal layer corresponding to alignment film material a is reduced, the ions are released quickly, and the RDC is significantly optimized. This indicates that the bridging agent can improve the compactness of the alignment film, reduce the accumulation of impurity ions at the alignment film interface, improve the migration and release rate of impurity ions, and reduce the residual DC voltage (RDC).

[0027] In some embodiments, the alignment membrane material further includes a solvent composition comprising a first solvent and a second solvent, wherein the boiling point of the first solvent is greater than that of the second solvent, and the surface tension of the first solvent is less than that of the second solvent. By adding a high-boiling-point, low-surface-tension solvent to the solvent system, the uniformity of solvent evaporation rates between the membrane edge and the center can be improved, the width of the Halo region can be reduced, the edge precision of the membrane can be improved, the straightness of the membrane edge can be improved, and the film formation quality can be further enhanced.

[0028] It is understandable that the solvent composition may also include a third solvent, a fourth solvent, a fifth solvent, etc. The boiling points and surface tensions of the solvents in the solvent composition may be different. The combination of solvents with multiple boiling points and multiple surface tensions can make the solvent evaporate in a gradient, while ensuring the spreadability of the material, thereby improving the coating properties and film uniformity of the alignment film material.

[0029] In some embodiments, the first solvent may be an ether solvent or a propylene glycol solvent, but is not limited thereto. Ether solvents include ethylene glycol monobutyl ether (BCS), dipropylene glycol methyl ether (DPM), dipropylene glycol dimethyl ether (DME), etc.; propylene glycol solvents include dipropylene glycol methyl ether (DPM), dipropylene glycol dimethyl ether (DME), etc., but are not limited thereto.

[0030] The second solvent can be an ester solvent or a pyrrolidone solvent, but is not limited to these. Among them, ester solvents include γ-butyrolactone (GBL); pyrrolidone solvents include N-ethylpyrrolidone (NEP) and N-methylpyrrolidone (NMP), but are not limited to these.

[0031] In some embodiments, the solvent composition may include (by weight percentage): 24% to 34% N-ethylpyrrolidone, 7% to 17% γ-butyrolactone, 15% to 25% ethylene glycol monobutyl ether, 20% to 30% dipropylene glycol methyl ether, and 5% to 15% dipropylene glycol dimethyl ether.

[0032] For example, the solvent composition may include (in weight percentages): 29.2% N-ethylpyrrolidone, 12% γ-butyrolactone, 20% ethylene glycol monobutyl ether, 25% dipropylene glycol methyl ether, and 10% dipropylene glycol dimethyl ether.

[0033] In this application, by combining solvents with different boiling points and surface tensions and optimizing the solvent ratio, the uniformity of solvent evaporation throughout the entire film layer can be further improved, thus ensuring the quality of film formation.

[0034] Please refer to Figure 2 , Figure 2 These are comparative images of the edges of alignment membranes formed using alignment membrane material c and alignment membrane material d. The solvents (by mass percentage) for alignment membrane material c include: NMP 45%, GBL 7%, and BCS 45%. The solvents for alignment membrane material d include: NEP 29.2%, GBL 12%, BCS 20%, DMP 25%, and DME 10%. All other components of alignment membrane materials c and d are identical. Figure 2 It can be seen that the alignment film material c exhibits poor edge straightness, while the alignment film material d shows significantly improved edge straightness. This indicates that adding a high-boiling-point, low-surface-tension solvent to the solvent system and optimizing the solvent ratio can significantly improve the edge straightness of the film.

[0035] Please refer to Table 1, which shows the Halo region width data of alignment films formed using alignment film material c and alignment film material d. As can be seen from the data in Table 1, the Halo region width of the alignment film formed using alignment film material d of this application is significantly reduced.

[0036] Table 1

[0037] In some embodiments, the alignment membrane material may also contain other additives, such as alignment modifiers, antioxidants, surfactants, defoamers, etc., but is not limited thereto.

[0038] This application also provides an alignment film 100, which is formed from the alignment film material described above. Please refer to... Figure 3 The alignment film 100 includes a first polymer layer 101 and a second polymer layer 102, which are connected by chemical bonds.

[0039] Furthermore, the first polymer layer 101 contains the aforementioned soluble polyimide, and the second polymer layer 102 contains polyimide formed by dehydrating the aforementioned polyamic acid.

[0040] In some embodiments, the soluble polyimide contained in the first polymer layer 101 may have a different structure than the polyimide contained in the second polymer layer 102, which is formed by dehydrating polyamic acid.

[0041] In some embodiments, the soluble polyimide contained in the first polymer layer 101 and the polyimide contained in the second polymer layer 102 formed by dehydration of polyamic acid may have the same structure. In this case, the polyamic acid may be a precursor of the soluble polyimide, that is, the polyimide formed by dehydration of polyamic acid is a soluble polyimide.

[0042] In the process of forming the alignment film 100, the components of the alignment film material are first mixed to form an alignment liquid, then the alignment liquid is uniformly coated on the substrate and pre-cured to form a semi-cured film, and then the semi-cured film is completely cured at high temperature to form the alignment film 100. In the above process, due to the difference in molecular structure between soluble polyimide and polyamic acid, during the coating and pre-curing stage, polyamic acid will aggregate towards the side closer to the substrate, while soluble polyimide will aggregate towards the side farther from the substrate. As the solvent evaporates, soluble polyimide and polyamic acid will separate into layers. The side closer to the substrate is the polyamic acid layer, and the side of the polyamic acid layer farther from the substrate is the soluble polyimide layer. In the further high-temperature curing film-forming stage, polyamic acid will dehydrate under high temperature conditions to form polyimide. That is, the cured alignment film 100 includes a first polymer layer 101 and a second polymer layer 102. The first polymer layer 101 contains the aforementioned soluble polyimide, and the second polymer layer 102 contains the polyimide formed by dehydrating the aforementioned polyamic acid.

[0043] In this application, both soluble polyimide and polyamic acid have good solubility. Combined with various solvents with different boiling points and surface tensions, the uniformity and coatability of the alignment liquid are significantly improved, allowing the alignment liquid to be uniformly coated on the substrate surface (including curved edges). Secondly, the compound system of soluble polyimide and polyamic acid undergoes delamination during the pre-curing stage. The polyamic acid layer is closer to the substrate side; due to its strong adhesion, it significantly improves adhesion to the substrate. The soluble polyimide layer is located on the side of the polyamic acid layer furthest from the substrate. During the high-temperature imidization of the polyamic acid, the surface soluble polyimide layer ensures the stability of the film layer, preventing edge shrinkage and deformation caused by polyamic acid imidization, which could lead to poor edge alignment of the alignment film 100. In addition, the crosslinking agent can enable the polymers to form a three-dimensional network structure through chemical bonds during the high-temperature curing stage, thereby improving the compactness of the alignment film 100. It can also compensate for the problem of decreased adhesion between the soluble polyimide and polyamic acid caused by the delamination, thus improving the overall film quality of the alignment film 100.

[0044] This application also provides a display panel 10, please refer to... Figure 4The display panel 10 includes a first substrate 210 and a second substrate 220 disposed opposite to each other, a liquid crystal layer 230, a first alignment film 110, and a second alignment film 120. The liquid crystal layer 230 is disposed between the first substrate 210 and the second substrate 220. The first alignment film 110 is disposed on the side of the first substrate 210 near the liquid crystal layer 230. The second alignment film 120 is disposed on the side of the second substrate 220 near the liquid crystal layer 230. The first alignment film 110 includes the alignment film 100 described above, and the second alignment film 120 includes the alignment film 100 described above. The first substrate 210 may be a TFT array substrate, and the second substrate may be a color filter substrate (CF), but is not limited thereto.

[0045] The alignment membrane materials of the first alignment membrane 110 and the second alignment membrane 120 may be the same or different.

[0046] In some embodiments, for a curved display panel 10, a first alignment film 110 is configured to generate a first pretilt angle for liquid crystal molecules adjacent to it, and a second alignment film 120 is configured to generate a second pretilt angle for liquid crystal molecules adjacent to it, wherein the directions of the first pretilt angle and the second pretilt angle are opposite. By using alignment films with different angles (Dual PI architecture) on the first substrate 210 side and the second substrate 220 side, the liquid crystals on the first substrate 210 side and the second substrate 220 side of the display panel 10 form different pretilt angles, which can meet the normal display requirements in a curved state and avoid the problem of uneven curved display (Mura).

[0047] The first alignment membrane 110 and the second alignment membrane 120 may be made of different alignment membrane materials. For example, the first alignment membrane 110 may be formed of a first alignment membrane material, which includes a first soluble polyimide, a first polyamic acid, a first crosslinking agent, and a first solvent composition; the second alignment membrane 120 may be formed of a second alignment membrane material, which includes a second soluble polyimide, a second polyamic acid, a second crosslinking agent, and a second solvent composition. The first soluble polyimide and the second soluble polyimide may be the same or different, the first polyamic acid and the second polyamic acid may be the same or different, the first crosslinking agent and the second crosslinking agent may be the same or different, and the first solvent composition and the second solvent composition may be the same or different. However, at least one of the first soluble polyimide and the first polyamic acid in the first alignment film material is different from the second soluble polyimide and the second polyamic acid in the second alignment film material, so as to ensure that the pretilt angles formed by the first alignment film 110 and the second alignment film 120 are different, thereby ensuring the curved surface display effect.

[0048] Furthermore, the first alignment film 110 includes a first polymer layer and a second polymer layer. The first polymer layer is located on the side of the second polymer layer away from the first substrate 210. The first polymer layer contains a first soluble polyimide, and the second polymer layer contains a first polyimide formed after dehydration of a first polyamic acid. The structure of the first polyimide may be the same as or different from the structure of the first soluble polyimide. The second alignment film 120 includes a third polymer layer and a fourth polymer layer. The third polymer layer is located on the side of the fourth polymer layer away from the second substrate 220. The third polymer layer contains a second soluble polyimide, and the fourth polymer layer contains a second polyimide formed after dehydration of a second polyamic acid. The structure of the second polyimide may be the same as or different from the structure of the second soluble polyimide.

[0049] Impurity ions 240 are typically present in the liquid crystal layer 230. During illumination or power application, these impurity ions 240 are adsorbed onto the surface of the alignment film. In curved display panels, due to the different characteristics of the first alignment film 110 and the second alignment film 120, their adsorption capacities for impurity ions 240 differ, leading to an increase in the time-dependent best common voltage shift (BFC Shift) of the display panel 10 and causing display unevenness issues such as flickering. Therefore, it is necessary to match the adsorption capacities of the first alignment film 110 and the second alignment film 120 for impurity ions 240.

[0050] In some embodiments, the first soluble polyimide and the second soluble polyimide may have similar chemical structures. For example, the main chain length, side chain position, or side chain polarity of the first soluble polyimide may be kept similar to those of the second soluble polyimide. This ensures that the pretilt angles formed by the first alignment film 110 and the second alignment film 120 are different, while reducing the difference in the adsorption capacity of the first alignment film 110 and the second alignment film 120 for impurity ions 240, thereby reducing Best VcomShift and improving display inhomogeneity (Mura) problems such as flickering.

[0051] Please refer to Figure 5 The first soluble polyimide can have the following properties: Figure 5 The structure shown in figure a indicates that the second soluble polyimide can have Figure 5 The structure shown in b is Figure 5 R1 can represent a macromolecular unit used to improve solubility, and R2 can represent an ion-releasing unit used to improve RDC properties, but is not limited to these.

[0052] Similarly, the first polyamic acid and the second polyamic acid can also have similar chemical structures. For example, the main chain length, side chain position or side chain polarity of the first polyamic acid can be similar to those of the second polyamic acid.

[0053] In this application, by making the first soluble polyimide and the second soluble polyimide have similar chemical structures, and / or the first polyamic acid and the second polyamic acid have similar chemical structures, the difference in the adsorption capacity of the first alignment film 110 and the second alignment film 120 for impurity ions can be effectively reduced, avoiding the generation of a built-in electric field during ultraviolet light alignment, thereby improving problems such as flickering and Mura deterioration caused by time-dependent Best Vcom Shift.

[0054] Please refer to Figures 6-9 ,in Figure 6 This is a schematic diagram of ion 240 adsorption when using polyimide alignment membrane 111 and polyimide alignment membrane 121 (the difference in ion adsorption capacity between polyimide alignment membrane 111 and polyimide alignment membrane 121 is relatively large). Figure 7 for Figure 6 A schematic diagram of the Best Vcom Shift test for the corresponding display panel over time; Figure 8 This is a schematic diagram of ion 240 adsorption when the first alignment membrane 110 and the second alignment membrane 120 of this application are used (the ion adsorption capacities of the first alignment membrane 110 and the second alignment membrane 120 are equivalent (or the same)). Figure 9 for Figure 8 A schematic diagram of the BestVcom Shift test for the corresponding display panel 10 over time. Among them, Figure 6 and Figure 8 In the diagram, a represents a schematic diagram of the pre-alignment ions 240 being free within the liquid crystal layer 230, b represents a schematic diagram of the post-alignment ions 240 being adsorbed on the surface of the alignment layer, and c represents a schematic diagram of the post-alignment ions 240 being adsorbed on the surface of the alignment layer after time.

[0055] Depend on Figure 6 and Figure 8 It can be seen that, Figure 6 The adsorption capacity of the alignment films on both sides of the liquid crystal layer 230 for ions 240 differs relatively greatly. Figure 8 Using the first alignment membrane 110 and the second alignment membrane 120 of this application, since the first alignment membrane 110 and the second alignment membrane 120 have similar structures, their ion adsorption capacities are comparable (or identical); Figure 7 and Figure 9 It can be seen that, Figure 7 In the middle, during time b (after alignment) compared to time a (before alignment), the ion adsorption capacity of the alignment films on both sides of the liquid crystal layer 230 is significantly different, resulting in a built-in electric field (unsteady state). During time c (after time), the ions are redistributed, the built-in electric field disappears (steady state), and Best VcomShift is generated. Figure 9In the first alignment phase (b) compared to the second alignment phase (a), the ion adsorption capacity of the alignment films on both sides of the liquid crystal layer 230 is comparable (or the same), and there is no built-in electric field (steady state). In the third alignment phase (c after time), ions do not redistribute, and there is no Best VcomShift. This indicates that by making the first soluble polyimide and the second soluble polyimide have similar chemical structures, the adsorption capacity of the first alignment film 110 and the second alignment film 120 for impurity ions is comparable (or the same), which can significantly improve the Best VcomShift problem.

[0056] In some embodiments, the time offset of the best common voltage of the display panel 10 is less than 50 mV. For example, the time offset of the best common voltage can be 0 mV, 10 mV, 20 mV, 30 mV, 40 mV, 50 mV, etc., which significantly improves the BestVcom Shift problem and enhances the display quality of the display panel 10.

[0057] The following specific embodiments further illustrate the improvement effect of the Best Vcom Shift of the display panel 10. The embodiments use the first alignment film 110 and the second alignment film 120 of this application, while the comparative examples use the existing polyimide alignment film (SN-3538 Nissan). When the embodiments and comparative examples are paired with liquid crystal A (TCL82400HCCH (Jiangsu Synthetic)), liquid crystal B (LCCC-21-1353 Shanghai Merck), and liquid crystal C (LCCC-21-2337 Shanghai Merck), respectively, the time offset of the best common voltage is shown in Table 2.

[0058] Table 2

[0059] As shown in Table 2, when the alignment film of this application is used with different liquid crystals, the time shift of the optimal common voltage is less than 50 mV. Compared with the comparative example, the time shift of the optimal common voltage is significantly reduced, and the improvement in the time shift of the optimal common voltage can reach more than 80%.

[0060] The display panel 10 of this application employs the aforementioned first alignment film 110 and second alignment film 120. Due to the use of a soluble polyimide and polyamic acid composite system and a crosslinking agent, the first alignment film 110 and second alignment film 120 significantly improve film quality and film density, preventing impurity ions 240 from other film layers from entering the liquid crystal layer 230, thus reducing the total amount of impurity ions 240 in the liquid crystal layer 230. Therefore, it can reduce the accumulation of impurity ions 240 at the alignment film interface, improve the migration and release rate of impurity ions 240, enhance the voltage holding capability (VHR) of the liquid crystal layer 230, and reduce the residual DC voltage (RDC), which is beneficial for improving the display. The first alignment film 110 and the second alignment film 120 use high-boiling-point, low-surface-tension solvents. By optimizing the solvent ratio, the width of the Halo region is effectively reduced while ensuring coating characteristics, improving the edge accuracy of the alignment film 100, and thus improving the edge straightness of the alignment film, which is beneficial for the design and development of narrow-bezel display products. In addition, the first alignment film 110 and the second alignment film 120 use polymers with similar structures (soluble polyimide and / or polyamic acid), which can improve the difference in the adsorption capacity of the first alignment film 110 and the second alignment film 120 for impurity ions 240, thereby reducing Best Vcom Shift and improving display unevenness (mura) problems such as flickering of the display panel 10.

[0061] This application also provides a display device, which includes the display panel as described above. The display device can be a mobile phone, tablet, computer, television, smart display, or vehicle display, but is not limited thereto.

[0062] This application provides an alignment film material, an alignment film, a display panel, and a display device. The alignment film material of this application includes 1.14%~1.52% soluble polyimide and 1.9%~2.47% polyamic acid. The alignment film material of this application uses a compound system of soluble polyimide and polyamic acid as the main material for film formation, and with appropriate ratios, it can effectively improve the coatability and stability of the alignment film material, thereby improving the film formation quality and performance of the alignment film, and improving problems such as edge defects of the alignment film and uneven display around the display panel.

[0063] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0064] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0065] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0066] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. An alignment film material characterized by comprising: The alignment film material comprises, in mass percentage: a soluble polyimide 1.14%~1.52%; and a polyamic acid 1.9%~2.47%.

2. The alignment film material according to claim 1, wherein The alignment film material further comprises, in mass percentage: a bridging agent 0.19%~0.38%.

3. The alignment film material according to claim 2, wherein, The bridging agent comprises at least one of a silane coupling agent, a titanate coupling agent, and a phosphorus-based coupling agent.

4. The alignment film material according to claim 1, wherein The alignment film material further comprises a solvent composition, the solvent composition comprising a first solvent and a second solvent, wherein the first solvent has a boiling point greater than that of the second solvent, and the first solvent has a surface tension less than that of the second solvent.

5. An alignment film characterized by comprising: The alignment film is formed from the alignment film material as claimed in any one of claims 1-4. The alignment film comprises a first polymer layer and a second polymer layer, the first polymer layer and the second polymer layer being connected by a chemical bond.

6. The alignment film according to claim 5, wherein The first polymer layer comprises the soluble polyimide, and the second polymer layer comprises a polyimide formed by dehydration of the polyamic acid, the structure of the polyimide being the same as or different from that of the soluble polyimide.

7. A display panel, characterized by The display panel comprises: a first substrate and a second substrate arranged oppositely; a liquid crystal layer arranged between the first substrate and the second substrate; a first alignment film arranged on a side of the first substrate close to the liquid crystal layer; and a second alignment film arranged on a side of the second substrate close to the liquid crystal layer; The first alignment film comprises the alignment film as claimed in claim 5 or 6, and the second alignment film comprises the alignment film as claimed in claim 5 or 6. The first alignment film is configured to generate a first pre-tilt angle in liquid crystal molecules close thereto, and the second alignment film is configured to generate a second pre-tilt angle in liquid crystal molecules close thereto, the direction of the first pre-tilt angle being different from that of the second pre-tilt angle.

8. The display panel of claim 7, wherein, The first alignment film comprises a first polymer layer and a second polymer layer, the first polymer layer being located on a side of the second polymer layer away from the first substrate, the first polymer layer comprising a first soluble polyimide, and the second polymer layer comprising a first polyimide formed by dehydration of a first polyamic acid, the structure of the first polyimide being the same as or different from that of the first soluble polyimide.

9. The display panel of claim 7, wherein, The second alignment film comprises a third polymer layer and a fourth polymer layer, the third polymer layer being located on a side of the fourth polymer layer away from the second substrate, the third polymer layer comprising a second soluble polyimide, and the fourth polymer layer comprising a second polyimide formed by dehydration of a second polyamic acid, the structure of the second polyimide being the same as or different from that of the second soluble polyimide. The structure of the first soluble polyimide is the same as or different from that of the second soluble polyimide, and / or the structure of the first polyamic acid is the same as or different from that of the second polyamic acid. The display panel comprises the display panel as claimed in any one of claims 7-9.

10. A display device, characterized by comprising: ​

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