Liquid crystal alignment agent, liquid crystal alignment film, liquid crystal display panel, and method for producing liquid crystal alignment film

Abstract

The present application provides a liquid crystal alignment agent, a liquid crystal alignment film, a liquid crystal display panel and a manufacturing method of the liquid crystal alignment film. The liquid crystal alignment agent comprises at least one of polyamide acid and polyimide and an additive, the additive has a structure as shown in general formula (1) or general formula (2), wherein R1-R3 are each independently selected from hydrogen, deuterium, a straight-chain alkyl group with 1-10 carbon atoms, a branched-chain alkyl group with 3-10 carbon atoms, an aromatic group with 6-10 ring atoms, a heteroaromatic group with 5-10 ring atoms, a cycloalkyl group with 3-10 ring atoms or an aliphatic heterocyclic group; and Ar1 is selected from an aromatic group with 6-10 ring atoms, a heteroaromatic group with 5-10 ring atoms, a cycloalkyl group with 3-10 ring atoms or an aliphatic heterocyclic group.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a liquid crystal alignment agent, a liquid crystal alignment film, a liquid crystal display panel and a manufacturing method of the liquid crystal alignment film. BACKGROUND

[0002] The liquid crystal alignment film is one of the important parts in the thin film transistor liquid crystal display (TFT-LCD), which plays a role in maintaining the ordered arrangement of liquid crystal molecules in the liquid crystal display.

[0003] Considering the heat resistance, mechanical strength, affinity with liquid crystal and other aspects, the liquid crystal alignment film material usually uses polyamide acid (PAA) and polyimide (PI). The polyimide in the liquid crystal alignment film can pre-orient the liquid crystal molecules to arrange the liquid crystal molecules in a certain direction, so that the liquid crystal molecules can respond horizontally when an electric field is applied subsequently, and the orientation changes to display images.

[0004] However, the phase separation degree of polyamide acid and polyimide in the existing liquid crystal alignment film is poor, which affects the aggregation of polyimide to the surface of the liquid crystal alignment film, thereby affecting the anchoring effect of polyimide in the liquid crystal alignment film on the liquid crystal molecules, and the horizontal response effect of the liquid crystal molecules when an electric field is applied subsequently is reduced. This will make the liquid crystal display have residual image when switching to the next new display picture, which can be observed by the naked eye, i.e. the residual image problem. SUMMARY

[0005] In view of this, the present application provides a liquid crystal alignment agent, a liquid crystal alignment film, a liquid crystal display panel and a liquid crystal display panel, which can enhance the anchoring effect of the liquid crystal alignment film on the liquid crystal molecules and improve the residual image problem of the liquid crystal display panel.

[0006] The present application provides a liquid crystal alignment agent, which comprises at least one of polyamide acid and polyimide and an additive, and the compound structure of the additive is shown in general formula (1) or general formula (2):

[0007]

[0008] wherein R1-R3 are each independently selected from hydrogen, deuterium, a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 10 carbon atoms, an aromatic group having 6 to 10 ring atoms, a heteroaromatic group having 5 to 10 ring atoms, a cycloalkyl group having 3 to 10 ring atoms or an aliphatic heterocyclic group;

[0009] Ar1 is selected from an aromatic group having 6 to 10 ring atoms, a heteroaromatic group having 5 to 10 ring atoms, a cycloalkyl group having 3 to 10 ring atoms, or an aliphatic heterocyclic group.

[0010] In some embodiments of the present application, the additive has a relative molecular mass of 50 to 800.

[0011] In some embodiments of the present application, the additive is selected from one or more of the following compounds:

[0012]

[0013]

[0014] In some embodiments of the present application, the additive has a mass of 5 to 75% of the total solute mass of the liquid crystal alignment agent.

[0015] The embodiments of the present application also provide a liquid crystal alignment film comprising a polyimide and an additive, the compound structure of the additive being shown in general formula (1) or general formula (2):

[0016]

[0017] wherein R1 to R3 are each independently selected from hydrogen, deuterium, a straight-chain alkyl group having 1 to 10 carbon atoms, a branched-chain alkyl group having 3 to 10 carbon atoms, an aromatic group having 6 to 10 ring atoms, a heteroaromatic group having 5 to 10 ring atoms, a cycloalkyl group having 3 to 10 ring atoms, or an aliphatic heterocyclic group;

[0018] Ar1 is selected from an aromatic group having 6 to 10 ring atoms, a heteroaromatic group having 5 to 10 ring atoms, a cycloalkyl group having 3 to 10 ring atoms, or an aliphatic heterocyclic group.

[0019] In some embodiments of the present application, the additive has a relative molecular mass of 50 to 800.

[0020] In some embodiments of the present application, the additive is selected from one or more of the following compounds:

[0021]

[0022] In some embodiments of the present application, the additive has a mass of 5 to 75% of the total solute mass of the liquid crystal alignment agent.

[0023] The embodiments of the present application also provide a liquid crystal display panel comprising the liquid crystal alignment film described in the above embodiments.

[0024] The embodiments of the present application also provide a manufacturing method of a liquid crystal alignment film, comprising the following steps:

[0025] Provide a substrate;

[0026] The liquid crystal alignment agent described in the above embodiments is coated onto the substrate;

[0027] The substrate is subjected to heat treatment at a temperature of 100–120°C.

[0028] The liquid crystal alignment agent, liquid crystal alignment film, liquid crystal display panel, and manufacturing method of liquid crystal alignment film provided in this application have the following advantages: the added compound structure, such as the additive shown in general formula (1) or general formula (2), also has the imide ring structure in polyimide. It has a very similar polarity to polyimide and can generate strong intermolecular interaction forces with polyimide. At the same time, in the process of liquid crystal alignment film formation, compared with high molecular weight polyimide, the additive is more likely to move to the surface of liquid crystal alignment film with the evaporation of liquid crystal alignment agent solvent. This drives polyimide to gather on the surface of liquid crystal alignment film, thereby enhancing the anchoring effect of polyimide in liquid crystal alignment film on liquid crystal molecules. This improves the effect of liquid crystal molecules responding at the same level when an electric field is applied in the future, improves the image retention problem of liquid crystal display panel, and improves the display effect of liquid crystal display panel. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the liquid crystal display panel provided in the embodiments of this application.

[0030] Figure 2 This is a flowchart of a method for manufacturing a liquid crystal alignment film provided in an embodiment of this application. Detailed Implementation

[0031] This application provides a liquid crystal alignment agent, a liquid crystal alignment film, a liquid crystal display panel, and a method for manufacturing the liquid crystal alignment film. Various embodiments of the present invention are described in the form of a range only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the invention. Therefore, the description of the range includes all possible sub-ranges as well as single numerical values ​​within that range. For example, it should be considered that a range description from 1 to 6 specifically discloses sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6. Furthermore, numerical ranges herein include any referenced numbers (fractions or integers) within the referred range.

[0032] In this invention, "ring atom number" refers to the total number of atoms constituting the ring itself in a compound obtained by atomic bonding to form a ring. For example, benzene has 6 ring atom numbers, naphthalene has 10 ring atom numbers, and thiophene has 5 ring atom numbers.

[0033] In the present application, "straight-chain alkyl" and "branched-chain alkyl" refer to monovalent groups obtained by removing one hydrogen atom from straight-chain alkane and branched-chain alkane molecules, respectively. Specific examples of straight-chain alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl; and specific examples of branched-chain alkyl groups include, but are not limited to, isopropyl, isobutyl, sec-butyl, t-butyl, 2-ethylbutyl, 3,3-dimethylbutyl, isoamyl, neopentyl, t-amyl, 1-methylpentyl, 3-methylpentyl, 2-ethylpentyl, 4-methyl-2-pentyl, 1-methylhexyl, 2-ethylhexyl, 2-butylhexyl, 1-methylheptyl, 2,2-dimethylheptyl, 2-ethylheptyl, t-octyl, 2-ethyloctyl, 3,7-dimethyloctyl.

[0034] In the present application, "aromatic group" refers to monovalent groups obtained by removing one hydrogen atom from the aromatic ring of an aromatic ring compound molecule, which can be a monocyclic aromatic group, a polycyclic aromatic group or a fused ring aromatic group. Specific examples of monocyclic aromatic groups include, but are not limited to, phenyl, biphenyl; and specific examples of fused ring aromatic groups include, but are not limited to, naphthyl, anthryl, phenanthryl, pyrenyl, perylenyl, fluorenyl.

[0035] In the present application, "heteroaromatic group" refers to groups obtained by replacing one or more aromatic ring carbons in an aromatic group with non-carbon atoms, which can be a monocyclic heteroaromatic group or a fused ring heteroaromatic group. The non-carbon atoms include, but are not limited to, nitrogen atoms, oxygen atoms, sulfur atoms. Specific examples of monocyclic heteroaromatic groups include, but are not limited to, pyrrolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, thienyl, furanyl, oxazolyl, thiazolyl, imidazolyl, triazolyl; and specific examples of fused ring heteroaromatic groups include, but are not limited to, indolyl, quinolyl, isoquinolyl, benzothienyl, benzofuranyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, quinoxalyl, quinazolyl, pyridopyrimidinyl, pyridopyrazinyl, pyrroloimidazolyl, pyrrolopyrrolyl, thienopyrrolyl, thienothienyl, furanopyrrolyl, furanofuranyl, thienofuranyl.

[0036] In the present application, "cycloalkyl" refers to monovalent groups obtained by removing one hydrogen atom from a cycloalkane molecule. Specific examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl.

[0037] In the present application, "aliphatic heterocyclic group" refers to groups obtained by replacing one or more ring-forming carbon atoms in a cycloalkyl group with non-carbon atoms, which include, but are not limited to, nitrogen atoms, oxygen atoms, sulfur atoms. Specific examples of aliphatic heterocyclic groups include, but are not limited to, aziridinyl, azetidinyl, tetrahydropyrrolyl, tetrahydropyridyl, piperidyl, azepanyl, morpholinyl, tetrahydrofuranyl, tetrahydrothienyl, dioxanyl, etc.

[0038] The embodiment of the present application provides a liquid crystal alignment agent, which comprises at least one of polyamic acid and polyimide and an additive, wherein the compound structure of the additive is shown in general formula (1) or general formula (2).

[0039]

[0040] wherein R1-R3 are each independently selected from hydrogen, deuterium, a linear alkyl group having 1-10 carbon atoms, a branched alkyl group having 3-10 carbon atoms, an aromatic group having 6-10 ring atoms, a heteroaromatic group having 5-10 ring atoms, a cycloalkyl group having 3-10 ring atoms, or an aliphatic heterocyclic group;

[0041] Ar1 is selected from an aromatic group having 6-10 ring atoms, a heteroaromatic group having 5-10 ring atoms, a cycloalkyl group having 3-10 ring atoms, or an aliphatic heterocyclic group.

[0042] In some embodiments of the present application, the polyamic acid can be obtained by polymerization of at least one tetracarboxylic dianhydride and at least one diamine. The tetracarboxylic dianhydride can be selected from one or more of aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aromatic tetracarboxylic dianhydride. Specific examples of the aliphatic tetracarboxylic dianhydride include, but are not limited to, butane tetracarboxylic dianhydride. Specific examples of the alicyclic tetracarboxylic dianhydride include, but are not limited to, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 2,3,5-tricarboxylic cyclopentyl acetic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-8-methyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, ethylenediaminetetraacetic dianhydride, cyclopentane tetracarboxylic dianhydride, ethylene glycol bis(dehydrated trimellitic acid ester), 1,3-propanediol bis(dehydrated trimellitic acid ester), p-phenylene bis(trimellitic acid monoester anhydride). Specific examples of the aromatic tetracarboxylic dianhydride include, but are not limited to, pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydride, bis(3,4-dicarboxyphenyl) sulfone dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride.

[0043] The diamine may be selected from one or more of aliphatic diamines, alicyclic diamines, and aromatic diamines. Specific examples of aliphatic diamines include, but are not limited to, m-phenylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, and 1,3-bis(aminomethyl)cyclohexane. Specific examples of alicyclic diamines include, but are not limited to, 1,4-diaminocyclohexane and 4,4'-methylenebis(cyclohexylamine). Specific examples of aromatic diamines include, but are not limited to, dodecyloxydiaminobenzene, tetradecyloxydiaminobenzene, pentadecyloxydiaminobenzene, hexadecyloxydiaminobenzene, octadecyloxydiaminobenzene, cholesteryloxydiaminobenzene, cholesteryl diaminobenzoate, cholesteryl diaminobenzoate, cholesteryl diaminobenzoate, lanosteryl diaminobenzoate, 3,6-bis(4-aminobenzoyloxy)cholestane, 3,6-bis(4-aminophenoxy)cholestane, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 1, 1-Bis(4-((aminophenyl)methyl)phenyl)-4-heptylcyclohexane, 1,1-bis(4-((aminophenoxy)methyl)phenyl)-4-heptylcyclohexane, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-(4-heptylcyclohexyl)cyclohexane, N-(2,4-diaminophenyl)-4-(4-heptylcyclohexyl)benzamide, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 4-aminophenyl-4'-aminobenzoate, 4,4'-diaminoazobenzene, 1,5-bis( 4-Aminophenoxy)pentane, 1,7-bis(4-aminophenoxy)heptane, bis[2-(4-aminophenyl)ethyl]adipic acid, N,N-bis(4-aminophenyl)methylamine, 1,5-diaminonaphthalene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,7-diaminofluorene, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 9,9-bis(4-aminophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)]propane [Phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-(p-phenylenediisopropylidene)bisaniline, 4,4'-(m-phenylenediisopropylidene)bisaniline, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 3,6-diaminocarbazole, 2,3-diaminopyridine, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 2,4-diamino6-hydroxypyrimidine, 2,4-diamino1,3,5-triazine, 2,6-diaminopurine, 3,5-diamino1,3,5-triazole.

[0044] Specifically, the polyamic acid of this application comprises repeating units as shown in general formula (3):

[0045]

[0046] wherein X is a 2-valent organic group derived from an aliphatic diamine, a cycloaliphatic diamine, or an aromatic diamine, and a plurality of X are the same as or different from each other;

[0047] Y is a 4-valent organic group derived from an aliphatic tetracarboxylic dianhydride, a cycloaliphatic tetracarboxylic dianhydride, or an aromatic tetracarboxylic dianhydride, and a plurality of Y are the same as or different from each other.

[0048] It can be understood that the polyimide can be imidized from the above-mentioned polyamic acid, i.e., the imide ring is formed by dehydration of the amino group and the carboxyl group in the repeating unit represented by general formula (3).

[0049] In some embodiments of the present application, the liquid crystal alignment agent further comprises a solvent, and the mass fraction of the solute in the liquid crystal alignment agent is 1% to 10%. The solvent used includes but is not limited to one or more of N-methyl-2-pyrrolidone, γ-butyrolactone, γ-butyrolactam, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-iso-propyl ether, ethylene glycol-n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, diisopentyl ether, ethylene carbonate, and propylene carbonate.

[0050] In the present application, since the added compound structure is the same as that of the additive represented by general formula (1) or general formula (2), it also has an imide ring structure in the polyimide, and has a very similar polarity to the polyimide, which can generate a strong intermolecular interaction force with the polyimide. At the same time, compared with the polyimide, the additive is more likely to move to the surface of the liquid crystal alignment film along with the volatilization of the solvent of the liquid crystal alignment agent during the film forming process of the liquid crystal alignment film, thereby driving the polyimide to the surface of the liquid crystal alignment film, thereby enhancing the anchoring effect of the polyimide in the liquid crystal alignment film on the liquid crystal molecules, and improving the horizontal response effect of the liquid crystal molecules when an electric field is subsequently applied.

[0051] In some embodiments of the present application, the additive has a relative molecular mass of 50-800. Specifically, the additive has a relative molecular mass of 50-600, and more specifically, the additive has a relative molecular mass of 90-400. The additive has a relative molecular mass of 50-800, and has a strong ability to move to the surface of the liquid crystal alignment film along with the evaporation of the solvent of the liquid crystal alignment agent during the film forming process of the liquid crystal alignment film, and can better drive the polyimide to the surface of the liquid crystal alignment film.

[0052] In some embodiments of the present application, the additive is selected from one or more of the compounds shown below:

[0053]

[0054]

[0055] In some embodiments of the present application, the additive has a mass accounting for 5-75% of the total solute mass of the liquid crystal alignment agent. Specifically, the additive has a mass accounting for 5-50% of the total solute mass of the liquid crystal alignment agent, and more specifically, the additive has a mass accounting for 30-50% of the total solute mass of the liquid crystal alignment agent, such as 30%, 32%, 37.5%, 40%, 45%, 48% or 50%, etc. When the percentage of the additive mass accounting for the total solute mass of the liquid crystal alignment agent is between 5-75%, the effect of driving the polyimide to the surface of the liquid crystal alignment film is better, and the anchoring effect of the polyimide in the liquid crystal alignment film on the liquid crystal molecules is enhanced, so that the effect of the liquid crystal molecules responding to the horizontal direction when a subsequent electric field is applied is better improved.

[0056] The embodiments of the present application also provide a liquid crystal alignment film formed by the above-mentioned liquid crystal alignment agent. It can be understood that due to the addition of the additive having a structure as shown in the general formula (1) or the general formula (2), the polyimide is promoted to gather to the surface of the liquid crystal alignment film, so that the anchoring effect of the polyimide in the liquid crystal alignment film on the liquid crystal molecules is enhanced.

[0057] In some embodiments of the present application, the additive has a mass accounting for 0.5-25% of the mass of the liquid crystal alignment film. Specifically, the additive has a mass accounting for 1-20% of the mass of the liquid crystal alignment film, and more specifically, the additive has a mass accounting for 2.5-20% of the mass of the liquid crystal alignment film, such as 2.5%, 4%, 7%, 10%, 12.5%, 14%, 16.5%, 18% or 20%, etc. When the percentage of the additive mass accounting for the mass of the liquid crystal alignment film is between 0.5-25%, the additive in the liquid crystal alignment film will not have a significant impact on the alignment function of the liquid crystal alignment film. Since the added additive can be heated and volatilized to the outside during the heat treatment process of the film forming process, the mass of the additive accounting for the mass of the liquid crystal alignment film can be maintained within the above range after the film forming process.

[0058] One embodiment of this application also provides a liquid crystal display panel, including the liquid crystal alignment film described above. Figure 1 This is a schematic diagram of the structure of a liquid crystal display panel provided in an embodiment of this application. The liquid crystal display panel 100 of this embodiment includes a first substrate 11, a second substrate 15, liquid crystal molecules 13 located between the first substrate 11 and the second substrate 15, a liquid crystal alignment film 12 disposed on the first substrate 11, and a liquid crystal alignment film 14 disposed on the second substrate 15. The first substrate 11 may be an array substrate, which may include multiple scan lines, multiple data lines, multiple thin film transistors, and multiple pixel electrodes disposed on a substrate. The second substrate 15 may be a color filter substrate, which may include a color filter, a black matrix, and an electrode layer disposed on the substrate. The driving method of the liquid crystal molecules 13 in the liquid crystal display panel 100 may be a twisted nematic (TN) type, a super twisted nematic (STN) type, a vertical alignment (VA) type, an in-plane switching (IPS) type, a fringe field switching (FFS) type, etc. Since the liquid crystal display panel 100 includes the liquid crystal alignment film provided in the aforementioned embodiments of this application, the anchoring effect of the liquid crystal molecules 13 in the liquid crystal display panel 100 is enhanced, and the effect of the liquid crystal molecules 13 responding at the same level when an electric field is subsequently applied is improved, thereby improving the image retention problem of the liquid crystal display panel 100 and enhancing the display effect.

[0059] The following describes the manufacturing method of the liquid crystal alignment agent, liquid crystal alignment film, liquid crystal display panel, and liquid crystal alignment film of this application through specific embodiments.

[0060] Example 1

[0061] 1.1 Preparation of liquid crystal alignment agent

[0062] Additives (N-ethylsuccinimide) was added to Nissan's liquid crystal alignment agent RB-093, and stirred at room temperature for 1 to 48 hours in an inert atmosphere until the additive was completely dissolved to obtain the liquid crystal alignment agent of this application. The mass of the additive added was 5% of the mass of the solute in the final liquid crystal alignment agent.

[0063] 1.2 Formation of Liquid Crystal Alignment Film

[0064] The prepared liquid crystal alignment agent was coated on the prepared pair of substrates by means of a printing plate, immersion, inkjet printing, spin coating or other processes. The substrate coated with the liquid crystal alignment agent was subjected to heat treatment at a temperature of 100°C, so that the solvent of the liquid crystal alignment agent was completely volatilized, and the liquid crystal alignment agent was finally solidified into a film. The polyimide film obtained had a thickness of about 100 nm.

[0065] 1.3 Preparation of liquid crystal display panel

[0066] The surface of one of the substrates was coated with a sealant to form a seal pattern, and then liquid crystal was added dropwise to the substrate with the seal pattern. The other substrate was then attached to the substrate with the seal pattern in a face-to-face manner. Finally, the sealant was cured to obtain a liquid crystal display panel.

[0067] 1.4 Performance detection

[0068] The surface characteristics of the obtained liquid crystal alignment film were analyzed by the following method: the surface of the liquid crystal alignment film was ion-bombed by a Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS), and the signal intensity of TOF-SIMS of the polyimide characteristic functional group was analyzed, so as to reflect the aggregation degree of the polyimide on the surface of the liquid crystal alignment film. The stronger the relevant signal, the more the polyimide aggregated on the surface of the liquid crystal alignment film, and the stronger the anchoring effect of the liquid crystal alignment film on the liquid crystal molecules.

[0069] The residual image of the obtained liquid crystal display panel was evaluated by the following method: after the liquid crystal display panel was lit for one hour under a black-and-white chessboard pattern, the pattern was switched to a gray scale pattern, and the residual situation of the black-and-white pattern in the gray pattern was observed, so as to obtain a JND (Just Noticeable Difference) value for evaluating the residual image. The larger the JND value, the more serious the residual image.

[0070] Examples 2-5 and Comparative Examples 1-2:

[0071] Examples 2-5 and Comparative Examples 1-2 were prepared by the same method as that of Example 1, except that the additives were added or not, the types of the additives were different, the addition amount of the additives was different, and the heat treatment temperature of the substrate was different. The specific implementation conditions and performance detection results are shown in Table 1.

[0072] Table 1: Performance detection results of Examples 1-5 and Comparative Examples 1-2

[0073]

[0074]

[0075] As shown in Table 1, compared with Comparative Examples 1-2 without the additive, the TOF-SIMS signal intensity of the polyimide characteristic functional group of the liquid crystal alignment film of Examples 1-2 is significantly higher, because the additive N-ethyl succinimide, which accounts for 5% of the total solute mass of the liquid crystal alignment agent, can drive the polyimide to the surface of the liquid crystal alignment film during film formation. The anchoring effect of the polyimide on the liquid crystal molecules in the liquid crystal alignment film of Examples 1-2 is stronger, which improves the horizontal response of the liquid crystal molecules when an electric field is subsequently applied, and the JND value of the residual image evaluation of the liquid crystal display panel is reduced, and the residual image problem is improved.

[0076] Meanwhile, when the heat treatment temperature of the substrate during the film formation of the liquid crystal alignment film is increased from 100°C to 120°C, the increase in the TOF-SIMS signal intensity of the polyimide characteristic functional group of the liquid crystal alignment film of Examples 1-2 is greater than that of Comparative Examples 1-2, which indicates that the increase in the heat treatment temperature of the substrate can further promote the aggregation of the polyimide to the surface of the liquid crystal alignment film when the additive is added. Therefore, the increase in the heat treatment temperature of the substrate can significantly improve the molecular thermal motion ability of the additive added in Examples 1-2, which further enhances the ability of the additive to drive the polyimide to the surface of the liquid crystal alignment film during film formation. In other words, the additive added in the present application and the increase in the heat treatment temperature of the substrate have a synergistic effect, which ultimately makes the effect of improving the residual image more significant. At the same time, the addition of the additive allows the heat treatment temperature of the substrate to be maintained at 100-120°C, which is more efficient than continuously increasing the heat treatment temperature of the substrate to enhance the aggregation of the polyimide to the surface of the liquid crystal alignment film, thereby optimizing the processing technology of the liquid crystal alignment film.

[0077] Further, according to Examples 3-4, as the amount of the additive increases, the TOF-SIMS signal intensity of the polyimide characteristic functional group of the liquid crystal alignment film continues to increase, which indicates that the degree of aggregation of the polyimide to the surface of the liquid crystal alignment film continues to increase, and accordingly, the residual image of the liquid crystal display panel is no longer visible (the JND value of the residual image evaluation is <1.8).

[0078] Please continue to refer to Example 5, the additive in the liquid crystal alignment agent provided by Example 5 is N-ethyl phthalimide. When the mass of the additive accounts for 10% of the total solute mass of the liquid crystal alignment agent, and the heat treatment temperature of the substrate is 120°C, the TOF-SIMS signal intensity of the polyimide characteristic functional group of the final liquid crystal alignment film shows a significant increase, and accordingly, the residual image of the liquid crystal display panel is no longer visible (the JND value of the residual image evaluation is <1.8).

[0079] To sum up, the liquid crystal alignment agent provided by the embodiments of the present application can improve the surface aggregation degree of polyimide during the film forming process, thereby enhancing the anchoring effect of polyimide in the liquid crystal alignment film on liquid crystal molecules, improving the horizontal response effect of liquid crystal molecules when an electric field is applied subsequently, and thus improving the residual image problem of the liquid crystal display panel.

[0080] The above describes in detail a liquid crystal alignment agent, a liquid crystal alignment film, a liquid crystal display panel and a manufacturing method of the liquid crystal alignment film provided by the embodiments of the present application. The above description of the embodiments is only used to help understand the method and the core idea of the present application, and should not be understood as a limitation of the present application.

Claims

1. A liquid crystal alignment agent, characterized in that, The liquid crystal alignment agent comprises at least one of polyamic acid and polyimide, and an additive having a relative molecular mass of 50 to 800, wherein the additive accounts for 5 to 75% of the total solute mass of the liquid crystal alignment agent. The additive is selected from one or more compounds listed below: 。 2. A liquid crystal alignment film, characterized in that, It includes polyimide and additives, wherein the relative molecular mass of the additives is 50-800, and the mass of the additives accounts for 5-75% of the total solute mass of the liquid crystal alignment agent; The additive is selected from one or more compounds listed below: 。 3. A liquid crystal display panel, characterized in that, Includes the liquid crystal alignment film as described in claim 2.

4. A method for manufacturing a liquid crystal alignment film, characterized in that, Includes the following steps: Provide a substrate; The liquid crystal alignment agent as described in claim 1 is applied onto the substrate; The substrate is subjected to heat treatment at a temperature of 100~120°C.

Images