Display panel and manufacturing method thereof

Abstract

The invention discloses a display panel and a manufacturing method thereof. The display panel comprises a first substrate, a second substrate, a display medium layer and a first alignment layer. The second substrate and the first substrate are oppositely arranged. The display medium layer is arranged between the first substrate and the second substrate and comprises a plurality of display medium molecules. The first alignment layer is arranged on the first substrate, the first alignment layer is formed by condensation polymerization of a dianhydride compound, a diamine compound with an alkyl side chain and a diamine compound without an alkyl side chain, and the mole ratio of the diamine compound with the alkyl side chain to the diamine compound without the alkyl side chain is 0.1-0.5; and the carbon number of the alkyl side chain of the diamine compound having the alkyl side chain is 1 to 12.

Description

Technical Field

[0001] The present invention relates to a photoelectric device and a manufacturing method thereof, and in particular to a display panel and a manufacturing method thereof. Background Art

[0002] Image sticking (IS) of bistable cholesterol liquid crystal displays has been a thorny issue that has been discussed for more than a decade. Due to the bistable characteristics of liquid crystal molecules, the image can remain for a day or even more than a week without a driving signal, resulting in image sticking that is often visible and difficult to eliminate. Summary of the invention

[0003] The invention provides a display panel, which can improve image sticking of the display panel.

[0004] The display panel of the present invention comprises a first substrate, a second substrate, a display medium layer and a first alignment layer. The second substrate is arranged opposite to the first substrate. The display medium layer is arranged between the first substrate and the second substrate and comprises a plurality of display medium molecules. The first alignment layer is arranged on the first substrate, wherein the first alignment layer is formed by condensation polymerization of a dianhydride compound, a diamine compound having an alkyl side chain and a diamine compound without an alkyl side chain, the molar ratio of the diamine compound having an alkyl side chain to the diamine compound without an alkyl side chain is 0.1 to 0.5, and the carbon number of the alkyl side chain of the diamine compound having an alkyl side chain is 1 to 12.

[0005] The invention also provides a method for manufacturing a display panel, which can improve image sticking of the display panel.

[0006] The method for manufacturing a display panel of the present invention includes reacting a dianhydride compound with a diamine compound having an alkyl side chain to generate a first precursor, and reacting the dianhydride compound with a diamine compound without an alkyl side chain to generate a second precursor. The above method also includes coating a mixture of the first precursor and the second precursor on a first substrate. The above method also includes curing the mixture to form a first alignment layer on the first substrate. The above method also includes assembling the first substrate and the second substrate together so that the first alignment layer faces the second substrate, and filling display medium molecules between the first alignment layer and the second substrate, wherein the display medium molecules have a pretilt angle less than or equal to 4°. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a partial cross-sectional schematic diagram of a display panel according to an embodiment of the present invention.

[0008] Figure 2 FIG. 4 is a flow chart of a method for manufacturing a display panel according to an embodiment of the present invention.

[0009] Figure 3 FIG. 4 is a test image diagram of a display panel according to an embodiment of the present invention.

[0010]

Explanation of symbols

[0011] 10: Display Panel

[0012] 20: Methods

[0013] 110,120:Substrate

[0014] 112,122,142: Surface

[0015] 130: Display medium layer

[0016] 140,150: Alignment layer

[0017] 160: Pixel array layer

[0018] 170: common electrode layer

[0019] 210~240: Steps

[0020] DM: Display medium molecule

[0021] PE: Pixel electrode

[0022] PX: Pixel DETAILED DESCRIPTION

[0023] In the accompanying drawings, for the sake of clarity, the thickness of layers, films, panels, regions, etc. is magnified. Throughout the specification, the same reference numerals represent the same elements. It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected to" another element, it may be directly on or connected to another element, or an intermediate element may also exist. On the contrary, when an element is referred to as being "directly on" or "directly connected to" another element, there is no intermediate element. As used herein, "connection" may refer to physical and / or electrical connection. Furthermore, "electrical connection" or "coupling" may be the presence of other elements between two elements.

[0024] It should be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers and / or portions, these elements, components, regions, layers and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or portion from another element, component, region, layer or portion. Therefore, the first "element", "component", "region", "layer" or "portion" discussed below may be referred to as a second element, component, region, layer or portion without departing from the teachings of this document.

[0025] The terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting. As used herein, unless the content clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms, including "at least one" or to mean "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the relevant listed items. It should also be understood that when used in this specification, the terms "comprising" and / or "including" specify the presence of the features, regions, wholes, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, parts and / or combinations thereof.

[0026] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element, as shown in the figures. It should be understood that relative terms are intended to include different orientations of the device in addition to the orientation shown in the figures. For example, if the device in one figure is turned over, the elements described as being on the "lower" side of the other elements will be oriented on the "upper" side of the other elements. Therefore, the exemplary term "lower" can include both "lower" and "upper" orientations, depending on the particular orientation of the figure. Similarly, if the device in one figure is turned over, the elements described as being "lower" or "below" other elements will be oriented as being "above" the other elements. Therefore, the exemplary terms "lower" or "below" can include both above and below orientations.

[0027] Taking into account the measurement in question and the specific amount of error associated with the measurement (i.e., the limitations of the measurement system), the terms "about", "approximately", or "substantially" as used herein include the stated value and the average value within an acceptable deviation range of the particular value determined by one of ordinary skill in the art. For example, "about" can mean within one or more standard deviations of the stated value, or within ±30%, ±20%, ±10%, ±5%. Furthermore, the terms "about", "approximately", or "substantially" as used herein may select a more acceptable deviation range or standard deviation depending on the optical property, etching property, or other property, and may not apply to all properties with one standard deviation.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and the present invention, and will not be interpreted as an idealized or overly formal meaning unless explicitly defined as such herein.

[0029] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic diagrams of idealized embodiments. Therefore, variations in the shapes of the illustrations as a result of, for example, manufacturing techniques and / or tolerances, can be expected. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions as shown herein, but rather include shape deviations that result, for example, from manufacturing. For example, a region shown or described as flat may typically have rough and / or nonlinear features. In addition, the sharp angles shown may be rounded. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of the regions and are not intended to limit the scope of the claims.

[0030] Figure 1 is a partial cross-sectional diagram of a display panel 10 according to an embodiment of the present invention. Figure 1 The display panel 10 may include a substrate 110, a substrate 120, a display medium layer 130 and an alignment layer 140. The substrate 120 is disposed opposite to the substrate 110. The display medium layer 130 is disposed between the substrate 110 and the substrate 120 and includes a plurality of display medium molecules DM. The alignment layer 140 is disposed on the substrate 110.

[0031] The substrate 110 and the substrate 120 may be transparent substrates. For example, the materials of the substrate 110 and the substrate 120 are glass, quartz, organic polymer or other appropriate materials. The substrate 110 and the substrate 120 may have the same or different materials. In some embodiments, the substrate 110 or the substrate 120 may be an opaque substrate. In some embodiments, the substrate 110 and / or the substrate 120 may be a flexible substrate.

[0032] The display medium layer 130 is located in the space surrounded by the substrate 120 and the substrate 110. The display medium molecules DM of the display medium layer 130 are, for example, cholesteric liquid crystal (CLC) molecules, but are not limited thereto. In some embodiments, the display medium molecules DM can switch between a focal conic state, a homeotropic state, and a planar state. For example, when the display medium molecules DM are in the focal conic state or the homeotropic state, the display medium layer 130 can present a penetrating state. When the display medium molecules DM are in the planar state, the display medium layer 130 can present a reflective state, thereby reflecting the light entering the display panel 10. In some embodiments, the wavelength of the light reflected by the display medium layer 130 can be determined by the pitch of the display medium molecules DM.

[0033] For example, the display panel 10 includes a plurality of pixels PX located in a display area, and the display area is, for example, an area where the pixels PX are located. When the display medium molecules DM in the pixel PX are all in a focal conic state or a vertical state, the display medium layer 130 in the pixel PX is in a penetrating state. When the display medium molecules DM in the pixel PX are all in a planar state, the display medium layer 130 in the pixel PX is in a reflective state. When a portion of the display medium molecules DM in the pixel PX is in a focal conic state or a vertical state and another portion of the display medium molecules DM is in a planar state, the display medium layer 130 in the pixel PX is in a state of partial penetration and partial reflection, so that the display medium layer 130 in the pixel PX can provide different degrees of penetration, thereby enabling the pixel PX to provide different degrees of grayscale. In this way, the display medium layer 130 in any pixel PX can switch between a reflective state (minimum penetration), a penetrating state (maximum penetration), and a penetration between the reflective state and the penetrating state.

[0034] In some embodiments, when the display medium molecules DM in the display medium layer 130 are all in a planar state, the transmittance of the display medium layer 130 is about 0%. In some embodiments, when the display medium molecules DM in the display medium layer 130 are all in a focal conic state or a vertical state, the transmittance of the display medium layer 130 can be as high as 90% or more. In some embodiments, when a portion of the display medium molecules DM in the display medium layer 130 are in a focal conic state or a vertical state and another portion of the display medium molecules DM are in a planar state, the transmittance of the display medium layer 130 can be between 0% and 90%, for example, about 25%, about 50%, or about 75%.

[0035] The alignment layer 140 may be located between the substrate 110 and the display medium layer 130 to arrange the display medium molecules DM of the display medium layer 130 in an orderly manner and exhibit a good rotation effect, thereby improving the image display quality. The alignment layer 140 may be formed by an imidization reaction of a dianhydride compound, a diamine compound having an alkyl side chain, and a diamine compound without an alkyl side chain.

[0036] Common dianhydride compounds include maleic anhydride, etc. In some embodiments, the dianhydride compound may have a structure shown in the following formula (1):

[0037]

[0038] wherein Ar represents an aromatic group having a 4- to 14-membered ring structure.

[0039] In some embodiments, Ar represents an aromatic group having a four-membered ring structure, a benzene ring structure or a biphenyl structure. In some embodiments, the dianhydride compound of formula (1) is pyromellitic dianhydride (PMDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) or dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride (HBPDA).

[0040] Common diamine compounds include aromatic diamines, such as 4,4'-oxydianiline (4,4'-ODA), p-phenylenediamine (PPD), dimethyl-benzenediamine (DMBDA), etc.; or alkyl diamines, such as 1,4-diaminobutane (1,4-Diaminobutane).

[0041] In some embodiments, the diamine compound having an alkyl side chain is a compound having a polycyclic aromatic group Ar' with at least two NH2 functional groups and at least one alkyl group attached to the ring. For example, the diamine compound having an alkyl side chain can be represented by the chemical formula shown in the following formula (2):

[0042]

[0043] Wherein, Ar' is a 5- to 14-membered aromatic group, L1 is a single bond, -O-, -C(O)- or -C(O)O-, and R1 is a C1 to C12 straight-chain alkyl group.

[0044] Alternatively, the diamine compound having an alkyl side chain may have a structure represented by the following formula (2'):

[0045]

[0046] Wherein, Ar' is a 5- to 14-membered aromatic group, L1 is a single bond, -O-, -C(O)- or -C(O)O-, and R1 is a C1 to C12 straight-chain alkyl group.

[0047] In some embodiments, Ar' in formula (2) and formula (2') is a 6-membered aromatic group or a 10-membered aromatic group. In some embodiments, Ar' in formula (2) and formula (2') is a benzene aromatic group or a naphthalene aromatic group.

[0048] In some embodiments, R1 is a C1 to C10 straight chain alkyl group. In some embodiments, R1 is a methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl or n-octyl group. In some embodiments, the diamine compound having an alkyl side chain is ethyl 3,5-diaminobenzoate, n-propyl 3,5-diaminobenzoate, n-butyl 3,5-diaminobenzoate, n-hexyl 3,5-diaminobenzoate or 3,5-diaminophenyl ether.

[0049] The diamine compound without an alkyl side chain may consist of only a main chain and two NH2 functional groups bonded to the main chain. In some embodiments, the main chain of the diamine compound without an alkyl side chain includes a diphenyl ether group or a dinaphthyl ether group. In some embodiments, the diamine compound without an alkyl side chain is 4,4'-diaminodiphenyl ether.

[0050] In some embodiments, the molar ratio of the diamine compound with an alkyl side chain to the diamine compound without an alkyl side chain is 0.1 to 0.5, such as 0.2, 0.3 or 0.4. In some embodiments, the molar ratio of the dianhydride compound to the diamine compound without an alkyl side chain is 1 to 1.5, such as 1.2, 1.3 or 1.4. In some embodiments, the molar ratio of the dianhydride compound, the diamine compound with an alkyl side chain and the diamine compound without an alkyl side chain is 1 to 1.5:0.1 to 0.5:1, such as 1.5:0.5:1.

[0051] In some embodiments, the display panel 10 further includes an alignment layer 150, and the alignment layer 150 may be located between the substrate 120 and the display medium layer 130. In some embodiments, the material of the alignment layer 150 is the same as that of the alignment layer 140, but is not limited thereto. In some embodiments, the material of the alignment layer 150 is different from that of the alignment layer 140.

[0052] In some embodiments, the display panel 10 further includes a pixel array layer 160, and the pixel array layer 160 may be located in the substrate 110 or on the surface 112 of the substrate 110 adjacent to the display medium layer 130. In some embodiments, the pixel array layer 160 includes a plurality of pixel electrodes PE, and the plurality of pixel electrodes PE may be arranged in the form of an array in the pixel array layer 160. For example, the pixel array layer 160 includes a plurality of pixel electrodes PE, a plurality of active elements (not shown), a plurality of data lines (not shown), and a plurality of scan lines (not shown), wherein the active elements are, for example, thin film transistors having a source, a gate, and a drain, the data lines may be electrically connected to the sources of the plurality of active elements, the scan lines may be electrically connected to the gates of the plurality of active elements, and the plurality of pixel electrodes PE may be electrically connected to the drains of the plurality of active elements, respectively, but not limited thereto.

[0053] In some embodiments, the display panel 10 further includes a common electrode layer 170, and the common electrode layer 170 may be located in the substrate 120 or on a side of the substrate 120 adjacent to the display medium layer 130. The electric field formed by the plurality of pixel electrodes PE of the pixel array layer 160 and the common electrode layer 170 can drive the display medium molecules DM in the display medium layer 130 to switch between different stable states.

[0054] In some embodiments, the display panel 10 further includes a color filter layer (not shown). The color filter layer may be located between the common electrode layer 170 and the substrate 120 , so that the display panel 10 has a full-color display effect.

[0055] Figure 2 FIG. 2 is a flow chart of a method 20 for manufacturing a display panel according to an embodiment of the present invention. In some embodiments, the alignment layer 140 may be formed on the substrate 110 in the following manner.

[0056] Please refer to Figure 2 First, in step 210, a dianhydride compound can be reacted with a diamine compound having an alkyl side chain to generate a first precursor, and a dianhydride compound can be reacted with a diamine compound without an alkyl side chain to generate a second precursor. For example, please refer to the following reaction formula 1, and the dianhydride compound (A) and the diamine compound (B) having an alkyl side chain are subjected to a condensation polymerization reaction in a polar solvent to generate a first precursor (P1). In addition, please refer to the following reaction formula 2, and the dianhydride compound (A) and the diamine compound (C) without an alkyl side chain are subjected to a condensation polymerization reaction in a polar solvent to generate a second precursor (P2). In some embodiments, the dianhydride compound (A), the diamine compound (B) having an alkyl side chain, and the diamine compound (C) without an alkyl side chain can be subjected to a condensation polymerization reaction in a polar solvent, and the molar ratio of the dianhydride compound (A): the diamine compound (B) having an alkyl side chain: the diamine compound (C) without an alkyl side chain can be 1 to 1.5: 0.1 to 0.5: 1. In some embodiments, the first precursor (P1) and the second precursor (P2) are polyamic acid compounds.

[0057] Reaction 1:

[0058]

[0059] Reaction 2:

[0060]

[0061] In some embodiments, the dianhydride compound (A) is pyromellitic dianhydride (PMDA). In some embodiments, the diamine compound (B) having an alkyl side chain is ethyl 3,5-diaminobenzoate, n-propyl 3,5-diaminobenzoate, n-butyl 3,5-diaminobenzoate, n-hexyl 3,5-diaminobenzoate or 3,5-diaminophenyl ether. In some embodiments, the diamine compound (C) without an alkyl side chain is 4,4'-diaminodiphenyl ether. In some embodiments, the polar solvent is dimethylformamide (DMF) or dimethyl sulfoxide (DMSO).

[0062] Next, in step 220, a mixture of the first precursor and the second precursor may be coated on the first substrate. For example, the first precursor (P1) and the second precursor (P2) may be mixed, and the molar ratio of the first precursor (P1) to the second precursor (P2) may be 0.1 to 0.5:1. In some embodiments, the molar ratio of the first precursor (P1) to the second precursor (P2) is 1:2. Then, please also refer to Figure 1 The mixture of the first precursor (P1) and the second precursor (P2) can be coated on the surface 112 of the substrate 110 facing the display medium layer 130 by, for example, scraping or spin coating. In some embodiments, the mixture of the first precursor (P1) and the second precursor (P2) can be coated on the surface of the substrate 110 on which the pixel array layer 160 is formed.

[0063] In some embodiments, the mixture of the first precursor (P1) and the second precursor (P2) may be coated on the surface 122 of the substrate 120 facing the display medium layer 130. In some embodiments, the mixture of the first precursor (P1) and the second precursor (P2) may be coated on the surface of the substrate 120 on which the common electrode layer 170 is formed.

[0064] Next, in step 230, the mixture of the first precursor and the second precursor may be cured to form a first alignment layer on the first substrate. For example, referring to the following reaction formula 3, the substrate 110 coated with the mixture of the first precursor (P1) and the second precursor (P2) may be heated to above 200°C, for example, 200°C to 250°C, so that the first precursor (P1) and the second precursor (P2) undergo a cyclization reaction and dehydrate and cure to generate a polyimide polymer (PI), and the polyimide polymer (PI) may form a polyimide film on the surface 112 of the substrate 110 as the alignment layer 140. In some embodiments, the heating may be continued for 30 to 60 minutes. Since the polyimide polymer (PI) of the alignment layer 140 includes an alkyl side chain R1, and the carbon number of the alkyl side chain R1 is less than or equal to 12, the angle between the alkyl side chain R1 and the horizontal surface 142 of the alignment layer 140 can make the display medium molecule DM have a pre-tilt angle θ less than or equal to 4°. Generally speaking, the pre-tilt angle θ can be measured using optical instruments such as Axsosan, RENTS, etc. In addition, since the polyimide polymer (PI) of the alignment layer 140 also includes a diphenyl ether functional group without a side chain, it can help avoid excessive interaction between the display medium molecule DM and the polyimide polymer (PI), thereby reducing factors that interfere with the arrangement of the display medium molecule DM.

[0065] Reaction 3:

[0066]

[0067] The alignment layer 140 may have a polyimide (PI) structure as shown in Reaction Formula 3. In some embodiments, in the polyimide (PI) structure as shown in Reaction Formula 3, n:n′ is 0.1 to 0.5:1, for example, 1:5 or 1:2.

[0068] In some embodiments, in step 230, the substrate 120 coated with the mixture of the first precursor (P1) and the second precursor (P2) can be heated and cured at the same time, so that the first precursor (P1) and the second precursor (P2) undergo a cyclization reaction, thereby forming a polyimide film as the alignment layer 150 on the surface 122 of the substrate 120. In some embodiments, the alignment layer 150 also has a polyimide (PI) structure shown in Reaction Formula 3.

[0069] Next, in step 240, the first substrate and the second substrate can be assembled together with the first alignment layer facing the second substrate, and the display medium molecules can be filled between the first alignment layer and the second substrate. For example, a sealant (not shown) can be first applied on the periphery of the surface 112 of the substrate 110 (or the surface of the alignment layer 140 opposite to the substrate 110) or on the periphery of the surface 122 of the substrate 120 (or the surface of the alignment layer 150 opposite to the substrate 120). Then, the display medium molecules DM are dropped into the space enclosed by the surface 112 (or the alignment layer 140) or the surface 122 (or the alignment layer 150) and the sealant. Afterwards, the alignment layer 140 can be made to face the alignment layer 150 to fix the substrate 110 and the substrate 120, and then in a near-vacuum environment, one of the substrate 110 and the substrate 120 is moved toward the other of the substrate 110 and the substrate 120, so that the substrate 110 and the substrate 120 are bonded to each other through the frame glue, thereby sealing the display medium molecules DM between the alignment layer 140 and the alignment layer 150 to form the display medium layer 130, and the display panel 10 can be manufactured. In some embodiments, the display medium molecules DM can be filled in by a liquid crystal drop filling method (one dropfill; ODF) to manufacture the display panel 10, but it is not limited thereto. In other embodiments, the display medium molecules DM can be filled in by a liquid crystal injection method (LC injection) or other appropriate methods to manufacture the display panel 10.

[0070] Figure 3 The display panel 10 is driven into a 3*1 grid black and white grid screen and then left at 50°C for 1 day for image sticking test. Figure 3 From Figure 3 It can be seen that there is almost no image sticking in the display panel 10 , which shows that the display panel of the present invention can indeed improve the image sticking effect.

[0071] In summary, the display panel of the present invention uses a diamine compound with an alkyl side chain and a diamine compound without an alkyl side chain to form an alignment layer, thereby avoiding excessive interaction between the display medium molecules and the surface of the alignment layer, and at the same time making the display medium molecules have a pre-tilt angle less than or equal to 4°, thereby improving the image sticking phenomenon of the display panel.

[0072] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims

1. A display panel, comprising: a first substrate; a second substrate, arranged opposite to the first substrate; A display medium layer is disposed between the first substrate and the second substrate and includes a plurality of display medium molecules; as well as A first alignment layer is disposed on the first substrate; The first alignment layer is formed by condensation polymerization of a dianhydride compound, a diamine compound with an alkyl side chain and a diamine compound without an alkyl side chain, the molar ratio of the diamine compound with an alkyl side chain to the diamine compound without an alkyl side chain is 0.1 to 0.5, and the carbon number of the alkyl side chain of the diamine compound with an alkyl side chain is 1 to 12. 2 . The display panel according to claim 1 , wherein the alkyl side chains of the diamine compound having alkyl side chains make the pretilt angle of the display medium molecules less than or equal to 4°. 3 . The display panel according to claim 1 , wherein a molar ratio of the dianhydride compound, the diamine compound having an alkyl side chain, and the diamine compound having no alkyl side chain is 1-1.5:0.1-0.5:

1.

4. The display panel according to claim 1, wherein the dianhydride compound has a structure represented by the following formula (1): wherein Ar represents an aromatic group having a 4- to 14-membered ring structure. 5 . The display panel according to claim 4 , wherein the aromatic group has a four-membered ring structure, a benzene ring structure or a biphenyl structure.

6. The display panel according to claim 1, wherein the diamine compound having an alkyl side chain is represented by the following chemical formula (2): Wherein Ar' is a 5- to 14-membered aromatic group, L1 is a single bond, -O-, -C(O)- or -C(O)O-, and R1 is a C1 to C12 straight-chain alkyl group. 7 . The display panel according to claim 6 , wherein the diamine compound having an alkyl side chain is ethyl 3,5-diaminobenzoate, n-propyl 3,5-diaminobenzoate, n-butyl 3,5-diaminobenzoate, n-hexyl 3,5-diaminobenzoate or 3,5-diaminophenethyl ether. 8 . The display panel as claimed in claim 1 , wherein the diamine compound without an alkyl side chain is 4,4′-diaminodiphenyl ether. 9 . The display panel according to claim 1 , further comprising a second alignment layer, wherein the first alignment layer is located between the first substrate and the display medium layer, and the second alignment layer is located between the second substrate and the display medium layer. 10 . The display panel as claimed in claim 9 , wherein the second alignment layer is made of the same material as the first alignment layer.

11. A method for manufacturing a display panel, comprising the following steps: A dianhydride compound is reacted with a diamine compound having an alkyl side chain to generate a first precursor, and the dianhydride compound is reacted with a diamine compound having no alkyl side chain to generate a second precursor; Applying a mixture of the first precursor and the second precursor on a first substrate; Allowing the mixture to undergo a curing reaction to form a first alignment layer on the first substrate; as well as The first substrate and the second substrate are assembled together with the first alignment layer facing the second substrate, and display medium molecules are filled between the first alignment layer and the second substrate, wherein the display medium molecules have a pretilt angle less than or equal to 4°. 12 . The method of claim 11 , wherein the molar ratio of the diamine compound having an alkyl side chain to the diamine compound without an alkyl side chain is 0.1 to 0.5, and the carbon number of the alkyl side chain of the diamine compound having an alkyl side chain is 1 to 12. 13 . The method according to claim 11 , wherein the ratio of the first precursor to the second precursor in the mixture is 0.1 to 0.5:

1.

14. The method of claim 11, wherein the curing reaction is performed at a temperature of 200 to 250°C for 30 to 60 minutes.

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