Flexible electronic device and preparation method

Abstract

The invention discloses a flexible electronic device, a polyimide precursor composition for the flexible electronic device, and a preparation method of the polyimide precursor composition. Coating the polyimide precursor composition on a substrate; a step for forming a laminate in which a polyimide film is laminated on the base material by heating and amidating at least part or all of the polyimide precursor composition to form the polyimide film; forming a conductive layer or a semiconductor layer on the polyimide film; and stripping the base material and the polyimide film through mechanical external force. The peel strength of the polyimide film is reduced to be less than or equal to 0.5 N / in (the reduction amplitude is 40% +), and laser-free mechanical peeling is realized; under the condition that the thickness of the polyimide film is 10 microns, Rth is less than or equal to 700 nm, the light transmittance at 400 nm is more than or equal to 80%, the 1% weight loss temperature is more than or equal to 450 DEG C, and the linear thermal expansion coefficient is less than or equal to 40 ppm / K. The polyimide film disclosed by the invention has process compatibility, can resist high-temperature treatment (such as 410 DEG C or above), and is suitable for reel-to-reel mass production.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic device manufacturing technology, specifically to a polyimide precursor composition that combines low peel strength, low optical phase difference, and high thermal stability, as well as the application of the polyimide precursor in flexible electronic devices such as flexible displays, touch panels, and solar cell substrates, and to a flexible display device. Background Technology

[0002] Flexible electronics technology involves fabricating electronic devices made of organic or inorganic materials on flexible substrates, maintaining their electronic properties on curved surfaces. This technology has the potential to revolutionize electronics, attracting widespread global attention and experiencing rapid development. The American journal *Science* listed advancements in organic electronics technology as one of the top ten scientific achievements of 2000, alongside major discoveries such as the draft human genome and biological cloning.

[0003] Flexible electronics technology is an emerging field in the industry. Its emergence not only integrates technologies from electronic circuits, electronic components, materials, flat panel displays, and nanotechnology, but also spans industries such as semiconductors, packaging and testing, materials, chemicals, printed circuit boards, and display panels. It can assist the transformation of traditional industries, such as plastics, printing, chemicals, and metal materials. Its importance in information, energy, medical, and manufacturing fields is increasingly prominent, and it has become a cutting-edge technology that many countries and multinational corporations are vying to develop. The United States, the European Union, the United Kingdom, Japan, and other countries have successively formulated flexible electronics development strategies and invested heavily in research and development, aiming to gain a competitive edge in future flexible electronics research and industrial development. However, the fabrication of flexible electronic devices faces challenges related to material properties.

[0004] Polyimide is a class of high-molecular polymers containing repeating imide rings (-CO-NH-CO-) in its main chain. Since the 1960s, polyimide has been widely used as a special engineering material in aerospace, microelectronics, nanotechnology, liquid crystal displays, and other fields, and is considered one of the most promising engineering plastics of the 21st century. With the continuous innovation of flexible display technology, the application of OLED screens in folding and rolling is gradually becoming more widespread, expanding from mobile phone screens to larger-sized display products such as televisions, thus bringing huge market potential to PI films. In flexible displays, polyimide films are mainly used in several key components such as display substrates, display packaging substrates, touch screen substrates, touch screen covers, and display screen covers.

[0005] As foldable electronic devices evolve towards being thinner, lighter, and more durable, increasingly stringent requirements are being placed on the mechanical properties of the core flexible substrate material. Traditional polyimide applications in flexible electronic devices suffer from the following drawbacks: 1) Mechanical peel damage problem: The peel strength of traditional polyimide / glass substrate is >0.8N / in, and more than 50% of the samples suffer circuit damage during mechanical peeling.

[0006] 2) Optical phase difference causes color shift: When the phase difference (Rth) in the thickness direction of the polyimide film is greater than 800nm, the viewing angle deviation of the liquid crystal display is greater than 15°, resulting in color distortion.

[0007] 3) Insufficient compatibility with high-temperature processes: Existing polyimides use phosphorus compounds for modification, but most phosphorus compounds (such as methylphosphonic acid with a boiling point of 197°C) decompose and become ineffective at temperatures above 300°C, thus failing to simultaneously meet the requirements of high-temperature imidization and interface modification. Summary of the Invention

[0008] The present invention provides a flexible electronic device, a polyimide precursor composition for the flexible electronic device, and a method for preparing the same, to solve the problems mentioned in the above-mentioned technical background.

[0009] The first aspect of the present invention is to provide a polyimide precursor having the structure shown in structural formula (I): (I) Wherein, X is a tetravalent organic group, Y is a divalent organic group, R1 and R2 are independently selected from H, alkyl, and alkylsilyl groups, and n is the degree of polymerization.

[0010] In a preferred embodiment, X and Y can be independently one of an aliphatic group or an aromatic group, or a combination of an aliphatic group or an aromatic group.

[0011] In a preferred embodiment, X and Y may each contain an aliphatic cyclic group independently.

[0012] In a preferred embodiment, the molar percentage of repeating units in the adipose ring structure can be ≤50 mol%, more preferably 20-50 mol%, more preferably 25-45 mol%, more preferably 30-40 mol%, for example 50 mol%, 45 mol%, 40 mol%, 35 mol%, 30 mol%, 25 mol%.

[0013] In a preferred embodiment, X may be a group selected from C5-C25 (preferably C6-C22, more preferably C6-C20, more preferably C6-C18, more preferably C6-C15, such as C7, C8, C9, C10, C11, C12, C13, C14, etc.), for example, X may be... , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , One or more combinations thereof.

[0014] In a preferred embodiment, Y can be a group selected from C1-C20 (preferably C2-C22, more preferably C3-C20, more preferably C4-C18, more preferably C5-C15, such as C6, C7, C8, C9, C10, C11, C12, C13, C14, etc.), for example, Y can be -CH2-, -CH2-CH2-, -CH2-CH2-NH-CH2-CH2, -CH2-NH-CH2-CH2-NH-CH2-, -CH2-CH2-NH-CH2-CH2-NH-CH2-, -CH2-C(CH3)2-C(CH3)2-, , , , , , , , , , , , , , , , , , , , , One or more combinations thereof.

[0015] In a preferred embodiment, R1 and R2 are independently selected from H, C1-C6 alkyl groups, and C3-C6 alkylmethylsilyl groups, respectively. For example, R1 and R2 are independently selected from H, -CH3, -CH2-CH3, -CH(CH3)2, -C(CH3)3, -CH2-CH2-CH3, -CH(CH3)-CH2-CH3, -C(CH3)2-CH2-CH3, -CH(CH3)-CH(CH3)2, -CH2-CH(CH3)2, -CH2-C(CH3)3, and -CH(CH3)-C(CH3)3. 3) One or more combinations of -C(CH3)2-C(CH3)3, -CH2-CH2-CH2-SiH3, -CH(CH3)-CH2-CH2-SiH3, -CH2-CH2-SiH2-CH3, -CH2-CH2-SiH2-CH2-CH3, -CH2-CH2-Si(CH3)3, -CH2-Si(CH3)3, -Si(CH3)3, -CH2-SiH(CH2-CH3)2, -Si(CH2-CH3)3, and -SiH(CH2-CH3)2.

[0016] A second aspect of the present invention is to provide a polyimide precursor composition comprising the polyimide precursor, a phosphorus compound, a compound containing an imidazole structure, and a solvent.

[0017] In a preferred embodiment, the phosphorus compound has a P(=O)(OR) structure, wherein R is selected from H, alkyl, especially from alkyl groups with ≥1 C atom, preferably ≥2, more preferably ≥3, and even more preferably ≥4, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, heptyl, octyl, 2,6-dimethyloctyl, decyl, nonyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, octadecyl, etc.

[0018] In a preferred embodiment, the phosphorus compound may be , , , , , , One or more combinations thereof, wherein R3, R4, and R5 are each independently selected from alkyl groups, especially from alkyl groups with ≥1 C atom, preferably ≥2, more preferably ≥3, and even more preferably ≥4, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, heptyl, octyl, 2,6-dimethyloctyl, decyl, nonyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, octadecyl, etc.

[0019] In a preferred embodiment, the phosphorus compound may be selected from: , , , , , , , , , , , , , , , , , One or more combinations thereof.

[0020] In a preferred embodiment, the phosphorus compound is 0.001-5% of the polyimide precursor, such as 0.005-4.5%, more preferably 0.01-4%, even more preferably 0.05-3%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, etc., in molar amounts.

[0021] In a preferred embodiment, the molecular weight of the phosphorus compound is ≤400, more preferably ≤350.

[0022] In a preferred embodiment, the boiling point of the phosphorus compound (at one atmosphere) is preferably ≥250°C, more preferably ≥300°C, more preferably ≥350°C, more preferably ≥400°C, more preferably ≥450°C, and more preferably ≥500°C.

[0023] In a preferred embodiment, the compound containing an imidazole structure is a compound containing... Compounds with a structure where the H in -NH- can also be replaced by a monovalent substituent are preferred, but preferably do not contain a pyrazoline structure. For example, compounds containing an imidazole structure may be... , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , One or more combinations thereof.

[0024] In a preferred embodiment, the compound containing an imidazole structure is preferably selected from one or more of alkylimidazolium and benzimidazole, or a combination of alkylimidazolium and benzimidazole.

[0025] In a preferred embodiment, the compound containing the imidazole structure is 0.05-1% of the polyimide precursor, such as 0.08-0.8%, more preferably 0.1-0.6%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., on a molar basis.

[0026] In a preferred embodiment, the molar ratio of the phosphorus compound to the compound containing the imidazole structure is 1:(0.1-10), preferably 1:(1-4), more preferably 1:(1.5-3.5), and even more preferably 1:(2-3).

[0027] In a preferred embodiment, the solvent is preferably an organic solvent, such as any one or more of pure ether, ester, ketone, hydrocarbon, halogenated hydrocarbon, heterocyclic compound, amide, sulfoxide, and nitrile. For example, it can be one or a combination of methanol, ethanol, propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, polyethylene glycol, diethyl ether, petroleum ether, acetone, ethyl acetate, butyl acetate, methyl acetate, benzene, toluene, xylene, chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, biphenyl, tetrahydrofuran, dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and acetonitrile.

[0028] In a preferred embodiment, the polyimide precursor composition may further include additives, such as any one or more combinations of defoamers, leveling agents, antioxidants, flame retardants, preservatives, lubricants, and anti-aging agents.

[0029] A second aspect of the present invention is to provide a method for preparing the polyimide precursor composition, comprising: A polyimide precursor solution is obtained by polycondensation of a diamine of structural formula (II) and an anhydride or its corresponding carboxylic acid of structural formula (III) in the solvent. Phosphorus compounds and compounds containing imidazole structures are added to a polyimide precursor solution.

[0030] In a preferred embodiment, an additive may be added to the polyimide precursor solution. Preferably, the additive may be added after the phosphorus compound and the compound containing the imidazole structure, or simultaneously with the phosphorus compound and the compound containing the imidazole structure.

[0031] In a preferred embodiment, the polyimide precursor solution has a viscosity of 100-500 Pa•s (at 25°C), and a phosphorus compound and a compound containing an imidazole structure are added to the polyimide precursor solution.

[0032] A fourth aspect of this invention is to provide a method for fabricating a flexible electronic device, comprising: The polyimide precursor composition is coated onto a substrate; Heating at least partially or completely of the polyimide precursor composition to amidate it, forming a polyimide film, thereby forming a laminate on the substrate with the polyimide film deposited thereon; A conductive layer or a semiconductor layer is formed on the polyimide film; The substrate and polyimide film are separated by mechanical force.

[0033] In a preferred embodiment, the substrate is a glass plate.

[0034] In a preferred embodiment, laser irradiation is not performed during the peeling process.

[0035] In a preferred embodiment, the heating temperature is preferably 250-500°C.

[0036] In a preferred embodiment, the heating is performed in two stages: First stage: Heat at 80-200℃ for 10-30 minutes; Second stage: Heat at 300-500℃ for 5~20 minutes.

[0037] In a preferred embodiment, the thickness of the polyimide film is 5-50 μm. In a preferred embodiment, the linear coefficient of thermal expansion of the polyimide film is ≤40ppm / K (at 150-250°C).

[0038] In a preferred embodiment, the polyimide film, with a thickness of 10 μm, has a transmittance of ≥80% at 400 nm and a total transmittance (380~780 nm) of ≥87%.

[0039] In a preferred embodiment, the peel strength between the polyimide film and the substrate and the thickness direction phase difference (Rth) of the laminate satisfy any one of the following: (a) Peel strength ≤ 0.5 N / in and Rth ≤ 1000 nm; (b) Peel strength ≤ 0.8 N / in and Rth ≤ 700 nm.

[0040] In a preferred embodiment, the 1% weight loss temperature of the laminate is ≥450°C.

[0041] A fifth aspect of the present invention is to provide an application of the laminate, which can be used in displays, touch panels or flexible solar cell substrates, wherein the surface of the polyimide film is covered with a gas barrier layer or a transparent conductive layer.

[0042] A sixth aspect of the present invention is to provide a flexible electronic device manufactured by the method described above.

[0043] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: 1) The peel strength of the polyimide film of the present invention is reduced to ≤0.5N / in (a reduction of 40%+), and laser-free mechanical peeling is achieved.

[0044] 2) When the polyimide film thickness of the present invention is 10μm, Rth≤700nm and transmittance≥80% at 400nm.

[0045] 3) The polyimide film of the present invention has a 1% weight loss temperature ≥450℃ and a linear thermal expansion coefficient ≤40ppm / K.

[0046] 4) The polyimide film of this invention has process compatibility: it can withstand high temperature treatment (such as above 410°C) and is suitable for roll-to-roll mass production. Detailed Implementation

[0048] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following examples further illustrate the invention in detail. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0049] It should be noted that the terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0050] The method for preparing polyimide precursors, compositions, and electronic devices according to the present invention is as follows: 1. Preparation of polyimide precursor compositions 1.1 Precursor Synthesis Method The polyimide precursor is prepared by the following steps: (a) Reaction vessel treatment: The reaction vessel was purged with nitrogen three times to ensure an oxygen content of <50 ppm. (b) Diamine dissolution: The diamine is dissolved in a dehydrating solvent (e.g., N-methylpyrrolidone or N,N-dimethylacetamide) at room temperature. Solid content control: Total monomers (tetracarboxylic dianhydride + diamine) comprise 15-25 wt% of the reaction system.

[0051] (c) Addition of tetracarboxylic acid dianhydride: Add tetracarboxylic dianhydride slowly under stirring conditions, with the molar ratio controlled as follows: diamine / tetracarboxylic dianhydride = 0.95-1.05.

[0052] (d) Polymerization reaction: Reaction temperature: 20-50℃ Reaction time: 12-48 hours Reaction endpoint determination: Solution viscosity reaches 100-500 Pa•s (measured at 25℃). 1.2 Introduction of Additives Phosphorus compounds and compounds containing imidazole structures are added as follows: (a) Selection criteria for phosphorus compounds: Boiling point ≥250℃ (e.g., tributyl phosphate 289℃).

[0053] Molecular weight < 400 (e.g., methylphosphonic acid 96 g / mol).

[0054] Preferred ingredients: Tributyl phosphate, diethylphosphonic acid.

[0055] (b) Selection criteria for compounds containing imidazole structures: Boiling point 180-300℃ (e.g. 1,2-dimethylimidazole 205℃).

[0056] Exclude imidazoline derivatives (such as 2-ethylimidazoline, which easily leads to gelation).

[0057] (c) Adding method: Dissolve the additive in a small amount of solvent (<5 wt% of the total system). Add the precursor solution dropwise with stirring and mix for 30 minutes.

[0058] (d) Proportional control: The proportion of phosphorus compound in the polyimide precursor is 0.001-5 mol%, and the proportion of imidazole-containing compound in the polyimide precursor is 0.05-1 mol%. More preferably, the molar ratio of phosphorus compound to imidazole-containing compound is 1:0.5-1:2.

[0059] 2. Polyimide film manufacturing process 2.1 Coating and Heat Treatment (a) Substrate preparation: Sodium-calcium glass (1.1 mm thick) or silicon wafer (525 μm thick) are treated with UV-Ozone (ultraviolet ozone surface cleaning) for 10 minutes.

[0060] (b) Coating process: The following coating methods can be selected: ① Spin coating: Coat at 500-1500 rpm for 30s; ② Slot coating: Travel speed is 1-5 m / min; ③ Film thickness control: 5-50μm.

[0061] (c) Two-stage heat treatment is adopted: The first stage of heat treatment is at a temperature of 80-200℃ for 10-30 minutes.

[0062] The second stage of heat treatment is carried out at a temperature of 300-500℃ for 5-20 minutes.

[0063] For manufacturing display substrates, the preferred temperature for the second-stage heat treatment is 380-420℃, as products manufactured within this temperature range exhibit better optical performance. For manufacturing solar cell substrates, the preferred temperature for the second-stage heat treatment is 450-480℃, as products manufactured within this temperature range demonstrate better temperature resistance.

[0064] 2.2 Stripping and Device Fabrication (a) Peeling method: Mechanical peeling, no laser irradiation required.

[0065] Stripping solution: Deionized water or a 1:1 mixture of ethanol and water. Peeling angle: 90° (refer to JIS K6854-1 standard) Peeling speed: 1-5 mm / min (b) Peel strength control: Key factor: Phosphorus compound enrichment concentration gradient Optimization method: Extending the processing time in stage 1 (>20 min) can reduce the intensity to 0.3 N / in.

[0066] (c) Device integration: A barrier layer is deposited on a polyimide film, followed by photolithography of the circuitry and bonding of the driver IC.

[0067] Gas barrier material: SiN x (Thickness 200 nm, PECVD deposition), x is a positive number.

[0068] Transparent electrode: ITO (resistance <50 Ω / sq).

[0069] Table 1, Performance Testing Methods performance Test Standards Instrument Model Peel strength JIS K6854-1 ORIENTEC TENSILON RTA-500 Phase difference Rth Wavelength 589 nm, incident angle 40° Prince Measurement KOBRA-WR Light transmittance ASTM E313 Japan Spectrum V-650DS thermal stability <![CDATA[TGA (N2 atmosphere)]]> TA Q5000IR Example 1: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0070] The diamine DABAN (4,4'-diaminobenzoyl aniline) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to the reaction vessel. The tetracarboxylic dianhydride CpODA (norbornane-2-spiro-α-cyclopentanone-α′-spiro-2′-norbornane-5,5′,6,6′-tetracarboxylic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1.

[0071]

[0072] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of tributyl phosphate to the polyimide precursor is 0.1 mol%, and the molar ratio of 1,2-dimethylimidazole to the polyimide precursor is 0.2 mol%. Tributyl phosphate and 1,2-dimethylimidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution with stirring to obtain the polyimide precursor composition.

[0073] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was 180°C for 20 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was 350°C for 10 minutes to reduce the phase difference and achieve imidization via imidazole.

[0074] Step 4, peel off the film The resulting film Rth (thickness 10μm): 850nm; peel strength 0.28N / in; transmittance at 400nm 86.2%; total transmittance from 380-780nm 89.1%; bending life (radius 1mm) > 200,000 times.

[0075] Step 5: Device integration and fabrication of flexible OLEDs A barrier layer (SiNx, where x is an integer) with a thickness of 200 nm was deposited on the thin film using PECVD. The circuitry was then photolithographically patterned, and a driver IC was bonded to it.

[0076] The product of this embodiment can be used in foldable mobile phone screens, with ultra-low peel strength, achieving a mechanical peel yield of 99.2% (far higher than the yield of ≤85% of traditional solutions), and high light transmittance ensures that the OLED luminous efficiency is 12% higher than that of traditional solutions.

[0077] Example 2: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0078] Diamine ODA (4,4'-diaminodiphenyl ether) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to the reaction vessel. Tetracarboxylic dianhydride PMDA (pyromellitic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of diamine to tetracarboxylic dianhydride monomers in the reaction solution was 20%.

[0079]

[0080] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of methylphosphonic acid to the polyimide precursor is 0.05 mol%, and the molar ratio of 1-methylimidazole to the polyimide precursor is 0.2 mol%. Methylphosphonic acid and 1-methylimidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution with stirring to obtain the polyimide precursor composition.

[0081] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was increased to 120°C for 30 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was increased to 400°C for 15 minutes, thereby reducing the phase difference and achieving imidization through imidazole.

[0082] Step 4, peel off the film The resulting film has a peel strength of 0.41 N / in; Rth (thickness 10 μm): 420 nm; transmittance at 400 nm: 88.7%; color difference ΔE*: 1.3; and coefficient of thermal expansion: 32 ppm / K.

[0083] Step 5: Device integration and fabrication of the touch panel This embodiment of the product can be used in touchscreens, such as field command terminals, and features a very low phase difference, ensuring a color difference ΔE* < 1.5 at -40°C. It has also passed MIL-STD-810G certification. The touchscreen exhibits no delamination after 500 temperature shocks (-40 to 85°C) and no performance degradation after 1000 hours of humid heat (40°C / 95%RH).

[0084] Example 3: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0085] Diamine TFMB (2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to a reaction vessel. Tetracarboxylic dianhydride 6FDA (4,4'-(hexafluoroisopropylidene) phthalic anhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of diamine to tetracarboxylic dianhydride monomers in the reaction solution was 18%.

[0086]

[0087] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of diethylphosphonic acid to the polyimide precursor is 0.3 mol%, and the molar ratio of imidazole to the polyimide precursor is 0.6 mol%. Diethylphosphonic acid and imidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution while stirring. This yields the polyimide precursor composition.

[0088] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was raised to 200°C for 10 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was raised to 450°C for 5 minutes, thereby reducing the phase difference and achieving imidization through imidazole.

[0089] Step 4, peel off the film The resulting film exhibited a peel strength of 0.35 N / in; phosphorus residue >95%; 1% weight loss temperature of 478 °C; and a power density (AMO illumination) of 1.2 kW / m². 2 Thermal cycling stability (-196℃ to 150℃): No cracking after 100 cycles.

[0090] Step 5: Device integration and fabrication of space solar cell substrate The product of this embodiment can be used in space photovoltaic substrates (such as the Artemis lunar base), and can withstand the lunar surface day-night temperature difference (-173 to 127°C) at a 1% weight loss temperature of 478°C, and retains a power density of >99% after 100 thermal cycles.

[0091] Example 4: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0092] Diamine tra-DACH (trans-1,4-diaminocyclohexane) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to a reaction vessel. Tetracarboxylic dianhydride CpODA (norbornane-2-spiro-α-cyclopentanone-α′-spiro-2′-norbornane-5,5′,6,6′-tetracarboxylic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of the diamine and tetracarboxylic dianhydride monomers in the reaction solution was 18%. The polyimide precursor contained 45 mol% alicyclic repeating units.

[0093] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of tributyl phosphate to the polyimide precursor is 0.1 mol%, and the molar ratio of 1,2-dimethylimidazole to the polyimide precursor is 0.2 mol%. Tributyl phosphate and 1,2-dimethylimidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution with stirring to obtain the polyimide precursor composition.

[0094] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was 150°C for 25 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was 380°C for 10 minutes to reduce the phase difference and achieve imidization via imidazole.

[0095] Step 4, peel off the film The resulting film has a peel strength of 0.31 N / in; Rth (thickness 10 μm): 380 nm; yellowing index b* is 1.2; and haze is 0.3%.

[0096] Step 5: Device integration and fabrication of low phase difference display substrate Example 5: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0097] Diamine PPD (p-phenylenediamine) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to a reaction vessel. Tetracarboxylic dianhydride CpODA (norbornane-2-spiro-α-cyclopentanone-α′-spiro-2′-norbornane-5,5′,6,6′-tetracarboxylic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of diamine to tetracarboxylic dianhydride monomers in the reaction solution was 22%.

[0098] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of tributyl phosphate to the polyimide precursor is 0.1 mol%, and the molar ratio of 1-methylimidazole to the polyimide precursor is 0.2 mol%. Tributyl phosphate and 1-methylimidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution while stirring. This yields the polyimide precursor composition.

[0099] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was 180°C for 20 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was 410°C for 10 minutes to reduce the phase difference and achieve imidization via imidazole.

[0100] Step 4, peel off the film The resulting film has a thickness of 8 μm, a transmittance of 86.5% at 400 nm, a total transmittance of 91.3% from 380 to 780 nm, a coefficient of thermal expansion of 28 ppm / K, a haze of 0.4%, and a peel strength of 0.29 N / in (for a thickness of 8 μm).

[0101] Step 5: Device integration and fabrication of an ultrathin transparent substrate The products in Examples 4-5 can be used as substrates for AR glasses lenses, with a haze of ≤0.4% at a film thickness of 8 μm (far lower than the industry requirement of ≤1%) and a yellowing index b*=1.2 (a level that is not perceptible to the naked eye).

[0102] Mass production indicators: slit coating yield reaches 98.5%, and transmittance consistency is ±0.3% (380-780 nm across the entire range).

[0103] Comparative Example 1: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0104] Diamine DABAN (4,4'-diaminobenzoyl aniline) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to a reaction vessel. Tetracarboxylic dianhydride CpODA (norbornane-2-spiro-α-cyclopentanone-α′-spiro-2′-norbornane-5,5′,6,6′-tetracarboxylic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight ratio of diamine to tetracarboxylic dianhydride monomers in the reaction solution was 18%.

[0105] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of tributyl phosphate to the polyimide precursor is 0.1 mol%. Tributyl phosphate can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution with stirring to obtain the polyimide precursor composition.

[0106] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was 180°C for 20 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was 350°C for 10 minutes to reduce the phase difference and achieve imidization via imidazole.

[0107] Step 4, peel off the film The resulting film has a Rth (thickness 10 μm) of 920 nm and a transmittance of 83.1% at 400 nm.

[0108] Comparative Example 2: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0109] Diamine TFMB (2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to a reaction vessel. Tetracarboxylic dianhydride 6FDA (4,4'-(hexafluoroisopropylidene) phthalic anhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of diamine to tetracarboxylic dianhydride monomers in the reaction solution was 18%.

[0110] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of methylphosphonic acid to the polyimide precursor is 0.3 mol%, and the molar ratio of imidazole to the polyimide precursor is 0.6 mol%. Methylphosphonic acid and imidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution while stirring. This yields the polyimide precursor composition.

[0111] Step 3, prepare thin film The process involves two stages of heating: the first stage is heating at 200℃ for 10 minutes, and the second stage is heating at 450℃ for 5 minutes.

[0112] Step 4, peel off the film The resulting film has a peel strength of 0.82 N / in and a phosphorus residue of <5%.

[0113] Comparative Example 3: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0114] Diamine tra-DACH (trans-1,4-diaminocyclohexane) was dissolved in the dehydrating solvent N-methylpyrrolidone and added to a reaction vessel at room temperature. Tetracarboxylic dianhydride CpODA (norbornane-2-spiro-α-cyclopentanone-α′-spiro-2′-norbornane-5,5′,6,6′-tetracarboxylic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of the diamine and tetracarboxylic dianhydride monomers in the reaction solution was 18%. The polyimide precursor contained 70 mol% alicyclic repeating units.

[0115] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of tributyl phosphate to the polyimide precursor is 0.1 mol%, and the molar ratio of 1,2-dimethylimidazole to the polyimide precursor is 0.2 mol%. Tributyl phosphate and 1,2-dimethylimidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution with stirring to obtain the polyimide precursor composition.

[0116] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was 150°C for 25 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was 380°C for 10 minutes to reduce the phase difference and achieve imidization via imidazole.

[0117] Step 4, peel off the film The resulting film peel strength Rth (thickness 10μm) was 980nm; the yellowing index b* was 3.8.

[0118] Comparative Example 4: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0119] Diamine PPD (p-phenylenediamine) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to a reaction vessel. Tetracarboxylic dianhydride CpODA (norbornane-2-spiro-α-cyclopentanone-α′-spiro-2′-norbornane-5,5′,6,6′-tetracarboxylic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of diamine to tetracarboxylic dianhydride monomers in the reaction solution was 22%.

[0120] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of tributyl phosphate to the polyimide precursor is 0.1 mol%, and the molar ratio of 1-methylimidazole to the polyimide precursor is 0.2 mol%. Tributyl phosphate and 1-methylimidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution while stirring. This yields the polyimide precursor composition.

[0121] Step 3, prepare thin film Only one stage of heating treatment is performed, heating at 410℃ for 30 minutes.

[0122] Step 4, peel off the film The resulting film had a peel strength of 0.85 (thickness 8 μm) and a haze of 1.2%.

[0123] Step 5: Device integration and fabrication of an ultrathin transparent substrate Comparative Example 5: Step 1, Synthesis of polyimide precursor The reaction vessel was purged with nitrogen three times to ensure that the oxygen content was less than 50 ppm.

[0124] Diamine ODA (4,4'-diaminodiphenyl ether) was dissolved in the dehydrating solvent N-methylpyrrolidone at room temperature and added to the reaction vessel. Tetracarboxylic dianhydride PMDA (pyromellitic dianhydride) was slowly added under stirring (200 rpm). The molar ratio of diamine to tetracarboxylic dianhydride was 1:1, and the total weight percentage of diamine to tetracarboxylic dianhydride monomers in the reaction solution was 20%.

[0125] Step 2, add additives Based on the molar amount of the polyimide precursor, the molar ratio of methylphosphonic acid to the polyimide precursor is 0.4 mol%, and the molar ratio of 1-methylimidazole to the polyimide precursor is 0.08 mol%. Methylphosphonic acid and 1-methylimidazole can be added to a small amount of solvent first, and then added dropwise to the polyimide precursor solution with stirring to obtain the polyimide precursor composition.

[0126] Step 3, prepare thin film A two-stage heating process was performed. In the first stage, the temperature was increased to 120°C for 30 minutes to form a phosphorus compound enrichment interface. In the second stage, the temperature was increased to 400°C for 15 minutes, thereby reducing the phase difference and achieving imidization through imidazole.

[0127] Step 4, peel off the film The resulting film Rth (thickness 10μm): 780nm; color difference ΔE* is 3.2.

[0128] The above comparison shows that: (a) Alicyclic units >50% will induce crystal orientation, resulting in yellowing and an increase in phase difference Rth.

[0129] (b) Layout of UI elements: TOF-SIMS depth profiles show that, using the two-stage heat treatment of this invention, the phosphorus concentration on the glass side is three times higher than that inside the film. In contrast, with a single-stage heating method, phosphorus compounds are not enriched at the interface. Furthermore, the first-stage heating temperature should not be too high; otherwise, low-boiling-point methylphosphonic acid will decompose, losing its interface modification function.

[0130] (c) Molecular orientation analysis: XRD full width at half maximum (FWHM) shows that the imidazole structure increases the FWHM of the (002) crystal plane diffraction peak by 50%.

[0131] (d) Thermal decomposition behavior: Simultaneous TG-DSC confirmed that compounds such as tributyl phosphate did not exhibit significant weight loss peaks at 350℃.

[0132] (e) An imbalance in the ratio of phosphorus compounds to compounds containing imidazole structures can lead to the failure of phase difference regulation, increasing phase difference Rth and color difference.

[0133] Table 2, Thin Film Properties of Examples 1-5

[0134] Table 3, Thin film properties of Comparative Examples 1-5

[0135] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A polyimide precursor, characterized in that, It has the structure shown in structural formula (I): （I） Wherein, X is a tetravalent organic group, Y is a divalent organic group, R1 and R2 are independently selected from H, alkyl, and alkylsilyl groups, and n is the degree of polymerization.

2. The polyimide precursor according to claim 1, characterized in that, X and Y each contain aliphatic cyclic groups independently; the molar percentage of repeating units of aliphatic cyclic structures is ≤50 mol%.

3. The polyimide precursor according to claim 1, characterized in that, X is selected from C5-C25 groups; Y is selected from C1-C20; R1 and R2 are independently selected from H, C1-C6 alkyl groups, and C3-C6 alkylmethylsilyl groups, respectively.

4. The polyimide precursor according to claim 3, characterized in that, X is selected from , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , One or more combinations of them; Y is selected from -CH2-, -CH2-CH2-, -CH2-CH2-NH-CH2-CH2, -CH2-NH-CH2-CH2-NH-CH2-, -CH2-CH2-NH-CH2-CH2-NH-CH2-, -CH2-C(CH3)2-C(CH3)2-, , , , , , , , , , , , , , , , , , , , , One or more combinations thereof.

5. A polyimide precursor composition, characterized in that, The mixture comprises the polyimide precursor of claim 1, a phosphorus compound, an imidazole-containing compound, and a solvent; the phosphorus compound has a P(=O)(OR) structure, wherein R is selected from H or alkyl groups; the imidazole-containing compound is a compound containing... Compounds with a specific structure.

6. The polyimide precursor composition according to claim 5, characterized in that, The phosphorus compound may be , , , , , , One or more combinations thereof, wherein R3, R4, and R5 are each independently selected from alkyl groups; the molecular weight of the phosphorus compound is ≤400; and the boiling point is ≥250℃.

7. The polyimide precursor composition according to claim 5, characterized in that, The phosphorus compound is selected from: , , , , , , , , , , , , , , , , , One or more combinations of them; The compounds containing the imidazole structure are selected from: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , One or more combinations thereof.

8. The polyimide precursor composition according to claim 5, characterized in that, On a molar basis, the compound containing the imidazole structure is 0.05-1% of the polyimide precursor, and the phosphorus compound is 0.001-5% of the polyimide precursor; or The molar ratio of the phosphorus compound to the compound containing the imidazole structure is 1:(0.1-10).

9. A method for fabricating a flexible electronic device, characterized in that, include: The polyimide precursor composition of claim 5 is coated onto a substrate; Heating at least partially or completely of the polyimide precursor composition to amidate it, forming a polyimide film, thereby forming a laminate on the substrate with the polyimide film deposited thereon; A conductive layer or a semiconductor layer is formed on the polyimide film; The substrate and polyimide film are separated by mechanical force.

10. The method for fabricating the flexible electronic device according to claim 9, characterized in that, The heating process is divided into two stages: First stage: Heat at 80-200℃ for 10-30 minutes; Second stage: Heat at 300-500℃ for 5~20 minutes.

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