A photosensitive ink for 3D printing, a preparation method thereof and a cured material prepared therefrom

Abstract

The present application relates to the technical field of 3D printing. Specifically, the present application provides a photosensitive ink for 3D printing and a preparation method thereof, and also relates to a cured material prepared from the photosensitive ink for 3D printing and the use thereof. The present application uses a photosensitive polyimide (PSPI) containing a diphenyl fluorene group, an asymmetric diphenyl ether group and a photocuring group as a prepolymer, and is compounded with a photoinitiator, an active dilution monomer and the like to obtain the photosensitive ink for 3D printing. The photosensitive ink is subjected to photocuring forming after 3D printing to obtain a cured material with a required shape structure, which has excellent mechanical properties, good thermal stability and heat resistance, and also has a low dielectric constant and dielectric loss, and can be applied to the high-tech fields of microelectronics, communication and the like.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology. Specifically, this invention relates to a photosensitive ink for 3D printing and its preparation method. This invention also relates to a cured material prepared from the photosensitive ink for 3D printing and its uses. Background Technology

[0002] As electronic warfare and information warfare capabilities become crucial components of modern defense, unmanned aerial vehicle (UAV) systems are playing an increasingly prominent role in intelligence, surveillance, reconnaissance, and collaborative operations. However, to effectively integrate into future joint operations systems and meet evolving battlefield demands, the radio frequency (RF) antenna systems carried by UAVs must evolve towards conformal, high-frequency, and lightweight designs. However, the planar stacking technology of printed circuit boards (PCBs) is limited by its molding process, making it difficult to meet the requirements of conformal RF front-ends in the fabrication of complex curved 3D circuits. Additive manufacturing, particularly 3D printing, offers a promising approach to addressing these challenges due to its layered and material-efficient nature.

[0003] Polyimide (PI) is widely used in chemical, aerospace, and biomedical fields due to its excellent mechanical strength, heat resistance, dielectric properties, low water absorption, and chemical stability. The alternating aromatic and heterocyclic structures in the polyimide backbone contribute to improved thermal stability and mechanical properties, while its molecular design flexibility allows for performance tailored to different applications. Building on these advantages, photosensitive polyimide (PSPI) possesses photosensitive groups, enabling it to be photocured while avoiding the processing challenges associated with high melting points.

[0004] Therefore, by designing the structure and optimizing the formula, a photosensitive polyimide ink with good thermal stability, mechanical properties, and dielectric properties, and which can also be photocured, has great application potential. Summary of the Invention

[0005] Purpose of the invention In view of the problems existing in the prior art described in the background section above, the object of the present invention is to provide a photosensitive ink for 3D printing and a method for preparing the same. The object of the present invention is also to provide a curing material prepared from the photosensitive ink for 3D printing and its uses.

[0006] Technical solution To achieve the above objectives, the present invention adopts the following technical solution: Option 1: A photosensitive ink for 3D printing, wherein the photosensitive ink for 3D printing comprises, based on the total mass of the photosensitive ink for 3D printing, About 15 to about 30% by weight, preferably about 20 to about 30% by weight, more preferably about 25% by weight of photosensitive polyimide prepolymer. Approximately 30% to approximately 45% by weight of reactive solvents, Approximately 10 to approximately 20% by weight of the active diluted monomer, About 10 to about 15% by weight of crosslinking agent, and Approximately 2 to 5% by weight of photoinitiator, The photosensitive polyimide prepolymer comprises repeating structural units having the following formulas (1) and (2): -(MG) a -(1) -(ME) b -(2) in a is the number of moles of the repeating structural unit (1). b is the number of moles of the repeating structural unit (2), and The number of moles a of the repeating structural unit (1) accounts for approximately 10 to approximately 30 mol% of the total number of moles (a+b) of the repeating structural units (1) and (2), for example, approximately 15 mol%, approximately 20 mol%, or approximately 25 mol%. The number of moles b of the repeating structural unit (2) accounts for approximately 70 to 90 mol% of the total number of moles (a+b) of the repeating structural units (1) and (2), for example, approximately 75 mol%, approximately 80 mol%, or approximately 85 mol%. M represents: , In the above structural formula representing M, the symbol Each occurrence independently represents any of the following structures: , , , , , , and ; In the above-mentioned representative symbols In each structural formula, the pair of single bonds on the left side, indicated by an asterisk "*", represent: In the structural formula representing M, in the symbol... The two single bonds on the left side of M represent the imide group; and the pair of single bonds on the right side, indicated by the asterisk "*", represent the two single bonds on the left side of M. The right side is connected to two single bonds of an imide group; G means: ;and E represents: or ; In the above structural formulas representing M, G and E, the single bonds indicated by the asterisk "*" on the left and right sides respectively represent: single bonds connected to the groups on the left and right sides of the structural formula in formula (1); Furthermore, the photosensitive polyimide prepolymer also has end groups containing double bonds, which are selected from: A- or AE-, Where A represents an amide group containing a double bond, preferably CH2=C(CH3)-CONH- or CH2=CH-CONH-. An additional condition is that, in the molecular structure of the photosensitive polyimide prepolymer, the repeating structural units of formulas (1) and (2) and the connection between the end groups are such that two N atoms are not directly connected to each other.

[0007] Option 2: The photosensitive ink for 3D printing according to Option 1 above, wherein the number-average molecular weight of the photosensitive polyimide prepolymer is in the range of about 9,000 to about 11,000 g / mol.

[0008] Option 3: The photosensitive ink for 3D printing according to Option 1 or 2 above, wherein the photosensitive polyimide prepolymer is prepared by the following preparation method, which includes the following steps: Step 1: The dianhydride monomer and diamine monomer are added to the polymerization solvent and reacted under a protective atmosphere, wherein... The dianhydride monomers include one or more of the following: pyromellitic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, hexafluorodianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, and bisphenol A type dianhydride; The diamine monomer comprises 3,4'-diaminodiphenyl ether and 9,9-bis(4-aminophenyl)fluorene, wherein the molar amount of 3,4'-diaminodiphenyl ether is about 10 to about 30 mol% of the total molar amount of the diamine monomer, and the molar amount of 9,9-bis(4-aminophenyl)fluorene is about 70 to about 90 mol% of the total molar amount of the diamine monomer. Step 2: Add an alkaline catalyst to the reaction system obtained from Step 1 and heat to carry out the reaction. After the reaction is complete, cool. Step 3: Add an acyl chloride containing a double bond to the reaction system obtained from Step 2 to obtain the photosensitive polyimide prepolymer.

[0009] Option 4: The photosensitive ink for 3D printing according to Option 3 above, wherein in step 1, the polymerization solvent includes one or more of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone and sulfolane.

[0010] Option 5: The photosensitive ink for 3D printing according to Option 3 or 4 above, wherein in step 1, the molar ratio between the total molar amount of the dianhydride monomer and the total molar amount of the diamine monomer is in the range of approximately (0.90-1.00):1.00.

[0011] Option 6: A photosensitive ink for 3D printing according to any one of Options 3 to 5 above, wherein in step 1, the total mass of the dianhydride monomer and the diamine monomer accounts for about 10 to about 30% of the total mass of the mixed solution containing the dianhydride monomer, the diamine monomer and the polymerization solvent.

[0012] Option 7: Photosensitive ink for 3D printing according to any one of Options 3 to 6 above, wherein in step 1, the protective atmosphere includes one or more of nitrogen, argon or helium.

[0013] Option 8: A photosensitive ink for 3D printing according to any one of Options 3 to 7 above, wherein in step 2, the alkaline catalyst includes one or more of piperidine, pyridine, diethylamine and triethylamine.

[0014] Option 9: A photosensitive ink for 3D printing according to any one of Options 3 to 8 above, wherein in step 2, the mass fraction ratio of the alkaline catalyst to the polymerization solvent is in the range of about 1:(2-10).

[0015] Option 10: A photosensitive ink for 3D printing according to any one of Options 3 to 9 above, wherein in step 3, the acyl chloride containing double bonds includes acryloyl chloride and / or methacryloyl chloride.

[0016] Option 11: A photosensitive ink for 3D printing according to any one of Options 3 to 10 above, wherein in step 3, the mass ratio of the acyl chloride containing double bonds to the polymerization solvent is in the range of about 1:(2-10).

[0017] Option 12: Photosensitive ink for 3D printing according to any one of Options 3 to 11 above, wherein the reaction temperature in step 1 is in the range of about 20 to about 30°C and the reaction time is in the range of about 10 to about 12 hours.

[0018] Option 13: Photosensitive ink for 3D printing according to any one of Options 3 to 12 above, wherein the reaction temperature in step 2 is in the range of about 150 to about 200°C, and the reaction time is in the range of about 5 to about 12 hours.

[0019] Option 14: Photosensitive ink for 3D printing according to any one of Options 3 to 13 above, wherein the reaction temperature of step 3 is in the range of about 0 to about 10°C and the reaction time is in the range of about 10 to about 20 hours.

[0020] Scheme 15: The photosensitive ink for 3D printing according to any one of Schemes 3 to 14 above, wherein after the reaction in step 3 is completed, the obtained reaction product is precipitated in ethanol, and then the precipitated solid is crushed, washed and dried to obtain the photosensitive polyimide prepolymer.

[0021] Option 16: A photosensitive ink for 3D printing according to any one of Options 1 to 15 above, wherein the reactive solvent comprises 4-acryloylmorpholine and / or N-vinylpyrrolidone; and / or Option 17: A photosensitive ink for 3D printing according to any one of Options 1 to 16 above, wherein the reactive diluent monomer comprises 1,10-bis(acryloyloxy)decane and / or polyethylene glycol diacrylate.

[0022] Option 18: A photosensitive ink for 3D printing according to any one of Options 1 to 17 above, wherein the crosslinking agent comprises tris(2-acryloyloxyethyl) isocyanurate.

[0023] Option 19: A photosensitive ink for 3D printing according to any one of Options 1 to 18 above, wherein the photoinitiator includes one or more of 1-hydroxycyclohexylphenyl ketone, ethyl 4-dimethylaminobenzoate and 2-isopropylthioxanthrone.

[0024] Scheme 20: A method for preparing photosensitive ink for 3D printing according to any one of claims 1 to 19, wherein the preparation method comprises the following steps: stirring and mixing the photosensitive polyimide prepolymer, the reactive solvent, the reactive diluent monomer, the crosslinking agent and the photoinitiator under light-protected conditions, and obtaining the photosensitive ink for 3D printing after degassing treatment.

[0025] Scheme 21: According to the preparation method described in Scheme 20 above, the bubble extraction process includes ultrasonic treatment and / or vacuum treatment.

[0026] Option 22: A curing material prepared from a photosensitive ink for 3D printing according to any one of claims 1 to 19 or a photosensitive ink for 3D printing prepared by the preparation method according to claim 20 or 21.

[0027] Option 23: The curing material according to Option 22 above, wherein the curing material has one or more of the following properties: The glass transition temperature of the cured material T g Within the range of approximately 160 to approximately 180°C; The tensile strength of the cured material is in the range of about 58 to about 80 MPa. The elongation at break of the cured material is in the range of about 6% to about 15%. The dielectric constant of the cured material at 20 GHz is in the range of about 2.3 to about 2.8; and The dielectric loss tangent of the cured material at 20 GHz is in the range of about 0.005 to about 0.009.

[0028] Option 24: The use of the curing material according to Option 23 above in the field of microelectronics or communications.

[0029] Technical effect This invention uses a photosensitive polyimide containing diphenylfluorene groups, asymmetric diphenyl ether groups, and photocurable groups as a prepolymer, and combines it with a photoinitiator, reactive diluent monomers, etc. to obtain a photosensitive ink for 3D printing. After 3D printing, the ink is photocured to obtain a cured material with the desired shape and structure. This cured material not only has excellent mechanical properties, good thermal stability and heat resistance, but also has a low dielectric constant and dielectric loss, and can be applied to high-tech fields such as microelectronics and communications.

[0030] Specifically, compared with the prior art, the technical solution of the present invention has at least the following technical effects: (1) The photosensitive ink for 3D printing of the present invention contains a photosensitive polyimide prepolymer. Specific ether bonds and a rigid, large-volume structure are introduced into the structure of this photosensitive polyimide prepolymer, further improving its solubility, thermal stability, and mechanical properties. Simultaneously, the unsaturated double bonds of the photosensitive polyimide prepolymer endow it with photocurability, enabling it to be used as a prepolymer in photosensitive ink systems. Given the aforementioned specific structure of the photosensitive polyimide prepolymer, it possesses excellent photosensitivity, thermal stability, mechanical properties, and dielectric properties, providing a foundation for its subsequent applications.

[0031] (2) The preparation method of the photosensitive polyimide prepolymer contained in the 3D printing photosensitive ink of the present invention is simple. The preparation method includes synthesizing the polyimide prepolymer in two steps to make it have good solubility, and then incorporating photosensitive groups by chemical grafting to obtain photocurable photosensitive polyimide prepolymer.

[0032] (3) The photosensitive ink for 3D printing provided by the present invention uses photocurable photosensitive polyimide as a prepolymer, which is compounded with reactive solvents, reactive diluent monomers, crosslinking agents, initiators, etc. In view of the characteristics of the photosensitive ink, it can be applied to the field of 3D printing.

[0033] (4) The curing material provided by the present invention is formed by the photosensitive ink for 3D printing. In view of the advantages of the photosensitive ink for 3D printing, the curing material has high mechanical properties, high thermal stability, low dielectric constant and low loss tangent, and can be applied to high-tech fields such as microelectronics and communications. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the specific embodiments of the present invention, the accompanying drawings involved in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 The hydrogen NMR spectra of prepolymer BAFL-PSPI-1585 obtained in Example 1 of the present invention, and prepolymers DAF-PSPI-1585, SA-1-PSPI-1585 and ODA-PSPI-1585 obtained from Comparative Examples 1 to 3 of the present invention. Figure 2 The infrared spectra of prepolymer BAFL-PSPI-1585 obtained in Example 1 of the present invention, and prepolymers DAF-PSPI-1585, SA-1-PSPI-1585 and ODA-PSPI-1585 obtained in Comparative Examples 1 to 3 of the present invention. Figure 3 Infrared spectra of the cured materials (films) obtained after curing the photosensitive inks for 3D printing prepared in ink examples E1-1 (using prepolymer BAFL-PSPI-1585) and ink comparative examples CE1 to CE3 (using prepolymers DAF-PSPI-1585, SA-1-PSPI-1585 and ODA-PSPI-1585, respectively). Figure 4To illustrate the comparison of dielectric constant (represented by solid columns) and dielectric loss (represented by hollow columns, which is expressed as the loss tangent) of the cured materials (films) obtained after curing the photosensitive inks for 3D printing prepared using the ink examples E1-1 to E1-4 of the present invention (all using prepolymer BAFL-PSPI-1585), the horizontal axis represents the mass fraction of the prepolymer (bisphenylfluorene-type photosensitive polyimide (BAFL-PSPI-1585)) in the photosensitive ink for 3D printing, which are 15% by weight, 20% by weight, 25% by weight, and 30% by weight, respectively. Figure 5 To illustrate the comparison of tensile strength (represented by solid columns) and breaking elongation (represented by hollow columns) of the cured materials (films) prepared from the photosensitive inks for 3D printing prepared by the ink examples E1-1 to E1-4 of the present invention (all using prepolymer BAFL-PSPI-1585), the horizontal axis represents the mass fraction of prepolymer (bisphenylfluorene-type photosensitive polyimide (BAFL-PSPI-1585)) in the photosensitive ink for 3D printing as 15 wt% (Sample 1), 20 wt% (Sample 2), 25 wt% (Sample 3), and 30 wt% (Sample 4), respectively. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely for the purpose of aiding understanding of this invention and should not be considered as specific limitations on this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Process parameters in the following embodiments that are not specifically specified are generally performed under conventional conditions.

[0037] In the description of this invention, the terms "left" and "right," etc., indicate orientations or positional relationships based on the structural formulas or drawings, and are used only for the convenience of describing the invention and not to require the invention to be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0038] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. The term "about" as used in this invention means that the number it modifies may fluctuate within ±20%, ±15%, ±10%, ±5%, or ±2% of that number. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and the individual point values ​​contained within them, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0039] According to a first aspect of the present invention, the present invention provides a photosensitive ink for 3D printing.

[0040] According to the first aspect of the present invention, the photosensitive ink for 3D printing comprises, based on the total mass of the photosensitive ink for 3D printing, Approximately 15% to approximately 30% by weight of photosensitive polyimide prepolymer, Approximately 30% to approximately 45% by weight of reactive solvents, Approximately 10 to approximately 20% by weight of the active diluted monomer, About 10 to about 15% by weight of crosslinking agent, and Approximately 2 to 5% by weight of photoinitiator.

[0041] The following describes in detail the various components of the photosensitive ink for 3D printing according to the first aspect of the present invention.

[0042] Photosensitive polyimide prepolymer The photosensitive polyimide prepolymer comprises repeating structural units having the following formulas (1) and (2): -(MG) a -(1) -(ME) b -(2) in a is the number of moles of the repeating structural unit (1). b is the number of moles of the repeating structural unit (2), and The number of moles a of the repeating structural unit (1) accounts for approximately 10 to approximately 30 mol% of the total number of moles (a+b) of the repeating structural units (1) and (2), for example, approximately 15 mol%, approximately 20 mol%, or approximately 25 mol%. The number of moles b of the repeating structural unit (2) accounts for approximately 70 to 90 mol% of the total number of moles (a+b) of the repeating structural units (1) and (2), for example, approximately 75 mol%, approximately 80 mol%, or approximately 85 mol%. M represents: , In the above structural formula representing M, the symbol Each occurrence independently represents any of the following structures: , , , , , , and ; In the above-mentioned representative symbols In each structural formula, the pair of single bonds on the left side, indicated by an asterisk "*", represent: In the structural formula representing M, in the symbol... The two single bonds on the left side of M represent the imide group; and the pair of single bonds on the right side, indicated by the asterisk "*", represent the two single bonds on the left side of M. The right side is connected to two single bonds of an imide group; G indicates ;and E represents: or ; In the above structural formulas representing M, G and E, the single bonds indicated by the asterisk "*" on the left and right sides respectively represent: single bonds connected to the groups on the left and right sides of the structural formula in formula (1); Furthermore, the photosensitive polyimide prepolymer also has end groups containing double bonds, which are selected from: A- or AE-, Wherein A represents an amide group containing a double bond, preferably selected from CH2=C(CH3)-CONH- or CH2=CH-CONH-. An additional condition is that, in the molecular structure of the photosensitive polyimide prepolymer, the repeating structural units of formulas (1) and (2) and the connection between the end groups are such that two N atoms are not directly connected to each other.

[0043] In the aforementioned photosensitive polyimide prepolymer, the inventors of this invention achieved control over the solubility, thermal properties, mechanical properties, and dielectric properties of the photosensitive polyimide prepolymer by controlling the values ​​of a and b. Specifically, by controlling the values ​​of a and b, the molecular weight of the photosensitive polyimide prepolymer is preferably in the range of about 9000 to about 11000 g / mol, for example, about 10000 g / mol, thereby avoiding any impact on its subsequent solubility in inks.

[0044] Furthermore, in the photosensitive polyimide prepolymer, the molar percentage value "a / (a+b)" of the number of moles of repeating structural unit (1) relative to the total number of moles (a+b) of repeating structural units (1) and (2) may affect the thermal, mechanical, and dielectric properties of the photosensitive polyimide prepolymer. Here, the value of a / (a+b) should be in the range of about 10 to about 30 mol%, for example, about 15 mol%, about 20 mol%, or about 25 mol%. The value of a / (a+b) should not be too high, for example, not exceeding about 30 mol%, otherwise it may lead to poor solubility of the photosensitive polyimide prepolymer, and poor solubility will affect the formulation of subsequent ink systems; the value of a / (a+b) should also not be too low, for example, not lower than about 10 mol%, otherwise it may be detrimental to the overall performance of the prepolymer, such as thermal, mechanical, and dielectric properties. In this invention, the molar percentage value "a / (a+b)" is particularly preferably in the range of about 15 to about 25 mol%, and the cured material formed from the prepolymer having a ratio within this range has better dielectric constant and dielectric loss, as well as better tensile strength and elongation at break. The molar percentage value "a / (a+b)" is especially preferably about 15 mol%, and the cured material formed from the prepolymer at this ratio has the best dielectric constant and dielectric loss, as well as the best tensile strength and elongation at break.

[0045] Furthermore, in the photosensitive polyimide prepolymer, the molar percentage value of "b / (a+b)" representing the number of moles of repeating structural unit (2) to the total number of moles of repeating structural units (1) and (2) (a+b) may affect the solubility of the photosensitive polyimide prepolymer. Here, the value of b / (a+b) should be in the range of 70 to 90 mol%, for example, about 75 mol%, about 80 mol%, or about 85 mol%. The value of b / (a+b) should not be too high, for example, not exceeding about 90 mol%, otherwise it may lead to a deterioration in the thermal, mechanical, and dielectric properties of the photosensitive polyimide prepolymer; the value of b / (a+b) should also not be too low, for example, not lower than about 70 mol%, otherwise it may affect the solubility of the prepolymer, which is detrimental to the formulation of the photosensitive ink of the present invention. The photosensitive ink of the present invention is a solvent-free photosensitive ink, which does not require the addition of additional solvents for formulation. The selected reactive solvent can also participate in the reaction during the subsequent curing process, eliminating the need for solvent removal and possessing better production and application potential.

[0046] As a particularly preferred embodiment of the first aspect of the present invention, the value of a / (a+b) is set to about 15 mol%, and the value of b / (a+b) is set to about 85 mol%, thereby optimizing the thermal, mechanical and dielectric properties of the prepared photosensitive ink by further limiting a and b.

[0047] A specific ratio of asymmetric diphenyl ether bonds and a rigid, bulky structure (diphenylfluorene structure) are introduced into the molecular structure of the photosensitive polyimide prepolymer, further improving its solubility, thermal stability, mechanical properties, and dielectric properties. Simultaneously, the unsaturated double bonds in the polyimide prepolymer endow it with photocurability, allowing it to be used as a prepolymer in ink systems. Given the aforementioned specific structure of the photosensitive polyimide prepolymer, it possesses excellent photosensitivity, thermal stability, mechanical properties, and dielectric properties, providing a foundation for its subsequent applications.

[0048] In addition, in the photosensitive polyimide prepolymer, the structural units of formulas (1) and (2) can exist in the main chain of the prepolymer in any distribution form, such as random, block and alternating.

[0049] Furthermore, the photosensitive polyimide prepolymer described above can be prepared by the following preparation method, which includes steps 1 to 3: Step 1: Step 1 involves adding dianhydride monomers and diamine monomers to a polymerization solvent and reacting them under a protective atmosphere. Specifically, in step 1, the dianhydride monomers and diamine monomers are subjected to low-temperature polycondensation to obtain a polyamic acid solution.

[0050] In step 1, the polymerization solvent is not particularly limited, as long as it can ensure that the dianhydride monomer and the diamine monomer can react smoothly therein. For example, in some exemplary embodiments, the polymerization solvent may include one or more of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and sulfolane.

[0051] In step 1, the protective atmosphere is not particularly limited, as long as it can protect the reaction system from interference from external air or other substances. For example, in some exemplary embodiments, the protective atmosphere may include one or more of nitrogen, argon, or helium.

[0052] In step 1, the dianhydride monomer refers to a molecule containing two carboxylic anhydride groups in one molecule. For example, in some exemplary embodiments of the present invention, the dianhydride monomer may include aromatic dianhydrides and / or cycloalkane dianhydrides, such as one or more of pyromellitic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bisphenol A dianhydride, hexafluorodianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

[0053] In step 1, the diamine monomer refers to a molecule containing two amino groups in one molecule. In this invention, a specific type of diamine monomer is used, including 3,4'-diaminodiphenyl ether and 9,9-bis(4-aminophenyl)fluorene. 3,4'-diaminodiphenyl ether, due to its asymmetric structure, can improve solubility, and the presence of ether bonds can enhance toughness; while 9,9'-bis(4-aminophenyl)fluorene, due to its rigid, bulky structure, can improve the solubility of photosensitive polyimide while simultaneously improving its thermal, mechanical, and dielectric properties.

[0054] In some further preferred embodiments, the molar amount of 3,4'-diaminodiphenyl ether in the diamine monomer can be about 10 to about 30 mol% of the total molar amount of the diamine monomer, for example, 15 mol%, about 20 mol%, or about 25 mol%, that is, the molar amount of 9,9-bis(4-aminophenyl)fluorene can correspondingly be about 70 to about 90 mol% of the total molar amount of the diamine monomer, for example, 75 mol%, about 80 mol%, or about 85 mol%. Here, the respective molar amounts of 3,4'-diaminodiphenyl ether and 9,9-bis(4-aminophenyl)fluorene should not be too high or too low. The present invention achieves the purpose of strictly controlling the solubility, thermal properties, mechanical properties, and dielectric properties of the prepolymer photosensitive polyimide by limiting the molar ratio between 3,4'-diaminodiphenyl ether and 9,9'-bis(4-aminophenyl)fluorene in the raw materials for synthesizing the prepolymer photosensitive polyimide.

[0055] In step 1, the total molar amount of the dianhydride monomer can be approximately the same as the total molar amount of the diamine monomer. However, to ensure that the polyamic acid generated in step 1 has amino groups (rather than anhydride groups) at both ends, the molar amount of the diamine monomer should slightly exceed the molar amount of the dianhydride monomer. For example, in some exemplary embodiments of the invention, the molar ratio between the total molar amount of the dianhydride monomer and the total molar amount of the diamine monomer can be in the range of about 0.90 to about 1.00, for example, about 0.93, about 0.95, or about 0.97. A molar ratio of dianhydride monomer to diamine monomer exceeding this range may result in the prepolymer being unable to achieve the designed molecular weight.

[0056] Furthermore, in step 1, the concentrations of the dianhydride monomer and the diamine monomer in the reaction system containing them are not particularly limited, as long as they can react to form the prepolymer. However, in some preferred embodiments of the present invention, the total mass of the dianhydride monomer and the diamine monomer accounts for about 10 to about 30% by mass of the total mass of the mixed solution containing the dianhydride monomer, the diamine monomer, and the polymerization solvent, for example, about 12% by mass, about 14% by mass, about 15% by mass, about 16% by mass, about 18% by mass, about 20% by mass, about 22% by mass, about 24% by mass, about 25% by mass, about 26% by mass, or about 28% by mass. Here, the total concentration of the dianhydride monomer and the diamine monomer should not be too high, for example, it should not exceed about 30% by mass, otherwise the monomer reactants may undergo explosive polymerization, resulting in a prepolymer with a molecular weight higher than the designed molecular weight; the total concentration of the dianhydride monomer and the diamine monomer should also not be too low, for example, it should not be lower than about 10% by mass, otherwise the probability of collision of the monomer reactants may be reduced, resulting in a prepolymer with a molecular weight lower than the designed molecular weight.

[0057] In step 1, the temperature and time for the reaction between the dianhydride monomer and the diamine monomer are not particularly limited. The reaction stage can be determined by sampling and viscosity testing. The reaction is considered complete and stopped when the viscosity no longer increases. For example, in some exemplary embodiments of the present invention, the reaction temperature in step 1 can be in the range of about 20 to about 30°C, such as about 22°C, about 24°C, about 25°C, or about 28°C, and the reaction time is in the range of about 10 to about 12 hours, such as about 11 hours.

[0058] Step 2: Step 2 involves adding an alkaline catalyst to the reaction system obtained from step 1 and heating it to carry out the reaction. Specifically, in step 2, polyimide is obtained by ring-closing and dehydration of the polyamic acid from step 1 through high temperature.

[0059] In step 2, the alkaline catalyst is preferably an organic weak base catalyst. The purpose of adding the alkaline catalyst is to enable the polyamic acid from step 1 to undergo dehydration and ring closure at an appropriate temperature to form polyimide, avoiding high-temperature depolymerization or side reactions that could lead to the formation of polyisoimide. In some preferred embodiments, the alkaline catalyst may include, for example, one or more of piperidine, pyridine, diethylamine, and triethylamine.

[0060] In step 2, the amount of alkaline catalyst added is not particularly limited, as long as it can achieve the catalytic effect. For example, in some exemplary embodiments, the mass ratio of the added alkaline catalyst to the polymerization solvent can be controlled in the range of about 1:(2-10), such as about 1:3, about 1:4, about 1:5, about 1:6, about 1:7, about 1:8, or about 1:9. Here, the amount of alkaline catalyst added should not be too high, for example, it should not exceed about 1 / 2 of the mass of the polymerization solvent, otherwise the system will be too alkaline, which may lead to depolymerization or side reactions; in addition, the amount of alkaline catalyst added should not be too low, for example, it should not be less than about 1 / 10 of the mass of the polymerization solvent, otherwise the catalytic activity may be insufficient and the polyimide ring closure may be incomplete.

[0061] In step 2, the temperature and time of the alkaline catalytic reaction are not particularly limited. The completion of the reaction can be determined by sampling and performing NMR spectroscopy. The reaction can be stopped when the proton peak of the amide bond disappears in the NMR spectrum. For example, in some exemplary embodiments of the present invention, the reaction temperature in step 2 can be in the range of about 150 to about 200°C, such as about 155°C, about 160°C, about 165°C, about 170°C, about 175°C, about 180°C, about 185°C, about 190°C, or about 195°C, and the reaction time is in the range of about 5 to about 12 hours, such as about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, or about 11 hours.

[0062] After the reaction in step 2 is completed, the reaction system is cooled.

[0063] Step 3 Step 3 involves adding an acyl chloride containing a double bond to the reaction system obtained from step 2. Specifically, step 3 involves obtaining the photosensitive polyimide prepolymer by performing a chemical grafting reaction on the polyimide molecules obtained from step 2.

[0064] In step 3, the purpose of adding the acyl chloride containing double bonds is to graft photosensitive groups onto the polyimide obtained from step 2, thereby enabling it to be photocurable. In some preferred embodiments, the acyl chloride containing double bonds may include, for example, one or more of acryloyl chloride and methacryloyl chloride.

[0065] In step 3, the amount of double-bonded acyl chloride added is not particularly limited, as long as it can completely react with the terminal amino groups contained in the prepolymer obtained from step 2. However, in some exemplary embodiments, the amount of double-bonded acyl chloride added can be controlled in the range of about 10 to about 50% by weight of the polymerization solvent, for example, about 20% by weight, about 30% by weight, or about 40% by weight. Here, the amount of double-bonded acyl chloride added should not be too high, for example, it should not exceed about 50% by weight of the polymerization solvent, otherwise excessive double-bonded acyl chloride may react with the water generated during the reaction to hydrolyze and generate hydrochloric acid. The hydrochloric acid reacts with the amino groups, causing the grafting of the photosensitive group to fail. In addition, the amount of alkaline catalyst added should not be too low, for example, it should not be less than about 10% by weight of the polymerization solvent, otherwise the hydrochloric acid generated in the reaction may react with the amino groups that have not formed amides, leading to grafting failure.

[0066] In step 3, the temperature and time of the grafting reaction are not particularly limited and can be checked by NMR spectroscopy to determine whether the reaction has ended. Specifically, the reaction is stopped when the proton peak of the amino group disappears and the proton peak of the acrylamide double bond appears, and the result is integrated. For example, in some exemplary embodiments of the invention, the reaction temperature in step 3 can be in the range of about 0 to about 10°C, for example, about 5°C, and the reaction time can be in the range of about 10 to about 20 hours, for example, about 11 hours, about 12 hours, about 13 hours, about 14 hours, about 15 hours, about 16 hours, about 17 hours, about 18 hours, or about 19 hours.

[0067] In addition, the preparation method preferably includes, after the reaction in step 3 is completed, precipitating the obtained reaction product in a sufficient amount of ethanol, and then crushing, washing and drying the precipitated solid to obtain the photosensitive polyimide prepolymer solid.

[0068] In summary, by further limiting the types and amounts of raw materials used in the preparation method of the polyimide prepolymer, the obtained photosensitive polyimide prepolymer exhibits good solubility. For example, the prepolymer obtained by this invention can be dissolved in commonly used organic solvents at room temperature, such as N-methylpyrrolidone, N,N'-dimethylformamide, N,N'-dimethylacetamide, tetrahydrofuran, 4-acryloylmorpholine, and N-vinylpyrrolidone.

[0069] The photosensitive ink for 3D printing according to the first aspect of the present invention, by including the photosensitive polyimide prepolymer, enables the ink to have a certain photocuring capability.

[0070] The photosensitive ink for 3D printing described in the first aspect of the present invention may contain about 15 to about 30% by weight (e.g., about 17% by weight, about 20% by weight, about 23% by weight, about 25% by weight, or about 27% by weight), preferably about 20% by weight, about 30% by weight, and more preferably about 25% by weight of the photosensitive polyimide prepolymer. The cured material obtained at this concentration exhibits optimal dielectric and mechanical properties. Here, the amount of the photosensitive polyimide prepolymer in the photosensitive ink for 3D printing should not be too high, for example, not exceeding about 30% by weight, otherwise the system viscosity may be too high, affecting the reactivity and thus the overall performance of the ink. Nor should it be too low, for example, not less than about 15% by weight, otherwise there will be insufficient curable active crosslinking sites, reducing the reactivity and thus affecting the overall performance of the ink.

[0071] reactive solvents In some further preferred embodiments of the present invention, the reactive solvent is not particularly limited, as long as it can dissolve the prepolymer and other components to participate in the photocuring reaction, and reduce the viscosity of the ink mixture. For example, the reactive solvent may include one or more of 4-acryloylmorpholine and N-vinylpyrrolidone.

[0072] The photosensitive ink for 3D printing according to the first aspect of the present invention may contain about 30 to about 45% by weight (e.g., about 33% by weight, about 35% by weight, about 38% by weight, about 40% by weight, or about 43% by weight) of the reactive solvent. Here, the amount of the reactive solvent in the photosensitive ink for 3D printing should not be too high, for example, not higher than about 45% by weight, otherwise the photoinitiator and prepolymer will not be able to absorb sufficient energy for curing, reducing the curing speed and the final degree of curing; nor should it be too low, for example, not lower than about 30% by weight, otherwise the viscosity may be too high, reducing the reactivity and ultimately affecting the overall performance of the ink.

[0073] Active dilution monomer In some further preferred embodiments of the present invention, the reactive diluent monomer is not particularly limited, as long as it can achieve the following objectives: on the one hand, it can reduce the viscosity of the ink mixture; on the other hand, the carbon-carbon double bonds in the reactive diluent monomer can increase the photocurability of the ink mixture, and during curing, it can drive the prepolymer to cure, forming a dense cross-linked network with each other, and synergistically improving the various properties of the ink material. For example, in some exemplary embodiments, the reactive diluent monomer may include 1,10-bis(acryloyloxy)decane (DTGDA) and polyethylene glycol diacrylate (PEGDA, M n One or more of the following: approximately 400, approximately 1000, or approximately 2000.

[0074] The preferred reactive diluents selected here all contain carbon-carbon double bond structures, which can drive the prepolymer to cure during the curing process and form a dense cross-linked network between them. By selecting one or more such reactive diluents and adding them in different proportions, the viscosity of the ink system, the thermal properties, mechanical properties and dielectric properties of the cured material can be appropriately adjusted.

[0075] The photosensitive ink for 3D printing described in the first aspect of this invention may contain about 10 to about 20% by weight (e.g., about 12% by weight, about 15% by weight, or about 18% by weight) of the active diluent monomer. Here, the amount of the active diluent monomer in the photosensitive ink for 3D printing should not be too high, for example, not exceeding about 20% by weight; otherwise, although it will give the cured material excellent flexibility, it will affect its mechanical strength, thermal properties, and dielectric properties, thus reducing performance. Nor should it be too low, for example, not less than about 10% by weight; otherwise, it may result in insufficient system flexibility, and the obtained cured film will be too hard and brittle, affecting its application.

[0076] Crosslinking agent In some further preferred embodiments of the present invention, the crosslinking agent is not particularly limited, as long as it can increase the crosslinking density of the system, thereby optimizing the thermal, dielectric, and mechanical properties of the system. For example, in some exemplary embodiments of the present invention, the crosslinking agent may include tris(2-acryloyloxyethyl) isocyanurate, the structure of which contains multiple acrylate groups. Selecting it as a crosslinking agent can improve the curing speed and crosslinking density of the ink system and accelerate the reaction process.

[0077] The photosensitive ink for 3D printing described in the first aspect of the present invention may contain about 10 to about 15% by weight (e.g., about 11% by weight, about 12% by weight, about 13% by weight, or about 14% by weight) of the crosslinking agent. Here, the amount of the crosslinking agent in the photosensitive ink for 3D printing should not be too high, for example, not higher than about 15% by weight, otherwise the photocurable active sites may be too dense, hindering deep curing, reducing the reaction rate and the final degree of curing, and thus affecting the overall performance; nor should it be too low, for example, not lower than 10% by weight, otherwise the curing rate and the final degree of curing of the ink may be affected due to too few photocurable active sites, thus affecting the overall performance.

[0078] Photoinitiator In some further preferred embodiments of the invention, the photoinitiator is not particularly limited, as long as it can initiate the curing of the ink system. For example, in some exemplary embodiments, the photoinitiator may include one or more of 1-hydroxycyclohexylphenyl ketone, ethyl 4-dimethylaminobenzoate, and 2-isopropylthioxanthraphenone.

[0079] The photoinitiator in the 3D printing photosensitive ink according to the first aspect of the present invention may contain about 2 to about 5% by weight (e.g., about 3% by weight or about 4% by weight). Here, the amount of the photoinitiator in the 3D printing photosensitive ink should not be too high, for example, not exceeding about 5% by weight; otherwise, excessive free radicals will mutually terminate each other, affecting the curing reaction, affecting deep curing, and may trigger side reactions, affecting the overall performance of the ink; nor should it be too low, for example, not less than 2% by weight; otherwise, insufficient initiation activity may affect the ink curing speed and final curing degree, ultimately affecting the overall performance of the ink.

[0080] In the first aspect of the present invention described above, a photocurable photosensitive polyimide is used as a prepolymer and compounded with a reactive solvent, an active diluent monomer, a crosslinking agent, and an initiator to obtain a photosensitive ink. Due to the properties of the photosensitive ink, it can be applied to the field of 3D printing.

[0081] According to a second aspect of the present invention, the present invention provides a method for preparing photosensitive ink for 3D printing according to the first aspect of the present invention described above.

[0082] The preparation method according to the second aspect of the present invention includes the following steps: stirring and mixing the reactive solvent, the photosensitive polyimide prepolymer, the reactive diluent monomer, the crosslinking agent, and the photoinitiator under light-protected conditions, and obtaining the low dielectric photosensitive ink for 3D printing after degassing treatment.

[0083] In the preparation method described in the second aspect of the present invention, the purpose of the degassing treatment is to eliminate air bubbles generated during the stirring process and avoid defects in the resulting cured material. In some exemplary embodiments of the present invention, the degassing treatment may include ultrasonic treatment and / or vacuum treatment.

[0084] According to a third aspect of the present invention, the present invention provides a curable material prepared using a photosensitive ink for 3D printing according to the first aspect of the present invention or a photosensitive ink for 3D printing prepared according to the preparation method described in the second aspect of the present invention, preferably a curable material obtained by 3D printing.

[0085] The curing material according to the third aspect of the present invention includes, but is not limited to, films, strips, and specimens. The curing material according to the third aspect of the present invention preferably possesses one or more of the following properties: The glass transition temperature of the cured material T g In the range of approximately 160 to approximately 180°C, for example, approximately 165°C, approximately 170°C, or approximately 175°C; The tensile strength of the cured material is in the range of about 58 to about 80 MPa, for example about 60 MPa, about 65 MPa, about 70 MPa, or about 75 MPa. The elongation at break of the cured material is in the range of about 6% to about 15%, for example, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, or about 14%. The dielectric constant of the cured material at about 20 GHz is in the range of about 2.3 to about 2.8, for example, about 2.4, about 2.5, about 2.6 or about 2.7; and The dielectric loss tangent of the cured material at about 20 GHz is in the range of about 0.005 to about 0.009, for example, about 0.006, about 0.0065, about 0.007, about 0.0075, about 0.008 or about 0.0085.

[0086] The cured material described above according to the third aspect of the present invention, used for determining the properties of the cured material, can be prepared by the following method: applying the 3D printing photosensitive ink provided in the first or second aspect of the present invention to a glass plate using a doctor blade, and then placing it in an ultraviolet oven for photocuring reaction to obtain the final cured material.

[0087] As an exemplary embodiment of the present invention, the coating thickness of the scraper can be from about 120 μm to about 200 μm. For example, it can be about 130 μm, about 140 μm, about 150 μm, about 160 μm, about 170 μm, about 180 μm, or about 190 μm.

[0088] According to a fourth aspect of the present invention, the present invention provides the use of the curing material described in the third aspect of the present invention in the fields of microelectronics or communications. In view of the advantages of the aforementioned photosensitive ink for 3D printing, the curing material possesses high mechanical properties, high thermal stability, low dielectric constant, and low loss tangent, and can be applied in high-tech fields such as microelectronics and communications.

[0089] Examples and Comparative Examples The present invention will now be described in further detail with reference to specific embodiments and comparative examples.

[0090] It should be noted that, unless otherwise specified, the test methods disclosed in the following embodiments and comparative examples are conventional methods and can be performed according to the techniques or conditions described in existing technical literature in this field or according to the product instructions. The sources and purities of the chemical raw materials used in the following embodiments are as follows: 9,9'-Bis(4-aminophenyl)fluorene (BAFL): Aladdin, 99%; 2,7-Diaminofluorene (DAF): Aladdin, 99%; 4,4'-Diaminodiphenyl ether (ODA): Aladdin, 99%; 9,9'-Dimethylfluorene-2,7-diamine (SA-1): Aladdin, 99%; 3,4'-Diaminodiphenyl ether (3,4'-ODA): Aladdin, 97%; Bisphenol A dianhydride (BPADA): Aladdin, 98%; Methacrylamide chloride (MC): Aladdin, 95%; 4-Acryloylmorpholine (ACMO): Aladdin, 98%; Tris(2-acryloyloxyethyl) isocyanurate (TAIC): Aladdin, ≥80%; Ethyl 4-dimethylaminobenzoate (EDB): Aladdin, 99%; 2-Isopropylthioxanthraquinone (ITX): Aladdin, 98%; N-Methylpyrrolidone (NMP): Tianjin Institute of Fine Chemicals, analytical grade; Triethylamine (TEA); Tianjin Institute of Fine Chemicals, analytical grade; Pyridine (Py): Tianjin Institute of Fine Chemicals, analytical grade; 1,10-Bis(acryloyloxy)decane (DTGDA): Shandong Keyuan Biochemical Co., Ltd., 90%.

[0091] All other chemical substances not explicitly stated are commercially available analytical grade chemicals.

[0092] Prepolymer Examples 1 to 5: Preparation of Prepolymers In a 100 mL three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, the amounts of diamine (9,9'-bis(4-aminophenyl)fluorene (BAFL) and 3,4'-diaminodiphenyl ether (3,4'-ODA)) and polymerization solvent (approximately 30 mL of N-methylpyrrolidone (NMP)) shown in Table 1 were added. After purging with nitrogen (N2), the mixture was stirred at room temperature until completely dissolved. Then, the amounts of dianhydride (bisphenol A dianhydride (BPADA)) shown in Table 1 were added. The mixture was stirred at room temperature (approximately 25°C) for approximately 10 hours to carry out the first step reaction to obtain polyamic acid. Then, an alkaline catalyst (approximately 5 mL of triethylamine and approximately 5 mL of pyridine) was added to the obtained reaction system. The temperature was raised to approximately 180°C and reacted for approximately 10 hours to carry out the second step reaction to obtain polyimide. The mixture was then cooled to room temperature, and a certain amount of acyl chloride containing double bonds (approximately 5 mL of triethylamine and approximately 5 mL of pyridine) was added under ice bath conditions (approximately 0°C). The reaction was carried out for approximately 12 hours with methacryloyl chloride (mL) for the third step. The resulting polymer product was then precipitated in sufficient ethanol, pulverized, washed, and dried to obtain the photosensitive polyimide prepolymers BAFL-PSPI-1585, BAFL-PSPI-1090, BAFL-PSPI-2080, BAFL-PSPI-2575, and BAFL-PSPI-3070 of Examples 1 to 5. The yields were calculated by weighing (the yields of Examples 1 to 5 were all approximately 87%). The number-average molecular weights of the photosensitive polyimide prepolymers obtained in Examples 1 to 5 were determined using gel permeation chromatography (GPC), a method commonly used in the art (shown in Table 1).

[0093] Comparative Examples 1 to 3 of Prepolymers: Preparation of Prepolymers Prepolymers of Comparative Examples 1 to 3 were prepared using a process similar to that of Examples 1 to 5, except that the diamine monomer BAFL used in Examples 1 to 5 was replaced with 2,7-diaminofluorene (DAF), 9,9'-dimethylfluorene-2,7-diamine (SA-1), and 4,4'-diaminodiphenyl ether (ODA) in Comparative Examples 1 to 3, respectively. This yielded photosensitive polyimide prepolymers DAF-PSPI-1585, SA-1-PSPI-1585, and ODA-PSPI-1585 of Comparative Examples 1 to 3. Yields were calculated by weighing (the yield of Comparative Example 1 was approximately 84%, and the yields of Comparative Examples 2 and 3 were approximately 85%). The number-average molecular weight of the prepolymers obtained in each comparative example was determined by GPC (shown in Table 1).

[0094] Comparative Examples 4 to 5: Preparation of Prepolymers Prepolymers for prepolymer comparative examples 4 and 5 were prepared using a similar process to that used in prepolymer Examples 1 to 5, except that the weight ratios of BAFL, 3,4'-ODA, and BPADA used in prepolymer Examples 1 to 5 were adjusted to obtain photosensitive polyimide prepolymers BAFL-PSPI-0595 and BAFL-PSPI-3565 for prepolymer comparative examples 4 and 5. Yields were calculated by weighing (the yields of prepolymer comparative examples 4 and 5 were approximately 85%). The number-average molecular weight of the prepolymers obtained for each prepolymer comparative example was determined by GPC (shown in Table 1).

[0095] Comparative Examples 6 to 7: Preparation of Prepolymers Prepolymers for Comparative Examples 6 and 7 were prepared using a process similar to that used in Prepolymer Examples 1 to 5, except that in Comparative Example 6, the reaction time of the second step was adjusted from approximately 10 hours in Prepolymer Example 1 to approximately 9 hours, and in Comparative Example 7, the reaction time of the second step was adjusted from approximately 10 hours in Prepolymer Example 1 to approximately 13 hours, thereby obtaining photosensitive polyimide prepolymers BAFL-PSPI-1585-8K and BAFL-PSPI-1585-13K for Comparative Examples 6 and 7. Yields were calculated by weighing (the yields of Comparative Examples 6 and 7 were approximately 87%). The number-average molecular weight of the prepolymers obtained for each Comparative Example 6 was determined by GPC (shown in Table 1).

[0096] Comparative Example 8: Preparation of Prepolymer Prepolymers for the comparative prepolymers were prepared using a process similar to that used in Examples 1 to 5, except that the diamine monomer 3,4'-ODA used in Examples 1 to 5 was replaced with symmetrical 4,4'-diaminodiphenyl ether (ODA), resulting in the photosensitive polyimide prepolymer BAFL(ODA)-PSPI-1585 for Comparative Prepolymer Example 8. Yields were calculated by weighing (the yield of Comparative Prepolymer Example 8 was approximately 85%). The number-average molecular weight of the prepolymers obtained in Comparative Prepolymer Example 8 was determined by GPC (shown in Table 1).

[0097] Table 1: Raw materials and products of prepolymer examples and comparative examples The prepolymers BAFL-PSPI-1585, BAFL-PSPI-1090, BAFL-PSPI-2080, BAFL-PSPI-2575, and BAFL-PSPI-3070 obtained in Examples 1 to 5, and the prepolymers BAFL-PSPI-0595, BAFL-PSPI-3565, BAFL-PSPI-1585-8K, and BAFL-PSPI-1585-13K obtained in Comparative Examples 4 to 7, all contain structural units having formulas (1) and (2) and have end groups A- or AE-, wherein M represents: G means: ; E represents: or ; A represents: CH2=C(CH3)-CONH-.

[0098] The prepolymers DAF-PSPI-1585, SA-1-PSPI-1585, and ODA-PSPI-1585 obtained in Comparative Examples 1 to 3 contain structural units having formulas (1) and (2) and have end groups A- or AE-, wherein the meanings of M, E, and A are the same as those of the symbols in Examples 1 to 5 above, and G in the molecular structure of the prepolymers DAF-PSPI-1585, SA-1-PSPI-1585, and ODA-PSPI-1585 in Comparative Examples 1 to 3 respectively represent: , and .

[0099] The prepolymer BAFL(ODA)-PSPI-1585 of Comparative Example 8 comprises structural units having formulas (1) and (2) and has end groups A- or AE-, wherein the meanings of M, G, and A are the same as those of the symbols in Examples 1 to 5 above, and E in the molecular structure of the prepolymer BAFL(ODA)-PSPI-1585 of Comparative Example 8 represents: .

[0100] The proton NMR and infrared spectra of prepolymer BAFL-PSPI-1585 obtained from prepolymer Example 1, and prepolymers DAF-PSPI-1585, SA-1-PSPI-1585, and ODA-PSPI-1585 obtained from prepolymer Comparative Examples 1 to 3 are shown in the appendix. Figure 1 and 2 .

[0101] From the appendix Figure 1The 1H NMR spectrum shows that the chemical shift (δ) peaks in the range of approximately 1 ppm to approximately 4 ppm correspond to the proton peaks of the methyl hydrogen on the C(CH3)2 group, -CO-C(CH3)=CH2 group, the solvent deuterated DMSO, and water. The peaks in the range of approximately 7 ppm to approximately 8 ppm correspond to the proton peaks of hydrogen on the benzene ring. The peak at approximately 9.88 ppm corresponds to the proton peak of hydrogen on the -NH group in the amide structure. The peaks in the range of approximately 5.49 ppm to approximately 6.15 ppm correspond to the proton peaks of hydrogen on the C=CH2 group in the amide structure. (See attached...) Figure 2 The infrared spectrum shows that at a wavenumber of approximately 1640 cm⁻¹ -1 A stretching vibration peak of the =CH bond in the aromatic ring was observed at a wavenumber of approximately 1413 cm⁻¹. -1 An in-plane deformation vibration peak of the =CH bond in the aromatic ring was observed at a wavenumber of approximately 1137 cm⁻¹. -1 An in-plane rocking vibration peak of the =CH bond in the aromatic ring was observed at a wavenumber of approximately 660 cm⁻¹. -1 Absorption peaks were observed at the =CH bonds in the aromatic ring. These spectra demonstrate that the target prepolymer was successfully prepared in the embodiments and comparative examples of this invention.

[0102] Ink Examples and Comparative Examples: Preparation of Photosensitive Inks for 3D Printing The prepolymers, reactive solvents, reactive diluent monomers, crosslinking agents, and photoinitiators obtained from Examples 1 to 5 and Comparative Examples 1 to 8 were thoroughly mixed under light-protected conditions by mechanical stirring according to the proportions shown in Table 2. The system was then subjected to defoaming treatment by ultrasonication and vacuuming to obtain the low-dielectric photosensitive ink for 3D printing.

[0103] The reactive solvent used in each of the embodiments and comparative examples is 4-acryloylmorpholine (ACMO), the reactive diluent monomer is 1,10-bis(acryloyloxy)decane (DTGDA), the crosslinking agent is tris(2-acryloyloxyethyl) isocyanurate (TAIC), and the photoinitiator is a mixture of ethyl 4-dimethylaminobenzoate (EDB) and 2-isopropylthioxanthone (ITX) in a weight ratio of approximately 1:1.

[0104] Table 2: Raw materials and amounts used in ink examples and comparative examples To further illustrate the technical effects of the above ink examples and comparative examples, the following experimental examples were conducted.

[0105] Experimental Example The photosensitive inks for 3D printing prepared in the ink examples and comparative examples of the present invention were coated onto a glass plate using a 200 μm doctor blade, and finally placed in an ultraviolet oven at approximately 50 mW / m 2 The photocuring reaction was carried out under the radiation power to obtain the final cured material. The obtained cured material was a thin film with a length of about 15 cm, a width of about 10 cm, and an average thickness of about 120 μm.

[0106] Infrared spectroscopy was performed on the cured materials (films) obtained by curing the photosensitive inks for 3D printing prepared in the above-mentioned ink examples and comparative examples of the present invention. See attached figures for details. Figure 3 As exemplarily shown, the infrared spectra of the cured materials obtained after curing the photosensitive inks for 3D printing prepared from ink example E1-1 (using prepolymer BAFL-PSPI-1585) and ink comparative examples CE1 to CE3 (using prepolymers DAF-PSPI-1585, SA-1-PSPI-1585, and ODA-PSPI-1585, respectively) show that during ultraviolet photopolymerization, the C=C double bonds gradually transform into saturated single bonds. In the infrared spectrum, this corresponds to the double bonds at a wavenumber of approximately 1407 cm⁻¹. -1 Approximately 1115 cm -1 Approximately 808 cm -1 The characteristic peaks at these points weaken or even disappear. Therefore, changes in unsaturated double bonds can be observed by tracking changes in the infrared peaks of double bonds in infrared spectra. (From the appendix...) Figure 3 It can be seen that at wavenumbers of approximately 1407 cm⁻¹ -1 Approximately 1115 cm -1 Approximately 808 cm -1 The peak at the specified location disappeared after UV curing. This phenomenon indicates that the ink systems of the embodiments and comparative examples of the present invention reacted completely under UV curing.

[0107] The cured materials (films) prepared from the ink examples and comparative examples above were subjected to differential scanning calorimetry (DSC) tests (specific test conditions: using a TA Q20 instrument, heating from approximately 30°C to approximately 300°C at a rate of approximately 10 K / min, with nitrogen gas introduced at a flow rate of approximately 50 ml / min), tensile property tests (specific test conditions: using an AnInstron-5869 machine, a load of approximately 100 N, a strain rate of approximately 2 mm / min, an effective tensile length of approximately 20 mm, and a width of approximately 6 mm), and dielectric property tests (specific test conditions: dielectric properties were determined using an Aglient E4980A impedance analyzer, and the dielectric constant and loss tangent were recorded at approximately 25°C in the 20 GHz frequency range). The test results are shown in Table 3 below. In addition, the dielectric constant, dielectric loss, tensile strength, and elongation at break of the cured materials obtained after curing the photosensitive inks for 3D printing prepared from ink examples E1-1 to E1-4 (all using prepolymer BAFL-PSPI-1585) are shown in the attached figures. Figure 4 and 5 As shown in the example.

[0108] Table 3 Figure 5 To illustrate the tensile strength and elongation at break of the cured materials (films) prepared from the photosensitive inks for 3D printing using Examples E1-1 to E1-4 of the present invention (all using prepolymer BAFL-PSPI-1585), the graph shows the mass fraction of the prepolymer (bisphenylfluorene-type photosensitive polyimide (BAFL-PSPI-1585)) in the photosensitive ink for 3D printing. In Example E1-1, the mass fraction of the prepolymer was about 15% by weight (Sample 1); in Example E1-2, the mass fraction of the prepolymer was about 20% by weight (Sample 2); in Example E1-3, the mass fraction of the prepolymer was about 25% by weight (Sample 3); and in Example E1-4, the mass fraction of the prepolymer was about 30% by weight (Sample 4). Figure 5 The error bars at the top of each bar represent the range of the measured data listed in Table 3. From Figure 5 As can be seen, when the mass fraction of the prepolymer in the ink reaches about 25% by weight, its tensile strength and elongation at break reach a better level.

[0109] In addition, Comparative Examples CE1, CE2, and CE3 are comparative experiments of Example E1-1, and they differ in that they are different types of prepolymers.

[0110] In actual experiments, it was found that due to the relatively weak rigidity of the 4,4'-diaminodiphenyl ether used in the preparation of the photosensitive polyimide in Comparative Example CE3, the prepared photosensitive ink exhibited inferior thermal, mechanical, and dielectric properties compared to Example E1-1. Therefore, it is evident that using diamine monomers containing fluorene groups for polymerization, and introducing the rigid, large-volume fluorene group structure, can significantly enhance the thermal, mechanical, and dielectric properties of the system. Furthermore, the use of 9,9'-bis(4-aminophenyl)fluorene in copolymerization with other monomers achieved superior technical results.

[0111] For comparative examples CE1 and CE2, the diamine monomers used in their photosensitive polyimide preparation are 2,7-diaminofluorene (DAF) and 9,9-dimethylfluorene-2,7-diamine (SA-1), respectively. Both directly incorporate the fluorene group structure into the main chain, resulting in excessively rigid main chains and significantly reduced chain segment mobility. During the photocuring reaction, this rigid structure inhibits the effective movement of the molecular chains, thereby slowing down the curing speed and reducing the final degree of curing, ultimately leading to a deterioration in the overall performance of the resulting photosensitive polyimide ink.

[0112] Comparative Examples E1-7 and E1-8 investigated the effects of the amount of each raw material in the photosensitive ink for 3D printing on the final material properties. As shown in Table 3, when the amount of crosslinking agent added to Comparative Example E1-7 increased and the amount of reactive solvent added decreased, the thermal, mechanical, and dielectric properties all decreased. This is mainly because excessive crosslinking agent content leads to a faster curing reaction, resulting in an uneven crosslinking network and consequently a decrease in mechanical and dielectric properties. When the amount of reactive diluent monomer added to Comparative Example E1-8 increased and the amount of reactive solvent decreased, although the elongation at break increased (mainly due to the improved flexibility of the system from the addition of the diluent), the thermal, tensile strength, and dielectric properties all decreased. This is mainly because the introduced flexible structure reduces the rigidity of the crosslinking network, leading to a decrease in performance.

[0113] For Comparative Example E1-5, due to the low content of prepolymer, there are insufficient curable active crosslinking sites in the system, which prevents the formation of a stable and dense crosslinking network during the curing reaction, thus leading to a reduction in the performance of the photosensitive ink.

[0114] For Comparative Example E1-6, due to the excessive prepolymer content, the viscosity of the system increases, reducing the chain segment mobility during the curing reaction and hindering the formation of the crosslinking network. At the same time, the excessive prepolymer results in too many curable active crosslinking sites in the system, which rapidly absorb a large number of initiator free radicals during the photocuring reaction, making it difficult for other components in the system to absorb enough free radicals to initiate curing. The synergistic effect of these two factors reduces the performance of the system.

[0115] For comparative example CE4, the rigidity of the system decreased due to the insufficient BAFL content in the prepolymer structure, which in turn reduced the thermal, mechanical, and dielectric properties of the photosensitive ink.

[0116] For comparative example CE5, due to the excessive BAFL content in the prepolymer structure, the system has excessive rigidity and reduced chain segment mobility, making it difficult to form a stable and dense cross-linked network during photocuring, thus reducing the system's performance.

[0117] For Comparative Example CE6, due to the decrease in molecular weight of the prepolymer, the intermolecular interaction forces decrease, resulting in a decrease in the thermal and dielectric properties of the photosensitive ink compared to Examples E1-3; at the same time, the decrease in molecular weight also reduces the free volume inside the photosensitive resin, thereby leading to a decrease in dielectric properties.

[0118] For Comparative Example CE7, due to the increased molecular weight of the prepolymer, the molecular chains form chain entanglements, which reduces the mobility of the chain segments. During the photocuring reaction, the entangled molecular chains have difficulty moving in time to form a stable and dense cross-linked network, which slows down the curing speed and reduces the final degree of curing, resulting in a decrease in the overall performance of the ink compared to Examples E1-3.

[0119] For Comparative Example CE8, the diamine monomers used in the preparation of its photosensitive polyimide are 9,9'-bis(4-aminophenyl)fluorene (BAFL) and symmetrical diamine monomer 4,4'-diaminodiphenyl ether (ODA). Their symmetrical structure causes the molecular chain segments to be tightly packed and arranged, which greatly hinders the movement of the chain segments. As a result, the mobility of the molecular chain segments decreases and the reactivity decreases during the photocuring reaction. This makes it difficult to form a dense and stable crosslinked network, resulting in a decrease in the overall performance of the ink compared to Examples E1-3.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions claimed by the present invention.

Claims

1. A photosensitive ink for 3D printing, characterized in that, The 3D printing photosensitive ink comprises, based on the total mass of the 3D printing photosensitive ink. 15 to 30% by weight of photosensitive polyimide prepolymer, 30 to 45% by weight of reactive solvents, 10 to 20% by weight of reactive diluted monomer, 10 to 15% by weight of crosslinking agent, and 2 to 5% by weight of photoinitiator, The photosensitive polyimide prepolymer comprises repeating structural units having the following formulas (1) and (2): -(M-G) a -(1) -(ALONG WITH) b -(2) in a is the number of moles of the repeating structural unit (1). b is the number of moles of the repeating structural unit (2), and The number of moles a of the repeating structural unit (1) accounts for 10 to 30 mol% of the total number of moles (a+b) of the repeating structural units (1) and (2), and The number of moles b of the repeating structural unit (2) accounts for 70 to 90 mol% of the total number of moles (a+b) of the repeating structural units (1) and (2). M represents: , In the above structural formula representing M, the symbol Each occurrence independently represents any of the following structures: 、 、 、 、 、 , and ； In the above-mentioned representative symbols In each structural formula, the pair of single bonds on the left, indicated by an asterisk "*", represent: In the structural formula representing M, in the symbol... The two single bonds on the left side connecting to the imide group; and the pair of single bonds on the right side indicated by the asterisk "*": In the structural formula representing M, the symbol... The right side is connected to two single bonds of an imide group; G means: ;and E represents: or ; In the above structural formulas representing M, G and E, the single bonds indicated by the asterisk "*" on the left and right sides respectively represent: single bonds connected to the groups on the left and right sides of the structural formula in formula (1); Furthermore, the photosensitive polyimide prepolymer also has end groups containing double bonds, which are selected from: A- or AE-, Where A represents an amide group containing a double bond, preferably CH2=C(CH3)-CONH- or CH2=CH-CONH-. An additional condition is that, in the molecular structure of the photosensitive polyimide prepolymer, the repeating structural units of formulas (1) and (2) and the connection between the end groups are such that two N atoms are not directly connected to each other.

2. The photosensitive ink for 3D printing according to claim 1, characterized in that, The number-average molecular weight of the photosensitive polyimide prepolymer is in the range of 9,000 to 11,000 g / mol.

3. The photosensitive ink for 3D printing according to claim 1 or 2, characterized in that, The photosensitive polyimide prepolymer is prepared by the following method, which includes the following steps: Step 1: The dianhydride monomer and diamine monomer are added to the polymerization solvent and reacted under a protective atmosphere, wherein... The dianhydride monomers include one or more of the following: pyromellitic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, hexafluorodianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, and bisphenol A type dianhydride; The diamine monomer comprises 3,4'-diaminodiphenyl ether and 9,9-bis(4-aminophenyl)fluorene, wherein the molar amount of 3,4'-diaminodiphenyl ether is 70 to 90 mol% of the total molar amount of the diamine monomer, and the molar amount of 9,9-bis(4-aminophenyl)fluorene is 10 to 30 mol% of the total molar amount of the diamine monomer. Step 2: Add an alkaline catalyst to the reaction system obtained from Step 1 and heat to carry out the reaction. After the reaction is completed, cool. and Step 3: Add an acyl chloride containing a double bond to the reaction system obtained from Step 2 to obtain the photosensitive polyimide prepolymer.

4. The photosensitive ink for 3D printing according to claim 3, characterized in that, In step 1, The polymerization solvent includes one or more of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and sulfolane; and / or The molar ratio between the total molar amount of the dianhydride monomer and the total molar amount of the diamine monomer is in the range of (0.90-1.00):1.00; and / or The total mass of the dianhydride monomer and the diamine monomer accounts for 10 to 30% of the total mass of the mixed solution comprising the dianhydride monomer, the diamine monomer, and the polymerization solvent; and / or The protective atmosphere includes one or more of nitrogen, argon, or helium; and / or In step 2, The alkaline catalyst includes one or more of piperidine, pyridine, diethylamine, and triethylamine; and / or The mass fraction ratio of the alkaline catalyst to the polymerization solvent is in the range of 1:(2-10); and / or In step 3, The acyl chloride containing a double bond includes acryloyl chloride and / or methacryloyl chloride; and / or The mass ratio of the acyl chloride containing the double bond to the polymerization solvent is in the range of 1:(2-10).

5. The photosensitive ink for 3D printing according to claim 3, characterized in that, The reaction temperature in step 1 is in the range of 20 to 30°C, and the reaction time is in the range of 10 to 12 hours; and / or The reaction temperature in step 2 is in the range of 150 to 200°C, and the reaction time is in the range of 5 to 12 hours; and / or The reaction temperature in step 3 is in the range of 0 to 10°C, and the reaction time is in the range of 10 to 20 hours; and / or After the reaction in step 3 is completed, the obtained reaction product is precipitated in ethanol, and then the precipitated solid is crushed, washed and dried to obtain the photosensitive polyimide prepolymer.

6. The photosensitive ink for 3D printing according to claim 1 or 2, characterized in that, The reactive solvent includes 4-acryloylmorpholine and / or N-vinylpyrrolidone; and / or The reactive diluent monomers include 1,10-bis(acryloyloxy)decane and / or polyethylene glycol diacrylate; and / or The crosslinking agent includes tris(2-acryloyloxyethyl) isocyanurate; and / or The photoinitiator includes one or more of 1-hydroxycyclohexylphenyl ketone, ethyl 4-dimethylaminobenzoate, and 2-isopropylthioxanthrone.

7. A method for preparing photosensitive ink for 3D printing according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: The photosensitive polyimide prepolymer, the reactive solvent, the reactive diluent monomer, the crosslinking agent, and the photoinitiator are stirred and mixed under light-protected conditions, and the resulting mixture is then subjected to a defoaming treatment to obtain the photosensitive ink for 3D printing.

8. The preparation method according to claim 7, characterized in that, The bubble extraction process includes ultrasonic treatment and / or vacuum treatment.

9. A curing material, characterized in that, The cured material is prepared from the photosensitive ink for 3D printing according to any one of claims 1 to 6 or the photosensitive ink for 3D printing prepared by the preparation method according to claim 7 or 8. Preferably, The glass transition temperature of the cured material T g Within the range of 160 to 180°C; and / or The tensile strength of the cured material is in the range of 58 to 80 MPa, and / or The elongation at break of the cured material is in the range of 6% to 15%; and / or The dielectric constant of the cured material at 20 GHz is in the range of 2.3 to 2.8; and / or The dielectric loss tangent of the cured material at 20 GHz is in the range of 0.005 to 0.

009.

10. The use of the cured material according to claim 9 in the field of microelectronics or communications.

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