Conductive powder dispersoid capable of being rapidly cured at low temperature as well as preparation method and application of conductive powder dispersoid

Abstract

The invention belongs to the field of conductive powder dispersions, and particularly relates to a low-temperature fast-curing conductive powder dispersion which comprises 80-99 parts by weight of a component A and 0.01-10 parts by weight of a component B, the component A is copolymer modified conductive powder; the component B is terminated polyurethane, and the NCO value range of the component B is controlled to be 3%-26%; in the component A, the copolymer is obtained by polymerizing a monomer a with a structure as shown in a formula 1 and a monomer b with a structure as shown in a formula 2. The invention also comprises preparation and application of the conductive dispersion. According to the conductive powder dispersion, on the premise that existing functional components are greatly omitted, low-temperature rapid curing can be achieved, and the conductive powder dispersion can still have excellent adhesive force and conductivity.

Description

Technical Field

[0001] This invention belongs to the field of conductive paste technology, specifically relating to a low-temperature curable conductive paste. Background Technology

[0002] Conductive pastes are commonly used in the fabrication of electronic components and have a wide range of applications, including aerospace, computer and communication equipment, medical devices, automotive manufacturing, integrated circuits, and various consumer electronics manufacturing industries. Existing pastes primarily consist of conductive fillers, a binder phase, and organic solvents. The binder phase is further divided into inorganic and organic binder phases. The organic binder phase acts as a carrier for the conductive phase; the conductive phase is suspended as a dispersed phase within the organic binder phase, ensuring thorough wetting and thus improving the conductive paste's abrasiveness and printability. Furthermore, the organic binder phase significantly enhances the adhesion of the conductive paste; however, the addition of the organic binder phase can negatively impact conductivity.

[0003] Based on the heat treatment temperature, conductive pastes can be divided into high-temperature conductive pastes and low-temperature conductive pastes. Existing low-temperature conductive pastes need to be cured at 100-200℃ for more than 20-30 minutes to ensure that the electronic paste is fully cured and achieves the required application function. In addition, there are problems such as low adhesion and easy peeling. Summary of the Invention

[0004] To address the problems of unsatisfactory low-temperature curing efficiency and effect of existing low-temperature conductive pastes, and the difficulty in balancing low-temperature curing efficiency, adhesion, and conductivity, this invention provides a low-temperature rapid-curing conductive powder dispersion, aiming to provide a conductive powder dispersion that can be rapidly cured at low temperatures while maintaining excellent adhesion and conductivity.

[0005] The second objective of this invention is to provide a method for preparing the aforementioned low-temperature rapid-curing conductive powder dispersion and its application.

[0006] Existing low-temperature conductive pastes exhibit slow low-temperature curing efficiency and unsatisfactory adhesion and conductivity. To address this issue, the main industry approach involves extending the low-temperature curing time and adding numerous auxiliary materials. While these methods can improve adhesion and other effects during low-temperature curing, the processing efficiency remains unsatisfactory, making it difficult to simultaneously achieve efficient low-temperature curing, high adhesion, and conductivity. To address this problem, this invention, after in-depth research, provides the following improvement:

[0007] A low-temperature, rapidly curing conductive powder dispersion comprises 80-99 parts by weight of component A and 0.01-10 parts by weight of component B; wherein component A is a copolymer-modified conductive powder; and component B is end-capped polyurethane, wherein the NCO value is controlled within the range of 3%-26%.

[0008] In component A, the copolymer is obtained by polymerization of monomer a of formula 1 and monomer b of formula 2;

[0009]

[0010] R1 is H or a C1-C6 alkyl group;

[0011] R2 is either hydroxyalkoxy or amino.

[0012] To address the problems of low low-temperature curing efficiency and unsatisfactory adhesion and conductivity of low-temperature cured dispersions in conductive pastes, this invention innovatively modifies the conductive powder using copolymers polymerized according to Formulas 1 and 2. Furthermore, by jointly controlling the content of component B and its NCO content, a synergistic effect is achieved. This allows for rapid low-temperature curing while improving the adhesion between conductive particles and the substrate through chemical chaining interactions between components. Additionally, it fosters a robust conductive network, optimizing conductivity. The conductive powder dispersion described in this invention achieves rapid low-temperature curing while maintaining excellent adhesion and conductivity, despite significantly reducing the amount of existing functional components.

[0013] In this invention, the monomer b includes monomer b1 with the structure of formula 2-1 and / or monomer b2 with the structure of formula 2-2;

[0014]

[0015]

[0016] In Formula 2-1, R1 is H, methyl, or ethyl; R3 is C1 to C2. 10 Alkylene;

[0017] In Formula 2-2, R1 is H, methyl, or ethyl.

[0018] Preferably, monomer b comprises monomer b1 and monomer b2; more preferably, the mass ratio of monomer b1 to monomer b2 in monomer b is 5-50:10-50. Research in this invention shows that using the combination of monomer b1 and monomer b2 in conjunction with monomer a for polymerization can optimize the polymerization structure, which helps to further improve its modification effect on conductive particles. Furthermore, combining it with component B can achieve even better low-temperature curing efficiency and effect.

[0019] In this invention, the weight ratio of monomer a to monomer b is (20-80):(15-100); further, it can be (20-80):(80-20).

[0020] Preferably, monomer a and monomer b undergo polymerization with the assistance of an initiator;

[0021] Preferably, the initiator is a free radical initiator;

[0022] Preferably, the polymerization temperature is 70-90℃.

[0023] In this invention, the weight-average molecular weight Mw of the copolymer is 35,000 to 45,000 Da.

[0024] In component A of this invention, the conductive powder is at least one selected from silver powder, copper powder, silver-coated copper powder, silver-coated aluminum powder, and silver-coated nickel powder. The particle size D50 of the conductive powder can be 1–500 nm.

[0025] Preferably, the copolymer-modified conductive powder is prepared by dispersing and modifying the conductive powder and the copolymer with a solvent, followed by solvent removal. The solvent is not particularly required; however, considering preparation efficiency and effectiveness, it can be a volatile component, such as a C1-C4 alcohol. The solvent volume can be reasonably adjusted as needed.

[0026] Preferably, in component A, the weight ratio of the conductive powder to the copolymer is 1:0.02 to 0.5, and more preferably 1:0.1 to 0.2.

[0027] In this invention, component B can be any end-capped polyurethane that conforms to the NCO value range.

[0028] In an embodiment of the present invention, component B is obtained by polymerizing raw material c and raw material d of formula 3, followed by adding a mixture of end-capping agent and organic solvent for end-capping reaction, wherein raw material d is polyester polyether and / or polyester polyol.

[0029]

[0030] The R4 mentioned is C1 to C 10 The carbon chain, substituted or unsubstituted non-aromatic ring, substituted or unsubstituted aromatic ring; the non-aromatic ring is at least one of saturated carbon monocyclic ring, bridged ring, spirocyclic ring, saturated carbon heterocyclic ring, and partially unsaturated carbon heterocyclic ring.

[0031] Further examples of the present invention include raw material c for preparing component B, which includes at least one of raw material c-1 of formula 3-1, raw material c-2 of formula 3-2, and raw material c-3 of formula 3-3.

[0032]

[0033] The R5 mentioned is H or C1~C 10 Alkyl groups; where n is an integer from 3 to 8.

[0034] In this invention, a catalyst is added during the polymerization reaction of raw material c and raw material d;

[0035] Preferably, the catalyst comprises dibutyltin dilaurate. The catalyst accounts for 0.01 to 0.5% of the total weight of the raw materials (total of raw material c and raw material d).

[0036] The raw material d can be any known polyester polyether and / or polyester polyol; for example, as an example, it can further be at least one of polyethylene glycol, polypropylene glycol, polycaprolactone, etc. The molecular weight of the polypropylene glycol can be 200-1000. The molecular weight of the polycaprolactone can be 300-1000.

[0037] In this invention, the capping agent includes at least one of butanone oxime, phenol, caprolactam, and malonate.

[0038] In this invention, the NCO value can be controlled by adjusting the amount of capping agent. For example, the molar ratio of the capping agent to raw material c is 0.2 to 2, preferably 0.3 to 1.8.

[0039] In this invention, the organic solvent includes at least one of esters, ketones, ethers, alcohols, and hydrocarbon solvents; more specifically, it can be one or more of butanone, acetone, cyclohexanone, isophorone, diethylene glycol butyl ether ester, diethylene glycol butyl ether, dodecyl alcohol ester, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether and dimethyl adipate, N,N-dimethylformamide, ethyl carbitol acetate, dimethyl sulfoxide, toluene, cyclohexane, n-hexane, or a diester mixture (DBE). Preferably, the organic solvent includes esters, and more specifically, it can be at least one of ethyl carbitol acetate, a diester mixture, diethylene glycol butyl ether ester, and dimethyl adipate. Studies have shown that the preferred organic solvent can further optimize the synergy of the components and further enhance the low-temperature curing efficiency and effect of the conductive dispersion.

[0040] In this invention, there are no special requirements for the amount of organic solvent used, which can be adjusted as needed. For example, it can be 1 to 3 times the weight of raw material c. Considering the overall performance of the conductive powder dispersion, it can be further 1 to 2.5 times.

[0041] In this invention, based on the combination of component A and component B, and further combined with the coating of conductive particles by component A and the joint control of NCO content in component B, a synergistic effect can be achieved, improving the curing efficiency and effect at low temperatures, and improving the adhesion and conductivity of low-temperature short-time curing.

[0042] Preferably, the NCO value of component B ranges from 5% to 25%, and more preferably from 9% to 20%. Studies have shown that component B with the preferred NCO value helps to further enhance its synergistic effect with component A, and can further enhance the low-temperature curing efficiency and effect of the conductive dispersion.

[0043] In the low-temperature rapid-curing conductive powder dispersion of the present invention, the weight parts of component A are 80-95 parts and the weight parts of component B are 2-10 parts. More preferably, the weight parts of component A are 90-95 parts and the weight parts of component B are 5-10 parts.

[0044] The low-temperature rapid-curing conductive powder dispersion of the present invention may also contain component C, which is an organic solvent, in parts by weight of 10 or less. Further, the weight of component C may be 1 to 5 parts. In the present invention, component C may be introduced during the preparation process of component B.

[0045] The component C includes one or more of butanone, acetone, cyclohexanone, isophorone, diethylene glycol butyl ether ester, diethylene glycol butyl ether, dodecyl alcohol ester, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether and dimethyl adipate, N,N-dimethylformamide, ethyl carbitol acetate, dimethyl sulfoxide, toluene, cyclohexane, n-hexane or a mixture of diesters (DBE); further comprising at least one of ethyl carbitol acetate, a mixture of diesters, diethylene glycol butyl ether ester, and dimethyl adipate.

[0046] The present invention also provides a method for preparing the low-temperature rapid curing conductive powder dispersion, wherein the components are mixed to obtain the dispersion.

[0047] The present invention also provides an application of the aforementioned low-temperature rapid-curing conductive powder dispersion in the preparation of low-temperature curing photovoltaic cell electrodes, wherein the low-temperature rapid-curing conductive powder dispersion is coated on the surface of a substrate and then cured at low temperature.

[0048] There are no special requirements for the low-temperature curing temperature, but thanks to the synergistic effect of the components, the present invention is particularly suitable for low-temperature curing applications, such as curing applications with a curing temperature of 100 to 200°C.

[0049] In this invention, there are no special requirements for the curing time. However, thanks to the synergistic effect of the components of this invention, it can exhibit superior application value and performance advantages in low-temperature rapid curing scenarios. The aforementioned low-temperature rapid curing refers to a curing time of 5–15 minutes.

[0050] Beneficial effects

[0051] This invention utilizes the combination of component A and component B of the special copolymer-coated conductive powder, further coordinated with the joint control of the NCO content of component B. This achieves synergy, enabling rapid low-temperature curing while improving the adhesion between conductive particles and the substrate through chemical chaining interactions. Furthermore, it forms a good conductive network, optimizing conductivity. The conductive powder dispersion of this invention, while significantly reducing the amount of existing functional components, achieves rapid low-temperature curing while still maintaining excellent adhesion, conductivity, and printability. Attached Figure Description

[0052] Figure 1 Example 1: Electron micrograph of conductive powder dispersion screen-printed on a blue film silicon wafer;

[0053] Figure 2 Comparative Example 4: Electron micrograph of conductive powder dispersion screen-printed on a blue silicon wafer; Detailed Implementation

[0054] 1.1 The enumerable component A can be prepared by the following steps:

[0055] Step S1, preparation of copolymer:

[0056] Free radical solution polymerization was carried out by sequentially adding monomer a (Formula 1) and monomer b (Formula 2) to a solvent under an inert gas atmosphere, followed by the addition of an initiator over a period of 1-6 hours. The reaction temperature was 70-90°C, and the total reaction time was 12-14 hours. After the reaction was completed, the product was discharged to obtain a copolymer with a solid content of 40-60% and a weight-average molecular weight (Mw) of 35,000-45,000 Da.

[0057] Step S2, Wrapping:

[0058] The conductive powder was dispersed in ethanol, and the copolymer prepared in step S1 was added. The mixture was stirred and ultrasonically dispersed. After vacuum drying, the copolymer-coated conductive powder was obtained.

[0059] Preferably, in step S1, the monomer combination of the synthesized copolymer can be a binary combination of monomer a and monomer b1; or a binary combination of monomer a and monomer b2; or a ternary combination of monomer a, monomer b1 and monomer b2.

[0060] The mass ratio of monomer a to monomer b is (20-80):(15-100), and can be further expressed as (20-80):(80-20).

[0061] In this invention, the copolymer is preferably synthesized using the ternary monomer combination containing monomer a, monomer b1 and monomer b2, and the mass ratio of the three can be (20-80):(5-50):(10-50); more preferably it can be 5:3:2.

[0062] Preferably, the initiator mass in step S1 is 3% to 8% of the total monomer mass (total weight of monomer a and monomer b), and more preferably 4% to 5%.

[0063] Preferably, the initiator is benzoyl peroxide (BPO), the ethanol is anhydrous ethanol, and the solvent is butanone.

[0064] Preferably, the mass ratio of conductive powder to anhydrous ethanol in step S2 is 0.1 to 0.8:1, and the mass ratio of conductive powder to copolymer is 1:0.02 to 0.50.

[0065] Further preferably, the mass ratio of conductive powder to anhydrous ethanol in step S2 is 0.2–0.5:1, and the mass ratio of conductive powder to macromolecular copolymer is 1:0.05–0.30. Even more preferably, the mass ratio of conductive powder to macromolecular copolymer is 1:0.125.

[0066] 1.2 The enumerable component B can be prepared by the following steps:

[0067] Preparation method of component B:

[0068] Under a nitrogen atmosphere and at a temperature of 70-80℃, raw material d (polypolyol or polypolyether) is slowly added dropwise to raw material c under stirring. Then, a catalyst (such as dibutyltin dilaurate (DBTDL)) is added dropwise to initiate the reaction. Finally, the blocking agent and solvent are mixed and slowly added dropwise to carry out the end-capping reaction.

[0069] The blocking agent is selected from one of methyl ethyl ketone oxime, phenol, caprolactam and malonate, with methyl ethyl ketone oxime being preferred.

[0070] Further alternative solutions:

[0071] Component B1: Under a nitrogen atmosphere and at 80℃, 22.2g of Formula 3-1 was added to a four-necked flask. While stirring at 300rpm, 20g of polypropylene glycol (molecular weight 400) was slowly added dropwise to a constant-pressure funnel over 1 hour. Simultaneously, 1 drop of dibutyltin dilaurate (DBTDL) was added to the flask using a 5mL disposable dropper. The total reaction time was 2 hours. Then, 9.14g of butanone oxime and 42g of diethylene glycol butyl ether acetate (solvent) were slowly added dropwise to a constant-pressure funnel over 30 minutes. The total reaction time was 2 hours. The product was then discharged. The NCO value was 9.96%.

[0072] Component B2: Under a nitrogen atmosphere and at 80℃, 22.2g of Formula 3-1 was added to a four-necked flask. While stirring at 300rpm, 15g of polypropylene glycol (molecular weight 400) was slowly added dropwise to a constant-pressure funnel over 1 hour. Simultaneously, 1 drop of dibutyltin dilaurate (DBTDL) was added to the flask using a 5mL disposable dropper. The total reaction time was 2 hours. Then, 11.42g of butanone oxime and 37g of diethylene glycol butyl ether acetate were slowly added dropwise to a constant-pressure funnel over 30 minutes. The total reaction time was 2 hours. The product was then discharged. The NCO value was 14.09%.

[0073] Component B3: Under a nitrogen atmosphere and at 80℃, 22.2g of Formula 3-1 was added to a four-necked flask. While stirring at 300rpm, 10g of polypropylene glycol (molecular weight 400) was slowly added dropwise to a constant-pressure funnel over 1 hour. Simultaneously, 1 drop of dibutyltin dilaurate (DBTDL) was added to the flask using a 5mL disposable dropper. The total reaction time was 2 hours. Then, 13.7g of butanone oxime and 32g of diethylene glycol butyl ether acetate were slowly added dropwise to a constant-pressure funnel over 30 minutes. The total reaction time was 2 hours before discharge. The NCO value was 19.52%.

[0074] Component B4: Under a nitrogen atmosphere and at 80℃, 22.2g of Formula 3-1 was added to a four-necked flask. While stirring at 300rpm, 6g of polypropylene glycol (molecular weight 400) was slowly added dropwise to a constant-pressure funnel over 1 hour. Simultaneously, 1 drop of dibutyltin dilaurate (DBTDL) was added to the flask using a 5mL disposable dropper. The total reaction time was 2 hours. Then, 15.53g of butanone oxime and 28g of diethylene glycol butyl ether acetate were slowly added dropwise to a constant-pressure funnel over 30 minutes. The total reaction time was 2 hours before discharge. The NCO value was 25.30%.

[0075] Component B5: Under a nitrogen atmosphere and at 80℃, 22.2g of Formula 3-1 was added to a four-necked flask. While stirring at 300rpm, 31g of polypropylene glycol (molecular weight 400) was slowly added dropwise to a constant-pressure funnel over 1 hour. Simultaneously, 1 drop of dibutyltin dilaurate (DBTDL) was added to the flask using a 5mL disposable dropper. The total reaction time was 2 hours. Then, 4.11g of butanone oxime and 53g of diethylene glycol butyl ether acetate were slowly added dropwise to a constant-pressure funnel over 30 minutes. The total reaction time was 2 hours. The product was then discharged. The NCO value was 3.52%.

[0076] Component B6: Under a nitrogen atmosphere and at 80℃, 25g of Formula 3-2 was added to a four-necked flask. While stirring at 300rpm, 26.5g of polycaprolactone (molecular weight 530) was slowly added dropwise to a constant-pressure funnel over 1 hour. Simultaneously, 1 drop of dibutyltin dilaurate (DBTDL) was added to the flask using a 5mL disposable dropper. The total reaction time was 2 hours. Then, 9.14g of butanone oxime and 51g of diethylene glycol butyl ether acetate were slowly added dropwise to a constant-pressure funnel over 30 minutes. The total reaction time was 2 hours. The product was then discharged. The NCO value was 6.93%.

[0077] Component B7: Compared with the preparation of B1, the only difference is that the solvent is replaced with an equal weight of xylene, and everything else is the same as the preparation of B1.

[0078] 1.3: Preparation of Conductive Powder Dispersions

[0079] The present invention also provides a method for preparing a conductive powder dispersion that cures rapidly at low temperature: component A and component B are added to a solvent in sequence and stirred thoroughly, and then the dispersion is obtained by grinding thoroughly with a three-roll mill.

[0080] Furthermore, solvents can be added.

[0081] The following is the specific implementation plan:

[0082] Example 1

[0083] Step (1): Preparation of component A:

[0084] Step (1-a): Preparation of ternary monomer copolymer composed of monomer a, monomer b1, and monomer b2

[0085] Copolymers of Formula 1 (monomer a) and Formula 2a (R1 is methyl, Formula 2-2 monomer (monomer b2)) and Formula 2b (R1 is methyl, R3 is ethylene, Formula 2-1 monomer (monomer b1)) as monomers polymerized;

[0086] Under a nitrogen atmosphere, 30g of butanone was added to a four-necked flask. Separately, 50g of formula 1, 20g of formula 2a, and 30g of formula 2b were dissolved in 50g of butanone and slowly added dropwise over a constant pressure funnel for 2 hours. Simultaneously, 4.5g of benzoyl peroxide (BPO) and 20g of butanone were slowly added dropwise to the four-necked flask over 4 hours. The reaction temperature was 80℃, and the total reaction time was 12 hours before discharge. The weight-average molecular weight (Mw) was 35000-45000 Da, and the solid content was 50%.

[0087] Step (1-b): Coating:

[0088] 20g of nano silver powder (D50 = 300nm, tap density 5.16g / mL) was mixed with 100mL of anhydrous ethanol and stirred to disperse it evenly. 2.5g of the copolymer obtained in step 1-a (the weight ratio of nano silver powder to copolymer was 1:0.125) was added, stirred for 30min, and ultrasonically dispersed for 1h. Finally, it was placed in a vacuum drying oven for drying to obtain modified silver powder 1 coated with copolymer.

[0089] Step (2): Preparation of conductive powder dispersion

[0090] Weigh 0.7g of component B (component B1), then add 9.3g of component A (modified silver powder 1 obtained in step 1-b). After thorough stirring, grind thoroughly using a three-roll mill to obtain a conductive powder dispersion.

[0091] The obtained dispersion was screen-printed onto a blue film silicon wafer and cured at 140°C for 10 min. The results are shown in Table 1.

[0092] Example 2

[0093] Compared with Example 1, component B was changed to component B2 obtained by the above method. All other operations, parameters and tests were the same as in Example 1. The results are shown in Table 1.

[0094] Example 3

[0095] Compared with Example 1, component B was changed to component B3 obtained by the above method. All other operations, parameters and tests were the same as in Example 1. The results are shown in Table 1.

[0096] Example 4

[0097] Compared with Example 1, the only difference is that the amount of component B1 is changed to 0.5g and 0.2g of diethylene glycol butyl ether acetate is added. All other operations, parameters and tests are the same as in Example 1. The results are shown in Table 1.

[0098] Example 5

[0099] Compared with Example 1, the only difference is that the copolymer in component A is replaced with a binary combination monomer copolymer of monomers a and b2. That is, monomer b1 is missing in the preparation process of the copolymer, and the missing part is made up by mass of monomer b2. Other operations, parameters and tests are the same as in Example 1. The results are shown in Table 1.

[0100] Example 6

[0101] Compared with Example 1, component B was changed to component B6 obtained by the above method. All other operations, parameters and tests were the same as in Example 1. The results are shown in Table 1.

[0102] Example 7

[0103] Compared with Example 1, the ratio of component A and component B was changed, with component A being 9g and component B being 1g. All other operations, parameters, and tests were the same as in Example 1, and the results are shown in Table 1.

[0104] Example 8

[0105] Compared with Example 1, the only difference is that in step 2, component B is component B5 (NCO content is 3.52%). All other operations, parameters, and tests are the same as in Example 1. The results are shown in Table 1.

[0106] Example 9

[0107] Compared with Example 1, the only difference is that in step 2, component B is component B4 (NCO content is 25.30%). All other operations, parameters, and tests are the same as in Example 1. The results are shown in Table 1.

[0108] Example 10

[0109] Compared with Example 1, the only difference is that in step 2, component B is component B7. All other operations, parameters, and tests are the same as in Example 1. The results are shown in Table 1.

[0110] Comparative Example 1

[0111] Compared with Example 1, the only difference is that in step 2, component B is replaced with 0.21g of bisphenol A epoxy resin (DER331), 0.01g of DMP-30, and 0.48g of diethylene glycol butyl ether acetate. All other operations and parameters are the same as in Example 1.

[0112] The dispersion prepared in Comparative Example 1 was screen-printed onto a blue silicon wafer and cured at 190°C for 10 min. The results are shown in Table 1.

[0113] Comparative Example 2

[0114] Compared with Example 1, the only difference is that in step 2, component B is replaced with 0.21g of bisphenol A epoxy resin (DER331), 0.01g of DMP-30, and 0.48g of diethylene glycol butyl ether acetate. All other operations, parameters, and tests are the same as in Example 1, and the results are shown in Table 1.

[0115] Comparative Example 3

[0116] Compared with Example 1, the only difference is that in step 2, component B is replaced with 0.7g of divalent ester DBE; all other operations, parameters, and tests are the same as in Example 1, and the results are shown in Table 1.

[0117] Comparative Example 4

[0118] Compared to Example 1, the only difference is that component A was replaced with an equal mass of commercially available ordinary silver powder. All other operations, parameters, and tests were the same as in Example 1, and the results are shown in Table 1.

[0119] The line resistance of the above-mentioned solidified and sintered grid material was tested with an external meter, the grid thickness was tested with a thickness gauge, and the volume resistivity was calculated. The adhesion was tested using the cross-cut adhesion test, and the results are shown in Table 1.

[0120] Table 1

[0121]

[0122] As shown in Table 1, the conductive powder dispersion provided by the present invention can achieve synergy by pre-modifying the conductive powder with the copolymer and then controlling component B and its NCO value. It can be rapidly cured at a low temperature of 140℃ for 10 minutes, and has good conductivity and high adhesion. The volume resistivity can be less than 7.36 μΩ·cm, the adhesion can reach 5B, and it is not easy to fall off.

[0123] As shown in the table above, compared with the epoxy resin and curing agent slurry system of Comparative Examples 1-2, Examples 1-10 can be rapidly cured at a low temperature of 140°C and have low volume resistivity and high adhesion.

[0124] As can be seen from Example 1 and Comparative Example 4, modifying the conductive powder with the copolymer described in this invention in advance can enhance its synergy with component B, improve the printing performance of the conductive powder dispersion, and obtain better low-temperature curing efficiency and effect, as well as enhance the adhesion and low resistivity of low-temperature rapid curing.

[0125] Examples 1-3 and 8-9 demonstrate that controlling the NCO value of component B within a preferred range results in superior component synergy, rapid curing at low temperatures, and improved adhesion and low resistivity. Furthermore, Examples 1 and 10 show that introducing a preferred solvent during the preparation of component B further optimizes its physicochemical properties, enhances its synergistic effect with component A, and achieves superior low-temperature curing efficiency and results.

Claims

1. A low-temperature, rapidly curing conductive powder dispersion, characterized in that, It includes 80-99 parts by weight of component A and 0.01-10 parts by weight of component B; component A is a copolymer-modified conductive powder; component B is end-capped polyurethane, and the NCO value therein is controlled in the range of 3%-26%. In component A, the copolymer is obtained by polymerization of monomer a of formula 1 and monomer b of formula 2; R1 is H or a C1-C6 alkyl group; R2 is either hydroxyalkoxy or amino.

2. The low-temperature rapid-curing conductive powder dispersion as described in claim 1, characterized in that, The monomer b includes monomer b1 of formula 2-1 and / or monomer b2 of formula 2-2; In Formula 2-1, R1 is H, methyl, or ethyl; R3 is C1 to C2. 10 Alkylene; In Formula 2-2, R1 is H, methyl, or ethyl; Preferably, the monomer b includes monomer b1 and monomer b2; more preferably, the mass ratio of monomer b1 to monomer b2 in monomer b is 5-50:10-50.

3. The low-temperature rapid-curing conductive powder dispersion as described in claim 2, characterized in that, The weight ratio of monomer a to monomer b is (20-80):(15-100); preferably (20-80):(80-20). Preferably, monomer a and monomer b undergo polymerization with the assistance of an initiator; Preferably, the initiator is a free radical initiator; Preferably, the polymerization temperature is 70-90℃.

4. The low-temperature rapid-curing conductive powder dispersion as described in claim 1, characterized in that, The weight-average molecular weight (Mw) of the copolymer is 35,000 to 45,000 Da.

5. The low-temperature rapid-curing conductive powder dispersion as described in claim 1, characterized in that, In component A, the conductive powder is at least one of silver powder, copper powder, silver-coated copper powder, silver-coated aluminum powder, and silver-coated nickel powder; Preferably, the copolymer-modified conductive powder is prepared by dispersing and modifying conductive powder and the copolymer with a solvent, followed by solvent removal; Preferably, the weight ratio of the conductive powder to the copolymer is 1:0.02 to 0.

5.

6. The low-temperature rapid-curing conductive powder dispersion as described in claim 1, characterized in that, The component B is obtained by polymerizing raw materials c and d according to Formula 3, followed by adding a mixture of end-capping agent and organic solvent for end-capping reaction. The raw material d is polyester polyether and / or polyester polyol. The R4 mentioned is C1 to C 10 The carbon chain, substituted or unsubstituted non-aromatic ring, substituted or unsubstituted aromatic ring; the non-aromatic ring is at least one of saturated carbon monocyclic ring, bridged ring, spirocyclic ring, saturated carbon heterocyclic ring, and partially unsaturated carbon heterocyclic ring; Preferably, the raw material c includes at least one of raw material c-1 of formula 3-1, raw material c-2 of formula 3-2, and raw material c-3 of formula 3-3; The R5 mentioned is H or C1~C 10 Alkyl groups; where n is an integer from 3 to 8.

7. The low-temperature rapid-curing conductive powder dispersion as described in claim 6, characterized in that, Catalysts were added during the polymerization reaction of raw materials c and d. Preferably, the catalyst comprises dibutyltin dilaurate; Preferably, the capping agent includes at least one of methyl ethyl oxime, phenol, caprolactam, and malonate; Preferably, the organic solvent includes one or more of butanone, acetone, cyclohexanone, isophorone, diethylene glycol butyl ether ester, diethylene glycol butyl ether, dodecyl alcohol ester, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether and dimethyl adipate, N,N-dimethylformamide, ethyl carbitol acetate, dimethyl sulfoxide, toluene, cyclohexane, n-hexane or a mixture of diesters (DBE); Preferably, the NCO value of component B ranges from 5% to 25%, and more preferably from 9% to 20%.

8. The low-temperature rapid-curing conductive powder dispersion according to any one of claims 1 to 7, characterized in that, It also contains component C, which is an organic solvent, in parts by weight less than or equal to 10 parts; Preferably, component C includes one or more of butanone, acetone, cyclohexanone, isophorone, diethylene glycol butyl ether ester, diethylene glycol butyl ether, dodecyl alcohol ester, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether and dimethyl adipate, N,N-dimethylformamide, ethyl carbitol acetate, dimethyl sulfoxide, toluene, cyclohexane, n-hexane or a mixture of diesters (DBE).

9. A method for preparing a low-temperature, rapidly curing conductive powder dispersion according to any one of claims 1 to 8, characterized in that, The ingredients are mixed together.

10. The application of the low-temperature rapid-curing conductive powder dispersion according to any one of claims 1 to 8 in the preparation of low-temperature curing photovoltaic cell electrodes, characterized in that, The conductive powder dispersion that cures rapidly at low temperatures is coated onto the surface of a substrate and then cured at low temperatures.

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