An inkjet printing conductive ink, its preparation method and application

Abstract

The present invention belongs to the technical field of conductive inks, and discloses an inkjet-printable conductive ink, a preparation method thereof, and an application thereof. The inkjet-printable conductive ink of the present invention comprises the following components in parts by weight: based on 100 parts, 25-65 parts of modified carbon nanotubes, 2-7 parts of a photocurable resin, 2-7 parts of a photocurable monomer, 0.02-2 parts of a photoinitiator, and the balance being a solvent. In the present invention, the surface of the carbon nanotubes is first modified to introduce acrylic groups, so that the carbon nanotubes have both photocurability and greatly improved dispersibility of the carbon nanotubes, and carbon nanotubes with photocuring properties are obtained. Then, the carbon nanotubes are used to prepare an inkjet-printable conductive ink, which not only greatly improves the problem that the carbon nanotubes are difficult to disperse, obtains a conductive ink with good dispersibility, excellent electrical conductivity, stable performance, and photocurability, but also effectively improves the wear resistance of the product, and can be widely applied to fields such as circuit printing, electromagnetic shielding, electronic touch screens, and flexible displays.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive inks, and particularly relates to an inkjet-printable conductive ink, a preparation method thereof, and an application thereof. Background Art

[0002] Fields such as solar cells, electronic touch screens, light-emitting diodes, and flexible displays have developed rapidly, and the demand for flexible conductive materials is becoming wider and wider; moreover, as electronic devices become more and more sophisticated, the requirements for high-precision construction of conductive materials are also getting higher and higher. The UV inkjet printing method is increasingly widely used in industries such as flexible displays and semiconductors because it can perform high-precision construction of fixed points and fixed quantities. At present, flexible conductive materials are basically obtained by combining nano-silver, resins, and additives to form inks, and then printing or coating; even after high-temperature sintering, leaving metallic silver as the conductive medium. However, nano-silver is expensive, which will greatly increase the cost during actual application.

[0003] Compared with expensive nano-silver, carbon nanotubes have the significant advantage of being inexpensive. Carbon nanotubes are a type of carbon material with a typical layered hollow structure. The tube body of the carbon nanotubes is composed of hexagonal graphite carbon ring structural units. It is a one-dimensional quantum material with a special structure and has some special electrical properties. Its tube wall is mainly composed of several to dozens of coaxial circular tubes, and the distance between layers is fixed. Since the structure of carbon nanotubes is the same as the lamellar structure of graphite, it has good electrical properties. Existing research has applied carbon nanotubes to conductive materials in the form of fillers to obtain materials with increased conductivity. However, due to the special structure of carbon nanotubes, their compatibility with other substances is poor, the dispersion of carbon nanotubes in the mixed solution is poor, the mixed solution is unstable, and carbon nanotubes are prone to deposition. This makes the wear resistance of the final product poor, and carbon nanotubes are easily scraped off, greatly affecting the wide application of carbon nanotubes. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide an inkjet-printable conductive ink.

[0005] In the inkjet-printable conductive ink of the present invention, modified carbon nanotubes are used, and acrylic groups are introduced onto its surface through modification, so that the carbon nanotubes have both photocurability and greatly improved dispersion, thereby obtaining a conductive ink with good dispersion.

[0006] Another object of the present invention is to provide a preparation method of the above-mentioned inkjet-printable conductive ink.

[0007] In the inkjet printing conductive ink of the present invention, the carbon nanotubes are first surface-modified to obtain carbon nanotubes with photocuring properties, and then used to prepare the inkjet printing conductive ink, which not only greatly improves the problem of difficult dispersion of carbon nanotubes, but also effectively improves the wear resistance of the product.

[0008] Another object of the present invention is to provide the application of the above inkjet printing conductive ink in the fields of circuit printing, electromagnetic shielding, electronic touch screens, flexible displays, etc.

[0009] The object of the present invention is achieved by the following solutions:

[0010] An inkjet printing conductive ink, comprising the following components in parts by weight: 25-65 parts of modified carbon nanotubes, 2-7 parts of photocurable resin, 2-7 parts of photocurable monomer, 0.02-2 parts of photoinitiator, and 30-70 parts of solvent.

[0011] Further, the photocurable resin may include at least one of polyurethane acrylate resin, epoxy acrylate resin, polyester acrylate resin, acrylate resin, etc.

[0012] Further, the photocurable monomer may be an acrylate monomer with three or more functional groups, such as but not limited to trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, etc.

[0013] Further, the photoinitiator may be a conventionally used photoinitiator in the art, such as but not limited to 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,6-difluoro-3-(1H-pyrrolyl-1)phenyl)titanocene, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-(3-benzoylphenyl)propionic acid guanidine, 9-anthrylmethyl N,1-(anthraquinon-2-yl)ethylimidazole carboxylate or N-diethylcarbamate, etc.

[0014] In the inkjet printing conductive ink of the present invention, the modified carbon nanotubes are prepared from the following components in parts by weight: 30-50 parts of hydroxylated carbon nanotubes, 10-20 parts of isocyanate group acrylate, catalyst, and 20-40 parts of solvent.

[0015] Further, the hydroxylated carbon nanotubes may include but not limited to hydroxylated single-walled carbon nanotubes and hydroxylated multi-walled carbon nanotubes, etc., and the structural characteristics include but not limited to armchair-shaped nanotubes, zigzag-shaped nanotubes and chiral nanotubes, etc.

[0016] Further, the isocyanate group acrylate may include at least one of ethyl isocyanate acrylate, isocyanatoethyl methacrylate, etc.

[0017] Further, the catalyst may be a catalyst for the reaction of isocyanate and hydroxyl group conventionally used in the art, such as but not limited to organic amines, organotin catalysts, organobismuth catalysts, etc.

[0018] Further, the dosage of the catalyst may be a catalytic amount, such as 0.02-2 parts by weight.

[0019] Further, the above solvents may be the same or different and may respectively include at least one of alcohol solvents, ester solvents, ether solvents, aromatic solvents, etc.

[0020] Further, the alcohol solvent may be an alcohol solvent conventionally used in the art, and may include but not limited to methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, etc.

[0021] Further, the ester solvent may be an ester solvent conventionally used in the art, and may include but not limited to ethyl formate, propyl formate, ethyl acetate, propyl acetate, isopropyl acetate, methyl propionate, ethyl propionate, etc.

[0022] Further, the ether solvent may be an ether solvent conventionally used in the art, and may include but not limited to diethyl ether, THF, MTBE, etc.

[0023] The present invention also provides a method for preparing the above-mentioned modified carbon nanotubes, which includes mixing each component in proportion and heating and reacting to obtain.

[0024] Further, the temperature of the heating reaction may be 50-120 °C; the reaction time may be 2-10 h.

[0025] The present invention also provides a method for preparing the above-mentioned inkjet printing conductive ink, which includes mixing each component evenly in proportion to obtain.

[0026] Further, the ink after mixing can be ground.

[0027] Further, the grinding time may be 30 min-10 h.

[0028] Further, the grinding can be carried out in a conventional sand mill in the art; such as a zirconia sand mill.

[0029] Further, the inkjet printing conductive ink after grinding can be filtered to prevent large particle impurities from clogging the nozzle during subsequent use; preferably a filter paper or filter membrane with a pore size of 1 um.

[0030] Further, the preparation method of the inkjet printing conductive ink includes the following specific steps:

[0031] (1) Mix 30 - 50 parts by weight of hydroxylated carbon nanotubes, 10 - 20 parts by weight of isocyanate group acrylate, a catalyst, and 20 - 40 parts by weight of a solvent, and stir and react at 50 - 120 °C for 2 - 10 h to obtain modified carbon nanotubes;

[0032] (2) Mix 25 - 65 parts by weight of the modified carbon nanotubes prepared in step (1), 2 - 7 parts by weight of a photocurable resin, 2 - 7 parts by weight of a photocurable monomer, 0.02 - 2 parts by weight of a photoinitiator, and 30 - 70 parts by weight of a solvent, and stir evenly to obtain the inkjet printing conductive ink.

[0033] The present invention also provides an application method of the above inkjet printing conductive ink, specifically injecting the ink into an ink cartridge, and using a UV inkjet printer to deposit the ink on a substrate and cure it to obtain a printed substrate.

[0034] In the inkjet printing conductive ink of the present invention, the surface of the carbon nanotubes is modified to introduce acrylic groups, so that the carbon nanotubes have both photocurability and greatly improve the dispersibility of the carbon nanotubes, obtaining carbon nanotubes with photocuring performance, and then used to prepare the inkjet printing conductive ink, which not only greatly improves the problem that carbon nanotubes are difficult to disperse, obtains a conductive ink with good dispersibility, but also effectively improves the wear resistance of the product.

[0035] The inkjet printing conductive ink of the present invention combines inexpensive carbon nanotubes with a photocurable resin to obtain an inkjet printing ink with excellent conductivity, stable performance, and photocurability, which can be widely used in fields such as circuit printing, electromagnetic shielding, electronic touch screens, and flexible displays. Specific Embodiments

[0036] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. The materials involved in the following embodiments can be obtained from commercial channels without special instructions. The methods are conventional methods without special instructions.

[0037] In one embodiment, an inkjet printing conductive ink includes the following components in parts by weight: 25 - 65 parts of modified carbon nanotubes, 2 - 7 parts of a photocurable resin, 2 - 7 parts of a photocurable monomer, 0.02 - 2 parts of a photoinitiator, and 30 - 70 parts of a solvent.

[0038] In one embodiment, the photocurable resin may include at least one of polyurethane acrylate resin, epoxy acrylate resin, polyester acrylate resin, acrylate resin, etc. In one embodiment, the photocurable resin is polyurethane acrylate resin; in another embodiment, the photocurable resin is epoxy acrylate resin; in yet another embodiment, the photocurable resin is polyester acrylate resin.

[0039] In one embodiment, the photocurable monomer may be an acrylate monomer with trifunctionality or higher, such as but not limited to trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, etc. In one embodiment, the photocurable monomer is trimethylolpropane triacrylate; in another embodiment, the photocurable monomer is pentaerythritol triacrylate; in yet another embodiment, the photocurable monomer is dipentaerythritol hexaacrylate.

[0040] In one embodiment, the photoinitiator may be a photoinitiator commonly used in the art, such as but not limited to 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanocene, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-(3-benzoylphenyl)propionic acid guanidine, 9-anthrylmethyl N,1-(anthraquinone-2-yl)ethylimidazole carboxylate or N-diethylcarbamate, etc.

[0041] In one embodiment, the photoinitiator is 2-hydroxy-2-methyl-1-phenylpropan-1-one; in another embodiment, the photoinitiator is 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one; in yet another embodiment, the photoinitiator is 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one.

[0042] In one embodiment, the modified carbon nanotubes are prepared from the following components in parts by weight: 30-50 parts of hydroxylated carbon nanotubes, 10-20 parts of isocyanate group acrylate, catalyst, 20-40 parts of solvent.

[0043] In one embodiment, the hydroxylated carbon nanotubes may include but not limited to hydroxylated single-walled carbon nanotubes and hydroxylated multi-walled carbon nanotubes, etc., and the structural features include but not limited to armchair-shaped nanotubes, zigzag-shaped nanotubes and chiral nanotubes, etc. In one embodiment, the hydroxylated carbon nanotubes are hydroxylated single-walled carbon nanotubes; in another embodiment, the hydroxylated carbon nanotubes are hydroxylated multi-walled carbon nanotubes.

[0044] In one embodiment, the isocyanate group acrylate may include at least one of ethyl isocyanate acrylate, isocyanatoethyl methacrylate, etc. In one embodiment, the isocyanate group acrylate is ethyl isocyanate acrylate; in another embodiment, the isocyanate group acrylate is isocyanatoethyl methacrylate.

[0045] In one embodiment, the catalyst is a catalyst for the reaction of isocyanate and hydroxyl group commonly used in the art. In one embodiment, the catalyst is an organic amine; in another embodiment, the catalyst is an organotin catalyst; in still another embodiment, the catalyst is an organobismuth catalyst.

[0046] In one embodiment, the amount of the catalyst used is a catalytic amount.

[0047] In one embodiment, the solvents include at least one of alcohol solvents, ester solvents, ether solvents, aromatic solvents, etc., which may be the same or different. In one embodiment, the solvent is an alcohol solvent; in another embodiment, the solvent is an ester solvent; in still another embodiment, the solvent is an ether solvent.

[0048] In one embodiment, a method for preparing the above-mentioned modified carbon nanotubes includes mixing the components in proportion and heating them for reaction to obtain the product.

[0049] In one embodiment, the temperature of the heating reaction is 50 - 120 °C; the reaction time is 2 - 10 h.

[0050] In one embodiment, a method for preparing the above-mentioned inkjet printing conductive ink includes mixing the components in proportion and uniformly mixing them to obtain the ink.

[0051] In one embodiment, the mixed ink can be ground.

[0052] In one embodiment, the grinding time is 30 min - 10 h.

[0053] In one embodiment, the grinding is carried out in a conventional sand mill in the art; in another embodiment, the grinding is carried out in a zirconia sand mill.

[0054] In one embodiment, the inkjet printing conductive ink after grinding is filtered; in another embodiment, the inkjet printing conductive ink after grinding is filtered using a filter paper or filter membrane with a pore size of 1 μm.

[0055] In one embodiment, the method for preparing the inkjet printing conductive ink includes the following specific steps:

[0056] (1) Mix 30 - 50 parts by weight of hydroxylated carbon nanotubes, 10 - 20 parts by weight of isocyanate group acrylate, a catalyst, and 20 - 40 parts by weight of a solvent, and stir and react at 50 - 120 °C for 2 - 10 h to obtain modified carbon nanotubes;

[0057] (2) Mix 25 - 65 parts by weight of the modified carbon nanotubes prepared in step (1), 2 - 7 parts by weight of a photocurable resin, 2 - 7 parts by weight of a photocurable monomer, 0.02 - 2 parts by weight of a photoinitiator, and 30 - 70 parts by weight of a solvent, and stir evenly to obtain an inkjet printing conductive ink.

[0058] In one embodiment, a method for applying the above inkjet printing conductive ink is specifically to inject the ink into an ink cartridge, and use a UV inkjet printer to deposit the ink on a substrate and cure it to obtain a printed substrate.

[0059] Example 1:

[0060] By weight, mix 30 parts of hydroxylated carbon nanotubes, 10 parts of ethyl isocyanate acrylate, 20 parts of butyl acetate, and 0.5 part of dibutyltin dilaurate, and stir and react at 50 - 120 °C for 2 - 10 h to obtain modified carbon nanotubes A; mix 30 parts of modified carbon nanotubes A, 2 parts of a hexafunctional polyurethane acrylate resin, 2 parts of a photocurable monomer TMPTA, 2 parts of an initiator 184, and 50 parts of 4 - butyrolactone, stir evenly, transfer to a 0.2 um zirconia sand mill, grind for 2 h, and filter with a 1 um pore size filter paper to obtain an inkjet printing conductive ink A.

[0061] Example 2:

[0062] By weight, mix 50 parts of hydroxylated carbon nanotubes, 20 parts of isocyanatoethyl methacrylate, 40 parts of toluene, and 0.5 part of dibutyltin dilaurate, and stir and react at 50 - 120 °C for 2 - 10 h to obtain modified carbon nanotubes B; mix 50 parts of modified carbon nanotubes B, 3 parts of a tetrafunctional polyester acrylate resin, 2 parts of a photocurable monomer PETA, 2 parts of an initiator TPO, and 40 parts of butanol, stir evenly, transfer to a 0.2 um zirconia sand mill, grind for 2 h, and filter with a 1 um pore size filter paper to obtain an inkjet printing conductive ink B.

[0063] Example 3:

[0064] By weight, 40 parts of hydroxylated carbon nanotubes, 13 parts of isocyanate ethyl acrylate, 30 parts of butyl acetate, and 1 part of dibutyltin dilaurate were mixed and stirred at 50 - 120 °C for 2 - 10 h to obtain modified carbon nanotubes C; 65 parts of modified carbon nanotubes C, 5 parts of difunctional epoxy acrylate resin, 2 parts of photo-curing monomer PETA, 2 parts of initiator 1173, and 60 parts of propylene glycol methyl ether were mixed and stirred evenly, then transferred to a 0.2 μm zirconia bead mill for grinding for 2 h, and filtered through a 1 μm pore size filter paper to obtain inkjet printing conductive ink C.

[0065] Comparative Example 1:

[0066] By weight, 50 parts of hydroxylated carbon nanotubes, 3 parts of tetrafunctional polyester acrylate resin, 2 parts of photo-curing monomer PETA, 2 parts of initiator TPO, and 40 parts of butanol were mixed and stirred evenly, then transferred to a 0.2 μm zirconia bead mill for grinding for 2 h, and filtered through a 1 μm pore size filter paper to obtain inkjet printing conductive ink D.

[0067] Comparative Example 2:

[0068] By weight, 50 parts of nano-silver, 3 parts of tetrafunctional polyester acrylate resin, 2 parts of photo-curing monomer PETA, 2 parts of initiator TPO, and 40 parts of butanol were mixed and stirred evenly, then transferred to a 0.2 μm zirconia bead mill for grinding for 2 h, and filtered through a 1 μm pore size filter paper to obtain inkjet printing conductive ink E.

[0069] Performance Testing

[0070] The inkjet printing conductive inks prepared in the above examples were subjected to performance testing, and the test standards were as follows:

[0071] (1) Conductivity test: EN 16813-2016;

[0072] (2) Viscosity test standard: GB / T9751-1988;

[0073] (3) Original particle size: The particle size within 20 min after the ink preparation was tested with a laser particle size analyzer;

[0074] (4) Stability test: The prepared ink was sealed and stored, and left standing at 80 °C for 4 days, and its viscosity change and dispersion condition were tested;

[0075] (5) Particle size after stability test: The particle size was tested with a laser particle size analyzer;

[0076] (6) Abrasion resistance test: Inject the ink of the present invention into the ink cartridges respectively. Use a UV inkjet printer to deposit the ink on the substrate and cure it to obtain the printed substrate. Fix the substrate with the coating on the working platform of the friction tester, place the white cloth on the coating, and press a 2 cm * 2 cm grinding head with a 200-gram weight. Start the abrasion resistance test. Observe every 10 times. When black appears on the surface of the white cloth, stop the test and record the number of readings as the abrasion resistance times.

[0077] The results are shown in Table 1 below:

[0078] Table 1 Performance of Inkjet-Printed Conductive Ink

[0079] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Conductivity (s / m) 101 403 287 420 2358 Original particle size (nm) 62 60 66 86 89 Particle size after stability test (nm) 76 69 71 2451 3016 Viscosity before stability test (cps / 25°C) 23 22 23 22 24 Viscosity during stability test (cps / 25°C) 24 23 25 25 26 Stability test No precipitation No precipitation No precipitation Precipitation Precipitation Abrasion resistance (times) 260 230 250 <10 <10

[0080] As can be seen from Table 1, the inkjet-printed conductive ink prepared from inexpensive carbon nanotubes in the present invention has excellent conductive properties similar to those of the ink with nano-silver as the conductive material, and its conductivity meets the requirements of material use. In the inkjet-printed conductive ink of the present invention, by surface-modifying the carbon nanotubes and introducing acrylic groups, the compatibility between the carbon nanotubes and the system resin is improved, the dispersibility of the carbon nanotubes is greatly improved, and the original particle size of the prepared ink is small; and it has excellent stability, is not easy to agglomerate, and there will be no precipitation phenomenon after standing at high temperature for a long time, and the particle size before and after is basically unchanged. At the same time, in the inkjet-printed conductive ink of the present invention, the introduction of acrylic groups endows the carbon nanotubes with photocurability. When using a UV inkjet printer for printing, during the UV curing process, the acrylic groups on the surface of the carbon nanotubes react with the ink matrix, so that the printed coating has excellent abrasion resistance, and the abrasion resistance times can reach 260 times. That is, the inkjet-printed conductive ink of the present invention has the characteristics of excellent conductive properties, stable performance, and photocurability, and can be widely used in fields such as circuit printing, electromagnetic shielding, electronic touch screens, and flexible displays.

[0081] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An inkjet printing conductive ink, characterized in that It comprises components in the following parts by weight: 25 - 65 parts of modified carbon nanotubes, 2 - 7 parts of photocurable resin, 2 - 7 parts of photocurable monomer, 0.02 - 2 parts of photoinitiator, and 30 - 70 parts of solvent; The modified carbon nanotubes are prepared from components in the following parts by weight: 30 - 50 parts of hydroxylated carbon nanotubes, 10 - 20 parts of isocyanate group acrylate, catalyst, and 20 - 40 parts of solvent; The isocyanate group acrylate includes at least one of ethyl isocyanate acrylate and isocyanatoethyl methacrylate; The photocurable resin includes at least one of polyurethane acrylate resin, epoxy acrylate resin, polyester acrylate resin, and acrylate resin; The photocurable monomer is an acrylate monomer with trifunctionality or more.

2. The inkjet printing conductive ink according to claim 1, wherein: The preparation method of the modified carbon nanotubes includes mixing the components in proportion and heating for reaction to obtain.

3. The inkjet printing conductive ink according to claim 2, wherein: The temperature of the heating reaction is 50 - 120 °C; the reaction time is 2 - 10 h.

4. The inkjet printing conductive ink according to claim 1, characterized in that: The solvents, which may be the same or different, respectively include at least one of alcohol solvents, ester solvents, ether solvents, and aromatic solvents.

5. A method for preparing the inkjet printing conductive ink according to any one of claims 1-4, characterized in that It includes mixing the components in proportion and uniformly mixing them to obtain.

6. Application of the inkjet printing conductive ink according to any one of claims 1 - 4 in the fields of circuit printing, electromagnetic shielding, electronic touch screen, and flexible display.