Conductive ink as well as preparation method and application thereof

Abstract

The invention discloses conductive ink and a preparation method and application thereof, and the conductive ink comprises the following components by mass: 4%-10% of a composite conductive filler, 10%-15% of a binder, 0.5%-3% of a dispersant, 0%-2% of a pore-foaming agent, 69%-85% of a solvent, 0-0.8% of a leveling agent, and 0.2%-0.8% of an antifoaming agent. The composite conductive filler comprises at least two of a nanowire-shaped conductive filler, a sheet-shaped conductive filler and a granular spherical conductive filler; the ratio T / A of the tap density to the apparent density of the composite conductive filler is lower than 1.5, and the specific surface area BET of the composite conductive filler is 32-60 m < 2 > / g. By compounding the conductive fillers with different morphologies, the flowability of the conductive ink is improved, and a flat conductive coating with high filler content and high tensile conductivity can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive inks, and in particular to a conductive ink and a preparation method and application thereof. Background Art

[0002] Conductive inks are widely used in the electronics, packaging, automotive, and energy industries. Printing on different substrates requires different performance from the conductive inks. Printing conductive coatings on flexible substrates such as wearable devices and fabrics requires the following inks: (1) high adhesion to flexible substrates (such as silicone, nylon, and polyester); (2) high softness of the conductive coating; (3) high tensile strength of the conductive coating; (4) low effect on conductivity when the conductive coating is stretched; and (5) low irritation to human skin. Currently, there are few reports on conductive inks based on flexible substrates, and their performance cannot meet the above requirements.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The present invention provides a conductive ink, which aims to improve the softness, flatness, tensile strength and conductive stability of a conductive coating.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a conductive ink comprising the following components, calculated by mass: 4% to 10% composite conductive filler, 10% to 15% binder, 0.5% to 3% dispersant, 0% to 2% porogen, 69% to 85% solvent, 0% to 0.8% leveling agent, and 0.2% to 0.8% defoamer; the composite conductive filler comprises at least two of nanowire conductive fillers, flake conductive fillers, and granular spherical conductive fillers; the ratio of tap density to bulk density (T / A) of the composite conductive filler is less than 1.5, and the specific surface area (BET) of the composite conductive filler is 32 to 60 m 2 / g.

[0007] The conductive ink provided by the present invention contains a composite conductive filler, and the composite conductive filler contains at least two of nano-wire conductive fillers, sheet-like conductive fillers, and granular spherical conductive fillers. The nano-wire conductive filler is beneficial to improving the softness and tensile properties of the conductive coating obtained after printing, and the sheet-like conductive filler is beneficial to increasing the contact area with the substrate and improving the adhesion ability; the granular spherical conductive filler has high processing fluidity and can be filled between sheet-like and / or linear conductive fillers, increasing the filler density without affecting the viscosity too much. The compounding of various shapes in the composite conductive filler can improve the filling performance of the filler. Furthermore, the ratio of the tap density to the loose density of the composite conductive filler is lower than 0.8, which is beneficial to improving the packing density and packing uniformity of the conductive filler particles in the conductive coating obtained after printing, so that it can take into account high conductivity, conductivity during stretching, and high coating smoothness. In addition, the BET specific surface area of the composite conductive filler provided by the present invention is as high as 32~60m 2 / g, which makes it have good adhesion to the substrate and helps to improve the stability of the coating.

[0008] In some embodiments, in the composite conductive filler, the mass ratio of nanowire conductive filler, flake conductive filler, and granular spherical conductive filler is 50%~80%: 5%~10%: 10%~40%.

[0009] In some embodiments, the conductive filler contains at least one of the following elements: silver, carbon, and copper.

[0010] In some embodiments, the nanowire-shaped conductive filler is at least one of silver nanowires, copper nanowires, carbon nanowires, silver-carbon composite nanowires, and zinc-carbon composite nanowires.

[0011] In some embodiments, the flake-shaped conductive filler is at least one of graphene, graphite flakes, silver flakes, and copper flakes.

[0012] In some embodiments, the granular spherical conductive filler is at least one of acetylene black, carbon black, silver powder, copper powder, silver-copper composite powder, silver-carbon composite powder, and copper-carbon composite powder.

[0013] In some embodiments, the conductive ink has a viscosity of 8 to 20 cP.

[0014] In some embodiments, the binder is one of hydroxypropyl methylcellulose, acrylic resin, epoxy resin, and phenolic resin.

[0015] In some embodiments, the dispersant is at least one of polyoxyethylene ether, polyoxypropylene ether, polyepoxysuccinic acid or its salt, and polyaspartic acid or its salt. The dispersant provided by the present invention has a good dispersing effect on conductive fillers, is relatively low in toxicity, and has soft molecular segments, which facilitates the production of a soft conductive coating and improves tensile stability.

[0016] In some embodiments, the porogen is at least one of propylene glycol methyl ether, n-butyl acetate, propylene glycol methyl ether acetate, and diacetone alcohol. The present invention selects an organic compound with a boiling point above 120°C as the porogen. After printing, the film is subjected to a staged heat treatment. In the low-temperature stage, the solvent evaporates, forming a smooth film layer through the cross-linking reaction and the action of the leveling agent. In the high-temperature stage, the porogen begins to vaporize due to heat, forming a uniform porous structure on the surface of the film layer. This porous structure can absorb applied strain, improving overall stretchability and mechanical stability.

[0017] In some embodiments, the solvent is at least one of water, ethanol, N,N-dimethylformamide, and N-methylpyrrolidone.

[0018] In some embodiments, the leveling agent is oil-based BYK-333.

[0019] In some embodiments, the defoaming agent is BYK-028, BYK-065, or Dow Corning DC-69.

[0020] In a second aspect, the present invention provides a method for preparing the conductive ink according to any of the above embodiments, comprising the following steps:

[0021] (1) At least two of the nanowire conductive filler, the flake conductive filler, and the granular spherical conductive filler are mixed in ethanol, polyvinyl pyrrolidone (PVP) is added and mechanically dispersed, and then acetone is added, and the mixture is allowed to stand and solid-liquid separation is performed to obtain a precipitate; the precipitate is dispersed again in ethanol, and the above operation is repeated 2 to 3 times to obtain a uniformly mixed precipitate, which is redispersed in a solvent, and a dispersant is added, and mechanical dispersion is performed to obtain phase A.

[0022] In some embodiments, the mixing ratio of the conductive filler or precipitate to ethanol is 1 mg: 10-20 mL according to the solid-liquid ratio.

[0023] In some embodiments, the mixing ratio of PVP to ethanol is 0.5-2:100 by mass.

[0024] In some embodiments, the mechanical dispersion is at least one of ultrasonic dispersion, vibration dispersion, and stirring dispersion.

[0025] In some embodiments, the volume ratio of acetone to ethanol is 1:2-4.

[0026] (2) Mechanically dispersing the binder in the solvent to obtain phase B;

[0027] (3) Mechanically dispersing the porogen, leveling agent, and defoamer in a solvent to obtain phase C;

[0028] (4) Phase B and phase C are mixed, and then phase A is added for mechanical mixing, and conductive ink is obtained after degassing.

[0029] In a third aspect, the present invention provides an embodiment of the conductive ink according to any of the above embodiments, comprising the following steps:

[0030] (1) Applying conductive ink to a flexible substrate using screen printing;

[0031] (2) The printed flexible substrate obtained in step (1) is subjected to a segmented heat treatment, including a first segment and a second segment, wherein the temperature of the first segment is 90-115°C and the time is 0.5-1h; the temperature of the second segment is 120-150°C and the time is 10-30min.

[0032] The flexible substrate includes polyester fabric, polyester film, silica gel, cotton fabric, cotton-polyester blended fabric or leather.

[0033] The present invention has the following beneficial effects:

[0034] (2) The present invention provides a conductive ink, which improves the fluidity of the conductive ink by compounding conductive fillers of different morphologies, and is conducive to obtaining a conductive coating with high filler content but high tensile conductivity and flatness.

[0035] (3) The present invention provides a method for preparing a conductive ink, which improves the mixing uniformity of the components in the composite conductive filler through multiple dispersion-precipitation cycles and the addition of a dispersant, thereby improving the compounding effect.

[0036] (4) The present invention provides an embodiment of a conductive ink, wherein the conductive ink is applied to the surface of a flexible substrate and subjected to a two-stage heat treatment. The porous structure formed thereby improves the stability of the conductivity during stretching, and the coating has high tensile cycle stability and is not prone to fracture and failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is a SEM image of a conductive coating prepared using the conductive ink of Example 1 in Application Example 1 of the present invention;

[0039] Figure 2 This is a SEM image of the conductive coating prepared using the conductive ink of Example 6 in Application Example 1 of the present invention. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0041] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0042] Reference herein to an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0043] In the embodiment of the present application, the term "or / and" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A or / and B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0044] In addition, the character “ / ” in this article generally indicates that the previous and next related objects are in an “or” relationship.

[0045] In the embodiments of the present application, the meaning of "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multi-layer" refers to more than two layers (including two layers), unless otherwise clearly specified and limited.

[0046] In the embodiments of the present application, “at least one” means one or more than one.

[0047] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0048] In a first aspect, the present invention provides a conductive ink comprising the following components, calculated by mass: 4% to 10% composite conductive filler, 10% to 15% binder, 0.5% to 3% dispersant, 0% to 2% porogen, 69% to 85% solvent, 0% to 0.8% leveling agent, and 0.2% to 0.8% defoamer; the composite conductive filler comprises at least two of nanowire conductive fillers, flake conductive fillers, and granular spherical conductive fillers; the ratio of tap density to bulk density (T / A) of the composite conductive filler is less than 1.5, and the specific surface area (BET) of the composite conductive filler is 32 to 60 m 2 / g.

[0049] The conductive ink provided by the present invention contains a composite conductive filler, and the composite conductive filler contains at least two of nano-wire conductive fillers, sheet-like conductive fillers, and granular spherical conductive fillers. The nano-wire conductive filler is beneficial to improving the softness and tensile properties of the conductive coating obtained after printing, and the sheet-like conductive filler is beneficial to increasing the contact area with the substrate and improving the adhesion ability; the granular spherical conductive filler has high processing fluidity and can be filled between sheet-like and / or linear conductive fillers, increasing the filler density without affecting the viscosity too much. The compounding of various shapes in the composite conductive filler can improve the filling performance of the filler. Furthermore, the ratio of the tap density to the loose density of the composite conductive filler is lower than 0.8, which is beneficial to improving the packing density and packing uniformity of the conductive filler particles in the conductive coating obtained after printing, so that it can take into account high conductivity, conductivity during stretching, and high coating smoothness. In addition, the BET specific surface area of the composite conductive filler provided by the present invention is as high as 32~60m 2 / g, which makes it have good adhesion to the substrate and helps to improve the stability of the coating.

[0050] In some embodiments, in the composite conductive filler, the mass ratio of nanowire conductive filler, flake conductive filler, and granular spherical conductive filler is 50%~80%: 5%~10%: 10%~40%.

[0051] In some embodiments, the conductive filler contains at least one of the following elements: silver, carbon, and copper.

[0052] In some embodiments, the nanowire-shaped conductive filler is at least one of silver nanowires, copper nanowires, carbon nanowires, silver-carbon composite nanowires, and zinc-carbon composite nanowires.

[0053] In some embodiments, the flake-shaped conductive filler is at least one of graphene, graphite flakes, silver flakes, and copper flakes.

[0054] In some embodiments, the granular spherical conductive filler is at least one of acetylene black, carbon black, silver powder, copper powder, silver-copper composite powder, silver-carbon composite powder, and copper-carbon composite powder.

[0055] In some embodiments, the conductive ink has a viscosity of 8 to 20 cP.

[0056] In some embodiments, the binder is one of hydroxypropyl methylcellulose, acrylic resin, epoxy resin, and phenolic resin.

[0057] In some embodiments, the dispersant is at least one of polyoxyethylene ether, polyoxypropylene ether, polyepoxysuccinic acid or its salt, and polyaspartic acid or its salt. The dispersant provided by the present invention has a good dispersing effect on conductive fillers, is relatively low in toxicity, and has soft molecular segments, which facilitates the production of a soft conductive coating and improves tensile stability.

[0058] In some embodiments, the porogen is at least one of propylene glycol methyl ether, n-butyl acetate, propylene glycol methyl ether acetate, and diacetone alcohol. The present invention selects an organic compound with a boiling point above 120°C as the porogen. After printing, the film is subjected to a staged heat treatment. In the low-temperature stage, the solvent evaporates, forming a smooth film layer through the cross-linking reaction and the action of the leveling agent. In the high-temperature stage, the porogen begins to vaporize due to heat, forming a uniform porous structure on the surface of the film layer. This porous structure can absorb applied strain, improving overall stretchability and mechanical stability.

[0059] In some embodiments, the solvent is at least one of water, ethanol, N,N-dimethylformamide, and N-methylpyrrolidone.

[0060] In some embodiments, the leveling agent is oil-based BYK-333.

[0061] In some embodiments, the defoaming agent is BYK-028, BYK-065, or Dow Corning DC-69.

[0062] In a second aspect, the present invention provides a method for preparing the conductive ink according to any of the above embodiments, comprising the following steps:

[0063] (1) At least two of the nanowire conductive filler, the flake conductive filler, and the granular spherical conductive filler are mixed in ethanol, polyvinyl pyrrolidone (PVP) is added and mechanically dispersed, and then acetone is added, and the mixture is allowed to stand and solid-liquid separation is performed to obtain a precipitate; the precipitate is dispersed again in ethanol, and the above operation is repeated 2 to 3 times to obtain a uniformly mixed precipitate, which is redispersed in a solvent, and a dispersant is added, and mechanical dispersion is performed to obtain phase A.

[0064] In some embodiments, the mixing ratio of the conductive filler or precipitate to ethanol is 1 mg: 10-20 mL according to the solid-liquid ratio.

[0065] In some embodiments, the mixing ratio of PVP to ethanol is 0.5-2:100 by mass.

[0066] In some embodiments, the mechanical dispersion is one of ultrasonic dispersion, vibration dispersion, and stirring dispersion.

[0067] In some embodiments, the volume ratio of acetone to ethanol is 1:2-4.

[0068] (2) Mechanically dispersing the binder in the solvent to obtain phase B;

[0069] (3) Mechanically dispersing the porogen, leveling agent, and defoamer in a solvent to obtain phase C;

[0070] (4) Phase B and phase C are mixed, and then phase A is added for mechanical mixing, and conductive ink is obtained after degassing.

[0071] In a third aspect, the present invention provides an embodiment of the conductive ink according to any of the above embodiments, comprising the following steps:

[0072] (3) Applying conductive ink to a flexible substrate using screen printing;

[0073] (4) The printed flexible substrate obtained in step (1) is subjected to a segmented heat treatment, including a first segment and a second segment, wherein the temperature of the first segment is 90-115°C and the time is 0.5-1 hour; the temperature of the second segment is 120-150°C and the time is 10-30 minutes.

[0074] The flexible substrate includes polyester fabric, polyester film, silica gel, cotton fabric, cotton-polyester blended fabric or leather.

[0075] Advantages and positive effects:

[0076] (5) The present invention provides a conductive ink, which improves the fluidity of the conductive ink by compounding conductive fillers of different morphologies, and is conducive to obtaining a conductive coating with high filler content but high tensile conductivity and flatness.

[0077] (6) The present invention provides a method for preparing a conductive ink, which improves the mixing uniformity of the components in the composite conductive filler through multiple dispersion-precipitation cycles and the addition of a dispersant, thereby improving the compounding effect.

[0078] (7) The present invention provides an embodiment of a conductive ink, wherein the conductive ink is applied to the surface of a polyester fabric and subjected to a two-stage heat treatment. The porous structure formed thereby improves the stability of the conductivity during stretching, and the coating has high tensile cycle stability and is not prone to fracture and failure.

[0079] 6. Illustrations and Their Descriptions

[0080] Example 1

[0081] The present invention provides a conductive ink, which comprises the following components, calculated by mass: 7% composite conductive filler, 12% binder, 1.4% dispersant, 1.5% propylene glycol methyl ether, 37.2% water, 40% ethanol, 0.4% BYK-333 leveling agent, and 0.5% BYK-028 defoaming agent.

[0082] The composite conductive filler is a mixture of silver nanowires, silver flakes, and carbon black in a 60%:10%:30% weight ratio. The silver nanowires have an average diameter of 90 nm and an average length of 20 μm and were purchased from Beijing Zhongke Keyou Technology Co., Ltd. The silver flakes have an average flake diameter of 2.4 μm and were also purchased from Beijing Zhongke Keyou Technology Co., Ltd. The carbon black has a median particle size (D50) of 40 nm. The defoamer and leveling agent were purchased from BYK Additives GmbH in Germany.

[0083] Among them, the binder is water-based acrylic resin with a solid content of 44%, which was purchased from Guangdong Xidun New Materials Technology Co., Ltd.

[0084] The dispersant is sodium polyepoxysuccinate with a molecular weight of 1000 g / mol, which was purchased from Xingrui Environmental Technology Co., Ltd.

[0085] The preparation method of conductive ink comprises the following steps:

[0086] (1) Various conductive fillers were mixed according to the formula to obtain a composite conductive filler, which was then dispersed in ethanol A. PVP (molecular weight 50,000 g / mol) was added and ultrasonically dispersed for 0.5 h. Acetone was then added, and the mixture was allowed to stand and solid-liquid separation was performed to obtain a precipitate. The precipitate was dispersed again in ethanol A, and the above operation was repeated 3 times to obtain a uniformly mixed precipitate. The precipitate was dispersed again in ethanol B, and a dispersant was added. Phase A was obtained by ultrasonically dispersing the precipitate for 0.5 h.

[0087] Among them, the mixing ratio of the conductive filler or precipitate and ethanol A is 1 mg:15 mL according to the solid-liquid ratio; ethanol B is added according to the formula amount (35% of the conductive ink); the mixing ratio of PVP and ethanol A is 1:100 according to the mass ratio; and the volume ratio of acetone to ethanol A is 1:3.

[0088] (2) Stir and disperse the adhesive in water to obtain phase B; the amount of water in phase B is 1 / 3 of that in the conductive ink.

[0089] (3) Mechanically stir the porogen, leveling agent and defoamer into the remaining water to obtain phase C.

[0090] (4) Phase C is added to phase B under stirring conditions and stirred evenly, then phase A is added and dispersed by ultrasonic vibration for 1 hour, and the conductive ink is obtained after degassing.

[0091] The bulk density of the composite conductive filler is measured according to the funnel method in GB / T 31057.1-2014 "Physical property test of granular materials Part 1: Measurement of bulk density"; the tap density is measured according to GB / T 31057.2-2018 "Physical property test of granular materials Part 2: Measurement of tap density"; the specific surface area BET is measured according to GB / T 13390-2008 "Metal powders - Determination of specific surface area - Nitrogen adsorption method".

[0092] The bulk density of the composite conductive filler is 1.26 g / cm 3 , tap density is 1.50g / cm 3 , the ratio of tap density to bulk density (T / A) is 0.84, and BET is 35m 2 / g.

[0093] Example 2

[0094] The difference from Example 1 is that the composite conductive filler is a mixture of silver nanowires, flake graphite, and nanosilver particles in a mass ratio of 50%:10%:40%; the silver nanowires have an average diameter of 90 nm and an average length of 20 μm and are purchased from Beijing Zhongke Keyou Technology Co., Ltd.; the nanosilver particles have an average particle size of 200 nm and are purchased from Beijing Zhongke Keyou Technology Co., Ltd.; and the flake graphite has an average sheet diameter of 3 μm and is purchased from Baijiaer Nano New Materials Co., Ltd. The ratio of the tap density to the bulk density (T / A) of the composite conductive filler is 1.42, and the BET is 54 m 2 / g.

[0095] Example 3

[0096] The difference from Example 1 is that the composite conductive filler is a mixture of silver nanowires, flake graphite, and nanosilver particles in a mass ratio of 65%:8%:27%; the silver nanowires have an average diameter of 90 nm and an average length of 20 μm and are purchased from Beijing Zhongke Keyou Technology Co., Ltd.; the nanosilver particles have an average particle size of 200 nm and are purchased from Beijing Zhongke Keyou Technology Co., Ltd.; and the flake graphite has an average sheet diameter of 3 μm and is purchased from Baijiaer Nano New Materials Co., Ltd. The ratio of the tap density to the bulk density (T / A) of the composite conductive filler is 1.21, and the BET is 43 m 2 / g.

[0097] Example 4

[0098] The present invention provides a conductive ink, which comprises the following components, calculated by mass: 4% composite conductive filler, 10% hydroxypropyl methylcellulose, 0.5% polyaspartic acid, 1% n-butyl acetate, 43.7% water, 40% ethanol, and 0.8% BYK-065 defoaming agent.

[0099] The composite conductive filler is a mixture of silver nanowires and graphene with a mass ratio of 80%:20%. The silver nanowires have an average diameter of 90 nm and an average length of 20 μm and were purchased from Beijing Zhongke Keyou Technology Co., Ltd. The graphene sheet diameter is ≤3 μm and the specific surface area is 750-850 m 2 / g, purchased from Shandong LiTe Nanotechnology Co., Ltd.

[0100] Hydroxypropyl methylcellulose, viscosity 8000 mcP, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0101] Sodium polyaspartate, molecular weight 4000 g / mol, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0102] The preparation method of the conductive ink is the same as that in Example 1.

[0103] The ratio of tap density to bulk density (T / A) of the composite conductive filler is 0.62, and the BET is 32m 2 / g.

[0104] Example 5

[0105] The present invention provides a conductive ink, which includes the following components, calculated by mass: 10% composite conductive filler, 15% water-based polyurethane resin, 3% polyoxyethylene lauryl ether, 2% diacetone alcohol, 29% water, 40% ethanol, 0.8% BYK-333 leveling agent, and 0.2% Dow Corning DC-69 defoaming agent.

[0106] The composite conductive filler is a mixture of flake graphite and copper powder with a mass ratio of 50%:50%. The flake graphite has an average sheet diameter of 3 μm and was purchased from Baijiaer Nano New Materials Co., Ltd. The average particle size of the nano copper powder is 500 nm and the BET is 4.5 μm. 2 / g, purchased from Beijing Dekedao Gold Technology Co., Ltd.

[0107] Waterborne polyurethane resin, SEAPUR 50K09, was purchased from Guangdong Xidun New Material Technology Co., Ltd.

[0108] Polyoxyethylene lauryl ether was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0109] The preparation method of the conductive ink is the same as that in Example 1.

[0110] The ratio of tap density to bulk density (T / A) of the composite conductive filler is 1.5, and the BET is 60m 2 / g.

[0111] Example 6

[0112] The present invention provides a conductive ink, which comprises the following components, calculated by mass: 7% composite conductive filler, 12% water-based acrylic resin, 1.4% sodium polyepoxysuccinate, 38.7% water, 40% ethanol, 0.4% BYK-333 leveling agent, and 0.5% BYK-028 defoaming agent.

[0113] Wherein, the composite conductive filler is the same as that in Example 1;

[0114] Sodium polyepoxysuccinate was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0115] The preparation method of the conductive ink is the same as that in Example 1.

[0116] Example 7

[0117] The difference from Example 1 is that the preparation method of the conductive ink includes the following steps:

[0118] (1) Various conductive fillers are mixed according to the formula to obtain a composite conductive filler, which is then dispersed in ethanol and a dispersant is added. Phase A is obtained by ultrasonically oscillating and dispersing for 0.5 h.

[0119] (2) Stir and disperse the adhesive in water to obtain phase B; the amount of water in phase B is 1 / 3 of that in the conductive ink.

[0120] (3) Mechanically stir the porogen, leveling agent and defoamer into the remaining water to obtain phase C.

[0121] (4) Phase C is added to phase B under stirring conditions and stirred evenly, then phase A is added and dispersed by ultrasonic vibration for 1 hour, and the conductive ink is obtained after degassing.

[0122] Comparative Example 1

[0123] The difference from Example 3 is that the composite conductive filler is a mixture of silver nanowires and nanosilver particles in a mass ratio of 70%:30%. The ratio of the tap density to the bulk density (T / A) of the composite conductive filler is 1.68, and the BET is 30m 2 / g.

[0124] Comparative Example 2

[0125] The difference from Example 3 is that the composite conductive filler is a mixture of silver flakes and graphene in a mass ratio of 60:40. The ratio of the tap density to the bulk density (T / A) of the composite conductive filler is 0.55, and the BET is 65m 2 / g.

[0126] Comparative Example 3

[0127] The difference from Example 3 is that no dispersant is added, and the conductive ink includes the following components, calculated by mass: 7% composite conductive filler, 12% binder, 1.5% propylene glycol methyl ether, 38.6% water, 40% ethanol, 0.4% BYK-333 leveling agent, and 0.5% BYK-028 defoaming agent.

[0128] Test Example 1 Ink Viscosity Test

[0129] The measurement was carried out according to the rotational viscosity method in GB / T 10247-2008 “Viscosity measurement method”, and the results are listed in Table 1.

[0130] Test Example 2 Ink Storage Stability Test

[0131] The storage stability of the ink was evaluated by the viscosity change rate and the average particle size change rate. The measurements were carried out in accordance with QB / T 5489-2020 "Test method for storage stability of inkjet inks". The results are listed in Table 1.

[0132] Table 1

[0133] Test samples Viscosity, cP Viscosity change rate, % Average particle size change rate, % Example 1 12 0.7 0.2 Example 2 18 0.9 0.7 Example 3 15 0.8 0.5 Example 4 6 0.5 0.4 Example 5 20 0.9 0.5 Example 6 10 0.6 0.3 Example 7 20 1.5 1.4 Comparative Example 1 10 0.6 0.4 Comparative Example 2 22 4.8 3.8 Comparative Example 3 18 2.6 2.4

[0134] As can be seen from Table 1, the viscosity of the conductive ink provided by the present invention is 8-20 cP, which meets the viscosity requirements of screen printing. Compared with Comparative Examples 1 and 3, the embodiments provided by the present invention have good storage stability. The better the storage stability, the lower the viscosity change rate and the average particle size change rate. The BET value of the composite conductive filler in the conductive ink prepared in Comparative Example 2 is higher than 60 m 2 / g, resulting in excessive surface energy of the solid particles, greater viscosity than Example 3, and lower storage stability than Example 3; Comparative Example 3 did not add a dispersant, resulting in significantly lower storage stability than Example 3. The composition of the composite conductive fillers in Examples 1 to 3 is different, resulting in differences in viscosity and storage stability. Specifically, as BET increases, the higher the viscosity of the conductive ink, the worse the storage stability. Examples 3 to 6 have the same composite conductive filler composition, but the types and contents of other components are different, which will also affect their viscosity and storage stability. Example 7 uses a different method to mix the composite conductive filler, resulting in its storage stability being worse than that of Example 3.

[0135] Application Example 1

[0136] The conductive inks of the examples and comparative examples were applied to the surface of the polyester film by screen printing, and the specific steps were as follows:

[0137] (1) Conductive ink was screen-printed on polyester film. The distance between the screen and the substrate was 2.5 mm, the scraper pressure was 0.4 MPa, the scraper was tilted 45°, and the ink was evenly scraped onto the substrate surface at a rate of 10 mm / s. The polyester film was cleaned with corona and ethanol before printing and dried.

[0138] (2) The printed polyester film was heat-treated at 100°C for 30 minutes, then transferred to 150°C for 20 minutes, and finally cooled at room temperature to obtain a polyester film printed with a conductive coating, forming a conductive coating with a film thickness of 30±0.05μm.

[0139] Application Comparative Example 3

[0140] The conductive ink of Example 3 is applied to the surface of the polyester film by screen printing. The specific steps are different from those of Application Example 1 in that, in step (2), the printed polyester film is subjected to heat treatment at 120°C for 1 hour and finally cooled at room temperature.

[0141] Test Example 3: Square Resistance Test

[0142] The printed material obtained in the corresponding case was used to measure the square resistance of the polyester film printed with a conductive coating according to DB13 / T 5255-2020 "Determination of the Square Resistance of Graphene Conductive Ink - Four-Probe Method". The thickness of the conductive coating was measured using a handheld digital thickness gauge, and the average value of 5 points was taken. The results are listed in Table 2.

[0143] Test Example 4 Coating Adhesion Test

[0144] The test was carried out in accordance with GB / T 9286-2021 "Paint and varnish cross-cut test" and the results are listed in Table 2

[0145] Test Example 5 Fatigue Resistance Test

[0146] A digital multimeter is used to test the initial resistance R0 of the polyester film printed with a conductive coating, and then it is repeatedly stretched to test the resistance R after 50 stretches. t , and calculate the resistance change rate after stretching several times = (R t -R0) / R0×100% was used to evaluate the fatigue resistance of the coating, and the results are listed in Table 2. The stretching procedure was as follows: the polyester film printed with the conductive coating was cut into 10×1 cm strips and stretched on a universal testing machine at a stretching rate of 20 mm / min until the strain reached 3%. After standing for 20 seconds, the tension was released and allowed to rebound naturally.

[0147] Table 2

[0148] Test samples Square resistance, Ω / sq Adhesion, grade Resistance change rate, % Example 1 5 4 0.6 Example 2 3 5 1.2 Example 3 2 4 0.8 Example 6 5 5 1.7 Example 7 7 3 2.1 Comparative Example 1 10 2 4.5 Comparative Example 2 8 5 0.8 Comparative Example 3 12 1 5.2

[0149] From the data in the table, it can be seen that the conductive coating formed on the polyester film by the conductive graphite provided by the present invention has good conductivity, adhesion and fatigue resistance. Since the composite conductive filler in Comparative Example 1 has a T / A greater than 1.5, its processing fluidity is poor and it is difficult to level, resulting in local unevenness of the coating, so its adhesion to the substrate is low, the square resistance is large, and the resistance change rate is large; Comparative Example 3 does not add a dispersant, so that the conductive filler in the conductive ink has poor dispersibility and is easy to agglomerate, resulting in local unevenness of the coating, so the square resistance is large, the adhesion is low, and the resistance change rate is large. Example 6 does not add a porogen relative to Example 1, and the square resistance and adhesion are similar, but the resistance change rate is large; Comparative Example 3 does not add a dispersant, so the conductive filler in the conductive ink has poor dispersibility and is easy to agglomerate, resulting in local unevenness of the coating, so the square resistance is large, the adhesion is low, and the resistance change rate is large. Figure 1 and 2 The morphologies of the conductive coatings formed in Examples 1 and 6 are shown, respectively. As can be seen, Example 1 possesses a large number of evenly distributed pores, which absorb applied strain and improve overall stretchability and mechanical stability. The conductive coating formed in Example 6, on the other hand, only has a few irregular pores locally due to uneven processing. Due to the different preparation method used in Example 7 compared to Example 1, the distribution uniformity of the composite conductive filler is less uniform, resulting in higher sheet resistance, lower adhesion, and a greater resistance change rate.

[0150] Application Example 2

[0151] The conductive inks of the examples and comparative examples were applied to the polyester surface by screen printing, and the specific steps were as follows:

[0152] (1) Conductive ink was screen-printed on polyester. The distance between the screen and the substrate was 2.5 mm, the scraper pressure was 0.45 MPa, the scraper was tilted 30°, and the ink was evenly scraped onto the substrate surface at a rate of 10 mm / s. The polyester (150D × 150 D) was soaked in ethanol and dried before printing.

[0153] (2) The printed polyester was heat treated at 90°C for 1 hour, then transferred to 130°C for 30 minutes, and finally cooled at room temperature to obtain a polyester film printed with a conductive coating.

[0154] Test Example 6 Coating Stiffness Test

[0155] The test was carried out using an automatic fabric stiffness tester in accordance with GB / T18318-2001 “Textile fabrics - Determination of bending length”. The results are listed in Table 3.

[0156] Table 3

[0157] Test samples Stiffness Example 1 46.8 Example 2 48.4 Example 3 40.5 Example 4 41.6 Example 6 50.9 Comparative Example 2 58.8 Comparative Example 3 46.7

[0158] As can be seen from the table, the conductive ink provided by the present invention can form a soft conductive coating when applied on a fabric. The composite conductive filler in Comparative Example 2 has a large specific surface area due to the large silver flake content, resulting in a high stiffness of the conductive coating. Compared with Example 3, Comparative Example 3 does not add a dispersant, and its conductive coating exhibits higher stiffness, indicating that the addition of a flexible dispersant can improve the dispersion uniformity of the conductive filler, thereby improving the softness of the coating. Compared with Example 1, Example 6 does not add a porogen, so the coating lacks a porous structure, resulting in its low softness.

[0159] In summary, the present invention provides a conductive ink suitable for screen printing, which has consistent viscosity and good storage stability. The conductive coating formed on the flexible substrate is soft, tensile-resistant, has strong adhesion and good conductive stability.

[0160] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A conductive ink, characterized in that: The invention comprises the following components, calculated by mass: 4% to 10% composite conductive filler, 10% to 15% binder, 0.5% to 3% dispersant, 0% to 2% porogen, 69% to 85% solvent, 0% to 0.8% leveling agent, and 0.2% to 0.8% defoamer; the composite conductive filler comprises at least two of nanowire conductive filler, sheet conductive filler, and granular spherical conductive filler; the ratio of the tap density to the bulk density T / A of the composite conductive filler is lower than 1.5, and the specific surface area BET of the composite conductive filler is 32 to 60 m 2 / g.

2. The conductive ink according to claim 1, characterized in that In the composite conductive filler, the mass ratio of the nanowire conductive filler, the flake conductive filler, and the granular spherical conductive filler is 50% to 80%: 5% to 10%: 10% to 40%.

3. The conductive ink according to claim 1 or 2, characterized in that: The nanowire-shaped conductive filler, the sheet-shaped conductive filler, and the particle-shaped conductive filler independently contain at least one of the following elements: silver, carbon, and copper.

4. The conductive ink according to claim 3, characterized in that The nanowire-shaped conductive filler is at least one of silver nanowires, copper nanowires, carbon nanowires, silver-carbon composite nanowires and zinc-carbon composite nanowires; And / or, the flaky conductive filler is at least one of graphene, graphite flakes, silver flakes and copper flakes; And / or, the granular spherical conductive filler is at least one of acetylene black, carbon black, silver powder, copper powder, silver-copper composite powder, silver-carbon composite powder and copper-carbon composite powder.

5. The conductive ink according to any one of claims 1 to 4, characterized in that: The viscosity of the conductive ink is 8-20 cP.

6. The conductive ink according to any one of claims 1 to 5, characterized in that: The binder is one of hydroxypropyl methylcellulose, acrylic resin, epoxy resin and phenolic resin; and / or, the dispersant is at least one of polyoxyethylene ether, polyoxypropylene ether, polyepoxysuccinic acid or its salt, and polyaspartic acid or its salt; and / or, the porogen is at least one of propylene glycol methyl ether, n-butyl acetate, propylene glycol methyl ether acetate, and diacetone alcohol; and / or, the solvent is at least one of water, ethanol, N,N-dimethylformamide and N-methylpyrrolidone; And / or, the leveling agent is oily BYK-333; And / or, the defoaming agent is BYK-028, BYK-065 or Dow Corning DC-69.

7. The method for preparing the conductive ink according to any one of claims 1 to 6, wherein: The following steps are involved: (1) At least two of the nanowire conductive filler, the flake conductive filler, and the granular spherical conductive filler are mixed in ethanol, polyvinyl pyrrolidone is added and mechanically dispersed, and then acetone is added, and the mixture is allowed to stand and solid-liquid separation is performed to obtain a precipitate; the precipitate is dispersed again in ethanol, and the above operation is repeated 2 to 3 times to obtain a uniformly mixed precipitate, which is redispersed in a solvent, and a dispersant is added, and mechanical dispersion is performed to obtain phase A; (2) Mechanically dispersing the binder in the solvent to obtain phase B; (3) Mechanically dispersing the porogen, leveling agent, and defoamer in a solvent to obtain phase C; (4) Phase B and phase C are mixed, and then phase A is added for mechanical mixing, and conductive ink is obtained after degassing.

8. The method for preparing the conductive ink according to claim 7, wherein: The mixing ratio of the conductive filler or the precipitate to the ethanol is 1 mg: 10-20 mL according to the solid-liquid ratio; And / or, the mixing ratio of the polyvinyl pyrrolidone to the ethanol is 0.5-2:100 by mass ratio; And / or, the mechanical dispersion is at least one of ultrasonic dispersion, vibration dispersion, and stirring dispersion; And / or, the volume ratio of acetone to ethanol is 1:2-4.

9. The use of the conductive ink according to claim 1, characterized in that: The conductive ink is applied to the surface of the flexible substrate by screen printing, and a conductive coating is obtained by heat treatment.

10. The use according to claim 9, characterized in that The heat treatment includes a first stage and a second stage, wherein the temperature of the first stage is 90-115°C and the time is 0.5-1 hour; the temperature of the second stage is 120-150°C and the time is 10-30 minutes; And / or, the flexible substrate includes polyester fabric, polyester film, silica gel, cotton fabric, cotton-polyester blended fabric or leather.

Images