A nanoimprinting conductive paste, its preparation method and application

Abstract

The present invention relates to a nanoimprint conductive paste, a preparation method thereof and an application thereof. In terms of parts by weight, the raw materials for preparing the nanoimprint conductive paste include: 2-8 parts of epoxy resin, 70-75 parts of conductive silver, 2-5 parts of functional additives and 16-20 parts of organic solvent, wherein the conductive silver includes micron silver flakes and nano silver powder. By regulating the composition of the nanoimprint conductive paste, the present invention enables the obtained nanoimprint conductive paste to have a lower sheet resistance when applied to a metal grid flexible conductive film; and the viscosity of the obtained nanoimprint conductive paste is relatively low, facilitating imprinting and scraping coating; and the curing temperature of the nanoimprint conductive paste is below 135°C, and the adhesion to the substrate after curing is above grade 4B.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive materials, and relates to a conductive paste, in particular to a nanoimprint conductive paste, a preparation method thereof and an application thereof. Background Art

[0002] Touch screens have been widely used in people's daily lives. With the in-depth development of the electronic information industry and the continuous growth of the demand for consumer electronics products, intelligent terminals such as smart phones, tablet computers, and touch-type notebooks will be further popularized, and various industrial products are also increasingly using touch operation interfaces to meet their intelligent and digital requirements.

[0003] Traditional touch screens are made by coating ITO (indium tin oxide) on a transparent substrate such as PET or peeling, and using methods such as etching and acid etching to make patterns on the ITO coating. Then, each channel in the TIO pattern is connected by a chip to record the current changes that occur during the touch process, so as to calculate the position of the touch point. However, when the surface resistance of ITO is low, there are problems of performance decline and easy fragmentation. The traditional ITO conductive film is a rigid material and is not suitable for folding mobile phones. Therefore, flexible materials are needed to replace it. Currently, the traditional material to replace ITO materials is a metal grid flexible conductive material.

[0004] The metal grid flexible conductive material is a conductive material formed by printing grid pattern grooves on a polymer film and filling the grooves with nanoimprint conductive silver paste by means of imprinting and scraping for curing. The flexibility, low surface resistance, and high light transmittance of the metal grid flexible conductive material are mainly achieved by the bend resistance, high conductivity, and ultra-fine line filling property of the nanoimprint conductive silver paste. The better the bendable performance of the nanoimprint conductive silver paste, the higher the flexibility of the metal grid flexible conductive material; the higher the conductivity of the nanoimprint conductive silver paste, the lower the surface resistance of the metal grid flexible conductive material; the smaller the particle size in the nanoimprint conductive silver paste and the lower the fillable line width, the higher the light transmittance of the metal grid flexible conductive material.

[0005] CN 113436781 A discloses an abrasion-resistant conductive paste and a preparation method thereof. The conductive paste, by weight, comprises: 0.1 - 1 part of a water-boiling adhesion promoter, 0.5 - 1 part of an anti-inking overflowing aid, 0.2 - 1 part of an antifoaming agent, 0.2 - 0.5 part of a dispersant, 0.1 - 0.2 part of a curing agent promoter, 5 - 40 parts of an organic solvent, 10 - 50 parts of an abrasion-resistant filler, 20 - 40 parts of flaky silver powder, 5 - 30 parts of a resin, and 0.5 - 0.8 part of a curing agent. By using an acrylic acid-modified polyurethane resin as a binder phase, the water-boiling performance and bending resistance of the conductive paste are improved, and it has good storage stability. Different low-temperature curing agents are compounded to ensure that the adhesion of the paste in a constant temperature and humidity environment is improved technically while other properties are maintained. By adding conductive silver powder and abrasion-resistant filler, it has high abrasion resistance and low conductivity. However, this conductive paste cannot meet the requirements for ≤3μm ultra-fine circuits.

[0006] CN 111446020 A discloses a conductive silver paste, a preparation method thereof, and a metal grid conductive film. The conductive silver paste therein consists of a liquid epoxy resin, an active diluent, a curing agent, nano silver powder, and an auxiliary agent. Among them, the content of the liquid epoxy resin is 6 - 10 parts by weight, the content of the active diluent is 1 - 4 parts by weight, the content of the curing agent is 0.2 - 1 part by weight, the content of the nano silver powder is 60 - 90 parts by weight, and the content of the auxiliary agent is 0.5 - 2 parts by weight. Since no solvent is added to the conductive silver paste, solvent volatilization does not occur during the curing stage, thus achieving the purpose of high filling amount. However, also because no solvent is added to the conductive silver paste, the process of filling the conductive silver paste into the metal grid grooves is complex, and the filling uniformity is low, making it difficult to stably carry out industrial operations.

[0007] CN 111261320 A discloses an epoxy resin-based low-temperature conductive silver paste and a preparation method thereof, including the following components in parts by weight: 55 - 75 parts by weight of silver powder, 5 - 15 parts by weight of epoxy resin, 0.3 - 10 parts by weight of a curing agent, 0.05 - 5 parts by weight of a curing promoter, 2 - 18 parts by weight of a diluent, 0.01 - 1 part by weight of an inhibitor, 0.1 - 3 parts by weight of a rheology aid, and 0.5 - 5 parts by weight of an additive. The epoxy resin-based low-temperature conductive silver paste provided has high conductivity, and has a low curing temperature and bonding strength. However, it cannot meet the requirements for ≤3μm ultra-fine circuits.

[0008] Therefore, in view of the increasing requirements for the flexibility, low surface resistance, and high light transmittance of flexible touch screens, it is necessary to provide a nanoimprint conductive silver paste that can meet the requirements for ≤3μm ultra-fine circuits, its preparation method, and applications. Summary of the Invention

[0009] Aiming at the deficiencies of the existing technologies, the purpose of the present invention is to provide a nanoimprint conductive paste, a preparation method and an application thereof. The nanoimprint conductive paste can meet the requirements of ultra-fine lines with a width of ≤ 3 μm, has excellent high-temperature and high-humidity resistance, low-temperature resistance and salt spray resistance, and has a low sheet resistance when applied to a metal grid flexible conductive film, and has excellent electrical conductivity.

[0010] To achieve this purpose, the present invention adopts the following technical solutions:

[0011] In the first aspect, the present invention provides a nanoimprint conductive paste. Calculated by weight parts, the raw materials for preparing the nanoimprint conductive paste include:

[0012]

[0013] The conductive silver includes micron silver flakes and nano silver powder.

[0014] Calculated by weight parts, the raw materials for preparing the nanoimprint conductive paste of the present invention include 2-8 parts of epoxy resin, for example, it can be 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts or 8 parts, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] Calculated by weight parts, the raw materials for preparing the nanoimprint conductive paste of the present invention include 70-75 parts of conductive silver, for example, it can be 70 parts, 71 parts, 72 parts, 73 parts, 74 parts or 75 parts, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] Calculated by weight parts, the raw materials for preparing the nanoimprint conductive paste of the present invention include 2-5 parts of functional additives, for example, it can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] Calculated by weight parts, the raw materials for preparing the nanoimprint conductive paste of the present invention include 16-20 parts of organic solvent, for example, it can be 16 parts, 17 parts, 18 parts, 19 parts or 20 parts, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] In the conventional metal grid flexible conductive films in this field, the width of the wire grooves is 5 - 10 μm. The nano silver powder can achieve good filling in the wire grooves, forming an effective interlayer lap effect of at least 5 layers. When the width of the wire grooves is reduced to less than 3 μm, the nano silver powder can only form 2 - 3 layers of lap in the wire grooves, the filling effect is reduced, and it is easy to cause an increase in local resistance or even an open circuit. Through the combination of micro silver flakes and nano silver powder, the present invention enables the conductive silver to form at least 5 layers of interlayer lap in the wire grooves with a width ≤ 3 μm, eliminates abnormal phenomena such as uneven resistance and open circuit, and realizes a substantial improvement in conductive performance.

[0019] Preferably, the mass ratio of the micro silver flakes to the nano silver powder is 1:(1 - 3). For example, it can be 1:1, 1:1.5, 1:2, 1:2.5, or 1:3, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the thickness of the micro silver flakes is 1 - 2 μm, and the equivalent diameter is 2 - 5 μm.

[0021] The thickness of the micro silver flakes in the present invention is 1 - 2 μm. For example, it can be 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, or 2 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0022] The equivalent diameter of the micro silver flakes in the present invention is 2 - 5 μm. For example, it can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0023] The thickness and equivalent diameter of the micro silver flakes in the present invention refer to the average thickness and average equivalent diameter of the micro silver flakes.

[0024] Preferably, the particle size range of the nano silver powder is 50 - 500 nm, and the median particle size D50 is 100 - 200 nm.

[0025] The particle size range of the nano silver powder in the present invention being 50 - 500 nm means that the minimum particle size of the nano silver powder is above 50 nm. For example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable; the maximum particle size of the nano silver powder is below 500 nm. For example, it can be 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, or 500 nm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] The median particle size D50 of the nano silver powder described in the present invention is 100 - 200 nm. For example, it can be 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm or 200 nm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the epoxy resin includes bisphenol A epoxy resin.

[0028] Preferably, the epoxy equivalent of the bisphenol A epoxy resin is 6000 - 9000 g / equivalent. For example, it can be 6000 g / equivalent, 6500 g / equivalent, 7000 g / equivalent, 7500 g / equivalent, 8000 g / equivalent, 8500 g / equivalent or 9000 g / equivalent, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] When the epoxy equivalent of the bisphenol A epoxy resin is less than 6000 g / equivalent, agglomeration is likely to occur in the obtained nanoimprint conductive paste; when the epoxy equivalent of the bisphenol A epoxy resin exceeds 9000 g / equivalent, the obtained nanoimprint conductive paste cannot be effectively cured, affecting its application in the metal grid flexible conductive film.

[0030] Preferably, the organic solvent includes any one or a combination of at least two of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate or ethylene glycol ethyl ether acetate. Typical but non-limiting combinations include the combination of diethylene glycol ethyl ether acetate and diethylene glycol butyl ether acetate, the combination of diethylene glycol ethyl ether acetate and ethylene glycol ethyl ether acetate, and the combination of diethylene glycol butyl ether acetate and ethylene glycol ethyl ether acetate.

[0031] Preferably, the functional additives include a thickener, a thixotropic agent, a reinforcing agent, a dispersant, a leveling agent, a curing agent and a low-temperature active catalyst with a mass ratio of 1:(1 - 3):(1 - 3):(1 - 3):(1 - 3):(1 - 3):(1 - 3).

[0032] Preferably, the thickener includes any one or a combination of at least two of ethyl cellulose, fumed silica, polyamide wax, polyvinyl alcohol or hydroxyethyl cellulose. Typical but non-limiting combinations include the combination of ethyl cellulose and fumed silica, the combination of polyamide wax and polyvinyl alcohol, the combination of polyamide wax, polyvinyl alcohol and hydroxyethyl cellulose, the combination of ethyl cellulose, fumed silica and polyamide wax, the combination of fumed silica, polyamide wax, polyvinyl alcohol and hydroxyethyl cellulose, or the combination of ethyl cellulose, fumed silica, polyamide wax, polyvinyl alcohol and hydroxyethyl cellulose.

[0033] Preferably, the thixotropic agent includes any one or a combination of at least two of BYK-410, BYK-420, or dibutyl phthalate. Typical but non-limiting combinations include the combination of BYK-410 and BYK-420, the combination of BYK-420 and dibutyl phthalate, or the combination of BYK-410, BYK-420, and dibutyl phthalate.

[0034] Preferably, the reinforcing agent includes any one or a combination of at least two of latent isocyanate, tetraethyl titanate, methylimidazole, or benzyl glycidyl ether. Typical but non-limiting combinations include the combination of latent isocyanate and tetraethyl titanate, the combination of methylimidazole and benzyl glycidyl ether, the combination of latent isocyanate, methylimidazole, and benzyl glycidyl ether, or the combination of latent isocyanate, tetraethyl titanate, methylimidazole, and benzyl glycidyl ether.

[0035] Preferably, the dispersant includes any one or a combination of at least two of polyvinylpyrrolidone, sodium dodecylsulfonate, or Span 80. Typical but non-limiting combinations include the combination of polyvinylpyrrolidone and sodium dodecylsulfonate, the combination of sodium dodecylsulfonate and Span 80, the combination of polyvinylpyrrolidone and Span 80, or the combination of polyvinylpyrrolidone, sodium dodecylsulfonate, and Span 80.

[0036] Preferably, the leveling agent includes any one or a combination of at least two of ethylene glycol monobutyl ether, silicone, or acrylate. Typical but non-limiting combinations include the combination of ethylene glycol monobutyl ether and silicone, the combination of silicone and acrylate, the combination of ethylene glycol monobutyl ether and acrylate, or the combination of ethylene glycol monobutyl ether, silicone, and acrylate.

[0037] Preferably, the curing agent includes any one or a combination of at least two of EP-500, methyltetrahydrophthalic anhydride, dicyandiamide, 2-ethyl-4-methylimidazole, mercaptothiol, 2-phenylimidazole, or acetylacetone transition metal complex. Typical but non-limiting combinations include the combination of EP-500 and methyltetrahydrophthalic anhydride, the combination of dicyandiamide and 2-ethyl-4-methylimidazole, the combination of mercaptothiol and 2-phenylimidazole, the combination of dicyandiamide, 2-phenylimidazole, and acetylacetone transition metal complex, the combination of EP-500, methyltetrahydrophthalic anhydride, dicyandiamide, 2-ethyl-4-methylimidazole, and mercaptothiol, or the combination of EP-500, methyltetrahydrophthalic anhydride, dicyandiamide, 2-ethyl-4-methylimidazole, mercaptothiol, 2-phenylimidazole, and acetylacetone transition metal complex.

[0038] Preferably, the low-temperature active catalyst includes any one or a combination of at least two of benzoic acid, n-decanoic acid, fluorine-modified surfactant, boron trifluoride complex, dodecanoic acid, silane coupling agent, p-phenylenediamine or stearic acid. Typical but non-limiting combinations include the combination of benzoic acid and n-decanoic acid, the combination of n-decanoic acid and fluorine-modified surfactant, the combination of boron trifluoride complexing agent and dodecanoic acid, the combination of dodecanoic acid, silane coupling agent, p-phenylenediamine and stearic acid, the combination of benzoic acid, n-decanoic acid, fluorine-modified surfactant and boron trifluoride complexing agent, the combination of boron trifluoride complexing agent, dodecanoic acid, silane coupling agent, p-phenylenediamine and stearic acid, or the combination of benzoic acid, n-decanoic acid, fluorine-modified surfactant, boron trifluoride complexing agent, dodecanoic acid, silane coupling agent, p-phenylenediamine and stearic acid.

[0039] In a second aspect, the present invention provides a method for preparing the nanoimprint conductive paste as described in the first aspect, characterized in that the preparation method includes the following steps:

[0040] (1) Mix epoxy resin and organic solvent according to the formula amount to obtain a primary carrier;

[0041] (2) Uniformly mix functional additives and the primary carrier obtained in step (1) according to the formula amount to obtain a secondary carrier;

[0042] (3) Uniformly mix conductive silver and the secondary carrier obtained in step (2), and grind and disperse to obtain the nanoimprint conductive paste.

[0043] Preferably, the temperature of the mixing in step (1) is 80 - 100 °C, for example, it can be 80 °C, 85 °C, 90 °C, 95 °C or 100 °C, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0044] Preferably, the time of the mixing in step (1) is 4 - 8 h, for example, it can be 4 h, 5 h, 6 h, 7 h or 8 h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0045] Preferably, the rotation speed of the mixing in step (1) is 800 - 1200 r / min, for example, it can be 800 r / min, 900 r / min, 1000 r / min, 1100 r / min or 1200 r / min, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0046] Preferably, the temperature of the mixing in step (2) is 18 - 25 °C, for example, it can be 18 °C, 19 °C, 20 °C, 21 °C, 22 °C, 23 °C, 24 °C or 25 °C, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0047] Preferably, the rotation speed of the mixing in step (2) is 800 - 1200 r / min. For example, it can be 800 r / min, 900 r / min, 1000 r / min, 1100 r / min, or 1200 r / min, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0048] Preferably, the temperature of the mixing in step (3) is 18 - 25 °C. For example, it can be 18 °C, 19 °C, 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, or 25 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0049] Preferably, the rotation speed of the mixing in step (3) is 800 - 1200 r / min. For example, it can be 800 r / min, 900 r / min, 1000 r / min, 1100 r / min, or 1200 r / min, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0050] Preferably, the grinding and dispersion in step (3) are carried out using a three - roll mill.

[0051] As a preferred technical solution of the preparation method described in the second aspect, the preparation method includes the following steps:

[0052] (1) Mix epoxy resin and organic solvent at 80 - 100 °C and a rotation speed of 800 - 1200 r / min for 4 - 8 h according to the formula amount to obtain a primary carrier.

[0053] (2) Uniformly mix functional additives and the primary carrier obtained in step (1) at 18 - 25 °C and a rotation speed of 800 - 1200 r / min according to the formula amount to obtain a secondary carrier.

[0054] (3) Uniformly mix conductive silver and the secondary carrier obtained in step (2) at 18 - 25 °C and a rotation speed of 800 - 1200 r / min according to the formula amount, and grind and disperse using a three - roll mill to obtain the nano - imprinted conductive paste.

[0055] In the third aspect, the present invention provides a metal grid flexible conductive film, and the metal grid flexible conductive film includes the nano - imprinted conductive paste described in the first aspect.

[0056] Preferably, the groove width of the metal grid flexible conductive film is ≤ 3 μm. For example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0057] The nanoimprint conductive paste provided by the present invention can be used for a metal grid flexible conductive film with a slot width ≤ 3 μm. When used for a metal grid flexible conductive film with a slot width ≤ 3 μm, the metal grid flexible conductive film can have a low surface resistance, and the adhesion between the nanoimprint conductive paste and the substrate after curing is ≥ 4B.

[0058] The numerical ranges described in the present invention include not only the exemplified point values above, but also any point values between the above numerical ranges not exemplified. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the described ranges.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] By adjusting the composition of the nanoimprint conductive paste, the present invention enables the sheet resistance to be low when applied to a metal grid flexible conductive film; and the obtained nanoimprint conductive paste has a low viscosity, facilitating imprinting and scraping coating; and the curing temperature of the nanoimprint conductive paste is below 135 °C, and the adhesion to the substrate after curing is above grade 4B. Detailed Embodiments

[0061] The technical solutions of the present invention will be further described below through specific embodiments.

[0062] Example 1

[0063] This example provides a nanoimprint conductive paste. In terms of parts by weight, the raw materials for preparing the nanoimprint conductive paste include:

[0064]

[0065] The conductive silver includes micro silver flakes and nano silver powder with a mass ratio of 1:2. The thickness of the micro silver flakes is 1.5 μm, and the equivalent diameter is 3 μm; the particle size range of the nano silver powder is 50 - 500 nm, and the median particle size D50 is 150 nm.

[0066] The epoxy resin is bisphenol A epoxy resin (epoxy resin 1256), and the epoxy equivalent of the bisphenol A epoxy resin is 7500 g / equivalent.

[0067] The organic solvent is diethylene glycol ethyl ether acetate.

[0068] The functional additives include a thickener, a thixotropic agent, a reinforcing agent, a dispersant, a leveling agent, a curing agent, and a low-temperature active catalyst with a mass ratio of 1:1:1:1:1:1:1; the thickener is hydroxyethyl cellulose; the thixotropic agent is BYK-410; the reinforcing agent is tetraethyl titanate; the dispersant is sodium dodecyl sulfate; the leveling agent is acrylate; the curing agent is EP-500; the low-temperature activation catalyst is n-decanoic acid.

[0069] The preparation method of the nanoimprint conductive paste comprises the following steps:

[0070] (1) mixing epoxy resin and organic solvent according to the formula amount at 90° C. and a rotation speed of 1000 r / min for 6 hours to obtain a primary carrier;

[0071] (2) at 22° C. and a rotation speed of 1000 r / min, uniformly mixing the functional additive and the primary carrier obtained in step (1) according to the formula amount to obtain a secondary carrier;

[0072] (3) At 22° C. and a rotation speed of 1000 r / min, the conductive silver and the secondary carrier obtained in step (2) were uniformly mixed according to the formula amount, and ground and dispersed using a three-roll grinder to obtain the nanoimprint conductive paste.

[0073] Example 2

[0074] This embodiment provides a nanoimprint conductive paste. The raw materials for preparing the nanoimprint conductive paste include, by weight:

[0075]

[0076] The conductive silver comprises micron silver flakes and nano silver powder in a mass ratio of 1:1. The thickness of the micron silver flakes is 1 μm and the equivalent diameter is 2 μm; the particle size of the nano silver powder ranges from 50 to 500 nm and the median particle size D50 is 100 nm.

[0077] The epoxy resin is bisphenol A epoxy resin (epoxy resin 1256), and the epoxy equivalent of the bisphenol A epoxy resin is 6000 g / equivalent.

[0078] The organic solvent is diethylene glycol butyl ether acetate.

[0079] The functional additives include a thickener, a thixotropic agent, a reinforcing agent, a dispersant, a leveling agent, a curing agent and a low-temperature active catalyst in a mass ratio of 1:1:1:1:1:1:1; the thickener is hydroxyethyl cellulose; the thixotropic agent is BYK-420; the reinforcing agent is methylimidazole; the dispersant is Span 80; the leveling agent is ethylene glycol butyl ether; the curing agent is 2-ethyl-4-methylimidazole; and the low-temperature activated catalyst is dodecanoic acid.

[0080] The preparation method of the nanoimprint conductive paste comprises the following steps:

[0081] (1) mixing epoxy resin and organic solvent according to the formula amount at 80° C. and a rotation speed of 800 r / min for 8 hours to obtain a primary carrier;

[0082] (2) Under the conditions of 18 °C and a rotation speed of 1200 r / min, uniformly mix the functional additives with the primary carrier obtained in step (1) according to the formulation amounts to obtain a secondary carrier;

[0083] (3) Under the conditions of 18 °C and a rotation speed of 1200 r / min, uniformly mix the conductive silver with the secondary carrier obtained in step (2) according to the formulation amounts, and grind and disperse using a three-roll grinder to obtain the nanoimprint conductive paste.

[0084] Example 3

[0085] This example provides a nanoimprint conductive paste. In terms of parts by weight, the raw materials for preparing the nanoimprint conductive paste include:

[0086]

[0087] The conductive silver includes micron silver flakes and nano silver powder with a mass ratio of 1:3. The thickness of the micron silver flakes is 2 μm, and the equivalent diameter is 5 μm; the particle size range of the nano silver powder is 50 - 500 nm, and the median particle size D50 is 200 nm.

[0088] The epoxy resin is bisphenol A epoxy resin (epoxy resin 4275), and the epoxy equivalent of the bisphenol A epoxy resin is 9000 g / equivalent.

[0089] The organic solvent is ethylene glycol monoethyl ether acetate.

[0090] The functional additives include a thickener, a thixotropic agent, a reinforcing agent, a dispersant, a leveling agent, a curing agent, and a low-temperature active catalyst with a mass ratio of 1:1:1:1:1:1:1; the thickener is hydroxyethyl cellulose; the thixotropic agent is dicyanate phthalate; the reinforcing agent is methylimidazole; the dispersant is Span 80; the leveling agent is ethylene glycol monobutyl ether; the curing agent is dicyandiamide; the low-temperature activation catalyst is p-phenylenediamine.

[0091] The preparation method of the nanoimprint conductive paste includes the following steps:

[0092] (1) Under the conditions of 100 °C and a rotation speed of 1200 r / min, mix the epoxy resin and the organic solvent for 4 h according to the formulation amounts to obtain a primary carrier;

[0093] (2) Under the conditions of 25 °C and a rotation speed of 800 r / min, uniformly mix the functional additives with the primary carrier obtained in step (1) according to the formulation amounts to obtain a secondary carrier;

[0094] (3) Under the conditions of 25 °C and a rotation speed of 800 r / min, uniformly mix the conductive silver with the secondary carrier obtained in step (2) according to the formulation amounts, and grind and disperse using a three-roll grinder to obtain the nanoimprint conductive paste.

[0095] Example 4

[0096] This example provides a nanoimprint conductive paste, which is the same as Example 1 except that the epoxy equivalent of bisphenol A epoxy resin is 5500 g / equivalent.

[0097] Example 5

[0098] This example provides a nanoimprint conductive paste, which is the same as Example 1 except that the epoxy equivalent of bisphenol A epoxy resin is 9500 g / equivalent.

[0099] Example 6

[0100] This example provides a nanoimprint conductive paste, which is the same as Example 1 except that diethylene glycol monoethyl ether acetate is replaced with a combination of diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate in equal mass, and the mass ratio of diethylene glycol monoethyl ether acetate to diethylene glycol monobutyl ether acetate is 1:1.

[0101] Example 7

[0102] This example provides a nanoimprint conductive paste, which is the same as Example 1 except that diethylene glycol monoethyl ether acetate is replaced with a combination of diethylene glycol monobutyl ether acetate and ethylene glycol monoethyl ether acetate in equal mass, and the mass ratio of diethylene glycol monobutyl ether acetate to ethylene glycol monoethyl ether acetate is 1:1.

[0103] Example 8

[0104] This example provides a nanoimprint conductive paste, which is the same as Example 1 except that diethylene glycol monoethyl ether acetate is replaced with a combination of diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate and ethylene glycol monoethyl ether acetate in equal mass, and the mass ratio of diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate to ethylene glycol monoethyl ether acetate is 1:1:1.

[0105] Comparative Example 1

[0106] This comparative example provides a nanoimprint conductive paste, which is the same as Example 1 except that the micron silver flakes are replaced with the nano silver powder in Example 1 in equal mass.

[0107] Comparative Example 2

[0108] This comparative example provides a nanoimprint conductive paste, which is the same as Example 1 except that the nano silver powder is replaced with the micron silver flakes in Example 1 in equal mass.

[0109] Performance Test

[0110] (1) Use a Brookfield DV-II viscometer. Under the condition of using rotor No. 51 at 100 r / min, test the viscosity of the nanoimprinted conductive pastes obtained in the above-mentioned examples and comparative examples. The obtained results are shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] (2) Provide a substrate with a groove width of 1.5 μm. Fill the nanoimprinted conductive pastes obtained in the above-mentioned examples and comparative examples into the grooves respectively. The curing temperature is 130 °C and the curing time is 30 min to obtain a metal grid flexible conductive film.

[0115] Use the cross-cut method to test the adhesion between the cured nanoimprinted conductive paste and the substrate;

[0116] Test the sheet resistance, boiling water resistance, high temperature and high humidity resistance, thermal shock resistance, salt spray resistance and bending resistance of the obtained metal grid flexible conductive film;

[0117] Use a multimeter to test the sheet resistance;

[0118] The test method for boiling water resistance is: use a water bath to boil at 100 °C for 30 min, and then use the cross-cut method to test the adhesion;

[0119] The test method for high temperature and high humidity resistance is to place the obtained metal grid flexible conductive film in an environment with a temperature of 85 °C and a relative humidity of 85% for 1200 h, and then test the adhesion according to the cross-cut method.

[0120] The test method for thermal shock resistance is to place the obtained metal grid flexible conductive film in a thermal shock chamber for 1200 h. The temperature in the thermal shock chamber cycles within the range of -48 °C to 80 °C with a period of 4 h, and then test the adhesion according to the cross-cut method.

[0121] The test method for salt spray resistance is to place the obtained metal grid flexible conductive film in a thermal shock chamber and conduct a 5% NaCl salt spray test at 35 °C for 42 h, and then test the adhesion according to the cross-cut method.

[0122] The test method for bending resistance is to continuously fold the obtained metal grid flexible conductive film in half for 1 min, and then test the adhesion according to the cross-cut method.

[0123] The obtained results are shown in Table 2 and Table 3.

[0124] Table 2

[0125] Sheet Resistance (Ω / □) Adhesion Water Boiling Resistance Example 1 2 4B 4B Example 2 3 4B 4B Example 3 3 4B 4B Example 4 6 3B 3B Example 5 10 3B 3B Example 6 5 3B 2B Example 7 4 3B 2B Example 8 5 3B 3B Comparative Example 1 4 4B 3B Comparative Example 2 6 4B 3B

[0126] Table 3

[0127]

[0128]

[0129] In summary, through the regulation of the composition of the nanoimprint conductive paste, the present invention has a low sheet resistance when applied to a metal grid flexible conductive film; and the obtained nanoimprint conductive paste has a low viscosity, which is convenient for imprinting and scraping; and the adhesion between the nanoimprint conductive paste and the substrate after curing is above grade 4B.

[0130] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A nanoimprinting conductive paste, characterized in that, The raw materials for preparing the nanoimprint conductive paste, by weight parts, include: The conductive silver consists of micron silver flakes and nano silver powder; The mass ratio of the micron silver flakes to the nano silver powder is 1:(1 - 3); The thickness of the micron silver flakes is 1 - 2 μm, and the equivalent diameter is 2 - 5 μm; The particle size range of the nano silver powder is 50 - 500 nm, and the median particle size D50 is 100 - 200 nm; The epoxy resin includes bisphenol A epoxy resin; The epoxy equivalent of the bisphenol A epoxy resin is 6000 - 9000 g / equivalent; The width of the wire groove filled by the nanoimprint conductive paste during the nanoimprint process is 1.5 μm; The organic solvent includes any one or a combination of at least two of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, or ethylene glycol ethyl ether acetate; The functional additives include a thickener, a thixotropic agent, a reinforcing agent, a dispersant, a leveling agent, a curing agent, and a low-temperature active catalyst with a mass ratio of 1:(1 - 3):(1 - 3):(1 - 3):(1 - 3):(1 - 3):(1 - 3); The thickener includes any one or a combination of at least two of ethyl cellulose, fumed silica, polyamide wax, polyvinyl alcohol, or hydroxyethyl cellulose; The thixotropic agent includes any one or a combination of at least two of BYK-410, BYK-420, or dibutyl phthalate; The reinforcing agent includes any one or a combination of at least two of latent isocyanate, tetraethyl titanate, methylimidazole, or benzyl glycidyl ether; The dispersant includes any one or a combination of at least two of polyvinylpyrrolidone, sodium dodecylsulfonate, or span 80; The leveling agent includes any one or a combination of at least two of ethylene glycol butyl ether, silicone, or acrylate; The curing agent includes any one or a combination of at least two of EP-500, methyltetrahydrophthalic anhydride, dicyandiamide, 2-ethyl-4-methylimidazole, mercaptothiol, 2-phenylimidazole, or acetylacetone transition metal complex; The low-temperature active catalyst includes any one or a combination of at least two of benzoic acid, n-decanoic acid, fluorine-modified surfactant, boron trifluoride complex, dodecanoic acid, silane coupling agent, p-phenylenediamine, or stearic acid; The preparation method of the nanoimprint conductive paste includes the following steps: (1) Mix the epoxy resin and the organic solvent according to the formula amount to obtain a primary carrier; (2) Uniformly mix the functional additives and the primary carrier obtained in step (1) according to the formula amount to obtain a secondary carrier; (3) Uniformly mix the conductive silver and the secondary carrier obtained in step (2), and grind and disperse to obtain the nanoimprint conductive paste.

2. The nanoimprinting conductive paste according to claim 1, characterized in that, The temperature of the mixing in step (1) is 80 - 100 °C; The time of the mixing in step (1) is 4 - 8 h; The rotation speed of the mixing in step (1) is 800 - 1200 r / min; The temperature of the mixing in step (2) is 18 - 25 °C; The rotation speed of the mixing in step (2) is 800 - 1200 r / min; The temperature of the mixing in step (3) is 18 - 25 °C; The rotation speed of the mixing in step (3) is 800 - 1200 r / min.

3. The nanoimprinting conductive paste according to claim 1, characterized in that, The grinding and dispersion in step (3) is carried out by a three-roll grinder.

4. The nanoimprinting conductive paste according to claim 1, characterized in that, The preparation method includes the following steps: (1) Under the conditions of 80 - 100 °C and a rotation speed of 800 - 1200 r / min, epoxy resin and an organic solvent are mixed in accordance with the formula amount for 4 - 8 h to obtain a primary carrier. (2) Under the conditions of 18 - 25 °C and a rotation speed of 800 - 1200 r / min, a functional additive and the primary carrier obtained in step (1) are uniformly mixed in accordance with the formula amount to obtain a secondary carrier. (3) Under the conditions of 18 - 25 °C and a rotation speed of 800 - 1200 r / min, conductive silver and the secondary carrier obtained in step (2) are uniformly mixed in accordance with the formula amount, and are ground and dispersed by a three-roll grinder to obtain the nanoimprint conductive paste.

5. A metal mesh flexible conductive film, characterized in that, The metal grid flexible conductive film includes the nanoimprint conductive paste as described in claim 1.

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