CN116285502B

CN116285502B - Preparation method of ink for reducing melting point of metal nanowire, optical invisible pattern electrode and electrode

Info

Publication number: CN116285502B
Application number: CN202310176253.3A
Authority: CN
Inventors: 刘贵师; 王宏腾; 陈雷; 辛祎佳; 陈耀飞; 罗云瀚
Original assignee: Jinan University
Current assignee: Jinan University
Priority date: 2023-02-27
Filing date: 2023-02-27
Publication date: 2023-10-20
Anticipated expiration: 2043-02-27
Also published as: CN116285502A

Abstract

The application relates to the technical field of electrode materials, firstly, providing an ink for reducing the melting point of metal nanowires, which specifically comprises 0.1-1 part of molten compound and 95.2-99.7 parts of polar solvent in parts by weight; the melting compound is selected from any two or more of metal halide, iodonium salt, nitrate, iodate, metal oxide, brine and monoacid, and the ink can obviously reduce the melting temperature of the metal nanowire, thereby reducing the heating cost and the processing difficulty. The application further provides a preparation method of the optically invisible pattern electrode, which has the advantages of simple process, high processing precision and strong practicability, can effectively enhance the photoelectric performance of the metal nanowire pattern electrode, and is suitable for large-scale production and application. The application further provides the optical invisible pattern electrode prepared by the method, which has the advantages of high transmittance, low scattering and the like, and has excellent overall optical performance.

Description

Preparation method of ink for reducing melting point of metal nanowire, optical invisible pattern electrode and electrode

Technical Field

The application relates to the technical field of electrode materials, in particular to an ink for reducing the melting point of metal nanowires, a preparation method of an optically invisible pattern electrode and the electrode.

Background

At present, the global flexible electronic market is in a rapid growth state, flexible electronic products such as flexible screen mobile terminals, wearable intelligent devices, implantable electronic medical devices, soft robots and the like are increasingly used, the application field is widened, and the demands of the market on flexible transparent electrodes are increased. The main current flexible transparent electrode material is mainly Indium Tin Oxide (ITO), and has the advantages of high transparency, good conductivity and the like. However, ITO films can develop a large number of cracks at low strains (2-3%), greatly affecting the durability of the flexible electronic device. Meanwhile, the defects of harsh high-temperature deposition condition, high energy consumption of devices and expensive metal indium in preparation are overcome.

The metal nanowire comprises a silver nanowire, a copper nanowire, an iron nanowire and the like, and the prepared transparent electrode has excellent conductivity, transmittance and flexibility, wherein the comprehensive performance of the silver nanowire is most outstanding. The metal nanowire can be synthesized by a chemical method and can be dispersed in a polar solution, and has the advantages of simple synthesis method, high cost performance and simple film forming process. They can be easily deposited on large area flexible substrates in a roll-to-roll fashion by solution processes such as knife coating, spray coating, screen printing, and the like. The film formed by deposition has the advantages of high light transmittance, good conductivity, excellent flexibility, low cost and the like, and is considered as an ideal substitute for an ITO electrode. However, the application of flexible transparent electrodes of metal nanowires in the field of optoelectronics, in particular in displays, also presents problems of optical visibility of patterned electrodes. Unlike thin film materials, metal nanowires have a significant scattering effect on visible light, resulting in significant optical differences between the conductive and non-conductive regions of the metal nanowire electrodes, enabling the human eye to observe electrode pattern traces. Pattern visibility will deteriorate the performance of the transparent optoelectronic device, such as the display quality of the display device. Currently, the metal nanowire network can realize electrode patterning through two technical routes of top-down and bottom-up. The common top-down methods include photolithography and laser ablation, and the bottom-up method mainly comprises inkjet printing, screen printing and transfer printing. Regardless of the process, the insulating region of the metal nanowire patterned electrode is free of metal nanowires, and the resulting refractive index differences and scattering differences inevitably lead to optical differences, i.e., visibility, of the electrode pattern.

There are several documents reporting techniques for patterning metal nanowires, which can be broadly divided into two strategies: (1) The trace of the nanowire in the insulating region is reserved to eliminate the trace of the pattern. Mainly comprises two methods of photoetching half-etching and laser fusing. Taking patent CN 103258596B as an example, an electrode area and a non-electrode area are firstly divided, the electrode area is protected by a photoresist protection film, the non-electrode area is etched by a half-etching method to be non-conductive, and silver nano-trace is kept, so that shadow elimination of the conductive film is realized; for another example, myeongkyu Lee et al uses nanosecond pulsed laser to selectively fuse a silver nanowire network, retaining nanowire segments of an insulating region, achieving conductivity patterning [ The Journal of Physical Chemistry C2016,120,20471-20477 ]. (2) The surface of the metal nanowire or surrounding medium is changed to reduce or even scattering of the electrode, so that the purpose of patterning shadow elimination is achieved. For example, patent CN 105960298B prepares a transparent conductive film by adsorbing a colored compound as a dye on a metal nanowire so as to prevent the occurrence of a black float phenomenon; the patent CN 108399977B realizes patterning shadow elimination by arranging a functional layer between a substrate and a nano silver wire transparent conductive layer, wherein the functional layer contains metal nano particles with strong diffuse reflectivity, and the difference between the haze and the conductive layer is smaller than 0.2 through thickness adjustment of the functional layer. However, the methods reported in the above documents and patents have disadvantages of complicated processes, expensive equipment, poor practicality, or deteriorated photoelectric properties of the electrodes. Therefore, aiming at the problem of metal nanowire pattern visibility, it is very necessary and challenging to develop a patterning technology which has the advantages of simple process, strong practicability, high processing precision and capability of enhancing the photoelectric performance of the metal nanowire pattern. The preparation requirement of the metal nanowire to meet the optical invisible patterned electrode is the key point of achieving the aim, so that the development of ink which meets the requirement and can be used for modifying the metal nanowire is particularly critical.

Disclosure of Invention

In view of the above-mentioned problems, it is an object of the present application to provide an ink for lowering the melting point of metal nanowires, specifically comprising 0.1 to 1 part of a molten compound, 95.2 to 99.7 parts of a polar solvent; wherein the molten compound is selected from any two or more of metal halides, iodonium salts, nitrates, iodates, metal oxides, brine and monoacids.

Further, the molten compound is selected from diphenyl iodine nitrate, silver nitrate composition or acetic acid, nitric acid, ferric oxide composition or diphenyl trifluoro methane sulfonic acid iodine, iodine water composition or diphenyl iodine nitrate, silver nitrate composition or silver iodide, potassium iodide, silver nitrate composition or silver iodate, silver nitrate, silver iodide composition;

and/or the polar solvent is selected from one or more of water, acetone, monohydric alcohol and polyhydric alcohol.

In some embodiments, the ink for lowering the melting point of the metal nanowires further comprises 0.1 parts to 0.8 parts of the metal nanowires in parts by weight.

Further, the metal nanowire is one or more of a silver nanowire, a copper nanowire and an iron nanowire;

and/or the diameter of the metal nanowire is smaller than 200nm.

In some embodiments, the ink for lowering the melting point of the metal nanowires further includes 0.1 parts to 1 part of a dispersant in parts by weight.

Further, the dispersing agent is selected from one or more of fluorine-containing nonionic surfactants, sodium dodecyl benzene sulfonate, sodium 3-mercapto-1-propane sulfonate, 4- (1, 3-tetramethylbutyl) phenyl-polyethylene glycol, hydroxypropyl methylcellulose, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, polyethyleneimine, polyvinylpyrrolidone, polyethylene glycol, chitosan and other polymers, polyether defoamers, polysiloxane defoamers, silicone defoamers, acrylic acids, acetylene glycols, silicones and fluorocarbon compounds.

The mechanism of the fusion temperature reduction of the fused compound in the application is as follows: the molten compound is in contact and mixing with the metal nanowire, the molten compound directly interacts with the metal nanowire to promote the diffusion behavior of atoms on the surface of the metal nanowire at low temperature, and then the rayleigh instability is induced at low temperature to break the nanowire network, so that the melting point of the metal nanowire is reduced macroscopically.

Another object of the present application is to provide a method for preparing an optically invisible pattern electrode,

in some embodiments, the method of making an optically invisible patterned electrode comprises the steps of:

s1, depositing a metal nanowire network on a substrate, and drying for later use;

s2, selectively depositing the ink for reducing the melting point of the metal nano wire on the substrate obtained in the step S1, wherein in a preferred embodiment, the ink does not contain the metal nano wire, the metal nano wire deposited with the ink forms a low melting point part, and the metal nano wire not deposited with the ink forms a high melting point part;

s3, heating the metal nano network obtained in the step S2 to fuse the metal nano wire at the low-melting point part, obtaining an insulating region fused by the metal nano wire at the low-melting point part, and obtaining a complete conductive region of the metal nano wire at the high-melting point part to form the optically invisible pattern electrode, wherein the preferable heating temperature is 50-300 ℃, and the more preferable heating temperature is 50-200 ℃.

s01, depositing the ink for reducing the melting point of the metal nanowire on a substrate, wherein the ink comprises the metal nanowire, and drying;

s02, patterning is achieved on the substrate obtained in the step S01: placing a mask plate above the substrate, wherein the mask plate is provided with an exposure area allowing light to pass through and a shading area shading the light; irradiating the mask plate by using a light source, wherein the exposure area forms a high-melting-point metal nanowire network, and the shading area forms a low-melting-point metal nanowire network;

in a specific embodiment, the patterning method in step S2 and step S02 may be a bottom-up method or a top-down method, where the bottom-up method includes methods such as inkjet printing, transfer printing, screen printing, etc., and the bottom-up method includes methods such as photolithography, laser irradiation, etc., and preferably, the electrode patterning is implemented by methods such as inkjet printing, screen printing, PDMS soft stamp, etc.

S03, heating the substrate obtained in the step S02, wherein the low-melting-point metal nanowire network is fused, and the high-melting-point metal nanowire network is kept intact, so that an optically invisible pattern electrode is formed, and the heating temperature is preferably 50-300 ℃, more preferably 50-200 ℃.

In some embodiments, in order to further reduce the reflectivity of the electrode, the process of preparing the optically invisible patterned electrode, before performing step S1 or step S01, further comprises the following steps: the substrate is coated with an anti-reflection layer, preferably a polymer film layer or a two-dimensional material coating.

It is still another object of the present application to provide an optically invisible pattern electrode manufactured by the method of manufacturing the optically invisible pattern electrode.

The preparation process of the optically invisible pattern electrode in the application utilizes the principle of Rayleigh instability, wherein the ink for reducing the melting point of the metal nanowire changes the heat resistance of the metal nanowire, and the decomposable compound in an irradiation area is decomposed by irradiating ultraviolet rays above a mask plate, so that the melting point reducing effect on the metal nanowire is lost, and the metal nanowire is used as a preset conductive area; and forming a thermal stability difference with the low-melting-point metal nanowire in the non-irradiated area, namely the preset insulating area. Thereafter, the heating temperature is adjusted so as to be higher than the melting point of the metal nanowire in the preset insulating region and lower than the melting point of the metal nanowire in the preset conductive region. After heating, the metal nanowire in the insulating region fuses and loses the conductive effect, and the metal nanowire in the conductive region is not affected, so that the required optically invisible pattern electrode is formed. The refractive index difference of the two areas of the pattern electrode which is invisible in optics and manufactured by the application is less than 0.2, and the haze difference is not more than 2%.

Compared with the prior art, the application has the beneficial effects that:

(1) After the ink for reducing the melting point of the metal nanowire is adopted to treat the metal nanowire, the fusing temperature of the metal nanowire can be obviously reduced, so that the heating cost during fusing is reduced;

(2) The ink for reducing the melting point of the metal nanowire is obtained by carrying out unique compound preparation on different molten compounds, and compared with the ink of a single molten compound, the ink prepared by compound preparation can reduce the total addition amount of the molten compound and simultaneously can also show better effect of reducing the melting temperature of the metal nanowire;

(3) The preparation method of the optical invisible pattern electrode can reduce optical difference and reflectivity, and in addition, the optical difference of the optical invisible pattern electrode is further reduced by adding an anti-reflection layer formed by two-dimensional materials or polymers between the substrate and the metal nanowire network;

(4) By adopting the preparation method of the optical invisible pattern electrode, the square resistance of the conductive area can be obviously reduced, the transmittance can be improved, and the scattering can be reduced;

(5) The preparation method of the optical invisible pattern electrode has the advantages of simple process, high processing precision and strong practicability, can effectively enhance the photoelectric performance of the metal nanowire pattern electrode, and is suitable for large-scale production and application;

(6) The electrode of the optical invisible pattern prepared by the application has small refractive index difference and haze difference between the insulating region and the conductive region, effectively improves the transmittance, reduces the scattering and has excellent overall optical performance.

Drawings

FIG. 1 is a schematic view of a substrate after ultraviolet irradiation in example 1 of the present application.

FIG. 2 is a schematic diagram of a heated substrate according to example 1 of the present application.

FIG. 3 is a scanning electron microscope image of a heated substrate according to example 1 of the present application.

Fig. 4 is a schematic diagram of a silver nanowire mesh after heating a substrate according to embodiment 2 of the present application.

Fig. 5 is a photograph of a substrate heated in example 3 of the present application.

FIG. 6 is a graph showing the ratio of the square resistance of the sample to the initial square resistance of the sample after heating different samples in example 6 of the present application.

Reference numerals: the silver nanowire network regions without deposited ink in example 1 form high melting point regions 01, the silver nanowire network regions with deposited ink in example 1 form low melting point regions 02, the conductive regions 1 of example 1, the insulating regions 2 of example 1.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the application. For better illustration of the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual product dimensions; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

Example 1

1.1 ink formulation

The ink for reducing the melting point of the metal nanowires is prepared from the following components in parts by weight,

melting the compound: diphenyl iodine nitrate 0.25 weight portions and AgNO ₃ 0.3 parts;

polar solvent: 25.9 parts of deionized water, 3.2 parts of acetone and 69.35 parts of absolute ethyl alcohol;

dispersing agent: 1 part of chitosan.

Wherein the AgNO ₃ Is a standard silver nitrate solution.

1.2 an invisible pattern electrode was prepared using the ink for lowering the melting point of metal nanowires of 1.1, as follows,

(1) Preparing a silver nanowire network: and spin-coating 30nm silver nanowire liquid on a polyethylene naphthalate (PEN) substrate to form a silver nanowire network.

(2) Patterning the decorated metal nanowires by ink: printing the ink for reducing the melting point of the metal nano wire on a polyethylene naphthalate substrate in a pattern manner by adopting a screen printing mode, and standing to dry the printing ink; the part of the silver nanowire network, on which the ink is not deposited, forms a high-melting-point region; the portion of the silver nanowire network where the ink is deposited forms a low melting point region.

(3) Heating the substrate to form a patterned electrode: heating the substrate, wherein when the low-melting-point region is heated, the silver nanowires on the substrate are destroyed and fuse to form an insulating region; the silver nanowires in the upper high melting point region are not obviously changed to form conductive regions, so that the required optically invisible pattern electrode is obtained, in the embodiment, the refractive index difference between the low melting point region and the high melting point region of the optically invisible pattern electrode is less than 0.2, the haze difference is not more than 0.2%,

1.3 the schematic diagram of the substrate obtained after screen printing in this embodiment is shown in fig. 1, wherein the hatched portion is the area where no ink is deposited, the high melting point is reserved, the area 01 is the high melting point area, the blank portion is the silver nanowire network area where ink is deposited, and the melting point is reduced, and the area 02 is the low melting point area.

In this example, the temperature of the heating stage was set to 110 ℃ during heating, and after the preheating was completed, the substrate was placed on the heating stage and heated for 2 minutes, to obtain the substrate shown in fig. 2. It can be measured that the blank portion shown in fig. 2 loses conductivity, i.e., the low melting point region 02 in fig. 1 forms an insulating region 2, and the resistance tends to be infinite; the hatched portion retains conductivity, i.e. the high melting point region 01 in fig. 1 forms a conductive region 1.

Fig. 3 is an electron microscope scan after the substrate is heated in this embodiment, with a broken line as a boundary, an electron microscope scan with an insulating region on the right side, and an electron microscope scan with a conductive region on the left side. The electron microscope scan of fig. 3 shows that the silver nanowire structure of the insulating region is broken and the silver nanowire of the conductive region is not broken.

Example 2

2.1 ink formulation

melting the compound: 0.2 part of acetic acid, 0.2 part of nitric acid and 0.2 part of ferric oxide;

polar solvent: 79.18 parts of deionized water and 20 parts of propylene glycol.

2.2 an invisible pattern electrode was prepared using the ink for lowering the melting point of metal nanowires of 2.1, as follows,

(1) Depositing a silver nanowire network on a clean glass slide substrate, and drying at a low temperature;

(2) Transmitting the desired pattern of nonconductive areas into inkjet printing electronic software;

(3) And (2) selectively depositing the ink for reducing the melting point of the metal nanowire in the step (2.1) on a silver nanowire network through ink-jet printing to form a silver nanowire film modified by ink patterning, wherein the part of the silver nanowire network on which the ink is deposited is a low-melting-point region, and the part of the silver nanowire network on which the ink is not deposited is a high-melting-point region.

(4) Heating the substrate to form a patterned electrode: the heating stage temperature was adjusted to 120 ℃ for preheating. After the completion of the preheating, the substrate is placed in the center of the heating table to be heated.

The silver nanowire network after heating in this embodiment is shown in fig. 4.

After being heated at 120 ℃, the silver nanowire in the low-melting-point region is damaged by Rayleigh instability, and is fused to form an insulating region; the silver nanowires in the high melting point area are not changed obviously, so that the optically invisible pattern electrode is manufactured.

In the step (3) of the preparation process of the optically invisible patterned electrode, the mode of selectively depositing the ink on the metal nanowire network can be top-down printing, including but not limited to photoetching patterning, laser ablation and adhesion difference method, or can be bottom-up printing, including but not limited to screen printing, gravure printing, hydrophilic-hydrophobic self-assembly, template auxiliary printing method, and the like, so as to realize the patterning of the ink for reducing the melting point of the metal nanowire on the metal nanowire network.

Example 3

3.1 ink formulation

melting the compound: 0.27 parts of diphenyl trifluoro methyl sulfonic acid iodine and 0.43 parts of iodine water;

polar solvent: 25.01 parts of deionized water, 3.43 parts of acetone and 70.62 parts of absolute ethyl alcohol.

3.2 an optically invisible patterned electrode was prepared using the ink of 3.1 for lowering the melting point of metal nanowires, as follows,

(1) Depositing a metal silver nanowire network on the PEN substrate, and drying at a low temperature;

(2) Transmitting the preset non-conductive area pattern to ink-jet printing electronic software;

(3) Selectively printing the ink for reducing the melting point of the metal nanowire in 3.1 on a metal nanowire network through ink jet to form a metal nanowire film modified by ink patterning; the part of the metal nanowire network, on which the ink is deposited, is a low-melting-point region, and the part of the metal nanowire network, on which the ink is not deposited, is a high-melting-point region.

(4) Heating the substrate to form a patterned electrode: the heating stage temperature was adjusted to 120 ℃ for preheating. The substrate is placed in the center of the heating table for heating after the preheating is completed.

After being heated at 120 ℃, the metal nanowire in the low-melting-point region is damaged by Rayleigh instability and is fused to form an insulating region; the metal nanowires in the high-melting-point area are not obviously changed, and the conductive areas are formed, so that the optically invisible pattern electrode is manufactured.

Wherein, optionally, in step (3) of this embodiment 3.2, the selective deposition of the ink on the metal nanowire network may be performed by a bottom-up method or a top-down method, where the bottom-up method is preferably an inkjet printing method, a transfer printing method, or a screen printing method, and the bottom-up method is preferably a photolithography method or a laser irradiation method.

The substrate obtained after heating in this example is shown in fig. 5.

Example 4

4.1 ink formulation

melting the compound: diphenyl iodine nitrate 0.26 weight portions and AgNO ₃ 0.33 parts;

polar solvent: 26 parts of deionized water, 3.5 parts of acetone and 69.69 parts of absolute ethyl alcohol;

metal nanowires: 0.22 parts of 30nm silver nanowire;

wherein the AgNO ₃ Is a standard silver nitrate solution.

The preparation method of the optically invisible pattern electrode comprises the following steps:

(1) SU-8 preparation mold: a certain amount of SU-8 photoresist is dripped on a clean glass substrate, the glass substrate is put into a photoresist homogenizer to uniformly coat the photoresist on the substrate, and the photoresist which is excessive at the edge of the substrate is removed. The substrate was heated by slowly heating to a constant temperature of 90℃for 20 minutes. And placing a mask plate above the substrate, wherein the mask plate is provided with a patterned light passing-allowing area. And (5) carrying out illumination for 30s above the mask plate. And removing the mask plate, slowly heating to 80 ℃ to heat the substrate, and determining the heating time according to the required seal depth. Propylene glycol methyl ether acetate (PEN) was coated on the substrate so that the photoresist completely showed the pattern of the mask plate described above. The SU-8 photoresist after the treatment is put into isopropanol until complete reaction.

(2) The PDMS copy mould forms a PDMS soft stamp: PDMS prepolymer (Sylgard 184 elastomer) and curing agent were mixed in a ratio of 10:1 and the mixture was thoroughly stirred with a glass rod. The mixture was placed in a vacuum machine to be evacuated and left to stand for 30 minutes. The bubble-free clear mixture was poured onto the SU-8 mold described above, allowing the mixture to naturally level. The heating station was preheated to 70 ℃ and the mold was heated to cure the PMDS. And stripping the cured PMDS to obtain the PDMS soft stamp.

(3) The clean PEN substrate was placed in an air plasma machine for hydrophilic treatment.

(4) And (3) spin-coating 30nm silver nanowire liquid on the PEN substrate obtained in the step (3) to form a metal nanowire network.

(5) And (3) placing the PDMS soft stamp prepared in the step (2) into a plasma machine for hydrophilic treatment.

(6) And (3) soaking the PDMS soft stamp obtained in the step (5) in the ink for reducing the melting point of the metal nanowire, which is 4.1.

(7) And (3) sticking the PDMS soft stamp carrying the ink obtained in the step (6) onto the target substrate PEN. And heating, wherein the patterned array can be transferred to the target substrate, wherein the metal nanowire network of the part pasted by the soft seal forms a low-melting-point area, and the metal nanowire network of the part not pasted by the soft seal forms a high-melting-point area.

(8) And heating the substrate at 120 ℃, fusing the metal nanowire in the low-melting-point region to form an insulating region, and keeping the metal nanowire in the high-melting-point region intact to form a conductive region, thereby obtaining the required patterned electrode.

Using the steps (1) - (7) of this example, a plurality of optically invisible patterned electrodes were prepared, and the transmittance at 550nm after irradiation with light was as follows:

sample numbering	Transmittance of soft seal sticking area	Transmittance of non-soft seal-pasted area
			1	91.70％	90.50％
2	92.10％	90.90％
			3	91.10％	90.30％
4	89.40％	88.90％
			5	91.80％	89.90％
6	92.40％	90.70％
			7	92.00％	91.40％
8	91.50％	91.00％
			9	91.90％	90.80％

The reflectance at 550nm after exposure and non-exposure of the sample prepared using steps (1) - (7) of this example is compared with the following table:

sample numbering	Reflectivity of soft seal sticking area	Reflectivity of non-soft seal bonded area
			1	5.40％	6.50％
2	5.10％	5.90％
			3	5.40％	6.20％
4	6.60％	6.60％
			5	5.40％	6.60％
6	5.50％	6.30％
			7	5.50％	5.10％
8	5.60％	6.20％
			9	5.50％	6.70％

The sample obtained in this example showed no more than 2% difference in transmittance at 550nm between the low-melting point region and the high-melting point region of the patterned invisible electrode.

The square resistance change of the sample in this example is shown in the following table.

Example 5

5.1 ink formulation

melting the compound: silver iodide 0.16 parts, potassium iodide 0.1 parts, agNO ₃ 0.33 parts;

polar solvent: 26 parts of deionized water, 3.5 parts of acetone and 69.56 parts of absolute ethyl alcohol;

metal nanowires: 0.22 parts of 30nm silver nanowire;

dispersing agent: 0.13 parts of HPMC;

the AgNO ₃ Is a standard silver nitrate solution.

Preparation of MXene/PET substrate: and (3) taking a plurality of clean PET substrates, putting the PET substrates into an air plasma machine for hydrophilic treatment, spin-coating an MXene solution with the concentration of 0.5mg/mL on the PET substrates, and standing to dry the PET substrates to form the PET substrates with the MXene two-dimensional anti-reflection layers.

(1) Suspending and coating 5.1 of the ink for reducing the melting point of the metal nanowire on an MXene/PET substrate, and standing to dry the ink;

(2) Placing a mask plate above the substrate obtained in the step (1), wherein the mask plate is provided with an exposure area allowing light to pass through and a shading area preventing the light from passing through;

(3) Illuminating the substrate above the mask plate by adopting a light source;

(4) The silver nanowire network corresponding to the exposure area on the substrate is kept intact by using the melted compound and illumination, and the original melting point is kept as a high melting point area; simultaneously, fusing a silver nanowire network corresponding to the shading area on the substrate to form a low-melting-point area; when the substrate is heated at 135 ℃, the silver nanowires in the low-melting-point material region are destroyed to form a non-conductive insulating region, and the silver nanowires in the high-melting-point material region are kept intact to form a conductive region, so that the optically invisible pattern electrode is manufactured.

Several samples were prepared using the method of this example, and their reflectivities at 550nm were measured at different regions, respectively, with the results shown in the following table.

Sample numbering	Reflectivity of conductive area of sample	Sample insulation area reflectivity
			1	5.00％	6.30％
2	5.50％	6.30％
			3	5.00％	6.00％
4	5.90％	6.40％
			5	5.10％	6.50％
6	5.30％	6.30％
			7	5.50％	6.20％
8	5.60％	6.20％
			9	5.50％	6.60％

Compared with the example 4, the anti-reflection layer is added on the original substrate, and the prepared experimental sample has lower reflectivity and more excellent optical performance.

The preparation method of the invisible pattern electrode is applicable to various flexible materials, including polydimethylsiloxane, polyethylene terephthalate, polyether sulfone resin, polyethylene, polyimide, polycarbonate, polyurethane, polyethylene naphthalate and the like.

Comparative example 1

The ink for reducing the melting point of the metal nanowire in the comparative example comprises the following components in parts by weight: agNO ₃ 0.1 part

Polar solvent deionized water: 99.9 parts.

The ink described above was deposited on a metal nanowire substrate with reference to example 3.

Experiments show that after 10 minutes of post-baking treatment at 200 ℃, the areas where the ink is not deposited are still conductive, and the areas where the ink is deposited are nonconductive.

Comparative example 2

The ink for reducing the melting point of the metal nanowire in the comparative example comprises the following components in parts by weight: agNO ₃ 1 part of

Polar solvent deionized water: 99 parts.

Comparative example 3

The ink for reducing the melting point of the metal nanowire in the comparative example comprises the following components in parts by weight: diphenyl iodine nitrate 1 part

Polar solvent: 99 parts of deionized water.

It was found experimentally that by heating the substrate at 145 c, the areas where the ink was not deposited remain conductive and the areas where the ink was deposited appear non-conductive.

Comparative example 4

The ink for reducing the melting point of the metal nanowire in the comparative example comprises the following components in parts by weight: 1 part of diphenyl trifluoro methyl sulfonic acid iodine

Polar solvent: 99 parts of deionized water.

It was found that by heating the substrate at 260 c, both the areas where the ink was not deposited and the areas where the ink was deposited still exhibited a conductive state, showing that the effect of lowering the melting point of the ink of this comparative example was not significant.

Comparative example 5

The ink for reducing the melting point of the metal nanowire in the comparative example comprises the following components in parts by weight: 1 part of 2, 4-dinitrophenylhydrazine hydrochloride

Polar solvent: 99 parts of deionized water.

It was found experimentally that by heating the substrate at 200 c, the areas where the ink was not deposited remain conductive and the areas where the ink was deposited appear non-conductive.

From the test data of comparative examples 1, 2, 3 and example 1, it is understood that the ink containing two molten compound components has a better effect of lowering the melting point after deposition on the metal nanowires than the ink containing only one molten compound component. In addition, as can be seen from comparing the ink formulations in comparative example 2 and example 1, by mixing the two molten compound components, on one hand, the effect of the prepared ink in reducing the melting point of the metal nanowires is improved, and on the other hand, the total addition amount of the molten compound in the ink is also reduced.

Example 6

The ink for reducing the melting point of the metal nanowire in this example comprises the following components in parts by weight,

dispersing agent: 1 part of chitosan.

Silver nanowire networks with the specifications of 60nm, 30nm and 17nm are respectively deposited on a plurality of substrates.

Invisible pattern electrodes were prepared with reference to example 1.

The melting point change condition of the metal nanowire modified or unmodified by the ink of the embodiment is shown in figure 6, wherein the ordinate is the substrate square resistance R after the substrate is heated _S And substrate sheet resistance R before heating the substrate ₀ Ratio of the two. Fig. 6 shows that the effect of significantly reducing the melting point of the metal nanowires can be achieved by modifying the different metal nanowires with the ink of the present embodiment.

Example 7

The ink for reducing the melting point of the metal nano wire comprises the following components in parts by weight,

melting the compound: diphenyl iodine nitrate 0.25 weight portions and AgNO ₃ 2.5 parts;

polar solvent: 23.7 parts of deionized water, 3.2 parts of acetone and 69.35 parts of absolute ethyl alcohol;

dispersing agent: 1 part of chitosan.

Invisible pattern electrodes were prepared with reference to example 1.

It was found that by adjusting the temperature of the heating station to 140 c to heat the substrate, the areas where no ink was deposited remain conductive and the areas where ink was deposited appear non-conductive.

Example 8

melting the compound: silver iodate 0.5 part, agNO ₃ 0.25 parts of silver iodide and 0.25 parts of silver iodide;

polar solvent: 25.5 parts of deionized water, 3.5 parts of acetone and 69 parts of absolute ethyl alcohol;

dispersing agent: 1 part of chitosan.

A 17nm metal silver nanowire network was deposited on a clean substrate and an invisible pattern electrode was prepared with reference to example 4.

It was found that after heating at 50 ℃ for 10 minutes on the heating table, the areas where the ink was not deposited remained conductive and the areas where the ink was deposited appeared non-conductive.

Example 9

The above examples and comparative examples can be arranged in the following table showing that the effect of ink composed of two molten compounds to lower the melting point of metal nano-networks is more remarkable than that of a single-component molten compound; further, the ink composed of three molten compounds has a melting point lowering effect superior to that of the ink composed of two molten compounds; in addition, the same mixture of molten compounds is added in different proportions to the metal nanonet, and there is a difference in the effect of lowering the melting point.

It should be understood that the foregoing examples of the present application are merely illustrative of the present application and are not intended to limit the present application to the specific embodiments thereof. Any modification, equivalent replacement, improvement, etc. that comes within the spirit and principle of the claims of the present application should be included in the protection scope of the claims of the present application.

Claims

1. An ink for reducing the melting point of metal nanowires, which is characterized by comprising the following components in parts by weight:

0.1 to 1 part of melted compound, 95.2 to 99.7 parts of polar solvent;

wherein the molten compound is selected from iodonium salt, nitrate composition or acetic acid, nitric acid, metal oxide composition or iodonium salt, brine composition or metal halide, nitrate composition or iodate, nitrate, metal halide composition.

2. The ink for lowering the melting point of metal nanowires according to claim 1, wherein the melted compound is selected from diphenyl iodide nitrate, a silver nitrate composition or acetic acid, nitric acid, an iron oxide composition or diphenyl triflate iodine, an iodowater composition or silver iodide, potassium iodide, a silver nitrate composition or a silver iodate, silver nitrate, silver iodide composition; and/or the polar solvent is selected from one or more of water, acetone, monohydric alcohol and polyhydric alcohol.

3. The ink for reducing the melting point of metal nanowires of claim 2, further comprising 0.1 to 0.8 parts by weight of metal nanowires.

4. The ink for reducing the melting point of metal nanowires according to claim 3, wherein the metal nanowires are one or more of silver nanowires, copper nanowires, iron nanowires; and/or the diameter of the metal nanowire is smaller than 200nm.

5. The ink for lowering the melting point of metal nanowires as recited in claim 2, further comprising 0.1 to 1 part of a dispersant in parts by weight.

6. The ink for lowering melting point of metal nanowires according to claim 5, wherein the dispersant is one or more selected from the group consisting of fluorine-containing nonionic surfactants, sodium dodecylbenzenesulfonate, sodium 3-mercapto-1-propanesulfonate, 4- (1, 3-tetramethylbutyl) phenyl-polyethylene glycol, hydroxypropyl methylcellulose, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylenimine, polyvinylpyrrolidone, polyethylene glycol, chitosan, polyether defoamers, acrylics, acetylenic glycols, silicones, fluorocarbons.

7. A method for preparing an optically invisible patterned electrode, comprising the steps of:

s2, selectively depositing the ink for reducing the melting point of the metal nanowires according to any one of claims 1 to 6 on the substrate obtained in the step S1, wherein the metal nanowires deposited with the ink for reducing the melting point of the metal nanowires according to any one of claims 1 to 6 form low melting point parts, and the metal nanowires not deposited with the ink for reducing the melting point of the metal nanowires according to any one of claims 1 to 6 form high melting point parts;

s3, heating the substrate obtained in the step S2 to fuse the metal nanowire at the low-melting point part, obtaining an insulating region fused by the metal nanowire at the low-melting point part, and obtaining a complete conductive region of the metal nanowire at the high-melting point part to form an optically invisible pattern electrode;

alternatively, the method comprises the following steps:

s01, depositing the ink for reducing the melting point of the metal nano wire in the method for reducing the melting point of the metal nano wire on a substrate, and drying;

s02, placing a mask plate above the substrate obtained in the step S01, wherein the mask plate is provided with an exposure area allowing light to pass through and a shading area preventing the light from passing through; a light source is adopted to irradiate the substrate above the mask plate, a high-melting-point metal nanowire network is formed on the substrate corresponding to the exposure area, and a low-melting-point metal nanowire network is formed on the substrate corresponding to the shading area;

s03, heating the substrate obtained in the step S02, fusing the low-melting-point metal nanowire network, and keeping the high-melting-point metal nanowire network intact, so that an optically invisible pattern electrode is formed.

8. The method of producing an optically invisible patterned electrode according to claim 7, further comprising, before performing step S1 or step S01, the steps of: and coating an anti-reflection layer on the substrate, wherein the anti-reflection layer is a polymer film layer or a two-dimensional material coating.

9. The method for producing an optically invisible patterned electrode according to claim 7 or 8, wherein in step S02, the light source wavelength for irradiation is 200nm to 1600nm; and/or, in step S3 or step S03, the heating temperature is 50 ℃ to 200 ℃.

10. An optically invisible patterned electrode produced by the production method according to any one of claims 7 to 9.