Femtosecond laser reduction direct writing ink, preparation method and application thereof

Abstract

The application provides a femtosecond laser reduction direct writing ink as well as a preparation method and application thereof. The method comprises the following steps: (1) dissolving a metal salt in a mixed solvent of water and a reducing low-carbon alcohol and stirring under heating to obtain an alkaline metal salt dispersion liquid; (2) mixing and stirring the alkaline metal salt dispersion liquid and a nano ferromagnetic material to obtain a suspension liquid; and (3) removing water from the suspension liquid under heating to obtain the femtosecond laser reduction direct writing ink. The nano ferromagnetic material is added in the ink, so that the magnetic permeability of a metal functional pattern can be optimized, the skin depth of electromagnetic waves in the metal layer is reduced, and the weight of a thin film antenna is reduced. The preparation process of the ink is simple and efficient, a special protective gas is not needed for protection, and the manufacturing cost is low.

Description

Technical Field

[0001] This invention relates to the field of laser direct writing technology, and in particular to a femtosecond laser reduction direct writing ink, its preparation method, and its application. Background Technology

[0002] Antennas are a key component of wireless communication systems. Thin-film antennas are an emerging type of antenna that uses polymer thin-film materials as a substrate to print or embed circuitry and electronic components onto the thin film. They offer unique advantages such as light weight, high flexibility, and bendability, and are mainly used in modern wireless communication, microwave radio frequency, and millimeter-wave communication, such as portable mobile devices, smart wearable devices, and satellite communication. To meet diverse application needs, the development of more flexible and lightweight thin-film antennas has become an inevitable trend.

[0003] The functional metallic patterns on the surface of thin-film antennas typically serve as the antenna's operating elements, radiating, receiving, and transmitting electromagnetic waves by forming a current distribution through conductive metal. The conductivity and permeability of the functional metallic patterns together determine the skin depth of the electromagnetic waves operating on the antenna's surface. The smaller the skin depth of the electromagnetic waves on the metal surface, the thinner the metal layer required for the electromagnetic waves to penetrate, which is more conducive to the fabrication of lightweight thin-film antennas.

[0004] Existing technologies for manufacturing metallic functional patterns for thin-film antennas mainly include patch methods, chemical plating, and etching. Compared to these technologies, laser reduction direct writing technology offers superior material adaptability and faster processing speed. Laser reduction direct writing is a maskless metallic pattern manufacturing technology that uses laser energy to reduce high-valence metal ions into elemental metals and deposit them along a specified path. It has achieved certain research results in flexible electronics, integrated circuits, and other fields. The inks used in existing laser reduction direct writing technologies mainly consist of metal salts / metal oxides, solvents, reducing agents, and dispersants. The resulting metallic patterns are primarily composed of elemental metals and a small amount of metal oxides, which are typically non-ferromagnetic semiconductor materials. In particular, the use of an oil film for metallic functional patterns that balance high conductivity and high magnetic permeability, required for thin-film antennas, has not yet been addressed. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in the prior art. Therefore, one object of this invention is to provide a femtosecond laser reduction direct-write ink, its preparation method, and its application.

[0006] In a first aspect, the present invention provides a method for preparing femtosecond laser reduction direct writing ink, the method comprising:

[0007] (1) Dissolve the metal salt in a mixed solvent of water and reducing low carbon alcohol and heat and stir to obtain a basic metal salt dispersion;

[0008] (2) The basic metal salt dispersion and the nano-ferromagnetic material are mixed and stirred to obtain a suspension;

[0009] (3) The suspension is heated to remove water, and femtosecond laser reduction direct writing ink is obtained.

[0010] According to the method for preparing femtosecond laser reduction direct-write ink provided by the present invention, firstly, a metal salt is dissolved in a mixed solvent of water and a reducing low-carbon alcohol and heated and stirred. Heating and stirring allow the metal salt and water to react fully, resulting in a basic metal salt dispersion. The inventors have discovered that only by first generating the above-mentioned basic metal salt dispersion and then using the ink prepared from it can the metal functional pattern of a thin-film antenna be obtained through laser direct writing. If only the metal salt solution is used to prepare the ink, the metal functional pattern of the thin-film antenna cannot be obtained. Furthermore, by adding the reducing low-carbon alcohol, which has the dual function of being both a metal salt solvent and a metal ion reducing agent, the reducing low-carbon alcohol reduces the metal ions to elemental metals under laser irradiation and volatilizes and removes them, thus avoiding any negative impact on the conductivity of the metal pattern. Then, the basic metal salt dispersion is mixed and stirred with nano-ferromagnetic materials to uniformly disperse the nanomaterials. After stirring for a period of time, a uniformly dispersed suspension is obtained. By adding nano-ferromagnetic materials, the permeability of the metal functional pattern can be optimized, and the skin depth of electromagnetic waves in the metal layer can be reduced. Finally, the suspension obtained above is heated to remove water, and femtosecond laser reduction direct writing ink can be obtained.

[0011] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, in step (1), the volume ratio of water to the reducing low-carbon alcohol is 1:(3-6). Controlling the volume ratio of water to reducing low-carbon alcohol within the above range can ensure the reducing ability of the material system, while effectively dissolving metal salts and maintaining the diffusion ability of metal ions.

[0012] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, in step (1), the mass ratio of water to metal salt is 1:(1-10). Controlling the mass ratio of water to metal salt within the above range can effectively dissolve the metal salt, release metal ions into the solution to participate in the reaction, and avoid the metal ions being unable to nucleate due to too low concentration, or the metal salt being incompletely dissolved due to insufficient solvent.

[0013] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, the reducing low-carbon alcohol is selected from one or more of methanol, ethylene glycol, propylene glycol, and glycerol.

[0014] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, the metal salt is selected from one of copper chloride, copper nitrate, copper formate, nickel chloride, nickel nitrate, and nickel formate.

[0015] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, in step (1), the heating temperature is 110-180℃ and the heating time is 10min-2h. By controlling the heating temperature and time within the above range, it can be ensured that the metal salt and water undergo sufficient hydrolysis reaction to obtain a uniform basic metal salt dispersion.

[0016] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, in step (2), the nano-ferromagnetic material is selected from one of iron, nickel, cobalt, iron-nickel alloy, spinel ferrite, ferric oxide, iron tetroxide, and cobalt oxide, preferably iron tetroxide or spinel ferrite. The inventors have found that by using the above-mentioned nano-ferromagnetic material, the permeability of the metal functional pattern can be significantly optimized, and the skin depth of electromagnetic waves in the metal layer can be effectively reduced.

[0017] In some embodiments of the present invention, the diameter of the nano-ferromagnetic material is 20 nm to 100 nm. For example, the diameter of the nano-ferromagnetic material is 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, etc., or any range between any two of the above values. The inventors have found that controlling the diameter of the nano-ferromagnetic material within the above range can achieve uniform dispersion of the nanomaterial and avoid severe agglomeration due to excessively high surface energy or precipitation due to excessive density. It should be noted that the shape of the nano-ferromagnetic material is granular, similar to a sphere, and the size of the nano-ferromagnetic material is represented by the diameter of the largest approximate spherical shape.

[0018] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, in step (2), the mass ratio of the nano-ferromagnetic material to the metal salt is 1:(1-100). For example, the mass ratio of the nano-ferromagnetic material to the metal salt is 1:1, 1:5, 1:10, 1:20, 1:30, 1:40, 1:80, 1:100, etc., or any range between any two of the above values. The inventors have found that controlling the mass ratio of the nano-ferromagnetic material to the metal salt within the above range can improve the permeability of the metal functional pattern, while avoiding excessive nanomaterial content that reduces the conductivity of the metal functional pattern.

[0019] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, in step (2), the stirring includes ultrasonic stirring, magnetic stirring, or mechanical stirring, and the stirring time is preferably 2h-4h. By selecting the preferred stirring method and time, the nanomaterials are uniformly dispersed, while avoiding the agglomeration and precipitation of basic salts formed by the reaction of metal ions with water.

[0020] According to the method for preparing femtosecond laser reduction direct writing ink provided by the present invention, in step (3), the heating temperature is 70-120℃, and the heating time is 12 h-24 h. Controlling the heating temperature and time within the above range effectively removes excess water from the ink.

[0021] In a second aspect, the present invention provides a femtosecond laser reduction direct-write ink, which is prepared by the method described above. Therefore, this femtosecond laser reduction direct-write ink can improve the permeability of the functional pattern in the metal, reduce the skin depth of electromagnetic waves in the metal layer, and contribute to weight reduction of thin-film antennas.

[0022] In some embodiments of the present invention, the ink viscosity is not less than 700 mP∙s.

[0023] In some embodiments of the present invention, the ink has a weakly acidic pH, preferably 3-4.

[0024] In a third aspect, the present invention proposes the application of the aforementioned femtosecond laser-reduced direct-write ink in the fabrication of metallic functional patterns on the surface of thin-film antennas. The present invention utilizes femtosecond laser reduction to directly write metallic functional patterns, which avoids the re-oxidation of the reduced metal caused by excessive thermal impact from long-pulse or continuous lasers, thus reducing the impact on the conductivity of the metallic pattern.

[0025] The application of femtosecond laser reduction direct-write ink provided by the present invention in the fabrication of metallic functional patterns on the surface of thin-film antennas, wherein the femtosecond laser fabrication process of the metallic functional patterns on the surface of the thin-film antenna includes: using a femtosecond laser equipped with a scanning galvanometer system, with a laser pulse width of 10... -15 -10 -12 The laser wavelength is 500-1100 nm, the pulse repetition frequency is 100 kHz-1 MHz, the average laser power is 1-8 W, the spot diameter is 10-300 μm, and the spot movement speed is 1-500 mm / s.

[0026] In some embodiments of the present invention, ink is applied to the surface of a flexible film to form a film, and then a femtosecond laser is used to recreate the direct-write metallic functional pattern. The above-mentioned coating method includes one of spin coating, blade coating, and drop coating; the above-mentioned flexible film includes one of polyimide, polyethylene terephthalate, and polycarbonate.

[0027] This invention has at least the following technical effects:

[0028] (1) The present invention adds nano-ferromagnetic materials to the ink, which can optimize the permeability of the metal functional pattern, reduce the skin depth of electromagnetic waves in the metal layer, and help reduce the weight of thin film antenna.

[0029] (2) The present invention uses low-carbon polyol in the ink preparation process, which has the dual function of metal salt solvent and metal ion reducing agent. Under the action of laser, the metal ions are reduced to metal element and volatilized and removed. Therefore, the negative impact on the conductivity of metal pattern is avoided, which helps to achieve weight reduction of thin film antenna.

[0030] (3) In the preparation process of ink, the present invention first allows metal salt ions and water to undergo a full hydrolysis reaction under heating and stirring to obtain basic metal salts. Stirring avoids the agglomeration and precipitation of basic metal salts, thereby effectively realizing the manufacturing of metal functional patterns for thin film antennas, greatly shortening the reaction time and improving production efficiency.

[0031] (4) The preparation process of the ink of the present invention is simple and efficient, requires no special protective gas protection, and has low manufacturing cost. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a photograph of the ink produced in Embodiment 1 of the present invention;

[0034] Figure 2 This is a physical image of the femtosecond laser-restored direct-write metal pattern obtained in Embodiment 1 of the present invention;

[0035] Figure 3 This is a photograph of the ink produced in Embodiment 2 of the present invention;

[0036] Figure 4 This is the relative permittivity diagram of the metal pattern obtained by measurement and calculation in Embodiment 2 of the present invention;

[0037] Figure 5 This is the relative permeability diagram of the metal pattern obtained by measurement and calculation in Embodiment 2 of the present invention. Detailed Implementation

[0038] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0039] Example 1

[0040] (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution.

[0041] (2) Heat the copper ion solution to 170°C for 25 min. After the solution produces bubbles and releases a yellow-brown gas, cool the solution to room temperature to obtain a basic copper nitrate dispersion.

[0042] (3) Weigh 50 mg of iron(III) oxide (diameter 80-100 nm) and add it to the basic copper nitrate dispersion. Place the mixed liquid in an ultrasonic vibrator with a frequency of 40 kHz and vibrate for 2 h to obtain a uniformly dispersed suspension.

[0043] (4) Place the suspension on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirring speed to 1000 r / min, heat for 12 h, and finally obtain copper ion ink;

[0044] (5) Apply the ink evenly to the surface of the polyimide film using a scraper;

[0045] (6) A femtosecond laser with a pulse width of 1030 nm, a repetition rate of 100 fs, and a repetition rate of 100 kHz was used to reduce the copper ion ink for direct writing of the copper pattern. The laser power was 3.5 W, the spot diameter was 40 μm, and the scanning speed was 30 mm / s. After processing, the excess metal ion film was rinsed off with deionized water and ethanol, and then dried with compressed air.

[0046] in, Figure 1 Here is a physical image of the copper ion ink obtained in Example 1; Figure 2 This is a physical image of the metal pattern obtained after femtosecond laser reconstruction and direct writing in Example 1. The measured conductivity of the functional metal pattern is 4.5 × 10⁻⁶. 4 S / m.

[0047] Example 2

[0048] (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution.

[0049] (2) Heat the copper ion solution to 170°C for 25 min. After the solution produces bubbles and releases a yellow-brown gas, cool the solution to room temperature to obtain a basic copper nitrate dispersion.

[0050] (3) Weigh 50 mg of spinel ferrite (40-50 nm in diameter) and add it to the basic copper nitrate dispersion. Place the mixed liquid in an ultrasonic vibrator with a frequency of 40 kHz and vibrate for 2 h to obtain a uniformly dispersed suspension.

[0051] (4) Place the suspension on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirring speed to 1000 r / min, heat for 12 h, and finally obtain copper ion ink;

[0052] (5) Apply the ink evenly to the surface of the polyethylene terephthalate film by scraping;

[0053] (6) A femtosecond laser with a pulse width of 100 fs and a repetition frequency of 600 kHz was used to reduce the copper ion ink for direct writing of the copper pattern. The laser power was 3 W, the spot diameter was 40 μm, and the scanning speed was 20 mm / s. After processing, the excess metal ion film was rinsed off with deionized water and ethanol, and then dried with compressed air.

[0054] in, Figure 3 Here is a physical image of the copper ion ink obtained in Example 2; Figure 4 The relative permittivity of the metal pattern was obtained by measurement and calculation in Example 2; Figure 5 This is the relative magnetic permeability of the metal pattern obtained through measurement and calculation in Example 2. From... Figure 4 It can be seen that when the incident electromagnetic wave frequency is <6 GHz, the real part of the relative permittivity of the metal pattern can reach below -20. As the electromagnetic wave frequency increases, the relative permittivity approaches 0, indicating that the metal pattern can store more electric field energy in the low-frequency region, reduce electromagnetic wave reflection, and increase absorption performance, while it is not sensitive to frequency in the high-frequency region and has more stable performance over a wide bandwidth. Figure 5 It can be seen that the real part of the relative permeability of the metal pattern reaches 2-3 in the electromagnetic wave band of 2-3 GHz, indicating that the metal pattern exhibits significant magnetic loss, which helps to optimize impedance matching. For high-frequency electromagnetic waves, the real part of the permeability gradually decreases and approaches 1, showing low magnetic loss and is not affected by relaxation effect. Figure 4-5 This demonstrates that the metal pattern manufactured in Example 2 can be selected according to the antenna application scenario and electromagnetic wave frequency band, such as miniaturized antennas, low-frequency communication antennas, high-frequency communication (5G) antennas, etc.

[0055] Comparative Example 1

[0056] (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution.

[0057] (2) Heat the copper ion solution to 170°C for 25 min. After the solution produces bubbles and releases a yellow-brown gas, cool the solution to room temperature to obtain a basic copper nitrate dispersion.

[0058] (3) Place the basic copper nitrate dispersion on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirrer speed to 1000 r / min, and heat for 12 h to finally obtain copper ion ink;

[0059] (4) Apply the ink evenly to the surface of the polyethylene terephthalate film by scraping;

[0060] (5) A femtosecond laser with a wavelength of 1030 nm, a pulse width of 100 fs, and a repetition frequency of 100 kHz was used to reduce the copper ion ink for direct writing of the metallic copper pattern. The laser power was 3.5 W, the spot diameter was 40 μm, and the scanning speed was 30 mm / s. After processing, the excess metal ion film was rinsed off with deionized water and ethanol, and then dried with compressed air.

[0061] Because the ink lacks ferromagnetic nanomaterials, the femtosecond laser processing area lacks non-uniform nucleation sites for metal atoms. Furthermore, compared to inks containing nanomaterials, the ink in Comparative Example 1 primarily absorbs laser energy through metal ions. This results in excessively deep laser beam penetration within the ink, leading to overly dispersed laser energy that fails to meet the required temperature for metal ion reduction. Consequently, the ink used in Comparative Example 1 cannot form a metallic pattern.

[0062] Comparative Example 2

[0063] (1) Measure 6 mL of ethylene glycol and 1.5 mL of deionized water and mix them evenly as a mixed solvent. Weigh 4 g of copper nitrate and add it to the mixed solvent until it is completely dissolved to obtain a copper ion solution.

[0064] (2) Weigh 50 mg of iron(III) oxide (40-50 nm in diameter) and add it to the copper ion solution. Place the mixed liquid in an ultrasonic vibrator with a frequency of 40 kHz and vibrate for 2 h to obtain a uniformly dispersed suspension.

[0065] (3) Place the suspension on a magnetic stirring platform with heating function, set the temperature to 120℃, set the magnetic stirring speed to 1000 r / min, heat for 12 h, and finally obtain copper ion ink;

[0066] (4) Apply the ink evenly to the surface of the polyethylene terephthalate film by scraping;

[0067] (5) A femtosecond laser with a wavelength of 1030 nm, a pulse width of 100 fs, and a repetition frequency of 100 kHz was used to reduce the copper ion ink for direct writing of the copper pattern. The laser power was 3 W, the spot diameter was 40 μm, and the scanning speed was 20 mm / s. After processing, the excess metal ion film was rinsed off with deionized water and ethanol, and then dried with compressed air.

[0068] Because the ink preparation process lacks the crucial step of heating and stirring to prepare a basic copper dispersion, the ink consists entirely of acidic salts dissolved in the solvent. Strong acid anions possess strong oxidizing properties. Compared to strong acid-weak base salts, basic salts are less stable and more easily decompose into intermediate products and be reduced to elemental metals under laser heating and reducing solvents. Therefore, the ink used in Comparative Example 2 also failed to produce a metallic copper pattern.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing femtosecond laser reduction direct-write ink, characterized in that, include: (1) Dissolve the metal salt in a mixed solvent of water and reducing low carbon alcohol and heat at 110-180℃ for 10 min-2 h with stirring to obtain a basic metal salt dispersion. (2) The basic metal salt dispersion and the nano-ferromagnetic material are mixed and stirred to obtain a suspension; (3) The suspension is heated at 70-120℃ for 12-24 hours to remove water, and femtosecond laser reduction direct writing ink is obtained; In step (2), the nano-ferromagnetic material is selected from one of iron, nickel, cobalt, iron-nickel alloy, spinel ferrite, ferric oxide, iron tetroxide, and cobalt oxide; The diameter of the nano-ferromagnetic material is 20nm-100nm; In step (1), the volume ratio of water to the reducing low-carbon alcohol is 1:(3-6). The mass ratio of water to metal salt is 1:(1-10). In step (2), the mass ratio of the nano-ferromagnetic material to the metal salt is 1:(1-100). The reducing lower alcohol is selected from one or more of methanol, ethylene glycol, propylene glycol, and glycerol; The metal salt is selected from one of copper chloride, copper nitrate, copper formate, nickel chloride, nickel nitrate, and nickel formate.

2. The method according to claim 1, characterized in that, In step (2), the nano-ferromagnetic material is selected from iron oxide or spinel ferrite.

3. The method according to claim 1, characterized in that, In step (2), the stirring includes ultrasonic stirring, magnetic stirring or mechanical stirring.

4. The method according to claim 3, characterized in that, The stirring time is 2-4 hours.

5. A femtosecond laser reduction direct writing ink, characterized in that, It is prepared by any one of the methods described in claims 1-3.

6. The application of the femtosecond laser reduction direct writing ink of claim 5 in the preparation of metallic functional patterns on the surface of thin-film antennas.

7. The application according to claim 6, characterized in that, The femtosecond laser fabrication process for the metallic functional pattern on the surface of the thin-film antenna includes: using a femtosecond laser equipped with a scanning galvanometer system, with a laser pulse width of 10. -15 -10 -12 The laser wavelength is 500-1100 nm, the pulse repetition frequency is 100 kHz-1 MHz, the average laser power is 1-8 W, the spot diameter is 10-300 μm, and the spot movement speed is 1-500 mm / s.

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