CN100424142C - A kind of water-based conductive ink and preparation method thereof - Google Patents

Abstract

The present invention provides water soluble conductive ink and a preparing method thereof. The water soluble conductive ink contains the components of the following weight percentage: 30 to 50% of water soluble high molecular resin, 15 to 25% of conductive pigment acetylene carbon ink, 12 to 20% of water, 8 to 12% of alcohol, 3 to 8% of ethylene glycol monobutyl ether, 4 to 9% of a silane surface treating agent, 2 to 5% of an antistatic agent and 1 to 3% of an auxiliary agent. The ink uses the water soluble high molecular resin as connection material. The water soluble high molecular resin, conductive pigment, a solvent and the related auxiliary agent are compounded and ground to form the water soluble conducting ink. The water soluble conductive ink has the characteristics of low resistivity, stable conductivity, high bending resistance and strong adhesion and has no damage to environment and a human body during utilization. The water soluble conductive ink overcomes the defects of environment pollution, damage to worker health and low yield and high cost of a silk screen printing mode of conventional solvent conductive ink. The water soluble conductive ink has the advantages of high ink density, low viscosity and high printing adaptability, is particularly suitable for soft plate printing and intaglio printing and can greatly enhance the production efficiency of electronic products.

Description

A kind of water-based conductive ink and preparation method thereof

technical field

The invention relates to a preparation technology of water-based conductive ink which is processed with water-based polymer resin as a linking material, conductive acetylene carbon ink as a pigment, and processed with water, ethanol and auxiliary agents.

Background technique

At present, microelectronics technology is infiltrating into various fields, and conductive printing technology emerges as a high-tech. For example, the membrane switch circuit board is made by printing ink on PET film, and then combining the printed film with decorative art panels; it has simple structure, beautiful appearance, excellent environmental resistance, and long service life (more than 1 million times) And other advantages, are widely used in fax machines, copiers, telephones, mobile phones, electronic toys, measuring devices and medical instruments. Ink printed circuit board has simple process, high efficiency, and saves metal copper. It is an effective way to reduce the cost of microelectronics products. Others are used in touch sensor panels, printed flat fine cables, low-cost solar cells, and liquid crystal displays. Current and infrared detection sensitive components, etc., have various applications in the field of microelectronics. In addition, the electrothermal film is made by printing ink between two layers of flame-retardant material PET. It converts electrical energy into heat energy through conductive ink and maintains a constant temperature method; its flexible products can be bent and can be designed according to user needs. Different power specifications; mainly used in: anti-fog mirrors, refrigerator defrosting, health care products, electric heating pads, electric heating clothes, electric heating belts, agricultural greenhouses, fish farming, industrial pipeline insulation, northern automobile mirrors, train sleepers and other industries field.

The traditional production method of the above products is to use conductive carbon paste or silver paste, and adopt the method of screen printing. Its conductive carbon paste or silver paste uses polyester, epoxy, and phenolic resins as linking materials, and uses aromatic hydrocarbons, esters/alcohols, ketones, alcohol ethers, etc. as solvents. During the use of these products, due to The volatilization of organic solvents not only pollutes the environment, but also endangers the health of operators. Moreover, the screen printing method has low output and high cost, and cannot be mass-produced. With the development of the times and the progress of mankind, people have paid more and more attention to environmental protection issues, so the need for environmentally friendly conductive printing inks is becoming more and more urgent.

Contents of the invention

In order to overcome the problems existing in the existing conductive printing technology, the present invention provides a water-based conductive ink that uses water-based polymer resin as the ink binder, and is processed by compound grinding with conductive pigments, solvents and related additives. The ink has the advantages of good conductivity, high stability, good adhesion, low curing temperature and wide material resources, and its preparation method is simple and feasible.

The technical solution provided by the invention is: a water-based conductive ink, containing 30-50% of a modified acrylic acid water-soluble resin prepared by graft copolymerization of organosilicon monomers and acrylic ester monomers, 15-25% Conductive pigment acetylene carbon ink, 12-20% water, 8-12% ethanol, 3-8% ethylene glycol butyl ether, 4-9% silane surface treatment agent, 2-5% antistatic agent And 1-3% of auxiliary agent, the auxiliary agent at least includes dispersant, defoamer, and leveling agent, and the above percentages are all mass percentages.

The preparation method of the above-mentioned ink provided by the present invention is: first carry out graft copolymerization with organosilicon monomer and propylene ester monomer to make modified acrylic acid water-soluble resin for use, then select acetylene carbon ink as conductive pigment, and then use The specific steps are as follows:

(1) Put the modified acrylic water-soluble resin, conductive pigment, water, ethanol, butyl glycol ether and silane surface treatment agent into the dispersing tank according to the formula, and stir well to disperse evenly.

(2) Transfer the dispersed material to a sand mill and grind until the fineness reaches below 10 μm.

(3) After the ground material is filtered and evenly dispersed with the antistatic agent and auxiliary agent, the required ink is obtained.

The salient features of the water-based conductive ink provided by the invention are:

1. Modified water-based acrylic resin can meet the characteristic requirements of conductive ink binder.

The linking material is the film-forming substance in the conductive ink. The linking material in the ink is not necessarily required to be a conductive polymer. It only requires that it does not produce resistivity as long as it is cured within a certain temperature range. This is the advantage of conductive inks. characteristic. The resin used as the linking material not only plays the role of sealing the conductive pigment in the ink, but also plays the role of connecting the conductive particles to form a film. Therefore, it is necessary to use a high molecular polymer with small resistance change and high stability as the linking material to make the conductive particles It has good dispersibility, small mobility, and small conductive error in the binder, which can endow the ink film with physical and chemical stability. The linking material makes the conductive pigment form a printing material with a certain viscosity before printing the graphics to complete the graphic transfer of the printing method. After printing, it undergoes a curing process to form a stable combination between the conductive pigment particles and the particles, and between the particles and the substrate. . Using the existing water-based resins on the market as adhesives to make water-based conductive inks, it was found that these binders have poor adhesion to PET films and high brittleness, which cannot meet the requirements for preparing conductive inks. So we consider grafting copolymerization of organosilicon monomers and acrylic monomers with good toughness, strong hydrophobicity and low surface tension to make water-soluble polymer resins, so as to improve the surface tension of water-based acrylic resins and reduce resin Improve the cohesion of the resin and improve the flexibility of the resin, thereby improving the adhesion of the resin to the PET film. The water-based acrylic resin is recognized as an environmentally friendly resin, and it also meets the requirements of conductive ink binders.

2. The conductive pigment acetylene carbon ink is cheap and good.

Conductive pigments are conductive particles, which require good conductivity, high stability, low curing temperature, and a wide range of material sources. Commonly used are gold powder, silver powder, copper powder, nickel powder, aluminum powder, carbon black, graphite and other composite powders. When choosing carbon black as the conductive pigment, consider that although the conductivity is not as high as silver powder, it is cheap and can meet the anti-static requirements. If the amount is appropriate, it will have little effect on the physical properties of the ink. Acetylene carbon ink is used as the conductive pigment of the ink, its average particle size is only 4 μm, the DET specific surface area is 65 (m ² /g), and the oil absorption value is 250 (g/100g); it takes into account the conductivity of the conductive ink and better coating Performance, and considering the need to reduce production costs as much as possible, the selected carbon black concentration is in the stable area of 15% to 30%. Such a comprehensive consideration finds that acetylene carbon ink is suitable as the conductive pigment of the ink.

3. Choosing deionized water, ethanol, etc. as the ink solvent is completely environmentally friendly.

The main function of the solvent in the conductive ink is (1) to dissolve the resin, to fully disperse the conductive particles (ie pigment) in the polymer, and to give the ink properties. (2) Adjust viscosity and give printing adaptability. (3) Adjust the drying speed of the ink. The solvent of water-based conductive ink is particularly required not only to be hydrophilic, but also to be environmentally friendly. The deionized water, ethanol and ethylene glycol butyl ether we choose as ink solvents are fully compatible with polymer water-based resins and conductive pigments, thus ensuring the environmental performance of water-based conductive inks.

4. Select the appropriate additives.

The addition of additives will have a negative impact on the conductivity of conductive inks. In the case of weighing the pros and cons, we selectively added some silane surface treatment agents, dispersants, defoamers, leveling agents, and antistatic agents. wait. The addition of these additives can improve the product quality of water-based conductive ink.

The main features of the water-based conductive ink products produced in this way are as follows:

(1) The product has no irritating odor and no volatilization of organic solvents (VOC), which is conducive to environmental protection and ensures the safety and health of the workers in the printing workshop.

(2) The product can be directly diluted with water during use, and the printing equipment can be washed with water directly after printing, which has no pollution to the environment of the printing workshop.

(3) The product is not only suitable for traditional screen printing, but also more suitable for today's advanced flexographic and gravure printing methods. Compared with screen printing, the production efficiency is increased by more than 20 times, and continuous production is possible.

(4) The product is cured at low temperature, the ink layer is cured quickly, the adhesion is good, and the curing temperature is within 100°C.

(5) It satisfies the use requirements of low resistivity, good electrical conductivity and high stability, and has a wide source of materials and low production cost, which is definitely a green product.

Detailed ways

The present invention will be further illustrated by the following examples, and the examples are only to illustrate the present invention and in no way limit the present invention.

Example 1: Graft copolymerization of organosilicon monomers and acrylic ester monomers to prepare a modified acrylic acid water-soluble resin capable of cross-linking and curing within 100°C without generating electrical resistivity. Take 36% modified acrylic water-soluble resin, 18% acetylene carbon ink, 18% water, 12% ethanol, 5% ethylene glycol butyl ether, 6% silane surface treatment agent, 3% antistatic agent, 2% additives, additives include 1% dispersant, 0.5% defoamer, 0.5% leveling agent, the above percentages are mass percentages. Put the resin, conductive pigment, water, ethanol, butyl glycol ether and silane surface treatment agent into the dispersing tank, stir well and disperse evenly. Then transfer the dispersed material to a sand mill and grind until the fineness reaches below 10 μm. Finally, filter the ground material and disperse it evenly with antistatic agent and auxiliary agent to obtain the required ink.

The main technical indicators of the water-based conductive ink product prepared according to the above ratio are as follows:

project Technical indicators Measured indicators Testing Standards Viscosity (coated - 4 cups) ＞30 seconds 60 seconds GB/T1723-1993 Fineness 3～10μm 5μm GB/T1724-1989 Hardness ≥2H 3H GB/T6739-1996 Adhesion 100/100 100/100 GB/T13217.7-1991 PH value 8～9 8.5 PH tester Surface resistance (Ω.cm²) ≤5 2 Volume resistance (Ω.cm) ≤1×10^-2 1×10^-3 (Ink film thickness 3μm) Heat resistance (85±2℃, 480h)  Resistance change rate＜10% <4% Humidity resistance (40℃, 90%RH, 480h)  Resistance change rate＜10% <6% Bending resistance (360° bending)  Resistance change rate＜15% <7%

The water-based conductive ink product is printed on the PET film by gravure printing, and the building electric heating film product (20W/piece) produced can be installed in the ceiling or in the floor in the civil building. The actual test of the user's trial And the ink quality inspection proves that the water-based conductive ink has reached the expected quality level.

Example 2: Graft copolymerization of organosilicon monomers and acrylic ester monomers to prepare a modified acrylic acid water-soluble resin capable of cross-linking and curing within 100°C without generating electrical resistivity. Take 42% modified acrylic water-soluble resin, 20% acetylene carbon ink, 16% water, 9% ethanol, 4% butyl glycol ether, 5% silane surface treatment agent, 2% antistatic agent, 2% Auxiliaries (including 1% dispersant, 0.5% defoamer, 0.5% leveling agent, etc.). The above percentages are all percentages by mass.

The specific operation steps of preparing conductive ink are the same as embodiment 1, and the main technical indicators of the prepared water-based conductive ink product are as follows:

Fineness: ≤10μm

Viscosity: 1000～3000cp

PH value: 8.0～9.0

Surface resistance: ≤5Ω/cm ² (can be adjusted as required)

Volume resistance (ink film thickness 10μm): ≤1×10 ^-2 Ω·cm (can be adjusted as required)

Pencil hardness: ≥3H

Adhesion: 100% (tape peel test)

Heat resistance: (85℃52℃, 480h) resistance value change within 10%

Humidity resistance: (40℃190%RH: 480h) resistance value changes within 10%

Bending resistance: Bending 3 times within 360 degrees, the change of resistance value is within 15%

This product is printed on the polyester film by screen printing, and the handwriting board produced is resistant to pressing, has no cracks, and has stable product performance. It can also be widely used for printing circuit boards of electronic products such as membrane switches, control instruments, industrial computers, and telecommunication instruments.

Example 3: Graft copolymerization of organosilicon monomers and acrylic monomers to prepare a modified acrylic acid water-soluble resin capable of cross-linking and curing within 100°C without generating electrical resistivity. Take 44% modified acrylic water-soluble resin, 16% acetylene carbon ink, 12% water, 10% ethanol, 6% butyl glycol ether, 7% silane surface treatment agent, 2% antistatic agent, 3% Auxiliaries (including 1% dispersant, 0.5% defoamer, 0.5% leveling agent, etc.). The above percentages are all percentages by mass.

The specific operation steps of preparing conductive ink are the same as embodiment 1, and the main technical indicators of the prepared water-based conductive ink product are as follows:

Fineness: ≤5μm

Viscosity: 1000～3000cp

PH value: 8.0～9.0

Surface resistance: ≤5Ω/cm ² (can be adjusted as required)

Volume resistance (ink film thickness 1.5μm): ≤1×10 ^-2 Ω·cm (can be adjusted as required)

Pencil hardness: ≥2H

Adhesion: 100% (tape peel test)

Heat resistance: (85°C 52°C, 480h) resistance value change within 10%

Humidity resistance: (40℃190%RH: 480h) resistance value change within 10%

Bending resistance: bend 3 times within 360 degrees, the change of resistance value is within 15%

This product is printed on PVC sheet by flexographic printing, and the electronic product packaging bag made has the function of screen.

Claims (2)

1. A water-based conductive ink, containing 30-50% of modified acrylic water-soluble resin prepared by graft copolymerization of organosilicon monomer and propylene ester monomer, and 15-25% of conductive pigment acetylene carbon ink , 12-20% water, 8-12% ethanol, 3-8% ethylene glycol butyl ether, 4-9% silane surface treatment agent, 2-5% antistatic agent and 1-3% auxiliary Agents, auxiliary agents at least include dispersants, defoamers and leveling agents, the above percentages are mass percentages. 2. The preparation method of the described water-based conductive ink of claim 1 is characterized in that first carry out graft copolymerization with organosilicon monomer and propylene ester monomer and make modified acrylic acid water-soluble resin stand-by, then select acetylene carbon ink for use As conductive pigment, adopt following specific steps to make again: (1) Put the modified acrylic water-soluble resin, conductive pigment, water, ethanol, butyl glycol ether and silane surface treatment agent into the dispersing tank according to the formula, and stir well to disperse evenly. (2) Transfer the dispersed material to a sand mill and grind until the fineness reaches below 10 μm. (3) After the ground material is filtered and evenly dispersed with the antistatic agent and auxiliary agent, the required ink is obtained.