TWI434911B - Conductive paste - Google Patents

Description

Conductive plastic

This invention relates to a conductive paste, and more particularly to a conductive paste comprising imidazole derivatives.

Conductive adhesive is a cured or dried adhesive that has been widely used in many electronic products (solar cells or light-emitting diodes) to help electronic components. Conduction and follow-up.

At present, in the research on conductive paste, some increase the conductivity by changing the solid content of the conductive particles, changing the particle shape of the conductive particles, and dispersing the conductive particles.

However, commercially available conductive pastes usually have a conductivity increase by increasing the content of the conductive metal, for example, in a conductive silver paste, 80-95% of silver powder is required to achieve the desired conductivity. However, the price of silver powder remains high, making the cost of conductive paste limited.

Therefore, there is an urgent need in the industry to provide a conductive adhesive which can have high conductivity without adding a high content of conductive particles to reduce the cost of the conductive adhesive.

The present invention provides a conductive paste comprising: a plurality of conductive particles; and an imidazole derivative, wherein the imidazole derivative has the following chemical formula (I) or (II): Wherein R ₁ includes a substituted or unsubstituted C ₁ -C ₂₀ alkyl group; and R ₂ and R ₃ each independently include a substituted or unsubstituted C ₁ -C ₂₀ alkyl group. (alkyl group); and Z ^- is an anion.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The present invention provides a conductive paste comprising a plurality of conductive particles; and an imidazole compound, wherein the imidazole compound has the following chemical formula (I) or (II): Wherein R ₁ includes a substituted or unsubstituted C ₁ -C ₂₀ alkyl group; R ₂ and R ₃ each independently comprise a substituted or unsubstituted C ₁ -C ₂₀ alkyl group; ^- is an anion.

The above R ₁ includes a C ₆ -C ₁₄ alkyl group such as C ₆ H ₁₃ , C ₁₀ H ₂₁ , C ₁₂ H ₂₅ , C ₁₄ H ₂₉ , C ₅ H ₁₀ COOH.

The above R ₂ or R ₃ each independently includes a C ₆ -C ₁₄ alkyl group such as C ₆ H ₁₃ , C ₁₂ H ₂₅ , C ₁₄ H ₂₉ , C ₅ H ₁₀ COOH, C ₆ H ₁₂ OH.

It should be noted that the above R ₁ , R ₂ , and R ₃ may also be a straight or branched C ₁ -C ₂₀ alkyl group, or may be saturated or saturated C ₁ -C ₂₀ alkyl.

The above Z ^- includes Br ^- , PF ₆ ^- , BF ₄ ^- or NO ₃ ^2- . It should be noted that in addition to the above anions, it is also within the scope of the present invention that other anions can form an ionic bond with the imidazole ring.

The above conductive particles include silver (silver, Ag), gold (gold), nickel (nickel), copper (copper, copper), platinum (platinum, Pt), palladium (Palladium) or the like. And the particle size of the conductive particles may be on the order of micrometers, or mixed with micron grade and nanometer grade, the micron scale has a particle size of about 0.1-10 μm, preferably 1-5 μm, and the nanometer particle size is about 10 -100 nm, preferably 20-50 nm.

In one embodiment, 2.5 μm of silver particles and the imidazole derivative of the formula (III) are mixed at a weight ratio of 6 to 4, and the electrical resistance can reach 10 ^-5 Ω ‧ cm.

In another embodiment, 2.5 μm silver particles (adding 0.01% by weight of 20 nm silver particles) and the imidazole derivative of the formula (IV) are mixed at a weight ratio of 6 to 4, and the resistance value is up to 10 ^-5 Ω. ‧cm.

The conductive particle component in the conventional conductive paste must be greater than 80% by weight to have the desired conductivity, and the imidazole derivative of the present invention accounts for about 0.1-40% by weight of the entire conductive paste, and the resistance value of the conductive paste (volume) The resistivity) is about 10 ² -10 ^-6 Ω ‧ cm. Since the imidazole derivative mainly plays the role of a dispersing agent, the conductive particles in the conductive paste can be uniformly dispersed. Therefore, in the conductive paste of the present invention, high conductivity can be achieved without adding too many conductive particles ( Low resistance value), which can reduce the cost of the conductive adhesive.

Conventional conductive adhesives are mostly made of a resin blending hardener to form a low-temperature conductive paste, which is then heat-hardened when used. However, the low-temperature conductive paste has the disadvantage that it must be stored in a low temperature environment (at -20 ° C to -40 ° C), and has a short operating life at room temperature.

Compared with the conventional low-temperature conductive adhesive, the imidazole derivative of the present invention has the chemical formula (II) as an ionic liquid, and the ionic liquid has a high dielectric constant, can dissolve many inorganic and organic compounds, and is not easily volatilized at room temperature. Therefore, the conductive paste of the present invention can be stored at room temperature (about 20-30 ° C).

Furthermore, the curing conditions of the conductive paste of the present invention are: 1-150 hours at a temperature of 150-180 °C. Therefore, the conductive paste does not cure at room temperature, so the conductive paste has a long working life at room temperature and high stability.

Table 1 and Table 2 show specific examples of the conductive paste of the present invention.

The synthesis of Table 1 is shown in Scheme 1 .

The reactant a (imidazole) was mixed with sodium hydroxide (NaOH), and tetrahydrofuran (THF) was added and stirred under nitrogen for 12 hours. The reactant b (R-Br) was then dissolved in THF and added dropwise to the mixed solution containing the reactant a at a rate of about once every 20 seconds under nitrogen. Thereafter, the mixture was stirred for 24 hours to complete the reaction. Thereafter, the solvent is removed, extracted, filtered, and dried to obtain product c.

The synthesis of Table 2 is shown in Scheme 2 .

The synthesis method can be divided into two types, the first being solvent heating and the second being fusion heating.

The solvent heating method is as follows: the reactant d and the reactant e are dissolved in anhydrous acetonitrile (acetonitride, CH ₃ CN), and heated under reflux at a temperature of 80 ° C for 12 hours, and filtered and dried to obtain a solid product f.

The hot melt method was as follows: The reactant d was mixed with the reactant e in a round bottom flask, and directly heated to 100 ° C for 18 hours, after which it was filtered and dried to obtain a solid product f.

In addition, the conductive paste of the present invention may be added with other additives, such as a curing agent, a leveling agent, an oxidation inhibiting agent, and a light stabilizing agent, depending on the needs of the actual application. ), plasticizer or surfactant.

In summary, the conductive paste of the present invention has high conductivity and is at room temperature. High stability and long working life, the future has great potential for application in electronic products, such as solar cells or light-emitting diodes (LEDs).

[Preparation example] Preparation Example 1 Synthesis of Compound 1

One equivalent of imidazole (imidazole, 5.00 g, 73.44 mol) was mixed with 1.15 equivalents of sodium hydroxide (NaOH, 3.34 g, 83.50 mmol), and stirred under nitrogen for 12 hours under nitrogen.

Separately, 0.75 equivalent of 1-bromo-hexane (C ₆ H ₁₃ -Br) was dissolved in THF, and dropped into a mixed solution containing imidazole at a rate of about once every 20 seconds under nitrogen. Thereafter, the mixture was stirred for 24 hours to complete the reaction.

Finally, the solvent is removed first. Was added dichloromethane, and methanol / water (volume ratio 1: 7) was extracted several times, and the organic layer was collected by filtration and removal of water with magnesium sulfate, followed by further drying, to obtain a compound.

Preparation 2 Synthesis of Compound 2

The synthesis method of Preparation Example 2 was similar to Preparation Example 1 , except that the reactant was changed to 0.75 equivalent of 1-bromo-decane (C ₁₀ H ₂₁ -Br) dissolved in THF, and the rest of the reaction conditions were the same.

Preparation Example 3 Synthesis of Compound 3

The synthesis method of Preparation Example 3 was similar to that of Preparation Example 1 , except that the reactant was changed to 0.75 equivalent of 1-bromo-dodecane (C ₁₂ H ₂₅ -Br) dissolved in THF, and the other reaction conditions were the same.

Preparation Example 4 Synthesis of Compound 4

The synthesis method of Preparation Example 4 was similar to that of Preparation Example 1 , except that the reactant was changed to 0.75 equivalent of 1-bromo-tetradecane (C ₁₄ H ₂₉ -Br) dissolved in THF, and the rest of the reaction conditions were the same.

Preparation Example 5 Synthesis of Compound 5

The synthesis method of Preparation Example 5 was similar to Preparation Example 1 , except that the reactant was changed to 0.75 equivalent of 1-bromo-hexanoic acid (C ₅ H ₁₀ COOH-Br) dissolved in THF, and the remaining reaction conditions. All the same.

Preparation Example 6 Synthesis of Compound 6

The hot melt method was used as follows: 1 equivalent of 1-hexyl-imidazole (5.00 g, 32.84 mmol) and 1 equivalent of 1-bromohexane (1-bromohexane, C ₆ H ₁₃ Br, 5.42). g, 32.84 mmol) was placed in a round bottom flask and heated directly to 100 ° C for 18 hours, then filtered and dried to give compound 6 .

Preparation Example 7 Synthesis of Compound 7

Solvent heating was used as follows: 1 equivalent of 1-dodecyl-imidazole and 1 equivalent of 1-bromododecane (C ₁₂ H ₂₅ Br) were dissolved in anhydrous The acetonitrile (acetonitride, CH ₃ CN) was heated under reflux at a temperature of 80 ° C for 12 hours, and filtered and dried to obtain a compound 7 .

Preparation Example 8 Synthesis of Compound 8

Solvent heating is used as follows: 1 equivalent of 1-dodecyl-imidazole is dissolved in 1 equivalent of 1-bromohexanoic acid (C ₅ H ₁₀ COOH-Br). The compound 8 was obtained by heating and refluxing in anhydrous acetonitrile (acetonitride, CH ₃ CN) at a temperature of 80 ° C for 12 hours.

Preparation 9 Synthesis of Compound 9

Solvent heating is used as follows: 1 equivalent of 1-tetradecyl-imidazole is dissolved with 1 equivalent of 1-bromohexanoic acid (C ₅ H ₁₀ COOH-Br). The compound 9 was obtained by heating and refluxing in anhydrous acetonitrile (acetonitride, CH ₃ CN) at a temperature of 80 ° C for 12 hours.

Preparation Example 10 Synthesis of Compound 10

Solvent heating was used as follows: 1 equivalent of 1-dodecyl-imidazole with 1 equivalent of 1-bromohexanol (6-bromohexan-1-ol, C ₆ H ₁₂ OH- Br) was dissolved in anhydrous acetonitrile (acetonitride, CH ₃ CN), and heated under reflux at a temperature of 80 ° C for 12 hours, and filtered and dried to give Compound 10 .

Preparation 11 Synthesis of Compound 11

Solvent heating was used as follows: 1 equivalent of 1-tetradecyl-imidazole and 1 equivalent of 1-bromohexanol (6-bromohexan-1-ol, C ₆ H ₁₂ OH- Br) was dissolved in anhydrous acetonitrile (acetonitride, CH ₃ CN) and heated under reflux at a temperature of 80 ° C for 12 hours, and filtered and dried to give compound 11 .

Preparation Example 12 Synthesis of Compound 12

(Compound 13-17, ion is BF ₄ ^- The imidazolium series is produced in a similar manner to compound 12 except that the starting species correspond to compound 7-11)

1 equivalent of 1-hexyl-imidazole (5.00 g, 32.84 mmol) and 1 equivalent of 1-bromohexane (C ₆ H ₁₃ Br, 5.42 g, 32.84 mmol) are dissolved in anhydrous The acetonitrile (acetonitride, CH ₃ CN) was heated to reflux at a temperature of 80 ° C for 12 hours, and the compound was dissolved in MeOH (15 mL). At the same time, AgBF _{4 was} dissolved in another MeOH (15 mL), the first imidazole slats solution was added dropwise, and AgBr _(s) precipitate was formed by stirring. The filtrate was collected, and the solvent was drained by a rotary volatizer, and 10 mL of H ₂ O was added. It was shaken several times, and the white solid was filtered and collected, crystallised from MeOH/ether. The yield can reach more than 80%.

Preparation 13 Synthesis of Compound 18

(Compound 19-23, ion is PF ₆ ^- The imidazolium series is produced in a similar manner to compound 18 except that the starting species correspond to compound 7-11)

1 equivalent of 1-hexyl-imidazole (5.00 g, 32.84 mmol) and 1 equivalent of 1-bromohexane (C ₆ H ₁₃ Br, 5.42 g, 32.84 mmol) are dissolved in anhydrous The acetonitrile (acetonitride, CH ₃ CN) was heated to reflux at a temperature of 80 ° C for 12 hours, and the compound was dissolved in MeOH (15 mL). At the same time, AgPF _{6 was} dissolved in another MeOH (15 mL), the first imidazole slats solution was added dropwise, and AgBr _(s) precipitate was formed by stirring. The filtrate was collected, and the solvent was drained by a rotary volatizer, and 10 mL of H ₂ O was added. It was shaken several times, and the white solid was filtered and collected, crystallised from MeOH/ether. The yield can reach more than 80%.

[Examples] Comparative example 1

Silver FP-5300TC (Fen Tepu Technology Co., Ltd.) is available for sale.

Example 1

Comparative Example 1 and Compound 3 were mixed at a weight ratio of 60:40, and then coated on a substrate ( primary glass) and cured at 150 ° C for 1-1.5 hours, after which the resistance value was detected.

Example 2

Comparative Example 1 and Compound 6 were mixed at a weight ratio of 60:40, and about 0.01% by weight of 20 nm silver nanoparticles were additionally added to Compound 6 , and then coated on a substrate and cured at 150 ° C for 1-1.5 hours, after which It can detect its resistance value.

Table 3 shows the resistance values and particle sizes of Comparative Example 1, Example 1 and Example 2 . As can be seen from Table 3, the water contents of Example 1 and Example 2 are the same as those of the comparative example (less than 0.5%), indicating that the conductive paste of the present invention has potential for application in packaging of electronic products in the future.

In addition, the particle sizes of Example 1 and Example 2 are similar to those of the comparative examples , indicating that the silver particles do not aggregate, and the resistance values of all three can reach 10 ^-5 grade, indicating that the invention adds 40%. The imidazole derivative can still maintain high conductivity. Therefore, the conductive paste of the present invention can greatly reduce the amount of conductive particles added, thereby reducing the cost of the conductive paste.

While the invention has been described above in terms of several preferred embodiments, it is not intended to limit the scope of the present invention, and any one of ordinary skill in the art can make any changes without departing from the spirit and scope of the invention. And the scope of the present invention is defined by the scope of the appended claims.

Claims (8)

A conductive paste comprising: a plurality of conductive particles; and an imidazole derivative, wherein the imidazole derivative has the following chemical formula (I) or (II): Wherein R ₁ includes C ₆ H ₁₃ , C ₁₀ H ₂₁ , C ₁₄ H ₂₉ or C ₅ H ₁₀ COOH; and R ₂ and R ₃ each independently include a substituted or unsubstituted C ₁ -C ₂₀ alkyl group (alkyl) Group); and Z ^- is an anion. The conductive paste of claim 1, wherein R ₂ or R ₃ each independently comprise a C ₆ -C ₁₄ alkyl group. The conductive paste of claim 1, wherein R ₂ or R ₃ each independently comprises C ₆ H ₁₃ , C ₁₂ H ₂₅ , C ₁₄ H ₂₉ , C ₅ H ₁₀ COOH or C ₆ H ₁₂ OH. The conductive paste of claim 1, wherein Z ^- comprises Br ^- , PF ₆ ^- , BF ₄ ^- or NO ₃ ^2- . The conductive paste of claim 1, wherein the imidazole compound accounts for about 0.1-40% by weight of the entire conductive paste. The conductive paste of claim 1, wherein the conductive particles comprise silver (silver, Ag), gold (gold), nickel (nickel, Ni), copper (copper, Cu), platinum (platinum) , Pt), palladium (Pd) or an alloy of the above. The conductive paste of claim 1, wherein the conductive particles have a particle size of about 20 nm to 10 μm. The conductive paste of claim 1, wherein the conductive adhesive has a volume resistivity of about 10 ² -10 ^-6 Ω ‧ cm.