Conductive ink

Abstract

Provided is a conductive ink including a conductive material and at least one benzoxazine-based compound. The conductive ink of the present invention can be easily formed into a thin film, is highly conductive after sintering, and has superior adhesion to various substrates. In addition, the use of the conductive ink according to the present invention facilitates the formation of a glossy, mirror-like metal thin film with high reflectance.

Claims

1. A conductive ink comprising a metal particle or a metal precursor and at least one benzoxazine-based compound selected from structures represented by the following Formulas 1-1 to 1-4: ##STR00010## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently hydrogen, halogen, amino, nitro, cyano, hydroxyl, carboxyl, substituted or unsubstituted C.sub.1-C.sub.30 alkyl, substituted or unsubstituted C.sub.3-C.sub.30 cycloalkyl, substituted or unsubstituted C.sub.6-C.sub.30 aryl, substituted or unsubstituted C.sub.6-C.sub.30 aralkyl, substituted or unsubstituted C.sub.1-C.sub.30 heteroalkyl, substituted or unsubstituted C.sub.2-C.sub.30 heterocycloalkyl, substituted or unsubstituted C.sub.5-C.sub.30 heteroaryl, or substituted or unsubstituted C.sub.5-C.sub.30 heteroaralkyl, with the proviso that R.sub.2 and R.sub.3, or R.sub.3 and R.sub.4, or R.sub.4 and R.sub.5 are optionally joined together to form a ring having one or more atoms selected from the group consisting of C, O, and N, L is a chemical bond, substituted or unsubstituted C.sub.1-C.sub.30 alkylene, substituted or unsubstituted C.sub.1-C.sub.30 heteroalkylene, substituted or unsubstituted C.sub.6-C.sub.30 arylene, substituted or unsubstituted C.sub.6-C.sub.30 heteroarylene, —O—, —C(O)—, —C(O)O—, —C(CH.sub.3).sub.2—, —C(CF.sub.3).sub.2—, —S— or —SO.sub.2—, R is substituted or unsubstituted C.sub.1-C.sub.30 alkylene, substituted or unsubstituted C.sub.3-C.sub.30 cycloalkylene, substituted or unsubstituted C.sub.6-C.sub.30 arylene, substituted or unsubstituted C.sub.1-C.sub.30 heteroalkylene, substituted or unsubstituted C.sub.2-C.sub.30 heterocycloalkylene, or substituted or unsubstituted C.sub.5-C.sub.30 heteroarylene, and m is an integer from 1 to 1000.

2. The conductive ink according to claim 1, wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently selected from the group consisting of hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, t-butyl, n-pentyl, amyl, n-hexyl, 2-ethylhexyl, n-heptyl, octyl, iso-octyl, nonyl, decyl, dodecyl, hexadecyl, octadecyl, docodecyl, cyclopropyl, cyclopentyl, cyclohexyl, allyl, propargyl, acetyl, benzoyl, hydroxyethyl, methoxyethyl, 2-hydroxypropyl, methoxypropyl, aminoethyl, cyanoethyl, mercaptoethyl, chloroethyl, methoxy, ethoxy, butoxy, hexyloxy, phenoxy, methoxyethoxyethyl, methoxyethoxyethoxyethyl, imidazolyl, carboxymethyl, trimethoxysilylpropyl, triethoxysilylpropyl, phenyl, methoxyphenyl, cyanophenyl, tolyl, and benzyl.

3. The conductive ink according to claim 1, wherein the benzoxazine-based compound is selected from structures represented by the following Formulas 2-1 to 2-13: ##STR00011## ##STR00012## ##STR00013## wherein each R.sub.c represents a cardanol-based alkyl and each R.sub.u is an urushiol-based alkyl.

4. The conductive ink according to claim 1, wherein at least one of R.sub.2, R.sub.3, R.sub.4, and R.sub.5 is a hydrocarbon group containing one or more double bonds.

5. The conductive ink according to claim 1, wherein the metal precursor compounds are metal carboxylates.

6. The conductive ink according to claim 1, wherein the metal precursor compounds are metal salts of fatty acids.

7. The conductive ink according to claim 5, wherein the metal of the metal carboxylates is silver (Ag) or gold (Au).

8. The conductive ink according to claim 1, further comprising one or more additives selected from the group consisting of solvents, complexing agents, resins, stabilizers, dispersants, reducing agents, coupling agents, leveling agents, surfactants, wetting agents, thickeners, and thixotropic agents.

9. The conductive ink according to claim 1, wherein the viscosity of the conductive ink is adjusted to the range of 0.1 to 50 cPs, as measured at room temperature 20° C., for inkjet printing.

10. A conductive ink in the form of a hybrid ink produced by mixing or reacting the conductive ink according to claim 8, further comprising one or more materials selected from the group consisting of metal powders, metal oxides, metal nanoparticles, metal wires, conductive polymers, and inks produced therefrom.

11. The conductive ink according to claim 1, wherein the conductive ink has a viscosity in the range of 1 to 100,000 cPs, as measured at room temperature 20° C.

12. A conductive thin film formed by deposition of the conductive ink according to claim 1.

13. The conductive thin film according to claim 12, wherein the conductive thin film comprises a polymer of the benzoxazine-based compound contained in the conductive ink.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a reflectance curve of a sample produced in Example 14.

(2) FIG. 2 is an optical image of a sample produced in Example 14.

(3) FIG. 3 is a surface electron microscopy (SEM) image of a sample produced in Example 14.

(4) FIG. 4 is an atomic force microscopy (AFM) image of a sample produced in Example 14.

MODE FOR CARRYING OUT THE INVENTION

(5) Reference will now be made in more detail to the embodiments of the present invention.

(6) <Synthesis of Benzoxazine Compounds>

Example 1

Synthesis of Cardanol-Based Methyl Benzoxazine (Formula 2-1, R1═CH3)

(7) 68.6 g (0.8 mol) of 35% aqueous formaldehyde was dissolved in 150 mL of dioxane in a 1000 mL three-neck flask fitted with a stirrer. The solution was cooled to 5° C. and a solution of 31.5 g (0.4 mol) of 40% aqueous methylamine in 100 mL of dioxane was slowly added dropwise thereto over a period of 30 min. After completion of the reaction, a solution of 120 g (0.4 mol) of cardanol in 100 mL of dioxane was slowly added to the reaction mixture. The reaction was continued with stirring at room temperature for additional 30 min. After the temperature was raised to 90° C., the reaction was allowed to proceed for 5 h. After the reaction was finished, the reaction mixture was evaporated under vacuum to completely remove the solvent. The residue was diluted with 500 mL of ethyl acetate and sufficiently washed sequentially with a 3 N aqueous solution of sodium hydroxide and brine (each 3×). The organic solution was separated, dried over anhydrous sodium sulfate, and evaporated under vacuum to completely remove the solvent, affording 135.5 g (yield: 95.2%) of the title compound as a viscous, light red liquid.

Example 2

Synthesis of Cardanol-Based Allyl Benzoxazine (Formula 2-1, R1=Allyl)

(8) 142.3 g (yield: 93.1%) of the title compound as a red liquid was obtained in the same manner as in Example 1, except that 22.8 g (0.4 mol) of allylamine was used instead of methylamine.

Example 3

Synthesis of Cardanol-Based Benzoxazine (Formula 2-2, R1=Cardanol)

(9) 51.4 g (0.6 mol) of 35% aqueous formaldehyde was dissolved in 150 mL of dioxane in a 1000 mL three-neck flask fitted with a stirrer. The solution was cooled to 5° C. and a solution of 11.4 g (0.2 mol) of 30% aqueous ammonia in 100 mL of dioxane was slowly added dropwise thereto over a period of 30 min. After completion of the reaction, a solution of 120 g (0.4 mol) of cardanol in 100 mL of dioxane was slowly added to the reaction mixture. The reaction was continued with stirring at room temperature for additional 30 min. After the temperature was raised to 80° C., the reaction was allowed to proceed for 6 h. After the reaction was finished, the reaction mixture was evaporated under vacuum to completely remove the solvent. The residue was diluted with 300 mL of chloroform and sufficiently washed three times with 300 mL of distilled water. The organic solution was separated, dried over anhydrous sodium sulfate, and evaporated under vacuum to completely remove the solvent, affording 123.1 g (yield: 94.2%) of the title compound as a viscous, deep reddish brown liquid.

Example 4

Synthesis of Urushiol-Based Methyl Benzoxazine (Formula 2-7, R1═CH3)

(10) 158.4 g (yield: 95.7%) of the title compound as a viscous, reddish brown liquid was obtained in the same manner as in Example 1, except that 143.5 g (0.4 mol) of urushiol was used instead of cardanol. The urushiol had been prepared by extracting raw urushi with ethanol and purifying the extract.

Example 5

Synthesis of Urushiol-Based Allyl Benzoxazine (Formula 2-7, R1=Allyl)

(11) 167.1 g (yield: 94.8%) of the title compound as a viscous, brown liquid was obtained in the same manner as in Example 2, except that 143.5 g (0.4 mol) of urushiol was used instead of cardanol.

Example 6

Synthesis of Urushiol-Based Benzoxazine (Formula 2-8, R1=Urushiol)

(12) 148.7 g (yield: 96.5%) of the title compound as a viscous, reddish brown liquid was obtained in the same manner as in Example 3, except that 143.5 g (0.4 mol) of urushiol was used instead of cardanol.

Example 7

Synthesis of Hydroquinone-Based 2-Ethylhexyl Benzoxazine (Formula 2-9 and/or 2-10, R1=2-Ethylhexyl, R2═H, R3═H)

(13) 68.4 g (0.8 mol) of 35% aqueous formaldehyde was dissolved in 150 mL of dioxane in a 1000 mL three-neck flask fitted with a stirrer. The solution was cooled to 5° C. and a solution of 51.7 g (0.4 mol) of 2-ethylhexylamine in 100 mL of dioxane was slowly added dropwise thereto over a period of 30 min. After completion of the reaction, a dispersion of 22.0 g (0.2 mol) of hydroquinone in 100 mL of dioxane was slowly added to the reaction mixture. The reaction was continued with stirring at room temperature for additional 30 min. After the temperature was slowly raised, the reaction was allowed to proceed under reflux for 12 h. After the reaction was finished, the reaction solution was evaporated under vacuum to completely remove the solvent. The residue was diluted with 500 mL of ethyl acetate and sufficiently washed sequentially with a 3 N aqueous solution of sodium hydroxide and brine (each 3×). The organic solution was separated, dried over anhydrous sodium sulfate, and evaporated under vacuum to completely remove the solvent, affording 78.5 g (yield: 87.9%) of the title compound as a viscous, brown liquid.

Example 8

Synthesis of Bisphenol A-Based 2-Ethylhexyl Benzoxazine (Formula 2-11, R1=2-Ethylhexyl, R2═H, ×=C(CH3)2)

(14) 97.1 g (yield: 85.9%) of the title compound as a viscous liquid was obtained in the same manner as in Example 7, except that 45.6 g (0.2 mol) of bisphenol A was used instead of hydroquinone.

Example 9

Synthesis of Hydroquinone-Based Benzoxazine Polymer (Formula 2-12, R═(CH2)6, R2═H, R3═H)

(15) 24.0 g (0.8 mol) of paraformaldehyde was mixed with 23.2 g (0.2 mol) of hexamethylenediamine in 300 mL of chloroform, and then the mixture was dissolved by heating. To the solution was slowly added 22.0 g (0.2 mol) of hydroquinone. After sufficiently mixing with stirring, the mixture was allowed to react under reflux for 6 h. After completion of the reaction, the reaction mixture was evaporated under vacuum to remove the solvent. The viscous residue was diluted with 500 mL of chloroform and sufficiently washed sequentially with a 3 N aqueous solution of sodium hydroxide and brine (each 3×). The organic solution was separated, dried over anhydrous sodium sulfate, and evaporated under vacuum to completely remove the solvent to give a highly viscous liquid. The liquid was diluted with 100 mL of chloroform and slowly added dropwise to 2 L of methanol to precipitate a solid. The precipitate was filtered and completely dried under vacuum, affording 53.4 g of the title compound as a light red solid.

Example 10

Synthesis of Polyvinylphenol-Based Benzoxazine (Formula 2-13, R1=2-Ethylhexyl)

(16) 24.0 g (0.8 mol) of paraformaldehyde, 51.7 g (0.4 mol) of ethylhexylamine, and 48.0 g of poly-4-vinylphenol were sufficiently mixed with stirring at room temperature. After the temperature was raised to 130° C., the mixture was allowed to react for 1 h. After completion of the reaction, the reaction mixture was diluted with 200 mL of chloroform and slowly added dropwise to 2 L of methanol to precipitate a solid. The solid was filtered and dried under vacuum, affording 102.1 g of the title compound as a light yellow solid.

Production and Evaluation of Metal Inks

Example 11

(17) 0.2 g of a solution of the cardanol-based methyl benzoxazine prepared in Example 1 in xylene (1:1, w/w) was slowly added dropwise to 2.0 g of a solution of silver neodecanoate in xylene (3:5, w/w). After sufficient mixing for 10 min, the resulting solution was passed through a 0.45 micron Teflon filter to obtain a yellow transparent silver precursor ink. The silver ink composition was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.30 Ω/□.

Example 12

(18) 0.2 g of a solution of the cardanol-based allyl benzoxazine prepared in Example 2 in toluene (1:1, w/w) was slowly added dropwise to 2.0 g of a solution of silver neodecanoate in toluene (3:5, w/w). After sufficient mixing for 10 min, the resulting solution was passed through a 0.45 micron Teflon filter to obtain a brown silver precursor ink. The silver ink composition was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.25 Ω/□.

Example 13

(19) 0.05 g of neodecanoic acid only was added to the ink produced in Example 11. The resulting ink was coated and sintered at 230° C. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.31 Ω/□.

Example 14

(20) An ink was produced in the same manner as in Example 11, except that the cardanol-based benzoxazine prepared in Example 3 was used. The ink was coated and sintered at the same temperature. As a result, a mirror-like silver film was well formed. The sample was measured to have an average reflectance of 92.3% in the wavelength range of 380-780 nm, an adhesive strength of 5 B, and a surface resistivity of 0.24 Ω/□.

Example 15

(21) The ink produced in Example 11 was sintered at 250° C. for 30 min to form a mirror-like silver film. The film had an adhesive strength of 5 B and a surface resistivity of 0.15 Ω/□.

Example 16

(22) The ink produced in Example 11 was sintered at 210° C. for 30 min to form a mirror-like silver film. The film had an adhesive strength of 5 B and a surface resistivity of 1.54 Ω/□.

Example 17

(23) The ink produced in Example 11 was coated on a glass substrate instead of the polyimide (PI) film and sintered under the same conditions. As a result, a silver film was well formed. The film had an adhesive strength of 5 B and a surface resistivity of 0.8 Ω/□.

Example 18

(24) 0.15 g of a solution of the urushiol-based methyl benzoxazine prepared in Example 4 in xylene (1:1, w/w) was slowly added dropwise to 2.0 g of a solution of silver neodecanoate in xylene (3:5, w/w). After sufficient mixing for 10 min, the resulting reddish brown solution was passed through a 0.45 micron Teflon filter to obtain a reddish brown ink. The silver ink composition was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.25 Ω/□.

Example 19

(25) An ink was produced in the same manner as in Example 18, except that the urushiol-based allyl benzoxazine prepared in Example 5 was used. The ink was coated and sintered at the same temperature. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.21 Ω/□.

Example 20

(26) An ink was produced in the same manner as in Example 18, except that the urushiol-based benzoxazine prepared in Example 6 was used. The ink was coated and sintered at the same temperature. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.20 Ω/□.

Example 21

(27) 0.2 g of a solution of the hydroquinone-based ethylhexyl benzoxazine prepared in Example 7 in xylene (1:1, w/w) was slowly added dropwise to 2.0 g of a solution of silver naphthenate in xylene (1:2, w/w). After sufficient mixing for 10 min, the resulting reddish brown solution was passed through a 0.45 micron Teflon filter to obtain a reddish brown ink. The silver ink was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.35 Ω/□.

Example 22

(28) 0.2 g of a solution of the bisphenol-based ethylhexyl benzoxazine prepared in Example 8 in xylene (1:1, w/w) was slowly added dropwise to 2.0 g of a solution of silver neodecanoate in xylene (3:5, w/w). After sufficient mixing for 10 min, the resulting reddish brown solution was passed through a 0.45 micron Teflon filter to obtain a clear transparent ink. The silver ink was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.45 Ω/□.

Example 23

(29) 0.1 g of a solution of the urushiol-based benzoxazine prepared in Example 6 in xylene (1:1, w/w) was slowly added dropwise to 2.0 g of a solution of silver sorbate in n-butylamine (1:2, w/w). After sufficient mixing for 10 min, the resulting solution was passed through a 0.45 micron Teflon filter to obtain a reddish brown silver precursor ink. The silver ink composition was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min to form a silver film. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.25 Ω/□.

Example 24

(30) An ink was produced in the same manner as in Example 11, except that the hydroquinone-based benzoxazine polymer obtained in Example 9 was used. The ink was coated and sintered at the same temperature. As a result, a silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.38 Ω/□.

Example 25

(31) An ink was produced in the same manner as in Example 11, except that the polyvinylphenol-based benzoxazine polymer prepared in Example 10 was used. The ink was coated and sintered at the same temperature. As a result, a silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.56 Ω/□.

Example 26

(32) 0.1 g of a solution of the urushiol-based benzoxazine prepared in Example 6 in xylene (1:1, w/w) was slowly added dropwise to 2.0 g of a solution of chloroauric acid hydrate (HAuCl.sub.4.xH.sub.2O) in isopropyl alcohol (4:6, w/w). After sufficient mixing for 10 min, the resulting solution was passed through a 0.45 micron Teflon filter to obtain a reddish brown gold precursor ink. The gold ink composition was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min. As a result, a mirror-like gold thin film was well formed. The thin film was measured to have an adhesive strength of 5 B and a surface resistivity of 3.2 Ω/□.

Comparative Example 1

(33) An ink was produced in the same manner as in Example 11, except that the cardanol-based methyl benzoxazine compound was not used and silver neodecanoate only was used. The ink was coated and sintered at the same temperature. As a result, a non-uniform silver film was formed. The film was measured to have an adhesive strength of 4B and an average surface resistivity of 13.2 Ω/□.

Comparative Example 2

(34) An ink was produced in the same manner as in Example 11, except that a phenoxy resin was used instead of the benzoxazine-based compound. The ink was coated and sintered at the same temperature. As a result, a dark film was formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 58.5 Ω/□.

Example 27

(35) 1.0 g of the cardanol-based allyl benzoxazine prepared in Example 2, 5.0 g of silver neodecanoate, 5.0 g of silver oxide, and 3.0 g of alpha-terpineol were sufficiently mixed using a hybrid mixer to obtain a homogeneous paste ink. The paste ink was thinly coated on a polyimide (PI) film using a bar coater and sintered at 230° C. for 30 min. As a result, a silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.08 Ω/□.

Example 28

(36) An ink was produced in the same manner as in Example 27, except that 0.5 g of silver nanoparticles having an average size of 80 nm were used instead of silver oxide. The ink was coated and sintered at the same temperature. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.10 Ω/□.

Example 29

(37) 5.0 g of the urushiol-based benzoxazine prepared in Example 6, 60.0 g of silver particles having an average diameter of 3 microns, 15.0 g of alpha-terpineol, and 20.0 g of butyl carbitol acetate were sufficiently mixed using a 3-roll mill to obtain a homogeneous paste ink. The paste ink was printed on ITO-coated glass using a screen printer and sintered at 230° C. for 30 min. As a result, a silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.15 Ω/□.

Example 30

(38) 0.15 g of a solution of the urushiol-based benzoxazine prepared in Example 6 in xylene (1:1, w/w) was mixed with 0.05 g of iron neodecanoate. The mixture solution was slowly added dropwise to 2.0 g of a solution of silver neodecanoate in xylene (3:5, w/w). After sufficient mixing for 10 min, the resulting reddish brown solution was passed through a 0.45 micron Teflon filter to obtain a reddish brown ink. The silver ink was coated on a polyimide (PI) film using a spin coater and sintered at 230° C. for 30 min. As a result, a mirror-like silver film was well formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.18 Ω/□.

Example 31

(39) An ink was produced in the same manner as in Example 30, except that a mixture solution of a solution (0.15 g) of the cardanol-based benzoxazine prepared in Example 3 in xylene (1:1, w/w) and stannous neodecanoate (0.05 g) was used. As a result of coating and sintering the ink, a dark mirror-like silver film was formed. The film was measured to have an adhesive strength of 5 B and a surface resistivity of 0.51 Ω/□.

(40) Measurements and Evaluations

(41) 1) Conductivity was evaluated by measuring the sheet resistance of a patterned rectangular sample (1 cm×3 cm) of each film using a four-point probe (CMT-SR1000N, AIT).

(42) 2) Adhesive strength was evaluated in accordance with the cross-cut tape test (ASTM D3359).

(43) 3) Reflectance was measured using a Varian Cary 5000 spectrophotometer in the wavelength range of 380 to 780 nm.