A METHOD OF MANUFACTURING A CONDUCTIVE PATTERN

Abstract

A method of preparing a conductive silver pattern on a substrate comprising the step of: —applying a silver ink on the substrate to form a silver pattern, and —sintering the applied silver pattern, characterized in that the silver ink comprises a compound which decomposes exothermally during sintering.

Claims

1.-15. (canceled)

16. A method of preparing a conductive silver pattern on a substrate, the method comprising: applying a silver ink on the substrate to form the silver pattern, and sintering the applied silver pattern, characterized in that the silver ink comprises a compound A which decomposes exothermally during sintering.

17. The method according to claim 16, wherein sintering is carried out by exposing the applied silver pattern to Near Infrared radiation.

18. The method according to claim 16, wherein the amount of compound A is at least 1 wt % relative to the weight of silver in the ink.

19. The method according to claim 17, wherein the amount of compound A is at least 1 wt % relative to the weight of silver in the ink.

20. The method according to claim 16, wherein compound A has a chemical structure according to Formulae Ito IV, ##STR00031## wherein Q represents the necessary atoms to form a substituted or unsubstituted five or six membered heteroaromatic ring; M is selected from the group consisting of hydrogen, a monovalent cationic group, and an acyl group; R1 and R2 are independently selected from the group consisting of a hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl or heteroaryl group, a hydroxyl group, a thioether, an ether, an ester, an amide, an amine, a halogen, a ketone, and an aldehyde; R1 and R2 may represent the necessary atoms to form a five to seven membered ring; R3 to R5 are independently selected from the group consisting of a hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl or heteroaryl group, a hydroxyl group, a thiol, a thioether, a sulfone, a sulfoxide, an ether, an ester, an amide, an amine, a halogen, a ketone, an aldehyde, a nitrile, and a nitro group; R4 and R5 may represent the necessary atoms to form a five to seven membered ring.

21. The method according to claim 19, wherein compound A has a chemical structure according to Formulae Ito IV, ##STR00032## wherein Q represents the necessary atoms to form a substituted or unsubstituted five or six membered heteroaromatic ring; M is selected from the group consisting of hydrogen, a monovalent cationic group, and an acyl group; R1 and R2 are independently selected from the group consisting of a hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl or heteroaryl group, a hydroxyl group, a thioether, an ether, an ester, an amide, an amine, a halogen, a ketone, and an aldehyde; R1 and R2 may represent the necessary atoms to form a five to seven membered ring; R3 to R5 are independently selected from the group consisting of a hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl or heteroaryl group, a hydroxyl group, a thiol, a thioether, a sulfone, a sulfoxide, an ether, an ester, an amide, an amine, a halogen, a ketone, an aldehyde, a nitrile, and a nitro group; R4 and R5 may represent the necessary atoms to form a five to seven membered ring.

22. The method according to claim 16, wherein compound A has a chemical structure according to Formula I, ##STR00033## wherein M is selected from the group consisting of hydrogen, a monovalent cationic group, and an acyl group; and Q represents the necessary atoms to form a five membered heteroaromatic ring.

23. The method according to claim 21, wherein compound A has a chemical structure according to Formula I, ##STR00034## wherein M is selected from the group consisting of hydrogen, a monovalent cationic group, and an acyl group; and Q represents the necessary atoms to form a five membered heteroaromatic ring.

24. The method according to claim 23, wherein M in Formula I is a hydrogen.

25. The method according to claim 23, wherein Q is a five membered heteroaromatic ring selected from the group consisting of an imidazole, a benzimidazole, a thiazole, a benzothiazole, an oxazole, a benzoxazole, a 1,2,3-triazole, a 1,2,4-triazole, an oxadiazole, a thiadiazole, and a tetrazole.

26. The method according to claim 23, wherein Q is a tetrazole.

27. The method according to claim 23, wherein compound A is selected from the group consisting of N,N-dibutyl-(2,5-dihydro-5-thioxo-1H-tetrazol-1-yl-acetamide, 5-heptyl-2-mercapto- 1,3 ,4-oxadiazole, 1-phenyl-5-mercaptotetrazol, 5-methyl-1,2,4-triazolo-(1,5-a) primidine-7-ol, and S-[5-[(ethoxycarbonyl)amino]-1,3,4-thiadiazol-2-yl] O-ethyl thiocarbonate.

28. The method according to claim 21, wherein the amount of Compound A is less than 5 wt % relative to the weight of the silver in the ink.

29. The method according to claim 28, wherein the silver ink is a silver inkjet ink.

30. The method according to claim 29, wherein a receiving layer is applied on the substrate before applying the silver ink.

31. The method according to claim 30, wherein the receiving layer has a roughness Ra between 0.5 and 20 μm.

32. The method according to claim 29, wherein the silver ink comprises a liquid carrier selected from the group consisting of 2-phenoxy ethanol, propylene carbonate, propylene glycol, n-butanol, and 2-pyrrolidone.

33. The method according to claim 29, wherein the inkjet ink is treated with ultrasound before loading it into a printhead.

Description

EXAMPLES

Materials

[0163] All materials used in the following examples were readily available from standard sources such as ALDRICH CHEMICAL Co. (Belgium) and ACROS (Belgium) unless otherwise specified. The water used was deionized water.

[0164] A-01 is the dispersion-stabilizing compound N-dibutyl-(2,5-dihydro-5-thioxo-1H-tetrazol-1-yl)acetamide (CASRN168612-06-4) commercially available from Chemosyntha.

##STR00030##

[0165] A-17 is a polyalkylene carbonate diol commercially available under the name DURANOL™ G3450J from Kowa Amerian Corp.

[0166] A-001 is a 1000 Mw polycarbonate diol commercially available under the name Converge Polyol 212-10 from Aramco Performance Materials.

Measurements Methods

Conductivity of the Silver Coatings

[0167] The surface resistance (SER) of the silver coatings was measured using a four-point collinear probe. The surface or sheet resistance was calculated by the following formula:

SER=(π/In2)*(V/I)

wherein [0168] SER is the surface resistance of the layer expressed in Ω/square; [0169] π is a mathematical constant, approximately equal to 3.14; [0170] In2 is a mathematical constant equal to the natural logarithmic of value 2, approximately equal to 0.693; [0171] V is voltage measured by voltmeter of the four-point probe measurement device; [0172] I is the source current measured by the four-point probe measurement device.

[0173] For each sample, six measurements were performed at different positions of the coating and the average value was calculated.

[0174] The silver content M.sub.Ag (g/m.sup.2) of the coatings was determined by WD-XRF.

[0175] The conductivity of the coated layers was then determined by calculating the conductivity as a percentage of the bulk conductivity of silver using the following formula:

[00001]$\%{\mathrm{Ag}}_{\left(\mathrm{bulk}\right)}=\frac{{\sigma }_{\mathrm{Coat}}}{{\sigma }_{\mathrm{Ag}}}\times 100$$\%{\mathrm{Ag}}_{\left(\mathrm{bulk}\right)}=\frac{{\rho }_{\mathrm{Ag}}}{{\sigma }_{\mathrm{Ag}}\times \mathrm{SER}\times M_{\mathrm{Ag}}}\times 100$

wherein σ.sub.Ag the specific conductivity of silver (equal to 6.3×10.sup.7S/m), σ.sub.Coat is the specific conductivity of the Ag coating and ρ.sub.Ag is the density of silver (1.049×10.sup.7 g/m.sup.3).

Viscosity Measurements

[0176] Unless otherwise provided, viscosities were measured at 25° C. at a shear rate of 1000 s.sup.−1 using a commercially available viscosimeter for example as a DHR-2 Rheometer (double wall ring) from TA Instruments.

Jetting Performance Evaluation

[0177] The jetting performance of the different prepared inkjet inks was evaluated at an industrial printhead i.e., KM1024i LHE integrated into a drop watcher from JetXpert. The jetting performance of the inks was evaluated based on the ability to provide a stable jetting within a wide frequency range (e.g. 1-25 kHz), as well as, to present no failing nozzles after continuous jetting during 1, 2 and 3 min within the selected frequency range.

Differential Scanning Calorimetry (DSC)

[0178] DSC measurements were carried out by using DSC Q1000 V9.9 Build 303 (from TA

[0179] Instruments). The nitrogen flow was 50 mL/min, with a sampling interval of 0.10 sec/pt and a ramp of 10.00 ° C./min from 0 ° C. to 250 ° C. Table 3 shows the onset temperature at which the analysed compounds started to decompose either exo- or endothermically.

[0180] Table 3 shows the results of such DSC measurements on compounds used in the Examples.

TABLE-US-00003 TABLE 3 Decomposition Compound Temperature (° C.) Exo- or Endothermal A-01 ±155 Exothermal A-17 ±200 Exothermal A-C01 ±200 Endothermal

Example 1

Preparation of the Silver Nanoparticle Dispersion NPD-01

[0181] 20.0 g of silver oxide (from Umicore) was added while stirring to a mixture of 40.0 g of ethanol and 23.0 g of 2-pyrrolidone. The pre-dispersion was then stirred for 24 hours.

[0182] Then, 2.67 ml of formic acid was added (1.25 ml/min) to the pre-dispersion while stirring and keeping the temperature at room temperature. After the addition of the formic acid, the mixture was further stirred for 2.5 hours at 23-25° C.

[0183] Then, the mixture was filtered using a 60 μm filter cloth. The filtrate was then concentrated at 40° C., first for 60 min at 110 mbar, then for 30 min at 60 mbar to obtain a silver nanoparticle dispersion containing ±45wt % of silver.

Preparation of the Silver Inks

[0184] The silver inks were prepared by mixing 50 wt % of NPD-01 with 25 wt % 2-fenoxy-ethanol and 25 wt % gamma-butyro-lactone and an amount of compound A as specified in the examples. The amount of compound A ([A]) is expressed as wt % relative to the weight of silver.

Example 2

[0185] The silver inkjet inks Sl-01 to Sl-07 were prepared as described above using compound A-17, which decomposes exothermally and a comparative compound A-001, which decomposes endothermally. The amounts of both compounds are specified in Table 4.

TABLE-US-00004 TABLE 4 Sheet Ag Bulk Silver Compound Resistance content Conductivity Ink A [A] (Ω/square) (g/m.sup.2) (%) SI-01 — 0.223 4.7 15.9 SI-02 A-17 0.1 0.232 4.73 15.2 SI-03 A-17 0.2 0.214 3.80 20.5 SI-04 A-17 0.3 0.163 2.68 38.2 SI-05 A-C01 0.1 0.187 5.18 17.2 SI-06 A-C01 0.2 0.242 4.11 16.7 SI-07 A-C01 0.3 0.141 6.61 17.9

[0186] The silver inkjet inks SI-01 to SI-07 were coated at a wet coating thickness of 10 μm on a Powercoat HO substrate. The coated samples were then placed in a belt system that runs below a NIR Lamp (NIR ADPHOS lamp, 1 bulb, 5.4 kW lamp power). All samples were passed below the lamp with a platform speed of 10 mm/s and by maintaining a lamp-substrate distance 24 mm).

[0187] The conductivities were measured as described above and are shown in Table 4

[0188] It is clear from Table 4 that the addition to the silver ink of a compound A-17 that decomposes exothermally (SI-02 to SI-04) results in a higher conductivity of the coated silver ink.

Example 3

[0189] The silver inkjet inks SI-08 to SI-11 were prepared as described above using

[0190] Compound A-01. The amount of A-01 [A-01], expressed as wt % relative to the weight of silver, is shown in Table 5. The silver inks were then printed on a

[0191] Powercoat HD substrate using a Dimatix printer (DMP2800, Fujifilm Dimatix). The printed silver was then sintered in an oven at a temperature of 150° C. during 30 minutes or NIR sintered with a NIR lamp (Adphos, 100% lamp power, 10 mm/s platform speed).

[0192] The jetting stability of the silver inks and the conductivity of the printed silver measured as described above are shown in Table 5.

TABLE-US-00005 TABLE 5 Bulk Jetting Sheet Ag Conduc- Silver Sta- Sintering Resistance content tivity Ink [A-01] bility Conditions (Ω/square) (g/m.sup.2) (%) SI-08 0.93 + 150°/30 min 0.178 7.27 12.9 NIR 0.104 22.1 SI-09 1.24 ++ 150°/30 min 0.182 6.81 13.5 NIR 0.081 30.2 SI-10 1.86 ++ 150°/30 min 0.175 9.01 10.6 NIR 0.049 37.8 SI-11 2.48 + 150°/30 min 0.463 8.02 4.5 NIR 0.112 18.6

[0193] From the results of Table 5 it is clear that NIR curing results in a higher conductivity compared to oven sintering at 150° C.

[0194] It is also clear that the conductivity increases when the amount of compound A-01 increases. At higher amounts of the compound A-01, the conductivity decreases again.

[0195] It is also clear that the presence of compound A-01 also influences the jetting stability of the silver inks.

[0196] Optimal conductivities and jetting stability are obtained when the amount of compound A-01 is higher than 1 wt % relative to the silver weight.

Example 4

[0197] The silver inkjet inks SI-12 to SI-16 were prepared as described above using Compound A-01. The amount of A-01 [A-01], expressed as wt % relative to the weight of silver, is shown in Table 6. The silver inks were then printed on a Powercoat HD substrate using a Dimatix printer (DMP2800, Fujifilm Dimatix). The printed silver was then sintered in an oven at a temperature of 150° C. during 30 minutes or NIR or sintered by with a NIR lamp (Adphos, 100% lamp power, 10 mm/s platform speed).

[0198] The jetting stability of the silver inks and the conductivity of the printed silver measured as described above are shown in Table 7.

TABLE-US-00006 TABLE 7 Sheet Ag Bulk Jetting Resistance content Conductivity Silver Ink [A-01] Stability (Ω/square) (g/m.sup.2) (%) SI-12 0.62 + 0.098 7.49 22.7 SI-13 0.93 ++ 0.083 7.52 26.7 SI-14 1.24 +++ 0.053 8.08 38.9 SI-15 1.86 ++++ 0.060 7.39 37.6 SI-16 2.48 − 0.061 8.04 34

[0199] From the results in Table 7 it is clear that the conductivity increases when the amount of Compound A-01 increases. At higher amounts of Compound A-01, the conductivity decreases again.

[0200] It is also clear that the presence of Compound A-01 also influences the jetting stability of the silver inks.

[0201] Optimal conductivities and jetting stability are obtained when the amount of compound A-01 is higher than 1 wt % relative to the silver weight.

Example 5

[0202] The jetting reliability of the silver inks SI-13 and SI-15 described above is shown in detail in Table 8.

[0203] For SI-15, the jetting reliability was evaluated with and without an ultrasound treatment of the ink. The ultrasound treatment was carried out during 30 minutes before the ink was loaded in the printhead.

TABLE-US-00007 TABLE 8 Jetting Ultrasound Frequency Failing Nozzles Silver Ink treatment (kHz) Start After 3 minutes SI-13 X 3 1 0 9 1 4 12 0 8 18 1 13 20 0 12 SI-15 X 3 0 0 6 0 1 12 0 3 18 0 1 23 0 3 SI-16 45 minutes 3 0 1 6 0 0 12 0 0 18 0 1 23 0 0

[0204] From the results in Table 8 it is clear that the jetting reliability of SI-15 is better than those of SI-13. As can be seen in Table 8, the difference between both inks is the amount of Compound A-01.

[0205] It is also clear from Table 8 that an ultrasound treatment of SI-15 results in a further improvement of the jetting reliability.