Pattern transfer sheets and methods employing a releasing layer and/or paste mixtures
Pattern transfer sheets and methods are provided for printing paste patterns (e.g., thin fingers) with a high aspect ratio and for increasing throughput in pattern transfer printing. Trenches in the pattern transfer sheets, that are configured to be filled with printing paste and to enable releasing the printing paste from the trenches onto a receiving substrate upon illumination by a laser beam—are coated internally by a coating configured to disintegrate upon the illumination. The coating is configured to enhance the releasing of the paste—increasing throughput and printing accuracy. The receiving substrate may be cleaned after paste deposition by removing disintegration products of the coating therefrom. Alternatively or complementarily, laser absorbing dye may be mixed into the printing paste to facilitate its release from the trenches.
1. A pattern transfer method comprising:
coating, internally with a coating solution, a plurality of trenches arranged in a specified pattern on a pattern transfer sheet to form a dried coating layer inside each trench of the plurality of trenches, wherein the coating solution is applied only within the trenches,
filling printing paste into the plurality of trenches, on top of the dried coating layer,
releasing the printing paste from the plurality of trenches onto a receiving substrate through illumination by a laser beam to yield transferred paste lines having the specified pattern on the receiving substrate,
wherein the dried coating layer disintegrates upon the illumination, to enhance the releasing of the printing paste, and
optionally cleaning the receiving substrate by removing disintegration products of the dried coating layer therefrom.
2. The pattern transfer method of claim 1 , wherein the coating is carried out by spreading the coating solution having a solid content between 10% and 20% and drying thereof to form the dried coating layer.
3. The pattern transfer method of claim 2 , wherein the coating is carried out by at least one of: gravure spreading, micro gravure spreading, transfer roll spreading, slot extrusion spreading, reverse comma spreading, Mayer rod spreading and doctor blade spreading.
4. The pattern transfer method of claim 1 , further comprising cleaning the receiving substrate by removing disintegration products of the dried coating layer therefrom, by at least one of: high temperature decomposition at a temperature of 200° C. to 300° C., selective laser vaporization, vacuum assisted vaporization, air blowing, solvent washing and/or by an illumination that is the same as the illumination used to release the printing paste.
5. The pattern transfer method of claim 1 , wherein the dried coating layer comprises at least one organic-based dye selected to absorb the illumination.
6. The pattern transfer method of claim 5 , wherein the illumination is in near infrared (NIR) and the at least one organic-based dye comprises at least one NIR absorbing dye comprising at least one of: a Diimonium ionic complex, a Dithiolene complex, phthalocyanine, derivatives, salts and/or combinations thereof.
7. The pattern transfer method of claim 1 , further comprising sintering the released printing paste on the receiving substrate at a sintering temperature that is any of: 850° C., 800° C., 750° C., 700° C., 650° C., 600° C., 550° C., 500° C., 450° C., 400° C. or 350° C., wherein disintegration products of the dried coating layer degrade or decompose below the sintering temperature.
8. The pattern transfer method of claim 1 , further comprising curing the released printing paste on the receiving substrate at a curing temperature that is any of: 300° C., 250° C. or 200° C., wherein disintegration products of the dried coating layer degrade or decompose below the curing temperature.
9. The pattern transfer method of claim 1 , wherein the dried coating layer is 1-10 μm thick.
10. The pattern transfer method of claim 1 , wherein the pattern transfer sheet is transparent to the illumination by the laser beam, and the plurality of trenches are formed into the pattern transfer sheet by press molding, pneumatic molding, laser molding or embossing.
11. The pattern transfer method of claim 1 , wherein a cross section of the plurality of trenches in the pattern transfer sheet is any of: trapezoid, rectangular, rounded or triangular.
12. The pattern transfer method of claim 1 , wherein the pattern transfer sheet comprises at least one polymer layer which is made of at least one of: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, fully aromatic polyester, aromatic-aliphatic copolyester, copolymer acrylate, polycarbonate, polyamide, polysulfone, polyether sulfone, polyether ketone, polyamideimide, polyether imide, aromatic polyimide, alicyclic polyimide, fluorinated polyimide, cellulose acetate, cellulose nitrate, aromatic polyamide, polyvinyl chloride, polyphenol, polyarylate, polyphenylene sulfide, polyphenylene oxide, or polystyrene.
13. The pattern transfer method of claim 1 , wherein the pattern transfer sheet comprises at least:
a top polymer layer comprising the plurality of trenches, and
a bottom polymer layer having a melting temperature that is higher than an embossing temperature of the top polymer layer.
14. The pattern transfer method of claim 13 , wherein the top polymer layer has a melting temperature below 170° C. in case it is made of semi-crystalline polymer, or a glass transition temperature below 160° C. in case it is made of amorphous polymer.
15. The pattern transfer method of claim 13 , wherein the top polymer layer has a melting temperature below 110° C. in case it is made of semi-crystalline polymer, or a glass transition temperature below 100° C. in case it is made of amorphous polymer.
16. The pattern transfer method of claim 13 , wherein the top polymer layer and the bottom polymer layer are each between 10 μm and 100 μm thick, are attached by an adhesive layer thinner than 10 μm that is transparent to the illumination by the laser beam, and wherein the bottom polymer layer is at least as thick as the top polymer layer.
17. The pattern transfer method of claim 13 , wherein the top polymer layer and the bottom polymer layer are each between 25 μm and 40 μm thick, are attached by an adhesive layer thinner than 2 μm that is transparent to the illumination by the laser beam, and wherein the bottom polymer layer is at least as thick as the top polymer layer.