Techniques for print ink droplet measurement and control to deposit fluids within precise tolerances

Patent metadata

Field	Value
Publication number	US-9802403-B2
Application number	US-201615135380-A
Country	US
Kind code	B2
Filing date	Apr 21, 2016
Priority date	Dec 27, 2012
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

An ink printing process employs per-nozzle droplet volume measurement and processing software that plans droplet combinations to reach specific aggregate ink fills per target region, guaranteeing compliance with minimum and maximum ink fills set by specification. In various embodiments, different droplet combinations are produced through different printhead/substrate scan offsets, offsets between printheads, the use of different nozzle drive waveforms, and/or other techniques. These combinations can be based on repeated, rapid droplet measurements that develop understandings for each nozzle of means and spreads for expected droplet volume, velocity and trajectory, with combinations of droplets being planned based on these statistical parameters. Optionally, random fill variation can be introduced so as to mitigate Mura effects in a finished display device. The disclosed techniques have many possible applications.

First claim

What is claimed is:

1. An apparatus to fabricate permanent layers on respective substrates, each permanent layer and respective substrate to form part of a respective electronic device, the apparatus comprising:
a print head to print a liquid onto each of the respective substrates, the liquid providing material to form the permanent layers, the print head having nozzles that each eject droplets of the liquid;
a substrate transport mechanism to transport each of the respective substrates in succession to-and-from a location in which each of the respective substrates can be printed on by the print head;
a print head transport mechanism to transport the print head between a first position, in which the print head can print the respective droplets of liquid onto the respective substrates, when at the location, and a second position; and
a system comprising a light source, a light detector, and a light path extending from the light source to the light detector, the light source, the light detector and the light path being mounted in fixed positional relationship relative to one another, the light detector providing an electronic output representing measurement of a characteristic of a droplet of the liquid ejected from a selected one of the nozzles during droplet flight;
wherein the apparatus further comprises a third transport mechanism to selectively move the system relative to the print head in at least two independent dimensions relative to the print head, so as to position the light path to intersect a flight path of the droplet of the liquid ejected from the selected one of the nozzles.

2. The apparatus of claim 1 , wherein the third transport mechanism is to selectively move the system relative to the print head in at least three independent dimensions, including in a dimension extending between a point of the intersection between the light path and the flight path and the selected one of the nozzles, so as position the flight path at a distance from the selected one of the nozzles at which measurement is to occur.

3. The apparatus of claim 1 , wherein the characteristic is droplet volume and wherein the electronic output is to vary depending on volume of the droplet of the liquid ejected from the selected one of the nozzles.

4. The apparatus of claim 1 , wherein the characteristic is one of trajectory or velocity and wherein the electronic output is to vary depending on the trajectory or velocity of the droplet of the liquid ejected from the selected one of the nozzles.

5. The apparatus of claim 1 , wherein the nozzles lie within a first plane, and wherein:
the system further comprises mirrors;
the light source, the light detector, the mirrors and the light path are all mounted by the system in fixed positional relationship relative to one another;
the third transport system is to move the system in the at least two dimensions so as to move a segment of the light path within a second plane, the second plane being parallel to the first plane; and
each of the light source and the light detector are positioned outside of the second plane.

6. The apparatus of claim 5 , wherein the system is to use interferometry to measure the characteristic, wherein the electronic output is dependent on an interference pattern measured at the light detector, and wherein the apparatus further comprises at least one processor to calculate a value for the characteristic for the droplet ejected from the selected one of the nozzles based upon the electronic output.

7. The apparatus of claim 6 , wherein:
the nozzles comprise at least one thousand nozzles; and
the third transport mechanism is to selectively move the segment while the print head is in the second position, so as to cause the segment to intersect a flight path of the droplet of the liquid ejected from any one of the at least one thousand nozzles.

8. The apparatus of claim 7 , wherein the third transport mechanism is to selectively move the system relative to the print head in at least three independent dimensions while the print head is in the second position, including in a dimension of distance between a point of the intersection between the light path and the flight path and the selected one of the nozzles, so as to adjust distance from the selected one of the nozzles at which interferometric measurement is to occur.

9. The apparatus of claim 1 , wherein:
the nozzles comprise at least one thousand nozzles;
the third transport mechanism is to selectively move the system relative to the print head in the at least two independent dimensions, so as to position the light path to intersect a flight path of the droplet of the liquid ejected from any one of the at least one thousand nozzles; and
the apparatus further comprises non-transitory storage to store a value for the characteristic respective to each of the nozzles.

10. The apparatus of claim 9 , wherein the light source is a laser.

11. The apparatus of claim 1 , wherein:
the system further comprises a collector for droplets ejected from the selected one of the nozzles while the light path is positioned to intersect the flight path of the droplet of the liquid ejected from the selected one of the nozzles, such that the selected one of the nozzles is to eject the droplet of liquid toward the collector when the system is positioned such that the light path intersects the flight path; and
the light source, the light detector, the collector and the light path are mounted by the system in fixed positional relationship relative to one another.

12. The apparatus of claim 1 , wherein:
the apparatus comprises an environmental enclosure to maintain a controlled atmosphere; and
the location and the first position lie within the environmental enclosure.

13. The apparatus of claim 1 , wherein the liquid comprises a liquid monomer.

14. The apparatus of claim 1 , wherein the apparatus further comprises an electronic control system to automatically control the print head transport mechanism, the system and the third transport mechanism during a time when none of the respective substrates are at the location, and to automatically measure the characteristic for a droplet from at least one of the nozzles in between printing of the liquid onto successive ones of the respective substrates, as a function of position of at least one of the successive ones.

15. A method of fabricating permanent layers on respective substrates, each permanent layer and respective substrate to form part of a respective electronic device, the method comprising:
using a print head to print a liquid onto each one of the respective substrates, the liquid providing material to form the permanent layer on the one the respective substrates, the print head having nozzles that each eject droplets of the liquid;
transporting each of the respective substrates in succession to-and-from a location in which each of the respective substrates can be printed on using the print head;
transporting the print head between a first position, in which the print head can print the respective droplets of liquid onto the respective substrates, when at the location, and a second position; and
selectively moving a system comprising a light source, a light detector, and a light path extending from the light source to the light detector in at least two independent dimensions relative to the print head, the light source, the light detector and the light path being mounted in fixed positional relationship relative to one another, to generate an electronic output representing measurement of a characteristic of a droplet of the liquid ejected from a selected one of the nozzles during

Assignees

• Kateeva Inc

Inventors

• Harjee Nahid
• Barkley Lucas D
• Hauf Christopher R
• Vronsky Eliyahu
• Madigan Conor F
• Lewis Gregory
• Ko Alexander Sou-Kang
• Gassend Valerie

Classifications

• B41J2/07

  characterised by jet control (B41J2/205 takes precedence) · CPC title

• B05C5/0291

  the material being discharged on the work through discrete orifices as discrete droplets, beads or strips that coalesce on the work or are spread on the work so as to form a continuous coating · CPC title

• B41J2/04581 Primary

  controlling heads based on piezoelectric elements · CPC title

• B41J2/04588

  using a specific waveform · CPC title

• B41J2/04593

  Dot-size modulation by changing the size of the drop · CPC title