US-12618136-B2 - Capacitive sensor for positioning in OVJP printing

Abstract

Devices and techniques that include use of a capacitive sensor to permit an OVJP print head to orient itself relative to conductive or dielectric traces on a printing substrate are disclosed. Such a sensor enables real-time measurement and closed-loop control of print head position with respect to substrate traces. This enables, for example, micron scale resolution in a dimension transverse to printing while permitting both the substrate and movement of the OVJP tool to scale to larger sizes than are achievable using conventional techniques and systems.

Inventors

• Bruno KERSSCHOT
• Ronald Stevens
• Eric KOSTERS
• Ron ASJES
• William E. Quinn
• Gregory McGraw

Assignees

• UNIVERSAL DISPLAY CORPORATION

Dates

Publication Date

20260505

Application Date

20180501

Claims (14)

1. 1 . An organic vapor jet printing (OVJP) apparatus comprising: an OVJP print head; a first capacitive sensor physically connected to the OVJP print head; a second capacitive sensor physically connected to the OVJP print head; a processing circuit in communication with the first capacitive sensor and the second capacitive sensor, and configured to provide a control signal based upon a signal provided by the first capacitive sensor; a stage position adjustor in communication with the processing circuit and configured to adjust the relative horizontal alignment of the OVJP print head and a substrate disposed below the OVJP print head based upon the control signal provided by the processing circuit.
2. 2 . The OVJP apparatus of claim 1 , wherein the stage position adjustor moves the OVJP print head relative to the substrate.
3. 3 . The OVJP apparatus of claim 1 , wherein the stage position adjustor moves the substrate relative to the OVJP print head.
4. 4 . The OVJP apparatus of claim 1 , wherein the first capacitive sensor comprises: a first comb comprising a first plurality of conductive electrodes connected to a first common bus.
5. 5 . The OVJP apparatus of claim 4 , wherein the first capacitive sensor further comprises: a second comb comprising a second plurality of conductive electrodes connected to a second common bus, wherein the second plurality of electrodes is interdigitated with the first plurality of electrodes.
6. 6 . The OVJP apparatus of claim 5 , further comprising one or more current sources in electrical communication with the first comb and the second comb and configured to provide an excitation signal to each of the first and second combs, and wherein the excitation signals provided to the first and second combs is in phase.
7. 7 . The OVJP apparatus of claim 1 , wherein the second capacitive sensor comprises: a first comb comprising a first plurality of conductive electrodes connected to a first common bus.
8. 8 . The OVJP apparatus of claim 7 , wherein the second capacitive sensor further comprises: a second comb comprising a second plurality of conductive electrodes connected to a second common bus, wherein the second plurality of electrodes is interdigitated with the first plurality of electrodes.
9. 9 . The OVJP apparatus of claim 7 , wherein the second capacitive sensor further comprises a second comb comprising a second plurality of conductive electrodes connected to a second common bus, wherein the second capacitive sensor is disposed within a length of one comb of the first capacitive sensor and offset laterally relative to the first capacitive sensor such that the first and second combs would form an interdigitated structure if placed in alignment.
10. 10 . The OVJP apparatus of claim 1 , wherein the OVJP print head is positioned between the first capacitive sensor and the second capacitive sensor.
11. 11 . The OVJP apparatus of claim 10 , wherein the first capacitive sensor is positioned ahead of the OVJP print head relative to a printing direction of motion of the OVJP print head across the substrate.
12. 12 . The OVJP apparatus of claim 1 , wherein the processing circuit operates the stage position adjustor to maintain the OVJP print head in alignment with a trace disposed on the substrate while the OVJP print head is operated to deposit a material on the substrate.
13. 13 . The OVJP apparatus of claim 1 , wherein the processing circuit provides a real-time closed-loop feedback system to maintain the OVJP print head in alignment with a trace disposed on the substrate.
14. 14 . The OVJP apparatus of claim 1 , further comprising a first electrode disposed in a plane with the first and/or second capacitive sensors, wherein the stage position adjustor is further configured to adjust the relative separation between the OVJP print head and the substrate based upon a measured capacitance of the first electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a non-provisional of, and claims the priority benefit of U.S. Provisional Patent Application Ser. No. 62/501,912, filed May 5, 2017, the entire contents of which are incorporated herein by reference. FIELD The present invention relates to systems and techniques for fabricating devices such as organic light emitting diodes and devices, such as organic light emitting diodes, made with or by and/or including the same. BACKGROUND Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting diodes/devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants. OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety. One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Alternatively the OLED can be designed to emit white light. In conventional liquid crystal displays emission from a white backlight is filtered using absorption filters to produce red, green and blue emission. The same technique can also be used with OLEDs. The white OLED can be either a single EML device or a stack structure. Color may be measured using CIE coordinates, which are well known to the art. As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the “small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules. As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between. As used herein, “solution processible” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form. A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand. As used herein, and as would be generally understood by one skilled in the art, a first “Highest Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or “higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to