KR20180108917A - Polythiophene-containing ink compositions for inkjet printing - Google Patents

Abstract

There is provided an ink composition comprising a polythiophene and a methicone blended for inkjet printing of a hole injection layer (HIL) of an organic light emitting diode (OLED). Also provided is a method of inkjet printing HIL using the ink composition.

Description

POLYTHIOPHENE-CONTAINING INK COMPOSITIONS FOR INKJET PRINTING FOR INKJET PRINTING

Cross-reference of related application - reference

This application claims priority to U.S. Provisional Patent Application No. 61/898343, filed October 31, 2013, the title of which is the polythiophene-containing ink composition for inkjet printing, the entirety of which is incorporated herein by reference . This application is a continuation-in-part of U.S. Patent Application No. 13 / 618,157, filed September 14, 2012, the entirety of which is a film-forming formulation for substrate printing, which application is filed on September 16, 61 / 535,413, the entire contents of which are incorporated herein by reference.

An ink composition for an inkjet printing layer in an organic light emitting diode (OLED) has been proposed. However, problems associated with improper invasiveness of the ink composition inhibit the development of printable inks, which may result in non-uniform film formation and improper illumination from the organic light emitting diode pixel introducing the printed film Because it causes. Another difficulty hindering the development of inkjet printable compositions for OLED applications is the inability to introduce high concentrations of active polymers into the ink while maintaining the sprayable ink formulation.

There is provided an ink composition comprising a polythiophene compounded for inkjet printing of a hole injection layer (HIL) of an OLED. Some embodiments of the ink composition are characterized by the inclusion of methicone as a pinning agent. Another embodiment is characterized by the inclusion of an aprotic solvent which enables the introduction of a high concentration of polythiophene in the ink. A method of inkjet printing HIL using an ink composition is also provided.

One embodiment of a method for forming an HIL for an organic light emitting diode comprises the steps of: inkjet printing a droplet of an ink composition (i.e., at least one droplet) on an electrode layer in a pixel cell of an organic light emitting diode Said pixel cell being defined by a pixel bank; And evaporating the volatile component of the ink composition, thereby forming a hole injection layer. Specific examples of ink compositions that can be used in the method include: electrically conductive polythiophenes; water; At least one organic solvent; And methicone, wherein the methicone is present in an amount that provides contact line fixation of the droplet within the pixel cell.

Some embodiments of the ink composition include: poly (3,4-ethylenedioxythiophene); water; At least one organic solvent having a surface tension of less than 55 dyne / cm at 25 DEG C, a viscosity of less than 15 cPs at 25 DEG C, and a boiling point of at least 200 DEG C; And methicone. The at least one organic solvent may be, for example, sulfolane.

Other key features and advantages of the invention will be apparent to those skilled in the art from the following drawings, detailed description, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments of the invention will be described hereinafter with reference to the accompanying drawings, wherein like numerals designate like elements.
Figure 1 is a block diagram illustrating an OLED inkjet printing system.
2 is a schematic view of a gas enclosure system capable of receiving the printing system shown in Fig.
3 is a schematic diagram of a flat panel display including a plurality of OLEDs arranged in a matrix of pixel cells, each pixel cell defined by a pixel bank.
4A is a micrographic image of an ink composition comprising 0.08 wt.% Methicone fixed in an OLED pixel cell.
4B is a black and white line drawing of the micrograph of FIG. 4A
5A is a micrographic image of a methicone-free ink composition over an OLED pixel cell.
FIG. 5B is a black and white line drawing of the microscope photograph of FIG. 5A. FIG.
6A is a micrographic image of a methicone-free ink composition dewetting an OLED pixel cell.
6B is a black and white line drawing of the micrograph of FIG. 6A.
7A is a photomicrograph of light emission from an OLED pixel having a printed HIL with an ink composition comprising a methicone as a fixative.
7B is a black and white line drawing of the micrograph of FIG. 7A.
8A is a photomicrograph of light emission from an OLED pixel having a printed HIL with an ink composition comprising a methicone as an immobilizing agent and sulfolane as an organic solvent.
FIG. 8B is a black and white line drawing of the microscope photograph of FIG. 8A. FIG.
9A is a photomicrograph of the emission emitted from an OLED pixel having a HIL printed with a containing ink composition comprising a methicone as a fixative and 1,3-propanediol as an organic solvent
FIG. 9B is a black and white line drawing of the microscope photograph of FIG. 9A.
10 is a graph of the drop volume over time for an ink composition before and after a 30 minute wait for an inkjet printing nozzle, as described in Example 2.
11 is a graph of the drop rate over time for ink compositions before and after a 30 minute wait for inkjet printing nozzles, as described in Example 2.
12 is a graph of the drop angle with time for the ink composition before and after a 30 minute wait of the inkjet printing nozzles, as described in Example 2. FIG.

There is provided an ink composition comprising a polythiophene compounded for inkjet printing of a HIL of an OLED. A method of inkjet printing HIL using an ink composition is also provided.

The ink composition is characterized by a high concentration of electrically conductive polythiophenes, such as poly (3,4-ethylenedioxythiophene) (PEDOT), but is well suited for inkjet printing on a pixilated substrate such as an OLED pixel cell Jetting, and latency characteristics that make it easier to achieve the desired results. In addition, the ink composition provides a printed HIL having a very uniform thickness and homogeneous composition. As a result, the printed HIL contributes to a very uniform emission profile to where they are introduced to the OLED. The improved printability provided by the ink composition can be at least partly due to realizing that, at an appropriate concentration, the methicone can act as a contact line immobilization agent for the droplets of the ink composition in the pixel cell. By providing contact line fixation, the methicone ensures that the footprint of the droplets of the ink composition deposited into the pixel cell remains unchanged from the initial shape during the drying process.

A basic embodiment of the ink composition is an aqueous solution comprising electrically conductive polythiophene, methicone, at least one organic solvent and water. A basic embodiment of a method of forming a HIL for an OLED using one of the ink compositions comprises depositing a droplet of an ink composition on a layer of an electrically conductive material (i.e., an anode) in a pixel cell of the organic light emitting diode array and Evaporating the volatile components of the ink composition, leaving a solid HIL. The step of evaporating the volatile components (e.g., water and organic solvent) can be accomplished by treating the printed ink composition with reduced pressure, i. E. By exposing it to vacuum, exposing the printed ink composition to high temperatures, Lt; / RTI >

Methicone is a silicone oil polymerized from siloxane. Also referred to as methylhydrogen siloxane or methyl siloxane. Mecicon is a commercially available surfactant sold under the trade name Botanisil® by Botanigenics (Northridge, CA). CM-13, CM-70, CP-33, CPM-10, CD-80, CD-90, CE-35, CM-12, , CS-50, CTS-45, DM-60M, DM-85, DM-90, DM-91, DM-92, DM-93, DM-94, DM-95, DM- GB-20, GB-23, GB-25, GB-35, L-23, ME-10, ME-12, PSS-150, PT-100, S-18 , S-19, S-20, TSA-16, and TSS-1. Methicone is also available from Lubrizol Corporation (Wickliffe, Ohio) under the trade name SilSense®. These include SilSense® Copolyol-1 silicone (PEG-33 and PEG-8 dimethicone and PEG 14), SilSense® DW-18 silicone (dimethicone PEG-7 isostearate), SilSense® SW-12 silicone Silicone < / RTI > PEG-7 cocoate), SilSense® IWS (dimethicone ester dimethicol stearate), SilSense® A-21 silicone -8 phosphate), and Ultrabee ™ WD silicone (dimethicone PEG-8 non-wax).

In this ink composition, the amount of methicone is carefully controlled so that methicone acts as a contact line fixing agent. This is important because it prevents the fixed ink composition droplet from moving (dewetting) from a portion of the bank of pixel cells, which is sometimes caused by over-spilling in another part of the pixel cell. It also prevents the ink composition from accumulating on the side of the pixel cell or spreading behind, as occurs with more complete infiltration.

The ink composition can be used to form HILs on various OLED electrode materials. Most commonly, the electrode substrate will comprise a transparent electrically conductive material, such as a transparent conductive oxide (TCO) or silicon. The appropriate concentration range for methicone in the ink composition will depend on the nature of the underlying substrate. However, for a given substrate, the concentration range over which methicone provides contact line fixation can be determined by observing the infiltration behavior of ink droplets having different methicone concentrations applied to the surface through a drop casting process . By way of example, some embodiments of the present ink composition comprise methicone in an amount of less than or equal to 0.15 weight percent (wt.%), Less than or equal to 0.12 wt.%, Or less than or equal to 0.1 wt.%, Based on the total weight of the ink composition . This includes embodiments of the ink composition wherein the methicone is present in an amount ranging from 0.02 to 0.15 wt.%, Based on the total weight of the ink composition, wherein the methicone is present in an amount within the range of 0.03 to 0.12 wt.% Further embodiments include those in which the methicone is present in an amount in the range of 0.05 to 0.1 wt.%. Such ranges are suitable when the HIL ink composition is printed on known anode materials used in OLED devices. For example, if the OLED device is an OLED device in which light is emitted through the anode (called bottom emitting), a transparent or semitransparent anode material is used. The transparent or translucent anode material may include indium oxide, zinc oxide, indium tin oxide (ITO), and indium zinc oxide (IZO). For OLED devices where light is emitted through the cathode (called top emitting), a reflective layer is formed below the transparent anode. The reflective layer materials include silver (Ag), silver-palladium-copper (APC), silver-rubidium-gold (ARA), molybdenum-chromium (MoCr), and the like.

The aqueous ink composition further comprises one or more electrically conductive polythiophenes. For example, a mixture of PEDOT and PEDOT and poly (styrenesulfonate) (PEDOT: PSS) may be included in the ink composition. In particular, as discussed in more detail below, in combination with suitable solvents, the polythiophenes can be incorporated into the ink composition at very high concentrations. For example, some embodiments of the ink composition may comprise at least 30 wt.% Polythiophene, at least 40 wt.% Polythiophene, at least 50 wt.% Polythiophene, at least 55 wt. % Polythiophene, or at least 60 wt.% Polythiophene. In such embodiments, the polythiophene may be PEDOT.

The aqueous ink composition comprises at least one organic solvent. For example, the composition may include a solvent that reduces the surface tension and / or viscosity of the composition, a solvent that increases the latency of the printed ink composition, or a combination of such solvents. The at least one organic solvent may be a solvent having a relatively high boiling point which increases the latency of the printed ink composition. This is advantageous because it helps prevent the ink composition from drying on the print nozzles or blocking the print nozzles during printing. Such a solvent preferably has a boiling point of at least < RTI ID = 0.0 > 200 C. < / RTI > More preferably at least 230 占 폚, at least 250 占 폚 or even at least 280 占 폚. Diols and glycols such as propanediol, pentanediol, diethylene glycol and triethylene glycol are examples of organic solvents that can be used to increase the latency. Unfortunately, however, diols and glycols have a tendency to have relatively high viscosity and surface tension that can degrade the jettability of the ink compositions containing them. Therefore, some embodiments of the present ink composition do not have a diol and glycol solvent. In these embodiments, an aprotic solvent having a boiling point of at least 240 캜, a viscosity of 15 cPs or less and a surface tension of 55 dyne / cm or less may be used instead of a diol or glycol. This includes an aprotic solvent having a viscosity of less than or equal to 12 cPs, and further includes those having a viscosity of less than or equal to 10 cPs. For the purposes of this disclosure, the boiling point referred to refers to the boiling point at atmospheric pressure. The referred viscosity and surface tension refer to the viscosity at the printing temperature and the surface tension. For example, when printing occurs at room temperature, the viscosity and surface tension are the viscosity and surface tension at about 25 ° C.

Sulfolane, 2,3,4,5-tetrahydrothiophen-1,1-dioxide is also known as tetramethylenesulfone and has a relatively high boiling point, which provides good latency without loss of jetting, a relatively lower viscosity, It is an example of a magnetic solvent. In addition, an ink composition containing sulfolane as an organic solvent may contain both a high concentration of solvent and a polythiophene while maintaining good jetting properties. For example, the ink composition may comprise sulfolane in an amount of at least 5 wt.%, At least 10 wt.%, Or at least 12 wt.%. Suitable concentration ranges for sulfolane in the ink composition include from about 3 wt% to about 15 wt%. At such a sulfolane concentration, the ink composition may contain a high concentration of PEDOT (e.g., 35 to 70 wt.%). In some ink compositions, sulfolane is the most solvent, i.e. it accounts for more than 50 wt.% Of the total organic solvent content of the ink composition. Other suitable solvents include 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone, also known as propylene carbonate and dimethylpropylene urea.

The ink composition may further comprise a co-solvent that serves as a surface tension reducing agent to improve the jetting properties of the composition. For example, an ink composition comprising a diol, glycol, sulfolane, or other high boiling point solvent may include additional solvents having a lower surface tension and typically a lower boiling point than such a solvent. Propylene glycol methyl ether or other similar ethers may be used for this purpose.

In general, for ink compositions useful for inkjet printing applications, the surface tension, viscosity, latency, and invasiveness of the ink compositions can be controlled at a temperature (e.g., room temperature; The composition must be adapted to be dispensed through the printing nozzles. Accordingly, the optimum characteristics will depend on factors such as nozzle size, printing speed, and printing temperature. Generally, acceptable viscosities will include those in the range of from about 1 to about 20 cPs and acceptable surface tensions will include those of less than or equal to about 50 dynes / cm. To avoid or minimize nozzle clogging, a waiting time of 20 minutes or more (e.g., 30 minutes or more) (at room temperature and without vacuum) is preferred, wherein the waiting time is significantly reduced in performance, for example, Refers to the time that the nozzle can be exposed and left before there is a reduction in the falling rate that affects it.

Inkjet printers suitable for ink composition printing include commercially available and drop-on-demand printheads, such as Fuji Film Dimatix (Lebanon, NH), Trident International (Brookfield, Conn ), Epson (Torrance, Calif.), Hitachi Data Systems Corporation of Santa Clara, Calif., Xaar PLC of Cambridge, United Kingdom, and Idanit Technologies, Limited of Rishon Le Zion, Inc. (Simi Valley, CA). For example, Dimatix Materials Printer DMP-3000 can be used.

As shown in the block diagram of FIG. 1, various embodiments of the OLED inkjet printing system 100 may be configured with a variety of devices, equipment, systems, etc. that enable reliable placement of ink drops at specific locations on the substrate . According to various embodiments of the system and method, the printing system may include, for example, but not limited to, a substrate transport system 110, a substrate support apparatus 120, a motion system 130, a printhead assembly 140 ), An ink delivery system 150, and a control system 160.

The OLED substrate can be inserted using the substrate transport system 110 and removed from the printing system 100. Depending on various embodiments of the printing system 100, the substrate transport system 110 may be a mechanical conveyor, a substrate float table with a gripper assembly, a robot with an end effector, and combinations thereof. have. Further, during the printing process, the substrate can be supported by the support equipment 120, which can be, for example, but is not limited to, a chuck or float table. As printing requires relative motion between the printhead and the substrate, various embodiments of the printing system 100 may have a motion system 130, which may include, for example, but not limited to, gantry or segmented axis XYZ system.

The printhead assembly 140 may include at least one printhead device that may be mounted to the motion system 130. [ At least one printhead device included in the printhead assembly 140 may have at least one inkjet printhead capable of ejecting drops of the ink composition through at least one orifice at a controlled rate, speed, and size . Various embodiments of the printing system 100 according to the present teachings may have from about 1 to about 60 printhead devices. In addition, various embodiments of the printhead apparatus may have from about 1 to about 30 inkjet printheads in each printhead apparatus, and each inkjet printhead may have from about 16 to about 2048 nozzles. According to various embodiments of the printhead assembly 140, each nozzle of each inkjet printhead may emit a drop volume of about 0.1 pL to about 200 pL. The printhead assembly 140 having at least one inkjet printhead may be in fluid communication with the ink composition delivery system 150 and may be configured to dispense the ink composition to one or more inkjet printheads of the printhead assembly 140 Can supply.

For various embodiments of the motion system 130, during the printing process, the printhead assembly 140 may move over a fixed substrate (support platform), or in the case of a split shaft configuration, the printhead assembly 140 and / All substrates can move. For various embodiments of the divided shaft configuration, Z-axis control may be provided by moving the printhead assembly 140 relative to the substrate. In another embodiment of the motion system, the printhead assembly 140 can be fixed, the substrate relative to the printhead assembly 140 can move in the X and Y axes, and the Z- Axis movement of the substrate or a Z-axis movement of the substrate. During the printing process, as the printhead assembly 140 moves relative to the substrate, a drop of the ink composition is dispensed at the desired location on the substrate at the correct time.

For various embodiments of the printing system 100, the control system 160 may be used to control the function of the printing process. Various embodiments of the control system 160 may be accessible to the end user through a user interface. The control system 180 controls and transmits data to and from the substrate transport system 110, the substrate support equipment 120, the motion system 130, the printhead assembly 140, and the ink composition delivery system 150, , And < / RTI > The control system 160 may be any type of electronic circuit capable of transmitting and receiving control and data and data information, such as a computer system, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) , And combinations thereof. The control system 160 may include a substrate transport system 110, a substrate support apparatus 120, a motion system 130, a printhead assembly 140, and an ink delivery system 140 for the purpose of, for example, And may include one electronic circuit or multiple electronic circuits distributed between the composition delivery systems 150. [

 Various embodiments of the control system 160 of the printing system 100 may also provide data processing and display and report preparation functions. All such device control functions may be locally dedicated to the printing system 100, or the control system 160 may provide remote control of some or all of the control, analysis, and reporting functions. Finally, various embodiments of the printing device 100 may be received in the enclosure 200 of FIG.

2 is a schematic diagram of a gas enclosure system 200 capable of receiving the printing system 100 of FIG. 1 in accordance with various embodiments. Various embodiments of the gas enclosure system 200 include a gas enclosure assembly 250 according to the present teachings, a gas purge loop 230 in fluid communication with the gas enclosure assembly 250, and at least one thermal conditioning system 240 . In addition, various embodiments of the gas enclosure system may include a pressurized inert gas recirculation system 260, which may provide an inert gas for operating various devices, such as a substrate float table for an OLED printing system. Various embodiments of the pressurized inert gas recirculation system 260 may utilize a compressor, a blower, and a combination of the two as a source for various embodiments of the inert gas recirculation system 260. In addition, the gas enclosure system 200 may have an internal filtration and circulation system (not shown) for the gas enclosure system 200, which provides a substantially low-particle printing environment with other components such as a float table can do.

As shown in Figure 2, for various embodiments of the gas enclosure assembly 200 according to the present teachings, the gas purge loop 230 is configured to remove gas from the gas enclosure assembly 250, to the solvent removal component 232, And a discharge line 231 to the system 234. The purified inert gas of the solvent and other reactive gaseous species such as oxygen and water vapor are then returned to the gas enclosure assembly 250 through the inlet line 233. The gas purge loop 230 may also include suitable conduits and connections, and sensors, such as oxygen, water vapor, and solvent vapor sensors. A gas circulation unit, such as a fan, blower or motor, may be provided separately or integrated into the gas purge system 234 to circulate the gas through, for example, the gas purge loop 230. According to various embodiments of the gas enclosure assembly, although the solvent removal system 232 and the gas purification system 234 may appear as discrete units in the schematic diagram shown in FIG. 2, the solvent removal system 232 and the gas purification system 234, (234) can be accommodated together as a single purifying unit. The thermal conditioning system 240 may include, for example, but is not limited to, at least one chiller 241, which includes a fluid discharge line 243 for circulating cooling water to the gas enclosure assembly, and And a fluid inlet line 245 for returning the cooling water to the chiller.

For various embodiments of the gas enclosure assembly 200, the gas source may be an inert gas, such as nitrogen, any inert gas, and combinations thereof. For various embodiments of the gas enclosure assembly 200, the gas source may be a source of gas such as clean dry air (CDA). For various embodiments of the gas enclosure assembly 200, the gas source may be a source that supplies a combination of inert gas and gas such as CDA.

The gas enclosure system 200 can provide a level for each species of a variety of reactive gas species including various reactive atmospheric gases such as water vapor and oxygen as well as organic solvent vapors below 100 ppm, for example, below 10 ppm , 1.0 ppm or less, or 0.1 ppm or less. In addition, various embodiments of gas enclosure assemblies can provide a low particulate environment that meets a range of specifications for particulate matter in the air, according to the cleanroom technology levels of ISO 14644 Class 1 to Class 5.

While the above given are typical OLED inkjet printing systems and gas enclosure systems, those skilled in the art will appreciate that such systems can be constructed with any combination of one or more of the apparatus and apparatus of FIGS. 1 and 2, as well as additional apparatus and equipment .

The final inkjet-printed product is a HIL having a very uniform thickness and composition. For example, a layer having a thickness variation of less than or equal to 10% over the entire width of the layer is possible. The thickness across the layer can be measured using a metrology tool, such as a stylus contact profilometer or an interferometer microscope. Suitable interferometers for optical interference measurements are commercially available from Zygo's instrumentation.

The ink composition can be used to print HIL directly on a multilayer OLED structure. A typical OLED includes a support substrate, an anode, a cathode, a HIL disposed over the anode, and a light emitting layer (EML) disposed between the HIL and the cathode. Other layers that may be present in the device include a hole transport layer provided between the HIL and the light emitting layer to assist transport of holes into the light emitting layer, and an electron transport layer (ETL) disposed between the EML and the cathode. The substrate is generally a transparent glass or plastic substrate.

In this multi-layer structure, not only the HIL but also one or more layers may be formed through inkjet printing, while the other layers may be deposited using other film-forming techniques. Typically, the various layers will be formed in one or more pixel cells. Each pixel cell is defined by a bank that contains the bottom and defines the boundary of the cell. The surface inside the cell may optionally be coated with a surface-modified coating, such as a surfactant. However, in some embodiments, such a surfactant is not present because it can quench the luminescence of the luminescent layer.

3 is a schematic diagram of a flat panel display including a plurality of OLEDs arranged in a matrix of pixel cells. 3 shows an enlarged view 320 of the panel region 300 and shows the alignment of a plurality of pixel cells including a red light emitting pixel cell 332, a green light emitting pixel cell 334 and a blue light emitting pixel cell 336 330). In addition, the integrated circuit 338 may be formed on the flat panel display substrate such that the circuit is adjacent each pixel cell for the purpose of applying a voltage to each pixel in a controlled manner during use. The pixel cell size, contour, aspect ratio may vary depending on, for example, the desired pixel, but is not limited thereto. For example, a pixel cell density of 100 ppi may suffice for a panel used in a computer display, where, for high resolution, for example, about 300 ppi to about 450 ppi may be used for effective packing of higher pixel density Lt; RTI ID = 0.0 > pixel cell < / RTI >

While the above disclosures focus on aqueous ink compositions formulated for ink jet printed polythiophene based HILs, another aspect of the present technique is the use of non-aqueous, organic solvent based inks formulated for HIL or HTL inkjet printing for OLEDs Lt; / RTI > Organic HIL / HTL ink compositions are commonly considered as infiltrants, but can be introduced into the HTL ink in a carefully controlled amount to provide uncontrolled spreading and pixel cell spill-over that can occur as a result of infiltration Contains ingredients that actually prevent it. In some embodiments, the organic ink comprises: (1) a hole injecting material or a hole transporting material; (2) at least one organic solvent that solubilizes the hole injecting or hole transporting material; And (3) a fluorosurfactant. The hole-injecting or hole-transporting material is typically present in an amount of up to about 5 wt.%, More typically up to 2 wt.%, And even more typically up to about 1 wt.%, To about 1 wt.%). The organic solvent typically accounts for from about 95 to about 99.8 wt.% Of the ink composition. Fluorinated surfactants are typically present in an amount of up to about 0.15 wt.%. For example, in some embodiments of the organic solvent-based ink composition, the fluorinated surfactant is present in an amount ranging from about 0.03 wt.% To about 0.1 wt.%.

Suitable hole injection materials for organic solvent based ink compositions include polythiophenes as described above. Suitable hole transport materials include, but are not limited to, polyvinylcarbazole or derivatives thereof, polysilanes or derivatives thereof, polysiloxane derivatives having aromatic amines in the side chain or main chain, pyrazoline derivatives, arylamine derivatives, stilbene derivative triphenyldiamine derivatives, Poly (p-phenylenevinylene) or derivatives thereof, poly (2,5-thienylene vinylene) or derivatives thereof, polyaniline or derivatives thereof, polythiophene or derivatives thereof, polyarylamine or derivatives thereof, polypyrrole or derivatives thereof, do.

Suitable organic solvents for HIL / HTL ink compositions include, but are not limited to, alkoxy alcohols, alkyl alcohols, alkyl benzenes, alkyl benzoates, alkyl naphthalenes, amyl octanoates, anisols, aryl alcohols, benzyl alcohols, butyl benzenes, Decalin, dipropylene glycol methyl ether, dodecylbenzene, mesitylene, methoxypropanol, methylbenzoate, methylnaphthalene, methylpyrrolidinone, phenoxyethanol, 1,3-propanediol, pyrrolidinone, Valerophenone, and mixtures thereof.

The fluorosurfactant is a surfactant comprising a fluorinated alkyl chain. E. I. du Pont de Nemours and Company (Wilmington, Delaware) sells fluorinated surfactants under the trade names Capstone and Zonyl. The fluorosurfactant may be, for example, a telomer B monoether having a fluorotelemer (e. G., Polyethylene glycol or 2-perfluoroalkyl) ethanol. Commercially available fluorosurfactants include Zonyl® FS 1033D, Zonyl® FS 1176, Zonyl® FSG, Zonyl® FS-300, Zonyl® FSN, Zonyl® FSH, Zonyl® FSN, Zonyl® FSO, Zonyl® FSO-100, Zonyl® FSH, Zonyl® FSN, Zonyl® FSO, Zonyl® FSN, Zonyl® FSN, Zonyl® FSN, Zonyl® 9361, Zonyl® FSA, FSP, FSE, FSJ, Zonyl® FSP, Zonyl® 9361, Zonyl® FSE, Zonyl® FSA, Zonyl® UR, Zonyl® 8867L, Zonyl® FSG, Zonyl® 8857A, Foraperle® 225, Forafac® 1268, Forafac® 1157, Forafac® 1183, Zonyl® 8929B, Zonyl® 9155, Zonyl® 9815, Zonyl® 9933LX, Zonyl® 9938, Zonyl® PFBI, Zonyl® PFBEI, Zonyl® PFBE, Zonyl® PFHI, Zonyl® BA, -8- Zonyl® PFHEI, Zonyl® TM, Zonyl® 8932, Zonyl® 7910, Zonyl® 7040, Foraperle® 321/325, Zonyl® 9464, Zonyl® NF, Zonyl® RP, Zonyl® 321, Zonyl® 8740 , Zonyl® 225, Zonyl® 227, Zonyl® 9977, Zonyl® 9027, Zonyl® 9671, Zonyl® 9338, and Zonyl® 9582, Capstone® ST-500, Capstone® ST-300 , Capstone® ST-200, Capstone® ST-110, Capstone® P-640, Capstone® P-623, Capstone® P-600 Capstone® FS-50, Capstone® FS-51, Capstone® FS-31, Capstone® FS-31, Capstone® FS-30 Capstone® FS-61, Capstone® FS-61, Capstone® FS-63, Capstone® FS-64, Capstone® FS-65 , Capstone® LPA, Capstone® 1460, Capstone® 1157, Capstone® 1157D, Capstone® 1183, Capstone® CPS, Capstone® E, Capstone® LMC, Capstone® CP, Capstone® PSB, Capstone® 4-I, Capstone® 42 I, Capstone® 42-U, Capstone® 6-I, Capstone® 62-AL, Capstone® 62-I, Capstone® 62-MA, Capstone® TC, Capstone® TR and Capstone® TS.

Example

Example 1 : Effect of methicone on in-pixel uniformity

The following examples illustrate the contact line fixing effect provided by the methicone in the HIL inkjet ink composition, and the improvement of the resulting uniformity of light emission.

Materials and methods .

Preparation of HIL ink composition :

HIL ink compositions A and B were prepared using the components and concentrations shown in Table 1. Both compositions A and B contain methicone at the indicated concentrations. As an example of comparison, an ink composition containing the components listed in Table 2, but not comprising methicone, was prepared (comparison composition).

ingredient Composition A Composition B Wt.% Wt.% PEDOT 34 34 H ₂ O 36.9 35.97 Dimethylpropylene glycol methyl ether (DPGME) 16 19 1,3-propanediol 13 11 Botanicil S18 0.1 0.03 Viscosity [cP] 11.1 13.60 ST [Dyne / cm] 43.4 43

ingredient Composition of comparison Wt.% PEDOT 34 H ₂ O 36 Dimethylpropylene glycol methyl ether (DPGME) 16 1,3-propanediol 13 Botanicil S18 0 Viscosity [cP] 11.1 ST [Dyne / cm] 43.4

A clean vial was placed on the balance and the desired amount of Botanisil S-18 was transferred to the vial using a Pasteur pipette to formulate the ink composition. The scale was chirped, and 1,3-propanediol, water and DPGME were transferred to the vial sequentially using a pipette. The vials were then removed from the scale, capped and rotated to mix the resulting aqueous solution. The vial was then placed back on the balance and the desired amount of PEDOT dispersion (Haraeus Clevios TM PVP A1 4083) was transferred to the vial using a pipette. The vial was then removed from the scale, capped and rotated to mix with PEDOT and other components of the mixture. The resulting PEDOT ink composition was then filtered using a polytetrafluoroethylene (PTFE) filter membrane (2.0 [mu] m) and the filtered composition was collected in a brown bottle. Ultimately, the bottle was sonicated for 15 minutes before use. Comparative ink compositions were prepared using the same procedure without Botanisil S-18.

Viscosity and surface tension measurements :

Viscosity measurements were performed using a DV-I Prime Brookfield flow meter. The surface tension was measured with a SITA bubble pressure tester. The measured values for the ink compositions (comparative compositions) in comparison with the methicone-containing ink compositions A and B are provided in Tables 1 and 2.

HIL inkjet printing and OLED manufacturing:

A HIL ink composition was printed on an ITO anode in an OLED structure. The substrate of the OLED was glass having a thickness of 0.5 mm and ITO (indium tin oxide) was patterned on a 60 nm anode on the glass. The bank material (also known as a pixel defining layer) was then patterned on ITO and the cell was formed where the inkjet printed layer was deposited. The bank material was a negative type photoresist designed for inkjet printing. The resulting cell had a bank having a height in the range of about 0.5 to 2 [mu] m inclined at 45 [deg.] To the bottom of the cell so that the opening of each cell was wider than the cell's base. The 45 [deg.] Angle is representative of a typical bank angle ranging from about 5 [deg.] To about 70 [deg.]. The cell width and length dimensions were about 60 x 175 μm. The HIL layer was then ink jet printed onto the cell using the ink compositions of Tables 1 and 2, dried under vacuum and water and solvent removed from the layer by bake at high temperature.

HIL ink compositions were printed at room temperature using the inkjet printing system described in PCT Patent Application No. WO 2013/158310, the entire disclosure of which is incorporated herein by reference. Ink-jet printing to the pixel cell was performed by filling the bulk ink reservoir with the HIL ink composition. The bulk ink reservoir is in fluid communication with the primary dispensing reservoir and a continuous supply of the HIL ink composition is provided to the primary dispensing reservoir during printing. The HIL ink composition was then fed to a printhead containing a plurality of nozzles through which the HIL ink composition was injected into the pixel cell. A typical drop volume during printing was about 10 pl and about 3 to 10 drops were printed in each cell to form droplets of the ink composition in the cell.

An OLED containing the printed HIL from the ink composition A is prepared as follows. The HTL layer was inkjet printed on the HIL layer, followed by drying under vacuum and baking at high temperature to remove the solvent and induce cross-linking of the cross-linkable polymer. The EML layer was then ink jet printed onto the HTL layer, followed by drying under vacuum and baking at high temperature to remove the solvent. The HTL and EML layers are inkjet printed using the printer described above. The HTL ink composition consists of a hole transporting polymeric material in an ester based solvent system composed of a mixture of distilled and deaerated 1: 1 by weight diethyloctanoate and octyl octanoate. The EML ink composition is composed of an organic electroluminescent material in diethyl sebacate.

The ETL layer, followed by the cathode layer, was then applied by vacuum thermal evaporation. The ETL material is composed of lithium quinolate (LiQ) as the luminescent material and the cathode layer is composed of aluminum of 100 nm.

result.

The droplets of the compositions A and B printed in the pixel cell are fixed in the pixel bank and do not undergo spill-over or pull-back. An image of the HIL layer made using composition A (0.1 wt.% Methicone), printed and fixed on the pixel cell, is shown in Figure 4A. On the other hand, the image of the comparison composition printed in the pixel cell (FIGS. 5 and 6) shows that in the absence of the mechicon, the ink composition unavoidably spreads over the side of the pixel cell 500 (FIG. 5A) (Dewetting) 600 to create a de-wetted zone 602 at the bottom of the cell (FIG. 6A).

A black and white line drawing for each of the micrographs shown above and shown in Figures 4A-6A and described below and shown in Figures 7A-9A is provided and is represented by the corresponding drawing 'B'.

The electroluminescent properties of OLED pixels made from composition A and including inkjet printed HIL were also studied. After the OLED was fabricated, the uniformity of the electroluminescence was examined by applying a current across the diode and imaging the emission. The resulting emission is shown in the micrograph of FIG. 7A. As can be seen in this figure, the HIL layer printed with the ink composition A contributed to the uniform emission to the place where the layer of the OLED pixel was introduced.

Example 2 : Effect of sulfolane on printability

The following examples illustrate improved printability imparted to HIL ink compositions by sulfolane.

Materials and methods.

Preparation of HIL ink composition :

Methicone, sulfolane, and other ingredients listed in Table 3 were prepared.

ingredient Wt.% PEDOT 59.9 DPGME 5 Sulfolane 10 H ₂ O 25 Surfactant (S18) 0.1 Viscosity [cP] 5.9 ST [Dyne / cm] 45.0

The ink composition was formulated as described in Example 1 except that sulfolane was used instead of 1,3-propanediol. Viscosity and surface tension measurements :

Viscosity and surface tension were measured as in Example 1.

HIL inkjet printing and OLED manufacturing:

The HIL ink composition was printed and OLED pixels were formed for electroluminescence test as described in Example 1.

Waiting time measurement :

The latency time for the ink was measured using the inkjet printing system described in PCT Patent Application No. WO 2013/158310. Measurements were performed by spraying one nozzle and measuring 300 data points of volume, velocity, and directionality. The nozzle was then allowed to stand for 30 minutes. After 30 minutes, the nozzle was restarted and more than 300 data points were recorded.

(Usually slowed down and volumetric change) at the start of the second data set (after a 30 minute wait) compared to the steady-state injection (end of the first data set, before 30 minutes wait) .

Latency measurements for the ink were also performed using a Dimatix Fuji film DMP-2831 printer. In the drop observation setting, all 16 nozzles were turned on and all the nozzles were sprayed. The injection was then stopped for 5 minutes. The spray was resumed and the test confirmed that all the nozzles were still operational. Thereafter, continuous injection was carried out for 15 and 30 minutes. The waiting time was measured as the time between the initiation of the injection and the start of drying of the ink in an uncapped nozzle resulting in improper droplet ejection. To determine when the ink composition was dried, they were observed under a microscope in white and fluorescent modes.

result.

After fabricating the OLED, the uniformity of the electroluminescence was examined by applying a current across each diode and imaging the light emission. Electroluminescence was measured for an OLED having a printed HIL from the ink composition of Table 3 and an OLED having a printed HIL from the ink composition of Table 1. A comparison of the micrographs of FIGS. 8 and 9 shows that the sulfolane in the HIL ink composition provides more uniform pixel emission (FIG. 8A) than propanediol (FIG. 9A).

In addition, the maximum stable jet frequency (1000 Hz) for the sulfolane-containing ink composition was higher than the frequency for the diol-containing ink composition. Finally, the waiting time for the sulfolane-containing ink composition was more than 30 minutes compared to only 15 minutes for the diol-containing ink composition. The results for the latency test measured using the inkjet printing system described in PCT Patent Application No. WO 2013/158310 are shown in Figures 10-12. In these graphs, the sulfolane-containing ink is designated P113. Figure 10 is a graph of the drop volume over 14 minutes for the ink composition after pre-atmospheric and 30 minutes atmospheric. Figure 11 is a graph of the drop rate over 14 minutes for the ink composition after pre-atmospheric and 30 minutes atmospheric. As can be seen in the figure, the drop rate at restart is only 4% below the pre-atmospheric drop rate. 12 is a graph of the drop angle over 14 minutes for the ink composition after pre-atmospheric and 30 minutes atmospheric. Significant differences in drop angle before and after observing the atmosphere were not observed.

The term " illustrative " is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as " exemplary " is not necessarily to be construed as preferred or advantageous over other aspects or designs. Also, for purposes of this disclosure and unless indicated otherwise, "a" or "an" means "one or more." Also, "and" The use of "and" or "or" is intended to include "and / or" unless otherwise indicated.

The foregoing description of the exemplary embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings, or may be acquired from practice of the invention. The embodiments have been chosen and described as the practical application of the present invention to illustrate the principles of the invention and to enable those skilled in the art to utilize various embodiments with various modifications as are suited to the particular use contemplated. The scope of the invention is defined by the claims appended hereto and their equivalents.

Claims (10)

An ink composition comprising:
A hole injecting material or a hole transporting material;
At least one organic solvent that solubilizes the hole injecting material or the hole transporting material; And
Fluorosurfactant;
Wherein the fluorine surfactant is present in an amount of 5 wt.% Or less based on the total weight of the ink composition. The ink composition according to claim 1, wherein the fluorine surfactant is present in an amount of 1 wt.% Or less based on the total weight of the ink composition. The ink composition according to claim 1, wherein the fluorine surfactant is present in an amount of 0.15 wt.% Or less based on the total weight of the ink composition. The ink composition according to claim 1, wherein the fluorine surfactant is fluoro-romor. The ink composition of claim 1, wherein the ink composition comprises 95 to 99.8 wt.% Organic solvent and 0.03 wt.% To 0.1 wt.% Fluorinated surfactant. 6. The ink composition according to claim 5, wherein the fluorine surfactant is fluoroelastomer. The ink composition of claim 1, wherein the ink composition comprises a hole injecting material comprising an electrically conductive polythiophene. The ink composition according to claim 7, wherein the fluorine surfactant is fluoroelastomer. 9. The ink composition of claim 8, wherein the fluoroelastomer is present in an amount of up to 0.15 wt.%, Based on the total weight of the ink composition. 2. The composition of claim 1, having a viscosity of from 1 cPs to 20 cPs at < RTI ID = 0.0 > 25 C &
An ink composition having a surface tension of less than 50 dyne / cm.

Images