U.S. patent application number 11/444655 was filed with the patent office on 2007-09-06 for process for making contained layers and devices made with same.
Invention is credited to Gary A. Johansson, Daniel David Lecloux, Eric Maurice Smith.
Application Number | 20070205409 11/444655 |
Document ID | / |
Family ID | 38610130 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070205409 |
Kind Code |
A1 |
Lecloux; Daniel David ; et
al. |
September 6, 2007 |
Process for making contained layers and devices made with same
Abstract
There is provided a process for forming a contained second layer
over a first layer, including the steps: forming the first layer
having a first surface energy; treating the first layer with a
reactive surface-active composition to form a treated first layer
having a second surface energy which is lower than the first
surface energy; exposing the treated first layer with radiation;
and forming the second layer. There is also provided an organic
electronic device made by the process.
Inventors: |
Lecloux; Daniel David;
(Wilmington, DE) ; Smith; Eric Maurice;
(Hockessin, DE) ; Johansson; Gary A.; (Hockessin,
DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128, 4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
38610130 |
Appl. No.: |
11/444655 |
Filed: |
June 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11401151 |
Apr 10, 2006 |
|
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11444655 |
|
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|
60751549 |
Mar 2, 2006 |
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Current U.S.
Class: |
257/40 ;
257/E51.02; 438/22 |
Current CPC
Class: |
H01L 51/0011 20130101;
H01L 51/0005 20130101; H01L 51/56 20130101; H01L 51/0004 20130101;
H01L 51/5012 20130101; H01L 51/0018 20130101; H01L 51/0003
20130101 |
Class at
Publication: |
257/40 ; 438/22;
257/E51.02 |
International
Class: |
H01L 51/00 20060101
H01L051/00; H01L 35/24 20060101 H01L035/24 |
Claims
1. A process for forming a contained second layer over a first
layer, said process comprising: forming the first layer having a
first surface energy; treating the first layer with a reactive
surface-active composition to form a treated first layer having a
second surface energy which is lower than the first surface energy;
exposing the treated first layer with radiation; and forming the
second layer.
2. The process of claim 1, wherein the reactive surface-active
composition is a fluorinated material.
3. The process of claim 1, wherein the reactive surface-active
composition is a radiation-hardenable material.
4. The process of claim 1, wherein the reactive surface-active
composition is a crosslinkable fluorinated surfactant.
5. The process of claim 1, wherein the reactive surface-active
composition is deposited with the first layer.
6. The process of claim 1, wherein the reactive surface-active
composition is applied as a separate layer over the first
layer.
7. The process of claim 1, wherein the radiation is applied in a
pattern to form exposed regions and unexposed region of the
reactive surface-active composition.
8. The process of claim 7, further comprising removing either the
exposed or unexposed regions of the reactive surface-active
composition.
9. The process of claim 8, wherein the regions are removed by
treating with a liquid.
10. The process of claim 8, wherein the regions are removed by
heating.
11. The process of claim 8, wherein the regions are removed by
contacting an outermost surface of the with an absorbent surface to
absorb or wick away the softer regions.
12. A process for making an organic electronic device comprising a
first organic active layer and a second organic active layer
positioned over an electrode, said process comprising forming the
first organic active layer having a first surface energy over the
electrode treating the first organic active layer with a reactive
surface-active composition to form a treated first organic active
layer, exposing the treated first organic active layer with
radiation, thereby reducing the first surface energy, and forming
the second organic active layer.
13. An organic electronic device comprising a first organic active
layer and a second organic active layer positioned over an
electrode, and further comprising a reactive surface-active
composition between the first organic active layer and the second
organic active layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation-in-Part of U.S. Ser. No.
11/401,151, filed Apr. 10, 2006, which claims priority to
provisional application Ser. No. 60/751,549, dated Mar. 2,
2006.
BACKGROUND INFORMATION
[0002] 1. Field of the Disclosure
[0003] This disclosure relates in general to a process for making
an electronic device. It further relates to the device made by the
process.
[0004] 2. Description of the Related Art
[0005] Electronic devices utilizing organic active materials are
present in many different kinds of electronic equipment. In such
devices, an organic active layer is sandwiched between two
electrodes.
[0006] One type of electronic device is an organic light emitting
diode (OLED). OLEDs are promising for display applications due to
their high power-conversion efficiency and low processing costs.
Such displays are especially promising for battery-powered,
portable electronic devices, including cell-phones, personal
digital assistants, handheld personal computers, and DVD players.
These applications call for displays with high information content,
full color, and fast video rate response time in addition to low
power consumption.
[0007] Current research in the production of full-color OLEDs is
directed toward the development of cost effective, high throughput
processes for producing color pixels. For the manufacture of
monochromatic displays by liquid processing, spin-coating processes
have been widely adopted (see, e.g., David Braun and Alan J.
Heeger, Appl. Phys. Letters 58, 1982 (1991)). However, manufacture
of full-color displays requires certain modifications to procedures
used in manufacture of monochromatic displays. For example, to make
a display with full-color images, each display pixel is divided
into three subpixels, each emitting one of the three primary
display colors, red, green, and blue. This division of full-color
pixels into three subpixels has resulted in a need to modify
current processes to prevent the spreading of the liquid colored
materials (i.e., inks) and color mixing.
[0008] Several methods for providing ink containment are described
in the literature. These are based on containment structures,
surface tension discontinuities, and combinations of both.
Containment structures are geometric obstacles to spreading: pixel
wells, banks, etc. In order to be effective these structures must
be large, comparable to the wet thickness of the deposited
materials. When the emissive ink is printed into these structures
it wets onto the structure surface, so thickness uniformity is
reduced near the structure. Therefore the structure must be moved
outside the emissive "pixel" region so the non-uniformities are not
visible in operation. Due to limited space on the display
(especially high-resolution displays) this reduces the available
emissive area of the pixel. Practical containment structures
generally have a negative impact on quality when depositing
continuous layers of the charge injection and transport layers.
Consequently, all the layers must be printed.
[0009] In addition, surface tension discontinuities are obtained
when there are either printed or vapor deposited regions of low
surface tension materials. These low surface tension materials
generally must be applied before printing or coating the first
organic active layer in the pixel area. Generally the use of these
treatments impacts the quality when coating continuous non-emissive
layers, so all the layers must be printed.
[0010] An example of a combination of two ink containment
techniques is CF.sub.4-plasma treatment of photoresist bank
structures (pixel wells, channels). Generally, all of the active
layers must be printed in the pixel areas.
[0011] All these containment methods have the drawback of
precluding continuous coating. Continuous coating of one or more
layers is desirable as it can result in higher yields and lower
equipment cost. There exists, therefore, a need for improved
processes for forming electronic devices.
SUMMARY
[0012] There is provided a process for forming a contained second
layer over a first layer, said process comprising: [0013] forming
the first layer having a first surface energy; [0014] treating the
first layer with a reactive surface-active composition to form a
treated first layer having a second surface energy which is lower
than the first surface energy; [0015] exposing the treated first
layer with radiation; and [0016] forming the second layer.
[0017] There is provided a process for making an organic electronic
device comprising a first organic active layer and a second organic
active layer positioned over an electrode, said process comprising:
[0018] forming the first organic active layer having a first
surface energy over the electrode; [0019] treating the first
organic active layer with a reactive surface-active composition to
form a treated first organic active layer having a second surface
energy which is lower than the first surface energy; [0020]
exposing the treated first organic active layer with radiation; and
[0021] forming the second organic active layer.
[0022] There is also provided an organic electronic device
comprising a first organic active layer and a second organic active
layer positioned over an electrode, and further comprising a
reactive surface-active composition between the first organic
active layer and the second organic active layer.
[0023] The foregoing general description and the following detailed
description are exemplary and explanatory only and are not
restrictive of the invention, as defined in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Embodiments are illustrated in the accompanying figures to
improve understanding of concepts as presented herein.
[0025] FIG. 1 includes a diagram illustrating contact angle.
[0026] FIG. 2 includes an illustration of an organic electronic
device.
[0027] FIG. 3 includes an illustration of a substrate with anode
lines.
[0028] FIG. 4 includes an illustration of the substrate of FIG. 3
coated with a buffer material.
[0029] FIG. 5 includes an illustration of the substrate of FIG. 4
further coated with a reactive surface-active composition.
[0030] FIG. 6 includes an illustration of the substrate of FIG. 5
after exposure and development.
[0031] Skilled artisans appreciate that objects in the figures are
illustrated for simplicity and clarity and have not necessarily
been drawn to scale. For example, the dimensions of some of the
objects in the figures may be exaggerated relative to other objects
to help to improve understanding of embodiments.
DETAILED DESCRIPTION
[0032] There is provided a process for forming a contained second
layer over a first layer, said process comprising: [0033] forming
the first layer having a first surface energy; [0034] treating the
first layer with a reactive surface-active composition to form a
treated first layer having a second surface energy which is lower
than the first surface energy; [0035] exposing the treated first
layer with radiation; and [0036] applying the second layer over the
treated and exposed first layer.
[0037] Many aspects and embodiments have been described above and
are merely exemplary and not limiting. After reading this
specification, skilled artisans appreciate that other aspects and
embodiments are possible without departing from the scope of the
invention.
[0038] Other features and benefits of any one or more of the
embodiments will be apparent from the following detailed
description, and from the claims. The detailed description first
addresses Definitions and Clarification of Terms followed by the
Reactive Surface-active composition, the Process, the Organic
Electronic Device, and finally Examples.
1. Definitions and Clarification of Terms
[0039] Before addressing details of embodiments described below,
some terms are defined or clarified.
[0040] The term "active" when referring to a layer or material, is
intended to mean a layer or material that exhibits electronic or
electro-radiative properties. In an electronic device, an active
material electronically facilitates the operation of the device.
Examples of active materials include, but are not limited to,
materials which conduct, inject, transport, or block a charge,
where the charge can be either an electron or a hole, and materials
which emit radiation or exhibit a change in concentration of
electron-hole pairs when receiving radiation. Examples of inactive
materials include, but are not limited to, planarization materials,
insulating materials, and environmental barrier materials.
[0041] The term "contained" when referring to a layer, is intended
to mean that the layer does not spread significantly beyond the
area where it is deposited. The layer can be contained by surface
energy affects or a combination of surface energy affects and
physical barrier structures.
[0042] The term "electrode" is intended to mean a member or
structure configured to transport carriers within an electronic
component. For example, an electrode may be an anode, a cathode, a
capacitor electrode, a gate electrode, etc. An electrode may
include a part of a transistor, a capacitor, a resistor, an
inductor, a diode, an electronic component, a power supply, or any
combination thereof.
[0043] The term "organic electronic device" is intended to mean a
device including one or more organic semiconductor layers or
materials. An organic electronic device includes, but is not
limited to: (1) a device that converts electrical energy into
radiation (e.g., a light-emitting diode, light emitting diode
display, diode laser, or lighting panel), (2) a device that detects
a signal using an electronic process (e.g., a photodetector, a
photoconductive cell, a photoresistor, a photoswitch, a
phototransistor, a phototube, an infrared ("IR") detector, or a
biosensors), (3) a device that converts radiation into electrical
energy (e.g., a photovoltaic device or solar cell), (4) a device
that includes one or more electronic components that include one or
more organic semiconductor layers (e.g., a transistor or diode), or
any combination of devices in items (1) through (4).
[0044] The term "fluorinated" when referring to an organic
compound, is intended to mean that one or more of the hydrogen
atoms in the compound have been replaced by fluorine. The term
encompasses partially and fully fluorinated materials.
[0045] The term(s) "radiating/radiation" means adding energy in any
form, including heat in any form, the entire electromagnetic
spectrum, or subatomic particles, regardless of whether such
radiation is in the form of rays, waves, or particles.
[0046] The term "reactive surface-active composition" is intended
to mean a composition that comprises at least one material which is
radiation sensitive, and when the composition is applied to a
layer, the surface energy of that layer is reduced. Exposure of the
reactive surface-active composition to radiation results in the
change in at least one physical property of the composition. The
term is abbreviated "RSA", and refers to the composition both
before and after exposure to radiation.
[0047] The term "radiation sensitive" when referring to a material,
is intended to mean that exposure to radiation results in at least
one chemical, physical, or electrical property of the material.
[0048] The term "surface energy" is the energy required to create a
unit area of a surface from a material. A characteristic of surface
energy is that liquid materials with a given surface energy will
not wet surfaces with a lower surface energy.
[0049] The term "layer" is used interchangeably with the term
"film" and refers to a coating covering a desired area. The term is
not limited by size. The area can be as large as an entire device
or as small as a specific functional area such as the actual visual
display, or as small as a single sub-pixel. Layers and films can be
formed by any conventional deposition technique, including vapor
deposition, liquid deposition (continuous and discontinuous
techniques), and thermal transfer.
[0050] The term "liquid composition" is intended to mean a liquid
medium in which a material is dissolved to form a solution, a
liquid medium in which a material is dispersed to form a
dispersion, or a liquid medium in which a material is suspended to
form a suspension or an emulsion. "Liquid medium" is intended to
mean a material that is liquid without the addition of a solvent or
carrier fluid, i.e., a material at a temperature above its
solidification temperature.
[0051] The term "liquid containment structure" is intended to mean
a structure within or on a workpiece, wherein such one or more
structures, by itself or collectively, serve a principal function
of constraining or guiding a liquid within an area or region as it
flows over the workpiece. A liquid containment structure can
include cathode separators or a well structure.
[0052] The term "liquid medium" is intended to mean a liquid
material, including a pure liquid, a combination of liquids, a
solution, a dispersion, a suspension, and an emulsion. Liquid
medium is used regardless whether one or more solvents are
present.
[0053] As used herein, the term "over" does not necessarily mean
that a layer, member, or structure is immediately next to or in
contact with another layer, member, or structure. There may be
additional, intervening layers, members or structures.
[0054] As used herein, the terms "comprises," "comprising,"
"includes," "including," "has," "having" or any other variation
thereof, are intended to cover a non-exclusive inclusion. For
example, a process, method, article, or apparatus that comprises a
list of elements is not necessarily limited to only those elements
but may include other elements not expressly listed or inherent to
such process, method, article, or apparatus. Further, unless
expressly stated to the contrary, "or" refers to an inclusive or
and not to an exclusive or. For example, a condition A or B is
satisfied by any one of the following: A is true (or present) and B
is false (or not present), A is false (or not present) and B is
true (or present), and both A and B are true (or present).
[0055] Also, use of "a" or "an" are employed to describe elements
and components described herein. This is done merely for
convenience and to give a general sense of the scope of the
invention. This description should be read to include one or at
least one and the singular also includes the plural unless it is
obvious that it is meant otherwise.
[0056] Group numbers corresponding to columns within the Periodic
Table of the elements use the "New Notation" convention as seen in
the CRC Handbook of Chemistry and Physics, 81.sup.st Edition
(2000-2001).
[0057] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
methods and materials similar or equivalent to those described
herein can be used in the practice or testing of embodiments of the
present invention, suitable methods and materials are described
below. All publications, patent applications, patents, and other
references mentioned herein are incorporated by reference in their
entirety, unless a particular passage is cited. In case of
conflict, the present specification, including definitions, will
control. In addition, the materials, methods, and examples are
illustrative only and not intended to be limiting.
[0058] To the extent not described herein, many details regarding
specific materials, processing acts, and circuits are conventional
and may be found in textbooks and other sources within the organic
light-emitting diode display, photodetector, photovoltaic, and
semiconductive member arts.
2. Reactive Surface-Active Composition
[0059] The reactive surface-active composition ("RSA") is a
radiation-sensitive composition. When exposed to radiation, at
least one physical property and/or chemical property of the RSA is
changed such that the exposed and unexposed areas can be physically
differentiated. Treatment with the RSA lowers the surface energy of
the material being treated.
[0060] In one embodiment, the RSA is a radiation-hardenable
composition. In this case, when exposed to radiation, the RSA can
become more soluble or dispersable in a liquid medium, less tacky,
less soft, less flowable, less liftable, or less absorbable. Other
physical properties may also be affected.
[0061] In one embodiment, the RSA is a radiation-softenable
composition. In this case, when exposed to radiation, the RSA can
become less soluble or dispersable in a liquid medium, more tacky,
more soft, more flowable, more liftable, or more absorbable. Other
physical properties may also be affected.
[0062] The radiation can be any type of radiation to which results
in a physical change in the RSA. In one embodiment, the radiation
is selected from infrared radiation, visible radiation, ultraviolet
radiation, and combinations thereof.
[0063] Physical differentiation between areas of the RSA exposed to
radiation and areas not exposed to radiation, hereinafter referred
to as "development," can be accomplished by any known technique.
Such techniques have been used extensively in the photoresist art.
Examples of development techniques include, but are not limited to,
treatment with a liquid medium, treatment with an absorbant
material, treatment with a tacky material, and the like.
[0064] In one embodiment, the RSA consists essentially of one or
more radiation-sensitive materials. In one embodiment, the RSA
consists essentially of a material which, when exposed to
radiation, hardens, or becomes less soluble, swellable, or
dispersible in a liquid medium, or becomes less tacky or
absorbable. In one embodiment, the RSA consists essentially of a
material having radiation polymerizable groups. Examples of such
groups include, but are not limited to olefins, acrylates,
methacrylates and vinyl ethers. In one embodiment, the RSA material
has two or more polymerizable groups which can result in
crosslinking. In one embodiment, the RSA consists essentially of a
material which, when exposed to radiation, softens, or becomes more
soluble, swellable, or dispersible in a liquid medium, or becomes
more tacky or absorbable. In one embodiment, the RSA consists
essentially of at least one polymer which undergoes backbone
degradation when exposed to deep UV radiation, having a wavelength
in the range of 200-300 nm. Examples of polymers undergoing such
degradation include, but are not limited to, polyacrylates,
polymethacrylates, polyketones, polysulfones, copolymers thereof,
and mixtures thereof.
[0065] In one embodiment, the RSA consists essentially of at least
one reactive material and at least one radiation-sensitive
material. The radiation-sensitive material, when exposed to
radiation, generates an active species that initiates the reaction
of the reactive material. Examples of radiation-sensitive materials
include, but are not limited to, those that generate free radicals,
acids, or combinations thereof. In one embodiment, the reactive
material is polymerizable or crosslinkable. The material
polymerization or crosslinking reaction is initiated or catalyzed
by the active species. The radiation-sensitive material is
generally present in amounts from 0.001% to 10.0% based on the
total weight of the RSA.
[0066] In one embodiment, the RSA consists essentially of a
material which, when exposed to radiation, hardens, or becomes less
soluble, swellable, or dispersible in a liquid medium, or becomes
less tacky or absorbable. In one embodiment, the reactive material
is an ethylenically unsaturated compound and the
radiation-sensitive material generates free radicals. Ethylenically
unsaturated compounds include, but are not limited to, acrylates,
methacrylates, vinyl compounds, and combinations thereof. Any of
the known classes of radiation-sensitive materials that generate
free radicals can be used. Examples of radiation-sensitive
materials which generate free radicals include, but are not limited
to, quinones, benzophenones, benzoin ethers, aryl ketones,
peroxides, biimidazoles, benzyl dimethyl ketal, hydroxyl alkyl
phenyl acetophone, dialkoxy actophenone, trimethylbenzoyl phosphine
oxide derivatives, aminoketones, benzoyl cyclohexanol, methyl thio
phenyl morpholino ketones, morpholino phenyl amino ketones, alpha
halogennoacetophenones, oxysulfonyl ketones, sulfonyl ketones,
oxysulfonyl ketones, sulfonyl ketones, benzoyl oxime esters,
thioxanthrones, camphorquinones, ketocoumarins, and Michler's
ketone. Alternatively, the radiation sensitive material may be a
mixture of compounds, one of which provides the free radicals when
caused to do so by a sensitizer activated by radiation. In one
embodiment, the radiation sensitive material is sensitive to
visible or ultraviolet radiation.
[0067] In one embodiment, the RSA is a compound having one or more
crosslinkable groups. Crosslinkable groups can have moieties
containing a double bond, a triple bond, a precursor capable of in
situ formation of a double bond, or a heterocyclic addition
polymerizable group. Some examples of crosslinkable groups include
benzocyclobutane, azide, oxiran, di(hydrocarbyl)amino, cyanate
ester, hydroxyl, glycidyl ether, C1-10 alkylacrylate, C1-10
alkylmethacrylate, alkenyl, alkenyloxy, alkynyl, maleimide,
nadimide, tri(C1-4)alkylsiloxy, tri(C1-4)alkylsilyl, and
halogenated derivatives thereof. In one embodiment, the
crosslinkable group is selected from the group consisting of
vinylbenzyl, p-ethenylphenyl, perfluoroethenyl,
perfluoroehtenyloxy, benzo-3,4-cyclobutan-1-yl, and
p-(benzo-3,4-cyclobutan-1-yl)phenyl.
[0068] In one embodiment, the reactive material can undergo
polymerization initiated by acid, and the radiation-sensitive
material generates acid. Examples of such reactive materials
include, but are not limited to, epoxies. Examples of
radiation-sensitive materials which generate acid, include, but are
not limited to, sulfonium and iodonium salts, such as
diphenyliodonium hexafluorophosphate.
[0069] In one embodiment, the RSA consists essentially of a
material which, when exposed to radiation, softens, or becomes more
soluble, swellable, or dispersible in a liquid medium, or becomes
more tacky or absorbable. In one embodiment, the reactive material
is a phenolic resin and the radiation-sensitive material is a
diazonaphthoquinone.
[0070] Other radiation-sensitive systems that are known in the art
can be used as well.
[0071] In one embodiment, the RSA comprises a fluorinated material.
In one embodiment, the RSA comprises an unsaturated material having
one or more fluoroalkyl groups. In one embodiment, the fluoroalkyl
groups have from 2-20 carbon atoms. In one embodiment, the RSA is a
fluorinated acrylate, a fluorinated ester, or a fluorinated olefin
monomer. Examples of commercially available materials which can be
used as RSA materials, include, but are not limited to, Zonyl.RTM.
8857A, a fluorinated unsaturated ester monomer available from E. I.
du Pont de Nemours and Company (Wilmington, Del.), and
3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-eneicosafluorododecyl
acrylate
(H.sub.2C.dbd.CHCO.sub.2CH.sub.2CH.sub.2(CF.sub.2).sub.9CF.sub.3- )
available from Sigma-Aldrich Co. (St. Louis, Mo.).
[0072] In one embodiment, the RSA is a fluorinated macromonomer. As
used herein, the term "macromonomer" refers to an oligomeric
material having one or more reactive groups which are terminal or
pendant from the chain. In some embodiments, the macromonomer has a
molecular weight greater than 1000; in some embodiments, greater
than 2000; in some embodiments, greater than 5000. In some
embodiments, the backbone of the macromonomer includes ether
segments and perfluoroether segments. In some embodiments, the
backbone of the macromonomer includes alkyl segments and
perfluoroalkyl segments. In some embodiments, the backbone of the
macromonomer includes partially fluorinated alkyl or partially
fluorinated ether segments. In some embodiments, the macromonomer
has one or two terminal polymerizable or crosslinkable groups.
[0073] In one embodiment, the RSA is an oligomeric or polymeric
material having cleavable side chains, where the material with the
side chains forms films with a different surface energy that the
material without the side chains. In one embodiment, the RSA has a
non-fluorinated backbone and partially fluorinated or fully
fluorinated side chains. The RSA with the side chains will form
films with a lower surface energy than films made from the RSA
without the side chains. Thus, the RSA can be can be applied to a
first layer, exposed to radiation in a pattern to cleave the side
chains, and developed to remove the side chains. This results in a
pattern of higher surface energy in the areas exposed to radiation
where the side chains have been removed, and lower surface energy
in the unexposed areas where the side chains remain. In some
embodiments, the side chains are thermally fugitive and are cleaved
by heating, as with an infrared laser. In this case, development
may be coincidental with exposure in infrared radiation.
Alternatively, development may be accomplished by the application
of a vacuum or treatment with solvent. In some embodiment, the side
chains are cleavable by exposure to UV radiation. As with the
infrared system above, development may be coincidental with
exposure to radiation, or accomplished by the application of a
vacuum or treatment with solvent.
[0074] In one embodiment, the RSA comprises a material having a
reactive group and second-type functional group. The second-type
functional groups can be present to modify the physical processing
properties or the photophysical properties of the RSA. Examples of
groups which modify the processing properties include plasticizing
groups, such as alkylene oxide groups. Examples of groups which
modify the photophysical properties include charge transport
groups, such as carbazole, triarylamino, or oxadiazole groups.
[0075] In one embodiment, the RSA reacts with the underlying area
when exposed to radiation. The exact mechanism of this reaction
will depend on the materials used. After exposure to radiation, the
RSA is removed in the unexposed areas by a suitable development
treatment. In some embodiments, the RSA is removed only in the
unexposed areas. In some embodiments, the RSA is partially removed
in the exposed areas as well, leaving a thinner layer in those
areas. In some embodiments, the RSA that remains in the exposed
areas is less than 50 .ANG. in thickness. In some embodiments, the
RSA that remains in the exposed areas is essentially a monolayer in
thickness.
3. Process
[0076] In the process provided herein, a first layer is formed, the
first layer is treated with a reactive surface-active composition
("RSA"), the treated first layer is exposed to radiation, and a
second layer is formed over the treated and exposed first
layer.
[0077] In one embodiment, the first layer is a substrate. The
substrate can be inorganic or organic. Examples of substrates
include, but are not limited to glasses, ceramics, and polymeric
films, such as polyester and polyimide films.
[0078] In one embodiment, the first layer is an electrode. The
electrode can be unpatterned, or patterned. In one embodiment, the
electrode is patterned in parallel lines. The electrode can be on a
substrate.
[0079] In one embodiment, the first layer is deposited on a
substrate. The first layer can be patterned or unpatterned. In one
embodiment, the first layer is an organic active layer in an
electronic device.
[0080] The first layer can be formed by any deposition technique,
including vapor deposition techniques, liquid deposition
techniques, and thermal transfer techniques. In one embodiment, the
first layer is deposited by a liquid deposition technique, followed
by drying. In this case, a first material is dissolved or dispersed
in a liquid medium. The liquid deposition method may be continuous
or discontinuous. Continuous liquid deposition techniques, include
but are not limited to, spin coating, roll coating, curtain
coating, dip coating, slot-die coating, spray coating, and
continuous nozzle coating. Discontinuous liquid deposition
techniques include, but are not limited to, ink jet printing,
gravure printing, flexographic printing and screen printing. In one
embodiment, the first layer is deposited by a continuous liquid
deposition technique. The drying step can take place at room
temperature or at elevated temperatures, so long as the first
material and any underlying materials are not damaged.
[0081] The first layer is treated with an RSA. The treatment can be
coincidental with or subsequent to the formation of the first
layer.
[0082] In one embodiment, the RSA treatment is coincidental with
the formation of the first organic active layer. In one embodiment,
the RSA is added to the liquid composition used to form the first
layer. When the deposited composition is dried to form a film, the
RSA migrates to the air interface, i.e., the top surface, of the
first layer in order to reduce the surface energy of the
system.
[0083] In one embodiment, the RSA treatment is subsequent to the
formation of the first layer. In one embodiment, the RSA is applied
as a separate layer overlying, and in direct contact with, the
first layer.
[0084] In one embodiment, the RSA is applied without adding it to a
solvent. In one embodiment, the RSA is applied by vapor deposition.
In one embodiment, the RSA is a liquid at room temperature and is
applied by liquid deposition over the first layer. The liquid RSA
may be film-forming or it may be absorbed or adsorbed onto the
surface of the first layer. In one embodiment, the liquid RSA is
cooled to a temperature below its melting point in order to form a
second layer over the first layer. In one embodiment, the RSA is
not a liquid at room temperature and is heated to a temperature
above its melting point, deposited on the first layer, and cooled
to room temperature to form a second layer over the first layer.
For the liquid deposition, any of the methods described above may
be used.
[0085] In one embodiment, the RSA is deposited from a second liquid
composition. The liquid deposition method can be continuous or
discontinuous, as described above. In one embodiment, the RSA
liquid composition is deposited using a continuous liquid
deposition method. The choice of liquid medium for depositing the
RSA will depend on the exact nature of the RSA material itself. In
one embodiment, the RSA is a fluorinated material and the liquid
medium is a fluorinated liquid. Examples of fluorinated liquids
include, but are not limited to, perfluorooctane, trifluorotoluene,
and hexafluoroxylene.
[0086] In some embodiments, the RSA treatment comprises a first
step of forming a sacrificial layer over the first layer, and a
second step of applying an RSA layer over the sacrificial layer.
The sacrificial layer is one which is more easily removed than the
RSA layer by whatever development treatment is selected. Thus,
after exposure to radiation, as discussed below, the RSA layer and
the sacrificial layer are removed in either the exposed or
unexposed areas in the development step. The sacrificial layer is
intended to facilitate complete removal of the RSA layer is the
selected areas and to protect the underlying first layer from any
adverse affects from the reactive species in the RSA layer.
[0087] After the RSA treatment, the treated first layer is exposed
to radiation. The type of radiation used will depend upon the
sensitivity of the RSA as discussed above. The exposure can be a
blanket, overall exposure, or the exposure can be patternwise. As
used herein, the term "patternwise" indicates that only selected
portions of a material or layer are exposed. Patternwise exposure
can be achieved using any known imaging technique. In one
embodiment, the pattern is achieved by exposing through a mask. In
one embodiment, the pattern is achieved by exposing only select
portions with a laser. The time of exposure can range from seconds
to minutes, depending upon the specific chemistry of the RSA used.
When lasers are used, much shorter exposure times are used for each
individual area, depending upon the power of the laser. The
exposure step can be carried out in air or in an inert atmosphere,
depending upon the sensitivity of the materials.
[0088] In one embodiment, the radiation is selected from the group
consisting of ultra-violet radiation (10-390 nm), visible radiation
(390-770 nm), infrared radiation (770-10.sup.6 nm), and
combinations thereof, including simultaneous and serial treatments.
In one embodiment, the radiation is thermal radiation. In one
embodiment, the exposure to radiation is carried out by heating.
The temperature and duration for the heating step is such that at
least one physical property of the RSA is changed, without damaging
any underlying layers of the light-emitting areas. In one
embodiment, the heating temperature is less than 250.degree. C. In
one embodiment, the heating temperature is less than 150.degree.
C.
[0089] In one embodiment, the radiation is ultraviolet or visible
radiation. In one embodiment, the radiation is applied patternwise,
resulting in exposed regions of RSA and unexposed regions of
RSA.
[0090] In one embodiment, after patternwise exposure to radiation,
the first layer is treated to remove either the exposed or
unexposed regions of the RSA. Patternwise exposure to radiation and
treatment to remove exposed or unexposed regions is well known in
the art of photoresists.
[0091] In one embodiment, the exposure of the RSA to radiation
results in a change in the solubility or dispersibility of the RSA
in solvents. When the exposure is carried out patternwise, this can
be followed by a wet development treatment. The treatment usually
involves washing with a solvent which dissolves, disperses or lifts
off one type of area. In one embodiment, the patternwise exposure
to radiation results in insolubilization of the exposed areas of
the RSA, and treatment with solvent results in removal of the
unexposed areas of the RSA.
[0092] In one embodiment, the exposure of the RSA to visible or UV
radiation results in a reaction which decreases the volatility of
the RSA in exposed areas. When the exposure is carried out
patternwise, this can be followed by a thermal development
treatment. The treatment involves heating to a temperature above
the volatilization or sublimation temperature of the unexposed
material and below the temperature at which the material is
thermally reactive. For example, for a polymerizable monomer, the
material would be heated at a temperature above the sublimation
temperature and below the thermal polymerization temperature. It
will be understood that RSA materials which have a temperature of
thermal reactivity that is close to or below the volatilization
temperature, may not be able to be developed in this manner.
[0093] In one embodiment, the exposure of the RSA to radiation
results in a change in the temperature at which the material melts,
softens or flows. When the exposure is carried out patternwise,
this can be followed by a dry development treatment. A dry
development treatment can include contacting an outermost surface
of the element with an absorbent surface to absorb or wick away the
softer portions. This dry development can be carried out at an
elevated temperature, so long as it does not further affect the
properties of the originally unexposed areas.
[0094] After treatment with the RSA, and exposure to radiation, the
first layer has a lower surface energy than prior to treatment. In
the case where part of the RSA is removed after exposure to
radiation, the areas of the first layer that are covered by the RSA
will have a lower surface energy that the areas that are not
covered by the RSA.
[0095] One way to determine the relative surface energies, is to
compare the contact angle of a given liquid on the first organic
active layer before and after treatment with the RSA. As used
herein, the term "contact angle" is intended to mean the angle
.phi. shown in FIG. 1. For a droplet of liquid medium, angle .phi.
is defined by the intersection of the plane of the surface and a
line from the outer edge of the droplet to the surface.
Furthermore, angle .phi. is measured after the droplet has reached
an equilibrium position on the surface after being applied, i.e.
"static contact angle". A variety of manufacturers make equipment
capable of measuring contact angles.
[0096] The second layer is then applied over the RSA-treated first
layer. The second layer can be applied by any deposition technique.
In one embodiment, the second layer is applied by a liquid
deposition technique. In this case, a liquid composition comprises
a second material dissolved or dispersed in a liquid medium,
applied over the RSA-treated first layer, and dried to form the
second layer. The liquid composition is chosen to have a surface
energy that is greater than the surface energy of the RSA-treated
first layer, but approximately the same as or less than the surface
energy of the untreated first layer. Thus, the liquid composition
will wet the untreated first layer, but will be repelled from the
RSA-treated areas. The liquid may spread onto the RSA-treated area,
but it will de-wet.
[0097] In one embodiment, the RSA is patterned and the second layer
is applied using a continuous liquid deposition technique. In one
embodiment, the second layer is applied using a discontinuous
liquid deposition technique.
[0098] In one embodiment, the RSA is unpatterned and the second
layer is applied using a discontinuous liquid deposition
technique.
[0099] In one embodiment, the first layer is applied over a liquid
containment structure. It may be desired to use a structure that is
inadequate for complete containment, but that still allows
adjustment of thickness uniformity of the printed layer. In this
case it may be desirable to control wetting onto the
thickness-tuning structure, providing both containment and
uniformity. It is then desirable to be able to modulate the contact
angle of the emissive ink. Most surface treatments used for
containment (e.g., CF4 plasma) do not provide this level of
control.
[0100] In one embodiment, the first layer is applied over a
so-called bank structure. Bank structures are typically formed from
photoresists, organic materials (e.g., polyimides), or inorganic
materials (oxides, nitrides, and the like). Bank structures may be
used for containing the first layer in its liquid form, preventing
color mixing; and/or for improving the thickness uniformity of the
first layer as it is dried from its liquid form; and/or for
protecting underlying features from contact by the liquid. Such
underlying features can include conductive traces, gaps between
conductive traces, thin film transistors, electrodes, and the like.
It is often desirable to form regions on the bank structures
possessing different surface energies to achieve two or more
purposes (e.g., preventing color mixing and also improving
thickness uniformity). One approach is to provide a bank structure
with multiple layers, each layer having a different surface energy.
A more cost effective way to achieve this modulation of surface
energy is to control surface energy via modulation of the radiation
used to cure a RSA. This modulation of curing radiation can be in
the form of energy dosage (power*exposure time), or by exposing the
RSA through a photomask pattern that simulates a different surface
energy (e.g., expose through a half-tone density mask).
[0101] In one embodiment of the process provided herein, the first
and second layers are organic active layers. The first organic
active layer is formed over a first electrode, the first organic
active layer is treated with a reactive surface-active composition
to reduce the surface energy of the layer, and the second organic
active layer is formed over the treated first organic active
layer.
[0102] In one embodiment, the first organic active layer is formed
by liquid deposition of a liquid composition comprising the first
organic active material and a liquid medium. The liquid composition
is deposited over the first electrode, and then dried to form a
layer. In one embodiment, the first organic active layer is formed
by a continuous liquid deposition method. Such methods may result
in higher yields and lower equipment costs.
[0103] In one embodiment, the RSA treatment is subsequent to the
formation of the first organic active layer. In one embodiment, the
RSA is is applied as a separate layer overlying, and in direct
contact with, the first organic active layer. In one embodiment,
the RSA is deposited from a second liquid composition. The liquid
deposition method can be continuous or discontinuous, as described
above. In one embodiment, the RSA liquid composition is deposited
using a continuous liquid deposition method.
[0104] The thickness of the RSA layer can depend upon the ultimate
end use of the material. In some embodiments, the RSA layer is at
least 100 .ANG. in thickness. In some embodiments, the RSA layer is
in the range of 100-3000 .ANG.; in some embodiments 1000-2000
.ANG..
[0105] After the RSA treatment, the treated first organic active
layer is exposed to radiation. The type of radiation used will
depend upon the sensitivity of the RSA as discussed above. The
exposure can be a blanket, overall exposure, or the exposure can be
patternwise.
[0106] In one embodiment, the exposure of the RSA to radiation
results in a change in solubility or dispersibility of the RSA in a
liquid medium. In one embodiment, the exposure is carried out
patternwise. This can be followed by treating the RSA with a liquid
medium, to remove either the exposed or unexposed portions of the
RSA. In one embodiment, the RSA is radiation-hardenable and the
unexposed portions are removed by the liquid medium.
4. Organic Electronic Device
[0107] The process will be further described in terms of its
application in an electronic device, although it is not limited to
such application.
[0108] FIG. 2 is an exemplary electronic device, an organic
light-emitting diode (OLED) display that includes at least two
organic active layers positioned between two electrical contact
layers. The electronic device 100 includes one or more layers 120
and 130 to facilitate the injection of holes from the anode layer
110 into the photoactive layer 140. In general, when two layers are
present, the layer 120 adjacent the anode is called the hole
injection layer or buffer layer. The layer 130 adjacent to the
photoactive layer is called the hole transport layer. An optional
electron transport layer 150 is located between the photoactive
layer 140 and a cathode layer 160. Depending on the application of
the device 100, the photoactive layer 140 can be a light-emitting
layer that is activated by an applied voltage (such as in a
light-emitting diode or light-emitting electrochemical cell), a
layer of material that responds to radiant energy and generates a
signal with or without an applied bias voltage (such as in a
photodetector). The device is not limited with respect to system,
driving method, and utility mode.
[0109] For multicolor devices, the photoactive layer 140 is made up
different areas of at least three different colors. The areas of
different color can be formed by printing the separate colored
areas. Alternatively, it can be accomplished by forming an overall
layer and doping different areas of the layer with emissive
materials with different colors. Such a process has been described
in, for example, published U.S. patent application
2004-0094768.
[0110] In one embodiment, the new process described herein can be
used to apply an organic layer (second layer) to an electrode layer
(first layer). In one embodiment, the first layer is the anode 110,
and the second layer is the buffer layer 120.
[0111] In some embodiments, the new process described herein can be
used for any successive pairs of organic layers in the device,
where the second layer is to be contained in a specific area. In
one embodiment of the new process, the second organic active layer
is the photoactive layer 140, and the first organic active layer is
the device layer applied just before layer 140. In many cases the
device is constructed beginning with the anode layer. When the hole
transport layer 130 is present, the RSA treatment would be applied
to layer 130 prior to applying the photoactive layer 140. When
layer 130 was not present, the RSA treatment would be applied to
layer 120. In the case where the device was constructed beginning
with the cathode, the RSA treatment would be applied to the
electron transport layer 150 prior to applying the photoactive
layer 140.
[0112] In one embodiment of the new process, the second organic
active layer is the hole transport layer 130, and the first organic
active layer is the device layer applied just before layer 130. In
the embodiment where the device is constructed beginning with the
anode layer, the RSA treatment would be applied to buffer layer 120
prior to applying the hole transport layer 130.
[0113] In one embodiment, the anode 110 is formed in a pattern of
parallel stripes. The buffer layer 120 and, optionally, the hole
transport layer 130 are formed as continuous layers over the anode
110. The RSA is applied as a separate layer directly over layer 130
(when present) or layer 120 (when layer 130 is not present). The
RSA is exposed in a pattern such that the areas between the anode
stripes and the outer edges of the anode stripes are exposed.
[0114] The layers in the device can be made of any materials which
are known to be useful in such layers. The device may include a
support or substrate (not shown) that can be adjacent to the anode
layer 110 or the cathode layer 150. Most frequently, the support is
adjacent the anode layer 110. The support can be flexible or rigid,
organic or inorganic. Generally, glass or flexible organic films
are used as a support. The anode layer 110 is an electrode that is
more efficient for injecting holes compared to the cathode layer
160. The anode can include materials containing a metal, mixed
metal, alloy, metal oxide or mixed oxide. Suitable materials
include the mixed oxides of the Group 2 elements (i.e., Be, Mg, Ca,
Sr, Ba, Ra), the Group 11 elements, the elements in Groups 4, 5,
and 6, and the Group 8-10 transition elements. If the anode layer
110 is to be light transmitting, mixed oxides of Groups 12, 13 and
14 elements, such as indium-tin-oxide, may be used. As used herein,
the phrase "mixed oxide" refers to oxides having two or more
different cations selected from the Group 2 elements or the Groups
12, 13, or 14 elements. Some non-limiting, specific examples of
materials for anode layer 110 include, but are not limited to,
indium-tin-oxide ("ITO"), aluminum-tin-oxide, gold, silver, copper,
and nickel. The anode may also comprise an organic material such as
polyaniline, polythiophene, or polypyrrole.
[0115] The anode layer 110 may be formed by a chemical or physical
vapor deposition process or spin-cast process. Chemical vapor
deposition may be performed as a plasma-enhanced chemical vapor
deposition ("PECVD") or metal organic chemical vapor deposition
("MOCVD"). Physical vapor deposition can include all forms of
sputtering, including ion beam sputtering, as well as e-beam
evaporation and resistance evaporation. Specific forms of physical
vapor deposition include rf magnetron sputtering and
inductively-coupled plasma physical vapor deposition ("IMP-PVD").
These deposition techniques are well known within the semiconductor
fabrication arts.
[0116] Usually, the anode layer 110 is patterned during a
lithographic operation. The pattern may vary as desired. The layers
can be formed in a pattern by, for example, positioning a patterned
mask or resist on the first flexible composite barrier structure
prior to applying the first electrical contact layer material.
Alternatively, the layers can be applied as an overall layer (also
called blanket deposit) and subsequently patterned using, for
example, a patterned resist layer and wet chemical or dry etching
techniques. Other processes for patterning that are well known in
the art can also be used. When the electronic devices are located
within an array, the anode layer 110 typically is formed into
substantially parallel strips having lengths that extend in
substantially the same direction.
[0117] The buffer layer 120 functions to facilitate injection of
holes into the photoactive layer and to smoothen the anode surface
to prevent shorts in the device. The buffer layer is typically
formed with polymeric materials, such as polyaniline (PANI) or
polyethylenedioxythiophene (PEDOT), which are often doped with
protonic acids. The protonic acids can be, for example,
poly(styrenesulfonic acid),
poly(2-acrylamido-2-methyl-1-propanesulfonic acid), and the like.
The buffer layer 120 can comprise charge transfer compounds, and
the like, such as copper phthalocyanine and the
tetrathiafulvalene-tetracyanoquinodimethane system (TTF-TCNQ). In
one embodiment, the buffer layer 120 is made from a dispersion of a
conducting polymer and a colloid-forming polymeric acid. Such
materials have been described in, for example, published U.S.
patent applications 2004-0102577 and 2004-0127637.
[0118] The buffer layer 120 can be applied by any deposition
technique. In one embodiment, the buffer layer is applied by a
solution deposition method, as described above. In one embodiment,
the buffer layer is applied by a continuous solution deposition
method.
[0119] Examples of hole transport materials for optional layer 130
have been summarized for example, in Kirk-Othmer Encyclopedia of
Chemical Technology, Fourth Edition, Vol. 18, p. 837-860, 1996, by
Y. Wang. Both hole transporting molecules and polymers can be used.
Commonly used hole transporting molecules include, but are not
limited to: 4,4',4''-tris(N,N-diphenyl-amino)-triphenylamine
(TDATA);
4,4',4''-tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine
(MTDATA);
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine
(TPD); 1,1-bis[(di-4-tolylamino) phenyl]cyclohexane (TAPC);
N,N'-bis(4-methylphenyl)-N,N'-bis(4-ethylphenyl)-[1,1'-(3,3'-dimethyl)bip-
henyl]-4,4'-diamine (ETPD); tetrakis-(3-methylphenyl)-N,N,
N',N'-2,5-phenylenediamine (PDA);
.alpha.-phenyl-4-N,N-diphenylaminostyrene (TPS);
p-(diethylamino)benzaldehyde diphenylhydrazone (DEH);
triphenylamine (TPA);
bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane
(MPMP);
1-phenyl-3-[p-(diethylamino)styryl]-5-[p-(diethylamino)phenyl]
pyrazoline (PPR or DEASP);
1,2-trans-bis(9H-carbazol-9-yl)cyclobutane (DCZB);
N,N,N',N'-tetrakis(4-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine
(TTB); N,N'-bis(naphthalen-1-yl)-N,N'-bis-(phenyl)benzidine
(.alpha.-NPB); and porphyrinic compounds, such as copper
phthalocyanine. Commonly used hole transporting polymers include,
but are not limited to, polyvinylcarbazole,
(phenylmethyl)polysilane, poly(dioxythiophenes), polyanilines, and
polypyrroles. It is also possible to obtain hole transporting
polymers by doping hole transporting molecules such as those
mentioned above into polymers such as polystyrene and
polycarbonate. In some embodiments, the hole transport material
comprises a cross-linkable oligomeric or polymeric material. After
the formation of the hole transport layer, the material is treated
with radiation to effect cross-linking. In some embodiments, the
radiation is thermal radiation.
[0120] The hole transport layer 130 can be applied by any
deposition technique. In one embodiment, the hole transport layer
is applied by a solution deposition method, as described above. In
one embodiment, the hole transport layer is applied by a continuous
solution deposition method.
[0121] Any organic electroluminescent ("EL") material can be used
in the photoactive layer 140, including, but not limited to, small
molecule organic fluorescent compounds, fluorescent and
phosphorescent metal complexes, conjugated polymers, and mixtures
thereof. Examples of fluorescent compounds include, but are not
limited to, pyrene, perylene, rubrene, coumarin, derivatives
thereof, and mixtures thereof. Examples of metal complexes include,
but are not limited to, metal chelated oxinoid compounds, such as
tris(8-hydroxyquinolato)aluminum (Alq3); cyclometalated iridium and
platinum electroluminescent compounds, such as complexes of iridium
with phenylpyridine, phenylquinoline, or phenylpyrimidine ligands
as disclosed in Petrov et al., U.S. Pat. No. 6,670,645 and
Published PCT Applications WO 03/063555 and WO 2004/016710, and
organometallic complexes described in, for example, Published PCT
Applications WO 03/008424, WO 03/091688, and WO 03/040257, and
mixtures thereof. Electroluminescent emissive layers comprising a
charge carrying host material and a metal complex have been
described by Thompson et al., in U.S. Pat. No. 6,303,238, and by
Burrows and Thompson in published PCT applications WO 00/70655 and
WO 01/41512. Examples of conjugated polymers include, but are not
limited to poly(phenylenevinylenes), polyfluorenes,
poly(spirobifluorenes), polythiophenes, poly(p-phenylenes),
copolymers thereof, and mixtures thereof.
[0122] The photoactive layer 140 can be applied by any deposition
technique. In one embodiment, the photoactive layer is applied by a
solution deposition method, as described above. In one embodiment,
the photoactive layer is applied by a continuous solution
deposition method.
[0123] Optional layer 150 can function both to facilitate electron
injection/transport, and can also serve as a confinement layer to
prevent quenching reactions at layer interfaces. More specifically,
layer 150 may promote electron mobility and reduce the likelihood
of a quenching reaction if layers 140 and 160 would otherwise be in
direct contact. Examples of materials for optional layer 150
include, but are not limited to, metal-chelated oxinoid compounds
(e.g., Alq.sub.3 or the like); phenanthroline-based compounds
(e.g., 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline ("DDPA"),
4,7-diphenyl-1,10-phenanthroline ("DPA"), or the like); azole
compounds (e.g.,
2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole ("PBD" or the
like), 3-(4-biphenylyl)4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole
("TAZ" or the like); other similar compounds; or any one or more
combinations thereof. Alternatively, optional layer 150 may be
inorganic and comprise BaO, LiF, Li.sub.2O, or the like.
[0124] The cathode 160, is an electrode that is particularly
efficient for injecting electrons or negative charge carriers. The
cathode layer 160 can be any metal or nonmetal having a lower work
function than the first electrical contact layer (in this case, the
anode layer 110). In one embodiment, the term "lower work function"
is intended to mean a material having a work function no greater
than about 4.4 eV. In one embodiment, "higher work function" is
intended to mean a material having a work function of at least
approximately 4.4 eV.
[0125] Materials for the cathode layer can be selected from alkali
metals of Group 1 (e.g., Li, Na, K, Rb, Cs,), the Group 2 metals
(e.g., Mg, Ca, Ba, or the like), the Group 12 metals, the
lanthanides (e.g., Ce, Sm, Eu, or the like), and the actinides
(e.g., Th, U, or the like). Materials such as aluminum, indium,
yttrium, and combinations thereof, may also be used. Specific
non-limiting examples of materials for the cathode layer 160
include, but are not limited to, barium, lithium, cerium, cesium,
europium, rubidium, yttrium, magnesium, samarium, and alloys and
combinations thereof.
[0126] The cathode layer 160 is usually formed by a chemical or
physical vapor deposition process.
[0127] In other embodiments, additional layer(s) may be present
within organic electronic devices.
[0128] When the device is made starting with the anode side, the
RSA treatment step of the new process described herein may be after
the formation of the anode 110, after the formation of the buffer
layer 120, after the hole transport layer 130, or any combination
thereof. When the device is made starting with the cathode side,
the RSA treatment step of the new process described herein, may be
after the formation of the cathode 160, the electron transport
layer 150, or any combination thereof.
[0129] The different layers may have any suitable thickness.
Inorganic anode layer 110 is usually no greater than approximately
500 nm, for example, approximately 10-200 nm; buffer layer 120, and
hole transport layer 130 are each usually no greater than
approximately 250 nm, for example, approximately 50-200 nm;
photoactive layer 140, is usually no greater than approximately
1000 nm, for example, approximately 50-80 nm; optional layer 150 is
usually no greater than approximately 100 nm, for example,
approximately 20-80 nm; and cathode layer 160 is usually no greater
than approximately 100 nm, for example, approximately 1-50 nm. If
the anode layer 110 or the cathode layer 160 needs to transmit at
least some light, the thickness of such layer may not exceed
approximately 100 nm.
EXAMPLES
[0130] The concepts described herein will be further described in
the following examples, which do not limit the scope of the
invention described in the claims.
Example 1
[0131] Example 1 demonstrates an RSA treatment that is coincidental
with the formation of the first layer. The first layer is an
organic active layer.
[0132] Coating 1: A first organic active layer of Material A (a
cross-linkable hole transport material from Sumitomo Chemical Col,
Tokyo, Japan) was spin-coated from p-xylene onto a glass slide.
[0133] Coating 2: A first organic active layer was made from a
solution containing 95% Material A and 5% of a fluorinated
unsaturated ester monomer as an RSA (Zonyl.RTM. 8857A, from E. I.
du Pont de Nemours and Company, Wilmington, Del.) by spin-coating
onto a glass slide.
[0134] Both coatings were dried at 130 C on a hot plate in air.
Spin coating conditions were adjusted to provide films with similar
thickness after drying. The coated materials were thermally cured
in a convection oven with a nitrogen atmosphere at 200.degree. C.
for 30 minutes. An emissive ink made of BD052 and BH140 (Idemitsu
Kosan Ltd., Chiba, Japan) in a ratio of 8:92, at 1.5% total solids,
in anisole, was printed onto each of the coatings using a MicroFab
printer, with a stage temperature of 50.degree. C. Spreading of the
ink on the two surfaces was compared by measuring the diameter of
the printed drops after drying. The ink spread 7% less on coating 2
containing the RSA vs. coating 1 devoid of RSA. The contact angle
of anisole was about 9 degrees on coating 1, and about 15 degrees
on the surface of coating 2 containing Zonyl.RTM. 8857A.
Example 2
[0135] Example 2 demonstrates an RSA treatment that is subsequent
to the formation of the first layer. The first layer is an organic
active layer.
[0136] Coatings of Material A were prepared on glass slides and
cured at 200.degree. C. for 30 minutes in a convection oven with a
nitrogen atmosphere. A solution of a fluorinated acrylate monomer
as an RSA (Zonyl.RTM. TA-N, from E. I. du Pont de Nemours and
Company, Wilmington, Del.) was spin-coated onto the cured Material
A surface. The RSA solution was about 20% solids in
hexafluoropropoxybenzene. The RSA was cured by heating at
130.degree. C. on a hot plate in air. Any uncured RSA was rinsed
off by soaking in trifluorotoluene in a petri dish for 15 minutes,
and dried at ambient temperature in air. The contact angle of the
cured, uncoated Material A was measured as about 9 degrees using
anisole. The contact angle of the cured, uncoated Material A was
identical within experimental error if the surface was simply
rinsed with trifluorotoluene (no RSA coating). The contact angle
was identical within experimental error if the RSA was coated onto
the Material A and washed off with trifluorotoluene without
reacting the RSA in the oven. The contact angle of the oven-cured
RSA surface was 27 degrees. This demonstrates that the RSA can be
applied and removed without affecting the underlying surface
energy, and the difference vs. the cured film can be readily
measured.
Example 3
[0137] Example 3 demonstrates an RSA treatment that is subsequent
to the formation of the first layer. The first layer is an organic
active layer.
[0138] Glass slides were coated with Material A and thermally cured
as described above. On some slides the Material A was overcoated
with a solution of RSA (Zonyl.RTM. TA-N) as described above, and
the RSA was dried at ambient. The thickness of the RSA coating was
determined to be about 100 Angstrom (A) using a VEECO NT3300
inteferometric profilometer. The RSA was exposed to actinic
radiation (365-405 nm, 2.7 Joule/cm 2) in air; half this glass
slide was masked off to prevent exposure. After exposure the
uncured RSA was washed off by soaking in trifluorotoluene for 3
minutes. The contact angle of anisole on the region where the RSA
had been exposed to actinic radiation was 40 degrees. The contact
angle in the unexposed region was identical to Material A within
experimental error, showing the unexposed RSA was completely
soluble and could be rinsed cleanly from the Material A surface. A
coating of Material A without RSA was exposed to actinic radiation
and the contact angle was unchanged. This demonstrates creating a
pattern in the RSA by exposure to actinic radiation, and the change
in surface energy is due to the RSA and not to the processing
steps.
Example 4
[0139] Example 4 demonstrates an RSA treatment that is subsequent
to the formation of the first layer. This example also demonstrates
containment as it would be practiced during printing of an emissive
ink. The example is shown in FIGS. 3 through 6.
[0140] A glass substrate, shown as 200 in FIG. 3, with a coating of
indium tin oxide (ITO) about 1100 .ANG. thick, was patterned
photolithographically to create an array of lines of ITO, shown as
210, with widths of about 90 microns, and spacing of 10 microns
between the lines. A layer 220 of Material A was coated over the
array of lines and cured at 200.degree. C. in a convection oven
with an nitrogen atmosphere for 30 minutes, as shown in FIG. 4. The
Material A-coated ITO lines are shown as 211. A coating 230 of
Zonyl.RTM. TA-N was applied over the Material A on one substrate by
spin coating from hexafluoropropoxybenzene, and dried in air, as
shown in FIG. 5. This coating was exposed to radiation from a
source with the majority of its emission in the range of 365-404 nm
using a negative photomask so the exposed regions covered the gaps
between the ITO lines, and 2-3 microns of the edge of the ITO line.
The exposure was about 3.8 J/cm 2. The plates were washed in
trifluorotoluene to remove the unexposed RSA. FIG. 6 shows the
piece after development, with RSA-covered areas 230 and Material
A-covered areas over the ITO, 211 and Material A-covered areas over
the glass, 220. An emissive ink comprising BH119 and BH215 (both
from Idemitsu) in a ratio of 8:92, at 1.5% total solids, in
anisole, was printed onto the ITO lines using a MicroFab printer,
at ambient. The drop volume was about 40-45 picoliters, and the
drop spacing was 0.08 mm, creating continuous lines of printing. On
the panel without the RSA the printed lines spread about 200-300
microns; that is, the ink spread across 3 ITO lines. This would
have resulted in unacceptable color mixing in an actual printing
process. On the panel with the patterned RSA the ink was contained
entirely within the region treated with the RSA, and would have
resulted in a high quality printed device.
Example 5
[0141] Example 5 demonstrates an RSA treatment that is subsequent
to the formation of the first layer.
[0142] Coatings of Material A were prepared and thermally cured as
described above. These were then overcoated with RSA coatings of
Zonyl.RTM. TA-N as described above. The RSA coatings received
blanket exposures up to about 4 J/cm 2. The coatings were washed in
trifluorotoluene after exposure, and contact angles were measured
with anisole. The anisole contact angle was modulated from about 9
degrees (Material A surface) to 40-45 degrees. No significant
difference was observed if the exposures were performed in air or
an inert atmosphere.
Example 6
[0143] Example 6 demonstrates an RSA treatment that is subsequent
to the formation of the first layer, where removal of unexposed
region is accomplished via sublimation.
[0144] Coatings of Material A were prepared and thermally cured as
described above. These were then overcoated with RSA coatings of
heneicosafluorododecylacrylate by spin coating from a 3% wt/vol
solution in perfluorooctance. One of the RSA coatings received a
blanket UV exposure of about 1.5 J/cm.sup.2; the other coating did
not receive a UV exposure. The two coatings were baked at
195.degree. C. for 20 minutes on a hot plate in air, and contact
angles were measured with anisole. The anisole contact angle was
about 55 degrees on the RSA coating that had been exposed to UV
radiation. The anisole contact angle was 10 degrees on the coating
that had not been exposed to UV radiation. This demonstrates that
the RSA that has not been exposed to UV radiation can be removed by
heating. If the RSA coating had been exposed to UV radiation in a
pattern, and then heated, the RSA would have remained in the
exposed areas with a contact angle of about 55 degrees, and the
unexposed areas would have had a contact angle of about 10
degrees.
[0145] Note that not all of the activities described above in the
general description or the examples are required, that a portion of
a specific activity may not be required, and that one or more
further activities may be performed in addition to those described.
Still further, the order in which activities are listed are not
necessarily the order in which they are performed.
[0146] In the foregoing specification, the concepts have been
described with reference to specific embodiments. However, one of
ordinary skill in the art appreciates that various modifications
and changes can be made without departing from the scope of the
invention as set forth in the claims below. Accordingly, the
specification and figures are to be regarded in an illustrative
rather than a restrictive sense, and all such modifications are
intended to be included within the scope of invention.
[0147] Benefits, other advantages, and solutions to problems have
been described above with regard to specific embodiments. However,
the benefits, advantages, solutions to problems, and any feature(s)
that may cause any benefit, advantage, or solution to occur or
become more pronounced are not to be construed as a critical,
required, or essential feature of any or all the claims.
[0148] It is to be appreciated that certain features are, for
clarity, described herein in the context of separate embodiments,
may also be provided in combination in a single embodiment.
Conversely, various features that are, for brevity, described in
the context of a single embodiment, may also be provided separately
or in any subcombination. Further, reference to values stated in
ranges include each and every value within that range.
* * * * *